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avr-libc Reference Manual

1. Variant of scanf where fmt resides in program memory Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 87 6 19 3 25 int snprintf char __s size_t__n const char __fmt Like sprintf but instead of assuming s to be of infinite size 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 6 19 3 26 snprintf_P char __s size_t__n const char _ fmt Variant of snprintf that uses a fmt string that resides in program memory 6 19 3 27 int sprintf char __s const char fmt Variant of printf that sends the formatted characters to string s 6 19 3 28 int sprintf_P char __s const char _ fmt Variant of sprint f that uses fmt string that resides in program memory 6 19 3 29 int sscanf const char x __ buf const char The function sscanf performs formatted input reading the input data from the buffer pointed to by buf See vfscanf for details 6 19 3 30 int sscanf_P const char x __buf const char Variant of sscanf using a fmt string in program memory 6 19 3 31 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 stream T
2. 204 8 3 25 Why are many interrupt flags cleared by writing a logical 17 205 8 3 26 Why have programmed fuses the bit value 0 206 8 3 27 Which AVR specific assembler operators are available 206 8 3 28 Why are interrupts re enabled in the middle of writing the stack i CRM m 206 8 3 29 Why are there five different linker scripts 207 co Hino o PP 207 841 UCC asm Statement oso o x m RR RERO 208 842 Assembler Code 222222222222 xm s 210 8 4 3 Inputand Output Operands ss n 210 SAA D p o ALD 214 8 45 Assembler Macros 216 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen CONTENTS vii 8 5 8 6 8 7 8 8 4 6 CStib Functions s o edos ee andi a eee 217 847 C Names Used in AssemblerCode 218 Pa MM meme 219 UM mar ree 219 5 5 1 ili I DN 219 8 5 2 Internal vs external RAM 220 85 3 Timablesformallec 4 a abe o ER 221 8 54 Implementation details 222 Release Numbering and Methodology 224 8 6 1 Release Version Numbering Scheme 224 6 2 Releasing AVR Libe lt 221231 ee eb ee sk m Rs 224 Memory Sections 4 1 104 23 4 4 640505 eR RE S 227 The dest Secho 222022225 5555 eS wn 227 Se The gee SECNOM 220522525255 s ka 228 Bio The 222222222222 V AMW A Ss 228 8 74 The prom Section s
3. long int val char x __s int _ radix Convert a long integer to a string The function Itoa converts the long integer value 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 20 lt stdlib h gt General utilities 99 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 6 20 4 15 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 6 20 4 16 void qsort void x __ base size_t __nmemb size_t __ size compa
4. funsigned char Make any unqualfied char type an unsigned char Without this option they default to a signed char 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 8 10 2 Options for the assembler avr as 8 10 2 1 Machine specific assembler options e mmcu architecture mncu 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 246 e mmall opcodes Turns off opcode checking for the actual MCU type and allows any possible AVR opcode to be assembled 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 deb
5. 43 lt ermo b gt System 2 22 2 22 45 6 14 1 Detailed Description 4 lt o s sis SH 93 99 ee RR 45 6 14 2 Define Documentation 45 lt inttypes h gt Integer Type conversions 46 6 15 1 Detailed DescripHon lt e lt spes ppa gd o ba s 3 ku 46 6 15 2 Define Documentation 49 6 15 3 Typedef Documentation 57 lt math h gt Mathematics 58 6 16 1 Detailed Description s oe secre 2 x Sed du wee es 58 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen CONTENTS iii 6 20 621 6 22 0 23 6 24 6 16 2 Define Documentation 59 6 16 3 Function 59 9 Non local gale e ce ecoa Bes BORE 62 6 17 1 Detaled Description 222 2222 2 62 6 17 2 Function Documentation 63 lt stdint h gt Standard Integer Types 64 6 18 1 Detailed Description lt e e s sis sss xXx gt 64 6 18 2 Define Documentation 68 6 18 3 Typedef Documentation v 24 44 0855 e EGG 73 lt stdio h gt Standard TO facilities os oss or ba Re 75 6 19 1 Detailed Description 75 6 19 2 Define Documentation ag i eas ret i a S 80 6 19 3 Function Documentation 83 General mies us x9 m RR e 4 94 6 20 1 Detaled Description 222
6. Assume int to be an 8 bit integer Note that this is not really supported by avr libc so it should normally not be used The default is to use 16 bit integers e 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 e mcall prologues 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 space at the cost of a slightly increased execution time e minit stack nnnn Set the initial stack pointer to nnnn By default the stack pointer is initialized to the symbol __stack which is set to RAMEND by the run time initialization code e mtiny stack Change only the low 8 bits of the stack pointer e mno tablejump 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 short calls Use rjmp rcall limited range on gt 8K devices On avr2 and avr4 architec tures less than 8 KB or flash memory th
7. ISR to handle timer 175 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 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 31 more sophisticated project 164 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 6 31 3 4 Part 4 Auxiliary functions The function handle mcucsr uses two attribute declarators to achieve specific goals First it will instruct the com piler to place the generated code into the init3 section of the output Thus it will be come 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 trigge
8. avr gcc g mmcu atmega8 o demo elf demo o Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 149 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 6 30 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 objdump 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 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
9. define INT8 MAX Ox7f define INT8 MIN INT8_MAX 1 define 8 MAX CONCAT INT8 MAX U 2U 1U define INTI6 MAX Ox7fff define INTI6 MIN 6 MAX 1 define UINTI6 MAX CONCAT INT16 MAX U 2U 1U define INT32 MAX Ox7fffffffL define INT32 MIN CCINT32 MAX IL define UINT32 CONCAT INT32 MAX U 2UL 1UL define INT64 MAX OXx7fffffffIfffffIfLL define INT64 MIN INT64 MAX ILL define UINT 4 CONCAT INT64 MAX U x 2ULL 1ULL Limits of minimum width integer types define INT LEAST8 MAX 8 MAX define INT LEAST8 MIN INT8 MIN define UINT_LEAST8 MAX UINT8 MAX define INT LEASTI6 MAX INTI6 MAX Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 65 define INT_LEAST16_MIN INT16_MIN define UINT_LEAST16_MAX UINT16_MAX define 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 MAX 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
10. Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 190 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 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 S compiler option seems to be warranted Back to FAQ Index 8 3 8 Shouldn t I 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 code 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
11. arbitration lost in SLA RW general call received ACK returned 6 25 2 16 define TW_SR_ARB_LOST_SLA_ACK 0x68 arbitration lost in SLA RW SLA W received ACK returned 6 25 2 17 define TW_SR_DATA_ACK 0x80 data received ACK returned 6 25 2 18 define TW_SR_DATA_NACK 0x88 data received NACK returned 6 25 2 19 define TW_SR_GCALL_ACK 0x70 general call received ACK returned 6 25 2 20 define TW_SR_GCALL_DATA_ACK 0x90 general call data received ACK returned 6 25 2 21 define TW_SR_GCALL_DATA_NACK 0x98 general call data received NACK returned 6 25 2 22 define TW_SR_SLA_ACK 0x60 SLA W received ACK returned 6 25 2 23 define TW SR STOP 0xA0 stop or repeated start condition received while selected 6 25 2 24 define TW ST LOST SLA 0xB0 arbitration lost in SLA RW SLA R received ACK returned Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 122 6 25 2 25 define TW ST DATA 0xB8 data transmitted ACK received 6 25 2 26 define TW ST DATA NACK 0xC0 data transmitted NACK received 6 25 2 27 define TW ST LAST DATA 0xC8 last data byte transmitted ACK received 6 25 2 28 TW ST SLA 0xA8 SLA R received ACK returned 6 25 2 29 define TW START 0x08 start condition transmitted 6 25 2 30 define STATUS TWSR amp TW STATUS MASK TWSR masked by TW STATUS MASK 6 25 2 31 define TW STATUS
12. read word near instead of pgm read byte far or 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 instructions 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 20 Defines define PROGMEM __ATTR_PROGMEM__ define PSTR s const PROGMEM char x s define pgm read byte near address short LPM uint16 t address short define pgm_read_word_near address_short LPM word uint16 t address short define pgm_read_dword_near address_short LPM dword uint16 t address_short define pgm_read_byte_far address_long _ ELPM uint32 t address long define pgm_read_word_far address_long __ELPM_word uint32_ t address_long define pgm_read_dword_far address_long ELPM dword uint32 t address long define read
13. 8 7 5 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 section noinit Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 7 Memory Sections 229 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 W1 section start noinit 0x802000 to the 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 dox for writing linker scripts 8 7 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
14. Upload the tarball to savannah Update the NEWS file and commit to cvs Add Changes since avr libe lt major gt _ lt minor gt _ lt patch gt 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 Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 7 Memory Sections 227 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 i set version to 1 0 1 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 a ci ib EKE set version to 1 1 90 lt date gt i set version to 1 2 cvs tag avr libc 1_2 release t cvs tag avr libc 2 0 branchpoint set version to 2 1 0 lt date gt t Figure 9 Release tree 8 7 Memory Sections Remarks Need to list all the sections which are available to the avr Weak Bindings FIXME need to discuss the weak directive The following describes the various sections available 8 7 1 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 sect
15. 21 avr libc Modules Here is a list of all modules Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 2 1 avr libc Modules 6 lt assert h gt Diagnostics 8 avr boot h gt Bootloader Support Utilities 9 lt avr eeprom h gt EEPROM handling 15 lt avr io h gt AVR device specific IO definitions 18 lt avr pgmspace h gt Program Space String Utilities 19 lt avr power h gt Power Reduction Management 28 lt avr sleep h gt Power Management and Sleep Modes 32 lt avr version h gt avr libc version macros 34 lt avr wdt h gt Watchdog timer handling 36 lt compat deprecated h gt Deprecated items 39 lt compat ina90 h gt Compatibility with IAR EWB 3 x 42 lt ctype h gt Character Operations 42 lt errno h gt System Errors 45 lt inttypes h gt Integer Type conversions 46 lt math h gt Mathematics 58 lt setjmp h gt Non local goto 62 lt stdint h gt Standard Integer Types 64 lt stdio h gt Standard IO facilities 75 lt stdlib h gt General utilities 94 lt string h gt Strings 103 lt util crc16 h gt CRC Computations 112 lt util delay h gt Busy wait delay loops 116 lt util parity h gt Parity bit generation 117 lt util twi h gt TWI bit mask definitions 118 lt avr interrupt h gt Interrupts 122 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 3 avr libc Hierarchical Index 7 lt avr sfr_defs h gt Special function registers 137 Additional notes from lt avr sf
16. Introduction to the Standard IO facilities This file declares the standard IO facili ties that are implemented in 1 Due to the nature of the underlying hardware only a limited subset of standard IO is implemented There is no actual file implementa tion available so only device IO can be performed 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 76 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 whi
17. 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 documentation 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 141 r24 lo8 pm somefunc ldi r25 hi8 pm somefunc call something This passes the address of function somefunc as the first parameter to function something 8 3 Frequently Asked Questions 8 3 1 FAQ Index 1 My program doesn t recognize a variable updated within an interrupt routine Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 186 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 xe 29001 SO R I get undefined reference to for functions like sin How to permanently bind a variable to a regist
18. 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 198 Back to FAQ Index 8 3 15 How do I 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 include lt avr pgmspace h gt PGM_P array 2 PROGMEM Poo Bar 1 int main void char 32 stropy P buf array 1 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 pgmspace h const char foo PROGMEM Foo const char bar PROGMEM Bar PGM P array 2 PROGMEM foo bar 1 int main void char 32 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 199 26 2e 00
19. avr objcopy j eeprom change section Ima eeprom 0 ihex demo elf demo eeprom hex The resulting demo_eeprom hex file contains which is an empty hex file which is expected since we didn t define any EEPROM variables Starting with version 2 17 of the GNU binutils the com mand 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 6 30 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 GNU version of make PRG demo OBJ demo o Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 A simple project 156 MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET M
20. 22 2 gt 94 6 20 2 Define Documentation 95 6 20 3 Typedef Documentation lt ss so socs crea emro 95 6 20 4 Function 96 6 20 5 Variable Documentation 103 L p CDD Tm 103 6 21 1 Detailed Description se lt c se segiteni m sk 5 103 621 2 Define Documentation c9 ooo 9x Rs 105 6 21 3 Function Documentation 105 SutilcreJ h CRC Computations 1 3 545 545 54886 112 6 22 1 Detaled Description 112 6 22 2 Function Documentation o s s me o Rn 113 util delay h Busy wait delay 116 6 23 1 Detaled Description lt sacs om cx e m d N 4 Rem Rn 116 6 23 2 Function Documentation gt o s eec s ecoa m ee 116 lt util parity h gt Parity 117 6 24 1 Detailed Description gt lt e secre sua Ea sa wea eS 117 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen CONTENTS iv 0 25 6 26 6 27 6 28 6 29 6 24 2 Define Documentation 118 lt util twi h gt TWI bit mask definitions 118 6 25 Detaled escripman 22222422455 9405 v RES 118 6 25 2 Define Documentatl l s so emear rip sewep a 119 cavrantermpt h Intertupts 22 122 6 26 1 Detailed Description xoxo o n 122 626 2 Deine Documentation cos ocs pss 85 54 ER 136 lt avr sfr
21. 6 15 2 91 define SCNxFAST16 x hexadecimal scanf format for uint_fast16_t 6 15 2 92 define SCNxFAST32 Ix hexadecimal scanf format for uint_fast32_t 6 15 2 93 define SCNxLEAST16 x hexadecimal scanf format for uint_least16_t 6 15 2 94 define SCNxLEAST32 Ix hexadecimal scanf format for uint_least32_t 6 15 2 95 define SCNxPTR SCNx16 hexadecimal scanf format for uintptr_t 6 15 3 Typedef Documentation 6 15 3 1 typedef int32_t int_farptr_t signed integer type that can hold a pointer gt 64 KB 6 15 3 2 typedef uint32_t uint_farptr_t unsigned integer type that can hold a pointer gt 64 KB Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 16 lt math h gt Mathematics 58 6 16 lt math h gt Mathematics 6 16 1 Detailed Description include lt math h gt This header file declares basic mathematics constants and functions Note In order to access the functions delcared herein it is usually also required to addi tionally link against the library 1ibm a See also the related FAQ entry Defines define M PI 3 141592653589793238462643 define M SORT2 1 4142135623730950488016887 Functions double cos double x __ ATTR CONST double fabs double ATTR CONST double fmod double __x double __y CONST double modf double __ value double double sin double __x CONST double sqrt double x ATTR_CONST double tan double x ATTR CONST
22. 8 3 Frequently Asked Questions 196 f 80 81 1d r24 Z fo 86 2b 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 data sheet 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 0 0 IIg 88 in r24 0x18 24 11e 80 6f ori r24 OxF0 240 120 88 bb out 0x18 r24 24 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 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 Seehttp mail nongnu org archive html a
23. Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 124 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 instructions inside the compiler generated function prologue to run with global in terrupts disabled The compiler can be instructed to insert an SEI instruction right at the beginning of an interrupt handler by declaring the handler the following way void XXX_vect void __attribute__ interrupt void XXX_vect void where XXX_vect is the name of a valid interrupt vector for the MCU type in question as explained below Chosing the vector Interrupt vector names 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
24. avr_pgmspace 26 strncpy avr_string 110 strncpy_P avr_pgmspace 26 strnlen avr_string 110 strnlen_P avr_pgmspace 27 strrchr avr_string 110 strrev avr_string 111 strsep avr_string 111 strstr avr_string 111 strstr_P avr_pgmspace 27 strtod avr_stdlib 100 strtok_r avr_string 112 strtol avr_stdlib 101 strtoul avr_stdlib 101 strupr avr_string 112 supported devices 2 tan avr_math 61 tanh avr_math 62 timer_enable_int deprecated_items 42 toascii ctype 44 tolower ctype 45 tools optional 233 tools required 233 toupper ctype 45 TW_BUS_ERROR util_twi 119 TW_MR_ARB_LOST util_twi 119 TW_MR_DATA_ACK util_twi 119 TW_MR_DATA_NACK util_twi 120 TW_MR_SLA_ACK util_twi 120 TW_MR_SLA_NACK util_twi 120 TW_MT_ARB_LOST util_twi 120 TW_MT_DATA_ACK util_twi 120 TW_MT_DATA_NACK util_twi 120 TW_MT_SLA_ACK util_twi 120 TW_MT_SLA_NACK util_twi 120 TW_NO_INFO util_twi 120 TW_READ Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 267 util_twi 120 TW_REP_START util_twi 120 TW_SR_ARB_LOST_GCALL_ACK util_twi 121 TW_SR_ARB_LOST_SLA_ACK util_twi 121 TW_SR_DATA_ACK util_twi 121 TW_SR_DATA_NACK util_twi 121 TW_SR_GCALL_ACK util_twi 121 TW_SR_GCALL_DATA_ACK util_twi 121 TW_SR_GCALL_DATA_NACK util_twi 121 TW_SR_SLA_ACK util_twi 121 TW_SR_STOP util_twi 121 TW_ST_ARB_LOST_SLA_ACK util_twi 121 TW_ST_DATA_ACK util_twi
25. define INT FAST64 MAX INT64 MAX define INT FAST64 MIN INT64 MIN define UINT FAST64 MAX UINT64 MAX 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 define INTMAX MAX INT64 MAX define INTMAX MIN INT64 MIN define UINTMAX MAX UINT64 MAX Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 66 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 define PTRDIFF MIN INT16 MIN define SIG ATOMIC MAX INT8 MAX 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 define INT16_C value value define UINT16_C value _ CONCAT value U define INT32_C value _ CONCAT value L define UINT32_C value _ CONCAT value UL define INT64_C value _ CONCAT value LL define UINT
26. double floor double x CONST double ceil double __x CONST double frexp double value int exp double ldexp double x int exp CONST double exp double __x _ ATTR CONST double cosh double x ATTR CONST double sinh double x ATTR CONST double tanh double x CONST double acos double x ATTR CONST double asin double x ATTR CONST double atan double x ATTR CONST double atan2 double __y double x CONST double log double x ATTR CONST double log10 double x __ ATTR CONST _ double pow double x double y CONST int isnan double x ATTR CONST int isinf double x ATTR CONST double square double __ x __ ATTR CONST Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 16 lt math h gt Mathematics 59 6 16 2 Define Documentation 6 16 2 1 define 3 141592653589793238462643 The constant pi 6 16 2 2 define M_SQRT2 1 4142135623730950488016887 The square root of 2 6 16 3 Function Documentation 6 16 3 1 double acos double __x 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 6 16 3 2 double asin double __x The asin function computes the principal value of the arc sine of x The returned value is
27. 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 Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 26 6 5 4 7 size t strlcpy_P char dst 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 Returns The strlcpy_P function returns strlen src If retval gt siz truncation occurred 6 5 4 8 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 The strlen function returns the number of characters in src 6 5 4 9 int strncasecmp_P const char 57 P s2 size Compare two strings ignoring case The strncasecmp 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 s2 A pointer to a string in the devices Flash n The maximum number of bytes to compare Returns The strcasecm
28. include stdlib h This file declares some basic C macros and functions as defined by the ISO standard plus some AVR specific extensions Data Structures struct div t struct ldiv t Non standard i e non ISO C functions define RANDOM MAX Ox7FFFFFFF char Itoa long int val char __s int radix char utoa unsigned int val char __s int __radix char ultoa unsigned long int __ val char __s int __radix long random void void srandom unsigned long __ seed long random_r unsigned long ctx char itoa int __ val char __s int radix Defines define RAND_MAX 0x7FFF Typedefs e typedef int x __compar_fn_t const void const void Functions e _ inline__ void abort void _ ATTR_NORETURN__ intabs int 1 CONST long labs long _ 1 ATTR CONST Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 20 lt stdlib h gt General utilities 95 __ size int __compar const void const void CONST__ CONST__ void qsort void base size_t __nmemb size t size compar fn t void bsearch const void __ key const void base size t nmemb size t div t div int _ num int _ denom divmodhid ATTR t ldiv long num long __denom __asm__ __divmodsi4 ATTR compar long strtol const char nptr char x __endptr int base inline__ long atol const char x__nptr PURE __inline
29. 6 19 lt stdio h gt Standard IO facilities 83 6 19 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 6 19 2 19 define stdout __iob 1 Stream that will be used as an output stream by the simplified functions that don t take a stream argument The first stream opened with write intent using fdevopen will be assigned to both stdin and stderr 6 19 3 Function Documentation 6 19 3 1 void clearerr FILE stream Clear the error and end of file flags of st ream 6 19 3 2 fclose FILE x __ 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 6 19 3 3 fdevopen int x char FILE 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
30. 6 21 3 27 char x strstr const char 57 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 22 lt util crc16 h gt CRC Computations 112 Returns The strstr 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 sl 6 21 3 28 char x strtok_r char x string const char delim char xx last Parses the string s into tokens strtok_r parses the string s 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 70 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 15 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 6 21 3 29 char strupr char x string Convert a string to upper case The strupr function will convert a string to upper case Only the lower case alphabetic characters a z
31. 8 4 6 CStub Functions Macro definitions will include the same assembler code whenever they are referenced This may not 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 uint16_t cnt asm volatile An L_dli n t mov 0 2 n t mov B0 B2 Xn IL 412 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 218 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 uint16_t inw uint8 t port uint16_t result asm volatile in 200 41 Manje in 0 1 1 r result I SFR IO ADDR port return result Note inw is supplied by avr libc 8 4 7 C Names Used in Assembler Code By default AVR GCC uses the same symbolic names of func
32. AT90CANGA ATmegal03 ATmegal28 ATmega16 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtinyl3 15 AT tiny26 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 ANALOG_ SIG_ Analog Com AT90PWM3 AT90PWM2 COMP_0_vect COMPARATOR parator 0 ANALOG_ SIG_ Analog Com AT90PWM3 AT90PWM2 COMP_1_vect COMPARATORI parator 1 ANALOG_ SIG_ Analog Com AT90PWM3 AT90PWM2 COMP_2_vect COMPARATORE parator 2 ANALOG_ SIG_ Analog Com AT90CANI28 AT90CAN32 AT90CANGA COMP_vect COMPARATOR parator ATmegal03 ATmegal28 ATmegal65 AT megal69 ATmega325 ATmega3250 AT mega329 ATmega3290 ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmegal68 ATmega48 AT mega88 ATmega640 ATmegal280 AT megal281 ATmega324 ATmegal64 AT mega644 ANA SIG Analog Com 9051200 AT90S2313 AT90S2333 COMP_vect COMPARATOR parator AT90S4414 AT90S4433 AT90S4434 AT90S8515 419058535 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 AT mega8515 ATmega8535 ATtiny11 ATtiny12 ATtiny13 ATtiny15 ATtiny2313 ATtiny26 ATtiny28 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 AT
33. AT90CANGA RX_vect UARTO_ Complete ATmegal28 ATmegal65 ATmegal69 AT RECV mega325 ATmega329 ATmega64 AT mega645 ATmega649 ATmega640 AT megal280 ATmegal281 ATmega324 AT megal64 ATmega644 USARTO SIG USARTO Tx ATmegal62 TXC vect USARTO Complete TRANS USARTO SIG USARTO Tx AT90CANI28 AT90CAN32 AT90CAN64 TX vect UARTO Complete ATmegal28 ATmegal65 ATmegal69 AT TRANS mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 USARTO SIG USARTO Data AT90CANI28 AT90CAN32 AT90CANGA UDRE vect UARTO Register Empty ATmegal28 ATmegal62 ATmegal65 AT DATA megal69 ATmega325 ATmega329 AT mega64 ATmega645 ATmega649 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 USARTI SIG USARTI Rx ATmegal62 RXC vect USARTI Complete RECV USARTI SIG USARTI Rx AT90CANI28 AT90CAN32 AT90CANGA RX_vect UARTI Complete ATmegal28 ATmega64 ATmega640 AT RECV megal280 ATmegal281 ATmega324 AT megal64 ATmega644 USARTI SIG USARTI Tx ATmegal62 TXC vect USARTI Complete TRANS Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 135 vect Vector name Old vector Description Applicabl
34. ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmegal64P ATmega324P ATmega644P AT mega644 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega406 AT90PWM2 AT90PWM3 AT90USB646 AT90USB647 AT9OUSB 1286 AT90USB 1287 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 11 lt compat deprecated h gt Deprecated items 39 6 10 2 11 define WDTO 500MS 5 See WDTO_15MS 6 10 2 12 define WDTO_60MS 2 WDTO_15MS 6 10 2 13 define WDTO_8S 9 See WDTO_15MS Note This is only available on the ATtiny2313 ATtiny24 AT tiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmegal64P ATmega324P ATmega644P AT mega644 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega406 AT90PWM2 AT90PWM3 AT90USB646 AT90USB647 AT90USB1286 AT90USB1287 6 11 lt compat deprecated h gt Deprecated items 6 11 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 include lt compat deprected h gt 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 Allowi
35. Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 147 F X bog opo 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 v 1 6 2 3 2006 01 05 21 33 08 joerg wunsch Exp include inttypes h include lt avr io h gt include lt avr interrupt h gt include lt avr sleep h gt include iocompat h Note 1 enum UP DOWN ISR TIMER1_OVF_vect Note 2 static uint16_t pwm x Note 3 static uint8_t direction switch direction Note 4 case UP if pwm direction DOWN break case DOWN if pwm 0 direction UP break OCR pwm x Note 5 void ioinit void x Note 6 x Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys TCCRIA TIMER1_PWM_INIT x Start timer 1 x TCCRIA TCCRIB could actually be the same register so x take care to not clobber it TCCRIB T
36. 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 ignore the warning If you are paranoid execute a 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 8 3 25 Why are many interrupt flags cleared by writing a logical 1 Usually each interrupt has its 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 SJART 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 hav
37. 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 210 8 4 22 Assembler Code You can use the 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 The 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 SP H Stack pointer high byte at address 0x3E VSP Stack pointer low byte at address 0x3D tmp reg Register rO used for temporary st
38. 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 6 31 3 2 Part 2 Variable definitions The intflags 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 application 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 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 Similarly the variable mcucsr is kept in the noinit section in order to prevent it from being cleared upon application startup 6 31 3 3 Part 3 Interrupt service routines
39. consider using the FFS macro instead 6 21 3 2 int ffsl long const Same as ffs for an argument of type long 6 21 3 3 int ffsll long Jong const Same as ffs for an argument of type long long 6 21 3 4 void x 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 mem ory area dest stopping when the character val is found Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 106 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 6 21 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 the given memory area 6 21 3 6 int memcmp const void 57 const void 52 size t len Compare memory areas The memcmp 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
40. lt sst erea o su t mm Rs 228 855 Che mom Sechan 222222222522 2552252 228 870 The MHN Sections p coce n e cec bos ks 229 872 The HIN Sections ea Nk Rx Re 230 8 7 8 Using Sections in Assembler 231 812 Using Sectionsin C Code scce enpas ud 9 o xs 231 Installing the GNU Tool Chain 232 88 1 Required ooh go saba RR RR 233 55 OnBiss Poole s s co cc o 9 S 4 B 233 8 8 3 GNU Binutils for the AVR 1 234 884 GCC forthe AVR target gt s eco 12 RR 235 93 JAVICLIBO cee s sd ur ba n ki 236 bo ouo ska si EES sanna 236 887 GDB iorthe AVE target oc 14 kkk kab b bud kk k k 236 5 5 8 SIM E 237 899 e aie RU n dud ee UE aes 237 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 1 AVR Libc 1 8 9 Using the avrdude 238 8 10 Using the GNU Tale 22222222229 UE RUE X 239 8 10 1 Options for the compiler 240 8 10 2 Options for the assembler 245 8 10 3 Controlling the linker avr ld 247 Ni JE nee 249 S12 Deprecated LISE lt o a do Rs 249 1 AVRLibc 11 Introduction The latest version of this document is always available from http savannah nongnu org projects avr libc The AVR Libc package provides a subset of the standard
