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1. avr5 atmega168p AVR ATmegal68P avr5 atmega169 AVR ATmegal69 avr5 atmegal69a AVR ATmegal69A avr5 atmega169p AVR ATmegal69P avr5 atmegal69pa __AVR_ATmegal69PA__ avr5 atmegal6a __AVR_ATmegal6A__ avr5 atmegal6hva AVR ATmegal6HVA avr5 atmegal 6hva2 __AVR_ATmegal6HVA2__ avr5 atmegal6hvb AVR ATmegal6HVB avr5 atmegal6hvbrevb AVR ATmegal6HVBREVB avr5 atmegal6m1 __AVR_ATmegal6M1__ avr5 atmegal6u4 __AVR_ATmegal6U4__ avr5 atmega32 AVR ATmega32 avr5 atmega323 AVR ATmega323 avr5 atmega324a ATmega324A avr5 atmega324p AVR ATmega324P avr5 atmega324pa AVR ATmega324PA avr5 atmega325 AVR ATmega325 avr5 atmega325a AVR ATmega325A avr5 atmega325p AVR ATmega325P avr5 atmega325pa ATmega325PA avr5 atmega3250 AVR ATmega3250 avr5 atmega3250a AVR ATmega3250A avr5 atmega3250p AVR ATmega3250P avr5 atmega3250pa AVR ATmega3250PA avr5 atmega328 AVR ATmega328 avr5 atmega328p AVR ATmega328P avr5 atmega329 AVR ATmega3290 avr5 atmega329a AVR ATmega329A avr5 atmega329p AVR ATmega329P avr5 atmega329pa __AVR_ATmega329PA__ avr5 atmega3290 AVR ATmega3290 avr5 atmega3290a AVR ATmega3290A avr5 atmega3290p AVR ATmega3290P avr5 atmega3290pa AVR ATmega3290PA avr5 atmega32c1 AVR ATmega32Cl avr5 atmega32hvb AVR ATmega32HVB avr5 atmega32hvbrevb _ AVR ATmega32H
2. setup stream with read intent 22 9 2 4 define FDEV SETUP RW SRD SWR setup stream with read write intent 22 0 2 5 define FDEV SETUP WRITE SWR fdev setup stream with write intent 22 9 2 6 define EOF 1 EOF declares the value that is returned by various standard IO functions in case of an error Since the AVR platform currently doesn t contain an abstraction for actual files its origin as end of file is somewhat meaningless here Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 188 22 0 2 7 define close This macro frees up any library resources that might be associated with st ream It should be called if st ream is no longer needed right before the application is going to destroy the stream object itself Currently this macro evaluates to nothing but this might change in future versions of the library 22 9 2 8 define get udata stream stream gt udata This macro retrieves a pointer to user defined data from a FILE stream object 22 0 2 0 define set udata stream do stream gt udata u while 0 This macro inserts a pointer to user defined data into a FILE stream object The user data can be useful for tracking state in the put and get functions supplied to the fdevopen function 22 9 2 10 zidefine setup stream stream put get rwflag Setup a user s
3. 1 Locate the archive library named 1 and use it to resolve currently unre solved symbols from it The library is searched along a path that consists of builtin pathname entries that have been specified at compile time e g usr local avr lib on Unix systems possibly extended by pathname entries as specified by L options that must precede the 1 options on the command line Lpath Additional location to look for archive libraries requested by 1 options e defsym symbol expr Define a global symbol symbol using expr as the value Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 3 Controlling the linker avr ld 119 M Print a linker map to stdout Map mapfile Print a linker map to mapfile cref Output a cross reference table to the map file in case Map is also present or to stdout section start sectionname org Start section sectionname at absolute address org Tbss org e Tdata org Ttext org Start the bss data or text section at org respectively e T scriptfile Use scriptfile as the linker script replacing the default linker script Default linker scripts are stored in a system specific location e g under usr local avr lib ldscripts on Unix systems and consist of the AVR architecture name avr2 through avr5 with the suffix x appended They describe how the various memory sections will be linked
4. define EEMEM attribute section eeprom Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 2214 lt avr eeprom h gt EEPROM handling 236 define eeprom is ready define eeprom busy wait do while is ready Functions uint8 t eeprom read byte const uint8 p PURE uint16 t eeprom read word const uint16 t ATTR_PURE uint32 t eeprom read dword const uint32 ATTR_PURE float eeprom read float const float p _ ATTR_PURE void eeprom read block void dst const void src size t n void eeprom write byte uint8 t p uint8 t value void eeprom write word uint16 p uintl6 t value void eeprom write dword uint32 p uint32 t value void eeprom write float float p float value void eeprom write block const void src void dst size t void eeprom update byte uint8 p uint8 t value void eeprom update word uint16 t p uintl6 t value void eeprom update dword uint32_t __p uint32_t value void eeprom update float float __p float __ value void eeprom update block const void src void __dst size_t __n IAR C compatibility defines define EEPUT addr val eeprom write byte uint8 t x addr uint8 t val define EEPUT addr val eeprom write byte uint8_t x addr uint8_t val define _EEGET var addr var eeprom read byte const uint8 t x
5. n the table the size includes all additional functions for example function to multiply two integers but they are only linked from the library Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 9 1 A few of functions 55 Expenses of time of performance of some functions essentially depend on param eters of a call for example qsort is recursive and sprintf receives parameters in a stack Different versions of the compiler can give a significant difference in code size and execution time For example the dtostre function compiled with avr gcc 3 4 6 requires 930 bytes After transition to avr gcc 4 2 3 the size become 1088 bytes 9 1 A few of libc functions Avr gcc version is 4 2 3 The size of function is given in view of all picked up functions By default Avr libc is compiled with mcall prologues option In brackets the size without taking into account modules of a prologue and an epilogue is resulted Both of the size can coincide if function does not cause a prologue epilogue Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 91 A few of libc functions Function Units Avr2 Avr25 Avr4 atoi 12345 Flash bytes 82 82 78 78 74 74 Stack bytes 2 2 MCU clocks 155 149 atol 12345 Flash bytes 122 122 118 118 118 118 Stack bytes 2 2 MCU clocks 221 219 dtostre 1 2345 Flash bytes 1184 10
6. vfprintf is the central facility of the print family of functions It outputs values to st ream under control of a format string passed in fmt The actual values to print are passed as a variable argument list ap vfprintf returns the number of characters written to stream or EOF in case of an error Currently this will only happen if st ream has not been opened with write intent The format string is composed of zero or more directives ordinary characters not which are copied unchanged to the output stream and conversion specifications each of which results in fetching zero or more subsequent arguments Each conversion specification is introduced by the character The arguments must properly correspond after type promotion with the conversion specifier After the the following appear in sequence Zero or more of the following flags The value should be converted to an alternate form For c d i s and u conversions this option has no effect For o conversions the precision of the number is increased to force the first character of the output string to a zero except if a zero value is printed with an explicit precision of zero Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 196 For x and X conversions a non zero result has the string or OX for X conversions prepended to it 0 zero Zero padding For all con
7. 3 1 Introduction Many of the devices that are possible targets of avr libc have a minimal amount of RAM The smallest parts supported by the C environment come with 128 bytes of RAM This needs to be shared between initialized and uninitialized variables sections data and bss the dynamic memory allocator and the stack that is used for calling subroutines and storing local automatic variables Also unlike larger architectures there is no hardware supported memory management which could help in separating the mentioned RAM regions from being overwritten by each other The standard RAM layout is to place data variables first from the beginning of the internal RAM followed by bss The stack is started from the top of internal RAM growing downwards The so called heap available for the dynamic memory allocator will be placed beyond the end of bss Thus there s no risk that dynamic memory will ever collide with the RAM variables unless there were bugs in the implementation of the allocator There is still a risk that the heap and stack could collide if there are large requirements for either dynamic memory or stack space The former can even happen if the allocations aren t all that large but dynamic memory allocations get fragmented over time such that new requests don t quite fit into the holes of previously freed regions Large stack space requirements can arise in a C function containing large and or numerous local variables
8. Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 17 Which O flag to use 77 a description how to do this using few lines of assembler code or to the chapter about memory sections for an example written in C The explanation of malloc contains a discussion about the use of internal RAM vs external RAM in particular with respect to the various possible locations of the heap area reserved for malloc It also explains the linker command line options that are required to move the memory regions away from their respective standard locations in internal RAM Finally if the application simply wants to use the additional RAM for private data storage kept outside the domain of the C compiler e g through a char variable initialized directly to a particular address it would be sufficient to defer the initial ization of the external RAM interface to the beginning of main so no tweaking of the init3 section is necessary The same applies if only the heap is going to be located there since the application start up code does not affect the heap It is not recommended to locate the stack in external RAM In general accessing exter nal RAM is slower than internal RAM and errata of some AVR devices even prevent this configuration from working properly at all Back to FAQ Index 11 17 Which O flag to use There s common misconception that larger numbers behind the O option might auto matically cause
9. Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 8 ctype h File Reference 376 24 7 1 Detailed Description 24 8 ctype h File Reference Functions Character classification routines These functions perform character classification They return true or false status depending whether the character passed to the function falls into the function s classification i e isdigit returns true if its argument is any value 0 though 9 inclusive If the input is not an unsigned char value all of this function return false e intisalnum int c e int isalpha int c e int isascii int e int isblank int c e intiscntrl int c e intisdigit int c e intisgraph int c e int islower int e int isprint int c intispunct int c e int isspace int e intisupper int c e intisxdigit int c Character convertion routines This realization permits all possible values of integer argument The toascii func tion clears all highest bits The tolower and toupper functions return an input argument as is if it is not an unsigned char value e inttoascii int e int tolower int c e inttoupper int c 24 81 Detailed Description 24 9 delay basic h File Reference Functions e void delay loop 1 uint8 t count e void delay loop 2 uint16 t count Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 10 errno h File Reference 377 24 9 1 Detailed Descripti
10. char strcpy P char x PGM P char strcpy PF char dest farptr t src size tstrcspn P const char s PGM P reject ATTR PURE size t strlcat P char P size t size tstrlcat PF char dst farptr t src size t siz size t strlcpy P char PGM P size t size t strlcpy PF char dst farptr t src size t siz size t strlen P PGM P size t strlen PF farptr t src int strncasecmp_P const char x PGM_P size_t __ATTR_PURE int strncasecmp_PF const char s1 uint_farptr_t s2 size tn ATTR_PURE_ char strncat_P char PGM P size_t char strncat PF char dest farptr t src size t len int strncmp P const char PGM P size t ATTR_PURE int strmcmp PF const char s1 farptr t s2 size tn PURE char strncpy_P char size t char strncpy PF char dest farptr t src size t len size t strnlen P PGM size t size t strnlen PF uint farptr t src size t len char strpbrk P const char s PGM P accept ATTR_PURE PGM P strrchr_P PGM_P int __ val char strsep P char sp PGM P delim size tstrspn P const char s PGM P accept ATTR_PURE char strstr P const char PGM P ATTR_ PURE char strstr PF const char s1 farptr t 52 char strtok_rP char s PGM P delim char last void memcocpy P void PGM VOID P int __ va
11. mandir installdir man infodir installdir info 2 amp 1 tee avarice configure log Make make all install 2 gt amp 1 tee avarice make log SimulAVR Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 Using the GNU tools 106 Open source code package Configure and build in a directory outside of the source code tree Set PATH in order lt executables gt x usr local bin usr bin bin install directory gt bin Configure export LDFLAGS static Sarchivedir configure prefix installdir datadir installdir disable tests disable versioned doc 2 amp 1 tee simulavr configure log Make make k all install 2 gt amp 1 tee simulavr make log make pdf install pdf 2 gt amp 1 tee simulavr pdf make log 13 Using the GNU tools This is a short summary of the AVR specific aspects of using the GNU tools Normally the generic documentation of these tools is fairly large and maintained in texinfo files Command line options are explained in detail in the manual page 13 1 Options for the C compiler avr gcc 13 1 1 Machine specific options for the AVR The following machine specific options are recognized by the C compiler frontend In addition to the preprocessor macros indicated in the tables below the preprocessor will define the macros __ AVR and AVR to the value 1 when compiling for an AVR target The macro AVR w
12. The variable ee pwm is not a variable in the classical C sense that could be used as an lvalue or within an expression to obtain its value Instead the attribute section eeprom marks it as belonging to the EEPROM section This section is merely used as a place holder so the compiler can arrange for each individual variable s location in EEPROM The compiler will also keep track of initial values assigned and usually the Makefile is arranged to extract these initial values into a separate load file Largedemo eeprom x in this case that can be used to initialize the EEPROM The actual EEPROM IO must be performed manually Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 38 A more sophisticated project 352 Similarly the variable mcucsr is kept in the noinit section in order to prevent it from being cleared upon application startup 22 38 3 3 Part 3 Interrupt service routines The ISR to handle timer 1 s overflow interrupt arranges for the software clock While timer 1 runs the PWM it calls its overflow handler rather frequently so the TMR1_ SCALE value is used as a postscaler to reduce the internal software clock frequency further If the software clock triggers it sets the tmr_int bitfield and defers all further tasks to the main loop The ADC ISR just fetches the value from the ADC conversion disables the ADC interrupt again and announces the presence of the new value in the adc_int
13. Timer Counter2 Compare Match A ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal28l ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 258 TIMER2 COMP vect SIG OUTPUT COMPARE2 Timer Counter2 Compare Match AT90S4434 419058535 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l AT megal62 ATmegal63 ATmegal65 AT megal65P ATmegal69 ATmegal69P AT mega32 ATmega323 ATmega325 AT mega3250 ATmega3250P ATmega329 AT mega3290 ATmega3290P ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmega8 ATmega8535 TIMER2 OVF vect SIG OVERFLOW2 Timer Counter2 Overflow AT90S4434 419058535 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 AT mega323 ATmega325 ATmega3250 ATmega3250P ATmega328P AT mega329 ATmega3290 ATmega3290P ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1286 AT90USB647 A
14. target target enable languages c ct with dwarf2 enable win32 registry WinAVR S release disable nls with gmp usr local with mpfr usr local enable doc disable libssp 2 gt amp 1 tee package configure log Make make all html install 2 gt amp 1 tee package make log Manually copy the HTML documentation from the source code tree to the installation tree avr libc Open source code package Configure and build at the top of the source code tree Set PATH in order usr local bin mingw bin bin lt MikTex executables gt lt install directory gt bin lt Doxygen executables gt lt NetPBM executables gt lt fig2dev executable lt Ghostscript executables gt c cygwin bin Configure Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 13 Building the Toolchain for Windows 103 configure host avr prefix installdir enable doc disable versioned doc enable html doc enable pdf doc enable man doc mandir installdir man datadir installdir 2 gt amp 1 tee package configure log Make make all install 2 gt amp 1 tee Spackage make log Manually change location of man page documentation Move the examples to the top level of the install tree Convert line endings in examples to Windows line endings Convert line endings in header files to Windows l
15. 22 8 2 9 define INT64 MIN INT64 MAX ILL 22 8 2 10 22 8 2 11 22 8 2 12 22 8 2 13 22 8 2 14 22 8 2 15 22 8 2 16 smallest negative value an int64 t can hold define INT8 C value int8 t value define a constant of type int8 t define INT8 MAX 0x7f largest positive value an int8 t can hold define INT8 MIN INT8 MAX 1 smallest negative value an int8 t can hold define INT FASTI6 MAX 16 largest positive value an int fast16 t can hold define INT FAST16 MIN INT16 MIN smallest negative value an int fast16 t can hold define INT FAST32 MAX INT32 MAX largest positive value an int fast32 t can hold define INT FAST32 MIN INT32 MIN smallest negative value an int fast32 t can hold Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 175 22 8 2 17 INT FAST64 MAX INT64 MAX largest positive value an int fast64 t can hold 22 8 2 18 define INT FAST64 MIN INT64 MIN smallest negative value an int fast 4 t can hold 22 8 2 19 define INT FAST8 MAX INT8 MAX largest positive value an int fast8 t can hold 22 8 2 20 define INT FAST8 MIN INT8 MIN smallest negative value an int fast8 t can hold 22 8 2 21 define INT LEASTI16 MAX INTI6 largest positive value an int least16 t can hold 22 8 2 22 itdefine INT LEAST16 MIN INT16 MIN smallest negative value an int least16 t
16. 3 avr31 and avr51 architectures is new in GCC 4 3 e morder1 e morder2 Change the order of register assignment The default is 124 r25 r18 r19 120 r21 r22 123 r30 r31 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 12 10 r1 Order 1 uses r18 r19 120 r21 122 123 r24 r25 r30 r31 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 15 r4 r3 12 10 r1 Order 2 uses 125 r24 123 122 121 r20 r19 r18 r30 r31 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r5 r4 r3 r2 r1 rO e mint8 Assume int to be an 8 bit integer Note that this is not really supported by avr libo so it should normally not be used The default is to use 16 bit integers mno interrupts Generates code that changes the stack pointer without disabling interrupts Normally the state of the status register SREG is saved in a temporary register interrupts are disabled while changing the stack pointer and SREG is restored Specifying this option will define the preprocessor macro INTERRUPTS to the value 1 e mcall prologues Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 114 Use subroutines for function prologue epilogue For complex functions that use many registers that needs to be saved restored on function entry exit this saves some
17. Early versions of these tools did not support C The stdc libs are not included with C for AVR due to the size limitations of the devices The official version of GCC might lack support for recent AVR devices A patch that adds more AVR types can be found at http www reebsd org cgi cvsweb cgi ports devel Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 6 AVRLibc 95 12 6 AVRLibc Warning You must install avr binutils avr gcc and make sure your path is set properly be fore installing avr libc Note If you have obtained the latest avr libc from cvs you will have to run the boot st rap script before using either of the build methods described below To build and install avr libc gunzip c avr libc version tar gz tar xf cd avr libc version configure prefix PREFIX build config guess host avr make make install Ur Xr X ror 12 7 AVRDUDE Note It has been ported to windows via MinGW or cygwin Linux and Solaris Other Unix systems should be trivial to port to avrdude is part of the FreeBSD ports system To install it simply do the following cd usr ports devel avrdude make install Note Installation into the default location usually requires root permissions However running the program only requires access permissions to the appropriate ppi 4 device Building and installing on other systems should use the configure system as such gu
18. Global timer enable int unsigned char ints 19 Module Index 19 1 Modules Here is a list of all modules lt alloca h gt Allocate space in the stack 134 lt assert h gt Diagnostics 135 lt ctype h gt Character Operations 136 lt errno h gt System Errors 139 lt inttypes h gt Integer Type conversions 139 math h Mathematics 152 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 19 1 Modules 129 lt setimp h gt Non local goto 166 lt stdint h gt Standard Integer Types 168 lt stdio h gt Standard IO facilities 181 lt stdlib h gt General utilities 201 lt string h gt Strings 213 lt avr boot h gt Bootloader Support Utilities 227 lt avr cpufunc h gt Special AVR CPU functions 234 lt avr eeprom h gt EEPROM handling 234 lt avr fuse h gt Fuse Support 239 lt avr interrupt h gt Interrupts 242 lt avr io h gt AVR device specific IO definitions 266 lt avr lock h gt Lockbit Support 267 lt avr pgmspace h gt Program Space Utilities 269 lt avr power h gt Power Reduction Management 291 lt avr sfr_defs h gt Special function registers 295 Additional notes from lt avr sfr_defs h gt 293 lt avr signature h gt Signature Support 297 lt avr sleep h gt Power Management and Sleep Modes 298 lt avr version h gt avr libc version macros 300 lt avr wdt h gt Watchdog timer handling 302 util atomic h gt Atomically and Non Atomically Executed Code Blocks 306 lt util
19. P const prog char define PGM VOID P const prog void x Typedefs typedef void PROGMEM prog void typedef char PROGMEM prog char typedef unsigned char PROGMEM prog uchar typedef int8 t PROGMEM prog int8 t typedef uint8 t PROGMEM prog uint8 t typedef int16 t PROGMEM prog int16 t typedef uint16 t PROGMEM prog uintl6 t typedef int32 t PROGMEM prog int32 t typedef uint32 t PROGMEM prog uint32 t typedef int 4 t PROGMEM prog int64 t typedef uint64_t PROGMEM prog uint64 t Functions char strtok P char s PGM P delim PGM VOID P memchr_P PGM VOID B int __ val size_t len int memcmp const void x PGM VOID size t ATTR_PURE int memcmp_PF const void farptr t size_t _ ATTR_PURE void memcpy P void PGM VOID size_t void memcpy PF void dest farptr t src size t len PGM VOID P memrchr P PGM VOID B int __ val size_t int strcasecmp P const char PGM ATTR PURE int strcasecmp PF const char 51 farptr 1582 PURE char strcat P char PGM P char strcat PF char dest farptr t src P strchr P PGM_P int __ val PGM P strchrnul_P PGM_P int __val int stremp_P const char x PGM_P __ATTR_PURE int stremp_PF const char 51 uint_farptr_t s2 _ ATTR_PURE Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 49 lt avr pgmspace h gt Program Space Utilities 272
20. include avr wdt h This header file declares the interface to some inline macros handling the watchdog timer present in many AVR devices In order to prevent the watchdog timer configura tion from being accidentally altered by a crashing application a special timed sequence is required in order to change it The macros within this header file handle the required sequence automatically before changing any value Interrupts will be disabled during the manipulation Note Depending on the fuse configuration of the particular device further restrictions might apply in particular it might be disallowed to turn off the watchdog timer Note that for newer devices ATmega88 and newer effectively any AVR that has the op tion to also generate interrupts the watchdog timer remains active even after a system reset except a power on condition using the fastest prescaler value approximately 15 ms It is therefore required to turn off the watchdog early during program startup the datasheet recommends a sequence like the following include lt stdint h gt include lt avr wdt h gt uint8 t mcusr mirror attribute section noinit Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 06 lt avr wdt h gt Watchdog timer handling 304 void get mcusr void attribute naked attribute section init3 void get mcusr void mcusr_mirror MCUSR MCUSR 0 wdt_disable
21. random 1 strtod strtol strtoul Uses the global variable errno toreturn success failure Ignore errno or protect calls with cli sei or ATOMIC BLOCK if the application can tolerate it Or use sccanf or sccanf P if allocate and free memory possible malloc realloc Uses the stack pointer Protect calls with calloc free and global variables to cli sei or ATOMIC BLOCKY if the application can tolerate it If using an OS use the OS provided memory allocator since the OS is likely modifying the stack pointer anyway fdevopen fclose Uses calloc and free Protect calls with cli sei or ATOMIC BLOCK if the application can tolerate it Or use setup stream or FDEV SETUP 5 Note fclose will only call free if the stream has been opened with fdevopen eeprom boot_ Accesses I O registers Protect calls with cliQ seiQ ATOMIC or use OS locking far Accesses I O register RAMPZ Starting with GCC 4 3 RAMPZ is automatically saved for ISRs so nothing further is needed if only using interrupts Some OSes may automatically preserve RAMPZ during context switching Check the OS Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen documentation before assuming it does Otherwise protect calls with cli sei ATOMIC BLOCKY or use explicit OS
22. so cgo SG ao ERR 407 24 60 1 Detailed Description 410 24 61stri at 5 File Reference 2 2 2 2 2 2222 410 24 61 1 Detailed Description 410 24 62stricat_P S File 410 262 1 Detailed Description lt e lt s sss scr REG 410 24653stlcpy s File Reference 2l cuo 410 263 1 Detailed Description sce o Rye RR 410 2 amp 648lcpy P S Pile Reference 2 coc RR rer ERG 410 2464 1 Detailed Description sso REG 410 24 65sten s File Reference 22 2 2 22 410 24 65 1 Detailed Desceripti D sos RR RR 410 24 66strlen_PS Fil Reference 22222 ox 4 410 24 06 1 Detailed Description 2 2 2222 5 410 24 67s wrS File Reference 2 2 410 2467 1 Detailed Description s sem 410 24 68stmcasecmp 5 File Reference 2o oz o o o x 410 24 68 Detailed Description gt eee Rr xS 410 24 09 strn ase mp_P5 File Reference 222 2 410 2469 1 Detailed Description 2 22222222 2 222 2 410 24 Ustracata File Reference lt 2 oom o go Re eS X REOR Ros 410 24 70 1 Detailed Description 410 24 11strncat_P S File Reference 410 24 71 1 Detailed Description RS 410 24 72strnemp S File Reference oso mm 410 24 72 1 Detailed Description cus sco RR RR 410 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen CON
23. uint32_t addr uint8_t __result asm N N ln cbmpsreg o 2 out 4 amp 2 SOLT TYNNE N movw r30 1 n t N elpm 0 Z n t N out 2 _ tmp reg N r result N Woo sxddr32 N I SFR IO ADDR RAMPZ N result N 24 35 2 11 define LPM classic addr Value extension N uintl6 t addrl6 uintl6 t addr uint8 t _ result N asm N N Lom n t N mov 0 r0 n t N r result N z qo addrl6 N By N result N 24 35 2 12 define LPM dword classic addr Value Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Reference 394 extension X uintl6 t addrl6 uint16_t addr N uint32 t _ result N asm N N lpm Ant x mov 0 ro TANNET adiw r30 1 NANET lpm N mov B0 ro adiw r30 1 n t lpm NpNE N mov 0 ro nie adiw r30 1 NANET lpm AnNE mov DO ro n t r result z addrl16 1 addrl6 N Pro M result X 24 35 2 13 define LPM dword enhanced addr Value extension N uintl6 t _ addrl6 uintl16 t addr N uint32 t _ result N asm N N lpm SAO Z lpm BO Z ANNE lpm 0 Z4 N lpm D0 2 n t r result z __addr16 I __addr16 result X 24 35 2 14 de
24. 13 2 1 Machine specific assembler options 13 2 2 Examples for assembler options passed through the C compiler 13 3 Controlling the lmkeravt ld o o coc reos 13 5 1 Selected linker aptions s sr cs ae or gg 13 3 2 Passing linker options from the C compiler 14 Using the avrdude program 15 Release Numbering and Methodology 15 1 Release Version Numbering Scheme 15 2 Releasing AVR 2 2 2 2 2222222 15 2 1 Creating an SVN branch oe cecce eae ee m REG 15 52 Malungarelease lt a RR GR ERREUR 16 Acknowledgments 17 Todo List 18 Deprecated List 19 Module Index 19 1 Modules oo ow a EUR A 20 Data Structure Index 20 1 Data SIMI tureg 2229 Ro Roy vo RR RR x GUERRE 21 File Index MISLE kad aa do BA SESS 22 Module Documentation 22 1 lt alloca h gt Allocate space inthe stack 22 1 1 Function Documentation 22 2 Assert Wot Diagnostics 2 22 a GE RS ee Ree 22 41 soo e 990909 3x 5 222 2 Defne Documentation slc oo RR RE 22 35 opel Character Operating lt c c ce m oro e RR 2231 Detailed Description gt lt ea cts os 42224225259 22 3 0 Function Documentation 105 105 105 113 115 115 117 117 117 118 120 122 122 122 122 123 125 126 126 127 127 129 129 129 129 Generated on Thu May 19 2011
25. 211 File List 132 memchr S 384 memchr P S 384 memcmp S 384 memcmp P S 384 memcmp PES 384 memcpy S 384 memcpy P S 384 memmem S 384 memmove S 384 memrchr S 384 memrchr_P S 384 memset S 384 parity h 384 pgmspace h 385 portpins h power h 396 project h setbaud h 396 setjmp h 397 sfr defs h signal h signature h 397 sleep h 397 stdint h 397 stdio h 401 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 211 File List 133 stdio private h 2 stdlib h 402 stdlib private h strcasecmp S 406 strcasecmp P S 406 strcasestr S 406 strcat S 406 strcat P S 406 strchr S 406 strchr P S 406 strchrnul S 406 strchrnul P S 406 stremp S 406 stremp_P S 406 strcpy S 406 strepy_P S 406 strcspn S 406 strcspn P S 406 strdup c 406 string h 407 strlcat S 410 strlcat P S 410 strlcpy S 410 stricpy_P S 410 strlen S 410 Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 211 File List 134 strlen P S 410 strlwr S 410 strncasecmp S 410 strncasecmp P S 410 strncat S 410 strncat P S 410 strncmp S 410 strncmp_P S 410 strncpy S 410 strncpy P S 410 strnlen S 410 strnlen P S 410 strpbrk S 410 strpbrk P S 410 strrchr S 410 strrchr P S 410 strrev S 410 strsep S 410 strsep P S 410 strspn S 410 strspn P S 410 strstr S 410 strstr P S 410 strtok c 410 strtok P c 411 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 Module Documentation 135 strtok r S 411
26. 24 38 setjmp h File Reference 398 24 37 1 Detailed Description 24 38 setjmp h File Reference Defines define ATTR_NORETURN__ __attribute__ __noreturn__ Functions int setimp buf __jmpb void longjmp jmp_buf __jmpb int ret ATTR NORETURN 24 38 1 Detailed Description 24 39 Ssignature h File Reference 24 39 1 Detailed Description 24 40 sleep h File Reference Defines define SLEEP CONTROL REG MCUCR define SLEEP ENABLE MASK BV SE Functions void sleep enable void void sleep disable void void sleep cpu void void sleep mode void void sleep bod disable void 24 40 1 Detailed Description 24 41 stdint h File Reference Defines define USING 8 0 define CONCATenate left right left right Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 41 stdint h File Reference 399 define___CONCATileft right _ CONCATenate left right Limits of specified width integer types C implementations should define these macros only when _ STDC LIMIT MACROS is defined before lt stdint h gt is included define INT8 MAX Ox7f define INT8 MIN 8 MAX 1 define UINTS MAX CONCAT INT8 MAX U 2U 1U define INTI6 MAX 0 7 define INTI6 MIN INT16 MAX 1 define UINTIG6 MAX CONCAT INT16 MAX U 2U 10 define INT32_ MAX Ox 7fffffffL define INT32 MIN CINT32 MAX IL define 2 MAX CONCAT
27. 320 avr watchdog 304 TW SR STOP 320 WDTO 250MS TW ST LOST SLA ACK 320 avr watchdog 304 ST DATA 320 WDTO 25 TW ST 320 avr watchdog 304 TW ST LAST DATA 320 WDTO 30MS TW ST SLA 320 avr watchdog 305 TW START 321 WDTO 4S TW STATUS 321 avr watchdog 305 TW STATUS MASK 321 WDTO 500MS TW WRITE 321 avr watchdog 305 utoa WDTO_60MS avr_stdlib 212 avr_watchdog 305 WDTO_8S vfprintf avr watchdog 305 avr stdio 194 vfprintf P avr stdio 197 vfscanf avr stdio 197 vfscanf P avr stdio 199 vprintf avr stdio 200 vscanf avr stdio 200 vsnprintf avr stdio 200 vsnprintf P avr stdio 200 vsprintf avr stdio 200 vsprintf P avr stdio 200 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen
28. AT90USB647 AT90USB646 TIMERI CMPA vect SIG OUTPUT COMPAREIA Timer Counter1 Compare Match 1 ATtiny26 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 256 TIMER 1_ CMPB vect SIG_ OUTPUT_ COMPAREIB Timer Counter1 Compare Match 1B ATtiny26 TIMERI COMPI vect SIG OUTPUT COMPAREIA Timer Counter1 Compare Match AT90S2313 TIMERI COMPA_vect SIG_ OUTPUT_ COMPAREIA Timer Counter1 Compare Match A AT9084414 419054434 9058515 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 ATtiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMERI COMPB vect SIG OUTPUT COMPAREIB Time
29. Checks for any printable character including space Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 3 lt ctype h gt Character Operations 139 22 3 2 10 intispunct int c Checks for any printable character which is not a space or an alphanumeric character 22 3 2 11 int isspace Checks for white space characters For the avr libc library these are space form feed f newline n carriage return r horizontal tab 72 and vertical tab v 22 3 2 12 int isupper int Checks for an uppercase letter 22 3 2 13 int isxdigit int Checks for a hexadecimal digits i e one of 0123456789abcdefABCDE F 22 3 2 14 int toascii int Converts c to a 7 bit unsigned char value that fits into the ASCII character set by clearing the high order bits Warning Many people will be unhappy if you use this function This function will convert accented letters into random characters 22 3 2 15 inttolower int Converts the letter c to lower case if possible 22 3 2 16 inttoupper int Converts the letter c to upper case if possible Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 4 lt errno h gt System Errors 140 224 lt errno h gt System Errors Defines define EDOM 33 define ERANGE 34 22 41 Detailed Description include lt errno h gt Some functions in the library set the global variabl
30. Returns The rounded long integer value If __x is not a finite number or an overflow was this realization returns the LONG MIN value 0x80000000 22 6 3 27 long lround double x The Iround function rounds x to the nearest integer but rounds halfway cases away from zero instead of to the nearest even integer This function is similar to round function but it differs in type of return value and in that an overflow is possible Returns The rounded long integer value If __x is not a finite number or an overflow was this realization returns the LONG MIN value 0x80000000 22 6 3 28 double modf double x double x iptr The modf function breaks the argument x into integral and fractional parts each of which has the same sign as the argument It stores the integral part as a double in the object pointed to by __iptr The modf function returns the signed fractional part of x Note This implementation skips writing by zero pointer However the GCC 4 3 can replace this function with inline code that does not permit to use NULL address for the avoiding of storing Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 166 22 6 3 29 float modff float float iptr The alias for modf 22 6 3 30 double pow double double y The function pow returns the value of __x to the exponent y 22 6 3 31 double round double The rou
31. String 2 String 3 String 4 String 5 and then you add your PROGMEM macro to end of the declaration char xstring table PROGMEM String 1 Strimq 2 String 3 String 4 String 5 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 5 4 Storing and Retrieving Strings in the Program Space 31 Right WRONG Unfortunately with GCC attributes they affect only the declaration that they are at tached to So in this case we successfully put the string table variable the array itself in the Program Space This DOES NOT put the actual strings themselves into Program Space At this point the strings are still in the Data Space which is probably not what you want In order to put the strings in Program Space you have to have explicit declarations for each string and put each string in Program Space char string 1 PROGMEM String 1 char string 2 PROGMEM String 2 char string 3 PROGMEM String 3 char string 4 PROGMEM String 4 char string 5 PROGMEM String 5 Then use the new symbols in your table like so PGM P string table PROGMEM string 1 string 2 string 3 string 4 string 5 Now this has the effect of putting string 1 in Program Space where string table is an array of pointers to characters strings where each pointer is a pointer to the Program Space where each string is also stored The PGM P type above
32. The strncasecmp_PF function is similar to strcasecmp_PF except it only compares the first n characters of s and the string in flash is addressed using a far pointer Parameters 51 A pointer to a string in SRAM 52 A far pointer to a string in Flash n The maximum number of bytes to compare Returns The strncasecmp_PF function returns an integer less than equal to or greater than zero if s or the first n bytes thereof is found respectively to be less than to match or be greater than s2 The contents of RAMPZ SFR are undefined when the function returns 22 19 4 29 char x strncat char x dest P src size tlen Concatenate two strings The strncat_P function is similar to strncat except that the src string must be located in program space flash Returns The strncat_P function returns a pointer to the resulting string dest 22 19 4 30 char x strncat PF char dst uint_farptr_t src size Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 49 lt avr pgmspace h gt Program Space Utilities 287 Concatenate two strings The strncat PF function is similar to strncat except that the src string must be located in program space flash and is addressed using a far pointer Parameters dst A pointer to the destination string in SRAM src far pointer to the source string in Flash n The maximum number of byte
33. define boot page fill address data boot page fill normal address data define boot page erase address boot page erase normal address define boot page write address boot page write normal address define boot rww boot rww enable define boot lock bits set lock bits boot lock bits set lock bits define boot page fill safe address data define boot page erase safe address define boot page write safe address define boot rww enable safe define boot lock bits set safe lock bits 22 12 1 Detailed Description include lt avr io h gt include lt avr boot h gt The macros in this module provide a C language interface to the bootloader support functionality of certain AVR processors These macros are designed to work with all sizes of flash memory Global interrupts are not automatically disabled for these macros It is left up to the programmer to do this See the code example below Also see the processor datasheet for caveats on having global interrupts enabled during writing of the Flash Note Not all AVR processors provide bootloader support See your processor datasheet to see if it provides bootloader support Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 12 avr boot h Bootloader Support Utilities 229 Todo From email with Marek On smaller devices all except ATmega64 128 SPM REG is in the I O space accessible with
34. define stdout __iob 1 define stderr __iob 2 define EOF 1 define fdev_set_udata stream u do stream gt udata u while 0 define fdev get udata stream stream gt udata define fdev setup stream stream put get rwflag define FDEV SETUP READ SRD define FDEV SETUP WRITE SWR define FDEV SETUP RW SRD SWR define FDEV ERR 1 define FDEV EOF 2 define FDEV SETUP STREAM put get rwflag define fdev_close define putc __c stream fputc stream define putchar __c fputc c stdout define getc __stream fgetc __stream define getchar fgetc stdin define SEEK_SET 0 define SEEK CUR 1 define SEEK 2 Functions int fclose FILE stream int vfprintf FILE stream const char fmt va_list int vfprintf P FILE stream const char fmt va list ap intfputc int __c FILE stream int printf const char int printf P const char fmt int vprintf const char fmt va list ap int sprintf char s constchar fmt int sprintf_P char __s const char x__fmt int snprintf char __s size_t __n const char __fmt Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 24 43 stdlib h File Reference 403 24 42 1 24 43 intsnprintf P char s size t n constchar fmt int vsprintf char __s const char __fmt va list ap int vsprintf P char 5 const char fmt va_list a
35. e m include macro expansions n omit forms processing s include symbols file set the name of the listing file The various sub options be combined into a single a option list file must be the last one in that case Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 3 Controlling the linker avr ld 118 13 2 2 Examples for assembler options passed through the C compiler Remember that assembler options can be passed from the C compiler frontend using Wa see above so in order to include the C source code into the assembler listing in file foo 1st when compiling foo the following compiler command line can be used c foo c o foo o Wa ahls foo lst In order to pass an assembler file through the C preprocessor first and have the assem bler generate line number debugging information for it the following command can be used avr gcc c x assembler with cpp o foo o foo S Wa gstabs Note that on Unix systems that have case distinguishing file systems specifying a file name with the suffix S upper case letter S will make the compiler automatically assume x assembler with cpp while using s would pass the file directly to the assembler no preprocessing done 13 3 Controlling the linker avr Id 13 3 1 Selected linker options While there are no machine specific options for avr ld a number of the standard op tions might be of interest to AVR users
36. except that src is a pointer to a string in program space Returns The strnlen_P function returns strlen_P src if that is less than len or len if there is no 0 character among the first 1 characters pointed to by src 22 19 4 36 size_t strnlen_PF uint farptr ts size t len Determine the length of a fixed size string The strnlen_PF function is similar to strnlen except that s is a far pointer to a string in program space Parameters s A far pointer to the string in Flash len The maximum number of length to return Returns The strnlen PF function returns strlen P s if that is less than len or len if there is no 0 character among the first len characters pointed to by s The contents of RAMPZ SFR are undefined when the function returns 22 19 4 37 char x strpbrk P const char s P accept The strpbrk function locates the first occurrence in the string s of any of the characters in the flash string accept This function is similar to strpbrk except that accept is a pointer to a string in program space Returns The strpbrk_P function returns a pointer to the character in s that matches one of the characters in accept or NULL if no such character is found The terminating Zero is not considered as a part of string if one or both args are empty the result will NULL 22 19 4 38 P strrchr P P s int val Generated on Thu May 19 20
37. sprintf P avr stdio 193 sqrt avr math 165 sqrtf avr math 160 square avr math 165 squaref avr math 160 srand avr stdlib 209 srandom avr stdlib 209 sscanf avr stdio 193 sscanf P avr stdio 194 stderr avr stdio 188 stdin avr stdio 188 stdint h 397 stdio h 401 stdlib h 402 stdout avr stdio 189 strcasecmp avr string 217 strcasecmp S 406 strcasecmp P avr pgmspace 278 strcasecmp_P S 406 strcasecmp avr pgmspace 279 strcasestr avr string 218 strcasestr S 406 P avr pgmspace 279 strcat avr string 218 strcat S 406 strcat P avr pgmspace 279 strcat_P S 406 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 435 strcat PF strlcat PF avr pgmspace 280 avr pgmspace 282 strchr strlcpy avr string 218 strchr S 406 strchr P avr pgmspace 280 strchr P S 406 strchrnul avr string 219 strchrnul S 406 strchrnul P avr pgmspace 280 strchrnul P S 406 strcmp avr string 219 strcmp S 406 strcmp P avr pgmspace 281 strcmp 5 406 strcmp PF avr pgmspace 281 strcpy avr string 219 strcpy S 406 strcpy P avr pgmspace 281 strepy_P S 406 strcpy PF avr pgmspace 281 strcspn avr string 220 strcspn S 406 strcspn P avr pgmspace 282 strcspn P S 406 strdup avr string 220 strdup c 406 string h 407 strlcat avr string 220 strlcat S 410 strlcat P avr pgmspace 282 strlcat P S 410 avr str
38. strchr const char int PURE char strchrnul const char x int ATTR_PURE int strcmp const char const char x __ATTR_PURE char strcpy char const char int strcasecmp const char const char x ATTR_PURE char strcasestr const char const char x ATTR PURE size tstrcspn const char s const char reject ATTR_PURE char strdup const char 51 size_t strlcat char const char size_t size t strlcpy char const char size t size t strlen const char x ATTR PURE char strlwr char char strncat char const char size_t int strncmp const char const char size_t _ ATTR PURE char strncpy char const char size_t int strncasecmp const char const char size t ATTR PURE size t strnlen const char size_t ATTR_PURE char strpbrk const char 5 const char accept ATTR_PURE Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 60 string h File Reference 409 char strrchr const char int PURE char strrev char x char strsep char const char size_t strspn const char __s const char __accept _ ATTR PURE char strstr const char const char x ATTR PURE char strtok char const char char strtok_r char const char char char strupr char Genera
39. 1 2345 494 492 tan 1 2345 4381 2426 tanh 1 2345 5126 3173 trunc 1 2345 178 178 10 Porting From IAR to AVR GCC 10 1 Introduction C language was designed to be a portable language There two main types of port ing activities porting an application to a different platform OS and or processor Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 10 2 Registers 58 and porting to a different compiler Porting to a different compiler can be exacerbated when the application is an embedded system For example the C language Standard strangely does not specify a standard for declaring and defining Interrupt Service Rou tines ISRs Different compilers have different ways of defining registers some of which use non standard language constructs This chapter describes some methods and pointers on porting an AVR application built with the IAR compiler to the GNU toolchain AVR GCC Note that this may not be an exhaustive list 10 2 Registers IO header files contain identifiers for all the register names and bit names for a par ticular processor IAR has individual header files for each processor and they must be included when registers are being used in the code For example include lt iom169 h gt Note IAR does not always use the same register names or bit names that are used in the AVR datasheet AVR GCC also has individual IO header files for each processor However the ac tual
40. 22 6 3 16 double fmin double x double y The fmin function returns the lesser of the two values __x and __y If an argument is NaN the other argument is returned If both arguments are NaN NaN is returned 22 6 3 17 double fmod double double The function fmod returns the floating point remainder of x y 22 6 3 18 double frexp double x int x pexp The frexp function breaks a floating point number into a normalized fraction and an integral power of 2 It stores the integer in the int object pointed to by pexp If ___xis anormal float point number the frexp function returns the value v such that v has a magnitude in the interval 1 2 1 or zero and __x equals v times 2 raised to the power pexp If __x is zero both parts of the result are zero If __x is not a finite number the frexp returns __x as is and stores 0 by pexp Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 164 Note This implementation permits a zero pointer as a directive to skip a storing the exponent 22 6 3 19 double hypot double x double y The hypot function returns sqrt __x __x __y __y This is the length of the hypotenuse of a right triangle with sides of length __x and __y or the distance of the point x y from the origin Using this function instead of the direct formula is wise since the error is much smaller No underflow with small __x an
41. 233 GET LOW FUSE BITS 233 avr cpufunc _MemoryBarrier 234 234 avr eeprom _EEGET 236 _EEPUT 236 EEGET 236 EEPUT 236 EEMEM 236 eeprom busy wait 237 eeprom is ready 237 eeprom read block 237 eeprom read byte 237 eeprom read dword 237 eeprom read float 237 eeprom read word 237 eeprom update block 237 eeprom update byte 238 eeprom update dword 238 eeprom update float 238 eeprom update word 238 eeprom write block 238 eeprom write byte 238 eeprom write dword 238 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 418 eeprom write float 238 eeprom write word 239 avr errno EDOM 139 ERANGE 139 avr interrupts BADISR_vect 262 cli 262 EMPTY INTERRUPT 262 ISR 262 5 ALIAS 263 5 ALIASOF 263 5 BLOCK 264 ISR NAKED 264 ISR_NOBLOCK 264 reti 265 sei 265 SIGNAL 265 avr inttypes int farptr t 152 PRId16 142 PRId32 142 PRId8 142 PRIdFAST 16 143 PRIdFAST32 143 PRIdFASTS 143 PRIdLEAST16 143 PRIdLEAST32 143 PRIdLEASTS 143 PRIdPTR 143 PRIi16 143 PRIi32 143 PRII8 143 PRIiFASTI6 144 PRIiFAST32 144 PRIiFASTS 144 PRIiLEAST16 144 PRIiLEAST32 144 PRIiLEASTS 144 PRIiPTR 144 PRIo16 144 PRIo32 144 PRIo8 144 PRIoFAST 16 145 PRIoFAST32 145 PRIoFASTS 145 PRIoLEASTI6 145 PRIoLEAST32 145 PRIoLEASTS 145 PRIoPTR 145 PRIu16 145 PRIu32 145 8 145 PRIuFASTI6 146 PRIuFAST32 146 PRIuFASTS 146 PRIu
42. 2824 2918 2808 1 2345 Stack bytes 63 63 amp x MCU clocks 2187 1833 strtod 1 2345 Flash bytes 1570 1458 1472 1362 1456 1346 amp p Stack bytes 22 22 MCU clocks 1237 971 strtol 12345 Flash bytes 942 830 874 764 808 698 amp p 0 Stack bytes 29 21 MCU clocks 1074 722 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 9 2 Math functions 57 9 2 Math functions The table contains the number of MCU clocks to calculate a function with a given argument s The main reason of a big difference between Avr2 and Avr4 is a hardware multiplication Function Avr2 Avr4 addsf3 1 234 5 678 113 108 mulsf3 1 234 5 678 375 138 divsf3 1 234 5 678 466 465 acos 0 54321 4411 2455 asin 0 54321 4517 2556 atan 0 54321 4710 2271 atan2 1 234 5 678 52770 2857 cbrt 1 2345 2684 2555 ceil 1 2345 177 177 cos 1 2345 3387 1671 cosh 1 2345 4922 2979 exp 1 2345 4708 2765 fdim 5 678 1 234 111 111 floor 1 2345 180 180 fmax 1 234 5 678 39 37 fmin 1 234 5 678 35 35 fmod 5 678 1 234 131 131 frexp 1 2345 0 42 41 hypot 1 234 5 678 1341 866 Idexp 1 2345 6 42 42 log 1 2345 4142 2134 log10 1 2345 4498 2260 modf 1 2345 0 433 429 pow 1 234 5 678 9293 5047 round 1 2345 150 150 sin 1 2345 3353 1653 sinh 1 2345 4946 3003 sqrt
43. 302 lt util delay_basic h gt Basic busy wait de lay loops 313 util parity h gt Parity bit generation 314 lt util setbaud h gt Helper macros for baud rate calculations 314 lt util twi h gt TWI bit mask definitions 31 PATH 90 PREFIX 90 prefix 90 _BV avr_sfr 296 _EEGET avr_eeprom 236 _EEPUT avr_eeprom 236 _FDEV_EOF avr_stdio 186 _FDEV_ERR avr_stdio 186 _FDEV_SETUP_READ avr_stdio 186 _FDEV_SETUP_RW avr_stdio 186 _FDEV_SETUP_WRITE avr_stdio 186 compat deprecated h gt Deprecated items _FFS 321 avr_string 214 lt compat ina90 h gt Compatibility with IAR_MemoryBarrier EWB 3 x 325 lt ctype h gt Character Operations 136 lt errno h gt System Errors 139 lt inttypes h gt Integer Type conversions 139 lt math h gt Mathematics 152 lt setjmp h gt Non local goto 166 lt stdint h gt Standard Integer Types 168 lt stdio h gt Standard IO facilities 181 lt stdlib h gt General utilities 201 lt string h gt Strings 213 avr_cpufunc 234 _NOP avr_cpufunc 234 AVR_LIBC_DATE avr_version 301 AVR LIBC DATE STRING avr version 301 AVR LIBC MAJOR avr version 301 AVR MINOR avr version 301 lt util atomic h gt Atomically and Non AtomicalsVR REVISION Executed Code Blocks 306 lt util crc16 h gt CRC Computations 309 avr version 301 AVR VERSION STRING INDEX 416 avr version 301 AVR L
44. 309 22 28 1 Detailed Description gt 0 22055 2550 m RR kon 309 22 28 2 Function Documentation 6 55 sb ee t o 310 22 29 lt util delay_basic h gt Basic busy wait delay loops 313 22 041 Detained Descriplian lt s lt cc doe Rob RR ER 313 22 29 2 Function 313 22 30 util parity h Parity bit generation 314 22 30 1 Detailed D scriptiad oos a ai i es 314 22 30 2 Define Documentation s s s o s se nac pio mk 314 22 31 lt util setbaud h gt Helper macros for baud rate calculations 314 22 31 Detailed Description uz xao ee bee eens 315 22 31 72 Define Documentation o xy EET 316 22 32 util twi h TWI bit mask definitions 317 2237 1 Detailed Descripfion s suus Rr Ro x RE RR s 318 22 327 Define Documentation s gact e sacos d EL 8 318 22 33 lt compat deprecated h gt Deprecated items 321 22 33 1 Detailed D seriptiod lt gt 264 se REEL RS 322 22 33 2 Define DOCUMENIATION gt s so seca mrep ee ee a 323 22 33 3 Function Documentation 325 22 34 lt compat ina90 h gt Compatibility with IAR EWB 3 x 325 22 35Demo DPOJE IS e csore no Roe wae a Pee ee ee 325 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen CONTENTS vii 22 35 1 Detailed Description 2 2 2 2 2 2 22 36Combining and assembly source files 22261 Hardware
45. 54221 xNatailad Dacerintian 24 35 pgmspace h File Reference 386 24 34 1 Detailed Description 24 35 pgmspace h File Reference Defines define __need_size_t define _ATTR_PROGMEM ____attribute__ __progmem__ define _ ATTR_PURE attribute__ __pure__ define PROGMEM ATTR PROGMEM define PSTR s const PROGMEM char s define LPM classic define LPM enhanced define _ LPM word classic define _ LPM word enhanced addr define dword classic addr define _ _ dword enhanced define LPM float classic addr define LPM float enhanced addr LPM addr LPM classic addr define _ LPM_word addr word classic addr define LPM dword addr LPM dword classic addr define _ LPM_float addr float classic addr define read byte near address short LPM uint16 t address short define read word near address short LPM word uintl6 t address short define read dword near address short LPM_dword uint16_t address_ short e define read float near address short LPM float uintl6 t address short define _ ELPM classic addr define _ ELPM enhanced addr define _ ELPM xmega addr define _ ELPM word classic addr define _ ELPM word enhanced addr define _ ELPM word xmega addr define _ ELPM dword classic addr define ELPM
46. 94 installation binutils 92 installation gcc 93 Installation gdb 95 installation simulavr 95 6 C avr stdint 172 INTI6 MAX avr stdint 172 INT16 MIN avr stdint 172 int16 t avr stdint 178 INT32 C avr stdint 172 INT32 MAX avr stdint 172 32 MIN avr stdint 172 int32 t avr stdint 178 INT64 C avr stdint 172 INT64 MAX avr stdint 173 INT64 MIN avr stdint 173 int64 t avr stdint 178 INT8_C avr_stdint 173 INT8_MAX avr_stdint 173 INT8_MIN avr_stdint 173 int8_t avr_stdint 178 int_farptr_t avr_inttypes 152 INT_FAST16_MAX avr_stdint 173 INT_FAST16_MIN avr_stdint 173 int_fast16_t avr_stdint 178 INT_FAST32_MAX avr_stdint 173 INT_FAST32_MIN avr_stdint 173 int_fast32_t avr_stdint 178 INT_FAST64_MAX avr_stdint 173 INT_FAST64_MIN avr_stdint 174 int_fast64_t avr_stdint 178 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 428 INT FASTS MAX avr stdint 174 INT FAST8 MIN avr stdint 174 int fast8 t avr stdint 178 INT 5 6 avr stdint 174 INT LEAST16 MIN avr stdint 174 int least16 t avr stdint 179 INT LEAST32 MAX avr stdint 174 INT LEAST32 MIN avr stdint 174 int least32 t avr stdint 179 INT LEAST64 MAX avr stdint 174 INT LEAST64 MIN avr stdint 174 int least64 t avr stdint 179 INT LEAST8 MAX avr stdint 174 INT LEAST8 MIN avr stdint 175 int least8 t avr stdint 179
47. AVR GCC 3 3 knows the following constraint characters Note The most up to date and detailed information on contraints for the avr can be found in the gcc manual The x register is r27 r26 the y register is r29 r28 and the z register is r31 r30 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 3 Input and Output Operands 43 Constraint Used for Range a Simple upper registers r16 to r23 b Base pointer registers Z pairs d Upper register r16 to r31 e Pointer register pairs X y Z q Stack pointer register SPH SPL r Any register r0 to r31 t Temporary register r0 w Special upper register r24 r26 r28 r30 pairs X Pointer register pair X X 127 126 y Pointer register pair Y y 129 r28 7 Pointer register pair Z z 31 130 G Floating point constant 0 0 I 6 bit positive integer 0 to 63 constant J 6 bit negative integer 63 to 0 constant K Integer constant 2 L Integer constant 0 1 Lower registers r0 to r15 M 8 bit integer constant 0 to 255 N Integer constant 1 O Integer constant 8 16 24 P Integer constant 1 Q GCC gt 4 2 x A memory address based on Y or Z pointer with displacement R GCC gt 4 3 x Integer 6 to 5 constant The selection of the proper contraint depends on the range of the constants or registers which must be acceptable to the AVR instruction they are used with The C compiler doesn t chec
48. Build MPFR for MinGW Version 2 3 2 lt http www mpfr org gt Build script configure with gmp usr local 2 gt amp 1 tee mpfr configure log make 2 amp 1 tee mpfr make log make check 2 amp 1 tee mpfr make check log make install 2 gt amp 1 tee mpfr make install log MPFR headers will be installed under usr local include and library in stalled under usr local lib Install Doxygen Version 1 5 6 lt http www stack nl dimitri doxygen gt Download and install Install NetPBM Version 10 27 0 From the GNUWin32 project lt http gnuwin32 sourceforge net packages html gt Download and install Install fig2dev Version 3 2 Patchlevel 5 From WinFig 2 2 lt http www schmidt web berlin de winfig gt Unzip the download file and install fig2dev exe in a location of your choice Install MiKTeX Version 2 7 lt http miktex org gt Download and install Install Ghostscript Version 8 63 lt http www cs wisc edu ghost gt Download and install In the bin subdirectory of the installaion copy gswin32c exe to gs exe Set the TEMP and TMP environment variables to c temp or to the short file name version This helps to avoid NTVDM errors during building Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 13 Building the Toolchain for Windows 101 12 13 Building the Toolchain for Windows direc
49. FreeBSD and Others The default behaviour for most of these tools is to install every thing under the usr local directory In order to keep the AVR tools separate from the base system it is usually better to install everything into usr local avr If the usr local avr di rectory does not exist you should create it before trying to install anything You will need root access to install there If you don t have root access to the system you can alternatively install in your home directory for example in HOME local avr Where you install is a completely arbitrary decision but should be consistent for all the tools You specify the installation directory by using the prefix dir option with the configure script It is important to install all the AVR tools in the same directory or some of the tools will not work correctly To ensure consistency and simplify the discussion we will use PREF IX to refer to whatever directory you wish to install in You can set this as an environment variable if you wish as such using a Bourne like shell PREFIX HOME local avr export PREFIX Note Be sure that you have your PATH environment variable set to search the direc tory you install everything in before you start installing anything For example if you use prefix S PREFIX you must have PREFIX bin in your exported PATH As such PATH PATH PREFIX bin export PATH Warning If you have CC set to anything other tha
50. Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 27 lt util atomic h gt Atomically and Non Atomically Executed Code 807 22 27 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks Defines e define ATOMIC BLOCK type e define NONATOMIC_BLOCK type define ATOMIC_RESTORESTATE define ATOMIC FORCEON define NONATOMIC RESTORESTATE define NONATOMIC FORCEOFF 22 27 1 Detailed Description include lt util atomic h gt Note The macros in this header file require the ISO IEC 9899 1999 ISO C99 feature of for loop variables that are declared inside the for loop itself For that reason this header file can only be used if the standard level of the compiler option std is set to either c99 or gnu99 The macros in this header file deal with code blocks that are guaranteed to be excuted Atomically or Non Atmomically The term Atomic in this context refers to the un ability of the respective code to be interrupted These macros operate via automatic manipulation of the Global Interrupt Status I bit of the SREG register Exit paths from both block types are all managed automatically without the need for special considerations i e the interrupt status will be restored to the same value it has been when entering the respective block A typical example that requires atomic access is a 16 or more bit variable that is shared between the main execution path and an ISR Wh
51. IO registers where the order of write access is critical like some timer registers All versions of avr gcc up to 3 3 will generate instructions that use the wrong access order in this situation since with normal memory operands where the order doesn t matter this sometimes yields shorter code See http mail nongnu org archive html avr libc dev 2003 01 msg00044 html for a possible workaround avr gcc versions after 3 3 have been fixed in a way where this optimization will be disabled if the respective pointer variable is declared to be volatile so the correct behaviour for 16 bit IO ports can be forced that way Back to FAQ Index 11 14 What registers are used by the C compiler Data types char is 8 bits int is 16 bits long is 32 bits Long long is 64 bits float and double are 32 bits this is the only supported floating point format pointers are 16 bits function pointers are word addresses to allow addressing up to 128K program memory space There is a mint8 option see Options for the C compiler avr gcc to make int 8 bits but that is not supported by avr libc and violates C standards int must be at least 16 bits It may be removed in a future release Call used registers r18 r27 r30 r31 May be allocated by gcc for local data You may use them freely in assembler subroutines Calling C subroutines can clobber any of them the caller is re sponsible for saving and restoring Call saved registers r2 r1
52. Lockbit API Each I O header file may define up to 3 macros that controls what kinds of lockbits are available to the user If LOCK BITS EXIST is defined then two lock bits are available to the user and 3 mode settings are defined for these two bits If BOOT LOCK BITS 0 EXIST is defined then the two BLBO lock bits are avail able to the user and 4 mode settings are defined for these two bits If BOOT LOCK BITS 1 EXIST is defined then the two BLB1 lock bits are avail able to the user and 4 mode settings are defined for these two bits If BOOT LOCK APPLICATION TABLE BITS EXIST is defined then two lock bits are available to set the locking mode for the Application Table Section which is used in the XMEGA family If BOOT LOCK APPLICATION BITS EXIST is defined then two lock bits are available to set the locking mode for the Application Section which is used in the XMEGA family If BOOT LOCK BOOT BITS EXIST is defined then two lock bits are available to set the locking mode for the Boot Loader Section which is used in the XMEGA family The AVR lockbit modes have inverted values logical 1 for an unprogrammed dis abled bit and logical 0 for a programmed enabled bit The defined macros for each individual lock bit represent this in their definition by a bit wise inversion of a mask For example the LB MODE 3 macro is defined as define LB MODE 3 OxFC Generated on Thu May 19 2011 13 29 12 for avr libc
53. Note The address is a byte address The address is in the program space 22 19 2 5 define read dword address short pgm read dword near address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 22 19 2 6 define read dword far address long ELPM dword uint32 t address long Read a double word from the program space with a 32 bit far address Note The address is a byte address The address is in the program space 22 19 2 7 define read dword near address short LPM dword uint16 t address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 22 19 2 8 read float address short pgm read float near address short Read a float from the program space with a 16 bit near address Note The address is a byte address The address is in the program space Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 avr pgmspace h gt Program Space Utilities 275 22 19 2 9 define pgm read float far address long ELPM float uint32 t address long Read a float from the program space with a 32 bit far address Note The address is a byte address The address is in the program space 22 19 2 10 define read float near address sh
54. Note The bit shift is performed by the compiler which then inserts the result into the code Thus there is no run time overhead when using BV 22 22 2 2 define bit is clear sfr bit SFR BYTE sfr amp BV bit include lt avr io h gt Test whether bit bit in IO register s r is clear This will return non zero if the bit is clear and a 0 if the bit is set 22 22 2 3 define bit is set sfr bit SFR BYTE sfr amp BV bit include lt avr io h gt Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 23 lt avr signature h gt Signature Support 298 Test whether bit bit in IO register sfr is set This will return a O if the bit is clear and non zero if the bit is set 22 22 2 4 define loop until bit is clear sfr bit do while bit is set sfr bit include lt avr io h gt Wait until bit bit in IO register s fr is clear 22 22 2 5 until bit is set sfr bit do while bit is clear sfr bit include lt avr io h gt Wait until bit bit in IO register s fr is set 22 23 lt avr signature h gt Signature Support Introduction The lt avr signature h gt header file allows the user to automatically and easily include the device s signature data in a special section of the final linked ELF file This value can then be used by programming software to compare the on device signa ture with the signature recorded in the ELF file to look for a matc
55. PRIXLEAST32 avr inttypes 148 PRIxLEAST32 avr inttypes 148 PRIXLEASTS8 avr inttypes 148 PRIxLEASTS avr inttypes 148 PRIXPTR avr inttypes 148 PRIxPTR avr inttypes 148 prog char avr pgmspace 275 avr pgmspace 275 prog int64 t avr pgmspace 275 prog int8 t avr pgmspace 275 prog uchar avr pgmspace 275 prog uint16 t avr pgmspace 276 prog uint32 t avr pgmspace 276 prog uint64 t avr pgmspace 276 prog uint8 t avr pgmspace 276 prog void avr pgmspace 276 PROGMEM avr pgmspace 275 PSTR avr pgmspace 275 PTRDIFF MAX avr stdint 175 PTRDIFF MIN avr stdint 175 putc avr stdio 188 putchar avr stdio 188 puts avr stdio 193 puts P avr stdio 193 qsort avr stdlib 208 quot div t 366 ldiv t 367 rand avr stdlib 208 RAND MAX Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 433 avr stdlib 203 rand r avr stdlib 208 random avr stdlib 208 RANDOM MAX avr stdlib 203 random r avr stdlib 209 realloc avr stdlib 209 rem div t 366 ldiv t 367 reti avr interrupts 265 round avr math 165 roundf avr math 159 sbi deprecated items 324 scanf avr stdio 193 scanf P avr stdio 193 SCNd16 avr_inttypes 148 SCNd32 avr_inttypes 148 SCNdFAST16 avr_inttypes 148 SCNdFAST32 avr_inttypes 149 SCNdLEAST16 avr_inttypes 149 SCNdLEAST32 avr_inttypes 149 SCNdPTR avr_inttypes 149 SCNi16 avr_inttype
56. Program Space Utilities 269 2219 1 Detailed Description 22222222255 RR mE FG 271 22 197 Define Documentation lt e sa i204 oro RR eee ees 272 22 193 Typedet Documentation sus oro RR Ros 275 22 19 4 Function Documentation 216 22 20 avr power h Power Reduction Management 291 22 21 Additional notes from lt avr sfr_defs h gt 293 22 22 lt avr sfr_defs h gt Special function 295 22 22 1 Detaled Description a o a 295 22 22 2 Define DOCUMENIATION s so s ceca m rar rewera 296 22 23 lt avr signature h gt Signature Support 297 22 24 lt avr sleep h gt Power Management and Sleep Modes 298 22 241 Detailed DescripHan lt ec e esk oy Rex 298 22 24 2 Function 300 22 25 lt avr version h gt avr libc version macros 300 22 25 1 Detailed Description muc ERAS s 300 22 25 2 Define Documentation lt s eos e s uoo Ros 301 22 26 lt avr wdt h gt Watchdog timer handling 302 22 26 1 Detailed Descriptio 2222 2 222 302 22 262 Define Documentation 303 22 27 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks306 22 21 1 Detailed Description oos m c Rx 306 22 21 2 Define DOCUMENIATION 222 222 2 22 308 22 28 lt util crc16 h gt CRC Computations
57. The compiler could have selected any other register though It may not explicitely load or store the value and it may even decide not to include your assembler code at all All these decisions are part of the compiler s optimization strategy For example if you never use the variable value in the remaining part of the C program the compiler will most likely remove your code unless you switched off optimization To avoid this you can add the volatile attribute to the asm statement asm volatile in 0 1 r value I SFR IO ADDR PORTD Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 2 Assembler Code 41 Alternatively operands can be given names The name is prepended in brackets to the constraints in the operand list and references to the named operand use the bracketed name instead of a number after the sign Thus the above example could also be written as asm in retval port retval r value port I SFR IO ADDR PORTD The last part of the asm instruction the clobber list is mainly used to tell the compiler about modifications done by the assembler code This part may be omitted all other parts are required but may be left empty If your assembler routine won t use any input or output operand two colons must still follow the assembler code string A good example is a simple statement to disable interrupts asm volatile cli 7 2 Assembler Code You can use the
58. a8 81 60 ori r24 0x01 1 aa 8e bd out 0x2e r24 46 if defined TIMER1 SETUP HOOK TIMER1 SETUP HOOK Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 340 endif x Set PWM value to 0 OCR 0 ac 1b bc out 0x2b r1 43 ae 1 bc out 0x2a r1 42 Enable as output DDROC BV OCI b0 82 eO ldi r24 0x02 2 b2 87 bb out 0x17 r24 23 Enable timer 1 overflow interrupt TIMSK BV TOIE1 b4 84 eO ldi r24 0x04 4 b6 89 bf out 0x39 r24 57 sei b8 78 94 sei ioinit lt loop forever the interrupts are doing the rest x for zr Note T Sleep mode ba 85 b7 lin x24 0x35 j 53 bc 80 68 ori r24 0x80 128 be 85 bf out 0x35 r24 53 c0 88 95 sleep c2 85 b in tAds 0x35 3 53 c4 8f 77 andi r24 0x7F 127 c6 85 bf out 0x35 r24 53 COS EB OE rjmp 16 Oxba lt main 0x18 gt 22 37 5 Linker Map Files avr objdump is very useful but sometimes it s necessary to see information about the link that can only be generated by the linker A map file contains this information A map file is useful for monitoring the sizes of your code and data It also shows where modules are loaded and which modules were loaded from libraries It is yet another view of your application To get a map file I usually add W1 Map demo map to my link command Relink the application using the following
59. and will include the appropri ate options to locate additional libraries as well as the application start up code crtXXX o and linker script Note that the invokation of the C preprocessor will be automatic when the filename provided for the assembler file ends in S the capital letter s This would even apply to operating systems that use case insensitive filesystems since the actual decision is made based on the case of the filename suffix given on the command line not based on the actual filename from the file system Alternatively the language can explicitly be specified using the x assembler with cpp option Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 6 3 Example program 34 6 3 Example program The following annotated example features a simple 100 kHz square wave generator using an AT90S1200 clocked with a 10 7 MHz crystal Pin PD6 will be used for the square wave output include lt avr io h gt work 16 tmp 17 inttmp 29 intsav 0 SQUARE PD6 tmconst 10700000 200000 fuzz 8 section text Note 1 Note 2 Note 3 Note 4 100 kHz gt 200000 edges s clocks in ISR until TCNTO is set global main Note 5 main rcall ioinit ls rjmp 1b Note 6 global TIMERO OVF vect Note 7 TIMERO OVF vect ldi inttmp 256 tmconst fuzz out SFR IO ADDR TCNTO inttmp Note 8 in intsav SFR IO ADDR SREG Note 9
60. avr stdint 177 uintmax t avr stdint 181 UINTPTR MAX avr stdint 177 uintptr t avr stdint 181 ultoa avr stdlib 211 ungetc avr stdio 194 USE 2X util setbaud 316 Using the standard IO facilities 353 util atomic ATOMIC BLOCK 308 ATOMIC FORCEON 308 ATOMIC RESTORESTATE 308 NONATOMIC BLOCK 308 NONATOMIC FORCEOFF 309 NONATOMIC RESTORESTATE 309 util crc crc16 update 310 ccitt update 311 crc ibutton update 311 crc xmodem update 312 util delay basic delay loop 1 313 delay loop 2 313 util parity parity even bit 314 util setbaud BAUD TOL 316 UBRR VALUE 316 UBRRH VALUE 316 UBRRL VALUE 316 USE 2X 316 util twi TW BUS ERROR 318 TW LOST 318 MR DATA ACK 318 DATA NACK 318 TW MR SLA ACK 318 TW 5 318 TW MT ARB LOST 318 TW MT ACK 318 MT DATA NACK 319 TW MT SLA ACK 319 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 439 TW MT SLA NACK 319 TW NO INFO 319 wdt h 412 wdt disable TW READ 319 avr watchdog 303 TW REP START 319 enable TW SR ARB LOST GCALL ACK avr watchdog 303 319 wdt reset TW SR LOST SLA ACK 319 avr watchdog 304 TW SR DATA ACK 319 WDTO_120MS TW SR DATA NACK 319 avr watchdog 304 TW SR GCALL 320 WDTO 15 5 TW SR GCALL DATA ACK 320 avr watchdog 304 TW SR GCALL NACK 320 WDTO 1S TW SR SLA
61. better optimization First there s no universal definition for better with optimization often being a speed vs code size trade off See the detailed discus sion for which option affects which part of the code generation A test case was run on an ATmegal28 to judge the effect of compiling the library itself using different optimization levels The following table lists the results The test case consisted of around 2 KB of strings to sort Test 1 used qsort using the standard library strcmp test 2 used a function that sorted the strings by their size thus had two calls to strlen per invocation When comparing the resulting code size it should be noted that a floating point version of fvprintf was linked into the binary in order to print out the time elapsed which is entirely not affected by the different optimization levels and added about 2 5 KB to the code Optimization Size of text Time for test 1 Time for test 2 flags 03 6898 903 us 19 7 ms O2 6666 972 us 20 1 ms Os 6618 955 us 20 1 ms Os 6474 972 us 20 1 ms mcall prologues The difference between 955 us and 972 us was just a single timer tick so take this Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 18 How do I relocate code to a fixed address 78 with a grain of salt So generally it seems Os mcall prologues is the most universal best opti mization level Only applications that
62. const char 5 const char __accept PURE char strstr const char const char x ATTR PURE Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 215 char x strtok char const char char x strtok_r char const char char char strupr char 22 11 1 Detailed Description finclude string h The string functions perform string operations on NULL terminated strings Note If the strings you are working on resident in program space flash you will need to use the string functions described in lt avr pgmspace h gt Program Space Utilities 22 11 2 Define Documentation 22 11 2 1 define FFS x This macro finds the first least significant bit set in the input value This macro is very similar to the function ffs except that it evaluates its argument at compile time so it should only be applied to compile time constant expressions where it will reduce to a constant itself Application of this macro to expressions that are not constant at compile time is not recommended and might result in a huge amount of code generated Returns The _FFSQ macro returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 Only 16 bits of argument are evaluted 22 11 3 Function Documentation
63. disabling the Global Interrupt Status flag bit This saves on flash space as the previous value of the SREG register does not need to be saved at the start of the block Care should be taken that NONATOMIC FORCEOFF is only used when it is known that interrupts are disabled before the block s execution or when the side effects of disabling global interrupts at the block s completion are known and understood 22 27 2 6 define NONATOMIC RESTORESTATE This is a possible parameter for NONATOMIC BLOCK When used it will cause the NONATOMIC BLOCK to restore the previous state of the SREG register saved before the Global Interrupt Status flag bit was enabled The net effect of this is to make the NONATOMIC BLOCK s contents guaranteed non atomic without changing the state of the Global Interrupt Status flag when execution of the block completes 22 28 lt utillcrc16 h gt CRC Computations Functions static inline uint16 t crc16 update 16 t crc uint8 t data static inline uintl6 t crc xmodem update uint16 t crc uint8 t data static inline uint16 t crc ccitt update uint16 t crc uint8 t data static __inline__ uint8 t crc ibutton update uint8 t crc uint8 t data 22 28 1 Detailed Description include util crcl6 h This header file provides a optimized inline functions for calculating cyclic redundancy checks CRC using common polynomials References Generated on T
64. function to make sure that the function has succeeded in allocating the memory 22 11 3 21 size tstrlcat char dst const char src size t siz Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 222 Concatenate two strings Appends src to string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred Appends src to string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 22 11 3 22 size tstrlcpy char dst const char src size_t siz Copy a string Copy src to string dst of size siz At most siz 1 characters will be copied Always NULL terminates unless siz 0 Returns The strlcpy function returns strlen src If retval gt siz truncation occurred Copy src to string dst of size siz At most siz 1 characters will be copied Always NULL terminates unless siz 0 Returns The strlcpy function returns strlen src If retval gt siz truncation oc
65. lt s 604 s Rr REGE 410 24 86s spn P5 File Reference 2 o o 9 A EROS 410 256 1 Detailed Description 2 22222222 22 2 2 410 cision Pile Referente ois ox CBee S 410 24 871 Detailed Description gt n se 69 n o RE REG 410 24 88ststr PS File Reference 410 24 88 1 Detailed Description sss RR RR 410 24 89stto0k c File Reference ooo oem s 410 2 89 1 Detailed Description 2 2 22 52 411 24 90strtok Pc File Refer nc o o eeror coo omo no Room os 411 24 501 Detailed Description au mm Rem eS 411 24 91 sittok S File Reference o 5 02064 o Ry om 411 24 911 Detailed Description uz e E RR rr eS 411 24 92 sirtok rES File Referenc 22 2 411 24 92 1 Detailed Description 2 22222222 2 2 2 411 24 93s550p 53 File Reference sso o m yo ee ER Us 411 24 93 1 Detailed Description lt lt lt a a ea Rcx RR 411 24 File Referent uisu ol eG KR 411 24 94 1 Detailed Description 412 24 95 wdt File Reference REOR ERREUR 412 2495 1 Detailed Description 413 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 AVR Libc 2 1 AVR Libc 1 1 Introduction The latest version of this document is always available from http savannah nongnu org projects avr The AVR Libc package provides a subset of the standard C library for Atmel AVR 8 bit RISC microcontr
