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avr-libc Reference Manual

1. Architecture MCU name Macro avr5 atmegal69 __AVR_ATmegal69__ avr5 atmegal69p __AVR_ATmegal69P__ avr5 atmegal 6hva __AVR_ATmegal6HVA__ avr5 atmega32 AVR ATmega32 avr5 atmega323 AVR ATmega323 avr5 atmega324p AVR ATmega324P avr5 atmega325 AVR ATmega325 avr5 atmega325p AVR ATmega325P avr5 atmega3250 AVR ATmega3250 avr5 atmega3250p AVR ATmega3250P avr5 atmega328p AVR ATmega328P avr5 atmega329 AVR ATmega320 avr5 atmega329p AVR ATmega329P avr5 atmega3290 AVR ATmega3290 avr5 atmega3290p AVR ATmega3290P avr5 atmega32c1 AVR ATMEGA32CI avr5 atmega32hvb AVR ATmega32HVB avr5 atmega32m1 _ AVR_ATMEGA32M1__ avr5 atmega32u4 AVR ATMEGA32UA 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__ avr5 avr51 3 atmegal28 AVR ATmegal28 avr5 avr51 3 atmegal280 AVR ATmegal280 avr5 avr51 3 atmegal281 AVR ATmegal281 avr5 avr51 3 atmegal284p AVR ATmegal284P avr5 avr51 3 at90can128 AVR ATO0CANI28 avr5 avr51 3 at90usb1286 AVR 9005 1286 avr5 avr51 3 at90usb1287 AVR AT90USBI287 __ avr6 atmega2560 AVR ATmega2560 avr6 atm
2. 154 lt avr version h gt avr libc version macros 154 6 231 Detailed Description 154 6 23 2 Define Documentatl d 22 222 2222 155 lt avr wdt h gt Watchdog timer handling 156 624 1 Detailed Description es s e a o RR 156 624 2 Define Documentation 157 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks160 251 Detailed Deseriphon solo 2444 ek 3 3 m S 4 BHR 160 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS iv 6 26 6 27 6 28 6 29 0 33 6 34 6 36 6 25 2 Define Documentation 162 CRC Computations s s lt s 522 163 6 26 1 Detailed Description s lt ea i ea kie pd v RE 163 6 26 2 Function 164 lt util delay h gt Convenience functions for busy wait delay loops 167 6211 Detailed Description 2222 2 2 167 627 2 Function Documentation o s s 2 k 55 167 lt util delay_basic h gt Basic busy wait delay loops 168 6 28 1 Detailed Description 1 121 201 nc o RR RR RA 168 6 28 2 Function 169 lt util parity h gt Parity bit 169 6 29 1 Detailed Description 22222222 2 2 52 2 169 6 292 Defne Documentation 2 ecs s es Sys be RR 169 lt util setbaud h gt Helpe
3. 358 9 12 3 Controlling the linker avr ld 359 9 13 Using the avrdude program 362 9 14 Release Numbering and Methodology 364 9 14 1 Release Version Numbering Scheme 364 9 14 2 Releasing AVR Libe lt lt 202 Es 364 915 Acknowledment 22222 2222 2 5 367 910 Toda LI 22 02 255 p most ex xw 368 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 1 AVR Libc 2 917 Deprecated List gt gt nouas eS kaw korek ssk ts BR 368 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 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
4. heap start malloc tunable 6 10 5 3 size t malloc margin malloc tunable 6 11 lt string h gt Strings 6 11 1 Detailed Description include lt string h gt The string functions perform string operations on NULL terminated strings Note If the strings you are working on resident in program space flash you will need to use the string functions described in lt avr pgmspace h gt Program Space Utilities Defines define _FFS x Functions int ffs int __val int 51 dong val int ffsll long long val void memccpy void const void int size_t void memchr const void int size_t PURE Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 84 int memcmp const void const void size t ATTR_PURE void memcpy void const void size_t void memmem const void size t const void size t PURE void memmove void const void size_t void memrchr const void int size t PURE void memset void int size t int strcasecmp const char const char x ATTR_PURE char strcasestr const char const char x ATTR PURE char strcat char const char char strchr const char int __ATTR_PURE char strchrnul const char x int ATTR_PURE int strcmp const char const char x ATTR PURE char strcpy char const char
5. Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 23 lt avr version h gt avr libc version macros 154 if some_condition sleep_enable sei sleep cpu sleep disable sei This sequence ensures an atomic testof 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 sure the device will really be put to sleep Functions void sleep_enable void void sleep_disable void void sleep_cpu void 6 22 2 Function Documentation 6 22 2 1 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 22 2 2 void sleep disable void Clear the SE sleep enable bit 6 22 2 3 void sleep enable void Set the SE sleep enable bit 6 23 lt avr version h gt avr libc version macros 6 23 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 23 lt avr version h gt avr libc version macros 155 The version number itself basically consists of three pieces that are separa
6. automake 1 8 1 9 is needed to build avr libc in MinGW http downloads sourceforge net mingw msys automake 1 8 2 tar bz2 use mirror internap gt Extract to c msys 1 0 Install Cygwin Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 344 Install everything all users UNIX line endings This will take a long time A fat internet pipe is highly recommended It is also recommended that you download all to a directory first and then install from that directory to your machine Note MPER requires GMP so build it first Build GMP for MinGW Version 4 2 1 lt http gmplib org gt Build script configure 2 gt 61 make 2 gt amp 1 make check 2 gt amp 1 make install 2 gt amp 1 tee gmp configure log tee gmp make log tee gmp make check log tee gmp make install log GMP headers will be installed under usr local include and library installed under usr local lib Build MPFR for MinGW Version 2 2 1 lt http www mpfr org gt Build script configure with gmp usr local 2 gt amp 1 tee mpfr configure log make 2 gt amp 1 tee mpfr make log make check 2 gt amp 1 tee mpfr make check log make install 2 gt amp 1 tee mpfr make install log MPFR headers will be installed under usr local include and library in stalled under usr local lib Install Doxygen Version 1 4 7 lt http www stac
7. decimal printf format for int fast16 t 6 5 2 5 define PRI4FAST32 Id decimal printf format for int fast32 t 6 5 2 6 define PRIdFASTS d decimal printf format for int fast8 t 6 5 2 7 fidefine PRIGLEAST16 decimal printf format for int least16 t 6 5 2 8 define PRIGLEAST32 Id decimal printf format for int_least32_t 6 5 2 9 define PRIdLEASTS d decimal printf format for int least8 t 6 5 2 10 define PRI4PTR PRId16 decimal printf format for intptr t 6 5 2 11 define PRIi16 i integer printf format for int16_t 6 5 2 12 ftdefine PRIi32 li integer printf format for int32 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 25 6 5 2 13 define PRIi8 i integer printf format for int8_t 6 5 2 14 define PRIiFASTI16 i integer printf format for int_fast16_t 6 5 2 15 define PRIiFAST32 li integer printf format for int_fast32_t 6 5 2 16 define PRIiFASTS i integer printf format for int_fast8_t 6 5 2 17 define PRIILEASTI6 i integer printf format for int_least16_t 6 5 2 18 define PRIILEAST32 li integer printf format for int_least32_t 6 5 2 19 define PRIILEASTS8 i integer printf format for int_least8_t 6 5 2 20 define PRIiPTR PRIi16 integer printf format for intptr_t 6 5 2 21 define PRIo16 octal printf format for uint16_t 6 5 2 22 define PRIo32 lo octal printf fo
8. 6 6 2 Define Documentation 6 6 2 1 define INFINITY builtin inf INFINITY constant 6 6 2 2 define 3 141592653589793238462643 The constant pi 6 6 2 3 define 5 2 1 4142135623730950488016887 The square root of 2 6 6 2 4 define NAN builtin NAN constant 6 6 3 Function Documentation 6 6 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 6 3 2 double asin double x The asin function computes the principal value of the arc sine of x The returned value is in the range pi 2 pi 2 radians A domain error occurs for arguments not in the range 1 1 6 6 3 3 double atan double x The atan function computes the principal value of the arc tangent of __x The returned value is in the range pi 2 pi 2 radians Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 35 6 6 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 6 6 3 5 double double x The ceil function returns the smallest integral value greater than or equal to x expressed as
9. TIFR _BV TOVO wrong x simply use TIFR _BV TOVO Back to FAQ Index 9 10 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 9 10 27 Which AVR specific assembler operators are available See Pseudo ops and operators Back to FAQ Index 9 10 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 r28 SP L in r SP H sbiw r28 20 in tmp reg SREG cla out SPH r29 out SREG tmp reg out SPL F28 prologue end size 10 x It reads the current stack pointer value decrements it by the required amount of bytes then disables interrupts writes back the high part of the stack pointer writes back the saved SREG which will eventually re enable interrupts if they have been enabled before and finally writes the low part of the stack pointer Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 333 At the first glance there s a race between restoring SREG and writing SPL However after enabling interrupts either
10. 12 09 55 09 2008 for avr libc by Doxygen CONTENTS 1 9 10 27 Which AVR specific assembler operators are available 332 9 10 28 Why are interrupts re enabled in the middle of writing the stack no A PC PL 332 9 10 29 Why are there five different linker scripts 333 9 10 30 How to add a raw binary image to linker output 333 9 10 31 How do I perform a software reset of AVR 334 9 10 32 I am using floating point math Why is the compiled code so big Why does my code not 335 9 11 Building and Installing the GNU Tool 335 9 11 1 Building and Installing under Linux FreeBSD and Others 335 9 11 2 Required Tools lt a uomo sua b dv M ees 336 9 T13 Opiomal Tools eee 336 9 11 4 GNU Binutils for the AVR 337 9 115 UCC for the AVR target 22222 G b d 804 4 4 4 RS 338 ILE AVR DD 22525455 gla RU RS dar ba a 339 9 17 AVRDUDE K k a eee ob e R 339 9 11 8 GDB f r AVR target 22 ba ee ee ee 340 VALS SHUAR ea 340 2G ee 808 x vU EUG 341 9 11 11 Building and Installing under Windows 341 9 11 12 Tools Required for Building the Toolchain for Windows 342 9 11 13 Building the Toolchain for Windows 345 9 12 Using tbe GNU tools m RR ERR 351 9 12 1 Options for the compiler 351 9 12 2 Options for the assembler avr as
11. 251 8 40 1 Detailed Description ob Re 251 stdlib h Pile Reference gt so on oo om bedrede 8 H 253 8 41 1 Detailed Description 22 2 253 siasecmp s Pile Reference RESO 257 8 42 1 Detailed Description 2 257 sireasecmp P S File Referente s o sore 24 or o RES 237 8 45 1 Detaled Description c 246mm ku 257 File Referente 22222522 255 25 25 k Ra a U 257 8441 Detailed Description 222 22 2 2 2 2 257 s cats File Reference 2 2 22 kiss RR 4 257 8 45 1 Detailed Description 222222222222 See Se eee eS 257 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS ix 8 46 8 47 8 48 8 49 8 50 8 51 852 8 53 8 54 8 55 8 56 8 57 8 58 8 59 8 60 8 61 sticat P S File Reference o Rr 257 846 1 Detailed Descnpiion e lt e ecs XE ERU 257 Pile Klit e e 257 8 47 1 Detailed Descriphon s ooo kO G do od 257 sehr PS File Reference 2 occ k bu be ad eb x R EAS 257 8 48 1 Detailed Description 257 simchenuls File Reien l2 mo OX EX RR 257 8491 Detailed Description 257 strchrnul PS File Reference 257 830 1 Detaled Destniption 22 5 5446 ba m 8 257 str mp S File Reference o 222 osos ooo m Rs 257 B5LI Detailed Description RR 257 strcmp P S Pile Reference gt
12. Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 85 Returns The _FFSQ macro returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 6 11 3 Function Documentation 6 11 3 1 int ffs int val This function finds the first least significant bit set in the input value Returns The ffs function returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 Note For expressions that are constant at compile time consider using the FFS macro instead 6 11 3 2 int ffsl long _ val Same as ffs for an argument of type long 6 11 3 3 int ffsll long long val Same as ffs for an argument of type long long 6 11 3 4 void x memccpy void x dest const void src int val size t len Copy memory area The memccpy function copies more than len bytes from memory area src to mem ory area dest stopping when the character val is found Returns The memccpy function returns a pointer to the next character in dest after val or NULL if val was not found in the first len characters of src 6 11 3 5 void memchr const void src int val size t len Scan memory for a character The memchr function scans the first len bytes of the memory area pointed to by src for the character
13. 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 7 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 Parameters jmpb Variable of type jmp_buf which holds the stack information such that the environment can be restored Returns setjmp returns O if returning directly and non zero when returning from longjmp using the saved context 6 8 lt stdint h gt Standard Integer Types 6 8 1 Detailed Description include stdint h Use u intN t if you need exactly N bits Since these typedefs are mandated by the C99 standard they are preferred over rolling your own typedefs Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 42 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 typed
14. oe Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 37 A more sophisticated project 201 echo empty 56 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 bin srec dox eps png pdf eps PRG eps png PRG png pdf pdf eps fig 5 FIG2DEV L eps lt 56 pdf fig FIG2DEV L pdf lt C amp png fig S FIG2DEV L png lt 8 6 36 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 37 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 37 1 Hardware setup The demo is set up in a way so it can be run on the ATmegal6 that ships with the STK500 development kit The only external part needed is a potentiometer attached to the ADC It is connected to a 10 pin ribbon cable for port A both ends of the
15. size tstrcspn const char s const char reject ATTR_PURE 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 const char size_t PURE char strpbrk const char s const char accept PURE char strrchr const char x int PURE char strrev char char strsep char const char size_t strspn const char __ const char x__ accept ATTR PURE char strstr const char const char x ATTR PURE char strtok_r char const char char char strupr char 6 11 2 Define Documentation 6 11 2 1 define FFS x This macro finds the first least significant bit set in the input value This macro is very similar to the function ffs except that it evaluates its argument at compile time so it should only be applied to compile time constant expressions where it will reduce to a constant itself Application of this macro to expressions that are not constant at compile time is not recommended and might result in a huge amount of code generated
16. 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 315 Example clock timer 2 with full IO clock CS2x 0b001 toggle OC2 output on compare match COM2x 0b01 and clear timer on compare match CTC2 1 Make OC2 PD7 an output TCCR2 BV COM20 BV CTC2 520 DDRD BV PD7 Back to FAQ Index 9 10 7 I use C on the AVR Basically yes C is supported assuming your compiler has been configured and compiled to support it of course Source files ending in cc cpp or C will automati cally cause the compiler frontend to invoke the C compiler Alternatively the C compiler could be explicitly called by the name avr c However there s currently no support for libstdc the standard support library needed for a complete C implementation This imposes a number of restrictions on the C programs that can be compiled Among them are Obviously none of the C related standard functions classes and template classes are available The operators new and delete are not implemented attempting to use them will cause the linker to complain about undefined external references This could perhaps be fixed Some of the supplied include files are not C safe i e they need to be wrapped into extern C This could certainly be fixed too Exceptions are not supported Since exceptions are enabled by default in the C frontend they explicitl
17. 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 C2 and Q1 can be omitted Normally for this experiment the external circuitry on RESET R1 C3 can be omitted as well leaving only the AVR the LED the bypass capacitor C4 and perhaps R2 For the ATmega8 48 88 168 use PB1 pin 15 at the DIP 28 package to connect the LED to Additionally this demo has been ported to many different other AVRs The lo cation of the respective OC pin varies between different AVRs and it is mandated by the AVR hardware Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 186 Rl SCK PB7 1 RESET _ MISO PB6 20 5_ c2 E g MOST PBS XTAL
18. hexadecimal scanf format for uint16 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 32 6 5 2 90 define SCNx32 Ix hexadecimal scanf format for uint32_t 6 5 2 91 define SCNxFAST16 x hexadecimal scanf format for uint_fast16_t 6 5 2 92 define SCNxFAST32 Ix hexadecimal scanf format for uint_fast32_t 6 5 2 93 define SCNxLEAST16 x hexadecimal scanf format for uint_least16_t 6 5 2 94 define SCNxLEAST32 Ix hexadecimal scanf format for uint_least32_t 6 5 2 95 define SCNxPTR SCNx16 hexadecimal scanf format for uintptr_t 6 5 3 Typedef Documentation 6 5 3 1 typedef int32_t int_farptr_t signed integer type that can hold a pointer gt 64 KB 6 5 3 2 typedef uint32 t uint farptr t unsigned integer type that can hold a pointer gt 64 KB 6 6 lt math h gt Mathematics 6 6 1 Detailed Description include lt math h gt This header file declares basic mathematics constants and functions Notes In order to access the functions delcared herein it is usually also required to additionally link against the library 1ibm a See also the related FAQ entry Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 33 Math functions do not raise exceptions and do not change the errno vari able Therefore the majority of them are declared with const attribute for better optimization by GCC Defines
19. 6 8 2 41 define UINT32_C value _ CONCAT value UL define a constant of type uint32_t 6 8 2 42 define UINT32 MAX CONCAT INT32 U 2UL 1UL largest value an uint32_t can hold 6 8 2 43 define UINT64_C value _ CONCAT value ULL define a constant of type uint64_t 6 8 444 define UINT64_MAX _ CONCAT INT64_MAX U 2ULL 1ULL largest value an uint64_t can hold 6 8 2 45 define UINT8_C value uint8 t _ CONCAT value U define a constant of type uint8_t 6 8 2 46 define UINT8_MAX _CONCAT INT8_MAX U 2U 10 largest value an uint8_t can hold 6 8 2 47 define UINT_FAST16_MAX UINT16_MAX largest value an uint_fast16_t can hold 6 8 2 48 define UINT FAST32 MAX UINT32 MAX largest value uint fast32 t can hold 6 8 2 49 define UINT FAST64 MAX UINT64 largest value an uint_fast64_t can hold 6 8 2 50 define UINT FAST8 MAX UINT8 MAX largest value an uint_fast8_t can hold Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 50 6 8 2 51 ffdefine UINT LEASTI16 MAX UINTI6 largest value an uint least16 t can hold 6 8 2 52 define UINT LEAST32 MAX UINT32 MAX largest value an uint least32 t can hold 6 8 2 53 define UINT LEAST64 MAX UINT64 MAX largest value an uint least64 t can hold 6 8 2 54 define UINT LEAST8 MAX UINT8 MAX largest value an uint least8 t can hold 6 8 2 55 define UINTMAX
20. CONTENTS iii 6 13 6 14 6 15 6 16 6 17 6 18 6 19 6 20 6 21 6 22 6 23 6 24 6 25 lt avr eeprom h gt EEPROM handling 101 151 Detailed Description 252m n9 Se YR Re ox eR ws 101 6 13 2 Defne Documentation ce ome v RR 102 6 13 3 Function Documentation gt o es cas Rt RR RR 103 avr fuse h Fuse Support 2 2 2 2 2 104 lt avr mterrupt h gt Interrupts zs oo woe 107 5 15 1 Detailed Descripfion 222222555559 555 107 6 15 2 Define Documentation 127 lt avr io h gt AVR device specific IO definitions 130 lt avilock h gt Lockbit Support lt 12 4 02554 ado 131 lt avr pgmspace h gt Program Space Utilities 134 6 16 1 Detailed Description 222222 s sencer tetepa 134 5 15 2 Defne Documentation e s 4 s mocs ox K a 136 6 18 3 Typedef Documentation 22222222222 252 2 138 6 18 4 Function 140 lt avr power h gt Power Reduction Management 146 Additional notes from lt avr sfr_defs h gt 149 lt avr sfr_defs h gt Special function 151 6 21 1 Detaled D scription 222 2222 2 2 151 6 21 2 Define Documentation 2222999 Rm 152 lt avr sleep h gt Power Management and Sleep 153 6 22 1 Detailed Description 2 153 6 22 2 Function Documentation
21. The GCC Team which produced a very capable set of development tools for an amazing number of platforms and processors e Denis Chertykov denisc overta ru for making the AVR specific changes to the GNU tools e Denis Chertykov and Marek Michalkiewicz marekm8linux org pl for developing the standard libraries and startup code for AVR GCC Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 9 16 Todo List 368 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 and for contributing documentation which describes how to use it Avr dude was previously called avrprog Weddington eweddington cso atmel com for maintaining the WinAVR package and thus making the continued improvements to the open source AVR toolchain available to many users Rich Neswold for writing the original avr tools document which he graciously allowed to be merged into this document and his improvements to the demo project Theodore A Roth for having been a long time maintainer of many of the tools AVR Libc the AVR port of GDB AVaRICE uisp avrdude All the people who currently maintain the tools and or have submitted sugges tions patches and
22. This header file requires that on entry values are already defined for F_CPU and BAUD In addition the macro BAUD_TOL will define the rate tolerance in percent that is acceptable during the calculations The value of BAUD_TOL will default to 2 This header file defines macros suitable to setup the UART baud rate prescaler registers of an AVR calculations are done using the preprocessor Including this header file causes no other side effects so it is possible to include this file more than once supposedly with different values for the BAUD parameter possibly even within the same function Assuming that the requested BAUD is valid for the given F CPU then the macro UBRR VALUE is set to the required prescaler value Two additional macros are pro vided for the low and high bytes of the prescaler respectively UBRRL VALUE is set to the lower byte of the UBRR VALUE and VALUE is set to the upper byte An additional macro USE 2X will be defined Its value is set to 1 if the desired BAUD rate within the given tolerance could only be achieved by setting the U2X bit in the UART configuration It will be defined to 0 if U2X is not needed Example usage include avr io h define F CPU 4000000 static void uart 9600 void define BAUD 9600 include lt util setbaud h gt UBRRH UBRRH VALUE UBRRL UBRRL_VALUE Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 30 lt util set
23. define INTMAX_C value __CONCAT value LL define UINTMAX_C value _CONCAT value ULL Typedefs Exact width integer types Integer types having exactly the specified width typedef signed char int8_t typedef unsigned char uint8_t 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 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 40 stdio h File Reference 251 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 fastl t typedef uintl6 tuint fastl t typedef int32 t int fast32 t typedef uint32 t fast32 t typedef int64 t int fast64 t typedef uint64 t fast64 t Greatest width integer type
24. define M PI 3 141592653589793238462643 define M SORT2 1 4142135623730950488016887 define NAN builtin nan define INFINITY _ builtin inf Functions double cos double x double fabs double __x double fmod double __x double y double modf double __x double iptr double sin double x double sqrt double x double tan double __x double floor double __x double ceil double __x double frexp double x int __pexp double Idexp double __x int exp double exp double x double cosh double x double sinh double __x double tanh double __x double acos double x double asin double __x double atan double x double atan2 double __y double __x double log double __x double log10 double __x double pow double __x double y int isnan double __ x int isinf double __ x double square double x static double copysign double x double y double double x double y double fma double x double y double 7 double fmax double __x double y Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 34 e double fmin double x double y e intsignbit double x e double double x static int isfinite double __x e double hypot double x double y e double round double x e long Iround double x e long lrint double
25. define PRIXLEAST32 IX define PRIXFAST32 IX define PRIOPTR PRIo16 define PRIUPTR PRIul6 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 23 define PRIxPTR PRIx16 define PRIXPTR PRIX16 define SCNd16 d define SCNdLEASTI6 d define SCNdFASTI16 d define SCNi16 1 define SCNiLEAST16 i define SCNIFASTI6 i define SCNd32 Id define SCNdLEAST32 Id define SCNdFAST32 define SCNi32 li define SCNiLEAST32 li define SCNiFAST32 li define SCNdPTR SCNd16 define SCNIPTR SCNi16 define SCNo16 define SCNoLEASTI6 o define SCNoFASTI16 o define SCNul6 u define SCNuLEASTI6 u define 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 lx define SCNxFAST32 Ix define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR SCNx16 6 5 2 Define Documentation 6 5 2 1 define PRId16 d decimal printf format for int16 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 24 6 5 2 2 define PRId32 Id decimal printf format for int32 t 6 5 2 3 define PRId8 decimal printf format for int8 t 6 5 2 4 define PRIdFASTI6
26. endif Set PWM value to 0 OCR 0 e4 1b bc out 0x2b r1 43 1 bc out 0 2 rl 42 Enable as output DDROC BV 0 1 8 82 0 ldi r24 0x02 2 ea 87 bb out 0x17 r24 23 Enable timer 1 overflow interrupt TIMSK BV TOIE1 ec 84 eO ldi r24 0x04 4 ee 89 bf out 0x39 r24 57 sei f0 78 94 sei 2 08 95 ret 000000f4 lt main gt int main void f4 83 ldi r24 0x83 131 f6 8f bd out 0x2f r24 47 Start timer 1 x NB TCCRIA and TCCRIB could actually be the same register so take care to not clobber it x TCCRIB TIMER1_CLOCKSOURCE 8 8e b5 in r24 0x2e 46 fa 81 60 ori r24 0x01 1 fc 8e bd out 0x2e r24 46 if defined TIMER1_SETUP_HOOk TIMER1_SETUP_HOOK endif x Set PWM value to 0 OCR 0 fe 1b bc out 0x2b r1 43 100 1 bc out 0 2 rl 42 Enable as output DDROC BV OCI 102 82 0 ldi r24 0 02 2 2 104 87 out 0 17 r24 23 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 195 Enable timer 1 overflow interrupt TIMSK TOIE1 106 84 e0 ldi r24 0x04 4 108 89 bf out 0x39 r24 57 sei 10a 78 94 sei Tl loop forever the interrupts are doing the rest x for Note 7 x Sleep mode 10c 85 b7 in r24 0x35 53 10e 80 68 ori r24 0x80 128 Or B
27. 0 characters are not compared 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 s1 6 11 3 35 char x strtok 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 94 token ends with a delimiter this delimiting character is overwritten with a 0 and a pointer to the next character is saved for the next call to strtok_r The delimiter string delim may be different for each call last is a user allocated char pointer It must be the same while parsing the same string strtok_r is a reentrant version of strtok Returns The strtok_r function returns a pointer to the next token or NULL when no more tokens are found 6 11 3 36 char x strupr char x s Convert a string to upper case The strupr function will convert a string to upper case Only the lower case alphabetic characters a z are converted Non alphabetic characters will not be changed Returns The strupr function returns a pointer to the converted string The pointer is the same as that pas
28. 2 300 4n 22 22 25 g ewe 300 97 22 How tbe Linker Works 300 9 7 3 Howto Design a 301 23 Creanga zo ee BAS 302 973 Usea LiB esea k eas k d he a ee 302 95 22222222222222 20 4 akk 303 functions 22226 m RR BR 304 982 bbu 25552225 k ROS e 306 9 9 Porting From to 306 991 lode 229 306 992 cuo ecco dox S kh 307 9 9 3 Interrupt Service Routines ISRS 308 994 Int nsc 22 22 308 9 05 Flash Variables 2 2 2 2 309 996 Non Returming mat e ec ea 24 Bee ea 310 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS xiv 997 Locking Registers 222 2 2 2 gt 310 9 10 Prequently Asked Questions 2 1 3 2 4 k o 252224 311 ua i Po sme 311 9 10 2 My program doesn t recognize a variable updated within an inierruptroufii 22222 orn Rm on eR k kms 312 9 10 3 I get undefined reference to for functions like sinQ 313 9 10 4 How to permanently bind a variable to a register 313 9 10 5 How to modify MCUCR or WDTCR 313 9 10 6 What is all this _BV stuff about LL 314 9 10 7 AVR RR 315 9 10 8 Shouldn t I initialize all my va
29. 6 11 3 21 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 Returns The strlcpy function returns strlen src If retval gt siz truncation occurred 6 11 3 22 size_t strlen const char x src Calculate the length of a string The strlen function calculates the length of the string src not including the terminat ing 0 character Returns The strlen function returns the number of characters in src 6 11 3 23 char x strlwr char x s Convert a string to lower case The strlwr function will convert a string to lower case Only the upper case alphabetic characters A Z are converted Non alphabetic characters will not be changed Returns The strlwr function returns a pointer to the converted string 6 11 3 24 int strncasecmp const char 51 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 len characters of s1 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 91 Returns The strncasecmp function returns an integer less than equal to or greater than Zero if 51 or the first Len bytes thereof is found respectively to be less than to match or be greater than s2 A consequence of the ordering u
30. AVR ARCH 1 AVR ASM ONLY AVR 2 BYTE PC avr2 AVR ARCH 2 AVR 2 BYTE PC 2 avr25 1 AVR ARCH 25 AVR HAVE MOVW 1 AVR HAVE LPMX AVR 2 BYTE P avr3 AVR ARCH 3 AVR MEGA 5 AVR HAVE JMP CALL 2 BYTE avr31 AVR_ARCH__ 31__AVR_MEGA AVR_HAVE_RAMPZ__ 4 _AVR_HAVE_ELPM__ 4 __ avr35 3 AVR ARCH 35 AVR MEGA 5 AVR HAVE JMP CALL AVR HAVE avr4 AVR ARCH 4 AVR ENHANCED 5 AVR HAVE MOVW AVR HAVE LPMX avr5 AVR ARCH 5 AVR MEGA 5 AVR ENHANCED 5 AVR HAVE JMP CALL 51 AVR_ARCH__ 51__AVR_MEGA AVR_ENHANCED AVR HAVE MOVW 1 AVE avr6 2 AVR ARCH 6 AVR MEGA 5 AVR ENHANCED 5 AVR HAVE JMP CALL Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 1 New 4 2 4 New in GCC 4 3 1 2 3 New in GCC 4 2 3 4 5 Obsolete 21 Unofficial patch for 4 1 By default code is generated for the avr2 architecture Note that when only using mmcu architecture but no mmcu MCU type including the file lt avr io h gt cannot work since it cannot decide which device s definitions to select e mncu MCU type The following MCU types are currently understood by avr gcc The table matches them against the corresponding avr gcc architecture name and shows the preprocessor symbol declared by the mmcu option Architecture MCU name Macro avr
31. Building upon these the public functions hd44780 outbyte and 4 44780 inbyte transfer one byte to from the controller The function 044780 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 214 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 38 3 5 This function declares the public interface of the higher level char acter IO LCD driver 6 38 3 6 lcd c The implementation of the higher level LCD driver This driver builds on top of the HD44780 low level LCD controller driver and offers a character IO interface suitable for direc
32. asm _ _ volatile movw r30 2 n t sts 0 1 n t spm n t i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE WRITE r uint16_t address r r30 y r31 OE ZO BEE tt VELA 8 5 2 12 define boot enable Value extension 4 asm _ volatile sts 0 1 n t spm n t i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT RWW ENABLE qui cud LEE ci qu 8 5 2 13 define boot rww enable alternate Value extension asm volatile sts 0 1 n t spm n t word Oxffff n t nop n t ae et Generated on Mon May 12 09 55 09 2008 for avr libc Doxygen 8 6 crc16 h File Reference 230 i SFR MEM ADDR 5 REG r uint8 t BOOT RWW ENABLE 8 6 crcl6 h File Reference 8 6 1 Detailed Description Functions e static _ inline uintl6 t crc16 update uint16 t crc uint8 t data e static inline uintl6 t crc xmodem 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 8 7 ctype h File Reference 8 7 1 Detailed Description Defines define 1 Functions Character classification routines These functions perform character classification They return true or false status depending whether the character passed to the func
33. avr_stdio 62 fscanf_P avr_stdio 62 fuse h 231 fwrite avr_stdio 63 GET_EXTENDED_FUSE_BITS avr_boot 100 GET_HIGH_FUSE_BITS avr_stdio 63 hypot avr_math 35 inb deprecated_items 177 INFINITY avr_math 33 inp deprecated_items 177 installation 334 installation avarice 340 installation avr libc 338 installation avrdude 338 installation avrprog 338 installation binutils 336 installation gcc 337 Installation gdb 339 installation simulavr 339 INT16 C avr stdint 44 INTI6 MAX avr stdint 44 INT16 MIN avr stdint 44 intl6 t avr stdint 49 INT32 C avr stdint 44 INT32 MAX avr stdint 44 INT32 MIN avr stdint 44 int32 t avr stdint 49 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 381 INT64_C int_least16_t avr_stdint 44 avr_stdint 50 INT64_MAX INT_LEAST32_MAX avr_stdint 45 avr_stdint 46 INT64_MIN INT_LEAST32_MIN avr_stdint 45 avr_stdint 46 int64_t int_least32_t avr_stdint 49 avr_stdint 50 INT8_C INT_LEAST64_MAX avr_stdint 45 avr_stdint 46 INT8_MAX INT_LEAST64_MIN avr_stdint 45 avr_stdint 46 INT8 MIN int least64 t avr stdint 45 avr stdint 50 int8 t INT LEAST8 MAX avr stdint 49 avr stdint 46 int farptr t INT LEAST8 MIN avr inttypes 31 INT FASTI6 MAX avr stdint 45 INT FAST16 MIN avr stdint 45 int fastl6 t avr stdint 50 INT FAST32 MAX avr stdint 45 INT FAST32 MIN avr stdint 45 int fast32 t avr stdint 50
34. boot page fill avr math 34 avr boot 97 cosh boot page fill safe avr math 34 avr boot 97 crc16 h 229 boot page write ctype avr boot 97 isalnum 17 boot page write safe isalpha 17 avr boot 98 isascii 17 boot_rww_busy isblank 17 avr boot 98 iscntrl 17 boot_rww_enable isdigit 17 avr_boot 98 isgraph 17 boot_rww_enable_safe islower 18 avr_boot 98 isprint 18 boot_signature_byte_get ispunct 18 avr boot 98 isspace 18 boot spm busy isupper 18 avr boot 99 isxdigit 18 boot spm busy wait toascii 18 avr boot 99 tolower 18 boot spm interrupt disable toupper 18 avr boot 99 ctype h 229 boot spm interrupt enable avr boot 99 delay h 230 BOOTLOADER SECTION delay basic h 230 avr boot 99 Demo projects 179 bsearch deprecated_items avr_stdlib 74 calloc avr_stdlib 75 cbi deprecated_items 177 cbi 177 enable_external_int 177 inb 177 inp 177 INTERRUPT 177 outb 178 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen INDEX 379 outp 178 enable_external_int sbi 178 deprecated_items 177 timer_enable_int 179 disassembling 189 div avr_stdlib 75 div_t 220 quot 220 rem 220 DTOSTR_ALWAYS_SIGN avr_stdlib 73 DTOSTR_PLUS_SIGN avr_stdlib 73 DTOSTR_UPPERCASE avr_stdlib 73 dtostre avr_stdlib 75 dtostrf avr_stdlib 75 EDOM avr_errno 19 EEMEM avr_eeprom 102 eeprom_busy_wait avr_eeprom 102 eeprom_is_ready avr_eeprom 102 eeprom_read_block
35. cd obj avr configure prefix PREFIX target avr make make install Ur X o X X d XY Note If you are planning on using avr gdb you will probably want to install either simulavr or avarice since avr gdb needs one of these to run as a a remote target backend 9 11 9 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 X X X X X XY Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 341 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 9 11 10 AVaRICE Note These install notes are not applicable to avarice 1 5 or older You probably don t want to use anything that old anyways since there have been many improvements and bug fixes since the 1 5 release AVaRICE also uses the configure system so to build and install gunzip c avarice lt version gt 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 dX d 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
36. export CFLAGS I libusb win32 device bin 1ibusb version include export LDFLAGS L libusb win32 device bin 1ibusb version lib gcc Configure configure prefix installdir datadir installdir sysconfdir installdir bin enable doc disable versioned doc 2 gt amp 1 tee package configure log Make make k all install 2 gt amp 1 tee Spackage make log Convert line endings in avrdude config file to Windows line endings Delete backup copy of avrdude config file in install directory if exists Insight GDB Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 349 mingw bin c cygwin bin install directory gt bin Configure CFLAGS D USE MINGW ACCESS LDFLAGS static Sarchivedir configure prefix installdir target avr with gmp usr local with mpfr usr local enable doc 2 amp 1 tee insight configure log Make make all install 2 gt amp 1 tee package make log SRecord Open source code package Configure and build at the top of the source code tree Set PATH in order MikTex executables gt us
37. g Wall OPTIMIZE mmcu TARGET DEFS Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 200 override LDFLAGS 1 5 map OBJCOPY avr objcopy OBJDUMP avr objdump all PRG elf lst text eeprom PRG elf 5 5 CFLAGS LDFLAGS 8 LIBS dependency demo o demo c iocompat h clean rm rf x o PRG elf eps png pdf x bak rm rf x lst map EXTRA_CLEAN_FILES lst PRG 1st 156 elf S OBJDUMP h S lt gt SG Rules for building the text rom images text hex bin srec hex bin PRG bin srec 6 hex elf 5 j text j data O ihex lt srec elf j text j data O srec lt C oe bin elf j text j data O binary lt Rules for building the eeprom rom images eeprom ehex ebin esrec ehex PRG eeprom hex PRG _eeprom bin esrec PRG eeprom srec oe eeprom hex elf 5 j eeprom change section lma eeprom 0 O ihex lt SR echo empty 508 not generated exit 0 oe eeprom srec elf 5 j eeprom change section Ima eeprom 0 O srec lt SR echo empty not generated exit 0 eeprom bin elf 5 j eeprom change section 1ma eeprom 0 O binary lt 8
38. in 0 Ay ET eli mne ld tmp reg al NE inc tmp reg MANET st al __tmp_reg__ out SREG 30 XANET amp r s e ptr memory The special clobber memory informs the compiler that the assembler code may mod ify any memory location It forces the compiler to update all variables for which the contents are currently held in a register before executing the assembler code And of course everything has to be reloaded again after this code In most situations a much better solution would be to declare the pointer destination itself volatile volatile uint8 t ptr This way the compiler expects the value pointed to by ptr to be changed and will load it whenever used and store it whenever modified Situations in which you need clobbers are very rare In most cases there will be better ways Clobbered registers will force the compiler to store their values before and reload them after your assembler code Avoiding clobbers gives the compiler more freedom while optimizing your code Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 298 9 6 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
39. int size_t void memchr const void int size_t PURE int memcmp const void const void x size t ATTR_PURE void memcpy void const void size_t void memmem const void size t const void size_t PURE void memmove void const void size t void memrchr const void int size t PURE void memset void int size t char strcat char const char char strchr const char int PURE char strchrnul const char x int ATTR_PURE int strcmp const char const char x ATTR PURE char strcpy char const char int strcasecmp const char const char __ ATTR_PURE char strcasestr const char const char x ATTR PURE size tstrcspn const char s const char reject ATTR_PURE size_t strlcat char const char size_t size t strlcpy char const char size_t size t strlen const char x ATTR PURE char strlwr char char strncat char const char size_t int strncmp const char const char size_t _ ATTR_PURE char strncpy char const char size_t int strncasecmp const char const char size t ATTR_PURE size t strnlen const char size_t ATTR_PURE char strpbrk const char 5 const char accept PURE char strrchr const char x int PURE char x strrev char x char strsep char const char size tst
40. printf_P 63 59 putchar 59 puts 63 puts_P 63 scanf 63 scanf_P 63 snprintf 63 snprintf_P 64 sprintf 64 sprintf P 64 sscanf 64 sscanf P 64 stderr 59 stdin 59 stdout 60 ungetc 64 vfprintf 64 vfprintf P 67 vfscanf 67 vfscanf P 70 vprintf 70 vscanf 70 vsnprintf 70 vsnprintf P 70 vsprintf 71 vsprintf P 71 avr stdlib compar fn t 73 malloc heap end 82 malloc heap start 82 malloc margin 82 abort 73 abs 73 atof 74 atoi 74 atol 74 bsearch 74 calloc 75 div 75 DTOSTR ALWAYS SIGN 73 DTOSTR PLUS SIGN 73 DTOSTR_UPPERCASE 73 dtostre 75 dtostrf 75 exit 76 free 76 itoa 76 labs 76 ldiv 77 Itoa 77 malloc 77 qsort 77 rand 78 RAND MAX 73 rand r 78 random 78 RANDOM MAX 73 random r 78 realloc 79 srand 79 srandom 79 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 377 strtod 79 AVR_LIBC_DATE_STRING__ strtol 79 154 strtoul 80 AVR LIBC MAJOR 154 ultoa 81 AVR MINOR __ 154 utoa 81 AVR_LIBC_REVISION__ 154 avr_string _ AVR VERSION _FFS 83 STRING 155 ffs 84 AVR LIBC VERSION 154 ffsl 84 avr watchdog ffsll 84 wdt disable 156 memccpy 84 wdt enable 156 memchr 84 wdt reset 157 mememp 85 WDTO_120MS 157 memcpy 85 WDTO_15MS 157 memmem 85 memmove 85 memrchr 86 memset 86 strcasecmp 86 strcasestr 86 strcat 87 strchr 87 strchr
41. t and vertical tab CW 6 3 2 12 int isupper int c Checks for an uppercase letter 6 3 2 13 int isxdigit int Checks for a hexadecimal digits i e 0 12345678 9 6 3 2 14 int toascii int Converts c to a 7 bit unsigned char value that fits into the ASCII character set by clearing the high order bits Warning Many people will be unhappy if you use this function This function will convert accented letters into random characters 6 3 2 15 int tolower int Converts the letter c to lower case if possible Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 4 lt errno h gt System Errors 20 6 3 2 16 int toupper int Converts the letter c to upper case if possible 6 4 lt errno h gt System Errors 6 4 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 4 2 Define Documentation 6 4 2 1 define EDOM 33 Domain error 6
42. tax of GCC with the progmem attribute This macro was created as a convenience to the end user as we will see below The PROGMEM macro is defined in the avr pgmspace h system header file It is difficult to modify GCC to create new extensions to the C language syntax so Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 4 Data in Program Space 278 instead avr libc has created macros to retrieve the data from the Program Space These macros are also found in the lt avr pgmspace h gt system header file 9 4 2 A Note On const Many users bring up the idea of using C s keyword const as a means of declaring data to be in Program Space Doing this would be an abuse of the intended meaning of the const keyword const is used to tell the compiler that the data is to be read only It is used to help make it easier for the compiler to make certain transformations or to help the compiler check for incorrect usage of those variables For example the const keyword is commonly used in many functions as a modifier on the parameter type This tells the compiler that the function will only use the parameter as read only and will not modify the contents of the parameter variable const was intended for uses such as this not as a means to identify where the data should be stored If it were used as a means to define data storage then it loses its correct meaning changes its semantics in other situations such as in th
43. 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 PRIILEAST8 i define PRIiFASTS i define PRId16 d define PRIdLEASTI6 d define PRIdFASTI6 d define PRIi16 i define PRILEASTI6 i define PRIiFAST 16 i define PRId32 Id define PRIGLEAST32 define PRI4FAST32 Id Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 22 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 PRIxFASTB8 x define PRIX8 X define PRIXLEASTS X define PRIXFASTS X define PRIo16 o define PRIOLEAST16 define PRIOFAST16 o define PRIu16 u define PRIULEAST16 u define PRIUFAST16 u define PRIx16 x define PRIXLEAST16 x define PRIxFAST16 x define PRIX16 X define PRIXLEASTI6 X define PRIXFAST16 X define PRIo32 lo define PRIOLEAST32 lo define PRIOFAST32 lo define PRIu32 lu define PRIULEAST32 lu define PRIuFAST32 lu define PRIx32 Ix define PRIxLEAST32 Ix define PRIxFAST32 Ix define PRIX32 IX
44. 1 4 avr libc License avr libc can be freely used and redistributed provided the following license conditions are met Portions of avr libc are Copyright c 1999 2007 Keith Gudger Bjoern Haase Steinar Haugen Peter Jansen Reinhard Jessich Magnus Johansson Artur Lipowski Marek Michalkiewicz Colin O Flynn Bob Paddock Reiner Patommel Michael Rickman Theodore A Roth Juergen Schilling Philip Soeberg Anatoly Sokolov Nils Kristian Strom Michael Stumpf Stefan Swanepoel Eric B Weddington Joerg Wunsch Dmitry Xmelkov The Regents of the University of California All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met Redistributions of source code must retain the above copyright Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 2 avr libc Module Index notice this list of conditions and the following disclaimer Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution Neither the name of the copyright holders nor the names of contributors may be used to endorse or promote products derived from this HIS SOFTWARE ND ANY EXPRESS OR IMPLIED WARRANTIES MPLIED WARRANTIES OF MERCHANTABILITY AN RE DISCLAIMED IN NO EVENT SHAL
45. 121 Vector name Old vector name Description Applicable for device TIMER 1_ OVF_vect SIG_ OVERFLOW 1 Timer Counter1 Overflow 9052333 9054434 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega48P AT mega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtinyl5 ATtiny2313 ATtiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 AT90S4414 9058515 AT9084433 AT90S8535 TIMER2_ COMPA_vect SIG_ OUTPUT_ COMPARE2A Timer Counter2 Compare Match A ATmegal68 ATmega48 ATmega88 mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER2_ COMPB_vect SIG OUTPUT COMPARE2B Timer Counter2 Compare Match A ATmegal68 ATmega48 ATmega88 AT mega640 ATmeg
46. 134 134 134 134 10 Stack bytes 4 4 MCU clocks 1172 1152 12345L s Flash bytes 220 220 200 200 200 200 10 Stack bytes 9 9 MCU clocks 3174 3136 malloc 1 Flash bytes 554 554 506 506 506 506 Stack bytes 4 4 MCU clocks 196 178 realloc void Flash bytes 1152 1040 1042 932 1042 932 0 1 Stack bytes 20 20 MCU clocks 303 280 qsort s Flash bytes 1242 1130 990 880 1008 898 sizeof s 1 cmp Stack bytes 38 38 MCU clocks 20914 16678 sprintf min s Flash bytes 1216 1104 1090 980 1086 976 12345 Stack bytes 59 59 MCU clocks 1846 1711 sprintf s Flash bytes 1674 1562 1542 1432 1498 1388 12345 Stack bytes 58 58 MCU clocks 1610 1528 sprintf fit s Flash bytes 3334 3222 3084 2974 3040 2930 1 2345 Stack bytes 66 66 MCU clocks 2513 2297 sscanf min Flash bytes 1540 1428 1354 1244 1354 1244 12345 Stack bytes 55 55 amp i MCU clocks 1339 1240 sscanf 12345 Flash bytes 1950 1838 1704 1594 1704 1594 amp i Stack bytes 53 53 MCU clocks 1334 1235 sscanf Flash bytes 1950 1838 1704 1594 1704 1594 point color Stack bytes 87 87 a z s MCU clocks 2878 2718 sscanf flt Flash bytes 3298 3186 2934 2824 2918 2808 1 2345 Stack bytes 63 63 amp x MCU clocks 2187 1833 strtod 1 2345 Flash bytes 1570 1458 1472 1362 1456 1346 amp p Stack bytes 22 22 MCU clocks 1237 971 strtol 12345 Fla
47. 2 G k 2 6446 8464 ee Bas 273 9 3 6 Sections 2 566544 RR RR Rm ERR 274 Us The TMN SeCUONS 252255 oy K 6 603309 Xo RR e 275 9 3 8 Using Sections Assembler 276 9359 Using Sections IN 276 Data in Program spite 222222225224 ba RS k 277 SAI EmnbeduchoW eee 2T 942 ANoteOnconst 2 22222 22 gt 278 9 4 3 Storing and Retrieving Data in the Program Space 278 9 4 4 Storing and Retrieving Strings in the Program Space 280 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen CONTENTS xiii 943 CAVERN 2o k edo G vi b l a Rog Rem 281 9 5 avr libc and assembler programs 282 MNR 4 1 1 52222 ed bO GTR edits BAR eS 282 9 5 2 l yokwedecomplet 2 ola SG A 9 RR RS 282 9 5 3 Exampleprogram 5 2 22 sos cot om Rm es 283 9 5 4 Pseudo opsandoperators 286 96 Inline Assembler Cookbook c co 46464 eR 5 288 9 61 GCC asm Statement 289 9 62 Assembler Code o cc ke ER RAR EAS 4 kg 3 4 4 290 9 6 3 Input and Output 291 964 CIOBBELE 2222 22 22 225 224 ee Rm 296 9 6 5 Assembler NJA IGS 222222222 2 2 298 966 Cub PURCHODS s cse ee YR ee AX 45 298 9 6 7 Names Used in Assembler 299 DOS LINKS 0 22 Go pei RR A 300 97 Howto Builda Library
48. 8 34 2 10 define _ LPM word classic addr Value extension 4 uint16_t __addr16 uint16_t addr uintl6 t _ result asm iu R HE a Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 35 power h File Reference 246 N lpm mov A0 ro minit X adiw r30 1 n t lpm n t X mov BO ro r result z addr16 N 1 addr16 N zo mp N _ result 8 34 2 11 define _ LPM word enhanced Value _ extension N uintl6 t _ addr16 uintl16 t addr N uintl6 t result N asm N N lpm 0 Z TA NE N lpm B0 2 n t r result z __addr16 1 Laddr16 _ result 8 35 power h File Reference 8 35 1 Detailed Description Defines define _ AVR POWER 1 define clock_prescale_set x define clock_prescale_get clock div t CLKPR amp uint8 t 1 lt lt CLKPS0 1 lt lt CLKPS1 1 lt lt CLKPS2 1 lt lt CLKPS3 Enumerations enum clock div t clock div 1 0 clock div 2 1 clock div 4 2 clock div 8 3 clock div 16 4 clock div 32 5 clock div 64 6 clock div 128 7 clock div 256 8 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 36 setbaud h File Reference 247 8 35 2 Define Documentation 8 35 2 1 define clock prescale set x Value uint8_t tmp _BV CLKP
49. 83 AVR_LIBC_DATE avr_version 154 AVR_LIBC_DATE_STRING__ avr_version 154 AVR_LIBC_MAJOR avr_version 154 AVR_LIBC_MINOR avr_version 154 __AVR_LIBC_REVISION__ avr_version 154 __AVR_LIBC_VERSION_STRING__ INDEX 371 avr_version 155 AVR VERSION avr version 154 ELPM classic pgmspace h 241 ELPM dword enhanced pgmspace h 241 ELPM enhanced pgmspace h 241 ELPM word classic pgmspace h 242 ELPM word enhanced pgmspace h 242 LPM classic pgmspace h 243 LPM dword classic pgmspace h 243 LPM dword enhanced pgmspace h 244 LPM enhanced pgmspace h 244 LPM word classic pgmspace h 244 LPM word enhanced pgmspace h 245 boot lock bits set boot h 224 boot lock bits set alternate boot h 224 boot page erase alternate boot h 224 boot page erase extended boot h 225 boot page erase normal boot h 225 boot page fill alternate boot h 225 boot page fill extended boot h 226 boot page fill normal boot h 226 boot page write alternate boot h 227 boot page write extended boot h 227 boot page write normal boot h 228 boot rww enable boot h 228 boot rww enable alternate boot h 228 compar fn t avr stdlib 73 malloc heap end avr stdlib 82 malloc heap start avr stdlib 82 malloc margin avr stdlib 82 crc16 update util crc 163 ccitt update util crc 164 crc ibutton update util crc 1
50. 9 41 Introduction So you have some constant data and you re running out of room to store it Many AVRs have limited amount of RAM in which to store data but may have more Flash space available The AVR is a Harvard architecture processor where Flash is used for the program RAM is used for data and they each have separate address spaces It is a challenge to get constant data to be stored in the Program Space and to retrieve that data to use it in the AVR application The problem is exacerbated by the fact that the C Language was not designed for Harvard architectures it was designed for Von Neumann architectures where code and data exist in the same address space This means that any compiler for a Harvard architecture processor like the AVR has to use other means to operate with separate address spaces Some compilers use non standard C language keywords or they extend the standard syntax in ways that are non standard The AVR toolset takes a different approach GCC has a special keyword attribute that is used to attach different at tributes to things such as function declarations variables and types This keyword is followed by an attribute specification in double parentheses In AVR GCC there is a special attribute called progmem This attribute is use on data declarations and tells the compiler to place the data in the Program Memory Flash AVR Libc provides a simple macro PROGMEM that is defined as the attribute syn
51. 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 9 10 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 a const char x type string since the AVR processor needs the special instruction LPM to access these strings Thus separate functions are needed that take this into account Many of the standard C library functions have equivalents available where one of the string arguments can be located in flash ROM Private func tions in the applications need to handle this too For example
52. NACK received 6 31 2 27 define TW ST LAST DATA 0xC8 last data byte transmitted ACK received 6 31 2 28 define TW ST SLA 0xA8 SLA R received ACK returned 6 31 2 29 define TW START 0x08 start condition transmitted 6 31 2 30 define TW STATUS TWSR amp TW STATUS MASK TWSR masked by TW STATUS MASK 6 31 2 31 define TW STATUS MASK Value BV TWS7 _BV TWS6 _BV TWS5 _BV TWS4 _BV TWS3 The lower 3 bits of TWSR are reserved on the ATmegal63 2 LSB carry the prescaler bits on the newer ATmegas 6 31 2 32 didefine TW WRITE 0 SLA W address 6 32 lt compat deprecated h gt Deprecated items 6 32 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 32 compat deprecated h gt Deprecated items 177 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 Allowing specific system wide interrupts In addition to globally enabling interrupts each device s particular interrupt needs to be enabled separately if interrupts for this device are desired Wh
53. TARGET macro in the Makefile needs to be adjusted appropriately for the alternative controller types Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 37 A more sophisticated project 205 The flash ROM and RAM consumption of this demo are way below the resources of even an ATmega48 and still well within the capabilities of an ATtiny2313 The major advantage of experimenting with the ATmega16 in addition that it ships together with an STK500 anyway is that it can be debugged online via JTAG Likewise the ATmega48 88 168 and ATtiny2313 devices can be debugged through debugWire using the Atmel JTAG ICE mkII or the low cost AVR Dragon Note that in the explanation below all port pin names are applicable to the ATmegal6 setup 6 37 2 Functional overview PD6 will be toggled with each internal clock tick approx 10 ms PD7 will flash once per second PDO and are configured as UART IO and be used to connect the demo kit to PC 9600 Bd 8N1 frame format The demo application talks to the serial port and it can be controlled from the serial port PD2 through PD4 are configured as inputs and control the application unless control has been taken over by the serial port Shorting PD2 to GND will decrease the current PWM value shorting PD3 to GND will increase it While PD4 is shorted to GND one ADC conversion for channel 0 ADC input is on PA0 will be triggered each internal clock tick and the r
54. The Iround function rounds x to the nearest integer but rounds halfway cases away from zero instead of to the nearest even integer This function is similar to round function but it differs in type of return value and in that an overflow is possible Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 38 Returns The rounded long integer value If __x is not a finite number an overflow was this realization returns the LONG MIN value 0x80000000 6 6 3 27 double modf double __x double The modf function breaks the argument x into integral and fractional parts each of which has the same sign as the argument It stores the integral part as a double in the object pointed to by iptr The modf function returns the signed fractional part of x Note This implementation skips writing by zero pointer 6 6 3 28 double pow double x double y The function pow returns the value of __x to the exponent y 6 6 3 29 double round double x The round function rounds x to the nearest integer but rounds halfway cases away from zero instead of to the nearest even integer Overflow is impossible Returns The rounded value If __x is an integral or infinite x itself is returned If __x is NaN then NaN is returned 6 6 3 30 int signbit double x The signbit function returns a nonzero value if the value of __x has its sign bit set T
55. The format string fmt is scanned for conversion specifications Anything that doesn t comprise a conversion specification is taken as text that is matched literally against the input White space in the format string will match any white space in the data including none all other characters match only itself Processing is aborted as soon as the data and format string no longer match or there is an error or end of file condition on stream Most conversions skip leading white space before starting the actual conversion Conversions are introduced with the character Possible options can follow the e a x indicating that the conversion should be performed but the conversion result is to be discarded no parameters will be processed from ap the character h indicating that the argument is a pointer to short int rather than int the2 characters hh indicating that the argument is a pointer to char 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 255 characters which is also the default value except for the c conversion that defaults to 1 The following conversion fl