41. 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 devices 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 Vcc R2 is needed Its value should be about 150 Ohms When operating the circuit at 3 V it can still be omitted though 6 30 2 The Source Code
42. 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 setup 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 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 ATmegal6 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 pag
43. 121 TW_ST_DATA_NACK util_twi 122 TW_ST_LAST_DATA util_twi 122 TW_ST_SLA_ACK util_twi 122 TW_START util_twi 122 TW_STATUS util_twi 122 TW_STATUS_MASK util_twi 122 TW_WRITE util_twi 122 UINT16_C avr_stdint 71 UINT16_MAX avr_stdint 71 uint16_t avr_stdint 74 UINT32_C avr_stdint 71 UINT32_MAX avr_stdint 71 uint32_t avr_stdint 74 UINT64_C avr_stdint 71 UINT64_MAX avr_stdint 71 uint64_t avr_stdint 74 UINT8_C avr_stdint 71 UINT8_MAX avr_stdint 72 uint8_t avr_stdint 74 uint_farptr_t avr_inttypes 57 UINT_FAST16_MAX avr_stdint 72 uint_fast16_t avr_stdint 74 UINT_FAST32_MAX avr_stdint 72 uint_fast32_t avr_stdint 74 UINT_FAST64_MAX avr_stdint 72 uint_fast64_t avr_stdint 74 UINT_FAST8_MAX avr_stdint 72 uint_fast8_t avr_stdint 75 UINT_LEAST16_MAX avr_stdint 72 uint_least16_t avr_stdint 75 UINT_LEAST32_MAX avr_stdint 72 uint_least32_t avr_stdint 75 UINT_LEAST64_MAX avr_stdint 72 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 268 uint_least64_t avr_stdint 75 UINT_LEAST8_MAX avr_stdint 72 uint_least8_t avr_stdint 75 UINTMAX_C avr_stdint 72 UINTMAX_MAX avr_stdint 72 uintmax_t avr_stdint 75 UINTPTR_MAX avr_stdint 73 uintptr_t avr_stdint 75 ultoa avr_stdlib 102 ungetc avr_stdio 87 Using the standard IO facilities 165 util_crc _crc16_update 113 _crc_ccitt_update 114 _crc_ibutton_update 114 _crc_x
44. 2 3 define wdt reset 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 10 lt avr wdt h gt Watchdog timer handling 38 6 10 24 define WDTO 120MS 3 See WDTO 15MS 6 10 2 5 ftdefine 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 6 10 2 6 define WDTO 1S 6 See WDTO 15MS 6 10 2 7 ftdefine WDTO 250MS 4 See WDTO 15MS 6 10 2 8 define WDTO 287 See WDTO 15MS 6 10 2 9 define WDTO 30MS 1 See WDTO 15MS 6 10 2 10 define WDTO 458 See WDTO_15MS Note This is only available on the ATtiny2313 ATtiny24 AT tiny44 ATtiny84
45. 45 6 13 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 1f you use this function This function will convert accented letters into random characters 6 13 2 15 int tolower int c Converts the letter c to lower case 1f possible 6 13 2 16 int toupper int c Converts the letter c to upper case if possible 6 14 lt errno h gt System Errors 6 14 1 Detailed Description include lt errno h gt Some functions in the library set the global variable 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 Defines define EDOM 33 define ERANGE 34 6 14 2 Define Documentation 6 14 2 1 define EDOM 33 Domain error Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 46 6 14 2 2 define ERANGE 34 Range error 6 15 lt inttypes h gt Integer Type conversions 6 15 1 Detailed Description include lt inttypes h gt This header file includes the exact
46. 86 inb deprecated_items 41 inp deprecated_items 41 installation 232 installation avarice 237 installation avr libc 236 installation avrdude 236 installation avrprog 236 installation binutils 234 installation gcc 235 Installation gdb 236 installation simulavr 237 INT16_C avr_stdint 68 INT16_MAX avr_stdint 68 INT16_MIN Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 260 avr_stdint 68 int16_t avr_stdint 73 INT32 C avr_stdint 68 INT32_MAX avr_stdint 68 INT32_MIN avr_stdint 68 int32_t avr_stdint 73 INT64_C avr_stdint 68 INT64_MAX avr_stdint 68 INT64_MIN avr_stdint 68 int64_t avr_stdint 73 INT8_C avr_stdint 68 INT8_MAX avr_stdint 68 INT8_MIN avr_stdint 68 int8_t avr_stdint 73 int_farptr_t avr_inttypes 57 INT_FAST16_MAX avr_stdint 69 INT_FAST16_MIN avr_stdint 69 int_fast16_t avr_stdint 73 INT_FAST32_MAX avr_stdint 69 INT_FAST32_MIN avr_stdint 69 int_fast32_t avr_stdint 73 INT_FAST64_MAX avr_stdint 69 INT_FAST64_MIN avr_stdint 69 int_fast64_t avr_stdint 73 INT_FAST8_MAX avr_stdint 69 INT_FAST8_MIN avr_stdint 69 int_fast8_t avr_stdint 73 INT_LEAST16_MAX avr_stdint 69 INT_LEAST16_MIN avr_stdint 69 int_least16_t avr_stdint 73 INT_LEAST32_MAX avr_stdint 69 INT_LEAST32_MIN avr_stdint 70 int_least32_t avr_stdint 73 INT_LEAST64_MAX avr_stdint 70 INT_LEAST64_MIN avr_stdint 70 int_least64_t avr
47. AT90CANI28 OVF vect OVERFLOW2 Overflow AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l AT megal62 ATmegal63 ATmegal65 AT megal69 ATmega32 ATmega323 AT mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT mega8 ATmega8535 ATmegal68 AT mega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega324 AT megal64 ATmega644 TIMER3 SIG INPUT Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA CAPT_vect CAPTURE3 Capture Event ATmegal28 ATmegal62 ATmega64 AT mega640 ATmegal280 ATmegal281 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPA_vect OUTPUT_ Compare Match ATmegal28 ATmegal62 ATmega64 COMPARE3A A mega640 ATmegal280 ATmegal281 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPB_vect OUTPUT_ Compare Match ATmegal28 ATmegal62 ATmega64 AT COMPARE3B B mega640 ATmegal280 ATmegal281 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPC_vect OUTPUT_ Compare Match ATmegal28 ATmega64 ATmega640 AT C mega1280 ATmegal281 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 133 Vector name Old vector Description Applicable for device name TIMER3_ SIG_ Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA OV
48. ATmega8535 vect USART_ Complete ATmegal68 ATmega48 ATmega88 AT TRANS tiny2313 SIG_UART_ TRANS USART_ SIG_ USART Data AT90PWM3 AT90PWM2 ATmegal6 AT UDRE_vect USART_ Register Empty mega32 ATmega323 ATmega3250 AT DATA SIG_ mega3290 ATmega6450 ATmega6490 AT UART_DATA mega8 ATmega8535 ATmegal68 mega48 ATmega88 ATtiny2313 USL SIG USI USI Overflow ATmegal65 ATmegal69 ATmega325 AT OVERFLOW OVERFLOW mega3250 ATmega329 ATmega3290 AT mega645 ATmega6450 ATmega649 AT mega6490 ATtiny2313 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 136 Vector name Old vector Description Applicable for device name USI_OVF_ SIG_USI_ USI Overflow ATtiny26 ATtiny24 ATtiny44 ATtiny84 vect OVERFLOW ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 USI_START_ SIG_USI_ USI Start Condi ATmegal65 ATmegal69 ATmega325 AT vect START tion mega3250 ATmega329 ATmega3290 AT mega645 ATmega6450 ATmega649 AT mega6490 2313 24 tiny44 ATtiny84 ATtiny45 ATtiny25 tiny85 ATtiny261 ATtiny461 ATtiny861 USI_STRT_ SIG_USI_ USI Start ATtiny26 vect START WDT_ SIG_ Watchdog Timer ATtiny2313 OVERFLOW_ WATCHDOG_ Overflow vect TIMEOUT SIG_WDT_ OVERFLOW WDT_vect SIG_WDT Watchdog Time AT90PWM3 AT90PWM2 ATmega406 SIG_ out Interrupt ATmegal68 A
49. C library for Atmel AVR 8 bit RISC microcontrollers 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 l1ists 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 describe
50. COMPAREO_ B TIMERO_ SIG_ Timer Counter0 AT90PWM3 AT90PWM2 COMP A OUTPUT Compare Match vect A SIG OUTPUT COMPAREO A TIMERO SIG Timer Counter0 AT90CAN128 AT90CAN32 AT90CANGA COMP_vect OUTPUT_ Compare Match ATmegal03 ATmegal28 ATmegal6 AT COMPAREO megal61 ATmegal62 ATmegal65 AT megal69 ATmega32 ATmega323 AT mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT mega8515 ATmega8535 TIMERO_ SIG_ Timer Counter0 AT90S2313 AT90S2323 AT90S2343 AT OVFO vect OVERFLOWO Overflow tiny22 ATtiny26 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 130 Vector name Old vector Description Applicable for device name TIMERO_ SIG_ Timer Counter0 AT90S1200 AT90S2333 AT90S4414 OVF_vect OVERFLOWO Overflow AT90S4433 AT90S4434 9058515 AT90S8535 AT90PWMS3 AT9IOPWM2 AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtinyl1 ATtinyl2 AT tiny15 ATtiny2313 ATtiny28 ATtiny261 ATtiny461 ATtiny861 TIMERI _ SIG
51. Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 avr libc Page Documentation 179 8 avr libc Page Documentation 8 1 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 Denis Chertykov denisc overta ru for making the AVR specific changes to the GNU tools Denis Chertykov and Marek Michalkiewicz marekm linux org pl for developing the standard libraries and startup code for AVR GCC 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 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 eric evcohs com for maintaining the WinAVR pack age and thus making the continued improvements to the Opensource 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 d
52. Id decimal printf format for int least32 t 6 15 2 9 define PRIdLEASTS d decimal printf format for int least8 t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 50 6 15 2 10 define PRIdPTR PRId16 decimal printf format for intptr t 6 15 2 11 define PRIi16 i integer printf format for int16_t 6 15 2 12 ffdefine PRIi32 li integer printf format for int32 t 6 15 2 13 define PRIi8 i integer printf format for int8 t 6 15 2 14 define PRIiFASTI6 i integer printf format for int_fast16_t 6 15 2 15 define PRIiFAST32 li integer printf format for int fast32 t 6 15 2 16 define PRIiFASTS i integer printf format for int fast8 t 6 15 2 17 define PRIILEASTI6 i integer printf format for int leastl6 t 6 15 2 18 define PRIILEAST32 li integer printf format for int least32 t 6 15 2 19 define PRIiLEASTS i integer printf format for int least8 t 6 15 2 20 define PRIiPTR PRIi16 integer printf format for intptr t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 51 6 15 2 21 define PRIo16 octal printf format for uint16_t 6 15 2 22 define PRIo32 lo octal printf format for uint32_t 6 15 2 23 define PRIo8 o octal printf format for uint8_t 6 15 2 24 define PRIoFAST16 octal printf format for uint_fast16_t 6 15 2
53. In other words the listing generated by this option reflects the actual code that the processor will run avr objdump h 5 demo elf gt demo lst Here s the output as saved in the demo 1st file demo elf file format elf32 avr Sections Idx Name Size VMA LMA File off Algn 0 text 000000de 00000000 00000000 00000074 2xx1 CONTENTS ALLOC LOAD READONLY CODE 1 bss 00000003 00800060 00800060 00000152 2xx0 ALLOC 2 stab 000007a4 00000000 00000000 00000154 2xx2 CONTENTS READONLY DEBUGGING 3 stabstr 00000658 00000000 00000000 000008 8 2xx0 CONTENTS READONLY DEBUGGING Disassembly of section text 00000000 lt __vectors gt 0 12 0 rjmp 36 0x26 lt __ctors_end gt 2 cO rjmp 216 Oxdc bad interrupt 4 6b cO rjmp 214 Oxdc bad interrupt 6 cO rjmp 212 Oxdc bad interrupt 8 69 cO rjmp 210 Oxdc interrupt a 68 cO rjmp 208 Oxdc bad interrupt 60 rjmp 206 Oxdc lt __bad_interrupt gt Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 150 e 66 0 rjmp 204 Oxdc lt __bad_interrupt gt 10 11 0 rjmp 34 0x34 lt __vector_8 gt 12 64 0 rjmp 200 Oxdc lt __bad_interrupt gt 14 63 0 rjmp 198 Oxdc lt __bad_interrupt gt 16 62 0 rjmp 196 Oxdc lt __bad_interrupt gt 18 61 0 rjmp 194 Oxdc lt __bad_interrupt gt la 60 0 rjmp 192 Oxdc lt __bad_interrupt gt Le
54. 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 LSB carry the prescaler bits on the newer ATmegas 6 25 2 32 define TW WRITE 0 SLA W address 6 26 lt avr interrupt h gt Interrupts 6 26 1 Detailed Description Note This discussion of interrupts was originally taken from Rich Neswold s document See Acknowledgments Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 123 Introduction to avr libe s interrupt handling It s nearly impossible to find compil ers 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 will 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 tagg
55. MAX largest value an uint least8 t can hold 6 18 2 55 UINTMAX_C value CONCAT value ULL define a constant of type uintmax t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 73 6 18 2 56 define UINTMAX MAX UINT64 MAX largest value an uintmax t can hold 6 18 2 57 UINTPTR MAX UINTI6 largest value an uintptr t can hold 6 18 3 Typedef Documentation 6 18 3 1 typedef signed int int16 t 16 bit signed type 6 18 3 2 typedef signed long int int32 t 32 bit signed type 6 18 3 3 typedef signed long long int int64 t 64 bit signed type 6 18 3 4 typedef signed char int8 t 8 bit signed type 6 18 3 5 typedef int16 tint fast16 t fastest signed int with at least 16 bits 6 18 3 6 typedef int32 t int fast32 t fastest signed int with at least 32 bits 6 18 3 7 typedef int64 t int fast64 t fastest signed int with at least 64 bits 6 18 3 8 typedef int8 t int fast8 t fastest signed int with at least 8 bits 6 18 3 9 typedef int16 tint least16 t signed int with at least 16 bits Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 74 6 18 3 10 typedef int32_t int_least32_t signed int with at least 32 bits 6 18 3 11 typedef int64_t int_least64_t signed int with at least 64 bits 6 18 3 12 typedef int8_t int_least8_t signed int with at least 8 b
56. Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 86 6 19 3 16 int fscanf_P FILE __ stream const char x fmt Variant of fscanf using a fmt string in program memory 6 19 3 17 size_t fwrite const void __ptr size_t __size size_t __nmemb FILE x _ 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 6 19 3 18 char gets char x __ str 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 6 19 3 19 int printf const char The function printf performs formatted output to stream stderr See vfprintf for details 6 19 3 20 int printf_P const char x Variant of print f that uses fmt string that resides in program memory 6 19 3 21 int puts const char x _ str Write the string pointed to by str and a trailing newline character to stdout 6 19 3 22 int puts_P const char x _ str Variant of puts where str resides in program memory 6 19 3 23 int scanf const char __fmt The function scanf performs formatted input from stream st din See vfscanf for details 6 19 3 24 int scanf_P const char
57. SE c0 rjmp 190 Oxdc lt __bad_interrupt gt le 5e c0 rjmp 188 Oxdc lt __bad_interrupt gt 20 5 0 rjmp 186 Oxdc lt __bad_interrupt gt 223 5660 rjmp 184 Oxdc bad interrupt 24 5b cO rjmp 182 Oxdc bad interrupt 00000026 ctors end 26 1124 eor rl rl 28 1f be out 0Ox3f rl g 63 2 cf 5 141 r28 Ox5F 95 2c d4 eO ldi r29 0x04 4 2e de bf out 0x3e r29 62 307 cd bf out 0x3d r28 61 32 4b cO rjmp 150 Oxca main 00000034 vector 8 enum UP DOWN J ISR TIMER1 OVF x Note 2 x 34 1f 92 push r1 363 0 92 push r0 38 Of b6 in 0 Ox8t 7 63 3a Of 92 push r0 3c 11 24 eor rl rl 2f 93 push r18 40 3 93 push r19 42 8f 93 push r24 static uintl6 t pwm Note 3 static uint8 t direction switch direction x Note 4 44 80 91 60 00 145 r24 0x0060 48 88 23 and r24 r24 4a 39 breq 14 Ox5a lt _SREG__ 0x1b gt 4c 81 30 cpi r24 0 01 1 4e b9 f0 breq 46 Ox7e lt __SREG__ 0x3f gt 50 20 91 61 00 145 r18 0x0061 54 30 91 62 00 145 19 0x0062 587 21 60 rjmp 66 Ox9c lt __SREG__ 0x5d gt case UP if pwm TIMER 20 91 61 00 145 r18 0x0061 30 91 62 00 145 r19 0x0062 62 2f SE subi r18 OxFF 255 64 4f sbci r19 OxFF 255 66 30 93 62 00 sts 0x0062 r19 6a 20 93 61 00 sts 0x0061 r18 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple proj
58. 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 uintl16 lt lt 8 hi8 crc uint8_t data gt gt 4 uint16 t data lt lt 3 6 22 2 3 static inline uint8 t crc ibutton update uint8 t crc uint8 t data static Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 22 lt util crc16 h gt CRC Computations 115 Optimized Dallas now Maxim iButton 8 bit CRC calculation Polynomial x 8 x 5 x4 1 0x8C Initial value 0x0 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 i lt 8 i if crc amp 0x01 crc crc gt gt 1 0x8C else crc gt gt 1 return crc 6 22 2 4 static _ inline uintl6_t _crc_xmodem_update uint16_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 uint16_t crc xmodem update uintl6_t crc uint8 t data int i crc crc uint16 t data lt lt 8 for i20 i 8 i if crc amp 0x8000 cre ere lt lt
59. Wl u vfprintf lprintr flt lm Limitations The specified width and precision can be at most 127 For floating point conversions trailing digits will be lost if a number close to DBL MAX is converted with a precision gt 0 6 19 3 33 int vfprintf P FILE stream const char fmt va list Variant of v printf that uses a fmt string that resides in program memory 6 19 3 34 int vfscanf FILE stream const char _ fmt va list Formatted input This function is the heart of the scanf family of functions Characters are read from st ream and processed in a way described by fmt Conver sion results will be assigned to the parameters passed via ap The format string mt 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 91 Most conversions skip leading white space before starting the actual conversion Conversions are introduced with the character Possible options can follow the e x indicating that the conversion sho
60. 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 al locator is compromised 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 5 Using malloc 223 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 When allocating 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 t
61. 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 r24 12 x 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 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
62. 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 to sleep but all peripheral clocks are still running and then call sleep_mode Unless it is the purpose to lock the CPU hard until a hardware reset interrupts need to be enabled at this point This macro automatically takes care to enable the sleep mode in the CPU before going to sleep and disable it again afterwards As this combined macro might cause race conditions in some situations the individual steps of manipulating the sleep enable SE bit and actually issuing the SLEEP in struction 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 Example include avr interrupt h include lt avr sleep h gt 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 interrupt could trigger it is
63. 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 7 Memory Sections 231 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 8 7 8 Using Sections in Assembler Code Example include lt avr io h gt section init1 ax progbits ldi r0 Oxff out _ IO ADDR PORTB out 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 8 7 9 Using Sections in C Code Example include lt avr io h gt void my_init_portb void __attribute__ naked __attribute__ section init3 void my_init_portb void PORTB Oxff DDRB Oxff Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 8 Installi
64. 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 W1 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 preferrably be placed into section init3 as the code in init2 ensures the internal regis ter zero reg is already cleared Back to FAQ Index 8 3 What is 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 189 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 a particular bit number as a byte value use the _BV mac
65. clock frequency in Hertz These functions operate on double typed arguments however when optimiza tion is turned on the entire floating point calculation will be done at compile time Note When using delay us delay ms the expressions passed as arguments to these functions shall be compile time constants otherwise the floating point cal culations to setup the loops will be done at run time thereby drastically increasing both the resulting code size as well as the time required to setup the loops Functions void delay loop 1 uint8 t count void delay loop 2 uintl6 t count void delay us double us void delay ms double __ms 6 23 2 Function Documentation 6 23 2 1 void delay loop 1 uint8 t count Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 624 lt util parity h gt Parity bit generation 117 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 6 23 2 2 void _delay_loop_2 uintl6 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 th
66. const void pointer ram void pointer eeprom size t n Write a block of n bytes to EEPROM address pointer eepromfrom pointer ram 6 3 3 5 void eeprom write byte uint8 t x addr uint8 t value Write a byte value to EEPROM address addr 6 3 3 6 void eeprom write word uint16 t addr uintl6 t value Write a word value to EEPROM address addr 6 4 lt avr io 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 spec ified by the mmcu compiler command line switch This is done by diverting to the appropriate file lt avr ioXXXX h gt which should never be included directly Some register names common to all AVR devices are defined directly within lt avr io h gt but most of the details come from the respective include file Note that this file always includes include lt avr sfr_defs h gt See lt avr sfr_defs h gt Special function registers for the details Included are definitions of the IO register set and their respective bit values as specified in the Atmel documentation Note that Atmel is not very consistent in its 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 are defined RAMEND A constant describing the last on chi
67. etc The public function 1cd_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 non blinking cursor enabled SRAM addresses are increasing so characters will be written left to right The public function 1 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
68. from ROM via P usually remains unnoticed since the compiler would then optimize the code for accessing array at compile time Back to FAQ Index Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 200 8 3 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 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 th
69. 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 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 character could not be sent to the device Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 84 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_FDEVOPEN_COMPAT_12 is declared before including lt stdio h gt a functio
70. in the range 0 pi radians A domain error occurs for arguments not in the range 1 1 6 16 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 0 pi radians A domain error occurs for arguments not in the range 1 1 6 16 3 4 double atan2 double __y double 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 If both x and y are zero the global variable errno is set to EDOM 6 16 3 5 double ceil double __x The ceil function returns the smallest integral value greater than or equal to x ex pressed as a floating point number 6 16 3 6 double cos double __x The cos function returns the cosine of x measured in radians Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 16 lt math h gt Mathematics 60 6 16 3 7 double cosh double __x The cosh function returns the hyperbolic cosine of x 6 16 3 8 double exp double __x The exp function returns the exponential value of x 6 16 3 9 double fabs double x The fabs function computes the absolute value of a floating point number x 6 16 3 10 double floor double x The floor function returns the largest integral value less than or equal to x expressed as a floating poi
71. including polling the busy flag so the R W line from the LCD controller needs to be connected Note that the LCD con Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 32 Using the standard IO facilities 167 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 on a single port are needed to connect the LCD yet all other ports are already partially in use port 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 6 32 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 hd44780 c Implementation of an HD44780 LCD display driver hd44780 h Interface declarations for the HD44780 driver lcd c Implementation of LCD character IO on top of the HD44780 driver lcd h Interface declarations for the LCD driver uart c Implementation of a character IO driver for the internal UART uart h Interface declarations for the UART driver 6 32 3 A code walkthrough 6 32 3 1 stdiodemo c As usual include files go first While conventionally system header files
72. 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 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 fdev_set_udata can be accessed inside 1cd_putchar using fdev_get_udata 6 32 3 7 uart h Public interface definition for the RS 232 UART driver much like in Icd h except there is now also a character input function available As RS 232 input is line buffered in this example the macro RX_BUF SIZE deter mines the size of that buffer 6 32 3 8 uart c This implements an stdio compatible RS 232 driver using AVR s standard UART or USART in asynchronous operation mode Both char acter output as well as character input operations are implemented Character output Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 32 Using the standard IO facilities 172 takes care of converting the internal newline n into its external representation carriage return line feed 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 Vr or newline n character is received from the terminal The line editing functions implemented are Vb back space or 1177 de
73. o e cs scs ss Se Re rx u 21 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen CONTENTS ii 6 6 6 7 6 8 6 9 6 12 6 13 6 14 6 5 3 Typedef Documentation 23 6 54 Function 24 lt avr power h gt Power Reduction Management 28 Additional notes from lt avr sfr_defs h gt 30 lt avr sleep h gt Power Management and Sleep Modes 32 6 5 1 Detailed Description lt 44 soe s o E 32 63 2 Defne Documentation 20 a e 85 554 og ER 4 33 6 8 3 Function 34 lt avr version h gt avr libc version macros 34 6591 Detailed Description lt lt eses creed kr SRR sku 34 6 9 2 Define Documentation 35 lt avr wdt h gt Watchdog timer handling 36 6 10 1 Detailed Description 2x ee ko 4 u kk wee CR 36 6 10 2 Define Documentation 22222222222 2 2 24 7 37 lt compat deprecated h gt Deprecated tems 39 6 11 1 Detailed Description 2 39 6 11 2 Define Documentation 40 6 41 3 Function 42 lt compat ina90 h gt Compatibility with IAR EWB3 x 42 Zetype h Character Operations 24 25 ea eee ede 42 6 13 1 Detailed Description se lt s pesset k b sku 42 6 13 2 Function
74. of any race condition that might accidentally clear another interrupt request bit So instead of writing TIFR _BV TOVO wrong x simply use TIFR _BV TOVO Back to FAQ Index 8 3 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 8 3 27 Which AVR specific assembler operators are available See Pseudo ops and operators Back to FAQ Index 8 3 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 this prologue frame size 20 push r28 push r29 in r28 SP L r29 SP_H__ sbiw r28 20 in tmp_reg__ SREG cli out SPH r29 out SREG tmp reg out BSP 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 207 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
75. on eache edge of the incoming signal The outgoing PWM is generated through OCOB of timer channel 0 PB 1 For demon stration purposes a LED should be connected to that pin like one of the LEDs of an 5 500 controllers run on their internal calibrated RC oscillators 1 2 on the Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 29 Combining and assembly source files 143 tiny13 and 1 0 MHz on the ATtiny45 6 29 2 A code walkthrough 6 29 2 1 asmdemo c After the usual include files two variables are defined The first one pwm_incoming is used to communicate the most recent pulse width de tected 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 pwm 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 ov
76. 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 De fault 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 together 8 10 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 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
77. 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 print f_P which takes a program space string The string is read into an internal buffer as one line of input using fgets While it would be also possible to use get s which implicitly reads from stdin gets has no control that the user s input does not overflow 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 fgets 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 preak 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 32 Using the standard IO facilities 169 When leaving the main loop a goodbye message is sent to sta
78. pairs X Pointer register pair X x r27 126 y Pointer register pair Y y 129 r28 7 Pointer register pair Z z r31 130 These definitions seem not to fit properly to the AVR instruction set The author s as sumption is that this part of the compiler has never been really finished in this version but that assumption may be wrong 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 check 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 assem bler 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 assembler 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 The following table shows all AVR assembler mnemonics which require oper
79. 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 191 implemented on it s usually not noticeable on larger machines like PCs while
80. program execution contin ues as if the corresponding call of setjmp had just returned the value __ret 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 Returns This function never returns 6 17 2 2 int setjmp jmp buf _ jmpb Save stack context for non local goto include lt setjmp h gt 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 64 Parameters jmpb Variable of type jmp_buf which holds the stack information such that the environment can be restored Returns setimp returns 0 if returning directly and non zero when returning from longjmp using the saved context 6 18 lt stdint h gt Standard Integer Types 6 18 1 Detailed Description include lt stdint h gt 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 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
81. qsort SCN132 avr_stdlib 99 avr_inttypes 55 quot SCNiFAST16 div_t 178 avr_inttypes 55 Idiv_t 178 SCNiFAST32 avr_inttypes 55 rand SCNiLEAST16 avr_stdlib 99 avr_inttypes 55 RAND_MAX SCNiLEAST32 avr_stdlib 95 avr_inttypes 55 rand_r SCNiPTR avr_stdlib 99 avr_inttypes 55 random SCNo16 avr_stdlib 100 avr_inttypes 55 RANDOM_MAX SCNo32 avr_stdlib 95 avr_inttypes 55 random_r SCNoFAST 16 avr_stdlib 100 avr_inttypes 56 realloc SCNoFAST32 avr_stdlib 100 avr_inttypes 56 rem SCNoLEAST16 div_t 178 avr_inttypes 56 Idiv_t 178 SCNoLEAST32 avr_inttypes 56 sbi SCNoPTR deprecated_items 42 avr_inttypes 56 scanf SCNul6 avr stdio 86 avr inttypes 56 scanf P SCNu32 avr stdio 86 avr inttypes 56 SCNd16 SCNuFAST16 avr_inttypes 54 avr_inttypes 56 SCNd32 SCNuFAST32 avr_inttypes 54 avr_inttypes 56 SCNdFAST16 SCNuLEAST16 avr_inttypes 54 avr_inttypes 56 SCNdFAST32 SCNuLEAST32 avr_inttypes 54 avr_inttypes 56 SCNdLEAST16 SCNuPTR avr_inttypes 54 avr_inttypes 57 SCNdLEAST32 SCNx16 avr_inttypes 55 avr_inttypes 57 SCNdPTR SCNx32 avr_inttypes 55 avr_inttypes 57 SCNi16 SCNxFAST16 avr_inttypes 55 avr_inttypes 57 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 265 SCNxFAST32 avr_inttypes 57 SCNxLEAST16 avr_inttypes 57 SCNxLEAST32 avr_inttypes 57 SCNxPTR avr_inttypes 57 set_sleep_mode avr_sleep 34 setjmp longjmp 63 setjmp 63 SIG ATOMIC MAX avr stdint 71 SIG