66. p 82 69 al ldd r22 Y433 0x21 84 7a al ldd r23 Y 34 0x22 86 ce 01 movw r24 r28 88 01 96 adiw r24 0x01 1 8a Oc 40 reall 24 Oxa4 This will finally copy the ROM string into the local buffer buf Variable p located at Y 33 is read and passed together with the address of buf Y 1 to strcpy P This will copy the string from ROM to buf Note that when using a compile time constant index omitting the first step reading the pointer from ROM via memcpy usually remains unnoticed since the compiler would then optimize the code for accessing array at compile time Back to FAQ Index 11 16 How to use external RAM Well there is no universal answer to this question it depends on what the external RAM is going to be used for Basically the bit SRE SRAM enable in the MCUCR register needs to be set in order to enable the external memory interface Depending on the device to be used and the application details further registers affecting the external memory operation like XMCRA and XMCRB and or further bits in MCUCR might be configured Refer to the datasheet for details If the external RAM is going to be used to store the variables from the C program i e the data and or bss segment in that memory area it is essential to set up the external memory interface early during the device initialization so the initialization of these variable will take place Refer to How to modify MCUCR or WDTCR early for
67. strtok rP S 411 strupr S 411 util twi h 411 compat twi h uart h version h wdt h 412 xtoa fast h 22 Module Documentation 221 lt alloca h gt Allocate space in the stack Functions void alloca size t size 22 1 1 Function Documentation 22 1 1 1 void alloca size t size Allocate size bytes of space in the stack frame of the caller This temporary space is automatically freed when the function that called alloca re turns to its caller Avr libc defines the alloca as a macro which is translated into the inlined builtin alloca function The fact that the code is inlined means that it is impossible to take the address of this function or to change its behaviour by linking with a different library Returns alloca returns a pointer to the beginning of the allocated space If the allocation causes stack overflow program behaviour is undefined Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 2 lt assert h gt Diagnostics 136 Warning Avoid use alloca inside the list of arguments of a function call 22 2 lt assert h gt Diagnostics Defines define assert expression 22 21 Detailed Description include lt assert h gt This header file defines a debugging aid AS there is no standard error output stream available for many applications using this library the generation of a printable error message is not enabled by default These message
68. that will be stored under s The caller is responsible for providing sufficient storage in 8 Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 97 will be the letter a Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 208 If radix is 10 and val is negative a minus sign will be prepended The itoa function returns the pointer passed as s 22 10 4 14 longlabs long i The labs function computes the absolute value of the long integer i Note The abs and labs functions are builtins of gcc 22 10 4 15 Idiv_t Idiv long num long denom The Idiv function computes the value num denom and returns the quotient and remainder in a structure named 1div t that contains two long integer members named quot and rem 22 10 4 16 char long int val char x s int radix Convert a long integer to a string The function Itoa converts the long integer va
69. this prologue frame size 20 x push r28 push r29 in r28 SPL __ in r29 SP HKH sbiw r28 20 in tmp reg SREG cli out SPH r29 out SREG tmp reg out SPL r28 prologue end size 10 x It reads the current stack pointer value decrements it by the required amount of bytes then disables interrupts writes back the high part of the stack pointer writes back the saved SREG which will eventually re enable interrupts if they have been enabled before and finally writes the low part of the stack pointer At the first glance there s a race between restoring SREG and writing SPL However after enabling interrupts either explicitly by setting the I flag or by restoring it as part of the entire SREG the AVR hardware executes at least the next instruction still with interrupts disabled so the write to SPL is guaranteed to be executed with interrupts disabled still Thus the emitted sequence ensures interrupts will be disabled only for the minimum time required to guarantee the integrity of this operation Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 20 Why are there five different linker scripts 84 Back to FAQ Index 11 29 Why are there five different linker scripts From a comment in the source code Which one of the five linker script files is actually used depends on command line options given to ld A script file is the default script A xr script is for linkin
70. x long lround double __x long lrint double __x x double __y Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 156 22 6 1 Detailed Description include lt math h gt This header file declares basic mathematics constants and functions Notes In order to access the functions delcared herein it is usually also required to additionally link against the library 1ibm See also the related FAQ entry Math functions do not raise exceptions and do not change the errno vari able Therefore the majority of them are declared with const attribute for better optimization by GCC 22 6 2 Define Documentation 22 6 2 1 define acosf acos The alias for acos 22 6 2 2 define asinf asin The alias for asin 22 6 2 3 define atan2f atan2 The alias for atan2 22 6 2 4 define atanf atan The alias for atan 22 6 2 5 define cbrtf cbrt The alias for cbrt 22 6 2 6 define ceilf ceil The alias for ceil Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 157 22 6 2 7 define copysignf copysign 22 6 2 8 define cosf cos 22 6 2 0 define coshf cosh 22 6 2 10 22 6 2 11 22 6 2 12 22 6 2 13 22 6 2 14 22 6 2 15 22 6 2 16 define expf exp define fabsf fabs define fdimf fdim define floorf floor define fmaf fma define fmaxf fmax defi
71. 11 14 What registers are used by the compiler 72 11 15How do I put an array of strings completely in ROM 73 1116Bowtouseextemal RAM c o a ku m RR 75 ILITWhich O to Use 2 2 222r RR BR 76 11 18How do I relocate code to a fixed 77 11 19My UART is generating nonsense My ATmega128 keeps crashing Port Fis completely broken TI 11 20Why do all my foo bar strings eat up the SRAM 78 11 21 Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit operation in assembly 79 11 22How to detect RAM memory and variable overlap problems 79 11 23Is it really impossible to program the ATtinyXX inC 80 11 24 What is this clock skew detected message 80 11 25 Why are many interrupt flags cleared by writing a logical 1 81 11 26 Why have programmed fuses the bit value 0 82 11 27 Which AVR specific assembler operators are available 82 11 28Why are interrupts re enabled in the middle of writing the stack pointer 82 11 29Why are there five different linker scripts 83 11 30How to add a raw binary image to linker output 83 11 31How do I perform a software reset of AVR 84 11 321 am using floating point math Why is the compiled code so big Why doss my fede not wok lt sos p ee ee o Rx Ros
72. 13 29 12 for avr libc by Doxygen CONTENTS 224 System Brot 2 soo Rm RR RE 139 224 1 Detaled Description 42 2522 mm o 139 22 4 2 Define Documentation s ses m c RR mm Rn 139 22 5 lt inttypes h gt Integer Type conversions 139 22 5 1 Detailed Description gt gt s lt 24 64 seso datoene 142 22553 Denne e e cee sape a i E 142 273 9 Typedef Documentatii 22 22946399 RS 152 220 lt math gt Mathematies uu ccoa ox RR E 152 226 1 Detailed Description lt lt s 22 29 554 94 e 2 e468 155 22 6 2 Define Documentation 155 22 6 3 Function 160 22 1 Non local goto lt sc spoe a 166 22 7 1 Detailed Description 22 999 m 844 166 22 12 Funchosm Documentation p s s 658 oom e eo 167 22 8 Standard Integer Types 2 lt re sa o 168 228 1 Detaled Descriphon x ve 43x 2 beds ee RS 172 22 62 Dene Doc mentafion uui e yp p TS ERE 172 22823 Typedef Documentation 02222222222 9 8 n 178 22 9 lt stdio h gt Standard 22 2 2 181 2291 Detaled Description 2 2222 Rs 183 22 9 2 Define Documentation gt s se sc x 186 229 3 Function 189 2210 cstdlib h General tliies RR 201 22 10 1 Detailed Description 202 22 10 2 Define Document
73. 2 6 Building Software Even though GCC Binutils and avr libc are the core projects that are used to build software for the AVR there is another piece of software that ties it all together Make GNU Make is a program that makes things and mainly software Make interprets and executes a Makefile that is written for a project A Makefile contains dependency rules showing which output files are dependent upon which input files and instructions on how to build output files from input files Some distributions of the toolchains and other AVR tools such as MFile contain a Makefile template written for the AVR toolchain and AVR applications that you can copy and modify for your application See the GNU Make User Manual for more information 2 7 AVRDUDE After creating your software you ll want to program your device You can do this by using the program AVRDUDE which can interface with various hardware devices to program your processor AVRDUDE is a very flexible package All the information about AVR processors and various hardware programmers is stored in a text database This database can be modified by any user to add new hardware or to add an AVR processor if it is not already listed 28 GDB Insight DDD The GNU Debugger GDB is a command line debugger that can be used with the rest of the AVR toolchain Insight is GDB plus a GUI written in Tcl Tk Both GDB and Insight are configured for the AVR and the main executables are prefi
74. 8 3 7 typedef int64 t int fast64 t fastest signed int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 180 22 8 3 8 typedef int8 t int fast8 t fastest signed int with at least 8 bits 22 8 3 9 typedef int16 t int 16 t signed int with at least 16 bits 22 8 3 10 typedef int32 t int least32 t signed int with at least 32 bits 22 8 3 11 typedef int64 t int least64 t signed int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect 22 8 3 12 typedef int8 t int least8 t signed int with at least 8 bits 22 8 3 13 typedef int64 t intmax t largest signed int available 22 8 3 14 typedef intl6 tintptr t Signed pointer compatible type 22 8 3 15 typedef unsigned int uint16 t 16 bit unsigned type 22 8 3 16 typedef unsigned long int uint32 t 32 bit unsigned type Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 181 22 8 3 17 typedef unsigned long long int uint64 t 64 bit unsigned type Note This type is not available when the compiler option mint8 is in effect 22 8 3 18 typedef unsigned char uint8 t 8 bit unsigned type 22 8 3 19 typedef uint16_t uint_fast16_t fastest unsigned int with at least 16 bits
75. 9054414 vect TRANS plete AT90S4433 9054434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_ SIG_UART_ UART Data Reg A190S2313 9052333 9054414 UDRE vect DATA ister Empty AT90S4433 9054434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 USARTO_ SIG_ USARTO Rx ATmegal62 RXC_vect USARTO Complete RECV USARTO SIG USARTO Rx AT90CAN128 AT90CAN32 ATOOCAN64 RX vect UARTO Complete ATmegal28 ATmegal284P ATmegal65 RECV ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega329 ATmega64 AT mega645 ATmega649 ATmega640 AT mega1280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmegal64P AT mega644P ATmega644 USARTO SIG USARTO Tx ATmegal62 TXC_vect USARTO Complete TRANS USARTO_ SIG_ USARTO Tx AT90CANI28 AT90CAN32 ATOOCAN64 TX_vect UARTO_ Complete ATmegal28 ATmegal284P ATmegal65 TRANS ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega329 ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 AT mega649 ATmega6490 ATmega640 AT mega1280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmegal 64P AT mega644P ATmega644 USARTO_ SIG_ USARTO Data AT90CANI28 AT90CAN32 AT9OCAN64 UDRE vect UARTO Register Empty ATmegal28 ATmegal284P ATmegal62 DATA ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega329 ATmega64 ATmega645 ATmega649 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATme
76. ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega406 ATmega48P ATmega64 AT mega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA 11 ATtiny12 ATtinyl3 ATtiny15 ATtiny22 ATtiny2313 ATtiny26 ATtiny28 ATtiny43U ATtiny48 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90OUSB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 vect SIG External Interrupt INTERRUPTI Request 1 AT90S2313 9052333 9054414 AT90S4433 9054434 9058515 9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal68P ATmega32 ATmega323 ATmega328P ATmega32HVB ATmega406 AT mega48P ATmega64 ATmega8 mega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 ATtiny28 ATtiny48 ATtiny261 ATtiny46l AT
77. ATtiny85 TIMI CAPT vect SIG INPUT CAPTUREI Timer Counter1 Capture Event ATtiny24 ATtiny44 ATtiny84 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 254 TIMI SIG_ Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 COMPA_vect OUTPUT_ Compare Match ATtiny25 ATtiny85 COMPAREIA A TIMI SIG Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 COMPB_vect OUTPUT_ Compare Match ATtiny25 ATtiny85 COMPAREIB B TIM1_OVF_ SIG_ Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 vect OVERFLOWI Overflow ATtiny25 ATtiny85 TIMERO SIG INPUT ADC Conversion ATtiny261 ATtiny461 ATtiny861 CAPT vect CAPTUREO Complete TIMERO SIG TimerCounter0 ATmegal68 ATmega48 ATmega88 AT COMPA_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal28l COMPAREOA A ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 ATtiny48 ATtiny261 ATtiny461 AT tiny861 AT9OUSB162 AT90OUSB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 TIMERO_ SIG_ Timer Counter 0 AT90PWM3 AT90PWM2 AT90PWMI COMPB vect OUTPUT Compare Match ATmegal284P ATmegal68P ATmega328P COMPAREOB B ATmega32HVB ATmega48P AT SIG mega88P ATmegal68 ATmega48 AT OUTPUT mega88 ATmega640 ATmega1280 ATmegal281 ATmega2560 ATmega25
78. Gecho define size int size sym gt gt x h Back to FAQ Index 11 31 dol perform a software reset of the AVR The canonical way to perform a software reset of non XMega AVR s is to use the watchdog timer Enable the watchdog timer to the shortest timeout setting then go into an infinite do nothing loop The watchdog will then reset the processor XMega parts have a specific bit RST SWRST RST CTRL register that gen erates a hardware reset RST SWRST bm is protected by the XMega Configuration Change Protection system The reason why using the watchdog timer or RST_SWRST_bm is preferable over jump ing to the reset vector is that when the watchdog or RST_SWRST_bm resets the AVR the registers will be reset to their known default settings Whereas jumping to the reset vector will leave the registers in their previous state which is generally not a good idea CAUTION Older AVRs will have the watchdog timer disabled on a reset For these older AVRs doing a soft reset by enabling the watchdog is easy as the watchdog will then be disabled after the reset On newer AVRs once the watchdog is enabled then it stays enabled even after a reset For these newer AVRs a function needs to be added to the init3 section i e during the startup code before main to disable the watchdog early enough so it does not continually reset the AVR Here is some example code that creates a macro that can be called
79. INT32 MAX U 2UL define 4 MAX 7 define INT64 MIN INT64 ILL define UINT64_MAX CONCAT INT64 MAX U 2ULL IULL Limits of minimum width integer types define INT LEAST8 MAX INT8 MAX define INT LEAST8 MIN INT8 MIN define UINT LEAST8 MAX UINT8 MAX define INT LEASTI6 INTI6 MAX define INT LEAST16 MIN INT16 MIN define UINT LEASTI6 MAX UINTIG6 MAX fdefine INT LEAST32 MAX INT32 MAX fdefine INT LEAST32 MIN INT32 MIN define UINT LEAST32 MAX UINT32 MAX define INT LEAST64 MAX INT64 define INT LEAST64 MIN INT64 MIN define UINT LEAST64 MAX UINT64 MAX Limits of fastest minimum width integer types define INT 8 MAX 8 MAX define INT FAST8 MIN INT8 MIN define UINT FASTS MAX UINT8 MAX define INT FASTI6 MAX INTI6 MAX define INT FASTI6 MIN INT16 MIN define UINT FASTI6 MAX UINTI6 MAX define INT FAST32 MAX INT32 MAX define INT FAST32 MIN INT32 MIN define UINT FAST32 MAX UINT32 MAX define INT FAST64 MAX INT64 MAX define INT FAST64 MIN INT64 MIN define UINT FAST64 MAX UINT64 MAX Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 41 stdint h File Reference 400 Limits of integer types capable of holding object pointers define INTPTR MAX INTI6 MAX define INTPTR MIN INT16 MIN define UINTPTR MAX UINTI6 MAX Limits of greatest width integer types e define INTMAX MAX INT64 MAX define INTMAX MIN INT64 MIN e d
80. Row byte at address For some MCU types this function can also retrieve the factory stored oscillator calibration bytes Parameter address be 0 0x1f as documented by the datasheet Note The values are MCU type dependent Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 12 avr boot h gt Bootloader Support Utilities 234 22 12 2 15 define boot busyi SPM REG amp uint8 t BV SPM ENABLE Check if the SPM instruction is busy 22 12 2 16 define boot busy wait do while boot_spm_busy Wait while the SPM instruction is busy 22 12 2 17 define boot spm interrupt disabl SPM REG amp uint8 t BV SPMIE Disable the SPM interrupt 22 12 2 18 define boot interrupt SPM uint8 t BV SPMIE Enable the SPM interrupt 22 12 2 19 define BOOTLOADER SECTION attribute section bootloader Used to declare a function or variable to be placed into a new section called bootloader This section and its contents can then be relocated to any address such as the bootloader NRWW area at link time 22 12 2 20 define GET EXTENDED FUSE BITS 0x0002 address to read the extended fuse bits using boot lock fuse bits get 22 12 2 21 define GET HIGH FUSE BITS 0 0003 address to read the high fuse bits using boot lock fuse bits get 22 12 2 22 ttdefine GET LOCK BITS 0x0001 address to read the lock bits using boot l
81. STK500 there are two options to connect them for this demo The second option for the yellow green cable is shown in parenthesis in the table Alternatively the squid cable from the JTAG ICE kit can be used if available Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 38 A more sophisticated project 348 Port Header Color Function Connect to DO 1 brown RxD RXD of the RS 232 header D1 2 grey TxD TXD of the RS 232 header D2 3 black button SWO pin 1 down switches header D3 4 red button up SWI pin 2 switches header D4 5 green button SW2 pin 3 ADC switches header D5 6 blue LED LEDO pin 1 LEDs header D6 7 green clock out LEDI pin 2 LEDs header D7 8 white 1 second LED2 pin 3 flash LEDs header GND 9 unused VCC 10 unused Figure 7 Wiring of the STK500 The following picture shows the alternate wiring where LEDI is connected but SW2 is Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 38 A more sophisticated project 349 2 Figure 8 Wiring option 2 of the STK500 As an alternative this demo can also be run on the popular ATmega8 controller or its successor ATmega88 as well as the ATmega48 and ATmegal68 variants of the latter These controllers do not have a port named A so their ADC inputs are located on port C instead thus the potentiometer needs to b
82. STREAM avr stdio 187 fdev setup stream avr stdio 187 fdevopen avr stdio 189 fdevopen c 376 fdim avr math 161 fdimf avr math 156 feof avr stdio 190 ferror avr stdio 190 fflush avr_stdio 190 ffs avr_string 214 ffs S 376 ffsl avr_string 215 ffsl S 376 ffsll avr_string 215 ffsll S 376 fgetc avr stdio 190 fgets avr stdio 191 FILE avr stdio 188 floor avr math 162 floorf avr math 156 fma avr math 162 fmaf avr math 156 fmax avr math 162 fmaxf avr math 156 fmin avr math 162 fminf avr math 156 fmod avr math 162 fmodf avr math 156 fprintf avr stdio 191 fprintf P avr stdio 191 fputc avr stdio 191 fputs avr stdio 191 fputs P avr stdio 191 fread avr stdio 191 free avr stdlib 206 frexp avr math 162 frexpf avr math 157 fscanf avr stdio 192 fscanf P Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 427 avr stdio 192 fuse h 376 fwrite avr stdio 192 GET EXTENDED FUSE BITS avr boot 233 GET HIGH FUSE BITS avr boot 233 GET LOCK BITS avr boot 233 GET LOW FUSE BITS avr boot 233 getc avr stdio 188 getchar avr stdio 188 gets avr stdio 192 hypot avr math 163 hypotf avr math 157 inb deprecated items 323 INFINITY avr math 157 inp deprecated items 323 installation 90 installation avarice 95 installation avr libc 94 installation avrdude 94 installation avrprog
83. This could for example be the case for interrupts that are solely enabled for the purpose of getting the controller out of sleep_mode A handler for such an interrupt vector can be declared using the EMPTY INTERRUPT macro EMPTY INTERRUPT ADC vect Note There is no body to this macro Manually defined 1586 some circumstances the compiler generated prologue and epi logue of the ISR might not be optimal for the job and a manually defined ISR could be considered particularly to speedup the interrupt handling One solution to this could be to implement the entire ISR as manual assembly code in a separate assembly file See Combining C and assembly source files for an example of how to implement it that way Another solution is to still implement the ISR in C language but take over the com piler s job of generating the prologue and epilogue This can be done using the ISR_ NAKED attribute to the ISR macro Note that the compiler does not generate any thing as prologue or epilogue so the final reti must be provided by the actual im plementation SREG must be manually saved if the ISR code modifies it and the compiler implied assumption of zero reg always being 0 could be wrong e g when interrupting right after of a MUL instruction ISR TIMER1 OVF ISR NAKED Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 247 PORTB BV 0 result
84. This is the same as the ISR macro without optional attributes Deprecated Do not use SIGNAL in new code Use ISR instead Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 17 lt avr io h gt AVR device specific IO definitions 267 22 17 lt avrlio h gt AVR device specific IO definitions include lt avr io h gt This header file includes the apropriate IO definitions for the device that has been specified by the mmcu compiler command line switch This is done by divert ing to the appropriate file lt avr ioXXXX h gt which should never be included di rectly Some register names common to all AVR devices are defined directly within lt avr common h gt which is included in lt avr io h gt but most of the details come from the respective include file Note that this file always includes the following files include avr sfr defs h include lt avr portpins h gt include lt avr common h gt include lt avr version h gt See lt avr sfr_defs h gt Special function registers for more details about that header file Included are definitions of the IO register set and their respective bit values as specified in the Atmel documentation Note that inconsistencies in naming conventions so even identical functions sometimes get different names on different devices Also included are the specific names useable for interrupt function definitions as docu mented here Finally the following macros
85. a lot of SRAM In Program Space String Utilities a method is described how such constant data can be moved out to flash ROM How ever a constant string located in flash ROM is no longer a valid argument to pass to a function that expects a const char x type string since the AVR processor needs the special instruction LPM to access these strings Thus separate functions are needed that take this into account Many of the standard C library functions have equivalents available where one of the string arguments can be located in flash ROM Private func tions in the applications need to handle this too For example the following can be used to implement simple debugging messages that will be sent through a UART include lt inttypes h gt include lt avr io h gt include lt avr pgmspace h gt int uart putchar char c if uart putchar Nr loop until bit is set USR UDRE UDR c return 0 so it could be used for fdevopen too void debug_P const char xaddr Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 21 Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit operation in assembly 80 ghar 3 while c read byte addr uart putchar oc int main void ioinit initialize UART debug P PSTR foo was here n return 0 Note By convention the suffix _P to the function name is
86. a way so it can be run on the ATmegal6 that ships with the STK500 development kit The UART port needs to be connected to the RS 232 spare port by a jumper cable that connects PDO to RxD and PDI to TxD The RS 232 channel is set up as standard input st din and standard output stdout respectively In order to have a different device available for a standard error channel stderr an industry standard LCD display with an HD44780 compatible LCD controller has been chosen This display needs to be connected to port A of the STK500 in the following way Port Header Function 1 LCD D4 AI 2 LCD D5 A2 3 LCD D6 A3 4 LCD D7 A4 5 LCD R W 5 6 LCDE A6 7 LCD RS AT 8 unused GND 9 GND VCC 10 Vec Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 39 Using the standard IO facilities 355 Figure 9 Wiring of the STK500 The LCD controller is used in 4 bit mode including polling the busy flag so the R W line from the LCD controller needs to be connected Note that the LCD con troller has yet another supply pin that is used to adjust the LCD s contrast V5 Typ ically that pin connects to a potentiometer between Vcc and GND Often it might work to just connect that pin to GND while leaving it unconnected usually yields an unreadable display Port A has been chosen as 7 pins are needed to connect the LCD yet all other ports are already partially in use port
87. addr define EEGET var addr var read byte const uint8 t addr 22 14 1 Detailed Description finclude lt avr eeprom h gt This header file declares the interface to some simple library routines suitable for han dling the data EEPROM contained in the AVR microcontrollers The implementation uses a simple polled mode interface Applications that require interrupt controlled EEPROM access to ensure that no time will be wasted in spinloops will have to deploy their own implementation Notes Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 4 lt avr eeprom h gt EEPROM handling 237 In addition to the write functions there is a set of update ones This functions read each byte first and skip the burning if the old value is the same with new The scaning direction is from high address to low to obtain quick return in common cases of the read write functions first make sure the EEPROM is ready to be ac cessed Since this may cause long delays if a write operation is still pending time critical applications should first poll the EEPROM e g using eeprom is ready before attempting any actual I O But this functions are not wait until SELFPRGEN in SPMCSR becomes zero Do this manually if your softwate contains the Flash burning As these functions modify IO registers they are known to be non reentrant If any of these functions are used from both standard and interrupt contex
88. allocated charx pointer It must be the same while parsing the same string strtok rP is a reentrant version of strtok_P The strtok_rP function is similar to strtok_r except that del im is pointer to a string in program space Returns The strtok_rP function returns a pointer to the next token or NULL when no more tokens are found 22 20 lt avr power h gt Power Reduction Management include lt avr power h gt Many AVRs contain a Power Reduction Register PRR or Registers PRRx that allow you to reduce power consumption by disabling or enabling various on board peripher als as needed There are many macros in this header file that provide an easy interface to enable or disable on board peripherals to reduce power See the table below Note Not all AVR devices have a Power Reduction Register for example the ATmega128 On those devices without a Power Reduction Register these macros are not avail able Not all AVR devices contain the same peripherals for example the LCD inter face or they will be named differently for example USART and USARTO Please consult your device s datasheet or the header file to find out which macros are applicable to your device Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 00 lt avr power h gt Power Reduction Management 293 Power Macro Description Applicable for device power adc enable Enable the Analog to Digital Conve
89. are defined RAMEND The last on chip RAM address XRAMEND The last possible RAM location that is addressable This is equal to RAMEND for devices that do not allow for external RAM For devices that allow external RAM this will be larger than RAMEND E2END The last EEPROM address FLASHEND The last byte address in the Flash program space SPM PAGESIZE For devices with bootloader support the flash pagesize in bytes to be used for the SPM instruction E2PAGESIZE The size of the EEPROM page Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 48 lt avr lock h gt Lockbit Support 268 22 48 lt avr lock h gt Lockbit Support Introduction The Lockbit API allows a user to specify the lockbit settings for the specific AVR device they are compiling for These lockbit settings will be placed in a special section in the ELF output file after linking Programming tools can take advantage of the lockbit information embedded in the ELF file by extracting this information and determining if the lockbits need to be programmed after programming the Flash and EEPROM memories This also allows a single ELF file to contain all the information needed to program an AVR To use the Lockbit API include the lt avr io h gt header file which in turn automatically includes the individual I O header file and the lt avr lock h gt file These other two files provides everything necessary to set the AVR lockbits
90. avr libc 1 2 branch set version to 1 1 90 lt date gt set version to 1 2 cvs tag avr libc 1 2 release U cvs tag avr libc 2 0 branchpoint set version to 2 1 0 lt date gt Figure 4 Release tree 16 Acknowledgments This document tries to tie together the labors of a large group of people Without these individuals efforts we wouldn t have a terrific free set of tools to develop AVR projects We all owe thanks to The GCC Team which produced a very capable set of development tools for an amazing number of platforms and processors e Denis Chertykov denisc overta ru for making the AVR specific changes to the GNU tools e Denis Chertykov and Marek Michalkiewicz marekm8linux org pl for developing the standard libraries and startup code for AVR GCC Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 17 Todo List 127 Uros Platise for developing the AVR programmer tool uisp Joerg Wunsch joerg FreeBSD ORG for adding all the AVR development tools to the FreeBSD http www freebsd org ports tree and for pro viding the basics for the demo project Brian Dean bsd amp bsdhome com for developing avrdude an alternative to uisp and for contributing documentation which describes how to use it Avr dude was previously called avrprog Eric Weddington eweddington cso atmel com maintaining the WinAVR package and thus making the continued improvements to
91. avr libc by Doxygen 2 5 avr libc 15 avr objdump Display information from object files including disassembly avr size List section sizes and total size avr nm List symbols from object files avr strings List printable strings from files avr strip Discard symbols from files avr readelf Display the contents of ELF format files avr addr2line Convert addresses to file and line avr c filt Filter to demangle encoded C symbols 2 5 avr libc GCC and Binutils provides a lot of the tools to develop software but there is one critical component that they do not provide a Standard C Library There are different open source projects that provide a Standard C Library depending upon your system time whether for a native compiler GNU Libc for some other embedded system newlib or for some versions of Linux uCLibc The open source AVR toolchain has its own Standard C Library project avr libc AVR Libc provides many of the same functions found in a regular Standard C Library and many additional library functions that is specific to an AVR Some of the Standard C Library functions that are commonly used on a PC environment have limitations or additional issues that a user needs to be aware of when used on an embedded system AV R Libc also contains the most documentation about the whole AVR toolchain Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 2 6 Building Software 16
92. bitfield The interrupt is kept disabled while not needed because the ADC will also be triggered by executing the SLEEP instruction in idle mode which is the default sleep mode Another option would be to turn off the ADC completely here but that increases the ADC s startup time not that it would matter much for this application 22 38 3 4 Part 4 Auxiliary functions The function handle mcucsr usestwo attribute declarators to achieve specific goals First it will instruct the compiler to place the generated code into the init3 section of the output Thus it will become part of the application initialization sequence This is done in order to fetch and clear the reason of the last hardware reset from MCUCSR as early as possible There is a short period of time where the next reset could already trigger before the current reason has been evaluated This also explains why the variable mcucsr that mirrors the register s value needs to be placed into the noinit section because otherwise the default initialization which happens after init3 would blank the value again As the initialization code is not called using CALL RET instructions but rather con catenated together the compiler needs to be instructed to omit the entire function pro logue and epilogue This is performed by the naked attribute So while syntactically handle mcucsr is a function to the compiler the compiler will just emit the in structions for it without se
93. by Doxygen 22 1 lt string h gt Strings 219 Returns The strcasecmp function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than 52 A consequence of the ordering used by strcasecmp is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 22 11 3 13 char x strcasestr const char s const char s2 The strcasestr function finds the first occurrence of the substring s2 in the string S1 This is like strstr except that it ignores case of alphabetic symbols in searching for the substring Glibc GNU extension Returns The strcasestr function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of zero length the function returns s1 22 11 3 14 char x strcat char dest const char src Concatenate two strings The strcat function appends the src string to the dest string overwriting the 0 char acter at the end of dest and then adds a terminating 70 character The strings may not overlap and the dest string must have enough space for the result Returns The strcat function returns a pointer to the resulting string dest 22 11 3 15 char x strchr const char src int val Locate character in string The strchr function returns a pointer to the first occurrence of the character val in the string
94. by Doxygen 22 48 lt avr lock h gt Lockbit Support 269 To combine the lockbit mode macros together to represent a whole byte use the bitwise AND operator like so LB MODE 3 amp BLBO_MODE_2 lt avr lock h gt also defines a macro that provides a default lockbit value LOCKBITS DEFAULT which is defined to be OxFF See the AVR device specific datasheet for more details about these lock bits and the available mode settings A convenience macro LOCKMEM is defined as a GCC attribute for a custom named section of lock A convenience macro LOCKBITS is defined that declares a variable lock of type unsigned char with the attribute defined by LOCKMEM This variable allows the end user to easily set the lockbit data Note If a device specific I O header file has previously defined LOCKMEM then LOCK MEM is not redefined If a device specific I O header file has previously defined LOCKBITS then LOCKBITS is not redefined LOCKBITS is currently known to be defined in the I O header files for the XMEGA devices API Usage Example Putting all of this together is easy include avr io h LOCKBITS LB MODE 1 BLBO MODE 3 amp 1 MODE 4 int main void return 0 include lt avr io h gt unsigned char __lock __attribute__ section lock LB MODE 1 amp BLBO MODE 3 amp BLBI_MODE_4 int main void return 0 Generated on Thu May 19 2011 13 29 12 for avr libc
95. by Doxygen 22 8 lt stdint h gt Standard Integer Types 171 Limits of specified width integer types C implementations should define these macros only when STDC LIMIT MACROS is defined before lt stdint h gt is included define INT8_MAX Ox7f define INT8_MIN INT8_MAX 1 define UINT8_MAX __CONCAT INT8_MAX U x 2U 1U define INT16_MAX Ox7fff define INT16_MIN INT16_MAX 1 define UINT16_MAX __CONCAT INT16_MAX U x 2U 1U define INT32 MAX Ox7fffffffL define INT32 MIN CCINT32 MAX IL fdefine UINT32 MAX CONCAT INT32 U 2UL 1UL define INT64 MAX 7 define INT64 MIN INT64 MAX ILL define UINT 4 MAX CONCAT INT64 MAX U x 2ULL 1ULL Limits of minimum width integer types define INT LEAST8 MAX 8 MAX fdefine INT LEAST8 MIN INT8 MIN define UINT LEASTS MAX UINT8 MAX define INT LEASTI6 INTI6 MAX define INT LEASTI6 MIN INT16 MIN define UINT LEASTI6 MAX UINTI6 MAX fdefine INT LEAST32 MAX INT32 MAX define INT LEAST32 MIN INT32 MIN define UINT LEAST32 MAX UINT32 MAX fdefine INT LEAST64 MAX INT64 MAX define INT LEAST64 MIN INT64 MIN define UINT LEAST64 MAX UINT64 MAX Limits of fastest minimum width integer types define INT FAST8 MAX 8 MAX define INT FAST8 MIN INT8 MIN define UINT FASTS MAX UINT8 MAX define INT FASTI6 define INT FASTI6 MIN INT16 MIN define UINT FASTI6 MAX UINTI6 M
96. can hold 22 8 2 23 define INT LEAST32 MAX INT32 MAX largest positive value an int least32 t can hold 22 8 2 24 define INT LEAST32 MIN INT32 MIN smallest negative value an int least32 t can hold 22 8 2 25 define INT LEAST64 MAX INT64 MAX largest positive value an int least64 t can hold 22 8 2 26 define INT LEAST64 MIN INT64 MIN smallest negative value an int least64 t can hold Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 176 22 8 2 27 define INT LEAST8 MAX INT8 MAX largest positive value an int least8 t can hold 22 8 2 28 define INT LEAST8 MIN INT8 MIN smallest negative value an int least8 t can hold 22 8 2 29 define INTMAX C value _ CONCAT value LL define a constant of type intmax t 22 8 2 30 define INTMAX MAX INT64 MAX largest positive value an intmax t can hold 22 8 2 31 define INTMAX MIN INT64 MIN smallest negative value an intmax t can hold 22 8 2 32 itdefine INTPTR MAX INT16 MAX largest positive value an intptr t can hold 22 8 2 33 define INTPTR MIN 6 MIN smallest negative value an intptr t can hold 22 8 2 34 define PTRDIFF INT16 largest positive value a ptrdiff t can hold 22 8 2 35 define PTRDIFF MIN INT16 MIN smallest negative value a ptrdiff t can hold 22 8 2 36 define SIG ATOMIC MAX INT8 largest positive value a sig atomic t can hold Generated o
97. change the value of flag anyway To tell the compiler that this variable could be changed outside the scope of its code path analysis e g from within an interrupt routine the variable needs to be declared like volatile uint8_t flag Back to FAQ Index Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 3 Iget undefined reference to for functions like sin 64 11 3 get undefined reference to for functions like sin In order to access the mathematical functions that are declared in lt math h gt the linker needs to be told to also link the mathematical library 1ibm a Typically system libraries like 1ibm a are given to the final C compiler command line that performs the linking step by adding a flag 1m at the end That is the initial lib and the filename suffix from the library are written immediately after a flag So for a libfoo a library 1foo needs to be provided This will make the linker search the library in a path known to the system An alternative would be to specify the full path to the 1ibm a file at the same place on the command line i e after all the object files However since this re quires knowledge of where the build system will exactly find those library files this is deprecated for system libraries Back to FAQ Index 11 4 How to permanently bind a variable to a register This can be done with register unsigned char counter asm r3 Typical
98. char utoa unsigned int val char x 5 int radix Convert an unsigned integer to a string The function utoa converts the unsigned integer value from val into an ASCII repre sentation that will be stored under s The caller is responsible for providing sufficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof unsigned int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 9 will be the letter a The utoa function returns the pointer passed as s 22 10 5 Variable Documentation 22 10 51 char malloc heap end malloc tunable 22 10 5 2 charx malloc heap start malloc tunable 22 10 5 3 size t malloc margin malloc tunable Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 214 22 11 lt string h gt Strings Defines define FFS x Functions int ffs int val int 51 long __ val int ffsll long long val void memccpy void const void int size_t void mem
99. character could not be sent to the device If the get function pointer is provided the stream is opened with read intent The function passed as get shall take a pointer to FILE as its single argument and return one character from the device passed as an int type If an error occurs when trying to read from the device it shall return FDEV ERR If an end of file condition was reached while reading from the device FDEV EOF shall be returned If both functions are provided the stream is opened with read and write intent The first stream opened with read intent is assigned to st din and the first one opened with write intent is assigned to both stdout and stderr fdevopen uses calloc und thus malloc in order to allocate the storage for the new stream Note If the macro _ STDIO COMPAT 12 is declared before including lt stdio h gt a function prototype for fdevopen will be chosen that is backwards compatible with avr libc version 1 2 and before This is solely intented for pro viding a simple migration path without the need to immediately change all source code Do not use for new code 22 9 3 4 intfeof FILE x stream Test the end of file flag of st ream This flag can only be cleared by a call to clearerr 22 9 3 5 intferror FILE x stream Test the error flag of stream This flag can only be cleared by a call to clearerr 22 9 3 6 int fflush FILE x stream Flus
100. character for a d conversion The value EOF is returned if an input failure occurs before any conversion such as an end of file Occurs If an error or end of file occurs after conversion has begun the number of conversions which were successfully completed is returned By default all the conversions described above are available except the floating point conversions and the width is limited to 255 characters The float point conversion will be available in the extended version provided by the library 1ibscanf flt a Also in this case the width is not limited exactly it is limited to 65535 characters To link a program against the extended version use the following compiler flags in the link stage Wl u vfscanf lscanf flt lm A third version is available for environments that are tight on space In addition to the restrictions of the standard one this version implements no specification This version is provided in the library 1ibscanf min a and can be requested using the following options in the link stage Wl u vfscanf l1scanf min lm Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 201 22 9 3 35 int vfscanf P FILE x stream const char fmt va list Variant of vfscanf using a mt string in program memory 22 9 3 36 int vprintf const char x fmt va list The function vprintf performs formatted output to stream stdout taking a var
101. characters of src are appended to dest Returns The strncat function returns a pointer to the resulting string dest Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 224 22 11 3 27 int strncmp const char 57 const char 52 size t len Compare two strings The strncmp function is similar to stremp except it only compares the first at most n characters of s1 and s2 Returns The strncmp function returns an integer less than equal to or greater than zero if s1 or the first n bytes thereof is found respectively to be less than to match or be greater than s2 22 11 3 28 char strncpy char x dest const char x src size t len Copy a string The strncpy function is similar to strcpy except that not more than n bytes of src are copied Thus if there is no null byte among the first n bytes of src the result will not be null terminated In the case where the length of src is less than that of n the remainder of dest will be padded with nulls Returns The strncpy function returns a pointer to the destination string dest 22 11 3 29 size tstrnlen const char src size t len Determine the length of a fixed size string The strnlen function returns the number of characters in the string pointed to by src not including the terminating 0 character but at most len In doing this strnlen looks only at the first len characters at
102. code size together This demo provides an example of how to do that The objective of the demo is to decode radio controlled model PWM signals and con Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 36 Combining C and assembly source files 328 trol an output PWM based on the current input signal s value The incoming PWM pulses follow a standard encoding scheme where a pulse width of 920 microseconds denotes one end of the scale represented as 0 pulse width on output and 2120 microseconds mark the other end 100 output PWM Normally multiple channels would be encoded that way in subsequent pulses followed by a larger gap so the en tire frame will repeat each 14 through 20 ms but this is ignored for the purpose of the demo so only a single input PWM channel is assumed The basic challenge is to use the cheapest controller available for the task an ATtiny13 that has only a single timer channel As this timer channel is required to run the out going PWM signal generation the incoming PWM decoding had to be adjusted to the constraints set by the outgoing PWM As PWM generation toggles the counting direction of timer 0 between up and down after each 256 timer cycles the current time cannot be deduced by reading TCNTO only but the current counting direction of the timer needs to be considered as well This requires servicing interrupts whenever the timer hits TOP 255 and BOTTOM 0 to learn about each c
103. code to swap high and low byte of a 16 bit value asm volatile mov tmp reg A0 n t mov A0 BO n t mov B0 tmp_reg__ n t r value 0 value First you will notice the usage of register tmp reg which we listed among other special registers in the Assembler Code section You can use this register without saving its contents Completely new are those letters A and B in A0 and BO In fact they refer to two different 8 bit registers both containing a part of value Another example to swap bytes of a 32 bit value asm volatile mov tmp reg 0 n t mov 0 0 MAKE Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 3 Input and Output Operands 46 mov D0 __tmp_reg__ n t mov tmp reg BO n t mov BO 0 NnNp mov CO tmp reg n t r value 0 value Instead of listing the same operand as both input and output operand it can also be declared as a read write operand This must be applied to an output operand and the respective input operand list remains empty asm volatile mov tmp reg AO0 n t mov 0 0 NnNE mov DO0 tmp reg n t mov tmp reg BO n t mov BO CO mov CO0 tmp reg n t r value If operands do not fit into a single register the compiler will automatically assign enough registers to hold the entire operand In the assembler code you
104. command to generate demo map a portion of which is shown below avr gcc g mmcu atmega8 Wl Map demo map o demo elf demo o Some points of interest in the demo map file are rela plt rela plt text 0x0000000000000000 Oxca vectors Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 341 vectors x progmem gccx progmemx 0x0000000000000000 0x0000000000000000 trampolines trampolines 0x0000000000000000 x trampolinesx 0x0000000000000000 jumptables jumptablesx lowtext lowtextx 0x0000000000000000 ALIGN 0x2 __trampolines_start 0 0 linker stubs __trampolines_end _ ctors_start The text segment where program instructions are stored starts at location 0x0 etext 0x0 load address 0x00000000000000ca PROVIDE start 0x0 demo o 0x0 home tools hudson workspace avr8 g nu toolchain avr8 gnu toolchain linux x86 64 lib gcc avr 4 5 1 avr4 libgcc a cle ALIGN 0x2 edata PROVIDE data 0x3 PROVIDE bss start 0x3 demo o 0x0 home tools hudson workspace avr8 g nu toolchain avr8 gnu toolchain linux x86 64 lib gcc avr 4 5 1 avr4 libgcc a cle fini2 finLi2 finil x finil finiO finiO 0x00000000000000ca data 0x0000000000800060 0x0000000000800060 x data data 0x0000000000800060 data 0x0000000000800060 ar_bss o x datax rodata
105. constraint string Using digit n tells the compiler to use the same register as for the n th operand starting with zero Here is an example asm volatile swap 0 r value 0 value This statement will swap the nibbles of an 8 bit variable named value Constraint 0 tells the compiler to use the same input register as for the first operand Note however that this doesn t automatically imply the reverse case The compiler may choose the same registers for input and output even if not told to do so This is not a problem in most cases but may be fatal if the output operator is modified by the assembler code before the input operator is used In the situation where your code depends on different registers used for input and output operands you must add the amp constraint modifier to your output operand The following example demonstrates this problem asm volatile in 0 1 out 1 2 n t amp r input I SFR IO ADDR port r output In this example an input value is read from a port and then an output value is written to the same port If the compiler would have choosen the same register for input and out put then the output value would have been destroyed on the first assembler instruction Fortunately this example uses the amp constraint modifier to instruct the compiler not to select any register for the output value which is used for any of the input operands Back to swapping Here is the
106. crc16 h gt CRC Computations 309 lt util delay_basic h gt Basic busy wait delay loops 313 lt util parity h gt Parity bit generation 314 lt util setbaud h gt Helper macros for baud rate calculations 314 Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 20 Data Structure Index 130 lt util twi h gt TWI bit mask definitions 317 compat deprecated h gt Deprecated items 321 lt compat ina90 h gt Compatibility with EWB 3 x 325 Demo projects 325 Combining C and assembly source files 326 A simple project 330 A more sophisticated project 345 Using the standard IO facilities 353 Example using the two wire interface TWI 361 20 Data Structure Index 20 1 Data Structures Here are the data structures with brief descriptions div t 366 ldiv t 366 21 File Index 21 1 File List Here is a list of all documented files with brief descriptions alloca h 22 assert h 367 atoi S 367 atol S 367 atomic h 367 boot h 368 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 211 File List 131 cpufunc h 374 crc16 h 374 ctype h 375 defines h delay basic h 375 deprecated h dtoa conv h eedef h eeprom h errno h 376 fdevopen c 376 ffs S 376 ffsl S 376 ffsll S 376 fuse h 376 hd44780 h ina90 h interrupt h 377 inttypes h 377 io h 380 iocompat h lock h 380 math h 380 memccpy S 384 Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen
107. data Value Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 5 boot h File Reference 373 extension 4 asm volatile movw r0 4 n t movw r30 A3 n t sts 1 C3 n t sts 0 2 n t spm n t Nele Sine mi SFR_MEM_ADDR SPM_REG _SFR_MEM_ADDR RAMPZ uint8 t BOOT PAGE FILLD uint32 t address T uintl16 t data VESI 1 yn 24 5 2 8 define boot page fill normal address data extension a asm Volatile movw r0 3 n t sts 0 1 n t spm n t sami 1 _SFR_MEM_ADDR SPM REG r uint8 t PAGE FILLD z uintl16 t address r uintl6 t data y 24 5 2 0 define boot page write alternate address extension 4 asm volatile sts 0 1 n t spm n t word Oxffff n t nop n t i _SFR_MEM_ADDR __SPM_REG d MEM M E E WB P EEE NP P DES E AVE Value Value Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 5 boot h File Reference 374 r uint8 t BOOT PAGE WRITE N z uint16 t address N 24 5 2 10 define boot page write extended address Value extension N asm 2 volatile N N movw r30 A3 n t N sts 1 C3 n t N sts 0 2 n t N spm n t E N i SFR MEM ADDR SPM REG N i SFR M
108. define SCNdFASTI6 decimal scanf format for int fast16 t 22 5 2 64 define SCNdFAST32 Id decimal scanf format for int_fast32_t 22 5 2 65 define SCNdLEAST16 d decimal scanf format for int_least16_t 22 5 2 66 define SCNdLEAST32 Id decimal scanf format for int least32 t 22 5 2 07 define SCNdPTR SCNd16 decimal scanf format for intptr t 22 5 2 08 define SCNi16 i generic integer scanf format for int16 t 22 5 2 69 define SCNi32 li generic integer scanf format for int32 t 22 5 2 70 define SCNiFASTI6 i generic integer scanf format for int fast16 t 22 5 2 71 define SCNiIFAST32 li generic integer scanf format for int fast32 t 22 5 2 72 define SCNILEASTI6 i generic integer scanf format for int leastl6 t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 151 22 5 2 73 define SCNILEAST32 li generic integer scanf format for int least32 t 22 5 2 74 define SCNiPTR SCNi16 generic integer scanf format for intptr_t 22 5 2 75 define SCNo16 o octal scanf format for uint16 t 22 5 2 76 define SCNo32 lo octal scanf format for uint32_t 22 5 2 77 define SCNoFASTI6 octal scanf format for uint_fast16_t 22 5 2 78 define SCNoFAST32 lo octal scanf format for uint_fast32_t 22 5 2 79 define SCNoLEAST16 o octal scanf format for uint_least16_t 22 5 2 80 define SCNoLEAST32 lo octal scanf
109. define boot page erase address boot page erase normal address define boot page write address boot page write normal address define boot rww boot rww enable define boot lock bits set lock bits boot lock bits set lock bits define boot page fill safe address data define boot page erase safe address define boot page write safe address define boot rww enable safe define boot lock bits set safe lock bits 24 5 1 Detailed Description 24 5 2 Define Documentation 24 5 2 1 define boot lock bits set lock bits Value extension uint8_t value uint8 t lock bits asm volatile ldi r30 1 ni tr idi 31 mov r0 2 n t sts 0 1 n t spm n t i SFR MEM ADDR SPM REG r uint8 t BOOT LOCK BITS SET r value EO 31 e EO uw au utut aut lj uw ur Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 5 boot h File Reference 371 24 5 2 define boot lock bits set alternate lock bits extension 4 uint8 t value uint8 t lock_bits asm volatile IdE x30 ldi x31 DANE mov r0 2 n t sts 0 1 n t spm n t word Oxffff n t nop n t i _SFR_MEM_ADDR __SPM_REG r uint8 t LOCK BITS SET ny r value 0 130 r31 24 5 2 3 define boot page erase alternate address extension
110. e a x indicating that the conversion should be performed but the conversion result is to be discarded no parameters will be processed from ap Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 199 the character h indicating that the argument is a pointer to short int rather than int the 2 characters hh indicating that the argument is a pointer to char rather than int the character 1 indicating that the argument is a pointer to long int rather than int for integer type conversions or a pointer to double for floating point conversions In addition a maximal field width may be specified as a nonzero positive decimal integer which will restrict the conversion to at most this many characters from the input stream This field width is limited to at most 255 characters which is also the default value except for the c conversion that defaults to 1 The following conversion flags are supported Matches a literal character This is not a conversion d Matches an optionally signed decimal integer the next pointer must be a pointer to int i Matches an optionally signed integer the next pointer must be a pointer to int The integer is read in base 16 if it begins with Ox or OX in base 8 if it begins with 0 and in base 10 otherwise Only characters that correspond to the base are used o Matches an octal integer the next pointer must be a pointer to uns
111. enable external int mask __EICR mask Deprecated This macro gives access to the GIMSK register or EIMSK register if using an AVR Mega device or GICR register for others Although this macro is essentially the same as assigning to the register it does adapt slightly to the type of device being used This macro is unavailable if none of the registers listed above are defined 22 33 2 3 define inb port port Deprecated Read a value from an IO port port 22 33 2 4 define inp port port Deprecated Read a value from an IO port port Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 33 lt compat deprecated h gt Deprecated items 325 22 33 2 5 define INTERRUPT signame Value void signame void attribute _ interrupt INTR ATTRS N void signame void Deprecated Introduces an interrupt handler function that runs with global interrupts initially en abled This allows interrupt handlers to be interrupted As this macro has been used by too many unsuspecting people in the past it has been deprecated and will be removed in a future version of the library Users who want to legitimately re enable interrupts in their interrupt handlers as quickly as possible are encouraged to explicitly declare their handlers as described above 22 33 2 6 define outb port val port val Deprecated Write val to IO port port 22 33 2 7 define outp val port port val
112. files avr strip Before we can build the C compiler these tools need to be in place Download and unpack the source files bunzip2 c binutils version tar bz2 tar xf cd binutils version Note Replace lt version gt with the version of the package you downloaded If you obtained a gzip compressed file gz use gunzip instead of bunzip2 It is usually a good idea to configure and build b nutils a subdirectory so as not to pollute the source with the compiled files This is recommended by the binutils developers mkdir obj avr cd obj avr The next step is to configure and build the tools This is done by supplying arguments to the configure script that enable the AVR specific options configure prefix PREFIX target avr disable nls If you don t specify the prefix option the tools will get installed in the usr local hierarchy i e the binaries will get installed in usr local bin the info pages get installed in usr local info etc Since these tools are changing frequently It is preferrable to put them in a location that is easily removed When configure is run it generates a lot of messages while it determines what is available on your operating system When it finishes it will have created several Makefiles that are custom tailored to your platform At this point you can build the project make Note BSD users should note that the project s Makefile uses GNU make syntax
113. from within an interrupt context could clobber the TEMP register data of an in progress transaction that has just started elsewhere To protect interrupt routines against other interrupt routines it s usually best to use the ISR macro when declaring the interrupt function and to ensure that interrupts are still disabled when accessing those 16 bit timer registers Within the main program access to those registers could be encapsulated in calls to the cli and sei macros If the status of the global interrupt flag before accessing one of those registers is uncertain something like the following example code can be used uint16_t read_timerl void uint8 t sreg uintl16 t val sreg SREG cli val TCNT1 SREG sreg return val Back to FAQ Index 11 10 How do use a define d constant in an asm statement So you tried this asm volatile sbi 0x18 0x07 Which works When you do the same thing but replace the address of the port by its macro name like this asm volatile sbi PORTB 0x07 you get a compilation error Error constant value required PORTB is a precompiler definition included in the processor specific file included in avr io h As you may know the precompiler will not touch strings and PORTB instead of 0x18 gets passed to the assembler One way to avoid this problem is asm volatile sbi 0 0x07 I SFR IO ADDR PORTB Generated on Thu May 19 2011 13 29 12 for avr
114. func tion named BADISR_vect which should be defined with ISRQ as such The name BADISR vect is actually an alias for vector default The latter must be used inside assembly code in case lt avr interrupt h gt is not included include avr interrupt h ISR BADISR vect user code here Nested interrupts The AVR hardware clears the global interrupt flag in SREG before entering an interrupt vector Thus normally interrupts will remain disabled inside the handler until the handler exits where the RETI instruction that is emitted by the com piler as part of the normal function epilogue for an interrupt handler will eventually re enable further interrupts For that reason interrupt handlers normally do not nest For most interrupt handlers this is the desired behaviour for some it is even required in order to prevent infinitely recursive interrupts like UART interrupts or level triggered external interrupts In rare circumstances though it might be desired to re enable the global interrupt flag as early as possible in the interrupt handler in order to not defer any other interrupt more than absolutely needed This could be done using an sei instruction right at the beginning of the interrupt handler but this still leaves few in structions inside the compiler generated function prologue to run with global interrupts disabled The compiler can be instructed to insert an SEI instruction right at the begin ning of an inter
115. gcc user manual The latest version of the gcc manual is always available here htt gcc gnu org onlinedocs 8 How to Build a Library 8 1 Introduction So you keep reusing the same functions that you created over and over Tired of cut and paste going from one project to the next Would you like to reduce your maintenance overhead Then you re ready to create your own library Code reuse is a very laudable goal With some upfront investment you can save time and energy on future projects by having ready to go libraries This chapter describes some background information design considerations and practical knowledge that you will need to create and use your own libraries Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 82 How the Linker Works 52 8 2 How the Linker Works The compiler compiles a single high level language file C language for example into a single object module file The linker Id can only work with object modules to link them together Object modules are the smallest unit that the linker works with Typically on the linker command line you will specify a set of object modules that has been previously compiled and then a list of libraries including the Standard C Library The linker takes the set of object modules that you specify on the command line and links them together Afterwards there will probably be a set of undefined references A reference is essentially a function call An undef
116. h Defines an empty interrupt handler function This will not generate any prolog or epilog code and will only return from the ISR Do not define a function body as this will define it for you Example EMPTY INTERRUPT ADC vect Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 264 22 16 2 4 define ISR vector attributes include avr interrupt h Introduces an interrupt handler function interrupt service routine that runs with global interrupts initially disabled by default with no attributes specified The attributes are optional and alter the behaviour and resultant generated code of the interrupt routine Multiple attributes may be used for a single function with a space seperating each attribute Valid attributes are ISR BLOCK ISR NOBLOCK ISR_NAKED and ISR_ALIASOF vect vector must be one of the interrupt vector names that are valid for the particular MCU type 22 16 2 5 define ISR_ALIAS vector target vector include avr interrupt h Aliases a given vector to another one in the same manner as the ISR_ALIASOF at tribute for the ISR macro Unlike the ISR_ALIASOF attribute macro however this is compatible for all versions of GCC rather than just GCC version 4 2 onwards Note This macro creates a trampoline function for the aliased macro This will result in two cycle penalty for the aliased vector compared to the ISR the vector is ali
117. int isfinite double __x static double copysign double int signbit double __ x double double x double y double fma double x double y double z double fmax double __x double y double fmin double x double y double double x double round double __ x long lround double __ x long lrint double x x double y Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 20 math h File Reference 384 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 21 memccpy S File Reference 385 24 20 1 Detailed Description 24 21 memcopy S File Reference 24 21 1 Detailed Description 24 22 memchr S File Reference 24 22 1 Detailed Description 24 23 memchr P S File Reference 24 23 1 Detailed Description 24 24 memcmp S File Reference 24 24 1 Detailed Description 24 25 memcmp P S File Reference 24 25 1 Detailed Description 24 26 memcmp PFS File Reference 24 26 1 Detailed Description 24 27 memopy SFile Reference 24 27 1 Detailed Description 24 28 memcpy 5 File Reference 24 28 1 Detailed Description 24 29 5 File Reference 24 29 1 Detailed Description 24 30 5 File Reference 24 30 1 Detailed Description 24 31 memrchr S File Reference Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 32 memrchr_P S File Reference 24 32 1 Detailed Description 24 33 memset S File Reference
118. is a reentrant version of strtok Returns The strtok_r function returns a pointer to the next token or NULL when no more tokens are found 22 11 3 38 char x strupr char xs Convert a string to upper case The strupr function will convert a string to upper case Only the lower case alphabetic characters a z are converted Non alphabetic characters will not be changed Returns The strupr function returns a pointer to the converted string The pointer is the same as that passed in since the operation is perform in place Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 12 avr boot h Bootloader Support Utilities 228 2212 lt avr boot h gt Bootloader Support Utilities Defines define BOOTLOADER SECTION attribute section bootloader define boot spm interrupt enable SPM REG uint8 t BV SPMIE define boot spm interrupt disable SPM REG amp uint8_t _BV SPMIE define boot is spm interrupt SPM REG amp uint8 t BV SPMIE define boot rww busy SPM REG amp uint8 t COMMON ASB define boot spm busy REG amp uint8 t SPM ENABLE define boot spm busy wait do while boot busy define GET LOW FUSE BITS 0x0000 define GET LOCK BITS 0x0001 define GET EXTENDED FUSE BITS 0x0002 define GET HIGH FUSE BITS 0 0003 define boot lock fuse bits get address fidefine boot signature byte get addr
119. is also a macro that defined as a pointer to a character in the Program Space Retrieving the strings are a different matter You probably don t want to pull the string out of Program Space byte by byte using the pgm read byte macro There are other functions declared in the lt avr pgmspace h gt header file that work with strings that are stored in the Program Space For example if you want to copy the string from Program Space to a buffer in RAM like an automatic variable inside a function that is allocated on the stack you can do this void foo void char buffer 10 for unsigned char i 0 i lt 5 itt strcpy_P buffer read word amp string table il Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 5 5 Caveats 32 Display buffer on LCD return Here the string table array is stored in Program Space so we access it normally as if were stored in Data Space then take the address of the location we want to access and use the address as a parameter to read word We use the read word macro to read the string pointer out of the string table array Remember that a pointer is 16 bits or word size The read word macro will return a 16 bit unsigned integer We then have to typecast it as a true pointer to program memory PGM P This pointer is an address in Program Space pointing to the string that we want to copy This pointer is then used
120. less than to match or be greater than 52 The contents of RAMPZ SFR are undefined when the function returns 22 19 4 11 char x strcasestr_P const char s PGM P s2 This funtion is similar to strcasestr except that s2 is pointer to a string in program space 22 19 4 12 char x strcat char gt dest P src The strcat_P function is similar to strcat except that the src string must be located in program space flash Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 49 lt avr pgmspace h gt Program Space Utilities 281 Returns The strcat function returns a pointer to the resulting string dest 22 19 4 13 char x strcat PF char dst uint farptr tsrc Concatenates two strings The strcat_PF function is similar to strcat except that the src string must be located in program space flash and is addressed using a far pointer Parameters dst A pointer to the destination string in SRAM src A far pointer to the string to be appended in Flash Returns The strcat_PF function returns a pointer to the resulting string dst The contents of RAMPZ SFR are undefined when the function returns 22 19 414 P strchr_P P s int val Locate character in program space string The strchr_P function locates the first occurrence of va1 converted to a char in the string pointed to by s in program space The terminating null character is consi
121. low level HD44780 driver deals with setting up controller SRAM addresses writing data to the controller s SRAM and controlling display functions like clearing the display or moving the cursor this high level driver allows to just write a character to the LCD in the assumption this will somehow show up on the display Control characters can be handled at this level and used to perform specific actions on the LCD Currently there is only one control character that is being dealt with a newline character is taken as an indication to clear the display and set the cursor into its initial position upon reception of the next character so a new line of text can be displayed Therefore a received newline character is remembered until more characters have been sent by the application and will only then cause the display to be cleared before continuing This provides a convenient abstraction where full lines of text can be sent to the driver and will remain visible at the LCD until the next line is to be displayed Further control characters could be implemented e g using a set of escape sequences That way it would be possible to implement self scrolling display lines etc The public function 1 init first calls the initialization entry point of the lower level HD44780 driver and then sets up the LCD in a way we d like to display cleared Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 39 Using the stan
122. lt inttypes h gt Integer Type conversions 147 22 5 2 33 define PRIu8 u decimal printf format for uint8 t 22 5 2 34 define PRIuFASTI16 decimal printf format for uint_fast16_t 22 5 2 35 define PRIuFAST32 lu decimal printf format for uint_fast32_t 22 5 2 36 define PRIuFASTS decimal printf format for uint_fast8_t 22 5 2 37 define PRIULEAST16 u decimal printf format for uint_least16_t 22 5 2 38 define PRIULEAST32 lu decimal printf format for least32 t 22 5 2 39 define PRIULEASTS decimal printf format for least8 t 22 5 2 40 define PRIuPTR PRIu16 decimal printf format for uintptr t 22 5 2 41 PRIx16 hexadecimal printf format for uint16 t 22 5 2 42 itdefine PRIX16 X uppercase hexadecimal printf format for uint16 t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 148 22 5 2 43 22 5 2 44 22 5 2 45 22 5 2 46 22 5 2 47 22 5 2 48 22 5 2 49 22 5 2 50 22 5 2 51 22 5 2 52 define PRIx32 Ix hexadecimal printf format for uint32 t define PRIX32 IX uppercase hexadecimal printf format for uint32 t define PRIx8 x hexadecimal printf format for uint8_t define PRIX8 X uppercase hexadecimal printf format for uint8_t define PRIxFAST16 hexadecimal printf format for uint_fast16_t define PRIXFAST16 X uppercase hexadecimal
123. more important parts of the code are Note 1 As the AVR microcontroller series has been developed during the past years new features have been added over time Even though the basic concepts of the timer counter are still the same as they used to be back in early 2001 when this sim ple demo was written initially the names of registers and bits have been changed slightly to reflect the new features Also the port and pin mapping of the output compare match 1A or 1 for older devices pin which is used to control the LED varies between different AVRs The file iocompat h tries to abstract between all this differences using some preprocessor i de f statements so the actual pro gram itself can operate on a common set of symbolic names The macros defined by that file are OCR the name of the OCR register used to control the PWM usually either OCR1 or OCR1A DDROC the name of the DDR data direction register for the OC output OCI the pin number of the OC1 A output within its port 1 TOP the TOP value of the timer used for the PWM 1023 for 10 bit PWMs 255 for devices that can only handle an 8 bit PWM e TIMER1 INIT the initialization bits to be set into control register in order to setup 10 bit or 8 bit phase and frequency correct PWM mode Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 333 e TIMER1 CLOCKSOURCE the clock bits to set
124. need to get the last few percent of speed benefit from using 03 Back to FAQ Index 11 18 How do I relocate code to a fixed address First the code should be put into a new named section This is done with a section attribute attribute section bootloader In this example bootloader is the name of the new section This attribute needs to be placed after the prototype of any function to force the function into the new section void boot void _ attribute section bootloader To relocate the section to a fixed address the linker flag section start is used This option can be passed to the linker using the W1 compiler option Wl section start bootloader 0x1E000 The name after section start is the name of the section to be relocated The number after the section name is the beginning address of the named section Back to FAQ Index 11 19 My UART is generating nonsense My ATmega128 keeps crashing Port is completely broken Well certain odd problems arise out of the situation that the AVR devices as shipped by Atmel often come with a default fuse bit configuration that doesn t match the user s expectations Here is a list of things to care for devices that have an internal RC oscillator ship with the fuse enabled that causes the device to run off this oscillator instead of an external crystal This often remains unnoticed until the first attempt is made to use something critical i
125. new and delete are not implemented attempting to use them will cause the linker to complain about undefined external references This could perhaps be fixed Some of the supplied include files are not C safe i e they need to be wrapped into extern C This could certainly be fixed too Exceptions are not supported Since exceptions are enabled by default in the C frontend they explicitly need to be turned off using no exceptions in the compiler options Failing this the linker will complain about an undefined external reference to gxx personality 510 Constructors and destructors are supported though including global ones When programming C in space and runtime sensitive environments like microcon trollers extra care should be taken to avoid unwanted side effects of the C calling conventions like implied copy constructors that could be called upon function invo cation etc These things could easily add up into a considerable amount of time and program memory wasted Thus casual inspection of the generated assembler code using the 5 compiler option seems to be warranted Back to FAQ Index Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 8 Shouldn t I initialize all my variables 67 11 8 Shouldn t initialize all my variables Global and static variables are guaranteed to be initialized to 0 by the C standard avr gcc does this by placing the appropriate co
126. not 22 14 3 Function Documentation 22 14 3 1 void eeprom read block void x 451 const void src size t 1 Read a block of __n bytes from EEPROM address __src to SRAM dst 22 14 3 2 uint8 t eeprom read byte constuint8 t x p Read one byte from EEPROM address p 22 14 3 3 uint32 t eeprom read dword const uint32_t x p Read 32 bit double word little endian from EEPROM address _ p 22 14 3 4 float eeprom read float const float p Read one float value little endian from EEPROM address p 22 14 3 5 uint16_t eeprom read word const uint16_t x p Read one 16 bit word little endian from EEPROM address p Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 2214 lt avr eeprom h gt EEPROM handling 239 22 14 3 6 void eeprom update block const void src void __dst size t _ Update a block of __n bytes to EEPROM address dst from src Note The argument order is mismatch with common functions like strcpy 22 14 3 7 void eeprom update byte uint8 uint8 t value Update a byte __ value to EEPROM address p 22 14 3 8 void eeprom update dword uint32_t uint32 t value Update 32 bit double word value to EEPROM address p 22 14 3 9 void eeprom update float float float value Update a float value to EEPROM address p 22 14 3 10 void eeprom update word uint16_t x p uintl6 t value Update a word value to EEPRO
127. on sleep but all peripheral clocks are still running and then call s1eep mode This macro automatically sets the sleep enable bit goes to sleep and clears the sleep enable bit Example include lt avr sleep h gt set_sleep_mode lt mode gt sleep_mode Note that unless your purpose is to completely lock the CPU until a hardware reset interrupts need to be enabled before going to sleep As the sleep_mode macro might cause race conditions in some situations the individual steps of manipulating the sleep enable SE bit and actually issuing the SLEEP instruction are provided in the macros sleep_enable sleep_disable and sleep_cpu This also allows for test and sleep scenarios that take care of not missing the interrupt that will awake the device from sleep Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 24 lt avr sleep h gt Power Management and Sleep Modes 300 Example include lt avr interrupt h gt include lt avr sleep h gt set sleep mode mode cli if some condition sleep enable sei sleep cpu sleep disable sei This sequence ensures an atomic test of some condition with interrupts being dis abled If the condition is met sleep mode will be prepared and the SLEEP instruction will be scheduled immediately after an SEI instruction As the intruction right after the SEI is guaranteed to be executed before an interr