56. 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 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 9 10 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 S ART by reading a particular hardware register that will normally happen anyway when processing the interrupt From the hardware s point of view an interrupt is asserted as long as the respective bit is set while global interrupts are enabled Thus it is essential to have the bit cleared before interrupts get re enabled again which usually happens when returning from a
57. and an error is returned will be limited to ITER Note 12 This is called master receiver mode the bus master still supplies the SCL clock but the device slave drives the SDA line with the appropriate data After 8 data bits the master responds with an ACK bit SDA driven low in order to request another data transfer from the slave or it can leave the SDA line high NACK indicating to the slave that it is going to stop the transfer now Assertion of ACK is handled by setting the TWEA bit in TWCR when starting the current transfer Note 13 The control word sent out in order to initiate the transfer of the next data packet is initially set up to assert the TWEA bit During the last loop iteration TWEA is de asserted so the client will get informed that no further transfer is desired Note 14 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 7 avr libc Data Structure Documentation 221 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 the one above sent before starting to read the device In case a master transmitter mode transfer is going
58. are applicable to your device Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 19 lt avr power h gt Power Reduction Management 148 Power Macro Description Applicable for device power_adc_enable Enable the Analog to Digital Converter module ATmega640 ATmega1280 ATmegal281 ATmega2560 ATmega2561 AT90USB646 AT90USB647 AT90USB 1286 AT90USB1287 AT90PWM 1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 ATmega165 ATmega165P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmegal69 ATmega169P ATmega329 ATmega3290 ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmegal68 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 power_adc_disable Disable the Analog to Digital Converter module ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 AT90USB646 AT90USB647 AT90USB 1286 AT90USB1287 AT90PWM 1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 ATmega165 ATmega165P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 ATmega164P ATmega324P ATmega644 ATmega48 ATmega88 ATmegal68 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 power_lcd_enable Enable the LCD module ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmeg
59. eeprom_read_block 102 eeprom_read_byte 102 eeprom_read_dword 102 eeprom_read_word 102 eeprom_write_block 102 eeprom_write_byte 103 eeprom_write_dword 103 eeprom_write_word 103 avr_errno EDOM 19 ERANGE 19 avr interrupts BADISR vect 126 cli 126 EMPTY INTERRUPT 126 ISR 127 5 ALIAS 127 5 ALIASOF 128 BLOCK 128 ISR_NAKED 128 ISR_NOBLOCK 128 reti 129 sei 129 SIGNAL 129 avr inttypes farptr t 31 PRId16 22 PRId32 22 PRId8 23 PRIdFAST16 23 PRIdFAST32 23 PRIdFASTS 23 PRIdLEAST16 23 PRIdLEAST32 23 PRIdLEASTS 23 PRIdPTR 23 PRIi16 23 PRIi32 23 PRIi8 23 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 373 5 16 24 PRIiFAST32 24 PRIFASTS 24 PRILEASTI6 24 PRIiLEAST32 24 PRIiLEASTS 24 PRIiPTR 24 1016 24 1032 24 1 8 24 PRIoFAST16 24 PRIoFAST32 25 PRIoFASTS 25 PRIoLEASTI6 25 PRIoLEAST32 25 PRIoLEASTS 25 PRIoPTR 25 PRIu16 25 PRIu32 25 8 25 PRIuFAST16 25 PRIuFAST32 25 PRIuFASTS 26 PRIuLEASTI6 26 PRIULEAST32 26 PRIuLEASTS 26 PRIuPTR 26 PRIX16 26 PRIx16 26 PRIX32 26 PRIx32 26 PRIX8 26 PRIX8 26 PRIXFAST16 27 PRIxFAST 16 27 PRIXFAST32 27 PRIxFAST32 27 PRIXFASTS 27 PRIxFASTS 27 PRIXLEASTIO6 27 PRIxLEASTI6 27 PRIXLEAST32 27 PRIxLEAST32 27 PRIXLEASTS 27 PRIxLEASTS 28 PRIXPTR 28 PRIxPTR 28 SCNd16 28 SCNd32 28 SCNdFAST16 28 SCNdFAST32 28 SCN
60. is the unique part of the filename that you create It makes it easier if the name part relates to what the library is about This name part must be prefixed by lib and it must have a file extension of a for archive The reason for the special form of the filename is for how the library gets used by the toolchain as we will see later on Note oq The filename is case sensitive Use a lowercase lib prefix and a lowercase a as the file extension The command line is fairly simple avr ar rcs library name list of object modules The r command switch tells the program to insert the object modules into the archive with replacement The c command line switch tells the program to create the archive And the s command line switch tells the program to write an object file index into the archive or update an existing one This last switch is very important as it helps the linker to find what it needs to do its job Note The command line switches are case sensitive There are uppercase switches that have completely different actions MFile and the WinAVR distribution contain a Makefile Template that includes the necessary command lines to build a library You will have to manually modify the template to switch it over to build a library instead of an application See the GNU Binutils manual for more information on the ar program 9 7 5 Using a Library To use a library use the 1 switch on your linker command line Th
61. lrint avr_math 36 lround avr_math 36 Itoa avr_stdlib 77 M_PI avr_math 33 M_SQRT2 avr_math 33 malloc avr_stdlib 77 math h 235 memccpy avr string 84 memcopy S 238 memchr avr string 84 memchr S 238 memchr P avr pgmspace 139 memchr_P S 238 memcmp avr_string 85 memcmp S 238 memcmp_P avr_pgmspace 139 memcmp_ P S 238 memcpy avr_string 85 memcpy S 238 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 383 memcpy_P avr_pgmspace 139 memcpy_P S 238 memmem avr_string 85 memmem S 238 memmem_P avr_pgmspace 139 memmove avr_string 85 memmove S 238 memrchr avr_string 86 memrchr S 238 memrchr_P avr_pgmspace 139 memrchr_P S 238 memset avr string 86 memset S 238 modf avr math 37 NAN avr math 33 NONATOMIC BLOCK util atomic 161 NONATOMIC FORCEOFF util atomic 162 NONATOMIC RESTORESTATE util atomic 162 outb deprecated items 178 outp deprecated items 178 parity h 238 parity even bit util parity 168 PGM P avr pgmspace 135 pgm read byte avr pgmspace 135 pgm read byte far avr pgmspace 135 pgm read byte near avr pgmspace 136 pgm read dword avr pgmspace 136 pgm read dword far avr pgmspace 136 pgm read dword near avr pgmspace 136 pgm read word avr pgmspace 136 pgm read word far avr pgmspace 137 pgm read word near avr pgmspace 137 PGM VOID P avr pgmspace 137 pgmspace h 239 ELPM classi
62. part of the version 9 Bring the build system up to date by running bootstrap and configure 10 Perform make distcheck and make sure it succeeds 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 7 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 14 Release Numbering and Methodology 366 9 14 2 2 Makingarelease stable release will only be done on 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 ac 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 make d
63. 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 macro evaluates to nothing but this might change in future versions of the library 6 9 2 8 fidefine get udata stream stream udata This macro retrieves a pointer to user defined data from a FILE stream object 6 9 2 9 define fdev set udata stream u do stream gt udata u while 0 This macro inserts a pointer to user defined data into a FILE stream object The user data can be useful for tracking state in the put and get functions supplied to the fdevopen function 6 9 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 9 2 11 define 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 May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 60 The arguments put and get are identical to those that need to be pass
64. 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 7 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 to by src 6 11 3 29 char strpbrk const char s const char accept The strpbrk function locates the first occurrence in the string s of any of the characters in the string accept Returns The strpbrk function returns a pointer to the character in s that matches one of the characters in accept or NULL if no such character is found The terminating Zero is not considered as a part of string if one or both args are empty the result will NULL 6 11 3 30 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 11 3 31 char x strrev char x s Reverse a string The strrev function reverses the order of the string Returns The
65. 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 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 35 Combining and assembly source files 181 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 e
66. 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 327 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 9 10 18 How do I relocate code to a fixed address First the code should be put into a new named section This is done with a section attribute attribute section bootloader In this example bootloader is the name of the new section This attribute needs to be placed after the prototype of any function to force the function into the new section void boot void attribute section bootloader To relocate the section to a fixed address the linker flag section start i
67. x trampolinesx 0x00000026 jumptables jumptables lowtext lowtextx 0x00000026 0x126 0x26 0x0 c avrdev avr libc avr libc avr lib avr4 atmega8 crtm8 o vectors vector default ALIGN 0x2 trampolines start linker stubs trampolines end ctors start The text segment where program instructions are stored starts at location 0x0 fini2 fini2 finil finil finiO finiO 0x00000122 finiO0 0x00000126 data 0x00800060 0x00800060 data data 0x00800060 data 0x00800060 data 0x00800060 data 0x00800060 data 0x00800060 data 0x00800060 x datax rodata x rodatax gnu linkonce d 0x00800060 0x00800060 0x00800060 bss 0x00800060 0x00800060 bss bss 0x00800060 bss 0x00800063 bss 0x00800063 bss 0x00800063 bss 0x00800063 0x4 0x0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0 3 0 0 0 0 0 0 0 0 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _exit o etext load address 0x00000126 PROVIDE data start demo o c avrdev avr libc avr libc avr lib avr4 atmega8 crtm8 o avrdev avr libc avr libc avr lib avr4 exit o winavr bin lib gcc avr 4 3 0 avr4 libgcc a _exit o winavr bin lib gcc avr 4 3 0 avr4 libgcc a _copy_data o c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _clear_bss o ALIGN 0x2 _edata PROVIDE __data_end load address 0x00000126 PRO
68. xxx master transmitter TW MR xxx master receiver TW ST xxx slave transmitter TW SR xxx slave receiver define START 0x08 fdefine TW REP START 0x10 define TW MT SLA ACK 0x18 define TW MT SLA NACK 0x20 define TW MT ACK 0x28 define TW MT DATA NACK 0x30 define TW MT ARB LOST 0x38 define TW MR ARB LOST 0x38 define TW MR SLA ACK 0x40 define TW MR SLA NACK 0x48 define TW MR DATA ACK 0x50 define TW MR DATA NACK 0x58 define TW ST SLA 0xA8 define TW ST LOST SLA OxBO define TW ST 0xB8 define TW ST DATA NACK 0xCO fdefine TW ST LAST DATA 0xC8 define TW SR ACK 0x60 define TW SR LOST SLA ACK 0x68 fdefine TW SR GCALL 0x70 fdefine TW SR LOST 0x78 fdefine TW SR DATA ACK 0x80 define TW SR DATA NACK 0x88 define TW SR GCALL DATA 0x90 fdefine TW SR GCALL DATA 0x98 define TW SR STOP OxAO define TW NO INFO OxF8 define TW BUS ERROR 0x00 define TW STATUS 5 define TW STATUS TWSR amp TW STATUS MASK R W bit in SLA R W address field define TW READ 1 define TW WRITE 0 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 89 wdt h File Reference 262 8 89 wdt h File Reference 8 89 1 Detailed Description Defines define wdt_reset volatile__ wdr define _WD_PS3_MASK 0x00 define WD_CONTROL_REG WDTCR define WD CHA
69. 0 which succeeds It then proceeds to test the high byte but that moment the ISR triggers and the main context is interrupted The ISR will decrement the variable from 0x100 to OxFF and the main context proceeds It now tests the high byte of the variable which is now also 0 so it concludes the variable has reached 0 and terminates the loop Using the macros from this header file the above code can be rewritten like finclude inttypes h include avr interrupt h finclude avr io h include util atomic h volatile uint16 t ctr ISR TIMERI1 OVF ctr int main void ctr 0x200 start_timer sei uintl6 t ctr copy do ATOMIC_BLOCK ATOMIC_FORCEON ctr_copy ctr while ctr_copy 0 This will install the appropriate interrupt protection before accessing variable ctr Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Block462 so it is guaranteed to be consistently tested If the global interrupt state were uncer tain before entering the ATOMIC_BLOCK it should be executed with the parameter ATOMIC_RESTORESTATE rather than ATOMIC_FORCEON Defines define ATOMIC_BLOCK type define NONATOMIC_BLOCK type define ATOMIC_RESTORESTATE define ATOMIC FORCEON define NONATOMIC RESTORESTATE define NONATOMIC FORCEOFF 6 25 2 Define Documentation 6 2
70. 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F 0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F 0 50 0 51 0 52 0 53 0 54 0 55 0 56 0 57 0 58 0 59 0x5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C Ox6D 1 That s it Now your data is in the Program Space You can compile link and check the map file to verify that mydat a is placed in the correct section Now that your data resides in the Program Space your code to access read the data will no longer work The code that gets generated will retrieve the data that is located at the address of the mydata array plus offsets indexed by the i and j variables However the final address that is calculated where to the retrieve the data points to the Data Space Not the Program Space where the data is actually located It is likely that you will be retrieving some garbage The problem is that AVR GCC does not intrinsically know that the data resides in the Program Space The solution is fairly simple The rule of thumb for accessing data stored in the Program Space is to access the data as you normally would as if the variable is stored in Data Space like so byte 11131 then take the address of the data byte amp mydata il jl then use the appropriate pgm read
71. 1 Detailed Description include lt avr sleep h gt Use of the SLEEP instruction can allow an application to reduce its power comsump tion considerably AVR devices can be put into different sleep modes Refer to the datasheet for the details relating to the device you are using There are several macros provided in this header file to actually put the device into sleep mode 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 on sleep but all peripheral clocks are still running and then call s1eep mode This macro automatically sets the sleep enable bit goes to sleep and clears the sleep enable bit Example include lt avr sleep h gt Set sleep mode mode Sleep mode Note that unless your purpose is to completely lock the CPU until a hardware reset interrupts need to be enabled before going to sleep As the sleep mode macro might cause race conditions in some situations the individual steps of manipulating the sleep enable SE bit and actually issuing the SLEEP instruction are provided in the macros sleep enable sleep disable 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 I Example include lt avr interrupt h gt include lt avr sleep h gt set sleep mode mode elit
72. 29 1 Detailed Description lt so sv oam 2525 239 Memrchr S File Referenc lt so ouo et 239 8 30 1 Detailed Description 239 memuchr PS Pile Referenc 2 222 2 2 5 239 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS viii 8 32 8 33 8 34 8 35 8 37 8 40 8 41 8 42 8 43 8 44 8 45 8 31 1 Detailed Description 2 239 memset Vile Reference o sacco ceos A 239 5221 Detailed Description uu zd mes k 239 pani File Reference ow nk su e a Gi o k i 239 8 33 1 Detailed Description lt es o e 66445 m Rs 239 pgmspace h File Reference 2 222222 2 2 2 2 2 240 5 34 1 Detailed Description RR Rn 240 8 34 2 Define Documentation 242 powerh Pile 222 85 24 5 246 8 35 1 Detaled Description 22 5 5446 bee RR 246 8 35 2 Define Documentation 247 File Reference oc sso oto RR RR 247 8 26 1 Detaled Descrphon gt e ece ssir kk c RR 247 setmp h Pile Referenc s sop 22222 R9 Rok Re RC o 247 8 37 1 Detailed Description 4 lt s soc es otro RR 247 sleep h File R f rence secco 4 rense erre 2 248 8381 Detailed Description 2 22 222 222 248 stdini h File Reference oss m RR RB RR 248 8 39 1 Detailed Description cov RR 248 Pile Reference xou mor oue xw
73. 4 2 2 fidefine ERANGE 34 Range error 6 5 lt inttypes h gt Integer Type conversions 6 5 1 Detailed Description include lt inttypes h gt This header file includes the exact width integer definitions from lt stdint h gt and extends them with additional facilities provided by the implementation Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 21 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 Far pointers for memory access gt 64K typedef int32_t int_farptr_t typedef uint32_t uint_farptr_t macros for printf and scanf format specifiers For C
74. 6 12 2 3 define boot_lock_bits_set_safe lock_bits Value do boot spm busy wait N eeprom busy wait N 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 12 2 4 ftdefine boot lock fuse bits get address Value _ extension N uint8 t _ result X _ asm _ volatile N 141 30 3 n t lai 2351 N sts 1 2 n t N lpm 0 ZXnXt N r result N i SFR MEM ADDR SPM REG N uint8_t BOOT LOCK BITS SET N M address N s r30U N _ result Read the lock or fuse bits at address Parameter address can be any of GET_LOW_FUSE_BITS GET_LOCK_BITS GET_EXTENDED_FUSE_ BITS or GET_HIGH_FUSE_BITS Note The lock and fuse bits returned are the physical values 1 e a bit returned as 0 means the corresponding fuse or lock bit is programmed Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 98 6 12 2 5 define boot_page_erase address boot page erase normal address Erase the flash page that contains address Note address is a byte address in flash not a word address 6 12 2 6 define boot page erase safe address Value do boot spm busy wait eeprom_busy_wait boot_page_erase address while 0 Same as boot
75. 6 6 2 Define Documentation 34 6 6 3 Function 34 lt setjmp h gt Non local goto 39 Detaled Desctipti h 22 2 2 222222 39 6 72 Funcion Documentation lt s cs arpa RET 40 lt stdint h gt Standard Integer Types 41 6 8 1 Detailed Description 222 222 2 525 41 63 2 Define Documentation lt sso sesar scene s s 45 6 6 2 Typedef Documentation 2221 20 x33 50 lt stdio h gt Standard IO 53 691 Detailed Description 53 6 9 2 Define Documentation 58 6 9 3 Function Documentation 61 stdhbh Generalu hfie 2 2 72 6 10 1 Detaled Desernpnan ue RR m mmm ys 72 6 10 2 Define Documentation 74 6 10 3 Typedef Documentation 74 6 10 4 Function Documentation 74 6 10 5 Variable Documentation 83 SUME o neee 83 6111 Detailed Description 2022 2222 2 2 83 61L2 Denne Documentation 6 4 c RES eR 0 84 6 11 3 Function Documentation 85 lt avr boot h gt Bootloader Support Utilities 94 6 12 1 Detailed Description 94 6 12 2 Define Documentation 22222222 96 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen
76. 8 bit value typecast before the not operator var amp unsigned char mask Back to FAQ Index Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 330 9 10 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 Memory Areas and Using malloc The amount of stack required for your application cannot be determined that easily For example if you recursively call a function and forget to break that recursion the amount of stack required is infinite You can look at the generated assembler code avr gcc S there s a comment in each generated assembler file that tells you the frame size for each generated function That s the amount of stack required for this func
77. ATTR_PURE inline uintl6_t eeprom_read_word const uint16_t __p static ATTR_PURE inline uint32_t eeprom_read_dword const uint32_t __p static __inline__ void eeprom_read_block void dst const void src size t n static inline void eeprom write byte uint8 t p uint8 t value static inline void eeprom write word uint16 p uintl t _ value static inline void eeprom write dword uint32 p uint32 t value static inline void eeprom write block const void src void dst size t n 6 13 2 Define Documentation 6 13 2 1 define _ EEGET var addr var eeprom read byte const uint8 t x addr Read a byte from EEPROM Compatibility define for IAR C Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 103 6 13 2 2 define EEPUT addr val eeprom write byte uint8_t addr uint8_t val Write a byte to EEPROM Compatibility define for IAR C 6 13 2 3 define EEMEM attribute Attribute expression causing a variable to be allocated within the eeprom section 6 13 2 4 define eeprom busy wait do while eeprom is ready Loops until the eeprom is no longer busy Returns Nothing 6 13 2 5 define eeprom is ready Returns 1 if EEPROM is ready for new read write operation 0 if not 6 13 3 Function Documentation 6 13 3 1 static inline void eepro
78. ATtiny15 ATtiny2313 ATtiny28 ATtiny48 ATtiny261 ATtiny46l AT tiny861 AT9OUSB162 9005 82 9005 1287 AT90USB1286 AT90USB647 AT90USB646 AT9084414 AT90S8515 TIMER 1 _ CAPTI vect SIG INPUT CAPTURE1 Timer Counter1 Capture Event 9052313 vect SIG_INPUT_ CAPTURE1 Timer Counter Capture Event 9052333 479054434 AT90S4414 9058515 9054433 9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 ATtiny48 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 119 Vector name Old vector Description Applicable for device name TIMERI SIG Timer Counter1 ATtiny26 CMPA_vect OUTPUT_ Compare Ma
79. Atomically or Non Atmomically The term Atomic in this context refers to the un ability of the respective code to be interrupted These macros operate via automatic manipulation of the Global Interrupt Status I bit of the SREG register Exit paths from both block types are all managed automatically without the need for special considerations i e the interrupt status will be restored to the same value it has been when entering the respective block A typical example that requires atomic access is a 16 or more bit variable that is shared between the main execution path and an ISR While declaring such a variable as volatile ensures that the compiler will not optimize accesses to it away it does not guarantee atomic access to it Assuming the following example finclude inttypes h include lt avr interrupt h gt include lt avr io h gt volatile uint16_t ctr ISR TIMER1_OVF_vect Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Blockd61 main void ctr 0x200 start_timer while ctr 0 wait There is a chance where the main context will exit its wait loop when the variable just reached the value OxFF This happens because the compiler cannot natively access a 16 bit variable atomically in an 8 bit CPU So the variable is for example at 0x100 the compiler then tests the low byte for
80. Batch file will ask Wow Do you wish to continue with the post install Press y and press enter Do you have MinGW installed Press y and press enter Where is your MinGW installation Type in c mingw without quotes and press enter Do you wish for me to add mount bindings for c mingw to mingw Press and press enter Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 343 It will display some messages on the screen then it will display Press any key to continue Press any key Edit c msys 1 0 msys bat Change line should be line 41 if EXIST rxvt exe goto startrxvt to rem if EXIST rxvt exe goto startrxvt to remark out this line Doing this will cause MSYS to always use the bash shell and not the rxvt shell Note The order of the next three is important Install MSYS Developer toolkit before the autotools MSYS Developer Toolkit version 1 0 1 This is needed to build avr libc in MinGW http downloads sourceforge net mingw msysDTK 1 0 1 exe use mirror internap gt Single file installer executable Install autoconf 2 59 from the MSYS Developer Toolkit release autoconf 2 59 2 60 is needed to build avr libc in MinGW http downloads sourceforge net mingw msys autoconf 2 59 tar bz2 use mirror internap gt Extract to c msys 1 0 automake 1 8 2
81. Controls a LED that can be directly connected from OC1 OC1A to GND 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 9 2006 01 05 21 30 10 joerg wunsch Exp clude lt inttypes h gt clude avr io h clude avr interrupt h clude lt avr sleep h gt clude iocompat h Note 1 m UP DOWN TIMER1 OVF vect x Note 2 x static uintl16 t pwm 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 d nit void Note 6 Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys x TCCRIA 1 INIT x Start timer 1 x TCCRIA TCCRIB could actually be the same register so Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 189 x take care to not clobber it TCCRIB TIMERI_CLOCKSOURCE 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 Enable as output DDROC BV OCI Enable timer 1 overflow interrupt TIMSK BV TOIE1 sei int main void ioinit l
82. MIN 46 int least8 t 50 INTMAX C 46 INTMAX MAX 47 INTMAX MIN 47 intmax t 50 INTPTR MAX 47 MIN 47 intptr_t 51 PTRDIFF MAX 47 PTRDIFF MIN 47 SIG ATOMIC MAX 47 SIG ATOMIC MIN 47 SIZE MAX 47 JINT16 C 47 JINT16 MAX 47 int16 t 51 JINT32 C 48 JINT32 MAX 48 int32 t 51 JINT64 C 48 JINT64 MAX 48 int64 t 51 JINTS C 48 INT8 MAX 48 int8 t 51 JINT FAST16 MAX 48 int fastl16 t 51 JINT FAST32 MAX 48 int fast32 t 51 JINT FAST64 MAX 48 int fast64 t 51 JINT 8 8 MAX 48 int fast8 t 51 JINT LEAST16 MAX 48 int least16 t 52 JINT LEAST32 MAX 49 int least32 t 52 JINT LEAST64 MAX 49 int least64 t 52 JINT LEAST8 MAX 49 int least8 t 52 JINTMAX C 49 JINTMAX MAX 49 intmax t 52 JINTPTR MAX 49 uintptr t 52 Ce C e Ce co Ce Ce Ce EE EC C c avr stdio _FDEV_EOF 57 FDEV ERR 57 FDEV SETUP READ 57 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 376 _FDEV_SETUP_RW 57 _FDEV_SETUP_WRITE 57 clearerr 60 EOF 58 fclose 60 fdev_close 58 fdev_get_udata 58 fdev_set_udata 58 FDEV_SETUP_STREAM 58 fdev_setup_stream 58 fdevopen 60 feof 61 ferror 61 fflush 61 fgetc 61 fgets 61 FILE 59 fprintf 62 fprintf_P 62 fputc 62 fputs 62 fputs_P 62 fread 62 fscanf 62 fscanf_P 62 fwrite 63 getc 59 getchar 59 gets 63 printf 63
83. MOLS Pile Referente 22 2 2 2 821 Detailed Description 83 atol S File Reference 8 3 1 Detailed Description SA sonnel Pile Referenc zm oos 8 41 Detailed Description 8 5 booth Pile Reference o o uuo ee an ha a 8 5 1 Detailed Description 8 5 2 Define Documentation 8 6 relh File 2 2 8 6 1 Detailed Description 57 Reference 22502222222 25 2 404 8 7 1 Detailed Description 8 8 delay h File Reference 8 8 1 Detailed Description 8 9 delay File Reference 8 9 1 Detailed Description 8 10 ermo h File Reference coco coz e Kalda da 8 10 1 Detailed Description 8 11 idevopen File Reference 22 8 11 1 Detailed Description 8 12 sS Pile Referente 2 4 s S k as R9 Pe 8 12 1 Detailed Description 8 13 MLS Pile Reference o 204 Gala oka o 8 13 1 Detailed Description 8 14 fisllS File Reference 2 ES 8 14 1 Detailed Description 8 15 fuse h File Reference 8 15 1 Detailed Description 2 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS vii 8 16 8 17 8 20 8 2 822 8 23 8 24 8 25 8 26 8 27 8 28 8 28 interrupt
84. Mon 12 09 55 09 2008 for avr libc by Doxygen 6 32 compat deprecated h gt Deprecated items 178 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 610 6 32 2 Define Documentation 6 32 2 1 define cbi port bit port amp 1 lt lt bit Deprecated Clear bit in IO port port 6 32 2 2 define enable external int mask EICR mask Deprecated This macro gives access to the GIMSK register or EIMSK register if using an AVR Mega device or GICR register for others Although this macro is essentially the same as assigning to the register it does adapt slightly to the type of device being used This macro is unavailable if none of the registers listed above are defined 6 32 2 3 define inb port port Deprecated Read a value from an IO port port 6 32 2 4 define inp port port Deprecated Read a value from an IO port port Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 32 compat deprecated h gt Deprecated items 179 6 32 2 5 define INTERRUPT signame Value void signame void __attribute__ interrupt INTR ATTRS N void signame void Deprecated Introduces an interrupt handler function that runs with global interrupts initially en abled This allows interrupt handlers to be interr
85. OVERFLOW WATCHDOG Overflow vect TIMEOUT SIG WDT OVERFLOW vect SIG WDT Watchdog Time AT90PWM3 AT90PWM2 AT90PWMI SIG out Interrupt ATmegal284P ATmegal68P ATmega328P WATCHDOG_ ATmega32HVB ATmega406 ATmega48P TIMEOUT ATmega88P ATmega168 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny13 ATtiny43U ATtiny48 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 AT tiny861 AT9OUSB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 127 Global manipulation of the interrupt flag The global interrupt flag is maintained in the I bit of the status register SREG define sei define cli Macros for writing interrupt handler functions define ISR vector attributes e define SIGNAL vector define EMPTY_INTERRUPT vector define ISR_ALIAS vector target vector define reti define BADISR vect ISR attributes define 5 BLOCK define ISR NOBLOCK define 5 NAKED e define ISR ALIASOF target vector 6 15 2 Define Documentation 6 15 2 1 define BADISR vect include avr interrupt h This is a vector which is aliased to vector default the vector executed when ISR fires with no accompanying ISR handler
86. P const prog char define PGM VOID P const prog void 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 uint6 4 t PROGMEM prog uint64 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt gt Program Space Utilities 136 Functions PGM_VOID_P memchr P PGM_VOID_P int val size t _ len int memcmp P const void PGM VOID size t ATTR_PURE void memcpy P void x VOID size_t VOID memrchr P PGM_VOID_P int val size t _ len int strcasecmp P const char PGM ATTR PURE char strcat P char PGM P PGM P strchr P PGM_P int __ val PGM P strchrnul P PGM P int val int stremp_P const char x PGM P PURE char strcpy P char PGM_P size tstrcspn P const char x__s PGM_P _ reject ATTR PURE size t strlcat P char PGM P size t size t strlcpy P char P size t size t strlen P PGM P int strncasecmp_P const char x PGM_P size_t _ ATTR_PURE char strncat_P char PGM P size t int strncmp P const char PGM P size t ATTR_PURE char str
87. a floating point number 6 6 3 6 static double copysign double x double y static The copysign function returns x but with the sign of y They work even if xor __y are NaN or zero 6 6 3 7 double cos double x The cos function returns the cosine of __x measured in radians 6 6 3 8 double cosh double x The cosh function returns the hyperbolic cosine of x 6 6 3 9 double exp double x The exp function returns the exponential value of x 6 6 3 10 double fabs double x fabs function computes the absolute value of a floating point number x 6 6 3 11 double fdim double _ double y The fdim function returns max __x 0 If __x or __y or both are NaN NaN 15 returned 6 6 3 12 double floor double x The floor function returns the largest integral value less than or equal to pressed as a floating point number Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 36 6 6 3 13 double fma double __x double __y double 2 The fma function performs floating point multiply add This is the operation __x _ Yy __z but the intermediate result is not rounded to the destination type This can sometimes improve the precision of a calculation 6 6 3 14 double fmax double __x double y The fmax function returns the greater of the two values __x and __y If an argument is NaN the other argument is
88. a single field byte which is an array of unsigned char with the size of the array being FUSE MEMORY SIZE A convenience macro FUSEMEM is defined as a GCC attribute for a custom named section of fuse A convenience macro FUSES is defined that declares a variable fuse of type fuse t with the attribute defined by FUSEMEM This variable allows the end user to easily set the fuse data Note If a device specific I O header file has previously defined FUSEMEM then FUSE MEM is not redefined If a device specific I O header file has previously defined FUSES then FUSES is not redefined Each AVR device I O header file has a set of defined macros which specify the actual fuse bits available on that device The AVR fuses have inverted values logical 1 for an unprogrammed disabled bit and logical 0 for a programmed enabled bit The defined macros for each individual fuse bit represent this in their definition by a bit wise inversion of a mask For example the FUSE EESAVE fuse in the ATmegal28 is defined as define FUSE EESAVE Note The _BV macro creates a bit mask from a bit number It is then inverted to repre sent logical values for fuse memory byte To combine the fuse bits macros together to represent a whole fuse byte use the bitwise AND operator like so FUSE_BOOTSZO amp FUSE_BOOTSZ1 amp FUSE EESAVE amp FUSE SPIEN amp FUSE JTAGEN Generated on Mon May 12 09 55 09 2008 for avr
89. address The address is in the program space 6 18 2 5 define read dword address short 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 18 2 6 define read dword far address long ELPM dword uint32 t address long Read a double word from the program space with a 32 bit far address Note The address is a byte address The address is in the program space 6 18 2 7 define read dword near address short _ LPM dword uint16 t address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 138 6 18 2 8 define read word address short pgm read word near address short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 18 2 9 define read word far address long ELPM word uint32 t address long Read a word from the program space with a 32 bit far address Note The address is a byte address The address is in the program space 6 18 2 10 define read word near address short LPM word uintl6 t ad
90. allows a user to specify the fuse settings for the specific AVR device they are compiling for These fuse settings will be placed in a special section in the ELF output file after linking Programming tools can take advantage of the fuse information embedded in the ELF file by extracting this information and determining if the fuses need to be programmed before programming the Flash and EEPROM memories This also allows a single ELF file to contain all the information needed to program an AVR To use the Fuse API include the lt avr io h gt header file which in turn automatically includes the individual I O header file and the avr fuse h file These other two files provides everything necessary to set the AVR fuses Fuse API Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 14 lt avr fuse h gt Fuse Support 105 Each I O header file must define the FUSE MEMORY SIZE macro which is defined to the number of fuse bytes that exist in the AVR device new type fuse t is defined as a structure The number of fields in this structure are determined by the number of fuse bytes in the FUSE MEMORY SIZE macro If FUSE MEMORY SIZE 1 there is only a single field byte of type unsigned char If FUSE MEMORY SIZE 2 there are two fields low and high of type unsigned char If FUSE MEMORY SIZE 3 there are three fields low high and extended of type unsigned char If FUSE MEMORY SIZE gt 3 there is
91. are used in a different way if they refer to expressions of your C program The connection between registers and C operands is specified in the second and third part of the asm instruction the list of input and output operands respectively The general form is asm code output operand list input operand list clobber list In the code section operands are referenced by a percent sign followed by a single digit O refers to the first 1 to the second operand and so forth From the above example 0 refers to r value and 1 refers to I SFR IO ADDR PORTD This may still look a little odd now but the syntax of an operand list will be explained soon Let us first examine the part of a compiler listing which may have been generated from our example 145 r24 value x in r24 12 NOAPP sts value r24 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 290 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 e
92. assert expression Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 8 2 atoi S File Reference 223 8 2 8 2 1 8 3 8 3 1 8 4 8 4 1 atoi S File Reference Detailed Description atol S File Reference Detailed Description atomic h File Reference Detailed Description Defines 8 5 8 5 1 define UTIL ATOMIC H 1 define ATOMIC BLOCK type define NONATOMIC_BLOCK type define ATOMIC_RESTORESTATE define ATOMIC_FORCEON define NONATOMIC_RESTORESTATE define NONATOMIC_FORCEOFF boot h File Reference Detailed Description Defines define AVR 1 define BOOTLOADER_SECTION __attribute__ section bootloader define _ COMMON_ASB RWWSB define COMMON ASRE RWWSRE define BLB12 5 define BLB11 4 define BLB02 3 define BLB01 2 define boot_spm_interrupt_enable SPM REG uint8 t BV SPMIE define interrupt disable SPM REG amp uint8 t BV SPMIE define boot is spm interrupt SPM REG amp uint8 t BV SPMIEB define boot rww busy SPM REG amp uint8 t COMMON ASB define boot spm busy SPM REG amp uint8 t SPM ENABLE define boot spm busy wait do while boot_spm_busy Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 5 boot h File Reference 224 define _ BOOT_PAGE_ERASE _BV __SPM_ENABLE BV PGERS define _ BOOT_PAGE_WRITE _BV __SPM_ENABLE BV PGW
93. 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 39 3 The Source Code The source code is installed under prefix share doc avr libc examples twitest twitest c where prefix isa configuration option For Unix systems it is usually set to either Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 218 usror usr local Note 1 The header file lt util twi h gt contains some macro definitions for symbolic con stants used in the TWI status register These definitions match the names used in the Atmel datasheet except that all names have been prefixed with TW Note 2 The clock is used in timer calculations done by the compiler for the UART baud rate and the TWI clock rate Note 3 The address assigned for the 24Cxx EEPROM consists of 1010 in the upper four bits The following three bits are normally available as slave sub addresses allowing to operate more than one device of the same type on a single bus where the actual sub address used for each device is configured by hardware strapping However since the next data packet following the device selection only allows for 8 bits that are used as an EEPROM address devices that require more than 8 address bits 24C04 and above steal subaddress bits and use them for the EEPROM c
94. 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 9 16 Todo List Group avr boot From email with Marek On smaller devices all except AT mega64 128 SPM 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 9 17 Deprecated List Global SIGNAL Do not use SIGNALO in new code Use ISR instead Global ISR ALIAS For new code the use of ISR ISR_ALIASOF is recom mended Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 17 Deprecated List 369 Global timer_enable_int Global enable_external_int Global INTERRUPT Global inp Global outp Global inb Global outb Global sbi Global cbi Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen Index PATH 335 PREFIX 334 prefix 334 lt alloca h gt Allocate space in the stack 15 lt assert h gt Diagnostics 15 lt avr boot h gt Bootloader Support Utili ties 93 lt avr eeprom h gt 100 lt avr fuse h gt Fuse Support 103 lt avr interrupt h gt Interrupts 106 lt avr io h gt AVR device specific IO defi nitions 129 lt avr lock h gt Lockbit Support 130 lt avr pgmspace h gt Pro
95. char Defines define STDLIB_H_ 1 define _ need NULL define need size t define need wchar t define ptr t void define RAND MAX Ox7FFF Typedefs typedef int compar fn t const void const void Functions void abort void NORETURN int abs int 1 longlabs long i void bsearch const void key const void base size t nmemb size t size int __compar const void const void div_t div int num int denom asm divmodhi4 tldiv long __num long __denom __asm__ __divmodsi4 void qsort void __base size_t __nmemb size t size compar fn t compar long strtol const char nptr char endptr int base unsigned long strtoul const char nptr char endptr int base long atol const char 5 PURE int atoi const char 5 PURE void exit int status ATTR NORETURN void x malloc size t size MALLOC void free void ptr void calloc size nele size t size ATTR MALLOC void realloc void ptr size t size MALLOC double strtod const char nptr char double atof const char nptr int rand void void srand unsigned int __ seed int rand unsigned long ctx Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 41 stdlib h File Reference 255 Variables e size_t__malloc_margin e char x _ malloc
96. character is not found Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 19 lt avr power h gt Power Reduction Management 146 6 18 4 24 char strsep P char sp P delim Parse a string into tokens The strsep_P function locates in the string referenced by sp the first occurrence of any character in the string delim the terminating 0 character and replaces it with a 0 The location of the next character after the delimiter character or NULL if the end of the string was reached is stored in sp An empty field i e one caused by two adjacent delimiter characters can be detected by comparing the location referenced by the pointer returned in to 7 07 This function is similar to strsep except that delim is a pointer to a string in program space Returns The strsep_P function returns a pointer to the original value of If is initially NULL strsep P returns NULL 6 18 4 25 size t strspn P const char s PGM P accept The strspn_P function calculates the length of the initial segment of s which con sists entirely of characters in accept This function is similar to strspn except that accept is a pointer to a string in program space Returns The strspn_P function returns the number of characters in the initial segment of s which consist only of characters from accept The terminating zero is not considered as a part of string 6 18 4
97. clears all highest bits The tolower and toupper functions return an input argument as is if it is not an unsigned char value inttoascii int c int tolower int __c int toupper int c 6 3 2 Function Documentation 6 3 2 1 intisalnum int Checks for an alphanumeric character It is equivalent to isalpha c isdigit c 6 3 2 2 intisalpha int Checks for an alphabetic character It is equivalent to isupper c islower c 6 3 2 3 intisascii int c Checks whether c is a 7 bit unsigned char value that fits into the ASCII character set 6 3 2 4 int isblank int c Checks for a blank character that 1s a space or a tab 6 3 2 5 intiscntrl int Checks for a control character 6 3 2 6 int isdigit int Checks for a digit 0 through 9 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 3 lt ctype h gt Character Operations 19 6 3 2 7 int isgraph int c Checks for any printable character except space 6 3 2 8 int islower int Checks for a lower case character 6 3 2 9 int isprint int Checks for any printable character including space 6 3 2 10 int ispunct int Checks for any printable character which is not a space or an alphanumeric character 6 3 2 11 int isspace int Checks for white space characters For the avr libc library these are space form feed P newline n carriage return r horizontal tab
98. 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 1 SREG sreg return val Back to FAQ Index 9 10 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 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 318 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 lt lt 7 The optimizer will take care to trans form this into a single SBI instruction assuming the operands allow for this Back to FAQ Index 9 10 11 Why does the PC randomly jump around when single stepping through my program in avr gdb When compiling a
99. compiler would not use them for C code This is arranged for in project h The file is divided into one section that will be used by the assembly source code and another one to be used by C code The assembly part is distinguished by the prepro cessing macro __ASSEMBLER__ which will be automatically set by the compiler 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 35 Combining and assembly source files 184 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 35 2 3 isrs S This file is a preprocessed assembly source file The C preprocessor will be run by the compiler front end first resolving all include define etc directives Th
100. define TW SR GCALL 0x70 fdefine TW SR LOST 0x78 define TW SR DATA ACK 0x80 define TW SR 0x88 fdefine TW SR GCALL DATA ACK 0x90 define TW SR GCALL DATA NACK 0x98 define TW SR STOP OxAO define TW INFO OxF8 fdefine TW BUS ERROR 0x00 define TW STATUS 5 fdefine TW STATUS TWSR amp TW STATUS 5 R W bit in SLA R W address field define TW READ 1 define TW WRITE 0 6 31 2 Define Documentation 6 31 2 1 define TW BUS ERROR 0x00 illegal start or stop condition 6 31 2 2 define TW MR LOST 0x38 arbitration lost in SLA R or NACK 6 31 2 3 define TW MR DATA 0x50 data received ACK returned Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 31 lt util twi h gt TWI bit mask definitions 174 6 31 2 4 define TW MR DATA NACK 0x58 data received NACK returned 6 31 2 5 define TW MR 81 ACK 0x40 SLA R transmitted ACK received 6 31 2 6 define TW MR SLA NACK 0x48 SLA R transmitted NACK received 6 31 2 7 define TW MT LOST 0x38 arbitration lost in SLA W or data 6 31 2 8 define TW MT DATA 0x28 data transmitted ACK received 6 31 2 9 define TW MT DATA NACK 0x30 data transmitted NACK received 6 31 2 10 define TW MT SLA ACK 0x18 SLA W transmitted ACK received 6 31 2 11 TW_MT_SLA_NACK 0x20 SLA W transmitted NACK received 6 31 2 12 define TW NO I
101. define boot page erase extended address Value L extension asm _ _ volatile movw r30 A3 n t sts Sf S03 ni t sts 0 2 n t spm n t i SFR MEM ADDR SPM REG i SFR MEM ADDR RAMPZ r uint8 t BOOT PAGE ERASE um uint32 t address Tr30 8 5 2 5 define boot page erase normal address Value extension asm volatile movw r30 2 n t Sts 0 SVINmNET spm n t VI SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE ERASE r uint16_t address LOPE EEE EA GP a A OP GEE GE Bg gt PE at P A Ba i Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 5 boot h File Reference 227 8 5 2 6 define boot page fill alternate address data Value extension asm _ _ volatile movw r0 3 n t movw r30 2 n t sts 0 1 n t spm n t word Oxffff n t nop n t Nelle eV ne i SFR MEM ADDR SPM REG uint8_t BOOT_PAGE_FILL r uint16_t address r uint16_t data ro Mr30U TEST POLE I EA E ut PZ GE 8 5 2 7 define boot page fill extended address data Value extension asm _ volatile movw r0 4 n t movw r30 A3 n t sts 1 SC3 n t sts 0 2 n t spm n t ele FINNET mi SFR_MEM_ADDR SPM REG SFR MEM ADDR RAMPZ uint8 t BOOT PAGE FILL uint32 t address mom ui
102. defined as define LB MODE 3 OxFC To combine the lockbit mode macros together to represent a whole byte use the bitwise AND operator like so LB MODE 3 amp BLBO MODE 2 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 17 lt avr lock h gt Lockbit Support 133 lt avr lock h gt also defines a macro that provides a default lockbit value LOCKBITS_ DEFAULT which is defined to be OxFF See the AVR device specific datasheet for more details about these lock bits and the available mode settings A convenience macro LOCKMEM is defined as a GCC attribute for a custom named section of lock A convenience macro LOCKBITS is defined that declares a variable lock of type unsigned char with the attribute defined by LOCKMEM This variable allows the end user to easily set the lockbit data Note If a device specific I O header file has previously defined LOCKMEM then LOCKMEM is not redefined If a device specific I O header file has previously defined LOCKBITS then LOCKBITS is not redefined LOCKBITS is currently known to be defined in the I O header files for the XMEGA devices API Usage Example Putting all of this together is easy include avr io h LOCKBITS LB MODE 1 BLBO MODE 3 amp 1 MODE 4 int main void return 0 include lt avr io h gt unsigned char lock attribute section lock LB MODE 1 BLBO_MODE_3 amp 1 MODE 4 i
103. executables are prefixed with the target name avr gdb and avr insight There is also a text mode GUI for GDB avr gdbtui DDD Data Display Debugger is another popular GUI front end to GDB available on Unix and Linux systems 9 1 9 AVaRICE AVaRICE is a back end program to AVR GDB and interfaces to the Atmel JTAG In Circuit Emulator ICE to provide emulation capabilities 9 1 10 SimulAVR SimulAVR is an AVR simulator used as a back end with AVR GDB Unfortunately this project is currently unmaintained and could use some help 9 1 11 Utilities There are also other optional utilities available that may be useful to add to your toolset SRecord is a collection of powerful tools for manipulating EPROM load files It reads and writes numerous EPROM file formats and can perform many different ma nipulations Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 267 MF ile is a simple Makefile generator is meant as an aid to quickly customize a Make file to use for your AVR application 9 1 12 Toolchain Distributions Distros All of the various open source projects that comprise the entire toolchain are normally distributed as source code It is left up to the user to build the tool application from its source code This can be a very daunting task to any potential user of these tools Luckily there are people who help out in this area Volunteers take the time to build th
104. 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 9 10 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 xdox create constructors Ur flag A xn script is for linking with n flag mix text and data on same page A xbn script is for linking with N flag mix text and data on same page Back to FAQ Index 9 10 30 How to add a raw binary image to linker output The GNU linker avr 1d cannot handle binary data directly However there s a com panion tool called avr objcopy This is already known from the output side it s used to extract the contents of the linked ELF file into an Intel Hex load file avr objcopy can create a relocatable object file from arbitrary binary input like avr objcopy I binary O elf32 avr foo bin foo o This will create a file named foo o with the contents of foo bin The contents
105. file The basic algorithm is to quickly evaluate the current system time by fetching the current timer value of TCNTO and combining it with the overflow part in counter hi If the counter is currently counting down rather than up the value fetched from TCNTO must be negated Finally if this pin change interrupt was triggered by a rising edge the time computed will be recorded as the start time only Then at the falling edge this start time will be subracted from the current time to compute the actual pulse width seen left in incoming and the upper layers are informed of the new value by setting bit 0 in the intbits flags At the same time this pin change interrupt will be disabled so no new measurement can be performed until the upper layer had a chance to process the current value 6 35 3 The source code The source code is installed under Sprefix share doc avr libc examples asmdemo Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 185 where prefix is a configuration option For Unix systems it is usually set to either usr or usr local 6 36 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 in an AVR project After reading this chapter you should have a better feel as to how the tools are used and how a Makefile can be configured 6 36 1
106. fmt int vprintf const char fmt va list int sprintf char s constchar fmt int sprintf_P char __s const char x__fmt int snprintf char __s size_t __n const char __fmt 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 x__fmt va list ap int vsnprintf P char __s size_t __n const char __fmt va list ap int fprintf FILE stream const char fmt int fprintf _P FILE stream const char fmt int fputs const char str FILE stream int fputs_P const char str FILE stream int puts const char str int puts P const char str size t fwrite const void ptr size t _ size size t nmemb FILE stream int fgetc FILE stream int ungetc int FILE stream char fgets char str int size FILE stream char gets char str size_t fread void size t size size t nmemb FILE stream Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 41 stdlib h File Reference 253 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 co
107. format for uint_least32_t 6 5 2 56 define PRIXLEAST32 Ix hexadecimal printf format for least32 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 29 6 5 2 57 define PRIXLEASTS X uppercase hexadecimal printf format for least8 t 6 5 2 58 define PRIXLEASTS x hexadecimal printf format for uint_least8_t 6 5 2 59 define PRIXPTR PRIX16 uppercase hexadecimal printf format for uintptr_t 6 5 2 60 define PRIxPTR PRIx16 hexadecimal printf format for uintptr t 6 5 2 61 define SCNd16 d decimal scanf format for int16 t 6 5 2 62 define SCNd32 Id decimal scanf format for int32_t 6 5 2 63 define SCNdFASTI6 decimal scanf format for int fastl6 t 6 5 2 64 define SCNdFAST32 Id decimal scanf format for int fast32 t 6 5 2 65 define SCNdLEASTI6 d decimal scanf format for int leastl6 t 6 5 2 66 define SCNdLEAST32 Id decimal scanf format for int least32 t 6 5 2 67 ftdefine SCNdPTR SCNd16 decimal scanf format for intptr t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 30 6 5 2 68 define SCNi16 i generic integer scanf format for int16_t 6 5 2 69 define SCNi32 li generic integer scanf format for int32_t 6 5 2 70 define SCNiIFASTI16 i generic integer scanf format for int fast16 t 6 5 2 71 define SCNiIFAST32 l
108. 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 controller s SRAM RS asserted macros are provided that build on the mentioned function primitives Finally macros are provided for all the controller commands to allow them to be used symbolically The HD44780 datasheet explains these basic functions of the controller in more detail 6 38 3 4 hd44780 c This is the implementation of the low level HD44780 LCD controller driver On top a few preprocessor glueing tricks are used to establish symbolic access to the hardware port pins the LCD controller is attached to based on the application s definitions made in defines h The h 44780 pulse e function asserts a short pulse to the controller s E en able pin Since reading back the data asserted by the LCD controller needs to be performed while E is active this function reads and returns the input data if the param eter readback is true When called with a compile time constant parameter that is false the compiler will completely eliminate the unused readback operation as well as the return value as part of its optimizations As the controller is used in 4 bit interface mode all byte IO to from the controller needs to be handled as two nibble IOs The functions hd44780_outnibble and hd44780_innibble implement this They do not belong to the public interface so they are declared static
109. h Aliases a given vector to another one in the same manner as the ISR_ALIASOF at tribute for the ISR macro Unlike the ISR_ALIASOF attribute macro however this is compatible for all versions of GCC rather than just GCC version 4 2 onwards Note This macro creates a trampoline function for the aliased macro This will result in a two cycle penalty for the aliased vector compared to the ISR the vector is aliased to due to the JMP RJMP opcode used Deprecated For new code the use of ISR ISR_ ALIASOF is recommended Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 129 Example ISR INTO_vect PORTB 42 ISR ALIAS INT1 vect INTO vect 6 15 2 6 define ISR ALIASOF target vector include avr interrupt h The ISR is linked to another ISR specified by the vect parameter This is compatible with GCC 4 2 and greater only Use this attribute in the attributes parameter of the ISR macro 6 15 2 7 define ISR BLOCK f include lt avr interrupt h gt Identical to an ISR with no attributes specified Global interrupts are initially disabled by the AVR hardware when entering the ISR without the compiler modifying this state Use this attribute in the attributes parameter of the ISR macro 6 15 2 8 define ISR NAKED include lt avr interrupt h gt ISR is created with no prologue or epilogue code The user code is responsible for pr
110. h File 5 233 8 16 1 Detailed DsscnpHon e lt e ecs pss ae Po g ee ed 233 Pile Rereren e 22 2 2209 945 mre 233 8 17 1 Detailed ss soc e oca RR ee 233 i amp h File Reference 2222 m o ob ok x Reb S on EORR 236 8 18 1 Detaled Description 222222222 222525 236 Refereneg eee 236 8 19 1 Detaled Description lt eu RI 224 236 File Reterenee 2 5 o OS Ek RU ROURURA 236 8 20 1 Detaled Description 2 5 5446 s Sors 236 memecpy S File Reference 2 4 05 6664 som 9 RR 239 8 21 1 Detaled Description se se ceres terit emerat 239 memeh S File Referente 4 HA eee GS RU s 239 8 22 1 Detailed Description s See p oka 239 memchr PS File 239 8 23 1 Detailed Description lt ssc e a oko mms 239 memenp S File Reference 2v RI n o eee eS 239 8 24 1 Detailed Description 2 239 mememp P S File Reference v 2 v L m 2552259 239 S20 Detailed Desenption uu oce xo m Rm eue BOE S 239 File Reference oak e x o dm obo RR RUE S 239 8 26 1 Detailed Description 239 memcpy PS File Reference 605 239 8 27 1 Detaled Description 222 939 5 S446 596 239 memmem S File Reference 1 1 0 k X V m 8 239 8 28 1 Detailed Descnpfi n s a soo RR RR RR 239 memmove s File Reterente suu sS Sk o kdo ba mS k 239 6
