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avr-libc Reference Manual

1. Vector name Old vector Description Applicable for device name SIG_INPUT_ Timer Counter AT90S2333 AT90S4414 AT90S4433 CAPT_vect CAPTURE Capture Event AT90S4434 479058515 AT90S8535 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 AT90USB162 9005 82 9005 1287 AT90USB1286 AT90USB647 AT90USB646 TIMERI SIG Timer Counter1 ATtiny26 CMPA_vect OUTPUT_ Compare Match COMPAREIA 1A TIMERI SIG Timer Counter1 ATtiny26 CMPB_vect OUTPUT_ Compare Match COMPAREIB 1B TIMERI SIG Timer Counter1 AT90S2313 COMPI vect OUTPUT Compare Match COMPAREIA TIMERI SIG Timer Counter1 AT90S4414 AT90S4434 9058515 COMPA _vect OUTPUT_ Compare Match AT90S8535 AT90PWM3 9 2 COMPAREIA A AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 161 ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250
2. 111 linker options Pass the listed options to the assembler or linker respectively 4 4 Generate debugging information that be used by avr gdb ffreestanding Assume a freestanding environment as per the C standard This turns off automatic builtin functions though they can still be reached by prepending builtin to the actual function name It also makes the compiler not complain when main is declared with a void return type which makes some sense in a microcontroller environment where the application cannot meaningfully provide a return value to its environment in most cases main won t even return anyway However this also turns off all optimizations normally done by the compiler which assume that functions known by a certain name behave as 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 351 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 r
3. 8 14 siS Pile Referente cc 24 s ss e w SU qua 8 14 1 Detailed Description 8 15 File Reference 222 o o 8 15 1 Detailed Description 8 16 mterrupt h File Referenc lt a o coe eae erene Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS 8 18 8 20 8 2 8 22 8 23 8 24 8 25 8 26 8 27 8 28 8 29 8 16 1 Detailed Description sc 2 o e s ear kus s eee 225 nt ypes h File Reference lt sa u as po gx eR e 226 8 17 1 Detailed Description 222222225954 m RR 226 iah Pile ReterenGe 222222222242 GS S AUS 228 5 18 1 Detailed Description 228 math Pile Referenee o uus oe ew 2 22 5 228 8 19 1 Detaled Description c se csee s 86554 ae 525 228 tnemeepy s Pile Reference 22 2 22 229 820 1 Detaled Description cu xx 66248 e i 229 menichrs File Rebergnee lt i poa ss cee eR 230 8 21 1 Detailed Description 2 230 miemchr_PS File Reference o seac cc o ooo RR aa 230 8 22 1 Detailed Description 22 2 54855 ROG g xS RR 230 t enicip s File Referente 02222222552 SUNSU QUN S ws 230 5 23 1 Detailed Deseripti lt lt s ss a RR 230 P S File Reference s ooo s coro wa m x Rs 230 8 24 1 Detaled Description 2 22 22 230 memcpby S File Reference o soe coc acsem eena ena 230 825 1 Detaled Description gt cesed re
4. 5 8 avr_inttypes 26 PRIxFASTS avr inttypes 27 PRIXLEAST16 avr_inttypes 27 PRIxLEAST16 avr_inttypes 27 PRIXLEAST32 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 378 avr_inttypes 27 PRIxLEAST32 avr_inttypes 27 PRIXLEAST8 avr_inttypes 27 PRIxLEASTS avr inttypes 27 PRIXPTR avr inttypes 27 PRIxPTR avr inttypes 27 prog char avr pgmspace 128 prog intl6 t avr pgmspace 128 prog int32 t avr pgmspace 128 prog int64 t avr pgmspace 128 prog int8 t avr pgmspace 129 prog uchar avr pgmspace 129 prog uint16 t avr pgmspace 129 prog uint32 t avr pgmspace 129 prog uint64 t avr pgmspace 129 prog uint8 t avr pgmspace 129 prog void avr pgmspace 129 PROGMEM avr pgmspace 128 PSTR avr pgmspace 128 PTRDIFF MAX avr stdint 45 PTRDIFF MIN avr stdint 46 putc avr stdio 58 putchar avr stdio 58 puts avr stdio 62 puts P avr stdio 62 qsort avr stdlib 76 quot div t 211 ldiv t 212 rand avr stdlib 76 RAND MAX avr stdlib 72 rand r avr stdlib 77 random avr stdlib 77 RANDOM MAX avr stdlib 72 random r avr stdlib 77 realloc avr stdlib 77 rem div t 211 ldiv t 212 reti avr interrupts 122 sbi deprecated items 170 scanf avr stdio 62 scanf P avr stdio 62 SCNd16 avr_inttypes 27 SCNd32 avr_inttypes 27 SCNdFAST 16 avr_inttypes 28 SCNdFAST32 avr_inttypes 28 SCNdLEAST16
5. Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 15 lt avr io h gt AVR device specific IO definitions 124 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 O in new code Use ISR instead 6 15 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 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 devices Also included are the speci
6. 8 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 AT megal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3_ CAPT_vect SIG_INPUT_ CAPTURE3 Timer Counter3 Capture Event AT90CAN128 AT90CAN32 AT90CANGA ATmegal28 ATmegal62 ATmega64 mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER3_ COMPA_vect SIG_ OUTPUT_ COMPARE3A Timer Counter3 Compare Match A AT90CAN128 AT90CAN32 AT90CANGA ATmegal28 ATmegal62 ATmega64 mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 116 Vector name Old vector Description Applicable for device name TIMER3_ SIG_ Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPB_vect OUTPUT_ Compare Match ATmegal28 ATmegal62 ATmega64 COMPARE3B B mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER3_ SIG_ Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPC_vect OUTPUT_ Compare Match ATmegal28 ATmega64 ATmega640 AT COMPARE3C C mega1280 ATmegal281 ATmega2560
7. Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 11 errno h File Reference 224 Functions static uint8_t _ attribute always_inline eeprom_read_byte const uint8 t addr Variables static void const void pointer_eeprom static void const void size_t size static void uint8_t value static void uint16_t value static void void pointer_eeprom static void void size_t size 8 11 errno h File Reference 8 11 1 Detailed Description Defines define ERRNO 1 define EDOM 33 define ERANGE 34 Variables int errno 8 12 fdevopen c File Reference 8 12 1 Detailed Description Functions FILE x fdevopen int put char FILE int get FILE Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 13 ffs S File Reference 225 8 13 ffs S File Reference 8 13 1 Detailed Description 8 14 ffsl S File Reference 8 14 1 Detailed Description 8 15 ffsll S File Reference 8 15 1 Detailed Description 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_v
8. 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 lack support for recent AVR devices A patch that adds more AVR types can be found at http www freebsd
9. 161 ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega406 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtinyll ATtinyl2 AT tiny13 ATtiny15 ATtiny22 ATtiny2313 ATtiny26 ATtiny28 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny46l AT tiny861 AT9OUSB162 9005 82 9005 1287 AT90USB 1286 9005 647 9005 646 Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 108 Vector name Old vector name Description Applicable for device INTI vect SIG INTERRUPTI External Interrupt Request 1 AT90S2313 419052333 AT90S4414 9054433 419054434 419058515 9058535 AT9OPWM3 9 2 AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 161 ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega406 ATmega64 ATmega8 AT mega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 ATtiny28 ATtiny261 ATtiny46l AT tiny861 ATOOUSBI62 9005 82
10. 20 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS ii 6 6 6 7 6 8 6 9 6 1 651 Detailed Description e oc ses operes erimas 20 052 Deme 2k o o o a RE 23 65 3 Typedef Documentation 222222545542 v RES 32 mal Matbenialie8 ooa s eso oj A 32 66 1 Detailed Description 32 6 6 2 Define Documentation 33 6 6 3 Function Documentation 4 04 2s RR RR 34 lt setjmp h gt Non local goto 38 Demiediesenptoh 222222225 55 38 6 72 Function Documentation s oss Ree 39 lt stdint h gt Standard Integer Types 40 681 Detaled Description lt s 2 ba RR bea RE 40 6 5 2 Documentation o ou Ro EGRE 44 6 5 3 Typedet Documentation 222222222 225226 eee es 49 lt stdio h gt Standard IO 52 691 Detailed Description 52 6 9 2 Define Documentation 2 2 57 69 3 Function Documentation 59 stdbhblho Oeneralu h es s e eoe cR 3 eos 71 6 10 1 Detaded Description lt gt s e secre sace 22 25 2559 71 6 10 2 Define Documentation 72 6 10 3 Typedef Documentation 73 6 10 4 Function Documentation 73 6 10 5 Variable Documentation 81 lt sting SUES sls crx RE E
11. E 82 6 11 1 Detaled Descripti nm 222 2222 2 gt 82 611 2 DehneDocumentatoH s og es ype C RR EET 83 6 11 3 Function Documentation 83 lt avr boot h gt Bootloader Support Utilities 93 6 12 1 Detailed Description 93 6 12 2 Defne Documentation 222522222222 4 2 95 Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS iii 6 13 6 14 6 15 6 16 6 17 6 18 6 19 6 20 6 2 6 22 6 23 lt avr eeprom h gt EEPROM handling 99 PISI Detailed Description gt sss s s sos xg 99 6 13 2 Dehne Documentation uc 5222252 v RS 100 6 13 3 Function 101 cavrantermpt h Interrupts lt o esos ooo s 102 6 14 1 Detailed Description 102 6 14 2 Defne Documentation gt c o o s es 8s RR RR Rs 121 lt avr io h gt AVR device specific IO definitions 124 lt avr pgmspace h gt Program Space Utilities 125 6 16 1 Detailed Description lt cs s o ee dee SRR 125 6 16 2 Define Documentation 127 6 16 3 Typedef Documentation 2 129 6 16 4 Function Documentation 131 lt avr power h gt Power Reduction Management 137 Additional notes from avr sfr 5 gt 140 lt avr sfr_defs h gt Special function
12. __addr3 _SFR_IO_ADDR RAMPZ r30 2 r31 d uint32_t _ addr32 uint32_t _ result asm i out movw elpm elpm elpm elpm tyr ms I r30 _ result 8 33 23 define _ ELPM_enhanced__ addr Value L extension 2 1 r30 1 A0 Z B0 Z SCO 2 D0 Z uint32_t addr n t AITYNEM mne L result __addr32 SFR IO ADDR RAMPZ r31 uint32_t __addr32 uihgB t lt asm out movw elpm EN atq I result result Zp SCTE mne 30 1 0 Z n t result t addr32 SFR IO ADDR RAMPZ r31 PPS OA Boat Be uint32_t addr EE ee ee ALE BE E ELPM_dword_enhanced__ addr Pu dd Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 33 pgmspace h File Reference 236 8 33 2 4 define _ ELPM_word_classic__ addr Value __extension__ uint32_t __addr32 uint32_t addr uintl6 t _ result N asm N N out 2 C1 n t mov r31 SBI n t mov r30 elpm mov 0 ro TANNET in 0 2 adiw r30 1 WAYNE M adc r0 __zero_reg__ n t out 2 ro n t elpm mov B0 ro n t r result Em e e addr Z I SFR IO ADDR RAMPZ N mpg
13. 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 __c FILE stream Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 40 stdlib h File Reference 246 8 40 char fgets char str int size FILE stream char gets char str size_t fread void size_t __size size_t __nmemb FILE stream void clearerr FILE stream int feof FILE stream int ferror FILE stream int vfscanf FILE stream const char fmt va list int vfscanf P FILE stream const char fmt va list int fscanf FILE stream const char fmt int fscanf P FILE stream const char fmt int scanf const char fmt int scanf_P const char fmt int vscanf const char fmt va_list ap int sscanf const char buf const char fmt int sscanf_P const char buf const char fmt int fflush FILE xstream stdlib h File Reference 8 40 1 Detailed Description Data Structures struct div t struct ldiv t Non standard i e non ISO C functions define RANDOM MAX Ox7FFFFFFF char itoa int val char __s int __ radix
14. Contains the upper byte of the calculated prescaler value UBRR VALUE 6 28 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 28 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 29 lt util twi h gt TWI bit mask definitions 6 29 1 Detailed Description include lt util twi h gt This header file contains bit mask definitions for use with the AVR TWI interface TWSR values Mnemonics TW_MT xxx master transmitter Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 29 lt util twi h gt TWI bit mask definitions 165 TW MR xxx master receiver TW ST xxx slave transmitter TW SR xxx slave receiver fdefine TW START 0x08 define TW START 0x10 define TW MT SLA ACK 0x18 define TW MT SLA NACK 0x20 fdefine TW MT DATA ACK 0x28 define TW MT DATA NACK 0x30 define TW MT ARB LOST 0x38 define TW LOST 0x38 fdefine TW SLA ACK 0x40 define TW MR SLA NACK 0x48 define TW DATA ACK 0x50 define TW MR DATA NACK 0x58 define TW ST 5 ACK 8 define TW ST ARB LOST SLA OxBO fdefine TW ST DATA ACK 0xB8 define TW ST DATA 0xCO define TW ST LAST DATA 0xC8 define TW SR SLA ACK 0x6
15. See the chapter about malloc usage for implementation details 6 10 4 18 void qsort void __base size_t nmemb size_t size compar fn t compar The qsort function is a modified partition exchange sort or quicksort The qsort function sorts an 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 78 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 functions operate on int arguments Since the underlying algorithm
16. Description Applicable for device TIMER2_ COMPA_vect SIG_ OUTPUT_ COMPARE2A Timer Counter2 Compare Match A ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER2_ COMPB_vect SIG_ OUTPUT_ COMPARE2B Timer Counter2 Compare Match A ATmegal68 ATmega48 ATmega88 mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER2_ COMP_vect SIG_ OUTPUT_ COMPARE2 Timer Counter2 Compare Match AT90S4434 9058535 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal61 megal62 ATmegal63 ATmegal65 AT megal65P ATmegal69 ATmegal69P AT mega32 ATmega323 ATmega325 AT mega3250 ATmega329 ATmega329P AT mega3290 ATmega3290P ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmega8 ATmega8535 TIMER2_ OVF_vect SIG_ OVERFLOW2 Timer Counter2 Overflow AT90S4434 9058535 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 AT mega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P AT mega64 ATmega645 ATmega6450 ATmega649 ATmega6490
17. Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 349 mcall prologues Use subroutines for function prologue epilogue For complex functions that use many registers that needs to be saved restored on function entry exit this saves some space at the cost of a slightly increased execution time e minit stack nnnn Set the initial stack pointer to nnnn By default the stack pointer is initialized to the symbol __stack which is set to RAMEND by the run time initialization code mtiny stack Change only the low 8 bits of the stack pointer e mno tablejump Do not generate tablejump instructions By default jump tables can be used to op timize switch statements When turned off sequences of compare statements are used instead Jump tables are usually faster to execute on average but in particular for switch statements where most of the jumps would go to the default label they might waste a bit of flash memory mshort calls Use rjmp rcall limited range on gt 8K devices 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
18. Reverse a string The strrev function reverses the order of the string Returns The strrev function returns a pointer to the beginning of the reversed string Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 11 lt string h gt Strings 92 6 11 3 32 char strsep char sp const char 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 the terminating 0 character and replaces it with a 707 The location of the next character after the delimiter character or NULL if the end of the string was reached is stored in sp An empty field i e one caused by two adjacent delimiter characters can be detected by comparing the location referenced by the pointer returned in 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 s
19. attiny2313 __AVR_ATtiny2313__ avr2 avr25 1 attiny24 __AVR_ATtiny24__ avr2 avr25 1 attiny25 __AVR_ATtiny25__ avr2 avr25 1 attiny261 __AVR_ATtiny261__ avr2 avr25 1 attiny43u __AVR_ATtiny43U__ avr2 avr25 1 attiny44 __AVR_ATtiny44__ avr2 avr25 1 attiny45 __AVR_ATtiny45__ avr2 avr25 1 attiny461 __AVR_ATtiny461__ avr2 avr25 1 attiny48 __AVR_ATtiny48__ avr2 avr25 1 attiny84 __AVR_ATtiny84__ avr2 avr25 1 85 __AVR_ATtiny85__ avr2 avr25 1 attiny861 __AVR_ATtiny861__ avr3 atmega103 AVR ATmegal03 avr3 atmega603 __AVR_ATmega603__ avr3 at43usb320 __AVR_AT43USB320__ avr3 at43usb355 __AVR_AT43USB355__ avr3 at76c711 __AVR_AT76C711__ avr4 atmega48 AVR ATmega48 avr4 atmega48p __AVR_ATmega48P__ avr4 atmega8 __AVR_ATmega8__ avr4 atmega8515 __AVR_ATmega8515__ avr4 atmega8535 AVR ATmega8535 avr4 atmega88 AVR ATmega88 avr4 atmega88p AVR ATmega88P Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 347 Architecture MCU name Macro avr4 atmega8hva __AVR_ATmega8HVA__ avr4 at90pwm 1 _ AVR ATOOPWMI avr4 at90pwm2 _ AVR_AT90PWM2__ avr4 at90pwm2b AVR_AT90PWM2B_ avr4 at90pwm3 AVR AT90PWM3 avr4 at90pwm3b AVR AT90PWMGB avr5 at90pwm216 AVR ATO0PWM216 avr5 at90pwm316 AVR ATO0PWM316
20. hexadecimal scanf format for uint_least32_t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 6 lt math h gt Mathematics 32 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 Note In order to access the functions delcared herein it is usually also required to addi tionally link against the library 110 See also the related FAQ entry Defines define PI 3 141592653589793238462643 define M SORT2 1 4142135623730950488016887 define NAN builtin nan define INFINITY _ builtin inf Functions double cos double x ATTR CONST double fabs double ATTR CONST double fmod double _ x double CONST double modf double __ value double double sin double _ x ATTR CONST double sqrt double ATTR CONST double tan double x ATTR CONST double floor double x ATTR CONST Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 6 lt math h gt Mathematics 33 double double x CONST do