82. resources available than in the default configuration 8 5 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 functions 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 5 Using malloc 221 8 5 3 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 dar
83. 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 change of the counting direction For PWM generation it is 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 6 29 1 Hardware setup The incoming PWM pulse train is fed into PB4 It will generate a pin change interrupt there
84. strings ignoring case The strcasecmp function compares the two strings sl and s2 ignoring the case of the characters Returns The strcasecmp function returns an integer less than equal to or greater than zero if sl is found respectively to be less than to match or be greater than 52 6 21 3 11 char x strcat char x 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 108 6 21 3 12 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 src Here character means byte these functions do not work with wide or multi byte characters Returns The strchr function returns a pointer to the matched character or NULL if the character is not found 6 21 3 13 stremp const char x 81 const char 52 Compare two strings The strcmp function compares the two strings sl and s2 Returns The strcmp function returns an integer less than equal to or greater than zero if s
85. stuffabout 188 83 7 AVR 2 46455 55 445 RR 189 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen CONTENTS vi 8 3 8 _ Shouldn t I initialize all my 2 190 8 3 9 Why do some 16 bit timer registers sometimes get trashed 191 8 3 10 How do I use a define d constant in an asm statement 192 8 3 11 Why does the PC randomly jump around when single stepping through my program in 192 8 3 12 How do I trace an assembler file in 193 8 3 13 How do I pass an IO port as a parameter to a function 194 8 3 14 What registers are used by the C compiler 196 8 3 15 How do I put an array of strings completely in ROM 198 8 3 16 How to use external 200 8 5 17 Which O flag to use 200 8 3 18 How do I relocate code to a fixed address 201 8 3 19 My UART is generating nonsense My ATmegal28 keeps crashing Port F is completely broken 202 8 3 20 Why do all my foo bar strings eat up the SRAM 202 8 3 21 Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit operation in assembly 203 8 3 22 How to detect RAM memory and variable overlap problems 204 8 3 23 Is it really impossible to program the ATtinyXX in C 204 8 3 24 What is this clock skew detected messsage
86. sure the device will really be put to sleep Sleep Modes Note Some of these modes are not available on all devices See the datasheet for target device for the available sleep modes Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 8 lt avr sleep h gt Power Management and Sleep Modes 33 define SLEEP_MODE_IDLE 0 define SLEEP_MODE_ADC _BV SMO define SLEEP_MODE_PWR_DOWN _BV SM1 define SLEEP_MODE_PWR_SAVE BV SMO _BV SMI define SLEEP MODE STANDBY _BV SM1 5 2 define SLEEP MODE EXT STANDBY BV SMO BV SMD BV SM2 Sleep Functions e void set sleep mode uint8 t mode void sleep mode void void sleep enable void void sleep disable void void sleep cpu void 6 8 2 Define Documentation 6 8 2 1 define SLEEP MODE ADC BV SM0 ADC Noise Reduction Mode 6 8 2 2 define SLEEP MODE EXT STANDBY 5 0 _BV SM1 BV SM2 Extended Standby Mode 6 8 2 3 define SLEEP MODE IDLE 0 Idle mode 6 8 2 4 define SLEEP MODE PWR DOWN _BV SM1 Power Down Mode 6 8 2 5 define SLEEP MODE PWR SAVE _BV SM0 BV SM1 Power Save Mode 6 8 2 6 define SLEEP MODE STANDBY BV SM1 BV SM2 Standby Mode Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 9 lt avr version h gt avr libc version macros 34 6 8 3 Function Documentation 6 8 3 1 void set sleep mode uint8 t mode Selec
87. take care to trans form this into a single SBI instruction assuming the operands allow for this Back to FAQ Index 8 3 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 optimzation is that variable usage is restricted to the area of code where it is actually used So if a variable was placed in a register at the beginning of Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 193 some function this same register can be re used later on if the compiler notices th
88. the C compiler command line Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 11 Todo List 249 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 they 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 def 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 t
89. 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 6 31 3 5 Part 5 main At the start of main a variable mode is declared to keep 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 32 Using the standard IO facilities 165 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 fun
90. those in angular brackets lt gt go before application specific header files in double quotes defines h comes as the first header file here The main reason is that this file defines the value of CPU which needs to be known before including utils delay h The function ioinit summarizes all hardware initialization tasks As this function is declared to be module internal only static the compiler will notice its simplic ity and with a reasonable optimization level in effect it will inline 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 lcd str set up two stdio streams The initial ization is done using the 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 32 Using the standard IO facilities 168 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 1cd_str which is specified to only perform output operations can be given as NULL The stream uart_str corresponds to inpu
91. to by src Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 111 6 21 3 24 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 6 21 3 25 char x strrev char string 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 6 21 3 26 char strsep char string const char delim Parse a string into tokens The strsep function locates in the string referenced by xstring 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 string 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 string to 0 Returns The strtok_r function returns a pointer to the original value of string If xstringp is initially NULL strsep returns NULL
92. to the base name of the assembler functions 6 3 2 2 define _EEGET var addr var eeprom read byte uint8_t x addr Read a byte from EEPROM Compatibility define for IAR C 6 3 2 3 define EEPUT addr val eeprom write byte uint8 t addr uint8 t val Write a byte to EEPROM Compatibility define for IAR C 6 3 2 4 define EEMEM attribute section eeprom Attribute expression causing a variable to be allocated within the eeprom section 6 3 2 5 define eeprom busy wait do while is ready Loops until the eeprom is no longer busy Returns Nothing 6 3 2 6 define eeprom is ready Returns 1 if EEPROM is ready for a new read write operation O if not 6 3 3 Function Documentation 6 3 3 1 void eeprom read block void pointer ram const void pointer eeprom size t n Read a block of n bytes from EEPROM address pointer eepromto pointer ram For constant n lt 256 bytes a library function is used For block sizes unknown at compile time or block sizes gt 256 an inline loop is expanded 6 3 3 2 uint8 t eeprom read byte const uint8 t addr Read one byte from EEPROM address addr Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 4 lt avr io h gt AVR device specific IO definitions 18 6 3 3 3 _ uint16_t eeprom read word const uint16 t addr Read one 16 bit word little endian from EEPROM address addr 6 3 3 4 void eeprom write block
93. update uint16 t crc uint8 t data e static _ inline uintl6 t crc ccitt update uint16 t crc uint8 t data e static _ inline uint8 t crc ibutton update uint8 t crc uint8 t data 6 22 2 Function Documentation 6 22 2 1 static inline uint16 t 16 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 uintl16 t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 22 lt util crc16 h gt CRC Computations 114 16 update uintl16 t crc uint8_t a irn u cre a for i 0 i lt 8 i if cre amp 1 crc crc gt gt 1 0 001 crc crc gt gt 1 return crc 6 22 2 2 static inline uint16 t crc 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
94. 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 The hexadecimal value of smallval is PRIx8 the decimal value of longval is PRId32 n smallval longval 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 define PRId8 d define PRIdLEASTS d define PRIdFASTS d define PRIi8 i define PRLiILEASTE i define PRIFAST8 i define PRId16 d define PRIdLEASTI6 d Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 47
95. zero if the first len bytes of s1 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 6 21 3 7 void memcpy void dest const void x 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 107 6 21 3 8 void x memmove void gt dest const void 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 6 21 3 9 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 6 21 3 10 strcasecmp const char s1 const char 52 Compare two
96. 1 used qsort using the standard library strcmp test 2 used a function that sorted the strings by their size thus had Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 201 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 02 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 with a grain of salt So generally it seems Os mcall prologues is the most universal best opti mization level Only applications that need to get the last few percent of speed benefit from using 03 Back to FAQ Index 8 3 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 vo
97. 16 generic integer scanf format for intptr_t 6 15 2 75 define SCNo16 o octal scanf format for uint16_t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 56 6 15 2 76 define SCNo32 lo octal scanf format for uint32_t 6 15 2 77 define SCNoFAST16 octal scanf format for uint_fast16_t 6 15 2 78 define SCNoFAST32 lo octal scanf format for uint_fast32_t 6 15 2 79 define SCNoLEAST16 octal scanf format for uint_least16_t 6 15 2 80 define SCNoLEAST32 lo octal scanf format for uint_least32_t 6 15 2 81 define SCNoPTR SCNo16 octal scanf format for uintptr_t 6 15 2 82 define SCNu16 decimal scanf format for uint16_t 6 15 2 83 define SCNu32 lu decimal scanf format for uint32_t 6 15 2 84 define SCNuFAST16 decimal scanf format for uint_fast16_t 6 15 2 85 define SCNuFAST32 lu decimal scanf format for uint_fast32_t 6 15 2 86 define SCNULEAST16 decimal scanf format for uint_least16_t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 57 6 15 2 87 define SCNuLEAST32 lu decimal scanf format for uint_least32_t 6 15 2 88 define SCNuPTR SCNu16 decimal scanf format for uintptr_t 6 15 2 89 define SCNx16 x hexadecimal scanf format for uint16_t 6 15 2 90 define SCNx32 Ix hexadecimal scanf format for uint32_t
98. 17 double 10210 double The 102100 function returns the logarithm of argument x to base 10 If the argument is less than or equal 0 a domain error will occur 6 16 3 18 double modf double value double iptr The modf function breaks the argument value 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 value 6 16 3 19 double pow double __x double y The function pow returns the value of x to the exponent y 6 16 3 20 double sin double x The sin function returns the sine of x measured in radians 6 16 3 21 double sinh double __x The sinh function returns the hyperbolic sine of x 6 16 3 22 double sqrt double __x The sqrt function returns the non negative square root of x 6 16 3 23 double square double _ The function square returns x x Note This function does not belong to the C standard definition Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 17 lt setjmp h gt Non local goto 62 6 16 3 24 double tan double __x The tan function returns the tangent of x measured in radians 6 16 3 25 double tanh double __x The tanh function returns the hyperbolic tangent of x 6 17 lt setjmp h gt Non local goto 6 17 1 Detailed Description While the C language has the dreaded goto state
99. 2 167 5 3313 A code walkthrough luo pss bS SVS K 4 Eo 167 224 M ici me 173 6 33 Example using the two wire interface TWI 173 6 33 1 Introduction into TWI 173 6 33 2 The TWI example project lt a s 22x RA 173 3 nus oet UU A 174 7 avr ibc Data Structure Documentation 177 GL div tStuct Reference cn ba bobo a o og ow RR e 177 711 Detailed Description 2 2 177 7 22 Field Documentation lt sc ie aem oeei 178 7 2 t Ser Reference 2 22529 s Sb RE s BR 178 Detaled Description se 622444285 552424 ad 178 TI PrebliDoogmenGHoR kia paa ms 178 8 avr libc Page Documentation 179 Acknowledgments ses se ad s B Rae EGER 179 8 2 avr libc and assembler programs 180 6 21 o Bae See me 180 S22 Invokmgthecompiler 20 0 e eae bee a g 5 180 8 23 Example program lt o o o eee omo Rs 181 8 2 4 Pseudo ops and operators 184 8 Frequently Asked Questions cco e 3 ur RR 185 NMM i ere BASES 185 8 3 2 My program doesn t recognize a variable updated within an interr uptroufi Rm rekt h 187 8 3 3 I get undefined reference to for functions like sin 187 8 34 How to permanently bind a variable to a register 187 8 3 5 How to modify MCUCR or WDTCR 188 8 3 6 What is all this_BVQ
100. 25 define PRIoFAST32 lo octal printf format for uint fast32 t 6 15 2 26 define PRIoFASTS o octal printf format for fast8 t 6 15 2 27 define PRIOLEASTIG o octal printf format for least16 t 6 15 2 28 define PRIOLEAST32 lo octal printf format for least32 t 6 15 2 29 define PRIOLEASTS o octal printf format for least8 t 6 15 2 30 define PRIoPTR PRIo16 octal printf format for uintptr t 6 15 2 31 define PRIu16 u decimal printf format for uint16_t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 52 6 15 2 32 define PRIu32 lu decimal printf format for uint32_t 6 15 2 33 define PRIu8 u decimal printf format for uint8_t 6 15 2 34 define PRIUFAST16 decimal printf format for uint_fast16_t 6 15 2 35 define PRIUFAST32 lu decimal printf format for uint_fast32_t 6 15 2 36 define PRIuFASTS u decimal printf format for uint_fast8_t 6 15 2 37 PRIULEAST16 u decimal printf format for uint_least16_t 6 15 2 38 PRIULEAST32 lu decimal printf format for uint_least32_t 6 15 2 39 define PRIULEASTS decimal printf format for uint_least8_t 6 15 2 40 define PRIuPTR PRIu16 decimal printf format for uintptr_t 6 15 2 41 define PRIX16 X uppercase hexadecimal printf format for uint16 t 6 15 2 42 define PRIx16 x hexadecimal printf format fo
101. 3 2 My program doesn t recognize a variable updated within an interrupt rou tine 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 change the value of 1ag 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 8 3 3 I 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 whe
102. 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 104 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 String Utilities Defines define _FFS x Functions int ffs int __attribute__ const int 51 long __attribute__ const int ffsll long long attribute const void memccpy void const void x int size t void memchr const void int size_t PURE int memcmp const void const void size t ATTR_PURE void memcpy void const void size t void memmove void const void x size_t void memset void int size t int strcasecmp const char const char __ ATTR_PURE char x strcat char const char char strchr const char int ATTR PURE int stremp const char const char x __ATTR_PURE char strcpy char const char 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 x 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_t size t strnlen cons
103. 31 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 1 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 from 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 ioml63 h gt define SPMCR _SFR_I08 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 SP
104. 5 lt avr interrupt h gt Interrupts 122 lt avr io h gt AVR device specific IO defi nitions 18 lt avr pgmspace h gt Program Space String Utilities 19 lt avr power h gt Power Reduction Man agement 27 lt avr sfr_defs h gt Special function regis ters 137 lt avr sleep h gt Power Management and Sleep Modes 32 lt avr version h gt avr libc version macros 34 avr wdt h Watchdog timer handling 36 lt compat deprecated h gt Deprecated items 39 lt compat ina90 h gt Compatibility with IAR EWB 3 x 42 lt ctype h gt Character Operations 42 lt errno h gt System Errors 45 lt inttypes h gt Integer Type conversions 46 lt math h gt Mathematics 58 lt setjmp h gt Non local goto 62 lt stdint h gt Standard Integer Types 64 lt stdio h gt Standard IO facilities 75 lt stdlib h gt General utilities 94 lt string h gt Strings 103 lt util crc16 h gt CRC Computations 112 lt util delay h gt Busy wait delay loops 116 lt util parity h gt Parity bit generation 117 lt util twi h gt TWI bit mask definitions 118 _BV avr_sfr 139 _EEGET avr_eeprom 16 _EEPUT avr_eeprom 16 _FDEV_EOF avr_stdio 80 _FDEV_ERR avr_stdio 80 _FDEV_SETUP_READ avr_stdio 80 _FDEV_SETUP_RW avr_stdio 80 _FDEV_SETUP_WRITE avr_stdio 80 _FFS avr_string 105 AVR_LIBC_DATE avr_version 35 AVR LIBC DATE STRING avr version 3
105. 5 AVR LIBC MAJOR avr version 35 AVR MINOR avr version 35 AVR LIBC REVISION avr version 35 AVR VERSION STRING avr version 35 AVR VERSION avr version 35 EEPROM REG LOCATIONS avr eeprom 16 compar fn t avr stdlib 95 malloc heap end avr stdlib 103 malloc heap start avr stdlib 103 malloc margin avr stdlib 103 INDEX 252 _crc16_update util_crc 113 _crc_ccitt_update util_crc 114 _crc_ibutton_update util_crc 114 _crc_xmodem_update util_crc 115 _delay_loop_1 util_delay 116 _delay_loop_2 util_delay 117 _delay_ms util_delay 117 _delay_us util_delay 117 A more sophisticated project 158 A simple project 144 abort avr_stdlib 96 boot_lock_bits_set_safe 11 boot_lock_fuse_bits_get 11 boot_page_erase 12 boot_page_erase_safe 12 boot_page_fill 12 boot_page_fill_safe 13 boot_page_write 13 boot_page_write_safe 13 boot_rww_busy 13 boot_rww_enable 14 boot_rww_enable_safe 14 boot_spm_busy 14 boot_spm_busy_wait 14 boot_spm_interrupt_disable 14 boot_spm_interrupt_enable 14 BOOTLOADER SECTION 14 GET_EXTENDED_FUSE_BITS 14 GET_HIGH_FUSE_BITS 15 GET_LOCK_BITS 15 GET_LOW_FUSE_BITS 15 abs avr_eeprom avr_stdlib 96 _EEGET 16 acos _EEPUT 16 avr_math 59 EEPROM REG LOCATIONS Additional notes from lt avr sfr_defs h gt _ 16 30 EEMEM 17 asin eeprom_busy_wait 17 avr_math 59 eeprom_is_ready 1
106. 5 Assembler Macros In order to 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 asm instead of asm and volatile instead of volatile These are equivalent aliases Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 217 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_ L_ sbic 0 1 n t N rjmp L N no outputs x N I SFR IO ADDR port I bit When used for the first time may be translated to 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 1 sbic 0 1 n t rime lb no outputs x I SFR IO ADDR port I bit
107. 54 SCNdLEAST16 54 SCNdLEAST32 55 SCNdPTR 55 SCNi16 55 SCNi32 55 SCNiFAST16 55 SCNiFAST32 55 SCNiLEAST16 55 SCNiLEAST32 55 SCNiPTR 55 SCNo106 55 SCNo32 55 SCNoFAST 16 56 SCNoFAST32 56 SCNoLEAST16 56 SCNoLEAST32 56 SCNoPTR 56 SCNul6 56 SCNu32 56 SCNuFAST 16 56 SCNuFAST32 56 SCNuLEAST16 56 SCNuLEAST32 56 SCNuPTR 57 SCNx16 57 SCNx32 57 SCNXxFASTI6 57 SCNxFAST32 57 SCNxLEASTI6 57 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 254 avr_pgmspace SCNxLEAST32 57 prog_int32_t 23 SCNxPTR 57 prog_int64_t 23 uint_farptr_t 57 prog_int8_t 23 avr_math prog_uchar 23 acos 59 prog_uint16_t 23 asin 59 prog_uint32_t 23 atan 59 prog_uint64_t 23 atan2 59 prog_uint8_t 23 ceil 59 prog_void 23 cos 59 PROGMEM 22 cosh 59 PSTR 22 exp 60 strcasecmp_P 24 fabs 60 strcat_P 24 floor 60 strcmp P 24 fmod 60 strepy_P 24 frexp 60 stricat_P 25 isinf 60 strlcpy_P 25 isnan 60 strlen_P 25 ldexp 60 strncasecmp_P 25 log 61 strncat_P 26 log10 61 strncmp_P 26 M_PI 59 strncpy_P 26 5 2 59 strnlen_ P 27 modf 61 strstr_P 27 pow 61 avr_sfr sin 61 _BV 139 sinh 61 bit_is_clear 139 sqrt 61 bit_is_set 140 square 61 loop_until_bit_is_clear 140 tan 61 loop_until_bit_is_set 140 tanh 62 avr_sleep set_sleep_mode 34 memcpy_P 24 sleep_cpu 34 PGM_P 21 sleep_disable 34 pgm_read_byte 21 sleep_enable 34 pgm_read_byte_far 21 sleep
108. 6 10 1 Detailed Description include lt avr wdt h gt 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 void get_mcusr void attribute naked attribute section init3 void get mcusr void mcusr_mirror MCUSR MCUSR 0 wdt disable Saving the value of MCUSR in mcusr_mirror is only needed if the application later wants to examine the reset source but clearing in particu
109. 6 20 lt stdlib h gt General utilities 100 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 6 20 4 19 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 6 20 4 20 long random r unsigned long ctx Variant of random 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 6 20 4 21 void realloc void __ptr size_t size The realloc function tries to change the size of the region allocated at pt r 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
110. 64_C value _ CONCAT value ULL define INTMAX_C value _ CONCAT value LL define UINTMAX_C value _ CONCAT value ULL Exact width integer types Integer types having exactly the specified width typedef signed char int8_t typedef unsigned char uint8_t typedef 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 67 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 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_t uint_least16_t typedef int32_t int_least32_t typedef uint32_t uint_least32_t typedef int64_t int_least64_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_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 widt
111. 7 assert eeprom_read_block 17 avr_assert 8 eeprom_read_byte 17 atan eeprom_read_word 17 avr_math 59 eeprom_write_block 17 atan2 eeprom_write_byte 17 avr_math 59 eeprom_write_word 18 atof avr_errno avr_stdlib 96 EDOM 45 atoi ERANGE 45 avr_stdlib 96 avr_interrupts atol EMPTY_INTERRUPT 136 avr_stdlib 96 ISR 136 avr_assert ISR_ALIAS 137 assert 8 SIGNAL 137 avr_boot avr_inttypes boot_is_spm_interrupt 11 boot_lock_bits_set 11 int_farptr_t 57 PRId16 49 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 253 PRId32 49 PRIxFASTI6 53 PRId8 49 PRIXFAST32 53 PRIdFAST 16 49 PRIdFAST32 49 PRIdFASTS 49 PRIdLEASTI6 49 PRIdLEAST32 49 PRIdLEASTS 49 PRIdPTR 49 PRIi16 50 PRIi32 50 PRIi8 50 5 16 50 PRIiFAST32 50 PRIFASTS 50 PRILEASTI6 50 PRIiLEAST32 50 PRIiLEASTS 50 PRIiPTR 50 PRIo16 50 PRIo32 51 PRI08 51 PRIoFAST16 51 PRIoFAST32 51 PRIoFASTS 51 PRIoLEASTI6 51 PRIoLEAST32 51 PRIoLEASTS 51 PRIoPTR 51 PRIu16 51 PRIu32 51 PRIu8 52 PRIuFASTI6 52 PRIuFAST32 52 PRIuFASTS 52 PRIuLEASTI6 52 PRIULEAST32 52 PRIuLEASTS 52 PRIuPTR 52 PRIX16 52 PRIx16 52 PRIX32 52 PRIx32 53 PRIX8 53 PRIx8 53 PRIXFAST16 53 PRIxFAST32 53 PRIXFASTS 53 PRIxFASTS 53 PRIXLEAST16 53 PRIxLEASTI6 53 PRIXLEAST32 54 PRIxLEAST32 54 PRIXLEASTS 54 PRIxLEASTS 54 PRIXPTR 54 PRIxPTR 54 SCNd16 54 SCNd32 54 SCNdFASTI6 54 SCNdFAST32
112. 75 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 all subaddress bits are 0 for the smaller devices so the E1 and E2 inputs of the 24Cxx must be grounded Note 4 For slow clocks enable the 2 x U SJART 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 the entire device memory if desired the counter would wrap around and start back from 0 when reaching the end of the device
113. 8 8e bd out 0x2e r24 46 x 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 ba 1b bc out Ox2b l 43 bc la bc out 0 2 rl 42 Enable 1 as output DDROC _BV 0 1 be 82 e0 141 r24 0x02 2 c0 87 bb out 0x17 r24 23 Enable timer 1 overflow interrupt TIMSK TOIE1 c2 84 eO ldi r24 0x04 4 c4 89 bf out 0x39y r24 5 57 sei c6 78 94 sei GU 08 95 ret 000000ca lt main gt int main void ioinit ca 2 af reall 28 0 0 lt ioinit gt loop forever the interrupts are doing the rest x for Note 7 sleep_mode cc 85 b7 in 124 0x35 53 ce 80 68 ori r24 0x80 128 d0 85 bf out 0x35 r24 53 2 88 95 sleep d4 85 b7 in r24 0x35 53 d6 8f 77 andi r24 Ox7F 127 d8 85 bf out 0x35 r24 53 da f8 cf rjmp 16 Oxcc lt main 0x2 gt 000000dc lt __bad_interrupt gt ger 91 timp 222 0x0 heap end 6 30 5 Linker Map Files avr objdump is very useful but sometimes it s necessary to see information about Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 153 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 modul
114. 8 2 26 define INT LEAST64 MIN INT64 MIN smallest negative value an int 1625464 t can hold 6 18 2 27 define INT LEAST8 MAX INT8 MAX largest positive value an int least8 t can hold 6 18 2 28 define INT LEAST8 MIN INT8 MIN smallest negative value an int least8 t can hold 6 18 2 29 define INTMAX_C value CONCAT value LL define a constant of type intmax t 6 18 2 30 INTMAX MAX INT64 MAX largest positive value an intmax t can hold 6 18 2 31 define INTMAX MIN INT64 MIN smallest negative value an intmax t can hold 6 18 2 32 define INTPTR MAX INT16 MAX largest positive value an intptr t can hold 6 18 2 33 INTPTR MIN 6 MIN smallest negative value an intptr t can hold Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 71 6 18 2 34 PTRDIFF_MAX INT16_MAX largest positive value a ptrdiff_t can hold 6 18 2 35 define PTRDIFF MIN INT16_MIN smallest negative value a ptrdiff_t can hold 6 18 2 36 define SIG ATOMIC MAX INT8_MAX largest positive value a sig_atomic_t can hold 6 18 2 37 define SIG ATOMIC MIN INT8 MIN smallest negative value a sig atomic t can hold 6 18 2 38 define SIZE MAX 16 MAX U largest value a size t can hold 6 18 2 39 define UINT16_C value __CONCAT value U define a constant of type uint16_t 6 18 2 40 define UINT16_MAX __CONCAT INT16_MA
115. ART and processed accordingly If the UART signalled a framing error FE bit set typically caused by the terminal sending a line break con dition start 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 33 Example using the two wire interface TWI 173 6 32 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 usr or usr local 6 33 Example using the two wire interface TWI Some newer devices of the ATmega series contain builtin support fo
116. ATOMIC MIN avr stdint 71 SIGNAL avr interrupts 137 sin avr math 61 sinh avr math 61 SIZE MAX avr stdint 71 sleep cpu avr sleep 34 sleep disable avr sleep 34 sleep enable avr sleep 34 sleep mode avr sleep 34 SLEEP MODE ADC avr sleep 33 SLEEP MODE EXT STANDBY avr sleep 33 SLEEP MODE IDLE avr sleep 33 SLEEP MODE PWR DOWN avr sleep 33 SLEEP MODE SAVE avr sleep 33 SLEEP MODE STANDBY avr sleep 33 snprintf avr stdio 86 snprintf P avr stdio 87 sprintf avr stdio 87 sprintf P avr stdio 87 sqrt avr math 61 square avr math 61 srand avr stdlib 100 srandom avr stdlib 100 sscanf avr stdio 87 sscanf P avr stdio 87 stderr avr stdio 82 stdin avr stdio 82 stdout avr stdio 83 strcasecmp avr string 107 strcasecmp P avr pgmspace 24 strcat avr string 107 strcat P avr pgmspace 24 strchr avr string 107 strcmp avr string 108 strcmp P avr pgmspace 24 strcpy avr string 108 strcpy P avr pgmspace 24 strlcat avr_string 108 strlcat P Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 266 avr_pgmspace 25 avr_string 109 strlcpy_P avr_pgmspace 25 strlen avr_string 109 strlen_P avr_pgmspace 25 strlwr avr_string 109 strncasecmp avr_string 109 strncasecmp_P avr_pgmspace 25 strncat avr_string 109 strncat_P avr_pgmspace 26 strncmp avr_string 110 strncmp_ P
117. ATTRS 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 6 11 2 6 define outb port val port val Deprecated Write val to IO port port Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 12 lt compat ina90 h gt Compatibility with EWB 3 x 42 6 11 2 7 define outp val port port val Deprecated Write val to IO port port 6 11 2 8 define sbi port bit port 1 lt lt bit Deprecated Set bit in IO port port 6 11 3 Function Documentation 6 11 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 6 12 lt compat ina90 h gt Compatibility with 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 d
118. ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega406 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8515 ATmega8535 ATmegal 8 ATmega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtinyll AT tiny12 ATtinylI3 ATtinyl5 ATtiny22 ATtiny2313 26 ATtiny28 AT tiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 vect SIG INTERRUPTI External Interrupt Request 1 AT90S2313 419052333 AT90S4414 AT90S4433 AT90S4434 9058515 AT90S8535 AT90PWMS3 AT90PWMO AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 16 ATmegal61 ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega406 ATmega64 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny2313 ATtiny28 AT tiny261 ATtiny461 ATtiny861 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 127 Vector name Old vector Description Applicable for device name INT2_vect SIG_ External Interrupt AT90PWM3 AT90PWM2 AT90CAN128 INTERRUPT2 Request 2 AT90CAN32 AT90CAN64 ATmegal03 ATmega128 ATmegal6 ATmegal61 AT megal62 ATmega32 ATmega323 AT mega406 ATmega64 ATmega8515 AT m
119. ATmega3290 ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmegal68 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 power_lcd_enable Enable the LCD module ATmegal69 ATmega169P ATmega329 ATmega3290 ATmega649 ATmega6490 power_lcd_disable Disable the LCD module ATmegal69 ATmega169P ATmega329 ATmega3290 ATmega649 ATmega6490 power pscO enable Enable the Power Stage Controller 0 module AT90PWMI AT90PWM2 AT90PWM3 power pscO disable Disable the Power Stage Controller 0 module AT90PWMI AT90PWM2 AT90PWM3 power pscl enable Enable the Power Stage Controller 1 module AT90PWMI AT90PWM2 AT90PWM3 power psc disableQ Disable the Power Stage AT90PWMI ATOOPWM2 Generated on Mon Oct 9 22 30 53 2006 fGicaxrdiberbly iDosyden AT90PWM3 power psc2 enable Enable the Power Stage Controller 2 module AT90PWMI AT90PWM2 AT90PWM3 power psc2 disable Disable the Power Stage Controller 2 module AT90PWMI AT90PWM2 AT90PWM3 power spi enable Enable the Serial Peripheral Interface module ATmega640 ATmegal280 ATmegal281 ATmega2560 67 Additional notes from lt avr sfr_defs h gt 30 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 f
120. C 6 30 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 or usr local 6 31 more 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 6 31 1 Hardware setup The demo is set up in a way so it can be run on the ATmega16 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 31 more sophisticated project 159 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 m N Figure 2 Setup of the STK500 The coloured patch cables are used to provide various interconnections As there are only four of them in the STK500 there are two options to connect them for this demo The second option for the yellow green cable is shown in parenthes