111. heap start e char x malloc heap end Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 41 stdlib h File Reference 256 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 42 strcasecmp S File Reference 257 8 42 8 42 1 8 43 8 43 1 8 44 8 44 1 8 45 8 45 1 8 46 8 46 1 8 47 8 47 1 8 48 8 48 1 8 49 8 49 1 8 50 8 50 1 8 51 8 51 1 8 52 8 52 1 8 53 strcasecmp S File Reference Detailed Description strcasecmp_P S File Reference Detailed Description strcasestr S File Reference Detailed Description strcat S File Reference Detailed Description strcat P S File Reference Detailed Description strchr S File Reference Detailed Description strchr P S File Reference Detailed Description strchrnul S File Reference Detailed Description strchrnul P S File Reference Detailed Description strcmp S File Reference Detailed Description strcemp P S File Reference Detailed Description strcpy S File Reference Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 53 1 8 54 8 54 1 Q AR Detailed Description strcpy P S File Reference Detailed Description ctrecnn S File Reference 8 57 string h File Reference 258 define _ need_NULL define __need_size_t define _ ATTR_PURE attribute__ __pure__ define _FFS x Functions int ffs int val int 51 long __ val int ffsll long long val void memccpy void const void
112. 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 RAM SP E h __malloc_heap_end heap end RAMEND __brkval bss end malloc heap start heap start data bss start 0x0100 Ox10FF 0x1100 0x200 Ox3FFF OxFFFF 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 271 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 margin is set to 32 9 2 4 Implementation details Dynamic memory allocation requests will be returned with a two byte header prepended that records the size of the allocation This is later used by free The returned add
113. int mydata AVR GCC uses Variable Attributes to achieve the same effect int mydata attribute progmem Note See the GCC User Manual for more information about Variable Attributes avr libc provides a convenience macro for the Variable Attribute finclude avr pgmspace h int mydata PROGMEM Note The PROGMEM macro expands to the Variable Attribute of progmem This macro requires that you include lt avr pgmspace h gt This is the canonical method for defining a variable in Program Space To read back flash data use the read macros defined lt avr pgmspace h gt Program Memory handling macros are defined there There is also a way to create a method to define variables in Program Memory that is common between the two compilers IAR and AVR GCC Create a header file that has these definitions fif defined IAR C Compiler define FLASH DECLARE x flash x endif fif defined __GNUC__ GNU Compiler define FLASH DECLARE x x __attribute__ __progmem__ endif Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 9 Porting From to AVR 310 This code snippet checks for the IAR compiler or for the GCC compiler and defines a macro FLASH_DECLARE x that will declare a variable in Program Memory using the appropriate method based on the compiler that is being used Then you would used it like so FLASH DEC
114. 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 9 10 17 Which O flag to use There s common misconception that larger numbers behind the O 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 ATmegal28 to judge the effect of compiling the library itself using different optimization levels The following table lists the results The test case consisted of around 2 KB of strings to sort Test 1 used qsort using the standard library stremp test 2 used a function that sorted the strings by their size thus had
115. it finds the function that matches the call the linker will then link in the object module in which the function is located This part is important the linker links in THE ENTIRE OBJECT MODULE in which the function is located Remember the linker knows nothing about the functions internal to an object module other than symbol names such as function names The smallest unit the linker works with is object modules When there are no more undefined references the linker has linked everything and is done and outputs the final application 9 7 3 How to Design a Library How the linker behaves is very important in designing a library Ideally you want to design a library where only the functions that are called are the only functions to be linked into the final application This helps keep the code size to a minimum In order to do this with the way the linker works is to only write one function per code module This will compile to one function per object module This is usually a very different way of doing things than writing an application There are always exceptions to the rule There are generally two cases where you would want to have more than one function per object module The first is when you have very complementary functions that it doesn t make much sense to split them up For example malloc and free If someone is going to use malloc they will very likely be using free or at least should be using free In this ca
116. 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 9 11 5 GCC for the AVR target Warning You must install avr binutils and make sure your path is set properly before in stalling avr gcc The steps to build avr gcc are essentially same as for binutils Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 339 bunzip2 c gcc lt version gt tar bz2 tar xf 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 X X XY 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 patch that adds more AVR types can be found at http www freebsd org cgi cvsweb cgi ports devel avr gcc files patch newdevi 9 11 6 AVR Libc Warning You must install avr binutils avr gcc and make
117. libc Data Structures Here are the data structures with brief descriptions div_t 221 Idiv_t 222 4 avr libc File Index 41 avr libc File List Here is a list of all documented files with brief descriptions assert h 222 atoi S 223 atol S 223 atomic h 223 boot h 223 crc16 h 230 ctype h 230 delay h 231 delay_basic h 231 errno h 232 fdevopen c 232 ffs S 232 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 41 avr libc File List 12 ffsl S 232 ffsll S 232 fuse h 232 interrupt h 233 inttypes h 233 io h 236 lock h 236 math h 236 memccpy S 239 memchr S 239 memchr_P S 239 memcmp S 239 memcmp P S 239 memcpy S 239 memcpy P S 239 memmem S 239 memmove S 239 memrchr S 239 memrchr_P S 239 memset S 239 parity h 239 pgmspace h 240 power h 246 setbaud h 247 setjmp h 247 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 41 avr libc File List 13 sleep h 248 stdint h 248 stdio h 251 stdlib h 253 strcasecmp S 257 strcasecmp P S 257 strcasestr S 257 strcat S 257 strcat P S 257 strchr S 257 strchr P S 257 strchrnul S 257 strchrnul P S 257 strcmp S 257 stremp_P S 251 strcpy S 257 strepy_P S 257 strcspn S 257 strespn_P S 257 string h 257 strlcat S 260 strlcat P S 260 stricpy S 260 stricpy_P S 260 strlen S 260 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 41 avr libc File List 14 strlen_P S 260 strlwr S 260 strncasecmp S 260 strncasecmp_P S 260 strn
118. libc by Doxygen 9 5 avr libc and assembler programs 286 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 AT90S1200 does not have RAM thus the memory mapped approach to access the IO registers is not available It would be slower than using in out instructions anyway Since the operation to reload TCCNTO is time critical it is even performed before saving SREG Obviously this requires that the instructions involved would not change any of the flag bits in SREG Note 9 Interrupt routines must not clobber the global CPU state Thus it is usually necessary to save at least the state of the flag bits in SREG Note that this serves as an example here only since actually all the following instructions would not modify SREG either but that s not commonly the case Also it must be made sure that registers used inside the interrupt routine do not conflict with those used outside In the case of a RAM less device like the 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 n
119. local data but often used for fixed purposes rO temporary register be clobbered by any C code except interrupt handlers which save it may be used to remember something for a while within one piece of assembler code rl assumed to be always zero in any code be used to remember something for a while within one piece of assembler code but must then be cleared after use r1 This includes any use of 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 124 not r25 16 bit r25 124 up to 32 bits in 122 125 up to 64 bits in r18 r25 8 bit return values are zero sign extended to 16 bits by the called function unsigned char is more efficient than signed char justclr r25 Arguments to functions with variable argument lists printf etc are all passed on stack and char is extended to int Warning There was no such alignment before 2000 07 01 including the old patches for gcc 2 95 2 Check your old assembler subroutines and
120. macro and the address of your data becomes the parameter to that macro byte pgm read byte amp mydata i j1 The read macros take an address that points to the Program Space and re trieves the data that is stored at that address This is why you take the address of the offset into the array This address becomes the parameter to the macro so it can gen erate the correct code to retrieve the data from the Program Space There are different read macros to read different sizes of data at the address given Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 4 Data in Program Space 280 9 4 4 Storing and Retrieving Strings in the Program Space Now that you can successfully store and retrieve simple data from Program Space you want to store and retrive strings from Program Space And specifically you want to store and array of strings to Program Space So you start off with your array like so char xstring table 1 String 1 String 2 String 3 String 4 otring S and then you add your PROGMEM macro to the end of the declaration char xstring table 1 String i String 2 String 3 String 4 String 3 Right WRONG PROGMEM Unfortunately with GCC attributes they affect only the declaration that they are at tached to So in this case we successfully put the string_table variable the array itself in the Program Space This DOES NOT
121. mmcu device flag in your compile command line and your linker command line to have the correct device selected and to have the correct I O header file included when you include lt avr io h gt You can print out the contents of the lock section in the ELF file by using this command line avr objdump s j lock ELF file 6 18 lt avr pgmspace h gt Program Space Utilities 6 18 1 Detailed Description include lt avr io h gt include lt avr pgmspace h gt The functions in this module provide interfaces for a program to access data stored in program space flash memory of the device In order to use these functions the target device must support either the LPM or ELPM instructions Note These functions are an attempt to provide some compatibility with header files that come with to make porting applications between different compilers easier This is not 100 compatibility though GCC does not have full support for multiple address spaces yet If you are working with strings which are completely based in ram use the stan dard string functions described in lt string h gt Strings If possible put your constant tables in the lower 64 KB and use pgm_read_byte_ near or pgm_read_word_near instead of pgm_read_byte_far or pgm_read_ word_far since it is more efficient that way and you can still use the upper 64K Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspa
122. 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference 241 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 PGM VOID P memchr P PGM_VOID_P int val size t _ len int memcmp P const void PGM VOID size t ATTR_PURE void memcpy P void PGM VOID size_t void memmem P const void x size t VOID P size t ATTR PURE PGM VOID P memrchr P PGM VOID B int __ val size_t len char strcat P char PGM P PGM _P strchr P PGM_P int __ val PGM P strchrnul P PGM_P int __val int stremp_P const char x PGM P PURE char strcpy P char x PGM_P int strcasecmp_P const char PGM_P __ATTR_PURE char strcasestr P const char x PGM_P __ATTR_PURE size tstrcspn P const char s PGM_P _ reject ATTR PURE size_t strlcat P char P size t size t strlcpy P cha
123. or may not be of use for you Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 337 AVRDUDE http savannah nongnu org projects avrdude Installation Usage Notes GDB http sources redhat com gdb Installation SimulAVR http savannah gnu org projects simulavr Installation AVaRICE http avarice sourceforge net Installation 9 114 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 version tar bz2 tar xf cd binutils version Note Replace lt version gt with the version of the package you downloaded If you obtained a gzip compressed file gz use gunzip instead of bunzip2 It is usually a good idea to configure and build 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 Generate
124. page erase except it waits for eeprom and spm operations to complete before erasing the page 6 12 2 7 define boot page fill address data boot page fill normal address data Fill the bootloader temporary page buffer for flash address with data word Note The address is a byte address The data is a word The AVR writes data to the buffer a word at a time but addresses the buffer per byte So increment your address by 2 between calls and send 2 data bytes in a word format The LSB of the data is written to the lower address the MSB of the data is written to the higher address 6 12 2 8 define boot page fill safe address data Value do boot spm busy wait eeprom_busy_wait boot_page_fill address data X while 0 Same as boot page fill except it waits for eeprom and spm operations to complete before filling the page Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 99 6 12 2 9 define boot page write address boot page write normal address Write the bootloader temporary page buffer to flash page that contains address Note address is a byte address in flash not a word address 6 12 2 10 define boot page write safe address Value do boot spm busy wait N eeprom busy wait boot_page_write address N while 0 Same as boot page write except it waits for eeprom and spm operations to
125. 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 mtiny stack Change only the low 8 bits of the stack pointer 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 356 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 e mshort calls Use rjmp rcall limited range on gt 8K devices On avr2 and avr4 architec tures less than 8 KB or flash memory this is always the case On avr3 and avr5 architectures calls and jumps to targets outside the current function will by default use jmp call instructions that can cover the entire address range but that require more flash ROM and execution time nrtl Dump the internal compilation result called RTL into comments in the generated assembler code Used for debugging avr gcc e msize Dump the address size and relative cost of each statement into comments in the gen erated assembler code Used for debugging avr gcc mdeb Generate lots of debugging info
126. push YH eor rl6 r16 start loop Idi YL lo8 sometable ldi YH hi8 sometable rjmp 2f jump to loop test at end 1 17 loop continues here breq 1f return from myfunc prematurely inc r16 2 cmp l 18 brlo 1b jump back to top of loop is pop YH pop YL pop 18 zl pop rig ret Back to FAQ Index 9 10 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 port mask void set bits func correct volatile uint8_t port uint8_t mask xport mask define set_bits_macro port mask port mask int main void set_bits_func_wrong PORTB Oxaa set_bits_func_correct amp PORTB 0x55 set bits macro PORTB 0 0 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 321 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 register using an IN instruction instead of passing the address of PORTB e g memory mapped io addr of 0x38 io port 0x18 for the mega128 This is seen clearly when looking at the disassembly of the call set bits func wrong PORTB Oxaa 10a 6a ea 141 r22
127. put the actual strings themselves into Program Space At this point the strings are still in the Data Space which is probably not what you want In order to put the strings in Program Space you have to have explicit declarations for each string and put each string in Program Space char char char char char string_1 string 2 string 3 string 4 string 5 PROGMEM PROGMEM PROGMEM PROGMEM PROGMEM String String String String String 1 2 5 3 4 5 Then use the new symbols in your table like so PGM P string table string 1 string 2 string 3 string 4 string 5 PROGMEM Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 4 Data in Program Space 281 Now this has the effect of putting string_table in Program Space where string_table is an array of pointers to characters strings where each pointer is a pointer to the Program Space where each string is also stored The PGM_P type above is also a macro that defined as a pointer to a character in the Program Space Retrieving the strings are a different matter You probably don t want to pull the string out of Program Space byte by byte using the pgm_read_byte macro There are other functions declared in the lt avr pgmspace h gt header file that work with strings that are stored in the Program Space For example if you want to copy the string from Program Space to a buffer in RAM like a
128. rjmp 194 Oxlle exit 0000005 lt __vector_8 gt include iocompat h x Note 1 x enum UP DOWN ISR TIMER1 x Note 2 Scr Lf 92 push l 5e Of 92 push r0 60 Of 56 IN EO r OXIE 53 62 Of 92 push r0 64 11 24 eor rl rl 66r Zf 93 push r18 68r 93 push 19 6a 8f 93 push r24 static uint16_t pwm Note 3 static uint8_t direction switch direction x Note 4 80 91 60 00 lds r24 0x0060 70 88 23 and r24 r24 72 61 4 brne 48 Oxa4 lt vector 840 48 gt case UP if pwm 74 20 91 61 00 lds r18 0 0061 78 30 91 62 00 lds r19 0x0062 EG 2f SE subi r18 OxFF 255 7e 3f 4f sbet rl9 OxEE 72 7255 80230 93 62 00 sta Ox0062 rl9 84 20 93 61 00 sts 0x0061 r18 88 83 e0 ldi r24 0x03 3 gas 2E cpi r18 OxFF 255 8c 38 07 cpc 19 r24 8e 09 f1 breq 66 Oxd2 vector 840 76 gt if pwm 0 direction UP break OCR pwm x Note 5 3b bd out 0x2b r19 43 92 2a bd out 0 2 r18 42 94 8 91 pop r24 962 81 r19 99 2f 9T pop r18 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 193 9a Of 90 pop 9c Of be out 0x3f r0 63 9e Of 90 pop a0 1f 90 pop rl age 28 95 reti ISR OVF vect x Note 2 static uint16_t Note 3 static uint8_t direction switch directi
129. same as the old pointer or a pointer to a completely different region The contents of the returned region up to either the old or the new size value whatever is less will be identical to the contents of the old region even in case a new region had to be allocated It is acceptable to pass ptr as NULL in which case realloc will behave identical to malloc If the new memory cannot be allocated realloc returns NULL and the region at pt x will not be changed 6 10 4 24 void srand unsigned int seed Pseudo random number generator seeding see rand 6 10 4 25 void srandom unsigned long seed Pseudo random number generator seeding see random 6 10 4 26 double strtod const char nptr char endptr The strtod function converts the initial portion of the string pointed to by nptr to double representation The expected form of the string is an optional plus or minus sign followed by a sequence of digits optionally containing a decimal point character op tionally followed by an exponent An exponent consists of an E or e followed by an optional plus or minus sign followed by a sequence of digits Leading white space characters in the string are skipped The strtod function returns the converted value if any If endptr is not NULL a pointer to the character after the last character used in the conversion is stored in the location referenced by endptr If no conversion is p
130. scce eaae ee 257 6 52 1 Detailed Description 622444086 See ee wakes 257 sttepyo Pile Referente uso tu RR RR 257 8 53 1 Detailed Description 222 2 22 257 stepy Ps File Reference 222222222252 8 55522 eS 257 8 54 1 Detailed Description 257 s cspn s File Reference 22 222 2 257 5 33 1 Detailed Description succ m Rm eue 257 strespn P S File Reference 2222 2 2 2 4 257 8 56 1 Detailed Description 257 sthup h Fil Reference ck eR Rm Re RR RS 257 8 57 1 Detaled Description se csser ppu 257 stricat 5 File Referenc 2 v Sus k G k dl V IRR W 260 8 58 1 Detaled De eripli n RR RR be s 260 stlcat P S File 2 22 2 2 2 45 4 260 8 391 Detaled Description 2222222 Gee k anu 260 Stl py S File Reference po 2 k 44 5 om RR 260 8 60 1 Detailed Description 260 PS File uo eee aud See n b 260 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS x 8 62 8 63 8 64 8 65 8 66 8 67 8 68 8 69 8 70 8 71 8 72 8 73 8 74 8 75 8 76 8 61 1 Detailed Description 2 260 Kule us uso uox m s Re FUROR EUR BAR es 260 662 Detailed Description 25222222255 ehe a 260 strlen PS File Reference o soe ee eR S 260 8 63 1 Detailed
131. seperate line asm volatile nopNnNt nop n t nop n t nop n t Generated on Mon May 12 09 55 09 2008 for avr libc Doxygen 9 6 Inline Assembler Cookbook 291 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 ISP He Stack pointer high byte at address 0 3 SP Stack pointer low byte at address 0x3D tmp reg Register rO used for temporary storage 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 new compiler version changes the register usage definitions 9 6 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 May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assemb
132. 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 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 37 3 4 Part 4 Auxiliary functions 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 trigger before the current reason has been evaluated This also explains why the variable mcucsr that mirrors the register s value needs to be placed into the noinit section because otherwise the default initialization which happens after init3 would blank the value agai
133. standard one this version implements no specification This version is provided in the library 1ibscanf min a and can be requested using the following options in the link stage Wl u vfscanf l1scanf min lm 6 9 3 35 int vfscanf_P FILE x stream const char _ fmt va_list Variant of vfscanf using a mt string in program memory 6 9 3 36 int vprintf const char x _ fmt va_list The function vprintf performs formatted output to stream stdout taking a vari able argument list as in vfprintf See vfprintf for details 6 9 3 37 int vscanf const char list The function vscanf performs formatted input from stream st din taking a variable argument list as in vfscanf See vfscanf for details 6 9 3 38 int vsnprintf char s size t __n const char fmt 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 72 6 9 3 39 int vsnprintf_P char _ 5 size_t__n const char x __ fmt va_list ap Variant of vsnprintf that uses a fmt string that resides in program memory 6 9 3 40 int vsprintf char __s const char fmt va_list ap Like sprintf
134. start is filled in by the linker to point just beyond bss and __ heap end is setto 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 J heap end 0x80ffff Note See explanation for offset 0x800000 See the chapter about using gcc for the w1 options Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 270 external RAM on board RAM 0x0100 Ox10FF 0x1100 OxFFFF SP J NI E __malloc_heap_end heap end RAMEND __brkval __malloc_heap_start __heap_start bss end data 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 variables in internal RAM something like the following could be used Note that for demonstration purposes the assignment of the various regions has not been made adjacent in this example so there are
135. string to an integer The atoi function converts the initial portion of the string pointed to by s to integer representation In contrast to int strtol s char NULL 10 this function does not detect overflow errno is not changed and the result value is not predictable uses smaller memory flash and stack and works more quickly 6 10 4 5 long atol const char s Convert a string to a long integer The atol function converts the initial portion of the string pointed to by s to long integer representation In contrast to strtol s char xx NULL 10 this function does not detect overflow errno is not changed and the result value is not predictable uses smaller memory flash and stack and works more quickly 6 10 4 6 void bsearch const void const void base size_t nmemb size t size int const void const void compar The bsearch function searches an array of nmemb objects the initial member of which is pointed to by base for a member that matches the object pointed to by key The size of each member of the array is specified by size Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 76 The contents of the array should be in ascending sorted order according to the compar ison function referenced by compar The compar routine is expected to have two arguments which point to the key object and to an array member in tha
136. strrev function returns a pointer to the beginning of the reversed string Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 93 6 11 3 32 char strsep char sp const char x delim Parse a string into tokens The strsep function locates in the string referenced by sp the first occurrence of any character in the string delim or the terminating VO character and replaces it with a 0 The location of the next character after the delimiter character or NULL if the end of the string was reached is stored in sp An empty field i e one caused by two adjacent delimiter characters can be detected by comparing the location referenced by the pointer returned in to 707 Returns The strsep function returns a pointer to the original value of If sp is initially NULL strsep returns NULL 6 11 3 33 size t strspn const char x s const char accept The strspn function calculates the length of the initial segment of s which consists entirely of characters in accept Returns The strspn function returns the number of characters in the initial segment of s which consist only of characters from accept The terminating zero is not considered as a part of string 6 11 3 34 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
137. 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 6 38 4 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 39 Example using the two wire interface TWI Some newer devices of the ATmega series contain builtin support for interfacing the microcontroller to a two wire bus called TWI This is essentially the same called I2C by Philips but that term is avoided in Atmel s documentation due to patenting issues For the original Philips documenta
138. the Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 13 Using the avrdude program 362 linker is typically called from the compiler frontend this can be achieved using a com piler option like Wl defsym stack 0x8003ff The above will make the code use stack space from RAM address Ox3ff downwards The amount of stack space available then depends on the bottom address of internal RAM for a particular device It is the responsibility of the application to ensure the stack does not grow out of bounds as well as to arrange for the stack to not collide with variable allocations made by the compiler sections data and bss 9 13 Using the avrdude program Note This section was contributed by Brian Dean bsd bsdhome com The avrdude program was previously called avrprog The name was changed to avoid confusion with the avrprog program that Atmel ships with AvrStudio avrdude is a program that is used to update or read the flash and EEPROM memories of Atmel AVR microcontrollers on FreeBSD Unix It supports the Atmel serial pro gramming protocol using the PC s parallel port and can upload either a raw binary file or an Intel Hex format file It can also be used in an 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
139. the Object File Now we have a binary file Can we do anything useful with it besides put it into the processor The GNU Binutils suite is made up of many useful tools for manipulating object files that get generated One tool is avr ob jdump which takes information from the object file and displays it in many useful ways Typing the command by itself will cause it to list out its options For instance to get a feel of the application s size the h option can be used The output of this option shows how much space is used in each of the sections the stab and stabstr sections hold the debugging information and won t make it into the ROM file An even more useful option is S This option disassembles the binary file and inter sperses the source code in the output This method is much better in my opinion than using the 5 with the compiler because this listing includes routines from the libraries and the vector table contents Also all the fix ups have been satisfied In other words the listing generated by this option reflects the actual code that the processor will run avr objdump h 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 00000126 00000000 00000000 00000074 2xx1 CONTENTS ALLOC LOAD READONLY CODE 1 ps 00000003 00800060 00000126 0000019 2xx0 ALLOC 2 debug arang
140. 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 the actual value Note that the stack will still remain in internal RAM through the symbol _ Stack that is provided by the run time startup code This is probably a good idea anyway since internal RAM access is faster and even required for some early devices that had hardware bugs preventing them from using a stack in external RAM Note also that the heap for malloc will still be placed after all the variables in the data section so in this situation no stack heap collision can occur In order to relocate the stack from its default location at the top of interns RAM the value of the symbol stack can be changed on the linker command line As
141. the following can be used to implement simple debugging messages that will be sent through a UART include lt inttypes h gt include lt avr io h gt include lt avr pgmspace h gt int uart putchar char if c n uart putchar Nr Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 329 loop until bit is set USR UDRE UDR c return 0 so it could be used for fdevopen too void debug_P const char xaddr while pgm_read_byte addr uart_putchar c 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 9 10 21 Why does the compiler compile an 8 bit operation that uses bitwise op erators into a 16 bit operation in assembly Bitwise operations in Standard C will automatically promote their operands to an int which is by default 16 bits in avr gcc To work around this use typecasts on the operands including literals to declare that the values are to be 8 bit operands This may be especially important when clearing a bit var amp mask wrong way The bitwise not operator will also promote the value in mask to an int To keep it an
142. 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 319 9 10 12 How do 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 this This is done using the GNU assembler option gstabs Example avr as mmcu atmegal28 gstabs o foo o foo s When the assembler is not called directly but through the C compiler frontend either implicitly by passing a source file en
143. this is not very useful because one can only turn bits off The only way to turn flash bits on is to erase the entire memory using avrdude s e option avrdude is part of the FreeBSD ports system To install it simply do the following cd usr ports devel avrdude make install Once installed avrdude can program processors using the contents of the hex file specified on the command line In this example the file main hex is burned into the flash memory avrdude p 2313 e m flash i main hex avrdude AVR device initialized and ready to accept instructions avrdude Device signature 0x1e9101 avrdude erasing chip avrdude done avrdude reading input file main hex Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 13 Using the avrdude program 363 avrdude input file main hex auto detected as Intel Hex avrdude writing flash 1749 0x00 avrdude 1750 bytes of flash written avrdude verifying flash memory against main hex avrdude reading on chip flash data 1749 0x00 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 b
144. to detect RAM memory and variable overlap problems 22 Is itreally impossible to program the ATtinyXX in C 23 What is this clock skew detected messsage 24 Why are many interrupt flags cleared by writing a logical 1 25 Why have programmed fuses the bit value 0 26 Which AVR specific assembler operators are available 27 Why are interrupts re enabled in the middle of writing the stack pointer 28 Why are there five different linker scripts 29 How to add a raw binary image to linker output 30 How do I perform a software reset of the AVR 31 I am using floating point math Why is the compiled code so big Why does my code not work 9 10 2 My program doesn t recognize a variable updated within an interrupt routine When using the optimizer in a loop like the following one uint8 t flag ISR SOME vect flag 1 while flag 0 the compiler will typically access flag only once and optimize further accesses com pletely away since its code path analysis shows that nothing inside the loop could 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 313 9 10 3 I get undefined reference to
145. 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 Unused User definable init2 In programs weakly bound to initialize the stack and to clear __zero_reg__ rl Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 3 Memory Sections 275 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 1018 Unused User definable init9 Jumps into main 9 3 7 finiN Sections These sections are used to define the exit code executed after return from main or a call to exit These all are subparts of the text section The finiN sections are executed in descending order from 9 to 0 finit9 Unused User definable This is effectively where _exit starts fini8 Unused User definable fini7 Unused User definable
146. 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 destination string dest 6 18 4 21 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 0 character among the first 1 characters pointed to by src 6 18 4 22 char x strpbrk P const char s P accept The strpbrk_P function locates the first occurrence in the string s of any of the char acters in the flash string accept This function is similar to strpbrk except that accept is a pointer to a string in program space Returns The strpbrk_P function returns a pointer to the character in s that matches one of the characters in accept or NULL if no such character is found The terminating Zero is not considered as a part of string if one or both args are empty the result will NULL 6 18 4 23 P strrchr P P s int val Locate character in string The strrchr_P function returns a pointer to the last occurrence of the character val in the flash string s Returns The strrchr_P function returns a pointer to the matched character or NULL if the
147. 0 indicating a write operation in order to transfer the EEPROM ad dress to start reading from This is called master transmitter mode Each completion of a particular step in TWI communication is indicated by an asserted TWINT bit in TWCR An interrupt would be generated if allowed After performing any actions that are needed for the next communication step the interrupt condition must be man ually cleared by setting the TWINT bit Unlike with many other interrupt sources this would even be required when using a true interrupt routine since as soon as TWINT is re asserted the next bus transaction will start Note 9 Since the TWI bus is multi master capable there is potential for a bus contention when one master starts to access the bus Normally the TWI bus interface unit will detect this situation and will not initiate a start condition while the bus is busy However in case two masters were starting at exactly the same time the way bus arbitration works there is always a chance that one master could lose arbitration of the bus during any transmit operation A master that has lost arbitration is required by the protocol to immediately cease talking on the bus in particular it must not initiate a stop condition in order to not corrupt the ongoing transfer from the active master In this example upon detecting a lost arbitration condition the entire transfer is going to be restarted This will cause a new start condition to be initiat
148. 10 Frequently Asked Questions 325 bar is at addr 0x002 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 725 77 1f 23 123 74 5 subi r22 OxDA 218 76 7f 4f sbci r23 OxFF 255 78 42 e0 1 r20 0 02 12 Ta 50 eo idi r21 0x00 2 0 Te ce 01 movw r24 r28 Te 81 96 adiw r24 0x21 2 99 80 08 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 P is called strcpy P buf p 82 69 al ldd r22 Y 33 0x21 84 7a al ldd r23 Y 34 0x22 86 ce 01 movw r24 r28 88 01 96 adiw r24 0x01 2 4 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 from ROM via P usually remains unnoticed since the compiler would then optimize the code for accessing array at c
149. 170 10c 88 b3 in r24 0x18 24 10e 0e 94 65 00 11 So the function once called only sees the value of the port register and knows nothing about which port it came from At this point whatever object code is generated for the function by the compiler is irrelevant The interested reader can examine the full disassembly to see that the function s body is completely fubar The second function shows how to pass by reference the memory mapped address of the io port to the function so that you can read and write to it in the function Here s the object code generated for the function call set_bits_func_correct amp PORTB 0x55 112 65 5 14 r22 0 55 4285 114 88 e3 141 r24 0 38 56 116 90 0 141 r25 0 00 2 10 118 0e 94 7 00 11 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 xport mask fa 80 81 1 r24 7 fe 86 2b or r24 r22 fe 80 83 st 2 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 322 N
150. 2 connection and performs a few simple actions based on the commands First a prompt is sent out using printf 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 get s 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 break condition extended start condition has been recognized on the serial line Common PC terminal programs allow to assert this condition as some kind of out of band signalling on an RS 232 connection When leaving the main loop a goodbye message is sent to standard error output i e to the LCD followed by three dots in one second spacing followed by a sequence that will clear the LCD Finally main will be terminated and the library will add an infinite loop so only a CPU reset will be abl
151. 2 1 define DTOSTR_ALWAYS_SIGN 0x01 Bit value that can be passed in flags to dtostre 6 10 2 2 define DTOSTR PLUS SIGN 0x02 Bit value that can be passed in 1ags to dtostre 6 10 2 3 define DTOSTR UPPERCASE 0x04 Bit value that can be passed in 1ags to dtostre 6 10 2 4 define RAND MAX 0x7FFF Highest number that can be generated by rand 6 10 2 5 define RANDOM MAX 0x7FFFFFFF Highest number that can be generated by random 6 10 3 Typedef Documentation 6 10 3 1 typedef int compar fn t const void const void Comparision function type for qsort just for convenience 6 10 4 Function Documentation 6 10 4 1 void abort void The abort function causes abnormal program termination to occur This realization disables interrupts and jumps to exit function with argument equal to 1 In the limited AVR environment execution is effectively halted by entering an infinite loop Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 75 6 10 4 2 int abs int The abs function computes the absolute value of the integer i Note The abs and labs functions are builtins of gcc 6 10 4 3 double atof const char nptr The atof function converts the initial portion of the string pointed to by nptr to double representation It is equivalent to calling strtod nptr char xx 0 6 10 4 4 int atoi const char x s Convert a
152. 2 PB4 18pf OCI PB3 XTAL1 18pf 2 ss AIN1 PB1 LED5MM R2 D1 H D See note 8 X INT1 PD3 GND INTO PD2 The source Gkb AINO PBO 4 ICP PDE GND T1 PD5 TO PD4 PRPFFE EEERRERE TXD PD1 RXD PDO AT90S2313P Figure 1 Schematic of circuit for demo project code is given in demo c For the sake of this example create a file called demo c containing this source code Some of the 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 counterl 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 mapping of the output compare match 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 ifdef statements so the actual 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 p
153. 2 data 4 return uintl16 lt lt 8 hi8 crc uint8 t data gt gt 4 uintl16 t data lt lt 3 6 26 2 3 static inline uint8 t crc ibutton update uint8 t crc uint8 t data static Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 26 lt utiV crc16 h gt CRC Computations 166 Optimized Dallas now Maxim iButton 8 bit CRC calculation Polynomial x 8 x 5 x 4 1 0x8C Initial value 0 0 See http www maxim ic com appnotes cfm appnote_number 27 The following is the equivalent functionality written in C uint8_t _crc_ibutton_update uint8_t crc 6 26 2 4 uint8 t data uint8 t i crc crc for i 0 L CEG else cro return crc data lt 8 i amp 0x01 crc gt gt 1 uint8_t data 0x8C static _ inline uint16 t crc xmodem update uintl6 t _ crc 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 int i crc crc for i 0 if CFE ere else return cre i lt 8 uint16_t crc uint8_t data uint16 lt lt 8 itt amp 0x8000 crc lt lt 1 lt lt 1 0x1021 Generated on Mon May 12 09 55 09 2008 for a
154. 26 char x strstr P const char 57 PGM 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 6 19 lt avr power h gt Power Reduction Management finclude lt avr power h gt Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 19 lt avr power h gt Power Reduction Management 147 Many AVRs contain a Power Reduction Register PRR or Registers PRRx that allow you to reduce power consumption by disabling or enabling various on board peripher als as needed There are many macros in this header file that provide an easy interface to enable or disable on board peripherals to reduce power See the table below Note Not all AVR devices have a Power Reduction Register for example the AT megal28 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
155. 286 AT90USB647 AT90USB646 TIMER3_ SIG_INPUT_ Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA CAPT_vect CAPTURE3 Capture Event ATmegal28 ATmegal284P ATmegal62 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB 1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3_ SIG_ Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPA_vect OUTPUT_ Compare Match ATmegal28 ATmegal284P ATmegal62 COMPARE3A A ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPB_vect OUTPUT_ Compare Match ATmegal28 ATmegal284P ATmegal62 COMPARE3B B ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPC_vect OUTPUT_ Compare Match ATmegal28 ATmega64 ATmega640 COMPARE3C C megal280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT9OUSB 1286 AT90USB647 AT90USB646 TIMER3_ SIG_ Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA OVF_vect OVERFLOW3 Overflow ATmegal28 ATmegal284P ATmegal62 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMERA SIG INPUT Timer Counter4 ATmega640 ATmegal280 ATmegal281 vect CAPTURE4 Capture Event ATmega2560 ATmega2561 TIMERA SIG T
156. 287 AT90USB 1286 AT90USB647 AT90USB646 EXT INTO SIG External Interrupt ATtiny24 ATtiny44 ATtiny84 vect INTERRUPTO Request 0 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 113 Vector name Old vector name Description Applicable for device INTO_vect SIG_ INTERRUPTO External Interrupt 0 AT90S1200 419052313 479052323 9052333 419052343 9054414 9054433 419054434 9058515 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega406 ATmega48P ATmega64 AT mega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 88 ATmegal68 ATmega48 ATmega88 ATmega640 megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtinyll ATtiny12 ATtinyl3 ATtinyl5 ATtiny22 ATtiny2313 ATtiny26 ATtiny28 ATtiny43U ATtiny48 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 AT tiny861 ATOOUSBI62 9005 82 9005 1287 901 5 1286 AT90USB647 AT90USB646 INTI_vect SIG_ I
157. 3 15 char x strchr const char src int val Locate character in string The strchr function returns a pointer to the first occurrence of the character val in the string 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 11 3 16 char x strchrnul const char s int c The strchrnul function is like strchr except that if c is not found in s then it returns a pointer to the null byte at the end of s rather than NULL Glibc GNU extension Returns The strchrnul function returns a pointer to the matched character or a pointer to the null byte at the end of s i e s str len s if the character is not found Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 89 6 11 3 17 stremp const char x 81 const char 52 Compare two strings The strcmp function compares the two strings 51 and 52 Returns The strcmp function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcmp is that if s1 is an initial substring of S2 then s1 is considered to be less than s2 6 11 3 18 char strcpy char dest const char src Copy a string The strcpy function c
158. 4_C value _ CONCAT value LL define UINT64_C value _ CONCAT value ULL define INTMAX_C value _ CONCAT value LL define UINTMAX_C value _ CONCAT value ULL 6 8 2 Define Documentation 6 8 2 1 define INT16_C value value define a constant of type int16_t 6 8 2 2 define INT16 MAX 0x7fff largest positive value an int16_t can hold 6 8 2 3 define INTI6 MIN 1 6 MAX 1 smallest negative value an int16 t can hold 6 8 2 4 define INT32_C value _ CONCAT value L define a constant of type int32 t 6 8 2 5 define INT32 MAX Ox7fffffffL largest positive value an int32 t can hold 6 8 2 6 define INT32 MIN INT32 MAX 1L smallest negative value an int32 t can hold Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 46 6 8 2 7 define INT64_C value CONCAT value LL define a constant of type int64 t 6 8 2 8 define INT6 4 OXx fEfffffffffffffLL largest positive value an int64 t can hold 6 8 2 9 define INT64 MIN INT64 MAX ILL smallest negative value an int64 t can hold 6 8 2 10 define INT8_C value int8 t value define a constant of type int8 t 6 8 2 11 define INT8 MAX 0x7f largest positive value an int8 t can hold 6 8 2 12 define INT8 MIN INT8 MAX 1 smallest negative value an int8 t can hold 6 8 2 13 ftdefine INT FASTI6 MAX INTI16 MAX largest positive value an int fast16 t
159. 5 out 0x35 r24 53 2 88 95 sleep 4 85 b7 in r24 0x35 53 6s 8f 77 andi r24 Ox7F 127 8 85 bf out 0x35 r24 53 as rjmp 16 Ox10c lt main 0x18 gt 0000011c lt __bad_interrupt gt STA rjmp 286 0 0 vectors 0000011e exit 11 8 94 120 00 50 rjmp 0 0x122 lt exit gt 00000122 exit 22 8 94 eri 00000124 lt __stop_program gt IZA VL FE erf fmp 2 0x124 stop program 6 36 5 Linker Map Files avr objdump is very useful but sometimes it s necessary to see information about the link that can only be generated by the linker A map file contains this information A map file is useful for monitoring the sizes of your code and data It also shows where modules are loaded and which modules were loaded from libraries It is yet another view of your application To get a map file I usually add 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 Wl1 Map demo map o demo elf demo o Some points of interest in the demo map file are rela plt rela plt Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 196 text 0x00000000 x vectors vectors 0x00000000 0x00000000 0x00000000 vectors progmem gcc progmem 0x00000026 0x00000026 trampolines trampolines 0x00000026
160. 5 21 define ATOMIC BLOCK type Creates a block of code that is guaranteed to be executed atomically Upon entering the block the Global Interrupt Status flag in SREG is disabled and re enabled upon exiting the block from any exit path Two possible macro parameters are permitted ATOMIC RESTORESTATE and ATOMIC FORCEON 6 25 2 22 ftdefine ATOMIC FORCEON This is a possible parameter for ATOMIC BLOCK When used it will cause the ATOMIC BLOCK to force the state of the SREG register on exit enabling the Global Interrupt Status flag bit This saves on flash space as the previous value of the SREG register does not need to be saved at the start of the block Care should be taken that ATOMIC FORCEON is only used when it is known that interrupts are enabled before the block s execution or when the side effects of enabling global interrupts at the block s completion are known and understood 6 25 2 3 define ATOMIC RESTORESTATE This is a possible parameter for ATOMIC BLOCK When used it will cause the ATOMIC BLOCK to restore the previous state of the SREG register saved before the Global Interrupt Status flag bit was disabled The net effect of this is to make the ATOMIC BLOCK s contents guaranteed atomic without changing the state of the Global Interrupt Status flag when execution of the block completes Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 26 lt utiV crc16 h gt CRC Computations 163 6 25 2 4 define N
161. 56 If streams initialized that way are no longer needed they can be destroyed by first calling the macro fdev_close and then destroying the object itself No call to fclose should be issued for these streams While calling fclose itself is harmless it will cause an undefined reference to free and thus cause the linker to link the malloc module into the application Notes Note 1 It might have been possible to implement a device abstraction that is compatible with fopen but since this would have required to parse a string and to take all the information needed either out of this string or out of an additional table that would need to be provided by the application this approach was not taken Note 2 This basically follows the Unix approach if a device such as a terminal needs special 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 An uart 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 pr
162. 64 crc xmodem update util crc 165 delay loop 1 util delay basic 168 delay loop 2 util delay basic 168 delay ms util delay 166 delay us util delay 167 A more sophisticated project 200 A simple project 184 abort avr stdlib 73 abs avr stdlib 73 acos avr math 33 Additional notes from lt avr sfr_defs h gt 148 alloca alloca 15 asin avr math 33 assert avr assert 16 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 372 assert h 221 atan avr_math 33 atan2 avr_math 33 atof avr_stdlib 74 atoi avr_stdlib 74 atoi S 222 atol avr_stdlib 74 atol S 222 atomic h 222 ATOMIC_BLOCK util_atomic 161 ATOMIC_FORCEON util_atomic 161 ATOMIC_RESTORESTATE util_atomic 161 avr_assert assert 16 avr_boot boot_is_spm_interrupt 95 boot_lock_bits_set 95 boot_lock_bits_set_safe 96 boot_lock_fuse_bits_get 96 boot_page_erase 96 boot_page_erase_safe 97 boot_page_fill 97 boot_page_fill_safe 97 boot_page_write 97 boot_page_write_safe 98 boot rww busy 98 boot rww enable 98 boot rww enable safe 98 boot signature byte get 98 boot spm busy 99 boot spm busy wait 99 boot spm interrupt disable 99 boot spm interrupt enable 99 BOOTLOADER SECTION 99 GET EXTENDED FUSE BITS 100 HIGH FUSE BITS 100 GET LOCK BITS 100 GET LOW FUSE BITS 100 avr eeprom _EEGET 101 _EEPUT 101 EEMEM 102 eeprom_busy_wait 102 eeprom_is_ready 102
163. 94FFCFBF FBECFE5D4E0DEBF05 6E2F1E002C005903E 0 0 6 0 001 0 DD061C01F920F92F8 F938F9380916000CE 09162002F5F3F4FCF 3E02F3F380709F12D F910F900FBEOF90C6 091610030916200F5 200215030403093A9 10511F71092600044 BCF83E88FBD8EB5FA 2E087BB84E089BFE7 EB581608EBD1BBC5A 9BF789485B7806899 001100085BF889585B78F7785BFF8CF71CFF89465 The j 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 avr objcopy j There is no eeprom hex file written as that file would be empty eeprom change section lma eeprom 0 O ihex demo elf demo eeprom hex Starting with version 2 17 of the GNU binutils the avr ob jcopy command that used to generate the empty EEPROM files now aborts because of the empty input section eeprom so these empty files are not generated It also signals an error to the Makefile which will be caught there and makes it print a message about the empty file not being generated 6 36 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 MCU_TARGET at90s231 MCU_TARGET at90s233 MCU_TARGET at90s441 MCU
164. AST32 MAX UINT32 MAX define INT FAST64 MAX INT64 MAX define INT FAST64 MIN INT64 MIN define UINT FAST64 MAX UINT64 Limits of integer types capable of holding object pointers define INTPTR MAX INTIG6 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 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 45 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 INT6
165. AT90PWM3 AT90PWM2 AT90PWMI vect USART_ Complete ATmegal68P ATmega328P ATmega48P TRANS ATmega8535 ATmega88P ATmegal68 SIG_UART_ ATmega48 ATmega88 ATtiny2313 TRANS USART_ SIG_ USART Data AT90PWM3 AT90PWM2 AT90PWMI UDRE_vect USART_ Register Empty ATmegal6 ATmegal68P ATmega32 DATA SIG mega323 ATmega3250 ATmega3250P AT UART DATA mega328P ATmega3290 ATmega3290P ATmega48P ATmega6450 ATmega6490 ATmega8 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 AT tiny2313 USL SIG USI USI Overflow ATmegal65 ATmegal65P ATmegal69 OVERFLOW_ OVERFLOW ATmegal69P ATmega325 ATmega3250 vect ATmega3250P ATmega329 ATmega3290 ATmega3290P ATmega645 ATmega6450 ATmega649 ATmega6490 ATtiny2313 USI_OVF_ SIG_USI_ USI Overflow ATtiny26 ATtiny43U ATtiny24 ATtiny44 vect OVERFLOW ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 USI START SIG USI USI Start Condi ATmegal65 ATmegal65P ATmegal69 vect START tion ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega329 ATmega3290 ATmega3290P ATmega645 ATmega6450 ATmega649 ATmega6490 ATtiny2313 ATtiny43U ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 USI_STRT_ SIG_USI_ USI Start ATtiny26 vect START USI_STR_ SIG USI USI START ATtiny24 ATtiny44 ATtiny84 vect START WATCHDOG SIG Watchdog Time ATtiny24 ATtiny44 ATtiny84 vect WATCHDOG out TIMEOUT WDT SIG Watchdog Timer ATtiny2313
166. AT90S2313 9052333 AT90S4414 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 RXC vect USARTO Complete RECV USARTO SIG USARTO Rx AT90CANI28 AT90CAN32 AT90CANGA RX_vect UARTO Complete ATmegal28 ATmegal284P ATmegal65 RECV ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega329 ATmega64 AT mega645 ATmega649 ATmega640 AT megal280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmegal64P AT mega644P ATmega644 USARTO SIG USARTO Tx ATmegal62 TXC vect USARTO Complete TRANS USARTO SIG USARTO Tx AT90CANI28 AT90CAN32 AT90CAN64 TX vect UARTO Complete ATmegal28 ATmegal284P ATmegal65 TRANS ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega329 ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 AT mega649 ATmega6490 ATmega640 AT mega1280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmegal64P AT mega644P ATmega644 USARTO SIG USARTO Data AT90CANI28 AT90CAN32 AT90CANGA UDRE vect UARTO Register Empty ATmegal28 ATmegal284P ATmegal62 DATA ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega329 ATmega64 ATmega645 ATmega649 ATmega640 ATmegal280 ATmegal281 AT
167. ATOMIC MAX avr stdint 47 SIG ATOMIC MIN avr stdint 47 SIGNAL avr interrupts 129 signbit avr math 37 sin avr math 37 sinh avr math 37 SIZE MAX avr stdint 47 sleep h 247 sleep cpu Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 387 avr_sleep 153 sleep_disable avr_sleep 153 sleep_enable avr_sleep 153 snprintf avr_stdio 63 snprintf_P avr_stdio 64 sprintf avr_stdio 64 sprintf_P avr_stdio 64 sqrt avr_math 38 square avr_math 38 srand avr_stdlib 79 srandom avr_stdlib 79 sscanf avr_stdio 64 sscanf_P avr_stdio 64 stderr avr_stdio 59 stdin avr_stdio 59 stdint h 247 stdio h 250 stdlib h 252 stdout avr_stdio 60 strcasecmp avr_string 86 strcasecmp S 256 strcasecmp_P avr_pgmspace 140 strcasecmp_P S 256 strcasestr avr_string 86 strcasestr S 256 strcasestr P avr pgmspace 140 strcat avr string 87 strcat S 256 strcat P avr pgmspace 140 strcat P S 256 strchr avr string 87 strchr S 256 strchr P avr pgmspace 140 strchr P S 256 strchrnul avr string 87 strchrnul S 256 strchrnul P avr pgmspace 141 strchrnul P S 256 strcmp avr string 87 strcmp S 256 strcmp P avr pgmspace 141 strcmp P S 256 strcpy avr string 88 strcpy S 256 strcpy P avr pgmspace 141 strepy_P S 256 strcspn avr string 88 strcspn S 256 strcspn P avr pgmspace 141 strcspn P S 256 string h 256 strlcat avr st
168. ATmega640 ATmegal280 ATmegal28l vect USART2_ Complete ATmega2560 ATmega2561 RECV USART2_ SIG_ USART2 Tx ATmega640 ATmegal280 ATmegal281 TX vect USART2 Complete ATmega2560 ATmega2561 TRANS USART2_ SIG_ USART2 Data ATmega640 ATmegal280 ATmegal28l UDRE vect USART2 register Empty ATmega2560 ATmega2561 DATA USART3 SIG USART3 Rx ATmega640 ATmegal280 ATmegal28l RX vect USART3 Complete ATmega2560 ATmega2561 RECV USART3 SIG USART3 Tx ATmega640 ATmegal280 ATmegal28l TX vect USART3 Complete ATmega2560 ATmega2561 TRANS USART3 SIG USART3 Data ATmega640 ATmegal280 ATmegal28l UDRE vect USART3 register Empty ATmega2560 ATmega2561 DATA USART SIG USART Rx ATmegal6 ATmega32 ATmega323 AT RXC vect USART Complete mega8 RECV SIG_ UART_RECV USART_RX_ SIG_ USART Rx AT90PWM3 AT90PWM2 AT90PWMI vect USART_ Complete ATmegal68P ATmega3250 ATmega3250P SIG ATmega328P ATmega3290 ATmega3290P UART RECV ATmega48P ATmega6450 ATmega6490 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATtiny2313 USART_ SIG_ USART Tx ATmegal6 ATmega32 ATmega323 AT TXC_vect USART_ Complete mega8 TRANS SIG_UART_ TRANS Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 126 Vector name Old vector Description Applicable for device name USART_TX_ SIG_ USART Tx