21. int main void ioinit loop forever the interrupts are doing the rest x for Note 7 sleep_mode return 0 6 34 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 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 5 avr gcc g Os mmcu atmega8 c demo c The compilation will create a demo o file Next we link it into a binary called demo elf avr gcc g mmcu atmega8 o demo elf demo o It is important to specify the MCU type when linking The compiler uses the mmcu option to choose start up files and run time libraries that get linked together If this Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 182 option isn t specified the compiler defaults to the 8515 processor environment which is most cert
22. more sophisticated project 197 6 35 3 1 Part 1 Macro definitions number of preprocessor macros are defined to improve readability and or portability of the application The first macros describe the IO pins our LEDs and pushbuttons are connected to This provides some kind of mini HAL hardware abstraction layer so should some of the connections be changed they don t need to be changed inside the code but only on top Note that the location of the PWM output itself is mandated by the hardware so it cannot be easily changed As the ATmega48 88 168 controllers belong to a more recent generation of AVRs a number of register and bit names have been changed there so they are mapped back to their ATmega8 16 equivalents to keep the actual program code portable The name F_CPU is the conventional name to describe the CPU clock frequency of the controller This demo project just uses the internal calibrated 1 MHz RC oscillator that is enabled by default Note that when using the lt util delay h gt functions F_CPU needs to be defined before including that file The remaining macros have their own comments in the source code The macro TMR1_SCALE shows how to use the preprocessor and the compiler s constant expres sion computation to calculate the value of timer 1 post scaler in a way so it only depends on F_CPU and the desired software clock frequency While the formula looks a bit complicated using a macro offers the advantage that t
23. octal scanf format for uint32_t 6 5 2 77 define SCNoFAST16 octal scanf format for uint_fast16_t 6 5 2 78 define SCNoFAST32 lo octal scanf format for uint_fast32_t 6 5 2 79 define SCNoLEAST16 octal scanf format for uint_least16_t 6 5 2 80 define SCNoLEAST32 10 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 31 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 decimal scanf format for least16 t 6 5 2 87 define SCNuLEAST32 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 hexadecimal scanf format for uint16 t 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 fastl6 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
24. 6 Oxc6 lt __vector_8 0x6a gt switch direction x Note 4 case UP if pwm TOP direction DOWN 0 81 0 Tdi r24 0x01 1 2 80 93 60 00 sts 0x0060 r24 if pwm 0 direction UP break OCR pwm Note 5 c6 3b bd out 0x2b r19 43 c8 2a ba out 0 2 r18 42 85 91 r24 dor 22 91 r19 2f 91 r18 dO Of 90 pop d2 Of be out 03 05 63 d4 0 90 pop 46 1 90 rl das 18 95 reti 000000da lt ioinit gt void ioinit void x Note 6 Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys TCCRIA 1 INIT da 83 8 141 r24 0x83 131 dc 8f bd out 0x2f r24 47 Start timer 1 NB TCCR1A and could actually be the same register take care to not clobber it x TCCRIB TIMER1_CLOCKSOURCE 8e b5 in r24 0x2e 46 e0 81 60 ori r24 0 01 1 e2 8e bd out 0x2e r24 46 if defined TIMER1_SETUP_HOOk TIMER1_SETUP_HOOK endif Set PWM value to 0 OCR 0 e4 lb bc out 0x2b r1 43 e6 la bc out Ox2a r1 42 Enable as output DDROC BV 0 1 e8 82 0 ldi r24 0x02 2 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 186 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
25. CHANGE tiny861 SIG_PCINT PSC0_ SIG_PSC0_ PSCO Capture AT90PWM3 AT90PWM2 AT90PWMI vect CAPTURE Event PSC0_EC_ SIG_PSC0_ PSC0 End Cycle AT90PWM3 AT90PWM2 AT90PWM 1 vect END_CYCLE PSCI SIG PSCI PSCI Capture AT90PWM3 AT90PWM2 AT90PWMI vect CAPTURE Event PSCI EC SIG PSCI PSC1 End Cycle AT90PWM3 AT90PWM2 AT90PWMI vect END CYCLE PSC2 SIG PSC2 PSC2 Capture AT90PWM3 AT90PWM2 AT90PWMI CAPT vect CAPTURE Event PSC2 EC SIG PSC2 PSC2 End Cycle AT90PWM3 AT90PWM2 AT90PWM 1 vect END_CYCLE SPI STC vect SIG SPI Serial Transfer AT90S2333 AT90S4414 479054433 Complete AT90S4434 479058515 AT90S8535 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 128 16 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8515 ATmega8535 AT megal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 SPM_RDY_ SIG SPM Store Program ATmegal6 ATmegal62 ATmega32 AT vect READY Memory Ready mega323 ATmega8 ATmega8515 AT mega8535 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxy
26. COMP_vect OUTPUT_ Compare Match ATmega103 ATmegal28 ATmegal6 AT COMPAREO megal61 ATmegal62 ATmegal65 megal65P ATmegal69 ATmegal69P AT mega32 ATmega323 ATmega325 AT mega3250 ATmega329 ATmega329P AT mega3290 ATmega3290P ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmega8515 ATmega8535 TIMERO_ SIG_ Timer Counter0 9052313 AT90S2323 AT90S2343 AT OVFO_vect OVERFLOWO Overflow tiny22 ATtiny26 TIMERO_ SIG_ Timer Counter0 AT90S1200 419052333 AT90S4414 OVF_vect OVERFLOWO Overflow 9054433 AT90S4434 9058515 AT90S8535 AT90PWMS3 AT9IOPWM2 AT90PWMI AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 AfTmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny11 ATtiny12 ATtiny15 ATtiny2313 ATtiny28 ATtiny261 ATtiny461 AT tiny861 AT9OUSB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER 1 _ SIG_INPUT_ Timer Counter1 AT90S2313 CAPTI_vect CAPTURE1 Capture Event Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 113
27. CONST__ Idiv_t Idiv long __num long __denom __asm__ __divmodsi4 __ATTR_ CONST__ void qsort void __base size_t __nmemb size t size compar fnt compar long strtol const char nptr char endptr int base unsigned long strtoul const char nptr char __endptr int base Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 41 strcasecmp S File Reference 248 long atol const char xs ATTR PURE int atoi const char xs PURE void exit int _ status ATTR NORETURN void 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 endptr double const char nptr int rand void void srand unsigned int __ seed int rand r unsigned long ctx Variables size t malloc margin char _ malloc heap start char heap end 8 41 strcasecmp S File Reference 8 411 Detailed Description 8 42 strcasecmp_P S File Reference 8 42 1 Detailed Description 8 43 strcasestr S File Reference 8 43 1 Detailed Description 8 44 strcat S File Reference 8 44 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 45 strcat_P S File Re
28. N Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 33 pgmspace h File Reference 238 lpm 0 Z lpm D0 7 n t r result z __addr16 N I __addr16 _ result 8 33 2 9 define _ _ Value __extension__ uintl6 t _ addrl6 uint16_t addr uint8_t __result asm N N lpm 0 Z n t N r result N z 1 addrl6 N _ result 8 33 2 10 define word classic Value __extension__ uintl6 t _ addrl6 uintl6 t addr N uintl6 t _ result asm lpm AnDnNEN N mov A0 ro r30 1 N lpm mov B0 ro M zr result z addrl6 N 1 addr16 N sy N _ result 8 33 2 11 define word enhanced Value Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 34 power h File Reference 239 __extension__ uintl6 t addr16 uint16_t addr uintl6 t result N asm N N lpm A0 Z lpm B0 Z n t r result z addrl16 N x lI addrl6 N _ result 8 34 power h File Reference 8 341 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
29. 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 constchar fmt Variant of snprintf that uses a fmt string that resides in program memory 6 9 3 27 int sprintf char x s constchar fmt Variant of printf that sends the formatted characters to string s 6 9 3 28 int sprintf_P char x _ 5 const char x fmt Variant of sprintf that uses a fmt string that resides in program memory Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 64 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 _ buf const char __ fmt Variant of sscanf using a fmt string in program memory 6 9 3 31 int ungetc int _ c FILE x stream The ungetc function pushes the character c converted to an unsigned char back onto the input stream pointed to by st ream The pushed back character will be returned by a subsequent read on the stream Currently only a single character can be pushed back onto the stream The ungetc function returns the character pushed back after the conversion or EOF if the operation fails If the value of the argument c character equals EOF the operation wi
30. 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 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 contribu he name of the copyright holders nor the names of ors may be used to endorse or promote products derived from this software without specific prior written permission POSSIBILITY SUCH DAMAGE HIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS ND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE MPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE RE DISCLAIMED IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE IA
31. This type is not available when the compiler option mint8 is in effect 6 16 3 5 prog int8 t Type of an int8 t object located in flash ROM 6 16 3 6 prog uchar Type of an unsigned char object located in flash ROM 6 16 3 7 prog uintl6 t Type of an uintl6 t object located in flash ROM 6 16 3 8 prog uint32 t Type of an uint32 t object located in flash ROM 6 16 3 9 prog uint64 t Type of an uint64 t object located in flash ROM Note This type is not available when the compiler option mint8 is in effect 6 16 3 10 prog uint8 t Type of an uint8 t object located in flash ROM 6 16 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 object in flash ROM Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pemspace h gt Program Space Utilities 131 6 16 4 Function Documentation 6 16 41 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 16 4 2 int memcmp P const void s1 52 size_t len
32. Version 10 27 0 From the GNUWin32 project lt http gnuwin32 sourceforge net packages html gt Download and install Install fig2dev Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 339 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 10 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 mingw bin c cygwin bin install directory gt bin Configure Generated on Mon Oct 29 20 02 34 2007
33. inttmp intsav SQUARE tmconst 1070000 fuzz 8 section global main rcall Abs rjmp global TIMERO_OVF_vect ldi out in sbic rjmp sbi rjmp des cbi 2 out reti ioinit sbi ldi out ldi out ldi out sei ret global _ vector default Note 1 16 Note 2 Li 19 0 PD6 Note 3 Note 4 0 200000 100 kHz 200000 edges s clocks in ISR until TCNTO is set text main H ote 5 ioinit 1b Note 6 TIMERO OVF ote 7 inttmp 256 tmconst fuzz SFR IO ADDR TCNTO inttmp 4 ote 8 intsav SFR IO ADDR SREG Note 9 work BV TOIEO work _BV CS00 SFR IO ADDR PORTD SQUARE SFR IO ADDR PORTD SQUARE SFR IO ADDR PORTD SQUARE SFR IO ADDR SREG intsav SFR IO ADDR DDRD SQUARE SFR IO ADDR TIMSK work tmr0 1 SFR IO ADDR ICCRO work work 256 tmconst SFR IO ADDR TCNTO work Note 10 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 283 vector default reti end Note 1 AS in C programs this includes the central processor specific file containing the IO port definitions for the device Note that not all include files can be included into assembler sources Note 2 Assignment of registers to symbolic names used locally Another option would be to use a C preprocessor macro instead define work 16 Note 3 Our bit
34. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 21 typedef uint32_t uint_farptr_t macros for printf and scanf format specifiers For C these are only included if STDC_LIMIT MACROS is defined before in cluding lt inttypes h gt define PRId8 d define PRIdLEASTS d define PRIdFASTS d define 1 define PRILEASTS i define PRUFASTS8 1 define PRId16 d define PRIGLEAST16 d define PRIGFAST16 d define PRIi16 i define PRIILEAST16 i define PRHFAST16 i define PR
35. rm 8 5 2 7 define _ boot_page fill extended address data Value __asm__ __volatile__ movw r0 4 n t movw r30 A3 n t sts 1 C3 n t PA AV LI uud uA LA LUE A AP uud uL uu FL mmu wu EE Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 5 boot h File Reference 219 sts 0 S2 n t spm n t rlNnNt alr 1 non d yn y y ro 8 5 2 8 define Value SFR_MEM_ADDR __SPM_REG SFR_MEM_ADDR RAMPZ uint8 t BOOT PAGE FILL uint32 t address uint16_t data r30 r31 2 EL E e boot_page_fill_normal address data __asm__ __volatile__ movw 0 3 n t movw r30 2 n t sts 0 1 n t spm n t rinit 1 20 8 5 2 9 Value SFR_MEM_ADDR __SPM_REG uint8_t BOOT_PAGE_FILL uint16 t address uint16 t data Y307 Ta Sq boot page write alternate address asm volatile movw r30 2 n t sts 0 1 n t spm n t word OxffffNnNXt nop n t 1 yn yn SFR MEM ADDR SPM REG uint8 t BOOT PAGE WRITE uint16 t address 30 r31 LEE DD OLD RED ie E DEVE Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 5 boot h File Reference 220 8 5 2 10 define boot page wr
36. uint16_t i uint8_t sreg Disable interrupts sreg SREG cli eeprom busy wait boot page erase page boot spm busy wait Wait until the memory is erased for i20 i SPM PAGESIZE i 2 Set up little endian word uintl6_t w buf w buf 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_enable _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 amp uint8_t _BV SPMIE define boot_rww_busy _SPM_REG amp uint8_t _ BV _COMMON_ASB Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 95 define boot_spm_busy __SPM_REG amp uint8_t _BV SPMEN 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_
37. value and 1 refers to I SFR IO ADDR PORTD This may still look a little odd now but the syntax of an operand list will be explained soon Let us first examine the part of a compiler listing which may have been generated from our example lds r24 value x r24 12 NOAPP x sts value r24 The comments have been added by the compiler to inform the assembler that the in cluded code was not generated by the compilation of C statements but by inline as sembler statements The compiler selected register r24 for storage of the value read from PORTD The compiler could have selected any other register though It may not explicitely load or store the value and it may even decide not to include your assembler code at all All these decisions are part of the compiler s optimization strategy For example if you never use the variable value in the remaining part of the C program the compiler will most likely remove your code unless you switched off optimization To avoid this you can add the volatile attribute to the asm statement asm volatile in 0 1 r value I SFR IO ADDR PORTD 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 ass
38. 2 Seay a eee 9 269 Memory SO NOM usu eoo Re RAG S 271 9 3 1 The text SGOLIOM lt ic nce S o Ro ee s 271 42 Sechin o uox ze 271 932 The DSSSeCHOR c p core nc sus yup s S BS E ER O s 272 934 The e prom Section 0e RR o RR y RR 272 eCOM udo um renum RS Eee BAGS s 272 9 3 6 SeCHONS ose sec immo goa Rom Ee eee 5 272 9 3 7 The Sections gt c o crec 9 x 9 Rs 274 9 3 8 Using Sections in Assembler 274 9398 Using Sectionin C Code 2 oro a eo 275 Data in Program Space oaos ee y m ERES 275 DAT JuoSUGHON 222222222255 5 275 942 A NOE UN CONEE 2252 2222 276 9 4 3 Storing and Retrieving Data in the Program Space 276 94 4 Storing and Retrieving Strings in the Program Space 278 9453 e 280 avr libc and assembler programs 280 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS xiii 9 6 49 9 8 99 dubodu BloW es epove 280 95 7 Invoking the compiler o coo ass s s 95 xg xe e 281 5 Example progra elec a a ee X X BAS 8 281 9 5 4 Pseudo ops and operators 285 Inline Assembler Cookbook 286 GCC asm SEMERE 2222222 222 22 RS 287 962 Assembler Code 22 2 pear 289 9 6 3 Input and Output 289 O EDDY codo Sus morum dero ba S ee es 293 9 65 Assembler Mattos o a ss
39. 479052333 419054414 vect RECV plete 9054433 AT90S4434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_TX_ SIG_UART_ UART Tx Com AT90S2313 419052333 419054414 vect TRANS plete AT90S4433 9054434 41719058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_ SIG_UART_ UART Data Reg AT90S2313 419052333 AT90S4414 UDRE_vect DATA ister Empty 9054433 AT90S4434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 USARTO SIG USARTO Rx ATmegal62 vect USARTO Complete RECV USARTO SIG USARTO Rx AT90CANI28 AT90CAN32 AT90CAN64 vect UARTO Complete ATmegal28 ATmegal65 ATmegal65P RECV ATmegal69 ATmegal69P ATmega325 ATmega329 ATmega329P ATmega64 ATmega645 ATmega649 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 USARTO SIG USARTO Tx ATmegal62 vect USARTO Complete TRANS Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 118 Vector name Old vector Description Applicable for device name USARTO SIG USARTO Tx AT90CANI28 AT90CAN32 AT90CAN64 TX vect UARTO Complete ATmegal28 ATmegal65 ATmegal65P TRANS ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATm
40. 57 sei f0 78 94 sei F2 08 95 ret 000000 4 lt main gt int main void fA cf e5 ldi r28 Ox5F 95 f6 d4 Tdi 22 Ox04 s 4 f8 de bf out 0x3e r29 62 cd bf out Ox3d r28 61 roinit J7 fc ee df reall 36 Oxda lt ioinit gt loop forever for Note 7 Sleep mode fe 85 b7 in r24 0x35 00 80 68 ori r24 0x80 02 85 bf out 0x35 r24 04 88 95 Sleep 06 85 b7 in r24 0x35 08 8f 77 andi r24 Ox7F 85 bf out 0x35 r24 Det I9 cf tmp 2 16 0000010 lt interrupt 0e 78 cf rjmp 272 00000110 exit finclude macros inc Section text global exit exit XJMP exit 110 00 rjmp 0 00000112 exit LIS RE tip 2 6 34 5 Linker Map Files the interrupts are doing the rest x 53 128 53 53 1217 53 Oxfe lt main 0xa gt 0x0 lt __heap_end gt 0x112 lt _exit gt 0x112 exit avr objdump is very useful but sometimes it s necessary to see information about Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 187 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