128. or when recursively calling function Note The pictures shown in this document represent typical situations where the RAM locations refer to an ATmegal28 The memory addresses used are not displayed in a linear scale LI 1 SP t RAMEND 0x10FF OxFFFF E external RAM 0x0100 on board RAM __brkval lt __malloc_margin gt malloc heap start __heap_start bss end data bss start data start Figure 1 RAM map of a device with internal RAM Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 32 Internal vs external RAM 19 On a simple device like a microcontroller it is a challenge to implement a dynamic memory allocator that is simple enough so the code size requirements will remain low yet powerful enough to avoid unnecessary memory fragmentation and to get it all done with reasonably few CPU cycles Microcontrollers are often low on space and also run at much lower speeds than the typical PC these days The memory allocator implemented in avr libc tries to cope with all of these con straints and offers some tuning options that can be used if there are more resources available than in the default configuration 3 2 Internal vs external RAM Obviously the constraints are much harder to satisfy in the default configuration where only internal RAM is available Extreme care must be taken to avoid a stack heap collision both by making sure f
129. program space Parameters 51 A pointer to the first string in SRAM 52 A far pointer to the second string in Flash Returns The strcmp PF function returns an integer less than equal to or greater than zero if 81 is found respectively to be less than to match or be greater than 52 The contents of RAMPZ SFR are undefined when the function returns 22 19 4 18 char x P char dest P src The strcpy P function is similar to strcpy except that src is a pointer to a string in program space Returns The strcpy P function returns a pointer to the destination string dest Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 283 22 19 4 19 char x PF char x dst uint farptr tsrc Duplicate a string The strcpy_PF function is similar to strcpy except that src is a far pointer to a string in program space Parameters dst pointer to the destination string in SRAM src A far pointer to the source string in Flash Returns The strcpy PF function returns a pointer to the destination string dst The con tents of RAMPZ SFR are undefined when the funcion returns 22 19 4 20 size tstrcspn P const char s P reject The strcspn P function calculates the length of the initial segment of s which consists entirely of characters not in reject This fun
130. receive the controller status RS signal clear and one to send or receive data to from the controller s SRAM RS asserted macros are provided that build on the mentioned function primitives Finally macros are provided for all the controller commands to allow them to be used symbolically The HD44780 datasheet explains these basic functions of the controller in more detail 22 39 3 4 hd44780 c This is the implementation of the low level HD44780 LCD controller driver On top a few preprocessor glueing tricks are used to establish symbolic access to the hardware port pins the LCD controller is attached to based on the application s definitions made in defines h The h 44780 pulse e function asserts a short pulse to the controller s E en able pin Since reading back the data asserted by the LCD controller needs to be performed while E is active this function reads and returns the input data if the param eter readback is true When called with a compile time constant parameter that is false the compiler will completely eliminate the unused readback operation as well as the return value as part of its optimizations As the controller is used in 4 bit interface mode all byte IO to from the controller needs to be handled as two nibble IOs The functions hd44780_outnibble and hd44780_innibble implement this They do not belong to the public interface so they are declared static Generated on Thu May 19 2011 13 29 12
131. reuse your assembler language parts it is useful to define them as macros and put them into include files AVR Libc comes with a bunch of them which could be found in the directory avr include Using such include files may produce compiler warnings if they are used in modules which are compiled in strict ANSI mode To avoid that you can write instead of asm and volatile instead of volatile These are equivalent aliases Another problem with reused macros arises if you are using labels In such cases you may make use of the special pattern which is replaced by a unique number on each asm statement The following code had been taken from avr include iomacros h define loop until bit is clear port bit asm volatile N L sbic 0 1 n t N rjmp L N no outputs x I SFR IO ADDR port I bit When used for the first time L_ may be translated to L_1404 the next usage might create 1405 or whatever In any case the labels became unique too Another option is to use Unix assembler style numeric labels They are explained in How do I trace an assembler file in avr gdb The above example would then look like define loop until bit is clear port bit asm volatile abies 0 1 rjmp 1b no outputs x I SFR IO ADDR port I bit 7 6 C Stub Functions Macro definitions will include the same assembler code whenever they are referenced This may n
132. same assembler instruction mnemonics as you d use with any other AVR assembler And you can write as many assembler statements into one code string as you like and your flash memory is able to hold Note The available assembler directives vary from one assembler to another To make it more readable you should put each statement on a seperate line asm volatile nop n t nop n t nop n t nop n t 22 linefeed and tab characters will make the assembler listing generated by the com piler more readable It may look a bit odd for the first time but that s the way the compiler creates it s own assembler code You may also make use of some special registers Symbol Register SREG Status register at address Ox3F e SPH Stack pointer high byte at address OX3E _ SPL Stack pointer low byte at address 0x3D tmp reg Register rO used for temporary storage zero reg Register r1 always zero Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 3 Input and Output Operands 42 Register rO may be freely used by your assembler code and need not be restored at the end of your code It s a good idea to use tmp reg and zero reg instead of rO or r1 just in case a new compiler version changes the register usage definitions 7 3 Input and Output Operands Each input and output operand is described by a constraint string followed by a C expression in parantheses
133. sbic _ IO ADDR PORTD SQUARE rjmp 1f sbi SFR IO ADDR PORTD SQUARE rjmp 2f cbi SFR IO ADDR PORTD SQUARE out SFR IO ADDR SREG intsav reti ioinit sbi SFR IO ADDR DDRD SQUARE ldi work BV TOIEO out _ IO ADDR TIMSK work ldi work _BV CS00 tmr0 CK 1 out _SFR_IO_ADDR TCCRO work ldi work 256 tmconst Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 6 3 Example program 35 out SFR IO ADDR ICNTO work sei ret global _ vector default Note 10 vector default reti end Note 1 AS in C programs this includes the central processor specific file containing the IO port definitions for the device Note that not all include files can be included into assembler sources Note 2 Assignment of registers to symbolic names used locally Another option would be to use a C preprocessor macro instead define work 16 Note 3 Our bit number for the square wave output Note that the right hand side consists of a CPP macro which will be substituted by its value 6 in this case before actually being passed to the assembler Note 4 The assembler uses integer operations in the host defined integer size 32 bits or longer when evaluating expressions This is in contrast to the C compiler that uses the C type int by default in order to calculate constant integer expressions In order to get a 100 kHz output we need to toggle the PD6 line 200000 ti
134. section in the ELF file will get its values from the initial variable assignment ONLY This means that you can NOT assign values to this variable in functions and the new values will not be put into the ELF fuse section The global variable is declared in the FUSES macro has two leading underscores which means that it is reserved for the implementation meaning the library so it will not conflict with a user named variable You must initialize ALL fields in the fuse t structure This is because the fuse bits in all bytes default to a logical 1 meaning unprogrammed Normal uninitialized data defaults to all locgial zeros So it is vital that all fuse bytes are initialized even with default data If they are not then the fuse bits may not programmed to the desired settings Be sure to have the mmcu device flag in your compile command line and your linker command line to have the correct device selected and to have the correct I O header file included when you include lt avr io h gt You can print out the contents of the fuse section in the ELF file by using this command line avr objdump s j fuse ELF file The section contents shows the address on the left then the data going from lower address to a higher address left to right 22 16 lt avr interrupt h gt Interrupts Global manipulation of the interrupt flag The global interrupt flag is maintained in the I bit of the status register SREG Handling interrupts freq
135. selected and to have the correct I O header file included when you include lt avr io h gt You can print out the contents of the lock section in the ELF file by using this command line avr objdump s j lock ELF file 22 19 lt avr pgmspace h gt Program Space Utilities Defines define PROGMEM __ATTR_PROGMEM__ define PSTR s const PROGMEM char x s define read byte near address short LPM uint16 t address short define read word near address short LPM_word uint16_t address_ short define read dword near address short LPM_dword uint16_t address_ short define read float near address short LPM float uintl6 t address short define read byte far address long ELPM uint32 t address long define pgm read word far address long ELPM word uint32 t address long Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 271 define read dword far address long ELPM dword uint32 t address long define read float far address long ELPM float uint32 t address long define pgm_read_byte address_short pgm_read_byte_near address_short define pgm_read_word address_short pgm_read_word_near address_short define pgm_read_dword address_short pgm_read_dword_near address_short define pgm_read_float address_short pgm_read_float_near address_short define
136. size t char strpbrk P const char s PGM P accept ATTR_PURE PGM P strrchr_P PGM_P int __ val char strsep P char sp PGM P delim size tstrspn P const char s PGM P accept _ ATTR_PURE char strstr P const char PGM P ATTR PURE char strtok P char s P _ delim char strtok_rP char s PGM P delim char last size t strlen PF uint_farptr_t src size t strnlen_PF uint farptr t src size t len void memcpy PF void dest farptr t src size t len char strcpy PF char dest uint_farptr_t src char strncpy_PF char dest farptr t src size t len char strcat PF char dest uint_farptr_t src size tstrlcat PF char dst farptr t src size_t siz char strncat PF char dest farptr t src size t len int stremp_PF const char s1 uint_farptr_t s2 _ ATTR_PURE int strncmp PF const char s1 uint_farptr_t s2 size tn PURE int strcasecmp PF const char s1 152 PURE int strncasecmp PF const char s1 uint_farptr_t s2 size tn ATTR_PURE_ char strstr PF const char 51 farptr t 52 size t strlcpy PF char dst farptr t src size t siz int memcmp PF const void farptr t size_t _ ATTR_PURE Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Ref
137. space Returns The strspn_P function returns the number of characters in the initial segment of s which consist only of characters from accept The terminating zero is not considered as a part of string 22 19 4 41 char x strstr_P const char s P s2 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 291 Locate a substring The strstr_P function finds the first occurrence of the substring s2 in the string s1 The terminating 0 characters are not compared The strstr_P function is similar to strstr except that s2 is pointer to a string in program space Returns The strstr_P function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of zero length the function returns s1 22 19 4 42 char x strstr PF const char 57 uint_farptr_t s2 Locate a substring The strstr_PF function finds the first occurrence of the substring s2 in the string 51 The terminating 0 characters are not compared The strstr_PF function is similar to strstr except that s2 is a far pointer to a string in program space Returns The strstr_PF function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of zero length the function returns s1 The contents of RAMPZ SFR are undefined when the func tion retur
138. space at the cost of a slightly increased execution time mtiny stack Change only the low 8 bits of the stack pointer mno tablejump Deprecated use no jump tables instead e mshort calls Use rjmp rcall limited range on gt 8K devices On avr2 and avr4 architec tures less than 8 KB or flash memory this is always the case On avr3 and avr5 architectures calls and jumps to targets outside the current function will by default use jmp call instructions that can cover the entire address range but that require more flash ROM and execution time nrtl Dump the internal compilation result called RTL into comments in the generated assembler code Used for debugging avr gcc e msize Dump the address size and relative cost of each statement into comments in the gen erated assembler code Used for debugging avr gcc e mdeb Generate lots of debugging information to stderr 13 1 2 Selected general compiler options The following general gcc options might be of some interest to AVR users On Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 115 Optimization level n Increasing n is meant to optimize more an optimization level of O means no optimization at all which is the default if no O option is present The special option Os is meant to turn on all 02 optimizations that are not expected to increase code size Note th
139. src Here character means byte these functions do not work with wide or multi byte characters Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 220 Returns The strchr function returns a pointer to the matched character or NULL if the character is not found 22 11 3 16 char x strchrnul const char x s intc The strchrnul function is like strchr except that if c is not found in s then it returns a pointer to the null byte at the end of s rather than NULL Glibc GNU extension Returns The strchrnul function returns a pointer to the matched character or a pointer to the null byte at the end of s i e s str len s if the character is not found 22 11 3 17 int strcmp const char 57 const char 52 Compare two strings The strcmp function compares the two strings s1 and s2 Returns The strcmp function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcmp is that if s1 is an initial substring of 52 then 51 is considered to be less than 52 22 11 3 18 char x strcpy char dest const char src Copy a string The strcpy function copies the string pointed to by src including the terminating 0 character to the array pointed to by dest The strings may not overlap and the destination stri
140. strncpy function is similar to strcpy except that not more than n bytes of src are copied Thus if there is no null byte among the first n bytes of src the result will not be null terminated In the case where the length of src is less than that of n the remainder of dest will be padded with nulls Returns The strncpy function returns a pointer to the destination string dest 22 19 4 34 char PF char x dst uint farptr t src size tn Duplicate a string until a limited length The strncpy_PF function is similar to strcpy PF except that not more than n bytes of src are copied Thus if there is no null byte among the first n bytes of src the result will not be null terminated In the case where the length of src is less than that of n the remainder of dst will be padded with nulls Parameters dst A pointer to the destination string in SRAM src far pointer to the source string in Flash n The maximum number of bytes to copy Returns The strncpy PF function returns a pointer to the destination string dst The con tents of RAMPZ SFR are undefined when the function returns 22 19 4 35 size tstrnlen P P src size t len Determine the length of a fixed size string Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 289 The strnlen function is similar to strnlen
141. that ATOMIC FORCEON is only used when it is known that interrupts are enabled before the block s execution or when the side effects of enabling global interrupts at the block s completion are known and understood 22 27 2 3 define ATOMIC RESTORESTATE This is a possible parameter for ATOMIC BLOCK When used it will cause the ATOMIC BLOCK to restore the previous state of the SREG register saved before the Global Interrupt Status flag bit was disabled The net effect of this is to make the ATOMIC BLOCK s contents guaranteed atomic without changing the state of the Global Interrupt Status flag when execution of the block completes 22 27 2 4 define NONATOMIC BLOCK type Creates a block of code that is executed non atomically Upon entering the block the Global Interrupt Status flag in SREG is enabled and disabled upon exiting the block from any exit path This is useful when nested inside ATOMIC BLOCK sections allowing for non atomic execution of small Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 28 util crc16 h CRC Computations 310 blocks of code while maintaining the atomic access of the other sections of the parent ATOMIC BLOCK Two possible macro parameters are permitted NONATOMIC RESTORESTATE and NONATOMIC FORCEOFF 22 27 2 5 define NONATOMIC FORCEOFF This is a possible parameter for NONATOMIC BLOCK When used it will cause the NONATOMIC BLOCK to force the state of the SREG register on exit
142. the compiler work with the wrong value but the assembler code does too The C program may have modified the value too but the compiler didn t update the memory location for optimization reasons The worst thing you can do in this case is uint8 t s asm volatile in 0 SREG TANNET WoT i ld tmp reg al TAXE inc tmp reg MANET st al tmp reg out SREG 0 sash aa eat amp r s e ptr memory The special clobber memory informs the compiler that the assembler code may mod ify any memory location It forces the compiler to update all variables for which the contents are currently held in a register before executing the assembler code And of course everything has to be reloaded again after this code In most situations a much better solution would be to declare the pointer destination itself volatile volatile uint8 t ptr This way the compiler expects the value pointed to by ptr to be changed and will load it whenever used and store it whenever modified Situations in which you need clobbers are very rare In most cases there will be better ways Clobbered registers will force the compiler to store their values before and reload them after your assembler code Avoiding clobbers gives the compiler more freedom while optimizing your code Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 5 Assembler Macros 49 7 5 Assembler Macros In order to
143. the given memory area Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 217 22 11 3 6 int memcmp const void s1 const void 52 size t len Compare memory areas The function compares the first len bytes of the memory areas sl and 52 The comparision is performed using unsigned char operations Returns The memcmp function returns an integer less than equal to or greater than zero if the first len bytes of 51 is found respectively to be less than to match or be greater than the first len bytes of s2 Note Be sure to store the result in a 16 bit variable since you may get incorrect results if you use an unsigned char or char due to truncation Warning This function is not mint8 compatible although if you only care about testing for equality this function should be safe to use 22 11 3 7 void memcpy void dest const void src size t len Copy a memory area The memcpy function copies len bytes from memory area src to memory area dest The memory areas may not overlap Use memmove if the memory areas do overlap Returns The memcpy function returns a pointer to dest 22 11 3 8 void x memmem const void s7 size t lenl const void 52 size t len2 The memmem function finds the start of the first occurrence of the substring 52 of length 1en2 in the memory area s1 of length 1en1 Returns The memmem functi
144. the open source AVR toolchain available to many users Rich Neswold for writing the original avr tools document which he graciously allowed to be merged into this document and his improvements to the demo project Theodore A Roth for having been a long time maintainer of many of the tools AVR Libc the AVR port of GDB AVaRICE uisp avrdude All the people who currently maintain the tools and or have submitted sugges tions patches and bug reports See the AUTHORS files of the various tools And lastly all the users who use the software If nobody used the software we would probably not be very motivated to continue to develop it Keep those bug reports coming 17 Todo List Group avr boot From email with Marek On smaller devices all except ATmega64 128 __SPM_REG is in the I O space accessible with the shorter in and out in structions since the boot loader has a limited size this could be an important optimization 18 Deprecated List Global cbi port bit Global enable external int mask Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 19 Module Index 128 Global inb port Global inp port Global INTERRUPT signame Global ISR ALIAS vector target vector For new code the use of ISR ISR ALIASOF is recommended Global outb port val Global outp val port Global sbi port bit Global SIGNAL vector Do not use SIGNAL in new code Use ISR instead
145. to build avr libc in MinGW http downloads sourceforge net mingw msysDTK 1 0 1 exe use mirror internap gt Single file installer executable Install autoconf 2 59 from the MSYS Developer Toolkit release autoconf 2 59 2 60 is needed to build avr libc in MinGW http downloads sourceforge net mingw msys autoconf 2 59 tar bz2 use mirror internap gt Extract to c msys 1 0 automake 1 8 2 automake 1 8 1 9 is needed to build avr libc in MinGW http downloads sourceforge net mingw msys automake 1 8 2 tar bz2 use mirror internap gt Extract to c msys 1 0 Install Cygwin Install everything all users UNIX line endings This will take a xlongx time A fat internet pipe is highly recommended It is also recommended that you download all to a directory first and then install from that directory to your machine Note GMP is a prequisite for building MPFR Build GMP first Build GMP for MinGW Version 4 2 3 lt http gmplib org gt Build script configure 2 gt amp 1 make 2 gt amp 1 make check 2 gt amp 1 make install 2 gt amp 1 tee gmp configure log tee gmp make log tee gmp make check log tee gmp make install log GMP headers will be installed under usr local include and library installed under usr local lib Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 12 Tools Required for Building the Toolchain for Windows 100
146. to develop software for the AVR It takes many tools working together Collectively the group of tools are called a toolset or commonly a toolchain as the tools are chained together to produce the final executable application for the AVR microcontroller The following sections provide an overview of all of these tools You may be used to cross compilers that provide everything with a GUI front end and not know what goes on underneath the hood You may be coming from a desktop or server computer Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen HIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS MPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE RE DISCLAIMED IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE UBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS NTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN ONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE 2 2 FSF and GNU 13 background and not used to embedded systems Or you may be just learning about the most common software development toolchain available on Unix and Linux systems Hopefully the following overview will be helpful in putting everything in perspective 2 2 FSFand GNU According to its website the Free Software Foundation FSF established in 1985 is dedica
147. to perform a soft Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1132 using floating point math Why is the compiled code so big Why does my code not work 86 reset include avr wdt h define soft reset do enable WDTO_15MS for while 0 PO PO AO OE Vu For newer AVRs such as the ATmega1281 also add this function to your code to then disable the watchdog after a reset e g after a soft reset include avr wdt h Function Pototype void wdt_init void __attribute__ naked __attribute__ section init3 Function Implementation void wdt_init void MCUSR 0 wdt disable return Back to FAQ Index 11 32 lam using floating point math Why is the compiled code so big Why does my code not work You are not linking in the math library from AVR LibC GCC has a library that is used for floating point operations but it is not optimized for the AVR and so it generates big code or it could be incorrect This can happen even when you are not using any floating point math functions from the Standard C library but you are just doing floating point math operations When you link in the math library from AVR LibC those routines get replaced by hand optimized AVR assembly and it produces much smaller code See I get undefined reference to for functions like sin for more details on how to link in the math library Generat
148. used in each of the sections the stab and stabstr sections hold the debugging information and won t make it into the ROM file An even more useful option is S This option disassembles the binary file and inter sperses the source code in the output This method is much better in my opinion than using the 5 with the compiler because this listing includes routines from the libraries and the vector table contents Also all the fix ups have been satisfied In other words the listing generated by this option reflects the actual code that the processor will run avr objdump h S demo elf demo lst Here s the output as saved in demo 1st file demo elf file format elf32 avr Sections Idx Name Size VMA LMA File off Algn 0 text 000000ca 00000000 00000000 00000074 2xx1 CONTENTS ALLOC LOAD READONLY CODE 1 00000003 00800060 00800060 0000013 2 0 ALLOC 2 debug aranges 00000020 00000000 00000000 0000013e 2xx0 CONTENTS READONLY DEBUGGING 3 debug pubnames 00000035 00000000 00000000 0000015 2xx0 CONTENTS READONLY DEBUGGING 4 debug info 00000108 00000000 00000000 00000193 2xx0 CONTENTS READONLY DEBUGGING 5 debug abbrev 000000cf 00000000 00000000 00000295 2 0 CONTENTS READONLY DEBUGGING 6 debug line 00000165 00000000 00000000 0000036a 2xx0 CONTENTS READONLY DEBUGGING 7 debug frame 00000040 00000000 00000000 000004d0 2 2 Generated on Thu May 19 2011
149. using a special form of the asm statement unsigned long value asm clock 3686400 This statement instructs the compiler to use the symbol name clock rather than value This makes sense only for external or static variables because local variables do not have symbolic names in the assembler code However local variables may be held in registers With AVR GCC you can specify the use of a specific register Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 8 Links 51 void Count void register unsigned char counter asm r3 some code asm volatile clr r3 more code The assembler instruction clr r3 will clear the variable counter AVR GCC will not completely reserve the specified register If the optimizer recognizes that the vari able will not be referenced any longer the register may be re used But the compiler is not able to check wether this register usage conflicts with any predefined register If you reserve too many registers in this way the compiler may even run out of registers during code generation In order to change the name of a function you need a prototype declaration because the compiler will not accept the asm keyword in the function definition extern long Calc void asm CALCULATE Calling the function Calc will create assembler instructions to call the function CALCULATE 7 8 Links For a more thorough discussion of inline assembly usage see the
150. util twi h gt TWI bit mask definitions 321 22 32 2 18 22 32 2 19 22 32 2 20 22 32 2221 22 32 2 22 22 32 2 23 22 32 2 24 22 32 2 25 22 32 2 26 22 32 2 27 define TW_SR_DATA_NACK 0x88 data received NACK returned define TW_SR_GCALL_ACK 0x70 general call received ACK returned define TW_SR_GCALL_DATA_ACK 0x90 general call data received ACK returned define TW_SR_GCALL_DATA_NACK 0x98 general call data received NACK returned define TW_SR_SLA_ACK 0x60 SLA W received ACK returned define TW_SR_STOP 0xA0 stop or repeated start condition received while selected define TW_ST_ARB_LOST_SLA_ACK 0xB0 arbitration lost in SLA RW SLA R received ACK returned define TW ST DATA ACK 0xB8 data transmitted ACK received define TW ST DATA NACK 0xC0 data transmitted NACK received define TW ST LAST DATA 0xC8 last data byte transmitted ACK received Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 33 lt compat deprecated h gt Deprecated items 322 22 32 2 28 TW ST SLA 0xA8 SLA R received ACK returned 22 32 2 29 TW START 0x08 start condition transmitted 22 32 2 30 TW STATUS TWSR amp TW STATUS MASK TWSR masked by TW STATUS MASK 22 32 2 31 define TW STATUS MASK Value BV TWS7 _BV TWS6 _BV TWS5 _BV TWS4 BV TWS3 The lower 3 bits of TWSR are reserved on the ATmegal63 The 2
151. values ie a bit returned as 0 means the corresponding fuse or lock bit is programmed 22 12 2 5 define boot page erase address boot page erase normal address Erase the flash page that contains address Note address is a byte address in flash not a word address 22 12 2 6 define boot page erase safe address Value do boot spm busy wait X eeprom busy wait boot_page_erase address while 0 Same as boot page erase except it waits for eeprom and spm operations to complete before erasing the page Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 12 avr boot h Bootloader Support Utilities 232 22 12 2 7 define boot page fill address data boot page fill normal address data Fill the bootloader temporary page buffer for flash address with data word Note The address is a byte address The data is a word The AVR writes data to the buffer a word at a time but addresses the buffer per byte So increment your address by 2 between calls and send 2 data bytes in a word format The LSB of the data is written to the lower address the MSB of the data is written to the higher address 22 12 2 8 define boot page fill safe address Value do boot spm busy wait X eeprom busy wait N boot page fill address data N while 0 Same as boot page fill except it waits for eeprom and spm operations to complete before filling the page
152. version tar gz tar xf cd avarice lt version gt mkdir obj avr Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 11 Building and Installing under Windows 97 cd obj avr configure prefix PREFIX make make install Note AVaRICE uses the BFD library for accessing various binary file formats You may need to tell the configure script where to find the lib and headers for the link to work This is usually done by invoking the configure script like this Replace hdr path with the path to the bfa h file on your system Replace 1ib path with the path to 1ibbfd a on your system CPPFLAGS I hdr path LDFLAGS L lib path configure prefix PREFIX 12 11 Building and Installing under Windows Building and installing the toolchain under Windows requires more effort because all of the tools required for building and the programs themselves are mainly designed for running under a POSIX environment such as Unix and Linux Windows does not natively provide such an environment There are two projects available that provide such an environment Cygwin and MinG W MSYS There are advantages and disadvantages to both Cygwin provides a very complete POSIX environment that allows one to build many Linux based tools from source with very little or no source modifications However POSIX functionality is provided in the form of a DLL that is linked to the application This DLL has to be r
153. which in turn automatically includes the individual I O header file and the lt avr fuse h gt file These other two files provides everything necessary to set the AVR fuses Fuse API Each I O header file must define the FUSE MEMORY SIZE macro which is defined to the number of fuse bytes that exist in the AVR device A new type fuse t is defined as a structure The number of fields in this structure are determined by the number of fuse bytes in the FUSE MEMORY SIZE macro If FUSE MEMORY SIZE 1 there is only a single field byte of type unsigned char If FUSE MEMORY SIZE 2 there are two fields low and high of type unsigned char If FUSE MEMORY SIZE 3 there are three fields low high and extended of type unsigned char If FUSE MEMORY SIZE gt 3 there is a single field byte which is an array of unsigned char with the size of the array being FUSE MEMORY SIZE Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 15 lt avr fuse h gt Fuse Support 241 A convenience macro FUSEMEM is defined as a GCC attribute for a custom named section of fuse A convenience macro FUSES is defined that declares a variable fuse of type fuse t with the attribute defined by FUSEMEM This variable allows the end user to easily set the fuse data Note If a device specific I O header file has previously defined FUSEMEM then FUSE MEM is not redefined If a device specific I O header file has
154. x rodatax gnu linkonce dx 0x0000000000800060 0x0000000000800060 0x0000000000800060 bss 0x0000000000800060 0x0000000000800060 bss bss 0x0000000000800060 bss 0x0000000000800063 ar bss o x bssx COMMON 0x0000000000800063 0x00000000000000ca data 0x00000000000000ca start SIZEOF data PROVIDE bss end load start LOADADDR data load end data load Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 342 noinit 0x0000000000800063 0x0 0x0000000000800063 PROVIDE noinit start noinit x 0x0000000000800063 PROVIDE noinit end 0x0000000000800063 end 0x0000000000800063 PROVIDE J heap start eeprom 0x0000000000810000 0x0 x eeprom x 0x0000000000810000 eeprom end The last address in the text segment is location 0x114 denoted by etext so the instructions use up 276 bytes of FLASH The data segment where initialized static variables are stored starts at location 0x 60 which is the first address after the register bank on an ATmega8 processor The next available address in the data segment is also location 0x60 so the application has no initialized data The bss segment where uninitialized data is stored starts at location 0x 60 The next available address in the bss segment is location 0x63 so the application uses 3 bytes of uninitialized data The eeprom segment where EEPROM va
155. yet and no program memory space is wasted if this feature is not used There should be no need to modify linker scripts anymore except for some very spe cial cases It is best to leave stack at its default value end of internal SRAM faster and required on some devices like ATmegal61 because of errata and add W1l Tdata 0x801100 to start the data section above the stack For more information on using sections see Memory Sections There is also an ex ample for Using Sections in C Code Note that in C code any such function would preferably be placed into section init3 as the code in init2 ensures the internal register zero reg is already cleared Back to FAQ Index 11 6 Whatis all this _BV stuff about When performing low level output work which is a very central point in microcon troller programming it is quite common that a particular bit needs to be set or cleared in some IO register While the device documentation provides mnemonic names for the various bits in the IO registers and the AVR device specific IO definitions reflect these names in definitions for numerical constants a way is needed to convert a bit number usually within a byte register into a byte value that can be assigned directly to the register However sometimes the direct bit numbers are needed as well e g in an SBI instruction so the definitions cannot usefully be made as byte values in the first place So in order to access
156. you want to store your data in Program Memory Use the PROGMEM macro found in lt avr pgmspace h gt and put it after the declaration of the variable but before the initializer like so finclude avr pgmspace h unsigned char mydata 11 10 PROGMEM 0x00 0x01 0 02 0x03 0x04 0 05 0 06 0 07 0 08 0 09 Ox0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D Ox1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F 0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 Ox5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D That s it Now your data is in the Program Space You can compile link and check the map file to verify that mydata is placed in the correct section Now that your data resides in the Program Space your code to access read the data will no longer work The code that gets generated will retrieve the data that is located at the address of the mydata array plus offsets indexed by the i and j variables However the final address that is calculated where to the retrieve the data points to the Data Space Not the Program Space where the data is actually located It is likely that you will be retr
157. 0 ANSI C standard as well as parts of their successor ISO IEC 9899 1999 C99 Some additions have been inspired by other standards like IEEE Std 1003 1 1988 POSIX 1 while other extensions are purely AVR specific like the entire program space string interface Unless otherwise noted functions of this library are not guaranteed to be reentrant In particular any functions that store local state are known to be non reentrant as well as functions that manipulate IO registers like the EEPROM access routines If these functions are used within both standard and interrupt contexts undefined behaviour will result See the FAQ for a more detailed discussion Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 3 Supported Devices 3 1 3 Supported Devices The following is a list of AVR devices currently supported by the library Note that actual support for some newer devices depends on the ability of the compiler assembler to support these devices at library compile time megaAVR Devices atmega 103 atmega 128 atmega1280 atmega1281 atmega1284p atmega16 atmegal61 atmega162 atmega 163 atmegal64a atmegal64p atmega 165 atmegal65a atmega165p atmega 168 atmegal68a atmegal68p atmegal6a atmega2560 atmega2561 atmega32 atmega323 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 3 Supported Devices atmega324a atmega324p atmega324pa a
158. 00 this can only be done by agreeing on a set of registers to be used exclusively inside the interrupt routine there would not be any other chance to save a register anywhere If the interrupt routine is to be linked together with C modules care must be taken to follow the register usage guidelines imposed by the C compiler Also any register modified inside the interrupt sevice needs to be saved usually on the stack Note 10 As explained in Interrupts a global catch all interrupt handler that gets all unassigned interrupt vectors can be installed using the name _ vector default This must be global and obviously should end in a reti instruction By default a jump to location 0 would be implied instead 6 4 Pseudo ops and operators The available pseudo ops in the assembler are described in the GNU assembler gas manual The manual can be found online as part of the current binutils release under http sources redhat com binutils As gas comes from a Unix origin its pseudo op and overall assembler syntax is slightly different than the one being used by other assemblers Numeric constants follow the C notation prefix for hexadecimal constants expressions use a C like syntax Some common pseudo ops include byte allocates single byte constants e ascii allocates a non terminated string of characters asciz allocates a VO terminated string of characters C string e data switches to the data section initia
159. 1 AVR HAVE MUL 1 AVR 2 BYTE PC 2 avr5 PBS AVR ARCH 5 PBS Enhanced CPU AVR MEGA 5 core 16 KB to 64 KB of AVR ENHANCED 5 ROM AVR HAVE JMP CALL 4 AVR HAVE MOVW I AVR HAVE LPMX 1 AVR HAVE MUL 11 AVR 2 BYTE PC 2 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 108 avr51 PBS AVR ARCH 51 PBS Enhanced AVR MEGA _ 5 core 128 KB of ROM _ AVR ENHANCED 5 AVR HAVE JMP CALL 4 AVR HAVE 1 AVR HAVE LPMX 1 AVR HAVE MUL 1 AVR HAVE RAMPZ 41 AVR HAVE ELPM 4 AVR HAVE ELPMX 4 AVR 2 BYTE PC 2 avr6 2 PBS AVR ARCH 6 PBS Enhanced CPU AVR MEGA 5 core 256 KB of ROM _ AVR ENHANCED 5 AVR HAVE JMP CALL 4 AVR HAVE 1 AVR HAVE LPMX 1 AVR HAVE MUL 1 AVR HAVE RAMPZ 141 AVR HAVE ELPM 4 AVR HAVE ELPMX 4 AVR 3 BYTE PC 2 1 New in GCC 42 2 Unofficial patch for GCC 4 1 3 New in GCC 4 2 3 4 New in GCC 4 3 5 Obsolete By default code is generated for the avr2 architecture Note that when only using mmcu architecture but no mmcu MCU type including the file lt avr io h gt cannot work since it cannot decide which device s definitions to select e mncu MCU type The following MCU types are currently understood by avr gcc The table matches them against the corresponding avr gcc architecture name an
160. 1 crc ibutton update util crc 311 crc xmodem update util crc 312 delay loop 1 util delay basic 313 delay loop 2 util delay basic 313 A more sophisticated project 345 A simple project 330 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 417 abort avr stdlib 203 abs avr stdlib 203 acos avr math 160 acosf avr math 155 Additional notes from lt avr sfr_defs h gt 293 alloca alloca 134 asin avr math 160 asinf avr math 155 assert avr assert 135 assert h 367 atan avr math 160 atan2 avr math 161 atan2f avr math 155 atanf avr math 155 atof avr stdlib 203 atoi avr_stdlib 204 atoi S 367 atol avr_stdlib 204 atol S 367 atomic h 367 ATOMIC_BLOCK util_atomic 308 ATOMIC_FORCEON util_atomic 308 ATOMIC_RESTORESTATE util_atomic 308 avr_assert assert 135 avr_boot boot_is_spm_interrupt 229 boot_lock_bits_set 229 boot_lock_bits_set_safe 229 boot_lock_fuse_bits_get 229 boot_page_erase 230 boot_page_erase_safe 230 boot_page_fill 230 boot_page_fill_safe 231 boot_page_write 231 boot_page_write_safe 231 boot_rww_busy 231 boot_rww_enable 232 boot_rww_enable_safe 232 boot_signature_byte_get 232 boot_spm_busy 232 boot_spm_busy_wait 233 boot_spm_interrupt_disable 233 boot_spm_interrupt_enable 233 BOOTLOADER_SECTION 233 GET EXTENDED FUSE BITS 233 GET HIGH FUSE BITS 233 GET BITS
161. 1 PI avr math 158 M 2 PI avr math 158 M 2 SORTPI avr math 158 ME avr math 158 M LNIO avr math 158 M LN2 avr math 158 M LOGIOE avr math 158 M LOG2E avr math 158 M PI avr math 158 M PI 2 avr math 159 M PI 4 avr math 159 M SQRTI 2 avr math 159 M SQRT2 avr math 159 malloc avr stdlib 207 math h 380 memccpy avr string 215 memccpy S 384 memccpy P avr pgmspace 276 memchr avr string 215 memchr S 384 memchr P avr pgmspace 276 memchr PS 384 memcmp avr_string 215 mememp S 384 memcmp_P avr_pgmspace 277 memcemp PS 384 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 430 memcmp PF avr pgmspace 277 memcmp PES 384 memcpy avr string 216 memcpy S 384 memcpy P avr pgmspace 277 memcpy_P S 384 PF avr pgmspace 278 memmem avr string 216 memmem S 384 memmem P avr pgmspace 278 memmove avr string 216 memmove S 384 memrchr avr string 217 memrchr S 384 memrchr P avr pgmspace 278 memrchr 5 384 memset avr string 217 memset S 384 modf avr math 164 avr math 164 NAN avr math 159 NONATOMIC BLOCK util atomic 308 NONATOMIC FORCEOFF util atomic 309 NONATOMIC RESTORESTATE util atomic 309 outb deprecated items 324 outp deprecated items 324 parity h 384 parity even bit util parity 314 pgm get far address pgmspace h 395 PGM P avr pgmspace 272 pgm read
162. 1 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 210 22 10 4 21 long random void The random function computes a sequence of pseudo random integers in the range of 0 to RANDOM MAX as defined by the header file lt stdlib h gt The srandom function sets its argument seed as the seed for a new sequence of pseudo random numbers to be returned by rand These sequences are repeatable by calling srandom with the same seed value If no seed value is provided the functions are automatically seeded with a value of 1 22 10 4 22 longrandom unsigned long _ ctx Variant of random that stores the context in the user supplied variable located at ctx instead of a static library variable so the function becomes re entrant 22 10 4 23 void realloc void ptr size t size The realloc function tries to change the size of the region allocated at pt x to the new size value It returns a pointer to the new region The returned pointer might be the same as the old pointer or a pointer to a completely different region The contents of the returned region up to either the old or the new size value whatever is less will be identical to the contents of the old region even in case a new region had to be allocated It is acceptable to pass ptr as NULL in which case realloc will behave identical to malloc If the new memory cannot be allocated realloc returns NULL and the region at pt
163. 11 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 290 Locate character in string The strrchr_P function returns a pointer to the last occurrence of the character val in the flash string s Returns The strrchr P function returns a pointer to the matched character or NULL if the character is not found 22 19 4 39 char x strsep P char xx sp P Parse a string into tokens The strsep_P function locates in the string referenced by the first occurrence of any character in the string delim or the terminating 0 character and replaces it with a 707 The location of the next character after the delimiter character or NULL if the end of the string was reached is stored in sp An empty field i e one caused by two adjacent delimiter characters can be detected by comparing the location referenced by the pointer returned in sp to 0 This function is similar to strsep except that delim is a pointer to a string in program space Returns The strsep_P function returns a pointer to the original value of If is initially NULL strsep P returns NULL 22 19 4 40 size tstrspn P const char s P accept The strspn_P function calculates the length of the initial segment of s which consists entirely of characters in accept This function is similar to strspn except that accept is a pointer to a string in program
164. 11 13 29 12 for avr libc by Doxygen 24 43 stdlib h File Reference 405 Non standard i e non ISO C functions define RANDOM MAX Ox7FFFFFFF char itoa int val char __s int radix char Itoa long int val char s int radix char unsigned int __val char x__s int radix char ultoa unsigned long int __ val char __s int __radix long random void void srandom unsigned long __seed long random unsigned long __ctx Conversion functions for double arguments Note that these functions are not located in the default library 1ibc a but in the mathematical library 1ibm a So when linking the application the 1m option needs to be specified define DTOSTR ALWAYS SIGN 0x01 define DTOSTR PLUS SIGN 0x02 define DTOSTR_UPPERCASE 0x04 char dtostre double val char s unsigned char prec unsigned char flags char dtostrf double __ val signed char __ width unsigned char __ prec char S Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 43 stdlib h File Reference 406 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 44 strcasecmp S File Reference 407 24 43 1 Detailed Description 24 44 strcasecmp S File Reference 24 44 1 Detailed Description 24 45 strcasecmp_P S File Reference 24 45 1 Detailed Description 2446 5 File Reference 24 46 1 Detailed Description 2447 strcat S File Refe
165. 13 29 12 for avr libc by Doxygen 22 37 Asimple project 337 CONTENTS READONLY DEBUGGING 8 debug str 000000cc 00000000 00000000 00000510 2xx0 CONTENTS READONLY DEBUGGING 9 debug pubtypes 0000002b 00000000 00000000 000005dc 2 0 CONTENTS READONLY DEBUGGING Disassembly of section text 00000000 ctors end 0 10 eO 101 r17 0x00 0 2 a0 e6 ldi r26 0x60 96 4 50 eO ldi r27 0x00 0 6 01 cO rjmp 2 Oxa do clear bss start 00000008 do clear bss loop 8 TA 92 St Xt 0000000a do clear bss start a a3 36 cpi r26 0x63 99 e bl 07 r27 17 e el 7 brne 8 0x8 do clear bss loop 00000010 vector 8 include iocompat h x Note 1 x enum UP DOWN ISR TIMER1 OVF x Note 2 x 10 Le 92 push rl 12 Of 92 push 14 Of b6 in rir Ox3f 63 16 Of 92 push 18 11 24 eor rl rl lac 2f 93 push r18 ler BF 3 push r24 le 9f 93 push r25 static uintl16 t pwm Note static uint8 t direction switch direction x Note 4 20 80 91 60 00 145 r24 0x0060 24 88 23 and r24 r24 26 b9 f4 brne 46 0x56 lt __SREG__ 0x17 gt case UP if pwm TOP 28 80 91 61 00 145 r24 0x0061 2c 90 91 62 00 145 r25 0x0062 30 01 96 adiw r24 0x01 1 32 90 93 62 00 sts 0x0062 r25 36 80 93 61 00 sts 0x0061 r24 3a 23 ldi r18 0x03 3 36s Bf B cpi r24 OxFF 255 3e 92 07 Cpe 25 tle 40 9 0 b
166. 2 Tx ATmega640 ATmegal280 ATmegal281 TX vect USART2 Complete ATmega2560 ATmega2561 TRANS USART2_ SIG_ USART2 Data ATmega640 ATmegal280 ATmegal28l UDRE vect USART2 register Empty ATmega2560 ATmega2561 DATA USART3 SIG USART3 Rx ATmega640 ATmegal280 ATmegal28l RX vect USART3 Complete ATmega2560 ATmega2561 RECV USART3_ SIG_ USART3 Tx ATmega640 ATmegal280 ATmegal281 TX vect USART3 Complete ATmega2560 ATmega2561 TRANS USARIS3 SIG USART3 Data ATmega640 ATmegal280 ATmegal28l UDRE vect USART3 register Empty ATmega2560 ATmega2561 DATA USART SIG USART Rx ATmegal6 ATmega32 ATmega323 AT RXC vect USART Complete mega8 RECV SIG UART RECV USART SIG USART Rx AT90PWM3 AT90PWM2 AT90PWMI vect USART Complete ATmegal68P ATmega3250 ATmega3250P RECV SIG ATmega328P ATmega3290 ATmega3290P UART RECV ATmega48P ATmega6450 ATmega6490 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATtiny2313 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 262 USART_ SIG_ USART Tx ATmegal6 ATmega32 ATmega323 AT TXC_vect USART_ Complete mega8 TRANS SIG_UART_ TRANS USART TX SIG USART Tx AT9OPWM3 AT90PWM2 AT90PWMI vect USART Complete ATmegal68P ATmega328P ATmega48P TRANS ATmega8535 ATmega88P ATmegal68 SIG_UART_ ATmega48 ATmega88 ATtin
167. 2 10 3 Typedef Documentation 22 10 3 1 typedef int compar fn t const void const void Comparision function type for qsort just for convenience 22 10 4 Function Documentation 22 10 4 1 void abort void The abort function causes abnormal program termination to occur This realization disables interrupts and jumps to _exit function with argument equal to 1 In the limited AVR environment execution is effectively halted by entering an infinite loop 22 10 4 2 intabs int i The abs function computes the absolute value of the integer i Note The abs and labs functions are builtins of gcc Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 205 22 10 4 3 double atof const char x nptr The atof function converts the initial portion of the string pointed to by nptr to double representation It is equivalent to calling strtod nptr char xx 0 22 10 4 4 int atoi const char s Convert a string to an integer The atoi function converts the initial portion of the string pointed to by s to integer representation In contrast to int strtol s char NULL 10 this function does not detect overflow errno is not changed and the result value is not predictable uses smaller memory flash and stack and works more quickly 22 10 4 5 long atol const char s Convert a string to a long integer The atol function con
168. 2 6 3 Function Documentation 22 6 3 1 double acos double x The alias for sinh The alias for sqrt The alias for square The alias for tan The alias for tanh The alias for trunc The acos function computes the principal value of the arc cosine of __x The returned value is in the range 0 pi radians A domain error occurs for arguments not in the range 1 1 22 6 3 2 doubleasin double x The asin function computes the principal value of the arc sine of __x The returned value is in the range pi 2 pi 2 radians A domain error occurs for arguments not in the range 1 1 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 162 22 6 3 3 double atan double x The atan function computes the principal value of the arc tangent of __x The returned value is in the range pi 2 pi 2 radians 22 6 3 4 double atan2 double y double x The atan2 function computes the principal value of the arc tangent of __y x using the signs of both arguments to determine the quadrant of the return value The returned value is in the range pi pi radians 22 6 3 5 double cbrt double x The cbrt function returns the cube root of x 22 6 3 6 double double x The ceil function returns the smallest integral value greater than or equal to __x expressed as a floating point number 22 6 3 7 static double copysign dou
169. 2 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 259 TIMER4 SIG_INPUT_ Timer Counter4 ATmega640 ATmegal280 ATmegal281 CAPT_vect CAPTURE4 Capture Event ATmega2560 ATmega2561 TIMER4 SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPA vect OUTPUT_ Compare Match ATmega2560 ATmega2561 COMPARE4A A TIMER4_ SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal28l COMPB vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARE4B B TIMER4_ SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal28l COMPC vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPAREAC C TIMER4_ SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal28l OVF vect OVERFLOW4 Overflow ATmega2560 ATmega2561 TIMERS SIG INPUT Timer Counter5 ATmega640 ATmegal280 ATmegal28l CAPT vect CAPTURES Capture Event ATmega2560 ATmega2561 TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal28l vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARESA A TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal28l COMPB vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARESB B TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal28l COMPC vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARESC TIMERS_ SIG_ Timer Counter5 ATmega640 ATmegal280 ATmegal28l OVF_vect OVERFLOW5 Overflow ATmega2560 ATmega25
170. 22 11 3 1 int ffs int val This function finds the first least significant bit set in the input value Returns The ffs function returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 2211 lt string h gt Strings 216 Note For expressions that are constant at compile time consider using the FFS macro instead 22 11 3 2 intffsl long val Same as ffs for an argument of type long 22 11 3 3 intffsll long long val Same as ffs for an argument of type long long 22 11 3 4 void memccpy void dest const void src int val size t len Copy memory area The memccpy function copies no more than len bytes from memory area src to memory area dest stopping when the character val is found Returns The memccpy function returns a pointer to the next character in dest after val or NULL if val was not found in the first Len characters of src 22 11 3 5 void memchr const void src int val size t len Scan memory for a character The memchr function scans the first len bytes of the memory area pointed to by src for the character val The first byte to match val interpreted as an unsigned character stops the operation Returns The memchr function returns a pointer to the matching byte or NULL if the character does not occur in
171. 22 12 2 9 define boot page write address boot page write normal address Write the bootloader temporary page buffer to flash page that contains address Note address is a byte address in flash not a word address 22 12 2 10 define boot page write safe address Value do boot spm busy wait eeprom_busy_wait boot_page_write address while 0 Same as boot page write except it waits for eeprom and spm operations to complete before writing the page Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 12 avr boot h Bootloader Support Utilities 233 22 12 2 11 define boot rww bus SPM REG amp uint8 t BV COMMON ASB Check if the RWW section is busy 22 12 2 12 define boot rww enable boot rww enable Enable the Read While Write memory section 22 12 2 13 define boot rww enable safe Value do boot spm busy wait N eeprom busy wait boot rww enable N while 0 Same as boot enable except waits for eeprom and spm operations to complete before enabling the RWW mameory 22 12 2 14 define boot signature byte get addr Value QL extension X uint8 t _ result asm__ _ volatile X N sts 1 2 n t N lpm 0 Z n t N r result N i SFR MEM ADDR SPM REG X r uint8 t SIGROW READ X 2 uintl16 t addr N result N Read the Signature
172. 22 36 2 A code walkthrough 22 36 2 1 asmdemo c After the usual include files two variables are defined The first one incoming is used to communicate the most recent pulse width detected by the incoming PWM decoder up to the main loop The second variable actually only constitutes of a single bit intbits pwm received This bit will be set whenever the incoming PWM decoder has updated incoming Both variables are marked volatile to ensure their readers will always pick up an up dated value as both variables will be set by interrupt service routines The function ioinit initializes the microcontroller peripheral devices In partic ular it starts timer 0 to generate the outgoing PWM signal on OCOB Setting OCROA to 255 which is the TOP value of timer 0 is used to generate a timer 0 overflow A interrupt on the ATtiny13 This interrupt is used to inform the incoming PWM decoder that the counting direction of channel 0 is just changing from up to down Likewise an overflow interrupt will be generated whenever the countdown reached BOTTOM value 0 where the counter will again alter its counting direction to upwards This informa tion is needed in order to know whether the current counter value of TCNTO is to be evaluated from bottom or top Further ioinit activates the pin change interrupt PCINTO on any edge of PB4 Finally PB1 OCOB will be activated as an output pin and global interrupts are being enabled In
173. 22 8 3 20 typedef uint32 t uint fast32 t fastest unsigned int with at least 32 bits 22 8 3 21 typedef uint64 t uint fast64 t fastest unsigned int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect 22 8 3 22 typedef uint8 t uint fast8 t fastest unsigned int with at least 8 bits 22 8 3 23 typedef uintl6 tuint least16 t unsigned int with at least 16 bits 22 8 3 24 typedef uint32 t uint least32 t unsigned int with at least 32 bits Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 182 22 8 3 25 typedef uint64 t uint least64 t unsigned int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect 22 8 3 26 typedef uint8 t uint least8 t unsigned int with at least 8 bits 22 8 3 27 typedef uint64 t uintmax t largest unsigned int available 22 8 3 28 typedef uintl6 t uintptr t Unsigned pointer compatible type 22 9 lt stdio h gt Standard IO facilities Defines define FILE struct file define stdin __iob 0 define stdout __iob 1 define stderr __iob 2 define EOF 1 define fdev_set_udata stream u do stream gt udata u while 0 define fdev get udata stream stream gt udata define fdev setup stream stream put get rwflag define FDEV SETUP READ SRD define FDEV SETUP WRITE SWR define FDEV SETUP RW S
174. 24 48strcat PS File Reference 406 24 48 1 Detailed Description 406 24 49strchr 5 File Referenc mm RR ERREUR 406 24 49 1 Detailed Description 406 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen CONTENTS x 24 5056 PS File Reference o o occ ac ooo o RR 406 24 50 1 Detailed Description sss m Res 406 24 51 strebrnul 5 File Reference 22 2 2 gt 406 251 1 Detailed Descrplian se e 44 052 56 n RR eee FG 406 24 52strchmrnul PS File Reference 406 2452 1 Detailed Descripfion 2222225 Se ee 406 24 So step File Reference lt oom bp wo m 9 sS 406 2454 1 Detailed Description s uoo RR ORE EET 406 24 54stremp_P S File Reference 406 24 54 1 Detailed Description 406 24 55 strepy S Pile Reference 2 22 22 406 2455 1 Detailed Description oso c ceram rar a 406 24 565trepy_P 5 File Reference s a co oc oso o ba o x ko m RB Rd 406 24 56 1 Detailed Description 406 24 57sbespn s File Reference lt o esu go Roo 406 24 51 1 Detaded Description iud Rxo 406 24 S8strcspn FS Pile Reference o cg oo snye a xr EUR 406 24 58 1 Detailed Description soc saora inie m x n Gn 406 24 595dup 6 Pile Befeven e 2 s e Rot og aa E 406 24 59 1 Detailed D seriptiod 407 24 00st np h File Referenc
175. 2_C value _ CONCAT value L Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 173 define UINT32_C value CONCAT value UL define INT64_C value _ CONCAT value LL define UINT64_C value _ CONCAT value ULL define INTMAX_C value _ CONCAT value LL define UINTMAX_C value CONCAT value ULL 22 8 1 Detailed Description include stdint h Use u intN t if you need exactly N bits Since these typedefs are mandated by the C99 standard they are preferred over rolling your own typedefs 22 8 2 Define Documentation 22 8 2 define INT16_C value value define a constant of type int16_t 22 8 2 2 ftdefine 6 MAX 0x7fff largest positive value an int16 t can hold 22 8 2 3 define 6 MIN 16 MAX 1 smallest negative value an int16 t can hold 22 8 2 4 define INT32 C value _CONCAT value L define a constant of type int32 t 22 8 2 5 define INT32 MAX Ox7fffffffL largest positive value an int32 t can hold 22 8 2 6 define INT32 MIN INT32 MAX IL smallest negative value an int32 t can hold Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 174 22 8 2 7 define INT64 C value CONCAT value LL define a constant of type int64 t 22 8 2 8 define INT64 OXx 7fffffffffffffffLL largest positive value an int64 t can hold
176. 3 91 Adewothbctunct oHR 22 coo 222 222 54 82 Nia IUDCHOHS voulu RR RR RR RC UR RR E 56 10 Porting From IAR to AVR GCC 56 IDI Introduction mene neee 56 lied gamma a mesne 57 10 3 Interrupt Service Routines 8 5 58 10 4 Intrinsic Routines 2 2222 222 2 58 10 3 Vanables 222252555 Rx C EE Fus eos 59 10 6 Non Returgmmg mun i2 x ERG 60 107 Lockie Registers suo ea e la i 5 REA ERG 60 11 Frequently Asked Questions 61 MAMI sl mp 61 11 2 My program doesn t recognize a variable updated within an interrupt op EM 62 11 3 I get undefined reference to for functions like sin 63 11 4 How to permanently bind a variable to a register 63 11 5 How to modify MCUCR or WDTCR early 63 11 6 Whatisallthis _BVQ stuff about 64 11 7 use C AVR 65 11 8 Shouldn t I initialize all my variables 66 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen CONTENTS iii 11 9 Why do some 16 bit timer registers sometimes get trashed 66 11 10How do I use a define d constant in an asm statement 67 11 11 Why does the PC randomly jump around when single stepping through my programi Wad Br s RS 68 11 12How do I trace an assembler file in avr gdb 68 11 13How do I pass an IO port as a parameter to a function 70
177. 4 asm volatile sts 0 1 n t spm n t word Oxffff n t nop n t i _SFR_MEM_ADDR __SPM_REG r uint8 t PAGE ERASE 2 uintl16 t address 24 5 2 4 define boot page erase extended address extension asm volatile movw r30 A3 n t sts I sC3 n t sts 0 2 n t Vw PE n E POP AO a gO a an an an an an an a an a an an a an a a Value Value Value Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 5 boot h File Reference 372 spm n t su i SFR_MEM_ADDR __SPM_REG SFR MEM ADDR RAMPZ 2 uint8_t __BOOT_PAGE_ERASE Tac uint32 t address r r30 r31 DA LE LM AV V LE 24 5 2 5 boot page erase normal address Value extension N asm volatile N N sts 0 SLANE N spm n t i SFR MEM ADDR 5 REG N r uint8 t BOOT PAGE ERASE N z uintl16 t address N 24 5 2 6 define boot page fill alternate address data Value extension 4 N asm volatile N N movw r0 3 n t N sts 0 SLAME N spm n t word Oxffff n t nop n t ele N i SFR MEM ADDR SPM REG N r uint8 t BOOT PAGE FILL N 2 uintl16 t address N r uintl6 t data N N 24 5 2 7 define boot page fill extended address
178. 40 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USBI62 9005 82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 INT6_vect SIG_ INTERRUPT6 External Interrupt Request 6 AT90CANI28 AT90CAN32 ATOOCAN64 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USBI62 9005 82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 INT7 vect SIG INTERRUPT7 External Interrupt Request 7 AT90CANI28 AT90CAN32 AT90CANGA4 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmega1280 ATmegal281 ATmega2560 AT mega2561 AT90USBI62 9005 82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 IO PINS vect SIG PIN SIG PIN CHANGE External Interrupt Request 0 ATtiny11 ATtiny12 ATtiny15 ATtiny26 LCD_vect SIG_LCD LCD Stat of Frame ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega3290P ATmega649 ATmega6490 LOWLEVEL IO PINS vect SIG PIN Low level Input on Port B ATtiny28 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 avr interrupt h Interrupts 252 OVRIT vect SIG CAN CAN Timer AT90CANI28 AT90CAN32 AT90CAN64 OVERFLOWI Overrun PCINTO vect SIG PIN Pin Change Inter ATmegal62 ATmegal65 ATmegal65P CHANGEO rupt Request 0 ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATm
179. 422255 a The ssc spa ee moo RR Using Sections in Assembler Code sine Sections in C Code s soa mion ona oko RR RR Data in Program Space s 5 2 5 3 5 4 A5 ido E ec ea hod mana epena Storing and Retrieving Data the Program 5 Storing and Retrieving Strings in the Program Space e s 21 22 22 22 23 23 23 25 25 26 CONTENTS ii 6 avr libc and assembler programs 31 IntfodHODON 2 2 oe ea omo om e 9 PS e RN 31 6 2 Invoking tbecompuef 6 obse RE 55 ERA 32 03 Example program 022 o i dew Bor Ue 33 6 4 Pseudo ops operators 36 Inline Assembler Cookbook 37 GCC i o s ul e 38 JAssemblert ode suu lg k O xS do RUE Ss 40 7 3 InputandOutputOperands 41 TA Iul ERU RUE RR Rx RS 46 22 uou Roue 48 TO PICHONS onu Ens 48 7 1 C Names Used in Assembler Code 49 Tae LUNES mo pepa 50 How to Build a Library 50 SI Inoduchol RU S 50 82 How the Linker Woks a 4p ERR 51 83 How to D signa Library s s mms 51 BA Creating LIBE 2124 E GRO RE g 52 Usme a Libary 2202 22 22 odo OS Red o i A 53 Benchmarks 5
180. 5 1 Detailed Description suo RR pa e ela aa 388 24 35 2 Define Documentation lt 2 244425586 24 04 24465 388 24 30powerrPue Reference uu oo v Rot OE RR i lt 396 24 36 1 Detailed Description 396 24 37setbaudh File Reference oco ok RR ERREUR 396 24 37 1 Detailed Description lt lt lt a som m Rs 397 24 38setjmp h File Reference o s o o RES 397 24 38 1 Detailed Description 397 24 39 sipnature h Pile Reference coss RR ee 397 2439 1 Detailed Description se lt s sso to ee 4 397 24 40sleep h Pile 222 22 22 2 397 24 40 1 Detailed Description 397 244 stdint b File Reference wc ke ce 22229222 2224 52 397 2141 1 Detailed Description 401 24 A425tdio h File 2 22 2 22 401 24 42 1 Detailed Description sso RR GR 402 24 A43stdhb h File Reference 22 22 2 402 2443 1 Detailed Description son a ERR 406 24 44strcasecmp S File Reference 406 24 44 1 Detailed Description 406 24 45 PS File Reference 406 24 45 1 Detailed Description s yc 406 24 46sticasestr s Pile Reference 4 4 cb a u oo RR 406 24 46 1 Detailed Description 406 24 4 9 File Reference o ma o m o go xS X 406 2147 1 Detailed Description 406
181. 5MS 22 26 2 0 define WDTO 30MS 1 See WDTO 15MS 22 26 2 10 define WDTO 458 See WDTO 15MS Note This is only available on the AT tiny2313 ATtiny24 ATtiny44 ATtiny84 ATtiny84A ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmega48P ATmega88P ATmegal68P ATmega328P ATmegal64P ATmega324P ATmega644P ATmega644 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega8HVA ATmegal6HVA ATmega32HVB ATmega406 ATmega1284P ATO0PWMI AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 AT90PWMB81 AT90PWM161 9005 82 AT90USB162 AT90USB646 AT90USB647 9005 1286 AT90USB 1287 ATtiny48 ATtiny88 22 26 2 11 define WDTO_500MS 5 See WDTO 15MS 22 26 2 12 define WDTO 60MS 2 WDTO 15MS 22 26 2 13 WDTO 85 9 See WDTO 15MS Note This is only available on the ATtiny2313 ATtiny24 ATtiny44 ATtiny84 ATtiny84A ATtiny25 ATtiny45 AT tiny85 ATtiny261 ATtiny461 ATtiny861 ATmega48 ATmega48A ATmega48PA ATmega88 ATmegal68 ATmega48P ATmega88P ATmegal68P ATmega328P AT megal64P ATmega324P ATmega644P ATmega644 ATmega640 ATmegal280 AT megal281 ATmega2560 ATmega2561 ATmega8HVA ATmegal6HVA ATmega32HVB ATmega406 ATmegal284P ATOOPWMI AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 AT90PWMB81 AT90PWM161 AT90USB82 AT90USB 162 AT90USB646 AT90USB647 AT90USB1286 AT9OUSB 1287 48 ATtiny88
182. 61 B ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 ATtiny48 ATtiny261 ATtiny46l AT tiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMERO SIG Timer Counter0 AT90PWM3 AT90PWM2 AT90PWM1 COMP_A_ OUTPUT_ Compare Match vect COMPAREOA A SIG OUTPUT COMPARED A TIMERO SIG Timer Counter0 90 128 AT90CAN32 ATOOCAN64 COMP_vect OUTPUT_ Compare Match ATmegal03 ATmegal28 ATmegal6 AT COMPAREO megal61 ATmegal62 ATmegal65 AT megal65P ATmegal69 ATmegal69P AT mega32 ATmega323 ATmega325 AT mega3250 ATmega3250P ATmega329 AT mega3290 ATmega3290P ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmega8515 ATmega8535 TIMERO_ SIG_ Timer Counter0 419052313 9052323 AT90S2343 AT OVFO vect OVERFLOWO Overflow tiny22 ATtiny26 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 255 TIMERO_ OVF_vect SIG_ OVERFLOWO Timer Counter0 Overflow AT90S1200 AT908S4433 9052333 9054434 9054414 AT90S8515 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega32
183. 61 TWI_vect SIG_2WIRE_ 2 wire Serial In AT90CANI28 AT90CAN32 AT90CANG6A SERIAL terface ATmegal28 ATmegal284P ATmegal6 ATmegal63 ATmegal68P ATmega32 AT mega323 ATmega328P ATmega32HVB ATmega406 ATmega48P ATmega64 ATmega8 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny48 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TXDONE_ SIG_ Transmission AT86RF401 vect TXDONE Done Bit Timer Flag 2 Interrupt TXEMPTY_ SIG_TXBE Transmit Buffer AT86RF401 vect Empty Bit Itmer Flag 0 Interrupt UARTO RX SIG UARTO Rx ATmegal61 vect UARTO Complete RECV UARTO TX SIG UARTO Tx ATmegal6l vect UARTO Complete TRANS UARTO SIG UARTO Data ATmegal6l UDRE vect UARTO Register Empty DATA UARTI SIG UARTI Rx ATmegal l vect UARTI Complete RECV Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 2216 lt avr interrupt h gt Interrupts 260 UARTI TX SIG UARTI Tx ATmegal6l vect UARTI Complete TRANS UARTI SIG UARTI Data ATmegal6l UDRE vect UARTI Register Empty DATA UART RX SIG UART UART Rx Com AT90S2313 419052333 419054414 vect RECV plete AT90S4433 9054434 419058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_TX_ SIG_UART_ UART Tx Com A190S2313 419052333
184. 6450 ATmega6490 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny48 PCINT vect SIG PIN ATtiny2313 ATtiny261 ATtiny461 AT CHANGE tiny861 SIG PCINT PSCO SIG PSCO PSCO Capture AT90PWM3 AT90PWM2 AT90PWM1 CAPT vect CAPTURE Event PSCO EC SIG PSCO PSCO End Cycle AT90PWM3 AT90PWM2 AT90PWM1 vect END_CYCLE PSCI SIG PSCI PSC1 Capture AT90PWM3 AT90PWM2 AT90PWM1 CAPT vect CAPTURE Event 5 EC SIG PSCI PSC1 End Cycle AT90PWM3 AT90PWM2 AT90PWM1 vect END_CYCLE PSC2_ SIG_PSC2_ PSC2 Capture AT90PWM3 AT90PWM2 AT90PWM1 vect CAPTURE Event Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 253 PSC2_EC_ vect SIG_PSC2_ END_CYCLE PSC2 End Cycle AT90PWM3 AT90PWM2 AT90PWM1 SPI_STC_vect SIG_SPI Serial Transfer Complete AT9082333 9054434 AT90S4414 9058515 9054433 9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWMS3 AT90PWM2 AT90PWMI 90 128 AT90CAN32 ATOOCAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 A
185. 7 r28 r29 May be allocated by gcc for local data Calling C subroutines leaves them un changed Assembler subroutines are responsible for saving and restoring these registers if changed r29 r28 Y pointer is used as a frame pointer points to local data on stack if necessary The requirement for the callee to save preserve the contents of these registers even applies in situations where the compiler as signs them for argument passing Fixed registers r0 r1 Never allocated by gcc for local data but often used for fixed purposes Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 15 How do I put an array of strings completely in ROM 74 rO temporary register can be clobbered by any C code except interrupt handlers which save it may be used to remember something for a while within one piece of assembler code rl assumed to be always zero in any code be used to remember something for a while within one piece of assembler code but must then be cleared after use clr r1 This includes any use of the mul s u instructions which return their result in rl r0 Interrupt handlers save and clear r1 on entry and restore r1 on exit in case it was non zero Function call conventions Arguments allocated left to right r25 to r8 All arguments are aligned to start in even numbered registers odd sized arguments including char have one free register above them This allows making bett
186. 72 1088 978 1088 978 s 6 0 Stack bytes 17 17 MCU clocks 1313 1152 dtostrf 1 2345 Flash bytes 1676 1564 1548 1438 1548 1438 15 6 s Stack bytes 36 36 MCU clocks 1608 1443 itoa 12345 s Flash bytes 150 150 134 134 134 134 10 Stack bytes 4 4 MCU clocks 1172 1152 Itoa 12345L s Flash bytes 220 220 200 200 200 200 10 Stack bytes 9 9 MCU clocks 3174 3136 malloc 1 Flash bytes 554 554 506 506 506 506 Stack bytes 4 4 MCU clocks 196 178 realloc void Flash bytes 1152 1040 1042 932 1042 932 0 1 Stack bytes 20 20 MCU clocks 303 280 qsort s Flash bytes 1242 1130 990 880 1008 898 sizeof s 1 cmp Stack bytes 38 38 MCU clocks 20914 16678 sprintf min s Flash bytes 1216 1104 1090 980 1086 976 d 12345 Stack bytes 59 59 MCU clocks 1846 1711 sprintf s Flash bytes 1674 1562 1542 1432 1498 1388 12345 Stack bytes 58 58 MCU clocks 1610 1528 sprintf fit s Flash bytes 3334 3222 3084 2974 3040 2930 e 1 2345 Stack bytes 66 66 MCU clocks 2513 2297 sscanf min Flash bytes 1540 1428 1354 1244 1354 1244 12345 Stack bytes 55 55 amp i MCU clocks 1339 1240 sscanf 12345 Flash bytes 1950 1838 1704 1594 1704 1594 amp i Stack bytes 53 53 MCU clocks 1334 1235 sscanf Flash bytes 1950 1838 1704 1594 1704 1594 point color Stack bytes 87 87 a z s MCU clocks 2878 2718 sscanf flt Flash bytes 3298 3186 2934
187. 8 _ AVR ATmega48 avr4 atmega48a AVR ATmega48A avr4 atmega48pa AVR ATmega48PA avr4 atmega48p AVR ATmega48P avr4 atmega8 AVR ATmega8 avr4 atmega8515 __AVR_ATmega8515__ avr4 atmega8535 __AVR_ATmega8535__ avr4 atmega88 AVR ATmega88 avr4 atmega88a AVR ATmega88A avr4 atmega88p AVR ATmega88P avr4 atmega88pa __AVR_ATmega88PA__ avr4 atmega8hva __AVR_ATmega8HVA__ avr4 at90pwml AVR_AT90PWM1__ avr4 at90pwm2 _ AVR_AT90PWM2__ avr4 at90pwm2b AVR ATO0OPWMOB avr4 at90pwm3 AVR AT90OPWM3 avr4 at90pwm3b AVR AT90PWMS3B avr4 at90pwm81 AVR AT90PWMSI avr5 at90can32 AVR ATO0OCAN32 avr5 at90can64 AVR_AT90CAN64__ avr5 at90pwm161 AVR AT90PWMI61 avr5 at90pwm216 AVR 216 avr5 at90pwm316 __AVR_AT90PWM316__ avr5 at90scr100 AVR AT9O0SCR100 avr5 at90usb646 AVR AT90USB646 avr5 at90usb647 AT90USB647 avr5 at94k AVR_AT94K avr5 atmegal6 __AVR_ATmegal6__ avr5 atmegal61 AVR ATmegal6l avr5 atmegal62 __AVR_ATmegal62__ avr5 atmega163 AVR ATmegal63 avr5 atmegal 64a __AVR_ATmegal64A__ avr5 atmegal64p AVR ATmegal64P avr5 atmega165 AVR ATmegal65 avr5 atmegal65a __AVR_ATmegal65A__ avr5 atmegal65p __AVR_ATmegal65P__ avr5 atmega168 AVR ATmegal68 avr5 atmegal 68a AVR ATmegal68A Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 111
188. 85 11 33 What pitfalls exist when writing reentrant 86 11 34 Why are some addresses of the EEPROM corrupted usually address 1 coke ee eee 88 11 35 Why is my baud rate wrong 89 11 360n a device with more than 128 of flash how to make function portes WORT sa s ga AUREUS 89 12 Building and Installing the GNU Tool Chain 90 12 1 Building and Installing under Linux FreeBSD and Others 90 122 Tabs lt tuos eee rS SERM ees 91 12 3 Optional Wools s se aoe E og rig a id Ret ER RUE s 91 12 4 GNU Binutils for the 92 12 5 GCC forthe AVR target scu m RR RR RR ooo 93 120 AVR LI ze 94 127 AVRDUDE AG Mae a 94 12 8 GDB forthe AVR tatget a occo os omo o xe 9 om md 95 128 SUAVE nek s Rem GE E eR RS Ee E 95 TZ WANS e eee 95 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen CONTENTS iv 12 11Building and Installing under Windows 12 12Tools Required for Building the Toolchain for Windows 12 13Building the Toolchain for Windows 13 Using the GNU tools 13 1 Options for the compiler 13 1 1 Machine specific options for the AVR 13 1 2 Selected general compiler options 13 2 Options for the assembler
189. 8P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtinyll ATtiny12 ATtiny15 ATtiny2313 ATtiny28 ATtiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90OUSB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER1_ CAPTI vect SIG INPUT CAPTURE1 Timer Counter1 Capture Event AT90S2313 TIMERI CAPT vect SIG INPUT CAPTUREI Timer Counter Capture Event 419052333 9054434 AT9084414 9058515 9054433 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWMS3 AT90PWM2 AT90PWMI 90 128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 ATtiny48 AT90USBI62 9005 82 AT90USB1287 AT90USB1286
190. 9 12 for avr libc by Doxygen 22 37 Asimple project 344 MCU_TARGET atmegal69 MCU_TARGET atmegal69p MCU_TARGET atmega2560 MCU_TARGET atmega2561 MCU_TARGET atmega32 MCU_TARGET atmega324p MCU_TARGET atmega325 MCU_TARGET atmega3250 MCU_TARGET atmega329 MCU_TARGET atmega3290 MCU_TARGET atmega48 MCU_TARGET atmega64 MCU_TARGET atmega640 MCU_TARGET atmega644 MCU_TARGET atmega644p MCU_TARGET atmega645 MCU_TARGET atmega6450 MCU_TARGET atmega649 MCU_TARGET atmega6490 MCU_TARGET atmega8 MCU_TARGET atmega8515 MCU_TARGET atmega8535 MCU_TARGET atmega88 MCU_TARGET attiny2313 MCU_TARGET attiny24 MCU_TARGET attiny25 MCU_TARGET attiny26 MCU_TARGET attiny26 MCU_TARGET attiny44 MCU_TARGET attiny45 MCU_TARGET attiny46 MCU_TARGET attiny84 MCU_TARGET attiny85 MCU_TARGET attiny86 OPTIMIZE 02 DEF S LIBS You should not have to change anything below here CC avr gcc Override is only needed by avr lib build system override CFLAGS g Wall OPTIMIZE mmcu TARGET DEFS override LDFLAGS W1 Map PRG map OBJCOPY avr objcopy OBJDUMP avr objdump all PRG elf lst text eeprom PRG elf 5 OBJ CC CFLAGS LDFLAGS o 8 LIBS dependency Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 345 demo o demo c iocompat h clean r
191. 90s2333 at90s2343 219054414 at90s4433 at90s4434 at90s8515 at90c8534 at90s8535 Note 1 Assembly only There is no direct support for these devices to be programmed in C since they do not have a RAM based stack Still it could be possible to program them in C see the FAQ for an option Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 4 avr libc License 11 Note 2 The at94K devices are a combination of FPGA and AVR microcontroller TRoth 2002 11 12 Not sure of the level of support for these More information would be welcomed Note 3 The at76c711 is a USB to fast serial interface bridge chip using an AVR core Note 4 The m3000 is a motor controller AVR ASIC from Intelligent Motion Systems IMS Schneider Electric 14 avr libc License avr libc can be freely used and redistributed provided the following license conditions are met Portions of avr libc are Copyright c 1999 2010 Werner Boellmann Dean Camera Pieter Conradie Brian Dean eith Gudger Wouter van Gulik Bjoern Haase Steinar Haugen Peter Jansen Reinhard Jessich Magnus Johansson Harald Kipp Carlos Lamas Cliff Lawson Artur Lipowski Marek Michalkiewicz Todd C Miller Rich Neswold Colin O Flynn Bob Paddock Andrey Pashchenko Reiner Patommel Florin Viorel Petrov Alexander Popov Michael Rickman Theodore A Roth Juergen Schilling Philip Soeberg Anatoly Sokolov Nils