121. CU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET MCU_TARGET OPTIMIZE DEFS LIBS You should not CC at90s2313 at90s2333 at90s4414 at90s4433 at90s4434 at90s8515 at90s8535 atmegal28 atmegal280 atmegal281 atmegal6 atmegal63 atmegal64p atmega165 atmegal65p atmegal68 atmegal69 atmegal69p atmega32 atmega324p atmega325 atmega3250 atmega329 atmega3290 atmega48 atmega64 atmega640 atmega644 atmega644p atmega645 atmega6450 atmega649 atmega6490 atmega8 atmega8515 atmega8535 atmega88 attiny2313 attiny24 attiny25 attiny26 attiny26 attiny44 attiny45 attiny46 attiny84 attiny85 attiny86 02 have to change anything below here avr gcc Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 157 Override is only needed by avr lib build system override CFLAGS g Wall OPTIMIZE mmcu MCU_TARGET DEFS override LDFLAGS W1 Map PRG map OBJCOPY avr objcopy OBJDUMP avr objdump all PRG elf lst text eeprom 5 PRG elf 5 OBJ 5 CFLAGS LDFLAGS o 8 LIBS dependency demo o demo c iocompat h clean rm rf PRG elf png pdf x bak rm rf x lst map EXTRA_CLEAN_FILES lst PRG Ist 1st e
122. F_vect OVERFLOW3 Overflow ATmegal28 ATmegal62 ATmega64 AT mega640 ATmegal280 ATmegal281 TIMERA SIG INPUT Timer Counter4 ATmega640 ATmega1280 ATmegal281 CAPT vect CAPTUREA Capture Event TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPA vect OUTPUT Compare Match COMPARE4A A TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPB vect OUTPUT Compare Match COMPAREAB B TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 vect OUTPUT Compare Match COMPAREAC C TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmega1281 OVF vect OVERFLOW4 Overflow TIMERS SIG INPUT Timer Counter5 ATmega640 ATmegal280 ATmegal281 CAPT vect 5 Capture Event TIMERS_ SIG_ Timer Counter5 ATmega640 ATmegal280 ATmegal281 COMPA vect OUTPUT Compare Match COMPARESA A TIMERS SIG Timer Counter5 ATmega640 ATmega1280 ATmegal281 COMPB vect OUTPUT Compare Match COMPARESB B TIMERS SIG Timer Counter5 ATmega640 ATmega1280 ATmegal281 COMPC vect OUTPUT Compare Match COMPARESC C TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 OVF vect OVERFLOW5 Overflow TWI_vect SIG_2WIRE_ 2 wire Serial In AT90CANI28 AT90CAN32 AT90CANGA SERIAL terface ATmegal28 ATmegal6 ATmegal63 AT mega32 ATmega323 ATmega406 AT mega64 ATmega8 ATmega8535 AT megal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 TXDO
123. I 0x1021 else crc lt lt 1 return cre Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 23 lt util delay h gt Busy wait delay loops 116 6 23 lt util delay h gt Busy wait delay loops 6 23 1 Detailed Description define F CPU 1000000UL 1 MHz tdefine CPU 14 7456E6 include util delay h Note As an alternative method it is possible to pass the F CPU macro down to the com piler from the Makefile Obviously in that case no define statement should be used 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 use 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 Two wrapper functions allow the specification of microsecond and millisecond delays directly using the application supplied macro F_CPU as the CPU
124. IMER1_CLOCKSOURCE Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 148 x Run device dependent timer 1 setup hook if present x 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 TOIE1 sei int main void ioinit loop forever the interrupts are doing the rest x for Note 7 Sleep mode return 0 6 30 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 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
125. INPUT Timer Counter1 AT90S2313 CAPTI_vect CAPTURE1 Capture Event TIMER 1 SIG_INPUT_ Timer Counter AT90S2333 AT90S4414 AT90S4433 CAPT_vect CAPTURE Capture Event AT90S4434 9058515 AT905S8535 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CANO4 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal28l ATmega324 ATmegal64 ATmega644 ATtiny2313 ATtiny24 ATtiny44 ATtiny84 TIMERI SIG Timer Counter1 ATtiny26 CMPA_vect OUTPUT_ Compare Match COMPAREIA 1A TIMERI SIG Timer Counter1 ATtiny26 CMPB_vect OUTPUT_ Compare Match COMPAREIB 1B TIMERI SIG Timer Counter1 AT90S2313 COMPI vect OUTPUT Compare Match COMPAREIA Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 131 Vector name Old vector Description Applicable for device name TIMER 1_ SIG_ Timer Counter1 AT90S4414 AT90S4434 9058515 COMPA _vect OUTPUT_ Compare Match AT90S8535 AT90PWM3 AT90PWM2 COMPAREIA A AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmeg
126. L and sets the error flag of stream which can be tested using ferror Otherwise a pointer to the string will be returned 6 19 3 9 int fprintf FILE __ stream const char _ fmt The function fprintf performs formatted output to stream See vfprintf for details 6 19 3 10 int fprintf_P FILE x __ stream const char Variant of fprintf that uses a fmt string that resides in program memory 6 19 3 11 int fputc int __c FILE x _ stream The function fputc sends the character c though given as type int to stream It returns the character or EOF in case an error occurred 6 19 3 12 int fputs const char str FILE stream Write the string pointed to by str to stream stream Returns 0 on success and EOF on error 6 19 3 13 int fputs_P const char __str FILE x stream Variant of fputs where st r resides in program memory 6 19 3 14 size t fread void __ptr size t size size t __nmemb FILE x _ stream Read nmemb objects size bytes each from stream to the buffer pointed to by pir 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 6 19 3 15 int fscanf FILE x stream const char x fmt The function f scanf performs formatted input reading the input data from st ream See vfscanf for details Generated on Mon
127. MCR 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 C programs all combinations of SFR 5 COMPAT and SFR OFFSET supported the SFR ADDR SPMCR macro be used to get the address of the SPMCR register 0x57 or 0x68 depending on device Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 8 lt avr sleep h gt Power Management and Sleep Modes 32 6 8 lt avr sleep h gt Power Management and Sleep Modes 6 8 1 Detailed Description include lt avr sleep h gt T 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
128. NE_ 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 ATmegal61 vect UARTO_ Complete TRANS UARTO_ SIG_ UARTO Data ATmegal61 UDRE_vect UARTO_ Register Empty DATA UARTI_RX_ SIG_ UARTI Rx ATmegal61 vect UARTI Complete RECV Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 134 Vector name Old vector Description Applicable for device name UART1_TX_ SIG_ UARTI Tx ATmegal61 vect UARTI Complete TRANS UARTI SIG UARTI Data ATmegal61 UDRE vect UARTI Register Empty DATA UART RX SIG UART UART Rx Com AT90S2313 AT90S2333 9054414 vect RECV plete AT90S4433 AT90S4434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_TX_ SIG_UART_ UART Tx Com AT90S2313 9052333 9054414 vect TRANS plete AT90S4433 AT90S4434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_ SIG_UART_ Data Reg AT90S2313 419052333 AT90S4414 UDRE_vect DATA ister Empty AT90S4433 9054434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 USARTO SIG USARTO Rx ATmegal62 vect USARTO Complete RECV USARTO SIG USARTO Rx AT90CANI28 AT90CAN32
129. Nd32 Id define SCNdLEAST32 Id define SCNdFAST32 define SCNi32 li define SCNiLEAST32 li define SCNiFAST32 li define SCNdPTR SCNd16 define SCNIPTR SCNi16 define SCNo16 define SCNoLEAST16 o define SCNoFAST16 o define SCNul6 u define SCNuLEASTI6 u define SCNuFAST16 u define SCNx16 x define SCNxLEAST16 x define SCNxFAST16 x 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 SCNol6 define SCNuPTR SCNu16 define SCNxPTR SCNx16 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 49 Far pointers for memory access gt 64K typedef int32_t int_farptr_t typedef uint32_t uint_farptr_t 6 15 2 Define Documentation 6 15 2 1 define PRId16 d decimal printf format for int16 t 6 15 2 2 ftdefine PRId32 Id decimal printf format for int32 t 6 15 2 3 define PRIdS d decimal printf format for int8 t 6 15 2 4 define PRIGFAST16 decimal printf format for int fast16 t 6 15 2 5 define PRIdFAST32 Id decimal printf format for int fast32 t 6 15 2 6 define PRIdFASTS decimal printf format for int fast8 t 6 15 2 7 define PRIGLEAST16 d decimal printf format for int least16 t 6 15 2 8 define PRI4LEAST32
130. Note 8 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 33 Example using the two wire interface TWI 176 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 lost arbitration is required by the protocol to immediately cease talking on the bus in particular it must not initiate a stop condi
131. PB1 connects to 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 ATmegal6 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 The TARGET macro in the Makefile needs to be adjusted appropriately The flash ROM and RAM consumption of this demo are way below the resources of even an ATmega48 The major advantage of experimenting with the ATmegal6 in addition that it ships together with an STK500 anyway is that it can be debugged online via JTAG Note that in the explanation below all port pin names are applicable to the ATmegal6 setup Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 31 more sophisticated project 162 6 31 2 Functional overview PD6 will be toggled with each internal clock tick approx 10 ms PD7 will flash once per second PDO are configured as UART IO and 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 ha
132. ROVIDE __data_end bss 0x00800060 0x3 0x00800060 PROVIDE bss start 2 bss bss 0x00800060 0x3 demo o bss 0x00800063 0x0 junk AVR avr libc 1 4 avr lib avr4 atmega8 crtm8 o x bssx COMMON 0x00800063 PROVIDE __bss_end 0x000000de _ data_load_start LOADADDR data 0x000000de data_load_end __data_load_start SIZEOF noinit 0x00800063 0x0 0x00800063 PROVIDE __noinit_start noinit x 0x00800063 PROVIDE __noinit_end 0x00800063 _end 0x00800063 PROVIDE __heap_start eeprom 0x00810000 0x0 x 0x00810000 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 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 0x60 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 variables 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 6 30 6 Generating Intel Hex Files We have a binary of the applicatio
133. STS X uppercase hexadecimal printf format for uint_least8_t 6 15 2 58 define PRIXLEASTS x hexadecimal printf format for uint_least8_t 6 15 2 59 define PRIXPTR PRIX16 uppercase hexadecimal printf format for uintptr t 6 15 2 60 define PRIxPTR PRIx16 hexadecimal printf format for uintptr t 6 15 2 61 define SCNd16 d decimal scanf format for int16 t 6 15 2 62 define SCNd32 Id decimal scanf format for int32 t 6 15 2 63 define SCNdFASTI6 decimal scanf format for int fastl6 t 6 15 2 64 define SCNdFAST32 Id decimal scanf format for int fast32 t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 55 6 15 2 65 define SCNALEAST16 d decimal scanf format for int_least16_t 6 15 2 66 define SCNdLEAST32 1d decimal scanf format for int_least32_t 6 15 2 67 define SCNdPTR SCNd16 decimal scanf format for intptr_t 6 15 2 68 define SCNi16 i generic integer scanf format for int16_t 6 15 2 69 define SCNi32 li generic integer scanf format for int32_t 6 15 2 70 define SCNiFASTI6 i generic integer scanf format for int_fast16_t 6 15 2 71 define SCNiIFAST32 li generic integer scanf format for int_fast32_t 6 15 2 72 define SCNILEASTI6 i generic integer scanf format for int_least16_t 6 15 2 73 define SCNILEAST32 li generic integer scanf format for int_least32_t 6 15 2 74 define SCNIPTR SCNi
134. TUS TWSR amp TW STATUS 5 R W bit in SLA R W address field fdefine TW READ 1 define TW WRITE 0 6 25 2 Define Documentation 6 25 2 1 define TW BUS ERROR 0x00 illegal start or stop condition 6 25 22 didefine TW MR LOST 0x38 arbitration lost in SLA R or NACK Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 25 lt util twi h gt TWI bit mask definitions 120 6 25 2 3 define TW MR DATA 0x50 data received ACK returned 6 25 24 define TW MR DATA NACK 0x58 data received NACK returned 6 25 2 5 define TW MR SLA ACK 0x40 SLA R transmitted ACK received 6 25 2 6 define TW MR SLA 0x48 SLA R transmitted NACK received 6 25 27 define TW LOST 0x38 arbitration lost in SLA W or data 6 25 2 define TW MT DATA 0x28 data transmitted ACK received 6 25 2 9 define TW MT DATA NACK 0x30 data transmitted NACK received 6 25 2 10 define TW MT SLA ACK 0x18 SLA W transmitted ACK received 6 25 2 11 define TW MT SLA 0x20 SLA W transmitted NACK received 6 25 2 12 ftdefine TW NO INFO 0xF8 no state information available 6 25 2 13 define TW READ 1 SLA R address Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 25 lt util twi h gt TWI bit mask definitions 121 6 25 2 14 define TW REP START 0x10 repeated start condition transmitted 6 25 2 15 define TW_SR_ARB_LOST_GCALL_ACK 0x78
135. Tmega48 ATmega88 AT WATCHDOG_ mega640 ATmegal280 ATmegal281 AT TIMEOUT mega324 ATmegal64 ATmega644 AT tiny13 ATtiny24 ATtiny44 ATtiny84 AT tiny45 ATtiny25 ATtiny85 ATtiny261 AT tiny461 ATtiny861 Macros for writing interrupt handler functions define ISR vector define SIGNAL vector define EMPTY_INTERRUPT vector define ISR_ALIAS vector target_vector 6 26 2 Define Documentation 6 26 2 1 define EMPTY_INTERRUPT vector include lt avr interrupt h gt 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 6 26 2 2 define ISR vector include lt avr interrupt h gt Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 27 lt avr sfr_defs h gt Special function registers 137 Introduces an interrupt handler function interrupt service routine that runs with global interrupts initially disabled vector must be one of the interrupt vector names that are valid for the particular MCU type 6 26 2 3 define ISR ALIAS vector target vector include lt avr interrupt h gt Defines vector to point to the same interrupt vector as target vector That way a single interrupt vector implementation can be used to serve several interrupt sources Do not define a function body Note Th
136. X U 2U 1U largest value an uint16_ t can hold 6 18 2 41 define UINT32_C value __CONCAT value UL define a constant of type uint32_t 6 18 2 42 define UINT32 MAX _CONCAT INT32_MAX U 2UL 100 largest value an uint32_t can hold 6 18 2 43 define UINT64_C value CONCAT value ULL define a constant of type uint64_t 6 18 2 44 define UINT64 MAX _CONCAT INT64_MAX U 2ULL 1ULL largest value an uint64_t can hold Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 72 6 18 2 45 define UINT8_C value uint8_t _ CONCAT value U define a constant of type uint8_t 6 18 2 46 define UINT8_MAX _CONCAT INT8_MAX U x 2U 1U largest value an uint8_t can hold 6 18 2 47 UINT_FAST16_MAX UINT16_MAX largest value an uint_fast16_t can hold 6 18 2 48 define UINT FAST32 MAX UINT32 MAX largest value fast32 t can hold 6 18 2 49 define UINT FAST64 MAX UINT64 largest value an uint fast64 t can hold 6 18 2 50 UINT FAST8 MAX UINT8 largest value an uint fast8 t can hold 6 18 2 51 define UINT LEASTI6 MAX UINTI6 MAX largest value an uint_least16_t can hold 6 18 2 52 define UINT LEAST32 MAX UINT32 MAX largest value an uint least32 t can hold 6 18 2 53 define UINT LEAST64 UINT64 MAX largest value an uint least64 t can hold 6 18 2 54 define UINT LEAST8 UINT8
137. _CONST char strstr_P const char PGM_P ATTR PURE 6 5 2 Define Documentation 6 5 2 1 define P const prog char Used to declare a variable that is a pointer to a string in program space 6 5 2 2 define read byte address short 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 6 5 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 6 5 2 4 define pgm read byte near address short LPM uint16 t 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 22 6 5 2 5 define pgm_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 6 5 2 6 define pgm_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 addres
138. __ int atoi const char nptr _ ATTR_PURE void exit int __ status ATTR_NORETURN__ void malloc size t size ATTR_MALLOC__ void free void ptr void realloc void size t size _ ATTR_MALLOC__ double strtod const char nptr char __endptr double atof const char __nptr int rand void void srand unsigned int seed int rand r unsigned long ctx Variables e size t malloc margin e char x malloc heap start e char x malloc heap end 6 20 2 Define Documentation 6 20 2 1 Zdefine RAND MAX 0x7FFF Highest number that can be generated by rand 6 20 2 2 define RANDOM MAX 0x7FFFFFFF Highest number that can be generated by random 6 20 3 Typedef Documentation 6 20 3 1 typedef int compar fn t const void const void Comparision function type for qsort just for convenience unsigned long strtoul const char nptr char endptr int base void calloc size t nele size t size MALLOC Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 20 lt stdlib h gt General utilities 96 6 20 4 Function Documentation 6 20 4 1 __inline__ void abort void The abort function causes abnormal program termination to occur In the limited AVR environment execution is effectively halted by entering an infinite loop 6 20 4 2 int abs int 1 The abs function computes the absolute value of the integer i Note The ab
139. _defs h gt Special function registers 137 6 27 1 Detailed Description 2 633 5 3 Seed 4 c a 137 6 212 Defne Documentation aces t 139 Demo 2 css A o m oon RA e Robo ee Rm od 140 628 1 Detailed Description zo sk be Rb 140 Combining C and assembly source files 142 6 29 1 Hardware setup lt x vd GS wes 142 6 29 2 A code Walkthrough lt lt eroe eera RR REA 143 A simple lt 2 44 4 doke e mw o t m he Roo m Rs 144 BOU The Pred osos g Sk ga eee ewe ee 144 6 30 2 The device Code nue nd ck Bu ak s suo u 8 kis 146 6 30 3 Compiling and 148 6 30 4 Examining the Object File 149 5 20 5 Linker Map Piles lt lusum b 152 6 30 6 Generating Intel Hex Files 154 6 30 7 Letting Make Build the 155 6 30 8 Reference tothe sourcecode os e o oreca crisper 158 A more sophisticated project 158 Hardware selip sec coe oeoa Se A AG 158 6312 PunchonalDVEPVSW s 0244 cee gd R SR RS 162 6 31 3 A code walkthrough ooo RR 162 6314 Tles0Urceto e lt so c 24 b k hk 3 kd hb RE Ea 165 Using the standard 165 5221 Hardware setup lt x oa u d b eka A EES s we eS 166 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen CONTENTS Y 6 32 2 Functional overview
140. _mode 34 pgm_read_byte_near 21 SLEEP_MODE_ADC 33 pgm_read_dword 21 SLEEP_MODE_EXT_STANDBY pgm_read_dword_far 21 33 pgm_read_dword_near 21 SLEEP_MODE_IDLE 33 pgm_read_word 22 SLEEP MODE PWR DOWN 33 pgm read word far 22 SLEEP MODE PWR SAVE 33 pgm read word near 22 SLEEP MODE STANDBY 33 PGM VOID P 22 avr stdint prog char 23 INT16 C 68 prog intl6 t 23 6 MAX 68 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 255 INT16_MIN 68 int16_t 73 INT32_C 68 INT32_MAX 68 INT32_MIN 68 int32_t 73 INT64_C 68 INT64_MAX 68 INT64_MIN 68 int64_t 73 INT8_C 68 INT8_MAX 68 INT8_MIN 68 int8_t 73 INT_FAST16_MAX 69 INT_FAST16_MIN 69 int_fast16_t 73 INT_FAST32_MAX 69 INT_FAST32_MIN 69 int_fast32_t 73 INT_FAST64_MAX 69 INT_FAST64_MIN 69 int_fast64_t 73 INT_FAST8_MAX 69 INT_FAST8_MIN 69 int_fast8_t 73 INT_LEAST16_MAX 69 INT_LEAST16_MIN 69 int_least16_t 73 INT_LEAST32_MAX 69 INT_LEAST32_MIN 70 int_least32_t 73 INT LEAST64 MAX 70 INT LEAST64 MIN 70 int least64 t 74 INT LEAST8 MAX 70 INT LEASTS8 MIN 70 int least8 t 74 INTMAX C 70 INTMAX MAX 70 MIN 70 intmax t 74 INTPTR MAX 70 MIN 70 intptr t 74 PTRDIFF MAX 70 PTRDIFF MIN 71 SIG ATOMIC MAX 71 SIG ATOMIC MIN 71 SIZE MAX 71 UINTI6 C 71 JINT16 MAX 71 int16 t 74 JINT32 C 71 JINT32 MAX 71 int32 t 74 JINT64 C 71 JINT64 MAX 71
141. _stdint 74 INT LEAST8 MAX avr stdint 70 INT LEAST8 MIN avr stdint 70 int least8 t avr stdint 74 INTERRUPT deprecated items 41 INTMAX C avr stdint 70 INTMAX MAX avr stdint 70 INTMAX MIN avr stdint 70 intmax t avr stdint 74 MAX avr stdint 70 INTPTR MIN avr stdint 70 intptr t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 261 avr_stdint 74 isalnum ctype 43 isalpha ctype 43 isascii ctype 43 isblank ctype 43 iscntrl ctype 44 isdigit ctype 44 isgraph ctype 44 isinf avr_math 60 islower ctype 44 isnan avr_math 60 isprint ctype 44 ispunct ctype 44 ISR avr_interrupts 136 ISR_ALIAS avr_interrupts 137 isspace ctype 44 isupper ctype 44 isxdigit ctype 44 itoa avr_stdlib 97 labs avr_stdlib 98 ldexp avr math 60 Idiv avr_stdlib 98 Idiv_t 178 quot 178 rem 178 log avr_math 61 log10 avr_math 61 longjmp setjmp 63 loop_until_bit_is_clear avr_sfr 140 loop_until_bit_is_set avr_sfr 140 Itoa avr_stdlib 98 M_PI avr_math 59 M_SQRT2 avr_math 59 malloc avr_stdlib 99 memccpy avr string 105 memchr avr string 106 memcmp avr string 106 memcpy avr_string 106 memcpy_P avr_pgmspace 24 memmove avr_string 106 memset avr_string 107 modf avr_math 61 outb deprecated_items 41 outp deprecated_items 41 parity_even_bit util_parity 118 PGM_P avr_pg
142. a3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny2313 ATtiny261 ATtiny461 ATtiny861 TIMERI SIG Timer Counter1 AT90S4414 AT90S4434 9058515 COMPB_vect OUTPUT_ Compare MatchB 419058535 AT90PWM3 AT90PWM2 COMPAREIB AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 128 16 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny2313 ATtiny261 ATtiny461 ATtiny861 TIMERI _ SIG Timer Counter1 AT90CAN128 AT90CAN32 AT90CANGA COMPC_vect OUTPUT_ Compare Match ATmegal28 ATmega64 ATmega640 AT COMPAREIC C mega1280 ATmegal281 TIMERI SIG Timer Counter1 ATtiny261 ATtiny461 ATtiny861 COMPD_vect OUTPUT_ Compare Match COMPAREOD D TIMER 1 _ SIG_ Timer Counter1 AT90S2333 AT90S4433 ATtiny15 COMP_vect OUTPUT_ Compare Match COMPAREIA TIMERI SIG Timer Counter1 AT908S2313 ATtiny26 OVFI vect OVERFLOWI Overflow Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr inter
143. alpha c isdigit c 6 13 2 2 int isalpha int Checks for an alphabetic character It is equivalent to isupper c islower c 6 13 2 3 int isascii int __c Checks whether c is a 7 bit unsigned char value that fits into the ASCII character set Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 13 lt ctype h gt Character Operations 44 6 13 2 4 int isblank int __c Checks for a blank character that 1s a space or a tab 6 13 2 5 int iscntrl int __c Checks for a control character 6 13 2 6 int isdigit int Checks for a digit 0 through 9 6 13 2 7 int isgraph int Checks for any printable character except space 6 13 2 8 int islower int Checks for a lower case character 6 13 2 9 int isprint int Checks for any printable character including space 6 13 2 10 int ispunct int Checks for any printable character which is not a space or an alphanumeric character 6 13 2 11 int isspace int c Checks for white space characters For the avr libc library these are space form feed newline n carriage return r horizontal tab t and vertical tab Cw 6 13 2 12 intisupper int Checks for an uppercase letter 6 13 2 13 int isxdigit int Checks for a hexadecimal digits i e one of 0123456789abcdefABCDEF Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 14 lt errno h gt System Errors
144. amp mask wrong way 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 204 var amp unsigned char mask Back to FAQ Index 8 3 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 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 the last avaialable 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 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 5 there s a comment in each generated assembler file t
145. ands 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 212 constants to the range 0 to 7 for bit set and bit clear operations Mnemonic Constraints Mnemonic Constraints adc LI add LI adiw LI andi d M asr r bclr I bid rl brbc Llabel brbs Llabel bset I bst rl cbi LI cbr dI com r cp Lr cpc LI cpi d M cpse LI dec r elpm tz eor LI in rl inc r ld re Idd rb ldi d M 146 r label lpm 52 Isl r Isr r mov LI movw LI mul LI neg r or Lr ori out Lr pop r push r rol r ror r sbc LI sbci sbi LI sbic LI sbiw sbr d M sbrc rl sbrs rl ser d st er std br sts labeLr sub LI subi d M 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 not supported by inline assembler amp Register should be used for output only Output operands must be write only and the C expression result must be lvalue which means that the operands must be valid on the left side of a
146. approach to access the IO registers is not available It would be slower than using in out instructions anyway Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 22 avr libc and assembler programs 184 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 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 aRAM less device like the AT90S1200 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 ca
147. ar fmt va list Variant of vfscanf using a mt string in program memory 6 19 3 36 int vprintf const char fmt va list _ ap The function vprintf performs formatted output to stream stdout taking a vari able argument list as in vfprintf See vfprintf for details 6 19 3 37 int vscanf const char fmt list The function vscanf performs formatted input from stream st din taking a variable argument list as in vfscanf See vfscanf for details 6 19 3 38 vsnprintf char x s size t n const char x 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 6 19 3 39 vsnprintf P char x s size t __n const char x fmt va list ap Variant of vsnprintf that uses a fmt string that resides in program memory 6 19 3 40 int vsprintf char __s const char x fmt list ap Like sprintf but takes a variable argument list for the arguments Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 20 lt stdlib h gt General utilities 94 6 19 3 41 int vsprintf_P char x __s const char x va_list ap Variant of vsprintf that uses a fmt string that resides in program memory 6 20 lt stdlib h gt General utilities 6 20 1 Detailed Description
148. 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 6 22 lt util crc16 h gt CRC Computations 6 22 1 Detailed Description include lt util crc16 h gt This header file provides a optimized inline functions for calculating cyclic redundancy checks CRC using common polynomials References Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 22 lt util crc16 h gt CRC Computations 113 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 _crc_ibutton_update crc serno i return crc must be 0 Functions e static inline uintl6 t crc16 update uint16 t __crc uint8_t _ data e static inline uintl6 t crc xmodem
149. art 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 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 31 more sophisticated project 163 The name F_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
150. at 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 8 3 12 How do I 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 So in order to debug an assembler input file possibly one that has to be passed through 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 th
151. ation Simulavr http savannah gnu org projects simulavr Installation Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 8 Installing the GNU Tool Chain 234 AVaRice http avarice sourceforge net Installation 8 8 5 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 1d 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 objdump and strip information from object 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 lt version gt tar bz2 tar xf cd binutils lt version gt 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 binutils in 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 targ
152. ation string dest 6 5 4 13 size_t strnlen P PGM P src size t len Determine the length of a fixed size string The strnlen function is similar to strnlen 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 VO character among the first 1 characters pointed to by src 6 5 4 14 char x strstr P const char s1 P s2 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 6 lt avr power h gt Power Reduction Management 28 6 6 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 N
153. avr libc Reference Manual 1 4 5 Generated by Doxygen 1 4 6 Mon Oct 9 22 30 54 2006 CONTENTS i Contents 1 AVRLibc 1 22 4 ss 4 44 4 S 4 K do eoe m eae Ru evo BA AA 1 1 2 General information about this library 1 12 Supported Devices su s bs ee gt RU Rk A 2 2 avr libc Module Index 5 21 ayrlibe Modules lt zo 64054 4604 ge RR y SOE e 5 3 avr libc Hierarchical Index 7 21 avrlibe Class Hierarchy 22222222522 Soe Sawa x ERR 7 4 avr libc Data Structure Index 7 Al vrlibe Data 4 2 2 5 4 kan be ee 42 9 7 5 avr libc Page Index Sl avrlibe Related 7 6 avr libc Module Documentation 8 amp l asserhocDhegHOS eS 2 22 suce xo s 8 611 Detailed Description 8 0 1 2 Documentation uu oe oo i RU 9 6 2 avr boot h Bootloader Support Utilities 9 6 21 Detailed Description 2 9 6 22 Define Documentation 22 11 6 3 lt avr eeprom h gt EEPROM handling 15 6 3 1 Detailed Description 2422 x EE 15 6 3 3 Define Documentation 16 6 3 3 Function 17 6 4 lt avr io h gt AVR device specific IO definitions 18 6 5 lt avr pgmspace h gt Program Space String Utilities 19 6 5 1 Detailed Description 19 652 Documentation
154. 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 Back to FAQ Index 8 3 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 X script file is the default script A xr script is for linking without relocation r flag A xu script is like xr but dox create constructors Ur flag 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 8 4 Inline Asm AVR GCC Inline Assembler Cookbook About this Document 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 compi
155. bits set 6 25 lt util twi h gt TWI bit mask definitions 6 25 1 Detailed Description include lt util twi h gt This header file contains bit mask definitions for use with the AVR TWI interface 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 START 0x08 define TW REP START 0x10 define TW MT SLA ACK 0x18 POE OE d d GO OO PP Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 25 lt util twi h gt TWI bit mask definitions 119 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 0x40 define TW MR SLA 0x48 define TW DATA 0x50 define TW DATA 0x58 define TW ST SLA 8 define TW ST ARB LOST SLA ACK OxBO define TW ST DATA ACK 0xB8 fdefine TW ST 0xCO define TW ST LAST DATA 0xC8 fdefine TW SR SLA ACK 0x60 define TW SR ARB LOST SLA ACK 0x68 define TW SR GCALL 0x70 define TW SR LOST GCALL 0x78 define TW SR DATA ACK 0x80 define TW SR 0x88 fdefine TW SR GCALL DATA ACK 0x90 fdefine TW SR GCALL DATA NACK 0x98 define TW SR STOP OxAO define NO INFO OxF8 define TW BUS ERROR 0x00 define TW STATUS 5 fdefine TW STA
156. byte address short read byte near address short define read word address short read word near address short define read dword address short read dword near address short define PGM 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 void memcpy P void VOID size_t int strcasecmp_P const char PGM P ATTR PURE char strcat P char PGM P int stremp_P const char x PGM P ATTR_PURE char strepy_P char x PGM_P size_t strlcat_P char size t size t strlcpy P char PGM_P size_t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 21 size_t strlen P PGM_P _ ATTR_CONST int strncasecmp_P const char PGM_ P size_t _ ATTR_PURE char strncat_P char x PGM P size_t int strncmp P const char x PGM_P size_t _ ATTR_PURE char strncpy_P char x size_t size_t strnlen P PGM_P size_t _ ATTR