41. 66 vfscanf 66 vfscanf P 69 vprintf 69 vscanf 69 vsnprintf 69 vsnprintf P 69 vsprintf 69 vsprintf P 69 avr stdlib compar fn t 72 malloc heap end 80 malloc heap start 80 malloc margin 81 abort 72 abs 72 atof 72 atoi 72 atol 73 bsearch 73 calloc 73 div 73 DTOSTR ALWAYS SIGN 71 DTOSTR PLUS SIGN 71 DTOSTR_UPPERCASE 72 dtostre 74 dtostrf 74 exit 74 free 74 itoa 75 labs 75 ldiv 75 75 malloc 76 qsort 76 rand 76 RAND MAX 72 rand r 77 random 77 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 370 RANDOM MAX 72 strtok r 91 random r 77 strupr 92 realloc 77 avr version srand 78 AVR DATE 147 srandom 78 LIBC DATE STRING strtod 78 147 strtol 78 AVR MAJOR 147 strtoul 79 AVR LIBC MINOR 147 ultoa 79 AVR REVISION _ 147 utoa 80 AVR LIBC VERSION avr string STRING 147 _FFS 82 AVR VERSION 147 ffs 82 avr watchdog ffsl 83 wdt disable 149 ffsll 83 wdt enable 149 memcopy 83 wdt reset 149 memchr 83 WDTO_120MS 150 mememp 83 WDTO_15MS 150 memcpy 84 WDTO 15 150 memmem 84 WDTO_250MS 150 memmove 84 WDTO_2S 150 memrchr 85 WDTO_30MS 150 memset 85 WDTO_4S 150 strcasecmp 85 WDTO_500MS 151 strcasestr 85 WDTO_60MS 151 strcat 86 WDTO_8S 151 strchr 86 avrdude usage 354 strchrnul 86 avrprog usage 354 st
42. ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 ATtiny261 ATtiny461 AT tiny861 AT90USB162 9005 82 9005 1287 9005 1286 AT90USB647 AT90USB646 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 114 Vector name Old vector Description Applicable for device name SIG_ Timer Counter1 AT90S4414 9054434 9058515 COMPB_vect OUTPUT_ Compare MatchB 419058535 AT90PWM3 AT90PWM2 COMPAREIB AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 ATtiny261 ATtiny461 AT tiny861 ATOOUSBI62 9005 82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMERI SIG Timer Counter1 AT90CAN128 AT90CAN32 AT90CANGA COMPC_vect O
43. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 54 static int uart putchar char c FILE xstream static FILE mystdout FDEV SETUP STREAM uart putchar NULL _FDEV_SETUP_WRITE static ant uart_putchar char c FILE xstream if n uart_putchar r stream loop_until_bit_is_set UCSRA UDRE UDR c return 0 int main void init_uart stdout amp mystdout printf Hello world Nn return 0 This example uses the initializer form FDEV_SETUP_STREAM rather than the function like fdev_setup_stream so all data initialization happens during C start up If streams initialized that way are no longer needed they can be destroyed by first calling the macro fdev_close and then destroying the object itself No call to fclose should be issued for these streams While calling fclose itself is harmless it will cause an undefined reference to free and thus cause the linker to link the malloc module into the application Notes Note 1 It might have been possible to implement a device abstraction that is compatible with
44. Configure export LDFLAGS static Sarchivedir configure N prefix installdir N datadir installdir N disable tests disable versioned doc N 2 gt amp 1 tee simulavr configure log Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 345 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 11 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 11 1 Options for the C compiler avr gcc 9 1111 Machine specific options for the AVR The following machine specific options are recognized by the C compiler frontend mmcu architecture Compile code for architecture Currently known architectures are Architecture Macros avrl AVR ARCH 1 AVR ASM ONLY AVR 2 BYTE PC 2 avr2 AVR ARCH 2 AVR 2 BYTE PC 2 avr25 1 AVR ARCH 25 AVR HAVE MOVW 1 AVR HAVE LPMX 1 AVR 2 BYTE P avr3 AVR ARCH 3 AVR MEGA AVR 2 BYTE PC __ 2 avr4 AVR ARCH 4 AVR ENHANCED AVR HAVE MOVW 1 AVR HAVE LPMX avr5 AVR ARCH 5 AVR MEGA AVR ENHANCED AVR HAVE MOVW 1 AVR avr6 2 AVR ARCH 6 AVR MEGA AVR ENHANCED AVR HAVE MOVW_
45. Diagnostics 16 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 lt assert h gt This header file defines a debugging aid As there is no standard error output stream available for many applications using this library the generation of a printable error message is not enabled by default These 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 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 given expression and if it is false the calling process is terminated A diagnostic message is written to stderr and the function abort is called effectively terminating the program If expression is true the assert macro does nothing The assert macro may be removed at compile time by defining NDEBUG as a macro e g by using the compiler option DNDEBUG Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 63 lt gt Character Operations 17 63 lt ctype h
46. Figure 3 Wiring of the STK500 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 35 more sophisticated project 195 The following picture shows the alternate wiring where LED1 is connected but SW2 is not Figure 4 Wiring option 2 of the STK500 As an alternative this demo can also be run on the popular ATmega8 controller or its successor ATmega88 as well as the ATmega48 and ATmegal68 variants of the latter These controllers do not have a port named A so their ADC inputs are located on port C instead thus the potentiometer needs to be attached to port C Likewise the output is not on port D pin 5 but on port B pin 1 PB1 Thus the above cabling scheme needs to be changed so that PB1 connects to LEDO pin PD6 remains unconnected When using the STK500 use one of the jumper cables for this connection All other port D pins should be connected the same way as described for the ATmegal6 above When not using an STK500 starter kit attach the LEDs through some resistor to Vcc low active LEDs and attach pushbuttons from the respective input pins to GND The internal pull up resistors are enabled for the pushbutton pins so no external resistors are needed 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
47. Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS Y 6 34 2 The Source Ode o ouo Rem m eh p ER 179 243 ComplingandLinkimg ea a 181 6 344 Examining the Object File 182 634 Linker Map Piles aaa sus g 6 186 6 34 6 Generating Intel Hex Files 189 6 34 7 Letting Make Build the Project 190 6 34 8 Reference to the sourcecode o o 25 0 8 ee ee o 192 6 35 more sophisticated project 192 6351 Hatbwae sep lt lt wea ce ee SOEs Ha W ARS 193 5 25 2 Funcional suos oe gor eee RR 196 6 35 3 A code walkthrough 196 5224 IDESONICE OdE slo ee a p CARERE S 199 6 36 Using the standard IO 200 630 1 Hardwsreseluj 225222225556 cad S 200 6 30 2 e ce apocr oe gs a Ua s w w RR 201 6 36 3 code walkthrough 202 6 36 4 The sourcecode 2 ccs t rre 207 6 37 Example using the two wire interface TWI 207 6 37 1 Introduetion mio TWI 2 207 6 37 2 The TWlexample project 222222222222 22 255 208 ERU Ar ja see 208 7 avr ibc Data Structure Documentation 212 Tl dut Struct Reference lt lt ce ce oot ee UE RR 212 TL Detaled Description lt sea e v RES 212 712 Field Documentation 2 600 A ks RR RRRA 212 a2 ldiv tStuet Referenc s spess oss os
48. 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 10 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 lt 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 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 Batch file will ask Do you wish to continue with the post install Press y and press e
49. architecture name avr2 through avr5 with the suffix x appended They describe how the various memory sections will be linked together 9 11 3 2 Passing linker options from the C compiler By default all unknown non option arguments on the avr gcc command line i e all filename arguments that don t have a suffix that is handled by avr gcc are passed straight to the linker Thus all files ending in o object files and a object libraries are provided to the linker System libraries are usually not passed by their explicit filename but rather using the 1 option which uses an abbreviated form of the archive filename see above avr libc ships two system libraries 1ibc a and libm a While the standard library libc a will always be searched for unresolved references when the linker is started using the C compiler frontend i e there s always at least one implied 1c option the mathematics library 1ibm a needs to be explicitly requested using 1m See also the entry in the FAQ explaining this Conventionally Makefiles use the make macro LDLIBS to keep track of 1 and possibly L options that should only be appended to 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 th
50. avr_inttypes 28 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 379 SCNdLEAST32 5 16 avr_inttypes 28 avr_inttypes 30 SCNdPTR SCNx32 avr_inttypes 28 avr_inttypes 30 SCNi16 SCNxFAST16 avr_inttypes 28 avr_inttypes 30 SCNi32 SCNxFAST32 avr_inttypes 28 avr_inttypes 30 SCNIFASTI6 SCNxLEASTI6 avr inttypes 28 avr inttypes 30 SCNiFAST32 SCNxLEAST32 avr_inttypes 28 avr_inttypes 30 SCNiLEAST16 SCNxPTR avr_inttypes 28 avr_inttypes 30 SCNiLEAST32 sei avr_inttypes 28 avr_interrupts 122 SCNiPTR set_sleep_mode avr_inttypes 29 avr_sleep 146 SCNo16 setbaud h 239 avr inttypes 29 setjmp SCNo32 longjmp 38 avr inttypes 29 setjmp 38 SCNoFAST16 setjmp h 239 avr_inttypes 29 SIG_ATOMIC_MAX SCNoFAST32 avr_stdint 46 avr_inttypes 29 SIG_ATOMIC_MIN SCNoLEAST16 avr_stdint 46 avr_inttypes 29 SIGNAL SCNoLEAST32 avr_interrupts 122 avr_inttypes 29 signbit SCNoPTR avr_math 36 avr_inttypes 29 sin SCNu16 avr math 36 avr inttypes 20 sinh SCNu32 avr math 36 avr inttypes 29 SIZE MAX SCNuFAST16 avr_stdint 46 avr_inttypes 29 sleep h 239 SCNuFAST32 sleep_cpu avr_inttypes 30 avr_sleep 146 SCNuLEAST16 sleep_disable avr_inttypes 30 avr_sleep 146 SCNuLEAST32 sleep_enable avr_inttypes 30 avr_sleep 146 SCNuPTR sleep_mode avr_inttypes 30 avr_sleep 146 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 380 SLEEP_MODE_ADC avr_sleep 145 SLEEP_MODE_EXT_STA
51. 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 9 18 How do I relocate code to a fixed address First the code should be put into a new named section This is done with a section attribute attribute section bootloader In this example bootloader is the name of the new section This attribute needs to be placed after the prototype of any function to force the function into the new section void boot void attribute section bootloader To relocate the section to a fixed address the linker flag section start is used This option can be passed to the linker using the W1 compiler option Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 322 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 9 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 All devices that have an internal RC oscillator ship with the fuse enabled that causes
52. define SCNIFAST32 li define SCNdPTR SCNd16 define SCNiPTR SCNi16 define SCNo16 o define SCNoLEAST16 o define SCNoFAST16 o define SCNul6 u Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 23 define SCNuLEASTI6 u define SCNuFAST16 u define SCNx16 x define SCNxLEAST16 x define SCNxFAST16 x define SCNo32 lo define SCNoLEAST32 lo define SCNoFAST32 lo define SCNu32 lu define SCNuLEAST32 lu define SCNuFAST32 lu define SCNx32 Ix define SCNXLEAST32 Ix define SCNxFAST32 Ix define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR SCNx16 6 5 2 Define Documentation 6 5 2 1 define PRId16 decimal printf format for int16 t 6 5 2 2 fidefine PRId32 Id decimal printf format for int32 t 6 5 2 3 define PRId8 d decimal printf format for int8 t 6 5 2 4 define PRIdFASTI6 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 24 6 5 2 7 define PRIGLEAST16 decimal printf format for int_least16_t 6 5 2 8 define PRI4LEAST32 Id decimal printf format for int_least32_t 6 5 2 9 fidefine PRIdLEASTS d decimal prin
53. for developing the standard libraries and startup code for AVR GCC Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 15 Todo List 361 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 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 15 Todo List Group avr_boot From email wi
54. 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 re ject The terminating zero is not considered as part of string 6 16 4 14 size t strlcat P char x dst size_t siz Concatenate two strings The strlcat_P function is similar to strlcat except that the src string must be located in program space flash Appends src to string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat_P function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 6 16 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 16 4 16 size_t strlen P PGM P src The strlen function is similar to strlen except that src is a pointer to a string in program space Returns The strlen function returns t
55. lt util delay_basic h gt Basic busy wait delay loops 160 6 26 1 Detailed Description 160 6 26 2 Function Documentation lt 2 ae s seos s eita esas 161 lt util parity h gt Parity bit 161 6 27 1 Detailed Description 161 6 27 2 Define Documentation 22 162 lt util setbaud h gt Helper macros for baud rate calculations 162 6 28 1 Detailed Description gt oe socra m twm 162 6 28 2 Define Documentation 22 164 lt util twi h gt TWI bit mask definitions 164 629 1 Detailed Description lt o c a sc es 202 erma Su v 164 6 29 2 Define Documentation 166 lt compat deprecated h gt Deprecated items 169 6 30 1 Detailed Description 2 22222 ea s Emm BA es 169 5 30 2 Define Doc mentaton lt c se segt s sua m nips 170 6 30 3 Function Documentation 172 lt compat ina90 h gt Compatibility with IAR EWB3 x 172 Demo 2 oe ee e ee 172 6 32 1 Detailed Description 172 Combining C and assembly source files 174 5 25 1 Hardware vs s s as g eee ee SRE 174 6 33 2 A Code walkthrough oos RR 175 6333 Thesomcecod soc eee c s was kb DRE h W ERG 177 A simple PROJECT so or eR ey v 3 177 5241 The Pie 24 40 eco qom due puis EU SUE ees 177
56. or OCR1A DDROC the name of the DDR data direction register for the OC output OCI the pin number of the OCI A output within its port TIMER1_TOP the TOP value of the timer used for the PWM 1023 for 10 bit PWMs 255 for devices that can only handle an 8 bit PWM TIMER1_PWM_INIT the initialization bits to be set into control register 1A in order to setup 10 bit or 8 bit phase and frequency correct PWM mode TIMER1_CLOCKSOURCE the clock bits to set in the respective control regis ter to start the PWM timer usually the timer runs at full CPU clock for 10 bit PWMs while it runs on a prescaled clock for 8 bit PWMs Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 179 Note 2 ISRO 16 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 in 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 inte
57. 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 9 14 Acknowledgments 360 HEAD 1 0 Branch 1 2 Branch cvs tag avr libc 1_0 branchpoint set version to 1 1 0 lt date gt M cvs tag b avr libc 1 0 branch set version to 0 90 90 lt date gt t set version to 1 0 cvs 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_1 release 1 cvs tag avr libc 1_2 branchpoint i set version to 1 3 0 lt date gt eys tag i aqa tibet 2 branch set version to 1 1 90 date set version to 1 2 cvs tag avr libc 1_2 release t cvs tag avr libc 2 0 branchpoint set version to 2 1 0 lt date gt M Figure 9 Release tree 9 14 Acknowledgments This document tries to tie together the labors of a large group of people Without these individuals efforts we wouldn t have terrific free set of tools to develop AVR projects We all owe thanks to The GCC Team which produced a very capable set of development tools for an amazing number of platforms and processors e Denis Chertykov denisc overta ru for making the AVR specific changes to the GNU tools e Denis Chertykov and Marek Michalkiewicz marekm8linux org pl
58. saves the stack context environment in __jmpb for later use longjmp The stack context will be invalidated if the function which called setjmp returns Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 40 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 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 uintl6 t uintptr t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 41 Minimum width integer types Integer type
59. 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 and distribute modified versions of this manual provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one This document describes version 3 3 of the compiler There may be some parts which hadn t been completely understood by the author himself and not all samples had been tested so far Because the author is German and not familiar with the English language there are definitely some typos and syntax errors in the text As a programmer the author knows that a wrong documentation sometimes might be worse than 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 docume
60. u g o a RE RE 295 966 C Stub Functions 222222 2 2 22 2 2 296 9 6 7 Names Used in Assembler 297 IIBER poe Pe ega 298 How to Builda Labraty lt ea da wai Gees E gg E SUNSU S 298 SS sn aa Re a 298 97 22 How the Linker Works 298 9 73 Howto Designa Library sree 0 5 2 64 k s emess 299 ITA Crea ng a Library un vu nd kk RR Bea e o S N 299 972 see Seemed puta RR RES 300 Potting From IAR to AVR GCC lt e secre omm BA es 301 Sl eo u e a e a sup Cu E 3 301 982 222222222222 225558284 ee BAS 301 9 8 3 Interrupt Service Routines ISRS 302 984 Inbinsi 222222225522 303 985 Flash Watiables oa lom R y RR ERR YS 303 9 50 Non Returning maith 304 98 7 Locking Revistes eod oops SR E 305 Frequently Asked Questions lt lt ess cee Rr RR 305 994 e 305 9 9 2 program doesn t recognize a variable updated within an 2222 22 22 22555 da 307 Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS 9 9 3 I get undefined reference to for functions like sinQ 307 9 9 4 How to permanently bind a variable to a register 308 9 9 5 How to modify MCUCR or WDTCR 308 9 9 6 What is all this stuff about 309 99