192. A reference to that private object can be at tached to the stream e g inside the function 1cd init that then also needs to be passed a reference to the stream using set udata and can be accessed inside putchar using fdev_get_udata 22 39 3 7 uart h Public interface definition for the RS 232 UART driver much like in lcd h except there is now also a character input function available As the RS 232 input is line buffered in this example the macro RX_BUF SIZE deter mines the size of that buffer 22 39 38 uart c This implements an stdio compatible RS 232 driver using an AVR s standard UART or USART in asynchronous operation mode Both character output as well as char acter input operations are implemented Character output takes care of converting the internal newline n into its external representation carriage return line feed V r n Character input is organized as a line buffered operation that allows to minimally edit the current line until it is sent to the application when either a carriage return r or newline n character is received from the terminal The line editing functions implemented are b back space or V 177 delete deletes the previous character Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 39 Using the standard IO facilities 361 u control U ASCII NAK deletes the entire input buffer w control W ASCII ETB deletes the previous input
193. AST8 MIN 174 int fast8 t 178 INT LEASTI6 MAX 174 INT LEASTI6 MIN 174 int least16 t 179 INT LEAST8 174 INT LEASTS MIN 175 int least8 t 179 INTMAX C 175 INTMAX MAX 175 INTMAX MIN 175 intmax t 179 INTPTR MAX 175 MIN 175 intptr t 179 PTRDIFF MAX 175 PTRDIFF MIN 175 SIG ATOMIC MAX 175 SIG ATOMIC MIN 175 SIZE MAX 176 JINT16_C 176 JINT16_MAX 176 intl6_t 179 JINT32_C 176 INT32_MAX 176 int32_t 179 JINT64_C 176 JINT64_MAX 176 int64 t 179 JINTS C 176 JINT8 MAX 176 int8 t 180 JINT FAST16 176 int fastl6 t 180 JINT FAST32 MAX 177 int fast32 t 180 JINT FAST64 MAX 177 int fast64 t 180 JINT FAST8 MAX 177 int fast8 t 180 JINT LEASTI6 MAX 177 int least16 t 180 JINT LEAST32 MAX 177 int least32 t 180 JINT LEAST64 MAX 177 ECECECE CE CE CECCECCECCECC E Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 422 uint_least64_t 180 UINT LEASTS8 MAX 177 uint least8 t 181 UINTMAX 177 UINTMAX MAX 177 uintmax t 181 UINTPTR MAX 177 uintptr t 181 avr stdio _FDEV_EOF 186 FDEV ERR 186 FDEV SETUP READ 186 FDEV SETUP RW 186 FDEV SETUP WRITE 186 clearerr 189 EOF 186 fclose 189 fdev close 186 fdev_get_udata 187 fdev set udata 187 FDEV SETUP STREAM 187 setup stream 187 fdevopen 189 feof 190 ferror 190 fflush 190 fgetc 190 fgets 191 FILE 188 fprintf 191 f
194. ASTS avr inttypes 143 PRIdPTR avr inttypes 143 PRIi16 avr inttypes 143 PRIi32 avr inttypes 143 PRIi8 avr_inttypes 143 PRIiFAST16 avr_inttypes 144 PRIiFAST32 avr inttypes 144 PRIiFASTS avr inttypes 144 PRIiLEASTI6 avr inttypes 144 avr inttypes 144 printf avr stdio 192 printf P avr stdio 192 PRIo16 avr inttypes 144 PRIo32 avr inttypes 144 PRIo8 avr_inttypes 144 PRIoFASTI6 avr inttypes 145 PRIoFAST32 avr inttypes 145 PRIoFASTS avr inttypes 145 PRIoLEASTI6 avr inttypes 145 PRIoLEAST32 avr inttypes 145 PRIoLEASTS avr inttypes 145 PRIoPTR avr inttypes 145 PRIu16 avr inttypes 145 PRIu32 avr inttypes 145 PRIu8 avr inttypes 145 PRIUFAST16 avr_inttypes 146 PRIuFAST32 avr inttypes 146 PRIuFASTS avr inttypes 146 PRIULEAST16 avr_inttypes 146 PRIULEAST32 avr_inttypes 146 Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen INDEX 432 PRIuLEASTS prog 11116 t avr inttypes 146 avr pgmspace 275 PRIuPTR prog int32 t avr inttypes 146 PRIX16 avr_inttypes 146 PRIx16 avr_inttypes 146 PRIX32 avr_inttypes 147 PRIx32 avr inttypes 146 PRIX8 avr_inttypes 147 PRIx8 avr inttypes 147 PRIXFAST16 avr_inttypes 147 PRIxFAST16 avr_inttypes 147 PRIXFAST32 avr_inttypes 147 PRIxFAST32 avr_inttypes 147 PRIXFAST8 avr_inttypes 147 PRIxFAST8 avr_inttypes 147 PRIXLEAST16 avr_inttypes 148 PRIxLEASTI6 avr inttypes 147
195. AX define INT FAST32 MAX INT32 MAX Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 172 define INT FAST32 MIN INT32 MIN define UINT FAST32 MAX UINT32 MAX define INT FAST64 MAX INT64 MAX e define INT FAST64 MIN INT64 MIN define UINT FAST64 MAX UINT64 MAX Limits of integer types capable of holding object pointers define INTPTR MAX INTIG6 MAX e define INTPTR MIN INT16 MIN define UINTPTR MAX UINTI6 MAX Limits of greatest width integer types e define INTMAX MAX INT64 MAX define INTMAX MIN INT64 MIN define UINTMAX MAX UINT64 MAX Limits of other integer types C implementations should define these macros only when STDC LIMIT MACROS is defined before lt stdint h gt is included define PTRDIFF MAX INT16_MAX e define PTRDIFF MIN INT16 MIN e define SIG ATOMIC MAX INT8 MAX e define SIG ATOMIC MIN INT8 MIN define SIZE MAX CONCAT INT16 MAX U Macros for integer constants C implementations should define these macros only when STDC CONSTANT MACROS is defined before lt stdint h gt is included These definitions are valid for integer constants without suffix and for macros defined as integer constant without suffix define INT8_C value int8 t value define UINT8_C value uint8 t CONCAT value U e define INT16 C value value define UINT16_C value CONCAT value U define INT3
196. B has the pins for in system programming ISP port C has the ports for JTAG can be used for debugging and port D is used for the UART connection 22 39 2 Functional overview The project consists of the following files stdiodemo c This is the main example file defines h Contains some global defines like the LCD wiring e hd44780 c Implementation of an HD44780 LCD display driver e hd44780 h Interface declarations for the HD44780 driver 1cd c Implementation of LCD character IO on top of the HD44780 driver 1cd h Interface declarations for the LCD driver Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 39 Using the standard IO facilities 356 uart c Implementation of a character IO driver for the internal UART uart h Interface declarations for the UART driver 22 39 3 Acode walkthrough 22 39 3 1 stdiodemo c As usual include files go first While conventionally system header files those in angular brackets lt gt go before application specific header files in double quotes defines hcomes as the first header file here The main reason is that this file defines the value of F_CPU which needs to be known before including lt utils delay h gt The function ioinit summarizes all hardware initialization tasks As this function is declared to be module internal only st at ic the compiler will notice its simplic ity and with a reasonable optimization level in effect it will inl
197. CNx16 typedef int32_t int_farptr_t typedef uint32_t uint_farptr_t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 18 io h File Reference 381 24 17 1 Detailed Description 24 18 File Reference 24 18 1 Detailed Description 24 19 lock h File Reference Defines define LOCKMEM attribute section lock define LOCKBITS unsigned char lock LOCKMEM define LOCKBITS DEFAULT OxFF 24 19 1 Detailed Description 24 20 math h File Reference Defines define M E 2 7182818284590452354 define M LOG2E 1 4426950408889634074 define M LOGIOE 0 43429448190325182765 define M LN2 0 69314718055994530942 define M_LN10 2 30258509299404568402 define M_PI 3 14159265358979323846 define M PI 2 1 57079632679489661923 define M PI 4 0 78539816339744830962 define 1 PI 0 31830988618379067154 define 2 PI 0 63661977236758134308 define M 2 SORTPI 1 12837916709551257390 define SORT2 1 41421356237309504880 define M SORTI 2 0 70710678118654752440 define NAN builtin nan define INFINITY builtin inf define cosf cos define sinf sin define tanf tan define fabsf fabs define fmodf fmod define sqrtf sqrt define cbrtf cbrt define hypotf hypot Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 24 20 math h File Reference 382 define squaref square define floorf floor define ceilf ceil define frexpf frexp define ldexpf ldexp define expf
198. CR register 0x57 or 0x68 depending on device Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 22 lt avr sfr_defs h gt Special function registers 296 22 2 lt avr sfr_defs h gt Special function registers Modules Additional notes from lt avr sfr_defs h gt Bit manipulation e define_BV bit 1 lt lt bit IO register bit manipulation e define bit_is_set sfr bit SFR BYTE sfr amp BV bit e define bit is clear sfr bit SFR BYTE sfr amp BV bit define loop until bit is set sfr bit do while bit is clear sfr bit define loop until bit is clear sfr bit do while bit is set sfr bit 22 22 1 Detailed Description When working with microcontrollers many tasks usually consist of controlling internal peripherals or external peripherals that are connected to the device The entire IO address space is made available as memory mapped IO i e it can be accessed using all the MCU instructions that are applicable to normal data memory For most AVR devices the IO register space is mapped into the data memory address space with an offset of 0x20 since the bottom of this space is reserved for direct access to the MCU registers Actual SRAM is available only behind the IO register area starting at some specific address depending on the device For example the user can access memory mapped IO registers as if they were globally defined variables like this PO
199. Deprecated Write val to IO port port 22 33 2 8 define sbi port bit port 1 lt lt bit Deprecated Set bit in IO port port Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 34 compat ina90 h gt Compatibility with EWB 3 x 326 22 33 3 Function Documentation 22 33 3 1 static inline void timer enable int unsigned char ints static Deprecated This function modifies the t imsk register The value you pass via ints is device specific 22 34 lt compat ina90 h gt Compatibility with IAR EWB 3 x include compat ina90 h This is an attempt to provide some compatibility with header files that come with IAR C to make porting applications between different compilers easier No 10096 compat ibility though Note For actual documentation please see the IAR manual 22 35 Demo projects Modules Combining C and assembly source files A simple project A more sophisticated project Using the standard IO facilities Example using the two wire interface TWI 22 35 1 Detailed Description Various small demo projects are provided to illustrate several aspects of using the open source utilities for the AVR controller series It should be kept in mind that these de mos serve mainly educational purposes and are normally not directly suitable for use in any production environment Usually they have been kept as simple as sufficient to demonstrate one particular f
200. EM ADDR RAMPZ N r uint8 t BOOT PAGE WRITE N r uint32 t address N r30 r31 N 24 5 2 11 define boot page write normal address Value extension N asm volatile N N sts 0 1 n t N spm n t N i SFR MEM ADDR SPM REG N r uint8 t BOOT PAGE WRITE N 2 uintl16 t address N 24 5 2 12 define boot rww enable Value extension N asm volatile N sts 0 1 n t N Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 6 cpufunc h File Reference 375 spm n t X i SFR MEM ADDR 5 REG N r uint8 t BOOT RWW ENABLE N 24 5 2 13 define boot rww enable alternate Value extension N asm volatile N N sts 0 1 n t N spm n t X word Oxffff n t N nop n t i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT RWW ENABLE N 24 6 cpufunc h File Reference Defines define define _MemoryBarrier 24 6 1 Detailed Description 24 7 crc16 h File Reference Functions static static static static inline uintl6 t crc16 update uint16 t crc uint8 t data inline uintl6 t crc xmodem update uint16 t crc uint8 t data inline uint16_t crc ccitt update uint16 t crc uint8 t data inline uint8 t crc ibutton update uint8 t crc uint8 t data
201. G 376 24 10ecno h Fila Reference oo 4 eso ok RR ERREUR 376 24 10 1 Detailed Description 376 24 lidevopen c File Relerence 2 222 2 376 211 1 Detailed Description c e ox yox RS RR 376 28 1215 5 PIS RONCE m su BA gesla BEES eyes 376 2 12 1 Detaled DSscripBatn ss lt sp gcs si RR e ela e 376 24 131545 File Reference 2 22 cu zoo 376 2313 1 Detailed Description ocu ok og Sed ba we YS Re 376 24 File Reference ee o a 2 54 22 376 Detaled Descriptio 2222 222 22 gt 376 24 15fuse h Pile Referetice o lt oe aco cue som ee mm 376 24 15 1 Detailed Deseripti n sso Rc B gt 3T 24 16intertupt h File Reference lt ee e e es 377 2416 1 Detailed Des nipliom sss ck 377 24 T Tipttypes h Vile Reference s ci les ro XR e aR 377 24 17 1 Detailed Description s xcu 6b 9 Rn 380 24 8G Pile Refetence uou lt coo Ea UR ER RR Us 380 24 18 1 Detailed Description 4 e bas rm A ES 380 24 h Fil Reference o cocca nanru m s RUE R FG 380 24 19 1 Detailed Description 522mm 380 24 20math h File Reference sooo komo RR Rm BR 380 24 20 1 Detailed Description 384 24 linemecpy gt File Reference soon b ERREUR 384 2421 1DetalledDescripion 384 24 22menmchr S File Referenc 222222222222 m euo y 384 2221 Detailed Description sud e cxx LA Re REO 384 24 2233memchr BS Fi
202. IBC VERSION avr version 301 EEGET avr eeprom 236 EEPUT avr eeprom 236 ELPM classic pgmspace h 388 ELPM dword enhanced pgmspace h 388 ELPM dword xmega pgmspace h 388 ELPM enhanced pgmspace h 389 ELPM float enhanced pgmspace h 389 float xmega pgmspace h 390 ELPM word classic pgmspace h 390 ELPM word enhanced pgmspace h 391 ELPM word xmega pgmspace h 391 ELPM xmega pgmspace h 392 LPM classic pgmspace h 392 LPM dword classic pgmspace h 392 LPM dword enhanced pgmspace h 393 LPM enhanced pgmspace h 393 LPM float classic pgmspace h 394 LPM float enhanced pgmspace h 394 word classic pgmspace h 394 LPM word enhanced pgmspace h 395 boot lock bits set boot h 369 boot lock bits set alternate boot h 369 boot page erase alternate boot h 370 boot page erase extended boot h 370 boot page erase normal boot h 371 boot page fill alternate boot h 371 boot page fill extended boot h 371 boot page fill normal boot h 372 boot page write alternate boot h 372 boot page write extended boot h 373 boot page write normal boot h 373 boot rww enable boot h 373 boot rww enable alternate boot h 374 compar fn t avr stdlib 203 malloc heap end avr stdlib 212 malloc heap start avr stdlib 212 malloc margin avr stdlib 212 crc16 update util crc 310 ccitt update util crc 31
203. INT FAST32 MAX UINT32 MAX largest value an uint fast32 t can hold define UINT FAST64 MAX UINT64 MAX largest value an uint_fast64_t can hold define UINT FAST8 MAX UINT8 MAX largest value uint fast8 t can hold define UINT LEASTI6 UINTI6 MAX largest value an least16 t can hold define UINT LEAST32 MAX UINT32 MAX largest value an uint_least32_t can hold define UINT LEAST64 MAX UINT64 MAX largest value an uint_least64_t can hold define UINT LEAST8 UINT8 largest value an uint least8 t can hold define UINTMAX C value CONCAT value ULL define a constant of type uintmax t define UINTMAX MAX UINT64 MAX largest value an uintmax t can hold Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 179 22 8 2 57 define UINTPTR MAX UINTI6 largest value an uintptr t can hold 22 8 3 Typedef Documentation 22 8 3 1 typedef signed int int16 t 16 bit signed type 22 8 3 2 typedef signed long int int32 t 32 bit signed type 22 8 3 3 typedef signed long long int int64 t 64 bit signed type Note This type is not available when the compiler option mint8 is in effect 22 8 3 4 typedef signed char int8 t 8 bit signed type 22 8 3 5 typedef int16 tint fastl6 t fastest signed int with at least 16 bits 22 8 3 6 typedef int32 t int fast32 t fastest signed int with at least 32 bits 22
204. INTERRUPT deprecated items 323 interrupt h 377 INTMAX C avr stdint 175 INTMAX MAX avr stdint 175 MIN avr stdint 175 intmax t avr stdint 179 MAX avr stdint 175 INTPTR MIN avr stdint 175 intptr t avr stdint 179 inttypes h 377 io h 380 isalnum ctype 137 isalpha ctype 137 isascli ctype 137 isblank ctype 137 iscntrl ctype 137 isdigit ctype 137 isfinite avr_math 163 isfinitef avr_math 157 isgraph ctype 137 isinf avr_math 163 isinff avr_math 157 islower ctype 137 isnan avr_math 163 isnanf avr_math 157 isprint ctype 137 ispunct ctype 137 ISR avr_interrupts 262 ISR_ALIAS avr_interrupts 263 ISR_ALIASOF avr_interrupts 263 ISR_BLOCK avr_interrupts 264 ISR_NAKED avr_interrupts 264 ISR_NOBLOCK Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 429 avr interrupts 264 isspace ctype 138 isupper ctype 138 isxdigit ctype 138 itoa avr stdlib 206 labs avr stdlib 207 ldexp avr math 163 Idexpf avr_math 157 Idiv avr_stdlib 207 ldiv t 366 quot 367 rem 367 lock h 380 log avr math 163 log10 avr math 163 log10f avr math 157 logf avr math 157 longjmp setjmp 167 loop_until_bit_is_clear avr_sfr 297 loop_until_bit_is_set avr_sfr 297 lrint avr_math 164 lrintf avr_math 157 lround avr_math 164 lroundf avr_math 158 Itoa avr_stdlib 207 M
205. Kristian Strom Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 2 Toolchain Overview 12 Michael Stumpf Stefan Swanepoel Helmut Wallner Eric B Weddington Joerg Wunsch Dmitry Xmelkov Atmel Corporation egnite Software GmbH The Regents of the University of California All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution Neither the name of the copyright holders nor the names of contributors may be used to endorse or promote products derived from this software without specific prior written permission ND ANY EXPRESS IMPLIED WARRANTIES INCLUDING BUT LIMITED IABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR ONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF POHNAH DP POSSIBILITY OF SUCH DAMAGE 2 Toolchain Overview 2 1 Introduction Welcome to the open source software development toolset for the Atmel AVR There is not a single tool that provides everything needed
206. LEASTI6 146 PRIuLEAST32 146 PRIuLEASTS 146 PRIuPTR 146 PRIX16 146 PRIx16 146 PRIX32 147 PRIx32 146 PRIX8 147 PRIx8 147 PRIXFAST 16 147 PRIxFASTI6 147 PRIXFAST32 147 PRIxFAST32 147 PRIXFASTS 147 PRIxFASTS 147 PRIXLEAST16 148 PRIxLEASTI6 147 PRIXLEAST32 148 PRIxLEAST32 148 PRIXLEASTS 148 PRIxLEASTS 148 PRIXPTR 148 PRIxPTR 148 SCNd16 148 SCNd32 148 SCNdFASTI6 148 SCNdFAST32 149 SCNdLEASTI6 149 SCNdLEAST32 149 SCNdPTR 149 SCNi16 149 SCNi32 149 SCNiFAST16 149 SCNiFAST32 149 SCNiLEAST16 149 Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen INDEX 419 SCNiLEAST32 149 SCNiPTR 150 SCNo16 150 SCNo32 150 SCNoFAST 16 150 SCNoFAST32 150 SCNoLEAST 16 150 SCNoLEAST32 150 SCNoPTR 150 SCNul6 150 SCNu32 150 SCNuFAST 16 151 SCNuFAST32 151 SCNuLEAST 16 151 SCNuLEAST32 151 SCNuPTR 151 SCNx16 151 SCNx32 151 SCNxFAST 16 151 SCNxFAST32 151 SCNxLEAST 16 151 SCNxLEAST32 152 SCNxPTR 152 uint_farptr_t 152 avr_math acos 160 acosf 155 asin 160 asinf 155 atan 160 atan2 161 atan2f 155 atanf 155 cbrt 161 cbrtf 155 ceil 161 ceilf 155 copysign 161 copysignf 155 cos 161 cosf 156 cosh 161 coshf 156 exp 161 expf 156 fabs 161 fabsf 156 fdim 161 fdimf 156 floor 162 floorf 156 fma 162 fmaf 156 fmax 162 fmaxf 156 fmin 162 fminf 156 fmod 162 fmodf 156 fre
207. LSB carry the prescaler bits on the newer ATmegas 22 32 2 32 define TW WRITE 0 SLA W address 22 33 lt compat deprecated h gt Deprecated items Allowing specific system wide interrupts In addition to globally enabling interrupts each device s particular interrupt needs to be enabled separately if interrupts for this device are desired While some devices maintain their interrupt enable bit inside the device s register set external and timer interrupts have system wide configuration registers Example Enable timer 1 overflow interrupts timer enable int BV TOIE1 Do some work Disable all timer interrupts timer enable int 0 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 33 lt compat deprecated h gt Deprecated items 323 Note Be careful when you use these functions If you already have a different interrupt enabled you could inadvertantly disable it by enabling another intterupt e static inline void timer enable int unsigned char ints define enable external int mask __EICR mask define INTERRUPT signame define _ INTR ATTRS used Obsolete IO macros Back in a time when AVR GCC and avr libc could not handle IO port access in the di rect assignment form as they are handled now all IO port access had to be done through specific macros that eventually resulted in inline assembly instructions performing the desired action These macros became obsolete
208. M address p 22 14 3 11 void eeprom write block const void src void x dst size t n Write a block of __n bytes to EEPROM address __ dst from src Note The argument order is mismatch with common functions like strcpy 22 14 3 12 void eeprom write byte uint8_t x p uint8 t value Write byte value to EEPROM address p 22 14 3 13 void eeprom write dword uint32 t x p uint32 t value Write 32 bit double word __value to EEPROM address _ Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 15 lt avr fuse h gt Fuse Support 240 22 14 3 14 void eeprom write float float x p float value Write a float __ value to EEPROM address p 22 14 3 15 void eeprom write word uint16 t x p uintl6 t value Write a word value to EEPROM address p 2215 lt avr fuse h gt Fuse Support Introduction The Fuse API allows a user to specify the fuse settings for the specific AVR device they are compiling for These fuse settings will be placed in a special section in the ELF output file after linking Programming tools can take advantage of the fuse information embedded in the ELF file by extracting this information and determining if the fuses need to be programmed before programming the Flash and EEPROM memories This also allows a single ELF file to contain all the information needed to program an AVR To use the Fuse API include the lt avr io h gt header file
209. ME need to discuss the weak directive The following describes the various sections available 41 The text Section The text section contains the actual machine instructions which make up your program This section is further subdivided by the initN and finiN sections dicussed below Note The avr size program part of binutils coming from a Unix background doesn t account for the data initialization space added to the text section so in order to know how much flash the final program will consume one needs to add the values for both text and data but not bss while the amount of pre allocated SRAM is the sum of data and bss 4 2 The data Section This section contains static data which was defined in your code Things like the fol lowing would end up in data char err str Your program has died a horrible death struct point pt 1 1 It is possible to tell the linker the SRAM address of the beginning of the data section This is accomplished by adding W1 Tdata addr to the avr gcc command used to the link your program Not that addr must be offset by adding 0x800000 the to real SRAM address so that the linker knows that the address is in the SRAM memory space Thus if you want the data section to start at 0x1100 pass 0x801100 at the address to the linker offset explained Note When using malloc in the application which could even happen inside library calls additional adjustments are re
210. OM AT9088535 ATmegal6 ATmegal6l READY ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 ATmega8515 ATmega8535 12 ATtinyl3 AT 0 15 ATtiny26 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 EE READY SIG EEPROM Ready AT90PWMS3 AT90PWMO2 AT90PWMI vect EEPROM 90 128 AT90CAN32 ATOOCAN64 READY ATmegal03 ATmegal28 ATmegal284P ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega406 ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P AT megal64P ATmega644P ATmega644 AT megal6HVA AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 EXT INTO SIG External Interrupt ATtiny24 ATtiny44 ATtiny84 vect INTERRUPTO Request 0 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 250 INTO_vect SIG_ External Interrupt INTERRUPTO 0 AT90S1200 419052313 419052323 419052333 419052343 9054414 419054433 9054434 419058515 419058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6
211. OR 0x00 illegal start or stop condition define TW MR ARB LOST 0x38 arbitration lost in SLA R or NACK define TW MR DATA ACK 0x50 data received ACK returned define TW MR DATA NACK 0x58 data received NACK returned define TW MR SLA ACK 0x40 SLA R transmitted ACK received define TW MR SLA NACK 0x48 SLA R transmitted NACK received define TW MT ARB LOST 0x38 arbitration lost in SLA W or data Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 32 lt util twi h gt TWI bit mask definitions 320 22 32 2 8 define TW MT DATA 0x28 data transmitted ACK received 22 32 2 9 define TW MT DATA NACK 0x30 22 32 2 10 22 32 2 11 22 32 2 12 22 32 2 13 22 32 2 14 22 32 2 15 22 32 2 16 22 32 2 17 data transmitted NACK received define TW MT SLA ACK 0x18 SLA W transmitted ACK received define TW MT SLA NACK 0x20 SLA W transmitted received define TW NO INFO 0xF8 no state information available define TW READ 1 SLA R address define TW START 0x10 repeated start condition transmitted define TW SR ARB LOST GCALL ACK 0x78 arbitration lost in SLA RW general call received ACK returned define TW SR ARB LOST SLA ACK 0x68 arbitration lost in SLA RW SLA W received ACK returned define TW SR DATA ACK 0x80 data received ACK returned Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 32 lt
212. PROM state machine will always complete the write in progress unless power is removed from the device As with all EEPROM technology if power fails during an EEPROM write the state of the byte being written is undefined In older generation AVRs the EEPROM Address Register EEAR is initialized to zero on reset be it from Brown Out Detect Watchdog or the Reset Pin If an EEPROM write has just started at the time of the reset the write will be completed but now at address zero instead of the requested address If the reset occurs later in the write process both the requested address and address zero may be corrupted To distinguish which AVRs may exhibit the corrupt of address zero while a write is in process during a reset look at the initial value section for the EEPROM Address Register If EEAR shows the initial value as 0x00 or 0x0000 then address zero and possibly the one being written will be corrupted Newer parts show the initial value as undefined these will not corrupt address zero during a reset unless it was address zero that was being written EEPROMs have limited write endurance The datasheet specifies the number of EEP ROM writes that are guaranteed to function across the full temperature specification of the AVR for a given byte A read should always be performed before a write to see if the value in the EEPROM actually needs to be written so not to cause unnecessary EEPROM vwear AVRs use a paging mechanism for
213. PWM1 ANALOG_ COMP_vect SIG_ COMPARATOR Analog parator Com 90 128 AT90CAN32 64 ATmegal03 ATmegal28 ATmegal284P ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmegal68 48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 ANA_ COMP_vect SIG_ COMPARATOR Analog parator Com AT90S1200 419052313 AT90S4414 419054433 AT90S8515 419058535 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 AT mega8515 ATmega8535 ATtinyll ATtiny12 ATtiny13 ATtiny15 ATtiny2313 ATtiny26 ATtiny28 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 9052333 9054434 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 249 CANIT vect SIG CAN CAN Transfer AT90CANI28 AT90CAN32 AT90CAN64 INTERRUPTI Complete or Error EEPROM SIG ATtiny2313 READY vect EEPROM READY SIG EE READY EE RDY vect SIG EEPROM Ready AT9082333 9054433 9054434 EEPR
214. RD SWR define FDEV ERR 1 define _FDEV_EOF 2 define FDEV SETUP STREAM put get rwflag define fdev_close define putc c stream fputc __c __ define putchar __c fputc c stdout define getc __stream fgetc __stream define getchar fgetc stdin stream Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 9 lt stdio h gt Standard IO facilities 183 Functions int fclose FILE __stream int vfprintf FILE __stream const char fmt va_list __ap int vfprintf P FILE stream const char fmt va list ap intfputc int __c FILE stream int printf const char int printf P const char fmt int vprintf const char fmt va list ap int sprintf char __s const char x__fmt int sprintf_P char __s const char x__fmt int snprintf char __s size_t __n const char __fmt int snprintf_P char __s size_t __n const char x__fmt int vsprintf char __s const char __fmt va list ap int vsprintf P char __s const char __fmt va list ap int vsnprintf 5 size_t __n const char x__fmt va list ap int vsnprintf P char __s size_t __n const char __fmt va list ap int fprintf FILE stream const char fmt int fprintf P FILE stream const char fmt int fputs const char str FILE stream int fputs_P const char str FILE stream int puts const char str in
215. ROGMEM 275 PSTR 275 strcasecmp P 278 strcasecmp 279 strcasestr P 279 strcat P 279 strcat PF 280 strchr P 280 strchrnul P 280 strcmp P 281 strcmp PF 281 strcpy P 281 strcpy PF 281 strcspn P 282 strlcat P 282 strlcat PF 282 strlcpy_P 283 PF 283 strlen P 284 strlen PF 284 strncasecmp_P 284 strncasecmp PF 285 strncat P 285 strncat PF 285 strncmp P 286 strncmp PF 286 strncpy P 287 strncpy PF 287 strnlen P 287 strnlen PF 288 strpbrk P 288 strrchr P 288 strsep P 289 strspn_P 289 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 421 strstr P 289 INT LEAST32 MAX 174 strstr PF 290 INT LEAST32 MIN 174 strtok P 290 int least32 t 179 strtok_rP 291 INT LEAST64 MAX 174 avr sfr INT LEAST64 MIN 174 BV 296 int least64 t 179 bit is clear 296 bit is set 296 loop until bit is clear 297 loop until bit is set 297 avr sleep sleep cpu 300 sleep disable 300 sleep enable 300 avr stdint 6 C 172 MAX 172 INT16_MIN 172 int16 t 178 INT32 C 172 INT32 MAX 172 INT32 MIN 172 int32_t 178 INT64 C 172 INT64 MAX 173 INT64 MIN 173 int64 t 178 INTS8 C 173 INT8 MAX 173 INT8_MIN 173 int8 t 178 INT FAST16 MAX 173 INT 8 16 MIN 173 int fast16 t 178 INT FAST32 MAX 173 INT FAST32 MIN 173 int fast32 t 178 INT FAST64 MAX 173 INT FAST64 MIN 174 int fast64 t 178 INT FAST8 MAX 174 INT F
216. RTA 0x33 unsigned char foo PINA The compiler will choose the correct instruction sequence to generate based on the address of the register being accessed The advantage of using the memory mapped registers in C programs is that it makes the programs more portable to other C compilers for the AVR platform Note that special care must be taken when accessing some of the 16 bit timer IO reg isters where access from both the main program and within an interrupt context can happen See Why do some 16 bit timer registers sometimes get trashed Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 22 lt avr sfr_defs h gt Special function registers 297 Porting programs that use the deprecated sbi cbi macros Access to the AVR single bit set and clear instructions are provided via the standard C bit manipulation commands The sbi and cbi macros are no longer directly supported sbi sfr bit can be replaced by sfr BV bit i e sbi PORTB PB1 is now PORTB 1 This actually is more flexible than having sbi directly as the optimizer will use a hard ware sbi if appropriate or a read or write operation if not appropriate You do not need to keep track of which registers sbi cbi will operate on Likewise cbi sfr bit is now sfr amp _BV bit 22 22 2 Define Documentation 22 22 21 define_BV bit 1 lt lt bit include lt avr io h gt Converts a bit number into a byte value
217. START 0x08 define TW START 0x10 define TW MT SLA ACK 0x18 define TW MT SLA NACK 0x20 define TW MT DATA ACK 0x28 define TW MT DATA NACK 0x30 define TW MT ARB LOST 0x38 define TW LOST 0x38 define TW SLA ACK 0x40 define TW MR SLA 0x48 define TW DATA ACK 0x50 define TW DATA NACK 0x58 define TW ST SLA 8 define TW ST ARB LOST SLA ACK OxBO define TW ST DATA 0xB8 fdefine TW ST DATA 0xCO define TW ST LAST DATA 0xC8 define TW SR SLA ACK 0x60 define TW SR ARB LOST SLA ACK 0x68 fdefine TW SR GCALL 0x70 define TW SR LOST GCALL 0x78 define TW SR DATA 0x80 define TW SR 0x88 define TW SR DATA ACK 0x90 fdefine TW SR DATA NACK 0x98 define TW SR STOP OxAO define NO INFO OxF8 define TW BUS ERROR 0x00 define TW STATUS MASK fdefine STATUS TWSR amp TW STATUS MASK Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 32 lt util twi h gt TWI bit mask definitions 319 R W bit in SLA R W address field define TW READ 1 define TW WRITEO 22 32 1 Detailed Description include util twi h This header file contains bit mask definitions for use with the AVR TWI interface 22 32 2 Define Documentation 22 32 2 1 22 32 2 2 22 32 2 3 22 32 2 4 22 32 2 5 22 32 2 6 22 32 2 7 define TW BUS ERR
218. Saving the value of MCUSR in mcusr mirror is only needed if the application later wants to examine the reset source but in particular clearing the watchdog reset flag before disabling the watchdog is required according to the datasheet 22 26 2 Define Documentation 22 26 2 1 define wdt disable Value asm volatile 05 in tmp reg SBEG X cli n t out 0 1 n t out 0 zero reg n t out SREG tmp reg n t no outputs x I SFR IO ADDR WD CONTROL REG uint8 t BV WD CHANGE BV WDE pn x Disable the watchdog timer if possible This attempts to turn off the Enable bit in the watchdog control register See the datasheet for details 22 26 2 2 define wdt enable value Value asm volatile in tmp reg SREG n t oli N wdr out 0 1 XAnNE out SREG tmp reg n t X out 0 2 no outputs I _SFR_IO_ADDR _WD_CONTROL_REG r BV WD CHANGE _BV WDE r uint8 t value amp 0x08 WD PS3 MASK 0x00 _BV WDE value amp 0x07 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 06 lt avr wdt h gt Watchdog timer handling 305 ro Enable the watchdog timer configuring it for expiry after t imeout which is a com bination of the WDPO through WDP2 bits to write into the WDTCR r
219. Sep s RR ERREUR RA 22 30 27 A code walkthrough 222255222255 UR ER FG raz SMI luv sr ze 22 24 Oe sunple pri je E lt s Y goga EE Re BL EEIDEBNIJE E o OS Meeks I ye ees 223727 VS duree Code o e ne ae 22 373 Compiling and Linking 222222 Rn 22 37 4 Examining the Object File 22 570 Linker Map Files 005 566 4 ce m RR RS 22 37 6 Generating Intel Hex Files 22 37 7 Letting Make Build the 22 37 8 Reference to the sGurce 0de o c s soca s rey 22 36 more sophisticated project s o s ooo og o 22 36 Hardware SEMP lt unb 4 ee a BEES ee eS 22 36 2 PUDCHORAILOVEIVIEW secc aj id ERE ee S 22 365 A code walkthrough uz raea 254846 240 22455 22 584 The Spree BOGE cu ness da ug Rok we eu E ROS 22 39Using the standard 2229 1 Hardware 8 222222222 RAG Mah aR RA 22 39 2 Functional overview gt 6 ese slm m mma 22 39 3 A code walkthrough conos Roc Rm n 22 394 Thesoumecod 22 2222 cr x vs 22 40Example using the two wire interface TWI 2240 1 Introduction into TWI 2 92 RR 2240 2 The TWI example project RR mA sm Sul kli dk Brera 23 Data Structure Documentation 23 1 div t Struct Reference 2 2 2222 2 2 25 5 231 1 Detailed Description o ccn co RR BR 23 1 2 Field Documentation 232 ldiv t Struct Reference 2321 DenaedD
220. T file system Since the FAT file system has only a granularity of 2 seconds for maintaining a file s timestamp and it seems that some MS DOS derivative Win9x perhaps rounds up the current time to the next sec ond when calculating the timestamp of an updated file in case the current time cannot be represented in FAT s terms this causes a situation where make sees a file coming from the future Since all make decisions are based on file timestamps and their dependencies make warns about this situation Solution don t use inferior file systems operating systems Neither Unix file systems nor HPFS aka NTFS do experience that problem Workaround after saving the file wait a second before starting make Or simply Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 25 Why are many interrupt flags cleared by writing a logical 1 82 ignore the warning If you are paranoid execute make clean all to make sure everything gets rebuilt In networked environments where the files are accessed from a file server this message can also happen if the file server s clock differs too much from the network client s clock In this case the solution is to use a proper time keeping protocol on both sys tems like NTP As a workaround synchronize the client s clock frequently with the server s clock Back to FAQ Index 11 25 Why are many interrupt flags cleared by writing a logical 1 Usually each interrupt has i
221. T16 u define SCNx16 x define SCNxLEAST16 x define SCNxFAST16 x define SCNo32 lo define SCNoLEAST32 lo define SCNoFAST32 lo Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 143 define SCNu32 lu define SCNuLEAST32 lu define SCNuFAST32 lu define SCNx32 Ix define SCNXLEAST322 Ix define SCNxFAST32 Ix define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR SCNx16 22 5 1 Detailed Description finclude inttypes h This header file includes the exact width integer definitions from lt stdint h gt and extends them with additional facilities provided by the implementation Currently the extensions include two additional integer types that could hold a far pointer i e a code pointer that can address more than 64 KB as well as standard names for all printf and scanf formatting options that are supported by the lt stdio h gt Standard IO facilities As the library does not support the full range of conversion specifiers from ISO 9899 1999 only those conversions that are actually implemented will be listed here The idea behind these conversion macros is that for each of the types defined by lt stdint h gt a macro will be supplied that portably allows formatting an object of that type in printf or scanf operations Example include lt inttypes h gt uint8_t smallval int32 t longval printf Th
222. T90USB646 TIMER3_ CAPT_vect SIG_INPUT_ CAPTURE3 Timer Counter3 Capture Event 90 128 AT90CAN32 ATOOCAN64 ATmegal28 ATmegal284P ATmegal62 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3_ COMPA_vect SIG_ OUTPUT_ COMPARE3A Timer Counter3 Compare Match A 90 128 AT90CAN32 ATOOCAN64 ATmegal28 ATmegal284P ATmegal62 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 COMPB vect SIG OUTPUT COMPARE3B Timer Counter3 Compare Match B 90 128 AT90CAN32 ATOOCAN64 ATmegal28 ATmegal284P ATmegal62 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3_ COMPC_vect SIG_ OUTPUT_ COMPARE3C Timer Counter3 Compare Match C AT90CANI28 AT90CAN32 AT90CANGA ATmegal28 ATmega64 ATmega640 AT mega1280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER3_ OVF_vect SIG_ OVERFLOW3 Timer Counter3 Overflow 90 128 AT90CAN32 ATOOCAN64 ATmegal28 ATmegal284P ATmegal62 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Thu May 19 2011 13 29 1
223. TENTS 1 24 T3stncmp PS File Reterenc o oe cp oo om m RR EU 410 24 73 1 Detailed Description scm Res 410 24 Mstmopyo File Referente 2 2 2 22 410 24 741 Detailed Description lt lt css eere rr REG 410 24 5stmcopy PS File Reference 2 xem o SRR eS 410 2475 1 Detailed Description lt e ee eos RR RU 410 24 Tostralen s File Reference lt ce bp wm a ARS 410 2976 1 Detailed Description ss uoo RR pedut ER pits 410 24 TTstnlen PS File Reference 2 410 24 77 1 Detailed Description 410 24 7 8strpbrk File Reference ce ee 410 278 1 Detailed Description lcg ceram he AS 410 24 7 9strpbrk_P S File 410 24 79 1 Detailed Description 2 2 2222 2 410 28 B0stchrs Pile Referente lt o ss ooo 52594462 410 2400 1 Detailed Description lt s Rx 410 a olstic hn FS File Reference 2i 04 e Ro id 558952 410 24 81 1 Detailed Description 25cm 9 AS 410 24 825506v 5 Pile Beferenee 222222225255 ER RR s 410 24 82 1 Detailed Description 410 2483s0sep 5 File Referens lt oo c eco AG 410 24 83 1 Detailed Description 410 24 84strsep P S File Reference 410 24 84 1 Detailed Description 410 24 89 5trspn amp File Referente ERA ER 410 2455 1 Detailed Description lt e
224. This means FreeBSD users may need to build the tools by using gmake Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 5 GCC for the AVR target 94 If the tools compiled cleanly you re ready to install them If you specified a destination that isn t owned by your account you ll need root access to install them To install make install You should now have the programs from binutils installed into SPREFIX bin Don t forget to set your PATH environment variable before going to build avr gcc Note The official version of binutils might lack support for recent AVR devices A patch that adds more AVR types can be found at http www reebsd org cgi cvsweb cgi ports devel 12 5 GCC for the AVR target Warning You must install avr binutils and make sure your path is set properly before in stalling avr gcc The steps to build avr gcc are essentially same as for binutils bunzip2 c gcc version tar bz2 tar xf cd gcc lt version gt mkdir obj avr cd obj avr configure prefix PREFIX target avr enable languages c c t disable nls disable libssp with dwarf2 make make install ur To save your self some download time you can alternatively download only the gcc core version tar bz2 gcc c lt version gt tar bz2 parts of the gcc Also if you don t need C support you only need the core part and should only enable the C language sup port Note
225. Tmega640 AT megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny48 AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 SPM_RDY_ vect SIG_SPM_ READY Store Program Memory Ready ATmegal6 ATmegal62 ATmega32 AT mega323 ATmega8 ATmega8515 AT mega8535 SPM READY vect SIG SPM READY Store Program Memory Read AT90PWMS3 AT90PWMO2 AT90PWMI 90 128 AT90CAN32 AT90CAN64 ATmegal28 ATmegal284P ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega406 ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMO_ COMPA_vect SIG_ OUTPUT Timer Counter Compare Match A ATtiny13 ATtiny43U ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 TIMO COMPB vect SIG OUTPUT COMPAREOB Timer Counter Compare Match B ATtiny13 ATtiny43U ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 TIMO OVF vect SIG OVERFLOWO Timer Counter0 Overflow ATtiny13 ATtiny43U ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25
226. VBREVB avr5 atmega32m 1 __AVR_ATmega32M1__ avr5 atmega32u4 AVR ATmega32U4 avr5 atmega32u6 AVR ATmega32U6 avr5 atmega406 AVR ATmega406 avr5 atmega64 AVR ATmega64 avr5 atmega640 AVR ATmega640 avr5 atmega644 AVR ATmega644 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 112 avr5 atmega644a AVR ATmega644A avr5 atmega644p AVR ATmega644P avr5 atmega644pa AVR_ATmega644PA__ avr5 atmega645 ATmega645 avr5 atmega645a AVR ATmega645A avr5 atmega645p ATmega645P avr5 atmega6450 AVR ATmega6450 avr5 atmega6450a ATmega6450A avr5 atmega6450p ATmega6450P avr5 atmega649 ATmega649 avr5 atmega649a AVR ATmega649A avr5 atmega6490 AVR ATmega6490 avr5 atmega6490a AVR ATmega6490A avr5 atmega6490p ATmega6490P avr5 atmega649p __AVR_ATmega649P__ avr5 atmega64c1 AVR_ATmega64C1__ avr5 atmega64hve __AVR_ATmega64HVE__ avr5 atmega64m 1 __AVR_ATmega64M1__ avr5 m3000 AVR M3000 avr5 avr51 3 at90can128 AVR 28 avr5 avr51 3 at90usb1286 AVR_AT90USB1286__ avr5 avr51 3 at90usb1287 AVR AT90USBI1287 avr5 avr51 3 atmegal28 ATmegal28 avr5 avr51 3 atmegal280 ATmegal280 avr5 a
227. Various actions depending on the operation mode follow Finally the 3 second backup timer is implemented that will write the PVM value back to EEPROM once it is not changing anymore The ADC interrupt will just adjust the PWM value only Finally the UART Rx interrupt will dispatch on the last character received from the UART All the string literals that are used as informational messages within main are placed in program memory so no SRAM needs to be allocated for them This is done by using the PSTR macro and passing the string to printstr Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 39 Using the standard IO facilities 354 22 38 4 The source code The source code is installed under Sprefix share doc avr libc examples largedemo largedemo c where prefix is a configuration option For Unix systems it is usually set to either usr usr local 22 39 Using the standard IO facilities This project illustrates how to use the standard IO facilities stdio provided by this library It assumes a basic knowledge of how the stdio subsystem is used in standard C applications and concentrates on the differences in this library s implementation that mainly result from the differences of the microcontroller environment compared to a hosted environment of a standard computer This demo is meant to supplement the documentation not to replace it 22 39 1 Hardware setup The demo is set up in
228. W SR STOP util twi 320 TW ST LOST SLA ACK util twi 320 TW ST DATA ACK util twi 320 TW ST DATA NACK util twi 320 TW ST LAST DATA util twi 320 TW ST SLA ACK util twi 320 TW START util twi 321 TW STATUS util twi 321 TW STATUS MASK util twi 321 TW WRITE util twi 321 twi h 411 UBRR VALUE util setbaud 316 UBRRH VALUE util setbaud 316 UBRRL VALUE util setbaud 316 UINT16 C avr stdint 176 UINT16 MAX avr stdint 176 uintl6 t avr stdint 179 UINT32 C avr stdint 176 UINT32 MAX avr stdint 176 uint32 t avr stdint 179 UINT64 C avr stdint 176 UINT64 MAX avr stdint 176 uint64 t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 438 avr stdint 179 UINT8 C avr stdint 176 8 MAX avr stdint 176 uint8 t avr stdint 180 uint farptr t avr inttypes 152 UINT FAST16 avr stdint 176 uint fastl6 t avr stdint 180 UINT FAST32 MAX avr stdint 177 uint fast32 t avr stdint 180 UINT FAST64 MAX avr stdint 177 uint fast64 t avr stdint 180 UINT FAST8 MAX avr stdint 177 uint fast8 t avr stdint 180 UINT LEASTI6 MAX avr stdint 177 uint least16 t avr stdint 180 UINT LEAST32 MAX avr stdint 177 uint least32 t avr stdint 180 UINT LEAST64 avr stdint 177 uint least64 t avr stdint 180 UINT LEASTS8 avr stdint 177 uint least8 t avr stdint 181 UINTMAX C avr stdint 177 UINTMAX MAX
229. _t signed integer type that can hold a pointer gt 64 KB 22 5 3 2 typedef uint32_t uint_farptr_t unsigned integer type that can hold a pointer gt 64 KB 22 6 lt math h gt Mathematics Defines define M_E 2 7182818284590452354 define M_LOG2E 1 4426950408889634074 define M LOGIOE 0 43429448 190325182765 define M_LN2 0 69314718055994530942 define M_LN10 2 30258509299404568402 define PI 3 14159265358979323846 define M 2 1 57079632679489661923 define PI 4 0 78539816339744830962 define 1 PI 0 31830988618379067154 define 2 PI 0 63661977236758134308 define M 2 SORTPI 1 12837916709551257390 define SORT2 1 41421356237309504880 define SORTI 2 0 70710678118654752440 define NAN builtin nan define INFINITY _ builtin inf Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 154 define cosf cos define sinf sin define tanf tan define fabsf fabs define fmodf fmod define sqrtf sqrt define cbrtf cbrt define hypotf hypot define squaref square define floorf floor define ceilf ceil define frexpf frexp define ldexpf ldexp define expf exp define coshf cosh define sinhf sinh define tanhf tanh define acosf acos define asinf asin define atanf atan define atan2f atan2 define logf log define log10f log10 define powf pow define isnanf isnan define isinff isinf define isfinitef isfinite define copysignf copys
230. a more recent generation of AVRs a number of register and bit names have been changed there so they are mapped back to their ATmega8 16 equivalents to keep the actual program code portable The name CPU is the conventional name to describe the CPU clock frequency of the controller This demo project just uses the internal calibrated 1 MHz RC oscillator that is enabled by default Note that when using the lt util delay h gt functions F CPU needs to be defined before including that file The remaining macros have their own comments in the source code The macro TMR1 SCALE shows how to use the preprocessor and the compiler s constant expres sion computation to calculate the value of timer 1 post scaler in a way so it only depends on F_CPU and the desired software clock frequency While the formula looks a bit complicated using a macro offers the advantage that the application will auto matically scale to new target softclock or master CPU frequencies without having to manually re calculate hardcoded constants 22 38 3 2 Part 2 Variable definitions The int flags structure demonstrates a way to allocate bit variables in memory Each of the interrupt service routines just sets one bit within that structure and the applica tion s main loop then monitors the bits in order to act appropriately Like all variables that are used to communicate values between an interrupt service routine and the main application it is declared volatile
231. a particular bit number as a byte value use the BV macro Of course the implementation of this macro is just the usual bit shift which is done by the compiler anyway thus doesn t impose any run time penalty so the following applies _BV 3 gt 1 lt lt 3 gt 0x08 However using the macro often makes the program better readable BV stands for bit value in case someone might ask you Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 117 Can I use C on the AVR 66 Example clock timer 2 with full IO clock CS2x 0b001 toggle OC2 output on compare match COM2x 0b01 and clear timer on compare match CTC2 1 Make OC2 PD7 an output TCCR2 BV COM20 BV CTC2 520 DDRD _BV PD7 Back to FAQ Index 11 7 Canluse C on the AVR Basically yes C is supported assuming your compiler has been configured and compiled to support it of course Source files ending in cc cpp or C will automati cally cause the compiler frontend to invoke the C compiler Alternatively the C compiler could be explicitly called by the name avr c However there s currently no support for libstdc the standard support library needed for a complete C implementation This imposes a number of restrictions on the C programs that can be compiled Among them are Obviously none of the C related standard functions classes and template classes are available The operators
232. ace h const char foo PROGMEM Foo const char bar PROGMEM Bar PGM P array 2 PROGMEM foo bar int main void char buf 32 PGM P p int i memcpy P amp p amp array i sizeof PGM_P strcpy P buf p return 0 Looking at the disassembly of the resulting object file we see that array is in flash as such 00000026 array 216 2e 00 word 0x002e 227 28 2a 00 word 0x002a 2 0000002a bar 2a 42 61 72 00 Bar 0000002e foo 2e 46 6f 6f 00 Foo foo is at addr 0x002e bar is at addr 0x002a array is at addr 0x0026 Then in main we see this memcpy P amp p amp array i sizeof PGM P 70 66 Of add r22 r22 7525 TAE adc B23 23 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 16 How to use external RAM 76 74 6a 5d subi r22 OxDA 218 16 7f 4 sbci r23 OxFF s 255 78 42 0 ldi r20 0x02 LES 7a 50 e0 idi r21 0x00 3 0 Ws ce 01 movw r24 r28 Te 81 96 adiw r24 0x21 7 33 80 08 do rcall 16 0x92 This code reads the pointer to the desired string from the ROM table array into a register pair The value of i in 22 123 is doubled to accommodate for the word offset required to access array then the address of array 0x26 is added by subtracting the negated address Oxffda The address of variable p is computed by adding its offset within the stack frame 33 to the Y pointer register and memcpy P is called strcpy P buf
233. ader Lock Bits to set Note In this context a set bit will be written to a zero value Note also that only BLBxx bits can be programmed by this command For example to disallow the SPM instruction from writing to the Boot Loader memory section of flash you would use this macro as such boot lock bits set BV BLB11 Note Like any lock bits the Boot Loader Lock Bits once set cannot be cleared again except by a chip erase which will in turn also erase the boot loader itself 22 12 2 3 define boot lock bits set safe lock_bits Value do boot spm busy wait N eeprom busy wait X boot lock bits set lock bits N while 0 Same as boot lock bits set except waits for eeprom and spm operations to complete before setting the lock bits Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 12 avr boot h Bootloader Support Utilities 231 22 12 2 4 define boot lock fuse bits get address Value extension N uint8 t _ result N asm volatile X N sts 1 2 n t N lpm 0 Z n t N o ex result X i SFR ADDR SPM REG N uint8 t BOOT LOCK BITS 5 N 2 uintl16 t address N result N Read the lock fuse bits at address Parameter address can be any of GET LOW FUSE BITS GET LOCK BITS GET EXTENDED FUSE BITS or GET HIGH FUSE BITS Note The lock and fuse bits returned are the physical
234. ader file contains optimized assembler code to calculate the parity bit for a byte 22 30 2 Define Documentation 22 30 2 1 define parity even bit val _t 1 gt gt 1 amp 1 Value extension N unsigned char t N asm N mov tmp reg 0 n t N swap 0 n t N eor 0 reg n t N mov _ tmp reg 0 n t N Wise 0 give Wise 0 eor 0 __tmp_reg__ X o dE N 0 unsigned char val N ro N N N Returns lif val has an odd number of bits set 22 31 lt utillsetbaud h gt Helper macros for baud rate calculations Defines define BAUD TOL 2 define VALUE define UBRRL VALUE define UBRRH VALUE define USE 2X 0 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 31 lt util setbaud h gt Helper macros for baud rate calculations 316 22 31 1 Detailed Description define F CPU 11059200 define BAUD 38400 include lt util setbaud h gt This header file requires that on entry values are already defined for F_CPU and BAUD In addition the macro BAUD_TOL will define the baud rate tolerance in percent that is acceptable during the calculations The value of BAUD_TOL will default to 2 This header file defines macros suitable to setup the UART baud rate prescaler registers of an AVR calculations are done using the C preprocessor Including this header file causes no other side e
235. after some seconds the watchdog will reset the MCU This situation can be figured out on startup by reading the MCUCSR register The current value of the PWM is backed up in an EEPROM cell after about 3 seconds of idle time after the last change If that EEPROM cell contains a reasonable i e non erased value at startup it is taken as the initial value for the PWM This virtually preserves the last value across power cycles By not updating the EEPROM immme diately but only after a timeout EEPROM wear is reduced considerably compared to immediately writing the value at each change 22 38 3 A code walkthrough This section explains the ideas behind individual parts of the code The source code has been divided into numbered parts and the following subsections explain each of these parts Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 38 A more sophisticated project 351 22 38 3 1 Part 1 Macro definitions A number of preprocessor macros are defined to improve readability and or portability of the application The first macros describe the IO pins our LEDs and pushbuttons are connected to This provides some kind of mini HAL hardware abstraction layer so should some of the connections be changed they don t need to be changed inside the code but only on top Note that the location of the PWM output itself is mandated by the hardware so it cannot be easily changed As the ATmega48 88 168 controllers belong to
236. aliased to both stdout and stderr Thus if the open was done with both read and write intent all three standard streams will be identical Note that these aliases are indistinguishable from each other thus calling fclose on such a stream will also effectively close all of its aliases note 3 It is possible to tie additional user data to a stream using fdev set udata The back end put and get functions can then extract this user data using fdev get udata and act appropriately For example a single put function could be used to talk to two different UARTS that way or the put and get functions could keep internal state between calls there Format strings in flash ROM All the printf and scanf family functions come in two flavours the standard name where the format string is expected to be in SRAM as well as a version with the suffix P where the format string is expected to reside in the flash ROM The macro PSTR explained in lt avr pgmspace h gt Program Space Utilities becomes very handy for declaring these format strings Running stdio without malloc By default fdevopen requires malloc As this is often not desired in the limited environment of a microcontroller an alternative option is provided to run completely without malloc The macro fdev setup stream is provided to prepare a user supplied FILE buffer for operation with stdio Example include lt stdio h gt static int uart putchar char c FILE xs
237. aloH v vol t RR REIS 202 22 Typedef Documenfalad 22 93 ERE 203 22 10 4 Function 203 22 10 5 Variable Documentation 212 ZA NEC ug p os np 255229 rr 213 22 1 1 Detailed Description 2 se m Ro x RR g 214 22 11 2 Define Documentation gt lt sooo REY 214 22 11 3 Function Documentation 0 a o a 214 22 12 lt avr boot h gt Bootloader Support Utilities 227 22 12 41 Detaled Description oss x ERR EE 227 22 12 2DefineDocumentation 229 22 13 lt avr cpufunc h gt Special AVR CPU functions 234 22 13 1 Detailed Description luu 6 SEAR SERE 234 22 13 2 Define Documentation uo Rome 234 22 14 avr eeprom h EEPROM handling 234 22 14 1 Detailed Description s o 22064620550 RR 235 2214 2 Deine Documenten vu ocs ses 236 22 14 3 Function Documentation 237 22 15 ave luse ho Pu e Support cs a ao ob EEG 239 22 16 lt avr interrupt h gt 242 22 16 1 Detailed Description sso RR RB 243 22 15 2 Define Documentation s s o om RE RS 262 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen CONTENTS vi 22 17 avr io h AVR device specific IO definitions 266 22 18 lt avrilock h gt Lockbit Support e 267 22 19 avr pgmspace h
238. an zero if the first Len bytes of s1 is found respectively to be less than to match or be greater than the first 1en bytes of s2 22 19 4 5 void memcepy P void x des VOID P src size memopy P function is similar to memcpy except the src string resides in program space Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 49 lt avr pgmspace h gt Program Space Utilities 279 Returns The memopy P function returns a pointer to dest 22 19 4 6 void memcepy PF void dest uint_farptr_t src size tn Copy a memory block from flash to SRAM The memopy PF function is similar to memcpy except the data is copied from the program space and is addressed using a far pointer Parameters dst A pointer to the destination buffer src A far pointer to the origin of data in flash memory The number of bytes to be copied Returns The memcpy_PF function returns a pointer to dst The contents of RAMPZ SFR are undefined when the function returns 22 19 47 void x memmem P const void 57 size t len VOID P s2 size t len2 The memmem_P function is similar to memmem except that 52 is pointer to a string in program space 22 19 4 8 VOID P memrchr P PGM VOID P src int val size tlen The memrchr_P function is like the memchr_P function except that it searches backwards from the end of the 1en bytes pointed t
239. are made MinGW MSYS http downloads sourceforge net mingw MinGW 5 1 4 exe use mirror superb east gt PutMinGW 5 1 4 exe in it s own directory for example C MinGWSetup Run MinGW 5 1 4 exe Select Download and install Select Current package Select type of install Full Install MSYS 1 0 10 exe package lt http prdownloads sf net mingw MSYS 1 0 10 exe download gt Default selections Batch file will ask Do you wish to continue with the post install Press y and press enter Do you have MinGW installed Press y and press enter Where is your MinGW installation Type in c mingw without quotes and press enter Do you wish for me to add mount bindings for c mingw to mingw Press y and press enter It will display some messages on the screen then it will display Press any key to continue Press any key Edit c msys 1 0 msys bat Change line should be line 41 if EXIST rxvt exe goto startrxvt to rem if EXIST rxvt exe goto startrxvt to remark out this line Doing this will cause MSYS to always use the bash shell and not the rxvt shell Note The order of the next three is important Install MSYS Developer toolkit before the autotools Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 12 Tools Required for Building the Toolchain for Windows 99 MSYS Developer Toolkit version 1 0 1 This is needed
240. as a parameter to the function st rcpy_P The function st rcpy P is just like the regular st rcpy function except that it copies string from Program Space the second parameter to a buffer in the Data Space the first parameter There are many string functions available that work with strings located in Program Space All of these special string functions have a suffix of P in the function name and are declared in the lt avr pgmspace h gt header file 5 5 Caveats The macros and functions used to retrieve data from the Program Space have to gen erate some extra code in order to actually load the data from the Program Space This incurs some extra overhead in terms of code space extra opcodes and execution time Usually both the space and time overhead is minimal compared to the space savings of putting data in Program Space But you should be aware of this so you can mini mize the number of calls within a single function that gets the same piece of data from Program Space It is always instructive to look at the resulting disassembly from the compiler 6 avr libc and assembler programs 6 1 Introduction There might be several reasons to write code for AVR microcontrollers using plain assembler source code Among them are Code for devices that do not have RAM and are thus not supported by the C compiler Code for very time critical applications Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 6 2 I
241. as reading and writing IO ports can be done by simply using the IO port name in an expression and all bit manipulation including those on IO ports can be done using generic C bit manipulation operators The macros in this group simulate the historical behaviour While they are supposed to be applied to IO ports the emulation actually uses standard C methods so they could be applied to arbitrary memory locations as well define inp port port define outp val port port val define inb port port define outb port val port val e define sbi port bit port 1 lt lt bit define cbi port bit port amp 1 lt lt bit 22 33 1 Detailed Description This header file contains several items that used to be available in previous versions of this library but have eventually been deprecated over time finclude compat deprecated h These items are supplied within that header file for backward compatibility reasons only so old source code that has been written for previous library versions could easily be maintained until its end of life Use of any of these items in new code is strongly discouraged Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 33 lt compat deprecated h gt Deprecated items 324 22 33 2 Define Documentation 22 33 2 1 define cbi port bit port amp 1 lt lt bit Deprecated Clear bit in IO port port 22 33 2 2 define
242. ased to due to the JMP RJMP opcode used Deprecated For new code the use of ISR ISR_ALIASOF is recommended Example ISR INTO_vect PORTB 42 ISR ALIAS INT1 vect INTO vect Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 265 22 16 2 6 define ISR_ALIASOF target_vector include avr interrupt h The ISR is linked to another ISR specified by the vect parameter This is compatible with GCC 4 2 and greater only Use this attribute in the attributes parameter of the ISR macro 22 16 2 7 define ISR BLOCK include lt avr interrupt h gt Identical to an ISR with no attributes specified Global interrupts are initially disabled by the AVR hardware when entering the ISR without the compiler modifying this state Use this attribute in the attributes parameter of the ISR macro 22 16 2 8 define ISR NAKED include lt avr interrupt h gt ISR is created with no prologue or epilogue code The user code is responsible for preservation of the machine state including the SREG register as well as placing a reti at the end of the interrupt routine Use this attribute in the attributes parameter of the ISR macro 22 16 2 9 define ISR NOBLOCK include lt avr interrupt h gt ISR runs with global interrupts initially enabled The interrupt enable flag is activated by the compiler as early as possible within the ISR to ensure m
243. at at O3 gcc attempts to inline all simple functions For the AVR target this will normally constitute a large pessimization due to the code increasement The only other optimization turned on with 03 is frename registers which could rather be enabled manually instead A simple O option is equivalent to 01 Note also that turning off all optimizations will prevent some warnings from being issued since the generation of those warnings depends on code analysis steps that are only performed when optimizing unreachable code unused variables See also the appropriate FAQ entry for issues regarding debugging optimized code Wa assembler options e Wl linker options Pass the listed options to the assembler or linker respectively ug Generate debugging information that can be used by avr gdb ffreestanding Assume a freestanding environment as per the C standard This turns off automatic builtin functions though they can still be reached by prepending builtin to the actual function name It also makes the compiler not complain when main is declared with a void return type which makes some sense in a microcontroller environment where the application cannot meaningfully provide a return value to its environment in most cases main won t even return anyway However this also turns off all optimizations normally done by the compiler which assume that functions known by a certain name behave as de
244. avr libc 1 7 1 Generated by Doxygen 1 7 3 Thu May 19 2011 13 29 12 Contents 1 AVR Libc V osos eno ORG y Bob RR da ROS ETE ds 1 2 General information about this library 122 Supported DEVICES uou eee ER ee ES RR Ds La avrbbe License ec eo or ue ee Ae RH Toolchain Overview 2 1 22 2a 2 4 23 2 6 2d 2 8 29 2 10 2 11 2 14 243 2 5 eee PSP igi GNU 12249 T wwe Ex sn pe GNU no sesa pesa E agi CPI eund y doen e UR ora AVRDUDE 464 pk ROS a wh aE Ak eos DDD os i Sl ao SE ee 5 AVARICE 20 4 26 ce ed Duces cx bee ae ee ECR X DOR ee peut nn A un ln CPC Toolchain Distributions Distros Open SOME Luis NOR FOE RUE Re Memory Areas and Using malloc 34 3 2 23 3 4 Lucin Pape Internal vs external RAM T nables for malloc lt lt sooo xo ko Rom Ro nebo Implementation details os sco RR RR Memory Sections 4 1 4 2 4 3 44 4 5 4 6 4 1 4 8 4 9 The fekt Sgen 20222225224 54 The data Section 2 46 74 246 bape ea 22025056254 Th pss so X CE REOR S KR ee UN ESO E Bie Re Th eeprom Seco ou 24 26 i VES ba AE 9 The noinit Section The ani 522225
245. avr pgmspace 290 strtod avr stdlib 209 strtok avr string 225 strtok c 410 strtok P avr pgmspace 290 strtok_P c 411 strtok avr string 226 strtok_r S 411 strtok_rP avr_pgmspace 291 strtok_rP S 411 strtol avr_stdlib 210 strtoul avr_stdlib 210 strupr avr_string 226 strupr S 411 supported devices 2 tan avr_math 166 tanf avr_math 160 tanh avr_math 166 tanhf avr_math 160 timer_enable_int deprecated_items 325 toascii ctype 138 tolower ctype 138 tools optional 91 tools required 91 toupper ctype 138 trunc Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX avr math 166 truncf avr math 160 TW BUS ERROR util twi 318 TW ARB LOST util twi 318 TW MR DATA ACK util twi 318 TW DATA NACK util twi 318 TW MR SLA ACK util twi 318 TW MR 5 util twi 318 TW MT ARB LOST util twi 318 TW MT ACK util twi 318 TW MT DATA NACK util twi 319 TW MT SLA ACK util twi 319 TW MT SLA util twi 319 TW NO INFO util twi 319 TW READ util twi 319 TW REP START util twi 319 TW SR ARB LOST GCALL ACK util twi 319 TW SR ARB LOST SLA ACK util twi 319 TW SR ACK util twi 319 TW SR NACK util twi 319 TW SR GCALL util twi 320 TW SR GCALL DATA util twi 320 TW SR GCALL DATA NACK util twi 320 TW SR 5 ACK util twi 320 T
246. bc it is just an alias for fgetc 22 0 2 14 define getchar void fgetc stdin The macro get char reads a character from st din Return values and error handling is identical to fgetc 22 9 2 15 define putc c _ stream fputc c stream The macro put c used to be a fast macro implementation with a functionality identical to fputc For space constraints in avr 1libc it is just an alias for fputc 22 9 2 16 define putchar c fputc c stdout The macro put char sends character c to stdout 22 9 2 17 stderr iob 2 Stream destined for error output Unless specifically assigned identical to stdout If stderr should point to another stream the result of another fdevopen must be explicitly assigned to it without closing the previous st derr since this would also close stdout Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 190 22 9 2 18 define stdin __iob 0 Stream that will be used as an input stream by the simplified functions that don t take a stream argument The first stream opened with read intent using fdevopen will be assigned to stdin 22 9 2 19 stdout __iob 1 Stream that will be used as an output stream by the simplified functions that don t take a st ream argument The first stream opened with write intent using fdevopen will be assigned to both stdin and stderr 22 9 3 Function Do
247. bc by Doxygen 22 37 Asimple project 331 this start time will be subracted from the current time to compute the actual pulse width seen left in incoming and the upper layers are informed of the new value by setting bit 0 in the intbits flags At the same time this pin change interrupt will be disabled so no new measurement can be performed until the upper layer had a chance to process the current value 22 36 3 The source code The source code is installed under Sprefix share doc avr libc examples asmdemo where prefix is a configuration option For Unix systems it is usually set to either usror usr local 22 37 Asimple project At this point you should have the GNU tools configured built and installed on your system In this chapter we present a simple example of using the GNU tools in an AVR project After reading this chapter you should have a better feel as to how the tools are used and how a Makefile can be configured 22 37 1 The Project This project will use the pulse width modulator PWM to ramp an LED on and off every two seconds An AT90S2313 processor will be used as the controller The circuit for this demonstration is shown in the schematic diagram If you have a development kit you should be able to use it rather than build the circuit for this project Note Meanwhile the AT90S2313 became obsolete Either use its successor the pin compatible ATtiny2313 for the project or perhaps th
248. ble x double y static The copysign function returns x but with the sign of __y They work even if x __y are NaN or zero 22 6 3 8 double cos double x The cos function returns the cosine of __x measured in radians 22 6 3 9 double cosh double x The cosh function returns the hyperbolic cosine of x 22 6 3 10 double exp double x The exp function returns the exponential value of x 22 6 3 11 double fabs double x The fabs function computes the absolute value of a floating point number __x Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 6 lt math h gt Mathematics 163 22 6 3 12 double double x double The fdim function returns max __x __y 0 If __x or __y or both are NaN NaN is returned 22 6 3 13 double floor double x X The floor function returns the largest integral value less than or equal to expressed as a floating point number 22 6 3 14 double fma double x double _ double 2 The fma function performs floating point multiply add This is the operation x y __z but the intermediate result is not rounded to the destination type This can sometimes improve the precision of a calculation 22 6 3 15 double fmax double x double The fmax function returns the greater of the two values __x and y If an argument is NaN the other argument is returned If both arguments are NaN NaN is returned
249. by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 270 However there are a number of caveats that you need to be aware of to use this API properly Be sure to include lt avr io h gt to get all of the definitions for the API The LOCKBITS macro defines a global variable to store the lockbit data This variable is assigned to its own linker section Assign the desired lockbit values immediately in the variable initialization The lock section in the ELF file will get its values from the initial variable assignment ONLY This means that you can NOT assign values to this variable in functions and the new values will not be put into the ELF lock section The global variable is declared in the LOCKBITS macro has two leading underscores which means that it is reserved for the implementation meaning the library so it will not conflict with a user named variable You must initialize the lockbit variable to some meaningful value even if it is the de fault value This is because the lockbits default to a logical 1 meaning unprogrammed Normal uninitialized data defaults to all locgial zeros So it is vital that all lockbits are initialized even with default data If they are not then the lockbits may not pro grammed to the desired settings and can possibly put your device into an unrecoverable state Be sure to have the mmcu device flag in your compile command line and your linker command line to have the correct device
250. byte avr pgmspace 272 pgm read byte far avr pgmspace 272 pgm read byte near avr pgmspace 272 pgm read dword avr pgmspace 273 pgm read dword far avr pgmspace 273 pgm read dword near avr pgmspace 273 pgm read float avr pgmspace 273 pgm read float far avr pgmspace 273 pgm read float near avr pgmspace 274 pgm read word avr pgmspace 274 pgm read word far avr pgmspace 274 pgm read word near avr pgmspace 274 VOID P avr pgmspace 274 pgmspace h 385 ELPM classic 388 ELPM dword enhanced 388 ELPM dword xmega 388 ELPM enhanced 389 ELPM float enhanced 389 ELPM float xmega 390 ELPM word classic 390 ELPM word enhanced 391 word xmega 391 ELPM_xmega__ 392 LPM_classic__ 392 LPM_dword_classic__ 392 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX LPM dword enhanced 393 PRIiLEAST32 LPM enhanced 393 avr inttypes 144 LPM float classic 394 PRIILEAST8 LPM float enhanced 394 avr inttypes 144 LPM word classic 394 PRUPTR LPM word enhanced 395 pgm get far address 395 pow avr math 165 power h 396 powf avr math 159 PRId16 avr inttypes 142 PRId32 avr_inttypes 142 PRId8 avr inttypes 142 PRIdFAST16 avr_inttypes 143 PRIdFAST32 avr_inttypes 143 PRIdFAST8 avr_inttypes 143 PRIdLEAST16 avr_inttypes 143 PRIdLEAST32 avr inttypes 143 PRIdLE
251. cally evaluate to 0 22 25 2 Define Documentation 22 25 21 define_ DATE 20110216UL Numerical representation of the release date 22 25 2 2 define AVR LIBC DATE STRING 20110216 String literal representation of the release date 22 25 2 3 define LIBC MAJOR 1 Library major version number 22 25 2 4 define AVR LIBC MINOR 7 Library minor version number 22 25 2 5 define AVR LIBC REVISION 1 Library revision number 22 25 2 6 define AVR LIBC VERSION 10701UL Numerical representation of the current library version In the numerical representation the major number is multiplied by 10000 the minor number by 100 and all three parts are then added It is intented to provide a monoton ically increasing numerical value that can easily be used in numerical checks 22 25 27 define VERSION STRING 1 7 1 String literal representation of the current library version Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 26 lt avr wdt h gt Watchdog timer handling 303 22 06 lt avr wdt h gt Watchdog timer handling Defines define wdt reset volatile wdr define wdt_enable value define wdt_disable define WDTO_15MS 0 define WDTO_30MS 1 define WDTO_60MS 2 define WDTO_120MS 3 define WDTO_250MS 4 define WDTO 500MS 5 define WDTO 1S 6 define WDTO_2S 7 define WDTO 4S 8 define WDTO_8S 9 22 26 1 Detailed Description
252. ch EEPROM as the 24C16 would offer One exception might be to use an externally connected EEPROM device that is removable e g SDRAM PC memory comes with an integrated TWI EEPROM that carries the RAM configuration information 22 40 3 The Source Code The source code is installed under prefix share doc avr libc examples twitest twitest c where prefix isa configuration option For Unix systems it is usually set to either usror usr local Note 1 The header file lt util twi h gt contains some macro definitions for symbolic con stants used in the TWI status register These definitions match the names used in the Atmel datasheet except that all names have been prefixed with TW Note 2 The clock is used in timer calculations done by the compiler for the UART baud rate and the TWI clock rate Note 3 The address assigned for the 24Cxx EEPROM consists of 1010 in the upper four bits The following three bits are normally available as slave sub addresses allowing to operate more than one device of the same type on a single bus where the actual sub address used for each device is configured by hardware strapping However since the next data packet following the device selection only allows for 8 bits that are used as an EEPROM address devices that require more than 8 address bits 24C04 and above steal subaddress bits and use them for the EEPROM cell address bits 9 to 11 as re quired This example simply assumes al
253. chr const void int size t ATTR_ PURE int memcmp const void const void size t ATTR_PURE void memcpy void const void size_t void memmem const void size t const void size_t X ATTR_ PURE void memmove void const void size_t void memrchr const void int size_t PURE void memset void int size t int strcasecmp const char const char x ATTR_PURE char strcasestr const char const char x ATTR PURE char strcat char const char char strchr const char int __ATTR_PURE char strchrnul const char x int ATTR_PURE int stremp const char const char x __ATTR_PURE char strcpy char const char size tstrcspn const char s const char reject ATTR PURE char strdup const char s1 size_t strlcat char const char size_t size t strlcpy char const char size_t size t strlen const char x ATTR PURE char strlwr char int strncasecmp const char const char size t ATTR_PURE char strncat char const char size_t int strncmp const char const char size t ATTR_PURE char strncpy char const char size 1 size t strnlen const char size_t ATTR_PURE char strpbrk const char s const char accept ATTR_PURE char strrchr const char int PURE char strrev char char strsep char const char size_t strspn
254. complementary functions that it doesn t make much sense to split them up For example malloc and free If someone is going to use malloc they will very likely be using free or at least should be using free In this case it makes more sense to aggregate those two functions in the same object module The second case is when you want to have an Interrupt Service Routine ISR in your library that you want to link in The problem in this case is that the linker looks for unresolved references and tries to resolve them with code in libraries A reference is the same as a function call But with ISRs there is no function call to initiate the ISR The ISR is placed in the Interrupt Vector Table IVT hence no call no reference and no linking in of the ISR In order to do this you have to trick the linker in a way Aggregate the ISR with another function in the same object module but have the other Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 8 4 Creating a Library 53 function be something that is required for the user to call in order to use the ISR like perhaps an initialization function for the subsystem or perhaps a function that enables the ISR in the first place 8 4 Creating a Library The librarian program is called ar for archiver and is found in the GNU Binutils project This program will have been built for the AVR target and will therefore be named avr ar The job of the librarian program
255. cription 24 95 wdt h File Reference Defines define wdt reset volatile wdr define _WD_PS3_MASK 0x00 define WD_CONTROL_REG WDTCR define WD CHANGE BIT WDCE define wdt_enable value define wdt_disable define WDTO_15MS 0 define WDTO_30MS 1 define WDTO_60MS 2 define WDTO_120MS 3 Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 24 95 wdt h File Reference 414 define WDTO_250MS 4 define WDTO 500MS 5 define WDTO 1S 6 define WDTO 2S 7 define WDTO 4S 8 define WDTO 8S 9 24 95 1 Detailed Description Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen Index lt alloca h gt Allocate space in the stack 134 lt assert h gt Diagnostics 135 lt avr boot h gt Bootloader Support Utili ties 227 lt avr cpufunc h gt Special AVR CPU func tions 234 lt avr eeprom h gt EEPROM handling 234 lt avr fuse h gt Fuse Support 239 lt avr interrupt h gt Interrupts 242 lt avr io h gt AVR device specific IO defi nitions 266 lt avr lock h gt Lockbit Support 267 lt avr pgmspace h gt Program Space Util ities 269 lt avr power h gt Power Reduction Man agement 291 lt avr sfr_defs h gt Special function regis ters 295 lt avr signature h gt Signature Support 297 lt avr sleep h gt Power Management and Sleep Modes 298 lt avr version h gt avr libc version macros 300 lt avr wdt h gt Watchdog timer handling