169. C as it removes this register from the control of the compiler which may make code generation worse Use at your own risk 9 10 Frequently Asked Questions 9 10 1 10 11 12 13 14 15 16 17 18 1 FAQ Index My program doesn t recognize a variable updated within an interrupt routine I get undefined reference to for functions like sin How to permanently bind a variable to a register How to modify MCUCR or WDTCR early What is all this BV stuff about Can I use C on the AVR Shouldn t I initialize all my variables Why do some 16 bit timer registers sometimes get trashed How do I use a define d constant in an asm statement Why does the PC randomly jump around when single stepping through my pro gram in avr gdb How do I trace an assembler file in avr gdb How do I pass an IO port as a parameter to a function What registers are used by the C compiler How do I put an array of strings completely in ROM How to use external RAM Which O flag to use How do I relocate code to a fixed address My UART is generating nonsense My ATmegal28 keeps crashing Port F is completely broken Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 312 19 Why do all my foo bar strings eat up the SRAM 20 Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit operation in assembly 21 How
170. C function containing large and or numerous local variables or when recursively calling function Note The pictures shown in this document represent typical situations where the RAM locations refer to an ATmegal28 The memory addresses used are not displayed in a linear scale external RAM Ox1tOFF o o x OxFFFF 2 on board RAM gt SP b RAMEND __brkval lt SP __malloc_margin Ec malloc heap start heap start bss end data bss start data start Figure 6 RAM map of a device with internal RAM On a simple device like a microcontroller it is a challenge to implement a dynamic memory allocator that is simple enough so the code size requirements will remain low yet powerful enough to avoid unnecessary memory fragmentation and to get it all done with reasonably few CPU cycles Microcontrollers are often low on space and also run at much lower speeds than the typical PC these days The memory allocator implemented in avr libc tries to cope with all of these con straints and offers some tuning options that can be used if there are more resources available than in the default configuration Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 269 9 2 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 ta
171. CE __asm__ _ volatile__ N in tmp_reg__ __SREG__ n t oli TAVNNET A sts Sl 30 MET ON sts 81 2 Mne CN out SREG tmp reg no outputs 5 d Emp N M SFR ADDR CLKPR ro g X 8 36 setbaud h File Reference 8 36 1 Detailed Description Defines define BAUD TOL 2 define UBRR VALUE define UBRRL VALUE define UBRRH VALUE define USE 2X 0 8 37 setjmp h File Reference 8 37 1 Detailed Description Defines define _ SETJMP H 1 define _ NORETURN aattribute noreturn Functions intsetjmp buf jmpb void longjmp jmp buf __jmpb int ret ATTR NORETURN Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 38 sleep h File Reference 248 8 38 sleep h File Reference 8 38 1 Detailed Description Defines define AVR SLEEP H 1 define SLEEP CONTROL REG MCUCR define SLEEP ENABLE MASK _BV SE Functions void sleep enable void void sleep disable void void sleep cpu void void sleep mode void 8 39 stdint h File Reference 8 39 1 Detailed Description Defines define _ USING MINT8 0 define _ CONCATenate left right left right define __ CONCAT left right _ CONCATenate left right Limits of specified width integer types C implementations should define these macros only when __STDC_LIMIT_ MACROS is defined before lt stdint h gt is inclu
172. Description 260 striwrno File Reference uuo in m a ai a gal do 260 5041 Detailed Description 111433 e i 9 8 Kd RR 260 strncasecmp S File 260 8 65 1 Detailed Description lt s sss o RR Rm RR 260 stracasecmp P S File Reference oos zr ba 88 k 260 8 66 1 Detailed Description 260 sttncat 5 File Reference uos som ki 252555254555 gt 260 5621 Detaled Description gt c e ec s ssar eorne k 260 PS File pe S 260 5 68 1 Detailed Description lt lt s s e 6 54 0822 2 b 843 260 strnomp S File Reference 2 222 260 802 1 Detailed Description lt 9x 5584 bb ee tad 260 strnemp P5 File Reference o 24 1 4 406 omm REGE eH ee 260 8 70 1 Detailed Description 260 sthepys File Referenc hee de e lea Rebus 260 BILI Detailed Description 222 g ba Re o s ki 260 stincpy_P S File R fer nc 222222229 Rr mero RE Ros 260 8 72 1 Detailed Description 260 simlen s Fle Reference ce ee uU X al 260 5 73 1 Detailed Description gt ese escreve deute 260 strnlen P S File Reference 260 8 74 1 Detailed Description Ee 260 strpbrk S File Reference 2 2 2 2222 260 8 75 1 Detaled Description ce ceras 260 strpbrk P S File Referene 2 2 5 RE s 260 8201 Detail
173. G PIN SIG PIN CHANGE External Interrupt Request 0 ATtiny11 ATtiny12 ATtiny15 ATtiny26 LCD_vect SIG_LCD LCD Start of Frame ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega3290P ATmega649 ATmega6490 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 115 Vector name Old name vector Description Applicable for device LOWLEVEL_ IO PINS vect SIG PIN Low level Input on Port B ATtiny28 OVRIT vect SIG CAN OVERFLOW 1 CAN Overrun Timer 90 128 AT90CAN32 AT90CAN64 PCINTO_vect SIG_PIN_ CHANGEO Pin Change Inter rupt Request 0 ATmegal62 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega406 ATmega48P ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmega168 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtinyl3 ATtiny43U ATtiny48 24 AT tiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 90 75 162 9005 82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 PCINTI vect SIG PIN CHANGEI Pin Change Inter rupt Request 1 ATmegal62 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250
174. Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 9 3 Memory Sections 276 fini6 Unused for C programs but used for destructors in C programs fini5 Unused User definable fini4 Unused User definable fini3 Unused User definable fini2 Unused User definable finil Unused User definable fini0 Goes into an infinite loop after program termination and completion of any _exit code execution of code in the fini9 gt finil sections 9 3 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 SFR IO ADDR DDRB Note The ax progbits tells the assembler that the section is allocatable a executable x and contains data 9 progbits For more detailed information on the section directive see the gas user manual 9 3 9 Using Sections in C Code Example Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 4 Data in Program Space 277 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 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 9 4 Data in Program Space
175. INT FAST64 MAX avr stdint 45 INT FAST64 MIN avr stdint 45 int fast64 t avr stdint 50 INT FASTS MAX avr stdint 46 INT FASTS8 MIN avr stdint 46 int fast8 t avr stdint 50 INT LEASTI6 avr stdint 46 INT LEAST16 MIN avr stdint 46 avr stdint 46 int least8 t avr stdint 50 INTERRUPT deprecated items 177 interrupt h 232 INTMAX C avr stdint 46 INTMAX MAX avr stdint 47 MIN avr stdint 47 intmax t avr stdint 50 MAX avr stdint 47 INTPTR MIN avr stdint 47 intptr t avr stdint 51 inttypes h 232 1o h 235 isalnum ctype 17 isalpha ctype 17 isascli ctype 17 isblank Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen INDEX 382 ctype 17 iscntrl ctype 17 isdigit ctype 17 isfinite avr_math 35 isgraph ctype 17 isinf avr_math 36 islower ctype 18 isnan avr_math 36 isprint ctype 18 ispunct ctype 18 ISR avr_interrupts 127 ISR_ALIAS avr_interrupts 127 ISR_ALIASOF avr_interrupts 128 ISR_BLOCK avr_interrupts 128 ISR_NAKED avr_interrupts 128 ISR_NOBLOCK avr_interrupts 128 isspace ctype 18 isupper ctype 18 isxdigit ctype 18 itoa avr_stdlib 76 labs avr_stdlib 76 ldexp avr math 36 Idiv avr_stdlib 77 ldiv t 221 quot 221 rem 221 lock h 235 log avr math 36 log10 avr math 36 longjmp setjmp 39 loop until bit is clear avr sfr 151 loop until bit is set avr sfr 151
176. L THE CO IABLE FOR ANY DIRECT INDIRECT ONSEQUENTIAL DAMAGES IS PROVIDED BY THE COPYRIG INCLUDING INCIDENTAL BUT NOT LIMITED TO software without specific prior written permission D FITNESS FOR A PARTICU PYRIGHT OWNER OR CONTRI SPECIAL EXEMPLARY PROCUREME HT HOLDERS AND CONTRIBUTORS BUT NOT LIMITED TO INCLUDING UBSTITUTE GOODS OR SERVICES NTERRUPTION ONTRACT STRICT LIABILITY OR TORT POSSIBILITY OF SUCH DAMAGE 2 avr libc Module Index 21 avr libc Modules Here is a list of all modules lt alloca h gt Allocate space in the stack lt assert h gt Diagnostics lt ctype h gt Character Operations lt errno h gt System Errors lt inttypes h gt Integer Type conversions lt math h gt Mathematics lt setjmp h gt Non local goto lt stdint h gt Standard Integer Types lt stdio h gt Standard IO facilities lt stdlib h gt General utilities lt string h gt Strings LOSS OF USE HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WH INCLUDING NEGLIGENCE OR OT RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE DATA OR PROFITS OR AS IS THE LAR PURPOSE BUTORS BE OR T OF BUSINESS ETHER IN HERWISE 16 16 17 20 20 32 39 41 53 72 83 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 2 11 avr libc Modules 10 lt avr boot h gt Bootloader Support Utiliti
177. LARE int mydata 9 9 6 Non Returning main To declare main to be a non returning function in IAR it is done like this C task void main void code To do the equivalent in AVR GCC do this void main void __attribute__ noreturn void main void Note See the GCC User Manual for more information on Function Attributes In AVR GCC a prototype for main is required so you can declare the function at tribute to specify that the main function is of type noreturn Then define main as normal Note that the return type for main is now void 9 9 7 Locking Registers The IAR compiler allows a user to lock general registers from r15 and down by using compiler options and this keyword syntax regvar init volatile unsigned int filteredTimeSinceCommutation 814 This line locks r14 for use only when explicitly referenced in your code thorugh the var name filteredTimeSinceCommutation This means that the compiler cannot dispose of it at its own will To do this in AVR GCC do this register unsigned char counter asm r3 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 311 Typi cally it should be possible to use r2 through r15 that way Note Do not reserve r0 or rl as these are used internally by the compiler for a temporary register and for a zero value Locking registers is not recommended in AVR GC
178. May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 107 The fuse section in the ELF file will get its values from the initial variable assignment ONLY This means that you can NOT assign values to this variable in functions and the new values will not be put into the ELF fuse section The global variable is declared in the FUSES macro has two leading underscores which means that it is reserved for the implementation meaning the library so it will not conflict with a user named variable You must initialize ALL fields in the __fuse_t structure This is because the fuse bits in all bytes default to a logical 1 meaning unprogrammed Normal uninitialized data defaults to all locgial zeros So it is vital that all fuse bytes are initialized even with default data If they are not then the fuse bits may not programmed to the desired settings Be sure to have the mmcu device flag in your compile command line and your linker command line to have the correct device selected and to have the correct I O header file included when you include lt avr io h gt You can print out the contents of the fuse section in the ELF file by using this command line avr objdump s j fuse lt ELF file gt The section contents shows the address on the left then the data going from lower address to a higher address left to right 6 15 lt avr interrupt h gt Interrupts 6 15 1 Detailed Description Note Thi
179. May 12 09 55 09 2008 for avr libc by Doxygen 8 17 inttypes h File Reference 235 define PRIXFAST32 IX define PRIoPTR PRIo16 define PRIuPTR PRIu16 define PRIxPTR PRIx16 define PRIXPTR PRIX16 define SCNd16 define SCNdLEAST16 d define SCNdFASTI6 d define SCNi16 1 define SCNiLEAST16 1 define SCNiFAST16 1 define SCNd32 Id define SCNdLEAST32 Id define SCNdFAST32 define SCNi32 li define SCNILEAST32 li define SCNiFAST32 li define SCNdPTR SCNd16 define SCNiPTR SCNi16 define SCNo16 o define SCNoLEAST16 o define SCNoFASTI6 o define SCNul6 u define SCNuLEASTI6 u define SCNuFASTI6 u define SCNx16 x define SCNxLEASTI16 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 lx define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR SCNx16 Typedefs Far pointers for memory access gt 64K typedef int32_t int_farptr_t typedef uint32_t uint_farptr_t Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 8 18 io h File Reference 236 8 18 io h File Reference 8 18 1 Detailed Description 8 19 lock h File Reference 8 19 1 Detailed Description Defines define _ AVR LOCK H 1 define LOCKMEM attribute section lock define LOCKBI
180. NFO 0xF8 no state information available 6 31 2 13 define TW READ 1 SLA R address 6 31 2 14 TW REP START 0x10 repeated start condition transmitted Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 31 lt util twi h gt TWI bit mask definitions 175 6 31 2 15 define TW_SR_ARB_LOST_GCALL_ACK 0x78 arbitration lost in SLA RW general call received ACK returned 6 31 2 16 define TW_SR_ARB_LOST_SLA_ACK 0x68 arbitration lost in SLA RW SLA W received ACK returned 6 31 2 17 define TW_SR_DATA_ACK 0x80 data received ACK returned 6 31 2 18 define TW_SR_DATA_NACK 0x88 data received NACK returned 6 31 2 19 define TW_SR_GCALL_ACK 0x70 general call received ACK returned 6 31 2 20 define TW_SR_GCALL_DATA_ACK 0x90 general call data received ACK returned 6 31 2 21 define TW SR GCALL DATA NACK 0x98 general call data received NACK returned 6 31 2 22 define TW SR SLA 0x60 SLA W received ACK returned 6 31 2 23 define TW SR STOP 0xA0 stop or repeated start condition received while selected 6 31 2 24 define TW ST LOST SLA 0xB0 arbitration lost in SLA RW SLA R received ACK returned 6 31 2 25 define TW ST DATA 0xB8 data transmitted ACK received Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 32 compat deprecated h gt Deprecated items 176 6 31 2 26 define TW ST DATA 0 0 data transmitted
181. NGA COMP_vect OUTPUT_ Compare Match ATmegal03 ATmegal28 ATmegal6 megal61 ATmegal62 ATmegal65 megal65P ATmegal69 ATmegal69P AT mega32 ATmega323 ATmega325 AT mega3250 ATmega3250P ATmega329 AT mega3290 ATmega3290P ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmega8515 ATmega8535 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 118 Vector name Old vector name Description Applicable for device TIMERO_ OVFO_vect SIG_ OVERFLOWO Timer Counter0 Overflow AT90S2313 AT90S2323 AT90S2343 tiny22 ATtiny26 TIMERO OVF vect SIG OVERFLOWO Timer Counter0 Overflow AT90S1200 419052333 AT90S4433 479054434 9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtinyll ATtiny12
182. NGE BIT WDCE define wdt_enable value define wdt_disable define WDTO_15MS 0 define WDTO_30MS 1 define WDTO_60MS 2 define WDTO_120MS 3 define WDTO_250MS 4 define WDTO_500MS 5 define WDTO 1S 6 define WDTO_2S 7 define WDTO_4S 8 define WDTO_8S 9 9 avr libc Page Documentation 91 Toolchain Overview 9 1 1 Introduction Welcome to the open source software development toolset for the Atmel AVR There is not a single tool that provides everything needed to develop software for the AVR It takes many tools working together Collectively the group of tools are called a toolset or commonly a toolchain as the tools are chained together to produce the final executable application for the AVR microcontroller The following sections provide an overview of all of these tools You may be used to cross compilers that provide everything with a GUI front end and not know what goes on underneath the hood You may be coming from a desktop or server computer background and not used to embedded systems Or you may be just learning about the most common software development toolchain available on Unix and Linux systems Hopefully the following overview will be helpful in putting everything in perspective Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 9 1 Toolchain Overview 263 9 1 2 FSF and GNU According to its website the Free Software Foundation FSF established in 1985 is dedicated to prom
183. NTERRUPTI External Interrupt Request 1 AT90S2313 419052333 AT90S4414 9054433 419054434 41719058515 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal68P ATmega32 ATmega323 ATmega328P ATmega32HVB ATmega406 AT mega48P ATmega64 ATmega8 AT mega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 28 ATtiny48 ATtiny261 ATtiny461 AT tiny861 AT9OUSB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 114 Vector name Old vector name Description Applicable for device INT2_vect SIG_ INTERRUPT2 External Interrupt Request 2 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmega32 ATmega323 ATmega32HVB ATmega406 ATmega64 ATmega8515 AT mega8535 ATmega640 ATmegal280 ATmegal 281 ATmega2560 AT mega2561 ATmega324P ATmegal64P ATmega644P ATmega644 AT megal6HVA AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 INT3
184. OGMEM __ATTR_PROGMEM__ define PSTR s const PROGMEM char s define _ LPM_classic__ addr define _ LPM enhanced addr define _ LPM_word_classic__ addr define __LPM_word_enhanced__ addr define _ LPM_dword_classic__ addr define _ LPM_dword_enhanced__ addr define __LPM addr __ LPM_classic__ addr define _ LPM_word addr _ LPM_word_classic__ addr define _ LPM_dword addr _ LPM_dword_classic__ addr 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 ELPM classic addr define _ ELPM enhanced addr define ELPM word classic addr define _ ELPM word enhanced addr define _ ELPM dword classic addr define ELPM dword enhanced define ELPM addr ELPM classic addr define _ ELPM_word addr ELPM word classic addr define ELPM dword addr ELPM dword classic addr define 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 byte address short read byte near address short define read word address short read word
185. OMPAREIB AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 ATtiny48 ATtiny261 ATtiny461 AT tiny861 9005 162 9005 82 9005 1287 AT90USB1286 AT90USB647 AT90USB646 TIMERI SIG Timer Counter1 AT90CAN128 AT90CAN32 AT90CANGA COMPC_vect OUTPUT_ Compare Match ATmegal28 ATmega64 ATmega640 COMPAREIC C ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 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 May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts
186. ONATOMIC BLOCK type Creates a block of code that is executed non atomically Upon entering the block the Global Interrupt Status flag in SREG is enabled and disabled upon exiting the block from any exit path This is useful when nested inside ATOMIC_BLOCK sections al lowing for non atomic execution of small blocks of code while maintaining the atomic access of the other sections of the parent ATOMIC_BLOCK Two possible macro parameters are permitted NONATOMIC_RESTORESTATE and NONATOMIC FORCEOFF 6 25 2 5 ftdefine NONATOMIC FORCEOFF This is a possible parameter for NONATOMIC BLOCK When used it will cause the NONATOMIC BLOCK to force the state of the SREG register on exit disabling the Global Interrupt Status flag bit This saves on flash space as the previous value of the SREG register does not need to be saved at the start of the block Care should be taken that NONATOMIC FORCEOFF is only used when it is known that interrupts are disabled before the block s execution or when the side effects of disabling global interrupts at the block s completion are known and understood 6 25 2 6 define NONATOMIC RESTORESTATE This is a possible parameter for NONATOMIC BLOCK When used it will cause the NONATOMIC BLOCK to restore the previous state of the SREG register saved before the Global Interrupt Status flag bit was enabled The net effect of this is to make the NONATOMIC BLOCK s contents guaranteed non atomic without changing the state of
187. P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega406 ATmega48P ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmega168 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny43U ATtiny48 AT tiny24 ATtiny44 ATtiny84 9005 162 AT90USB82 PCINT2_vect SIG_PIN_ CHANGE2 Pin Change Inter rupt Request 2 ATmega3250 ATmega3250P ATmega328P ATmega3290 ATmega3290P ATmega48P ATmega6450 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P AT megal64P ATmega644P ATmega644 AT tiny48 PCINT3_vect SIG_PIN_ CHANGE3 Pin Change Inter rupt Request 3 ATmega3250 ATmega3250P ATmega3290 ATmega3290P ATmega6450 ATmega6490 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny48 PCINT vect SIG PIN CHANGE SIG PCINT ATtiny2313 ATtiny261 ATtiny461 AT tiny861 PSCO vect SIG PSCO CAPTURE PSCO Event Capture AT90PWM3 AT90PWM2 AT90PWM1 PSCO EC vect SIG PSCO END CYCLE PSCO End Cycle AT90PWM3 AT90PWM2 AT90PWM 1 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 116 Vector name Old name vector Description Applicable for device PSCI vect
188. RT define BOOT_PAGE_FILL _BV __SPM_ENABLE define _ BOOT RWW ENABLE SPM ENABLE _BV _ COMMON_ASRE define BOOT_LOCK_BITS_SET SPM ENABLE BV BLBSET define boot page fill normal address data define boot page fill alternate address data define boot page fill extended address data fdefine boot page erase normal address fdefine boot page erase alternate address fdefine boot page erase extended address define boot page write normal address define boot page write alternate address define boot page write extended address define __boot_rww_enable define __boot_rww_enable_alternate define __boot_lock_bits_set lock_bits define __boot_lock_bits_set_alternate lock_bits define GET_LOW_FUSE_BITS 0x0000 define GET_LOCK_BITS 0x0001 define GET EXTENDED FUSE BITS 0x0002 define GET HIGH FUSE BITS 0x0003 define boot lock fuse bits get address define _ BOOT SIGROW READ SPM ENABLE BV SIGRD fidefine boot signature byte get addr define boot page fill address data boot page fill normal address data 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
189. SIG PSCI CAPTURE PSCI Event Capture AT90PWM3 AT90PWM2 AT90PWM1 PSCI EC vect SIG PSCI END CYCLB End Cycle AT90PWM3 AT90PWM2 AT90PWM1 PSC2_ CAPT_vect SIG_PSC2_ CAPTURE PSC2 Event Capture AT90PWM3 AT90PWM2 AT90PWM1 PSC2_EC_ vect SIG_PSC2_ END_CYCLE PSC2 End Cycle AT90PWM3 AT90PWM2 AT90PWM1 SPI_STC_vect SIG_SPI Serial Transfer Complete AT9082333 AT9084434 AT9084414 9058515 9054433 9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny48 AT90USBI62 9005 82 9005 1287 AT90USB1286 AT90USB647 AT90USB646 SPM RDY SIG SPM vect READY Store Program Memory Ready ATmegal6 ATmegal62 ATmega32 AT mega323 ATmega8 ATmega8515 mega8535 SPM_ READY vect SIG SPM READY Store Program Memo
190. T90USB646 9005 647 AT90USB1286 AT90USB 1287 ATtiny48 ATtiny88 6 24 2 11 define WDTO 500MS 5 See WDTO 15MS 6 24 2 12 define WDTO 60MS 2 WDTO 15MS 6 24 2 13 ftdefine WDTO 85 9 See WDTO 15MS Note This is only available on the ATtiny2313 ATtiny24 AT ny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks 60 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmega48P ATmega88P AT megal68P ATmega328P ATmegal64P ATmega324P ATmega644P ATmega644 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega8HVA ATmegal6HVA ATmega32HVB ATmega406 ATmegal284P AT90PWMI AT90PWM2 AT90PWM2B AT9O0PWM3 AT9OPWM3B 9 216 AT90PWM316 9005 82 AT90USBI162 9005 646 9005 647 AT90USB1286 AT90USB1287 48 ATtiny88 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks 6 25 1 Detailed Description include util atomic h Note The macros in this header file require the ISO IEC 9899 1999 ISO C99 feature of for loop variables that are declared inside the for loop itself For that reason this header file can only be used if the standard level of the compiler option std is set to either c99 or gnu99 The macros in this header file deal with code blocks that are guaranteed to be excuted
191. TS avr inttypes 26 PRIULEAST16 avr_inttypes 26 PRIULEAST32 avr_inttypes 26 PRIuLEASTS avr inttypes 26 PRIuPTR avr inttypes 26 PRIX16 avr inttypes 26 PRIx16 avr inttypes 26 PRIX32 avr inttypes 26 PRIx32 avr inttypes 26 PRIX8 avr_inttypes 26 PRIx8 avr_inttypes 26 PRIXFAST16 avr_inttypes 27 PRIxFAST16 avr_inttypes 27 PRIXFAST32 avr_inttypes 27 PRIxFAST32 avr_inttypes 27 PRIXFAST8 avr_inttypes 27 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen INDEX 385 PRIxFAST8 PTRDIFF_MIN avr_inttypes 27 avr_stdint 47 PRIXLEAST16 putc avr_inttypes 27 avr_stdio 59 PRIxLEAST16 putchar avr_inttypes 27 avr_stdio 59 PRIXLEAST32 puts avr_inttypes 27 avr_stdio 63 PRIxLEAST32 puts_P avr_inttypes 27 avr_stdio 63 PRIXLEASTS avr inttypes 27 qsort PRIxLEASTS avr stdlib 77 avr inttypes 28 quot PRIXPTR div t 220 avr inttypes 28 Idiv_t 221 PRIxPTR avr inttypes 28 rand prog_char avr_stdlib 78 avr_pgmspace 137 RAND_MAX prog_int16_t avr_stdlib 73 avr_pgmspace 137 rand_r prog int32 t avr stdlib 78 random avr pgmspace 138 prog int64 t avr pgmspace 138 prog int8 t avr pgmspace 138 prog uchar avr pgmspace 138 prog uint16 t avr pgmspace 138 prog uint32 t avr pgmspace 138 prog uint64 t avr pgmspace 138 prog uint8 t avr pgmspace 138 prog void avr pgmspace 138 PROGMEM avr pgmspace 137 PSTR avr pgmspace 137 PTRDIFF MAX avr
192. TS unsigned char _ lock LOCKMEM define LOCKBITS DEFAULT OxFF 8 20 math h File Reference 8 20 1 Detailed Description Defines define PI 3 141592653589793238462643 define M SORT2 1 4142135623730950488016887 define NAN builtin nan define INFINITY builtin inf Functions double cos double __ x double fabs double __x double fmod double x double y double modf double __x double iptr double sin double x double sqrt double __x double tan double __x double floor double __x double ceil double __x double frexp double __x int __pexp double Idexp double __ x int exp double exp double x double cosh double x double sinh double __x double tanh double __x Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 20 math h File Reference double acos double x double asin double __x double atan double x double atan2 double __y double __x double log double __x double log10 double __x double pow double __x double y int isnan double __ x int double __x double square double x static double copysign double __x double __y e double fdim double __x double y double fma double __x double __y double 7 e double fmax double _ x double y e double fmin double __x double y int signbit double __x double trunc double __x static int isfinite doubl
193. 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 36 6 Generating Intel Hex Files We have a binary of the application but how do we get it into the processor Most if not all programmers will not accept a GNU executable as an input file so we need to do a little more processing The next step is to extract portions of the binary and save the information into hex files The GNU utility that does this is called avr objcopy The ROM contents can be pulled from our project s binary and put into the file demo hex using the following command avr objcopy j text j data O ihex demo elf demo hex The resulting demo hex file contains 1000000012C08CC08BCO8ACO89C088C087C086CO1F Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 198 1000100025C084C083C082C081C080C07FC07EC034 00020007DC07C 0003000CDBF10 00040000D92A0 00050001D92A3 00060000FB60F 100070008823C1 0008000309362 00090003BBD2A 000A0001F9018 000 000 20 000C000620020 1000D000DFCF81 1000E00081608E 1000F000789408 00100001ABC82 0601200000 0 8 00000001FF C07BC011241 6 36B107D9F71 36B107E1F74 9211242 933 F4209161003 00209361008 BD8F913F912 95813029F02 91610030916 93610021153 E080936000D BD1BBC1ABC8 9583E88FBD8 E087BB84E08
194. This may be used along with the ISR macro to create a catch all for undefined but used ISRs for debugging purposes 6 15 2 2 define cli include avr interrupt h Disables all interrupts by clearing the global interrupt mask This function actually compiles into a single line of assembly so there is no function call overhead Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 128 6 15 2 3 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 15 2 4 define ISR vector attributes include avr interrupt h Introduces an interrupt handler function interrupt service routine that runs with global interrupts initially disabled by default with no attributes specified The attributes are optional and alter the behaviour and resultant generated code of the interrupt routine Multiple attributes may be used for a single function with a space seperating each attribute Valid attributes ISR BLOCK ISR NOBLOCK ISR NAKED ISR ALIASOF vect vector must be one of the interrupt vector names that are valid for the particular MCU type 6 15 2 5 define ISR ALIAS vector target vector include avr interrupt
195. VIDE __bss_start demo o c avrdev avr libc avr libc avr lib avr4 atmega8 crtm8 o c avrdev avr libc avr libc avr lib avr4 exit o c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _exit o c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _copy_data o Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 197 bss 0x00800063 0 0 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _clear_bss o x bssx COMMON 0x00800063 PROVIDE 55 0x00000126 data load start LOADADDR data 0x00000126 data load end data load start SIZEOF Jo Int 0x00800063 0x0 0x00800063 PROVIDE noinit start noinit x 0x00800063 PROVIDE noinit 0x00800063 _end 0x00800063 PROVIDE heap start eeprom 0x00810000 0 0 x eeprom x 0x00810000 eeprom end The last address in the text segment is location 0x114 denoted by _et ext 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 0x 60 The next available address in the bss segment is location 0x63 so the application uses 3 bytes of uninitialized data
196. X avr stdint 47 uintl6 t avr stdint 51 UINT32 C avr stdint 48 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 390 UINT32_MAX UINT_LEAST8_MAX avr_stdint 48 avr_stdint 49 uint32_t uint_least8_t avr_stdint 51 avr_stdint 52 UINT64_C UINTMAX_C avr_stdint 48 avr_stdint 49 UINT64_MAX UINTMAX_MAX avr_stdint 48 avr_stdint 49 uint64_t uintmax_t avr_stdint 51 avr_stdint 52 UINT8 C UINTPTR MAX avr stdint 48 avr stdint 49 UINT8 uintptr t avr stdint 48 avr stdint 52 uint8 t ultoa avr stdint 51 avr stdlib 81 uint farptr t ungetc avr inttypes 31 avr stdio 64 UINT FAST16 USE 2X avr stdint 48 uint fastl6 t avr stdint 51 UINT FAST32 MAX avr stdint 48 uint fast32 t avr stdint 51 UINT FAST64 MAX avr stdint 48 uint fast64 t avr stdint 51 UINT FAST8 MAX avr stdint 48 uint fast8 t avr stdint 51 UINT LEASTI16 MAX avr stdint 48 uint least16 t avr stdint 52 UINT LEAST32 MAX avr stdint 49 uint least32 t avr stdint 52 UINT LEAST64 avr stdint 49 uint least64 t avr stdint 52 util setbaud 171 Using the standard IO facilities 208 util atomic ATOMIC BLOCK 161 ATOMIC FORCEON 161 ATOMIC RESTORESTATE 161 NONATOMIC BLOCK 161 NONATOMIC FORCEOFF 162 NONATOMIC RESTORESTATE 162 util crc _crc16_update 163 ccitt update 164 crc ibutton update 164 crc xmodem update 165 util delay delay ms 166 delay us 167 util del
197. X define INT FAST64 MIN INT64 MIN define UINT FAST64 MAX UINT64 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 MAX UINT64 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 INTI6 MAX define PTRDIFF MIN INT16 MIN define SIG ATOMIC MAX INT8 MAX define SIG ATOMIC MIN 8 MIN Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 39 stdint h File Reference 250 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 stdint h is included These definitions are valid for integer constants without suffix and for macros de fined as integer constant without suffix define INT8_C value int8 t value define UINT8_C value uint8_t _ CONCAT value U define INT16 C value value define UINT16_C value CONCAT value U define INT32_C value _ CONCAT value L define UINT32_C value _ CONCAT value UL define INT64_C value _ CONCAT value LL define UINT64_C value _ CONCAT value ULL
198. _C value __CONCAT value ULL define a constant of type uintmax_t 6 8 2 56 define UINTMAX MAX UINT64 MAX largest value an uintmax t can hold 6 8 2 57 define UINTPTR MAX UINT16 MAX largest value an uintptr t can hold 6 8 3 Typedef Documentation 6 8 3 1 typedef signed int int16 t 16 bit signed type 6 8 3 2 typedef signed long int int32 t 32 bit signed type 6 8 3 3 typedef signed long long int int64 t 64 bit signed type Note This type is not available when the compiler option mint8 is in effect Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 51 6 8 3 4 typedef signed char int8_t 8 bit signed type 6 8 3 5 typedef int16_t int_fast16_t fastest signed int with at least 16 bits 6 8 3 6 typedef int32_t int_fast32_t fastest signed int with at least 32 bits 6 8 3 7 typedef int64_t int_fast64_t fastest signed int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect 6 8 3 8 typedef int8_t int_fast8_t fastest signed int with at least 8 bits 6 8 3 9 typedef int16_t int_least16_t signed int with at least 16 bits 6 8 3 10 typedef int32_t int_least32_t signed int with at least 32 bits 6 8 3 11 typedef int64_t int_least64_t signed int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect 6 8 3 12 typedef int8_t int_l
199. _TARGET at90s443 MCU_TARGET at90s443 MCU_TARGET at90s851 3 3 4 3 4 5 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 199 MCU_TARGET at90s8535 MCU_TARGET atmegal28 MCU_TARGET atmegal280 MCU_TARGET atmegal281 MCU_TARGET atmegal284p MCU_TARGET atmegal6 MCU_TARGET atmegal63 MCU_TARGET atmegal64p MCU_TARGET atmega165 MCU_TARGET atmegal65p MCU_TARGET atmegal68 MCU_TARGET atmegal69 MCU_TARGET atmegal69p MCU_TARGET atmega2560 MCU_TARGET atmega2561 MCU_TARGET atmega32 MCU_TARGET atmega324p MCU_TARGET atmega325 MCU_TARGET atmega3250 MCU_TARGET atmega329 MCU_TARGET atmega3290 MCU_TARGET atmega48 MCU_TARGET atmega64 MCU_TARGET atmega640 MCU_TARGET atmega644 MCU_TARGET atmega644p MCU_TARGET atmega645 MCU_TARGET atmega6450 MCU_TARGET atmega649 MCU_TARGET atmega6490 MCU_TARGET atmega8 MCU_TARGET atmega8515 MCU_TARGET atmega8535 MCU_TARGET atmega88 MCU_TARGET attiny2313 MCU_TARGET attiny24 MCU_TARGET attiny25 MCU_TARGET attiny26 MCU_TARGET attiny26 MCU_TARGET attiny44 MCU_TARGET attiny45 MCU_TARGET attiny46 MCU_TARGET attiny84 MCU_TARGET attiny85 MCU_TARGET attiny86 OPTIMIZE 02 DEF S LIBS You should not have to change anything below here CE avr gcc Override is only needed by avr lib build system override CFLAGS
200. _vect SIG_ INTERRUPT3 External Interrupt Request 3 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmega32HVB ATmega406 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 4 vect SIG INTERRUPT4 External Interrupt Request 4 AT90CAN128 AT90CAN32 ATIOCAN64 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmega1280 ATmegal281 ATmega2560 AT mega2561 AT90USBI62 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 5 vect SIG_ INTERRUPTS External Interrupt Request 5 AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 AT mega64 ATmega640 ATmega1280 ATmegal281 ATmega2560 AT mega2561 9005 162 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 INT6_vect SIG_ INTERRUPT6 External Interrupt Request 6 AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 AT mega64 ATmega640 ATmega1280 ATmegal 281 ATmega2560 AT mega2561 AT90USB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 INT7 vect SIG INTERRUPT7 External Interrupt Request 7 AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 AT mega64 ATmega640 ATmega1280 ATmegal281 ATmega2560 AT mega2561 AT90USBI62 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 IO PINS vect SI
201. a649 ATmega6490 power lcd disable Disable the LCD module ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 power pscO enable Enable the Power Stage Controller 0 module AT90PWMI AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B Gamuedsa MdisNile 22 09 55 09 200 inahle tix Controller 0 module AT90PWMI AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B power_psc1_enable Enable the Power Stage Controller 1 module AT90PWMI AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B power_psc1_disable Disable the Power Stage Controller 1 module AT90PWMI AT90PWM2 AT90PWM2B AT90PWM3 6 20 Additional notes from lt avr sfr_defs h gt 149 Some of the newer AVRs contain a System Clock Prescale Register CLKPR that allows you to decrease the system clock frequency and the power consumption when the need for processing power is low Below are two macros and an enumerated type that can be used to interface to the Clock Prescale Register Note Not all AVR devices have a Clock Prescale Register On those devices without a Clock Prescale Register these macros are not available typedef enum lock div 1 lock div 2 lock div 4 m lock_div_8 7 lock div 16 4 lock div 32 5 lock div 64 6 lock div 128 7 clock div 256 8 clock div t I WwWNHO 0O O O Q GO O Clock prescaler setting enumerations clock_prescale_se
202. able e extern declares a symbol to be externally defined this is effectively a comment only as gas treats all undefined symbols it encounters as globally undefined any way Note that org is available in gas as well but is a fairly pointless pseudo op in an as sembler environment that uses relocatable object files as it is the linker that determines the final position of some object in ROM or RAM Along with the architecture independent standard operators there are some AVR specific operators available which are unfortunately not yet described in the official 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 ldi r24 lo8 pm somefunc 141 r25 hi8 pm somefunc call something This passes the address of function somefunc as the first parameter to function something Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 288 9 6 Inline Assembler Cookbook AVR GCC Inline Assembler Cookbook About this Document The GNU C compiler for Atmel AVR RISC processors offers to embed assembly languag
203. access them But this will not work if SFR OFFSET 0x20 so use a different macro defined only if SFR OFFSET 0x20 for safety sts _SFR_ADDR SPMCR r24 In programs all 3 combinations of SFR 5 COMPAT and SFR OFFSET are supported the SFR ADDR SPMCR macro can be used to get the address of the SPMCR register 0x57 or 0x68 depending on device Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 21 lt avr sfr_defs h gt Special function registers 151 6 21 lt avr sfr_defs h gt Special function registers 6 21 1 Detailed Description When working with microcontrollers many tasks usually consist of controlling internal peripherals or external peripherals that are connected to the device The entire IO address space is made available as memory mapped IO i e it can be accessed using all the MCU instructions that are applicable to normal data memory For most AVR devices the IO register space is mapped into the data memory address space with an offset of 0x20 since the bottom of this space is reserved for direct access to the MCU registers Actual SRAM is available only behind the IO register area starting at some specific address depending on the device For example the user can access memory mapped IO registers as if they were globally defined variables like this PORTA 0x33 unsigned char foo PINA The compiler will choose the correct instruction sequence to generate ba
204. adjust them accordingly Back to FAQ Index 9 10 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 324 finclude avr pgmspace h PGM P array 2 PROGMEM Foo Bar int main void char 32 strcpy 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 17 int main void char buf 32 PGM_P p int i memcpy P amp p amp array i sizeof PGM_P strcpy P buf p return 0 Looking at the disassembly of the resulting object file we see that array is in flash as such 00000026 array 26 2e 00 word 28 2a 00 word 0000002a lt bar gt 2 42 61 72 00 0000002 lt foo gt 2 46 6 6 00 foo is at addr 0x002e Ox002e Ox002a Bar Foo Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9
205. ags 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen lt stdio h gt Standard IO facilities 70 u Matches an optionally signed decimal integer the next pointer must be a pointer to unsigned int x Matches an optionally signed hexadecimal integer the next pointer must be a pointer to unsigned int f Matches an optionally signed floating point number the next pointer must be a pointer to float 9 F E G Equivalent to f s Matches a sequence of non white space characters the next pointer must be a pointer to char and the array must be large enough to accept all the sequence and the terminating NUL character The input string stops at white space or at the maximum field width whichever occurs first c Matches a sequence of width count characters default 1 the next pointer must be a pointer to char and there must be enough room for all the characters no terminating NUL is added The usual skip of
206. ait 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 uint16_t w xbuf w xbuf lt lt 8 boot_page_fill page i w boot_page_write page Store buffer in flash page boot spm busy wait Wait until the memory is written Reenable RWW section again We need this if we want to jump back to the application after bootloading boot rww enable Re enable interrupts if they were ever enabled SREG sreg Defines define BOOTLOADER SECTION attribute section bootloader define boot spm interrupt SPM REG uint8 t BV SPMIE e 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 rww busy SPM REG amp uint8 t COMMON ASB Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 96 define boot_spm_busy __SPM_REG amp uint8_t _BV __SPM_ENABLE define boot_spm_busy_wait do while boot spm busy define GET_LOW_FUSE_BITS 0x0000 define GET_LOCK_BITS 0x0001 define GET_EXTENDED_FUSE_BITS 0 0002 define GET_HIGH_FUSE_BITS 0x0003 define boot_lock_fuse_bits_get address define boot_signature_byte_get addr define boot page fil
207. al280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER2_ COMP_vect SIG_ OUTPUT_ COMPARE2 Timer Counter2 Compare Match AT90S4434 AT90S8535 90 128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal61 megal62 ATmegal63 ATmegal65 AT megal65P ATmegal69 ATmegal69P AT mega32 ATmega323 ATmega325 AT mega3250 ATmega3250P ATmega329 AT mega3290 ATmega3290P ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmega8 ATmega8535 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 122 Vector name Old vector Description Applicable for device name TIMER2_ SIG_ Timer Counter2 AT90S4434 9058535 AT90CANI28 OVF_vect OVERFLOW2 Overflow AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 AT mega323 ATmega325 ATmega3250 ATmega3250P ATmega328P AT mega329 ATmega3290 ATmega3290P ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1
208. alloc does not initialize the returned memory to zero bytes See the chapter about malloc usage for implementation details Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 79 6 10 4 18 void qsort void size_t __nmemb size_t __ size compar fn t compar The qsort function is a modified partition exchange sort or quicksort The qsort function sorts an 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 10 4 19 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 fun
209. an unsigned char back onto the input stream pointed to by stream The pushed back character will be returned by a subsequent read on the stream Currently only a single character can be pushed back onto the stream The ungetc function returns the character pushed back after the conversion or EOF if the operation fails If the value of the argument character equals EOF the operation will fail and the stream will remain unchanged 6 9 3 32 int vfprintf FILE stream const char x fmt list Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 66 vfprintf is the central facility of the print f family of functions It outputs values to stream under control of a format string passed mt 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 sequ
210. and for target it is known as a native compiler If a compiler has different systems for host and target it is known as a cross compiler And if all three build host and target systems are different it is known as a Canadian cross compiler but we won t discuss that here When GCC is built to execute on a host system such as FreeBSD Linux or Windows and it is built to generate code for the AVR microcontroller target then it is a cross compiler and this version of GCC is commonly known as AVR GCC In documentation or discussion AVR GCC is used when referring to GCC targeting specifically the AVR or something that is AVR specific about GCC The term GCC is usually used to refer to something generic about GCC or about GCC as a whole GCC is different from most other compilers GCC focuses on translating a high level language to the target assembly only AVR GCC has three available compilers for the AVR C language C and Ada The compiler itself does not assemble or link the final code GCC is also known as a driver program in that it knows about and drives other programs seamlessly to create the final output The assembler and the linker are part of another open source project called GNU Binutils GCC knows how to drive the Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 1 Toolchain Overview 264 GNU assembler gas to assemble the output of the compiler GCC knows how to drive the GNU linker Id t
211. 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 SPMCR r24 endif You 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 145 55 to
212. 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 n1 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 215 The single static function internal variable 1 seen works for this purpose If mul tiple LCDs should be controlled using the same set of driver functions that would not work anymore as a way is needed to distinguish between the various displays This is where the second parameter can be used the reference to the stream itself instead of keeping the state inside a private variable of the function it can be kept inside a private ob
213. ase 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 3 Memory Sections 272 tail of the region that is no longer to be used is passed to the standard free function for insertion into the freelist Checks are first made whether the tail chunk is large enough to hold a chunk of its own at all otherwise realloc will simply do nothing and return the original region When growing the region it is first checked whether the existing a
214. asy maintenance time critical parts are written directly in manually optimized assembly language for shortest execution times possi ble Naturally this kind of project is very closely tied to the hardware design thus it is custom tailored to a particular controller type and peripheral 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 the OCR1 A output the large and stdio demos are mainly targeted to the Atmel STK500 starter kit and the TWI example requires a controller where some 24Cxx two wire EEPPROM can be connected to For the STK500 demos the default CPU either an AT90S8515 or ATmega8515 should be removed from its socket and the ATmegal6 that ships with the kit should be inserted into socket SCKT3100A3 The ATmega16 offers an on board ADC that is used in the large demo and all AVRs with an ADC feature a different pinout than the industry standard com patible devices In order to fully utilize the large demo a female 10 pin header with cable connecting to a 10 kOhm potentiometer will be useful For the stdio demo an industry standard HD44780 compatible LCD display of at least 16x1 characters will be needed Among other things the LCD4L
215. atted input from stream st din See vfscanf for details 6 9 3 24 int scanf_P const char fmt Variant of scanf where fmt resides in program memory Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 65 6 9 3 25 int snprintf char s size t __n const char Like sprintf but instead of assuming s to be of infinite size no more than n characters including the trailing NUL character will be converted to s Returns the number of characters that would have been written to s if there were enough space 6 9 3 26 int snprintf_P char x s size t n const char x fmt Variant of snprintf that uses a fmt string that resides in program memory 6 9 3 27 int sprintf char x __s const char fmt Variant of printf that sends the formatted characters to string s 6 9 3 28 int sprintf_P char x __s const char fmt Variant of sprintf that uses a fmt string that resides in program memory 6 9 3 29 int sscanf const char __buf const char fmt The function sscanf performs formatted input reading the input data from the buffer pointed to by buf See vfscanf for details 6 9 3 30 int sscanf_P const char x buf const char __fint Variant of sscanf using a mt string in program memory 6 9 3 31 int ungetc int __c FILE x stream The ungetc function pushes the character c converted to
216. avr libc Reference Manual 1 6 2 Generated by Doxygen 1 5 2 Mon May 12 09 55 09 2008 CONTENTS Contents 1 AVRLibc 1 1 Introduction 1 2 General information about this library 1 3 Supported Devices LA avt libe License 22222 2 avr libc Module Index 2 avr libc Modules 3 avr libc Data Structure Index 3 1 avr libc Data Structures 4 avr libc File Index 4 avr libc File List 5 avr libc Page Index 5 11 avr libc Related 6 avr libc Module Documentation 6 1 alloca h Allocate space in the stack 6 1 Detailed Description 6 1 2 Function Documentation 6 2 asserth Diagnostics 6 2 1 Detailed Description 6 2 2 Define Documentation 6 3 ctype h Character Operations 6 3 1 Detailed Description 6 3 2 Function Documentation 6 4 lt ermo h gt System Errors 6 4 1 Detailed Description 6 4 2 Define Documentation 6 5 lt inttypes h gt Integer Type conversions ow N N N Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen CONTENTS ii 6 6 6 7 6 8 6 9 6 11 63 1 Detailed Description 2 20 56 5 2 Delme Documentation 2 2 2222 24 23 6 5 3 Typedef Documentation 22 299 ew RES 32 ema 2s ou eso m RR ERROR ee 32 66 1 Detailed Description 32
217. avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 346 mingw bin c cygwin bin install directory gt bin Configure CFLAGS D USE MINGW ACCESS Sarchivedir configure prefix installdir target avr disable nls enable doc datadir installdir doc binutils with gmp usr local with mpfr usr local 2 amp 1 tee binutils configure log Make make all html install install html 2 gt amp 1 tee binutils make log Manually change documentation location GCC Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin install directory gt bin Configure CFLAGS D USE MINGW ACCESS gcc version configure prefix installdir target target enable languages c c t with dwarf2 enable win32 registry WinAVR release disable nls with gmp usr local with mpfr usr local enable doc disable libssp 2 gt amp 1 tee package configure log Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 347 Make make all html install 2 gt amp 1 tee package make log Manually copy the HTML documentation from the source code tree to the installat
218. avr_eeprom 102 eeprom_read_byte avr_eeprom 102 eeprom_read_dword avr_eeprom 102 eeprom_read_word avr_eeprom 102 eeprom_write_block avr_eeprom 102 eeprom_write_byte avr_eeprom 103 eeprom_write_dword avr_eeprom 103 eeprom_write_word avr_eeprom 103 EMPTY_INTERRUPT avr_interrupts 126 EOF avr_stdio 58 ERANGE avr_errno 19 errno h 231 Example using the two wire interface TWD 215 exit avr stdlib 76 exp avr math 34 fabs avr math 34 FAQ 310 fclose avr stdio 60 fdev close avr stdio 58 fdev get udata avr stdio 58 fdev set udata avr stdio 58 FDEV SETUP STREAM avr stdio 58 fdev setup stream avr stdio 58 fdevopen avr stdio 60 fdevopen c 231 fdim avr math 34 feof avr stdio 61 ferror avr stdio 61 fflush avr stdio 61 ffs avr string 84 ffs S 231 ffsl avr string 84 ffsl S 231 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 380 ffsll avr_boot 100 avr_string 84 GET_LOCK_BITS ffsll S 231 avr_boot 100 fgetc GET LOW FUSE BITS avr stdio 61 avr boot 100 fgets getc avr stdio 61 avr stdio 59 FILE getchar avr_stdio 59 avr_stdio 59 floor gets avr_math 34 fma avr_math 34 fmax avr_math 35 fmin avr_math 35 fmod avr_math 35 fprintf avr_stdio 62 fprintf_P avr_stdio 62 fputc avr_stdio 62 fputs avr_stdio 62 fputs_P avr_stdio 62 fread avr_stdio 62 free avr_stdlib 76 frexp avr_math 35 fscanf
219. ay basic delay loop 1 168 delay loop 2 168 util parity parity even bit 168 util setbaud BAUD TOL 170 UBRR VALUE 170 UBRRH VALUE 170 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX UBRRL VALUE 171 vfscanf USE 2X 171 avr stdio 67 util twi vfscanf P TW BUS ERROR 172 avr stdio 70 TW MR LOST 172 vprintf TW MR DATA 172 avr stdio 70 TW MR DATA NACK 172 vscanf TW SLA 173 avr stdio 70 TW MR SLA NACK 173 vsnprintf TW MT ARB LOST 173 avr stdio 70 TW MT DATA 173 vsnprintf P TW MT DATA NACK 173 avr stdio 70 TW MT SLA 173 vsprintf TW MT SLA NACK 173 avr stdio 71 TW NO INFO 173 vsprintf_P TW READ 173 avr stdio 71 TW REP START 173 TW SR ARB LOST GCALL wdt h 261 ACK 173 wdt disable TW SR LOST SLA ACK avr watchdog 156 174 wdt enable TW SR DATA ACK 174 avr watchdog 156 TW SR DATA NACK 174 wdt reset TW SR 174 avr watchdog 157 TW SR GCALL DATA ACK 174 WDTO 120MS TW SR GCALL NACK avr watchdog 157 avr stdio 64 vfprintf P avr stdio 67 174 WDTO 15 5 TW SR SLA ACK 174 avr watchdog 157 TW SR STOP 174 WDTO 15 TW ST ARB LOST SLA ACK avr watchdog 158 174 WDTO_250MS ST DATA 174 avr_watchdog 158 TW_ST_DATA_NACK 174 WDTO_2S TW_ST_LAST_DATA 175 avr_watchdog 158 TW ST SLA ACK 175 WDTO_30MS TW_START 175 a
220. baud h gt Helper macros for baud rate calculations 171 dif USE 2X UCSRA 1 lt lt U2X else UCSRA amp 1 lt lt U2X endif static void uart_38400 void undef BAUD avoid compiler warning define BAUD 38400 include lt util setbaud h gt UBRRH UBRRH_VALUE UBRRL UBRRL_VALUE dif USE 2X UCSRA 1 lt lt U2X else UCSRA amp 1 lt lt U2X endif In this example two functions are defined to setup the UART to run at 9600 38400 Bd respectively Using a CPU clock of 4 MHz 9600 Bd can be achieved with an acceptable tolerance without setting U2X prescaler 25 while 38400 Bd require U2X to be set prescaler 12 Defines define BAUD TOL 2 define UBRR VALUE define VALUE define UBRRH VALUE define USE 2X 0 6 30 2 Define Documentation 6 30 2 1 define TOL 2 Input and output macro for lt util setbaud h gt Define the acceptable baud rate tolerance in percent If not set on entry it will be set to its default value of 2 6 30 2 2 define UBRR VALUE Output macro from lt util setbaud h gt Contains the calculated baud rate prescaler value for the UBRR register Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 31 lt util twi h gt TWI bit mask definitions 172 6 30 2 3 define UBRRH VALUE Output macro from lt util setbaud h gt Contains the upper byte of the calculated presca
221. ble for the AVR that use a similar naming con vention The historical naming style might become deprecated in a future release so it is not recommended for new projects Note The ISR macro cannot really spell check the argument passed to them Thus by misspelling one of the names below in a call to ISR a function will be created that while possibly being usable as an interrupt function is not actually wired into the interrupt vector table The compiler will generate a warning if it detects a sus piciously looking name of a ISR function i e one that after macro replacement does not start with vector Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 111 Vector name Old name vector Description Applicable for device ADC_vect SIG_ADC ADC Conversion Complete 9052333 AT90S4433 AT90S4434 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega2560 ATmega2561 AT
222. bled In a C context global destructors will be called before halting execution 6 10 4 12 void free void x ptr The free function causes the allocated memory referenced by pt r to be made avail able for future allocations If ptr is NULL no action occurs 6 10 4 13 charx itoa int __val char 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 Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 97 will be the letter a If radix is 10 and val is negative a minus sign will be prepended The itoa function returns the pointer passed as s Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 78 6 10 4 14 long labs long 1 The labs function computes the absolute value of the long in
223. but takes a variable argument list for the arguments 6 9 3 41 int vsprintf_P char __s const char fmt va_list ap Variant of vsprintf that uses a fmt string that resides in program memory 6 10 lt stdlib h gt General utilities 6 10 1 Detailed Description include lt stdlib h gt This file declares some basic C macros and functions as defined by the ISO standard plus some AVR specific extensions Data Structures struct div_t struct ldiv t Non standard i e non ISO C functions char Itoa long int val char __s int radix char utoa unsigned int __val char x__s int radix char ultoa unsigned long int __val char __s int __radix long random void void srandom unsigned long __seed long random r unsigned long ctx char x itoa int __val char __s int __ radix define RANDOM MAX Ox7FFFFFFF Conversion functions for double arguments Note that these functions are not located in the default library 1ibc a but in the mathematical library 1ibm a So when linking the application the 1m option needs to be specified Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 73 char dtostre double __val char s unsigned char prec unsigned char _ flags char dtostrf double __ val signed char width unsigned char __ prec char 8 define DTOSTR_ALWAYS_SIGN 0x01 define DTOSTR_PLUS_SIGN 0x02