61. x Note 4 80 91 60 00 lds r24 0x0060 70 88 23 r24 r24 72 79 A brne 30 0x92 lt __vector_8 0x36 gt case UP if pwm TOP 74 20 91 61 00 145 r18 0 0061 78 30 91 62 00 dds 19 0x0062 70 2f BE subi r18 OxFF 255 3f 4f Spet 41 9 ORFE 5255 80 30 93 62 00 sts 0x0062 r19 84 20 93 61 00 sta OxDODl 16 88 83 0 141 24 0x03 3 8 2f 3f cpi r18 OxFF 255 86 38 07 19 r24 8e d9 f4 brne 54 Oxc6 lt __vector_8 0x6a gt 90 17 0 rjmp 46 0 0 lt __vector_8 0x64 gt ISR TIMER1_OVF_vect x Note 2 static uintl6_t pwm Note 3 static uint8_t direction switch direction x Note 4 92 81 30 cpi r24 0 01 1 94 29 fO breq 10 0 vector 8 0 44 gt 96 20 91 61 00 145 r18 0x0061 9 30 91 62 00 1ds r19 0x0062 9e 13 cO rjmp 38 Oxc6 vector 8 0 gt if pwm TIMER TOP direction DOWN break case DOWN if pwm 0 a0 20 91 61 00 145 r18 0 0061 a4 30 91 62 00 145 r19 0 0062 8 21 50 subi 18 0x01 1 aa 30 40 spot 19 0x00 0 ac 30 93 62 00 sts 0x0062 r19 b0 20 93 61 00 sts 0 0061 r18 b4 21 15 cp I b6 31 05 cpe rl9 b8 31 4 brne 12 Oxc6 lt vector 8 0 gt direction UP Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 185 ba 10 92 60 00 sts 0 0060 r1 be 03 rjmp
62. 1 AVR 1 New in GCC 42 2 Unofficial patch for GCC 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 346 Architecture MCU name Macro avrl at90s1200 __AVR_AT90S1200__ attiny11 AVR AT nyll avrl attiny12 AVR AT nyl2 avri attiny15 AVR ATt nyl5 avri attiny28 AVR AT ny28 avr2 29052313 AVR 479052313 avr2 at90s2323 AVR AT9082323 avra at90s2333 AVR_AT90S2333_ avr2 at90s2343 AVR_AT90S2343__ avr2 attiny22 __AVR_ATtiny22__ avr2 attiny26 __AVR_ATtiny26__ 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_AT86RF401__ avr2 avr25 1 attiny13 __AVR_ATtiny13__ avr2 avr25 1
63. 18 char strcpy char dest const char src Copy a string The strcpy function copies the string pointed to by src including the terminating 0 character to the array pointed to by dest The strings may not overlap and the destination string dest must be large enough to receive the copy Returns The strcpy function returns a pointer to the destination string dest Note If the destination string of a strcpy is not large enough that is if the programmer was stupid lazy and failed to check the size before copying then anything might happen Overflowing fixed length strings is a favourite cracker technique 6 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 Appendis src to string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 11 lt string h gt Strings 89 Returns The strlcat function r
64. 1cd_init first calls the initialization entry point of the lower level HD44780 driver and then sets up the LCD in a way we d like to display cleared non blinking cursor enabled SRAM addresses are increasing so characters will be written left to right The public function lcd_putchar takes arguments that make it suitable for be ing passed as a put function pointer to the stdio stream initialization functions and macros fdevopen FDEV_SETUP_STREAM etc Thus it takes two argu ments the character to display itself and a reference to the underlying stream object and it is expected to return 0 upon success This function remembers the last unprocessed newline character seen in the function local static variable nl seen If a newline character is encountered it will simply set this variable to a true value and return to the caller As soon as the first non newline character is to be displayed with n1 seen still true the LCD controller is told to clear the display put the cursor home and restart at SRAM address 0 All other characters are sent to the display Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 36 Using the standard IO facilities 206 The single static function internal variable nl_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
65. 2 Define Documentation 6 13 21 define EEPROM REG LOCATIONS __ 1C1D1E In order to be able to work without a requiring a multilib approach for dealing with controllers having the EEPROM registers at different positions in memory space the eeprom functions evaluate _ LOCATIONS It is assumed to be Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 101 defined by the device io header and contains 6 uppercase hex digits encoding the ad dresses of EECR EEDR EEAR First two letters EECR address Second two letters EEDR address Last two letters EEAR address The default ICIDIE corre sponds to the register location that is valid for most controllers The value of this define symbol is used for appending it to the base name of the assembler functions 6 13 2 2 define _EEGET var addr var eeprom read byte uint8_t addr Read a byte from EEPROM Compatibility define for C 6 13 2 3 define _EEPUT addr val eeprom write byte uint8_t addr uint8_t val Write a byte to EEPROM Compatibility define for 6 13 2 4 define EEMEM __attribute__ section eeprom Attribute expression causing a variable to be allocated within the eeprom section 6 13 2 5 define eeprom busy wait do while eeprom is ready Loops until the eeprom is no longer busy Returns Nothing 6 13 2 6 define eeprom is re
66. 26 define TW ST DATA 0 0 data transmitted NACK received 6 29 2 27 define TW ST LAST DATA 0xC8 last data byte transmitted ACK received 6 29 2 28 define TW ST SLA 0xA8 SLA R received ACK returned 6 29 2 29 define TW START 0x08 start condition transmitted 6 29 2 30 define TW STATUS TWSR amp TW STATUS MASK TWSR masked by TW STATUS MASK 6 29 2 31 define TW STATUS MASK Value _BV TWS7 _BV TWS6 _BV TWS5 _BV TWS4 _BV TWS3 The lower 3 bits of TWSR are reserved on the ATmegal63 The 2 LSB carry the prescaler bits on the newer ATmegas 6 29 2 32 define TW WRITE 0 SLA W address Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 30 lt compat deprecated h gt Deprecated items 169 6 30 lt compat deprecated h gt Deprecated items 6 301 Detailed Description This header file contains several items that used to be available in previous versions of this library but have eventually been deprecated over time include lt compat deprected h gt These items are supplied within that header file for backward compatibility reasons only so old source code that has been written for previous library versions could easily be maintained until its end of life Use of any of these items in new code is strongly discouraged Allowing specific system wide interrupts In addition to globally enabling interrupts each device s particular interrupt needs to be enabled sep
67. 27 Which AVR specific assembler operators are available 326 9 9 28 Why are interrupts re enabled in the middle of writing the stack DOMI a eae eee boe E de e 326 9 9 29 Why are there five different linker 2 327 9 9 30 How to add a raw binary image to linker output 327 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS 1 9 9 31 How do I perform a software reset of the 328 9 10 Building and Installing the GNU Tool 329 9 10 1 Building and Installing under Linux FreeBSD and Others 329 9 10 2 Tools s c eso c wo k a rape eea 330 9 10 3 Optional Tools 22222 2 m e n x n RR Rs 330 9 10 4 GNU Binutils for the 331 9 10 5 GCC forthe AVR target o oss s Sos ER os 332 9 106 AVR EIDE eem eS RE RASSE RS 333 Oe 2 iu mas deb eS ee ee eS 333 910 8 GDB for the AVR target lt o os u s ek ER RS 334 9 10 9 SIMNIAVE 2o omm b n n v N Q S 334 DIO AU ANSBICE oc bo md REESE RR EG REI 335 9 10 11 Building and Installing under Windows 335 9 10 12 Tools Required for Building the Toolchain for Windows 336 9 10 13 Building the Toolchain for Windows 330 9 11 Using the GNU tools 345 9 11 1 Options for the C compiler 345 9 11 2 Optionsfortheassembleravr as 351 9 11 3 Cont
68. 46 JINT16 C 46 16 MAX 46 int16 t 49 JINT32 C 46 JINT32 MAX 46 int32 t 49 JINT64 C 46 JINT64 MAX 46 int64 t 49 8 C 46 JINT8 MAX 47 int8 t 50 JINT FAST16 47 int fastl6 t 50 JINT FAST32 MAX 47 int fast32 t 50 JINT FAST64 MAX 47 int fast64 t 50 JINT FAST8 MAX 47 int fast8 t 50 JINT LEASTI6 MAX 47 int 16 t 50 JINT LEAST32 MAX 47 int least32 t 50 INT LEAST64 MAX 47 int least64 t 50 INT LEAST8 MAX 47 int least8 t 50 JINTMAX C 47 JINTMAX MAX 47 intmax t 51 JINTPTR MAX 48 Ce GE ECCECE E Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 369 uintptr_t 51 avr_stdio _FDEV_EOF 56 _FDEV_ERR 56 _FDEV_SETUP_READ 56 _FDEV_SETUP_RW 56 _FDEV_SETUP_WRITE 56 clearerr 58 EOF 56 fclose 58 fdev_close 56 fdev_get_udata 56 fdev_set_udata 56 FDEV_SETUP_STREAM 57 fdev_setup_stream 57 fdevopen 59 feof 59 ferror 60 fflush 60 fgetc 60 fgets 60 FILE 57 fprintf 60 fprintf P 60 fputc 60 fputs 60 fputs P 61 fread 61 fscanf 61 fscanf P 61 fwrite 61 getc 57 getchar 57 gets 61 printf 61 printf P 62 putc 58 putchar 58 puts 62 puts P 62 scanf 62 scanf P 62 snprintf 62 snprintf P 62 sprintf 62 sprintf P 62 sscanf 62 sscanf P 63 stderr 58 stdin 58 stdout 58 ungetc 63 vfprintf 63 vfprintf P
69. 9 9 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 reset For these older AVRs doing a soft reset by enabling the watchdog is easy as the watchdog will then be disabled after the reset On newer AVRs once the watchdog is enabled then it stays enabled even after a reset For these newer AVRs a function needs to be added to the init3 section i e during the startup code before main to disable the watchdog early enough so it does not continually reset the AVR Here is some example code that creates a macro that can be called to perform a soft reset include avr wdt h define soft reset do wdt_enable WDTO_15MS for while 0 PO GOGO GO GG Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 329 For newer AVRs such as the ATmega1281 also add this functio
70. AT mega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3_ SIG_ Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA OVF_vect OVERFLOW3 Overflow ATmegal28 ATmegal62 ATmega64 mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER4 SIG_INPUT_ Timer Counter4 ATmega640 ATmegal280 ATmegal281 CAPT_vect CAPTURE4 Capture Event ATmega2560 ATmega2561 TIMER4 SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPA vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARE4A A TIMER4 SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPB vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPAREAB B TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 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 ATmegal281 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
71. ATmega2560 ATmega2561 COMPARESC C TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 OVF vect OVERFLOWS Overflow ATmega2560 ATmega2561 TWI vect SIG 2WIRE 2 wire Serial In AT90CANI28 AT90CAN32 AT90CAN64 SERIAL terface ATmegal28 ATmegal6 ATmegal63 ATmega32 323 ATmega406 ATmega64 ATmega8535 ATmegal68 ATmega48 ATmega88 mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 117 Vector name Old vector Description Applicable for device name 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 UART0_ Complete TRANS UARTO_ SIG_ UARTO Data ATmegal61 UDRE_vect UARTO_ Register Empty DATA UART1_RX_ SIG_ UARTI Rx ATmegal61 vect UARTI Complete RECV UARTI TX SIG UARTI Tx ATmegal61 vect UARTI Complete TRANS UARTI SIG UARTI Data ATmegal61 UDRE vect UARTI Register Empty DATA UART RX SIG UART UART Rx Com AT90S2313
72. Ix hexadecimal printf format for uint32_t 6 5 2 45 define PRIX8 X uppercase hexadecimal printf format for uint8_t 6 5 2 46 define PRIx8 x 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 IX uppercase hexadecimal printf format for uint fast32 t 6 5 2 50 define PRIxFAST32 Ix hexadecimal printf format for fast32 t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 28 6 5 2 51 define PRIXFASTS X uppercase hexadecimal printf format for uint fast8 t 6 5 2 52 define PRIxFASTS 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 PRIXLEAST16 hexadecimal printf format for uint_least16_t 6 5 2 55 define PRIXLEAST32 IX uppercase hexadecimal printf format for uint_least32_t 6 5 2 56 define PRIXLEAST32 Ix hexadecimal printf format for uint_least32_t 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 least8 t 6 5 2 59 define PRIXPTR PRIX16 uppercase hexadecimal printf format for uintptr t 6 5 2 60 define PRIx
73. Oct 29 20 02 34 2007 for avr libc by Doxygen 13 Supported Devices at90pwm2 at90pwm2b at90pwm216 at90pwm3 at90pwm3b e at90pwm316 Smart Battery AVR Devices atmega8hva atmegal6hva atmega406 USB AVR Devices at90usb82 at90usb162 at90usb646 at90usb647 at90usb1286 at90usb1287 Miscellaneous Devices at94K 2 at76c711 3 at43usb320 at43usb355 at86rf401 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 14 avr libc License 7 Classic AVR Devices 319051200 1 at90s2313 at90s2323 at90s2333 at90s2343 219054414 219054433 219054434 219058515 at90c8534 at90s8535 Note 1 Assembly only There is no direct support for these devices to be programmed in C since they do not have a RAM based stack Still it could be possible to program them in C see the FAQ for an option 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 1 4 avr libc License avr libc can be freely used and redistributed provided the following license conditions are met Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 1 4 avr libc License Portions of avr libc are Copyright c 1999 2007 Keith Gudger Bjoern Haase
74. Ox3D Ox3E 0x40 0x41 0x42 0x43 0x44 0x45 0 46 0 47 0 48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 0x5A 0x5B 0x5C 0x5D 0x5E Ox5F 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0Ox6A 0x6B 0x6C 0x6D and later your code you access this data in a function and store a single byte into 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 pomspace h gt and put it after the declaration of the variable but before the initializer like so include lt avr pgmspace h gt unsigned char mydata 11 10 PROGMEM 0x00 0 01 0 02 0 03 0 04 0 05 0 06 0 07 0 08 0x09 0 0 0 0 0 0 0 0 0 0 0 0 0 10 0 11 0 12 0 13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D Ox1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F 0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 Ox5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D That s it Now your data is in the Program Space You compile link and check the map file to verify that mydata is placed
75. PROGMEM Bar P array 2 PROGMEM 1 foo bar int main void char 32 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 319 PGM_P int i memcpy P amp p strcpy P buf return 0 amp array i sizeof PGM_P Looking at the disassembly of the resulting object file we see that array is in flash as such 00000026 lt array gt 26 2e 00 28 2a 00 0x002e 0 002 word word 0000002a lt bar gt 2 42 61 72 00 0000002 lt foo gt 2 46 6 6 00 foo is at addr 0x002e bar is at addr 0x002a array is at addr 0x0026 Then in main we see this memcpy_P amp p amp arraylil 2999 27277 sizeof PGM_P 70 66 0 add r225 522 ag eats adc 23 123 74 5 subi r22 OxDA j TGL 7f 4f sbci r23 OxFF 78 42 0 ldi 20 0x02 Ta 50 0 idi r21 0 00 F 7 01 movw r24 r28 7e 81 96 adiw r24 0x21 r 80 08 rcall 16 Bar Foo 218 255 33 0 92 This code reads pointer to the desired string from 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 poi
76. SLA W transmitted NACK received Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 629 lt util twi h gt TWI bit mask definitions 167 6 29 2 12 define TW NO INFO 0xF8 no state information available 6 29 2 13 define TW READ 1 SLA R address 6 29 2 14 define TW REP START 0x10 repeated start condition transmitted 6 29 2 15 define TW_SR_ARB_LOST_GCALL_ACK 0x78 arbitration lost in SLA RW general call received ACK returned 6 29 2 16 define TW_SR_ARB_LOST_SLA_ACK 0x68 arbitration lost in SLA RW SLA W received ACK returned 6 29 2 17 define TW_SR_DATA_ACK 0x80 data received ACK returned 6 29 2 18 define TW_SR_DATA_NACK 0x88 data received NACK returned 6 29 2 19 define TW_SR_GCALL_ACK 0x70 general call received ACK returned 6 29 2 20 define TW_SR_GCALL_DATA_ACK 0x90 general call data received ACK returned 6 29 2 21 define TW_SR_GCALL_DATA_NACK 0x98 general call data received NACK returned 6 29 2 22 define TW_SR_SLA_ACK 0x60 SLA W received ACK returned Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 629 lt util twi h gt TWI bit mask definitions 168 6 29 2 23 define TW SR STOP 0xA0 stop or repeated start condition received while selected 6 29 2 24 define TW ST LOST SLA 0 0 arbitration lost in SLA RW SLA R received ACK returned 6 29 2 25 itdefine TW ST DATA 0xB8 data transmitted ACK received 6 29 2
77. SMO define SLEEP_MODE_PWR_DOWN _BV SM1 define SLEEP_MODE_PWR_SAVE _BV SMO _BV SM1 define SLEEP MODE STANDBY 5 1 BV SM2 define SLEEP MODE EXT STANDBY BV SMO BV SMD BV SM2 6 20 2 Define Documentation 6 20 2 1 define SLEEP MODE BV SMO ADC Noise Reduction Mode 6 20 2 2 define SLEEP MODE EXT STANDBY BV SM0 BV SMI1 BV SM2 Extended Standby Mode 6 20 2 3 define SLEEP MODE IDLE 0 Idle mode 6 20 2 4 define SLEEP MODE PWR DOWN BV SMI Power Down Mode 6 20 2 5 define SLEEP MODE PWR SAVE BV SM0 BV SM1 Power Save Mode 6 20 2 6 define SLEEP MODE STANDBY _BV SM1 BV SM2 Standby Mode Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 621 lt avr version h gt avr libc version macros 147 6 20 3 Function Documentation 6 20 3 1 void set_sleep_mode uint8_t mode Select a sleep mode 6 20 3 2 void sleep_cpu void Put the device into sleep mode The SE bit must be set beforehand and it is recom mended to clear it afterwards 6 20 3 3 void sleep_disable void Clear the SE sleep enable bit 6 20 3 4 void sleep_enable void Set the SE sleep enable bit 6 20 3 5 void sleep_mode void Put the device in sleep mode How the device is brought out of sleep mode depends on the specific mode selected with the set_sleep_mode function See the data sheet for your device for more details 6 21 lt avr version