256. ction is similar to strcspn except that re ject is a pointer to a string in program space Returns The strcspn_P function returns the number of characters in the initial segment of s which are not in the string re ject The terminating zero is not considered as part of string 22 19 4 21 size tstrlcat P char x dst PGM P src size tsiz Concatenate two strings The strlcat_P function is similar to strlcat except that the src string must be located in program space flash Appends src to string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat_P function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 284 22 19 4 22 size tstrlcat PF char dst uint_farptr_t src size Concatenate two strings The strlcat_PF function is similar to strlcat except that the src string must be located in program space flash and is addressed using a far pointer Appends src to string dst of size n unlike strncat n is the full size of dst not space left At most n characters will be copied Always NULL terminates unless n lt strlen dst Parameters dst A pointer to the destination s
257. cumentation 22 9 3 1 void clearerr FILE stream Clear the error and end of file flags of st ream 22 9 3 2 int fclose FILE stream This function closes st ream and disallows and further IO to and from it When using fdevopen to setup the stream a call to fclose is needed in order to free the internal resources allocated If the stream has been set up using fdev_setup_stream or FDEV SETUP STREAM use fdev_close instead It currently always returns 0 for success 22 9 3 3 FILE fdevopen int char FILE x put int FILE x get This function is a replacement for fopen It opens a stream for a device where the actual device implementation needs to be provided by the application If successful a pointer to the structure for the opened stream is returned Reasons for a possible failure currently include that neither the put nor the get argument have been provided thus attempting to open a stream with no IO intent at all or that insufficient dynamic memory is available to establish a new stream Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 9 lt stdio h gt Standard IO facilities 191 If the put function pointer is provided the stream is opened with write intent The function passed as put shall take two arguments the first a character to write to the device and the second a pointer to FILE and shall return 0 if the output was successful and a nonzero value if the
258. curred 22 11 3 23 size_t strlen const char x src Calculate the length of a string The strlen function calculates the length of the string src not including the terminat ing 0 character Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 223 Returns The strlen function returns the number of characters in src 22 11 3 24 char x strlwr char s Convert a string to lower case The strlwr function will convert a string to lower case Only the upper case alphabetic characters A Z are converted Non alphabetic characters will not be changed Returns The strlwr function returns a pointer to the converted string 22 11 3 25 int strncasecmp const char 57 const char 52 size t len Compare two strings ignoring case The strncasecmp function is similar to strcasecmp except it only compares the first len characters of s1 Returns The strncasecmp function returns an integer less than equal to or greater than zero if s1 or the first Len bytes thereof is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strncasecmp is that if s1 is an initial substring of s2 then s1 is considered to be less than 52 22 11 3 26 char x strncat char x dest const char x src size t len Concatenate two strings The strncat function is similar to strcat except that only the first n
259. d Since there s no operating system the application needs to provide enough details about their devices in order to make them usable by the standard IO facilities Due to space constraints some functionality has not been implemented at all like some of the printf conversions that have been left out Nevertheless potential users of this implementation should be warned the printf and scanf families of functions although usually associated with presumably simple things like the famous Hello world program are actually fairly complex which causes their inclusion to eat up a fair amount of code space Also they are not fast due to the nature of interpreting the format string at run time Whenever possible resorting to the sometimes non standard predetermined conversion facilities that are offered by avr libc will usually cost much less in terms of speed and code size Tunable options for code size vs feature set order to allow programmers a code size vs functionality tradeoff the function vfprintf which is the heart of the printf family can be selected in different flavours using linker options See the documentation of vfprintf for a detailed description The same applies to vfscanf and the scanf family of functions Outline of the chosen API The standard streams st din stdout and stderr are pro vided but contrary to the C standard since avr libc has no knowledge about applicable devices these streams are not already p
260. d char prece char __s The dtostrf function converts the double value passed in val into an ASCII representationthat will be stored under s The caller is responsible Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 207 for providing sufficient storage in s Conversion is done in the format d ddd The minimum field width of the output string including the and the possible sign for negative values is given in width and prec determines the number of digits after the decimal sign width is signed value negative for left adjustment The dtostrf function returns the pointer to the converted string s 22 10 4 11 void exit int status The exit function terminates the application Since there is no environment to return to status is ignored and code execution will eventually reach an infinite loop thereby effectively halting all code processing Before entering the infinite loop interrupts are globally disabled In a C context global destructors will be called before halting execution 22 10 4 12 void free void x _ ptr The free function causes the allocated memory referenced by pt r to be made available for future allocations If pt x is NULL no action occurs 22 10 4 13 charx itoa int val char s int radix Convert an integer to a string The function itoa converts the integer value from val into an ASCII representation
261. d shows the preprocessor symbol declared by the mmcu option Architecture MCU name Macro avrl at90s1200 AVR AT90S1200 avrl attinyll AVR AT nyll Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 109 attiny12 _ AVR AT nyl2 avrl attiny15 AVR AT nyl5 avrl attiny28 AVR AT ny28 avr2 at90s2313 AVR_AT90S2313__ avr2 at90s2323 AVR 479052323 avr2 at90s2333 AVR 479052333 avr2 at90s2343 AVR_AT90S2343__ avr2 attiny22 _ AVR AT ny22 avr2 attiny26 AVR AT ny26 avr2 at90s4414 AVR_AT90S4414__ avr2 at90s4433 AVR_AT90S4433__ avr2 at90s4434 AVR_AT90S4434__ avr2 at90s8515 AVR ATO90S8515 avr2 at90c8534 AVR 4790 8534 avr2 at90s8535 AVR_AT90S8535_ avr2 avr25 1 at86rf401 AVR ATS86RF401 avr2 avr25 1 ata6289 AVR_ATA6289__ avr2 avr25 1 attiny13 AVR AT nyl3 avr2 avr25 1 attiny13a AVR AT nyl3A avr2 avr25 1 attiny2313 AVR_ATtiny2313__ avr2 avr25 1 attiny2313a AVR_ATtiny2313A__ avr2 avr25 1 attiny24 AVR AT ny24 avr2 avr25 1 attiny24a AVR AT ny24A avr2 avr25 1 attiny25 _ AVR AT ny25 avr2 avr25 1 attiny261 AVR AT ny261 avr2 avr25 1 attiny261a AVR_ATtiny261A__ avr2 avr25 1 attiny4313 AVR_ATti
262. d y No overflow if result is in range 22 6 3 20 static int isfinite double x static The isfinite function returns a nonzero value if xis finite not plus or minus infinity and not NaN 22 6 3 21 intisinf double x The function isinf returns 1 if the argument x is positive infinity 1 if xis negative infinity and 0 otherwise Note The GCC 4 3 can replace this function with inline code that returns the 1 value for both infinities gcc bug 35509 22 6 3 22 int isnan double x The function isnan returns 1 if the argument x represents a not a number NaN object otherwise 0 22 6 3 23 double ldexp double x int exp The Idexp function multiplies a floating point number by an integral power of 2 It returns the value of __x times 2 raised to the power exp 22 6 3 24 double log double x The log function returns the natural logarithm of argument x Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 165 22 6 3 25 double log10 double x The 105100 function returns the logarithm of argument x to base 10 22 6 3 26 longlrint double x The Irint function rounds x to the nearest integer rounding the halfway cases to the even integer direction That is both 1 5 and 2 5 values are rounded to 2 This function is similar to rint function but it differs in type of return value and in that an overflow is possible
263. dard The AVR toolset takes a different approach GCC has a special keyword attribute that is used to attach different at tributes to things such as function declarations variables and types This keyword is followed by an attribute specification in double parentheses In AVR GCC there is a special attribute called progmem This attribute is use on data declarations and tells the compiler to place the data in the Program Memory Flash AVR Libc provides a simple macro PROGMEM that is defined as the attribute syntax of GCC with the progmem attribute This macro was created as a convenience to the end user as we will see below The PROGMEM macro is defined in the lt avr pgmspace h gt system header file It is difficult to modify GCC to create new extensions to the C language syntax so instead avr libc has created macros to retrieve the data from the Program Space These macros are also found in the lt avr pgmspace h gt system header file 5 2 ANote On const Many users bring up the idea of using C s keyword const as a means of declaring data to be in Program Space Doing this would be an abuse of the intended meaning of the const keyword const is used to tell the compiler that the data is to be read only It is used to help make it easier for the compiler to make certain transformations or to help the compiler check for incorrect usage of those variables For example the const keyword is commonly used in many functio
264. dard IO facilities 360 non blinking cursor enabled SRAM addresses are increasing so characters will be written left to right The public function lcd_putchar takes arguments that make it suitable for be ing passed as a put function pointer to the stdio stream initialization functions and macros fdevopen FDEV SETUP STREAM etc Thus it takes two argu ments the character to display itself and a reference to the underlying stream object and it is expected to return 0 upon success This function remembers the last unprocessed newline character seen in the function local static variable nl seen If a newline character is encountered it will simply set this variable to a true value and return to the caller As soon as the first non newline character is to be displayed with n1 seen still true the LCD controller is told to clear the display put the cursor home and restart at SRAM address 0 All other characters are sent to the display The single static function internal variable n1 seen works for this purpose If mul tiple LCDs should be controlled using the same set of driver functions that would not work anymore as a way is needed to distinguish between the various displays This is where the second parameter can be used the reference to the stream itself instead of keeping the state inside a private variable of the function it can be kept inside a private object that is attached to the stream itself
265. de into section init4 see The initN Sections With respect to the standard this sentence is somewhat simplified because the standard allows for machines where the actual bit pattern used differs from all bits being 0 but for the AVR target in general all integer type variables are set to 0 all pointers to a NULL pointer and all floating point variables to 0 0 As long as these variables are not initialized 1 e they don t have an equal sign and an initialization expression to the right within the definition of the variable they go into the bss section of the file This section simply records the size of the variable but otherwise doesn t consume space neither within the object file nor within flash memory Of course being a variable it will consume space in the target s SRAM In contrast global and static variables that have an initializer go into the data section of the file This will cause them to consume space in the object file in order to record the initializing value and in the flash ROM of the target device The latter is needed since the flash ROM is the only way that the compiler can tell the target device the value this variable is going to be initialized to Now if some programmer wants to make doubly sure their variables really get a 0 at program startup and adds an initializer just containing 0 on the right hand side they waste space While this waste of space applies to virtually any platform C is implemen
266. def signed int int16 t typedef unsigned int uint16_t typedef signed long int int32 t typedef unsigned long int uint32 t typedef signed long long int int64 t typedef unsigned long long int uint64 t Integer types capable of holding object pointers These allow you to declare variables of the same size as a pointer Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 170 typedef int16 t intptr t e typedef uint16_t uintptr_t Minimum width integer types Integer types having at least the specified width typedef int8 t int least8 t typedef uint8 t uint least8 t typedef int16 t int least16 t typedef uint16 tuint leastl6 t typedef int32 t int least32 t typedef uint32 t least32 t typedef int64 t int least64 t typedef uint64 t least64 t Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8 t int fast8 t typedef uint8 t uint fast8 t typedef int16 t int fast16 t typedef uint16_t uint_fast16_t typedef int32_t int_fast32_t typedef uint32_t uint_fast32_t typedef int64_t int_fast64_t typedef uint64_t uint_fast64_t Greatest width integer types Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category typedef int64_t intmax_t typedef uint64_t uintmax_t Generated on Thu May 19 2011 13 29 12 for avr libc
267. dered to be part of the string The strchr P function is similar to strchr except that s is pointer to a string in program space Returns The strchr_P function returns a pointer to the matched character or NULL if the character is not found 22 19 415 P strchrnul P PGM P s intc The strchrnul P function is like strchr P except that if c is not found in s then it returns a pointer to the null byte at the end of s rather than NULL Glibc GNU extension Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 282 Returns strchrnul P function returns a pointer to the matched character or a pointer to the null byte at the end of s i e ststrlen s if the character is not found 22 19 4 16 int strcemp P const char 57 P s2 The strcmp P function is similar to strcmp except that 52 is pointer to a string in program space Returns The strcmp function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcmp P is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 22 19 4 17 int strcemp PF const char s1 uint_farptr_t s2 Compares two strings The stremp_PF function is similar to stremp except that 52 is a far pointer to a string in
268. ding up to a release Be sure to leave the lt date gt part of the version Bring the build system up to date by running bootstrap and configure Perform a make distcheck and make sure it succeeds This will create the snapshot source tarball This should be considered the first release candidate Upload the snapshot tarball to savannah Update the bug tracker interface on Savannah Bugs gt Edit field values gt Release Fixed Release Announce the branch and the branch tag to the avr libc dev list so other devel opers can checkout the branch 15 2 2 Making a release A stable release will only be done on a branch not from the SVN trunk The following steps should be taken when making a release 1 Make sure the source tree you are working from is on the correct branch svn switch svn ssh Susername svn savannah nongnu org avr libc branches avr minor branch Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 15 2 Releasing AVR Libc 125 10 11 12 13 Update the package version in configure ac and commit it to SVN Update the gnu tool chain version requirements in the README and commit to SVN Update the ChangeLog file to note the release and commit to SVN on the branch Add Released avr libc this release Update the NEWS file with pending release number and commit to SVN Change Changes since avr libc last release to Changes in avr libc lt th
269. doing EEPROM writes This is almost entirely Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 1135 Why is my baud rate wrong 90 transparent to the user with one exception When a byte is written to the EEPROM the entire EEPROM page is also transparently erased and re written which will cause wear to bytes that the programmer did not explicitly write If it is desired to extend EEPROM write lifetimes in an attempt not to exceed the datasheet EEPROM write endurance specification for a given byte then writes must be in multiples of the EEP ROM page size and not sequential bytes The EEPROM write page size varies with the device The EEPROM page size is found in the datasheet section on Memory Pro gramming generally before the Electrical Specifications near the end of the datasheet The failure mechanism for an overwritten byte page is generally one of stuck bits 1 e a bit will stay at a one or zero state regardless of the byte written Also a write followed by a read may return the correct data but the data will change with the passage of time due the EEPROM s inability to hold a charge from the excessive write wear Back to FAQ Index 11 35 Why is my baud rate wrong Some AVR datasheets give the following formula for calculating baud rates F CPU UART_BAUD_RATE 16L 1 Unfortunately that formula does not work with all combinations of clock speeds and baud rates due to integer truncation during the div
270. dword enhanced define _ ELPM_dword_xmega__ addr define _ ELPM_float_classic__ addr define _ ELPM_float_enhanced__ addr define _ ELPM_float_xmega__ addr define _ ELPM addr __ELPM_classic__ addr Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 24 35 pgmspace h File Reference 387 define ELPM word addr ELPM word classic addr define _ ELPM_dword addr dword classic addr define _ ELPM float addr float classic define read byte far address long ELPM uint32 t address long define read word far address long ELPM word uint32 t address long define read dword far address long ELPM dword uint32 t address long e define read float far address long ELPM float uint32 t address long define pgm_read_byte address_short pgm_read_byte_near address_short define pgm_read_word address_short pgm_read_word_near address_short define pgm_read_dword address_short pgm_read_dword_near address_short define pgm_read_float address_short pgm_read_float_near address_short define PGM P const prog char define PGM VOID P const prog void x define pgm get far address var Typedefs typedef void PROGMEM prog void typedef char PROGMEM prog char typedef unsigned char PROGMEM prog uchar typedef int8 t PROGMEM prog int8 t typedef uint8 t PROGMEM prog uint8
271. e ATmega8 or one of its successors ATmega48 88 168 which have become quite popular since the origi nal demo project had been established For all these more modern devices it is no longer necessary to use an external crystal for clocking as they ship with the inter nal 1 MHz oscillator enabled so C2 and Q1 can be omitted Normally for this experiment the external circuitry on RESET R1 C3 can be omitted as well leaving only the AVR the LED the bypass capacitor C4 and perhaps R2 For the ATmega8 48 88 168 use pin 15 at the DIP 28 package to connect the LED to Additionally this demo has been ported to many different other AVRs The lo cation of the respective OC pin varies between different AVRs and it is mandated by the AVR hardware Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 332 T LO RESET XTAL2 XTAL1 vcc GND 5 o a SCK PB7 MISO PB6 MOST PB5 PB4 OCI PB3 PB2 AIN1 PB1 AINO PBO ICP PD6 T1 PD5 TO PD4 INT1 PD3 INTO PD2 TXD PD1 RXD PDO AT90S2313P Figure 5 Schematic of circuit for demo project 39 18 11 15 zz Di bre See note 8 Na 13 12 GND 11 es 8 7 _ L6 3 _ 2 The source code is given in demo c For the sake of this example create a file called demo c containing this source code Some of the
272. e EMPTY INTERRUPT vector define 5 ALIAS vector target vector define reti define BADISR vect ISR attributes define ISR BLOCK define ISR NOBLOCK define ISR_NAKED e define ISR_ALIASOF target_vector 24 16 1 Detailed Description 24 17 inttypes h File Reference Defines macros for printf and scanf format specifiers For C these are only included if _ STDC LIMIT MACROS is defined before including lt inttypes h gt Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 17 inttypes h File Reference 379 define PRId8 d define PRIdLEASTS define PRIdFASTS d define PRII8 1 define PRIILEASTS 1 define PRIiFASTS i define PRId16 d define PRIdLEASTI6 d define PRIdFAST16 d define PRLi16 i define PRIILEASTI6 i define PRIIFAST16 i define PRId32 define PRIdLEAST32 Id define PRIdFAST32 Id define PRIi32 li define PRIILEAST32 li define PRIIFAST32 li define PRIdPTR PRId16 define PRII116 define PRIo8 o define PRIOLEASTS o define PRIOFASTS o define PRIu8 u define PRIULEASTS8 u define PRIUFASTS u define PRIx8 x define PRIXLEASTS x define PRIXFASTS x define PRIX8 X define PRIXLEASTS X define PRIXFASTS X define PRIo16 o define PRIOLEASTI6 o define PRIoFAST16 o define PRIu16 u define PRIULEAST16 u define PRIUFAST16 u define PRIx16 x defi
273. e attached to port C Likewise the output is not on port D pin 5 but on port B pin 1 PB1 Thus the above cabling scheme needs to be changed so that PB1 connects to the LEDO pin PD6 remains unconnected When using the STK500 use one of the jumper cables for this connection All other port D pins should be connected the same way as described for the ATmega16 above When not using an STK500 starter kit attach the LEDs through some resistor to Vcc low active LEDs and attach pushbuttons from the respective input pins to GND The internal pull up resistors are enabled for the pushbutton pins so no external resistors are needed Finally the demo has been ported to the ATtiny2313 as well As this AVR does not offer an ADC everything related to handling the ADC is disabled in the code for that MCU type Also port D of this controller type only features 6 pins so the 1 second flash LED had to be moved from PD6 to PD4 PD4 is used as the ADC control button on the other MCU types but that is not needed here OCIA is located at PB3 on this device The TARGET macro in the Makefile needs to be adjusted appropriately for the alternative controller types The flash ROM and RAM consumption of this demo are way below the resources Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 38 A more sophisticated project 350 of even an ATmega48 and still well within the capabilities of an ATtiny2313 The majo
274. e errno when an error occurs The file lt errno h gt provides symbolic names for various error codes Warning The errno global variable is not safe to use in a threaded or multi task system A race condition can occur if a task is interrupted between the call which sets error and when the task examines errno If another task changes errno during this time the result will be incorrect for the interrupted task 22 4 2 Define Documentation 22 4 21 define EDOM 33 Domain error 22 4 2 2 define ERANGE 34 Range error 22 5 lt inttypes h gt Integer Type conversions Far pointers for memory access gt 64K typedef int32 t int farptr t typedef uint32 t uint farptr t macros for printf and scanf format specifiers For C these are only included if STDC LIMIT MACROS is defined before in cluding lt inttypes h gt Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 141 define PRId8 d define PRIdLEASTS define PRIdFASTS d define PRLi8 i define PRILEASTS i define PRIIFASTS 1 define PRId16 d define PRIGLEAST16 d define PRIGFAST16 d define PRIi16 i define PRILEASTI6 i define PRIiFAST16 i define PRId32 1 define PRIGLEAST32 define PRIdFAST32 ld define PRIi32 li define PRULEAST32 li define PRIiFAST32 li define PRI4PTR PRId16 define PRII16 define PRIo8 o def
275. e hexadecimal value of smallval is PRIx8 the decimal value of longval is PRId32 n smallval longval 22 5 2 Define Documentation 22 5 21 define PRId16 d decimal printf format for int16 t 22 5 2 2 define PRId32 Id decimal printf format for int32 t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 144 22 5 2 3 define PRIdS d decimal printf format for int8 t 22 5 2 4 define PRIGFAST16 decimal printf format for int fast16 t 22 5 2 5 define PRIdFAST32 Id decimal printf format for int fast32 t 22 5 2 6 define PRIdFASTS decimal printf format for int fast8 t 22 5 2 7 define PRIGLEAST16 d decimal printf format for int_least16_t 22 5 2 8 define PRIGLEAST32 1d decimal printf format for int_least32_t 22 5 2 9 define PRIGLEASTS8 d decimal printf format for int_least8_t 22 5 2 10 define PRIdPTR PRId16 decimal printf format for intptr t 22 5 2 11 define PRIi16 i integer printf format for int16 t 22 5 2 12 define PRIi32 li integer printf format for int32 t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 145 22 5 2 13 ffdefine PRIi8 i integer printf format for int8 t 22 5 2 14 define PRIiFASTI6 i integer printf format for int fast16 t 22 5 2 15 define PRIiFAST32 Ili integer printf format
276. e last available address in internal SRAM Thus the region between end and the end of SRAM is what is available for stack If your application uses malloc which e g also can happen inside printf the heap for dynamic memory is also located there See Memory Areas and Using malloc The amount of stack required for your application cannot be determined that easily For example if you recursively call a function and forget to break that recursion the amount of stack required is infinite You can look at the generated assembler code avr gcc S there s a comment in each generated assembler file that tells you the frame size for each generated function That s the amount of stack required for this function you have to add up that for all functions where you know that the calls could be nested Back to FAQ Index 11 23 15 it really impossible to program the ATtinyXX in While some small AVRs are not directly supported by the C compiler since they do not have a RAM based stack and some do not even have RAM at all itis possible anyway to use the general purpose registers as a RAM replacement since they are mapped into the data memory region Bruce D Lightner wrote an excellent description of how to do this and offers this together with a toolkit on his web page http lightner net avr ATtinyAvrGcc html Back to FAQ Index 11 24 What is this clock skew detected message It s a known problem of the MS DOS FA
277. e memory 13 2 Options for the assembler avr as 13 2 1 Machine specific assembler options mmcu architecture mmcu MCU name avr as understands the same mmcu options as avr gcc By default avr2 is assumed but this can be altered by using the appropriate arch pseudo instruction inside the assembler source file e mmall opcodes Turns off opcode checking for the actual MCU type and allows any possible AVR opcode to be assembled Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 2 Options for the assembler avr as 117 e mno skip bug Don t emit a warning when trying to skip a 2 word instruction with a CPSE SBIC SBIS SBRC SBRS instruction Early AVR devices suffered from a hardware bug where these instructions could not be properly skipped e mno wrap For RIMP RCALL instructions don t allow the target address to wrap around for de vices that have more than 8 KB of memory gstabs Generate stabs debugging symbols for assembler source lines This enables avr gdb to trace through assembler source files This option must not be used when assembling sources that have been generated by the C compiler these files already contain the appropriate line number information from the C source files e a cdhlmns file Turn on the assembler listing The sub options are c omit false conditionals e d omit debugging directives h include high level source 1 include assembly
278. eature Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 36 Combining C and assembly source files 327 The simple project is somewhat like the Hello world application for a microcon troller about the most simple project that can be done It is explained in good detail to allow the reader to understand the basic concepts behind using the tools on an AVR microcontroller The more sophisticated demo project builds on top of that simple project and adds some controls to it It touches a number of avr libc s basic concepts on its way A comprehensive example on using the standard IO facilities intends to explain that complex topic using a practical microcontroller peripheral setup with one RS 232 con nection and an HD44780 compatible industry standard LCD display The Example using the two wire interface TWI project explains the use of the two wire hardware interface also known as I2C that is present on many AVR controllers Finally the Combining C and assembly source files demo shows how C and assem bly language source files can collaborate within one project While the overall project is managed by a C program part for easy maintenance time critical parts are written directly in manually optimized assembly language for shortest execution times possi ble Naturally this kind of project is very closely tied to the hardware design thus it is custom tailored to a particular controller type and peripheral se
279. ect interrupt void MotorPWMBottom code In AVR GCC you declare an ISR like so ISR PCINT1_vect code AVR GCC uses the ISR macro to define an ISR This macro requries the header file include avr interrupt h The names of the various interrupt vectors are found in the individual processor IO header files that you must include with lt avr io h gt Note The names of the interrupt vectors in AVR GCC has been changed to match the names of the vectors in IAR This significantly helps in porting applications from IAR to AVR GCC 10 4 Intrinsic Routines TAR has a number of intrinsic routine such as enable interrupts disable interrupts __watchdog_reset These intrinsic functions compile to specific AVR opcodes SEL CLI WDR There are equivalent macros that are used in AVR GCC however they are not located in a single include file AVRGCChassei for enable interrupts andcli for disable interrupts Both of these macros are located in lt avr interrupts h gt AVR GCC has the macro wdt reset inplaceof watchdog reset How ever there is a whole Watchdog Timer API available in AVR GCC that can be found in lt avr wdt h gt Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 10 5 Flash Variables 60 10 5 Flash Variables The C language was not designed for Harvard architecture processors with separate memory spaces This means that there are various non standard
280. ect located in flash ROM 22 19 3 2 prog intl6 t Type of an int16 t object located in flash ROM 22 19 3 3 prog int32 t Type of an int32 t object located in flash ROM 22 19 3 4 prog int64 t Type of 10164 t object located in flash ROM Note This type is not available when the compiler option mint8 is in effect 22 19 3 5 prog int8 t Type of an int8 t object located in flash ROM Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 271 22 19 3 6 prog uchar Type of an unsigned char object located in flash ROM 22 19 3 7 prog uintl6 t Type of an uint16 t object located in flash ROM 22 19 3 8 prog uint32 t Type of an uint32 t object located in flash ROM 22 19 3 9 prog uint64 t Type of an uint64 t object located in flash ROM Note This type is not available when the compiler option mint8 is in effect 22 19 3 10 prog uint8 t Type of an uint8 t object located in flash ROM 22 19 3 11 prog void Type of a void object located in flash ROM Does not make much sense by itself but can be used to declare a void x object in flash ROM 22 19 4 Function Documentation 22 19 4 1 void x memccpy_P void x dest VOID P src int val size t len This function is similar to memccpy except that src is pointer to a string in program space 2219 42 VOID P memchr P PGM VOID P s int val size t
281. ed on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 33 What pitfalls exist when writing reentrant code 87 Back to FAQ Index 11 33 What pitfalls exist when writing reentrant code Reentrant code means the ability for a piece of code to be called simultaneously from two or more threads Attention to re enterability is needed when using a multi tasking operating system or when using interrupts since an interrupt is really a temporary thread The code generated natively by gcc is reentrant But only some of the libraries in avr libc are explicitly reentrant and some are known not to be reentrant In general any library call that reads and writes global variables including I O registers is not reentrant This is because more than one thread could read or write the same storage at the same time unaware that other threads are doing the same and create inconsistent and or erroneous results A library call that is known not to be reentrant will work if it is used only within one thread and no other thread makes use of a library call that shares common storage with it Below is a table of library calls with known issues Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 33 What pitfalls exist when writing reentrant code 88 Library call Reentrant Issue Workaround Alterna tive rand random Uses global variables to keep state information Use special reentrant versions rand r
282. ed stack context include lt setjmp h gt longjmp restores the environment saved by the last call of setjmp with the corre sponding jmpb argument After longjmp is completed program execution contin ues as if the corresponding call of setjmp had just returned the value rer Note longjmp cannot cause 0 to be returned If longjmp is invoked with a second argument of 0 1 will be returned instead Parameters jmpb Information saved by a previous call to setjmp ret Value to return to the caller of setjmp Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 169 Returns This function never returns 22 7 2 intsetjmp jmp buf jmpb Save stack context for non local goto finclude set jmp h setjmp saves the stack context environment in jmpb for later use by longjmp The stack context will be invalidated if the function which called setjmp returns Parameters jmpb Variable of type jmp_buf which holds the stack information such that the environment can be restored Returns setjmp returns 0 if returning directly and non zero when returning from longjmp using the saved context 22 8 lt stdint h gt Standard Integer Types Exact width integer types Integer types having exactly the specified width typedef signed char int8 t typedef unsigned char uint8 t type
283. ed to setup the UART to run at 9600 Bd and 38400 Bd respectively Using a CPU clock of 4 MHz 9600 Bd can be achieved with an acceptable tolerance without setting U2X prescaler 25 while 38400 Bd require U2X to be set prescaler 12 22 31 2 Define Documentation 22 31 2 1 define BAUD TOL 2 Input and output macro for lt util setbaud h gt Define the acceptable baud rate tolerance in percent If not set on entry it will be set to its default value of 2 22 31 2 2 define UBRR_VALUE Output macro from lt util setbaud h gt Contains the calculated baud rate prescaler value for the UBRR register 22 31 23 UBRRH VALUE Output macro from lt util setbaud h gt Contains the upper byte of the calculated prescaler value UBRR_VALUE 22 31 2 4 define UBRRL VALUE Output macro from lt util setbaud h gt Contains the lower byte of the calculated prescaler value UBRR VALUE 22 31 2 5 define USE 2X 0 Output bacro from lt util setbaud h gt Contains the value 1 if the desired baud rate tolerance could only be achieved by setting the U2X bit in the UART configuration Contains 0 otherwise Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 32 lt util twi h gt TWI bit mask definitions 318 22 32 lt util twi h gt TWI bit mask definitions TWSR values Mnemonics TW MT xxx master transmitter TW MR xxx master receiver TW ST xxx slave transmitter TW SR xxx slave receiver define TW
284. edistributed with your application and there are issues if the Cygwin DLL already ex ists on the installation system and different versions of the DLL On the other hand MinGW MSYS can compile code as native Win32 applications However this means that programs designed for Unix and Linux i e that use POSIX functionality will not compile as MinGW MSYS does not provide that POSIX layer for you Therefore most programs that compile on both types of host systems usually must provide some sort of abstraction layer to allow an application to be built cross platform MinGW MSYS does provide somewhat of a POSIX environment that allows you to build Unix and Linux applications as they woud normally do with a configure step and a make step Cygwin also provides such an environment This means that building the AVR toolchain is very similar to how it is built in Linux described above The main differences are in what the PATH environment variable gets set to pathname differences and the tools that are required to build the projects under Windows We ll take a look at the tools next 12 12 Tools Required for Building the Toolchain for Windows These are the tools that are currently used to build WinAVR 20070525 or later This list may change either the version of the tools or the tools themselves as improve Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 12 Tools Required for Building the Toolchain for Windows 98 ments
285. efine MAX UINT64 MAX Limits of other integer types C implementations should define these macros only when STDC LIMIT MACROS is defined before lt stdint h gt is included define PPFRDIFF MAX INTI6 MAX define MIN INT16 MIN define SIG ATOMIC MAX INT8 MAX define SIG ATOMIC MIN INT8 MIN define SIZE MAX CONCAT INTI6 MAX U Macros for integer constants C implementations should define these macros only when _STDC_CONSTANT_ MACROS is defined before lt stdint h gt is included These definitions are valid for integer constants without suffix and for macros de fined as integer constant without suffix define INT8_C value int8 t value define UINT8_C value uint8 t CONCAT value U define INT16 C value value define UINT16_C value CONCAT value U define INT32_C value _ CONCAT value L define UINT32_C value UL define INT64_C value _ CONCAT value LL define UINT64_C value _ CONCAT value ULL define INTMAX_C value _ CONCAT value LL define UINTMAX_C value _ CONCAT value ULL Typedefs Exact width integer types Integer types having exactly the specified width typedef signed char int8 t typedef unsigned char uint8 t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 41 stdint h File Reference 401 typedef signed int int16 t typedef unsigned int uint16 t typedef signed long int int32 t typedef
286. ega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega406 ATmega48P 45 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny13 ATtiny43U 48 24 AT tiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 PCINTI vect SIG PIN Pin Change Inter ATmegal62 ATmegal65 ATmegal65P CHANGEI rupt Request 1 ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega406 ATmega48P 45 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny43U ATtiny48 AT tiny24 ATtiny44 ATtiny84 AT90USB 162 AT90USB82 PCINT2_vect SIG_PIN_ Pin Change Inter ATmega3250 ATmega3250P ATmega328P CHANGE2 rupt Request 2 ATmega3290 ATmega3290P ATmega48P ATmega6450 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P AT megal64P ATmega644P ATmega644 AT tiny48 PCINT3 vect SIG PIN Pin Change Inter ATmega3250 ATmega3250P ATmega3290 CHANGE3 rupt Request 3 ATmega3290P ATmega
287. egister For those devices that have a WDTCSR register it uses the combination of the WDPO through WDP3 bits See also the symbolic constants WDTO 15MS et al 22 26 2 3 define wdt_reset asm volatile wdr Reset the watchdog timer When the watchdog timer is enabled a call to this instruction is required before the timer expires otherwise a watchdog initiated device reset will occur 22 26 2 4 define WDTO 120MS 3 See WDTO 15MS 22 26 2 5 itdefine WDTO 15MS 0 Symbolic constants for the watchdog timeout Since the watchdog timer is based on a free running RC oscillator the times are approximate only and apply to a supply voltage of 5 V At lower supply voltages the times will increase For older devices the times will be as large as three times when operating at Vcc 3 V while the newer devices e g ATmegal28 ATmega8 only experience a negligible change Possible timeout values are 15 ms 30 ms 60 ms 120 ms 250 ms 500 ms 1 s 2 s Some devices also allow for 4 s and 8 s Symbolic constants are formed by the prefix WDTO_ followed by the time Example that would select a watchdog timer expiry of approximately 500 ms enable WDTO_500MS 22 26 2 6 define WDTO 1S 6 See WDTO 15MS 22 26 2 7 define WDTO 250MS 4 See WDTO 15MS Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 06 lt avr wdt h gt Watchdog timer handling 306 22 26 2 8 define WDTO 2S 7 See WDTO 1
288. entire string was valid The strtoul function return either the result of the conversion or if there was a lead ing minus sign the negation of the result of the conversion unless the original non negated value would overflow in the latter case strtoul returns ULONG MAX and errno is set to ERANGE If no conversion could be performed 0 is returned 22 10 4 29 char ultoa unsigned long int val char x s int radix Convert an unsigned long integer to a string The function ultoa converts the unsigned long integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing suf ficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof unsigned long int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 213 Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 9 will be the letter a The ultoa function returns the pointer passed as s 22 10 4 30
289. er use of the movw instruction on the enhanced core If too many those that don t fit are passed on the stack Return values 8 bit in r24 not r25 16 bit in r25 124 up to 32 bits in 122 125 up to 64 bits in r18 r25 8 bit return values are zero sign extended to 16 bits by the called function unsigned char is more efficient than signed char justclr r25 Arguments to functions with variable argument lists printf etc are all passed on stack and char is extended to int Warning There was no such alignment before 2000 07 01 including the old patches for gcc 2 95 2 Check your old assembler subroutines and adjust them accordingly Back to FAQ Index 11 15 How dol put an array of strings completely in ROM There are times when you may need an array of strings which will never be modified In this case you don t want to waste ram storing the constant strings The most obvious and incorrect thing to do is this finclude avr pgmspace h PGM P array 2 PROGMEM Foo Bar int main void char buf 32 strcpy P buf array 1 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 15 How do I put an array of strings completely in ROM 75 return 0 The result is not what you want though What you end up with is the array stored in ROM while the individual strings end up in RAM in the data section To work around this you need to do something like this finclude avr pgmsp
290. erence 389 24 35 1 Detailed Description 24 35 2 Define Documentation 24 35 2 define ELPM classic addr extension N uint32 t addr32 uint32 t addr uint8 t _ result asm N N out 2 SGI TANNE N Hoy x31 SBI mne N Nov r30 SAT Mit N elpm n t N mov 0 r0 n t N r result N r __addr32 N I SFR IO ADDR RAMPZ ro r30 r31 N result N 24 35 2 2 define ELPM dword enhanced addr extension uint32 t addr32 uint32 t addr uint32 t _ result asm out 2 1 n t movw r30 1 n t elpm A0 Z elpm 0 Z n t elpm CO 2 AnNt elpm DO Z TANNET r result Ng dadde32 I SFR IO ADDR RAMPZ Ypr30 NEST result 24 35 23 define ELPM dword xmega addr Psu u dd Value Value Value Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Reference 390 extension N uint32 t addr32 uint32_t addr uint32 t _ result N asm N N tmp reg 2 n t out 2 SCIT TANNET M movw r30 1 n t N elpm 0 Z AnNt N elpm B0 Z4 n t N elpm CO Ze n t N elpm 0 7 n t out 2 tmp_reg__ N r _ result E add 32 N I SFR IO ADDR RAMPZ N NASO meam N result N 24 35 2 4 define ELPM e
291. erflow the input buffer provided so it should never be used at all If fgets fails to read anything the main loop is left Of course normally the main loop of a microcontroller application is supposed to never finish but again for demon strational purposes this explains the error handling of stdio gets will return NULL in case of an input error or end of file condition on input Both these condi tions are in the domain of the function that is used to establish the stream uart_ putchar in this case In short this function returns EOF in case of a serial line break condition extended start condition has been recognized on the serial line Common PC terminal programs allow to assert this condition as some kind of out of band signalling on an RS 232 connection When leaving the main loop a goodbye message is sent to standard error output i e to the LCD followed by three dots in one second spacing followed by a sequence that will clear the LCD Finally main will be terminated and the library will add an infinite loop so only a CPU reset will be able to restart the application There are three commands recognized each determined by the first letter of the line entered converted to lower case The q quit command has the same effect of leaving the main loop The LCD command takes its second argument and sends it to the LCD The u UART command takes its second argument and sends it back to t
292. errno 22 10 4 27 long strtol const char x __nptr char xx endptr int base The strtol function converts the string in to a long value The conversion is done according to the given base which must be between 2 and 36 inclusive or be the special value 0 The string may begin with an arbitrary amount of white space as determined by iss pace followed by a single optional or sign If base is zero or 16 the string may then include a Ox prefix and the number will be read in base 16 otherwise a zero base is taken as 10 decimal unless the next character is 0 in which case it is taken as 8 octal The remainder of the string is converted to a long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 represents 11 and so forth with Z representing 35 If endptr is not NULL strtol stores the address of the first invalid character in endptr If there were no digits at all however strtol stores the original value of nptr in endptr Thus if npt r is not VO but xxendptr is 0 on return the entire string was valid The strtol function returns the result of the conversion unless the value would under flow or overflow If no conversion could be performed 0 is returned If an overflow or underflow occurs
293. errno is set to ERANGE and the function return value is clamped to LONG MIN or LONG MAX respectively Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 212 22 10 4 28 unsigned long strtoul const char x nptr char endptr int base The strtoul function converts the string in to an unsigned long value The conversion is done according to the given base which must be between 2 and 36 inclusive or be the special value 0 The string may begin with an arbitrary amount of white space as determined by iss pace followed by a single optional or sign If base is zero or 16 the string may then include a Ox prefix and the number will be read in base 16 otherwise a zero base is taken as 10 decimal unless the next character is 0 in which case it is taken as 8 octal The remainder of the string is converted to an unsigned long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 B represents 11 and so forth with 2 representing 35 If endptr is not NULL strtoul stores the address of the first invalid character in xendptr If there were digits at all however strtoul stores the original value of nptr in endptr Thus if npt r is not NO but xxendptr is 0 on return the
294. erted in the format d ddde dd where there is one digit before the decimal point character and the number of digits after it is equal to the precision if the precision is missing it is taken as 6 if the precision is zero no decimal point character appears An E conversion uses the letter E rather than to introduce the exponent The exponent always contains two digits if the value is zero the exponent is 00 F The double argument is rounded and converted to decimal notation in the format ddd dda where the number of digits after the decimal point character is equal to the precision specification If the precision is missing it is taken as 6 if the precision is explicitly zero no decimal point character appears If a decimal point appears at least one digit appears before it gG The double argument is converted in style or e or F or E for conver sions The precision specifies the number of significant digits If the precision is missing 6 digits are given if the precision is zero it is treated as 1 Style e is used if the exponent from its conversion is less than 4 or greater than or equal to the precision Trailing zeros are removed from the fractional part of the result a decimal point appears only if it is followed by at least one digit S Similar to the s format except the pointer is expected to point to a program memory ROM string instead of a RAM string In no case does a non ex
295. etely ignored for the ATtiny45 option Next are the two interrupt service routines for timer 0 compare A match timer 0 hits TOP as OCROA is set to 255 and timer 0 overflow timer 0 hits BOTTOM As dis cussed above these are kept as short as possible They only save SREG as the flags will be modified by the INC instruction increment the counter hi variable which forms the high part of the current time counter the low part is formed by querying TCNTO directly and clear or set the variable flags respectively in order to note the current counting direction The RETI instruction terminates these interrupt service routines Total cycle count is 8 CPU cycles so together with the 4 CPU cycles needed for interrupt setup and the 2 cycles for the RJMP from the interrupt vector to the han dler these routines will require 14 out of each 256 CPU cycles or about 5 of the overall CPU time The pin change interrupt PCINTO will be handled in the final part of this file The basic algorithm is to quickly evaluate the current system time by fetching the current timer value of TCNTO and combining it with the overflow part in counter hi If the counter is currently counting down rather than up the value fetched from TCNTO must be negated Finally if this pin change interrupt was triggered by a rising edge the time computed will be recorded as the start time only Then at the falling edge Generated on Thu May 19 2011 13 29 12 for avr li
296. eturns the character or EOF in case an error occurred 22 9 3 12 intfputs const char str FILE stream Write the string pointed to by str to stream st ream Returns 0 on success and EOF on error 22 9 3 13 intfputs const char str FILE stream Variant of fputs where st x resides in program memory Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 193 22 9 3 14 size_t fread void p r size t size size t nmemb FILE x stream Read nmemb objects size bytes each from st ream to the buffer pointed to by ptr Returns the number of objects successfully read i e nmemb unless an input error occured or end of file was encountered feof and ferror must be used to distinguish between these two conditions 22 9 3 15 intfscanf FILE stream const char x _ fmt The function scan performs formatted input reading the input data from stream See vfscanf for details 22 9 3 16 intfscanf P FILE stream const char x fmt Variant of fscanf using a mt string in program memory 22 9 3 17 size_t fwrite const void _ ptr size t size size t nmemb FILE stream Write nmemb objects size bytes each to stream The first byte of the first object is referenced by ptr Returns the number of objects successfully written i e nmemb unless an output error occured 22 9 3 18 char gets char
297. exp define coshf cosh define sinhf sinh define tanhf tanh define acosf acos define asinf asin define atanf atan define atan2f atan2 define logf log define log10f log10 define powf pow define isnanf isnan define isinff isinf define isfinitef isfinite define copysignf copysign define signbitf signbit define fdimf fdim define fmaf fma define fmaxf fmax define fminf fmin define truncf trunc define roundf round define lroundf lround define lrintf lrint Functions double cos double __x double sin double __x double tan double __x double fabs double __x double fmod double __x double y double modf double __x double iptr float modff float x float iptr double sqrt double x double cbrt double __x double hypot double __x double y Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 20 math h File Reference 383 double square double x double floor double __x double ceil double x double frexp double x int __pexp double Idexp double __x int exp double exp double x double cosh double __ x double sinh double x double tanh double __x double acos double x double asin double __x double atan double x double atan2 double y double x double log double x double log10 double x double pow double __x double y intisnan double x int isinf double x static
298. f eps fig 5 FIG2DEV L eps lt amp pdf 5 FIG2DEV L pdf lt S png fig FIG2DEV L png lt SG 22 37 8 Reference to the source code The source code is installed under Sprefix share doc avr libc examples demo where prefix is a configuration option For Unix systems it is usually set to either usr usr local 22 38 Amore sophisticated project This project extends the basic idea of the simple project to control a LED with a PWM output but adds methods to adjust the LED brightness It employs a lot of the basic concepts of avr libc to achieve that goal Understanding this project assumes the simple project has been understood in full as well as being acquainted with the basic hardware concepts of an AVR microcontroller 22 38 1 Hardware setup The demo is set up in a way so it can be run on the ATmegal6 that ships with the STK500 development kit The only external part needed is a potentiometer attached to the ADC It is connected to a 10 pin ribbon cable for port A both ends of the poten tiometer to pins 9 GND and 10 VCC and the wiper to pin 1 port A0 A bypass capacitor from pin 1 to pin 9 like 47 nF is recommendable Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 38 A more sophisticated project 347 Figure 6 Setup of the STK500 The coloured patch cables are used to provide various interconnections As there are only four of them in the
299. ffects so it is possible to include this file more than once supposedly with different values for the BAUD parameter possibly even within the same function Assuming that the requested BAUD is valid for the given F CPU then the macro UBRR VALUE is set to the required prescaler value Two additional macros are pro vided for the low and high bytes of the prescaler respectively UBRRL VALUE is set to the lower byte of the UBRR VALUE and VALUE is set to the upper byte An additional macro USE 2X will be defined Its value is set to 1 if the desired BAUD rate within the given tolerance could only be achieved by setting the U2X bit in the UART configuration It will be defined to 0 if U2X is not needed Example usage include avr io h define F CPU 4000000 static void uart 9600 void define BAUD 9600 include lt util setbaud h gt UBRRH UBRRH_VALUE UBRRL UBRRL_VALUE dif USE 2X UCSRA 1 U2X else UCSRA amp 1 lt lt U2X endif static void uart_38400 void undef BAUD avoid compiler warning define BAUD 38400 include lt util setbaud h gt UBRRH UBRRH_VALUE UBRRL UBRRL_VALUE dif USE 2X Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 31 lt util setbaud h gt Helper macros for baud rate calculations 317 UCSRA 1 lt lt U2X else UCSRA amp 1 lt lt U2X endif In this example two functions are defin
300. figure prefix installdir target avr with gmp usr local with mpfr usr local enable doc 2 amp 1 tee insight configure log Make make all install 2 gt amp 1 tee Spackage make log SRecord Open source code package Configure and build at the top of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 13 Building the Toolchain for Windows 105 mingw bin c cygwin bin install directory gt bin Configure configure prefix installdir infodir installdir info mandir installdir man 2 gt amp 1 tee package configure log Make make all install 2 gt amp 1 tee package make log Build the tools below in Cygwin AVaRICE Open source code package Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin install directory gt bin Set location of LibUSB headers and libraries export CPPFLAGS I startdir libusb win32 device bin 1ibusb version include export CFLAGS I startdir libusb win32 device bin 1ibusb version include export LDFLAGS static L startdir libusb win32 device bin 1ibusb version lib gc Configure Sarchivedir configure prefix installdir datadir installdir doc
301. fine LPM enhanced addr Value extension N uintl16 t addrl16 uintl16 t addr uint8 t result N asm N N lpm 0 Z n t N Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Reference 395 r result N z addrl16 N result N 24 35 2 15 define _LPM_float_classic__ addr Value __extension__ uintl6 t addrl6 uint16_t addr N float result N asm X X lpm mov A0 ro mne adiw r30 1 n t N lpm n t mov B0 ro NONU N adiw r30 1 lpm n t mov CO ro n t N adiw r30 1 n t lpm n t mov DO ro N r result z addr16 I addrl16 X ro X result N 24 35 2 16 define LPM float enhanced addr Value extension 4 uintl16 t addrl16 uintl16 t addr float _ result asm lpm A0 Z lpm B0 Z lpm CO Z n t lpm DO Z n t r result z addr16 1 addr16 result Generated Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Reference 396 24 35 2 17 define word classic addr Value extension N uintl6 t _ addrl6 uintl6 t addr N uintl6 t result N asm N lpm Nux N mov 0 ro n t adiw r30 1 NN RET A lpm n t mov B0
302. for avr libc by Doxygen 22 39 Using the standard IO facilities 359 Building upon these the public functions hd44780 outbyte and hd44780_ inbyte transfer one byte to from the controller The function hd44780 wait ready waits for the controller to become ready by continuously polling the controller s status which is read by performing a byte read with the RS signal cleard and examining the BUSY flag within the status byte This function needs to be called before performing any controller IO Finally hd44780 init initializes the LCD controller into 4 bit mode based on the initialization sequence mandated by the datasheet As the BUSY flag cannot be examined yet at this point this is the only part of this code where timed delays are used While the controller can perform a power on reset when certain constraints on the power supply rise time are met always calling the software initialization routine at startup ensures the controller will be in a known state This function also puts the interface into 4 bit mode which would not be done automatically after a power on reset 22 39 3 5 cd h This function declares the public interface of the higher level character IO LCD driver 22 39 3 6 Icd c The implementation of the higher level LCD driver This driver builds on top of the HD44780 low level LCD controller driver and offers a character IO interface suitable for direct use by the standard IO facilities Where the
303. for int fast32 t 22 5 2 16 define PRIiFASTS i integer printf format for int fast8 t 22 5 2 17 PRIiLEASTIG i integer printf format for int leastl6 t 22 5 2 18 define PRIILEAST32 li integer printf format for int least32 t 22 5 2 19 define PRIiLEASTS i integer printf format for int least8 t 22 5 2 20 define PRIiPTR PRIi16 integer printf format for intptr t 22 5 2 21 define PRIo16 o octal printf format for uint16 t 22 5 2 22 define PRIo32 lo octal printf format for uint32 t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 146 22 5 2 23 define PRIo8 octal printf format for uint8 t 22 5 2 24 define PRIoFASTI6 octal printf format for fast16 t 22 5 2 25 define PRIoFAST32 lo octal printf format for uint_fast32_t 22 5 2 26 define PRIoFASTS o octal printf format for fast8 t 22 5 2 27 define PRIOLEASTIG o octal printf format for uint_least16_t 22 5 2 28 define PRIOLEAST32 lo octal printf format for uint_least32_t 22 5 2 29 define PRIOLEASTS o octal printf format for uint_least8_t 22 5 2 30 define PRIoPTR PRIo16 octal printf format for uintptr_t 22 5 2 31 define PRIu16 u decimal printf format for uint16 t 22 5 2 32 define PRIu32 lu decimal printf format for uint32_t Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 5
304. for target it is known as a native compiler If a compiler has different systems for host and target it is known as a cross compiler And if all three build host and target systems are different it is known as a Canadian cross compiler but we won t discuss that here When GCC is built to execute on a host system such as FreeBSD Linux or Windows and it is built to generate code for the AVR microcontroller target then it is a cross compiler and this version of GCC is commonly known as AVR GCC In documentation or discussion AVR GCC is used when referring to GCC targeting specifically the AVR or something that is AVR specific about GCC The term GCC is usually used to refer to something generic about GCC or about GCC as a whole GCC is different from most other compilers GCC focuses on translating a high level language to the target assembly only AVR GCC has three available compilers for the AVR C language C and Ada The compiler itself does not assemble or link the Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 2 4 GNU Binutils 14 final code GCC is also known as a driver program in that it knows about and drives other programs seamlessly to create the final output The assembler and the linker are part of another open source project called GNU Binutils GCC knows how to drive the GNU assembler gas to assemble the output of the compiler GCC knows how to drive the GNU linker Id to link all
305. format for uint_least32_t 22 5 2 81 define SCNoPTR SCNo16 octal scanf format for uintptr t 22 5 2 82 define SCNu16 decimal scanf format for uint16 t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 152 22 5 2 83 define SCNu32 decimal scanf format for uint32_t 22 5 2 84 define SCNuFASTI6 u decimal scanf format for uint fastl6 t 22 5 2 85 define SCNuFAST32 decimal scanf format for fast32 t 22 5 2 86 define SCNULEAST16 decimal scanf format for leastl6 t 22 5 2 87 define SCNuLEAST32 lu decimal scanf format for least32 t 22 5 2 88 define SCNuPTR SCNu16 decimal scanf format for uintptr t 22 5 2 89 define SCNx16 x hexadecimal scanf format for uint16 t 22 5 2 90 define SCNx32 Ix hexadecimal scanf format for uint32_t 22 5 2 91 define SCNxFAST16 x hexadecimal scanf format for uint_fast16_t 22 5 2 92 define SCNxFAST32 Ix hexadecimal scanf format for uint_fast32_t Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 6 lt math h gt Mathematics 153 22 5 2 93 define SCNxLEAST16 x hexadecimal scanf format for uint leastl6 t 22 5 2 94 define SCNxLEAST32 Ix hexadecimal scanf format for uint_least32_t 22 5 2 95 define SCNxPTR SCNx16 hexadecimal scanf format for uintptr_t 22 5 3 Typedef Documentation 22 5 3 1 typedef int32_t int_farptr
306. g Sections in C Code Example include avr io h void my init portb void _ attribute naked attribute section init3 void my init portb void PORTB Oxff DDRB Oxff Note Section init3 is used in this example as this ensures the inernal zero reg has already been set up The code generated by the compiler might blindly rely on zero reg being really 0 5 Data in Program Space 5 1 Introduction So you have some constant data and you re running out of room to store it Many AVRs have limited amount of RAM in which to store data but may have more Flash space available The AVR is a Harvard architecture processor where Flash is used for the program RAM is used for data and they each have separate address spaces It is a challenge to get constant data to be stored in the Program Space and to retrieve that data to use it in the AVR application The problem is exacerbated by the fact that the C Language was not designed for Harvard architectures it was designed for Von Neumann architectures where code and Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 5 2 A Note On const 28 data exist in the same address space This means that any compiler for a Harvard architecture processor like the AVR has to use other means to operate with separate address spaces Some compilers use non standard C language keywords or they extend the standard syntax in ways that are non stan
307. g memory first the freelist is walked to see if it could satisfy the request If there s a chunk available on the freelist that will fit the request exactly it will be taken disconnected from the freelist and returned to the caller If no exact match could be found the closest match that would just satisfy the request will be used The chunk will normally be split up into one to be returned to the caller and another smaller one that will remain on the freelist In case this chunk was only up to two bytes larger than the request the request will simply be altered internally to also account for these additional bytes since no separate freelist entry could be split off in that case If nothing could be found on the freelist heap extension is attempted This is where malloc margin will be considered if the heap is operating below the stack or where malloc heap end will be verified otherwise If the remaining memory is insufficient to satisfy the request NULL will eventually be returned to the caller When calling free a new freelist entry will be prepared An attempt is then made to aggregate the new entry with possible adjacent entries yielding a single larger entry available for further allocations That way the potential for heap fragmentation is hopefully reduced When deallocating the topmost chunk of memory the size of the heap is reduced A call to realloc first determines whether the operation is about to grow or shrink t
308. g without relocation r flag A xu script is like xr but dox create constructors Ur flag A xn script is for linking with n flag mix text and data on same page A xbn script is for linking with N flag mix text and data on same page Back to FAQ Index 11 30 How to add a raw binary image to linker output The GNU linker avr 1d cannot handle binary data directly However there s a com panion tool called avr objcopy This is already known from the output side it s used to extract the contents of the linked ELF file into an Intel Hex load file avr objcopy can create a relocatable object file from arbitrary binary input like avr objcopy I binary O elf32 avr foo bin foo o This will create a file named foo o with the contents of foo bin The contents will default to section data and two symbols will be created named binary foo bin start and binary foo bin end These symbols can be referred to inside a C source to access these data Ifthe goal is to have those data go to flash ROM similar to having used the PROGMEM attribute in C source code the sections have to be renamed while copying and it s also useful to set the section flags avr objcopy rename section data progmem data contents alloc load readonly dat a I binary O elf32 avr foo bin foo o Note that all this could be conveniently wired into a Makefile so whenever oo bin changes it will trigger the recreation of foo o and a subsequent relink of t
309. ga324P ATmegal64P ATmega644P ATmega644 USARTI SIG USARTI Rx ATmegal62 RXC vect USARTI Complete RECV Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 261 USARTI SIG USARTI Rx AT90CAN128 AT90CAN32 ATOOCAN64 RX_vect UARTI Complete ATmegal28 ATmegal284P ATmega64 RECV ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 USARTI SIG USARTI Tx ATmegal62 TXC vect USARTI Complete TRANS USARTI SIG USARTI Tx AT90CANI28 AT90CAN32 AT90CANOGA TX vect UARTI Complete ATmegal28 ATmegal284P ATmega64 TRANS ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 USARTI SIG USARTI Data AT90CANI28 AT90CAN32 AT90CAN64 UDRE vect UARTI Register Empty ATmegal28 ATmegal284P ATmegal62 DATA ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 USART2_ SIG_ USART2 Rx ATmega640 ATmegal280 ATmegal28l RX vect USART2 Complete ATmega2560 ATmega2561 RECV USART2_ SIG_ USART
310. ga329a atmega329p atmega329pa atmega3290 atmega3290a atmega3290p atmega3290pa atmega649 atmega649a atmega6490 atmega6490a atmega6490p atmega649p Lighting AVR Devices Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 3 Supported Devices at90pwml at90pwm2 at90pwm2b at90pwm216 at90pwm3 at90pwm3b at90pwm316 at90pwm161 at90pwm81 Smart Battery AVR Devices atmega8hva atmegal6hva atmegal6hva2 atmegal6hvb atmegal6hvbrevb atmega32hvb atmega32hvbrevb atmega64hve atmega406 USB AVR Devices at90usb82 at90usb162 at90usb646 at90usb647 at90usb1286 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 3 Supported Devices at90usb1287 atmega8u2 atmegal6u2 atmegal6u4 atmega32u2 atmega32u4 atmega32u6 XMEGA Devices atxmegal6a4 atxmegal6d4 atxmega32a4 atxmega32d4 atxmega64al atxmega64alu atxmega64a3 atxmega64d3 atxmegal28al atxmegal28alu atxmegal28a3 atxmegal28bl atxmegal28d3 atxmegal92a3 atxmega192d3 atxmega256a3 atxmega256a3b atxmega256a3bu Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 3 Supported Devices 10 atxmega256d3 Miscellaneous Devices at94K 2 at76c711 3 at43usb320 at43usb355 at86rf401 at90scr100 ata6289 m3000 4 Classic AVR Devices at90s1200 1 at90s2313 at90s2323 at
311. gen 24 43 stdlib h File Reference 404 Defines define need NULL define need size t define need wchar t e define __ptr_t void define RAND MAX Ox7FFF Typedefs e typedef int x __compar_fn_t const void const void Functions void abort void NORETURN int abs int 1 long labs long i void bsearch const void key const void base size_t __nmemb size t size int __compar const void const void div tdiv int num int asm divmodhi4 tldiv long __num long __denom __asm__ __divmodsi4 void qsort void __base size_t __nmemb size t size compar fn t compar long strtol const char nptr char endptr int base unsigned long strtoul const char nptr char endptr int base long atol const char 5 ATTR_PURE int atoi const char 5 PURE void exit int status ATTR_NORETURN_ void malloc size t 5125 ATTR MALLOC void free void ptr void calloc size t nele size t size ATTR MALLOC void realloc void ptr size_t __size _ ATTR_MALLOC__ double strtod const char nptr char endptr double const char nptr int rand void void srand unsigned int __ seed int rand unsigned long ctx Variables e size t malloc margin e char x malloc heap start e char x malloc heap end Generated on Thu May 19 20
312. ger not larger in absolute value 22 7 lt setjmp h gt Non local goto Functions e int setimp buf jmpb e void longjmp jmp buf jmpb int ret ATTR NORETURN 22 7 1 Detailed Description While the C language has the dreaded goto statement it can only be used to jump to a label in the same local function In order to jump directly to another non local function the C library provides the setjmp and longjmp functions setjmp and longjmp are useful for dealing with errors and interrupts encountered in a low level subroutine of a program Note setjmp and longjmp make programs hard to understand and maintain If possi ble an alternative should be used longjmp can destroy changes made to global register variables see How to per manently bind a variable to a register For a very detailed discussion of setimp longjmp see Chapter 7 of Advanced Pro gramming in the UNIX Environment by W Richard Stevens Example Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 7 lt setjmp h gt Non local goto 168 include lt setjmp h gt jmp buf env int main void foo void setjmp env handle error main processing loop which calls foo some where void blah blah blah df longjmp env 1 22 7 2 Function Documentation 22 7 2 void longjmp buf jmpb int ret Non local jump to a sav
313. gt 1 return crc 22 28 2 2 static inline uintl6 t crc ccitt update uint16_t crc uint8 t data static Optimized CRC CCITT calculation Polynomial x 16 x 12 x 5 1 0x8408 Initial value Oxffff This is the CRC used by PPP and IrDA See RFC1171 PPP protocol and IrDA IrLAP 1 1 Note Although the CCITT polynomial is the same as that used by the Xmodem protocol they are quite different The difference is in how the bits are shifted through the alorgithm Xmodem shifts the MSB of the CRC and the input first while CCITT shifts the LSB of the CRC and the input first The following is the equivalent functionality written in C uintl16 t crc ccitt update uintl16 t crc uint8 t data data 108 crc data data lt lt 4 return uint1l6_t data lt lt 8 hi8 crc uint8_t data gt gt 4 uint16 t data lt lt 3 22 28 2 3 static uint8 t crc ibutton update uint8 t crc uint8 t data static Optimized Dallas now Maxim iButton 8 bit CRC calculation Polynomial x 8 x 5 x 4 1 Ox8C Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 28 lt util crc16 h gt CRC Computations 313 Initial value 0 0 See http www maxim ic com appnotes cfm appnote number 27 The following is the equivalent functionality written in C uint8_t Crc ibutton update uint8 t crc uint8 t data uint8 t i crc crc data for i 0 l
314. gy 123 15 Release Numbering and Methodology 15 1 Release Version Numbering Scheme Release numbers consist of three parts a major number a minor number and a revision number each separated by a dot The major number is currently 1 and has always been It will only be bumped in case a new version offers a major change in the API that is not backwards compatible In the past up to 1 6 x even minor numbers have been used to indicate stable re leases and odd minor numbers have been reserved for development branches versions As the latter has never really been used and maintaining a stable branch that eventually became effectively the same as the development version has proven to be just a cum bersome and tedious job this scheme has given up in early 2010 so starting with 1 7 0 every minor number will be used Minor numbers will be bumped upon judgement of the development team whenever it seems appropriate but at least in cases where some API was changed Starting with version 1 4 0 a file avr version h indicates the library version of an installed library tree 15 2 Releasing AVR The information in this section is only relevant to AVR Libc developers and can be ignored by end users Note In what follows I assume you know how to use SVN and how to checkout multiple source trees in a single directory without having them clobber each other If you don t know how to do this you probably shouldn t be making
315. h before programming the device API Usage Example Usage is very simple just include the header file include lt avr signature h gt Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 24 lt avr sleep h gt Power Management and Sleep Modes 299 This will declare a constant unsigned char array and it is initialized with the three signature bytes MSB first that are defined in the device I O header file This array is then placed in the signature section in the resulting linked ELF file The three signature bytes that are used to initialize the array are these defined macros in the device I O header file from MSB to LSB SIGNATURE 2 SIGNATURE 1 SIGNATURE_0 This header file should only be included once in an application 22 24 lt avr sleep h gt Power Management and Sleep Modes Functions void sleep_enable void void sleep_disable void void sleep_cpu void 22 24 1 Detailed Description finclude lt avr sleep h gt Use of the SLEEP instruction can allow an application to reduce its power comsump tion considerably AVR devices can be put into different sleep modes Refer to the datasheet for the details relating to the device you are using There are several macros provided in this header file to actually put the device into sleep mode The simplest way is to optionally set the desired sleep mode using set Sleep mode it usually defaults to idle mode where the CPU is put
316. h it over to build a library instead of an application See the GNU Binutils manual for more information on the ar program Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 8 5 Usinga Library 54 8 5 Usinga Library To use a library use the 1 switch on your linker command line The string immedi ately following the 1 is the unique part of the library filename that the linker will link in For example if you use im this will expand to the library filename libm a which happens to be the math library included in avr libc If you use this on your linker command line lgrinut flt then the linker will look for a library called libprintf flt a This is why naming your library is so important when you create it The linker will search libraries in the order that they appear on the command line Whichever function is found first that matches the undefined reference it will be linked in There are also command line switches that tell GCC which directory to look in 1 for the libraries that are specified to be linke in with 1 See the GNU Binutils manual for more information on the GNU linker ld program 9 Benchmarks The results below can only give a rough estimate of the resources necessary for using certain library functions There is a number of factors which can both increase or reduce the effort required Expenses for preparation of operands and their stack are not considered
317. h stream This is a null operation provided for source code compatibility only as the standard IO implementation currently does not perform any buffering Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 192 22 9 3 7 intfgetc FILE x stream The function get c reads a character from st ream It returns the character or EOF in case end of file was encountered or an error occurred The routines feof or ferror must be used to distinguish between both situations 22 9 3 8 char fgets char x str int size FILE stream Read at most size 1 bytes from st ream until a newline character was encountered and store the characters in the buffer pointed to by st r Unless an error was encountered while reading the string will then be terminated with a NUL character If an error was encountered the function returns NULL and sets the error flag of stream which can be tested using ferror Otherwise a pointer to the string will be returned 22 9 3 9 int fprintf FILE x __ stream const char x fmt The function fprintf performs formatted output to stream See vfprintf for details 22 9 3 10 int fprintf P FILE x stream const char x fmt Variant of fprintf that uses a fmt string that resides in program memory 22 9 3 11 int fputc int c FILE stream The function fputc sends the character c though given as type int to st ream It r