157. ch 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 stdin stdout and stderr are provided but contrary to the C standard since avr libc has no knowledge about appli cable devices these streams are not already pre 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 differentiation 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 character to be sent before the linefeed its put routine must implement this see note 2 As an alternative method to fdevopen the macro fdev_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 s
158. command line not based on the actual filename from the file system Alternatively the language explicitly be specified using the assembler with cpp option 8 2 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 avr io h Note 1 work 16 Note 2 tmp 17 inttmp 19 intsav 0 SQUARE PD6 Note 3 Note 4 tmconst 10700000 200000 100 kHz 200000 edges s fuzz 8 clocks in ISR until TCNTO is set section text global main Note 5 main rcall ioinit T3 rjmp 1b Note 6 global TIMERO_OVF_vect Note 7 TIMERO_OVF_vect 141 inttmp 256 tmconst fuzz out _SFR_IO_ADDR TCNTO inttmp Note 8 in intsav SFR IO ADDR SREG Note 9 sbic _ IO ADDR PORTD SQUARE rjmp 1f sbi _ IO ADDR PORTD SQUARE rjmp 2f 45 cbi _SFR_IO_ADDR PORTD SQUARE 23 out _SFR_IO_ADDR SREG intsav Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 22 avr libc and assembler programs 182 reti ioinit sbi SFR IO ADDR DDRD SQUARE ldi work BV TOIEO out SFR IO ADDR TIMSK work ldi work _BV CS00 tmr0 1 out SFR IO ADDR ICCRO work ldi work 256 tmconst out _SFR_IO_ADDR TCNTO work sei ret global __vector_default Note 10 vector default reti end Not
159. cro 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 8 2 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 and will include the appropri ate options to locate additional libraries as well as the application start up code crtXXX o and linker script Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 22 avr libc and assembler programs 181 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
160. ctions 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 Various actions depending on the operation mode follow Finally the 3 second backup timer is implemented that will write the PWM 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_p 6 31 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 or usr local 6 32 Using the standard IO facili
161. d 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 A is written No argument is converted The complete conversion specifica tion is 9696 eE The double argument is rounded and converted in the format d dddesdd where there is one digit before the decimal point charac ter 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 ddd 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 G 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 us
162. d 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 and 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 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 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 Tdata 0x801100 defsym end 0x80ffff Note See explanation for offset 0x800000 See the chapter about using gcc for the w1 options on board RAM external RAM 0x0100 Ox10FF 0x1100 OxFFFF SP 1 malloc heap end heap end RAMEND brkval malloc heap start heap start bss end data end bss start data start Figure 7 Internal RAM stack only external RAM variables and heap If dynamic memory should be placed in external RAM while keeping the variab
163. d by Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 1 3 Supported Devices 2 the ANSI X3 159 1989 and ISO IEC 9899 1990 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 guarenteed 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 context undefined behaviour will result 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 AT90S Type Devices at90s1200 1 at90s2313 at90s2323 at90s2333 at90s2343 219054414 219054433 219054434 219058515 at90c8534 at90s8535 ATmega Type Devices atmega8 atmegal03 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 1 3 Supported Devices atmega128 atmega1280 atmega1281 atmega16 atmegal61 atmega162 atmega 163 atmegal64p atmega 165 atmega165p atme
164. ddresses but that is not covered by this example 6 33 2 TWI example project The ATmega TWI hardware supports both master and slave operation This example will 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 33 Example using the two wire interface TWI 174 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 Usually there is probably not much need to add more EEPROM to an ATmega system that way the smallest possible AVR d
165. define PRIGFAST16 d define PRIi16 i define PRIiLEASTI16 i define PRIFAST16 i define PRId32 ld define PRIGLEAST32 define PRIdFAST32 Id define PRIi32 li define PRIiLEAST32 li define PRIiFAST32 li define PRId16 define PRIiPTR PRIi16 define PRIo8 o define PRIOLEASTS o define PRIOFASTS 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 PRIX 16 X define PRIXLEAST16 X define PRIXFAST16 X define PRIo32 lo define PRIOLEAST32 lo define PRIoFAST32 lo define PRIu32 lu define PRIULEAST32 lu define PRIuFAST32 lu define PRIx32 lx Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 48 define PRIXLEAST32 lx 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 SCNdLEAST16 d define SCNdFAST16 d define SCNi16 i define SCNiLEAST16 i define SCNIFASTI6 i define SC
166. e addr N Bytes 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 gt 8 10 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 240 8 10 1 Options for the C compiler avr gcc 8 10 1 1 Machine specific options for the AVR The following machine specific options are recognized by the C compiler frontend mmcu architecture Compile code for architecture Currently known architectures are avrl Simple CPU core only assembler support avr2 Classic CPU core up to 8 KB of ROM avr3 Classic CPU core more than 8 KB of ROM avr4 Enhanced CPU core up to 8 KB of ROM avr5 Enhanced CPU core more than 8 KB of ROM avr6 Enhanced CPU core Program Counter of 3 bytes By default code is generated for th
167. e 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 22 avr libc and assembler programs 183 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 times 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 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
168. e describes many things around these displays including common pinouts Modules Combining C and assembly source files e A simple project A more sophisticated project Using the standard IO facilities Example using the two wire interface TWI Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 29 Combining and assembly source files 142 6 29 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 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 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
169. e application defines the macro __ASSERT_USE_STDERR before including the lt assert h gt header file By default only abort will be called to halt the application Defines define assert expression Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 2 lt avr boot h gt Bootloader Support Utilities 9 6 1 2 Define Documentation 6 1 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 6 2 lt avr boot h gt Bootloader Support Utilities 6 2 1 Detailed Description include avr io h 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 pr
170. e 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 and shows the preprocessor symbol declared by the mmcu option Architecture MCU name Macro avrl at90s1200 __AVR_AT90S1200__ avr attiny 11 __AVR_ATtiny11__ attiny12 __AVR_ATtiny12__ avrl attiny 15 __AVR_ATtiny15__ avrl attiny28 __AVR_ATtiny28__ avr2 at90s2313 __AVR_AT90S2313__ avr2 at90s2323 AVR AT9082323 avr2 at90s2333 __AVR_AT90S2333__ avr2 at90s2343 AVR 479052343 avr2 attiny22 __AVR_ATtiny22__ avr2 attiny24 __AVR_ATtiny24__ Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 241 Architecture MCU name Macro avr2 attiny25 __AVR_ATtiny25__ avr2 attiny26 __AVR_ATtiny26__ avr2 attiny261 __AVR_ATtiny261__ avr2 attiny44 __AVR_ATtiny44__ avr2 attiny45 __AVR_ATtiny45__ avr2 attiny461 __AVR_ATtiny461__ avr2 attiny84 __AVR_ATtiny84__ avr2 attiny85 __AVR_ATtiny85__ avr2 attiny86 1 __AVR_ATtiny861__ avr2 at90s44 14 __AVR_AT90S4414__ av
171. e bug fixes and under some circumstances additional functionality e g adding support for a new device If major version number has changed this implies that the required versions of gcc and binutils have changed Consult the README file in the toplevel directory of the AVR Libc source for which versions are required 8 6 1 2 Development Versions The major version number of a development series is always the same as the last stable release The minor version number of a development series is always an odd number and is 1 more than the last stable release The patch version number of a development series is always 0 until a new branch is cut at which point the patch number is changed to 90 to denote the branch is approaching a release and the date appended to the version to denote that it is still in development All versions in development in cvs will also always have the date appended as a fourth version number The format of the date will be YY YYMMDD So the development version number will look like this 1 1 0 20030825 While a pre release version number on a branch destined to become either 1 2 or 2 0 will look like this 1 1 90 20030828 8 6 2 Releasing AVR Libc 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 cvs and how to checkout multiple source trees in a single directory without having them clobber each o
172. e 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 For x and X conversions a non zero result has the string 0 or OX for X conversions prepended to it 0 zero Zero padding For all conversions 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 An 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 adjustm ment flag has been given to fill out the field width An optional precision in the form of a period followed by an optional digit string If the digi
173. e for device name USARTI SIG USARTI Tx AT90CANI28 AT90CAN32 AT90CAN64 TX vect UARTI Complete ATmegal28 ATmega64 ATmega640 AT TRANS megal280 ATmegal281 ATmega324 AT megal64 ATmega644 USARTI SIG USARTI Data AT90CANI28 AT90CAN32 AT90CAN64 UDRE vect UARTI Register Empty ATmegal28 ATmegal62 ATmega64 AT DATA mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 USART2_ SIG_ USART2 Rx ATmega640 ATmegal280 ATmega1281 RX_vect USART2_ Complete RECV USART2 SIG USART2 Tx ATmega640 ATmegal280 ATmegal281 TX vect USART2 Complete TRANS USART2_ SIG_ USART2 Data ATmega640 ATmegal280 ATmegal281 UDRE vect USART2 register Empty DATA USART3 SIG USART3 Rx ATmega640 ATmegal280 ATmegal281 RX_vect USART3 Complete RECV USART3 SIG USART3 Tx ATmega640 ATmegal280 ATmegal281 TX vect USART3 Complete TRANS USART3 SIG USART3 Data ATmega640 ATmegal280 ATmegal281 UDRE vect USART3 register Empty DATA USART SIG USART Rx ATmegal6 ATmega32 ATmega323 AT RXC vect USART Complete mega8 RECV SIG_ UART_RECV USART_RX_ SIG_ USART Rx AT90PWM3 AT90PWM2 ATmega3250 vect USART_ Complete ATmega3290 ATmega6450 ATmega6490 SIG ATmega8535 ATmegal68 ATmega48 AT UART RECV mega88 ATtiny2313 USART SIG USART Tx ATmegal6 ATmega32 ATmega323 AT TXC vect USART Complete mega8 TRANS SIG_UART_ TRANS USART_TX_ SIG_ USART Tx AT90PWM3 AT90PWM2
174. e 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 C compiler e g through a char variable initialized directly to a particular address it would be sufficient to defer the initializa tion 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 8 3 17 Which O flag to use There s a common misconception that larger numbers behind the option might auto matically cause better optimization First there s no universal definition for better with optimization often being a speed vs code size tradeoff See the detailed discus sion for which option affects which part of the code generation A test case was run on an ATmega128 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
175. e 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 6 23 2 3 void _delay_ms double __ms Perform a delay of __ms milliseconds using _delay_loop_2 The macro F_CPU is supposed to be defined to a constant defining the CPU clock frequency in Hertz The maximal possible delay is 262 14 ms F_CPU in MHz 6 23 2 4 void delay us double us Perform a delay of __us microseconds using delay loop 10 The macro CPU is supposed to be defined to a constant defining the CPU clock frequency in Hertz The maximal possible delay is 768 us F CPU in MHz 6 24 lt util parity h gt Parity bit generation 6 24 1 Detailed Description finclude lt util parity h gt This header file contains optimized assembler code to calculate the parity bit for a byte Defines define parity even bit val Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 25 lt util twi h gt TWI bit mask definitions 118 6 24 2 Define Documentation 6 24 2 1 define parity even bit val Value extension unsigned char t asm mov tmp reg 0 n t swap 0 n t eor 0 tmp reg n t mov tmp reg 0 n t ler S0 Tat Wier 20 eor 0 __tmp_reg__ EE wt LE 0 unsigned char val 0 _t 1 gt gt 1 amp 1 Returns lif val has an odd number of
176. e 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 already 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 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 206 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
177. e to run as a a remote target backend 8 8 8 Simulavr Simulavr also uses the configure system so to build and install gunzip c simulavr version tar gz tar xf cd simulavr lt version gt mkdir obj avr cd obj avr configure prefix PREFIX make make install Xr Xr Xr d ox xn or 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 8 8 9 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 version tar gz tar xf cd avarice lt version gt mkdir obj avr cd obj avr configure prefix PREFIX make make install AY X X X X d WH 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 9 Using the avrdude program 238 work This is usually done by invoking the configure script like this Replace hdr path with the path to the b d 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 confi
178. e value and ERANGE is stored in errno If the correct value would cause underflow zero is returned and ERANGE is stored in errno FIXME HUGE VAL needs to be defined somewhere The bit pattern is Ox7fffffff but what number would this be 6 20 4 25 long strtol const char __nptr char __endptr int __base The strtol function converts the string in nptr 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 15 zero or 16 the string may then include a 0x 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 xendptr If there were digits at all however strtol stores the original value of nptr in endptr Thus if npt r is not NO but xxendptr is 0 on
179. ear avr_sfr 139 bit_is_set avr_sfr 140 boot_is_spm_interrupt avr_boot 11 boot_lock_bits_set avr_boot 11 boot_lock_bits_set_safe avr_boot 11 boot_lock_fuse_bits_get avr_boot 11 boot_page_erase avr_boot 12 boot_page_erase_safe avr_boot 12 boot_page_fill avr_boot 12 boot_page_fill_safe avr_boot 13 boot_page_write avr_boot 13 boot_page_write_safe avr_boot 13 boot_rww_busy avr_boot 13 boot_rww_enable avr_boot 14 boot_rww_enable_safe avr_boot 14 boot_spm_busy avr_boot 14 boot_spm_busy_wait avr_boot 14 boot_spm_interrupt_disable avr_boot 14 boot_spm_interrupt_enable avr_boot 14 BOOTLOADER_SECTION Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 258 avr_boot 14 bsearch avr_stdlib 96 calloc avr_stdlib 97 cbi deprecated_items 40 ceil avr_math 59 clearerr avr_stdio 83 Combining C and assembly source files 142 cos avr_math 59 cosh avr_math 59 ctype isalnum 43 isalpha 43 isascii 43 isblank 43 iscntrl 44 isdigit 44 isgraph 44 islower 44 isprint 44 ispunct 44 isspace 44 isupper 44 isxdigit 44 toascii 44 tolower 45 toupper 45 Demo projects 140 deprecated_items cbi 40 enable_external_int 40 inb 41 inp 41 INTERRUPT 41 outb 41 outp 41 sbi 42 timer_enable_int 42 disassembling 149 div avr_stdlib 97 div_t 177 quot 178 rem 178 EDOM avr_errno 45 EEMEM avr_eeprom 17 eeprom_busy_wait avr_eeprom 17
180. ect 151 6e 83 e0 Idi 124 0 03 3 70 2f 3f cpi r18 OxFF 255 728 38 07 ope r19 124 74 99 FA brne 38 Ox9c lt __SREG__ 0x5d gt direction DOWN 76 81 eO ldi r24 0x01 1 78 80 93 60 00 sts 0x0060 r24 Je Qf c0 rjmp 30 Ox9c lt __SREG__ 0x5d gt break case DOWN if pwm 0 7e 20 91 61 00 145 r18 0x0061 82 30 91 62 00 145 r19 0x0062 66 21250 subi r18 0x01 1 88 30 40 sbci r19 0x00 0 8a 30 93 62 00 sts 0x0062 r19 8e 20 93 61 00 sts 0x0061 r18 923 21 15 cp r18 rl 94 31 05 rl19 el 96 11 4 brne 4 Ox9c lt __SREG__ 0x5d gt direction UP 98 10 92 60 00 sts 0x0060 r1 break OCR pwm x Note 5 9c 3b bd out 0x2b r19 43 9e 2a bd out 0 2 r18 42 a0 8f 91 pop r24 a2 3f 91 pop r19 a4 2f 91 pop r18 a6 Of 90 pop a8 Of be out 0x3f r0 63 aa Of 90 pop 90 1 18 95 reti 000000b0 lt ioinit gt void ioinit void x Note 6 Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys TCCRIA TIMER1_PWM_INIT b0 83 e8 Tdi r24 0x83 131 b2 8f bd out 0x2f r24 47 x Start timer 1 x TCCRIA TCCRIB could actually be the same register x take care to not clobber it x TCCRIB TIMER1_CLOCKSOURCE b4 8e b5 in r24 0x2e 46 b6 81 60 ori r24 0 01 1 so Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 152 b
181. ed 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 90 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 existent 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 none of the additional options that can be specified using conversion flags these flags are parsed correctly from the format spec ification but then simply ignored This version can be requested using the following compiler options Wl u vfprintf lprintf min If the full functionality including the floating point conversions is required the follow ing options should be used
182. eeprom_is_ready avr_eeprom 17 eeprom_read_block avr_eeprom 17 eeprom_read_byte avr_eeprom 17 eeprom_read_word avr_eeprom 17 eeprom_write_block avr_eeprom 17 eeprom_write_byte avr_eeprom 17 eeprom_write_word avr_eeprom 18 EMPTY_INTERRUPT avr_interrupts 136 enable_external_int deprecated_items 40 EOF avr_stdio 81 ERANGE avr_errno 45 Example using the two wire interface TWD 173 exit avr_stdlib 97 exp avr_math 60 fabs avr_math 60 FAQ 185 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 259 fclose fread avr_stdio 83 avr_stdio 85 fdev_close free avr_stdio 81 avr_stdlib 97 fdev_get_udata frexp avr_stdio 81 avr_math 60 fdev_set_udata fscanf avr_stdio 81 avr_stdio 85 FDEV_SETUP_STREAM fscanf_P avr_stdio 81 avr_stdio 85 fdev_setup_stream fwrite avr_stdio 81 fdevopen avr_stdio 83 feof avr_stdio 84 ferror avr_stdio 84 fflush avr_stdio 84 ffs avr_string 105 ffsl avr_string 105 ffsll avr_string 105 fgetc avr_stdio 84 fgets avr_stdio 84 FILE avr_stdio 82 floor avr_math 60 fmod avr_math 60 fprintf avr_stdio 85 fprintf_P avr_stdio 85 fputc avr_stdio 85 fputs avr_stdio 85 fputs_P avr_stdio 85 avr_stdio 86 GET_EXTENDED_FUSE_BITS avr_boot 14 GET_HIGH_FUSE_BITS avr_boot 15 GET_LOCK_BITS avr_boot 15 GET_LOW_FUSE_BITS avr_boot 15 getc avr_stdio 82 getchar avr_stdio 82 gets avr_stdio
183. ega649 ATmega6490 AT megal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 AT tiny13 ATtiny24 ATtiny44 ATtiny84 AT tiny45 ATtiny25 ATtiny85 PCINTI vect SIG PIN Pin Change Inter ATmegal62 ATmegal65 ATmegal69 AT CHANGEI rupt Request 1 mega325 ATmega3250 ATmega329 AT mega3290 ATmega406 ATmega645 AT mega6450 ATmega649 ATmega6490 AT megal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 AT tiny24 ATtiny44 ATtiny84 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 128 Vector name Old vector Description Applicable for device name PCINT2_vect SIG_PIN_ Pin Change Inter ATmega3250 ATmega3290 ATmega6450 CHANGE2 rupt Request 2 ATmega6490 ATmegal68 ATmega48 AT mega88 ATmega640 ATmegal280 AT megal281 ATmega324 ATmegal64 AT mega644 PCINT3_vect SIG_PIN_ Pin Change Inter ATmega3250 ATmega3290 ATmega6450 CHANGE3 rupt Request 3 ATmega6490 ATmega324 ATmegal64 ATmega644 PCINT vect SIG PIN ATtiny2313 ATtiny261 ATtiny461 AT CHANGE tiny861 SIG PCINT PSCO SIG PSCO PSCO Capture AT90PWM3 AT90PWM2 vect CAPTURE Event PSCO EC SIG PSCO PSCO End Cycle AT90PWM3 AT90PWM2 vect END CYCLE PSCI SIG PSCI PSCI Capture AT90PWM3 AT90PWM2 CAPT vect CAPTURE E
184. ega8535 ATmega640 ATmegal280 megal281 ATmega324 ATmegal64 AT mega644 INT3 vect SIG External Interrupt AT90PWM3 AT90PWM2 AT90CAN128 INTERRUPT3 Request 3 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmega406 ATmega64 AT mega640 ATmegal280 ATmegal281 INT4_vect SIG_ External Interrupt AT90CANI28 AT90CAN32 AT90CAN64 INTERRUPT4 Request 4 ATmegal03 ATmegal28 ATmega64 AT mega640 ATmegal280 ATmegal281 INTS vect SIG External Interrupt AT90CANI28 AT90CAN32 AT9OCAN64 INTERRUPTS Request 5 ATmegal03 ATmegal28 ATmega64 AT mega640 ATmegal280 ATmegal281 INT6_vect SIG_ External Interrupt AT90CANI28 AT90CAN32 AT90CAN64 INTERRUPT6 Request 6 ATmegal03 ATmegal28 ATmega64 AT mega640 ATmegal280 ATmegal281 INT7_vect SIG_ External Interrupt AT90CANI28 AT90CAN32 AT9OCAN64 INTERRUPT7 Request 7 ATmegal03 ATmegal28 ATmega64 AT mega640 ATmegal280 ATmegal281 IO PINS vect SIG PIN External Interrupt ATtinyll ATtiny12 ATtiny15 ATtiny26 SIG PIN Request 0 CHANGE LCD vect SIG LCD LCD Stat of ATmegal69 ATmega329 ATmega3290 Frame ATmega649 ATmega6490 LOWLEVEL SIG PIN Low level Input ATtiny28 IO PINS vect on Port B OVRIT vect SIG CAN CAN Timer AT90CANI28 AT90CAN32 AT90CAN64 OVERFLOW 1 Overrun PCINTO vect SIG PIN Pin Change Inter ATmegal62 ATmegal65 ATmegal69 AT CHANGEO rupt Request 0 mega325 ATmega3250 ATmega329 AT mega3290 ATmega406 ATmega645 AT mega6450 ATm
185. emo 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 22 avr libc and assembler programs 180 8 22 avr libc and assembler programs 8 2 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 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 ma
186. er 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 ATmega128 keeps crashing Port F 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 operation 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 messsage Why are many interrupt flags cleared by writing a logical 1 Why have programmed fuses the bit value 0 Which AVR specific assembler operators are available Why are interrupts re enabled in the middle of writing the stack pointer Why are there five different linker scripts Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 187 8
187. erflow 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 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 6 29 2 2 project h In order for the interrupt service routines to be as fast as possi ble some of the CPU registers are set aside completely for use by these routines so the compiler wou
188. es 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 Wl Map demo map to my link command Relink the application using the following 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 0x00000000 Oxde vectors vectors 0x00000000 0x26 junk AVR avr libc 1 4 avr lib avr4 atmega8 crtm8 o 0x00000000 vectors 0x00000000 vector default vectors x progmem gccx x progmem x 0x00000026 ALIGN 0x2 0x00000026 trampolines start trampolines trampolines 0x00000026 0 0 linker stubs x trampolinesx 0x00000026 trampolines end jumptables x jumptables x x lowtext x lowtextx 0x00000026 ctors start The text segment where program instructions are stored starts at location 0x0 fini2 fini2 finil sftinal1 fini0 tini 0x000000de _etext data 0x00800060 0x0 load address 0x000000de 0x00800060 PROVIDE __data_start data data 0x00800060 0x0 demo o data 0x00800060 0x0 junk AVR avr libc 1 4 avr lib avr4 atmega8 crtm8 o datax rodata rodatax gnu linkonce dx Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 154 0x00800060 ALIGN 0x2 0x00800060 _edata 0x00800060 P
189. ess 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 values ie a bit returned as 0 means the corresponding fuse or lock bit is programmed 6 2 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 2 lt avr boot h gt Bootloader Support Utilities 13 6 2 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 6 2 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 6 2 2 8 define boot page fill safe address data Value do boot spm busy wait eeprom_busy_wai
190. ess 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 either address 0x60 or Ox100 depending on the device AVR Libc supports both these paradigms While by default the implementation uses memory mapped IO access this is hidden from the programmer So the programmer can access IO registers either with a special function like out b include lt avr io h gt outb PORTA 0x33 or they can assign a value directly to the symbolic address PORTA 0x33 The compiler s choice of which method to use when actually accessing the IO port is completely independent of the way the programmer chooses to write the code So even if the programmer uses the memory mapped paradigm and writes PORTA 0x40 the compiler can optimize this into the use of an sbi instruction of course provided the target address is within the allowable range for this instruction and the right hand side of the expression is a constant value known at compile time The advantage of using the memory mapped paradigm in C programs is that it makes the programs more portable to other C compilers for the AVR platform Some people might also feel that this is more readable For example the following two statements would be equivalent outb DDRD inb DDRD amp LCDBITS DDRD amp LCDBITS The generated code is identical for b
191. et avr disable nls If you don t specify the prefix option the tools will get installed in the usr ilocal 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 chang ing 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 8 Installing the GNU Tool Chain 235 Note BSD users should note that the project s Makefile uses GNU make syntax This means FreeBSD users may need to build the tools by using gmake 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 freebsd org cgi cvsweb cgi ports devel avr binutils files patch ne 8 8 4 GCC for the AVR tar
192. evice 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 much 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 6 33 3 The Source Code The source code is installed under Sprefix share doc avr libc examples twitest twitest c where prefix is a configuration option For Unix systems it is usually set to either usr or 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 33 Example using the two wire interface TWI 1
193. ext digit after 97 will be the letter a Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 103 The ultoa function returns the pointer passed as s 6 20 4 28 char utoa unsigned int val char x s 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 97 will be the letter a The utoa function returns the pointer passed as s 6 20 5 Variable Documentation 6 20 5 1 charx malloc heap end malloc tunable 6 20 5 2 charx malloc heap start malloc tunable 6 20 5 3 size t malloc margin malloc tunable 6 21 lt string h gt Strings 6 21 1 Detailed Description finclude string h Generated on Mon Oct 9 22
194. f 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 x fdevopen int put char FILE int xget FILE 6 19 2 Define Documentation 6 19 2 1 define FDEV EOF 2 Return code for an end of file condition during device read To be used in the get function of fdevopen 6 19 2 2 define FDEV ERR 1 Return code for an error condition during device read To be used in the get function of fdevopen 6 19 2 3 define FDEV SETUP READ SRD fdev setup stream with read intent 6 19 2 4 define FDEV SETUP RW SRD SWR setup stream with read write intent Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 81 6 19 2 5 define FDEV SETUP WRITE SWR fdev setup stream with write intent 6 19 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 6 19 2 7 define fdev close This macro frees up any library resources that might be associated with stream It should be called if st ream is no longer needed right before the application is going to destroy the st ream object itself Currently this macr
195. ga168 atmega169 atmega169p atmega2560 atmega2561 atmega32 atmega323 atmega324p atmega325 atmega3250 atmega329 atmega3290 atmega48 atmega406 atmega64 atmega640 atmega644 atmega644p Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 1 3 Supported Devices atmega645 atmega6450 atmega649 atmega6490 atmega8515 atmega8535 atmega88 ATtiny Type Devices attiny11 1 attiny12 1 attiny 13 attiny15 1 attiny22 attiny24 attiny25 attiny26 attiny261 attiny28 1 attiny2313 attiny44 attiny45 attiny46 1 attiny84 attiny85 attiny861 Misc Devices Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 2 avr libc Module Index 5 at94K 2 at76c711 3 at43usb320 at43usb355 at86rf401 at90can32 at90can64 at90can128 at90pwm2 at90pwm3 at90usb646 at90usb647 at90usb1286 at90usb1287 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 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 2 avr libc Module Index
196. get 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 5 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 disable nls disable libssp with dwarf2 make make install To save your self some download time you can alternatively download only the gcc core version tar bz2 and 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 support Note 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 freebsd org cgi cvsweb cgi ports devel avr gcc files patch newdevi Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 8 Installing the GNU Tool Chain 236 8 8 5 AVRLibc Warning You must install avr binutils avr gcc and make sure your path is set properly before installing avr libc Note If you have obtained the latest avr libc from cvs you will have to run the bootstrap script before using either of the build methods described below To bui
197. gure prefix PREFIX 8 9 Using the avrdude program Note This section was contributed by Brian Dean bsd bsdhome com 1 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 interactive 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 c