78. Some of these modes are not available on all devices See the datasheet for target device for the available sleep modes define SLEEP_MODE_IDLE 0 define SLEEP_MODE_ADC _BV SM0 define SLEEP_MODE_PWR_DOWN _BV SM1 define SLEEP_MODE_PWR_SAVE BV SMO _BV SM1 define SLEEP MODE STANDBY _BV SM1 BV SM2 define SLEEP MODE EXT STANDBY BV SMO _BV SMI BV SM2 Functions Sleep Functions void set_sleep_mode uint8_t mode void sleep_mode void void sleep_enable void void sleep_disable void void sleep_cpu void 8 38 stdint h File Reference 8 38 1 Detailed Description Defines define USING MINT8 0 define _ CONCATenate left right left right define __CONCAT Ieft right _ CONCATenate left right Limits of specified width integer types C implementations should define these macros only when __ STDC LIMIT MACROS is defined before lt stdint h gt is included define INT8 MAX Ox7f define INT8 MIN 8 MAX 1 define UINTS MAX CONCAT INT8 MAX U 2U 1U define INTI6 MAX Ox7fff define INTI6 MIN INT16 MAX 1 define UINTIG6 MAX CONCAT INT16 MAX U 2U 1U define INT32 MAX Ox 7fffffffL define INT32 MIN INT32 MAX IL define UINT322 MAX CONCAT INT32 MAX U 2UL define INT64_MAX Ox 7fffffffffffffIfLL Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 38 stdint h File Reference 242 defi
79. The sin function returns the sine of x measured in radians 6 6 3 29 double sinh double x The sinh function returns the hyperbolic sine of x 6 6 3 30 double sqrt double x The sqrt function returns the non negative square root of x 6 6 3 31 double square double x The function square returns x x Note This function does not belong to the C standard definition 6 6 3 32 double tan double __x The tan function returns the tangent of x measured in radians 6 6 3 33 double tanh double __x The tanh function returns the hyperbolic tangent of x Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 7 lt setjmp h gt Non local goto 38 6 6 3 34 double trunc double x The trunc function rounds x to 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 got o 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 longjmp functions setjmp and longjmp are useful for dealing with errors and interrupts encountered in a low level subroutine of a program Note setjmp and longjmp make programs hard to understand and maintain If possi ble an alternative should be used longjmp can destroy changes made to global register variables see How to pe
80. To use interactive mode use the t option avrdude 2313 t avrdude AVR device initialized and ready to accept instructions avrdude Device signature 0 1 9101 avrdude gt The command displays list of valid commands avrdude gt gt gt gt Valid commands dump dump memory dump lt memtype gt 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 13 Release Numbering and Methodology 357 Use the part command to display valid memory types for use with the dump and write commands avrdude gt 9 13 Release Numbering and Methodology 9 13 1 Release Version Numbering Scheme 9 13 1 1 Stable Versions stable release will always have a minor number that is an even number This implies that you should be able to upgrade to a new version of the library with the same major and minor numbers without fear that any of the APIs have changed The only changes that should be made to a stable branch are bug fixes and under some circumstances additional functionality e g adding support for a new device If major version n
81. UINT32 MAX CONCAT INT32 U 2UL 100 define INT64 MAX 0x7 define INT64 MIN INT64 MAX ILL define UINT 4 MAX _ CONCAT INT64 MAX U x 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 MAX 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 Limits of fastest minimum width integer types define INT FAST8 MAX 8 MAX define INT FAST8 MIN INT8 MIN define UINT FASTS MAX UINT8 MAX define INT FASTI6 MAX MAX define INT FASTI6 MIN INTI6 MIN define UINT FASTI6 MAX UINTI6 MAX define INT FAST32 MAX INT32 define INT FAST32 MIN INT32 MIN define UINT FAST32 MAX UINT32 MAX define INT FAST64 MAX INT64 MAX define INT FAST64 MIN INT64 MIN define UINT FAST64 MAX UINT64 MAX Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 43 Limits of integer types capable of holding object pointers define INTPTR_MAX INT16_MAX define INTPTR_MIN INT16_MIN define UINTPTR_MAX UINT16_MAX Limits of greatest width integer types define IN
82. a program space string Note also the use of the PSTRQ macro Back to FAQ Index 9 9 21 Why does the compiler compile an 8 bit operation that uses bitwise oper ators into a 16 bit operation in assembly Bitwise operations in Standard C will automatically promote their operands to an int which is by default 16 bits in avr gcc Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 324 To work around this use typecasts on the operands including literals to declare that the values are to be 8 bit operands This may be especially important when clearing a bit var amp mask wrong way x The bitwise not operator will also promote the value in mask to an int To keep it an 8 bit value typecast before the not operator var amp unsigned char mask Back to FAQ Index 9 9 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
83. 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 unsigned long ctx 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 unsigned long ctx Variant of random that stores the context in the user supplied variable located at ct x instead of a static library variable so the function becomes re entrant 6 10 4 23 void realloc void __ptr size_t size The realloc function tries to change the size of the region allocated at pt r to the new size value It returns a pointer to the new region The returned pointer might be the same as the old pointer or a pointer to a completely different region The contents of the returned region up to either the old or the new size value whatever is less will be id
84. an alphabetic character It is equivalent to isupper c islower c 6 3 2 3 int isascii int 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 is a space or a tab 6 3 2 5 int iscntrl int Checks for a control character 6 3 2 6 int isdigit int Checks for a digit 0 through 9 6 3 2 7 int isgraph int Checks for any printable character except space 6 3 2 8 int islower int _ c 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 newline C Nn carriage return r horizontal tab t and vertical tab CN Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 4 lt errno h gt System Errors 19 6 3 2 12 intisupper int Checks for an uppercase letter 6 3 2 13 intisxdigit int _ c Checks for a hexadecimal digits i e oneof0123456789abcdefABCDEE 6 3 2 14 toascii int c 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 us
85. avr5 at90can32 AVR AT90CAN32 avr5 at90can64 _ _AVR_AT90CAN64__ avr5 at90can128 AVR AT90CANI28 avr5 at90usb82 AVR AT90USB82 avr5 at90usb162 AVR AT90USBIG2 avr5 at90usb646 __AVR_AT90USB646__ avr5 at90usb647 AVR AT90USB647 avr5 at90usb1286 _ AT90USBI1286 avr5 at90usb1287 AVR AT90USBI1287 avr5 atmegal28 AVR ATmegal28 avr5 atmegal280 AVR ATmegal280 avr5 atmegal281 AVR ATmegal281 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 ATmegal 8 avr5 atmegal68p AVR ATmegal68P avr5 atmegal69 AVR ATmegal69 avr5 atmegal69p AVR ATmegal69P avr5 atmegal6hva _ 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 348 Architecture MCU name Macro avr5 atmega3290p AVR ATmega3290P
86. avr_inttypes 22 PRIdFASTS avr inttypes 22 PRIdLEAST16 avr_inttypes 22 PRIdLEAST32 avr_inttypes 23 PRIdLEASTS avr inttypes 23 PRIdPTR avr inttypes 23 PRIi16 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 377 avr_inttypes 23 PRIi32 avr_inttypes 23 8 avr_inttypes 23 PRIFASTI16 avr inttypes 23 PRIFAST32 avr inttypes 23 PRIFAST8 avr_inttypes 23 PRILEAST16 avr_inttypes 23 PRILEAST32 avr inttypes 23 8 avr_inttypes 24 PRIiPTR avr_inttypes 24 printf avr_stdio 61 printf_P avr_stdio 62 PRIo16 avr inttypes 24 PRIo32 avr inttypes 24 PRIo8 avr inttypes 24 PRIoFAST16 avr_inttypes 24 PRIoFAST32 avr_inttypes 24 PRIoFAST8 avr_inttypes 24 PRIoLEASTI6 avr inttypes 24 PRIoLEAST32 avr inttypes 24 PRIoLEASTS avr inttypes 24 PRIoPTR avr inttypes 25 PRIu16 avr inttypes 25 PRIu32 avr inttypes 25 PRIu8 avr inttypes 25 PRIuFAST16 avr_inttypes 25 PRIuFAST32 avr_inttypes 25 PRIuFASTS avr inttypes 25 PRIULEAST16 avr_inttypes 25 PRIULEAST32 avr_inttypes 25 PRIuLEASTS avr inttypes 25 PRIuPTR avr inttypes 25 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 26 PRIxFAST16 avr_inttypes 26 PRIXFAST32 avr_inttypes 26 PRIxFAST32 avr_inttypes 26
87. by Doxygen 611 lt string h gt Strings 91 6 11 3 28 size t strnlen const char src size_t len Determine the length of a fixed size string The strnlen function returns the number of characters in the string pointed to by src not including the terminating 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 s
88. can hold 6 8 2 3 define INT16_MIN INT16_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 6 8 2 7 define INT64_C value CONCAT value LL define a constant of type int64 t 6 8 2 8 define INT64 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 45 6 8 2 12 define INT8 MIN INT8 MAX 1 smallest negative value an int8 t can hold 6 8 2 13 define INT FASTI6 MAX INTI6 largest positive value an int fast16 t 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 MAX 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
89. char Itoa long int __val char x__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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 40 stdlib h File Reference 247 Conversion functions for double arguments Note that these functions are not located in the default library 1ibc a but in the mathematical library 1ibm a So when linking the application the 1m option needs to be specified define DTOSTR_ALWAYS_SIGN 0x01 define DTOSTR_PLUS_SIGN 0x02 define DTOSTR_UPPERCASE 0x04 e char dtostre double __val char s unsigned char __ prec unsigned char flags char dtostrf double __val signed char __ width unsigned char prec char S Defines define STDLIB H 1 define need NULL define need size t define need wchar t define ptr t void define RAND MAX 0x7FFF Typedefs typedef int x compar fn t const void const void Functions e inline void abort void ATTR NORETURN int abs int 1 ATTR CONST long labs long __i CONST 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 _ ATTR
90. converted The complete conversion specifica tion is eE The double argument is rounded and converted in the format d ddde dd where there is one digit before the decimal point charac ter and the number of digits after it is equal to the precision if the precision is missing it is taken as 6 if the precision is zero no decimal point character appears An E conversion uses the letter E rather than to introduce the exponent The exponent always contains two digits if the value is zero the exponent is 00 F The double argument is rounded and converted to decimal notation in the format ddd ddd where the number of digits after the decimal point character is equal to the precision specification If the precision is missing it is taken as 6 if the precision is explicitly zero no decimal point character appears If a decimal point appears at least one digit appears before it gG The double argument is converted in style or e or F or E for G conver sions The precision specifies the number of significant digits If the precision is missing 6 digits are given if the precision is zero it is treated as 1 Style e is used if the exponent from its conversion is less than 4 or greater than or equal to the precision Trailing zeros are removed from the fractional part of the result a decimal point appears only if it is followed by at least one digit S Similar to the s format except the pointer is
91. decrease the current PWM value shorting PD3 to GND will increase it While PD4 is shorted to GND one ADC conversion for channel 0 ADC input is on PAO will be triggered each internal clock tick and the resulting value will be used as the PWM value So the brightness of the LED follows the analog input value on PCO VAREF on the STK500 should be set to the same value as VCC When running in serial control mode the function of the watchdog timer can be demon strated by typing an r This will make the demo application run in a tight loop without retriggering the watchdog so after some seconds the watchdog will reset the MCU This situation can be figured out on startup by reading the MCUCSR register The current value of the PWM is backed up in an EEPROM cell after about 3 seconds of idle time after the last change If that EEPROM cell contains a reasonable i e non erased value at startup it is taken as the initial value for the PWM This virtually preserves the last value across power cycles By not updating the EEPROM immme diately but only after a timeout EEPROM wear is reduced considerably compared to immediately writing the value at each change 6 35 3 code walkthrough This section explains the ideas behind individual parts of the code The source code has been divided into numbered parts and the following subsections explain each of these parts Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 35
92. 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 2 1 Creating a cvs branch The following steps should be taken to cut a ch in cvs Check out a fresh source tree from cvs HEAD 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 Set the branch point tag setting lt major gt and lt minor gt accordingly cvs tag avr libe major minor branchpoint Create the branch cvs tag b avr libe major minor branch Update the package version in configure ac and commit configure ac to cvs HEAD Change minor number to next odd value Update the NEWS file and commit to cvs HEAD Add Changes since avr libc lt this_release gt Check out a new tree for the branch CO r avr libe major minor branch Update the package version in configure ac and commit configure ac to cvs branch Change the patch number to 90 to denote that this now a branch leading up to a release Be sure to leave the lt date gt part of the version Bring the build system up to date by running bootstrap and configure Perform a make distcheck and make sure it succeeds This will create the snapshot source tarball This should be considered the first release candidate Upload the snapshot ta
93. executed when ISR fires with no accompanying ISR handler This may be used along with the ISR macro to create a catch all for undefined but used ISRs for debugging purposes 6 14 2 2 define cli include lt avr interrupt h gt 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 6 14 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 14 2 4 define ISR vector attributes include lt avr interrupt h gt Introduces an interrupt handler function interrupt service routine that runs with global interrupts initially disabled by default with no attributes specified The attributes are optional and alter the behaviour and resultant generated code of the interrupt routine Multiple attributes may be used for a single function with a space seperating each attribute Valid attributes are ISR BLOCK ISR_NOBLOCK ISR NAKED and ISR ALIASOF vect vector must be one of the interrupt vector names that are valid for the particular MCU type Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 122 6 14 2 5 d
94. 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 full functionality including the floating point conversions is required the follow ing options should be used Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 69 lt stdio h gt Standard IO facilities 67 Wl u vfprintf lprintf_flt lm Limitations e The specified width and precision can be at most 255 Notes e 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 wil
95. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 69 lt stdio h gt Standard IO facilities 55 int uart_putchar char c FILE xstream if c n uart_putchar r loop_until_bit_is_set UCSRA UDRE UDR return 0 Note 3 This implementation has been chosen because the cost of maintaining an alias is considerably smaller than the cost of maintaining full copies of each stream Yet providing an implementation that offers the complete set of standard streams was deemed to be useful Not only that writing printf instead of fprintf mystream saves typing work but since avr gcc needs to re sort to pass all arguments of variadic functions on 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 FI
96. for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 340 CFLAGS D_ USF_MINGW_ACCESS N Sarchivedir configure N prefix installdir N target avr N disable nls N enable doc N datadir installdir doc binutils N with gmp usr local N with mpfr usr local N 2 gt 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 Open source code pacakge patch necessary Configure and build in a directory outside of the source code tree Set PATH in order lt MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin lt install directory gt bin Configure CFLAGS D_ USF_MINGW_ACCESS N gcc Sversion configure N prefix installdir N target target N enable languages c c with dwarf2 N enable win32 registry WinAVR release disable nls N with gmp usr local N with mpfr usr local N enable doc N disable libssp N 2 gt amp 1 tee Spackage configure log Make make all html install 2 gt amp 1 tee package make log Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 341 Manually copy the HTML documentation from the source code tree to the installation tree avr libc Open source code package Config
97. for avr libc by Doxygen 9 9 Frequently Asked Questions 306 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 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 ATmega128 keeps crashing Port F is completely broken Why do all my foo bar strings eat up the SRAM Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit operation in assembly How to detect RAM memory and variable overlap problems Is it really impossible to program the ATtinyXX in C What is this clock skew detected messsage Why are many interrupt flags cleared by writing a logical 1 Why have programmed fuses the bit value 0 Which AVR specific assemb