318. hange of the counting direction For PWM generation itis usually desired to run it at the highest possible speed so filtering the PWM frequency from the modulated output signal is made easy Thus the PWM timer runs at full CPU speed This causes the overflow and compare match interrupts to be triggered each 256 CPU clocks so they must run with the minimal number of processor cycles possible in order to not impose a too high CPU load by these interrupt service routines This is the main reason to implement the entire interrupt handling in fine tuned assembly code rather than in C In order to verify parts of the algorithm and the underlying hardware the demo has been set up in a way so the pin compatible but more expensive ATtiny45 or its siblings ATtiny25 and ATtiny85 could be used as well In that case no separate assembly code is required as two timer channels are avaible 22 36 1 Hardware setup The incoming PWM pulse train is fed into PB4 It will generate a pin change interrupt there on eache edge of the incoming signal The outgoing PWM is generated through OCOB of timer channel 0 PB1 For demon stration purposes a LED should be connected to that pin like one of the LEDs of an STK500 The controllers run on their internal calibrated RC oscillators 1 2 MHz on the AT tiny13 and 1 0 MHz on the ATtiny45 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 36 Combining C and assembly source files 329
319. he UART connection Command recognition is done using sscanf where the first format in the format string just skips over the command itself as the assignment suppression modifier x is given 22 39 3 2 defines h This file just contains a few peripheral definitions Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 39 Using the standard IO facilities 358 The F_CPU macro defines the CPU clock frequency to be used in delay loops as well as in the UART baud rate calculation The macro UART_BAUD defines the RS 232 baud rate Depending on the actual CPU frequency only a limited range of baud rates can be supported The remaining macros customize the IO port and pins used for the HD44780 LCD driver Each definition consists of a letter naming the port this pin is attached to and a respective bit number For accessing the data lines only the first data line gets its own macro line D4 on the HD44780 lines DO through D3 are not used in 4 bit mode all other data lines are expected to be in ascending order next to D4 22 39 3 3 hd44780 h This file describes the public interface of the low level LCD driver that interfaces to the HD44780 LCD controller Public functions are available to initialize the controller into 4 bit mode to wait for the controller s busy bit to be clear and to read or write one byte from or to the controller As there are two different forms of controller IO one to send a command or
320. he current allocation When shrinking the case is easy the existing chunk is split and the tail of the region that is no longer to be used is passed to the standard free function for insertion into the freelist Checks are first made whether the tail chunk is large enough to hold a chunk of its own at all otherwise realloc will simply do nothing and return the original region When growing the region it is first checked whether the existing allocation can be ex tended in place If so this is done and the original pointer is returned without copying any data contents As a side effect this check will also record the size of the largest chunk on the freelist If the region cannot be extended in place but the old chunk is at the top of heap and the above freelist walk did not reveal a large enough chunk on the freelist to satisfy the new request an attempt is made to quickly extend this topmost chunk and thus the heap so no need arises to copy over the existing data If there s no more space available in the heap same check is done as in malloc the entire request will fail Otherwise malloc will be called with the new request size the existing data will be copied over and free will be called on the old region 4 Memory Sections Remarks Need to list all the sections which are available to the avr Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 4 1 The text Section 23 Weak Bindings FIX
321. he final ELF file Below are two Makefile fragments that provide rules to convert a txt file to an object file and to convert a bin file to an object file 5 0 txt Gecho Converting Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 31 How do I perform a software reset of the AVR 85 cp lt tmp echo n 0 tr 0 N000 gt gt x tmp 85 I binary O elf32 avr rename section data progmem data contents alloc load readonly data redefine sym binary tmp start redefine sym binary tmp end end redefine sym binary tmp size x size sym x tmp echo extern const char PROGMEM gt x h Gecho extern const char x end PROGMEM gt gt x h Gecho extern const char size sym gt gt x h Gecho define 5 size int size sym gt gt x h Grm x tmp OBJDIR 0 bin echo Converting lt 85 OBJCOPY I binary O elf32 avr rename section data progmem data contents alloc load readonly data redefine sym _binary_ x_bin_start x redefine sym binary bin end x end redefine sym binary x bin size size sym 5 lt Gecho extern const char PROGMEM gt x h Gecho extern const char x _end PROGMEM gt gt x h Gecho extern const char size sym gt gt x h
322. he strlen function returns the number of characters in src 22 19 4 26 size tstrlen PF uint farptr ts Obtain the length of a string The strlen_PF function is similar to strlen except that s is a far pointer to a string in program space Parameters s A far pointer to the string in flash Returns The strlen_PF function returns the number of characters in s The contents of RAMPZ SFR are undefined when the function returns 22 19 4 27 int strncasecmp P const char s P 52 size tn Compare two strings ignoring case The strncasecmp P function is similar to strcasecmp_P except it only compares the first n characters of s1 Parameters 51 A pointer to a string in the devices SRAM 52 A pointer to a string in the devices Flash n maximum number of bytes to compare Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 49 lt avr pgmspace h gt Program Space Utilities 286 Returns The strncasecmp_P function returns an integer less than equal to or greater than zero if s1 or the first n bytes thereof is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strncasecmp P is that if s1 is an initial substring of s2 then 51 is considered to be less than s2 22 19 4 28 int strncasecmp PF const char s1 uint farptr 52 size tn Compare two strings ignoring case
323. ht out of sleep mode depends on the specific mode selected with the set sleep mode function See the data sheet for your device for more details Set the SE sleep enable bit 22 5 lt avriversion h gt avr libc version macros Defines e define _ VERSION STRING 1 7 1 e define _ LIBC VERSION 10701UL e define _ LIBC DATE STRING 20110216 e define _ DATE 20110216UL e define _ MAJOR 1 e define _ MINOR 7 e define _ LIBC REVISION 1 22 25 1 Detailed Description include avr version h This header file defines macros that contain version numbers and strings describing the current version of avr libc The version number itself basically consists of three pieces that are separated by a dot the major number the minor number and the revision number For development versions which use an odd minor number the string representation additionally gets the date code YY YYMMDD appended Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 25 lt avr version h gt avr libc version macros 302 This file will also be included by lt avr io h gt That way portable tests can be implemented using lt avr io h gt that can be used in code that wants to remain backwards compatible to library versions prior to the date when the library version API had been added as referenced but undefined C preprocessor macros automati
324. hu May 19 2011 13 29 12 for avr libe by Doxygen 22 28 util crc16 h CRC Computations 311 See the Dallas Semiconductor app note 27 for 8051 assembler example and general CRC optimization suggestions The table on the last page of the app note is the key to understanding these implementations Jack Crenshaw s Implementing CRCs article in the January 1992 isue of Embedded Systems Programming This may be difficult to find but it explains CRC s in very clear and concise terms Well worth the effort to obtain a copy A typical application would look like Dallas iButton test vector uint8 t serno 0x02 Oxlc 0xb8 0x01 0 0 0 Oxa2 int checkcrc void uint8_t cre 0 i for i 0 i lt sizeof serno sizeof serno 0 i crc cro ibutton update crc serno i return crc must be 0 22 28 2 Function Documentation 22 28 2 1 static inline uint16_t crc16 update uint16_t crc uint8 t data static Optimized CRC 16 calculation Polynomial x 16 x 15 x 2 1 0xa001 Initial value Oxffff This CRC is normally used in disk drive controllers The following is the equivalent functionality written in C uintl6 t crcl6 update uintl16 t crc uint8 t a int i crc a Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 28 util crc16 h CRC Computations 312 for i 0 i lt 8 i if crc amp 1 crc crc gt gt 1 0xA001 crc crc gt
325. i dM asr r bclr I bid rl brbc Llabel brbs Llabel bset I bst rl cbi LI cbr d l com r cp Lr LI cpi LI dec r elpm tz eor rr in rl inc r ld re Idd rb ldi d M 146 r label lpm 52 Isl r Isr r mov rr movw rr mul rr neg r or Lr ori out Lr pop r push r rol r sbc rr sbci sbi LI sbic LI sbiw sbr sbrc rl sbrs rl ser d st e r std b r sts label r sub rr subi swap r Constraint characters may be prepended by a single constraint modifier Contraints without a modifier specify read only operands Modifiers are Modifier Specifies Write only operand usually used for all output operands Read write operand amp Register should be used for output only Output operands must be write only and the C expression result must be an lvalue which means that the operands must be valid on the left side of assignments Note that the compiler will not check if the operands are of reasonable type for the kind of Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 3 Input and Output Operands 45 operation used in the assembler instructions Input operands are you guessed it read only But what if you need the same operand for input and output As stated above read write operands are not supported in inline assembler code But there is another solution For input operators it is possible to use a single digit in the
326. iable argument list as in vfprintf See vfprintf for details 22 9 3 37 int vscanf const char fmt va list The function vscanf performs formatted input from stream st din taking a variable argument list as in vfscanf See vfscanf for details 22 9 3 38 vsnprintf char x s size t const char x fmt va_list ap Like vsprintf but instead of assuming s to be of infinite size no more than n characters including the trailing NUL character will be converted to s Returns the number of characters that would have been written to s if there were enough space 22 9 3 39 int vsnprintf P char x s size t const char x fmt va list ap Variant of vsnprintf that uses a mt string that resides in program memory 22 9 3 40 int vsprintf char x s const char x fmt va_list ap Like sprintf but takes a variable argument list for the arguments 22 9 3 41 int vsprintf_P char x s const char x fmt va_list ap Variant of vsprintf that uses a fmt string that resides in program memory Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 202 22 10 lt stdlib h gt General utilities Data Structures struct div t struct ldiv t Defines fdefine RAND MAX Ox7FFF Typedefs typedef int compar fn t const void const void Functions void abort void NORETURN int abs int 1 long labs long i vo
327. id bsearch const void __key const void base size t nmemb size t size int __compar const void const void div_t div int num int asm divmodhi4 tldiv long __num long __denom __asm__ __divmodsi4 void qsort void base size_t __nmemb size t size compar fn t compar long strtol const char nptr char endptr int base unsigned long strtoul const char nptr char endptr int base long atol const char ATTR_PURE int atoi const char 5 PURE void exit int status NORETURN void malloc size t size ATTR MALLOC void free void ptr void calloc size nele size t size MALLOC void realloc void size t size ATTR_MALLOC__ double strtod const char nptr char endptr double const char nptr int rand void void srand unsigned int seed int rand unsigned long ctx Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 203 Variables e size t malloc margin e char x _ malloc heap start e char x heap end Non standard i e non ISO C functions e char long int char __s int __radix char unsigned int __val char x__s int radix char ultoa unsigned long int __ val char __s int __radix long random void void srandom unsigned
328. ies the device id and is matched up with the device of the same id in avrdude s configuration file usr local etc avrdude conf To list valid parts specify the v option The e option instructs avrdude to perform a chip erase before programming this is almost always necessary before programming the flash The m flash option indicates that we want to upload data into the flash memory while i main hex specifies the name of the input file The EEPROM is uploaded in the same way the only difference is that you would use m eeprom instead of m flash To use interactive mode use the t option avrdude p 2313 t avrdude AVR device initialized and ready to accept instructions avrdude Device signature 0x1e9101 avrdude The command displays a list of valid commands avrdude gt gt gt 7 Valid commands dump dump memory dump lt memtype gt addr lt N Bytes gt read alias for dump write write memory write lt memtype gt addr bl lt b2 gt lt bN gt erase perform a chip erase sig display device signature bytes part display the current part information send send a raw command send bl lt b2 gt b3 lt b4 gt help help 2 help quit quit Use the part command to display valid memory types for use with the dump and write commands avrdude Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 15 Release Numbering and Methodolo
329. ieving some garbage The problem is that AVR GCC does not intrinsically know that the data resides in the Program Space Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 5 4 Storing and Retrieving Strings in the Program Space 30 The solution is fairly simple The rule of thumb for accessing data stored in the Program Space is to access the data as you normally would as if the variable is stored in Data Space like so byte mydata i 3 then take the address of the data byte amp mydata il jl then use the appropriate pgm read macro and the address of your data becomes the parameter to that macro byte pgm read byte amp mydata i j1 The read macros take an address that points to the Program Space and re trieves the data that is stored at that address This is why you take the address of the offset into the array This address becomes the parameter to the macro so it can gen erate the correct code to retrieve the data from the Program Space There are different read macros to read different sizes of data at the address given 5 4 Storing and Retrieving Strings in the Program Space Now that you can successfully store and retrieve simple data from Program Space you want to store and retrive strings from Program Space And specifically you want to store and array of strings to Program Space So you start off with your array like so char xstring table String 1
330. ign define signbitf signbit define fdimf fdim define fmaf fma define fmaxf fmax define fminf fmin define truncf trunc define roundf round define lroundf lround define lrintf lrint Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 155 Functions double cos double __x double sin double __x double tan double __x double fabs double __x double fmod double __x double y double modf double __x double iptr float modff float x float double sqrt double x double cbrt double __x double hypot double x double y double square double x double floor double __x double ceil double __x double frexp double x int __pexp double Idexp double __x int exp double exp double __x double cosh double __x double sinh double x double tanh double __x double acos double x double asin double __x double atan double x double atan2 double y double x double log double x double log10 double x double pow double __x double y intisnan double x int isinf double x static int isfinite double __x static double copysign double int signbit double x double double x double y double fma double x double __y double 7 double fmax double __x double y double fmin double x double y double double x double round double
331. igned int u Matches an optionally signed decimal integer the next pointer must be a pointer to unsigned int x Matches an optionally signed hexadecimal integer the next pointer must be a pointer to unsigned int f Matches an optionally signed floating point number the next pointer must be a pointer to float E Equivalent to f s Matches a sequence of non white space characters the next pointer must be a pointer to char and the array must be large enough to accept all the sequence and the terminating NUL character The input string stops at white space or at the maximum field width whichever occurs first c Matches a sequence of width count characters default 1 the next pointer must be a pointer to char and there must be enough room for all the characters no terminating NUL is added The usual skip of leading white space is suppressed To skip white space first use an explicit space in the format Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 200 Matches a nonempty sequence of characters from the specified set of accepted characters the next pointer must be a pointer to char and there must be enough room for all the characters in the string plus a terminating NUL character The usual skip of leading white space is suppressed The string is to be made up of characters in or not in a particular set the set is defined by the charac
332. ile declaring such a variable as volatile ensures that the compiler will not optimize accesses to it away it does not guarantee atomic access to it Assuming the following example include lt inttypes h gt finclude avr interrupt h finclude avr io h volatile uint16 t ctr ISR TIMER1_OVF_vect Gers Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 207 lt util atomic h gt Atomically and Non Atomically Executed Code Blocl808 main void ctr 0x200 start timer while ctr 0 wait There is a chance where the main context will exit its wait loop when the variable ct x just reached the value OxFF This happens because the compiler cannot natively access a 16 bit variable atomically in an 8 bit CPU So the variable is for example at 0x100 the compiler then tests the low byte for 0 which succeeds It then proceeds to test the high byte but that moment the ISR triggers and the main context is interrupted The ISR will decrement the variable from 0x100 to OxFF and the main context proceeds It now tests the high byte of the variable which is now also 0 so it concludes the variable has reached 0 and terminates the loop Using the macros from this header file the above code can be rewritten like include lt inttypes h gt include lt avr interrupt h gt include lt avr io h gt include lt util atomic h gt volatile uint16_t ctr ISR TIMER1_OVF_vect c
333. ill be defined as well when using the standard levels gnu89 default and gnu99 but not with c89 and c99 mmcu architecture Compile code for architecture Currently known architectures are Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 107 Architecture PBSMacros PBSDescription avrl PBS_AVR_ARCH__ 1 PBSSimple CPU core AVR ASM ONLY only assembler support AVR 2 BYTE PC 2 avra PBS AVR ARCH 2 PBS Classic CPU core 2 2 up to 8 KB of ROM avr25 1 PBS AVR ARCH 25 PBS Classic CPU AVR HAVE MOVW 1 core with MOVW AVR HAVE LPMX 1 and Rx Z AVR 2 BYTE PC 2 instruction up to 8 KB of ROM avr3 PBS AVR ARCH 3 PBS Classic CPU core AVR MEGA 5 16 KB to 64 KB of ROM AVR HAVE JMP CALL 4 AVR 2 BYTE PC 2 avr31 PBS AVR ARCH 31 PBS Classic CPU core AVR MEGA 5 128 KB of ROM AVR HAVE JMP CALL 4 AVR HAVE RAMPZ _ 4 AVR HAVE ELPM 4 AVR 2 BYTE PC 2 avr35 3 PBS AVR ARCH 35 PBS Classic CPU AVR MEGA 5 core with MOVWw AVR HAVE JMP CALL 4 and LPM Rx AVR HAVE MOVW 1 instruction 16 KB to 64 AVR HAVE LPMX 1 KB of ROM AVR 2 BYTE PC 2 avr4 PBS AVR ARCH 4 PBS Enhanced CPU AVR ENHANCED 5 core up to 8 KB of AVR HAVE MOVW I ROM AVR HAVE LPMX
334. in the respective control regis ter to start the PWM timer usually the timer runs at full CPU clock for 10 bit PWMs while it runs on a prescaled clock for 8 bit PWMs Note 2 ISR is a macro that marks the function as an interrupt routine In this case the function will get called when timer 1 overflows Setting up interrupts is explained in greater detail in lt avr interrupt h gt Interrupts Note 3 The PWM is being used in 10 bit mode so we need a 16 bit variable to remember the current value Note 4 This section determines the new value of the PWM Note 5 Here s where the newly computed value is loaded into the PWM register Since we are in an interrupt routine it is safe to use a 16 bit assignment to the register Outside of an interrupt the assignment should only be performed with interrupts disabled if there s a chance that an interrupt routine could also access this register or another register that uses TEMP see the appropriate FAQ entry Note 6 This routine gets called after a reset It initializes the PWM and enables interrupts Note 7 The main loop of the program does nothing all the work is done by the interrupt routine The sleep mode puts the processor on sleep until the next interrupt to conserve power Of course that probably won t be noticable as we are still driving a LED it is merely mentioned here to demonstrate the basic principle Note 8 Early AVR device
335. ine PRIOLEASTS o define PRIoFAST8 o define PRIu8 u define PRIULEASTS u define PRIUFASTS u define PRIx8 x define PRIXLEASTS x define PRIxFAST8 x define PRIX8 X define PRIXLEASTS X define PRIXFASTS X define PRIo16 o define PRIOLEAST16 define PRIOFAST16 o define PRIu16 u define PRIULEAST16 u define PRIUFAST16 u define PRIx16 x define PRIXLEAST16 x define PRIXFAST16 x define PRIX16 X define PRIXLEASTI6 X Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 142 define PRIXFAST16 X define PRIo32 lo define PRIOLEAST32 lo define PRIoFAST32 lo define PRIu32 lu define PRIULEAST32 lu define PRIuFAST32 lu define PRIx32 Ix define PRIXLEAST32 Ix define PRIxFAST32 Ix define PRIX32 IX define PRIXLEAST32 IX define PRIXFAST32 IX define PRIOPTR PRIo16 define PRIuPTR PRIu16 define PRIxPTR PRIx16 define PRIXPTR PRIX16 define SCNd16 d define SCNdLEASTI6 d define SCNdFAST16 d define SCNi16 i define SCNiLEAST16 i define SCNIFASTI6 i define SCNd32 Id define SCNdLEAST32 Id define SCNdFAST32 define SCNi32 li define SCNiLEAST32 li define SCNIFAST32 li define SCNdPTR SCNd16 define SCNIPTR SCNi16 define SCNo16 define SCNoLEASTI6 o define SCNoFASTI16 o define SCNul6 u define SCNuLEASTI6 u define SCNuFAS
336. ine boot_spm_busy_wait do while boot busy BOOT PAGE ERASE SPM BV PGERS define BOOT_PAGE_WRITE _BV __SPM_ENABLE _BV PGWRT define BOOT PAGE FILL SPM ENABLE define BOOT RWW ENABLE SPM ENABLE COMMON ASRE define boot page fill normal address data define boot page_fill_alternate address data define boot page fill extended address data define boot page_erase_normal address define boot page_erase_alternate address define boot page_erase_extended address define boot page_write_normal address define boot page_write_alternate address define boot page_write_extended address define define boot boot rww enable rww enable alternate define boot lock_bits_set lock_bits Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 5 boot h File Reference 370 define boot lock bits set alternate lock bits define GET LOW FUSE BITS 0x0000 define GET BITS 0x0001 define GET EXTENDED FUSE BITS 0x0002 define GET HIGH FUSE BITS 0x0003 define boot lock fuse bits get address define_ _ BOOT SIGROW READ SPM ENABLE BV SIGRD fidefine boot signature byte get addr define boot page fill address data boot page fill normal address data
337. ine endings AVRDUDE Open source code package Configure and build at the top of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin install directory gt bin Set location of LibUSB headers and libraries export CPPFLAGS I libusb win32 device bin 1libusb version include export CFLAGS I libusb win32 device bin 1ibusb version include export LDFLAGS L libusb win32 device bin 1ibusb version lib gcc Configure configure prefix installdir datadir installdir sysconfdir installdir bin enable doc disable versioned doc 2 gt amp 1 tee package configure log Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 13 Building the Toolchain for Windows 104 Make make k all install 2 gt amp 1 tee Spackage make log Convert line endings in avrdude config file to Windows line endings Delete backup copy of avrdude config file in install directory if exists Insight GDB Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin install directory gt bin Configure CFLAGS D USE MINGW ACCESS LDFLAGS static Sarchivedir con
338. ine that function That needs to be kept in mind when debugging because the inlining might cause the debug ger to jump around wildly at a first glance when single stepping The definitions of uart str and str set up two stdio streams The initial ization is done using the FDEV SETUP STREAM initializer template macro so a static object can be constructed that can be used for IO purposes This initializer macro takes three arguments two function macros to connect the corresponding output and input functions respectively the third one describes the intent of the stream read write or both Those functions that are not required by the specified intent like the input function for 1 str which is specified to only perform output operations can be given as NULL The stream uart str corresponds to input and output operations performed over the RS 232 connection to a terminal e g from to a PC running a terminal program while the 1 str stream provides a method to display character data on the LCD text display The function delay 1s suspends program execution for approximately one sec ond This is done using the delay ms function from lt util delay h gt which in turn needs the F CPU macro in order to adjust the cycle counts As the _ 1 ms function has a limited range of allowable argument values depending on F CPU a value of 10 ms has been chosen as the base delay which would be safe for CPU f
339. ined reference is a function call with no defined function to match the call The linker will then go through the libraries in order to match the undefined references with function definitions that are found in the libraries If it finds the function that matches the call the linker will then link in the object module in which the function is located This part is important the linker links in THE ENTIRE OBJECT MODULE in which the function is located Remember the linker knows nothing about the functions internal to an object module other than symbol names such as function names The smallest unit the linker works with is object modules When there are no more undefined references the linker has linked everything and is done and outputs the final application 8 3 How to Design a Library How the linker behaves is very important in designing a library Ideally you want to design a library where only the functions that are called are the only functions to be linked into the final application This helps keep the code size to a minimum In order to do this with the way the linker works is to only write one function per code module This will compile to one function per object module This is usually a very different way of doing things than writing an application There are always exceptions to the rule There are generally two cases where you would want to have more than one function per object module The first is when you have very
340. ing 221 strlcpy S 410 strlcpy P avr pgmspace 283 strlcpy P S 410 strlcpy PF avr pgmspace 283 strlen avr string 221 strlen S 410 strlen P avr pgmspace 284 strlen P S 410 strlen PF avr pgmspace 284 strlwr avr_string 222 strlwr S 410 strncasecmp avr_string 222 strncasecmp S 410 strncasecmp_P avr_pgmspace 284 strncasecmp_P S 410 strncasecmp_PF avr_pgmspace 285 strncat avr_string 222 strncat S 410 strncat_P avr_pgmspace 285 strncat_P S 410 strncat PF avr pgmspace 285 strncmp avr string 222 strncmp S 410 strncmp P avr pgmspace 286 strncmp 5 410 strncomp PF avr pgmspace 286 strncpy Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 436 avr string 223 strncpy S 410 strncpy_P avr_pgmspace 287 strncpy_P S 410 strncpy PF avr pgmspace 287 strnlen avr string 223 strnlen S 410 strnlen P avr pgmspace 287 strnlen_P S 410 strnlen_PF avr_pgmspace 288 strpbrk avr_string 223 strpbrk S 410 strpbrk_P avr_pgmspace 288 strpbrk_P S 410 strrchr avr_string 224 strrchr S 410 strrchr_P avr_pgmspace 288 strrchr_P S 410 strrev avr_string 224 strrev S 410 strsep avr_string 224 strsep S 410 strsep_P avr_pgmspace 289 strsep_P S 410 strspn avr_string 225 strspn S 410 strspn_P avr_pgmspace 289 strspn_P S 410 strstr avr_string 225 strstr S 410 strstr_P avr_pgmspace 289 strstr_P S 410 strstr PF
341. inimal processing delay for nested interrupts Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 16 lt avr interrupt h gt Interrupts 266 This may be used to create nested ISRs however care should be taken to avoid stack overflows or to avoid infinitely entering the ISR for those cases where the AVR hard ware does not clear the respective interrupt flag before entering the ISR Use this attribute in the attributes parameter of the ISR macro 22 16 2 10 define reti include avr interrupt h Returns from an interrupt routine enabling global interrupts This should be the last command executed before leaving an ISR defined with the ISR_NAKED attribute This macro actually compiles into a single line of assembly so there is no function call overhead 22 16 2 11 define sei include lt avr interrupt h gt Enables interrupts by setting the global interrupt mask This function actually compiles into a single line of assembly so there is no function call overhead However the macro also implies a memory barrier which can cause additional loss of optimization In order to implement atomic access to multi byte objects consider using the macros from lt util atomic h gt rather than implementing them manually with cli and sei 22 16 2 12 define SIGNAL vector include avr interrupt h Introduces an interrupt handler function that runs with global interrupts initially dis abled
342. ion Result type for function ldiv 23 2 2 Field Documentation 23 2 2 1 long Idiv_t quot 23 2 2 2 long Idiv_t rem The Quotient The Remainder The documentation for this struct was generated from the following file stdlib h 24 File Documentation 24 1 assert h File Reference Defines define assert expression 24 1 1 Detailed Description 24 2 atoi S File Reference 24 2 1 Detailed Description 24 3 atol S File Reference 24 3 1 Detailed Description 244 atomic h File Reference Defines e define ATOMIC BLOCK type Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 5 boot h File Reference 369 define NONATOMIC BLOCK type define ATOMIC RESTORESTATE define ATOMIC FORCEON define NONATOMIC RESTORESTATE define NONATOMIC FORCEOFF 24 4 1 Detailed Description 24 5 boot h File Reference Defines define define BOOTLOADER SECTION __attribute__ section bootloader define _ COMMON_ASB RWWSB define COMMON_ASRE RWWSRE define BLB12 5 define BLB11 4 define BLB02 3 define BLB01 2 define boot_spm_interrupt_enable __SPM_REG uint8 t BV SPMIE define boot_spm_interrupt_disable SPM REG amp uint8_t _BV SPMIE define boot is spm interrupt __SPM_REG amp uint8_t _BV SPMIE define boot_rww_busy L_SPM_REG amp uint8_t _ BV _COMMON_ASB define boot_spm_busy __SPM_REG amp uint8_t _BV __SPM_ENABLE def
343. ire interface TWI 366 recommended in the 24Cxx datasheet in order to minimize the busy wait time when writing Note that in case a device is broken and never responds to a selection e g since it is no longer present at all this will cause an infinite loop Thus the maximal number of iterations made until the device is declared to be not responding at all and an error is returned will be limited to ITER Note 12 This is called master receiver mode the bus master still supplies the SCL clock but the device slave drives the SDA line with the appropriate data After 8 data bits the master responds with an ACK bit SDA driven low in order to request another data transfer from the slave or it can leave the SDA line high NACK indicating to the slave that it is going to stop the transfer now Assertion of ACK is handled by setting the TWEA bit in TWCR when starting the current transfer Note 13 The control word sent out in order to initiate the transfer of the next data packet is initially set up to assert the TWEA bit During the last loop iteration TWEA is de asserted so the client will get informed that no further transfer is desired Note 14 Except in the case of lost arbitration all bus transactions must properly be terminated by the master initiating a stop condition Note 15 Writing to the EEPROM device is simpler than reading since only a master transmitter mode transfer is needed Note that the fi
344. is simple aggregate a list of object modules into a single library archive and create an index for the linker to use The name that you create for the library filename must follow a specific pattern libname a The name part is the unique part of the filename that you create It makes it easier if the name part relates to what the library is about This name part must be prefixed by lib and it must have a file extension of a for archive The reason for the special form of the filename is for how the library gets used by the toolchain as we will see later on Note The filename is case sensitive Use a lowercase lib prefix and a lowercase a as the file extension The command line is fairly simple avr ar rcs library name list of object modules The r command switch tells the program to insert the object modules into the archive with replacement The c command line switch tells the program to create the archive And the s command line switch tells the program to write an object file index into the archive or update an existing one This last switch is very important as it helps the linker to find what it needs to do its job Note The command line switches are case sensitive There are uppercase switches that have completely different actions MFile and the WinAVR distribution contain a Makefile Template that includes the necessary command lines to build a library You will have to manually modify the template to switc
345. is_ relelase gt Bring the build system up to date by running bootstrap and configure Perform a make distcheck and make sure it succeeds This will create the source tarball Tag the release svn copy svntssh Susername svn savannah nongnu org avr libc tags avr li minor patch release or svn copy svntssh username8svn savannah nongnu org avr libc branches avr 1l minor branch svn ssh username svn savannah nongnu org avr libc tags avr minor patch release Upload the tarball to savannah Update the NEWS file and commit to SVN Add Changes since avr libc major minor patch Update the bug tracker interface on Savannah Bugs gt Edit field values gt Release Fixed Release Generate the latest documentation and upload to savannah Announce the release The following hypothetical diagram should help clarify version and branch relation ships Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 16 Acknowledgments 126 HEAD 1 0 Branch 1 2 Branch cvs tag avr libc 1 0 branchpoint set version to 1 1 0 lt date gt cvs tag b avr libc 1 0 branch set version to 0 90 90 lt date gt set version to 1 0 cvs tag avr libc 1 0 release set version to 1 0 0 lt date gt 1 set version to 1 0 1 cvs tag avr libc 1_0_1 release 1 cvs tag avr libc 1_2 branchpoint i set version to 1 3 0 lt date gt cvs tag b
346. ision operator When doing integer division it is usually better to round to the nearest integer rather than to the lowest To do this add 0 5 i e half the value of the denominator to the numerator before the division resulting in the formula F_CPU UART BAUD RATE 8L UART BAUD RATE 16L 1 This is also the way it is implemented in lt util setbaud h gt Helper macros for baud rate calculations Back to FAQ Index 11 36 Ona device with more than 128 KiB of flash how to make function pointers work Function pointers beyond the magical 128 KiB barrier s on larger devices are sup posed to be resolved through so called trampolines by the linker so the actual pointers used in the code can remain 16 bits wide In order for this to work the option mre1ax must be given on the compiler command line that is used to link the final ELF file Older compilers did not implement this option for the AVR use W1 relax instead Back to FAQ Index Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 Building and Installing the GNU Tool Chain 91 12 Building and Installing the GNU Tool Chain This chapter shows how to build and install from source code a complete develop ment environment for the AVR processors using the GNU toolset There are two main sections one for Linux FreeBSD and other Unix like operating systems and another section for Windows 12 1 Building and Installing under Linux
347. istent or small field width cause truncation of a numeric field if the result of a conversion is wider than the field width the field is expanded to contain the conversion result Since the full implementation of all the mentioned features becomes fairly large three different flavours of vfprintf can be selected using linker options The default vf printf implements all the mentioned functionality except floating point conversions A minimized version of vfprintf is available that only implements the very basic in teger and string conversion facilities but only the additional option can be specified using conversion flags these flags are parsed correctly from the format specification but then simply ignored This version can be requested using the following compiler options Wl u vfprintf lprintf min Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 198 If the full functionality including the floating point conversions is required the follow ing options should be used Wl u vfprintf lprintf flt im Limitations The specified width and precision can be at most 255 Notes For floating point conversions if you link default or minimized version of vfprintf the symbol will be output and double argument will be skiped So you output below will not be crashed For default version the width field and the pad to left symbol minus optio
348. k any line of your assembler code But it is able to check the constraint against your C expression However if you specify the wrong constraints then the compiler may silently pass wrong code to the assembler And of course the assembler will fail with some cryptic output or internal errors For example if you specify the constraint r and you are using this register with an ori instruction in your as sembler code then the compiler may select any register This will fail if the compiler chooses r2 to r15 It will never choose r0 or r1 because these are uses for special purposes That s why the correct constraint in that case is d On the other hand if you use the constraint M the compiler will make sure that you don t pass anything else but an 8 bit value Later on we will see how to pass multibyte expression results to the assembler code Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 3 Input and Output Operands 44 The following table shows all AVR assembler mnemonics which require operands and the related contraints Because of the improper constraint definitions in version 3 3 they aren t strict enough There is for example no constraint which restricts integer constants to the range 0 to 7 for bit set and bit clear operations Mnemonic Constraints Mnemonic Constraints adc rr add rr adiw rr and
349. l size t void memmem_P const void x size t VOID P size t ATTR PURE char strcasestr P const char x P PURE 22 19 1 Detailed Description include lt avr io h gt include lt avr pgmspace h gt The functions in this module provide interfaces for a program to access data stored in program space flash memory of the device In order to use these functions the target device must support either the LPM or ELPM instructions Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 49 lt avr pgmspace h gt Program Space Utilities 273 Note These functions are an attempt to provide some compatibility with header files that come with IAR C to make porting applications between different compilers easier This is not 100 compatibility though GCC does not have full support for multiple address spaces yet If you are working with strings which are completely based in ram use the stan dard string functions described in lt string h gt Strings If possible put your constant tables in the lower 64 KB and use pgm read byte near or pgm read word near instead of pgm read byte far or pgm read word far since it is more efficient that way and you can still use the upper 64K for executable code All functions that are suffixed with a _P require their ar guments to be in the lower 64 KB of the flash ROM as they do not use ELPM instructio
350. l subaddress bits are 0 for the smaller devices so the EO E1 and E2 inputs of the 24Cxx must be grounded Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 40 Example using the two wire interface TWI 364 Note 3a EEPROMs of type 24C32 and above cannot be addressed anymore even with the sub address bit trick Thus they require the upper address bits being sent separately on the bus When activating the WORD ADDRESS 16BIT define the algorithm implements that auxiliary address byte transmission Note 4 For slow clocks enable the 2 x U S ART clock multiplier to improve the baud rate error This will allow a 9600 Bd communication using the standard 1 MHz calibrated RC oscillator See also the Baud rate tables in the datasheets Note 5 The datasheet explains why a minimum TWBR value of 10 should be maintained when running in master mode Thus for system clocks below 3 6 MHz we cannot run the bus at the intented clock rate of 100 kHz but have to slow down accordingly Note 6 This function is used by the standard output facilities that are utilized in this example for debugging and demonstration purposes Note 7 In order to shorten the data to be sent over the TWI bus the 24Cxx EEPROM s support multiple data bytes transfered within a single request maintaining an internal address counter that is updated after each data byte transfered successfully When reading data one request can read
351. l284P ATmegal68P ATmega328P WATCHDOG_ ATmega32HVB ATmega406 ATmega48P TIMEOUT ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny13 ATtiny43U ATtiny48 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 AT tiny861 19005 1620 AT90OUSB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 263 22 16 2 Define Documentation 22 16 2 1 define BADISR vect finclude lt avr interrupt h gt This is a vector which is aliased to vector default the vector executed when an ISR fires with no accompanying ISR handler This may be used along with the ISR macro to create a catch all for undefined but used ISRs for debugging purposes 22 16 2 2 define include avr interrupt h Disables all interrupts by clearing the global interrupt mask This function actually compiles into a single line of assembly so there is no function call overhead However the macro also implies a memory barrier which can cause additional loss of optimiza tion In order to implement atomic access to multi byte objects consider using the macros from lt util atomic h gt rather than implementing them manually with cli and sei 22 16 2 3 define EMPTY INTERRUPTY vector include avr interrupt
352. latforms and sometimes packaging the tools for convenient installation by the end user These packages contain the binary executables of the tools pre made and ready to use These packages are known as distributions of the AVR toolchain or by a more shortened name distros AVR toolchain distros are available on FreeBSD Windows Mac OS X and certain flavors of Linux 2 13 Open Source of these tools from the original source code in the multitude of projects to the various distros are put together by many many volunteers All of these projects could always use more help from other people who are willing to volunteer some of their time There are many different ways to help for people with varying skill levels abilities and available time You can help to answer questions in mailing lists such as the avr gcc list or on forums at the AVR Freaks website This helps many people new to the open source AVR tools If you think you found a bug in any of the tools it is always a big help to submit a good bug report to the proper project A good bug report always helps other volunteers to analyze the problem and to get it fixed for future versions of the software You can also help to fix bugs in various software projects or to add desirable new features Volunteers are always welcome Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 3 Memory Areas and Using malloc 18 3 Memory Areas and Using malloc
353. le Reference ss ecce eea o RR 384 2423 3 Detailed Description 2r cR REEF 384 2424 mememp S Pile Reference olor Eos 384 2424 1 Detailed Description 222222522259 5 384 24 25memcmp PSFileReference 384 225 1 Detailed Description 222 22 5 384 24 26memcmp PES File Reference 384 24 26 1 Detailed Description 384 242Tmemepy 5 File Referenc os os ocu soo e RR 384 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen CONTENTS ix 24 27 1 Detailed Description 384 24 28memepy_PS File Reference 384 24 28 1 Detailed Descrpti n soos rap reketa 384 242 memmem s Pile Referente o o uoo EX 384 24 29 1 Detailed Description 384 24 30memmoyve S File oou o goo RR Ros 384 24 30 1 Detailed Description o lt e ea ceca sr tk 384 243l memicbr S File Reference oca ug RR gogoo 8 EUER S 384 2431 1 Detailed Description lt zr o Ro e eae 384 24 32memrzchr PS File Reference 2 384 24 32 1 Detailed Description 2 384 24 33memser5 File Reference cis roo o UR Bh a 384 24 33 1 Detailed Description gt lt oo so a o oka i mms 384 24 34 panty File Referenc sco ek o om hem b bm 384 2544 1 Detailed Description c lt e uox oye x tiks 385 24 File Reference 2o wrea aa REY 385 243
354. len Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 49 lt avr pgmspace h gt Program Space Utilities 278 Scan flash memory for a character The memchr_P function scans the first len bytes of the flash memory area pointed to by s for the character va1 The first byte to match va1 interpreted as an unsigned character stops the operation Returns The memchr P function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 22 19 4 3 int memcmp P const void 81 VOID P 52 size t len Compare memory areas The memcmp_P function compares the first Len bytes of the memory areas 51 and flash s2 The comparision is performed using unsigned char operations Returns memcmp P function returns an integer less than equal to or greater than zero if the first Len bytes of s1 is found respectively to be less than to match or be greater than the first 1en bytes of s2 22 19 4 4 int memcmp const void s7 uint farptr 152 size t len Compare memory areas The memcmp function compares the first len bytes of the memory areas 51 and flash s2 The comparision is performed using unsigned char operations It is an equivalent of memcmp P function except that it is capable working on all FLASH including the exteded area above 64kB Returns The memcmp PF function returns an integer less than equal to or greater th
355. les in the data section so in this situation no stack heap collision can occur In order to relocate the stack from its default location at the top of interns RAM the value of the symbol stack can be changed on the linker command line As the linker is typically called from the compiler frontend this can be achieved using a com piler option like Wl defsym stack 0x8003ff The above will make the code use stack space from RAM address Ox3ff downwards The amount of stack space available then depends on the bottom address of internal Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 14 Using the avrdude program 121 RAM for a particular device It is the responsibility of the application to ensure the stack does not grow out of bounds as well as to arrange for the stack to not collide with variable allocations made by the compiler sections data and bss 14 Using the avrdude program Note This section was contributed by Brian Dean bsd bsdhome com The avrdude program was previously called avrprog The name was changed to avoid confusion with the avrprog program that Atmel ships with AvrStudio avrdude is a program that is used to update or read the flash and EEPROM memories of Atmel AVR microcontrollers on FreeBSD Unix It supports the Atmel serial pro gramming protocol using the PC s parallel port and can upload either a raw binary file or an Intel Hex format file It can also be used in an interacti
356. libc by Doxygen 11 11 Why does the PC randomly jump around when single stepping through my program in avr gdb 69 Note For C programs rather use the standard C bit operators instead so the above would be expressed as PORTB 1 7 The optimizer will take care to trans form this into a single SBI instruction assuming the operands allow for this Back to FAQ Index 11 11 Why does the PC randomly jump around when single stepping through my program in avr gdb When compiling a program with both optimization and debug information 9 which is fortunately possible in avr gcc the code watched in the debugger is opti mized code While it is not guaranteed very often this code runs with the exact same optimizations as it would run without the g switch This can have unwanted side effects Since the compiler is free to reorder code ex ecution as long as the semantics do not change code is often rearranged in order to make it possible to use a single branch instruction for conditional operations Branch instructions can only cover a short range for the target PC 63 through 64 words from the current PC If a branch instruction cannot be used directly the compiler needs to work around it by combining a skip instruction together with a relative jump r jmp instruction which will need one additional word of ROM Another side effect of optimization is that variable usage is restricted to the area of code where it is ac
357. ling it is in the domain of the terminal device driver to provide this functionality Thus a simple function suitable as put for fdevopen that talks to a UART interface might look like this int uart putchar char c FILE xstream if c uart_putchar r loop_until_bit_is_set UCSRA UDRE UDR c return 0 Note 3 This implementation has been chosen because the cost of maintaining an alias is considerably smaller than the cost of maintaining full copies of each stream Yet Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 187 providing an implementation that offers the complete set of standard streams was deemed to be useful Not only that writing printf insteadof fprintf mystream saves typing work but since avr gcc needs to resort to pass all arguments of variadic functions on the stack as opposed to passing them in registers for func tions that take a fixed number of parameters the ability to pass one parameter less by implying stdin or stdout will also save some execution time 22 9 Define Documentation 22 9 21 define__FDEV_EOF 2 Return code for an end of file condition during device read To be used in the get function of fdevopen 22 0 2 2 define FDEV_ERR 1 Return code for an error condition during device read To be used in the get function of fdevopen 22 0 2 3 define FDEV SETUP READ SRD
358. lized RAM variables Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 Inline Assembler Cookbook 38 text switches to the text section code and ROM constants set declares a symbol as a constant expression identical to equ global or globl declares a public symbol that is visible to the linker e g function entry point global variable extern declares a symbol to be externally defined this is effectively a comment only as gas treats all undefined symbols it encounters as globally undefined any way Note that org is available in gas as well but is a fairly pointless pseudo op in an as sembler environment that uses relocatable object files as it is the linker that determines the final position of some object in ROM or RAM Along with the architecture independent standard operators there are some AVR specific operators available which are unfortunately not yet described in the official documen tation The most notable operators are 108 Takes the least significant 8 bits of a 16 bit integer hi8 Takes the most significant 8 bits of a 16 bit integer pm Takes a program memory ROM address and converts it into a RAM ad dress This implies a division by 2 as the AVR handles ROM addresses as 16 bit words e g in an IJMP or ICALL instruction and can also handle relocatable symbols on the right hand side Example ldi r24 lo8 pm somefunc ldi r25 hi8 pm somefunc call somethi
359. ll be called when the corresponding interrupt occurs The device library provides a set of default interrupt routines which will get used if you don t define your own Patching into the vector table is only one part of the problem The compiler uses by convention a set of registers when it s normally executing compiler generated code It s important that these registers as well as the status register get saved and restored The extra code needed to do this is enabled by tagging the interrupt function with attribute signal These details seem to make interrupt routines a little messy but all these details are handled by the Interrupt API An interrupt routine is defined with ISR This macro register and mark the routine as an interrupt handler for the specified peripheral The following is an example definition of a handler for the ADC interrupt include lt avr interrupt h gt ISR ADC vect user code here Refer to the chapter explaining assembler programming for an explanation about inter rupt routines written solely in assembler language Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 245 Catch all interrupt vector If an unexpected interrupt occurs interrupt is enabled and no handler is installed which usually indicates a bug then the default action is to reset the device by jumping to the reset vector You can override this by supplying a
360. locking printf printf_P vprintf vprintf_P Alters flags and character count in global FILE puts puts PO stdout Use only in one thread Or if returned character count is unimportant do 11 34 Why are some addresses of the EEPROM corrupted usually address zero 89 Note It s not clear one would ever want to do character input simultaneously from more than one thread anyway but these entries are included for completeness An effort will be made to keep this table up to date if any new issues are discovered or introduced Back to FAQ Index 11 34 Why are some addresses of the EEPROM corrupted usually address zero The two most common reason for EEPROM corruption is either writing to the EEP ROM beyond the datasheet endurance specification or resetting the AVR while an EEPROM write is in progress EEPROM writes can take up to tens of milliseconds to complete So that the CPU is not tied up for that long of time an internal state machine handles EEPROM write requests The EEPROM state machine expects to have all of the EEPROM registers setup then an EEPROM write request to start the process Once the EEPROM state machine has started changing EEPROM related registers during an EEPROM write is guaranteed to corrupt the EEPROM write process The datasheet always shows the proper way to tell when a write is in progress so that the registers are not changed by the user s program The EE
361. long __seed long random unsigned long __ctx char itoa int __val char __s int radix define RANDOM MAX Ox7FFFFFFF Conversion functions for double arguments Note that these functions are not located in the default library 1ibc a but in the mathematical library 1ibm a So when linking the application the 1m option needs to be specified char dtostre double val char flags e char dtostrf double val signed char __ width unsigned char prec char S define DTOSTR ALWAYS SIGN 0x01 define DTOSTR PLUS SIGN 0x02 define DTOSTR_UPPERCASE 0x04 s unsigned char prec unsigned char 22 10 1 Detailed Description include lt stdlib h gt This file declares some basic C macros and functions as defined by the ISO standard plus some AVR specific extensions 22 10 2 Define Documentation 22 10 2 1 define DTOSTR ALWAYS SIGN 0x01 Bit value that can be passed in 1ags to dtostre Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 204 22 10 2 2 define DTOSTR PLUS SIGN 0x02 Bit value that can be passed in flags to dtostre 22 10 2 3 define DTOSTR UPPERCASE 0x04 Bit value that can be passed in flags to dtostre 22 10 2 4 define RAND MAX 0x7FFF Highest number that can be generated by rand 22 10 2 5 define RANDOM MAX 0x7FFFFFFF Highest number that can be generated by random 2
362. lready carries a logical 1 when reading it so why does writing a logical 1 to it clear the interrupt bit The solution is simple writing a logical 1 to it requires only a single OUT instruction and it is clear that only this single interrupt request bit will be cleared There is no need to perform a read modify write cycle like an SBI instruction since all bits in these control registers are interrupt bits and writing a logical 0 to the remaining bits as it is done by the simple OUT instruction will not alter them so there is no risk of any race condition that might accidentally clear another interrupt request bit So instead of writing TIFR BV TOVO wrong x simply use Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 26 Why have programmed fuses the bit value 0 83 TIFR _BV TOVO Back to FAQ Index 11 26 Why have programmed fuses the bit value 0 Basically fuses are just a bit in a special EEPROM area For technical reasons erased E E PROM cells have all bits set to the value 1 so unprogrammed fuses also have a logical 1 Conversely programmed fuse cells read out as bit value 0 Back to FAQ Index 11 27 Which AVR specific assembler operators are available See Pseudo ops and operators Back to FAQ Index 11 28 Why are interrupts re enabled in the middle of writing the stack pointer When setting up space for local variables on the stack the compiler generates code like
363. lue from val into an ASCII represen tation that will be stored under s The caller is responsible for providing sufficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof long int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 97 will be the letter a If radix is 10 and val is negative a minus sign will be prepended The ltoa function returns the pointer passed as s Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 209 22 10 4 17 void malloc size t size The malloc function allocates size bytes of memory If malloc fails a NULL pointer is returned Note that malloc does not initialize the returned memory to zero bytes See the chapter about malloc usage for implementation details 22 10 4 18 void qsort void __ base size t nmemb size t _ size compar fn t compar The qsort function is a modified partition exchange sort or quicksort The qsort function sorts an ar
364. lus all further nested function calls must not require more stack space or they will risk colliding with the data segment The default value of malloc margin is set to 32 3 4 Implementation details Dynamic memory allocation requests will be returned with a two byte header prepended that records the size of the allocation This is later used by free The returned address points just beyond that header Thus if the application accidentally writes before the returned memory region the internal consistency of the memory allocator is compro mised The implementation maintains a simple freelist that accounts for memory blocks that have been returned in previous calls to free Note that all of this memory is considered to be successfully added to the heap already so no further checks against stack heap collisions are done when recycling memory from the freelist The freelist itself is not maintained as a separate data structure but rather by modifying the contents of the freed memory to contain pointers chaining the pieces together That way no additional memory is reqired to maintain this list except for a variable that keeps track of the lowest memory segment available for reallocation Since both a chain pointer and the size of the chunk need to be recorded in each chunk the minimum chunk size on the freelist is four bytes Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 4 Memory Sections 22 When allocatin
365. ly it should be safe to use r2 through r7 that way Registers r8 through r15 can be used for argument passing by the compiler in case many or long arguments are being passed to callees If this is not the case throughout the entire application these registers could be used for register variables as well Extreme care should be taken that the entire application is compiled with a consistent set of register allocated variables including possibly used library functions See C Names Used in Assembler Code for more details Back to FAQ Index 11 5 How to modify MCUCR or WDTCR early The method of early initialization MCUCR WDTCR or anything else is different and more flexible in the current version Basically write a small assembler file which looks like this begin xram S finclude avr io h Section initl ax progbits Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 6 What is all this BV stuff about 65 ldi r16 BV SRE BV SRW out SFR IO ADDR MCUCR r16 end xram S Assemble it link the resulting xram o with other files in your program and this piece of code will be inserted in initialization code which is run right after reset See the linker script for comments about the new initN sections which one to use etc The advantage of this method is that you can insert any initialization code you want just remember that this is very early startup no stack and no zero reg
366. m rf x o S PRG elf png pdf x bak rm rf x lst map CLEAN FILES lst PRG 1st lst elf S OBJDUMP h S lt gt Rules for building the text rom images text hex bin srec hex PRG hex bin PRG bin srec PRG srec hex elf j text j data O ihex lt 560 oe srec elf j text j data O srec lt 6 oe bin elf j text j data O binary lt Rules for building the eeprom rom images eeprom ehex ebin esrec ehex PRG eeprom hex PRG _eeprom bin esrec PRG eeprom srec oe eeprom hex elf j eeprom change section Ima eeprom 0 O ihex lt SR echo empty 8 not generated exit 0 eeprom srec elf OBJCOPY j eeprom change section lma eeprom 0 O srec lt 8 echo empty 8 not generated exit 0 ur o eeprom bin elf OBJCOPY j eeprom change section lma eeprom 0 O binary S echo empty 8 not generated exit 0 oe ur Every thing below here is used by avr libc s build system and can be ignored by the casual user FIG2DEV fig2dev EXTRA CLEAN FILES bin srec dox eps png pdf eps PRG eps Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 38 A more sophisticated project 346 png PRG png pdf pd
367. mended in AVR GCC as it removes this register from the control of the compiler which may make code generation worse Use at your own risk Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 Frequently Asked Questions 62 11 11 1 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Frequently Asked Questions FAQ Index My program doesn t recognize a variable updated within an interrupt routine I get undefined reference to for functions like sin How to permanently bind a variable to a register How to modify MCUCR or WDTCR early What is all this BV stuff about Can I use C on the AVR Shouldn t I initialize all my variables Why do some 16 bit timer registers sometimes get trashed How do I use a define d constant in an asm statement Why does the PC randomly jump around when single stepping through my pro gram in avr gdb How do I trace an assembler file in avr gdb How do I pass an IO port as a parameter to a function What registers are used by the C compiler How do I put an array of strings completely in ROM How to use external RAM Which O flag to use How do I relocate code to a fixed address My UART is generating nonsense My ATmegal28 keeps crashing Port is completely broken Why do all my foo bar strings eat up the SRAM Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit ope
368. mes per second Since we use timer 0 without any prescaling options in order to get the de sired frequency and accuracy we already run into serious timing considerations while accepting and processing the timer overflow interrupt the timer already continues to Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 6 3 Example program 36 count When pre loading the TCCNTO register we therefore have to account for the number of clock cycles required for interrupt acknowledge and for the instructions to reload TCCNTO 4 clock cycles for interrupt acknowledge 2 cycles for the jump from the interrupt vector 2 cycles for the 2 instructions that reload TCCNTO This is what the constant fuzz is for Note 5 External functions need to be declared to be global main is the application entry point that will be jumped to from the ininitalization routine in crt 81200 o Note 6 The main loop is just a single jump back to itself Square wave generation itself is completely handled by the timer 0 overflow interrupt service A sleep instruction using idle mode could be used as well but probably would not conserve much energy anyway since the interrupt service is executed quite frequently Note 7 Interrupt functions can get the usual names that are also available to C programs The linker will then put them into the appropriate interrupt vector slots Note that they must be declared global in order to be acceptable for thi
369. n DOWN 118 0x01 1l 0x0060 r18 Gt rjmp 70 0x42 lt __SREG__ 0x3 gt lt ioinit gt void x Note 6 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 339 Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys TCCRIA 1 INIT 88 83 e8 ldi r24 0x83 131 8a 8f bd out 0x2f r24 47 Start timer 1 x NB TCCR1A and TCCRIB could actually be the same register so take care to not clobber it x TCCRIB TIMER1_CLOCKSOURCE 8c 8e b5 in r24 0x2e 46 8e 81 60 ori r24 0x01 1 90 8e bd out 0x2e r24 46 if defined TIMER1 SETUP HOOK TIMER1 SETUP HOOK endif x Set PWM value to 0 OCR 0 92 1bobec out 0x2b r1 43 94 1 bc out 0x2a r1 42 Enable as output DDROC BV OCI 96 82 e0 ldi r24 0x02 2 98 87 bb Oxl7 r24 i 23 Enable timer 1 overflow interrupt TIMSK BV TOIE1 9a 84 eO ldi r24 0x04 4 9c 89 bf out 0x39 r24 57 sei 9e 78 94 sei 0 08 95 ret 000000a2 main void ioinit void x Note 6 Timer 1 is 10 bit 8 bit PWM on some ATtinys TCCRIA 1 INIT a2 83 e8 ldi r24 0x83 131 a4 8f bd out 0x2f r24 47 Start timer 1 x NB TCCR1A and TCCRIB could actually be the same register so take care to not clobber it x TCCRIB TIMER1_CLOCKSOURCE a6 8e b5 in r24 0x2e 46
370. n Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 177 22 8 2 37 22 8 2 38 22 8 2 39 22 8 2 40 22 8 2 41 22 8 2 42 22 8 2 43 22 8 2 44 22 8 2 45 22 8 2 46 define SIG ATOMIC MIN INT8 MIN smallest negative value a sig atomic t can hold define SIZE MAX CONCAT INTI6 MAX U largest value a size t can hold define UINT16 C value CONCAT value U define a constant of type uint16 t define UINTI6 MAX CONCAT INTI6 MAX U 2U 10 largest value an uint16 t can hold define UINT32 C value CONCAT value UL define a constant of type uint32 t define UINT32 MAX CONCAT INT32 MAX U 2UL largest value an uint32 t can hold define UINT64 C value CONCAT value ULL define a constant of type uint64 t define UINT 4 MAX CONCAT INT64 U 2ULL 1ULL largest value an uint64_t can hold define UINT8 C value uint8 t CONCAT value U define a constant of type uint8 t define UINT8 MAX CONCAT INT8 U x 20 10 largest value an uint8_t can hold Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 8 lt stdint h gt Standard Integer Types 178 22 8 2 47 22 8 2 48 22 8 2 49 22 8 2 50 22 8 2 51 22 8 2 52 22 8 2 53 22 8 2 54 22 8 2 55 22 8 2 56 define UINT FASTI6 MAX UINTI6 MAX largest value an uint fast16 t can hold define U
371. n avr gcc in your environment this will cause the configure script to fail It is best to not have CC set at all Note It is usually the best to use the latest released version of each of the tools Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 2 Required Tools 92 12 2 12 3 Required Tools GNU Binutils http sources redhat com binutils Installation GCC http gcc gnu org Installation AVR Libc http savannah gnu org projects avr libc Installation Optional Tools You can develop programs for AVR devices without the following tools They may or may not be of use for you AVRDUDE http savannah nongnu org projects avrdude Installation Usage Notes GDB http sources redhat com gdb Installation SimulAVR http savannah gnu org projects simulavr Installation AVaRICE http avarice sourceforge net Installation Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 124 GNU Binutils for the AVR target 93 124 GNU Binutils for the AVR target The binutils package provides all the low level utilities needed in building and ma nipulating object files Once installed your environment will have an AVR assembler avr as linker avr 13G and librarian avr ar and avr ranlib In addi tion you get tools which extract data from object files avr objcopy dissassem ble object file information avr ob and strip information from object
372. n t ld r24 0 An Nt inc r24 An NE St a0 r24 n t sei Nn e ptr r24 The compiler might produce the following code cli ld r24 Z inc r24 st 27 r24 sei One easy solution to avoid clobbering register r24 is to make use of the special tem porary register reg defined by the compiler asm volatile nebi Nini ld _ tmp reg a0 WARNE inc _ tmp reg n t St a0 __tmp_reg__ Kn tX sei TANNE e ptr The compiler is prepared to reload this register next time it uses it Another problem with the above code is that it should not be called in code sections where interrupts are disabled and should be kept disabled because it will enable interrupts at the end We may store the current status but then we need another register Again we can solve this without clobbering a fixed but let the compiler select it This could be done with the help of a local C variable Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 4 Clobbers 48 uint8_t s asm volatile in 0 __SREG__ An Nen cli An NET ld tmp reg al MATINET inc tmp reg MANEN st Sal _ tmp reg out SREG 0 n t amp r s e ptr Now every thing seems correct but it isn t really The assembler code modifies the variable that pt x points to The compiler will not recognize this and may keep its value in any of the other registers Not only does
373. n timing like UART communication The ATmegal28 ships with the fuse enabled that turns this device into AT megal03 compatibility mode This means that some ports are not fully usable Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 20 Why do all my foo bar strings eat up the SRAM 79 and in particular that the internal SRAM is located at lower addresses Since by default the stack is located at the top of internal SRAM a program compiled for an ATmegal28 running on such a device will immediately crash upon the first function call or rather upon the first function return Devices with a JTAG interface have the JTAGEN fuse programmed by default This will make the respective port pins that are used for the JTAG interface un available for regular IO Back to FAQ Index 11 20 Why do all my foo bar strings eat up the SRAM By default all strings are handled as all other initialized variables they occupy RAM even though the compiler might warn you when it detects write attempts to these RAM locations and occupy the same amount of flash ROM so they can be initialized to the actual string by startup code The compiler can optimize multiple identical strings into a single one but obviously only for one compilation unit i e a single C source file That way any string literal will be a valid argument to any C function that expects a const char argument Of course this is going to waste
374. n will work in this case The hh length modifier is ignored char argument is promouted to int More exactly this realization does not check the number of h symbols But the 11 length modifier will to abort the output as this realization does not operate long long arguments The variable width or precision field an asterisk symbol is not realized and will to abort the output 22 9 3 33 int vfprintf P FILE stream constchar fmt va list Variant of v printf that uses a mt string that resides in program memory 22 9 3 34 int vfscanf FILE stream const char fmt va_list ap Formatted input This function is the heart of the scanf family of functions Characters are read from stream and processed in a way described by fmt Conversion results will be assigned to the parameters passed via ap The format string fmt is scanned for conversion specifications Anything that doesn t comprise a conversion specification is taken as text that is matched literally against the input White space in the format string will match any white space in the data including none all other characters match only itself Processing is aborted as soon as the data and format string no longer match or there is an error or end of file condition on stream Most conversions skip leading white space before starting the actual conversion Conversions are introduced with the character 96 Possible options can follow the 96
375. nd function rounds x to the nearest integer but rounds halfway cases away from zero instead of to the nearest even integer Overflow is impossible Returns The rounded value If x is an integral or infinite x itself is returned If __x is NaN then NaN is returned 22 6 3 32 int signbit double x The signbit function returns a nonzero value if the value of __x has its sign bit set This is not the same as __x lt 0 0 because IEEE 754 floating point allows zero to be signed The comparison 0 0 lt 0 0 is false but signbit 0 0 will return a nonzero value 22 6 3 33 double sin double x The sin function returns the sine of x measured in radians 22 6 3 34 double sinh double x The sinh function returns the hyperbolic sine of x 22 6 3 35 double sqrt double x The sqrt function returns the non negative square root of __x 22 6 3 36 double square double x The function square returns __x __x Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 227 lt setjmp h gt Non local goto 167 Note This function does not belong to the C standard definition 22 6 3 37 double tan double x The tan function returns the tangent of __x measured in radians 22 6 3 38 double tanh double x The tanh function returns the hyperbolic tangent of __x 22 6 3 39 double double x The trunc function rounds x to the nearest inte
376. nd heap end is set to 0 which makes malloc assume the heap is below the stack If the heap is going to be moved to external RAM _ malloc heap end must be adjusted accordingly This can either be done at run time by writing directly to this variable or it can be done automatically at link time by adjusting the value of the Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 3 3 Tunables for malloc 20 symbol heap end The following example shows a linker command to relocate the entire data and bss segments and the heap to location 0x1100 in external RAM The heap will extend up to address Oxffff avr gcc Wl section start data 0x801100 defsym heap end 0x80ffff Note See explanation for offset 0x800000 See the chapter about using gcc for w1 options The ld linker user manual states that using Tdata lt x gt is equivalent to using section start data lt x gt However you have to use section start as above be cause the GCC frontend also sets the Tdata option for all MCU types where the SRAM doesn t start at 0x800060 Thus the linker is being faced with two Tdata options Sarting with binutils 2 16 the linker changed the preference and picks the wrong option in this situation 0x0100 on board RAM external RAM Ox10FF 0x1100 OxFFFF 4 SP d t __malloc_heap_end heap end RAMEND __brkval malloc heap start heap start bs
377. ndom 208 strspn 225 RANDOM MAX 203 strstr 225 random r 209 strtok 225 realloc 209 strtok 226 srand 209 strupr 226 srandom 209 avr version strtod 209 AVR LIBC DATE 301 strtol 210 DATE STRING 301 strtoul 210 AVR MAJOR 301 ultoa 211 AVR LIBC MINOR 301 utoa 212 AVR REVISION 301 avr string AVR LIBC VERSION STRING _FFS 214 _ 301 ffs 214 AVR VERSION 301 ffsl 215 avr watchdog ffsll 215 wdt disable 303 wdt enable 303 wdt reset 304 WDTO 120MS 304 WDTO 15MS 304 WDTO 15 304 WDTO 250MS 304 WDTO 25 304 WDTO 30MS 305 WDTO 45 305 WDTO 500MS 305 WDTO_60MS 305 WDTO 8S 305 avrdude usage 120 avrprog usage 120 BADISR vect avr interrupts 262 BAUD TOL util setbaud 316 bit 1s clear avr sfr 296 bit is set avr sfr 296 boot h 368 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 424 boot lock bits set 369 boot lock bits set alternate 369 boot page erase alternate 370 boot page erase extended 370 boot page erase normal 371 boot page fill alternate 371 boot page fill extended 371 boot page fill normal 372 boot page write alternate 372 boot page write extended 373 boot page write normal 373 boot rww enable 373 boot rww enable alternate 374 boot is spm interrupt avr boot 229 boot lock bits set avr boot 229 boot lock bits set safe avr boot 229 boot lock fuse bits get avr bo
378. ne M E 2 7182818284590452354 The constant e 22 6 2 33 define M LNI10 2 30258509299404568402 The natural logarithm of the 10 22 6 2 34 define M LN2 0 69314718055994530942 The natural logarithm of the 2 22 6 2 35 define M LOGIOE 0 43429448190325182765 The logarithm of the e to base 10 22 6 2 36 define M LOGZ2E 1 4426950408889634074 The logarithm of the e to base 2 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 160 22 6 2 37 define M PI 3 14159265358979323846 The constant pi 22 6 2 38 define PI 2 1 57079632679489661923 The constant pi 2 22 6 2 39 define M PI 4 0 78539816339744830962 The constant pi 4 22 6 2 40 define M SORTI 2 0 70710678118654752440 The constant 1 sqrt 2 22 6 2 41 define M SQRT2 1 41421356237309504880 The square root of 2 22 6 2 42 define NAN builtin nan NAN constant 22 6 2 43 define powf pow The alias for pow 22 6 2 44 define roundf round The alias for round 22 6 2 45 define signbitf signbit The alias for signbit 22 6 2 46 define sinf sin The alias for sin Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 161 22 6 2 47 22 6 2 48 22 6 2 49 22 6 2 50 22 6 2 51 22 6 2 52 define sinhf sinh define sqrtf sqrt define squaref square define tanf tan define tanhf tanh define truncf trunc 2
379. ne PRIXLEASTI6O x define PRIXFASTI16 x define PRIX16 X define PRIXLEASTI6 X define PRIXFASTI6 X define PRIo32 lo define PRIOLEAST32 lo define PRIoFAST32 lo define PRIu32 lu define PRIULEAST32 lu define PRIuFAST32 lu Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 17 inttypes h File Reference 380 Typedefs Far pointers for memory access gt 64K define PRIx32 Ix ftdefine PRIXLEAST32 Ix define PRIxFAST32 Ix define PRIX32 IX define PRIXLEAST32 IX define PRIXFAST32 IX define PRIoPTR PRIo16 define PRIuPTR PRIu16 define PRIxPTR PRIx16 define PRIXPTR PRIX16 define SCNd16 define SCNdLEASTI6 d define SCNdFASTI6 define SCNi16 1 define SCNiLEAST16 i define SCNiFAST16 1 define SCNd32 Id define SCNdLEAST32 Id define SCNdFAST32 define SCNi32 li define SCNILEAST32 li define SCNiFAST32 li define SCNdPTR SCNd16 define SCNiPTR SCNi16 define SCNo16 o define SCNoLEAST16 o define SCNoFASTI6 o define SCNul6 u define SCNuLEASTI6 u define SCNuFASTI6 u define SCNx16 x define SCNxLEAST16 x define SCNxFAST16 define SCNo32 lo define SCNoLEAST32 lo define SCNoFAST32 lo define SCNu32 lu define SCNuLEAST32 lu define SCNuFAST32 lu define SCNx32 Ix define SCNxLEAST32 Ix define SCNxFAST32 Ix define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR S