198. h 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 Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 68 6 18 2 Define Documentation 6 18 2 1 define INT16_C value value define a constant of type int16_t 6 18 2 2 define INT16_MAX 0x7fff largest positive value an int16_t can hold 6 18 2 3 define INT16_MIN INT16_MAX 1 smallest negative value an int16_t can hold 6 18 2 4 define INT32_C value __CONCAT value L define a constant of type int32_t 6 18 2 5 define INT32 MAX Ox7fffffffL largest positive value an int32_t can hold 6 18 2 6 define INT32 MIN INT32 MAX IL smallest negative value an int32 t can hold 6 18 2 7 ftdefine INT64_C value __CONCAT value LL define a constant of type int64 t 6 18 2 8 define INT64 MAX OXx7fffffffffffffffLL largest positive value an int64 t can hold 6 18 2 9 define INT64 MIN INT64 MAX ILL smallest negative value an int64 t can hold 6 18 2 10 define INT8 C value int8 t value define a constant of type int8 t 6 18 2 11 define INT8 MAX 0x7f largest positive value an int8 t can hold Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 69 6 18 2 12 defi
199. hat 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 8 323 Is it really impossible to program the ATtinyXX in C 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 8 3 1 What is this clock skew detected messsage It s a known problem of the MS DOS FAT 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 205 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
200. hdog 38 WDTO 2S avr watchdog 38 WDTO 30MS avr watchdog 38 WDTO 45 avr watchdog 38 WDTO 500MS avr watchdog 38 WDTO 60MS avr watchdog 39 WDTO 8S avr watchdog 39 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen
201. he ac tual value Note that unless a minit stack option has been given when compiling the C source file that contains the function main the stack will still remain in inter nal 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 variables in the data section so in this situation no stack heap collision can occur 8 11 Todo List Group avr_boot_ From email with Marek On smaller devices all except AT mega64 128 SPM_REG 15 in the I O space accessible with the shorter in and out instructions since the boot loader has a limited size this could be an important optimization 8 12 Deprecated List Global enable_external_int Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 12 Deprecated List 250 Global INTERRUPT Global timer_enable_int Global inp Global outp Global inb Global outb Global sbi Global cbi Global SIGNAL Do not use anymore in new code Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen Index PATH 232 PREFIX 232 prefix 232 lt assert h gt Diagnostics 8 lt avr boot h gt Bootloader Support Utili ties 9 lt avr eeprom h gt EEPROM handling 1
202. he 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 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 7 avr libc Data Structure Documentation 7 1 div_t Struct Reference 7 1 Detailed Description Result type for function div Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 7 2 ldiv t Struct Reference 178 Data Fields int quot int rem 7 1 2 Field Documentation 7 1 21 int div t quot The Quotient 7 1 2 2 int div_t rem The Remainder The documentation for this struct was generated from the following file stdlib h 7 2 1div_t Struct Reference 7 2 Detailed Description Result type for function Idiv Data Fields long quot e long rem 7 2 2 Field Documentation 7 2 2 1 long Idiv_t quot The Quotient 7 2 2 1 long Idiv_t rem The Remainder The documentation for this struct was generated from the following file stdlib h
203. he 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 6 19 3 32 vfprintf FILE __ stream const char __fmt va list Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 88 vfprintf is the central facility of the print f family of functions It outputs values to stream 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 stream 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 b
204. he stack as opposed to passing them in registers for functions that take a fixed number of parameters the ability to pass one parameter less by implying st din will also save some execution time Defines define FILE struct file Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 79 define stdin __iob 0 define stdout __iob 1 define stderr __iob 2 define EOF 1 define fdev_set_udata stream u do stream udata u while 0 define fdev_get_udata stream stream 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 c __ define putchar __c fputc c stdout define getc __stream fgetc __stream define getchar fgetc stdin stream 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 constchar fmt int sprintf_P char __s const char x__fmt int snprintf char __
205. hip 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 239 1749 0x00 avrdude verifying avrdude 1750 bytes of flash verified avrdude done Thank you The 2313 option lets avrdude know that we are operating on an 419052313 chip This option specifies 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 memtyp
206. id attribute 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 202 8 3 19 My UART is generating nonsense My ATmega128 keeps crashing Port F 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 All 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 in 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 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 runn
207. if changed r29 r28 Y pointer is used as a frame pointer points to local data on stack if necessary Fixed registers r0 r1 Never allocated by gcc for local data but often used for fixed purposes 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 may 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 better 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 caller unsigned char is more efficient than signed char just clr r25 Argu ments to functions with variable argument lists printf etc are all passed on stack and char is extended to int
208. ifies the variable that ptr points to The compiler will not recognize this and may keep its value in any of the other registers Not only does 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 __5 __ ENG VE cli NND ld _ tmp reg al Wo NE inc tmp reg uA st al tmp reg ene out SREG 0 Yn 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 8 4
209. ing 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 8 3 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 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 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 st
210. ing 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 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 function named vector default which should be defined with ISR as such include lt avr interrupt h gt ISR __vector_default user code here Nested interrupts AVR hardware clears the global interrupt flag in SREG be fore 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 compiler as part of the normal function epilogue for an interrupt handler will even tually re enable further interrupts For that reason interrupt handlers normally do not
211. int64 t 74 JINTS C 71 INT8 MAX 72 int8_t 74 JINT FAST16 MAX 72 int fast16 t 74 JINT FAST32 MAX 72 int fast32 t 74 JINT FAST64 MAX 72 int fast64 t 74 JINT FAST8 MAX 72 int fast8 t 75 JINT LEAST16 72 int least16 t 75 JINT LEAST32 MAX 72 int least32 t 75 JINT LEAST64 MAX 72 int least64 t 75 JINT LEAST8 MAX 72 int least8 t 75 JINTMAX 72 JINTMAX MAX 72 intmax t 75 MAX 73 uintptr t 75 CE C Eg Cc e Ce avr_stdio _FDEV_EOF 80 _FDEV_ERR 80 _FDEV_SETUP_READ 80 _FDEV_SETUP_RW 80 _FDEV_SETUP_WRITE 80 clearerr 83 EOF 81 fclose 83 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 256 fdev_close 81 fdev_get_udata 81 fdev_set_udata 81 FDEV_SETUP_STREAM 81 fdev_setup_stream 81 fdevopen 83 feof 84 ferror 84 fflush 84 fgetc 84 fgets 84 FILE 82 fprintf 85 fprintf_P 85 fputc 85 fputs 85 fputs_P 85 fread 85 fscanf 85 fscanf_P 85 fwrite 86 getc 82 getchar 82 gets 86 printf 86 printf_P 86 pute 82 putchar 82 puts 86 puts_P 86 scanf 86 scanf_P 86 snprintf 86 snprintf_P 87 sprintf 87 sprintf P 87 sscanf 87 sscanf P 87 stderr 82 stdin 82 stdout 83 ungetc 87 vfprintf 87 vfprintf P 90 vfscanf 90 vfscanf P 93 vprintf 93 vscanf 93 vsnprintf 93 vsnprintf P 93 vsprintf 93 vsprintf P 93 avr std
212. 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 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 6 32 3 5 Icd h This function declares the public interface of the higher level char acter IO LCD driver 6 32 3 6 Icd c The implementation of the higher level LCD driver This driver b
213. 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 crts1200 0 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 this 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
214. ion returns a pointer to the resulting string dest 6 21 3 21 int strncmp const char s1 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 sl and s2 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 match or be greater than s2 6 21 3 22 char strncpy char dest const char 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 6 21 3 23 size t strnlen const char x 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 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
215. ions dicussed below Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 7 Memory Sections 228 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 8 7 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 required 8 7 3 The bss Section Uninitialized global or static variables end up in the bss section 8 7 4 The eeprom Section This is where eeprom variables are stored
216. is 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 assembler with cpp the compiler frontend needs to be told to pass the gstabs option down to the assembler 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 194 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 function 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 refere
217. is in the table Alternatively the squid cable from the JTAG ICE kit can be used if available Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 31 more sophisticated project 160 Port Header Color Function Connect to D0 1 brown RxD RXD of the RS 232 header DI 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 LED 1 pin 2 LEDs header D7 8 white 1 second LED 3 flash LEDs header GND 9 unused VCC 10 unused Figure 3 Wiring of the STK500 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 31 more sophisticated project 161 The following picture shows the alternate wiring where LEDI is connected but SW2 is not Figure 4 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 be 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
218. is 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 244 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 mdeb Generate lots of debugging information to stderr 8 10 1 2 Selected general compiler options The following general gcc options might be of some interest to AVR users On Optimization level n Increasing n is meant to optimize more an optimization level of 0 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 that 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 al
219. is requires a recent version of AVR GCC to work GCC 4 2 or patched GCC 4 x Example ISR INTO_vect PORTB 42 ISR_ALIAS INTI_vect INTO 6 26 2 4 define SIGNAL vector include lt avr interrupt h gt Introduces an interrupt handler function that runs with global interrupts initially dis abled This is the same as the ISR macro Deprecated Do not use anymore in new code 6 27 lt avr sfr_defs h gt Special function registers 6 27 1 Detailed Description When working with microcontrollers many of the tasks usually consist of controlling the peripherals that are connected to the device respectively programming the subsys Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 27 lt avr sfr_defs h gt Special function registers 138 tems that are contained in the controller which by itself communicate with the circuitry connected to the controller The AVR series of microcontrollers offers two different paradigms to perform this task There s a separate IO address space available as it is known from some high level CISC CPUs that can be addressed with specific IO instructions that are applicable to some or all of the IO address space in out sbi etc The entire IO address space is also made available as memory mapped IO i e it can be accessed using all the MCU instructions that are applicable to normal data memory The IO register space is mapped into the data memory addr
220. it 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 6 27 2 Define Documentation 6 27 21 define_BV bit 1 lt lt bit include lt avr io h gt Converts a bit number into a byte value 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 28 Demo projects 140 6 27 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 sfr is clear This will return non zero if the bit is clear and a 0 if the bit is set 6 27 2 3 define bit is set sfr bit _SFR_BYTE sfr amp _BV bit include lt avr io h gt Test whether bit bit in IO register sfr is set This will return a 0 if the bit is clear and non zero if the bit is set 6 27 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 6 27 2 5 define loop_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 6 28 Demo projects 6 28 1 Detailed Description Various small demo projects are provided to illustrate several aspects of using
221. ite 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 6 19 2 12 define FILE struct file FILE is the opaque structure that is passed around between the various standard IO functions 6 19 2 13 define getc stream fgetc stream The macro get c used to be a fast macro implementation with a functionality iden tical to fgetc For space constraints in avr libc itis just an alias for getc 6 19 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 6 19 2 15 define putc c __ stream stream The macro put c used to be a fast macro implementation with a functionality iden tical to fputc For space constraints in avr libc it is just an alias for fputc 6 19 2 16 putchar __c fputc __c stdout The macro put char sends character c to stdout 6 19 2 17 define 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 Mon Oct 9 22 30 53 2006 for avr libc by Doxygen
222. ite 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 MAX_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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 7 avr libc Data Structure Documentation 177 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 first 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 t
223. its 6 18 3 13 typedef int64_t intmax_t largest signed int available 6 18 3 14 typedef int16_t intptr_t Signed pointer compatible type 6 18 3 15 typedef unsigned int uint16_t 16 bit unsigned type 6 18 3 16 typedef unsigned long int uint32_t 32 bit unsigned type 6 18 3 17 typedef unsigned long long int uint64_t 64 bit unsigned type 6 18 3 18 typedef unsigned char uint8_t 8 bit unsigned type 6 18 3 19 typedef uint16_t uint_fast16_t fastest unsigned int with at least 16 bits 6 18 3 20 typedef uint32_t uint_fast32_t fastest unsigned int with at least 32 bits Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 75 6 18 3 21 typedef uint64_t uint_fast64_t fastest unsigned int with at least 64 bits 6 18 3 22 typedef uint8_t uint_fast8_t fastest unsigned int with at least 8 bits 6 18 3 23 typedef uint16_t uint_least16_t unsigned int with at least 16 bits 6 18 3 24 typedef uint32_t uint_least32_t unsigned int with at least 32 bits 6 18 3 25 typedef uint64_t uint_least64_t unsigned int with at least 64 bits 6 18 3 26 typedef uint8 t uint_least8_t unsigned int with at least 8 bits 6 18 3 27 typedef uint64_t uintmax t largest unsigned int available 6 18 3 28 typedef uint16_t uintptr_t Unsigned pointer compatible type 6 19 lt stdio h gt Standard IO facilities 6 19 1 Detailed Description include lt stdio h gt
224. ix 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 8 10 3 Controlling the linker avr ld 8 10 3 1 Selected linker options While there are no machine specific options for avr ld a number of the standard options might be of interest to AVR users lname Locate the archive library named libname a and use it to resolve currently unresolved symbols from it The library is searched along a path that con sists 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 defsym symbol expr Define a global symbol symbol using expr as the value Print linker map to stdout Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 248 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 Itext
225. l 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 xnptr is not NO but xxendptr is 0 on return the 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 6 20 4 27 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 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 n
226. l is found respectively to be less than to match or be greater than s2 6 21 3 14 char 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 string dest must be large enough to receive the copy Returns The strcpy function returns a pointer to the destination string dest 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 6 21 3 15 size t strlcat char x dst const char x src size t siz 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 109 Returns The strlcat function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 6 21 3 16 size_t strlcpy 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 Re
227. l 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 W1l linker options Pass the listed options to the assembler or linker respectively 59 Generate debugging information that used avr gdb Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 245 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 described 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
228. lar the watchdog reset flag before disabling the watchdog is required according to the datasheet Defines define wdt_reset volatile__ wdr define wdt_disable define wdt_enable timeout _wdt_write timeout Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 10 lt avr wdt h gt Watchdog timer handling 37 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 6 10 2 Define Documentation 6 10 2 1 define wdt_disable Value __asm__ _ volatile in tmp_reg__ SREG Maker X cli nNE X out 0 SLE n t out 0 zero reg n t out SREG tmp reg n t no outputs I SFR IO ADDR WD CONTROL REG r uint8 t WD CHANGE BV WDE ro Disable the watchdog timer if possible This attempts to turn off the Enable bit in the watchdog control register See the datasheet for details 6 10 2 2 define wdt_enable timeout wdt write timeout 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 register For those devices that have a WDTCSR register it uses the combination of the WDPO through WDP 3 bits See also the symbolic constants WDTO_15MS et al 6 10
229. ld and install avr libc gunzip c avr libc version tar gz tar xf cd avr libc lt version gt configure prefix PREFIX build config guess host avr make make install Xr X X XY 8 8 6 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 gunzip c avrdude version tar gz tar xf cd avrdude lt version gt mkdir obj avr cd obj avr configure prefix PREFIX make make install X X Xr XY Xo 8 8 7 GDB for the AVR target Gdb also uses the configure system so to build and install Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 8 Installing the GNU Tool Chain 237 bunzip2 c gdb lt version gt tar bz2 tar xf cd gdb lt version gt mkdir obj avr cd obj avr configure prefix PREFIX target avr make make install Xr X X ro Xr 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 thes
230. ld not use them for 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 cessing macro __ASSEMBLER__ which will be automatically set by the compiler Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 144 front end when preprocessing 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 flags 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 6 29 2 3 isrs S This file is a preprocessed assembly source file The preproces sor will be run by the compiler front end first resolving all include define etc directives The resulting program text will
231. ler 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 208 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 versions 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 no
232. les in internal RAM something like the following could be used Note that for demonstration Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 5 Using malloc 222 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 heap end 0x803fff external RAM S s 2 on board zx amp oo o o o sP 1 malloc heap end heap end RAMEND brkval bss end malloc heap start heap start data bss start data start Figure 8 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 plus 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 marginis set to 32 8 5 4 Implementation details Dynamic memory
233. lete deletes the previous character u control U ASCII NAK deletes the entire input buffer w control W ASCII ETB deletes the previous input 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 U
234. lf 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 5 j text j data O ihex lt 560 oe srec elf OBJCOPY j text j data O srec lt 6 oe bin elf j text j data O binary lt 50 Rules for building the eeprom rom images eeprom ehex ebin esrec ehex PRG eeprom hex PRG _eeprom bin esrec PRG eeprom srec o eeprom hex elf 5 j eeprom change section Ima eeprom 0 O ihex lt SR echo empty not generated exit 0 o eeprom srec elf 5 j eeprom change section Ima eeprom 0 O srec lt SR echo empty not generated exit 0 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 31 more sophisticated project 158 o eeprom bin elf 5 j eeprom change section lma eeprom 0 O binary lt 8 echo empty not generated exit 0 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 hex srec dox eps png pdf eps PRG eps png PRG png pdf pdf fig 5 FIG2DEV L eps lt Spat S EIG 5 FIG2DEV L pdf lt C png fig 5 FIG2DEV L png lt
235. lib compar fn t 95 malloc heap end 103 malloc heap start 103 malloc margin 103 abort 96 abs 96 atof 96 atoi 96 atol 96 bsearch 96 calloc 97 div 97 exit 97 free 97 itoa 97 labs 98 Idiv 98 Itoa 98 malloc 99 qsort 99 rand 99 RAND MAX 95 rand r 99 random 100 RANDOM MAX 95 random r 100 realloc 100 srand 100 srandom 100 strtod 100 strtol 101 strtoul 101 ultoa 102 utoa 103 avr string _FFS 105 ffs 105 ffsl 105 ffsll 105 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 257 memccpy 105 memchr 106 memcmp 106 memcpy 106 memmove 106 memgset 107 strcasecmp 107 strcat 107 strchr 107 strcmp 108 strcpy 108 strlcat 108 109 strlen 109 strlwr 109 strncasecmp 109 strncat 109 strncmp 110 strncpy 110 strnlen 110 strrchr 110 strrev 111 strsep 111 strstr 111 strtok_r 112 strupr 112 avr_version AVR_LIBC_DATE_ 35 AVR LIBC DATE STRING 35 AVR LIBC MAJOR 35 AVR LIBC MINOR 35 AVR REVISION 35 AVR LIBC VERSION STRING 35 AVR VERSION avr watchdog wdt disable 37 wdt enable 37 wdt reset 37 WDTO 120MS 37 WDTO 15MS 38 WDTO 1S 38 WDTO_250MS 38 WDTO 25 38 WDTO 30MS 38 im WDTO_4S 38 WDTO_500MS 38 WDTO_60MS 39 WDTO_8S 39 avrdude usage 238 avrprog usage 238 bit_is_cl
236. lly 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 uintl16 t read timerl void uint8_t sreg uint16_t val sreg SREG cli val TCNTI SREG sreg return val Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 192 Back to FAQ Index 8 3 10 How do I 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 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
237. matically assign enough registers to hold the entire operand In the assembler code you use A0 to refer to the lowest byte of the first operand 1 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 ptr and the compiler selects register Z 130 r31 then 0 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 r24 a0 with a lower case a following the percent sign then the compiler will create the proper assembler line 8 4 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 Generated on Mo
238. ment 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 setjmp longjmp see Chapter 7 of Advanced Pro gramming in the UNIX Environment by W Richard Stevens Example include lt setjmp h gt jmp buf env int main void if setjmp env handle error main processing loop which calls foo some where void foo void Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 17 lt setjmp h gt Non local goto 63 blah blah blah if err longjmp env 1 Functions e int setjmp imp_buf __jmpb void longjmp jmp_buf __jmpb int _ ATTR_NORETURN__ 6 17 2 Function Documentation 6 17 21 void longjmp jmp buf __jmpb int ret Non local jump to a saved 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
239. modem_update 115 util_delay _delay_loop_1 116 _delay_loop_2 117 _delay_ms 117 _delay_us 117 util_parity parity_even_bit 118 util_twi TW_BUS_ERROR 119 TW_MR_ARB_LOST 119 TW_MR_DATA_ACK 119 TW_MR_DATA_NACK 120 TW_MR_SLA_ACK 120 TW_MR_SLA_NACK 120 TW MT ARB LOST 120 MT DATA ACK 120 TW MT DATA NACK 120 TW MT SLA ACK 120 TW MT SLA NACK 120 TW INFO 120 utoa TW READ 120 TW REP START 120 TW SR ARB LOST GCALL ACK 121 TW SR ARB LOST SLA ACK 121 TW SR DATA 121 TW SR DATA NACK 121 TW SR GCALL ACK 121 TW SR GCALL DATA ACK 121 TW SR GCALL DATA NACK 121 TW SR SLA ACK 121 TW SR STOP 121 TW ST ARB LOST SLA ACK 121 TW ST DATA ACK 121 TW ST DATA 122 TW ST LAST DATA 122 TW ST SLA ACK 122 TW START 122 TW STATUS 122 TW STATUS MASK 122 TW WRITE 122 avr stdlib 103 vfprintf avr stdio 87 vfprintf P avr stdio 90 vfscanf avr stdio 90 vfscanf P avr stdio 93 vprintf avr stdio 93 vscanf avr stdio 93 vsnprintf avr stdio 93 vsnprintf P avr stdio 93 vsprintf avr stdio 93 vsprintf P Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 269 avr_stdio 93 wdt_ disable avr_watchdog 37 wdt_enable avr_watchdog 37 wdt_reset avr_watchdog 37 WDTO_120MS avr_watchdog 37 WDTO_15MS avr_watchdog 38 WDTO IS avr watchdog 38 WDTO 250MS avr watc
240. mspace 21 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 262 pgm_read_byte avr_pgmspace 21 pgm_read_byte_far avr_pgmspace 21 pgm_read_byte_near avr_pgmspace 21 pgm_read_dword avr_pgmspace 21 pgm_read_dword_far avr_pgmspace 21 pgm_read_dword_near avr_pgmspace 21 pgm_read_word avr_pgmspace 22 pgm_read_word_far avr_pgmspace 22 pgm_read_word_near avr_pgmspace 22 PGM_VOID_P avr_pgmspace 22 pow avr_math 61 PRId16 avr_inttypes 49 PRId32 avr_inttypes 49 PRId8 avr_inttypes 49 PRIdFAST 16 avr_inttypes 49 PRIdFAST32 avr_inttypes 49 PRIdFAST8 avr_inttypes 49 PRIdLEASTI6 avr inttypes 49 PRIdLEAST32 avr inttypes 49 PRIdLEASTS avr inttypes 49 PRIdPTR avr inttypes 40 PRIi16 avr inttypes 50 PRIi32 avr inttypes 50 PRIi8 avr_inttypes 50 PRIiFASTI6 avr inttypes 50 PRIiFAST32 avr inttypes 50 PRIiFAST8 avr_inttypes 50 PRIiLEASTI6 avr inttypes 50 PRIiLEAST32 avr inttypes 50 PRIiLEASTS avr inttypes 50 PRIiPTR avr inttypes 50 printf avr stdio 86 printf P avr stdio 86 PRIo16 avr_inttypes 50 PRIo32 avr inttypes 51 PRIo8 avr_inttypes 51 PRIoFAST16 avr_inttypes 51 PRIoFAST32 avr_inttypes 51 PRIoFASTS avr inttypes 51 PRIoLEAST16 avr_inttypes 51 PRIoLEAST32 avr_inttypes 51 PRIoLEASTS avr inttypes 51 PRIoPTR avr inttypes 51 PRIul6 avr_inttypes 51 PRIu32 avr_inttypes 51 PRIu8s avr_inttype
241. n 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 155 avr objcopy j text j data ihex demo elf demo hex The resulting demo hex file contains 000000012C06CC06BC06ACO69C068C067C066COFF 000100011 064 063 062 061 060 05 05 028 00020005DC05CC0O5BC011241FBECFESD4EODEBF65 0003000CDBF4BC01F920F920FB60F9211242F937A 100040003F938F9380916000882339F08130B9F01D 10005000209161003091620021C0209161003091B7 1000600062002F5F3F4F309362002093610083E076 00070002F3F380799F481E0809360000FC02091F2 00080006100309162002150304030936200209333 000900061002115310511F4109260003BBD2ABDAD 000A0008F913F912F910F900FBE0F901F90189539 1000B00083E88FBD8EB581608EBD1BBC1IABC82E00B 1000C00087BB84E089BF78940895F2DF85B78068A4 0E00D00085BF889585B78F7785BFF8CF91CF14 00000001FF The 1 option indicates that 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
242. n Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 215 asm volatile oli IND 14 r24 0 ARNE inc r24 n t st a0 r24 mane sei e ptr r24 The compiler might produce the following code eli ld r24 7 inc r24 st 7 r24 sei One easy solution to avoid clobbering register r24 is to make use of the special tem porary register tmp reg defined by the compiler asm volatile cli ld _tmp_reg__ a0 inc __tmp_reg__ st a0 __tmp_reg__ sel e ptr n t n t n t n t n t 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 uint8_t s asm volatile in 30 cli _ SREG__ ld _tmp_reg__ 1 inc tmp_reg__ st Sal __tmp_reg__ out SREG 0 amp r 8 e ptr NN NA VE n t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 216 Now every thing seems correct but it isn t really The assembler code mod
243. n 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 6 Release Numbering and Methodology 224 8 6 Release Numbering and Methodology 8 6 1 Release Version Numbering Scheme 8 6 1 1 Stable Versions stable release will always have a minor number that is an even number This implies that you should be able to upgrade to a new version of the library with the same major and minor numbers without fear that any of the APIs have changed The only changes that should be made to a stable branch ar
244. n 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 8 2 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 e asciz allocates a VO terminated string of characters C string Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 185 data switches to the data section initialized RAM variables 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
245. n compares the two strings s1 and s2 ignoring the case of the characters Parameters 81 A pointer to a string in the devices SRAM s2 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 sl is found respectively to be less than to match or be greater than s2 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 25 6 5 4 3 char x strcat_P char x dest PGM P src The strcat_P function is similar to strcat except that the src string must be located in program space flash Returns The strcat function returns a pointer to the resulting string dest 6 5 4 4 int stremp_P const char s1 52 The stremp_P function is similar to strcmp except that s2 is pointer to a string in program space Returns The strcmp P function returns an integer less than equal to or greater than zero if sl is found respectively to be less than to match or be greater than s2 6 5 4 5 char x 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 6 5 4 6 size tstrlcat P char dst PGM_P size_t siz Concatenate two strings The strlcat_P function is similar to strlcat