98. 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 plus a GUI written in TcI Tk Both and Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 1 Toolchain Overview 265 Insight are configured for the AVR and the main 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 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 al
99. from the controller needs to be handled as two nibble IOs The functions hd44780_outnibble and hd44780_innibble implement this They do not belong to the public interface so they are declared static Building upon these the public functions hd44780_outbyte and hd44780_ inbyte transfer one byte to from the controller The function hd44780 wait ready waits for the controller to become ready by continuously polling the controller s status which is read by performing a byte read with the RS signal cleard and examining the BUSY flag within the status byte This function needs to be called before performing any controller IO Finally hd44780 init initializes the LCD controller into 4 bit mode based on the initialization sequence mandated by the datasheet As the BUSY flag cannot be examined yet at this point this is the only part of this code where timed delays are used While the controller can perform a power on reset when certain constraints on Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 336 Using the standard IO facilities 205 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 36 3 5 Icd h This function declares the public interface of the higher level char acter IO LCD driv
100. h gt avr libc version macros 6 21 1 Detailed Description include lt avr version h gt This header file defines macros that contain version numbers and strings describing the current version of avr libc The version number itself basically consists of three pieces that are separated by a dot the major number the minor number and the revision number For development versions which use an odd minor number the string representation additionally gets the date code 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 621 lt avr version h gt avr libc version macros 148 Defines define AVR_LIBC_VERSION_STRING__ AVR_LIBC_VERSION define __AVR_LIBC_VERSION__ AVR_LIBC_VERSION_ NUMERIC UL define _ AVR DATE STRING AVR_LIBC_RELDATE define _ AVR DATE AVR LIBC RELDATEQGUL define _ AVR MAJOR AVR LIBC MAJORG define _ AVR LIBC MINOR AVR_LIBC_MINOR AVR LIBC REVISION QAVR_LIBC_REVISION 6 21 2 Define Documentation 6 21 21 define AVR DATE AVR RELDATEGUL
101. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 4 Data in Program Space 278 byte mydata i 3 then take the address of the data byte amp mydata i j then use the appropriate pgm read macro and the address of your data becomes the parameter to that macro byte pgm read byte amp mydata i j1 The read macros take an address that points to the Program Space and re trieves the data that is stored at that address This is why you take the address of the offset into the array This address becomes the parameter to the macro so it can gen erate the correct code to retrieve the data from the Program Space Ther
102. is a long int rather than int The h is ignored as short int isequivalent to int 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 The void xargumentis taken as an unsigned integer and converted similarly as a x command would do c The int argument is converted to an unsigned char and the resulting character is written s The char x argument is expected to be a pointer to an array of character type pointer to a string Characters from the array are written up to but not including a terminating NUL character if a precision is specified no more than Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 69 lt stdio h gt Standard IO facilities 66 the number specified are written If a precision is given no null character need be present if the precision is not specified or is greater than the size of the array the array must contain a terminating NUL character A is written No argument is
103. 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 myfunc push push push push push t lt lt H hH n eor idi idi rjmp 6 r16 start loop L lo8 sometable H hi8 sometable f jump to loop test at end 7 Y loop continues here H No Ho HH breq 1f return from myfunc prematurely r16 2 cmp brlo 1b jump back to top of loop H Lr pop pop pop pop pop ret HH H lt lt Back to FAQ Index 9 9 13 How do I pass an IO port as a parameter to a function Consider this example code Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 315 include lt inttypes h gt include lt avr io h gt void set_bits_func_wrong volatile uint8_t port uint8_t mask port mask void set bits func correct volatile uint8_t xport uint8 t mask xport mask de
104. names like PORTA directly in C expressions also on the left side of assignment operators and GCC will do the right thing use short I O instructions if possible The SFR OFFSET definition is not used in any way in this case Define SFR 5 COMPAT as 1 to make these names work as simple constants ad dresses of the I O registers This is necessary when included in preprocessed assem bler S source files so it is done automatically if ASSEMBLER is defined By default all addresses are defined as if they were memory addresses used in 1ds st s instructions To use these addresses in in out instructions you must subtract 0x20 from them For more backwards compatibility insert the following at the start of your old assem bler source file define _ SFR OFFSET 0 This automatically subtracts 0x20 from I O space addresses but it s a hack so it is recommended to change your source wrap such addresses in macros defined here as shown below After this is done the___SFR_OFF SET definition is no longer necessary and can be removed Real example this code could be used in a boot loader that is portable between devices with SPMCR at different addresses lt avr ioml63 h gt define SPMCR _SFR_I08 0x37 lt avr iom128 h gt define SPMCR _SFR_MEM8 0x68 dif SFR IO REG P SPMCR out SFR IO ADDR SPMCR r24 else sts _SFR_MEM_ADDR SPMCR r24 endif You can use the in out cbi sbi sbic sb
105. 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 Memory Sections There is also an ex ample for Using Sections in C Code Note that in C code any such function would preferrably be placed into section init3 as the code in init2 ensures the internal regis ter zero reg is already cleared Back to FAQ Index Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 309 9 9 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
106. o Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 188 data 0x00800060 0x0 usr local lib gcc avr 4 2 2 avr4 libgcc a _clear_bss o x datax x rodata x rodatax gnu linkonce dx 0x00800060 ALIGN 0x2 0x00800060 _edata 0x00800060 PROVIDE __data_end bss 0x00800060 0x3 load address 0x00000114 0x00800060 PROVIDE __bss_start x bss bss 0x00800060 0 3 demo o bss 0x00800063 0 0 home joerg src avr libc avr lib avr4 atmega8 crtm8 o bss 0x00800063 0 0 home joerg src avr libc avr lib avr4 exit o bss 0x00800063 0x0 usr local lib gcc avr 4 2 2 avr4 libgcc a _exit o bss 0x00800063 0 0 usr local lib gcc avr 4 2 2 avr4 libgcc a _copy_data o bss 0x00800063 0 0 usr local lib gcc avr 4 2 2 avr4 libgcc a _clear_bss o x bssx COMMON 0x00800063 PROVIDE __bss_end 0x00000114 _ data_load_start LOADADDR data 0x00000114 data_load_end __data_load_start SIZEOF data noinit 0x00800063 0x0 0x00800063 PROVIDE __noinit_start noinit 0x00800063 PROVIDE __noinit_end 0x00800063 _end 0x00800063 PROVIDE __heap_start eeprom 0x00810000 0 0 0 00810000 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 ad
107. object is referenced by ptr 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 if any will not be stored in the string It is the caller s responsibility to provide enough storage to hold the characters read 6 9 3 19 int printf const char fmt Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 63 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 print that uses a fmt string that resides in program memory 6 9 3 21 int puts const char s r 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 formatted input from stream st din See vfscanf for details 6 9 3 24 int scanf_P const char fmt Variant of scanf where mt resides in program memory 6 9 3 25 int snprintf char x s size t n constchar fmt Like sprintf but instead of assuming s to be of infinite size no more than n characters including the trailing NUL character will be converted to s
108. of the Global Interrupt Status flag when execution of the block completes 6 23 2 4 define NONATOMIC_BLOCK type Creates a block of code that is executed non atomically Upon entering the block the Global Interrupt Status flag in SREG is enabled and disabled upon exiting the block from any exit path This is useful when nested inside ATOMIC_BLOCK sections 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 23 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 23 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
109. of the STK500 The LCD controller is used in 4 bit mode including polling the busy flag so the R W line from the LCD controller needs to be connected Note that the LCD con troller has yet another supply pin that is used to adjust the LCD s contrast V5 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 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 36 2 Functional overview The project consists of the following files stdiodemo c This is the main example file defines h Contains some global defines like the LCD wiring hd44780 c Implementation of an HD44780 LCD display driver 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 336 Using the standard IO facilities 202 uart c Implementation of a character IO driver for the internal UART uart h Interface declarations for the UART driver 6 36 3 A code walkthrough 6 36 3 1 stdiodem
110. on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 88 wdt h File Reference 260 8 88 wdt h File Reference 8 88 1 Detailed Description Defines define wdt reset asm volatile wdr define WD PS3 MASK 0x00 define WD CONTROL REG WDTCR define WD CHANGE BIT WDCE define wdt write value define wdt_disable define wdt_enable timeout _wdt_write timeout 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 8 88 2 Define Documentation 8 88 2 1 define _wdt_write value Value __asm__ __volatile__ N in tmp_reg__ __SREG__ n t tali mynyt n t out 0 81 n t N out SREG tmp reg n t N out 0 2 no outputs N I _SFR_IO_ADDR _WD_CONTROL_REG r BV WD CHANGE BIT _BV WDE N r uint8 t value amp 0x08 WD PS3 0x00 _BV WDE value amp 0x07 SU pM X Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 avr libc Page Documentation 261 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
111. over the RS 232 connection to a terminal e g from to a PC running a terminal program while 1cd_str stream provides a method to display character data on the LCD text display The function delay_1s suspends program execution for approximately one sec ond This is done using the delay ms function from lt util delay h gt which in turn needs the F_CPU macro in order to adjust the cycle counts As the _delay_ms function has a limited range of allowable argument values depending on F_CPU a value of 10 ms has been chosen as the base delay which would be safe for CPU frequencies of up to about 26 MHz This function is then called 100 times to accomodate for the actual one second delay In a practical application long delays like this one were better be handled by a hardware timer so the main CPU would be free for other tasks while waiting or could be put on sleep At the beginning of main after initializing the peripheral devices the default stdio streams stdin stdout and stderr are set up by using the existing static FILE stream objects While this is not mandatory the availability of stdin and stdout allows to use the shorthand functions e g printf instead of fprintf and stderr can mnemonically be referred to when sending out diagnostic messages Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 336 Using the standard IO facilities 203 Just for demonstration purposes stdin and st
112. path with the path to the h file on your system Replace 1ib path with the path to 1ibbfd a on your system 5 CPPFLAGS I hdr path LDFLAGS L lib path configure prefix PREFIX 9 10 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 336 that programs designed for Unix and Linux i e that use POSIX functionality will not compile as MinGW MSYS does not provide that POSIX layer for you
113. pwm so others can use it in calculations In order to allow for a simple calculation of a percentage value without requiring floating point mathematics the maximal value of the PWM is restricted to 1000 rather than 1023 so a simple division by 10 can be used Due to the nature of the human eye the difference in LED brightness between 1000 and 1023 is not noticable anyway Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 35 more sophisticated project 199 6 35 3 5 Part 5 main At the start of main a variable mode is declared to keep the current mode of operation 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 charac
114. respectively to be less than to match or be greater than s2 A consequence of the ordering used by strncasecmp is that if s1 is an initial substring of s2 then s1 is considered to be less than 52 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 The strncat function returns a pointer to the resulting string dest 6 11 3 26 int strncmp const char s1 const char s2 size_t len Compare two strings The strncmp function is similar to stremp except it only compares the first at most n characters of sl and s2 Returns strncmp function returns an integer less than equal to or greater than zero if sl or the first n bytes thereof is found respectively to be less than to match or be greater than s2 6 11 3 27 char strncpy char dest const char src size_t len Copy a string The strncpy function is similar to strcpy except that not more than n bytes of src are copied Thus if there is no null byte among the first n bytes of src the result will not be null terminated In the case where the length of src is less than that of n the remainder of dest will be padded with nulls Returns The strncpy function returns a pointer to the destination string dest Generated on Mon Oct 29 20 02 34 2007 for avr libc
115. returns a pointer to dest 6 11 3 8 void memmem const void gt s7 size t len const 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 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 11 lt string h gt Strings 86 6 11 3 9 void x memmove void dest const void src size t len Copy memory area 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 src int val size t len memrchr function is like the memchr function except that it searches back wards from the end of the 1en bytes pointed to by src instead of forwards from the front Glibc GNU extension Returns The memrchr function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 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 pointe
116. 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 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 291 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 cle
117. set aside completely for use by these routines so the compiler would not use them for C code This is arranged for in project h The file is divided into one section that will be used by the assembly source code and another one to be used by C code The assembly part is distinguished by the prepro cessing macro __ASSEMBLER__ which will be automatically set by the compiler Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 33 Combining C and assembly source files 176 front end when preprocessing an assembly language file and it contains Just macros that give symbolic names to a number of CPU registers The preprocessor will then replace the symbolic names by their right hand side definitions before calling the as sembler In C code the compiler needs to see variable declarations for these objects This is done by using declarations that bind a variable permanently to a CPU register see How to permanently bind a variable to a register Even in case the C code never has a need to access these variables declaring the register binding that way causes the compiler to not use these registers in C code at all The flags variable needs to be in the range of r16 through r31 as it is the target of a load immediate or SER instruction that is not applicable to the entire register file 6 33 2 3 isrs S This file is a preprocessed assembly source file The C preprocessor will be run by the compiler front end f
118. that are guaranteed to be excuted Atomically or Non Atmomically The term Atomic in this context refers to the un ability of the respective code to be interrupted These macros operate via automatic manipulation of the Global Interrupt Status T bit of the SREG register Exit paths from both block types are all managed automatically Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 23 lt util atomic h gt Atomicly and Non Atomically Executed Code Blocks 153 without the need for special considerations 1 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 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 include lt inttypes h gt include lt avr interrupt h gt include lt avr io h gt volatile uint16_t ctr 5 OVF Gtr int main void ctr 0x200 start timer while ctr 0 wait There is a chance where the main context will exit its wait loop when the variable ct r 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 exam