380. ne fminf fmin The alias for copysign The alias for cos The alias for cosh The alias for exp The alias for fabs The alias for fdim The alias for floor The alias for fma The alias for fmax The alias for fmin Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 158 22 6 2 17 22 6 2 18 22 6 2 19 22 6 2 20 22 6 2 21 22 6 2 22 22 6 2 23 22 6 2 24 22 6 2 25 22 6 2 26 define fmodf fmod define frexpf frexp define hypotf hypot define INFINITY builtin inf define isfinitef isfinite define isinff isinf define isnanf isnan define Idexpf Idexp define log10f log10 define logf log The alias for fmod The alias for frexp The alias for hypot INFINITY constant The alias for isfinite The alias for isinf The alias for isnan The alias for ldexp The alias for log10 The alias for log Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 6 lt math h gt Mathematics 159 22 6 2 27 define Irintf Irint The alias for lrint 22 6 2 28 Iroundf lround The alias for lround 22 6 2 29 define M 1 PI 0 31830988618379067154 The constant pi 22 6 2 30 define M 2 PI 0 63661977236758134308 The constant 2 pi 22 6 2 3 define 2 SQRTPI 1 12837916709551257390 The constant 2 sqrt pi 22 6 2 32 defi
381. ng This passes the address of function somefunc as the first parameter to function something 7 Inline Assembler Cookbook AVR GCC Inline Assembler Cookbook About this Document Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 1 GCC asm Statement 39 The GNU C compiler for Atmel AVR RISC processors offers to embed assembly language code into C programs This cool feature may be used for manually optimizing time critical parts of the software or to use specific processor instruction which are not available in the C language Because of a lack of documentation especially for the AVR version of the compiler it may take some time to figure out the implementation details by studying the compiler and assembler source code There are also a few sample programs available in the net Hopefully this document will help to increase their number It s assumed that you are familiar with writing AVR assembler programs because this is not an AVR assembler programming tutorial It s not a C language tutorial either Note that this document does not cover file written completely in assembler language refer to avr libc and assembler programs for this Copyright C 2001 2002 by egnite Software GmbH Permission is granted to copy and distribute verbatim copies of this manual provided that the copyright notice and this permission notice are preserved on all copies Permis sion is granted to copy and distribute modified ver
382. ng dest must be large enough to receive the copy Returns The strcpy function returns a pointer to the destination string dest Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 221 Note If the destination string of a strcpy is not large enough that is if the programmer was stupid lazy and failed to check the size before copying then anything might happen Overflowing fixed length strings is a favourite cracker technique 22 11 3 19 size tstrcspn const char s const char reject The strcspn function calculates the length of the initial segment of s which consists entirely of characters not in re ject Returns The strcspn function returns the number of characters in the initial segment of s which are not in the string reject The terminating zero is not considered as a part of string 22 11 3 20 char x strdup const char 57 Duplicate a string The strdup function allocates memory and copies into it the string addressed by 51 including the terminating null character Warning The strdup function calls malloc to allocate the memory for the duplicated string The user is responsible for freeing the memory by calling free Returns The strdup function returns a pointer to the resulting string dest If malloc cannot allocate enough storage for the string strdup will return NULL Warning Be sure to check the return value of the strdup
383. nhanced addr Value extension N uint32 t addr32 uint32 t addr uint8 t _ result N asm N N out 2 SCOTI nic N movw r30 1 n t N elpm 0 Z n t N r result N TEM addriz I SFR IO ADDR RAMPZ NBO mpg N result N 24 35 2 5 define ELPM float enhanced addr Value extension 4 uint32 t addr32 uint32 t addr float _ result asm out 2 1 mina movw r30 1 n t rr ee Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Reference 391 elpm A0 Z n t N elpm B0 Z4 n t N elpm C0 Z4 X elpm 0 7 n t r result N r addr32 I SFR IO ADDR RAMPZ Ne ESOW result N 24 35 2 6 define ELPM float xmega addr Value extension N uint32 t __addr32 uint32 t addr float result N asm N N in tmp reg 2 n t X oub 2 SCIT n t movw r30 1 n t N elpm 0 Z N elpm B0 Z4 n t N elpm CO Z n t N elpm D0 7 n t N out 2 tmp reg r _ result N wr add 32 N I SFR IO ADDR RAMPZ N E30 result N 24 35 27 define ELPM word classic addr Value extension N uint32 t addr32 uint32 t addr uintl16 t result N asm N N out 2 sci l
384. not found If s2 points to a string of zero length the function returns s1 22 11 3 36 char x strtok char s const char delim Parses the string s into tokens Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 227 strtok parses the string s into tokens The first call to strtok should have s as its first argument Subsequent calls should have the first argument set to NULL If a token ends with a delimiter this delimiting character is overwritten with a 0 and a pointer to the next character is saved for the next call to strtok The delimiter string delim may be different for each call Returns The strtok function returns a pointer to the next token or NULL when no more tokens are found Note strtok is NOT reentrant For a reentrant version of this function see strtok rij 22 11 3 37 char x strtok_r char x string const char x delim char last Parses string into tokens strtok r parses string into tokens The first call to strtok r should have string as its first argument Subsequent calls should have the first argument set to NULL If a token ends with a delimiter this delimiting character is overwritten with a VO and a pointer to the next character is saved for the next call to strtok_r The delimiter string delim may be different for each call last is a user allocated char pointer It must be the same while parsing the same string strtok r
385. ns 22 19 4 43 charx strtok P char s P Parses the string into tokens strtok_P parses the string s into tokens The first call to strtok_P should have s as its first argument Subsequent calls should have the first argument set to NULL If a token ends with a delimiter this delimiting character is overwritten with a 70 and a pointer to the next character is saved for the next call to strtok_P The delimiter string delim may be different for each call The strtok function is similar to strtok except that delim is pointer to a string in program space Returns The strtok_P function returns a pointer to the next token or NULL when no more tokens are found Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 00 lt avr power h gt Power Reduction Management 292 Note strtok_P is NOT reentrant For a reentrant version of this function see strtok rP 22 19 4 44 char x strtok char x string P delim char last Parses string into tokens The strtok_rP function parses st ring into tokens The first call to strtok_rP should have string as its first argument Subsequent calls should have the first argument set to NULL If a token ends with a delimiter this delimiting character is overwritten with a VO and a pointer to the next character is saved for the next call to strtok rP The delimiter string delim may be different for each call Last is a user
386. ns This is normally not a big concern as the linker setup arranges any program space constants declared using the macros from this header file so they are placed right after the interrupt vectors and in front of any executable code However it can become a problem if there are too many of these constants or for bootloaders on devices with more than 64 KB of ROM All these functions will not work in that situation For Xmega devices make sure the NVM controller command register CMD CMD is set to 0x00 NOP before using any of these functions 22 19 2 Define Documentation 22 19 2 1 define P const prog char Used to declare a variable that is a pointer to a string in program space 22 19 2 2 define read byte address short pgm read byte near address short Read a byte from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 22 19 2 3 define pgm read byte far address long ELPM uint32 t address long Read a byte from the program space with a 32 bit far address Note The address is a byte address The address is in the program space Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 avr pgmspace h gt Program Space Utilities 274 22 19 2 4 define read byte near address short LPM uint16 t address short Read a byte from the program space with a 16 bit near address
387. ns as a modifier on the parameter type This tells the compiler that the function will only use the parameter as read only and will not modify the contents of the parameter variable const was intended for uses such as this not as a means to identify where the data should be stored If it were used as a means to define data storage then it loses its correct meaning changes its semantics in other situations such as in the function pa rameter example 5 3 Storing and Retrieving Data in the Program Space Let s say you have some global data unsigned char mydata 11 10 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 5 3 Storing and Retrieving Data in the Program Space 29 0x0A 0x0B 0x0C OxOD OxOE OxOF 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D Ox1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0 28 0 29 0 2 0 2 0 2 0 2 0 2 0 2 0 30 0 31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 Ox5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D and later in your code you access this data in function and store a single byte into variable like so byte mydata i j Now
388. ntisprint int c int ispunct int c e int isspace int __c e int isupper int e int isxdigit int c Character convertion routines This realization permits all possible values of integer argument The toascii function clears all highest bits The tolower and toupper functions return an input argument as is if it is not an unsigned char value e int toascii int c int tolower int __c int toupper int c 22 31 Detailed Description These functions perform various operations on characters include lt ctype h gt Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 3 lt ctype h gt Character Operations 138 22 3 2 Function Documentation 22 3 2 1 intisalnum int Checks for an alphanumeric character It is equivalent to isalpha c isdigit c 22 3 2 intisalpha int Checks for an alphabetic character It is equivalent to isupper islower c 22 3 2 3 intisascii int Checks whether c is a 7 bit unsigned char value that fits into the ASCII character set 22 3 2 4 intisblank int Checks for a blank character that is a space or a tab 22 3 2 5 intiscntrl int Checks for a control character 22 3 2 6 int isdigit int c Checks for a digit 0 through 9 22 32 7 intisgraph int Checks for any printable character except space 22 3 2 8 intislower int Checks for a lower case character 22 3 2 9 intisprint int c
389. nvoking the compiler 33 Special tweaks that cannot be done in C Usually all but the first could probably be done easily using the inline assembler facility of the compiler Although avr libc is primarily targeted to support programming AVR microcontrollers using the C and C language there s limited support for direct assembler usage as well The benefits of it are Use of the C preprocessor and thus the ability to use the same symbolic constants that are available to C programs as well as a flexible macro concept that can use any valid C identifier as a macro whereas the assembler s macro concept is basically targeted to use a macro in place of an assembler instruction Use of the runtime framework like automatically assigning interrupt vectors For devices that have RAM initializing the RAM variables can also be utilized 6 2 Invoking the compiler For the purpose described in this document the assembler and linker are usually not invoked manually but rather using the C compiler frontend avr gcc that in turn will call the assembler and linker as required This approach has the following advantages e There is basically only one program to be called directly avr gcc regardless of the actual source language used The invokation of the C preprocessor will be automatic and will include the appropriate options to locate required include files in the filesystem The invokation of the linker will be automatic
390. ny4313__ avr2 avr25 1 attiny43u AVR AT ny43U avr2 avr25 1 attiny44 AVR AT ny44 avr2 avr25 1 attiny44a AT ny44A avr2 avr25 1 attiny45 _ AVR AT ny45 avr2 avr25 1 attiny461 AVR_ATtiny461__ avr2 avr25 1 attiny46la AVR AT ny461A avr2 avr25 1 attiny48 AVR AT ny48 avr2 avr25 1 attiny84 AVR 84 avr2 avr25 1 attiny84a AVR AT ny84A avr2 avr25 1 attiny85 AVR AT ny85 avr2 avr25 1 attiny861 AVR_ATtiny861__ avr2 avr25 1 attiny86la AVR AT ny861A avr2 avr25 1 attiny87 _ AVR AT ny87 avr2 avr25 1 attiny88 AVR 88 avr3 atmega603 AVR ATmega603 avr3 at43usb355 AVR AT43USB355 avr3 avr31 3 atmegal03 AVR ATmegal03 avr3 avr31 3 at43usb320 AVR AT43USB320 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 110 avr3 avr35 2 at90usb82 AVR_AT90USB82__ avr3 avr35 2 at90usb162 AVR AT9O0USBI162 avr3 avr35 2 atmega8u2 ATmega8U2 avr3 avr35 2 atmegal6u2 AVR ATmegal6U2 avr3 avr35 2 atmega32u2 ATmega32U2 avr3 avr35 2 attiny167 AVR_ATtiny167__ avr3 avr35 2 attiny1634 AVR AT nyl634 avr3 at76c711 AVR AT76C711 avr4 atmega4
391. nzip c avrdude version tar gz tar xf cd avrdude lt version gt mkdir obj avr cd obj avr configure prefix PREFIX make make install Xr Xo or Xr wn Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 8 GDB for the AVR target 96 12 8 GDB for the AVR target GDB also uses the con igure system so to build and install bunzip2 c gdb version tar bz2 tar xf cd gdb version mkdir obj avr cd obj avr configure prefix PREFIX target avr make make install Ur X X Xr or XY Note If you are planning on using avr gdb you will probably want to install either simulavr or avarice since avr gdb needs one of these to run as a a remote target backend 12 9 SimulAVR SimulAVR also uses the configure system so to build and install gunzip c simulavr version tar gz tar xf cd simulavr version mkdir obj avr cd obj avr configure prefix PREFIX make make install Ur Xo or Xr Xo Note You might want to have already installed avr binutils avr gcc and avr libc if you want to have the test programs built in the simulavr source 12 10 AVaRICE Note These install notes are not applicable to avarice 1 5 or older You probably don t want to use anything that old anyways since there have been many improvements and bug fixes since the 1 5 release AVaRICE also uses the configure system so to build and install gunzip c avarice
392. o by src instead of forwards from the front Glibe GNU extension Returns The memrchr_P function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 22 19 4 9 intstrcasecmp P const char 51 P s2 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 280 Compare two strings ignoring case The strcasecmp_P function compares the two strings s1 and s2 ignoring the case of the characters Parameters 51 A pointer to a string in the devices SRAM 52 A pointer to a string in the devices Flash Returns The strcasecmp_P function returns an integer less than equal to or greater than Zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcasecmp_P is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 22 19 4 10 int strcasecmp PF const char 57 uint farptr t s2 Compare two strings ignoring case The strcasecmp PF function compares the two strings s 52 ignoring the case of the characters Parameters 51 A pointer to the first string in SRAM 52 A far pointer to the second string in Flash Returns The strcasecmp_PF function returns an integer less than equal to or greater than zero if 81 is found respectively to be
393. object code which is not even close to what is intended The major problem arises when the function is called When the compiler sees this call it will actually pass the value of the PORTB register using an IN instruction instead of passing the address of PORTB e g memory mapped io addr of 0x38 io port 0x18 for the mega128 This is seen clearly when looking at the disassembly of the call Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 13 How do pass an IO port as a parameter to a function 72 set bits func wrong PORTB Oxaa 10a 6a ea 1 r22 OxAA 21070 10 88 b3 r24 0 18 24 10 0e 94 65 00 11 So the function once called only sees the value of the port register and knows nothing about which port it came from At this point whatever object code is generated for the function by the compiler is irrelevant The interested reader can examine the full disassembly to see that the function s body is completely fubar The second function shows how to pass by reference the memory mapped address of the io port to the function so that you can read and write to it in the function Here s the object code generated for the function call set bits func correct amp PORTB 0x55 112 65 5 141 r22 0x55 j 85 114 88 e3 141 r24 0x38 56 116 90 eO 141 r25 0 00 0 118 0e 94 7c 00 call Oxf8 You can clearly see that 0x0038 is correctly passed for the address of the io port L
394. ocate nele elements of size each Identical to calling malloc using nele size as argument except the allocated memory will be cleared to zero 22 10 4 8 div tdiv int int denom The div function computes the value num denom and returns the quotient and remainder in a structure named div t that contains two int members named quot and rem 22 10 4 9 char dtostre double val char x s unsigned char prec unsigned char flags The dtostre function converts the double value passed in va1 into an ASCII representation that will be stored under s The caller is responsible for providing sufficient storage in s Conversion is done in the format d ddde dd where there is one digit before the decimal point character and the number of digits after it is equal to the precision prec if the precision is zero no decimal point character appears If 1ags has the DTOSTRE UPPERCASE bit set the letter E rather than e will be used to introduce the exponent The exponent always contains two digits if the value is zero the exponent is 00 If 1ags has the DTOSTRE ALWAYS SIGN bit set a space character will be placed into the leading position for positive numbers If flags has the DTOSTRE PLUS SIGN bit set a plus sign will be used instead of a space character in this case The dtostre function returns the pointer to the converted string s 22 10 4 10 char dtostrf double val signed char width unsigne
395. ocessing an assembly language file and it contains just macros that give symbolic names to a number of CPU registers The preprocessor will then replace the symbolic names by their right hand side definitions before calling the as sembler In C code the compiler needs to see variable declarations for these objects This is done by using declarations that bind a variable permanently to a CPU register see How to permanently bind a variable to a register Even in case the C code never has a need to access these variables declaring the register binding that way causes the compiler to not use these registers in C code at all The 1ags variable needs to be in the range of r16 through r31 as it is the target of a load immediate or SER instruction that is not applicable to the entire register file 22 36 2 3 isrs S This file is a preprocessed assembly source file The C preprocessor will be run by the compiler front end first resolving all include define etc directives The resulting program text will then be passed on to the assembler As the C preprocessor strips all C style comments preprocessed assembly source files can have both C style as well as assembly style comments At the top the IO register definition file avr io h and the project declaration file project hare included The remainder of the file is conditionally assembled only if the target MCU type is ATtiny13 so it will be compl
396. ock fuse bits get Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 43 lt avr cpufunc h gt Special AVR CPU functions 235 22 12 2 23 define GET LOW FUSE BITS 0x0000 address to read the low fuse bits using boot lock fuse bits get 22 13 lt avr cpufunc h gt Special AVR CPU functions Defines define__NOP e define _MemoryBarrier 22 13 1 Detailed Description include lt avr cpufunc h gt This header file contains macros that access special functions of the AVR CPU which do not fit into any of the other header files 22 13 2 Define Documentation 22 13 21 _ Implement a read write memory barrier memory barrier instructs the compiler to not cache any memory data in registers beyond the barrier This can sometimes be more effective than blocking certain optimizations by declaring some object with a volatile qualifier See optim code reorder for things to be taken into account with respect to compiler optimizations 22 13 2 2 define NOP Execute a no operation NOP CPU instruction This should not be used to implement delays better use the functions from lt util delay_basic h gt or lt util delay h gt for this For debugging purposes a NOP can be useful to have an instruction that is guaranteed to be not optimized away by the compiler so it can always become a breakpoint in the debugger 22 14 avrleeprom h gt EEPROM handling Defines
397. of the object modules into a final executable The two projects GCC and Binutils are very much interrelated and many of the same volunteers work on both open source projects When GCC is built for the AVR target the actual program names are prefixed with avr So the actual executable name for AVR GCC is avr gcc The name avr gcc is used in documentation and discussion when referring to the program itself and not just the whole AVR GCC system See the GCC Web Site and GCC User Manual for more information about GCC 2 4 GNU Binutils The name GNU Binutils stands for Binary Utilities It contains the GNU assembler gas and the GNU linker 14 but also contains many other utilities that work with binary files that are created as part of the software development toolchain Again when these tools are built for the AVR target the actual program names are prefixed with avr For example the assembler program name for a native assembler is as even though in documentation the GNU assembler is commonly referred to as gas But when built for an AVR target it becomes avr as Below is a list of the programs that are included in Binutils avr as The Assembler avr ld The Linker avr ar Create modify and extract from libraries archives avr ranlib Generate index to library archive contents avr objcopy Copy and translate object files to different formats Generated on Thu May 19 2011 13 29 12 for
398. ollers In addition the library provides the basic startup code needed by most applications There is a wealth of information in this document which goes beyond simply describ ing the interfaces and routines provided by the library We hope that this document provides enough information to get a new AVR developer up to speed quickly using the freely available development tools binutils gcc avr libc and many others If you find yourself stuck on a problem which this document doesn t quite address you may wish to post a message to the avr gcc mailing list Most of the developers of the AVR binutils and gcc ports in addition to the devleopers of avr libc subscribe to the list so you will usually be able to get your problem resolved You can subscribe to the list at http 1ists nongnu org mailman listinfo avr gcc list Before posting to the list you might want to try reading the Frequently Asked Ques tions chapter of this document Note If you think you ve found a bug or have a suggestion for an improvement ei ther in this documentation or in the library itself please use the bug tracker at https savannah nongnu org bugs group avr libc to ensure the issue won t be forgotten 1 2 General information about this library In general it has been the goal to stick as best as possible to established standards while implementing this library Commonly this refers to the C library as described by the ANSI X3 159 1989 and ISO IEC 9899 199
399. on 24 10 errno h File Reference Defines define EDOM 33 define ERANGE 34 Variables int errno 24 10 1 Detailed Description 24 11 fdevopen c File Reference Functions FILE x fdevopen int xput char FILE int get FILE 24 11 1 Detailed Description 24 12 ffs S File Reference 24 12 1 Detailed Description 24 13 ffsl S File Reference 24 13 1 Detailed Description 24 14 ffsll S File Reference 24 14 1 Detailed Description 24 15 fuse h File Reference Defines define FUSEMEM attribute section fuse define FUSES fuse t fuse FUSEMEM Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 16 interrupt h File Reference 378 24 15 1 Detailed Description 24 16 interrupt h File Reference Defines Global manipulation of the interrupt flag The global interrupt flag is maintained in the I bit of the status register SREG Handling interrupts frequently requires attention regarding atomic access to ob jects that could be altered by code running within an interrupt context see lt util atomic h gt Frequently interrupts are being disabled for periods of time in order to perform certain operations without being disturbed see optim code reorder for things to be taken into account with respect to compiler optimizations define sei define cli Macros for writing interrupt handler functions define ISR vector attributes define SIGNAL vector defin
400. on and restrict anything else to local labels Local labels consist just of a number only References to these labels consist of the number followed by the letter b for a backward reference or f for a forward reference These local labels may be re used within the source file references will pick the closest label with the same number and given direction Example myfunc push r16 push r17 push r18 push YL push YH eor rl6 r16 start loop ldi YL lo8 sometable ldi YH hi8 sometable Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 13 How do pass an IO port as a parameter to a function 71 rjmp 2f jump to loop test at end 13 1 rl7 Y loop continues here breq 1f return from myfunc prematurely inc r16 2 rlo 18 brlo 1b jump back to top of loop 13 pop YH pop YL pop r18 pop rl6 ret Back to FAQ Index 11 13 How do pass an IO port as a parameter to a function Consider this example code include lt inttypes h gt include lt avr io h gt void set_bits_func_wrong volatile uint8_t port uint8_t mask port mask void set bits func correct volatile uint8_t xport uint8 t mask port mask define set bits macro port mask port mask int main void set bits func wrong PORTB Oxaa set bits func correct amp PORTB 0x55 set bits macro PORTB Oxf0 return 0 The first function will generate
401. on returns a pointer to the beginning of the substring or NULL if the substring is not found If 1en2 is zero the function returns s1 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 218 22 11 3 9 void x memmove void dest const void x src size t len Copy memory area The memmove function copies len bytes from memory area src to memory area dest The memory areas may overlap Returns The memmove function returns a pointer to dest 22 11 3 10 void x memrchr const void src int val size t len The memrchr function is like the memchr function except that it searches backwards from the end of the 1en bytes pointed to by src instead of forwards from the front Glibc GNU extension Returns The memrchr function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 22 11 3 11 void memset void dest int val size t len Fill memory with a constant byte The memset function fills the first len bytes of the memory area pointed to by dest with the constant byte val Returns The memset function returns a pointer to the memory area dest 22 11 3 12 int strcasecmp const char 57 const char 52 Compare two strings ignoring case The strcasecmp function compares the two strings s1 and s2 ignoring the case of the characters Generated on Thu May 19 2011 13 29 12 for avr libc
402. only demonstrate how to use an AVR microcontroller as TWI master The imple mentation is kept simple in order to concentrate on the steps that are required to talk to a TWI slave so all processing is done in polled mode waiting for the TWI interface to indicate that the next processing step is due by setting the TWINT interrupt bit If it is desired to have the entire TWI communication happen in background all this can be implemented in an interrupt controlled way where only the start condition needs to be triggered from outside the interrupt routine There is a variety of slave devices available that can be connected to a TWI bus For the purpose of this example an EEPROM device out of the industry standard 24Cxx series has been chosen where xx can be one of 01 02 04 08 or 16 which are available from various vendors The choice was almost arbitrary mainly triggered by the fact that an EEPROM device is being talked to in both directions reading and writing the slave device so the example will demonstrate the details of both Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 40 Example using the two wire interface TWI 363 Usually there is probably not much need to add more EEPROM to an ATmega system that way the smallest possible AVR device that offers hardware TWI support is the ATmega8 which comes with 512 bytes of EEPROM which is equivalent to an 24C04 device The ATmegal28 already comes with twice as mu
403. ooking at the disassembled object code for the body of the function we can see that the function is indeed performing the operation we intended void set bits func correct volatile uint8 t port uint8 t mask f8 fc 01 movw r30 r24 xport mask fa 80 81 ld r24 Z 86 25 or r24 r22 fe 80 83 st Z r24 100 08 95 ret Notice that we are accessing the io port via the LD and ST instructions The port parameter must be volatile to avoid a compiler warning Note Because of the nature of the IN and OUT assembly instructions they can not be used inside the function when passing the port in this way Readers interested in the details should consult the Instruction Set datasheet Finally we come to the macro version of the operation In this contrived example the macro is the most efficient method with respect to both execution speed and code size set bits macro PORTB Oxf0 116 88 b3 r24 0 18 24 11 80 6f ori r24 OxF0 240 120 88 bb out 0x18 r24 24 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 14 What registers are used by the C compiler 73 Of course in a real application you might be doing a lot more in your function which uses a passed by reference io port address and thus the use of a function over a macro could save you some code space but still at a cost of execution speed Care should be taken when such an indirect port access is going to one of the 16 bit
404. ort LPM float uint16 t address short Read a float from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 22 19 2 11 define read word address short pgm read word near address short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 22 19 2 12 define read word far address long ELPM word uint32 t address long Read a word from the program space with a 32 bit far address Note The address is a byte address The address is in the program space 22 19 2 13 define read word near address short LPM word uintl16 t address short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 avr pgmspace h gt Program Space Utilities 276 22 19 2 14 define VOID P const prog void Used to declare a generic pointer to an object in program space 22 19 2 15 define PROGMEM ATTR PROGMEM Attribute to use in order to declare an object being located in flash ROM 22 19 2 16 define PSTR s const PROGMEM char s Used to declare a static pointer to a string in program space 22 19 3 Typedef Documentation 22 19 3 1 prog char Type of a char obj
405. ost arbitration is required by the protocol to immediately cease talking on the bus in particular it must not initiate a stop condition in order to not corrupt the ongoing transfer from the active master In this example upon detecting a lost arbitration condition the entire transfer is going to be restarted This will cause a new start condition to be initiated which will normally be delayed until the currently active master has released the bus Note 10 Next the device slave is going to be reselected using a so called repeated start con dition which is meant to guarantee that the bus arbitration will remain at the current master using the same slave address SLA but this time with read intent R W bit set to 1 in order to request the device slave to start transfering data from the slave to the master in the next packet Note 11 If the EEPROM device is still busy writing one or more cells after a previous write request it will simply leave its bus interface drivers at high impedance and does not respond to a selection in any way at all The master selecting the device will see the high level at SDA after transfering the SLA R W packet as a NACK to its selection request Thus the select process is simply started over effectively causing a repeated start condition until the device will eventually respond This polling procedure is Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 40 Example using the two w
406. ot 229 boot page erase avr boot 230 boot page erase safe avr boot 230 boot page fill avr boot 230 boot page fill safe avr boot 231 boot page write avr boot 231 boot page write safe avr boot 231 boot rww busy avr boot 231 boot rww enable avr boot 232 boot rww enable safe avr boot 232 boot signature byte get avr boot 232 boot spm busy avr boot 232 boot spm busy wait avr boot 233 boot spm interrupt disable avr boot 233 boot spm interrupt enable avr boot 233 BOOTLOADER SECTION avr boot 233 bsearch avr stdlib 204 calloc avr stdlib 205 cbi deprecated items 323 cbrt avr math 161 cbrtf avr math 155 ceil avr math 161 ceilf avr math 155 clearerr avr stdio 189 cli avr interrupts 262 Combining C and assembly source files 326 copysign avr math 161 copysignf avr math 155 cos avr_math 161 cosf avr_math 156 cosh avr_math 161 coshf avr_math 156 cpufunc h 374 crc16 h 374 ctype isalnum 137 isalpha 137 isascii 137 isblank 137 iscntrl 137 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 425 isdigit 137 isgraph 137 islower 137 isprint 137 ispunct 137 isspace 138 isupper 138 isxdigit 138 toascii 138 tolower 138 toupper 138 ctype h 375 delay_basic h 375 Demo projects 325 deprecated_items cbi 323 enable_external_int 323 inb 323 inp 323 INTERRUPT 323
407. ot be acceptable for larger routines In this case you may define a C stub function containing nothing other than your assembler code void delay uint8 t ms uintl6 t cnt asm volatile Nn L dll n t mov A0 A2 n t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 77 C Names Used in Assembler Code 50 mov 350 SB 12 n t sbiw A0 1 n t brne L 12 n t dec 1 n t brne L_dli n t amp w cnt r ms r delay_count The purpose of this function is to delay the program execution by a specified number of milliseconds using a counting loop The global 16 bit variable delay count must contain the CPU clock frequency in Hertz divided by 4000 and must have been set before calling this routine for the first time As described in the clobber section the routine uses a local variable to hold a temporary value Another use for a local variable is a return value The following function returns a 16 bit value read from two successive port addresses uintl6 t inw uint8 t port uintl6 t result asm volatile in 0 1 n t in BO 1 1 r result I SFR IO ADDR port return result Note inw is supplied by avr libc 7 7 Names Used in Assembler Code By default AVR GCC uses the same symbolic names of functions or variables in C and assembler code You can specify a different name for the assembler code by
408. ough the C preprocessor it s the assembler that needs to be told to include line number information into the output file Other debug information like data types and variable allocation cannot be generated since unlike a compiler the assembler basically doesn t know about this This is done using the GNU assembler option gstabs Example avr as mmcu atmegal28 gstabs o foo o foo s When the assembler is not called directly but through the C compiler frontend either implicitly by passing a source file ending in S or explicitly using x assembler with cpp the compiler frontend needs to be told to pass the gst abs option down to the as sembler This is done using Wa gstabs Please take care to only pass this option when compiling an assembler input file Otherwise the assembler code that results from the C compilation stage will also get line number information which confuses the debugger Note You can also use Wa gstabs since the compiler will add the extra for you Example EXTRA OPTS Wall mmcu atmegal28 x assembler with cpp avr gcc Wa gstabs EXTRA_OPTS c o foo o foo S Also note that the debugger might get confused when entering a piece of code that has a non local label before since it then takes this label as the name of a new function that appears to have been entered Thus the best practice to avoid this confusion is to only use non local labels when declaring a new functi
409. ounter1 Compare Match AT908S2333 AT90S4433 ATtiny15 TIMERI OVFI vect SIG OVERFLOWI Timer Counter1 Overflow 9052313 ATtiny26 OVF vect SIG OVERFLOWI Timer Counter1 Overflow AT9082333 9054434 AT9084414 9058515 AT9084433 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWMS3 AT90PWMO2 AT90PWMI 90 128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega48P AT mega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtinyl5 ATtiny2313 ATtiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER2_ COMPA_vect SIG_ OUTPUT_ COMPARE2A Timer Counter2 Compare Match A ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER2_ COMPB_vect SIG_ OUTPUT_ COMPARE2B
410. outb 324 outp 324 sbi 324 timer_enable_int 325 disassembling 335 div avr_stdlib 205 div_t 366 quot 366 rem 366 DTOSTR_ALWAYS_SIGN avr_stdlib 202 DTOSTR_PLUS_SIGN avr_stdlib 202 DTOSTR_UPPERCASE avr_stdlib 203 dtostre avr_stdlib 205 dtostrf avr_stdlib 205 EDOM avr_errno 139 EEMEM avr_eeprom 236 eeprom_busy_wait avr_eeprom 237 eeprom_is_ready avr_eeprom 237 eeprom_read_block avr_eeprom 237 eeprom_read_byte avr_eeprom 237 eeprom_read_dword avr_eeprom 237 eeprom_read_float avr_eeprom 237 eeprom_read_word avr_eeprom 237 eeprom_update_block avr_eeprom 237 eeprom_update_byte avr_eeprom 238 eeprom_update_dword avr_eeprom 238 eeprom_update_float avr_eeprom 238 eeprom_update_word avr_eeprom 238 eeprom_write_block avr_eeprom 238 eeprom_write_byte avr_eeprom 238 eeprom_write_dword avr_eeprom 238 eeprom_write_float avr_eeprom 238 eeprom_write_word avr_eeprom 239 EMPTY_INTERRUPT avr_interrupts 262 enable_external_int deprecated_items 323 EOF avr_stdio 186 ERANGE avr_errno 139 errno h 376 Example using the two wire interface TWI 361 exit Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 426 avr stdlib 206 exp avr math 161 expf avr math 156 fabs avr math 161 fabsf avr math 156 FAQ 61 fclose avr stdio 189 fdev close avr stdio 186 fdev get udata avr stdio 187 set udata avr stdio 187 FDEV SETUP
411. ov SBIT Mi LT mew x30 SAI Mne N elpm n t mov 0 ro n t in r0 2 N Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Reference 392 adiw r30 1 NINE N adc r0 zero reg AnNt N out 2 ro n t elpm XIAMEN N mov B0 ro mne r result N r __addr32 N I SFR IO ADDR RAMPZ TEQU Tesi result N 24 35 2 8 define ELPM word enhanced addr extension N uint32 t _ addr32 uint32 t addr uintl6 t result N asm N N out 2 SCIT N movw r30 1 n t N elpm 0 Z N elpm BO Z XnNE r _ result N ewe addr Zy I SFR IO ADDR RAMPZ TSONA sl result N 24 35 2 9 define _EKLPM_word_xmega__ __extension__ uint32 t __addr32 uint32 t addr uintl16 t result N asm N N vin tmp 2 n t N out 2 C1 n t N novw r30 1 X elpm 0 Z N elpm BO 7 NEN N out 2 tmp reg N r _ result daddr32 N I SFR IO ADDR RAMPZ addr Value Value Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Reference 393 130 eq result N 24 35 2 10 define_ELPM_xmega_ addr Value __extension__ uint32_t __addr32
412. ox for writing linker scripts 4 6 The initN Sections These sections are used to define the startup code from reset up through the start of main These all are subparts of the text section The purpose of these sections is to allow for more specific placement of code within your program Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 4 6 The initN Sections 25 Note Sometimes it is convenient to think of the initN and finiN sections as functions but in reality they are just symbolic names which tell the linker where to stick a chunk of code which is not a function Notice that the examples for asm and C can not be called as functions and should not be jumped into The initN sections are executed in order from 0 to 9 init0 Weakly bound to __init If user defines _ init it will be jumped into immedi ately after a reset initi Unused User definable init2 In C programs weakly bound to initialize the stack and to clear zero reg r1 init3 Unused User definable init4 For devices with gt 64 KB of ROM init4 defines the code which takes care of copying the contents of data from the flash to SRAM For all other devices this code as well as the code to zero out the bss section is loaded from libgcc a init5 Unused User definable 1016 Unused for C programs but used for constructors programs init7 Unused User definable init8 Unused Use
413. p int vsnprintf 5 size_t __n const char x__fmt va list ap int vsnprintf_P char __s size_t __n const char __fmt va list ap int fprintf FILE stream const char fmt int fprintf P FILE stream const char fmt int fputs const char str FILE stream intfputs P const char str FILE stream int puts const char str int puts P const char str size_t fwrite const void 5126 t size size nmemb FILE stream int fgetc FILE stream int ungetc int FILE stream char fgets char str int size FILE stream char gets char str size_t fread void size_t size size t nmemb FILE stream void clearerr FILE stream int feof FILE stream int ferror FILE stream int vfscanf FILE stream const char fmt va list int vfscanf P FILE stream const char fmt va list int fscanf FILE stream const char fmt int fscanf P FILE stream const char fmt int scanf const char fmt int scanf P const char fmt int vscanf const char fmt va_list int sscanf const char buf const char fmt int sscanf P const char buf const char fmt int fflush FILE xstream Detailed Description stdlib h File Reference Data Structures struct div t struct ldiv t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxy
414. pecifies the type of conversion to be applied The conversion specifiers and their meanings are diouxX The int or appropriate variant argument is converted to signed decimal d and i unsigned octal 0 unsigned decimal u or unsigned hexadecimal x and X notation The letters abcdef are used for x conversions the letters ABCDEF are used for X conversions The precision if any gives the minimum number of digits that must appear if the converted value requires fewer digits it is padded on the left with zeros e p The void xargumentis taken as an unsigned integer and converted similarly as a x command would do c The int argument is converted to an unsigned char and the resulting character is written Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 197 s The char x argument is expected to be a pointer to an array of character type pointer to a string Characters from the array are written up to but not including a terminating NUL character if a precision is specified no more than the number specified are written If a precision is given no null character need be present if the precision is not specified or is greater than the size of the array the array must contain a terminating NUL character e is written No argument is converted The complete conversion specifica tion is 9 eE The double argument is rounded and conv
415. previously defined FUSES then FUSES is not redefined Each AVR device I O header file has a set of defined macros which specify the actual fuse bits available on that device The AVR fuses have inverted values logical 1 for an unprogrammed disabled bit and logical for a programmed enabled bit The defined macros for each individual fuse bit represent this in their definition by a bit wise inversion of a mask For example the FUSE EESAVE fuse in the ATmegal28 is defined as define FUSE EESAVE _BV 3 Note The _BV macro creates a bit mask from a bit number It is then inverted to repre sent logical values for a fuse memory byte To combine the fuse bits macros together to represent a whole fuse byte use the bitwise AND operator like so FUSE BOOTSZO amp FUSE_BOOTSZ1 amp FUSE_EESAVE amp FUSE SPIEN amp FUSE JTAGEN Each device I O header file also defines macros that provide default values for each fuse byte that is available LFUSE DEFAULT is defined for a Low Fuse byte HFUSE DEFAULT is defined for a High Fuse byte EFUSE DEFAULT is defined for Ex tended Fuse byte If FUSE MEMORY SIZE gt 3 then the I O header file defines macros that pro vide default values for each fuse byte like so FUSEO0 DEFAULT FUSEI DEFAULT FUSE2 DEFAULT FUSE3 DEFAULT FUSE4 DEFAULT API Usage Example Putting all of this together is easy Using C99 s designated initializers include avr io h Generated on Th
416. printf P 191 fputc 191 fputs 191 fputs P 191 fread 191 fscanf 192 fscanf P 192 fwrite 192 getc 188 getchar 188 gets 192 printf 192 printf P 192 putc 188 putchar 188 puts 193 puts P 193 scanf 193 scanf P 193 snprintf 193 snprintf P 193 sprintf 193 sprintf P 193 sscanf 193 sscanf P 194 stderr 188 stdin 188 stdout 189 ungetc 194 vfprintf 194 vfprintf P 197 vfscanf 197 vfscanf P 199 vprintf 200 vscanf 200 vsnprintf 200 vsnprintf P 200 vsprintf 200 vsprintf P 200 avr stdlib compar fn t 203 malloc heap end 212 malloc heap start 212 malloc margin 212 abort 203 abs 203 atof 203 atoi 204 atol 204 bsearch 204 calloc 205 div 205 DTOSTR ALWAYS SIGN 202 DTOSTR PLUS SIGN 202 DTOSTR UPPERCASE 203 dtostre 205 dtostrf 205 exit 206 free 206 itoa 206 labs 207 Idiv 207 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen memcopy 215 memchr 215 mememp 215 memcpy 216 memmem 216 memmove 216 memrchr 217 memset 217 strcasecmp 217 strcasestr 218 strcat 218 strchr 218 strchrnul 219 strcmp 219 strcpy 219 strcspn 220 strdup 220 strlcat 220 strlcpy 221 strlen 221 strlwr 222 strncasecmp 222 strncat 222 strcmp 222 INDEX 423 Itoa 207 strncpy 223 malloc 207 strnlen 223 qsort 208 strpbrk 223 rand 208 strrchr 224 RAND MAX 203 strrev 224 rand r 208 strsep 224 ra
417. printf format for uint_fast16_t define PRIxFAST32 Ix hexadecimal printf format for uint_fast32_t define PRIXFAST32 IX uppercase hexadecimal printf format for fast32 t define PRIXFASTS X uppercase hexadecimal printf format for uint fast8 t define PRIxFASTS x hexadecimal printf format for uint_fast8_t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 149 22 5 2 53 22 5 2 54 22 5 2 55 22 5 2 56 22 5 2 57 22 5 2 58 22 5 2 59 22 5 2 60 22 5 2 61 22 5 2 62 define PRIXLEASTI6 x hexadecimal printf format for leastl t define PRIXLEASTIG X uppercase hexadecimal printf format for uint leastl t define PRIXLEAST32 Ix hexadecimal printf format for least32 t define PRIXLEAST32 IX uppercase hexadecimal printf format for uint least32 t define PRIXLEASTS hexadecimal printf format for uint_least8_t define PRIXLEASTS X uppercase hexadecimal printf format for uint least8 t define PRIxPTR PRIx16 hexadecimal printf format for uintptr_t define PRIXPTR PRIX16 uppercase hexadecimal printf format for uintptr_t define SCNd16 d decimal scanf format for int16 t define SCNd32 Id decimal scanf format for int32_t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 5 lt inttypes h gt Integer Type conversions 150 22 5 2 63
418. processor type is specified as a command line flag to the compiler Using the mmcu processor flag This is usually done in the Makefile This allows you to specify only a single header file for any processor type include lt avr io h gt Note The forward slash in the lt avr io h gt file name that is used to separate subdirecto ries can be used on Windows distributions of the toolchain and is the recommended method of including this file The compiler knows the processor type and through the single header file above it can Pull in and include the correct individual IO header file This has the advantage that you only have to specify one generic header file and you can easily port your application to another processor type without having to change every file to include the new IO header file The AVR toolchain tries to adhere to the exact names of the registers and names of the bits found in the AVR datasheet There may be some descrepencies between the register names found in the IAR IO header files and the AVR GCC IO header files Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 10 3 Interrupt Service Routines ISRs 59 10 3 Interrupt Service Routines ISRs As mentioned above the C language Standard strangely does not specify a standard way of declaring and defining an ISR Hence every compiler seems to have their own special way of doing so IAR declares an ISR like so pragma vector TIMERO OVF v
419. quired 43 The bss Section Uninitialized global or static variables end up in the bss section Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 4 4 The eeprom Section 24 4 4 Section This is where eeprom variables are stored 45 The noinit Section This sections is a part of the bss section What makes the noinit section special is that variables which are defined as such int foo attribute noinit will not be initialized to zero during startup as would normal bss data Only uninitialized variables can be placed in the noinit section Thus the following code will cause avr gcc to issue an error int bar attribute section noinit Oxaa It is possible to tell the linker explicitly where to place the noinit section by adding Wl section start noinit 0x802000 to avr gcc command line at the linking stage For example suppose you wish to place the noinit section at SRAM address 0x2000 avr gcc Wl section start noinit 0x802000 Note Because of the Harvard architecture of the AVR devices you must manually add 0x800000 to the address you pass to the linker as the start of the section Oth erwise the linker thinks you want to put the noinit section into the text section instead of data bss and will complain Alternatively you can write your own linker script to automate this FIXME need an example or ref to d
420. r will not be changed 22 10 4 24 void srand unsigned int seed Pseudo random number generator seeding see rand 22 10 4 25 void srandom unsigned long seed Pseudo random number generator seeding see random 22 10 4 26 double strtod const char char endptr The strtod function converts the initial portion of the string pointed to by nptr to double representation Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 211 The expected form of the string is an optional plus or minus sign followed by a sequence of digits optionally containing a decimal point character op tionally followed by an exponent An exponent consists of an E or e followed by an optional plus or minus sign followed by a sequence of digits Leading white space characters in the string are skipped The strtod function returns the converted value if any If endptr is not NULL a pointer to the character after the last character used in the conversion is stored in the location referenced by endptr If no conversion is performed zero is returned and the value of nptr is stored in the location referenced by endptr If the correct value would cause overflow plus or minus INFINITY is returned ac cording to the sign of the value and ERANGE is stored in errno If the correct value would cause underflow zero is returned and ERANGE is stored in
421. r Counter1 Compare MatchB AT90S4414 419054434 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 9058515 ATtiny48 261 ATtiny46l AT tiny861 19005 1620 9005 82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 257 TIMERI COMPC vect SIG OUTPUT COMPAREIC Timer Counter1 Compare Match C 90 128 AT90CAN32 ATOOCAN64 ATmegal28 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMERI COMPD vect SIG OUTPUT COMPAREOD Timer Counter1 Compare Match D ATtiny261 ATtiny461 ATtiny861 TIMERI COMP vect SIG OUTPUT COMPAREIA Timer C
422. r advantage of experimenting with the ATmega16 in addition that it ships together with an STK500 anyway is that it can be debugged online via JTAG Likewise the ATmega48 88 168 and ATtiny2313 devices can be debugged through debugWire using the Atmel JTAG ICE mkII or the low cost AVR Dragon Note that in the explanation below all port pin names are applicable to the ATmegal6 setup 22 38 2 Functional overview PD6 will be toggled with each internal clock tick approx 10 ms PD7 will flash once per second PDO and are configured as UART IO and can be used to connect the demo kit to a PC 9600 Bd 8N1 frame format The demo application talks to the serial port and it can be controlled from the serial port PD2 through PD4 are configured as inputs and control the application unless control has been taken over by the serial port Shorting PD2 to GND will decrease the current PWM value shorting PD3 to GND will increase it While PD4 is shorted to GND one ADC conversion for channel 0 ADC input is on PA0 will be triggered each internal clock tick and the resulting value will be used as the PWM value So the brightness of the LED follows the analog input value on PCO VAREF on the STK500 should be set to the same value as VCC When running in serial control mode the function of the watchdog timer can be demon strated by typing an r This will make the demo application run in a tight loop without retriggering the watchdog so
423. r definable init9 Jumps into main Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 4 7 The finiN Sections 26 4 7 The finiN Sections These sections are used to define the exit code executed after return from main or a call to exit These all are subparts of the text section The finiN sections are executed in descending order from 9 to 0 finit9 Unused User definable This is effectively where exit starts fini8 Unused User definable fini7 Unused User definable fini6 Unused for C programs but used for destructors in C programs fini5 Unused User definable fini4 Unused User definable fini3 Unused User definable fini2 Unused User definable finil Unused User definable fini0 Goes into an infinite loop after program termination and completion of any exit code execution of code in the fini9 gt finil sections 4 8 Using Sections in Assembler Code Example Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 4 9 Using Sections in C Code 27 include lt avr io h gt section 1 progbits ldi r0 Oxff out _ IO ADDR PORTB out SFR IO ADDR DDRB Note The ax progbits tells the assembler that the section is allocatable a executable x and contains data progbits For more detailed information on the section directive see the gas user manual 4 9 Usin
424. ration in assembly How to detect RAM memory and variable overlap problems Is it really impossible to program the ATtinyXX in C What is this clock skew detected message Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 2 My program doesn t recognize a variable updated within an interrupt routine 63 24 Why are many interrupt flags cleared by writing a logical 1 25 Why have programmed fuses the bit value 0 26 Which AVR specific assembler operators are available 27 Why are interrupts re enabled in the middle of writing the stack pointer 28 Why are there five different linker scripts 29 How to add a raw binary image to linker output 30 How do I perform a software reset of the AVR 31 I am using floating point math Why is the compiled code so big Why does my code not work 32 What pitfalls exist when writing reentrant code 33 Why are some addresses of the EEPROM corrupted usually address zero 34 Why is my baud rate wrong 35 On a device with more than 128 KiB of flash how to make function pointers work 11 2 My program doesn t recognize a variable updated within an interrupt routine When using the optimizer in a loop like the following one uint8 t flag ISR SOME vect flag 1 while flag 0 the compiler will typically access flag only once and optimize further accesses com pletely away since its code path analysis shows that nothing inside the loop could
425. ray of nmemb objects the initial member of which is pointed to by base The size of each object is specified by size The contents of the array base are sorted in ascending order according to a comparison function pointed to by compar which requires two arguments pointing to the objects being compared The comparison function must return an integer less than equal to or greater than zero if the first argument is considered to be respectively less than equal to or greater than the second 22 10 4 19 intrand void The rand function computes a sequence of pseudo random integers in the range of 0 to RAND MAX as defined by the header file lt stdlib h gt The srand function sets its argument seed as the seed for a new sequence of pseudo random numbers to be returned by rand These sequences are repeatable by calling srand with the same seed value If no seed value is provided the functions are automatically seeded with a value of 1 In compliance with the C standard these functions operate on int arguments Since the underlying algorithm already uses 32 bit calculations this causes a loss of preci sion See random for an alternate set of functions that retains full 32 bit precision 22 10 4 20 int rand r unsigned long c x Variant of rand that stores the context in the user supplied variable located at ct x instead of a static library variable so the function becomes re entrant Generated on Thu May 19 201
426. re initialized at application startup Also since there is no notion of file whatsoever to avr libc there is no function fopen that could be used to associate a stream to some device See note 1 Instead the function fdevopen is provided to associate a stream to a device where the device needs to provide a function to send a character to receive a character or both There is no dif ferentiation between text and binary streams inside avr libc Character n is sent literally down to the device s put function If the device requires a carriage return Ax character to be sent before the linefeed its put routine must implement this see note 2 As an alternative method to fdevopen the macro setup stream might be used to setup a user supplied FILE structure It should be noted that the automatic conversion of a newline character into a carriage return newline sequence breaks binary transfers If binary transfers are desired no automatic conversion should be performed but instead any string that aims to issue a Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 185 CR LF sequence must use r n explicitly For convenience the first call to fdevopen that opens a stream for reading will cause the resulting stream to be aliased to st din Likewise the first callto fdevopen that opens a stream for writing will cause the resulting stream to be
427. releases or cutting branches 15 2 1 Creating an SVN branch The following steps should be taken to cut a branch in SVN assuming username is set to your savannah username 1 Check out a fresh source tree from SVN trunk 2 Update the NEWS file with pending release number and commit to SVN trunk Change Changes since avr libc last release7 to Changes in avr libc lt this_ relelase gt Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 15 2 Releasing AVR Libc 124 10 11 12 13 Set the branch point tag setting major and minor accordingly svn copy svn ssh Susername svn savannah nongnu org avr libc trunk svntssh username8svn savannah nongnu org avr libc tags avr libc major lt minor gt branchpoint Create the branch svn copy svn ssh Susername svn savannah nongnu org avr libc trunk svntssh username8svn savannah nongnu org avr libc branches avr libc majo minor branch Update the package version in configure ac and commit configure ac to SVN trunk Change minor number to next odd value Update the NEWS file and commit to SVN trunk Add Changes since avr libc this release Check out a new tree for the branch svn co svn ssh Susername svn savannah nongnu org avr libc branches avr lik lt minor gt branch Update the package version in configure ac and commit configure ac to SVN branch Change the patch number to 90 to denote that this now a branch lea
428. rence 24 47 1 Detailed Description 2448 strcat P S File Reference 24 48 1 Detailed Description 2449 strchr S File Reference 24 49 1 Detailed Description 24 50 strchr P S File Reference 24 50 1 Detailed Description 24 51 strchrnul S File Reference 24 51 1 Detailed Description 24 52 strchrnul P S File Reference 24 52 1 Detailed Description 24 53 strcmp S File Reference 24 53 1 Detailed Description 24 54 strcmp 5 File Reference Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 55 5 File Reference 24 55 1 Detailed Description 24 56 strcpy P S File Reference 41 nDetailar Dacerintian 24 60 string h File Reference 408 24 59 1 Detailed Description 24 60 File Reference Defines define need NULL define need size t define _ ATTR_PURE attribute__ __pure__ define _FFS x Functions int ffs int val int 51 dong __ val int ffsll long long val void memccpy void const void x int size t void memchr const void int size_t PURE int memcmp const void const void x size t ATTR_PURE void memcpy void const void size t void memmem const void size t const void size_t ATTR_PURE void memmove void const void size_t void memrchr const void int size_t PURE void memset void int size_t char strcat char const char char
429. req 62 0x80 lt __SREG__ 0x41 gt if pwm 0 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 338 OCR 42 9b 44 8a 46 9f 48 8f 4a 2f 4c Of 4e Of 50 Of 525 Xf 54 18 direct break Note bd out bd out 91 pop 91 pop 91 pop 90 pop be out 90 pop 90 pop 95 ret ISR TIMER1_OVF_vect ion UP Eo 7 0 2 r25 43 Ox2a r24 42 r25 r24 r18 ro Ox3f rO 63 ro rl X x Note 2 static uint16_t x Note static uint8_t direction switch direction 56 58 5a 5e 62 64 68 66 6e 2 76 TEs 7 7e 81 29 80 90 ef 80 90 01 90 80 00 21 10 el Note 4 30 cpi r24 0x01 1 0 breq 10 0x64 lt __SREG__ 0x25 gt 91 61 00 145 r24 0 0061 91 62 00 145 r25 0 0062 cf rjmp 34 0x42 lt lt 5 0x3 if pwm TIMER TOP direction DOWN break case DOWN if pwm 0 91 61 00 145 91 62 00 145 r24 0x0061 r25 0x0062 OF sbiw r24 0x01 1 93 62 00 sts 0x0062 r25 93 61 00 sts 0x0061 r24 97 sbiw r24 0x00 O 7 brne 56 0x42 lt __SREG__ 0x3 gt direction UP 92 60 00 sts 0x0060 r1 cf rjmp 62 0x42 lt lt SREG 0x3 switch direction 807 21 82 20 86 dd 00000088 void ioinit case UP if pwm direct e0 ldi 93 60 00 sts Note 4 TIMER TOP io
430. requencies of up to about 26 MHz This function is then called 100 times to accomodate for the actual one second delay Ina practical application long delays like this one were better be handled by a hardware timer so the main CPU would be free for other tasks while waiting or could be put on sleep At the beginning of main after initializing the peripheral devices the default stdio streams stdin stdout and stderr are set up by using the existing static FILE stream objects While this is not mandatory the availability of stdin and stdout Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 39 Using the standard IO facilities 357 allows to use the shorthand functions e g printf instead of fprintf and stderr can mnemonically be referred to when sending out diagnostic messages Just for demonstration purposes stdin and stdout are connected to a stream that will perform UART IO while stderr is arranged to output its data to the LCD text display Finally a main loop follows that accepts simple commands entered via the RS 232 connection and performs a few simple actions based on the commands First a prompt is sent out using printf which takes a program space string The string is read into an internal buffer as one line of input using get s While it would be also possible to use get s which implicitly reads from st din gets has no control that the user s input does not ov
431. riables are stored starts at location 0x0 The next available address in the eeprom segment is also location 0x0 so there aren t any EEPROM variables 22 37 6 Generating Intel Hex Files We have a binary of the application but how do we get it into the processor Most if not all programmers will not accept a GNU executable as an input file so we need to do a little more processing The next step is to extract portions of the binary and save the information into hex files The GNU utility that does this is called avr objcopy The ROM contents can be pulled from our project s binary and put into the file demo hex using the following command avr objcopy j text j data O ihex demo elf demo hex The resulting demo hex file contains 1000000010E0A0E6B0E001C01D92A336B107E1F711 100010001F920F920FB60F9211242F938F939F93DD 10002000809160008823B9F4809161009091620012 100030000196909362008093610023E08F3F9207C6 10004000F9F09BBD8ABD9F918F912F910F900FBEAC 100050000F901F901895813029F080916100909148 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 343 100060006200EFCF809161009091620001979093C0 10007000620080936100009721F710926000E1CF49 1000800021E020936000DDCF83E88FBD8EB58160D5 100090008EBD1BBC1ABC82E087BB84E089BF78940C 1000A000089583E88FBD8EB581608EBDIBBClABCEO 1000B00082E087BB84E089BF789485B7806885BF7C 0A00C000889585B78F7785BFF8CFCC 00000001FF The 1 option indicates tha
432. ro XX N r result z addr16 I addrl16 N ro X result N 24 35 2 18 define word enhanced addr Value extension N uintl6 t _ addrl6 uintl6 t addr N uintl6 t result N asm N N lpm SAO Z ARNEY lpm BO Z r result z __addr16 1 __addr16 result N 24 35 2 19 define get far address var Value t N uint farptr t tmp N N asm volatile N N idi lo8 1 AINET adi BO hi8 1 Idi 8 0 hh8 1 Mne elr 0 n t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 36 power h File Reference 397 q tmp X p amp var N tmp N 24 36 power h File Reference Defines define clock prescale get clock div 0 CLKPR amp uint8_t 1 lt lt CLKPS0 1 lt lt CLKPS 1 1 lt lt CLKPS2 Enumerations enum clock div t clock div 1 0 clock div 2 1 clock div 4 2 clock div 8 3 clock div 16 4 clock div 32 5 clock div 64 6 clock div 128 7 clock div 256 8 Functions e static inline void clock prescale set clock div t attribute always inline 24 36 1 Detailed Description 24 37 setbaud h File Reference Defines define BAUD TOL 2 define VALUE define UBRRL VALUE define UBRRH VALUE define USE 2X 0 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen
433. rom I O space addresses but it s a hack so it is recommended to change your source wrap such addresses in macros defined here as shown below After this is done the __SFR_OFF SET definition is no longer necessary and can be removed Real example this code could be used in a boot loader that is portable between devices with SPMCR at different addresses lt avr iom163 h gt define SPMCR _SFR_IO8 0x37 lt avr iom128 h gt define SPMCR _SFR_MEM8 0x68 dif _SFR_IO_REG_P SPMCR out _SFR_IO_ADDR SPMCR r24 else sts _SFR_MEM_ADDR SPMCR r24 endif You can use the in out cbi sbi sbic sbis instructions without the SFR_ IO REG P test if you know that the register is in the I O space as with SREG for example If it isn t the assembler will complain I O address out of range 0 0x3f so this should be fairly safe If you do not define SFR OFFSET so it will be 0x20 by default all special register addresses are defined as memory addresses so SREG is Ox5f and if code size and speed are not important and you don t like the ugly if above you can always use lds sts to access them But this will not work if SFR OFFSET 0x20 so use a different macro defined only if SFR OFFSET 0x20 for safety sts SFR ADDR SPMCR r24 In programs all combinations of SFR 5 COMPAT and SFR OFFSET supported the SFR ADDR SPMCR macro can be used to get the address of the SPM
434. rst packet after the SLA W selection is always considered to be the EEPROM address for the next operation This packet is exactly the same as the one above sent before starting to read the device In case a master transmitter mode transfer is going to send more than one data packet all following packets will be considered data bytes to write at the indicated address The internal address pointer will be incremented after each write operation Note 16 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 23 Data Structure Documentation 367 24Cxx devices can become write protected by strapping their WC pin to logic high Leaving it unconnected is explicitly allowed and constitutes logic low level i e no write protection In case of a write protected device all data transfer attempts will be NACKed by the device Note that some devices might not implement this 23 Data Structure Documentation 23 1 div t Struct Reference Data Fields int quot int rem 23 1 1 Detailed Description Result type for function div 23 1 2 Field Documentation 23 1 2 1 int div_t quot The Quotient 23 1 2 2 int div_t rem The Remainder The documentation for this struct was generated from the following file stdlib h 23 2 Idiv_t Struct Reference Data Fields long quot e long rem Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 File Documentation 368 23 2 1 Detailed Descript
435. rter module ATmega640 ATmegal280 ATmegal281 ATmegal28RFA1 ATmega2560 ATmega2561 AT90USB646 AT90USB647 AT90USB 1286 AT90USB1287 ATO0PWMI AT90PWM2 AT90PWM2B AT90PWM3 AT90PWMGB AT90PWM216 AT90PWM316 AT90PWMB81 ATmegal65 ATmega165P ATmega325 ATmega325A ATmega325PA ATmega3250 ATmega3250A ATmega3250PA ATmega645 ATmega6450 ATmegal69 ATmegal69P ATmega329 ATmega329A ATmega3290 ATmega3290A ATmega3290PA ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmegal68 ATtiny24 ATtiny44 ATtiny84 ATtiny84A ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 power adc disable Disable the Analog to Digital Converter module ATmega640 ATmegal280 ATmegal 281 ATmegal28RFAl ATmega2560 ATmega2561 AT90USB646 AT90USB647 AT90USB 1286 AT90USB1287 ATO0PWMI AT90PWM2 AT90PWM2B AT90PWM3 AT90PWMGB AT90PWM216 AT90PWM316 AT90PWMB81 ATmegal65 ATmegal65P ATmega325 ATmega325A ATmega325PA ATmega3250 ATmega3250A ATmega3250PA ATmega645 ATmega6450 ATmegal69 ATmegal69P ATmega329 ATmega329A ATmega3290 ATmega3290A ATmega3290PA ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmegal68 ATtiny24 ATtiny44 ATtiny84 ATtiny84A ATtiny25 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 power lcd enable Enable the LCD mod
436. rupt handler by declaring the handler the following way ISR XXX vect ISR NOBLOCK where XXX_vect is the name of a valid interrupt vector for the MCU type in question as explained below Two vectors sharing the same code In some circumstances the actions to be taken upon two different interrupts might be completely identical so a single implementation for the ISR would suffice For example pin change interrupts arriving from two different ports could logically signal an event that is independent from the actual port and thus interrupt vector where it happened Sharing interrupt vector code can be accomplished using the ISR_ALIASOF attribute to the ISR macro ISR PCINTO vect Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 246 Code to handle the event ISR PCINTI_vect ISR ALIASOF PCINTO vect Note There is no body to the aliased ISR Note that the ISR_ALIASOF feature requires GCC 4 2 or above or a patched version of GCC 4 1 x See the documentation of the ISR_ALIAS macro for an implementa tion which is less elegant but could be applied to all compiler versions Empty interrupt service routines rare circumstances in interrupt vector does not need any code to be implemented at all The vector must be declared anyway so when the interrupt triggers it won t execute the BADISR vect code which by default restarts the application
437. s 149 SCNi32 avr_inttypes 149 SCNIFASTI6 avr inttypes 149 SCNiFAST32 avr inttypes 149 SCNiLEAST16 avr_inttypes 149 SCNiLEAST32 avr inttypes 149 SCNiPTR avr inttypes 150 SCNo16 avr inttypes 150 SCNo32 avr_inttypes 150 SCNoFAST 16 avr_inttypes 150 SCNoFAST32 avr_inttypes 150 SCNoLEAST16 avr_inttypes 150 SCNoLEAST32 avr_inttypes 150 SCNoPTR avr_inttypes 150 SCNu16 avr_inttypes 150 SCNu32 avr_inttypes 150 SCNuFAST16 avr_inttypes 151 SCNuFAST32 avr_inttypes 151 SCNuLEAST16 avr_inttypes 151 SCNuLEAST32 avr_inttypes 151 SCNuPTR avr_inttypes 151 SCNx16 avr_inttypes 151 SCNx32 avr_inttypes 151 SCNxFAST16 avr_inttypes 151 SCNxFAST32 avr_inttypes 151 SCNxLEAST16 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 434 avr inttypes 151 SCNxLEAST32 avr_inttypes 152 SCNxPTR avr_inttypes 152 sel avr_interrupts 265 setbaud h 396 setjmp longjmp 167 setjmp 168 setjmp h 397 SIG ATOMIC MAX avr stdint 175 SIG ATOMIC MIN avr stdint 175 SIGNAL avr interrupts 265 signature h 397 signbit avr math 165 signbitf avr math 159 sin avr math 165 sinf avr math 159 sinh avr math 165 sinhf avr math 159 SIZE MAX avr stdint 176 sleep h 397 sleep cpu avr sleep 300 sleep disable avr sleep 300 sleep enable avr sleep 300 snprintf avr stdio 193 snprintf P avr stdio 193 sprintf avr stdio 193
438. s r Similar to fgets except that it will operate on stream st din and the trailing newline if any will not be stored in the string It is the caller s responsibility to provide enough storage to hold the characters read 22 9 3 19 int printf const char fmt The function printf performs formatted output to stream stdout See vfprintf for details Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 194 22 9 3 20 int printf P const char x fmt Variant of printf that uses a fmt string that resides in program memory 22 9 3 21 int puts const char _ str Write the string pointed to by st r and a trailing newline character to stdout 22 9 3 22 int puts_P const char str Variant of puts where st r resides in program memory 22 9 3 23 int scanf const char _ fmt The function scanf performs formatted input from stream st din See vfscanf for details 22 9 3 24 int scanf_P const char fmt Variant of scanf where fmt resides in program memory 22 9 3 25 int snprintf char x 5 size_t__n const char x __fmt Like sprintf but instead of assuming s to be of infinite size no more than n characters including the trailing NUL character will be converted to s Returns the number of characters that would have been written to s if there were enough space 22 9 3 26 intsnprintf P char x s si
439. s end data bss start data start Figure 2 Internal RAM stack only external RAM variables and heap If dynamic memory should be placed in external RAM while keeping the variables in internal RAM something like the following could be used Note that for demonstration purposes the assignment of the various regions has not been made adjacent in this example so there are holes below and above the heap in external RAM that remain completely unaccessible by regular variables or dynamic memory allocations shown in light bisque color in the picture below avr gcc Wl defsym heap start 0x802000 defsym Jheap end 0x803fff Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 3 4 Implementation details 21 external RAM 0x0100 Ox10FF 0x1100 0x200 Ox3FFF OxFFFF on board RAM SP _ t __malloc_heap_end __heap_end RAMEND brkval bss end malloc heap start heap start data bss start data start Figure 3 Internal RAM variables and stack external RAM heap If malloc heap endis 0 the allocator attempts to detect the bottom of stack in order to prevent a stack heap collision when extending the actual size of the heap to gain more space for dynamic memory It will not try to go beyond the current stack limit decreased by malloc margin bytes Thus all possible stack frames of interrupt routines that could interrupt the current function p
440. s in SBI which does not affect SREG Choosing the vector Interrupt vector names The interrupt is chosen by supplying one of the symbols in following table There are currently two different styles present for naming the vectors One form uses names starting with SIG followed by a relatively verbose but arbitrarily chosen name describing the interrupt vector This has been the only available style in avr libc up to version 1 2 x Starting with avr libc version 1 4 0 a second style of interrupt vector names has been added where a short phrase for the vector description is followed by vect The short phrase matches the vector name as described in the datasheet of the respective device and in Atmel s XML files with spaces replaced by an underscore and other non alphanumeric characters dropped Using the suffix vect is intented to improve portability to other C compilers available for the AVR that use a similar naming con vention The historical naming style might become deprecated in a future release so it is not recommended for new projects Note The ISR macro cannot really spell check the argument passed to them Thus by misspelling one of the names below in a call to ISR a function will be created that while possibly being usable as an interrupt function is not actually wired into the interrupt vector table The compiler will generate a warning if it detects a sus piciously looking name of a ISR function i e one that af
441. s purpose This will only work if lt avr io h gt has been included Note that the assembler or linker have no chance to check the correct spelling of an interrupt function so it should be double checked When analyzing the resulting object file using avr objdump or avr nm a name like vector N should appear with N being a small integer number Note 8 As explained in the section about special function registers the actual IO port address should be obtained using the macro SFR IO ADDR The 905 1200 does not have RAM thus the memory mapped approach to access the IO registers is not available It would be slower than using in out instructions anyway Since the operation to reload TCCNTO is time critical it is even performed before saving SREG Obviously this requires that the instructions involved would not change any of the flag bits in SREG Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 6 4 Pseudo ops and operators 37 Note 9 Interrupt routines must not clobber the global CPU state Thus it is usually necessary to save at least the state of the flag bits in SREG Note that this serves as an example here only since actually all the following instructions would not modify SREG either but that s not commonly the case Also it must be made sure that registers used inside the interrupt routine do not conflict with those used outside In the case of a RAM less device like the AT90S12
442. s saturate their outputs at rather low currents when sourcing cur rent so the LED can be connected directly the resulting current through the LED will be about 15 mA For modern parts at least for the ATmega 128 however Atmel has drastically increased the IO source capability so when operating at 5 V Vcc R2 is needed Its value should be about 150 Ohms When operating the circuit at 3 V it can still be omitted though Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 334 22 37 2 The Source Code gt ob fin fin enu ISR voi ioi THE BEER WARE LICENSE Revision 42 lt joerg FreeBSD ORG gt wrote this file As long as you retain this notice you can do whatever you want with this stuff If we meet some day and you think this stuff is worth it you can buy me a beer in return Joerg Wunsch Simple AVR demonstration Controls a LED that can be directly connected from OC1 OC1A to GND The brightness of the LED is controlled with the PWM After each period of the PWM the PWM value is either incremented or decremented that s all Id demo c 1637 2008 03 17 21 49 412 joerg wunsch clude lt inttypes h gt clude avr io h clude avr interrupt h clude avr sleep h clude iocompat h Note 1 m UP DOWN TIMER1 OVF vect x Note 2 x static uintl16 t pwm Note 3 static