224. c 241 ELPM dword enhanced 241 ELPM enhanced 241 ELPM word classic 242 ELPM word enhanced 242 classic 243 LPM dword classic 243 LPM dword enhanced 244 LPM enhanced 244 LPM word classic 244 LPM word enhanced 245 pow avr math 37 power h 245 clock prescale set 246 PRId16 avr inttypes 22 PRId32 avr_inttypes 22 PRId8 avr_inttypes 23 PRIdFAST16 avr_inttypes 23 PRIdFAST32 avr_inttypes 23 PRIdFASTS avr inttypes 23 PRIdLEASTI6 avr inttypes 23 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 384 PRIdLEAST32 PRIoLEASTS avr inttypes 23 avr inttypes 25 PRIdLEASTS PRIoPTR avr inttypes 23 avr inttypes 25 PRIdPTR PRIu16 avr inttypes 23 PRIi16 avr inttypes 23 PRIi32 avr inttypes 23 PRIi8 avr_inttypes 23 PRIiFAST16 avr_inttypes 24 PRIiFAST32 avr inttypes 24 PRIiFASTS avr inttypes 24 PRIiLEASTI6 avr inttypes 24 PRIiLEAST32 avr inttypes 24 PRIiLEAST8 avr inttypes 24 PRIiPTR avr inttypes 24 printf avr stdio 63 printf P avr stdio 63 PRIo16 avr inttypes 24 PRIo32 avr inttypes 24 PRIo8 avr inttypes 24 PRIoFAST16 avr_inttypes 24 PRIoFAST32 avr_inttypes 25 PRIoFAST8 avr_inttypes 25 PRIoLEAST16 avr_inttypes 25 PRIoLEAST32 avr_inttypes 25 avr_inttypes 25 PRIu32 avr inttypes 25 PRIu8 avr inttypes 25 PRIuFAST16 avr_inttypes 25 PRIuFAST32 avr_inttypes 25 PRIuFAS
225. can hold 6 8 2 14 ftdefine INT FAST16 MIN INT16 MIN smallest negative value an int fast16 t can hold 6 8 2 15 define INT FAST32 MAX INT32 largest positive value an int fast32 t can hold 6 8 2 16 define INT FAST32 MIN INT32 MIN smallest negative value an int fast32 t can hold 6 8 2 17 define INT FAST64 MAX INT64 MAX largest positive value an int fast64 t can hold Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 47 6 8 2 18 define INT FAST64 MIN INT64 MIN smallest negative value an int fast64 t can hold 6 8 2 19 define INT FAST8 MAX INT8 MAX largest positive value an int fast8 t can hold 6 8 2 20 define INT FAST8 MIN INT8 MIN smallest negative value an int fast8 t can hold 6 8 2 21 define INT LEASTI6 MAX INTI6 largest positive value an int least16 t can hold 6 8 2 22 define INT LEASTI6 MIN INT16 MIN smallest negative value an int least16 t can hold 6 8 2 23 define INT LEAST32 INT32 MAX largest positive value an int least32 t can hold 6 8 2 24 define INT LEAST32 MIN INT32 MIN smallest negative value an int least32 t can hold 6 8 2 25 define INT LEAST64 MAX INT64 largest positive value an int least64 t can hold 6 8 2 26 define INT LEAST64 MIN INT64 MIN smallest negative value an int_least64_t can hold 6 8 2 27 define INT LEAST8 MAX INT8 MAX largest positive val
226. cat S 260 strncat_P S 260 strncmp S 260 strncmp 5 260 strncpy S 260 strncpy_P S 260 strnlen S 260 strnlen_P S 260 strpbrk S 260 strpbrk_P S 260 strrchr S 260 strrchr_P S 260 strrev S 260 strsep S 260 strsep_P S 260 strspn S 260 strspn_P S 260 strstr S 260 strstr P S 260 strtok r S 260 strupr S 260 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 5 avr libc Page Index 15 util twi h wdt h 5 avr libc Page Index 5 1 avr libc Related Pages Here is a list of all related documentation pages Toolchain Overview Memory Areas and Using malloc Memory Sections Data in Program Space avr libc and assembler programs Inline Assembler Cookbook How to Build a Library Benchmarks Porting From IAR to AVR GCC Frequently Asked Questions Building and Installing the GNU Tool Chain Using the GNU tools Using the avrdude program Release Numbering and Methodology Acknowledgments Todo List Deprecated List 260 262 262 267 272 277 282 288 300 303 306 311 335 351 362 364 367 368 368 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 avr libc Module Documentation 16 6 avr libc Module Documentation 6 1 lt alloca h gt Allocate space in the stack 6 1 1 Detailed Description Functions void x alloca size t size 6 1 2 Function Documentation 6 1 2 1 voidx alloca size t size Allocate size bytes of space in the s
227. ce 8 10 1 Detailed Description Defines define ERRNO 1 define EDOM 33 define ERANGE 34 Variables int errno 8 11 fdevopen c File Reference 8 11 1 Detailed Description Functions FILE x fdevopen int put char FILE int get FILE 8 12 ffs S File Reference 8 12 1 Detailed Description 8 13 ffsl S File Reference 8 13 1 Detailed Description 8 14 ffsll S File Reference 8 14 1 Detailed Description 8 15 fuse h File Reference 8 15 1 Detailed Description Defines define AVR FUSE H 1 define FUSEMEM attribute section fuse define FUSES fuse t fuse FUSEMEM Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 16 interrupt h File Reference 233 8 16 interrupt h File Reference 8 16 1 Detailed Description et Defines Global manipulation of the interrupt flag The global interrupt flag is maintained in the I bit of the status register SREG define sei define cli Macros for writing interrupt handler functions define ISR vector attributes define SIGNAL vector define EMPTY_INTERRUPT vector define ISR_ALIAS vector target_vector define reti define BADISR_vect ISR attributes define ISR BLOCK define ISR_NOBLOCK define ISR_NAKED define ISR_ALIASOF target_vector 8 17 inttypes h File Reference 8 17 1 Detailed Description Defines macros for printf and scanf format specifiers For C these are onl
228. ce h gt Program Space Utilities 135 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 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 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 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 byte address short read byte near address short define read word address short pgm read word near address short define read dword address short read dword near address short define PGM
229. char fmt va list ap int sprintf char s constchar fmt int sprintf P char __s const char x__fmt int snprintf char __s size_t __n const char __fmt int snprintf_P char __s size_t __n const char x__fmt int vsprintf char __s const char __fmt va_list ap int vsprintf P char __s const char __fmt va_list ap int vsnprintf 5 size_t __n const char fmt va_list ap int vsnprintf_P char __s size_t __n const char va_list ap int fprintf FILE stream const char fmt int fprintf P FILE stream const char fmt intfputs 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 May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 58 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 fm
230. chieved 6 28 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 the overhead the compiler requires to setup the counter register pair Thus at a CPU speed of 1 MHz delays of up to about 262 1 milliseconds can be achieved 6 29 lt util parity h gt Parity bit generation 6 29 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 6 29 2 Define Documentation 6 29 2 1 define parity even bit val Value extension 4 unsigned char t asm mov __tmp_reg__ 0 n t swap 50 NnNt eor 0 tmp reg n t mov tmp reg 0 n t lsr so n t lsr 50 nit qut uut ut uet utu GO GO ur Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 30 lt util setbaud h gt Helper macros for baud rate calculations 170 _t 1 gt gt 1 amp 1 eor 0 tmp reg N sb Ct E N 0 unsigned char val N EO Returns lif val has an odd number of bits set 6 30 lt util setbaud h gt Helper macros for baud rate calculations 6 30 1 Detailed Description define F CPU 11059200 define BAUD 38400 include lt util setbaud h gt
231. closing the previous st derr since this would also close stdout Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 61 6 9 2 18 define stdin iob 0 Stream that will be used as an input stream by the simplified functions that don t take stream argument The first stream opened with read intent using fdevopen will be assigned to stdin 6 9 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 9 3 Function Documentation 6 9 3 1 void clearerr FILE __ stream Clear the error and end of file flags of st ream 6 9 3 2 int fclose FILE stream This function closes st ream and disallows and further IO to and from it When using fdevopen to setup the stream a call to fclose is needed in order to free the internal resources allocated If the stream has been set up using fdev_setup_stream or FDEV_SETUP_ STREAMO O use fdev_close instead It currently always returns 0 for success 6 9 33 FILE fdevopen int 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 struct
232. complete before writing the page 6 12 2 11 define boot rww SPM REG uint8 t BV COMMON ASB Check if the RWW section is busy 6 12 2 12 define boot rww enable boot rww enable Enable the Read While Write memory section 6 12 2 13 define boot rww enable safe Value do boot spm busy wait X eeprom busy wait N boot rww enable N while 0 Same as boot rww enable except waits for eeprom and spm operations to complete before enabling the RWW mameory Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 100 6 12 2 14 boot signature byte get addr Value _ extension N uintl6 t addrl16 uintl6 t addr N uint8 t result N asm volatile N sts 1 2 n t N lpm 0 2 n t N result i SFR MEM ADDR SPM REG N r uint8 t BOOT SIGROW READ N addr16 A A _ result Read the Signature Row byte at address For some MCU types this function can also retrieve the factory stored oscillator calibration bytes Parameter address can be 0 0x1f as documented by the datasheet Note The values are MCU type dependent 6 12 215 define boot spm busy _SPM_REG amp uint8 t SPM ENABLE Check if the SPM instruction is busy 6 12 2 16 boot spm busy wait do while boot_spm_busy Wait while t
233. ctions 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 10 4 20 int rand_r unsigned long _ 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 10 4 21 long random void The random function computes a sequence of pseudo random integers in the range of 0 to RANDOM MAX as defined by the header file lt stdlib h gt The srandom function sets its argument seed as the seed for a new sequence of pseudo random numbers to be returned by rand These sequences are repeatable by calling srandom with the same seed value If no seed value is provided the functions are automatically seeded with a value of 1 6 10 4 22 long random r unsignedlong c x Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 80 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 10 4 23 void realloc void _ ptr size t size The realloc function tries to change the size of the region allocated at pt x to the new size value It returns a pointer to the new region The returned pointer might be the
234. cut and paste going from one project to the next Would you like to reduce your maintenance overhead Then you re ready to create your own library Code reuse is a very laudable goal With some upfront investment you can save time and energy on future projects by having ready to go libraries This chapter describes some background information design considerations and practical knowledge that you will need to create and use your own libraries 9 7 2 How the Linker Works The compiler compiles a single high level language file C language for example into a single object module file The linker 1d can only work with object modules to link Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 7 How to Build a Library 301 them together Object modules are the smallest unit that the linker works with Typically on the linker command line you will specify a set of object modules that has been previously compiled and then a list of libraries including the Standard C Library The linker takes the set of object modules that you specify on the command line and links them together Afterwards there will probably be a set of undefined references A reference is essentially a function call An undefined reference is a function call with no defined function to match the call The linker will then go through the libraries in order to match the undefined references with function definitions that are found in the libraries If
235. d on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 338 The next step is to configure and build the tools This is done by supplying arguments to the configure script that enable the AVR specific options configure prefix PREFIX target avr disable nls If you don t specify the prefix option the tools will get installed in the usr 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 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
236. d on param eters of a call for example qsort is recursive and sprintf receives parameters in a stack Different versions of the compiler can give a significant difference in code size and execution time For example the dtostre function compiled with avr gcc 3 4 6 requires 930 bytes After transition to avr gcc 4 2 3 the size become 1088 bytes Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 8 Benchmarks 304 9 8 1 A few of libc functions Avr gcc version is 4 2 3 The size of function is given in view of all picked up functions By default Avr libc is compiled with mcall prologues option In brackets the size without taking into account modules of a prologue and an epilogue is resulted Both of the size can coincide if function does not cause a prologue epilogue Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 8 Benchmarks 305 Function Units Avr2 Avr25 Avr4 atoi 12345 Flash bytes 82 82 78 78 74 74 Stack bytes 2 2 MCU clocks 155 149 atol 12345 Flash bytes 122 122 118 118 118 118 Stack bytes 2 2 MCU clocks 221 219 dtostre 1 2345 Flash bytes 1184 1072 1088 978 1088 978 s 6 0 Stack bytes 17 17 MCU clocks 1313 1152 dtostrf 1 2345 Flash bytes 1676 1564 1548 1438 1548 1438 15 6 s Stack bytes 36 36 MCU clocks 1608 1443 itoa 12345 s Flash bytes 150 150
237. dLEAST16 28 SCNdLEAST32 28 SCNdPTR 28 SCNi16 28 SCNi32 29 SCNiFAST16 29 SCNiFAST32 29 SCNiLEAST16 29 SCNiLEAST32 29 SCNiPTR 29 SCNo16 29 SCNo32 29 SCNoFAST 16 29 SCNoFAST32 29 SCNoLEAST16 29 SCNoLEAST32 30 SCNOoPTR 30 SCNu16 30 SCNu32 30 SCNuFAST16 30 SCNuFAST32 30 SCNuLEAST16 30 SCNuLEAST32 30 SCNuPTR 30 SCNx16 30 SCNx32 30 SCNxFAST 16 31 SCNxFAST32 31 SCNxLEASTI16 31 SCNxLEAST32 31 SCNxPTR 31 uint_farptr_t 31 avr_math acos 33 asin 33 atan 33 atan2 33 ceil 34 copysign 34 cos 34 cosh 34 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 374 34 fabs 34 fdim 34 floor 34 fma 34 fmax 35 fmin 35 fmod 35 frexp 35 hypot 35 INFINITY 33 isfinite 35 isinf 36 isnan 36 ldexp 36 log 36 log10 36 lrint 36 lround 36 M_PI 33 M_SQRT2 33 modf 37 NAN 33 pow 37 round 37 signbit 37 sin 37 sinh 37 sqrt 38 square 38 tan 38 tanh 38 trunc 38 avr_pgmspace memchr_P 139 mememp P 139 memcpy_P 139 memmem P 139 memrchr P 139 PGM P 135 read byte 135 pgm read byte far 135 pgm read byte near 136 pgm read dword 136 pgm read dword far 136 pgm read dword near 136 read 136 pgm read word far 137 read near 137 PGM VOID P 137 prog char 137 prog int16 t 137 prog int32 t 138 prog 11164 t 138 prog in
238. 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 5 boot h File Reference 225 8 5 2 Define Documentation 8 5 2 1 define boot lock bits set lock bits Value extension uint8 t value uint8 t lock bits asm volatile Idi 30 1XnXt Idi x31 DAVE mov r0 2 n t sts 0 1 n t spm n t i SFR MEM ADDR SPM REG r uint8 t BOOT LOCK BITS SET r value y r30 r31 8 5 2 2 define boot lock bits set alternate lock bits Value extension 4 uint8_t value uint8_t lock_bits __asm__ __volatile__ Irai r30 lamu tidi r31 OXnic mov r0 2 n t sts 0 1 n t spm n t word Oxffff n t hopinXt i SFR MEM ADDR SPM REG r uint8 t BOOT LOCK BITS SET r value EO 30 Lal 8 5 2 3 define boot page erase alternate address Value _ extension N a an an an a PP Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 5 boot h File Reference 226 asm volatile movw r30 2 n t sts 0 1 n t spm n t word Oxffff n t nop n t Yir SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE ERASE r uint16_t address 730 my 8 5 2 4
239. ded define INT8 MAX Ox7f define 8 MIN 8 MAX 1 define UINT8_MAX CONCAT INT8 MAX U x 2U 1U define INTI6 MAX Ox7fff define INTI6 MIN 6 MAX 1 define UINTIG6 MAX CONCAT INT16 MAX U 2U 1U define INT32 MAX Ox7fffffffL define INT32 MIN CCINT32 MAX IL define UINT32 MAX CONCAT INT32 U x 2UL 1UL define INT64 MAX 7 define INT64 MIN INT64 MAX ILL define UINT 4 MAX CONCAT INT64 MAX U 2ULL LULL Limits of minimum width integer types define INT LEAST8 MAX 8 MAX define INT LEAST8 MIN INT8 MIN define UINT LEASTS MAX UINT8 MAX fdefine INT LEASTI6 INTI6 MAX define INT LEASTI6 MIN INT16 MIN define UINT LEASTI6 MAX UINTI6 MAX fdefine INT LEAST32 MAX INT32 MAX define INT LEAST32 MIN INT32 MIN define UINT LEAST32 MAX UINT32 MAX fdefine INT LEAST64 MAX INT64 MAX define INT LEAST64 MIN INT64 MIN define UINT LEAST64 MAX UINT64 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 44 Limits of fastest minimum width integer types define INT_FAST8_MAX INT8_MAX define INT_FAST8_MIN INT8_MIN define UINT FASTS MAX UINT8 MAX define INT FASTI6 INTIG6 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 F
240. ded define INT8_MAX Ox7f define INT8_MIN INT8_MAX 1 define UINT8_MAX __CONCAT INT8_MAX U 20 1U define INT16_MAX Ox7fff define INT16_MIN INT16_MAX 1 define UINT16_MAX CONCAT INT16 MAX U 2U 1U define INT32_ MAX Ox7fffffffL define INT32_MIN INT32_MAX 1L define UINT32_ 2 MAX U x 2UL define INT64_MAX 7 define INT64 MIN INT64 MAX ILL define UINT64_MAX CONCAT INT64 MAX U 2ULL 1ULL Limits of minimum width integer types Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 39 stdint h File Reference 249 define INT_LEAST8_MAX INT8_MAX define INT_LEAST8_MIN INT8_MIN define UINT_LEAST8_MAX UINT8_MAX define INT LEASTI6 MAX INT16_MAX define INT LEAST16 MIN INT16 MIN define UINT LEASTI6 MAX UINTI6 MAX fdefine INT LEAST32 MAX INT32 MAX define INT LEAST32 MIN INT32 MIN define UINT LEAST32 MAX UINT32 MAX define INT LEAST64 MAX INT64 define INT LEAST64 MIN INT64 MIN define UINT LEAST64 MAX UINT64 MAX Limits of fastest minimum width integer types define INT 8 MAX 8 MAX define INT FAST8 MIN INT8 MIN define UINT FASTS MAX UINT8 MAX define INT FASTI6 MAX INTI6 MAX define INT FASTI6 MIN INT16 MIN define UINT FASTI6 MAX UINTI6 MAX define INT FAST32 MAX INT32 MAX define INT FAST32 MIN INT32 MIN define UINT FAST32 MAX UINT32 MAX define INT FAST64 MAX INT64 MA
241. default reti end Note 1 SQU SQU SQU ints SQUA wor wor wor ARE ARE ARE av RE tmr0 CK 1 K Note 10 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 285 Our bit number for the square wave output Note that the right hand side consists of a CPP macro which will be substituted by its value 6 in this case before actually being passed to the assembler Note 4 The assembler uses integer operations in the host defined integer size 32 bits or longer when evaluating expressions This is in contrast to the compiler that uses the 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 regist
242. define DTOSTR_UPPERCASE 0x04 Defines define RAND MAX 0x7FFF Typedefs typedef int __compar_fn_t const void const void Functions void abort void ATTR NORETURN int abs int 1 long labs long i void bsearch const void key const void base size_t __nmemb size t size int __compar const void const void div_t div int num int denom asm divmodhi4 tldiv long __num long __denom __asm__ __divmodsi4 void qsort void base size_t __nmemb size t size compar fn t compar long strtol const char nptr char endptr int base unsigned long strtoul const char nptr char endptr int base long atol const char PURE int atoi const char 5 PURE void exit int status NORETURN void x malloc size t size MALLOC void free void ptr void calloc size t nele size t size MALLOC void realloc void ptr size t size ATTR_MALLOC__ double strtod const char nptr char endptr double const char nptr int rand void void srand unsigned int seed int rand unsigned long ctx Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 74 Variables e size_t___malloc_margin e char __malloc_heap_start e char x __malloc_heap_end 6 10 2 Define Documentation 6 10
243. ding in S or explicitly using x 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 5 avr gcc Wa gstabs EXTRA_OPTS c o foo o foo S Also note that the debugger might get confused when entering a piece of code that has a non local label before since it then takes this label as the name of a new function that appears to have been entered Thus the best practice to avoid this confusion is to only use non local labels when declaring a new 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 reference or f for a forward reference These local labels may be re used within the source file references will pick the closest label with the same number and given direction Example Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 320 myfunc push rl6 push rl7 push r18 push YL
244. dress 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 18 2 11 define P const prog void Used to declare a generic pointer to an object in program space 6 18 2 12 define PROGMEM ATTR PROGMEM Attribute to use in order to declare an object being located in flash ROM 6 18 2 13 define PSTR s const PROGMEM char x s Used to declare a static pointer to a string in program space 6 18 3 Typedef Documentation 6 18 3 1 prog char Type of a char object located in flash ROM Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 139 6 18 3 2 prog_int16 t Type of an int16 t object located in flash ROM 6 18 3 3 prog int32 t Type of an int32 t object located in flash ROM 6 18 3 4 prog int64 t Type of an int64 t object located in flash ROM Note This type is not available when the compiler option mint8 is in effect 6 18 3 5 prog int8 t Type of an int8 t object located in flash ROM 6 18 3 6 prog uchar Type of an unsigned char object located in flash ROM 6 18 3 7 prog uintl6 t Type of an uintl6 t object located in flash ROM 6 18 3 8 prog uint32 t Type of an uint32 t object located in flash ROM 6 18 3 9 prog uint64 t Type of an uint64 t object located in flash ROM Note This type is not available whe
245. e application from source code on particular host platforms and sometimes packaging the tools for convenient installation by the end user These packages contain the binary executables of the tools pre made and ready to use These packages are known as distributions of the AVR toolchain or by a more shortened name distros AVR toolchain distros are available on FreeBSD Windows Mac OS X and certain flavors of Linux 9 1 13 Open Source All of these tools from the original source code in the multitude of projects to the various distros are put together by many many volunteers All of these projects could always use more help from other people who are willing to volunteer some of their time There are many different ways to help for people with varying skill levels abilities and available time You can help to answer questions in mailing lists such as the avr gcc list or on forums at the AVR Freaks website This helps many people new to the open source AVR tools If you think you found a bug in any of the tools it is always a big help to submit a good bug report to the proper project A good bug report always helps other volunteers to analyze the problem and to get it fixed for future versions of the software You can also help to fix bugs in various software projects or to add desirable new features Volunteers are always welcome 9 2 Memory Areas and Using malloc 9 2 1 Introduction Many of the devices that are p
246. e __x double hypot double __x double y double round double __ x long lround double __ x long lrint double __x Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 20 math h File Reference 238 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 821 memccpy S File Reference 239 8 21 memccpy S File Reference 8 21 4 Detailed Description 8 22 memchrS File Reference 8 22 1 Detailed Description 8 23 memchr PS File Reference 8 23 1 Detailed Description 8 24 memcmp S File Reference 8 241 Detailed Description 8 25 memcmp PS File Reference 8 25 1 Detailed Description 8 26 memcpy S File Reference 8 26 1 Detailed Description 8 27 PS File Reference 8 27 1 Detailed Description 8 28 memmem S File Reference 8 28 1 Detailed Description 8 29 memmove S File Reference 8 29 1 Detailed Description 8 30 memrchr S File Reference 8 30 1 Detailed Description 8 31 memrchr_P S File Reference 8 31 4 Detailed Description 8 32 memset S File Reference Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 32 1 Detailed Description 8 33 parity h File Reference 8 33 1 Detailed Description Defines 8 34 pgmspace h File Reference 240 8 34 pgmspace h File Reference 8 34 1 Detailed Description Defines define PGMSPACEH 1 define need size t Zdefine _ ATTR PROGMEM __attribute__ __progmem__ define _ ATTR_PURE attribute__ __pure__ define PR
247. e code into C programs This cool feature may be used for manually optimizing time critical parts of the software or to use specific processor instruction which are not available in the C language Because of a lack of documentation especially for the AVR version of the compiler it may take some time to figure out the implementation details by studying the compiler and assembler source code There are also a few sample programs available in the net Hopefully this document will help to increase their number It s assumed that you are familiar with writing AVR assembler programs because this is not an AVR assembler programming tutorial It s not a C language tutorial either Note that this document does not cover file written completely in assembler language refer to avr libc and assembler programs for this Copyright C 2001 2002 by egnite Software GmbH Permission is granted to copy and distribute verbatim copies of this manual provided that the copyright notice and this permission notice are preserved on all copies Permis sion is granted to copy and distribute modified 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 fam
248. e function pa rameter example 9 4 3 Storing and Retrieving Data in the Program Space Let s say you have some global data unsigned char mydata 11 10 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 Ox0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D Ox1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F 0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 Ox5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D 1 and later in your code you access this data in a function and store a single byte into a variable like so byte mydata i j Now you want to store your data in Program Memory Use the PROGMEM macro found in lt avr pgmspace h gt and put it after the declaration of the variable but before the initializer like so Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 4 Data in Program Space 279 include lt avr pgmspace h gt unsigned char mydata 11 10 PROGMEM 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x20 0x21 0x22 0x23
249. e resulting program text will then be passed on to the assembler As the C preprocessor strips all C style comments preprocessed assembly source files can have both C style as well as assembly style comments At the top the IO register definition file avr io h and the project declaration file project hare included The remainder of the file is conditionally assembled only if the target MCU type is an 13 so it will be completely ignored for the ATtiny45 option Next are the two interrupt service routines for timer 0 compare A match timer 0 hits as OCROA is set to 255 and timer 0 overflow timer 0 hits BOTTOM As dis cussed above these are kept as short as possible They only save SREG as the flags will be modified by the INC instruction increment the counter hi variable which forms the high part of the current time counter the low part is formed by querying TCNTO directly and clear or set the variable flags respectively in order to note the current counting direction The RETI instruction terminates these interrupt service routines Total cycle count is 8 CPU cycles so together with the 4 CPU cycles needed for interrupt setup and the 2 cycles for the RJMP from the interrupt vector to the han dler these routines will require 14 out of each 256 CPU cycles or about 5 96 of the overall CPU time The pin change interrupt PCINTO will be handled in the final part of this
250. e string immedi ately following the 1 is the unique part of the library filename that the linker will link in For example if you use im Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 8 Benchmarks 303 this will expand to the library filename libm a which happens to be the math library included in avr libc If you use this on your linker command line lprintf flt then the linker will look for a library called libprintf flt a This is why naming your library is so important when you create it The linker will search libraries in the order that they appear on the command line Whichever function is found first that matches the undefined reference it will be linked in There are also command line switches that tell GCC which directory to look in L for the libraries that are specified to be linke in with 1 See the GNU Binutils manual for more information on the GNU linker ld program 9 8 Benchmarks The results below can only give a rough estimate of the resources necessary for using certain library functions There is a number of factors which can both increase or reduce the effort required Expenses for preparation of operands and their stack are not considered In the table the size includes all additional functions for example function to multiply two integers but they are only linked from the library Expenses of time of performance of some functions essentially depen
251. e the watchdog timer if possible This attempts to turn off the Enable bit in the watchdog control register See the datasheet for details Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 24 lt avr wdt h gt Watchdog timer handling 158 6 24 2 2 define wdt_enable value Value __asm__ __volatile__ in tmp_reg__ __SREG__ n t Tolar NnXQ n t out 50 61 Manje X out SREG__ __tmp_reg__ n t out 0 2 no outputs I SFR IO ADDR WD CONTROL REG r BV WD CHANGE BV WDE r uint8 t value amp 0x08 WD PS3 MASK 0x00 _BV WDE value amp 0x07 zo qmm 0 Enable the watchdog timer configuring it for expiry after timeout 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 WDP3 bits See also the symbolic constants WDTO_15MS et al 6 24 2 3 define wdt reset asm volatile wdr Reset the watchdog timer When the watchdog timer is enabled a call to this instruction is required before the timer expires otherwise a watchdog initiated device reset will occur 6 24 2 4 define WDTO 120MS 3 See WDTO_15MS 6 24 2 5 define WDTO_15MS 0 Symbolic constants for the watchdog timeout Since the watchdog timer is based on a free running RC oscillator the times are appr
252. e 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 38 3 2 defines h This file just contains a few peripheral definitions 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 213 The remaining macros customize the IO port and pins used for the HD44780 LCD driver 6 38 3 3 hd44780 h This file describes the public interface of the low level LCD driver that interfaces to the HD44780 LCD controller Public functions are available to initialize the controller into 4 bit mode to wait for the controller s busy bit to be clear and to read or write one byte from or to the controller As there are two different
253. eader file here The main reason is that this file defines the value of CPU which needs to be known before including lt utils delay h gt The function ioinit summarizes all hardware initialization tasks As this function is declared to be module internal only 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 FDEV SETUP STREAM initializer template macro so static object can be constructed that can be used for IO purposes This initializer macro takes three arguments two function macros to connect the corresponding output and input functions respectively the third one describes the intent of the stream read write or both Those functions that are not required by the specified intent like the input function for 1 str which is specified to only perform output operations can be given as NULL The stream uart str corresponds to input and output operations performed over the RS 232 connection to a terminal e g from to a PC running a terminal program while the 1 str stream provides a method to display character data the LCD text display The function delay 1
254. east8_t signed int with at least 8 bits Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 52 6 8 3 13 typedef int64_t intmax_t largest signed int available 6 8 3 14 typedef int16_t intptr_t Signed pointer compatible type 6 8 3 15 typedef unsigned int uint16_t 16 bit unsigned type 6 8 3 16 typedef unsigned long int uint32_t 32 bit unsigned type 6 8 3 17 typedef unsigned long long int uint64_t 64 bit unsigned type Note This type is not available when the compiler option mint8 is in effect 6 8 3 18 typedef unsigned char uint8_t 8 bit unsigned type 6 8 3 19 typedef uint16_t uint_fast16_t fastest unsigned int with at least 16 bits 6 8 3 20 typedef uint32_t uint_fast32_t fastest unsigned int with at least 32 bits 6 8 3 21 typedef uint64_t uint_fast64_t fastest unsigned int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 53 6 8 3 22 typedef uint8 t uint fast8 t fastest unsigned int with at least 8 bits 6 8 3 23 typedef uintl6 tuint least16 t unsigned int with at least 16 bits 6 8 3 24 typedef uint32 t uint least32 t unsigned int with at least 32 bits 6 8 3 25 typedef uint64 t uint least64 t unsigned int with at least 64 bits Note This type
255. ecify the installation directory by using the prefix dir option with the configure script It is important to install all the AVR tools in the same directory or some of the tools will not work correctly To ensure consistency and simplify the discussion we will use 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 336 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 8 PATH PATH PREFIX bin 5 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 Note It is usually the best to use the latest released version of each of the tools 9 11 2 Required Tools GNU Binutils http sources redhat com binutils Installation http gee gnu org Installation AVR Libc http savannah gnu org projects avr libc Installation 9 11 3 Optional Tools You can develop programs for AVR devices without the following tools They may
256. ect This can happen even when you are not using any floating point math functions from the Standard C library but you are just doing floating point math operations When you link in the math library from AVR LibC those routines get replaced by hand optimized AVR assembly and it produces much smaller code See I get undefined reference to for functions like sin for more details on how to link in the math library Back to FAQ Index 9 11 Building and Installing the GNU Tool Chain This chapter shows how to build and install from source code a complete develop ment environment for the AVR processors using the GNU toolset There are two main sections one for Linux FreeBSD and other Unix like operating systems and another section for Windows 9 11 1 Building and Installing under Linux FreeBSD and Others 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 sp
257. ect files including disassembly avr size List section sizes and total size Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 1 Toolchain Overview 265 avr nm List symbols from object files avr strings List printable strings from files avr strip Discard symbols from files avr readelf Display the contents of ELF format files avr addr2line Convert addresses to file and line avr c filt Filter to demangle encoded C symbols 9 1 5 avr libc GCC and Binutils provides a lot of the tools to develop software but there is one critical component that they do not provide a Standard C Library There are different open source projects that provide a Standard C Library depending upon your system time whether for a native compiler GNU Libc for some other embedded system newlib or for some versions of Linux uCLibc The open source AVR toolchain has its own Standard C Library project avr libc AVR Libc provides many of the same functions found in a regular Standard C Library and many additional library functions that is specific to an AVR Some of the Standard C Library functions that are commonly used on a PC environment have limitations or additional issues that a user needs to be aware of when used on an embedded system AN R Libc also contains the most documentation about the whole AVR toolchain 9 1 6 Building Software Even though GCC Binutils and avr libc are the core proj
258. ects that are used to build software for the AVR there is another piece of software that ties it all together Make GNU Make is a program that makes things and mainly software Make interprets and executes a Makefile that is written for a project A Makefile contains dependency rules showing which output files are dependent upon which input files and instructions on how to build output files from input files Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 1 Toolchain Overview 266 Some distributions of the toolchains and other AVR tools such as MFile contain a Makefile template written for the AVR toolchain and AVR applications that you can copy and modify for your application See the GNU Make User Manual for more information 9 1 7 AVRDUDE After creating your software you ll want to program your device You can do this by using the program AVRDUDE which can interface with various hardware devices to program your processor AVRDUDE is a very flexible package All the information about AVR processors and various hardware programmers is stored in a text database This database can be modified by any user to add new hardware or to add an AVR processor if it is not already listed 9 1 8 GDB Insight DDD The GNU Debugger GDB is a command line debugger that can be used with the rest of the AVR toolchain Insight is GDB plus a GUI written in TcI Tk Both GDB and Insight are configured for the AVR and the main
259. ed which will normally be delayed until the currently active master has released the bus Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 220 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 infinite loop Thus the maximal number of iterations made until the device is declared to be not responding at all
260. ed Description como a an kb 260 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS xi 8 77 streehrS5 File Reference 2 2 2 ee 260 5721 Detmu edDsschpHon e e m 35 86 g aa EUR X3 ER 260 6 76 sthchr PS File Reference 222222222222 2222 bow BA Sw 260 8 78 1 Detailed lt 22k RR RR Bp d a 260 8 79 strrevS File Refer tic 222 b o 4 k a e 5 260 8 79 1 Detaled Description oo 222525 260 58 00 s sep o Pile Reference co os k u s k o SR 59 E i Res 260 8 80 1 Detailed Description 260 5 81 PS File Kletti 2 2 1 1 2 acna a aa E E G 260 8 81 1 Detaled Description 0 55 628s c RR 260 8 82 strspn S File Reference 2o cs om o ne b on RR m 260 5 82 1 Detailed Description 22222 222 2 22 2 2 5 260 Soo PS Pile Reference ccc ee ee A a 260 6 33 1 Detailed Description 222222225522 See ee eae es 260 5 84 strstr5 File Reference 2 4 o tr RT 260 8 84 1 Detailed Description 260 8 85 s str P S File Reference lt o c o rx 260 8 85 1 Detailed Description 2 2 260 8 86 rS File Referente 1 2 3 V o s eR USE LS 260 8 00 1 Detailed Description lt sos secre klk Rm eue 260 287 smijes Pile Esferenbe scs 24 X c x alk a k goda 4 4 9 260 8 87 1 Detailed Description 260 5 88 Fil Reire s cuo oou ee RR GRE eU mn 260 8 98 1 D
261. ed to fdevopen The rwflag argument can take one of the values FDEV SETUP READ FDEV_ SETUP WRITE or FDEV SETUP RW for read write or read write intent respec tively Note No assignments to the standard streams will be performed by fdev setup stream If standard streams are to be used these need to be assigned by the user See also under Running stdio without malloc 6 9 2 12 define FILE struct file FILE is the opaque structure that is passed around between the various standard IO functions 6 9 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 it is just an alias for fgetc 6 9 2 14 ftdefine getchar void fgetc stdin The macro get char reads a character from st din Return values and error handling is identical to fgetc 6 9 2 15 define putc c stream fputc c 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 9 2 16 define putchar fputc __c stdout The macro put char sends character c to stdout 6 9 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
262. ee ons 198 6 36 8 Reference to the source 201 6 37 A more sophisticated proje t 201 5271 Hardware setip 222222222245 r4 RR 201 6 37 2 Functional overvieW 2 2222 222 2 2 2 5 205 6373 A ode walkthrough lt o s se bs eps oj k 3 205 5274 The sourcecode lt sso s SAK ee N a 208 6 38 Using the standard IO 209 6 38 1 Hardware s ttp 1 1 c 4 40 ala k d eana ee GS 209 6 35 2 Functional 22 2 2 210 6 28 3 A Code walkthrough lt c zoo ribns 211 6 35 4 Thesenree code apa me b umm b li 216 6 39 Example using the two wire interface TWI 216 6 39 1 Intr duction mta TWI s soe zoo ao m 216 6 39 2 The TWI example project lt ssc 55s ek m RR 217 6 39 3 The Source Code 41 246 kiu cp or RR seks st n 217 7 avr ibc Data Structure Documentation 221 hv t5uuetReferenok 22 2222 eR Sl u a a a 221 T Detaled Description s ep coo ke RR RR 221 LLZ Field Documentation s 1 33 24 sr duk 221 72 hiv t Struct Keleretice gt oo 6 sk S kV l b 4 v k 4 4 oom 222 7121 Detaled Description B ksa 222 722 Field Documentation 2 222 8 avr ibc File Documentation 222 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS 8 asserthFileReference 8 1 1 Detailed Description 2 6 2
263. eeds to be saved usually on the stack Note 10 As explained in Interrupts a global catch all interrupt handler that gets all unassigned interrupt vectors can be installed using the _ 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 9 5 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 287 Some common pseudo ops include byte allocates single byte constants e ascii allocates a non terminated string of characters asciz allocates a VO terminated string of characters C string e data switches to the data section 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 vari
264. ef signed long long int int64 t typedef unsigned long long int uint64 t Integer types capable of holding object pointers These allow you to declare variables of the same size as a pointer typedef int16 t intptr t e typedef uint16_t uintptr_t Minimum width integer types Integer types having at least the specified width typedef int8 t int least8 t typedef uint8 t uint least8 t typedef int16 t int least16 t typedef uint16 tuint leastl6 t typedef int32 t int least32 t typedef uint32 t uint_least32_t typedef int64 t int least64 t typedef uint64_t least64 t Fastest minimum width integer types Integer types being usually fastest having at least the specified width e typedef int8 t int fast8 t e typedef uint8 t fast8 t e typedef int16 t int fastl6 t e typedef uint16 tuint fastl6 t typedef int32 t int fast32 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 43 typedef uint32 tuint fast32 t e typedef int64 t int fast64 t e typedef uint64 t fast 4 t Greatest width integer types Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category typedef int64 t intmax t e typedef uint64 t uintmax t 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 inclu
265. efine 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 without optional attributes Deprecated Do not use SIGNAL in new code Use ISR instead 6 16 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 specified by the mmcu compiler command line switch This is done by divert ing to the appropriate file lt avr ioXXXX h gt which should never be included di rectly Some register names common to all AVR devices are defined directly within Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 17 lt avr lock h gt Lockbit Support 131 lt avr common h gt which is included in lt avr io h gt but most of the details come from the respective include file Note that this file always includes the following files include lt avr sfr_defs h gt include lt avr portpins h gt include lt avr common h gt include lt avr version h gt See lt avr sfr_defs h gt Special function registers for more details about that header file Included are definitions of the IO register set and their respective bit values as specified in the Atmel documentation Note that inconsistencies in naming conventions so even identical functions sometimes get different names on different device
266. efore 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 memtype lt addr gt lt N Bytes gt read alias for dump write write memory write lt memtype gt addr bl lt b2 gt lt bN gt erase perform a chip erase sig display device signature bytes part display the current part information send send a raw command send bl lt b2 gt lt b3 gt lt b4 gt help help 2 help quit quit Use the part command to display valid memory types for use with the dump and write commands avrdude Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 14 Release Numbering and Methodology 364 9 14 Release Numbering and Methodology 9 14 1 Release Version Numbering Scheme 9 14 1 1 Stable Versions stable release will always have a minor number that is an even number This implies that you should be able t
267. ega2561 AVR ATmega2561 avrxmega5 atxmega64a1 _ AVR_ATxmega64A1__ avrxmega7 atxmegal28al _ ATxmegal28Al 1 avr25 architecture is new in GCC 4 2 2 avr35 architecture is new in GCC 4 2 3 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 355 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 113 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 12 10 r1 Order 1 uses r18 r19 r20 121 122 r23 r24 r25 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 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 13 r2 r1 rO e mint8 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 mno interrupts Generates code that changes the stack pointer without disabling interrupts Normally the state of the status register SREG is saved in a temporary register interrupts are disabled while changing the stack pointer and SREG is restored Specifying this option will define the preprocessor macro NO INTERRUPTS to the value 1 e mcall prologues Use subroutines for function
268. ell address bits 9 to 11 as re quired This example simply assumes all subaddress bits are 0 for the smaller devices so the EO E1 and E2 inputs of the 24Cxx must be grounded Note 4 For slow clocks enable the 2 x U S ART clock multiplier to improve the baud rate error This will allow a 9600 Bd communication using the standard 1 MHz calibrated RC oscillator See also the Baud rate tables in the datasheets Note 5 The datasheet explains why a minimum TWBR value of 10 should be maintained when running in master mode Thus for system clocks below 3 6 MHz we cannot run the bus at the intented clock rate of 100 kHz but have to slow down accordingly Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 219 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 Note 8 When reading the EEPROM a first device selection must be made with write intent R W bit set to
269. en calls there Format strings in flash ROM All the printf and scanf family functions come in two flavours the standard name where the format string is expected to be in SRAM as well as a version with the suffix _P where the format string is expected to reside in the flash ROM The macro PSTR explained in lt avr pgmspace h gt Program Space Utilities becomes very handy for declaring these format strings Running stdio without malloc default fdevopen requires malloc As this is often not desired in the limited environment of a microcontroller an alternative option is provided to run completely without malloc The macro fdev_setup_stream is provided to prepare a user supplied FILE buffer for operation with stdio Example include lt stdio h gt static int uart putchar char c FILE xstream static FILE mystdout FDEV SETUP STREAM uart putchar NULL FDEV SETUP WRITE static int uart putchar char c FILE stream if n uart_putchar r stream loop_until_bit_is_set UCSRA UDRE UDR return 0 int main void init_uart stdout amp mystdout printf Hello world n return 0 This example uses the initializer form FDEV_SETUP_STREAMO rather than the function like fdev_setup_stream so all data initialization happens during C start up Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities
270. en s1 is considered to be less than s2 6 18 4 7 char x strcasestr P const char 81 PGM P 52 This funtion is similar to strcasestr except that s2 is pointer to a string in program space 6 18 4 8 char x strcat P char 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 142 6 18 4 9 strchr_P PGM P s int val Locate character in program space string The strchr_P function locates the first occurrence of va1 converted to a char in the string pointed to by s in program space The terminating null character is considered to be part of the string The strchr_P function is similar to strchr except that s is pointer to a string in program space Returns The strchr_P function returns a pointer to the matched character or NULL if the character is not found 6 18 4 10 P strchrnul_P PGM P s int c The strchrnul P function is like strchr_P except that if c is not found in s then it returns a pointer to the null byte at the end of s rather than NULL Glibc GNU extension Returns The strchrnul P function returns a pointer to the matched character or a pointer to the null byte at the end of s i e ststr
271. en 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 360 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 M Print a linker map to stdout Map mapfile Print a linker map to mapfile cref Output a cross reference table to the map file in case Map is also present or to stdout section start sectionname org Start section sectionname at absolute address org Tbss org e Tdata org Itext 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 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 361 9 12 3 2 Passing linker options from the C compiler default all unknown non option arguments on the avr gcc com
272. ence Zero or more of the following flags The value should be converted to an alternate form For 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 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 adjustment flag has been given to fill out the field width optional precision in the fo
273. er we therefore have to account for the number of clock cycles required for interrupt acknowledge and for the instructions to reload TCCNTO 4 clock cycles for interrupt acknowledge 2 cycles for the jump from the interrupt vector 2 cycles for the 2 instructions that reload TCCNTO This is what the constant fuzz is for Note 5 External functions need to be declared to be global main is the application entry point that will be jumped to from the ininitalization routine in crt 81200 o Note 6 The main loop is just a single jump back to itself Square wave generation itself is completely handled by the timer 0 overflow interrupt service A sleep instruction using idle mode could be used as well but probably would not conserve much energy anyway since the interrupt service is executed quite frequently Note 7 Interrupt functions can get the usual names that are also available to C programs The linker will then put them into the appropriate interrupt vector slots Note that they must be declared global in order to be acceptable for 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 Generated on Mon May 12 09 55 09 2008 for avr
274. er 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 295 asm volatile mov tmp reg 0 mov 0 DO mov DO tmp reg mov tmp reg BO mov BO CO mov CO tmp reg r value 0 value NnNEU mne ATK AnNE mne MATINET Instead of listing the same operand as both input and output operand it can also be declared as a read write operand This must be applied to an output operand and the respective input operand list remains empty asm volatile X tmp reg 0 mov 0 mov DO mov BO mov CO 6 0 tmp reg mov tmp reg BO SCO __tmp_reg__ r value ARNE manat NND mne MATINET If operands do not fit into a single register the compiler will automatically assign enough registers to hold the entire operand In the assembler code you use A0 to refer to the lowest byte of the first operand 1 to the lowest byte of the second operand 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 ma
275. erformed zero is returned and the value of nptr is stored in the location referenced by endptr If the correct value would cause overflow plus or minus INFINITY is returned ac cording to the sign of the value and ERANGE is stored in errno If the correct value would cause underflow zero is returned and ERANGE is stored in errno Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 81 6 10 4 27 long strtol const char _ nptr char xx __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 Ox prefix and the number will be read in base 16 otherwise a zero base is taken as 10 decimal unless the next character is 0 in which case it is taken as 8 octal The remainder of the string is converted to a long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 represents 11 and so forth with Z representing 35 If endptr is not NULL strtol stores the add
276. es 00000020 00000000 00000000 0000019a 2xx0 CONTENTS READONLY DEBUGGING 3 debug pubnames 00000035 00000000 00000000 000001ba 2xx0 CONTENTS READONLY DEBUGGING 4 debug info 00000105 00000000 00000000 000001ef 2xx0 CONTENTS READONLY DEBUGGING 5 debug abbrev 000000cf 00000000 00000000 000002 4 2 0 CONTENTS READONLY DEBUGGING 6 debug line 00000147 00000000 00000000 000003c3 2xx0 CONTENTS READONLY DEBUGGING 7 debug frame 00000040 00000000 00000000 0000050c 2xx2 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 191 CONTENTS READONLY DEBUGGING 8 debug_str 000000ab 00000000 00000000 0000054c 2xx0 CONTENTS READONLY DEBUGGING Disassembly of section text 00000000 vectors 12 60 rjmp 36 0x26 ctors end 2 BS e rjmp 280 Oxllc bad interrupt 4 8b cO rjmp 278 0 interrupt 6 cO rjmp 276 0 11 lt pad interrupt 8 89 cO rjmp 274 0 11 interrupt a 88 cO rjmp 272 0 11 bad interrupt rjmp 270 0 11 bad interrupt e 86 0 rjmp 268 0 11 _ interrupt LO 25 lt Q rjmp 74 Ox5c vector 8 12 84 cO rjmp 264 0 11 interrupt 14 83 cO rjmp 262 0 bad interrupt 16 82 cO rjmp 260 0 11 interrupt 18 81 cO rjmp 258 0 11 interrupt la 80 cO rjmp 256 Oxile bad inte
277. es 94 lt avr eeprom h gt EEPROM handling 101 lt avr fuse h gt Fuse Support 104 lt avr interrupt h gt Interrupts 107 lt avr io h gt AVR device specific IO definitions 130 lt avr lock h gt Lockbit Support 131 lt avr pgmspace h gt Program Space Utilities 134 lt avr power h gt Power Reduction Management 146 lt avr sfr_defs h gt Special function registers 151 Additional notes from lt avr sfr_defs h gt 149 lt avr sleep h gt Power Management and Sleep Modes 153 lt avr version h gt avr libc version macros 154 lt avr wdt h gt Watchdog timer handling 156 util atomic h gt Atomically and Non Atomically Executed Code Blocks 160 util crc16 h Computations 163 util delay h gt Convenience functions for busy wait delay loops 167 util delay basic h gt Basic busy wait delay loops 168 lt util parity h gt Parity bit generation 169 lt util setbaud h gt Helper macros for baud rate calculations 170 lt util twi h gt TWI bit mask definitions 172 lt compat deprecated h gt Deprecated items 176 lt compat ina90 h gt Compatibility with EWB 3 x 180 Demo projects 180 Combining C and assembly source files 181 A simple project 185 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 3 avr libc Data Structure Index 11 A more sophisticated project 201 Using the standard IO facilities 209 Example using the two wire interface TWI 216 3 avr libc Data Structure Index 3 1 avr
278. es for both text and data but not bss while the amount of pre allocated SRAM is the sum of data and bss Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 3 Memory Sections 273 9 3 22 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 9 3 3 The bss Section Uninitialized global or static variables end up in the bss section 9 3 4 The eeprom Section This is where eeprom variables are stored 9 3 5 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 will not be initialized to zero during startup as
279. eservation of the machine state including the SREG register as well as placing a reti at the end of the interrupt routine Use this attribute in the attributes parameter of the ISR macro 6 15 2 9 define ISR NOBLOCK include lt avr interrupt h gt ISR runs with global interrupts initially enabled The interrupt enable flag is activated by the compiler as early as possible within the ISR to ensure minimal processing delay for nested interrupts Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 16 lt avr io h gt AVR device specific IO definitions 130 This may be used to create nested ISRs however care should be taken to avoid stack overflows or to avoid infinitely entering the ISR for those cases where the AVR hard ware does not clear the respective interrupt flag before entering the ISR Use this attribute in the attributes parameter of the ISR macro 6 15 2 10 define reti include lt avr interrupt h gt Returns from an interrupt routine enabling global interrupts This should be the last command executed before leaving an ISR defined with the ISR_NAKED attribute This macro actually compiles into a single line of assembly so there is no function call overhead 6 15 2 11 define sei include lt avr interrupt h gt Enables interrupts by setting the global interrupt mask This function actually compiles into a single line of assembly so there is no function call overhead 6 15 2 12 d
280. eset For these older AVRs doing a soft reset by enabling the watchdog is easy as the watchdog will then be disabled after the reset On newer AVRs once the watchdog is enabled then it stays enabled even after a reset For these newer AVRs a function needs to be added to the init3 section i e during the startup code before main to disable the watchdog early enough so it does not continually reset the AVR Here is some example code that creates a macro that can be called to perform a soft reset include avr wdt h define soft reset do wdt_enable WDTO_15MS for while 0 a a an an an a For newer AVRs such as the ATmega1281 also add this function to your code to then disable the watchdog after a reset e g after a soft reset include lt avr wdt h gt Function Pototype void wdt_init void attribute naked attribute section init3 Function Implementation void wdt init void MCUSR 0 disable Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 335 return Back to FAQ Index 9 10 32 I am using floating point math Why is the compiled code so big Why does my code not work You are not linking in the math library from AVR LibC GCC has a library that is used for floating point operations but it is not optimized for the AVR and so it generates big code or it could be incorr