119. 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 TARGET macro in the Makefile needs to be adjusted appropriately for the alternative controller types Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 35 more sophisticated project 196 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 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 35 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 a PC 9600 Bd 8N1 frame format The demo application talks to the serial port and it can be controlled from the serial port PD2 through PD4 are configured as inputs and control the application unless control has been taken over by the serial port Shorting PD2 to GND will
120. 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 330 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 PREFIX 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 10 2 Required Tools GNU Binutils http sources redhat com binutils Installation http gcc gnu org Installation AVR Libc http savannah gnu org projects avr libc Installation 9 10 3 Optional Tools You can develop programs for AVR devices without the following tools They may or may not be of use for you Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and In
121. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 12 Using the avrdude program 356 avrdude Device signature 0 1 9101 avrdude erasing chip avrdude done avrdude reading input file main hex avrdude input file main hex auto detected as Intel Hex avrdude writing flash 1749 0 00 avrdude 1750 bytes of flash written avrdude verifying flash memory against main hex avrdude reading on chip flash data 1749 0 00 avrdude verifying avrdude 1750 bytes of flash verified avrdude done Thank you The 2313 option lets avrdude know that we are operating on 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 option instructs avrdude to perform a chip erase before programming this is almost always necessary before programming the flash The m flash option indicates that we want to upload data into the flash memory while i main hex specifies the name of the input file The EEPROM is uploaded in the same way the only difference is that you would use m eeprom instead of m flash
122. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 53 since there is no notion of file whatsoever to avr libc there is no function fopen that could be used to associate a stream to some device See note 1 Instead the function fdevopen is provided to associate a stream to a device where the device needs to provide a function to send a character to receive a character or both There is no differentiation between text and binary streams inside avr libc Character n is sent literally down to the device s put function If the device requires a carriage return N r character to be sent before the linefeed its put routine must implement this see note 2 As an alternative method to fdevopen the macro fdev_setup_stream might be used to setup a user supplied FILE structure It should be noted that the automatic conversion of a newline character into a carriage return newline sequence breaks binary transfers If binary transfers are desired no automatic conversion should be perfor
123. 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 5 there s a comment in each generated assembler file that tells you the frame size for each generated function That s the amount of stack required for this function you have to add up that for all functions where you know that the calls could be nested Back to FAQ Index 9 9 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 325 http lightner net avr ATtinyAvrGcc html Back to FAQ Index 9 9 24 What is this clock skew detected messsage I
124. this is to make the NONATOMIC BLOCK s contents guaranteed non atomic without changing the state of the Global Interrupt Status flag when execution of the block completes Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 24 lt util crc16 h gt CRC Computations 156 6 24 lt util crc16 h gt CRC Computations 6 241 Detailed Description include util crcl6 h This header file provides a optimized inline functions for calculating cyclic redundancy checks CRC using common polynomials References 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 Oxb8 0 01 0 0 0 Oxa2 int checkcrc void uint8_t cre 0 i for i 0 i lt sizeof serno sizeof serno 0 i crc _crc_ibutton_update crc serno i return crc must be 0 Functions e static _ inline __uint16_t _crc16_update uint16 t crc uint8_t _ data e static inline uintl6 t crc xmodem update uint16 t crc uint8 t data e sta
125. timeout _wdt_write timeout 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 22 2 Define Documentation 6 22 21 define wdt_disable Value asm__ __volatile__ N in tmp_reg__ n t X ala n t out 0 1 n t N uut 0 zero reg n t X out SREG tmp reg n t no outputs I SFR IO ADDR WD CONTROL REG r uint8 t WD CHANGE BV WDE x CX Disable the watchdog timer if possible This attempts to turn off the Enable bit in the watchdog control register See the datasheet for details 6 22 2 2 define wdt enable timeout wdt write timeout 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 22 lt avr wdt h gt Watchdog timer handling 151 6 22 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
126. 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 strcpy_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 some extra code in order to actually load the data from the Program Space This incurs some extra overhead in terms of code space extra opcodes and execution time Usually both the space and time overhead is minimal compared to the space savings of putting data in Program Space But you should be aware of this so you can mini mize the number of calls within a single function that gets the same piece of data from Program Space It is always in
127. 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 near address short define pgm read dword address short read dword near address short define PGM 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 uint64_t PROGMEM prog uint64 t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 33 pgmspace h File Reference 234 Functions CONST__ int memcmp_P const void x PGM VOID size t ATTR_PURE void memcpy P void VOID size_t void memmem_P const void size t PGM VOID size t PGM VOID P memchr PGM VOID P s int val size t len ATTR ATTR PURE CONST char strcat P char PGM P PGM P strchr P PGM P s int val ATTR CONST PGM P strchrnul P PGM P s int val _ ATTR_CONST int stremp_P const char PGM_P __ATTR_PURE char strcpy_P cha
128. 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 internal RAM Finally if the application simply wants to use the additional RAM for private data storage kept outside the domain of the C compiler e g through a char variable initialized directly to a particular address it would be sufficient to defer the 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxyg
129. watchdog initiated device reset will occur 6 22 2 4 define WDTO 120MS 3 See WDTO 15MS 6 22 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 approximate only and apply to a supply voltage of 5 V At lower supply voltages the times will increase For older devices the times will be as large as three times when operating at Vcc 3 V while the newer devices e g ATmegal28 ATmega8 only experience a negligible change Possible timeout values are 15 ms 30 ms 60 ms 120 ms 250 ms 500 ms 1 s 2 s Some devices also allow for 4 s and 8 s Symbolic constants are formed by the prefix WDTO_ followed by the time Example that would select a watchdog timer expiry of approximately 500 ms enable WDTO_500MS 6 22 2 6 define WDTO 1S 6 See WDTO 15MS 6 22 27 define WDTO 250MS 4 See WDTO 15MS 6 22 2 8 define WDTO 287 See WDTO 15MS 6 22 2 9 define WDTO 30MS 1 See WDTO 15MS 6 22 2 10 define WDTO 45 8 See WDTO_15MS Note This is only available on the ATtiny2313 ATtiny24 AT tiny44 ATtiny84 ATtiny25 45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 23 lt util atomic h gt Atomicly and Non Atomically Executed Code Blocks 152 ATmega48 ATmega88 ATmegal68 ATmega48P ATmega88P ATmegal68P AT mega328P ATmegal64P ATme
130. 0 define TW SR ARB LOST SLA 0x68 define TW SR GCALL 0x70 define TW SR LOST GCALL 0x78 define TW SR DATA ACK 0x80 define TW SR 0x88 define TW SR DATA ACK 0x90 fdefine TW SR GCALL DATA NACK 0x98 define TW SR STOP OxAO define NO INFO OxF8 define TW BUS ERROR 0x00 define TW STATUS 5 define STATUS TWSR amp TW STATUS 5 R W bit in SLA R W address field define TW READ 1 define TW_WRITE 0 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 629 lt util twi h gt TWI bit mask definitions 166 6 29 2 Define Documentation 6 29 2 1 define TW BUS ERROR 0x00 illegal start or stop condition 6 29 2 define TW MR LOST 0x38 arbitration lost in SLA R or NACK 6 29 2 3 define TW MR DATA 0x50 data received ACK returned 6 29 2 4 define TW MR DATA NACK 0x58 data received NACK returned 6 29 2 5 ididefine TW MR SLA ACK 0x40 SLA R transmitted ACK received 6 29 2 6 define TW MR SLA 0x48 SLA R transmitted NACK received 6 29 2 7 define TW MT LOST 0x38 arbitration lost in SLA W or data 6 29 2 8 define TW MT DATA 0x28 data transmitted ACK received 6 29 2 9 define TW MT DATA NACK 0x30 data transmitted NACK received 6 29 2 10 define TW MT SLA ACK 0x18 SLA W transmitted ACK received 6 29 2 11 TW MT SLA 0x20
131. 007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 72 Typedefs typedef int __compar_fn_t const void const void Functions inline void abort void _ ATTR_NORETURN_ int abs int i CONST long labs long __i _ ATTR_CONST 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 divmodhid _ ATTR CONST__ ldiv t Idiv long __num long __denom __asm__ __divmodsi4 __ATTR_ CONST__ 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 xs ATTR PURE int atoi const char xs ATTR PURE void exit int status NORETURN void malloc size t size MALLOC void free void ptr void calloc size t nele size t size ATTR MALLOC void realloc void ptr size t size MALLOC double strtod const char nptr char endptr double atof const char nptr int rand void void srand unsigned int __ seed int rand r unsigned long ctx Variables size t malloc margin char __ heap start char malloc heap end 6 10 2 Define Documentation 6 10 2 1 fdefine DTOSTR ALWAYS SIG
132. 02 34 2007 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 77 strlen PS File Reference 25 m RR EET 252 8 02 1 Detaled Description lt ecs pss 8 ss EUR ER SUN 252 22222222422 eae X ed uos 253 5 63 1 Detailed Description scs s neas rapace ia 253 strncasecmp S File 253 8 64 1 Detailed Description 253 strncasecmp PS File Reference 22 2 2 22 2 2 253 8 65 1 Detailed Description 253 sinet Pule cu soe aoei y Os did s Rs 253 8 66 1 Detailed Description s p scs cs Sa SUR 253 strncat_PS File Relereice o u a 2 2 u s Q eq m boo 253 5 67 1 Detailed Deseripliom ue cR RR 253 simompos File Referente o suus uot oko o Ro OY Y A RO De 254 6 08 1 Detaled Description 622444885 Rx se xS 254 stracmp P S File RETefen e vocem a on UR Rs 254 8 69 1 Detailed Description lt es e a o koa sss sa 254 File Referenee 22222222225 222 5552554 254 8 70 1 Detailed Descriptio 2 254 s ncpy P S Pile Referenc uec be 22222 255 6 3L Detaled Description lt s sie seora me BASES 255 Pile Reference co eR KS ee 255 8 72 1 Detailed Description 255 strnlen P S File 22 ro o o m 255 8231 D
133. 0USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 USART2_ SIG_ USART2 Rx ATmega640 ATmegal280 ATmegal281 RX_vect USART2 Complete ATmega2560 ATmega2561 RECV USART2 SIG USART2 Tx ATmega640 ATmegal280 ATmegal28l TX vect USART2 Complete ATmega2560 ATmega2561 TRANS Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 119 Vector name Old vector Description Applicable for device name USART2_ SIG_ USART2 Data ATmega640 ATmegal280 ATmegal281 UDRE vect USART2 register Empty ATmega2560 ATmega2561 DATA USART3 SIG USART3 Rx ATmega640 ATmegal280 ATmegal281 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 ATmegal281 UDRE vect USART3 register Empty ATmega2560 ATmega2561 DATA USART SIG USART Rx ATmegal6 ATmega32 ATmega323 AT vect USART Complete mega8 RECV SIG_ UART_RECV USART_RX_ SIG_ USART Rx AT90PWM3 AT90PWM2 AT90PWMI vect USART_ Complete ATmega3250 ATmega3290 ATmega3290P SIG ATmega6450 ATmega6490 ATmega8535 UART RECV ATmegal68 ATmega48 ATmega88 AT tiny2313 USART SIG USART Tx ATmegal6 ATmega32 ATmega323 AT TXC vect USAR
134. 0e 94 7c 00 11 Oxf8 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 316 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 01 movw r30 r24 port mask 80 81 1 r24 7 Fo 86 2b or r24 r22 fe 80 83 st Z r24 100 08 95 ret Notice that we are accessing the io port via the LD and ST instructions The port parameter must be volatile to avoid a compiler warning Note Because of the nature of the IN and OUT assembly instructions they can not be used inside the function when passing the port in this way Readers interested in the details should consult the Instruction Set data sheet Finally we come to the macro version of the operation In this contrived example the macro is the most efficient method with respect to both execution speed and code size set bits macro PORTB 0 0 Lies 88 b3 in r24 0x18 24 11e 80 6f ori r24 OxF0 240 120 88 bb out 0x18 r24 24 Of course in a real application you might be doing a lot more in your function which uses a passed by reference io port address and thus the use of a function over a macro could save you some code space but still at a cost of exec
135. 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 8 34 2 Define Documentation 8 34 2 define clock prescale set x Value uint8_t tmp _BV CLKPCE __asm__ _ volatile in tmp_reg__ __SREG__ n t n t Sts 1 0 XnNEU N SES 1 2 X out SREG__ tmp_reg__ no outputs N s gd Y Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 35 setbaud h File Reference 240 M SFR MEM ADDR CLKPR qr x rO y N 8 35 setbaud h File Reference 8 35 1 Detailed Description Defines define 2 define VALUE define UBRRL VALUE define UBRRH VALUE define USE 2X 0 8 36 setjmp h File Reference 8 36 1 Detailed Description Defines define 1 define _ ATTR_NORETURN__ __attribute__ __noreturn__ Functions int setimp jmp buf __jmpb void longjmp jmp_buf __jmpb int ATTR NORETURN 8 37 sleep h File Reference 8 371 Detailed Description Defines define_AVR_SLEEP_H_ 1 define_SLEEP_CONTROL_REG MCUCR Sleep Modes Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 38 stdint h File Reference 241 Note
136. 198 6 35 3 3 Part 3 Interrupt service routines ISR to handle timer 175 overflow interrupt arranges for the software clock While timer runs the PWM it calls its overflow handler rather frequently so the TMR1_SCALE value is used as a postscaler to reduce the internal software clock frequency further If the software clock triggers it sets the tmr_int bitfield and defers all further tasks to the main loop The ADC ISR just fetches the value from the ADC conversion disables the ADC interrupt again and announces the presence of the new value in the adc_int bitfield The interrupt is kept disabled while not needed because the ADC will also be triggered by executing the SLEEP instruction in idle mode which is the default sleep mode 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 35 3 4 Part 4 Auxiliary functions The function handle mcucsr uses two attribute declarators to achieve specific goals First it will instruct the com piler to place the generated code into the init3 section of the output Thus it will be come part of the application initialization sequence This is done in order to fetch and clear the reason of the last hardware reset from MCUCSR as early as possible There is a short period of time where the next reset could already trigger before the current reason has been evaluated This also expl
137. 2 2 19 define GET EXTENDED FUSE BITS 0x0002 address to read the extended fuse bits using boot lock fuse bits get 6 12 2 20 define GET HIGH FUSE BITS 0 0003 address to read the high fuse bits using boot lock fuse bits get 6 12 2 21 define GET LOCK BITS 0 0001 address to read the lock bits using boot lock fuse bits get 6 12 2 22 define GET LOW FUSE BITS 0 0000 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 Applications that require interrupt controlled EEPROM access to ensure that no time will be wasted in spinloops will have to deploy their own implementation Note All of the read write functions first make sure the EEPROM is ready to be ac cessed Since this may cause long delays if a write operation is still pending time critical applications should first poll the EEPROM e g using eeprom is ready before attempting any actual I O Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 100 avr This header file declares inline functions that call the assembler subroutines di rectly This prevents that the compiler gen
138. 21 BLOCK 121 5 NAKED 121 ISR_NOBLOCK 122 reti 122 sei 122 SIGNAL 122 avr inttypes farptr t 31 PRId16 22 PRId32 22 PRId8 22 PRIdFAST16 22 PRIdFAST32 22 PRIdFASTS 22 PRIdLEAST16 22 PRIdLEAST32 23 PRIdLEASTS 23 PRIdPTR 23 PRIi16 23 PRIi32 23 PRIi8 23 PRIiFASTI16 23 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 366 PRHFAST32 23 PRIFASTS 23 PRILEASTI6 23 PRILEAST32 23 PRIiLEASTS 24 PRIiPTR 24 PRIo16 24 1032 24 1 8 24 PRIoFASTI6 24 PRIoFAST32 24 PRIoFASTS 24 PRIoLEASTI6 24 PRIoLEAST32 24 PRIoLEASTS 24 PRIoPTR 25 PRIu16 25 PRIu32 25 8 25 PRIuFAST16 25 PRIuFAST32 25 PRIuFASTS 25 PRIuLEASTI6 25 PRIuLEAST32 25 PRIuLEASTS 25 PRIuPTR 25 PRIX16 26 PRIx16 26 PRIX32 26 PRIx32 26 PRIX8 26 PRIx8 26 PRIXFAST16 26 PRIxFASTI6 26 PRIXFAST32 26 PRIxFAST32 26 PRIXFASTS 26 PRIxFASTS 27 PRIXLEASTIO 27 PRIxLEASTI6 27 PRIXLEAST32 27 PRIxLEAST32 27 PRIXLEASTS 27 PRIxLEASTS 27 PRIXPTR 27 PRIxPTR 27 SCNd16 27 SCNd32 27 SCNdFAST 16 28 SCNdFAST32 28 SCNdLEAST 16 28 SCNdLEAST32 28 SCNdPTR 28 SCNi16 28 SCNi32 28 SCNiFAST16 28 SCNiFAST32 28 SCNiLEAST16 28 SCNiLEAST32 28 SCNiPTR 29 SCNo16 29 SCNo32 29 SCNoFAST 16 29 SCNoFAST32 29 SCNoLEAST 16 29 SCNoLEAST32 29 SCNoPTR 29 SCNul6 29 SCNu32 29 SCNuFASTI16 29 SCNuFAST32 30 SCNuLEAST 16 30 SCNuLEAS