246. n 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 6 19 3 4 int feof FILE stream Test the end of file flag of st ream This flag can only be cleared by a call to clearerr 6 19 3 5 int ferror FILE x stream Test the error flag of st ream This flag can only be cleared by a call to clearerr 6 19 3 6 int fflush FILE x stream Flush st ream This is a null operation provided for source code compatibility only as the standard IO implementation currently does not perform any buffering 6 19 3 7 intfgetc FILE 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 6 19 3 8 char fgets char _ str int size FILE x stream Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 85 Read at most size 1 bytes from st ream until a newline character was encoun tered and store the characters in the buffer pointed to by str 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 NUL
247. nce 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 push push push push KKK RAK eor idi idi rjmp 6 r16 start loop L lo8 sometable H hi8 sometable f jump to loop test at end 7 Y loop continues here HNK KA breq Jf return from myfunc prematurely inc r16 23 cmp brlo 1b jump back to top of loop H K Hn la pop pop pop Pop pop ret HH H KK Back to FAQ Index 8 3 13 How do I 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 mask void Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 195 set bits func correct volatile uint8 t xport uint8 t mask xport mask define set bits macro port mask port mask int main void set_bits_func_wrong PORTB set_bits_func_correct amp PORTB 0x55 set bits macro PORTB 0 0 return 0 The first function will generate 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 regi
248. ndard 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 the 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 6 32 3 2 defines h This file just contains a few peripheral definitions The 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 6 32 3 3 hd44780 h This file describes the public interface of 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 f
249. ne 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 8 4 11 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 PORID Each asm statement is devided by colons into up to four parts 1 The assembler instructions defined as a single string constant in 0 1 2 A list of output operands separated 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 209 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
250. ne INT8_MIN INT8_MAX 1 smallest negative value an int8_t can hold 6 18 2 13 define INT_FAST16_MAX INT16_MAX largest positive value an int_fast16_t can hold 6 18 2 14 define INT_FAST16_MIN INT16_MIN smallest negative value an int_fast16_t can hold 6 18 2 15 define INT FAST32 MAX INT32 MAX largest positive value an int fast32 t can hold 6 18 2 16 define INT FAST32 MIN INT32 MIN smallest negative value an int fast32 t can hold 6 18 2 17 define INT FAST64 MAX INT64 MAX largest positive value an int fast64 t can hold 6 18 2 18 define INT FAST64 MIN INT64 MIN smallest negative value an int fast64 t can hold 6 18 2 19 define INT FAST8 MAX INT8 MAX largest positive value an int fast8 t can hold 6 18 2 20 define INT FAST8 MIN INT8 MIN smallest negative value an int fast8 t can hold 6 18 2 21 define INT LEASTI6 MAX INTI6 MAX largest positive value an int least16 t can hold 6 18 2 22 define INT LEAST16 MIN INT16 MIN smallest negative value an int least16 t can hold Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 18 lt stdint h gt Standard Integer Types 70 6 18 2 23 define INT LEAST32 MAX INT32 MAX largest positive value an int least32 t can hold 6 18 2 24 INT LEAST32 MIN INT32 MIN smallest negative value an int least32 t can hold 6 18 2 25 define INT LEAST64 MAX INT64 MAX largest positive value an int least64 t can hold 6 1
251. ng in program space 6 5 3 Typedef Documentation 6 5 3 1 prog char Type of a char object located in flash ROM 6 5 3 2 prog int16 t Type of an int16 t object located in flash ROM 6 5 3 3 prog int32 t Type of an int32 t object located in flash ROM 6 5 3 4 prog int64 t Type of an int64 t object located in flash ROM 6 5 3 5 prog int8 t Type of an int8 t object located in flash ROM 6 5 3 6 prog uchar Type of an unsigned char object located in flash ROM Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 24 6 5 3 7 prog uintl6 t Type of an uintl6 t object located in flash ROM 6 5 3 8 prog uint32 t Type of an uint32 t object located in flash ROM 6 5 3 9 prog uint64 t Type of an uint64 t object located in flash ROM 6 5 3 10 prog uint8 t Type of an uint8 t object located in flash ROM 6 5 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 6 5 4 Function Documentation 6 5 4 1 void x memcpy_P void gt dest VOID P src size_t n The memcpy_P function is similar to memcpy except the src string resides in pro gram space Returns The memopy function returns a pointer to dest 6 5 4 2 int strcasecmp P const char 57 P s2 Compare two strings ignoring case The strcasecmp P functio
252. ng of the output compare match 1 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 f def statements so the ac tual program 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 or OCR1A DDROC the name of the DDR data direction register for the OC output OCI the pin number of the OCI A output within its port TIMER1_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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 146 TIMER1_PWM_INIT the initialization bits to be set into control register 1A in order to setup 10 bit or 8 bit phase and frequency correct PWM mode TIMER1_CLOCKSOURCE the clock bits to set 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 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
253. ng 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 Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 11 lt compat deprecated h gt Deprecated items 40 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 define enable_external_int mask __EICR mask define INTERRUPT signame define _ INTR_ATTRS used e static inline void timer enable int unsigned char ints 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 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
254. ng the GNU Tool Chain 232 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 beingreally 0 8 8 Installing the GNU Tool Chain Note This discussion was taken directly from Rich Neswold s document See Acknowl edgments This discussion is Unix specific FIXME troth 2002 08 13 we need a volunteer to add windows specific notes to these instructions This chapter shows how to build and install a complete development environment for the AVR processors using the GNU toolset The default behaviour for most of these tools is to install every thing under the usr ilocal 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 directory 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 exam ple in SHOME 10cal 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 con
255. nput 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 code to swap high and low byte of a 16 bit value asm volatile mov tmp reg 3A0 n t mov 0 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 B0 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__ 5 0 n t mov 0 0 NN p mov D0 tmp reg n t mov tmp reg BO n t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 214 mov B0 0 ANNAT mov C0 __tmp_reg__ n t r value 0 value If operands do not fit into a single register compiler will auto
256. nt number 6 16 3 11 double fmod double __x double y The function fmod returns the floating point remainder of x y 6 16 3 12 double frexp double __value int __ exp 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 exp The frexp function returns the value x such that x is a double with magnitude in the interval 1 2 1 or zero and value equals x times 2 raised to the power exp If value is zero both parts of the result are zero 6 16 3 13 int isinf double x The function isinf returns 1 if the argument x is either positive or negative infinity otherwise 0 6 16 3 14 int isnan double x The function isnan returns 1 if the argument x represents a not a number NaN object otherwise 0 6 16 3 15 double Idexp double __x int _ exp The Idexp function multiplies a floating point number by an integral power of 2 The Idexp function returns the value of x times 2 raised to the power exp Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 16 lt math h gt Mathematics 61 If the resultant value would cause an overflow the global variable errno is set to ERANGE and the value NaN is returned 6 16 3 16 double log double __x The log function returns the natural logarithm of argument x If the argument is less than or equal 0 a domain error will occur 6 16 3
257. o call the function CALCULATE 8 4 8 Links For a more thorough discussion of inline assembly usage see the gcc user manual The latest version of the gcc manual is always available here http gcc gnu org onlinedocs 8 5 Using malloc 8 5 1 Introduction On a simple device like a microcontroller implementing dynamic memory allocation is quite a challenge 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 fo
258. o evaluates to nothing but this might change in future versions of the library 6 19 2 8 define fdev get udata stream stream udata This macro retrieves a pointer to user defined data from a FILE stream object 6 19 2 9 define set udata stream u do stream 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 6 19 2 10 define FDEV SETUP STREAM put get rwflag 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 6 19 2 11 define fdev setup stream stream put get rwflag Setup a user supplied 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 82 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 wr
259. o 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 A call to realloc first determines whether the operation is about to grow or shrink the 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 ow
260. ocumentation please see the IAR manual 6 13 lt ctype h gt Character Operations 6 13 1 Detailed Description These functions perform various operations on characters include lt ctype h gt Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 13 lt ctype h gt Character Operations 43 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 functions classifi cation i e isdigit returns true if its argument is any value 0 though 9 inclusive int isalnum int ATTR CONST intisalpha int c ATTR CONST int isascii int c ATTR CONST int isblank int ATTR CONST intiscntrl int c ATTR CONST int isdigit int ATTR CONST int isgraph int ATTR CONST int islower int ATTR CONST intisprint int ATTR CONST int ispunct int ATTR CONST int isspace int ATTR CONST int isupper int CONST int isxdigit int ATTR CONST Character convertion routines If c is not an unsigned char value or EOF the behaviour of these functions is undefined int toascii int ATTR CONST int tolower int ATTR CONST int toupper int ATTR CONST 6 13 2 Function Documentation 6 13 2 1 int isalnum int Checks for an alphanumeric character It is equivalent to is
261. ompar routine is expected to have two 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 6 20 4 7 void calloc size t nele size t size Allocate nele elements of size each Identical to calling malloc using nele size as argument except the allocated memory will be cleared to zero 6 20 4 8 div tdiv int int denom The div function computes the value num denom and returns the quotient and re mainder in a structure named div t that contains two int members named quot and rem 6 20 4 9 void exit int status The exit function terminates the application Since there is no environment to re turn to status is ignored and code execution will eventually reach an infinite loop thereby effectively halting all code processing In a C context global destructors will be called before halting execution 6 20 4 10 void free void x ptr The free function causes the allocated memory referenced by pt x to be made avail able for future allocations If ptr is NULL no action occurs 6 20 4 11 charx itoa int __val char
262. optionally signed floating point number the next pointer must be a pointer to float g E G Equivalent to 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 92 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 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 characters 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 cha
263. or 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 lock div 2 lock div 4 lock div 8 lock div 16 lock div 32 E lock div 64 6 lock div 128 7 clock div 256 8 clock div t ll nu fs Clock prescaler setting enumerations clock_prescale_set x Set the clock prescaler register select bits selecting a system clock division setting They 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 6 7 Additional notes from lt avr sfr_defs h gt The lt avr sfr_defs h gt file is included by all of lt avr ioXxxXx h gt 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 define PORTA _SFR_I08 0x02 define EEAR _SFR_IO16 0x21 define UDRO _SFR_MEMB8 0xC6 define TCNT3 _SFR_MEM16 0x94 define CANIDT _SFR_MEM32 0xF0 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 67 Additional notes from lt avr sfr_defs h gt
264. or 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 receive the controller status RS signal clear and one to send or receive data to from the controllers 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 6 32 3 4 hd44780 c This is the implementation of the low level HD44780 LCD controller driver Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 32 Using the standard IO facilities 170 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 applications definitions made in defines h The hd44780_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
265. orage zero reg Register r1 always zero 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 8 4 3 Input and Output Operands Each input and output operand is described by a constraint string followed by a C expression in parantheses 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 Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 211 Constraint Used for Range a Simple upper registers r16 to r23 b Base pointer registers 2 pairs d Upper register r16 to 131 e Pointer register pairs y Z 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 Stack pointer register SPH SPL r Any register r0 to 131 t Temporary register r0 Ww Special upper register 124 126 r28 r30
266. ote Not all AVR devices have a Power Reduction Register for example the AT mega128 On those devices without a Power Reduction Register these macros are not available 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 Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 6 lt avr power h gt Power Reduction Management 29 Power Macro Description Applicable for device power_adc_enable Enable the Analog to Digital Converter module ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 AT90USB646 AT90USB647 AT90USB1286 AT90USB1287 AT90PWM 1 AT90PWM2 AT90PWM3 ATmegal65 ATmega165P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmegal69 ATmega169P ATmega329 ATmega3290 ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmega168 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 power_adc_disable Disable the Analog to Digital Converter module ATmega640 ATmega1280 ATmegal281 ATmega2560 ATmega2561 AT90USB646 AT90USB647 AT90USB 1286 AT90USB1287 AT90PWM 1 AT90PWM2 AT90PWM3 ATmegal65 ATmega165P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmegal69 ATmega169P ATmega329
267. oth Without optimization the compiler strictly generates code following the memory mapped paradigm while with optimization turned on code is generated using the faster and smaller in out MCU instructions Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 27 lt avr sfr_defs h gt Special function registers 139 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 Porting programs that use sbi cbi As described above access to the AVR single bit set and clear instructions are provided via the standard C bit manipulation commands The sbi and cbi commands are no longer directly supported sbi sfr bit can be replaced by sfr _BV bit ie 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 if not 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 Modules Additional notes from lt avr sfr_defs h gt Bit manipulation e define BV bit 1 lt lt bit IO register bit manipulation define bit_is_set sfr bit SFR BYTE sfr amp BV bit define bit is clear sfr bit SFR BYTE sfr amp BV b
268. ovide bootloader support See your processor datasheet to see if it provides bootloader support Todo From email with Marek On smaller devices all except ATmega64 128 5 REG is in the I O space accessible with 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 2 lt avr boot h gt Bootloader Support Utilities 10 void boot program page uint32 t page uint8 t xbuf uintl6 t i uint8 t sreg Disable interrupts sreg SREG cli 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 uintl16 t w xbuf w t buft 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 Defines define BOOTLOADER SECTION __attribute__ section bootloader define boot_spm_inter
269. p 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 match or be greater than s2 6 5 4 10 char x strncat_P char dest PGM P src size_t len 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 27 6 5 4 11 int strncmp_P const char s1 P 52 size_t n The strncmp P function is similar to strcmp 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 6 5 4 12 char x strncpy P char dest P src size_t n The strncpy_P function is similar to strepy_P 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 P function returns a pointer to the destin
270. p RAM location Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 19 XRAMEND A constant describing the last possible location in RAM This is equal to RA MEND for devices that do not allow for external RAM E2END A constant describing the addres FLASHEND s of the last EEPROM cell A constant describing the last byte address in flash ROM SPM PAGESIZE For devices with bootloader support the flash pagesize in bytes to be used for the SPM instruction 6 5 lt avr pgmspace h gt Program Space String Utilities 6 5 1 Detailed Description include avr io h include avr pgmspace h The functions in this module provide interfaces for a program to access data stored in program space flash memory of the d device must support either the LPM or Note evice In order to use these functions the target ELPM instructions 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 10096 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
271. r fnt compar The qsort function is a modified partition exchange sort or quicksort The qsort function sorts an array 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 6 20 4 17 int rand 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 6 20 4 18 int rand r unsigned long ctx Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen
272. r 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 setting 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 handled by an ISR There are two string output functions printstr and printstr 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 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
273. r declaring these format strings Running stdio without malloc By default fdevopen as well as the floating point versions of the printf and scanf family require 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 If floating point operation is desired a user supplied buffer can as well be passed for the internal buffering for the floating point numbers and processing of scanf data Example include lt stdio h gt static int uart_putchar char c FILE xstream static FILE mystdout FDEV SETUP STREAM uart putchar NULL _FDEV_SETUP_WRITE static int uart_putchar char c FILE xstream if n uart putchar Nr stream loop until bit is set UCSRA UDR 2 c return 0 int main void init_uart stdout amp mystdout printf Hello world n return 0 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 78 This example uses the initializer form FDEV SETUP STREAMYO 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
274. r 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 or when recursively calling function Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 5 Using malloc 220 Note The pictures shown in this document represent typical situations where the RAM locations refer to an ATmega128 The memory addresses used are not displayed in a linear scale on board RAM 0x0100 Ox10FF 0x1100 OxFFFF external RAM 1 sP RAMEND brkval lt SP malloc margin gt malloc heap start __heap_start _ bss end data 055 start data start Figure 6 RAM map of a device with internal RAM Finally there s a challenge to make the memory allocator 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 since microcon trollers aren t only often low on space but 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
275. r 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 documentation due to patenting issues For the original Philips documentation see http www semiconductors philips com buses i2c index html 6 33 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 a
276. r uint16 t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 53 6 15 2 43 define PRIX32 IX uppercase hexadecimal printf format for uint32_t 6 15 2 44 define PRIx32 Ix hexadecimal printf format for uint32_t 6 15 2 45 define PRIX8 X uppercase hexadecimal printf format for uint8_t 6 15 2 46 define PRIx8 x hexadecimal printf format for uint8_t 6 15 2 47 define PRIXFASTI6 X uppercase hexadecimal printf format for uint fastl6 t 6 15 2 48 define PRIxFASTIG x hexadecimal printf format for uint_fast16_t 6 15 2 49 define PRIXFAST32 IX uppercase hexadecimal printf format for uint fast32 t 6 15 2 50 define PRIxFAST32 Ix hexadecimal printf format for uint fast32 t 6 15 2 51 PRIXFASTS X uppercase hexadecimal printf format for uint fast8 t 6 15 2 52 itdefine PRIxFASTS x hexadecimal printf format for fast8 t 6 15 2 53 define PRIXLEASTIG X uppercase hexadecimal printf format for uint_least16_t Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 15 lt inttypes h gt Integer Type conversions 54 6 15 2 54 define PRIXLEASTI6 x hexadecimal printf format for uint_least16_t 6 15 2 55 define PRIXLEAST32 IX uppercase hexadecimal printf format for uint_least32_t 6 15 2 56 define PRIXLEAST32 Ix hexadecimal printf format for uint_least32_t 6 15 2 57 define PRIXLEA
277. r2 at90s4433 __AVR_AT90S4433__ avr2 at90s4434 AVR AT90S4434 avr2 at90s8515 __AVR_AT90S8515__ avr2 at90c8534 AVR AT90C8534 avr2 at90s8535 479058535 avr2 at86rf401 AVR AT86RF401 avr2 attiny 13 AVR ATtnyl3 avr2 attiny2313 AVR ATtiny2313 avr3 atmega103 __AVR_ATmegal03__ avr3 atmega603 __AVR_ATmega603__ avr3 at43usb320 AVR_AT43USB320__ avr3 at43usb355 AVR_AT43USB355__ avr3 at76c711 __AVR_AT76C711__ avr4 atmega48 __AVR_ATmega48__ avr4 atmega8 __AVR_ATmega8__ avr4 atmega8515 _ AVR ATmega8515 avr4 atmega8535 AVR ATmega8535 avr4 atmega88 __AVR_ATmega88__ avr4 at90pwm2 _ AVR_AT90PWM2__ avr4 at90pwm3 __AVR_AT90PWM3__ avr5 at90can32 AVR AT90CAN32 avr5 at90can64 __AVR_AT90CAN64__ avr5 at90can128 AVR AT90CANI28 avr5 at90usb646 AVR AT90USB646 avr5 at90usb647 AVR AT90USB647 avr5 at90usb1286 AVR AT90USBI1286 avr5 at90usb1287 AVR AT90USBI1287 avr5 atmega128 AVR ATmegal28 avr5 atmegal280 AVR ATmegal280 avr5 atmegal281 _ AVR ATmegal281l avr5 atmega16 __AVR_ATmegal6__ avr5 atmegal61 AVR ATmegal6l avr5 atmega162 __AVR_ATmegal62__ Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 242 Architecture MCU name Macro avr5 atmega 163 __AVR_ATmegal63__ avr5 atmegal64p AVR ATmegal64P avr5 atmega 165 AVR ATmegal65 a
278. r_defs h gt 30 Demo projects 140 Combining C and assembly source files 142 A simple project 144 A more sophisticated project 158 Using the standard IO facilities 165 Example using the two wire interface TWI 173 3 avr libc Hierarchical Index 3 1 avr libc Class Hierarchy This inheritance list is sorted roughly but not completely alphabetically div_t 177 Idiv_t 178 4 avr libc Data Structure Index 4 1 avr libc Data Structures Here are the data structures with brief descriptions div_t 177 Idiv_t 178 5 avr libc Page Index 5 1 avr libc Related Pages Here is a list of all related documentation pages Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 avr libc Module Documentation Acknowledgments avr libc and assembler programs Frequently Asked Questions Inline Asm Using malloc Release Numbering and Methodology Memory Sections Installing the GNU Tool Chain Using the avrdude program Using the GNU tools Todo List Deprecated List 6 avr libc Module Documentation 6 1 lt assert h gt Diagnostics 6 1 1 Detailed Description include assert h This header file defines a debugging aid 179 180 185 207 219 224 227 232 238 239 249 249 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 messages will only be generated if th
279. racter 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 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 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 con
280. re the build system will exactly find those library files this is deprecated for system libraries Back to FAQ Index 8 3 4 How to permanently bind a variable to a register This can be done with Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 188 register unsigned char counter asm r3 Typically it should be possible to use 12 through r15 that way See C Names Used in Assembler Code for more details Back to FAQ Index 8 3 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 include lt avr io h gt section init1 ax progbits idi 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 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
281. 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 errno is set to ERANGE and the function return value is clamped to LONG MIN or LONG respectively Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 20 lt stdlib h gt General utilities 102 6 20 4 26 unsigned long strtoul const char x __nptr char xx __endptr int base The strtoul function converts the string in npt to an unsigned long value The con version 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 0x 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 strtou
282. rhaps R2 For the ATmega8 48 88 168 use PB1 pin 15 at the DIP 28 package to connect the LED Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 30 simple project 145 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 R1 SCK PB7 19 n Ts LO RESET MISO PB6 18 20k n ZP c2 5 17 9 a 8 MOST PB5 LED5MM re XTAL2 16 R2 D1 ES 5 D 225 ran 2 14 see note 8 XX 18pf 13 20 vec AIN1 PB1 GND an PBO 12 ICP PD6 FAL 1 2 GND 8 INT1 PD3 Z GND INTO PD2 6 TxD PD1 3 2 AT90S2313P Figure 1 Schematic of circuit for demo project The source code is given in demo c For the sake of this example create a file called containing this source code Some of the 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 counter1 are still the same as they used to be back in early 2001 when this simple demo was written initially the names of registers and bits have been changed slightly to reflect the new features Also the port and pin mappi
283. ring 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 203 include lt inttypes h gt include lt avr io h gt include lt avr pgmspace h gt int uart_putchar char c if n vart 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 addr char Gs while pgm_read_byte addr uart 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 used as an indication that this function is going to accept a program space string Note also the use of the PSTR macro Back to FAQ Index 8 3 21 Why does the compiler compile an 8 bit operation that uses bitwise oper ators 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
284. ro 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 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 _BV CS20 DDRD _BV PD7 Back to FAQ Index 8 3 7 Can I use C 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 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
285. rom_is_ready uint8 t eeprom read byte const uint8 t addr uint16 t eeprom read word const uint16_t addr void eeprom read block void pointer ram const void xpointer eeprom size t n void eeprom write byte uint8 t addr uint8 t value void eeprom write word uint16 t uint16 t value void eeprom write block const void pointer ram void xpointer eeprom size t n IAR C compatibility defines e define EEPUT addr val eeprom write byte uint8 t uint8 t val define _ EEGET var addr var eeprom read byte uint8 t x addr Defines define _ EEPROM REG LOCATIONS 1C1D1E 6 3 2 Define Documentation 6 3 2 1 define EEPROM REG LOCATIONS 1CIDIE In o rder to be able to work without a requiring a multilib approach for dealing with controllers having the EEPROM registers at different positions in memory space the eeprom functions evaluate _ LOCATIONS It is assumed to be Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 3 lt avr eeprom h gt EEPROM handling 17 defined by the device io header and contains 6 uppercase hex digits encoding the ad dresses of EECR EEDR and EEAR First two letters EECR address Second two letters EEDR address Last two letters EEAR address The default ICIDIE corre sponds to the register location that is valid for most controllers The value of this define symbol is used for appending it
286. rupt h gt Interrupts 132 Vector name Old vector Description Applicable for device name TIMER 1_ SIG_ Timer Counter1 AT90S2333 AT90S4414 AT90S4433 OVF_vect OVERFLOW1 Overflow 9054434 9058515 AT90S8535 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 AT tiny15 ATtiny2313 ATtiny261 ATtiny461 ATtiny861 TIMER2_ SIG_ Timer Counter2 ATmega168 ATmega48 ATmega88 AT COMPA_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal281 AT COMPARE2A A mega324 ATmegal64 ATmega644 TIMER2_ SIG_ Timer Counter2 ATmegal68 ATmega48 ATmega88 AT COMPB_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal281 AT COMPARE2B A mega324 ATmegal64 ATmega644 TIMER2_ SIG_ Timer Counter2 AT90S4434 AT90S8535 AT90CANI28 COMP vect OUTPUT Compare Match AT90CAN32 AT90CAN64 ATmegal03 COMPARE2 ATmegal28 ATmegal6 ATmegal61 AT megal62 ATmegal63 ATmegal65 AT megal69 ATmega32 ATmega323 AT mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT mega8 ATmega8535 TIMER2 SIG Timer Counter2 AT90S4434 AT90S8535
287. rupt_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 SPMIEB define boot busy SPM REG amp uint8 t COMMON ASB define boot spm busy SPM REG amp uint8 t BV SPMEN 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 2 lt avr boot h gt Bootloader Support Utilities 11 define GET_HIGH_FUSE_BITS 0 0003 define boot_lock_fuse_bits_get address e 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 enable 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 6 2 2 Define Documentation 6 2 2 1 define boot is interrupt SPM REG amp uint8 t BV SPMIE Check if the SPM interrupt is enabled 6 2 2 2 define boo