281. esulting 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 37 3 A code walkthrough This section explains the ideas behind individual parts of the code The source code has been divided into numbered parts and the following subsections explain each of these parts Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 37 A more sophisticated project 206 6 37 3 1 Part 1 Macro definitions A number of preprocessor macros are defined to improve readability and or portability of the application The first macros describe the IO
282. etailed Description 222 o 8 4 260 8 89 File Reference 12 2222 9o ee yos 262 8 89 1 Detailed 1 4 a ko RR Rm RR 262 9 avr libc Page Documentation 262 Pool scp ko Sj oe se ete 262 SLI InfoducHoH rese e ea RR R eR yx s 262 L2 TSP and 26 ze d ened ok xw EE 263 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS xii 9 2 42 9 4 ee eve 263 SIA GNU 2 2222 kk ko 5 s k K os 264 111 re ree 265 9 1 6 Building SONRWA c cce ola SG AS o 4 4 265 91 7 AVRDUDE cs 544860644 rya o ik eae 266 4215s GRB Insight DDD o 244 4 kd eee Ges 266 DG Lo ee e 266 SIMNIAVE i s oe d b Re al D 4 S 266 ARAN 11 Ze 266 9 1 12 Toolchain Distributions 267 9 1 13 Open Source o 4 ooo s o e kon RR mem R n 267 Memory Areas and Using 267 inboducHON um es HOS RE X 267 9 22 Interna ys extemal RAM 222222222252 e 24445 269 9 23 _ Tunables for 269 9 24 Implementation details 271 Memory ee eRe Xr 272 9340 The text Section s coe ARR A BS Wk H 272 932 The data Section eco ab ee xo x 273 42 3 The RS ode Ree leda BAM 4 273 9 34 The eeprom Section ce eoo eae be ES a ee S 273 935 The momit Section c
283. first operand Note however that this doesn t automatically imply the reverse case The compiler may choose the same registers for input and output even if not told to do so This is not a problem in most cases but may be fatal if the output operator is modified by the assembler code before the input operator is used In the situation where your code depends on different registers used for input and output operands you must add the amp constraint modifier to your output operand The following example demonstrates this problem asm volatile in 0 1 out 1 2 n t amp r input I SFR IO ADDR port r output In this example an input value is read from a port and then an output value is written to the same port If the compiler would have choosen the same register for input and out put then the output value would have been destroyed on the first assembler instruction Fortunately this example uses the amp constraint modifier to instruct the compiler not to select any register for the output value which is used for any of the input operands Back to swapping Here is the code to swap high and low byte of a 16 bit value asm volatile mov tmp reg 0 n t mov 0 0 NoNEN 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 regist
284. for functions like sin In order to access the mathematical functions that are declared in lt math h gt the linker needs to be told to also link the mathematical library 1ibm a Typically system libraries like 1ibm a are given to the final C compiler command line that performs the linking step by adding a flag 1m at the end That is the initial lib and the filename suffix from the library are written immediately after a flag So for a libfoo a library 1foo needs to be provided This will make the linker search the library in a path known to the system An alternative would be to specify the full path to the 1ibm a file at the same place on the command line i e after all the object files However since this re quires knowledge of where the build system will exactly find those library files this is deprecated for system libraries Back to FAQ Index 9 10 4 How to permanently bind a variable to a register This can be done with register unsigned char counter asm r3 Typically it should be save to use r2 through r7 that way Registers r8 through r15 can be used for argument passing by the compiler in case many or long arguments are being passed to callees If this is not the case throughout the entire application these registers could be used for register variables as well Extreme care should be taken that the entire application is compiled with a consistent set of register allocated variables including po
285. fr amp _BV bit define loop until bit is set sfr bit do while bit is clear sfr bit define loop until bit is clear sfr bit do while bit is set sfr bit 6 21 2 Define Documentation 6 21 2 1 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 6 21 2 2 define bit_is_clear sfr bit SFR BYTE sfr amp _BV bit include lt avr io h gt Test whether bit bit in IO register s r is clear This will return non zero if the bit is clear and a O if the bit 1s set 6 21 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 21 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 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 22 lt avr sleep h gt Power Management and Sleep Modes 153 6 21 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 22 lt avr sleep h gt Power Management and Sleep Modes 6 22
286. ftupt gt 16 FE 0 rjmp 254 0 bad interrupt le 7e rjmp 252 0 11 interrupt 20 7d c0 rjmp 250 0 11 interrupt 225 18 60 rjmp 248 0 lt __bad_interrupt gt 24 7b cO rjmp 246 0 lt bad interrupt 00000026 ctors end 26 11 24 eor rl rl 28 1f be out Ox3f Tl 63 2 s ct 5 Idi E28 0x5E 295 2c d4 eO ldi r29 0x04 4 2e de bf out 0x3e r29 62 30 cd bf out 0x3d r28 61 00000032 copy data 32 10 eO Idi 117 00x00 0 34 a0 e6 ldi r26 0x60 96 36 0 eO ldi r27 0x00 0 38 e6 e2 Idi r30 0x26 38 fl eO 141 r31 0 01 1 02760 rjmp 4 0 42 lt do_copy_data_start gt 0000003e do data loop 3e 05 90 lpm r0 Z 40 Od 92 st X ro 00000042 do data start 42 a0 36 cpi r26 0x60 96 44 bl 07 epe r27 rlT 46 d9 7 brne 10 Ox3e do copy data loop 00000048 clear bss 48 10 eO ldi r17 0x00 O 4a a0 e6 ldi r26 0x60 96 4c bo eO ldi r27 0x00 0 4e 01 cO rump 2 0x52 do clear bss start Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 192 00000050 do clear bss loop 50 1d 92 st X 00000052 do clear bss start 52 a3 36 cpi r26 0x63 99 54 bl 07 27 56 el 7 brne 8 0x50 do clear bss loop 58 4d rcall 154 Oxf4 main 61 0
287. g 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 ultoa function returns the pointer passed as s 6 10 4 30 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 83 Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 9 will be the letter a The utoa function returns the pointer passed as s 6 10 5 Variable Documentation 6 10 5 1 charx malloc heap end malloc tunable 6 10 5 2 charx
288. ge but take over the com piler s job of generating the prologue and epilogue This can be done using the ISR_ NAKED attribute to the ISRQ macro Note that the compiler does not generate any thing as prologue or epilogue so the final reti must be provided by the actual im plementation SREG must be manually saved if the ISR code modifies it and the compiler implied assumption of __zero_reg__ always being 0 could be wrong e g when interrupting right after of a MUL instruction ISR TIMER1_OVF_vect ISR_NAKED PORTB _BV 0 results in SBI which does not affect SREG reti Choosing 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 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 availa
289. gram Space Util ities 133 lt avr power h gt Power Reduction Man agement 145 lt avr sfr_defs h gt Special function regis ters 150 lt avr sleep h gt Power Management and Sleep Modes 152 EEPROM handling lt avr version h gt avr libc version macros 153 avr wdt h Watchdog timer handling 155 lt compat deprecated h gt Deprecated items 175 lt compat ina90 h gt Compatibility with EWB 3 x 179 lt ctype h gt Character Operations 16 lt errno h gt System Errors 19 lt inttypes h gt Integer Type conversions 19 lt math h gt Mathematics 31 lt setjmp h gt Non local goto 38 lt stdint h gt Standard Integer Types 40 lt stdio h gt Standard IO facilities 52 lt stdlib h gt General utilities 71 lt string h gt Strings 82 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks 159 lt util crc16 h gt CRC Computations 162 lt util delay h gt Convenience functions for busy wait delay loops 166 lt util delay_basic h gt Basic busy wait delay loops 167 lt util parity h gt Parity bit generation 168 lt util setbaud h gt Helper macros for baud rate calculations 169 lt util twi h gt TWI bit mask definitions 171 _BV avr_sfr 151 _EEGET avr_eeprom 101 _EEPUT avr_eeprom 101 _FDEV_EOF avr_stdio 57 _FDEV_ERR avr_stdio 57 _FDEV_SETUP_READ avr_stdio 57 _FDEV_SETUP_RW avr_stdio 57 _FDEV_SETUP_WRITE avr_stdio 57 _FFS avr_string
290. h ATtiny25 ATtiny85 COMPAREIA A TIMI SIG Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 COMPB_vect OUTPUT_ Compare Match ATtiny25 ATtiny85 COMPAREIB B OVF SIG Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 vect OVERFLOWI Overflow ATtiny25 ATtiny85 TIMERO SIG INPUT ADC Conversion ATtiny261 ATtiny461 ATtiny861 CAPT vect CAPTUREO Complete TIMERO SIG TimerCounter0 ATmegal68 ATmega48 ATmega88 COMPA_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal281 COMPAREOA A ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 ATtiny48 ATtiny261 ATtiny461 AT tiny861 AT9OUSB162 9005 82 9 1287 AT90USB 1286 AT90USB647 AT90USB646 TIMERO SIG_ Timer Counter 0 AT90PWM3 AT90PWM2 AT90PWMI COMPB_vect OUTPUT_ Compare Match ATmegal284P ATmegal68P ATmega328P COMPAREOB B ATmega32HVB ATmega48P AT SIG_ mega88P ATmegal68 ATmega48 AT OUTPUT mega88 ATmega640 ATmega1280 COMPAREO ATmegal281 ATmega2560 ATmega2561 B ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 ATtiny48 ATtiny261 ATtiny46l AT tiny861 ATOOUSBI62 9005 82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMERO SIG Timer Counter0 AT90PWM3 AT90PWM2 AT90PWM 1 COMP A OUTPUT Compare Match vect COMPAREOA A SIG OUTPUT COMPAREO A TIMERO SIG Timer Counter0 AT90CAN128 AT90CAN32 AT90CA
291. 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 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 device that offers hardware TWI support is the ATmega8 which comes with 512 bytes of EEPROM which is equivalent to an 24C04 device The ATmegal28 already comes with twice as much EEPROM as the 24C16 would offer One exception might
292. he following is an example definition of a handler for the ADC interrupt include avr interrupt h 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 BADISR_vect which should be defined with ISR as such The name BADISR vect is actually an alias for __vector_default The latter must be used inside assembly code in case lt avr interrupt h gt is not included include lt avr interrupt h gt ISR BADISR_vect 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 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 t
293. he SPM instruction is busy 6 12 2 17 boot spm interrupt disable SPM REG amp uint8_t _ BV SPMIE Disable the SPM interrupt 6 12 2 18 define boot spm interrupt enable SPM REG uint8 t BV SPMIE Enable the SPM interrupt Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 101 6 12 2 19 define BOOTLOADER SECTION _ attribute section boot Used to declare a function or variable to be placed into 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 12 2 20 define GET EXTENDED FUSE BITS 0x0002 address to read the extended fuse bits using boot lock fuse bits get 6 12 2 21 define GET HIGH FUSE BITS 0 0003 address to read the high fuse bits using boot lock fuse bits get 6 12 2 22 define GET LOCK BITS 0 0001 address to read the lock bits using boot lock fuse bits get 6 12 2 23 define GET LOW FUSE BITS 0x0000 address to read the low fuse bits using boot lock fuse bits get 6 13 lt avr eeprom h gt EEPROM handling 6 13 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 Applicatio
294. he maximum number of bytes to compare Returns The strncasecmp function returns an integer less than equal to or greater than zero if s1 or the first n bytes thereof is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strncasecmp P is that if s1 is an initial substring of s2 then 51 is considered to be less than s2 6 18 4 18 char x strncat P char dest 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 6 18 4 19 int strncmp P const char 81 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 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 145 6 18 4 20 char strncpy P char x dest PGM P src size_t n The strncpy_P function is similar to strcpy 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
295. her 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 37 A more sophisticated project 208 6 37 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 exit into anyway At the beginning of the loop the watchdog timer will be retriggered If that timer is not triggered for about 2 seconds it will issue a hardware reset Care needs to be taken that no code path blocks longer than this or it needs to frequently perform watchdog resets of its own An example of such a code path would be the string IO functions for an overly large string to print about 2000 characters at 9600 Bd they might block for too long The loop itself then acts on the interrupt indication bitfields as appropriate and will eventually put the CPU on sleep at its end to conserve power The firs
296. here is no body to the aliased ISR Note that the ISR_ALIASOF feature requires GCC 4 2 or above or a patched version of GCC 4 1 x See the documentation of the ISR_ALIAS macro for an implementa tion which is less elegant but could be applied to all compiler versions Empty interrupt service routines In rare circumstances in interrupt vector does not need any code to be implemented at all The vector must be declared anyway so when the interrupt triggers it won t execute the BADISR vect code which by default restarts the application This could for example be the case for interrupts that are solely enabled for the purpose of getting the controller out of sleep moder A handler for such an interrupt vector can be declared using the EMPTY INTERRUPT macro EMPTY_INTERRUPT ADC_vect Note There is no body to this macro Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 110 Manually defined ISRs In some circumstances the compiler generated prologue and epilogue of the ISR might not be optimal for the job and a manually defined ISR could be considered particularly to speedup the interrupt handling One solution to this could be to implement the entire ISR as manual assembly code in a separate assembly file See Combining C and assembly source files for an example of how to implement it that way Another solution is to still implement the ISR in C langua
297. his is not the same as x lt 0 0 because IEEE 754 floating point allows zero to be signed The comparison 0 0 lt 0 0 is false but signbit 0 0 will return a nonzero value Note This implementation returns 1 if sign bit is set 6 6 3 31 double sin double x The sin function returns the sine of x measured in radians Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 7 lt setjmp h gt Non local goto 39 6 6 3 32 double sinh double x The sinh function returns the hyperbolic sine of x 6 6 3 33 double sqrt double x The sqrt function returns the non negative square root of x 6 6 3 34 double square double x The function square returns x x Note This function does not belong to the C standard definition 6 6 3 35 double tan double x The tan function returns the tangent of __x measured in radians 6 6 3 36 double tanh double x The tanh function returns the hyperbolic tangent of x 6 6 3 37 double trunc double x The trunc function rounds the nearest integer not larger in absolute value 6 7 lt setjmp h gt Non local goto 6 7 1 Detailed Description While the C language has the dreaded goto statement it can only be used to jump to a label in the same local function In order to jump directly to another non local function the C library provides the setjmp and longjmp functions setjmp and longjmp are
298. i generic integer scanf format for int fast32 t 6 5 2 72 define SCNILEASTIG i generic integer scanf format for int leastl6 t 6 5 2 73 define SCNILEAST32 li generic integer scanf format for int least32 t 6 5 2 74 define SCNIPTR SCNi16 generic integer scanf format for intptr t 6 5 2 75 define SCNo16 o octal scanf format for uint16 t 6 5 2 76 define SCNo32 lo octal scanf format for uint32 t 6 5 2 77 define SCNoFAST16 o octal scanf format for uint fastl6 t 6 5 2 78 define SCNoFAST32 lo octal scanf format for uint fast32 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 31 6 5 2 79 define SCNoLEAST16 octal scanf format for uint_least16_t 6 5 2 80 define SCNoLEAST32 lo octal scanf format for uint_least32_t 6 5 2 81 define SCNoPTR SCNol16 octal scanf format for uintptr t 6 5 2 82 define SCNu16 decimal scanf format for uint16 t 6 5 2 83 define SCNu32 lu decimal scanf format for uint32 t 6 5 2 84 define SCNuFASTI6 decimal scanf format for uint fastl6 t 6 5 2 85 define SCNuFAST32 lu decimal scanf format for uint fast32 t 6 5 2 86 define SCNULEAST16 u decimal scanf format for least16 t 6 5 2 87 define SCNuLEAST22 lu decimal scanf format for uint least32 t 6 5 2 88 define SCNuPTR SCNu16 decimal scanf format for uintptr t 6 5 2 89 define SCNx16 x
299. ic LI sbiw sbr sbrc rl sbrs rl ser d st er std br sts label r 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 amp Register should be used for output only Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 294 Output operands must be write only and the C expression result must be an lvalue which means that the operands must be valid on the left side of assignments Note that the compiler will not check if the operands are of reasonable type for the kind of operation used in the assembler instructions Input operands are you guessed it read only But what if you need the same operand for input and output As stated above read write operands are not supported in inline assembler code But there is another solution For input operators it is possible to use a single digit in the constraint string Using digit n tells the compiler to use the same register as for the n th operand starting with zero Here is an example asm volatile swap 0 r value 0 value This statement will swap the nibbles of an 8 bit variable named value Constraint 0 tells the compiler to use the same input register as for the
300. icant digits If the precision is missing 6 digits are given if the precision is zero it is treated as 1 Style e is used if the exponent from its conversion is less than 4 or greater than or equal to the precision Trailing zeros are removed from the fractional part of the result a decimal point appears only if it is followed by at least one digit Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 68 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 only the additional option can be specified using conversion flags these flags are parsed correctly from the format specification but then simply ignored This version can be requested using the following compiler options Wl u vfprintf lprintf min If the fu
301. ile include lt avr interrupt h gt The names of the various interrupt vectors are found in the individual processor IO header files that you must include with lt avr io h gt Note The names of the interrupt vectors in AVR GCC has been changed to match the names of the vectors in IAR This significantly helps in porting applications from TAR to AVR GCC 9 9 4 Intrinsic Routines has a number of intrinsic routine such as enable interrupts __disable_interrupts watchdog reset These intrinsic functions compile to specific AVR opcodes SEI CLI WDR There are equivalent macros that are used in AVR GCC however they are not located in a single include file AVR GCC has sei for enable interrupts and cli fo _ disable interrupts Both of these macros are located in lt avr interrupts h gt Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 9 Porting From to AVR 309 AVR GCC has the macro wdt_reset in place of __watchdog_reset However there is a whole Watchdog Timer API available in AVR GCC that can be found in lt avr wdt h gt 9 9 5 Flash Variables The C language was not designed for Harvard architecture processors with separate memory spaces This means that there are various non standard ways to define a vari able whose data resides in the Program Memory Flash IAR uses a non standard keyword to declare a variable in Program Memory flash
302. ile 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 Note Be careful when you use these functions If you already have a different interrupt enabled you could inadvertantly disable it by enabling another intterupt e static inline void timer enable int unsigned char ints define enable external int mask EICR mask define INTERRUPT signame define _ INTR ATTRS used Obsolete IO macros Back in a time when AVR GCC and avr libc could not handle IO port access in the di rect assignment form as they are handled now all IO port access had to be done through specific macros that eventually resulted in inline assembly instructions performing the desired action These macros became obsolete as reading and writing IO ports can be done by simply using the IO port name in an expression and all bit manipulation including those on IO ports can be done using generic C bit manipulation operators The macros in this group simulate the historical behaviour While they are supposed to be applied to IO ports the emulation actually uses standard C methods so they could be applied to arbitrary memory locations as well define inp port port Generated on
303. iliar with the English language there are definitely some typos and syntax errors in the text As a programmer the author knows that a wrong documentation sometimes might be worse than none Any way he decided to offer his little knowledge to the public in the hope to get enough response to improve this document Feel free to contact the author via e mail For the latest release check http www ethernut de Herne 17th of May 2002 Harald Kipp harald kipp at egnite de Note As of 26th of July 2002 this document has been merged into the documentation for avr libc The latest version is now available at http savannah nongnu org projects avr libc Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 289 9 6 1 GCC asm Statement Let s start with a simple example of reading a value from port D asm in 0 1 r value I SFR IO ADDR 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 You can write assembler instructions in much the same way as you would write assem bler programs However registers and constants
304. imer Counter4 ATmega640 ATmegal280 ATmegal28l COMPA vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARE4A A TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal28l COMPB vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPAREAB B Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 123 Vector name Old vector Description Applicable for device name TIMER4 SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPC_vect OUTPUT_ Compare Match ATmega2560 ATmega2561 COMPAREAC C TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 OVF vect OVERFLOWA Overflow ATmega2560 ATmega2561 TIMERS SIG INPUT Timer Counter5 ATmega640 ATmegal280 ATmegal28l CAPT vect CAPTURES Capture Event ATmega2560 ATmega2561 TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 COMPA vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARESA A TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 COMPB vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARESB B TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARESC C TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 OVF vect OVERFLOWS Overflow ATmega2560 ATmega2561 TWI vect SIG 2WIRE 2 wire Serial I
305. imilar to memcpy except the src string resides in pro gram space Returns The memopy function returns a pointer to dest 6 18 4 4 void x memmem P const void sZ size t len VOID P 52 size t len2 The memmem_P function is similar to memmem except that s2 is pointer to a string in program space Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 141 6 18 4 5 VOID P memrchr P VOID P src int val size t len The memrchr P function is like the memchr_P function except that it searches backwards from the end of the 1en bytes pointed to by src instead of forwards from the front Glibc GNU extension Returns The memrchr_P function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 18 4 6 int strcasecmp_P const char s1 52 Compare two strings ignoring case The strcasecmp_P function compares the two strings s1 and s2 ignoring the case of the characters Parameters 51 A pointer to a string in the devices SRAM 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 s1 is found respectively to be less than to match or be greater than s2 consequence of the ordering used by strcasecmp_P is that if s1 is an initial substring of s2 th
306. in modules which are compiled in strict ANSI mode To avoid that you can write instead of asm and volatile instead of volatile These are equivalent aliases Another problem with reused macros arises if you are using labels such cases you may make use of the special pattern which is replaced by a unique number on each asm statement following code had been taken from avr include iomacros h define loop until bit is clear port bit asm volatile N L sbic 0 1 n t N rjmp L N no outputs x N I SFR IO ADDR port I bit When used for the first time L_ may be translated to L_1404 the next usage might create 1405 or whatever In any case the labels became unique too Another option is to use Unix assembler style numeric labels They are explained in How do I trace an assembler file in avr gdb The above example would then look like define loop until bit is clear port bit LL asm volatile 1 0 1 n t rjmp 1b no outputs x I SFR IO ADDR port I bit 9 6 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 uintl6 t cnt asm volatile An L dll n t Generated on Mon May 12 09 55 09 2008 f
307. in number of the OCI A output within its port 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 TIMI 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 187 e 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 1 overflows Setting up interrupts is explained in greater detail in lt avr interrupt h gt Interrupts Note 3 The PWM is being used in 10 bit mode so we need a 16 bit variable to remember the current value Note 4 This section determines the new value of the PWM Note 5 Here s where the newly computed value is loaded into the PWM register Since we are in an interrupt routine it is safe to use a 16 bit assignment to the register Outside of an interrupt the assignment should only be performed with interrupts disabled if there s a chance that an interrupt routine could also access this register or another register that uses TEMP see the a
308. ine PRIULEASTS decimal printf format for uint_least8_t 6 5 2 40 define PRIuPTR PRIu16 decimal printf format for uintptr_t 6 5 2 41 define PRIX16 X uppercase hexadecimal printf format for uint16_t 6 5 2 42 define PRIx16 x hexadecimal printf format for uint16_t 6 5 2 43 define PRIX32 IX uppercase hexadecimal printf format for uint32_t 6 5 2 44 define PRIx32 Ix hexadecimal printf format for uint32_t 6 5 2 45 define PRIX8 X uppercase hexadecimal printf format for uint8_t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 28 6 5 2 46 define PRIx8 hexadecimal printf format for uint8_t 6 5 2 47 define PRIXFAST16 X uppercase hexadecimal printf format for uint_fast16_t 6 5 2 48 define PRIxFASTI16 x hexadecimal printf format for uint_fast16_t 6 5 2 49 define PRIXFAST32 uppercase hexadecimal printf format for uint_fast32_t 6 5 2 50 define PRIxFAST32 Ix hexadecimal printf format for uint_fast32_t 6 5 2 51 define PRIXFASTS X uppercase hexadecimal printf format for uint fast8 t 6 5 2 52 define PRIxFASTS x hexadecimal printf format for uint_fast8_t 6 5 2 53 define PRIXLEAST16 X uppercase hexadecimal printf format for uint_least16_t 6 5 2 54 define PRIXLEASTI6 x hexadecimal printf format for uint_least16_t 6 5 2 55 define PRIXLEAST32 IX uppercase hexadecimal printf
309. intf instead of fprintf mystream savestyping work but since avr gcc needs to re sort to pass all arguments of variadic functions on the 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 May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 57 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 int fputc int __c FILE stream int printf const char fmt int printf P const char fmt int vprintf const
310. inux project page 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 6 35 Combining and assembly source files For time or space critical applications it can often be desirable to combine 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 35 Combining and assembly source files 182 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 ru
311. iny88 AVR AT ny88 avr3 atmega603 AVR ATmega603 avr3 at43usb320 AVR AT43USB320 avr at43usb355 AVR AT43USB355 avr3 avr31 3 atmegal03 AVR ATmegal03 avr3 avr35 2 at90usb82 AVR_AT90USB82_ avr3 avr35 2 at90usb162 AVR_AT90USB162__ avr3 avr35 2 attiny167 _ AVR_ATtiny167__ avr3 at76c711 AVR AT76C711 avr4 atmega48 _ AVR ATmega48 avr4 atmega48p __AVR_ATmega48P__ avr4 atmega8 AVR_ATmega8__ avr4 atmega8515 AVR ATmega8515 avr4 atmega8535 AVR ATmega8535 avr4 atmega88 AVR ATmega88 avr4 atmega88p AVR ATmega88P avr4 atmega8hva __AVR_ATmega8HVA__ avr4 at90pwm 1 _ AVR AT90OPWMI avr4 at90pwm2 _ AVR_AT90PWM2__ avr4 at90pwm2b AVR_AT90PWM2B__ avr4 at90pwm3 AVR AT90PWM3 avr4 at90pwm3b AVR AT90OPWMS3B avr5 at90pwm216 _ _AVR_AT90PWM216__ avr5 at90pwm316 AVR AT90PWM316 avr5 at90can32 AVR_AT90CAN32__ avr5 at90can64 __AVR_AT90CAN64__ avr5 at90usb646 AVR_AT90USB646__ avr5 at90usb647 AVR ATO0USB647 avr5 atmegal6 __AVR_ATmegal6__ avr5 atmegal61 __AVR_ATmegal61__ avr5 atmegal62 __AVR_ATmegal62__ avr5 atmegal 3 AVR ATmegal63 avr5 atmegal64p __AVR_ATmegal64P__ avr5 atmega165 AVR ATmegal65 avr5 atmegal65p __AVR_ATmegal65P__ avr5 atmegal68 __AVR_ATmegal68__ avr5 atmegal68p __AVR_ATmegal68P__ Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 354
312. ion tree avr libc Open source code package Configure and build at the top of the source code tree Set PATH in order usr local bin mingw bin bin lt MikTex executables gt lt install directory gt bin lt Doxygen executables gt lt NetPBM executables gt lt fig2dev executables gt lt Ghostscript executables gt c cygwin bin Configure configure host avr prefix installdir enable doc disable versioned doc enable html doc enable pdf doc enable man doc mandir installdir man datadir installdir 2 gt amp 1 tee Spackage configure log Make make all install 2 gt amp 1 tee Spackage make log Manually change location of man page documentation Move the examples to the top level of the install tree Convert line endings in examples to Windows line endings Convert line endings in header files to Windows line endings Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 348 AVRDUDE Open source code package Configure and build at the top of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin install directory gt bin Set location of LibUSB headers and libraries export CPPFLAGS I libusb win32 device bin 1libusb version include
313. ired to turn off the watchdog early during program startup the datasheet recommends a sequence like the following include lt stdint h gt include lt avr wdt h gt uint8_t mcusr_mirror _attribute_ section noinit void get mcusr void attribute naked attribute section init3 void get mcusr void mcusr mirror MCUSR MCUSR 0 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 24 lt avr wdt h gt Watchdog timer handling 157 wdt_disable Saving the value of MCUSR in mcusr_mirror is only needed if the application later wants to examine the reset source but in particular clearing the watchdog reset flag before disabling the watchdog is required according to the datasheet Defines define wdt_reset asm volatile__ define wdt_enable value define wdt_disable define WDTO_15MS 0 define WDTO_30MS 1 define WDTO 60MS 2 define WDTO_120MS 3 define WDTO_250MS 4 define WDTO_500MS 5 define WDTO 1S 6 define WDTO 2S 7 define WDTO 4S 8 define WDTO 8S 9 6 24 2 Define Documentation 6 24 2 1 define wdt_disable Value asm volatile__ in tmp reg SREG X ali n t X out 0 1 n t N out 0 _ zero reg n t out SREG tmp reg n t no outputs I SFR IO ADDR WD CONTROL REG r uint8 t BV WD CHANGE BV WDE s roma Disabl
314. is not available when the compiler option mint8 is in effect 6 8 3 26 typedef uint8 t uint least8 t unsigned int with at least 8 bits 6 8 3 27 typedef uint64 t uintmax t largest unsigned int available 6 8 3 28 typedef uint16 t uintptr t Unsigned pointer compatible type 6 9 lt stdio h gt Standard IO facilities 6 9 1 Detailed Description include lt stdio h gt 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 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 May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 54 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
315. istcheck and make sure it succeeds This will create the source tarball Tag the release cvs tag avr libe major minor patch release Upload the tarball to savannah Update the NEWS file and commit to cvs Add Changes since avr libc major minor patch 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 May 12 09 55 09 2008 for avr libc by Doxygen 9 15 Acknowledgments 367 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 tag avr libc 1_0 release set version to 1 0 0 lt date gt set version to 1 0 1 cvs tag avr libc 1 0 l release 1 cvs tag avr libc 1_2 branchpoint set version to 1 3 0 lt date gt cvs tag b avr libc 1 2 branch set version to 1 1 90 lt date gt set version to 1 2 cvs tag avr libc 1_2 release 1 cvs tag avr libc 2 0 branchpoint set version to 2 1 0 lt date gt Figure 9 Release tree 9 15 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
316. ject 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 and can be accessed inside putchar using fdev_get_udata 6 38 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 38 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 takes care of converting the internal newline n into its external representation carriage return line feed V r n Character input is organized as a line buffered operation that allows to minimally edit the current line until it is sent to the application when either a carriage return Vr or newline character is received from the terminal The line editing functions implemented are b back space or 1177 delete 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
317. k nl dimitri doxygen gt Download and install Install NetPBM Version 10 27 0 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 345 From the GNUWin32 project http gnuwin32 sourceforge net packages html Download and install Install fig2dev Version 3 2 Patchlevel 5 alpha7 From WinFig 1 71 lt http www schmidt web berlin de winfig gt Unzip the download file and install in a location of your choice Install MiKTex Version 2 5 lt http miktex org gt Download and install Install Ghostscript Version 8 54 lt http www cs wisc edu ghost gt Download and install Set the TEMP and TMP environment variables to c temp or to the short file name version This helps to avoid NTVDM errors during building 9 11 13 Building the Toolchain for Windows All directories in the PATH enviornment variable should be specified using their short filename 8 3 version This will also help to avoid NTVDM errors during building These short filenames can be specific to each machine Build the tools below in MSYS Binutils Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin Generated on Mon May 12 09 55 09 2008 for
318. ken 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 9 2 3 Tunables for malloc There are a number of variables that can be tuned to adapt the behavior of malloc to the expected requirements and constraints of the application Any changes to these tunables should be made before the very first call to malloc Note that some library functions might also use dynamic memory notably those from the lt stdio h gt Stan dard IO facilities so make sure the changes will be done early enough in the startup sequence The variables malloc heap start and malloc heap end can be used to restrict the malloc function to a certain memory region These variables are stati cally initialized to point to __ heap start and heap end respectively where heap
319. l 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 12 2 Define Documentation 6 12 2 1 define boot is spm interrupt SPM REG uint8 t BV SPMIE Check if the SPM interrupt is enabled 6 12 2 2 define boot 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 BLB11 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 97 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
320. l at90s1200 AVR_AT90S1200__ attiny11 _ AVR AT nyll avrl attiny12 _ AVR AT nyl2 avri attiny15 AVR ATt nyl5 avri attiny28 AVR AT ny28 avr2 at90s2313 AVR AT908S2313 avra at90s2323 AVR AT9082323 avra at90s2333 AVR_AT90S2333__ avr2 at90s2343 AVR_AT90S2343__ avr2 attiny22 __AVR_ATtiny22__ avr2 attiny26 AVR AT ny26 avr2 at90s4414 AVR_AT90S4414__ avr2 at90s4433 AVR_AT90S4433__ avr2 at90s4434 AVR_AT90S4434__ avr2 at90s8515 AVR_AT90S8515_ avr2 at90c8534 AVR_AT90C8534__ avr2 at90s8535 AVR_AT90S8535_ avr2 avr25 1 at86rf401 AVR ATS6RF401 avr2 avr25 1 attiny13 AVR AT nyl3 avr2 avr25 1 attiny2313 AVR_ATtiny2313__ avr2 avr25 1 attiny24 AVR AT ny24 avr2 avr25 1 attiny25 AVR AT ny25 avr2 avr25 1 attiny261 AVR_ATtiny261__ avr2 avr25 1 attiny43u __AVR_ATtiny43U__ avr2 avr25 1 attiny44 __AVR_ATtiny44__ Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 353 Architecture MCU name Macro avr2 avr25 1 attiny45 _ AVR AT ny45 avr2 avr25 1 attiny461 AVR ATt ny461 avr2 avr25 1 attiny48 AVR AT ny48 avr2 avr25 1 attiny84 AVR AT ny84 avr2 avr25 1 attiny85 AVR AT ny85 avr2 avr25 1 attiny861 AVR ATt ny861 avr2 avr25 1 att
321. 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 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 character after the open bracket or the circumflex any other position will end the set The hyphen character is also special when placed between two other characters it adds all intervening characters to the set To include a hyphen make it the last character before the final close bracket For instance 0 9 means the set of every thing except close bracket zero through nine and hyphen The string ends with the appearance of a character not in the or with a circumflex in set or when the field width runs out Note that usage of this conversion enlarges the stack expense p Matches a pointer value as printed by p in printf the next pointer must be a pointer to void n Nothing is expected instead the number
322. len s if the character is not found 6 18 4 11 int stremp P const char s1 52 The stremp_P function is similar to stremp except that s2 is pointer to a string in program space Returns The strcmp function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcmp P is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 6 18 4 12 char x char dest P src The strcpy function is similar to strcpy except that src is a pointer to a string in program space Returns The strcpy P function returns a pointer to the destination string dest Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 143 6 18 4 13 size_t strcspn P const char s PGM P reject The strespn_P function calculates the length of the initial segment of s which consists entirely of characters not in reject This function is similar to strcspn except that reject is a pointer to a string in program space Returns The strcspn function returns the number of characters in the initial segment of s which are not in the string reject The terminating zero is not considered as a part of string 6 18 4 14 size t strlcat P char x dst P size t siz Concatenate two st
323. lename suffix given on the command line not based on the actual filename from the file system Alternatively the language explicitly be specified using the assembler with cpp option 9 5 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 gt 200000 edges s fuzz 8 clocks in ISR until TCNTO is set section text global main Note 5 main rcall ioinit PRE rjmp ib Note 6 global TIMERO OVF vect Note 7 TIMERO OVF vect lu inttmp 256 tmconst fuzz out _ IO ADDR TCNTO inttmp Note 8 in intsav SFR IO ADDR SREG Note 9 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 284 sbic rjmp sbi rjmp 1 4 cbi out reti ioinit sbi ldi out ldi out ldi out sei ret FR IO ADD FR IO ADD FR IO ADD FR IO ADD FR IO ADD work BV T S FR IO ADD work BV C S FR IO ADD work 256 S FR IO ADD R PORTD R PORTD R PORTD R SREG R DDRD OIEO R TIMSK S00 R TCCRO tmconst R TCNTO global _ vector default vector
324. ler Cookbook 292 Constraint Used for Range a Simple upper registers r16 to r23 b Base pointer registers y Z pairs d Upper register r16 to 131 e Pointer register pairs y Z q Stack pointer register SPH SPL r Any register r0 to 131 t Temporary register r0 W Special upper register 124 126 r28 r30 pairs x Pointer register pair X X 127126 y Pointer register pair Y y 129 r28 7 Pointer register pair Z z r31 130 G Floating point constant 0 0 I 6 bit positive integer 0 to 63 constant J 6 bit negative integer 63 to 0 constant K Integer constant 2 L Integer constant 0 1 Lower registers rO to r15 M 8 bit integer constant 0 to 255 N Integer constant 1 O Integer constant 8 16 24 P Integer constant 1 Q GCC gt 4 2 x A memory address based on Y or Z pointer with displacement R GCC gt 4 3 x Integer 6 to 5 constant The selection of the proper contraint depends on the range of the constants or registers which must be acceptable to the AVR instruction they are used with The C compiler doesn t 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 assembler And of course the assembler will fail with some cryptic output or internal errors For example if you specify the constraint
325. ler value UBRR VALUE 6 30 2 4 define UBRRL VALUE Output macro from lt util setbaud h gt Contains the lower byte of the calculated prescaler value UBRR VALUE 6 30 2 5 define USE 2X 0 Output bacro from lt util setbaud h gt Contains the value 1 if the desired baud rate tolerance could only be achieved by setting the U2X bit in the UART configuration Contains 0 otherwise 6 31 lt util twi h gt TWI bit mask definitions 6 31 1 Detailed Description include util twi h 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 START 0x10 define TW MT SLA ACK 0x18 fdefine 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 31 lt util twi h gt TWI bit mask definitions 173 define TW MR SLA ACK 0x40 define TW MR SLA 0x48 define TW DATA ACK 0x50 define TW DATA 0x58 define TW ST 5 8 define TW ST LOST SLA OxBO define TW ST DATA ACK 0xB8 define TW ST 0xCO define TW ST LAST DATA 0xC8 fdefine TW SR SLA ACK 0x60 define TW SR LOST SLA ACK 0x68
326. lers might not do that optimization and as the standard guarantees the initialization it is safe to rely on it Back to FAQ Index Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 317 9 10 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 usually best to use the ISR macro when declaring the interrupt function and to ensure that interrupts are still disabled when accessing those 16 bit timer registers Within the main program access to those registers could be encapsulated in calls to the
327. libc by Doxygen 6 14 lt avr fuse h gt Fuse Support 106 Each device I O header file also defines macros that provide default values for each fuse byte that is available LFUSE DEFAULT is defined for a Low Fuse byte HFUSE DEFAULT is defined for a High Fuse byte EFUSE DEFAULT is defined for Ex tended Fuse byte If FUSE MEMORY SIZE gt 3 then the I O header file defines macros that pro vide default values for each fuse byte like so FUSEO0 DEFAULT FUSEI DEFAULT FUSE2 DEFAULT FUSE3 DEFAULT FUSE4 DEFAULT API Usage Example Putting all of this together is easy include avr io h FUSES low LFUSE DEFAULT high FUSE 570 amp FUSE BOOTSZ1 amp FUSE EESAVE amp FUSE SPIEN amp FUSE JTAGEN extended EFUSE DEFAULT int main void return 0 Or include avr io h fuse t fuse attribute section fuse low LFUSE DEFAULT high FUSE BOOTSZO amp FUSE BOOTSZ1 amp FUSE EESAVE amp FUSE SPIEN amp FUSE JTAGEN extended EFUSE DEFAULT int main void return 0 However there are a number of caveats that you need to be aware of to use this API properly Be sure to include avr io h to get all of the definitions for the API The FUSES macro defines a global variable to store the fuse data This variable is assigned to its own linker section Assign the desired fuse values immediately in the variable initial ization Generated on Mon
328. libc subscribe to the list so you will usually be able to get your problem resolved You can subscribe to the list at http lists nongnu org mailman listinfo avr gcc list Before posting to the list you might want to try reading the Frequently Asked Ques tions chapter of this document Note If you think you ve found a bug or have a suggestion for an improvement ei ther in this documentation or in the library itself please use the bug tracker at https savannah nongnu org bugs group avr libc to ensure the issue won t be forgotten 1 2 General information about this library In general it has been the goal to stick as best as possible to established standards while implementing this library Commonly this refers to the C library as described by the ANSI X3 159 1989 and ISO IEC 9899 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 purely AVR specific like the entire program space string interface Unless otherwise noted functions of this library are not guaranteed to be reentrant In particular any functions that store local state are known to be non reentrant as well as functions that manipulate IO registers like the EEPROM access routines If these Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 1 3 Supported Devices 3 functions are used withi
329. ll functionality including the floating point conversions is required the follow ing options should be used Wl u vfprintf lprintf flt lm Limitations The specified width and precision can be at most 255 Notes For floating point conversions if you link default or minimized version of vfprintf the symbol will be output and double argument will be skiped So you output below will not be crashed For default version the width field and the pad to left symbol minus option will work in this case The hh length modifier is ignored char argument is promouted to int More exactly this realization does not check the number of h symbols But the 11 length modifier will to abort the output as this realization does not operate long long arguments The variable width or precision field an asterisk symbol is not realized and will to abort the output 6 9 3 33 int vfprintf P FILE x stream const char x fmt va list Variant of v printf that uses a fmt string that resides in program memory Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 69 6 9 3 34 int vfscanf FILE stream const char x fmt va list Formatted input This function is the heart of the scanf family of functions Characters are read from stream and processed in a way described by fmt Conversion results will be assigned to the parameters passed via ap
330. llocation 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 9 3 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 9 3 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 sections dicussed below Note The avr size program part of binutils coming from a Unix background doesn t account for the data initialization space added to the text section so in order to know how much flash the final program will consume one needs to add the valu
331. lt r addr32 N I SFR IO ADDR RAMPZ X Tp30T yg N _ result 8 34 2 3 define _ ELPM enhanced Value Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference 243 _ extension N uint32 t __addr32 uint32 t addr uint8 t _ result N asm N N 2 SLI TANNET N movw r30 1 n t N elpm 0 Z n t N r result N Wa s lt addr32 N I SFR IO ADDR RAMPZ Nr 30 GSI _ result N 8 34 2 4 define _ ELPM_word_classic_ addr Value __extension__ uint32_t __addr32 uint32_t addr uintl6 t _ result N asm N N out 2 1 ANNET N mov 1 n t mov r30 A1 n t elpm n t mov 0 ro n t Yn D 27 n t adiw r30 1 n t adc r0 zero reg n t N out 2 ro A Np N elpm mov BO ro r result mr 24432 I SFR IO ADDR RAMPZ N Qm x30 N _ result 8 34 2 5 define _ ELPM_word_enhanced__ addr Value __extension__ uint32 t __addr32 uint32 t addr uintl6 t result N asm N Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference 244 out 2 C1 ima juove 30 SIT TINET elpm A0 Z AnNt N elpm BO 7 AS VM N r resul
332. m read block void dst const void x _ _src size t _n static Read a block of __n bytes from EEPROM address __src to SRAM dst 6 13 3 2 static _ ATTR_PURE inline uint8 t eeprom read byte const uint8 static Read one byte from EEPROM address p 6 13 3 3 static PURE inline uint32 t eeprom read dword const uint32 static Read 32 bit double word little endian from EEPROM address p 6 13 3 4 static _ ATTR PURE inline uint16 t eeprom read word const uintl6 t p static Read one 16 bit word little endian from EEPROM address p Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 14 lt avr fuse h gt Fuse Support 104 6 13 3 5 static inline void eeprom write block const void __src void dst size t n static Write a block of __n bytes to EEPROM address __dst from __ src Note The argument order is mismatch with common functions like strcpy 6 13 3 6 static inline void eeprom write byte uint8 t p uint8 t value static Write a byte value to EEPROM address p 6 13 3 7 static inline void eeprom write dword uint32 t x p uint32 t _value static Write 32 bit double word value to EEPROM address p 6 13 3 8 static inline void eeprom write word uint16 t x _ uint16_t value static Write a word value to EEPROM address _ 6 14 lt avr fuse h gt Fuse Support Introduction The Fuse API
333. mand 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 See also the entry in the FAQ explaining this Conventionally Makefiles use the make macro LDLIBS to keep track of 1 and possibly L options that should only be appended to the C compiler command line when linking the final binary In contrast the macro LDFLAGS is used to store other command line options to the C compiler that should be passed as options during the linking stage The difference is that options are placed early on the command line while libraries are put at the end since 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
334. mega169p atmega329 atmega329p Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 1 3 Supported Devices e atmega3290 atmega3290p atmega649 atmega6490 Lighting AVR Devices at90pwml at90pwm2 at90pwm2b at90pwm216 at90pwm3 at90pwm3b at90pwm316 Smart Battery AVR Devices atmega8hva atmegal6hva atmega32hvb atmega406 USB AVR Devices at90usb82 at90usb162 at90usb646 at90usb647 at90usb1286 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 1 3 Supported Devices at90usb1287 atmega32u4 XMEGA Devices atxmegal28al atxmega64al Miscellaneous Devices at94K 2 at76c711 3 at43usb320 at43usb355 at86rf401 Classic AVR Devices at90s1200 1 at90s2313 at90s2323 at90s2333 at90s2343 at90s4414 at90s4433 at90s4434 at90s8515 at90c8534 at90s8535 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 1 4 avr libc License 8 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
335. mega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 USARTI SIG USARTI Rx ATmegal62 RXC_vect USARTI Complete RECV USARTI SIG USARTI Rx AT90CANI28 AT90CAN32 AT90CANGA RX vect UARTI Complete ATmegal28 ATmegal284P ATmega64 RECV ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 125 Vector name Old vector Description Applicable for device name USARTI SIG USARTI Tx ATmegal62 TXC vect USARTI Complete TRANS USARTI SIG USARTI Tx AT90CANI28 AT90CAN32 AT90CAN64 TX vect UARTI Complete ATmegal28 ATmegal284P ATmega64 TRANS ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 USARTI SIG USARTI Data AT90CANI28 AT90CAN32 AT90CANGA UDRE vect UARTI Register Empty ATmegal28 ATmegal284P ATmegal62 DATA ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 USART2_ SIG_ USART2 Rx
336. mega324P ATmegal64P ATmega644P ATmega644 ATtinyl3 AT 0 15 ATtiny26 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 9005 1287 AT90USB1286 AT90USB647 AT90USB646 ANALOG_ COMP_0_vect SIG_ Analog Com COMPARATOR parator 0 AT90PWM3 AT90PWM2 AT90PWM 1 ANALOG_ COMP_1_vect SIG_ COMPARATOR Analog Com parator 1 AT90PWM3 AT90PWM2 AT90PWM1 ANALOG_ COMP_2_vect SIG Analog Com COMPARATOR parator 2 AT90PWM3 AT90PWM2 AT90PWM1 ANALOG_ COMP_vect SIG_ COMPARATOR Analog Com parator AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal284P ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmega168 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 112 Vector name Old vector Description Applicable for device name ANA_ SIG_ Analog Com 9051200 419052313 AT90S2333 COMP_vect COMPARATOR pa
337. mplement this see note 2 As an alternative method to fdevopen the macro setup stream might be used to setup a user supplied FILE structure It should be noted that the automatic conversion of a newline character into a carriage return newline sequence breaks binary transfers If binary transfers are desired no automatic conversion should be performed but instead any string that aims to issue a 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 udata The back end put and get functions can then extract this user data using fdev get udata and act Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 55 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 betwe
338. n 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 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 rat
339. n AT90CANI28 AT90CAN32 AT90CAN64 SERIAL terface ATmegal28 ATmegal284P ATmegal6 ATmegal63 ATmegal68P ATmega32 AT mega323 ATmega328P ATmega32HVB ATmega406 ATmega48P ATmega64 ATmega8 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny48 AT90USB1287 9005 1286 AT90USB647 AT90USB646 TXDONE_ SIG_ Transmission AT86RF401 vect TXDONE Done Bit Timer Flag 2 Interrupt TXEMPTY_ SIG_TXBE Transmit Buffer AT86RF401 vect Empty Bit Itmer Flag 0 Interrupt UARTO RX SIG UARTO Rx ATmegal61 vect UARTO Complete RECV UARTO TX SIG UARTO Tx 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 UARTI TX SIG UARTI Tx ATmegal6l vect UARTI Complete TRANS UARTI SIG UARTI Data ATmegal61 UDRE vect UARTI Register Empty DATA Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 124 Vector name Old vector Description Applicable for device name UART_RX_ SIG_UART_ UART Com AT90S2313 419052333 AT90S4414 vect RECV plete AT90S4433 AT90S4434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_TX_ SIG_UART_ UART Tx Com
340. n 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 I to it clear the interrupt bit The solution is simple writing a logical 1 to it requires only a single OUT instruction and it is clear that only this single interrupt request bit will be cleared There is no need to perform a read modify write cycle like an SBI instruction since all bits in these control registers are interrupt bits and writing a logical O to the remaining bits as it is done by the simple OUT instruction will not alter them so there is no risk of any race condition that might accidentally clear another interrupt request bit So instead of writing Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 332
341. n automatic variable inside a function that is allocated on the stack you can do this void foo void char buffer 10 for unsigned char i 0 i lt 5 itt strcpy_P buffer PGM P pgm read word amp string table i Display buffer on LCD return Here the string_table array is stored in Program Space so we access it normally as if were stored in Data Space then take the address of the location we want to access and use the address as a parameter to pgm_read_word We use the pgm_read_ word macro to read the string pointer out of the string_table array Remember that a pointer is 16 bits or word size The pgm_read_word macro will return a 16 bit unsigned integer We then have to typecast it as a true pointer to program memory PGM_P This pointer is an address in Program Space pointing to the string that we want to copy This pointer is then used as a parameter to the function st rcpy_P The function st rcpy P is just like the regular st rcpy function except that it copies a string from Program Space the second parameter to a buffer in the Data Space the first parameter There are many string functions available that work with strings located in Program Space All of these special string functions have a suffix of P in the function name and are declared in the lt avr pgmspace h gt header file 9 4 5 Caveats The macros and functions used to retrieve data from the Program Space have to gen erate
342. n both standard and interrupt contexts 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 megaAVR Devices atmega 103 atmega128 atmega1280 atmega1281 atmega1284p atmega16 161 atmega162 atmega 163 atmegal64p atmega 165 atmega165p atmega 168 atmegal68p atmega2560 atmega2561 atmega32 atmega323 atmega324p atmega325 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 1 3 Supported Devices atmega325p atmega3250 atmega3250p atmega328p atmega48 atmega48p atmega64 atmega640 atmega644 atmega644p atmega645 atmega6450 atmega8 atmega88 atmega88p atmega8515 atmega8535 tinyAVR Devices attiny11 1 attiny12 1 attiny 13 attiny15 1 attiny22 attiny24 attiny25 attiny26 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 1 3 Supported Devices attiny26 1 attiny28 1 attiny2313 attiny43u attiny44 attiny45 attiny46 1 attiny48 attiny84 attiny85 attiny861 attiny88 Automotive AVR Devices e atmega32cl atmega32m1 attiny167 CAN AVR Devices at90can32 at90can64 at90can128 LCD AVR Devices atmega169 at