443. s to append Returns The strncat_PF function returns a pointer to the resulting string dst The contents of RAMPZ SFR are undefined when the function returns 22 19 4 31 int strncmp P const char s P 52 size The strncmp_P function is similar to stremp_P except it only compares the first at most n characters of s1 and s2 Returns The strncmp_P function returns an integer less than equal to or greater than zero if s1 or the first n bytes thereof is found respectively to be less than to match or be greater than s2 22 19 4 32 int strncmp PF const char s1 uint farptr ts2 size tn Compare two strings with limited length The strncmp PF function is similar to stremp_PF except it only compares the first at most n characters of s and 52 Parameters 51 A pointer to the first string in SRAM 52 A far pointer to the second string in Flash n The maximum number of bytes to compare Returns The strncmp function returns an integer less than equal to or greater than zero if sl or the first n bytes thereof is found respectively to be less than to Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 19 lt avr pgmspace h gt Program Space Utilities 288 match or be greater than s2 The contents of RAMPZ SFR are undefined when the function returns 22 19 4 33 char strncpy P char x dest P src size tn The
444. s will only be generated if the application defines the macro ASSERT_USE_STDERR before including the assert h gt header file By default only abort will be called to halt the application 22 2 2 Define Documentation 22 2 2 1 define assert expression Parameters expression Expression to test for The assert macro tests the given expression and if it is false the calling process is terminated A diagnostic message is written to stderr and the function abort is called effectively terminating the program If expression is true the assert macro does nothing The assert macro may be removed at compile time by defining NDEBUG as a macro e g by using the compiler option DNDEBUG Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 3 lt ctype h gt Character Operations 137 22 3 lt ctype h gt Character Operations Character classification routines These functions perform character classification They return true or false status de pending whether the character passed to the function falls into the function s classifi cation i e isdigit returns true if its argument is any value 0 though 9 inclusive If the input is not an unsigned char value all of this function return false e int isalnum int c e intisalpha int c e intisascii int e int isblank int e intiscntrl int c e intisdigit int c e intisgraph int c e int islower int c e i
445. scribed by the standard E g applying the function strlen to a literal string will normally cause the compiler to immediately replace that call by the actual length of the string while with f freestanding it will always call strlen at run time e funsigned char Make any unqualfied char type an unsigned char Without this option they default to a signed char Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 2 Options for the assembler avr as 116 e funsigned bitfields Make any unqualified bitfield type unsigned By default they are signed fshort enums Allocate to an enum type only as many bytes as it needs for the declared range of possible values Specifically the enum type will be equivalent to the smallest integer type which has enough room fpack struct Pack all structure members together without holes e no jump tables Do not generate tablejump instructions By default jump tables can be used to op timize switch statements When turned off sequences of compare statements are used instead Jump tables are usually faster to execute on average but in particular for switch statements where most of the jumps would go to the default label they might waste a bit of flash memory NOTE The tablejump instructions use the LPM assembler instruction for access to jump tables Always use no jump tables switch if compiling a bootloader for devices with more than 64 KB of cod
446. scription 24 93 5 File Reference 24 93 1 Detailed Description 24 94 twi h File Reference Defines TWSR values Mnemonics TW MT xxx master transmitter TW MR xxx master receiver TW ST xxx slave transmitter TW SR xxx slave receiver e define TW START 0x08 define TW START 0x10 define TW MT SLA ACK 0x18 define TW MT SLA NACK 0x20 define TW MT DATA 0x28 define TW MT DATA NACK 0x30 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 95 wdt h File Reference 413 fdefine TW MT ARB LOST 0x38 define TW MR ARB LOST 0x38 define TW MR SLA ACK 0x40 define TW MR SLA NACK 0x48 define TW MR DATA ACK 0x50 define TW MR DATA NACK 0x58 define TW ST SLA 0xA8 define TW ST ARB LOST SLA ACK OxBO define TW ST 0xB8 define TW ST DATA NACK 0xCO define TW ST LAST DATA 0xC8 define TW SR 5 ACK 0x60 fdefine TW SR LOST SLA 0x68 fdefine TW SR GCALL 0x70 define TW SR LOST 0x78 fdefine TW SR DATA ACK 0x80 define TW SR DATA NACK 0x88 fdefine TW SR GCALL DATA 0x90 fdefine TW SR GCALL DATA NACK 0x98 define TW SR STOP OxAO define TW NO INFO OxF8 define TW BUS ERROR 0x00 define TW STATUS MASK define TW STATUS TWSR amp TW STATUS MASK R W bit in SLA R W address field 24 94 1 define TW READ 1 define TW WRITE 0 Detailed Des
447. se of hardware timers is much preferrable as they free the CPU and allow for concurrent processing of other events while the timer is running However in particular for very short delays the overhead of setting up a hardware timer is too much compared to the overall delay time Two inline functions are provided for the actual delay algorithms 22 29 2 Function Documentation 22 29 21 void delay loop 1 uint8 t count Delay loop using an 8 bit counter count so up to 256 iterations are possible The value 256 would have to be passed as 0 The loop executes three CPU cycles per iteration not including the overhead the compiler needs to setup the counter register Thus at a CPU speed of 1 MHz delays of up to 768 microseconds can be achieved 22 29 2 2 void delay loop 2 uint16 t count Delay loop using a 16 bit counter count so up to 65536 iterations are possible The value 65536 would have to be passed as 0 The loop executes four CPU cycles per iteration not including the overhead the compiler requires to setup the counter register pair Thus at a CPU speed of 1 MHz delays of up to about 262 1 milliseconds can be achieved Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 30 lt util parity h gt Parity bit generation 315 22 30 lt util parity h gt Parity bit generation Defines define parity_even_bit val 22 30 1 Detailed Description include lt util parity h gt This he
448. sions of this manual provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one This document describes version 3 3 of the compiler There may be some parts which hadn t been completely understood by the author himself and not all samples had been tested so far Because the author is German and not familiar with the English language there are definitely some typos and syntax errors in the text As a programmer the author knows that a wrong documentation sometimes might be worse than none Any way he decided to offer his little knowledge to the public in the hope to get enough response to improve this document Feel free to contact the author via e mail For the latest release check http www ethernut de Herne 17th of May 2002 Harald Kipp harald kipp at egnite de Note As of 26th of July 2002 this document has been merged into the documentation for avr libc The latest version is now available at http savannah nongnu org projects avr libc 7 1 GCC asm Statement Let s start with a simple example of reading a value from port D asm in 0 1 r value I SFR IO ADDR PORTD Each asm statement is devided by colons into up to four parts 1 The assembler instructions defined as a single string constant Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 1 GCC asm Statement 40 in 0 1 2 A list of output operands separa
449. src and never beyond src len Returns The strnlen function returns strlen src if that is less than len or len if there is no 0 character among the first len characters pointed to by src Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 225 22 11 3 30 char x strpbrk const char s const char accept The strpbrk function locates the first occurrence in the string s of any of the characters in the string accept Returns The strpbrk function returns a pointer to the character in s that matches one of the characters in accept or NULL if no such character is found The terminating Zero is not considered as a part of string if one or both args are empty the result will NULL 22 11 3 31 char x strrchr const char x src int val Locate character in string The strrchr function returns a pointer to the last occurrence of the character val in the string src Here character means byte these functions do not work with wide or multi byte characters Returns The strrchr function returns a pointer to the matched character or NULL if the character is not found 22 11 3 32 char x strrev char x s Reverse a string The strrev function reverses the order of the string Returns The strrev function returns a pointer to the beginning of the reversed string 22 11 3 33 char x strsep char sp const char x delim Parse a string into
450. sscHphon suc Rx eR RR FG 23 2 2 Field Documentation 24 File Documentation 24 1 asserth File Reference 24 1 Detailed Description lt lt o s s ese ek eee ee ee 24 2 atol5 File Reference 6 6 65 bk ooo ok Rm s 42421 Detaled Description gt gt ss c eei 9x x REG aS 24 3 atalS File Reference 2 243 1 Detaled Description 2 2 2 c Rr Rx 24 4 atomic h File 2441 Detailed Description lt lt s ec s 09x RR 325 326 327 328 330 330 330 333 334 335 339 341 342 345 345 345 349 349 353 353 353 354 355 360 361 361 361 362 366 366 366 366 366 367 367 367 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen CONTENTS viii 24 5 booth bileRefen H e so c ca m Rm m RR a ER 368 2451 Detailed Description gt gt lt se sesse m Res 369 245 2 Def neDocume ntatloh lt coc ok 369 24 6 Pile Reference 2 2725 o n RR goa E 374 246 1 Detailed Description 2 2 2 2 2 374 24 1 Pile Reference lt lt goga ai RR ROUES X 374 243 1 Detailed Description lt o se 2400885 beds ae RS 375 24 8 type h File Reference 222222424255 RR goa ida 8 375 248 1 Detailed Description lt lt 224 524 6494 54 xm 375 24 9 delay_basic h File Reference 375 249 1 Detaled Description gt 22cm RR MA
451. t 8 i if crc amp 0x01 crc crc gt gt 1 0x8C else crc gt gt 1 return crc 22 28 2 4 static inline uint16 t crc xmodem update uintl6 t crc uint8 t data static Optimized CRC XMODEM calculation Polynomial x 16 x 12 x 5 1 0x1021 Initial value 0 0 This is the CRC used by the Xmodem CRC protocol The following is the equivalent functionality written in C uintl16 t crc xmodem update uintl6 t crc uint8 t data int i crc crc uint16 lt lt 8 for i20 i 8 i if crc amp 0x8000 crc crc lt lt 1 0x1021 else crc lt lt 1 return crc Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 29 lt util delay_basic h gt Basic busy wait delay loops 314 22 29 lt util delay_basic h gt Basic busy wait delay loops Functions e void delay loop 1 uint8 t count e void delay loop 2 uint16 t count 22 29 1 Detailed Description include lt util delay_basic h gt The functions in this header file implement simple delay loops that perform a busy waiting They are typically used to facilitate short delays in the program execution They are implemented as count down loops with a well known CPU cycle count per loop iteration As such no other processing can occur simultaneously It should be kept in mind that the functions described here do not disable interrupts In general for long delays the u
452. t the applications must ensure proper protection e g by disabling interrupts before accessing them All write functions force erase and write programming mode For Xmega the EEPROM start address is 0 like other architectures The reading functions add the 0x2000 value to use EEPROM mapping into data space 22 14 2 Define Documentation 22 14 21 define EEGET var addr var eeprom_read_byte const uint8 t x addr Read a byte from EEPROM Compatibility define for IAR C 22 14 2 2 define EEPUT addr val eeprom write byte uint8 t addr uint8 t val Write a byte to EEPROM Compatibility define for IAR C 22 14 2 3 define var addr var eeprom read byte const uint8 t addr Read a byte from EEPROM Compatibility define for IAR C 22 14 2 4 define EEPUT addr val eeprom write byte uint8 t addr uint8_t val Write a byte to EEPROM Compatibility define for IAR C Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 44 lt avr eeprom h gt EEPROM handling 238 22 14 2 5 define EEMEM __attribute__ section eeprom Attribute expression causing a variable to be allocated within the eeprom section 22 14 2 6 define eeprom busy wait do while eeprom_is_ready Loops until the eeprom is no longer busy Returns Nothing 22 14 27 define eeprom is ready Returns 1 if EEPROM is ready for a new read write operation 0 if
453. t typedef int16 t PROGMEM prog int16 t typedef uint16 t PROGMEM prog uintl6 t typedef int32 t PROGMEM prog int32 t typedef uint32 t PROGMEM prog uint32 t typedef int 4 t PROGMEM prog int64 t typedef uint64_t PROGMEM prog uint64 t Functions PGM VOID P memchr P PGM VOID int __val size_t len int memcmp P const void x PGM VOID size t ATTR_PURE void memccpy_P void PGM VOID int val size t void memcpy P void x PGM VOID size_t void memmem P const void x size t VOID P size t ATTR PURE PGM VOID memrchr P PGM_VOID_P int val size t len char strcat P char P Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 35 pgmspace h File Reference 388 PGM_P strchr P PGM_P int __ val PGM_P strchrnul_P PGM_P int __ val int stremp_P const char x PGM_P _ ATTR_PURE char strepy_P char x PGM_P int strcasecmp_P const char PGM PURE char strcasestr P const char x PGM_P __ATTR_PURE size tstrcspn P const char s PGM P _ reject PURE size t strlcat P char P size t size t strlcpy P char PGM_P size t size t strlen P PGM P size t strnlen P size_t int strncmp P const char PGM P size t ATTR_PURE int strncasecmp P const char x PGM_P size_t _ ATTR_PURE char strncat_P char PGM P size_t char strncpy P char
454. t condition held much longer than one character period the function will return an end of file condition using _FDEV_EOF If there was a data overrun condi tion on input DOR bit set an error condition will be returned as FDEV ERR Line editing characters are handled inside the loop potentially modifying the buffer status If characters are attempted to be entered beyond the size of the line buffer their reception is refused and a Va character is sent to the terminal If a Vr or n character is seen the variable rxp receive pointer is set to the beginning of the buffer the loop is left and the first character of the buffer will be returned to the application If no other characters have been entered this will just be the newline character and the buffer is marked as being exhausted immediately again 22 39 4 The source code The source code is installed under Sprefix share doc avr libc examples stdiodemo where prefix is a configuration option For Unix systems it is usually set to either usror usr local Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 40 Example using the two wire interface TWI 362 22 40 Example using the two wire interface TWI Some newer devices of the ATmega series contain builtin support for interfacing the microcontroller to a two wire bus called TWI This is essentially the same called I2C by Philips but that term is avoided in Atmel s doc
455. t puts P const char str size_t fwrite const void 5126 t size size t nmemb FILE stream int fgetc FILE stream int ungetc int FILE stream char fgets char str int size FILE stream char gets char str size_t fread void x__ptr size_t size size t nmemb FILE stream void clearerr FILE stream int feof FILE stream int ferror FILE stream int vfscanf FILE stream const char fmt va list ap int vfscanf P FILE stream const char fmt va list int fscanf FILE stream const fmt int fscanf P FILE stream const char fmt int scanf const char fmt int scanf P const char fmt int vscanf const char fmt va list int sscanf const char buf const char fmt int sscanf P const char buf const char fmt int fflush FILE xstream FILE fdevopen int put char FILE int get FILE Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 184 22 9 1 Detailed Description finclude lt stdio h gt Introduction to the Standard IO facilities This file declares the standard IO facilities that are implemented in avr libc Due to the nature of the underlying hardware only a limited subset of standard IO is implemented There is no actual file implementation available so only device IO can be performe
456. t we want the information from the text and data segment extracted If we specify the EEPROM segment we can generate a hex file that can be used to program the EEPROM avr objcopy j eeprom change section Ima eeprom 0 O ihex demo elf demo eeprom hex There is no demo eeprom hex file written as that file would be empty Starting with version 2 17 of the GNU binutils the avr ob jcopy command that used to generate the empty EEPROM files now aborts because of the empty input section eeprom so these empty files are not generated It also signals an error to the Makefile which will be caught there and makes it print a message about the empty file not being generated 22 37 7 Letting Make Build the Project Rather than type these commands over and over they can all be placed in a make file To build the demo project using make save the following in a file called Makefile Note This Makefile can only be used as input for the GNU version of make PRG demo OBJ demo o fMCU TARGET at90s2313 fMCU TARGET at90s2333 MCU_TARGET at90s4414 MCU_TARGET at90s4433 MCU_TARGET at90s4434 MCU_TARGET at90s8515 MCU_TARGET at90s8535 MCU_TARGET atmegal28 MCU_TARGET atmegal280 MCU_TARGET atmegal281 MCU_TARGET atmegal284p MCU_TARGET atmegal6 MCU_TARGET atmegal63 MCU_TARGET atmegal64p MCU_TARGET atmega165 MCU_TARGET atmegal65p MCU_TARGET atmegal68 Generated on Thu May 19 2011 13 2
457. ted by commas Our example uses just one r value 3 A comma separated list of input operands Again our example uses one operand only I SFR IO ADDR PORTD 4 Clobbered registers left empty in our example You can write assembler instructions in much the same way as you would write assem bler programs However registers and constants are used in a different way if they refer to expressions of your C program The connection between registers and C operands is specified in the second and third part of the asm instruction the list of input and output operands respectively The general form is asm code output operand list input operand list clobber list In the code section operands are referenced by a percent sign followed by a single digit O refers to the first 1 to the second operand and so forth From the above example 0 refers to r value and 1 refers to I SFR IO ADDR PORTD This may still look a little odd now but the syntax of an operand list will be explained soon Let us first examine the part of a compiler listing which may have been generated from our example lds r24 value x in r24 12 NOAPP sts value r24 The comments have been added by the compiler to inform the assembler that the in cluded code was not generated by the compilation of C statements but by inline as sembler statements The compiler selected register r24 for storage of the value read from PORTD
458. ted on it s usually not noticeable on larger machines like PCs while the waste of flash ROM storage can be very painful on a small microcontroller like the AVR So in general variables should only be explicitly initialized if the initial value is non Zero Note Recent versions of GCC are now smart enough to detect this situation and revert variables that are explicitly initialized to O to the bss section Still other compilers might not do that optimization and as the C standard guarantees the initialization it is safe to rely on it Back to FAQ Index 11 9 Why do some 16 bit timer registers sometimes get trashed Some of the timer related 16 bit IO registers use a temporary register called TEMP in the Atmel datasheet to guarantee an atomic access to the register despite the fact that two separate 8 bit IO transfers are required to actually move the data Typically this includes access to the current timer counter value register TCNTn the input capture register ICRn and write access to the output compare registers OCRnM Refer to the actual datasheet for each device s set of registers that involves the TEMP register Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 10 How do I use a define d constant in an asm statement 68 When accessing one of the registers that use TEMP from the main application and possibly any other one from within an interrupt routine care must be taken that no access
459. ted on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 60 string h File Reference 410 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 61 strlcat S File Reference 411 24 60 1 Detailed Description 24 61 Sstrlcat S File Reference 24 61 1 Detailed Description 24 62 Sstrlcat P S File Reference 24 62 1 Detailed Description 24 63 Sstrlcpy S File Reference 24 63 1 Detailed Description 24 64 strlcpy P S File Reference 24 64 1 Detailed Description 24 65 Sstrlen S File Reference 24 65 1 Detailed Description 24 66 P S File Reference 24 66 1 Detailed Description 24 67 strlwr S File Reference 24 67 1 Detailed Description 24 68 strncasecmp S File Reference 24 68 1 Detailed Description 24 69 strncasecmp P S File Reference 24 69 1 Detailed Description 24 70 5 File Reference 24 70 1 Detailed Description 24 71 strncat_P S File Reference Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 72 strncmp S File Reference 24 72 1 Detailed Description 24 73 strncmp_P S File Reference 54721 Natailad Dacerintian 24 90 strtok P c File Reference 412 Variables e static char p 24 89 1 Detailed Description 24 90 File Reference Functions char x strtok_P char xs PGM P delim 24 90 1 Detailed Description 24 91 strtok_r S File Reference 24 91 1 Detailed Description 24 92 strtok_rP S File Reference 24 92 1 Detailed De
460. ted to promoting computer users rights to use study copy modify and redis tribute computer programs The FSF promotes the development and use of free soft ware particularly the GNU operating system used widely in its GNU Linux variant The FSF remains the primary sponsor of the GNU project The GNU Project was launched in 1984 to develop a complete Unix like operating system which is free software the GNU system GNU is a recursive acronym for GNU s Not Unix it is pronounced guh noo approximately like canoe One of the main projects of the GNU system is the GNU Compiler Collection or GCC and its sister project GNU Binutils These two open source projects provide a foun dation for a software development toolchain Note that these projects were designed to originally run on Unix like systems 2 3 GCC GCC stands for GNU Compiler Collection GCC is highly flexible compiler system It has different compiler front ends for different languages It has many back ends that generate assembly code for many different processors and host operating systems All share a common middle end containing the generic parts of the compiler including a lot of optimizations In GCC a host system is the system processor OS that the compiler runs on A target system is the system that the compiler compiles code for And a build system is the system that the compiler is built from source code on If a compiler has the same system for host and
461. ter macro replacement does not start with vector Vector name Old vector Description Applicable for device name Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 248 ADC_vect SIG_ADC ADC Conversion Complete AT90S2333 9054433 9054434 9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 169 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtinyl3 AT tinyl5 ATtiny26 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 ANALOG_ COMP_0_vect SIG_ Analog COMPARATORDO parator 0 Com AT90PWM3 AT90PWM2 AT90PWM1 ANALOG_ COMP 1 vect SIG COMPARATOR Analog 1 parator 1 Com AT90PWM3 AT90PWM2 AT90PWMI ANALOG_ COMP_2_vect SIG_ Analog COMPARATOR parator 2 Com AT90PWM3 AT90PWM2 AT90
462. ters between the open bracket character and a close bracket character The set excludes those characters if the first character after the open bracket is a circum flex To include a close bracket in the set make it the first character after the open bracket or the circumflex any other position will end the set The hyphen character is also special when placed between two other characters it adds all intervening characters to the set To include a hyphen make it the last character before the final close bracket For instance 0 9 means the set of every thing except close bracket zero through nine and hyphen The string ends with the appearance of a character not in the or with a circumflex in set or when the field width runs out Note that usage of this conversion enlarges the stack expense p Matches a pointer value as printed by p in printf the next pointer must be a pointer to void n Nothing is expected instead the number of characters consumed thus far from the input is stored through the next pointer which must be a pointer to int This is not a conversion although it can be suppressed with the flag These functions return the number of input items assigned which can be fewer than provided for or even zero in the event of a matching failure Zero indicates that while there was input available no conversions were assigned typically this is due to an invalid input character such as an alphabetic
463. the ATtiny45 setup the C code contains an ISR for PCINTO At each pin change interrupt it will first be analyzed whether the interrupt was caused by a rising or a falling edge In case of the rising edge timer 1 will be started with a prescaler of 16 after clearing the current timer value Then at the falling edge the current timer value will be recorded and timer 1 stopped the pin change interrupt will be suspended and the upper layer will be notified that the incoming PWM measurement data is available Function main first initializes the hardware by calling ioinit and then waits until some incoming PWM value is available If it is the output PWM will be adjusted by computing the relative value of the incoming PWM Finally the pin change interrupt is re enabled and the CPU is put to sleep 22 36 2 2 project h In order for the interrupt service routines to be as fast as possible some of the CPU registers are set aside completely for use by these routines so the compiler would not use them for C code This is arranged for in project h The file is divided into one section that will be used by the assembly source code and another one to be used by C code The assembly part is distinguished by the prepro Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 36 Combining C and assembly source files 330 cessing macro __ASSEMBLER__ which will be automatically set by the compiler front end when prepr
464. the current mode of operation An enumeration is used to improve the readability By default the compiler would allocate a variable of type int for an enumeration The packed attribute declarator instructs the compiler to use the smallest possible integer type which would be an 8 bit type here After some initialization actions the application s main loop follows In an embedded application this is normally an infinite loop as there is nothing an application could exit into anyway At the beginning of the loop the watchdog timer will be retriggered If that timer is not triggered for about 2 seconds it will issue a hardware reset Care needs to be taken that no code path blocks longer than this or it needs to frequently perform watchdog resets of its own An example of such a code path would be the string IO functions for an overly large string to print about 2000 characters at 9600 Bd they might block for too long The loop itself then acts on the interrupt indication bitfields as appropriate and will eventually put the CPU on sleep at its end to conserve power The first interrupt bit that is handled is the software timer at a frequency of approx imately 100 Hz The CLOCKOUT pin will be toggled here so e g an oscilloscope can be used on that pin to measure the accuracy of our software clock Then the LED flasher for LED2 We are alive LED is built It will flash that LED for about 50 ms and pause it for another 950 ms
465. the entire device memory if desired the counter would wrap around and start back from 0 when reaching the end of the device Note 8 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 40 Example using the two wire interface TWI 365 When reading the EEPROM a first device selection must be made with write intent R W bit set to 0 indicating a write operation in order to transfer the EEPROM ad dress to start reading from This is called master transmitter mode Each completion of a particular step in TWI communication is indicated by an asserted TWINT bit in TWCR An interrupt would be generated if allowed After performing any actions that are needed for the next communication step the interrupt condition must be man ually cleared by setting the TWINT bit Unlike with many other interrupt sources this would even be required when using a true interrupt routine since as soon as TWINT is re asserted the next bus transaction will start Note 9 Since the TWI bus is multi master capable there is potential for a bus contention when one master starts to access the bus Normally the TWI bus interface unit will detect this situation and will not initiate a start condition while the bus is busy However in case two masters were starting at exactly the same time the way bus arbitration works there is always a chance that one master could lose arbitration of the bus during any transmit operation A master that has l
466. the shorter in and out instructions since the boot loader has a limited size this could be an important optimization API Usage Example The following code shows typical usage of the boot API include lt inttypes h gt include lt avr interrupt h gt include lt avr pgmspace h gt void boot program page uint32 t page uint8 t xbuf uintl16 t i uint8 t sreg Disable interrupts sreg SREG el eeprom busy wait boot page erase page boot spm busy wait Wait until the memory is erased for i20 i SPM PAGESIZE i 2 Set up little endian word uintl6 t xbuf w xbuf lt lt 8 boot_page_fill page i w boot_page_write page Store buffer in flash page boot spm busy wait Wait until the memory is written Reenable RWW section again We need this if we want to jump back to the application after bootloading boot rww enable Re enable interrupts if they were ever enabled SREG sreg Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 12 avr boot h Bootloader Support Utilities 230 22 12 2 Define Documentation 22 12 21 define boot is spm interrupt SPM REG amp uint8 t BV SPMIE Check if the SPM interrupt is enabled 22 12 2 2 define boot lock bits set bits boot lock bits set lock bits Set the bootloader lock bits Parameters lock bits A mask of which Boot Lo
467. tiny861 AT90USB162 9005 82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 251 INT2_vect SIG_ INTERRUPT2 External Interrupt Request 2 AT90PWMS3 AT90PWMO2 AT90PWMI 90 128 AT90CAN32 ATOOCAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmega32 ATmega323 ATmega32HVB ATmega406 ATmega64 ATmega8515 AT mega8535 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmegal64P ATmega644P ATmega644 AT megal6HVA AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 INT3_vect SIG_ INTERRUPT3 External Interrupt Request 3 AT90PWM3 AT90PWM2 AT90PWMI 90 128 AT90CAN32 ATOOCAN64 ATmegal03 ATmegal28 ATmega32HVB ATmega406 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 INT4_vect SIG_ INTERRUPT4 External Interrupt Request 4 AT90CANI28 AT90CAN32 ATOOCAN64 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USBI62 9005 82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 5 vect SIG INTERRUPTS External Interrupt Request 5 AT90CANI28 AT90CAN32 ATOOCAN64 ATmegal03 ATmegal28 AT mega64 ATmega6
468. tmega325 atmega325a atmega325p atmega325pa atmega3250 atmega3250a atmega3250p atmega3250pa atmega328 atmega328p atmega48 atmega48a atmega48pa atmega48p atmega64 atmega640 atmega644 atmega644a atmega644p atmega644pa atmega645 atmega645a atmega645p atmega6450 atmega6450a Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 3 Supported Devices atmega6450p atmega8 atmega88 atmega88a atmega88p atmega88pa atmega8515 atmega8535 tinyAVR Devices attiny4 attiny5 attiny 10 attiny11 1 attiny12 1 attiny 13 attiny13a attiny15 1 attiny20 attiny22 attiny24 attiny24a attiny25 attiny26 attiny261 attiny261a attiny28 1 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 3 Supported Devices attiny2313 attiny2313a attiny40 attiny4313 attiny43u attiny44 attiny44a attiny45 attiny461 attiny461a attiny48 attiny84 attiny84a attiny85 attiny861 attiny861a attiny87 attiny88 attiny 1634 Automotive AVR Devices atmegal6m1 atmega32c atmega32ml atmega64c 1 atmega64m 1 attiny 167 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 1 3 Supported Devices CAN AVR Devices at90can32 at90can64 at90can128 LCD AVR Devices atmegal69 atmegal69a atmegal60p atmegal69pa atmega329 atme
469. together 13 3 2 Passing linker options from the C compiler By default all unknown non option arguments on the avr gcc command line i e all filename arguments that don t have a suffix that is handled by avr gcc are passed straight to the linker Thus all files ending in o object files and a object libraries are provided to the linker System libraries are usually not passed by their explicit filename but rather using the 1 option which uses an abbreviated form of the archive filename see above avr libc ships two system libraries 1ibc a and libm a While the standard library Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 3 Controlling the linker avr ld 120 libc a will always be searched for unresolved references when the linker is started using the C compiler frontend i e there s always at least one implied 1c option the mathematics library 1ibm a needs to be explicitly requested using 1m See also the entry in the FAQ explaining this Conventionally Makefiles use the make macro LDLIBS to keep track of 1 and possibly L options that should only be appended to the C compiler command line when linking the final binary In contrast the macro LDFLAGS is used to store other command line options to the C compiler that should be passed as options during the linking stage The difference is that options are placed early on the command line while libraries are put at the end since the
470. tokens Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 1 lt string h gt Strings 226 The strsep function locates in the string referenced by sp the first occurrence of any character in the string delim the terminating 0 character and replaces it with a 707 The location of the next character after the delimiter character or NULL if the end of the string was reached is stored in sp An empty field i e one caused by two adjacent delimiter characters can be detected by comparing the location referenced by the pointer returned in sp to 707 Returns The strsep function returns a pointer to the original value of If sp is initially NULL strsep returns NULL 22 11 3 34 size tstrspn const char x s const char accept The strspn function calculates the length of the initial segment of s which consists entirely of characters in accept Returns The strspn function returns the number of characters in the initial segment of s which consist only of characters from accept The terminating zero is not considered as a part of string 22 11 3 35 char x strstr const char s1 const char s2 Locate a substring The strstr function finds the first occurrence of the substring s2 in the string s1 The terminating 0 characters are not compared Returns The strstr function returns a pointer to the beginning of the substring or NULL if the substring is
471. tories in the PATH enviornment variable should be specified using their short filename 8 3 version This will also help to avoid NTVDM errors during building These short filenames can be specific to each machine Build the tools below in MSYS Binutils Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin install directory gt bin Configure CFLAGS D USE MINGW ACCESS Sarchivedir configure prefix installdir target avr disable nls enable doc datadir installdir doc binutils with gmp usr local with mpfr usr local 2 amp 1 tee binutils configure log Make make all html install install html 2 gt amp 1 tee binutils make log Manually change documentation location GCC Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 12 13 Building the Toolchain for Windows 102 usr bin bin mingw bin c cygwin bin lt install directory gt bin Configure CFLAGS D USE MINGW ACCESS gcc version configure prefix installdir
472. tr int main void ctr 0x200 start timer sei uintl6 t ctr copy do ATOMIC BLOCK ATOMIC FORCEON ctr copy ctr while ctr copy 0 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 207 lt util atomic h gt Atomically and Non Atomically Executed Code Blocl809 This will install the appropriate interrupt protection before accessing variable ctr so it is guaranteed to be consistently tested If the global interrupt state were uncer tain before entering the ATOMIC BLOCK it should be executed with the parameter ATOMIC RESTORESTATE rather than ATOMIC FORCEON See optim code reorder for things to be taken into account with respect to compiler optimizations 22 27 2 Define Documentation 22 27 21 define ATOMIC BLOCK type Creates a block of code that is guaranteed to be executed atomically Upon entering the block the Global Interrupt Status flag in SREG is disabled and re enabled upon exiting the block from any exit path Two possible macro parameters are permitted ATOMIC RESTORESTATE and ATOMIC FORCEON 22 27 22 define ATOMIC FORCEON This is a possible parameter for ATOMIC BLOCK When used it will cause the ATOMIC BLOCK to force the state of the SREG register on exit enabling the Global Interrupt Status flag bit This saves on flash space as the previous value of the SREG register does not need to be saved at the start of the block Care should be taken
473. tream static FILE mystdout FDEV SETUP STREAM uart putchar NULL FDEV SETUP WRITE static int uart putchar char c FILE xstream if c An uart putchar Nr stream loop until bit is set UCSRA UDR 2 c return 0 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 186 int main void init uart stdout amp mystdout printf Hello world in return 0 This example uses the initializer form FDEV SETUP STREAM Y rather than the function like fdev setup stream so all data initialization happens during C start up If streams initialized that way are no longer needed they can be destroyed by first calling the macro fdev close and then destroying the object itself No call to fclose should be issued for these streams While calling fclose itself is harmless it will cause an undefined reference to free and thus cause the linker to link the malloc module into the application Notes Note 1 It might have been possible to implement a device abstraction that is compatible with fopen but since this would have required to parse a string and to take all the information needed either out of this string or out of an additional table that would need to be provided by the application this approach was not taken Note 2 This basically follows the Unix approach if a device such as a terminal needs special hand
474. tring in SRAM src A far pointer to the source string in Flash n The total number of bytes allocated to the destination string Returns The strlcat_PF function returns strlen src MIN n strlen initial dst If retval gt n truncation occurred The contents of RAMPZ SFR are undefined when the funcion returns 22 19 4 23 size tstrlcpy P char x dst PGM P src size_t siz Copy a string from progmem to RAM Copy src to string dst of size siz At most siz 1 characters will be copied Always NULL terminates unless siz 0 The strlcpy_P function is similar to strlcpy except that the src is pointer to a string in memory space Returns The strlcpy_P function returns strlen src If retval gt siz truncation occurred 22 19 4 24 size tstrlcpy PF char x dst uint_farptr_t src size t siz Copy a string from progmem to RAM Copy src to string dst of size siz At most siz 1 characters will be copied Always NULL terminates unless siz 0 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 49 lt avr pgmspace h gt Program Space Utilities 285 Returns The strlcpy PF function returns strlen src If retval gt siz truncation occurred The contents of RAMPZ SFR are undefined when the function returns 22 19 4 25 size tstrlen P PGM P src The strlen_P function is similar to strlen except that src is a pointer to a string in program space Returns T
475. ts own interrupt flag bit in some control register indicating the specified interrupt condition has been met by representing a logical 1 in the respec tive bit position When working with interrupt handlers this interrupt flag bit usually gets cleared automatically in the course of processing the interrupt sometimes by just calling the handler at all sometimes e g for the U S ART by reading a particular hardware register that will normally happen anyway when processing the interrupt From the hardware s point of view an interrupt is asserted as long as the respective bit is set while global interrupts are enabled Thus it is essential to have the bit cleared before interrupts get re enabled again which usually happens when returning from an interrupt handler Only few subsystems require an explicit action to clear the interrupt request when using interrupt handlers The notable exception is the TWI interface where clearing the interrupt indicates to proceed with the TWI bus hardware handshake so it s never done automatically However if no normal interrupt handlers are to be used or in order to make extra sure any pending interrupt gets cleared before re activating global interrupts e g an external edge triggered one it can be necessary to explicitly clear the respective hardware interrupt bit by software This is usually done by writing a logical 1 into this bit position This seems to be illogical at first the bit position a
476. tting up any stack frame and not even a RET instruction at the end Function ioinit centralizes all hardware setup The very last part of that function demonstrates the use of the EEPROM variable ee pwm to obtain an EEPROM address that can in turn be applied as an argument to eeprom read word The following functions handle UART character and string output UART input is han dled by an ISR There are two string output functions printstr andprintstr p The latter function fetches the string from program memory Both functions translate a newline character into a carriage return newline sequence so a simple n can be used in the source code Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 38 A more sophisticated project 353 The function set pwm propagates the new PWM value to the PWM performing range checking When the value has been changed the new percentage will be an nounced on the serial link The current value is mirrored in the variable pwm so others can use it in calculations In order to allow for a simple calculation of a percentage value without requiring floating point mathematics the maximal value of the PWM is restricted to 1000 rather than 1023 so a simple division by 10 can be used Due to the nature of the human eye the difference in LED brightness between 1000 and 1023 is not noticable anyway 22 38 3 5 Part 5 main At the start of main a variable mode is declared to keep
477. tually used So if a variable was placed in a register at the beginning of some function this same register can be re used later on if the compiler notices that the first variable is no longer used inside that function even though the variable is still in lexical scope When trying to examine the variable in avr gdb the displayed result will then look garbled So in order to avoid these side effects optimization can be turned off while debugging However some of these optimizations might also have the side effect of uncovering bugs that would otherwise not be obvious so it must be noted that turning off opti mization can easily change the bug pattern In most cases you are better off leaving optimizations enabled while debugging Back to FAQ Index 11 12 How dol trace an assembler file in avr gdb When using the g compiler option avr gcc only generates line number and other debug information for C and C files that pass the compiler Functions that don t have line number information will be completely skipped by a single step command in gdb This includes functions linked from a standard library but by default also functions defined in an assembler source file since the g compiler switch does not apply to the assembler Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 12 How do I trace an assembler file in avr gdb 70 So in order to debug an assembler input file possibly one that has to be passed thr
478. tup As an alternative to the assembly language solution this project also offers a C only implementation de ploying the exact same peripheral setup based on a more sophisticated and thus more expensive but pin compatible controller While the simple demo is meant to run on about any AVR setup possible where a LED could be connected to the OCR1 A output the large and stdio demos are mainly targeted to the Atmel STK500 starter kit and the TWI example requires a controller where some 24Cxx two wire EEPPROM can be connected to For the STK500 demos the default CPU either an AT90S8515 or an ATmega8515 should be removed from its socket and the ATmegal6 that ships with the kit should be inserted into socket SCKT3100A3 The ATmega16 offers an on board ADC that is used in the large demo and all AVRs with an ADC feature a different pinout than the industry standard com patible devices In order to fully utilize the large demo a female 10 pin header with cable connecting to a 10 kOhm potentiometer will be useful For the stdio demo an industry standard HD44780 compatible LCD display of at least 16x1 characters will be needed Among other things the LCD4Linux project page describes many things around these displays including common pinouts 22 36 Combining C and assembly source files For time or space critical applications it can often be desirable to combine C code for easy maintenance and assembly code for maximal speed or minimal
479. u May 19 2011 13 29 12 for avr libc by Doxygen 22 15 lt avr fuse h gt Fuse Support 242 FUSES low LFUSE DEFAULT high FUSE BOOTSZO amp FUSE 571 amp FUSE EESAVE amp FUSE SPIEN amp FUSE JT AGEN EFUSE DEFAULT i int main void return 0 Or using the variable directly instead of the FUSES macro include lt avr io h gt fuse_t fuse attribute section fuse low LFUSE DEFAULT high FUSE BOOTSZO amp FUSE BOOTSZ1 amp FUSE EESAVE amp FUSE SPIEN amp FUSE JT AGEN extended EFUSE DEFAULT 1 int main void return 0 If you are compiling in C you cannot use the designated intializers so you must do include lt avr io h gt FUSES LFUSE DEFAULT low FUSE BOOTSZO amp FUSE BOOTSZ1 amp FUSE EESAVE amp FUSE SPIEN amp FUSE JTAGEN high EFUSE DEFAULT extended int main void return 0 However there are a number of caveats that you need to be aware of to use this API properly Be sure to include lt avr io h gt to get all of the definitions for the API The FUSES macro defines a global variable to store the fuse data This variable is assigned to its own linker section Assign the desired fuse values immediately in the variable initial ization Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 16 lt avr interrupt h gt Interrupts 243 The fuse
480. uded by all of the cavr ioXXXX h files which use macros defined here to make the special function register definitions look like C variables or simple constants depending on the SFR ASM COMPAT define Some examples from lt avr iocanxx h gt to show how to define such macros fdefine PORTA SFR IOS8 0x02 fdefine EEAR _SFR_IO16 0x21 define UDRO _SFR_MEMB8 0xC6 define TCNT3 _SFR_MEM16 0x94 define CANIDT _SFR_MEM32 0xF0 Generated on Thu May 19 2011 13 29 12 for avr libe by Doxygen 22 21 Additional notes from lt avr sfr_defs h gt 295 If SFR ASM COMPAT is not defined C programs can use names like PORTA directly in C expressions also on the left side of assignment operators and GCC will do the right thing use short I O instructions if possible The SFR OFFSET definition is not used in any way in this case Define SFR 5 COMPAT as to make these names work as simple constants ad dresses of the I O registers This is necessary when included in preprocessed assem bler S source files so it is done automatically if ASSEMBLER___ is defined By default all addresses are defined as if they were memory addresses used in 1ds st s instructions To use these addresses in in out instructions you must subtract 0x20 from them For more backwards compatibility insert the following at the start of your old assem bler source file define SFR OFFSET 0 This automatically subtracts 0x20 f
481. uently requires attention regarding atomic access to objects that could be altered by code running within an interrupt context see lt util atomic h gt Frequently interrupts are being disabled for periods of time in order to perform certain operations without being disturbed see optim_code_reorder for things to be taken into account with respect to compiler optimizations define sei define cli Macros for writing interrupt handler functions define ISR vector attributes define SIGNAL vector define EMPTY INTERRUPT vector Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 16 lt avr interrupt h gt Interrupts 244 define ISR_ALIAS vector target vector define reti define BADISR vect ISR attributes define 5 BLOCK define ISR NOBLOCK define 5 NAKED e define ISR ALIASOF target vector 22 16 1 Detailed Description Note This discussion of interrupts was originally taken from Rich Neswold s document See Acknowledgments Introduction to avr libc s interrupt handling It s nearly impossible to find compilers that agree on how to handle interrupt code Since the C language tries to stay away from machine dependent details each compiler writer is forced to design their method of support In the AVR GCC environment the vector table is predefined to point to interrupt rou tines with predetermined names By using the appropriate name your routine wi
482. uint8 t direction switch direction Note 4 case UP if pwm direction DOWN break case DOWN if pwm 0 direction UP break OCR pwm Note 5 d nit void Note 6 Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys x TCCRIA TIMER INIT Start timer 1 x NB TCCRIA and TCCRIB could actually be the same register so Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 335 take care to not clobber it x TCCRIB TIMER1_CLOCKSOURCE Run device dependent timer 1 setup hook if present if defined TIMER1_SETUP_HOOK TIMER1_SETUP_HOOK endif x Set PWM value to 0 OCR 0 Enable as output DDROC BV OCI Enable timer 1 overflow interrupt TIMSK BV TOIE1 sei int main void iornit 0 loop forever the interrupts are doing the rest x for Note 7 sleep mode return 0 22 37 3 Compiling and Linking This first thing that needs to be done is compile the source When compiling the compiler needs to know the processor type so the mmcu option is specified The Os option will tell the compiler to optimize the code for efficient space usage at the possible expense of code execution speed The g is used to embed debug info The debug info is useful for disassemblies and doesn t end
483. ule ATmegal69 ATmegal69P ATmega329 ATmega329A ATmega3290 ATmega3290A ATmega649 ATmega6490 ATxmegal28B1 Pa Cae eRe Oh Elsa aba EM ca Fy eee EC AT Seu zi Dal EE 22 21 Additional notes from lt avr sfr_defs h gt 294 Some of the newer AVRs contain a System Clock Prescale Register CLKPR that allows you to decrease the system clock frequency and the power consumption when the need for processing power is low Below are two macros and an enumerated type that can be used to interface to the Clock Prescale Register Note Not all AVR devices have a Clock Prescale Register On those devices without a Clock Prescale Register these macros are not available typedef enum lock div 1 0 lock div 2 1 lock div 4 2 lock div 8 3 lock div 16 4 lock div 32 5 lock div 64 6 lock div 128 7 lock div 256 8 clock div 1 rc 15 ATmegal28RFA1 only clock div t N Clock prescaler setting enumerations clock prescale set x Set the clock prescaler register select bits selecting a system clock division setting This function is inlined even if compiler optimizations are disabled The type of x is clock div t clock prescale get Gets and returns the clock prescaler register setting The return type is clock div t 22 21 Additional notes from lt avr str_defs h gt The avr sfr defs h file is incl
484. umentation due to patenting issues For further documentation see http www nxp com documents user manual UM10204 pdf 22 40 1 Introduction into TWI The two wire interface consists of two signal lines named SDA serial data and SCL serial clock plus a ground line of course All devices participating in the bus are connected together using open drain driver circuitry so the wires must be terminated using appropriate pullup resistors The pullups must be small enough to recharge the line capacity in short enough time compared to the desired maximal clock fre quency yet large enough so all drivers will not be overloaded There are formulas in the datasheet that help selecting the pullups Devices can either act as a master to the bus i e they initiate a transfer or as a slave they only act when being called by a master The bus is multi master capable and a particular device implementation can act as either master or slave at different times Devices are addressed using a 7 bit address coordinated by Philips transfered as the first byte after the so called start condition The LSB of that byte is R W i e it determines whether the request to the slave is to read or write data during the next cycles There is also an option to have devices using 10 bit addresses but that is not covered by this example 22 40 2 The TWI example project The ATmega TWI hardware supports both master and slave operation This example will
485. unctions aren t nesting too deeply and don t require too much stack space for local variables as well as by being cautious with allocating too much dynamic memory If external RAM is available it is strongly recommended to move the heap into the ex ternal RAM regardless of whether or not the variables from the data and bss sections are also going to be located there The stack should always be kept in internal RAM Some devices even require this and in general internal RAM can be accessed faster since no extra wait states are required When using dynamic memory allocation and stack and heap are separated in distinct memory areas this is the safest way to avoid a stack heap collision 3 3 Tunables for malloc There are a number of variables that can be tuned to adapt the behavior of malloc to the expected requirements and constraints of the application Any changes to these tunables should be made before the very first call to malloc Note that some library functions might also use dynamic memory notably those from the lt stdio h gt Stan dard IO facilities so make sure the changes will be done early enough in the startup sequence The variables malloc heap start and malloc heap end can be used to restrict the malloc function to a certain memory region These variables are stati cally initialized to point to heap start and heap end respectively where heap start is filled in by the linker to point just beyond bss a
486. unsigned long int uint32 t typedef signed long long int int64 t typedef unsigned long long int uint64 t Integer types capable of holding object pointers These allow you to declare variables of the same size as a pointer typedef int16 t intptr t e typedef uintl6 t uintptr t Minimum width integer types Integer types having at least the specified width typedef int8 t int least8 t typedef uint8 t uint least8 t typedef int16 t int least16 t typedef uint16 tuint leastl6 t typedef int32 t int least32 t typedef uint32 t uint least32 t typedef int64 t int least 4 t typedef uint64 t uint least64 t Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8 t int fast8 t typedef uint8 t uint fast8 t typedef int16 t int fastl t typedef uintl6 tuint fastl t typedef int32 t int fast32 t typedef uint32 t uint fast32 t typedef int64 t int fast64 t typedef uint64 t uint fast64 t Greatest width integer types Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category e typedef int64 t intmax t e typedef uint64 t uintmax t Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 24 42 stdio h File Reference 402 24 4 1 Detailed Description 24 42 Stdio h File Reference Defines define need NULL define need size t define FILE struct file define stdin __iob 0
487. up in the hex files so I usually specify it Finally the c tells the compiler to compile and stop don t link This demo is small enough that we could compile and link in one step However real world projects will have several modules and will typically need to break up the building of the project into several compiles and one link avr gcc g Os mmcu atmega8 c demo c The compilation will create a demo o file Next we link it into a binary called demo elf Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 37 Asimple project 336 avr gcc g mmcu atmega8 o demo elf demo o It is important to specify the MCU type when linking The compiler uses the mmcu option to choose start up files and run time libraries that get linked together If this option isn t specified the compiler defaults to the 8515 processor environment which is most certainly what you didn t want 22 37 4 Examining the Object File Now we have a binary file Can we do anything useful with it besides put it into the processor The GNU Binutils suite is made up of many useful tools for manipulating object files that get generated One tool is avr ob jdump which takes information from the object file and displays it in many useful ways Typing the command by itself will cause it to list out its options For instance to get a feel of the application s size the h option can be used The output of this option shows how much space is
488. upplied buffer as an stdio stream This macro takes a user supplied buffer st ream and sets it up as a stream that is valid for stdio operations similar to one that has been obtained dynamically from fdevopen The buffer to setup must be of type FILE The arguments put and get are identical to those that need to be passed to fdevopen The rwflag argument can take one of the values FDEV SETUP READ FDEV SETUP WRITE or FDEV SETUP RW for read write or read write intent respec tively Note No assignments to the standard streams will be performed by fdev setup stream If standard streams are to be used these need to be assigned by the user See also under Running stdio without malloc 22 9 2 11 define FDEV SETUP put get rwflag Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 189 Initializer for a user supplied stdio stream This macro acts similar to fdev setup stream but it is to be used as the initializer of a variable of type FILE The remaining arguments are to be used as explained in fdev_setup_stream 22 9 2 12 define FILE struct file FILE is the opaque structure that is passed around between the various standard IO functions 22 9 2 13 define getc _ stream fgetc stream The macro get c used to be a fast macro implementation with a functionality identical to fgetc For space constraints in avr li
489. upt could trigger it is sure the device will really be put to sleep Some devices have the ability to disable the Brown Out Detector BOD before going to sleep This will also reduce power while sleeping If the specific AVR device has this ability then an additional macro is defined sleep bod disable This macro generates inlined assembly code that will correctly implement the timed sequence for disabling the BOD before sleeping However there is a limited number of cycles af ter the BOD has been disabled that the device can be put into sleep mode otherwise the BOD will not truly be disabled Recommended practice is to disable the BOD sleep bod disable set the interrupts sei and then put the device to sleep sleep cpu like so include lt avr interrupt h gt include lt avr sleep h gt set sleep mode mode elrxQ if some condition sleep_enable sleep_bod_disable sei sleep cpu sleep disable sei Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 25 lt avr version h gt avr libc version macros 301 22 24 22 Function Documentation 22 24 21 void sleep_cpu void Put the device into sleep mode The SE bit must be set beforehand and it is recommended to clear it afterwards 22 24 2 2 void sleep disable void Clear the SE sleep enable bit 22 24 2 3 void sleep enable void Put the device in sleep mode How the device is broug
490. use A0 to refer to the lowest byte of the first operand A1 to the lowest byte of the second operand and so on The next byte of the first operand will be B0 the next byte CO and so on This also implies that it is often neccessary to cast the type of an input operand to the desired size A final problem may arise while using pointer register pairs If you define an input operand e ptr and the compiler selects register Z r30 r31 then refers to r30 and BO refers to r31 But both versions will fail during the assembly stage of the compiler if you explicitely need 7 like in ld r24 2 If you write ld r24 a0 with a lower case a following the percent sign then the compiler will create the proper assembler line Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 7 4 Clobbers 47 7 4 Clobbers As stated previously the last part of the asm statement the list of clobbers may be omitted including the colon seperator However if you are using registers which had not been passed as operands you need to inform the compiler about this The following example will do an atomic increment It increments an 8 bit value pointed to by a pointer variable in one go without being interrupted by an interrupt routine or another thread in a multithreaded environment Note that we must use a pointer because the incremented value needs to be stored before interrupts are enabled asm volatile eli
491. used it like so FLASH DECLARE int mydata Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 10 6 Non Returning main 61 10 6 Non Returning main To declare main to be a non returning function in IAR it is done like this C task void main void code To do the equivalent in AVR GCC do this void main void attribute noreturn void main void Note See the GCC User Manual for more information on Function Attributes In AVR GCC a prototype for main is required so you can declare the function at tribute to specify that the main function is of type noreturn Then define main as normal Note that the return type for main is now void 10 7 Locking Registers The IAR compiler allows a user to lock general registers from r15 and down by using compiler options and this keyword syntax regvar _ no init volatile unsigned int filteredTimeSinceCommutation 814 This line locks r14 for use only when explicitly referenced in your code thorugh the var name filteredTimeSinceCommutation This means that the compiler cannot dispose of it at its own will To do this in AVR GCC do this register unsigned char counter asm r3 Typically it should be possible to use r2 through r15 that way Note Do not reserve rO or rl as these are used internally by the compiler for a temporary register and for a zero value Locking registers is not recom
492. used as an indication that this function is going to accept a program space string Note also the use of the PSTRQ macro Back to FAQ Index 11 21 Why does the compiler compile an 8 bit operation that uses bitwise opera tors into a 16 bit operation in assembly Bitwise operations in Standard C will automatically promote their operands to an int which is by default 16 bits in avr gcc To work around this use typecasts on the operands including literals to declare that the values are to be 8 bit operands This may be especially important when clearing a bit var amp mask wrong way x The bitwise not operator will also promote the value in mask to an int To keep it an 8 bit value typecast before the not operator var amp unsigned char mask Back to FAQ Index 11 22 How to detect RAM memory and variable overlap problems You can simply run avr nm on your output ELF file Run it with the n option and it will sort the symbols numerically by default they are sorted alphabetically Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 11 23 Isit really impossible to program the ATtinyXX in C 81 Look for the symbol end that s the first address in RAM that is not allocated by a variable avr gcc internally adds 0x800000 to all data bss variable addresses so please ignore this offset Then the run time initialization code initializes the stack pointer by default to point to th
493. ve mode to individually update EEPROM cells fuse bits and or lock bits if their access is supported by the Atmel serial programming protocol The main flash instruction memory of the AVR can also be programmed in interactive mode however this is not very useful because one can only turn bits off The only way to turn flash bits on is to erase the entire memory using avrdude s e option avrdude is part of the FreeBSD ports system To install it simply do the following cd usr ports devel avrdude make install Once installed avrdude can program processors using the contents of the hex file specified on the command line In this example the file main hex is burned into the flash memory avrdude p 2313 e m flash i main hex avrdude AVR device initialized and ready to accept instructions avrdude Device signature 0x1e9101 avrdude erasing chip avrdude done avrdude reading input file main hex avrdude input file main hex auto detected as Intel Hex avrdude writing flash 1749 0x00 avrdude 1750 bytes of flash written avrdude verifying flash memory against main hex avrdude reading on chip flash data 1749 0x00 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 14 Using the avrdude program 122 avrdude verifying avrdude 1750 bytes of flash verified avrdude done Thank you The p 2313 option lets avrdude know that we are operating on an 419052313 chip This option specif
494. versions the converted value is padded on the left with zeros rather than blanks If a precision is given with a numeric conversion d i o u i x and X the 0 flag is ignored A negative field width flag the converted value is to be left adjusted on the field boundary The converted value is padded on the right with blanks rather than on the left with blanks or zeros A overrides a 0 if both are given space A blank should be left before a positive number produced by a signed conversion d or i A sign must always be placed before a number produced by a signed conversion A overrides a space if both are used optional decimal digit string specifying a minimum field width If the con verted value has fewer characters than the field width it will be padded with spaces on the left or right if the left adjustment flag has been given to fill out the field width optional precision in the form of a period followed by an optional digit string If the digit string is omitted the precision is taken as zero This gives the minimum number of digits to appear for d i o u x and X conversions or the maximum number of characters to be printed from a string for s conversions An optional 1 or h length modifier that specifies that the argument for the d i U or X conversion isa long int rather than int The h is ignored as short int isequivalent to int A character that s
495. verts the initial portion of the string pointed to by s to long integer representation In contrast to strtol s char NULL 10 this function does not detect overflow errno is not changed and the result value is not predictable uses smaller memory flash and stack and works more quickly 22 10 4 6 bsearch const void const void base size t nmemb size t size int const void const void compar The bsearch function searches an array of nmemb objects the initial member of which is pointed to by base for a member that matches the object pointed to by key The size of each member of the array is specified by size The contents of the array should be in ascending sorted order according to the compar ison function referenced by compar The compar routine is expected to have two Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 10 lt stdlib h gt General utilities 206 arguments which point to the key object and to an array member in that order and should return an integer less than equal to or greater than zero if the key object is found respectively to be less than to match or be greater than the array member The bsearch function returns a pointer to a matching member of the array or a null pointer if no match is found If two members compare as equal which member is matched is unspecified 22 10 4 7 void calloc size t nele size t size All
496. vr51 3 atmegal281 AVR ATmegal281 avr5 avr51 3 atmegal284p AVR ATmegal284P avr6 atmega2560 AVR ATmega2560 avr6 atmega2561 AVR ATmega2561 avrxmega2 atxmegal6a4 AVR ATxmegal6A4 avrxmega2 atxmega16d4 __AVR_ATxmegal6D4__ avrxmega2 atxmega32a4 AVR ATxmega32A4 avrxmega2 atxmega32d4 AVR ATxmega32DA avrxmega4 atxmega64a3 AVR ATxmega64A3 avrxmega4 atxmega64d3 AVR ATxmega64D3 avrxmega5 atxmega64a1 AVR_ATxmega64A1__ avrxmega5 atxmega64alu AVR ATxmega64A1U avrxmega6 atxmega128a3 _ AVR_ATxmega128A3__ avrxmega6 atxmega128b1 __AVR_ATxmega128B1__ avrxmega6 atxmega128d3 AVR_ATxmega128D3__ avrxmega6 atxmega192a3 _ AVR_ATxmega192A3__ avrxmega6 atxmega192d3 AVR ATxmegal92D3 avrxmega6 atxmega256a3 __AVR_ATxmega256A3__ avrxmega6 atxmega256a3b AVR ATxmega256A3B avrxmega6 atxmega256a3bu AVR ATxmega256A3BU avrxmega6 atxmega256d3 AVR ATxmega256D3 avrxmega7 atxmegal28al AVR ATxmegal28Al Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 13 1 Options for the C compiler avr gcc 113 avrxmega7 atxmegal28alu ATxmegal28A1U avrtiny 10 attiny4 AVR_ATtiny4 avrtiny 10 attiny5 AVR_ATtiny5 avrtiny 10 attiny9 AVR_ATtiny9 avrtiny 10 attiny 10 __AVR_ATtiny10__ avrtiny 10 attiny20 __AVR_ATtiny20__ avrtiny 10 attiny40 __AVR_ATtiny40__ 1 avr25 architecture is new in GCC 4 2 2 avr35 architecture is new in GCC 4 2 3
497. ways to define a vari able whose data resides in the Program Memory Flash IAR uses a non standard keyword to declare a variable in Program Memory flash int mydata AVR GCC uses Variable Attributes to achieve the same effect int mydata _ attribute progmem Note See the GCC User Manual for more information about Variable Attributes avr libc provides a convenience macro for the Variable Attribute finclude avr pgmspace h int mydata PROGMEM Note The PROGMEM macro expands to the Variable Attribute of progmem This macro requires that you include lt avr pgmspace h gt This is the canonical method for defining a variable in Program Space To read back flash data use read macros defined in lt avr pgmspace h gt All Program Memory handling macros are defined there There is also a way to create a method to define variables in Program Memory that is common between the two compilers IAR and AVR GCC Create a header file that has these definitions fif defined IAR C Compiler define FLASH DECLARE x flash x endif if defined __GNUC__ GNU Compiler define FLASH DECLARE x x __attribute__ __progmem_ endif This code snippet checks for the IAR compiler or for the GCC compiler and defines a macro FLASH_DECLARE x that will declare a variable in Program Memory using the appropriate method based on the compiler that is being used Then you would
498. word delimited by white space r control R ASCII DC2 sends a Vr then reprints the buffer refresh t tabulator will be replaced by a single space The function uart init takes care of all hardware initialization that is required to put the UART into a mode with 8 data bits no parity one stop bit commonly referred to as 8N1 at the baud rate configured in defines h At low CPU clock frequencies the U2X bit in the UART is set reducing the oversampling from 16x to 8x which allows for a 9600 Bd rate to be achieved with tolerable error using the default 1 MHz RC oscillator The public function uart_putchar again has suitable arguments for direct use by the stdio stream interface It performs the n into r n translation by recursively calling itself when it sees a n character Just for demonstration purposes the a audible bell ASCII BEL character is implemented by sending a string to stderr so it will be displayed on the LCD The public function uart_getchar implements the line editor If there are char acters available in the line buffer variable rxp is not NULL the next character will be returned from the buffer without any UART interaction If there are no characters inside the line buffer the input loop will be entered Charac ters will be read from the UART and processed accordingly If the UART signalled a framing error FE bit set typically caused by the terminal sending a line break con dition star
499. xed with the target name avr gdb and avr insight There is also a text mode GUI for GDB avr gdbtui DDD Data Display Debugger is another popular GUI front end to GDB available on Unix and Linux systems 2 9 AVaRICE AVaRICE is a back end program to AVR GDB and interfaces to the Atmel JTAG In Circuit Emulator ICE to provide emulation capabilities 2 10 SimulAVR SimulAVR is an AVR simulator used as a back end with AVR GDB Unfortunately this project is currently unmaintained and could use some help Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 2 11 Utilities 17 2 11 Utilities There are also other optional utilities available that may be useful to add to your toolset SRecord is a collection of powerful tools for manipulating EPROM load files It reads and writes numerous EPROM file formats and can perform many different ma nipulations MFile is a simple Makefile generator is meant as an aid to quickly customize a Make file to use for your AVR application 2 12 Toolchain Distributions Distros of the various open source projects that comprise the entire toolchain are normally distributed as source code It is left up to the user to build the tool application from its source code This can be a very daunting task to any potential user of these tools Luckily there are people who help out in this area Volunteers take the time to build the application from source code on particular host p
500. xp 162 frexpf 157 hypot 163 hypotf 157 INFINITY 157 isfinite 163 isfinitef 157 isinf 163 isinff 157 isnan 163 isnanf 157 Idexp 163 Idexpf 157 log 163 log10 163 log10f 157 logf 157 lrint 164 lrintf 157 lround 164 lroundf 158 1 PI 158 M 2 PI 158 M 2 SORTPI 158 E 158 M LNIO 158 M LN2 158 LOGIOE 158 LOG2E 158 158 2 159 4 159 SORTI 2 159 Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen INDEX 420 SQRT2 159 modf 164 modff 164 NAN 159 pow 165 powf 159 round 165 roundf 159 signbit 165 signbitf 159 sin 165 sinf 159 sinh 165 sinhf 159 sqrt 165 sqrtf 160 square 165 squaref 160 tan 166 tanf 160 tanh 166 tanhf 160 trunc 166 truncf 160 avr pgmspace memcopy P 276 memchr P 276 mememp P 277 mememp 277 memopy P 277 memcpy PF 278 memmem P 278 memrchr P 278 P 272 pgm read byte 272 pgm read byte far 272 pgm read byte near 272 pgm read dword 273 pgm read dword far 273 pgm read dword near 273 pgm read float 273 pgm read float far 273 read float near 274 pgm read word 274 pgm read word far 274 pgm read word near 274 PGM VOID P 274 prog char 275 prog intl6 t 275 prog int32 t 275 prog 11164 t 275 prog int8 t 275 prog uchar 275 prog uintl6 t 276 prog uint32 t 276 prog uint64 t 276 prog uint8 t 276 prog void 276 P
501. y are to be used to resolve global symbols that are still unresolved at this point Specific linker flags can be passed from the C compiler command line using the W1 compiler option see above This option requires that there be no spaces in the appended linker option while some of the linker options above like Map or de f sym would require a space In these situations the space can be replaced by an equal sign as well For example the following command line can be used to compile foo c into an executable and also produce a link map that contains a cross reference list in the file foo map avr gcc O o foo out Wl Map foo map Wl cref foo c Alternatively a comma as a placeholder will be replaced by a space before passing the option to the linker So for a device with external SRAM the following command line would cause the linker to place the data segment at address 0x2000 in the SRAM avr gcc mmcu atmegal28 o foo out Wl Tdata 0x802000 See the explanation of the data section for why 0x800000 needs to be added to the actual value Note that the stack will still remain in internal RAM through the symbol _ Stack that is provided by the run time startup code This is probably a good idea anyway since internal RAM access is faster and even required for some early devices that had hardware bugs preventing them from using a stack in external RAM Note also that the heap for malloc will still be placed after all the variab
502. y2313 TRANS USART SIG USART Data AT90PWM3 AT90PWM2 AT90PWMI UDRE vect USART Register Empty ATmegal6 ATmegal68P ATmega32 AT DATA SIG mega323 ATmega3250 ATmega3250P AT UART DATA mega328P ATmega3290 ATmega3290P ATmega48P ATmega6450 ATmega6490 ATmega8 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 AT tiny2313 USI SIG USI USI Overflow ATmegal65 ATmegal65P ATmegal69 OVERFLOW_ OVERFLOW ATmegal69P ATmega325 ATmega3250 vect ATmega3250P ATmega329 ATmega3290 ATmega3290P ATmega645 ATmega6450 ATmega649 ATmega6490 ATtiny2313 USI OVF SIG USI USI Overflow ATtiny26 ATtiny43U ATtiny24 ATtiny44 vect OVERFLOW ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 USI START SIG USI USI Start Condi ATmegal65 ATmegal65P ATmegal69 vect START tion ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega329 ATmega3290 ATmega3290P ATmega645 ATmega6450 ATmega649 ATmega6490 ATtiny2313 ATtiny43U ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 USI STRT SIG USI USI Start ATtiny26 vect START USI STR SIG USI USI START ATtiny24 ATtiny44 ATtiny84 vect START WATCHDOG_ SIG Watchdog Time ATtiny24 ATtiny44 ATtiny84 vect WATCHDOG out TIMEOUT WDT SIG Watchdog Timer ATtiny2313 OVERFLOW WATCHDOG Overflow vect TIMEOUT SIG WDT OVERFLOW vect SIG WDT Watchdog Time AT90PWMS3 AT90PWM2 AT90PWMI SIG out Interrupt ATmega
503. ze t const char x fmt Variant of snprintf that uses a mt string that resides in program memory 22 9 3 27 int sprintf char x s const char x _ fmt Variant of printf that sends the formatted characters to string s 22 9 3 28 intsprintf P char x 5 const char x fmt Variant of sprintf that uses a fmt string that resides in program memory Generated on Thu May 19 2011 13 29 12 for avr libc by Doxygen 22 9 lt stdio h gt Standard IO facilities 195 22 9 3 29 intsscanf const char x buf const char x _ fmt The function sscanf performs formatted input reading the input data from the buffer pointed to by buf See vfscanf for details 22 9 3 30 intsscanf P const char buf const char x fmt Variant of sscanf using a fmt string in program memory 22 9 3 31 int ungetc int c FILE _ stream The ungetc function pushes the character c converted to an unsigned char back onto the input stream pointed to by st ream The pushed back character will be returned by a subsequent read on the stream Currently only a single character can be pushed back onto the stream The ungetc function returns the character pushed back after the conversion or EOF if the operation fails If the value of the argument c character equals EOF the operation will fail and the stream will remain unchanged 22 9 3 32 int vfprintf FILE _ stream const char fmt va list

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