288. s and labs functions are builtins of gcc 6 20 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 NULL 6 20 4 4 int atoi const char x string Convert a string to an integer The atoi function converts the initial portion of the string pointed to by nptr to integer representation It is equivalent to int strtol nptr char NULL 10 except that atoi does not detect errors 6 20 4 5 long int atol const char string Convert a string to a long integer The atol function converts the initial portion of the string pointed to by stringp to integer representation It is equivalent to strtol nptr char xx NULL 10 except that atol does not detect errors Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 20 lt stdlib h gt General utilities 97 6 20 4 6 void bsearch const void x 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 c
289. s 52 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 263 PRIuFAST16 PRIXLEAST8 avr_inttypes 52 avr_inttypes 54 PRIuFAST32 PRIxLEASTS avr inttypes 52 avr inttypes 54 PRIuFAST8 PRIXPTR avr_inttypes 52 avr_inttypes 54 PRIULEAST16 PRIxPTR avr_inttypes 52 avr_inttypes 54 PRIuLEAST32 prog_char avr_inttypes 52 avr_pgmspace 23 PRIuLEASTS prog 11116 t avr inttypes 52 avr pgmspace 23 PRIuPTR prog_int32_t avr_inttypes 52 avr_pgmspace 23 PRIX16 prog_int64_t avr_inttypes 52 PRIx16 avr_inttypes 52 PRIX32 avr_inttypes 52 PRIx32 avr_inttypes 53 PRIX8 avr_inttypes 53 PRIx8 avr_inttypes 53 PRIXFAST16 avr_inttypes 53 PRIxFAST16 avr_inttypes 53 PRIXFAST32 avr_inttypes 53 PRIxFAST32 avr_inttypes 53 PRIXFASTS8 avr inttypes 53 PRIxFAST8 avr_inttypes 53 PRIXLEAST16 avr_inttypes 53 PRIxLEAST16 avr_inttypes 53 PRIXLEAST32 avr_inttypes 54 PRIxLEAST32 avr_inttypes 54 avr_pgmspace 23 prog_int8_t avr_pgmspace 23 prog_uchar avr_pgmspace 23 prog_uintl6_t avr_pgmspace 23 prog_uint32_t avr_pgmspace 23 prog_uint64_t avr_pgmspace 23 prog_uint8_t avr_pgmspace 23 prog_void avr_pgmspace 23 PROGMEM avr_pgmspace 22 PSTR avr_pgmspace 22 PTRDIFF_MAX avr_stdint 70 PTRDIFF_MIN avr_stdint 71 pute avr_stdio 82 putchar avr_stdio 82 puts avr_stdio 86 puts_P avr_stdio 86 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen INDEX 264
290. s This will create the snapshot source tarball This should be considered the first release candidate 11 Upload the snapshot tarball to savannah 12 Announce the branch and the branch tag to the avr libc dev list so other devel opers can checkout the branch Note CVS tags do not allow the use of periods Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 6 Release Numbering and Methodology 226 8 6 2 2 Making a release stable release will only be done a branch not from the cvs HEAD The following steps should be taken when making a release 10 11 12 Make sure the source tree you are working from is on the correct branch cvs update r avr libc lt major gt _ lt minor gt branch Update the package version in configure in and commit it to cvs Update the gnu tool chain version requirements in the README and commit to CVS Update the ChangeLog file to note the release and commit to cvs on the branch Add Released avr libc lt this_release gt Update the NEWS file with pending release number and commit to cvs Change Changes since avr libc lt last_release gt to Changes in avr libc this relelase 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 cvs tag avr libe major minor patch release
291. 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 char x__s size_t __n const char __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 int puts P const char str Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 80 size_t fwrite const void __ptr size_t __size size t nmemb FILE stream int fgetc FILE __ stream int ungetc int c 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 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 vscan
292. s 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 PAO 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 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 6 31 3 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 6 31 3 1 P
293. s is a byte address The address is in the program space 6 5 2 7 define pgm_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 6 5 2 8 define pgm_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 6 5 2 9 define pgm_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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 5 lt avr pgmspace h gt Program Space String Utilities 23 6 5 2 10 define pgm_read_word_near address_short _ LPM word uint16 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 6 5 2 11 define const prog void Used to declare a generic pointer to an object in program space 6 5 2 12 define PROGMEM __ATTR_PROGMEM__ Attribute to use in order to declare an object being located in flash ROM 6 5 2 13 define PSTR s const PROGMEM char s Used to declare a static pointer to a stri
294. sistency and simplify the discussion we will use SPREF 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 PREFIX you must have SPREFIX bin in your exported PATH As such PATH PATH PREFIX bin export PATH Warning If you have CC set to anything other than avr gcc in your environment this will cause the configure script to fail It is best to not have CC set at all Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 8 Installing the GNU Tool Chain 233 Note It is usually the best to use the latest released version of each of the tools 8 8 1 Required Tools GNU Binutils http sources redhat com binutils Installation 7008 gnuo ora Installation AVR Libc http savannah gnu org projects avr libc Installation 8 8 2 Optional Tools You can develop programs for AVR devices without the following tools They may or may not be of use for you uisp http savannah gnu org projects uisp Installation avrdude http savannah nongnu org projects avrdude Installation Usage Notes GDB http sources redhat com gdb Install
295. ssignments Note that the compiler will not check if the operands are of reasonable type for the kind of operation used in the assembler instructions Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 4 Inline Asm 213 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 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 30 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 mne out 1 2 n t amp r i
296. ster 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 set bits func wrong PORTB 10a 6a ea 141 r22 170 10c 88 b3 in r24 0x18 224 10e 0e 94 65 00 call Oxca 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 idi r22 0x55 ES 114 88 e3 141 r24 0x38 56 116 90 141 r25 0 00 4 50 1185 94 7c 00 call Oxf8 You can clearly see that 0x0038 is correctly passed for the address of the io port Looking 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 xport uint8 t mask 8 fc 01 movw r30 r24 port mask Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen
297. struction is busy 6 2 2 16 define boot interrupt disable SPM REG amp uint8_t _ BV SPMIE Disable the SPM interrupt Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 3 lt avr eeprom h gt EEPROM handling 15 6 2 2 17 define_boot_spm_interrupt_enable _SPM_REG uint8 t BV SPMIE Enable the SPM interrupt 6 2 2 18 define BOOTLOADER SECTION attribute section boot loader Used to declare a function or variable to be placed into a new section called boot loader This section and its contents can then be relocated to any address such as the bootloader NRWW area at link time 6 2 2 19 define GET EXTENDED FUSE BITS 0 0002 address to read the extended fuse bits using boot lock fuse bits get 6 2 2 20 define GET HIGH FUSE BITS 0 0003 address to read the high fuse bits using boot lock fuse bits get 6 2 2 21 define GET LOCK BITS 0x0001 address to read the lock bits using boot lock fuse bits get 6 2 2 22 define GET LOW FUSE BITS 0 0000 address to read the low fuse bits using boot lock fuse bits get 6 3 lt avr eeprom h gt EEPROM handling 6 3 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 interrup
298. t boot_page_fill address data while 0 Same as boot_page_fill except it waits for eeprom and spm operations to complete before filling the page 6 2 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 2 lt avr boot h gt Bootloader Support Utilities 14 6 2 2 10 define boot page write safe address Value do boot spm busy wait eeprom_busy_wait boot_page_write address X while 0 Same as boot_page_write except it waits for eeprom and spm operations to complete before writing the page 6 2 2 11 define boot_rww_busy SPM REG amp uint8 t BV COMMON ASB Check if the RWW section is busy 6 2 2 12 define boot rww enable boot rww enable Enable the Read While Write memory section 6 2 2 13 define boot rww enable safe Value do boot spm busy wait N eeprom busy wait boot_rww_enable X while 0 Same as boot rww enable except waits for eeprom and spm operations to complete before enabling the RWW mameory 6 2 2 14 define boot spm busy REG amp uint8 t BV SPMEN Check if the SPM instruction is busy 6 2 2 15 define boot busy wait do while boot_spm_busy Wait while the SPM in
299. t a sleep mode 6 8 3 2 void sleep cpu void Put the device into sleep mode The SE bit must be set beforehand and it is recom mended to clear it afterwards 6 8 3 3 void sleep disable void Clear the SE sleep enable bit 6 8 3 4 void sleep enable void Set the SE sleep enable bit 6 8 3 5 void sleep mode void Put the device in sleep mode How the device is brought 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 6 9 lt avr version h gt avr libc version macros 6 9 1 Detailed Description include lt avr version h gt 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 YYYYMMDD appended This file will also be included by lt avr io h gt That way portable tests can be imple mented 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 automatically evaluate to 0 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Dox
300. t 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 delay 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 frequencies of up to about 26 MHz This function is then called 100 times to accomodate for the actual one second delay In a 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 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
301. t char size_t ATTR_PURE char strrchr const char x int PURE char strrev char char strsep char const char char strstr const char const char x ATTR PURE char strtok_r char const char char char strupr char Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 105 6 21 2 Define Documentation 6 21 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 _FFS 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 6 21 3 Function Documentation 6 21 3 1 int ffs int val const 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 Note For expressions that are constant at compile time
302. t controlled EEPROM access to ensure that no time will be wasted in spinloops will have to deploy their own implementation Note All 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 3 lt avr eeprom h gt EEPROM handling 16 avr This header file declares inline functions that call the assembler subroutines di rectly This prevents that the compiler generates push pops for the call clobbered registers This way also a specific calling convention could be used for the eep rom routines e g by passing values in tmp reg eeprom addresses in X and memory addresses in Z registers Method is optimized for code size Presently supported are two locations of the EEPROM register set 0x 1F 0x20 0x21 and 0x1C 0x1D 0x1E see _ EEPROM REG LOCATIONS _ 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 context the applica tions must ensure proper protection e g by disabling interrupts before accessing them libc declarations define EEMEM attribute section eeprom define eeprom is ready define busy wait do while eep
303. t lock bits set lock bits boot lock bits set lock bits Set the bootloader lock bits Parameters lock bits A mask of which Boot Loader 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 BLB12 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 2 lt avr boot h gt Bootloader Support Utilities 12 6 2 2 3 define boot_lock_bits_set_safe lock_bits Value do boot_spm_busy_wait eeprom_busy_wait boot_lock_bits_set lock_bits while 0 Same as boot_lock_bits_set except waits for eeprom and spm operations to complete before setting the lock bits 6 2 2 4 define boot lock fuse bits get address Value _ extension N uint8 t _ result N asm volatile N N ldi r30 3 n t N Idi r31 O n t N sts 1 2 n t N lpm 0 Z n t N r result N i SFR ADDR __SPM_REG N r uint8 t BOOT LOCK BITS SET N M address X VO ESL X _ result Read the lock or fuse bits at addr
304. t 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 length modifier that specifies that the argument for the d i o u x or X conversion is a long int rather than int Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 89 A character that specifies 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 argument is 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 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 specifie
305. text section The purpose of these sections is to allow for more specific placement of code within your program 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 1161 Unused User definable Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 7 Memory Sections 230 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 init6 Unused for C programs but used for constructors in C programs init7 Unused User definable 11168 Unused User definable init9 Jumps into main 8 7 7 finiN Sections These sections are used to define the exit code executed after return from main or a call to exit These all
306. 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 0 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 8 3 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 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 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 usua
307. 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 handling 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 An putchar Nr 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 providing an implementation that offers the complete set of standard streams was deemed to be useful Not only that writing printf instead of fprintf mystream saves typing work but since avr gcc needs to re sort to pass all arguments of variadic functions on t
308. 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 feature 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 28 Demo projects 141 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
309. 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 6 30 simple 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 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 6 30 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 the 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 C1 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 pe
310. ther If you don t know how to do this you probably shouldn t be making releases or cutting branches Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 6 Release Numbering and Methodology 225 8 6 2 1 Creating a branch following steps should be taken to cut a branch in cvs 1 Check out a fresh source tree from cvs HEAD 2 Update the NEWS file with pending release number and commit to cvs HEAD Change Changes since avr libc lt last_release gt to Changes in avr libc lt this_relelase gt 3 Set the branch point tag setting lt major gt and lt minor gt accordingly cvs tag avr libc lt major gt _ lt minor gt branchpoint 4 Create the branch cvs tag b avr libc lt major gt _ lt minor gt branch 5 Update the package version in configure ac and commit configure ac to cvs HEAD Change minor number to next odd value 6 Update the NEWS file and commit to cvs HEAD Add Changes since avr libc lt this_release gt 7 Check out a new tree for the branch cvs CO r avr libc lt major gt _ lt minor gt branch 8 Update the package version in configure ac and commit configure ac to cvs branch Change the patch number to 90 to denote that this now a branch leading up to a release Be sure to leave the lt date gt part of the version 9 Bring the build system up to date by running bootstrap and configure 10 Perform a make distcheck and make sure it succeed
311. ties 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 32 Using the standard IO facilities 166 6 32 1 Hardware setup The demo is set up in a way so it can be run the ATmega16 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 PD1 to TxD The RS 232 channel is set up as standard input st din and standard output st dout 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 AO 1 LCD D4 Al 2 LCD D5 A2 3 LCD D6 A3 4 LCD D7 A4 5 LCD R W A5 6 LCD E A6 7 LCD RS AT 8 unused GND 9 GND VCC 10 Vec Figure 5 Wiring of the STK500 The LCD controller is used in 4 bit mode
312. tiny861 CANIT_vect SIG_CAN_ CAN Transfer AT90CAN128 AT90CAN32 AT90CAN64 INTERRUPTI Complete or Error EEPROM SIG ATtiny2313 READY vect EEPROM READY SIG EE READY Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 126 Vector name Old vector name Description Applicable for device EE RDY vect SIG EEPROM READY EEPROM Ready 9052333 AT90S4433 AT90S4434 AT9088535 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 ATmega8515 AT mega8535 ATtiny12 ATtiny13 ATtiny15 ATtiny26 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 EE_READY_ vect SIG_ EEPROM_ READY EEPROM Ready AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal65 ATmegal69 AT mega325 ATmega3250 ATmega329 AT mega3290 ATmega406 ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmegal68 ATmega48 AT mega88 ATmega640 ATmegal280 AT megal281 ATmega324 ATmegal64 AT mega644 INTO vect SIG INTERRUPTO External Interrupt 0 9051200 419052313 9052323 9052333 419052343 AT90S4414 9054433 419054434 419058515 AT90S8535 AT90PWM3 9 2 AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323
313. tion 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 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 infin
314. tions or variables in C and assembler code You can specify a different name for the assembler code by 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 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 5 Using malloc 219 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 t
315. 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 ISRQ 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 after macro replacement does not start with vector Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 26 lt avr interrupt h gt Interrupts 125 Vector name Old vector Description Applicable for device name ADC_vect SIG_ADC ADC Conversion AT90S2333 9054433 9054434 Complete AT90S8535 AT90PWMS3 9 2 AT90CAN128 AT90CAN32
316. tring that aims to issue a 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 stdin Likewise the first call to fdevopen that opens a stream for writing will cause the resulting stream to be 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 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 77 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 String Utilities becomes very handy fo
317. turns The strlcpy function returns strlen src If retval gt siz truncation occurred 6 21 3 17 size t strlen const char src Calculate the length of a string The strlen function calculates the length of the string src not including the terminat ing 0 character Returns The strlen function returns the number of characters in src 6 21 3 18 char x strlwr char string 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 6 21 3 19 int strncasecmp const char s1 const char x s2 size t len Compare two strings ignoring case The strncasecmp function is similar to strcasecmp except it only compares the first n characters of s1 Returns The strncasecmp 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 match or be greater than s2 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 21 lt string h gt Strings 110 6 21 3 20 char x strncat char x dest const char src size_t len Concatenate two strings The strncat function is similar to strcat except that only the first n characters of src are appended to dest Returns The strncat funct
318. ugging 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 cdhimns file Turn on the assembler listing The sub options are c omit false conditionals d omit debugging directives h include high level source 1 include assembly 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 Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 247 8 10 2 2 Examples for assembler options passed through the C compiler Re member 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 c the following compiler command line can be used 5 avr gcc c foo c 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 Un
319. uilds 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 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 mov ing 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 Vn is taken as an indication to clear the display and set the cursor Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 32 Using the standard IO facilities 171 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
320. uld be performed but the conversion result is to be discarded no parameters will be processed from ap e the character h indicating that the argument is a pointer to short int rather than int e 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 127 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 unsigned 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
321. 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 define sbi port bit port 1 lt lt bit define cbi port bit port amp 1 lt lt bit 6 11 2 Define Documentation 6 11 2 1 define cbi port bit port amp 1 lt lt bit Deprecated Clear bit in IO port port 6 11 2 2 define enable external int mask __EICR mask Deprecated Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 11 lt compat deprecated h gt Deprecated items 41 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 6 11 2 3 define inb port port Deprecated Read a value from an IO port port 6 11 2 4 define inp port port Deprecated Read a value from an IO port port 6 11 2 5 define INTERRUPT signame Value void signame void __attribute__ interrupt __INTR_
322. vent PSCI EC SIG PSCI End Cycle AT90PWM3 AT90PWM2 vect END_CYCLE PSC2_ SIG_PSC2_ PSC2 Capture AT90PWM3 AT90PWM2 CAPT_vect CAPTURE Event PSC2_EC_ SIG_PSC2_ PSC2 End Cycle AT90PWM3 AT90PWM2 vect END_CYCLE SPI STC vect SIG SPI Serial Transfer AT90S2333 AT90S4414 9054433 Complete AT90S4434 AT90S8515 AT90S8535 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 SPM_RDY_ SIG_SPM_ Store Program ATmegal6 ATmegal62 ATmega32 AT vect READY Memory Ready mega323 ATmega8 ATmega8515 AT mega8535 SPM SIG SPM Store Program AT90PWM3 AT90PWM2 AT90CANI28 READY vect READY Memory Read AT90CAN32 AT90CAN64 ATmegal28 ATmegal65 ATmegal69 ATmega325 AT mega3250 ATmega329 ATmega3290 AT mega406 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT megal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 TIMO SIG Timer Counter ATtinyl3 ATtiny24 ATtiny44 ATtiny84 COMPA vect OUTPUT Compare Match ATtiny45 ATtiny25 ATtiny85 COMPAREOA A Generated on Mon Oct 9 22 30 53 2006 for avr libc b
323. versions described above are available except the floating point conversions and the conversion These conversions will be available in the ex tended version provided by the library 1ibscanf flt a Note that either of these conversions requires the availability of a buffer that needs to be obtained at run time using malloc If this buffer cannot be obtained the operation is aborted returning the value EOF To link a program against the extended version use the following compiler flags in the link stage Wl u vfscanf lscanf flt im A third version is available for environments that are tight on space This version is Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 19 lt stdio h gt Standard IO facilities 93 provided in the library 1ibscanf min a and can be requested using the following options in the link stage Wl u vfscanf 1scanf min lm In addition to the restrictions of the standard version this version implements no field width specification no conversion assignment suppression flag no n specification and no general format character matching at all All characters in mt that do not comprise a conversion specification will simply be ignored including white space that is normally used to consume any amount of white space in the input stream However the usual skip of initial white space in the formats that support it is implemented 6 19 3 35 int vfscanf P FILE stream const ch
324. vr 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 8 3 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 the whole Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 3 Frequently Asked Questions 197 128K program memory space on the ATmega devices with gt 64 KB of flash ROM There is a mint 8 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 r17 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
325. vr5 atmegal65p AVR ATmegal65P avr5 atmega 168 __AVR_ATmegal68__ avr5 atmega169 AVR ATmegal69 avr5 atmegal69p _ AVR ATmegal69P avr5 atmega32 AVR ATmega32 avr5 atmega323 AVR ATmega323 avr5 atmega324p AVR ATmega324P avr5 atmega325 AVR ATmega325 avr5 atmega3250 _ AVR ATmega3250 avr5 atmega329 AVR ATmega3290 avr5 atmega3290 AVR ATmega3290 avr5 atmega406 AVR_ATmega406__ avr5 atmega64 AVR ATmega64 avr5 atmega640 AVR ATmega640 avr5 atmega644 AVR ATmega644 avr5 atmega644p _ AVR ATmega644P avr5 atmega645 AVR ATmega645 avr5 atmega6450 AVR ATmega6450 avr5 atmega649 AVR ATmega649 avr5 atmega6490 AVR ATmega6490 avr5 at94k AVR_AT94K avr6 atmega2560 AVR ATmega2560 avr6 atmega2561 _AVR_ATmega2561__ e morder1 e morder2 Change the order of register assignment The default is 124 r25 r18 r19 120 r21 r22 r23 r30 131 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 13 12 10 r1 Order 1 uses r18 r19 120 121 122 123 r24 r25 r30 131 r26 127 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 12 r0 r1 Order 2 uses 125 r24 123 122 121 r20 r19 r18 r30 131 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 r2 r1 rO e mint8 Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 8 10 Using the GNU tools 243
326. will behave identical to malloc If the new memory cannot be allocated realloc returns NULL and the region at pt r will not be changed 6 20 4 22 void srand unsigned int __seed Pseudo random number generator seeding see rand 6 20 4 23 void srandom unsigned long __seed Pseudo random number generator seeding see random 6 20 4 24 double strtod const char x __nptr char __endptr The strtod function converts the initial portion of the string pointed to by nptr to double representation Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 20 lt stdlib h gt General utilities 101 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 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 endpt r If no conversion is performed zero is returned and the value of is stored in the location referenced by endpt If the correct value would cause overflow plus or minus HUGE_VAL is returned ac cording to the sign of th
327. word 0x002e 28 2 00 word 0 002 7 777 0000002a lt bar gt 2a 42 61 72 00 Bar 0000002e lt foo gt 2e 46 6f 6f 00 Foo foo is at addr 0x002e bar is at addr 0 002 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 TAR 77 1 adc t23 x23 74 6a 5d subi r22 OxDA 218 76 TE AE sbci r23 OxFF 255 78 42 0 141 r20 0 02 2 7a 50 e0 ldi r21 0x00 0 Tos ce 01 movw r24 r28 7e 81 96 adiw r24 0x21 x 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 r22 r23 is doubled to accomodate 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 is called strcpy P buf p 82 69 al lada r22 Y 33 0x21 84 7a al 14 r23 Y 34 0x22 86 ce 01 movw r24 r28 88 01 96 adiw r24 0 01 I 8a Oc 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 strepy_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
328. x s int radix Convert an integer to a string The function itoa converts the integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing sufficient storage in s Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 20 lt stdlib h gt General utilities 98 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 9 will be the letter a If radix is 10 and val is negative a minus sign will be prepended The itoa function returns the pointer passed as s 6 20 4 12 long labs long The labs function computes the absolute value of the long integer i Note The abs and labs functions are builtins of gcc 6 20 4 13 Idiv_t Idiv long __num long denom The ldiv function computes the value num denom and returns the quotient and re mainder in a structure named 1div_t that contains two long integer members named quot and rem 6 20 4 14 char
329. y Doxygen 6 26 lt avr interrupt h gt Interrupts 129 Vector name Old vector Description Applicable for device name TIMO_ SIG_ Timer Counter ATtiny13 ATtiny24 ATtiny44 ATtiny84 COMPB_vect OUTPUT_ Compare Match ATtiny45 ATtiny25 ATtiny85 TIMO SIG Timer Counter0 ATtiny13 ATtiny24 ATtiny44 ATtiny84 vect OVERFLOWO Overflow ATtiny45 ATtiny25 ATtiny85 TIM1_ 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 TIMI OVF SIG Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 vect OVERFLOWI Overflow ATtiny25 ATtiny85 TIMERO SIG INPUT ADC Conversion ATtiny261 ATtiny461 ATtiny861 vect CAPTUREO Complete TIMERO SIG TimerCounter0 ATmegal68 ATmega48 ATmega88 AT COMPA_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 tiny2313 ATtiny261 ATtiny461 ATtiny861 TIMERO_ SIG_ Timer Counter 0 AT90PWM3 AT9OPWM2 ATmegal68 COMPB_vect OUTPUT_ Compare Match ATmega48 ATmega88 ATmega640 COMPAREOB B megal280 ATmegal281 ATmega324 AT SIG_ megal64 ATmega644 ATtiny2313 AT OUTPUT_ tiny261 ATtiny461 ATtiny861
330. ygen 6 9 lt avr version h gt avr libc version macros 35 Defines define __ AVR VERSION STRING 14 5 define __ AVR VERSION 1040501 fdefine __ DATE STRING 20061009 fdefine LIBC 20061009UL define __ AVR MAJOR 1 fdefine __ AVR LIBC MINOR 4 fdefine __ AVR REVISION _ 5 6 9 2 Define Documentation 6 9 2 1 define AVR DATE 20061009UL Numerical representation of the release date 6 9 2 2 define DATE STRING 20061009 String literal representation of the release date 6 9 2 3 define _ MAJOR 1 Library major version number 6 9 2 4 define _ LIBC MINOR 4 Library minor version number 6 9 2 5 define AVR REVISION 5 Library revision number 6 9 2 6 define AVR VERSION 1040501 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 6 9 2 7 define AVR VERSION STRING __ 1 4 5 String literal representation of the current library version Generated on Mon Oct 9 22 30 53 2006 for avr libc by Doxygen 6 10 lt avr wdt h gt Watchdog timer handling 36 6 10 lt avr wdt h gt Watchdog timer handling

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