343. n the compiler option mint8 is in effect 6 18 3 10 prog uint8 t Type of an uint8 t object located in flash ROM Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 140 6 18 3 11 prog void Type of a void object located in flash ROM Does not make much sense by itself but be used to declare a void x object in flash ROM 6 18 4 Function Documentation 6 18 41 VOID P memchr P VOID P s int val size t len Scan flash memory for a character The memchr_P function scans the first len bytes of the flash memory area pointed to by s for the character va1 The first byte to match va1 interpreted as an unsigned character stops the operation Returns The memchr P function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 18 4 2 int memcmp P const void s7 VOID P 52 size t len Compare memory areas memcmp_P function compares the first Len bytes of the memory areas s1 and flash s2 The comparision is performed using unsigned char operations Returns memcmp_P function returns an integer less than equal to or greater than zero if the first Len bytes of s1 is found respectively to be less than to match or be greater than the first 1en bytes of s2 6 18 4 3 void x memcpy_P void dest PGM VOID P src size_t n The memcpy_P function is s
344. n the out going PWM signal generation the incoming PWM decoding had to be adjusted to the constraints set by the outgoing PWM As PWM generation toggles the counting direction of timer 0 between up and down after each 256 timer cycles the current time cannot be deduced by reading TCNTO only but the current counting direction of the timer needs to be considered as well This requires servicing interrupts whenever the timer hits TOP 255 and BOTTOM 0 to learn about each change of the counting direction For PWM generation itis usually desired to run it at the highest possible speed so filtering the PWM frequency from the modulated output signal is made easy Thus the PWM timer runs at full CPU speed This causes the overflow and compare match interrupts to be triggered each 256 CPU clocks so they must run with the minimal number of processor cycles possible in order to not impose a too high CPU load by these interrupt service routines This is the main reason to implement the entire interrupt handling in fine tuned assembly code rather than in C In order to verify parts of the algorithm and the underlying hardware the demo has been set up in a way so the pin compatible but more expensive ATtiny45 or its siblings ATtiny25 and ATtiny85 could be used as well In that case no separate assembly code is required as two timer channels are avaible 6 35 1 Hardware setup The incoming PWM pulse train is fed into PB4 It will generate a pin cha
345. ncpy P char size t size t strnlen P size_t char strpbrk P const s PGM P accept ATTR_PURE PGM P strrchr P PGM_P int __val char strsep P char sp PGM P delim size tstrspn P const char s PGM P accept PURE char strstr P const char PGM P ATTR PURE void memmem_P const void x size t VOID P size t ATTR PURE char strcasestr P const char x P PURE 6 18 2 Define Documentation 6 18 2 1 define P const prog char Used to declare a variable that is a pointer to a string in program space 6 18 2 2 ftdefine 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 137 6 18 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 18 2 4 define read byte near address short LPM uintl6 t address short Read a byte from the program space with a 16 bit near address Note The address is a byte
346. ne AVR_LIBC_VERSION__ 10602UL 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 23 27 define AVR LIBC VERSION STRING 1 6 2 String literal representation of the current library version 6 24 lt avr wdt h gt Watchdog timer handling 6 24 1 Detailed Description include avr wdt h This header file declares the interface to some inline macros handling the watchdog timer present in many AVR devices In order to prevent the watchdog timer configura tion from being accidentally altered by a crashing application a special timed sequence is required in order to change it The macros within this header file handle the required sequence automatically before changing any value Interrupts will be disabled during the manipulation Note Depending on the fuse configuration of the particular device further restrictions might apply in particular it might be disallowed to turn off the watchdog timer Note that for newer devices ATmega88 and newer effectively any AVR that has the op tion to also generate interrupts the watchdog timer remains active even after a system reset except a power on condition using the fastest prescaler value approximately 15 ms It is therefore requ
347. nge interrupt there on eache edge of the incoming signal The outgoing PWM is generated through OCOB of timer channel 0 PB1 For demon stration purposes a LED should be connected to that pin like one of the LEDs of an STK500 The controllers run on their internal calibrated RC oscillators 1 2 MHz on the AT tiny13 and 1 0 MHz on the ATtiny45 6 35 2 code walkthrough 6 35 21 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 35 Combining and assembly source files 183 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 it starts timer 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 Like
348. nite double x static Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 37 The isfinite function returns a nonzero value if xis finite not plus or minus infinity and not NaN 6 6 3 20 int isinf double x The function isinf returns 1 if the argument xis positive infinity 1 if __x is negative infinity and 0 otherwise 6 6 3 21 int isnan double x The function isnan returns 1 if the argument __x represents a not a number NaN object otherwise 0 6 6 3 22 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 6 6 3 23 double log double x The log function returns the natural logarithm of argument x 6 6 3 24 double log10 double x The log10 function returns the logarithm of argument x to base 10 6 6 3 25 long Irint double x The lrint function rounds the nearest integer rounding the halfway cases to the even integer direction That is both 1 5 and 2 5 values are rounded to 2 This function is similar to rint function but it differs in type of return value and in that an overflow is possible Returns The rounded long integer value If __x is not a finite number or an overflow was this realization returns the LONG MIN value 0x80000000 6 6 3 26 long Iround double x
349. ns that require interrupt controlled EEPROM access to ensure that no time will be wasted in spinloops will have to deploy their own implementation Note of the read write functions first make sure the EEPROM is ready to be ac cessed Since this may cause long delays if a write operation is still pending time critical applications should first poll the EEPROM e g using eeprom is ready before attempting any actual I O But this functions are not wait until SELFPRGEN in SPMCSR becomes zero Do this manually if your softwate con tains the Flash burning Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 102 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 All write functions force erase_and_write programming mode compatibility defines define _EEPUT addr val eeprom write byte uint8 t uint8 t val define _ EEGET var addr var eeprom_read_byte const uint8_t x addr Defines define EEMEM __attribute__ section eeprom define eeprom_is_ready define eeprom_busy_wait do while eeprom_is_ready Functions static PURE inline__ uint8_t eeprom_read_byte const uint8_t __p static
350. nst char fmt int fscanf P FILE stream const char fmt int scanf const char fmt int scanf P const char fmt int vscanf const char fmt va list int sscanf const char buf const char fmt int sscanf P const char buf const char fmt int fflush FILE xstream 8 41 stdlib h File Reference 8 41 1 Detailed Description Data Structures struct div t struct ldiv t Non standard i e non ISO C functions define RANDOM MAX Ox7FFFFFFF char x itoa int __val char __s int radix char Itoa long int __val char s int radix char utoa unsigned int val char x__s int radix char ultoa unsigned long int __val char __s int radix long random void void srandom unsigned long __ seed long random unsigned long ctx Conversion functions for double arguments Note that these functions are not located in the default library 1ibc a but in the mathematical library 1ibm a So when linking the application the 1m option needs to be specified define DTOSTR ALWAYS SIGN 0x01 define DTOSTR PLUS SIGN 0x02 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 41 stdlib h File Reference 254 define DTOSTR_UPPERCASE 0x04 char dtostre double val char flags char dtostrf double __ val signed char __ width unsigned char __ prec char 8 s unsigned char __prec unsigned
351. nt main void return 0 However there are a number of caveats that you need to be aware of to use this API properly Be sure to include lt avr io h gt to get all of the definitions for the API The LOCKBITS macro defines a global variable to store the lockbit data This variable is assigned to Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 lt gt Program Space Utilities 134 its own linker section Assign the desired lockbit values immediately in the variable initialization The lock section in the ELF file will get its values from the initial variable assignment ONLY This means that you can NOT assign values to this variable in functions and the new values will not be put into the ELF lock section The global variable is declared in the LOCKBITS macro has two leading underscores which means that it is reserved for the implementation meaning the library so it will not conflict with a user named variable You must initialize the lockbit variable to some meaningful value even if it is the de fault value This is because the lockbits default to a logical 1 meaning unprogrammed Normal uninitialized data defaults to all locgial zeros So it is vital that all lockbits are initialized even with default data If they are not then the lockbits may not pro grammed to the desired settings and can possibly put your device into an unrecoverable state Be sure to have the
352. nt16_t data TE Y A TEST 1 yn P E PA EA E M E 8 5 2 8 fidefine boot page fill normal address data Value _ extension N Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 5 boot h File Reference 228 asm volatile movw r0 3 n t movw r30 2 n t sts 0 1 n t spm n t tetr sline 1 SFR_MEM_ADDR SPM REG uint8 t BOOT PAGE FILL uint16 t address Le uint16_t data EO sO MESIN B LEA ED EE A E a Lr 8 5 2 9 define boot page write alternate address Value _ extension asm volatile movw r30 2 n t sts 0 1 n t spm n t word Oxffff n t nop n t i SFR MEM ADDR SPM REG r uint8 t BOOT PAGE WRITE my uint16 t address E30 r3 ERE E Ld 8 5 2 10 define boot page write extended address Value extension asm _ volatile movw r30 A3 n t sts 81 O3Xn Nc sts 0 2 n t spm n t su i su 1 SFR_MEM_ADDR SPM_REG _SFR_MEM_ADDR RAMPZ uint8_t BOOT_PAGE_WRITE uint32_t address rm Bl um P A AER di rm Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 5 boot h File Reference 229 r30 8 5 2 11 define boot page write normal address Value extension 4
353. nul 87 strcmp 87 strcpy 88 strcspn 88 strlcat 88 strlcpy 89 strlen 89 strlwr 89 strncasecmp 89 strncat 90 strncmp 90 strncpy 90 strnlen 90 strpbrk 91 strrchr 91 strrev 91 strsep 91 strspn 92 strstr 92 strtok 92 strupr 93 avr version AVR LIBC DATE 154 WDTO 15 158 WDTO_250MS 158 WDTO_2S 158 WDTO_30MS 158 WDTO_4S 158 WDTO_500MS 158 WDTO_60MS 158 WDTO_8S 158 avrdude usage 361 avrprog usage 361 BADISR_vect avr_interrupts 126 BAUD_TOL util_setbaud 170 bit_is_clear avr_sfr 151 bit_is_set avr_sfr 151 boot h 222 boot_lock_bits_set 224 boot_lock_bits_set_alternate 224 boot_page_erase_alternate 224 boot_page_erase_extended 225 boot_page_erase_normal 225 boot_page_fill_alternate 225 boot_page_fill_extended 226 boot_page_fill_normal 226 boot_page_write_alternate 227 boot_page_write_extended 227 boot_page_write_normal 228 boot rww enable 228 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 378 boot_rww_enable_alternate 228 ceil boot_is_spm_interrupt avr_math 34 avr_boot 95 clearerr boot_lock_bits_set avr_stdio 60 avr boot 95 cli boot lock bits set safe avr interrupts 126 avr boot 96 clock prescale set boot lock fuse bits get power h 246 avr boot 96 Combining C and assembly source files boot page erase 180 avr boot 96 copysign boot page erase safe avr math 34 avr boot 97 COS
354. o link all of the object modules into a final executable The two projects GCC and Binutils are very much interrelated and many of the same volunteers work on both open source projects When GCC is built for the AVR target the actual program names are prefixed with avr So the actual executable name for AVR GCC is avr gcc The name avr gcc is used in documentation and discussion when referring to the program itself and not just the whole AVR GCC system See the GCC Web Site and GCC User Manual for more information about GCC 9 1 4 GNU Binutils The name GNU Binutils stands for Binary Utilities It contains the GNU assembler gas and the GNU linker ld but also contains many other utilities that work with binary files that are created as part of the software development toolchain Again when these tools are built for the AVR target the actual program names are prefixed with avr For example the assembler program name for a native assembler is as even though in documentation the GNU assembler is commonly referred to as gas But when built for an AVR target it becomes avr as Below is a list of the programs that are included in Binutils avr as The Assembler avr ld The Linker avr ar Create modify and extract from libraries archives avr ranlib Generate index to library archive contents avr objcopy Copy and translate object files to different formats avr objdump Display information from obj
355. o 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 are 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 9 14 1 2 Development Versions major version number of a development se ries 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 versions in development in cvs will also always have the date appended as a fourth version number The format of the date will be YYYYMMDD 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 9 14 2 Releasing AVR Libc The information in this section is only relevant to AVR Libc developer
356. 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 71 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 conversions described above are available except the floating point conversions and the width is limited to 255 characters The float point conversion will be available in the extended version provided by the library 1ibscanf flt a Also in this case the width is not limited exactly it is limited to 65535 characters To link a program against the extended version use the following compiler flags in the link stage Wl u vfscanf lscanf flt 1m A third version is available for environments that are tight on space In addition to the restrictions of the
357. omatic 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 e 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 358 9 12 2 Options for the assembler avr as 9 12 2 1 Machine specific assemble
358. ompare two strings ignoring case The strcasecmp function compares the two strings s1 and s2 ignoring the case of the characters Returns The strcasecmp function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than 52 A consequence of the ordering used by strcasecmp is that if 51 is an initial substring of s2 then s1 is considered to be less than s2 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 88 6 11 3 13 char x strcasestr const char s1 const char s2 The strcasestr function finds the first occurrence of the substring s2 in the string s1 This is like strstr except that it ignores case of alphabetic symbols in searching for the substring Glibc GNU extension Returns The strcasestr function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of zero length the function returns s1 6 11 3 14 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 6 11
359. ompile time Back to FAQ Index 9 10 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 326 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 the linker command line options that are required to move the memory regions away from their respective standard locations in
360. on x Note 4 a4 81 30 cpi r24 0x01 1 a6 29 f0 breq 10 Oxb2 vector 8 0 56 gt a8 20 91 61 00 145 r18 0x0061 30 91 62 00 145 r19 0 0062 b0 ef cf rjmp 34 0x90 vector 8 0 34 gt if pwm TOP direction DOWN break case DOWN if pwm 0 b2 20 91 61 00 145 r18 0x0061 b6 30 91 62 00 1ds r19 0x0062 ba 21 50 subir tle O0xO0Il 1 bc 30 40 sbor 19 0x00 7 0 be 30 93 62 00 sts 0x0062 r19 c2 20 93 61 00 sts 0x0061 r18 cor 21 15 ep f18 ri c8 31 05 rl9 T ca 11 f7 brne 60 0x90 vector 8 0 34 gt direction UP cc 10 92 60 00 sts 0x0060 r1 dO df cf rjmp 66 0x90 vector 8 0 34 gt switch direction x Note 4 case UP if pwm TIMER TOP direction DOWN d2 81 eO ldi r24 0x01 1 d4 80 93 60 00 sts 0x0060 r24 de db cf rjmp 74 0x90 vector 8 0 34 gt 000000da lt ioinit gt OCR pwm Note 5 void ioinit void x Note 6 da 83 8 141 r24 0x83 131 dc 8f bd out 0x2f r24 47 x Start timer 1 x TCCRIA TCCRIB could actually be the same register so x take care to not clobber it Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 194 x TCCRIB TIMER1_CLOCKSOURCE de 8e b5 in r24 0x2e 46 0 81 60 ori r24 0 01 1 e2 8e bd out 0x2e r24 46 if defined TIMER1 SETUP HOOK TIMER1 SETUP HOOK
361. on of microsecond and millisecond delays directly using the application supplied macro CPU as the CPU clock frequency in Hertz Functions e void delay us double us void delay ms double __ms 6 27 2 Function Documentation 6 27 2 1 void delay ms double Perform a delay of __ms milliseconds using delay loop 20 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 28 lt util delay_basic h gt Basic busy wait delay loops 168 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 When the user request delay which exceed the maximum possible one delay ms provides a decreased resolution functionality In this mode delay ms will work with a resolution of 1 10 ms providing delays up to 6 5535 seconds independent from CPU frequency The user will not be informed about decreased resolution 6 27 2 2 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 If the user requests a delay greater than the maximal possible one delay us will automatically call delay ms instead The user will not be informed about this case 6 28 lt util delay_basic h gt Basic busy wait delay loops 6 28 1 Detailed De
362. onst void s2 size t len2 The memmem function finds the start of the first occurrence of the substring s2 of length 1en2 in the memory area s1 of length 1en1 Returns The memmem function returns a pointer to the beginning of the substring or NULL if the substring is not found If 1en2 is zero the function returns s1 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 87 6 11 3 9 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 11 3 10 void memrchr const void x src int val size_t len The memrchr function is like the memchr function except that it searches back wards from the end of the len bytes pointed to by src instead of forwards from the front Glibc GNU extension Returns The memrchr function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 11 3 11 void x memset void x 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 11 3 12 int strcasecmp const char s1 const char 52 C
363. oop forever the interrupts are doing the rest for Note 7 Sleep mode return 0 6 36 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 demo c The compilation will create a demo o file Next we link it into a binary called demo elf Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 190 avr gcc g mmcu atmega8 demo elf demo o It is important to specify the MCU type when linking The compiler uses the mmcu option to choose start up files and run time libraries that get linked together If this option isn t specified the compiler defaults to the 8515 processor environment which is most certainly what you didn t want 6 36 4 Examining
364. opies 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 11 3 19 size_t strcspn const char x s const char x reject The strcspn function calculates the length of the initial segment of s which consists entirely of characters not in re ject Returns The strcspn function returns the number of characters in the initial segment of s which are not in the string reject The terminating zero is not considered as a part of string 6 11 3 20 size_t strlcat char 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 May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 90 Returns The strlcat function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred
365. or avr libc by Doxygen 9 6 Inline Assembler Cookbook 299 mov 0 A2 n t mov B0 B2 An L_dl2 n t sbiw A0 1 n t brne L 412 n t dec 81 n t brne L_dli n t 6w cnt ms r delay count The purpose of this function is to delay the program execution by a specified number of milliseconds using a counting loop The global 16 bit variable delay count must contain the CPU clock frequency in Hertz divided by 4000 and must have been set before calling this routine for the first time As described in the clobber section the routine uses a local variable to hold a temporary value Another use for a local variable is a return value The following function returns a 16 bit value read from two successive port addresses uintl6 t inw uint8 t port uintl6 t result asm volatile in 0 1 n t in BO 1 1 r result I _SFR_IO_ADDR port return result Note inw is supplied by avr libc 9 6 7 C Names Used in Assembler Code By default AVR GCC uses the same symbolic names of functions or variables in C and assembler code You can specify a different name for the assembler code by 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 no
366. orage for the new stream Note If the macro __ STDIO COMPAT 12 is declared before including lt stdio h gt a function prototype for fdevopen will be chosen that is backwards compatible with avr libc version 1 2 and before This is solely intented for pro viding a simple migration path without the need to immediately change all source code Do not use for new code 6 9 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 9 3 5 ferror FILE stream Test the error flag of st ream This flag can only be cleared by a call to clearerr 6 9 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 0 3 7 intfgetc FILE x __ stream The function get c reads a character from st ream It returns the character or EOF in case end of file was encountered or an error occurred The routines feof or ferror must be used to distinguish between both situations 6 9 3 8 fgets char _ str int size FILE x stream Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 63 Read at most size 1 bytes from stream until a newline character was encoun tered and store the characters in the buffer pointed to by str Unless an error
367. orced that way Back to FAQ Index 9 10 14 What registers are used by the C compiler Data types char is 8 bits int is 16 bits Long is 32 bits Long long is 64 bits float and double are 32 bits this is the only supported floating point format pointers are 16 bits function pointers are word addresses to allow addressing up to 128K program memory space There is a mint8 option see Options for the C compiler avr gcc to make int 8 bits but that is not supported by avr libc and violates C standards int must be at least 16 bits It may be removed in a future release Call used registers r18 r27 r30 r31 May be allocated by gcc for local data You may use them freely in assembler subroutines Calling C subroutines can clobber any of them the caller is re sponsible for saving and restoring Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 323 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 if changed r29 r28 Y pointer is used as a frame pointer points to local data on stack if necessary The requirement for the callee to save preserve the contents of these registers even applies in situations where the compiler as signs them for argument passing Fixed registers r0 r1 Never allocated by gcc for
368. ort ing activities porting an application to a different platform OS and or processor Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 9 Porting From to AVR 307 and porting to a different compiler Porting to a different compiler can be exacerbated when the application is an embedded system For example the C language Standard strangely does not specify a standard for declaring and defining Interrupt Service Rou tines ISRs Different compilers have different ways of defining registers some of which use non standard language constructs This chapter describes some methods and pointers on porting an AVR application built with the IAR compiler to the GNU toolchain AVR GCC Note that this may not be an exhaustive list 9 9 2 Registers IO header files contain identifiers for all the register names and bit names for a par ticular processor has individual header files for each processor and they must be included when registers are being used in the code For example include lt iom169 h gt Note IAR does not always use the same register names or bit names that are used in the AVR datasheet AVR GCC also has individual IO header files for each processor However the ac tual processor type is specified as a command line flag to the compiler Using the mmcu processor flag This is usually done in the Makefile This allows you to specify only a single header file for any processo
369. ory 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 isalready cleared Back to FAQ Index 9 10 6 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 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 macro Of course the implementation of this macro is just the usual bit shift which is done by the compiler anyway thus doesn t impose any run time penalty so the following applies _BV 3 gt 1 lt lt 3 gt 0x08 However using the macro often makes the program better readable BV stands for bit value in case someone might ask you Generated on Mon
370. ossible 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 268 subroutines and storing local automatic variables Also unlike larger architectures there is no hardware supported memory management which could help in separating the mentioned RAM regions from being overwritten by each other The standard RAM layout is to place data variables first from the beginning of the internal RAM followed by bss The stack is started from the top of internal RAM growing downwards The so called heap available for the dynamic memory allocator will be placed beyond the end of bss Thus there s no risk that dynamic memory will ever collide with the RAM variables unless there were bugs in the implementation of the allocator There is still a risk that the heap and stack could collide if there are large requirements for either dynamic memory or stack space The former can even happen if the allocations aren t all that large but dynamic memory allocations get fragmented over time such that new requests don t quite fit into the holes of previously freed regions Large stack space requirements can arise in a
371. ote 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 Oxf0 Tie 88 b3 in r24 0x18 24 11 80 6 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 avr libc dev 2003 01 msg00044 html for a possible workaround avr gcc versions after 3 3 have been fixed in a way where this optimization will be disabled if the respective pointer variable is declared to be volatile so the correct behaviour for 16 bit IO ports can be f
372. oting computer users rights to use study copy modify and redis tribute computer programs The FSF promotes the development and use of free soft ware particularly the GNU operating system used widely in its GNU Linux variant The FSF remains the primary sponsor of the GNU project The GNU Project was launched in 1984 to develop a complete Unix like operating system which is free software the GNU system GNU is a recursive acronym for GNU s Not Unix it is pronounced guh noo approximately like canoe One of the main projects of the GNU system is the GNU Compiler Collection or GCC and its sister project GNU Binutils These two open source projects provide a foun dation for a software development toolchain Note that these projects were designed to originally run on Unix like systems 913 stands for GNU Compiler Collection is highly flexible compiler system It has different compiler front ends for different languages It has many back ends that generate assembly code for many different processors and host operating systems All share a common middle end containing the generic parts of the compiler including a lot of optimizations In a host system is the system processor OS that the compiler runs on target system is the system that the compiler compiles code for And a build system is the system that the compiler is built from source code on If a compiler has the same system for host
373. oximate 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 24 lt avr wdt h gt Watchdog timer handling 159 wdt_enable WDTO_500MS 6 24 2 6 define WDTO 1S 6 See WDTO 15MS 6 24 27 ftdefine WDTO 250MS 4 See WDTO 15MS 6 24 2 8 define WDTO 2S 7 See WDTO 15MS 6 24 2 9 define WDTO 30MS 1 See WDTO 15MS 6 24 2 10 define WDTO 45 8 See WDTO 15MS Note This is only available on the ATtiny2313 24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmega48P ATmega88P AT megal68P ATmega328P ATmegal64P ATmega324P ATmega644P ATmega644 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega8HVA ATmegal6HVA ATmega32HVB ATmega406 ATmegal284P 9 AT90PWM2 AT90PWM2B AT90PWM3 9 216 AT90PWM316 9005 82 AT90USBI162 A
374. 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 The name CPU is the conventional name to describe the CPU clock frequency of the controller This demo project just uses the internal calibrated 1 MHz RC oscillator that is enabled by default Note that when using the lt util delay h gt functions F CPU needs to be defined before including that file The remaining macros have their own comments in the source code The macro TMR1 SCALE shows how to use the preprocessor and the compiler s constant expres sion computation to calculate the value of timer 1 s post scaler a way so it only depends on CPU and the desired software clock frequency While the formula looks a bit complicated using a macro offers the advantage that the application will auto matically scale to new target softclock or master CPU frequencies without having to manually re calculate hardcoded constants 6 37 3 2 Part 2 Variable definitions The intflags s
375. poten tiometer to pins 9 GND and 10 VCC and the wiper to pin 1 port A0 A bypass capacitor from pin 1 to pin 9 like 47 nF is recommendable Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 37 A more sophisticated project 202 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 parenthesis in the table Alternatively the squid cable from the JTAG ICE kit can be used if available Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 37 A more sophisticated project 203 Port Header Color Function Connect to DO 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 LEDI pin2 LEDs header D7 8 white 1 second LED2 pin 3 flash LEDs header GND 9 unused VCC 10 unused Figure 3 Wiring of the STK500 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 37 A more sophisticated project 204 The following picture shows the alternate wiring where LEDI i
376. pported devices 2 tan avr_math 38 tanh avr_math 38 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen INDEX 389 timer_enable_int deprecated_items 179 toascii ctype 18 tolower ctype 18 tools optional 335 tools required 335 toupper ctype 18 trunc avr_math 38 TW_BUS_ERROR util_twi 172 TW_MR_ARB_LOST util_twi 172 TW_MR_DATA_ACK util_twi 172 TW_MR_DATA_NACK util_twi 172 TW_MR_SLA_ACK util_twi 173 TW_MR_SLA_NACK util_twi 173 TW_MT_ARB_LOST util_twi 173 TW_MT_DATA_ACK util_twi 173 TW_MT_DATA_NACK util_twi 173 TW_MT_SLA_ACK util_twi 173 TW_MT_SLA_NACK util_twi 173 TW_NO_INFO util_twi 173 TW_READ util_twi 173 TW_REP_START util_twi 173 TW_SR_ARB_LOST_GCALL_ACK util_twi 173 TW SR ARB LOST SLA ACK util twi 174 TW SR ACK util twi 174 TW SR DATA NACK util twi 174 TW SR GCALL ACK util twi 174 TW SR GCALL DATA ACK util twi 174 TW SR GCALL DATA NACK util twi 174 TW SR SLA ACK util twi 174 TW SR STOP util twi 174 TW ST ARB LOST SLA ACK util twi 174 TW ST DATA ACK util twi 174 TW ST DATA NACK util twi 174 TW ST LAST DATA util twi 175 TW ST SLA ACK util twi 175 TW START util twi 175 TW STATUS util twi 175 TW STATUS MASK util twi 175 TW WRITE util twi 175 twi h 259 UBRR VALUE util setbaud 170 UBRRH VALUE util setbaud 170 UBRRL VALUE util setbaud 171 UINT16 C avr stdint 47 UINT16 MA
377. ppropriate 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 V Vcc R2 is needed Its value should be about 150 Ohms When operating the circuit at 3 V it can still be omitted though Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 36 simple project 188 6 36 2 Source Code gt 3 w 3b fin enu ISR voi ioi THE BEER WARE LICENSE Revision 42 lt joerg FreeBSD ORG gt wrote this file As long as you retain this notice you can do whatever you want with this stuff If we meet some day and you think this stuff is worth it you can buy me a beer in return Joerg Wunsch Simple AVR demonstration
378. 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 some function this same register can be re used later on if the compiler notices that the first variable is no longer used inside that function even though the variable is still in lexical scope When trying to examine the variable in avr gdb the displayed result will then look garbled So in order to avoid these side effects optimization can be turned off while debugging However some of these optimizations might also have
379. r P size t size t strlen P PGM P size t strnlen P PGM P size t int strncmp P const char PGM P size 0 PURE int strncasecmp_P const char x P size 0 PURE char strncat_P char PGM P size_t char strncpy P char x size t char strpbrk P const char x s PGM P accept ATTR_PURE PGM P strrchr P PGM_P int __val char strsep P char sp PGM P delim size tstrspn P const char s PGM P accept PURE char strstr P const char PGM P ATTR PURE Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference 242 8 34 2 Define Documentation 8 34 2 1 define _ ELPM_classic__ addr Value extension N uint32 t __addr32 uint32 t addr uint8 t _ result N asm N N out 2 SCIT n t N nov r31 SBI Matt N Hoy 30 SAT N elpm n t N mov 0 r0 n t N r result N r addr32 N I SFR IO ADDR RAMPZ TEOT ESO N _ result 8 34 2 2 define _ dword enhanced Value extension N uint32 t addr32 uint32 t addr uint32 t _ result N asm N N out 2 C1 ANNET movw r30 1 n t elpm 0 2 n t elpm BO n t elpm CO Z elpm 0 2 r resu
380. r and you are using this register with an ori instruction in your as sembler code then the compiler may select any register This will fail if the compiler chooses r2 to r15 It will never choose r0 or r1 because these are uses for special purposes That s why the correct constraint in that case is d On the other hand if you use the constraint M the compiler will make sure that you don t pass anything else but an 8 bit value Later on we will see how to pass multibyte expression results Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 293 to the assembler code The following table shows all AVR assembler mnemonics which require operands and the related contraints Because of the improper constraint definitions in version 3 3 they aren t strict enough There is for example no constraint which restricts integer constants to the range 0 to 7 for bit set and bit clear operations Mnemonic Constraints Mnemonic Constraints adc 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 LI dec r elpm 52 eor LI in LI inc r ld re ldd rb ldi d M 146 r label lpm 52 Is r Isr r mov LI movw LI mul LI neg r or Lr ori dM out Lr pop r push r rol r ror r sbc LI sbci sbi LI sb
381. r local bin usr bin bin mingw bin c cygwin bin install directory gt bin Configure configure prefix installdir infodir installdir info mandir installdir man 2 gt amp 1 tee package configure log Make make all install 2 gt amp 1 tee Spackage make log Build the tools below in Cygwin Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 350 AVaRICE Open source code package Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin install directory gt bin Set location of LibUSB headers and libraries export CPPFLAGS I startdir libusb win32 device bin libusb_version include export CFLAGS I startdir libusb win32 device bin libusb_version include export LDFLAGS static L startdir libusb win32 device bin 1ibusb version lib gc Configure Sarchivedir configure prefix installdir datadir installdir doc mandir installdir man infodir installdir info 2 gt amp 1 tee avarice configure log Make make all install 2 gt amp 1 tee avarice make log SimulAVR Open source code package Configure and build in a directory outside of the source code tree Set PATH in order MikTex executables gt usr local bin u
382. r lock h gt file These other two files provides everything necessary to set the AVR lockbits Lockbit API Each I O header file may define up to 3 macros that controls what kinds of lockbits are available to the user If LOCK BITS EXIST is defined then two lock bits are available to the user and 3 mode settings are defined for these two bits If BOOT LOCK BITS 0 EXIST is defined then the two BLBO lock bits are avail able to the user and 4 mode settings are defined for these two bits If BOOT LOCK BITS 1 EXIST is defined then the two BLB1 lock bits are avail able to the user and 4 mode settings are defined for these two bits If BOOT LOCK APPLICATION TABLE BITS EXIST is defined then two lock bits are available to set the locking mode for the Application Table Section which is used in the XMEGA family If BOOT LOCK APPLICATION BITS EXIST is defined then two lock bits are available to set the locking mode for the Application Section which is used in the XMEGA family If BOOT LOCK BOOT BITS EXIST is defined then two lock bits are available to set the locking mode for the Boot Loader Section which is used in the XMEGA family The AVR lockbit modes have inverted values logical 1 for an unprogrammed dis abled bit and logical 0 for a programmed enabled bit The defined macros for each individual lock bit represent this in their definition by a bit wise inversion of a mask For example the LB MODE 3 macro is
383. r macros for baud rate calculations 170 6 30 1 Detailed Description 222 222 2 170 6 30 2 Define Documentation 171 lt util twi h gt TWI bit mask definitions 172 6 31 1 Detailed Description 26k RR RR ERR 172 6312 Define Documentation 173 lt compat deprecated h gt Deprecated tems 176 6 32 1 Detailed Description lt lt s s see bee ARR 5 176 6 322 Define Documentation 22 2 2 2 178 6 32 3 Function Documentation 180 lt compat ina90 h gt Compatibility with IAR EWB3 x 180 Demo prejieis ecce ee eee ee ee Ee aes 180 6 34 1 Detaled Description 222 2 2222 2 2 2 180 Combining and assembly source files 181 6 33 1 Hardware setup o 22225 ox orc ERPS 182 6 35 2 A code walkthrough 222 222 2 2 182 6 35 3 Thesoutc code 184 ASe aa ea e ue oss SE RR E S d es 185 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen CONTENTS Y 636 1 The Project i452 bl Ro Roe 25255552 185 522 The Saute Code s ne eee UR RR REUS H 4 188 6 36 3 Compiling and Linking gt lt sa a ea kie o RR 189 6 364 Examining the Object File o o cs 48544 k kop 24 190 6 36 5 Linker Map Piles 65 05 6544 cm ob o 06 a5 195 6 36 6 Generating Intel Hex Files 197 6 36 7 Letting Make Build the Project 65 sc
384. r options mmcu architecture mmcu MCU name avr as understands the same mmcu options as avr gcc By default avr2 is assumed but this can be altered by using the appropriate arch pseudo instruction inside the assembler source file e mmall opcodes Turns off opcode checking for the actual MCU type and allows any possible AVR opcode to be assembled e mno skip bug Don t emit a warning when trying to skip a 2 word instruction with a CPSE SBIC SBIS SBRC SBRS instruction Early AVR devices suffered from a hardware bug where these instructions could not be properly skipped e mno wrap For RIMP RCALL instructions don t allow the target address to wrap around for de vices that have more than 8 KB of memory gstabs Generate stabs debugging symbols for assembler source lines This enables avr gdb to trace through assembler source files This option must not be used when assembling sources that have been generated by the C compiler these files already contain the appropriate line number information from the C source files e a cdhimns file Turn on the assembler listing The sub options are c omit false conditionals d omit debugging directives h include high level source Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 359 1 include assembly m include macro expansions n omit forms processing s include symbols file set
385. r type include lt avr io h gt Note The forward slash in the lt avr io h gt file name that is used to separate subdirecto ries can be used on Windows distributions of the toolchain and is the recommended method of including this file The compiler knows the processor type and through the single header file above it can Pull in and include the correct individual IO header file This has the advantage that you only have to specify one generic header file and you can easily port your application to another processor type without having to change every file to include the new IO header file The AVR toolchain tries to adhere to the exact names of the registers and names of the bits found in the AVR datasheet There may be some descrepencies between the register names found in the IAR IO header files and the AVR GCC IO header files Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 9 9 Porting From IAR to AVR GCC 308 9 9 3 Interrupt Service Routines ISRs As mentioned above the C language Standard strangely does not specify a standard way of declaring and defining an ISR Hence every compiler seems to have their own special way of doing so IAR declares an ISR like so pragma vector TIMERO OVF vect interrupt void MotorPWMBottom code In AVR GCC you declare an ISR like so ISR PCINTI_vect code AVR GCC uses the ISR macro to define an ISR This macro requries the header f
386. rator AT90S4414 AT90S4433 AT90S4434 AT90S8515 419058535 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 AT mega8515 ATmega8535 ATtinyll ATtiny12 ATtiny13 ATtiny15 ATtiny2313 ATtiny26 ATtiny28 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 CANIT vect SIG CAN CAN Transfer AT90CAN128 AT90CAN32 AT90CANG64 INTERRUPTI Complete or Error EEPROM SIG ATtiny2313 READY vect EEPROM READY SIG EE READY EE RDY vect SIG EEPROM Ready 9052333 AT90S4433 AT90S4434 EEPROM AT9088535 ATmegal6 ATmegal6l READY ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 ATmega8515 ATmega8535 12 ATtinyl3 AT tinyl5 ATtiny26 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 EE READY SIG EEPROM Ready AT90PWMS3 AT90PWM2 AT90PWMI vect EEPROM AT90CAN128 AT90CAN32 AT90CANGA READY ATmegal03 ATmegal28 ATmegal284P ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega406 ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P AT megal64P ATmega644P ATmega644 AT megal6HVA AT90USB162 AT90USB82 AT90USB 1
387. register reg defined by the compiler asm volatile oli n t ld _ tmp_reg__ a0 NnNE inc tmp reg n t st a0 _ tmp reg NnNEM sei nnm e ptr The compiler is prepared to reload this register next time it uses it Another problem with the above code is that it should not be called in code sections where interrupts are disabled and should be kept disabled because it will enable interrupts at the end We may store the current status but then we need another register Again we can solve this without clobbering a fixed but let the compiler select it This could be done with the help of a local variable Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 297 uint8 t s asm volatile in 0 SREG cli n t ld tmp reg al n t inc tmp_reg__ MANEN st al _ tmp reg out __SREG__ 0 n t amp r s e ptr Now every thing seems correct but it isn t really The assembler code modifies the variable that pt x points to The compiler will not recognize this and may keep its value in any of the other registers Not only does 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
388. 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 216 calling itself when it sees a n character Just for demonstration purposes the a audible bell ASCII BEL character is implemented by sending a string to stderr so it will be displayed on the LCD The public function uart_getchar implements the line editor If there are char acters available in the line buffer variable rxp is not NULL the next character will be returned from the buffer without any UART interaction If there are no characters inside the line buffer the input loop will be entered Charac ters will be read from the UART and processed accordingly If the UART signalled a framing error FE bit set typically caused by the
389. ress of the first invalid character in endptr If there were no digits at all however strtol stores the original value of nptr in endptr Thus if xnptr is not VO but xxendptr is 0 on return the entire string was valid The strtol function returns the result of the conversion unless the value would under flow or overflow If no conversion could be performed 0 is returned If an overflow or underflow occurs errno is set to ERANGE and the function return value is clamped to LONG MIN or LONG respectively 6 10 4 28 unsigned long strtoul const char x __nptr char endptr int base The strtoul function converts the string in npt r 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 repre
390. ress 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 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 to the caller If no exact match could be found the closest match that would just satisfy the request will be used The chunk will normally be split up into one to be returned to the caller and another smaller one that will remain on the freelist In c
391. returned If both arguments are NaN NaN is returned 6 6 3 15 double fmin double __x double y The fmin function returns the lesser of the two values __x and y If an argument is NaN the other argument is returned If both arguments are NaN NaN is returned 6 6 3 16 double fmod double __x double y The function fmod returns the floating point remainder of x y 6 6 3 17 double frexp double __x int x pexp The frexp function breaks a floating point number into a normalized fraction and an integral power of 2 It stores the integer in the int object pointed to by pexp If xisanormal float point number the frexp function returns the value v such that v has a magnitude in the interval 1 2 1 or zero and __x equals v times 2 raised to the power pexp If __x is zero both parts of the result are zero If __x is not a finite number the frexp returns __x as is and stores 0 by pexp Note This implementation permits a zero pointer as a directive to skip a storing the exponent 6 6 3 18 double hypot double x double y The hypot function returns sqrt __x __x y This is the length of the hy potenuse of a right triangle with sides of length __x and __y or the distance of the point __x __y from the origin Using this function instead of the direct formula is wise since the error is much smaller No underflow with small x and y No overflow if result is in range 6 6 3 19 static int isfi
392. riables 316 9 10 9 Why do some 16 bit timer registers sometimes get trashed 317 9 10 10 How do I use a define d constant in an asm statement 317 9 10 11 Why does the PC randomly jump around when single stepping through my program in 318 9 10 12 How do I trace an assembler file in avr gdb 319 9 10 13 How do I pass an IO port as a parameter to a function 320 9 10 14 What registers are used by compiler 322 9 10 15 How do I put an array of strings completely in ROM 323 9 10 16 How to use external 325 9 10 17 Which O Dag to use b s o RE i 326 9 10 18 How do I relocate code to a fixed address 327 9 10 19 My is generating nonsense ATmegal28 keeps crashing Port F is completely broken 327 9 10 20 Why do all my foo bar strings eat up the SRAM 328 9 10 21 Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit operation in assembly 329 9 10 22 How to detect RAM memory and variable overlap problems 330 9 10 23 Is it really impossible to program the ATtinyXX C 330 9 10 24 What is this clock skew detected messsage 330 9 10 25 Why are many interrupt flags cleared by writing a logical 1 331 9 10 26 Why have programmed fuses the bit value 02 332 Generated on Mon
393. riggered 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 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 109 ISR XXX vect ISR NOBLOCK where XXX_vect is the name of a valid interrupt vector for the MCU type in question as explained below Two vectors sharing the same code In some circumstances the actions to be taken upon two different interrupts might be completely identical so a single implementa tion for the ISR would suffice For example pin change interrupts arriving from two different ports could logically signal an event that is independent from the actual port and thus interrupt vector where it happened Sharing interrupt vector code can be accomplished using the ISR_ALIASOF attribute to the ISR macro ISR PCINTO_vect Code to handle the event ISR PCINTI_vect ISR ALIASOF PCINTO vect Note T
394. ring Characters from the array are written up to but not including a terminating NUL character if a precision is specified no more than the number specified are written If a precision is given no null character need be present if the precision is not specified or is greater than the size of the array the array must contain a terminating NUL character 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 dddezdd 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 f or e or F or E for G conver sions The precision specifies the number of signif
395. ring 88 strlcat S 259 strlcat P avr pgmspace 142 strlcat P S 259 strlcpy avr string 80 strlcpy S 259 strlcpy P Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 388 avr_pgmspace 142 strlcpy_P S 259 strlen avr_string 89 strlen S 259 strlen_P avr_pgmspace 142 strlen_P S 259 strlwr avr_string 89 strlwr S 259 strncasecmp avr_string 89 strncasecmp S 259 strncasecmp_P avr_pgmspace 142 strncasecmp_P S 259 strncat avr_string 90 strncat S 259 strncat_P avr_pgmspace 143 strncat_P S 259 strncmp avr_string 90 strncmp S 259 strncmp P avr pgmspace 143 strncmp_ P S 259 strncpy avr string 90 strncpy S 259 strncpy_P avr_pgmspace 143 strncpy_P S 259 strnlen avr_string 90 strnlen S 259 strnlen_P avr_pgmspace 144 strnlen_P S 259 strpbrk avr_string 91 strpbrk S 259 strpbrk_P avr_pgmspace 144 strpbrk_P S 259 strrchr avr string 91 strrchr S 259 strrchr P avr pgmspace 144 strrchr_P S 259 strrev avr_string 91 strrev S 259 strsep avr_string 91 strsep S 259 strsep_P avr_pgmspace 144 strsep_P S 259 strspn avr_string 92 strspn S 259 strspn_P avr_pgmspace 145 strspn_P S 259 strstr avr_string 92 strstr S 259 strstr_P avr_pgmspace 145 strstr_P S 259 strtod avr_stdlib 79 strtok_r avr_string 92 strtok_r S 259 strtol avr_stdlib 79 strtoul avr_stdlib 80 strupr avr_string 93 strupr S 259 su
396. rings The strlcat_P function is similar to strlcat except that the src string must be located in program space flash Appends src to string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat_P function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 6 18 4 15 size_t strlcpy P char dst P 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 function returns strlen src If retval gt siz truncation occurred 6 18 4 16 size_t strlen P PGM P src The 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 18 avr pgmspace h Program Space Utilities 144 6 18 4 17 int strncasecmp P const char s1 P s2 size Compare two strings ignoring case The strncasecmp P function is similar to strcasecmp_P except it only compares the first n characters of s1 Parameters 51 A pointer to a string in the devices SRAM s2 A pointer to a string in the devices Flash n T
397. rm of a period followed by an optional digit string If the digit string is omitted the precision is taken as zero This gives the minimum number of digits to appear for d i o u x and X conversions or the maximum number of characters to be printed from a string for s conversions An optional 1 or h length modifier that specifies that the argument for the d i u or X conversion isa long int rather than int The h is ignored as short int isequivalent to int Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 67 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 1 unsigned octal 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 Thevoid 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 st
398. rmat for uint32_t 6 5 2 23 define PRIo8 octal printf format for uint8 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 26 6 5 2 24 define PRIOFAST16 octal printf format for uint_fast16_t 6 5 2 25 define PRIoFAST32 lo octal printf format for uint_fast32_t 6 5 2 26 define PRIoFASTS octal printf format for uint fast8 t 6 5 2 27 define PRIOLEASTI16 o octal printf format for least16 t 6 5 2 28 define PRIOLEAST32 lo octal printf format for least32 t 6 5 2 29 define PRIOLEASTS o octal printf format for least8 t 6 5 2 30 define PRIoPTR PRIo16 octal printf format for uintptr t 6 5 2 31 define PRIu16 decimal printf format for uint16 t 6 5 2 32 define PRIu32 lu decimal printf format for uint32 t 6 5 2 33 define PRIu8 u decimal printf format for uint8 t 6 5 2 34 define PRIUFASTI6 decimal printf format for uint_fast16_t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 27 6 5 2 35 define PRIuFAST32 decimal printf format for uint_fast32_t 6 5 2 36 define PRIUFASTS decimal printf format for uint_fast8_t 6 5 2 37 define PRIULEAST16 u decimal printf format for uint_least16_t 6 5 2 38 define PRIULEAST32 decimal printf format for uint_least32_t 6 5 2 39 def
399. rmation to stderr 9 12 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 O means no optimization at all which is the default if no O option is present The special option Os is meant to turn on all 02 optimizations that are not expected to increase code size Note 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 O3 is frename registers which could rather be enabled manually instead A simple O option is equivalent to O1 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 357 Note also that turning off all optimizations will prevent some warnings from being issued since the generation of those warnings depends on code analysis steps that are only performed when optimizing unreachable code unused variables See also the appropriate FAQ entry for issues regarding debugging optimized code Wa assembler options e W1l linker options Pass the listed options to the assembler or linker respectively 4 4 Generate debugging information that can be used by avr gdb ffreestanding Assume a freestanding environment as per the C standard This turns off aut
400. rspn const char 65 const char __accept _ ATTR_PURE char strstr const char const char x ATTR PURE char strtok_r char const char char char strupr char Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 8 57 string h File Reference 259 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 58 strlcat S File Reference 260 8 58 8 58 1 8 59 8 59 1 8 60 8 60 1 8 61 8 61 1 8 62 8 62 1 8 63 8 63 1 8 64 8 64 1 8 65 8 65 1 8 66 8 66 1 8 67 8 67 1 8 68 8 68 1 8 69 strlcat S File Reference Detailed Description strlcat P S File Reference Detailed Description strlcpy S File Reference Detailed Description strlcpy_P S File Reference Detailed Description strlen S File Reference Detailed Description strlen P S File Reference Detailed Description striwr S File Reference Detailed Description strncasecmp S File Reference Detailed Description strncasecmp P S File Reference Detailed Description strncat S File Reference Detailed Description strncat P S File Reference Detailed Description strncmp S File Reference Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 69 1 8 70 8 70 1 Q 71 Detailed Description strncmp P S File Reference Detailed Description ctrnenv File Reference 8 88 twi h File Reference 261 TWSR values Mnemonics TW MT
401. ry Read AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CANGA ATmegal28 ATmegal284P ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega406 ATmega48P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega88P ATmega168 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 TIMO_ COMPA_vect SIG_ OUTPUT_ Timer Counter Compare Match A ATtiny13 ATtiny43U ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 117 Vector name Old vector Description Applicable for device name TIMO_ SIG_ Timer Counter ATtiny13 ATtiny43U ATtiny24 ATtiny44 COMPB_vect OUTPUT_ Compare Match ATtiny84 ATtiny45 ATtiny25 ATtiny85 COMPAREOB B TIMO OVF SIG Timer Counter0 ATtiny13 ATtiny43U ATtiny24 ATtiny44 vect OVERFLOWO Overflow ATtiny84 ATtiny45 ATtiny25 ATtiny85 TIMI SIG INPUT Timer Counter1 ATtiny24 ATtiny44 ATtiny84 CAPT_vect CAPTURE1 Capture Event TIM1_ SIG_ Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 COMPA_vect OUTPUT_ Compare Matc
402. s 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 chip RAM location XRAMEND A constant describing the last possible location in RAM This is equal to MEND for devices that do not allow for external RAM E2END A constant describing the address of the last EEPROM cell FLASHEND 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 17 lt avr lock h gt Lockbit Support Introduction The Lockbit API allows a user to specify the lockbit settings for the specific AVR device they are compiling for These lockbit settings will be placed in a special section in the ELF output file after linking Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 17 lt avr lock h gt Lockbit Support 132 Programming tools can take advantage of the lockbit information embedded in the ELF file by extracting this information and determining if the lockbits need to be programmed after programming the Flash and EEPROM memories This also allows a single ELF file to contain all the information needed to program an AVR To use the Lockbit API include the lt avr io h gt header file which in turn automatically includes the individual I O header file and the lt av
403. s Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category 8 40 typedef int64 t intmax t typedef uint64 t uintmax t stdio h File Reference 8 40 1 Detailed Description Defines define STDIO H 1 define need NULL define need size t define FILE struct file define stdin __iob 0 define stdout __iob 1 define stderr __iob 2 define EOF 1 define fdev_set_udata stream u do stream 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 40 stdio h File Reference 252 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 define SEEK_SET 0 define SEEK_CUR 1 define SEEK_END 2 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 fmt int printf P const char
404. s 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 Ina practical application long delays like this one were better be handled by a hardware timer so the main CPU would be free for other tasks while waiting or could be put on sleep At the beginning of main after initializing the peripheral devices the default stdio streams stdin stdout and stderr are set up by using the existing static FILE stream objects While this is not mandatory the availability of stdin and stdout allows to use the shorthand functions e g printf instead of fprintf and stderr can mnemonically be referred to when sending out diagnostic messages Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 212 Just for demonstration purposes st din and stdout are connected to a stream that will perform UART IO while stderr is arranged to output its data to the LCD text display Finally a main loop follows that accepts simple commands entered via the RS 23
405. s 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 other If you don t know how to do this you probably shouldn t be making releases or cutting branches Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 14 Release Numbering and Methodology 365 9 14 2 1 Creating a cvs 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 this relelase 3 Set the branch point tag setting major and lt minor gt accordingly cvs tag avr libe major minor branchpoint 4 Create the branch cvs tag b avr libe major minor 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 this release 7 Check out a new tree for the branch cvs CO r avr libe major minor 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
406. s 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 PB1 connects to the LEDO pin PD6 remains unconnected When using the STK500 use one of the jumper cables for this connection All other port D pins should be connected the same way as described for the ATmega16 above When not using an STK500 starter kit attach the LEDs through some resistor to Vcc low active LEDs and attach pushbuttons from the respective input pins to GND The internal pull up resistors are enabled for the pushbutton pins so no external resistors are needed Finally the demo has been ported to the ATtiny2313 as well As this AVR does not offer an ADC everything related to handling the ADC is disabled in the code for that MCU type Also port D of this controller type only features 6 pins so the 1 second flash LED had to be moved from PD6 to PD4 PD4 is used as the ADC control button on the other MCU types but that is not needed here is located at PB3 on this device The
407. s discussion of interrupts was originally taken from Rich Neswold s document See Acknowledgments 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 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 108 The extra code needed to do this is enabled by tagging the interrupt function with attribute signal These details seem to make interrupt routines a little messy but all these details are handled by the Interrupt API An interrupt routine is defined with ISR This macro register and mark the routine as an interrupt handler for the specified peripheral T
408. s 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 9 10 19 My UART is generating nonsense My ATmegal28 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 328 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 running on such a device will immediately crash upon the first function call or rather upon the first function return
409. scription include util delay basic h 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 Functions e void delay loop 1 uint8 t count e void delay loop 2 uint16 t count Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 29 lt util parity h gt Parity bit generation 169 6 28 2 Function Documentation 6 28 2 1 void delay loop 1 uint8 t count Delay loop using an 8 bit counter count so up to 256 iterations are possible The value 256 would have to be passed as 0 The loop executes three CPU cycles per iteration not including the overhead the compiler needs to setup the counter register Thus at a CPU speed of 1 MHz delays of up to 768 microseconds can be a
410. se it makes more sense to aggregate those two functions in the same object module The second case is when you want to have an Interrupt Service Routine ISR in your library that you want to link in The problem in this case is that the linker looks for unresolved references and tries to resolve them with code in libraries A reference is the same as a function call But with ISRs there is no function call to initiate the ISR The ISR is placed in the Interrupt Vector Table IVT hence no call no reference and no linking in of the ISR In order to do this you have to trick the linker in a way Aggregate the ISR with another function in the same object module but have the other function be something that is required for the user to call in order to use the ISR like perhaps an initialization function for the subsystem or perhaps a function that enables the ISR in the first place Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 7 How to Build a Library 302 9 7 4 Creating a Library The librarian program is called ar for archiver and is found in the GNU Binutils project This program will have been built for the AVR target and will therefore be named avr ar The job of the librarian program is simple aggregate a list of object modules into a single library archive and create an index for the linker to use The name that you create for the library filename must follow a specific pattern libname a The name part
411. sed by strncasecmp is that if s1 is an initial substring of s2 then s1 is considered to be less than 52 6 11 3 25 char x strncat char 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 strncat function returns a pointer to the resulting string dest 6 11 3 26 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 s1 and s2 Returns The strncmp function returns an integer less than equal to or greater than zero if s1 or the first n bytes thereof is found respectively to be less than to match or be greater than s2 6 11 3 27 char strncpy char x 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 92 6 11 3 28 size t strnlen const char x src
412. sed in since the operation is perform in place 6 12 lt avr boot h gt Bootloader Support Utilities 6 12 1 Detailed Description include lt avr io h gt include lt avr boot h gt The macros in this module provide a language interface to the bootloader support functionality of certain AVR processors These macros are designed to work with all sizes of flash memory Global interrupts are not automatically disabled for these macros It is left up to the programmer to do this See the code example below Also see the processor datasheet for caveats on having global interrupts enabled during writing of the Flash Note Not all AVR processors provide bootloader support See your processor datasheet to see if it provides bootloader support 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 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 95 API Usage Example The following code shows typical usage of the boot API include lt inttypes h gt include lt avr interrupt h gt include lt avr pgmspace h gt void boot program page uint32 t page uint8 t xbuf uint16_t i uint8_t sreg Disable interrupts sreg SREG cli eeprom busy w
413. sed on the address of the register being accessed The advantage of using the memory mapped registers in C programs is that it makes the programs more portable to other C compilers for the AVR platform Note that special care must be taken when accessing some of the 16 bit timer IO reg isters where access from both the main program and within an interrupt context can happen See Why do some 16 bit timer registers sometimes get trashed Porting programs that use the deprecated sbi cbi macros Access to the AVR single bit set and clear instructions are provided via the standard C bit manipulation commands The sbi and cbi macros are no longer directly supported sbi sfr bit can be replaced by sfr _BV bit i e sbi PORTB PB1 is now PORTB 1 This actually is more flexible than having sbi directly as the optimizer will use a hard ware sbi if appropriate or a read or write operation if not appropriate You do not need to keep track of which registers sbi cbi will operate on Likewise cbi sfr bit is now sfr amp _BV bit Modules Additional notes from lt avr sfr_defs h gt Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 21 lt avr sfr_defs h gt Special function registers 152 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 e define bit is clear sfr bit SFR BYTE s
414. sents 11 and so forth with 2 representing 35 If endptr is not NULL strtoul stores the address of the first invalid character in xendptr If there were digits at all however strtoul stores the original value of nptr in endptr Thus if npt r is not NO but xxendptr is 0 on return the entire string was valid Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 82 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 10 4 29 char ultoa unsigned long int __val char x s int radix Convert an unsigned long integer to a string The function ultoa converts the unsigned long integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing suf ficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof unsigned long int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warnin
415. sh bytes 942 830 874 764 808 698 amp p 0 Stack bytes 29 21 MCU clocks 1074 722 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 9 Porting From IAR to AVR GCC 306 9 8 2 Math functions The table contains the number of MCU clocks to calculate a function with a given argument s The main reason of a big difference between Avr2 and Avr4 is a hardware multiplication Function Avr2 Avr4 addsf3 1 234 5 678 113 108 mulsf3 1 234 5 678 375 138 divsf3 1 234 5 678 466 465 acos 0 54321 4648 2689 asin 0 54321 4754 2790 atan 0 54321 4710 2271 atan2 1 234 5 678 5270 2857 ceil 1 2345 177 177 1 2345 3381 1665 cosh 1 2345 4922 2979 exp 1 2345 4708 2765 fdim 5 678 1 234 111 111 floor 1 2345 180 180 fmax 1 234 5 678 39 37 fmin 1 234 5 678 35 35 fmod 5 678 1 234 132 132 frexp 1 2345 0 37 36 hypot 1 234 5 678 1556 1078 Idexp 1 2345 6 42 42 log 1 2345 4142 2134 log10 1 2345 4498 2260 modf 1 2345 0 433 429 pow 1 234 5 678 9293 5047 round 1 2345 150 150 sin 1 2345 3347 1647 sinh 1 2345 4946 3003 sqrt 1 2345 709 704 tan 1 2345 4375 2420 tanh 1 2345 5126 3173 trunc 1 2345 178 178 9 9 Porting From to AVR 9 9 1 Introduction language was designed to be a portable language There two main types of p
416. some extra code in order to actually load the data from the Program Space This Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 282 incurs some extra overhead in terms of code space extra opcodes and execution time Usually both the space and time overhead is minimal compared to the space savings of putting data in Program Space But you should be aware of this so you can mini mize the number of calls within a single function that gets the same piece of data from Program Space It is always instructive to look at the resulting disassembly from the compiler 9 5 avr libc and assembler programs 9 5 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
417. sr bin bin install directory gt bin Configure Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 12 Using the GNU tools 351 export LDFLAGS static Sarchivedir configure prefix installdir datadir installdir disable tests disable versioned doc 2 gt amp 1 tee simulavr configure log Make make k all install 2 gt amp 1 tee simulavr make log make pdf install pdf 2 gt amp 1 tee simulavr pdf make log 9 12 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 9 12 1 Options for the C compiler avr gcc 9 12 1 4 Machine specific options for the AVR following machine specific options are recognized by the C compiler frontend In addition to the preprocessor macros indicated in the tables below the preprocessor will define the macros _ AVR and __AVR__ to the value 1 when compiling for an AVR target The macro AVR will be defined as well when using the standard levels gnu89 default and gnu99 but not with c89 and c99 mmcu architecture Compile code for architecture Currently known architectures are Architecture Macros avrl
418. ssibly used library functions See C Names Used in Assembler Code for more details Back to FAQ Index 9 10 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 initl ax progbits Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 314 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 cases It is best to leave stack at its default value end of internal SRAM faster and required on some devices like ATmegal61 because of errata and add W1l Tdata 0x801100 to start the data section above the stack For more information on using sections see Mem
419. stdint 47 avr stdlib 78 RANDOM MAX avr stdlib 73 random r avr stdlib 78 realloc avr stdlib 79 rem div t 220 ldiv t 221 reti avr interrupts 129 round avr math 37 sbi deprecated items 178 scanf avr stdio 63 scanf P avr stdio 63 SCNd16 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 386 avr_inttypes 28 SCNd32 avr_inttypes 28 SCNdFAST16 avr_inttypes 28 SCNdFAST32 avr_inttypes 28 SCNdLEASTI6 avr inttypes 28 SCNdLEAST32 avr inttypes 28 SCNdPTR avr inttypes 28 SCNi16 avr_inttypes 28 SCNi32 avr_inttypes 29 SCNIFASTI6 avr inttypes 29 SCNIFAST32 avr inttypes 20 SCNiLEAST16 avr_inttypes 29 SCNiLEAST32 avr_inttypes 29 SCNiPTR avr_inttypes 29 SCNo16 avr inttypes 29 SCNo32 avr inttypes 29 SCNoFAST16 avr_inttypes 29 SCNoFAST32 avr_inttypes 29 SCNoLEAST16 avr_inttypes 29 SCNoLEAST32 avr_inttypes 30 SCNoPTR avr_inttypes 30 SCNul6 avr inttypes 30 SCNu32 avr inttypes 30 SCNuFAST16 avr_inttypes 30 SCNuFAST32 avr_inttypes 30 SCNuLEASTI6 avr inttypes 30 SCNuLEAST32 avr inttypes 30 SCNuPTR avr inttypes 30 SCNx16 avr inttypes 30 SCNx32 avr inttypes 30 SCNxFAST16 avr_inttypes 31 SCNxFAST32 avr_inttypes 31 SCNxLEASTI6 avr inttypes 31 SCNxLEAST32 avr inttypes 31 SCNxPTR avr inttypes 31 sei avr interrupts 129 setbaud h 246 setjmp longjmp 39 setjmp 40 setjmp h 246 SIG
420. 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 build 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 Xr UF dr 9 11 7 AVRDUDE Note It has been ported to windows via MinGW or cygwin Linux and Solaris Other Unix systems should be trivial to port to Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 340 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 XY X Xr X dod 9 11 8 GDB for the AVR target GDB also uses the configure system so to build and install bunzip2 c gdb version tar bz2 tar xf cd gdb version mkdir obj avr
421. t int fscanf P FILE stream const char fmt int scanf const char fmt int scanf P const char int vscanf const char fmt va list int sscanf const char buf const char fmt int sscanf P const char buf const char fmt int fflush FILE xstream FILE x fdevopen int put char FILE int xget FILE 6 9 2 Define Documentation 6 9 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 9 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 9 2 3 define FDEV SETUP READ SRD setup stream with read intent 6 9 2 4 define FDEV SETUP RW SRD SWR setup stream with read write intent Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 59 6 9 2 5 define FDEV SETUP WRITE SWR setup stream with write intent 6 9 2 6 define EOF 1 EOF declares the value that is returned by various standard IO functions in case of an error Since the AVR platform currently doesn t contain an abstraction for actual files its origin as end of file is somewhat meaningless here 6 9 2 7 define close This macro frees up any library resources that might be associated with stream It
422. t N r addr32 N I SFR IO ADDR RAMPZ TESO Tp _ result 8 34 2 6 define _ LPM classic Value __extension__ uintl6 t __addrl6 uint16_t addr uint8 t _ result N asm N N lpm n t N mov 0 0 n t N r result N z addrl16 N EO _ result 8 34 2 7 define _ LPM_dword_classic__ addr Value __extension__ uintl6 t addrl6 uint16_t addr N uint32 t _ result N asm N N lpm NnNE N mov 0 ro Nin X adiw r30 1 A A N lpm ApnNE N mov B0 ro male adiw r30 1 hat lpm An NE N mov C0 ro NENE adiw r30 1 n t N lpm n t mov DO ro r result z __addr16 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference 245 1 __addr16 ro result 8 34 2 8 define _ LPM_dword_enhanced__ addr Value __extension__ uint16_t addri6 uint16_t addr uint32_t _ result _ asm lpm 0 Z An NE lpm B0 Z4 lpm CO Z nt lpm 0 Z NnNE r result z addr16 1 addrl16 result 8 34 2 9 define _ LPM enhanced __ Value __extension__ uintl6 t addrl6 uint16_t addr uint8 t _ result N asm N N lpm 0 2 n t X r result N addr16 N result N
423. t have symbolic names in the assembler code However local variables may be held in registers With AVR GCC you can specify the use of a specific register Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 7 How to Build a Library 300 void Count void register unsigned char counter asm r3 some code asm volatile clr r3 more code The assembler instruction clr r3 will clear the variable counter AVR GCC will not completely reserve the specified register If the optimizer recognizes that the vari able will not be referenced any longer the register may be re used But the compiler is not able to check wether this register usage conflicts with any predefined register If you reserve too many registers in this way the compiler may even run out of registers during code generation In order to change the name of a function you need a prototype declaration because the compiler will not accept the asm keyword in the function definition extern long Calc void asm CALCULATE Calling the function Calc will create assembler instructions to call the function CALCULATE 9 6 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 9 7 How to Build a Library 9 7 1 Introduction So you keep reusing the same functions that you created over and over Tired of
424. t 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 20 Additional notes from lt avr sfr_defs h gt The lt avr sfr_defs h gt file is included by all of the 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_IO8 0x02 define EEAR _SFR_IO16 0x21 define UDRO _SFR_MEMB8 0xC6 define TCNT3 _SFR_MEM16 0x94 define CANIDT _SFR_MEM32 0xF0 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 20 Additional notes from lt avr sfr_defs h gt 150 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
425. 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 implemented on it s usually not noticeable on larger machines like PCs while the waste of flash ROM storage can be very painful on a small microcontroller like the AVR So in general variables should only be explicitly initialized if the initial value is non Zero Note Recent versions of GCC are now smart enough to detect this situation and revert variables that are explicitly initialized to 0 to the bss section Still other compi
426. t 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 PVM value back to EEPROM once it is not changing anymore The ADC interrupt will just adjust the PWM value only Finally the UART Rx interrupt will dispatch on the last character received from the UART All the string literals that are used as informational messages within main are placed in program memory so no SRAM needs to be allocated for them This is done by using PSTR macro and passing the string to printstr p 6 37 4 The source code The source code is installed under Sprefix share doc avr libc examples largedemo largedemo c where prefix is a configuration option For Unix systems it is usually set to either usr usr local Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 209 6 38 Using the standard IO facilities This project illustrates how to use the standard IO facilities stdio provided by this library It assumes a basic knowledge of how the stdio subs
427. t 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 10 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 10 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 10 4 9 char dtostre double val char s unsigned char __prec unsigned char __flags The dtostre function converts the double value passed in val into an ASCII repre sentation that will be stored under s The caller is responsible for providing sufficient storage in s Conversion is done in the format d ddde dd where there is one digit before the decimal point character and the number of digits after it is equal to the precision prec if the precision is zero no decimal point character appears If flags has the DTOSTRE_UPPERCASE bit set the letter E rather than e will be used to introduce the exponent The exponent always contains
428. t 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 into its initial position upon reception of the next character so a new line of text can be displayed Therefore a received newline character is remembered until more characters have been sent by the application and will only then cause the display to be cleared before continuing This provides a convenient abstraction where full lines of text can be sent to the driver and will remain visible at the LCD until the next line is to be displayed Further control characters could be implemented e g using a set of escape sequences That way it would be possible to implement self scrolling display lines etc The public function 1 init first calls the initialization entry point of the lower level HD44780 driver and then sets up the LCD in a way we d like to display cleared non blinking cursor enabled SRAM addresses
429. t8 t 138 prog uchar 138 prog uintl6 t 138 prog uint32 t 138 prog uint64 t 138 prog uint8 t 138 prog void 138 PROGMEM 137 PSTR 137 strcasecmp P 140 strcasestr P 140 strcat P 140 strchr P 140 strchrnul P 141 strcmp P 141 strcpy P 141 strcspn P 141 strlcat P 142 strlcpy P 142 strlen P 142 strncasecmp P 142 strncat P 143 strncmp P 143 strncpy P 143 strnlen P 144 strpbrk P 144 strrchr P 144 strsep P 144 strspn_P 145 strstr P 145 avr sfr BV 151 bit is clear 151 bit is set 151 loop until bit is clear 151 loop until bit is set 151 avr sleep sleep cpu 153 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen INDEX 375 sleep_disable 153 sleep_enable 153 avr_stdint INT16_C 44 INTI6_MAX 44 6 44 int16 t 49 INT32 C 44 INT32 MAX 44 32 MIN 44 int32_t 49 INT64 C 44 INT64 MAX 45 INT64 MIN 45 int64 t 49 INTS C 45 INT8 MAX 45 INT8_MIN 45 int8 t 49 INT FAST16 MAX 45 INT FAST16 MIN 45 int fastl16 t 50 INT FAST32 MAX 45 INT FAST32 MIN 45 int fast32 t 50 INT FAST64 MAX 45 INT FAST64 MIN 45 int fast64 t 50 INT FAST8 MAX 46 INT FAST8 MIN 46 int fast8 t 50 INT LEASTI6 MAX 46 INT LEASTI6 MIN 46 int least16 t 50 INT LEAST32 MAX 46 INT LEAST32 MIN 46 int least32 t 50 INT LEAST64 MAX 46 INT LEAST64 MIN 46 int least64 t 50 INT LEAST8 MAX 46 INT LEASTS
430. tack frame of the caller This temporary space is automatically freed when the function that called alloca re turns to its caller Avr libc defines the alloca as a macro which is translated into the inlined _ builtin alloca function The fact that the code is inlined means that it is impossible to take the address of this function or to change its behaviour by linking with a different library Returns alloca returns a pointer to the beginning of the allocated space If the allocation causes stack overflow program behaviour is undefined Warning Avoid use alloca inside the list of arguments of a function call 6 2 lt assert h gt Diagnostics 6 2 1 Detailed Description include assert h This header file defines a debugging aid As there is no standard error output stream available for many applications using this library the generation of a printable error message is not enabled by default These messages will only be generated if the application defines the macro ASSERT USE STDERR before including the assert h gt header file By default only abort will be called to halt the application Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 3 lt gt Character Operations 17 Defines define assert expression 6 2 2 Define Documentation 6 2 2 1 define assert expression Parameters expression Expression to test for The assert macro tests the gi
431. tch COMPAREIA 1A TIMERI SIG Timer Counter1 ATtiny26 CMPB_vect OUTPUT_ Compare Match COMPAREIB 1B SIG Timer Counter1 AT90S2313 COMPI vect OUTPUT Compare Match COMPAREIA SIG Timer Counter1 AT90S4414 419054434 41719058515 COMPA_vect OUTPUT_ Compare Match AT90S8535 AT90PWM216 COMPAREIA A AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal284P ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P ATmega168 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 ATtiny48 ATtiny261 ATtiny461 AT tiny861 9005 162 9005 82 9005 1287 AT90USB 1286 9005 647 9005 646 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 120 Vector name Old vector Description Applicable for device name TIMER 1_ SIG_ Timer Counter1 AT90S4414 419054434 419058515 COMPB_vect OUTPUT_ Compare MatchB 479058535 AT90PWM216 C
432. ted by a dot the major number the minor number and the revision number For development versions which use an odd minor number the string representation additionally gets the date code YY YYMMDD appended This file will also be included by lt avr io h gt That way portable tests can be implemented using lt avr io h gt that can be used in code that wants to remain backwards compatible to library versions prior to the date when the library version API had been added as referenced but undefined C preprocessor macros automatically evaluate to 0 Defines define VERSION STRING 1 6 2 e define __ LIBC VERSION J 10602UL e define _ LIBC DATE STRING 20080403 e define _ LIBC 20080403UL e define _ MAJOR 1 e define _ LIBC MINOR 6 e define _ AVR REVISION 2 6 23 2 Define Documentation 6 23 2 1 define AVR LIBC DATE 20080403UL Numerical representation of the release date 6 23 2 22 define LIBC DATE STRING 20080403 String literal representation of the release date 6 23 2 3 define MAJOR 1 Library major version number 6 23 2 4 define _ AVR MINOR 6 Library minor version number 6 23 2 5 define LIBC REVISION 2 Library revision number Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 24 lt avr wdt h gt Watchdog timer handling 156 6 23 2 6 defi
433. teger i Note The abs and labs functions are builtins of gcc 6 10 4 15 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 10 4 16 char long int __val char x _ s int radix Convert a long integer to a string The function Itoa converts the long integer 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 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 ltoa function returns the pointer passed as s 6 10 4 17 void malloc size t __ size The malloc function allocates size bytes of memory If malloc fails a NULL pointer is returned Note that m
434. the Global Interrupt Status flag when execution of the block completes 6 206 lt util crc16 h gt CRC Computations 6 26 1 Detailed Description include util crcl6 h This header file provides a optimized inline functions for calculating cyclic redundancy checks CRC using common polynomials References Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 26 lt util crc16 h gt CRC Computations 164 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 J 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 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 ibu
435. the name of the listing file The various sub options can be combined into a single a option list file must be the last one in that case 9 12 2 2 Examples for assembler options passed through the C compiler Re member that assembler options 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 avr gcc O foo c foo o Wa ahls foo lst In order to pass an assembler file through the C preprocessor first and have the assem bler generate line number debugging information for it the following command can be used avr gcc c x assembler with cpp o foo o foo S Wa gstabs Note that on Unix systems that have case distinguishing file systems specifying a file name with the suffix S upper case letter S will make the compiler automatically assume x assembler with cpp while using s would pass the file directly to the assembler no preprocessing done 9 12 3 Controlling the linker avr ld 9 12 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 be
436. 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 featureset In order to allow programmers a code size vs functionality tradeoff the function vfprintf which is the heart of the printf family can be selected in different flavours using linker options See the documentation of vfprintf for a detailed description The same applies to vfscanf and the scanf family of functions Outline of the chosen API 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 devopen 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 Vn 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 i
437. tion see http www semiconductors philips com buses i2c index html 6 39 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 217 using appropriate pullup resistors The pullups must be small enough to recharge the line capacity in short enough time compared to the desired maximal clock fre quency yet large enough so all drivers will not be overloaded There are formulas in the datasheet that help selecting the pullups Devices can either act as a master to the bus i e they initiate a transfer or as a slave they only act when being called by a master The bus is multi master capable and a particular device implementation can act as either master or slave at different times Devices are addressed using a 7 bit address coordinated by Philips transfered as the first byte after the so called start condition The LSB of that byte is R W i e it determines whether the request to the slave is to read or write data during the next cycles There is also an option to have devices using 10 bit addresses but that is not covered by this example 6 39 2 The TWI example project The ATmega TWI
438. tion you have to add up that for all functions where you know that the calls could be nested Back to FAQ Index 9 10 23 Is it really impossible to program the ATtinyXX in C While some small 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 9 10 24 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 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 331 Solution don t use inferior file systems operating systems Neither Unix file systems nor HPFS
439. tion f scanf performs formatted input reading the input data from st ream See vfscanf for details Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 64 6 9 3 16 int fscanf_P FILE x _ stream const char fmt Variant of fscanf using a fmt string in program memory 6 9 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 pt r Returns the number of objects successfully written i e nmemb unless an output error occured 6 9 3 18 char gets char x str Similar to fgets except that it will operate on stream st din and the trailing newline Gf any will not be stored in the string It is the caller s responsibility to provide enough storage to hold the characters read 6 9 3 19 int printf const char fmt The function printf performs formatted output to stream stderr See vfprintf for details 6 9 3 20 int printf_P const char _ fmt Variant of printf that uses a fmt string that resides in program memory 6 9 3 21 int puts const char __ str Write the string pointed to by str and a trailing newline character to stdout 6 9 3 22 int puts P const char str Variant of puts where st r resides in program memory 6 9 3 23 int scanf const char fmt The function scanf performs form
440. tion falls into the function s classification i e isdigit returns true if its argument is any value 0 though 9 inclusive If the input is not an unsigned char value all of this function return false e intisalnum int c e intisalpha int c e intisascii int c e intisblank int c e intiscntrl int c e intisdigit int c e intisgraph int c e int islower int e int isprint int c e int ispunct int e int isspace int c e int isupper int c Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 8 8 delay h File Reference 231 e intisxdigit int c Character convertion routines This realization permits all possible values of integer argument The toascii func tion clears all highest bits The tolower and toupper functions return an input argument as is if it is not an unsigned char value inttoascii int c e inttolower int e int toupper int c 8 8 delay h File Reference 8 8 1 Detailed Description Defines define_UTIL_DELAY_H_ 1 define F_CPU 1000000UL Functions e void delay us double __us void delay ms double __ms 8 9 delay basic h File Reference 8 9 11 Detailed Description Defines define UTIL DELAY BASIC H 1 Functions e void delay loop 1 uint8 t count e void delay loop 2 uintl6 t count Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 10 errno h File Reference 232 8 10 File Referen
441. 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 Data Fields int quot int rem 7 1 2 Field Documentation 7 1 21 int div t quot The Quotient Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 7 2 1div_t Struct Reference 222 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 long rem 7 2 2 Field Documentation 7 2 2 1 long Idiv_t quot The Quotient 7 2 2 2 long Idiv_t rem The Remainder The documentation for this struct was generated from the following file stdlib h 8 avr libc File Documentation 8 1 assert h File Reference 8 1 1 Detailed Description Defines define
442. to 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 configure prefix PREFIX 9 11 11 Building and Installing under Windows Building and installing the toolchain under Windows requires more effort because all of the tools required for building and the programs themselves are mainly designed for running under a POSIX environment such as Unix and Linux Windows does not natively provide such an environment There are two projects available that provide such an environment Cygwin and MinGW MSYS There are advantages and disadvantages to both Cygwin provides a very complete POSIX environment that allows one to build many Linux based tools from source with very little or no source modifications However POSIX functionality is provided in the form of a DLL that is linked to the application This DLL has to be redistributed with your application and there are issues if the Cygwin DLL already exists on the installation system and different versions of the DLL On the other hand MinGW MSYS can compile code as native Win32 applications However this means Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 342 that programs designed for Unix and Linux i e that use POSIX f
443. tructure 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 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 37 A more sophisticated project 207 6 37 3 3 Part 3 Interrupt service routines ISR to handle timer 1 s overflow interrupt arranges for the software clock While timer 1 runs the PWM it calls its overflow handler rather frequently
444. tton update uint8 t crc uint8 t data 6 26 2 Function Documentation 6 26 2 1 static inline uint16_t crc16 update uint16 t _ crc uint8 t data static Optimized CRC 16 calculation Polynomial x 16 x 15 x 2 1 0xa001 Initial value Oxffff This CRC is normally used in disk drive controllers The following is the equivalent functionality written in C Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 26 lt utiV crc16 h gt CRC Computations 165 uint16_t crc16_update uint16_t crc uint8_t a int i cre for i 0 i lt 8 i if ere amp 1 cre cre gt gt 1 0 001 else cre cre gt gt 1 return crc 6 26 2 2 static inline uint16 t crc ccitt update uint16 t __crc uint8_t_ data static Optimized CRC CCITT calculation Polynomial x 16 x 12 x 5 1 0x8408 Initial value Oxffff This is the CRC used by PPP and IrDA See RFC1171 PPP protocol and IrDA IrLAP 1 1 Note Although the CCITT polynomial is the same as that used by the Xmodem protocol they are quite different The difference is in how the bits are shifted through the alorgithm Xmodem shifts the MSB of the CRC and the input first while CCITT shifts the LSB of the CRC and the input first The following is the equivalent functionality written in C uintl16 t crc ccitt update uintl16 t crc uint8 t data data 108 crc data
445. two digits if the value is zero the exponent is 00 If flags has the DTOSTRE_ALWAYS_SIGN bit set a space character will be placed into the leading position for positive numbers If flags has the DTOSTRE_PLUS_SIGN bit set a plus sign will be used instead of a space character in this case The dtostre function returns the pointer to the converted string s 6 10 4 10 char dtostrf double _ val signed char _ width unsigned char prec char x s The dtostrf function converts the double value passed in 1 into an ASCII repre sentationthat will be stored under s The caller is responsible for providing sufficient Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 77 storage in s Conversion is done in the format d ddd The minimum field width of the output string including the and the possible sign for negative values is given in width and prec determines the number of digits after the decimal sign width is signed value negative for left adjustment The dtostrf function returns the pointer to the converted string s 6 10 4 11 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 Before entering the infinite loop inter rupts are globally disa
446. ue an int least8 t can hold 6 8 2 28 INT LEAST8 MIN INT8 MIN smallest negative value an int least8 t can hold Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 48 6 8 2 29 define INTMAX_C value LL define a constant of type intmax_t 6 8 2 30 define INTMAX MAX INT64 MAX largest positive value an intmax_t can hold 6 8 2 31 define INTMAX MIN INT64 MIN smallest negative value an intmax_t can hold 6 8 2 32 define INTPTR MAX 6 MAX largest positive value an intptr t can hold 6 8 2 33 define INTPTR MIN INT16 MIN smallest negative value an intptr t can hold 6 8 2 34 define PTRDIFF MAX INTI6 MAX largest positive value a ptrdiff t can hold 6 8 2 35 define PTRDIFF MIN INT16 MIN smallest negative value a ptrdiff t can hold 6 8 2 36 define SIG ATOMIC MAX INT8 MAX largest positive value a sig atomic t can hold 6 8 2 37 ftdefine SIG ATOMIC MIN INT8 MIN smallest negative value a sig atomic t can hold 6 8 2 38 define SIZE MAX CONCAT INTI6 U largest value a size t can hold 6 8 2 39 define UINT16_C value CONCAT value U define a constant of type uint16 t Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 49 6 8 2 40 define UINTI6 MAX CONCAT INTI6 MAX U x 20 1U largest value an uint16 t can hold
447. unctionality will not compile as MinGW MSYS does not provide that POSIX layer for you Therefore most programs that compile on both types of host systems usually must provide some sort of abstraction layer to allow an application to be built cross platform MinGW MSYS does provide somewhat of a POSIX environment that allows you to build Unix and Linux applications as they woud normally do with a configure step and a make step Cygwin also provides such an environment This means that building the AVR toolchain is very similar to how it is built in Linux described above The main differences are in what the PATH environment variable gets set to pathname differences and the tools that are required to build the projects under Windows We ll take a look at the tools next 9 11 12 Tools Required for Building the Toolchain for Windows These are the tools that are currently used to build WinAVR 20070525 or later This list may change either the version of the tools or the tools themselves as improve ments are made MinGW MSYS http downloads sourceforge net mingw MinGW 5 1 3 exe use mirror superb east gt Put MinGW 5 1 3 exe in it s own directory for example C MinGWSetup Run MinGW 5 1 3 exe Select Download and install Select Current package Select type of install Full Install MSYS 1 0 10 exe package lt http prdownloads sf net mingw MSYS 1 0 10 exe download gt Default selections
448. upted 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 32 2 6 define outb port val port val Deprecated Write val to IO port port 6 32 2 7 define outp val port port val Deprecated Write val to IO port port 6 32 2 8 define sbi port bit port 1 lt lt bit Deprecated Set bit in IO port port Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 33 lt compat ina90 h gt Compatibility with EWB 3 x 180 6 32 3 Function Documentation 6 32 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 33 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 100 compat ibility though Note For actual documentation please see the IAR manual 6 34 Demo projects 6 34 1 Detailed Description Various small demo projects are provided to illustrate several aspects of using the open
449. ure for the opened stream is returned Reasons for a possible failure currently include that neither the put nor the get argument have been provided thus attempting to open a stream with no IO intent at all or that insufficient dynamic memory is available to establish a new stream 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 May 12 09 55 09 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 62 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 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 st
450. 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 7 lt setjmp h gt Non local goto 40 For a very detailed discussion of setimp longjmp see Chapter 7 of Advanced Pro gramming in the UNIX Environment by W Richard Stevens Example include setjmp h jmp buf env int main void if setjmp env handle error main processing loop which calls foo void foo void blah blah blah if err longjmp env 1 Functions int setjmp jmp buf __jmpb e void longjmp jmp_buf jmpb int ATTR NORETURN 67 2 Function Documentation 6 7 2 1 void longjmp jmp buf __jmpb int ret Non local jump to a saved stack context finclude set jmp h longjmp restores the environment saved by the last call of setjmp with the corre sponding jmpb argument After longjmp is completed program execution contin ues as if the corresponding call of setjmp had just returned the value ret Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 41
451. val The first byte to match val interpreted as an unsigned character stops the operation Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 86 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 11 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 memcmp function returns an integer less than equal to or greater than zero if the first len bytes of s1 is found respectively to be less than to match or be greater than the first 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 11 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 6 11 3 8 void memmem const void gt s1 size t len c
452. valid C identifier as a macro whereas the assembler s macro concept is basically targeted to use a macro in place of an assembler instruction Use of the runtime framework like automatically assigning interrupt vectors For devices that have RAM initializing the RAM variables can also be utilized 9 5 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 283 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 crt XXX o and linker script Note that the invokation of the C preprocessor will be automatic when the filename provided for the assembler file ends in S the capital letter s This would even apply to operating systems that use case insensitive filesystems since the actual decision is made based on the case of the fi
453. ven 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 3 lt ctype h gt Character Operations 6 3 1 Detailed Description These functions perform various operations on characters include lt ctype h gt Character classification routines These functions perform character classification They return true or false status de pending whether the character passed to the function falls into the function s classifi cation i e isdigit returns true if its argument is any value 0 though 9 inclusive If the input is not an unsigned char value all of this function return false intisalnum int c e int isalpha int c int isascii int int isblank int int iscntrl int e intisdigit int c e intisgraph int c int islower int c Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 3 lt ctype h gt Character Operations 18 e int isprint int c e int ispunct int e int isspace int e int isupper int c e intisxdigit int c Character convertion routines This realization permits all possible values of integer argument The toascii function
454. vr libc by Doxygen 6 27 lt util delay h gt Convenience functions for busy wait delay loops 167 6 27 lt util delay h gt Convenience functions for busy wait delay loops 6 27 1 Detailed Description define F CPU 100000001 1 MHz define 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 def ine statement should be used The functions in this header file are wrappers around the basic busy wait functions from util delay basic h They are meant as convenience functions where actual time values can be specified rather than a number of cycles to wait for The idea behind is that compile time constant expressions will be eliminated by compiler optimization so floating point expressions can be used to calculate the number of delay cycles needed based on the CPU frequency passed by the macro F CPU Note In order for these functions to work as intended compiler optimizations must be enabled and the delay time must be an expression that is a known constant at compile time If these requirements are not met the resulting delay will be much longer and basically unpredictable and applications that otherwise do not use floating point calculations will experience severe code bloat by the floating point library routines linked into the application The functions available allow the specificati
455. vr_watchdog 158 TW_STATUS 175 WDTO_4S TW_STATUS_MASK 175 avr_watchdog 158 TW_WRITE 175 WDTO_500MS avr_watchdog 158 avr_stdlib 81 WDTO_60MS avr_watchdog 158 vfprintf WDTO 8S avr watchdog 158 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen
456. was encountered while reading the string will then be terminated with a NUL character If an error was encountered the function returns NULL and sets the error flag of stream which can be tested using ferror Otherwise a pointer to the string will be returned 6 9 3 0 int fprintf FILE x stream const char fmt The function fprintf performs formatted output to stream See vfprintf for details 6 9 3 10 intfprintf P FILE stream const char fmt Variant of fprintf that uses a fmt string that resides in program memory 6 9 3 11 int fputc int __c FILE stream The function fputc sends the character c though given as type int to st ream It returns the character or EOF in case an error occurred 6 9 3 12 intfputs const char str FILE x stream Write the string pointed to by str to stream st ream Returns 0 on success and EOF on error 6 9 3 13 int fputs_P const char str FILE stream Variant of fputs where st resides in program memory 6 9 3 14 size t fread void ptr size t _ size size_t nmemb FILE x stream Read nmemb objects size bytes each from st ream to the buffer pointed to by ptr Returns the number of objects successfully read i e nmemb unless an input error occured or end of file was encountered feof and ferror must be used to distinguish between these two conditions 6 9 3 15 intfscanf FILE x stream const char fmt The func
457. will default to section data and two symbols will be created named binary foo bin start and binary foo bin end These symbols can be referred to inside a C source to access these data Ifthe goal is to have those data go to flash ROM similar to having used the PROGMEM attribute in C source code the sections have to be renamed while copying and it s also useful to set the section flags avr objcopy rename section data progmem data contents alloc load readonly data I binary O elf3 Note that all this could be conveniently wired into a Makefile so whenever oo bin changes it will trigger the recreation of and a subsequent relink of the final ELF file Back to FAQ Index Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 334 9 10 31 How do I perform a software reset of the AVR The canonical way to perform a software reset of the AVR is to use the watchdog timer Enable the watchdog timer to the shortest timeout setting then go into an infinite do nothing loop The watchdog will then reset the processor The reason why this is preferrable over jumping to the reset vector is that when the watchdog resets the AVR the registers will be reset to their known default settings Whereas jumping to the reset vector will leave the registers in their previous state which is generally not a good idea CAUTION Older AVRs will have the watchdog timer disabled on a r
458. wise an overflow interrupt will be generated whenever the countdown reached BOTTOM value 0 where the counter will again alter its counting direction to upwards This informa tion is needed in order to know whether the current counter value of TCNTO is to be evaluated from bottom or top Further ioinit activates the pin change interrupt PCINTO on any edge of PB4 Finally PB1 OCOB will be activated as an output pin and global interrupts are being enabled In 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 35 2 2 project h 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
459. 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 Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 3 Memory Sections 274 It is possible to tell the linker explicitly where to place the noinit section by adding Wl 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 9 3 6 initN Sections These sections are used to define the startup code from reset up through the start of main These all are subparts of the text section The purpose of these sections is to allow for more specific placement of code within your program Note Sometimes it is convenient to think of the initN and finiN sections as functions but in reality they are just symbolic names
460. xample 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 Alternatively operands can be given names The name is prepended in brackets to the constraints in the operand list and references to the named operand use the bracketed name instead of a number after the sign Thus the above example could also be written as asm in retval port retval r value port I SFR IO ADDR PORTD The last part of the asm instruction the clobber list is mainly used to tell the compiler about modifications done by the assembler code This part may be omitted all other parts are required but may be left empty If your assembler routine won t use any input or output operand two colons must still follow the assembler code string A good example is a simple statement to disable interrupts asm volatile cli 9 6 2 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
461. y arise while using pointer register pairs If you define an input operand e ptr and the compiler selects register Z 130 131 then A0 refers to x30 and BO refers to r31 But both versions will fail during the assembly stage of the compiler if you explicitely need Z like in 1 24 7 If you write r24 0 with a lower case a following the percent sign then the compiler will create the proper assembler line Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 296 9 6 4 Clobbers As stated previously the last part of the asm statement the list of clobbers may be omitted including the colon seperator However if you are using registers which had not been passed as operands you need to inform the compiler about this The following example will do an atomic increment It increments an 8 bit value pointed to by a pointer variable in one go without being interrupted by an interrupt routine or another thread in a multithreaded environment Note that we must use a pointer because the incremented value needs to be stored before interrupts are enabled asm volatile cp ld r24 a0 n t inc x24 ARNE st a0 r24 NN EN sei mne e ptr r24 The compiler might produce the following code cli ld r24 Z inc r24 st Z r24 sei One easy solution to avoid clobbering register r24 is to make use of the special tem porary
462. y included if STDC LIMIT MACROS is defined before including lt inttypes h gt define PRId8 d define PRIdLEASTS d define PRIdFASTS d define PRIi8 i define PRILEASTS i Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 8 17 inttypes h File Reference define PRIiFASTS i define PRId16 d define PRIdLEASTI6 define PRIGFAST16 d define PRLi16 i define PRIILEASTI6 1 define PRIiFASTI6 i define PRId32 define PRIdLEAST32 define PRIdFAST32 Id define PRIi32 li define PRILEAST32 li define PRILFAST32 li define PRIdPTR PRId16 define PRIi16 define PRIo8 define PRIOLEASTS o define PRIOFASTS o define PRIu8 u define PRIULEASTS u define PRIUFASTS8 u define PRIx8 x define PRIXLEASTS x define PRIXFASTS x define PRIX8 X define PRIXLEASTS X define PRIXFASTS X define PRIo16 o define PRIOLEASTI6 o define PRIoFAST16 o define PRIu16 u define PRIULEAST16 u define PRIUFAST16 u define PRIx16 x define PRIXLEAST16 x define PRIxFAST16 x define PRIX16 X define PRIXLEAST16 X define PRIXFASTI6 X define PRIo32 lo define PRIOLEAST32 lo define PRIoFAST32 lo define PRIu32 lu define PRIULEAST32 lu define PRIUFAST32 lu define PRIx32 Ix define PRIXLEAST32 Ix define PRIXFAST32 Ix define PRIX32 IX define PRIXLEAST32 IX Generated on Mon
463. y need to be turned off using no exceptions in the compiler options Failing this the linker will complain about an undefined external reference to gxx personality 510 Constructors and destructors are supported though including global ones When programming C in space and runtime sensitive environments like microcon trollers extra care should be taken to avoid unwanted side effects of the C calling conventions like implied copy constructors that could be called upon function invo cation etc These things could easily add up into a considerable amount of time and Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 316 program memory wasted Thus casual inspection of the generated assembler code using the 5 compiler option seems to be warranted Back to FAQ Index 9 10 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 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
464. y 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 38 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 HD44780 LCD display driver e hd44780 h Interface declarations for the HD44780 driver 1cd c Implementation of LCD character IO on top of the HD44780 driver 1cd h Interface declarations for the LCD driver Generated on Mon May 12 09 55 09 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 211 uart c Implementation of a character IO driver for the internal UART uart h Interface declarations for the UART driver 6 38 3 code walkthrough 6 38 3 1 stdiodemo c As usual include files go first While conventionally system header files those in angular brackets lt gt go before application specific header files in double quotes defines h comes as the first h
465. ystem 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 6 38 1 Hardware setup The demo is set up in a way so it can be run on the ATmegal6 that ships with the STK500 development kit The 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 stdout respectively In order to have a different device available for a standard error channel stderr an industry standard LCD display with an HD44780 compatible LCD controller has been chosen This display needs to be connected to port A of the STK500 in the following way Port Header Function 0 1 LCD D4 1 2 LCD D5 2 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 Generated on Mon 12 09 55 09 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 210 Figure 5 Wiring of the STK500 The LCD controller is used in 4 bit mode including polling the busy flag so the R W line from the LCD controller needs to be connected Note that the LCD con troller has yet another suppl

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