139. 25 t strspn P const char s 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 16 4 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 52 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 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 17 lt avr power h gt Power Reduction Management finclude lt avr power h gt Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 17 lt avr power h gt Power Reduction Management 138 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 inter
140. 258 util twi h 258 wdt h 260 5 avr libc Page Index 5 1 avr libc Related Pages Here is a list of all related documentation pages Toolchain Overview 261 Memory Areas and Using malloc 266 Memory Sections 271 Data in Program Space 275 avr libc and assembler programs 280 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 avr libc Module Documentation 15 Inline Assembler Cookbook 286 How to Build a Library 298 Porting From IAR to AVR GCC 301 Frequently Asked Questions 305 Building and Installing the GNU Tool Chain 329 Using the GNU tools 345 Using the avrdude program 355 Release Numbering and Methodology 357 Acknowledgments 360 Todo List 361 Deprecated List 361 6 avr libc Module Documentation 6 1 lt alloca h gt Allocate space in the stack 6 1 1 Detailed Description Functions void alloca size t size 6 1 2 Function Documentation 6 1 2 1 void alloca size t size Allocate size bytes of space in the stack frame of the caller This temporary space is automatically freed when the function that called alloca re turns to its caller Avr libc defines the alloca as a macro which is translated into the inlined builtin alloca function The fact that the code is inlined means that it is impossible to take the address of this function or to change its behaviour by linking with a different library Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 2 lt assert h gt
141. 2_t int_farptr_t typedef uint32_t uint_farptr_t 8 18 io h File Reference 8 18 1 Detailed Description 8 19 math h File Reference 8 19 1 Detailed Description Defines define PI 3 141592653589793238462643 define M SORT2 1 4142135623730950488016887 define builtin nan define INFINITY _ builtin inf Functions double cos double x ATTR CONST double fabs double _ x CONST double fmod double _ x double CONST double modf double __ value double double sin double x CONST double sqrt double _ x _ ATTR CONST double tan double x ATTR_CONST double floor double __x _ ATTR_CONST double ceil double x ATTR CONST double frexp double __ value int exp double ldexp double _ int exp CONST double exp double _ x ATTR CONST Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 20 memccpy S File Reference 229 double cosh double x ATTR CONST double sinh double x ATTR CONST double tanh double x ATTR CONST double acos double x ATTR CONST double asin double x ATTR CONST double atan double x ATTR CONST double atan2 double y double x CONST double log double _ x CONST double log10 double _ x ATTR CONST double pow double x double __y ATTR CONST int isnan double x ATTR CONST int double ATTR CONST double square d
142. 2e de bf out 0 3 r29 62 30 cd bf out 0x3d r28 61 00000032 copy data 32 10 eO ldi ri7 0x00 0 34 a0 e6 ldi r26 0x60 96 36 0 eO x27 0x00 0 38 e4 el 141 r30 0x14 20 fl eO 141 r31 0 01 1 36s 02 60 rjmp 4 0x42 do copy data start 0000003e do copy loop 3e 05 90 lpm r0 Z 40 Od 92 st X ro 00000042 lt do_copy_data_start gt 42 a0 36 cpi r26 0x60 96 44 bl 07 Gp 27 17 46 9 7 brne 10 Ox3e lt 5 gt 00000048 lt __do_clear_bss gt 48 10 e0 riz 0x00 0 4a a0 e6 ldi r26 0x60 96 4c bo eO ldi r27 0x00 0 4e 01 cO rjmp 2 0x52 do clear bss start 00000050 do clear bss loop 503 Td 92 st Xt 00000052 do clear bss start 52 a3 36 cpi r26 0x63 99 54 bl 07 EDE S27 17 56 el f7 brne 8 0x50 do clear bss loop 58 4d d0 rcall 154 Oxf4 main 5 0 rjmp 180 Ox110 exit 0000005 vector 8 include iocompat h Note 1 enum UP DOWN ISR TIMER1 OVF x Note 2 x Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 50 2 92 push rl Of 92 push r0 60 Of b6 in 0 0x3f 5 63 62 Of 92 push r0 64 11 24 eor rl rl 66 2f 93 push r18 68 3f 93 push r19 8f 93 push r24 static uintl6_t pwm Note 3 static uint8_t direction switch direction
143. 4 vect START WATCHDOG_ SIG_ Watchdog Time ATtiny24 ATtiny44 ATtiny84 vect WATCHDOG_ TIMEOUT WDT_ SIG_ Watchdog Timer ATtiny2313 OVERFLOW_ WATCHDOG_ Overflow vect TIMEOUT SIG_WDT_ OVERFLOW WDT_vect SIG_WDT Watchdog Time AT90PWM3 AT90PWM2 AT90PWMI SIG_ out Interrupt ATmega406 ATmegal68 ATmega48 WATCHDOG_ ATmega88 ATmega640 ATmegal280 TIMEOUT ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtinyl3 45 AT tiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 AT90USBI62 9005 82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 121 6 14 2 Define Documentation 6 14 2 1 define BADISR vect include avr interrupt h This is a vector which is aliased to _ vector default the vector
144. 4 lt avr interrupt h gt Interrupts 109 Vector name Old name vector Description Applicable for device INT6_vect SIG_ INTERRUPT6 External Interrupt Request 6 AT90CAN128 AT90CAN32 ATIOCAN64 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmega1280 ATmegal 281 ATmega2560 AT mega2561 AT90USBI62 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 ATmegal 281 ATmega2560 AT mega2561 AT90USBI62 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 IO PINS vect SIG PIN SIG PIN CHANGE External Interrupt Request 0 ATtinyll ATtiny12 ATtiny15 ATtiny26 LCD vect SIG LCD LCD Stat of Frame ATmegal69 ATmegal69P ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega649 ATmega6490 LOWLEVEL_ IO PINS vect SIG PIN Low level Input on Port B ATtiny28 OVRIT vect SIG CAN OVERFLOWI CAN Overrun Timer 90 128 AT90CAN32 AT90CAN64 PCINTO vect SIG PIN CHANGEO Pin Change Inter rupt Request 0 ATmegal62 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega406 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmeg
145. 46 uint32_t avr_stdint 49 UINT64_C avr_stdint 46 UINT64_MAX avr_stdint 46 uint64_t avr_stdint 49 UINT8_C avr_stdint 46 UINT8_MAX avr_stdint 47 uint8_t avr_stdint 50 uint_farptr_t avr_inttypes 31 UINT_FAST16_MAX avr_stdint 47 uint_fast16_t avr_stdint 50 UINT_FAST32_MAX avr_stdint 47 uint_fast32_t avr_stdint 50 UINT_FAST64_MAX avr_stdint 47 uint_fast64_t avr_stdint 50 UINT_FAST8_MAX avr_stdint 47 uint_fast8_t avr_stdint 50 UINT_LEAST16_MAX avr_stdint 47 uint_least16_t avr_stdint 50 UINT_LEAST32_MAX avr_stdint 47 uint_least32_t avr_stdint 50 UINT_LEAST64_MAX avr_stdint 47 uint_least64_t avr_stdint 50 UINT_LEAST8_MAX avr_stdint 47 uint_least8_t avr_stdint 50 UINTMAX_C avr_stdint 47 UINTMAX_MAX avr_stdint 47 uintmax_t avr_stdint 51 UINTPTR_MAX avr_stdint 48 uintptr_t avr_stdint 51 ultoa avr_stdlib 79 ungetc avr_stdio 63 USE_2X util_setbaud 163 Using the standard IO facilities 199 util_atomic ATOMIC_BLOCK 153 ATOMIC_FORCEON 153 ATOMIC_RESTORESTATE 154 NONATOMIC_BLOCK 154 NONATOMIC_FORCEOFF 154 NONATOMIC_RESTORESTATE 154 util_crc _crc16_update 156 _crc_ccitt_update 156 _crc_ibutton_update 157 _crc_xmodem_update 157 util_delay _delay_ms 159 _delay_us 159 util_delay_basic _delay_loop_1 160 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 384 _delay_loop_2 160 util_parity parity_even_bit 161 ut
146. 6 lt lt 8 for i20 i 8 i XR ere cro else ere return crc amp 0 8000 cre lt lt 1 0x1021 lt lt 1 6 25 lt util delay h gt Convenience functions for busy wait delay loops 6 25 1 Detailed Description define F CPU 1000000UL 1 MHz define F CPU 14 7456E6 include util delay h Note As an alternative method it is possible to pass the F CPU macro down to the com piler from the Makefile Obviously in that case no define statement should be used The functions in this header file 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 in
147. 6 AT90USB 1287 AT90PWM 1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 ATmega165 ATmega165P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmega169 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 ATmega169P ATmega329 ATmega3290 ATmega649 ATmega6490 power_lcd_disable Disable the LCD module ATmegal69 ATmega169P ATmega329 ATmega3290 ATmega649 ATmega6490 power pscO enable Enable the Power Stage Controller 0 module AT90PWMI AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B 20 02 34 20 7 Ris ablelihe RoVerygtage 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 18 Additional notes from lt avr sfr_defs h gt 140 Some of the newer AVRSs 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 en
148. 6 lt math h gt Mathematics 34 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 33 double atan double x The atan function computes the principal value of the arc tangent of x The returned value is in the range 0 pi radians A domain error occurs for arguments not in the range 1 1 6 6 3 4 double atan2 double __y double The atan2 function computes the principal value of the arc tangent of 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 ceil double x The ceil function returns the smallest integral value greater than or equal to x ex pressed as a floating point number 6 6 3 6 ATTR CONST double copysign double x double y The copysign function returns x but with the sign of y They work even if x or 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 f
149. 64_t 64 bit unsigned type Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 51 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 6 8 3 22 typedef uint8_t uint_fast8_t fastest unsigned int with at least 8 bits 6 8 3 23 typedef uint16_t uint_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 is not available when the compiler option mint8 is in effect Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 52 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 Descripti
150. 7 CanluseCi on the AVR 309 9 9 8 Shouldn t I initialize all my variables 310 9 9 9 Why do some 16 bit timer registers sometimes get trashed 311 9 9 10 How do I use a define d constant in an asm statement 312 9 9 11 Why does the PC randomly jump around when single stepping through my program in 312 9 9 12 How do I trace an assembler file in avr gdb 313 9 9 13 How do I pass an IO port as a parameter to a function 314 9 9 14 What registers are used by C compiler 317 9 9 15 How do I put an array of strings completely in ROM 318 9 9 16 How to use external 320 9917 Which Oflagtouse 321 9 9 18 How do I relocate code to a fixed address 321 9 9 19 UART is generating nonsense ATmegal28 keeps crashing Port F is completely broken 322 9 9 20 Why do all my foo bar strings eat up the SRAM 322 9 9 21 Why does the compiler compile an 8 bit operation that uses bitwise operators into 16 bit operation in assembly 323 9 9 22 How to detect RAM memory and variable overlap problems 324 9 9 23 Is it really impossible to program the ATtinyXX in C 324 9 9 24 What is this clock skew detected messsage 325 9 9 25 Why are many interrupt flags cleared by writing alogical 1 325 9 9 26 Why have programmed fuses the bit value 0 326 9 9
151. 7 for avr libc by Doxygen 69 lt stdio h gt Standard IO facilities 65 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 0 u i x and X the 0 flag is ignored 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 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 An optional precision in the form of a period followed by an optional digit string If the digit string is omitted the precision is taken as zero This gives the minimum number of digits to appear for d i o u x and X conversions or the maximum number of characters to be printed from a string for s conversions An optional 1 or h length modifier that specifies that the argument for the d i u or X conversion
152. 710E0A0E6BOEO01C0OEC 00050001D92A336B107E1F74DD05AC01F920F92FF 00060000FB60F9211242F933F938F9380916000CE 0007000882379F420916100309162002F5F3F4F17 0008000309362002093610083E02F3F3807D9F45A 1000900017C0813029F0209161003091620013C0B7 1000A0002091610030916200215030403093620015 000 000209361002115310531 41092600003 006 000C00081E0809360003BBD2ABD8F913F912F91CD 000D0000F900FBE0F901F90189583E88FBD8EB5BF 000E00081608EBD1BBC1ABC82E087BB84E089BFE7 000F00078940895CFE5DA4EODEBFCDBFEEDF85B7BD 10010000806885BF889585B78F7785BFF8CF78CF12 0401100000COFFCF5D 00000001FF The 1 option indicates that we want the information from the text and data segment extracted If we specify the EEPROM segment we can generate a hex file that can be used to program the EEPROM avr objcopy j eeprom change section lma eeprom 0 O ihex demo elf demo eeprom hex There is no demo eeprom hex file written as that file would be empty Starting with version 2 17 of the GNU binutils the avr ob jcopy command that used to generate the empty EEPROM files now aborts because of the empty input section eeprom so these empty files are not generated It also signals an error to the Makefile which will be caught there and makes it print a message about the empty file not being generated Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 190 6 34 7 Letting Make Build the Project Rather than type these command
153. 8 tolower ctype 18 tools optional 329 tools required 329 toupper ctype 18 trunc avr_math 36 TW_BUS_ERROR util_twi 165 TW_MR_ARB_LOST util_twi 165 TW_MR_DATA_ACK util_twi 165 TW_MR_DATA_NACK util_twi 165 TW_MR_SLA_ACK util_twi 165 TW_MR_SLA_NACK util_twi 165 TW_MT_ARB_LOST util_twi 165 TW_MT_DATA_ACK util_twi 165 TW_MT_DATA_NACK util_twi 165 TW_MT_SLA_ACK util_twi 165 TW_MT_SLA_NACK util_twi 165 TW_NO_INFO util_twi 165 TW_READ util_twi 166 TW_REP_START util_twi 166 TW_SR_ARB_LOST_GCALL_ACK util_twi 166 TW SR ARB LOST SLA ACK util twi 166 SR DATA ACK util twi 166 TW SR NACK util twi 166 TW SR GCALL util twi 166 TW SR GCALL DATA ACK util twi 166 TW SR GCALL NACK util twi 166 TW SR SLA ACK util twi 166 TW SR STOP util twi 166 TW ST LOST SLA ACK util twi 167 TW ST DATA ACK util twi 167 TW ST DATA NACK util twi 167 TW ST LAST DATA util twi 167 TW ST SLA ACK util twi 167 TW START util twi 167 TW STATUS util twi 167 TW STATUS MASK util twi 167 TW WRITE util twi 167 twi h 257 UBRR VALUE util setbaud 163 UBRRH VALUE util setbaud 163 UBRRL VALUE util setbaud 163 UINTI16 C Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 383 avr_stdint 46 UINT16_MAX avr_stdint 46 uintl6_t avr_stdint 49 UINT32_C avr_stdint 46 UINT32_MAX avr_stdint
154. 8 5 boot h File Reference 216 define GET_HIGH_FUSE_BITS 0x0003 define boot_lock_fuse_bits_get 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 8 5 2 Define Documentation 8 5 2 1 define boot lock bits set lock bits Value 4 uint8_t value uint8_t lock_bits __asm__ __volatile__ idi 30 T n t 31 O n t mov r0 2 n t sts 0 1 n t spm n t i SFR MEM ADDR SPM REG r int8 t BOOT LOCK BITS SET r value EST r31 8 5 2 2 define boot lock bits set alternate lock bits Value uint8_t value uint8_t lock bits __asm__ __volatile__ Idi r30 1 n t r31 O n t mov r0 2 n t sts 0 1 n t POLO ut GOGO uu GO PE uw Pdl a m d 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 5 boot h File Reference 217 spm n t word Oxffff n t nop n t i SFR
155. 9 9 1 1 Ts 1O RESET 18 20K S 2 2 8 MOSI PB5 17 LED EK H XTAL2 16 R2 D1 18 OCT PB3 15 LI b XTAL1 PB2 14 See note 8 Na id 18pf 20 AIN1 PB1 13 AINO PBO 12 TE IcP PD6 HH T1 PDS 2 M 8 INT1 PD3 GND INTO PD2 6 TxD PD1 3 RxD PDO 2 AT90S2313P Figure 1 Schematic of circuit for demo project The source code is given in demo c For the sake of this example create a file called 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 IA 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
156. 9005 1287 AT90USB1286 AT90USB647 AT90USB646 INT2_vect SIG_ INTERRUPT2 External Interrupt Request 2 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 16 ATmegal61 ATmegal62 ATmega32 ATmega323 ATmega406 ATmega64 ATmega8515 ATmega8535 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 INT3_vect SIG_ INTERRUPT3 External Interrupt Request 3 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmega406 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USBI62 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 INT4_vect SIG_ INTERRUPT4 External Interrupt Request 4 AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmega1280 ATmegal 281 ATmega2560 AT mega2561 AT90USBI62 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 INT5_vect SIG_ INTERRUPTS External Interrupt Request 5 AT90CANI28 AT90CAN32 AT90CANGA4 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmega1280 ATmegal 281 ATmega2560 AT mega2561 AT90USB162 9005 82 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 1
157. AM 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 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 taken to avoid a stack heap collision both by making sure functions aren t nesting too deeply and don t require too much stack space for local variables as well as by being cautious with allocating too much dynamic memory If external RAM is available it is strongly recommended to move the heap into the ex ternal RAM regardless of whether or not the variables from the data and bss sections are also going to be located there The stack should always be kept in internal RAM Some devices even require this and in general internal RAM can be accessed faster since no extra wait states are required When using dynamic memory allocation and stack and heap are separated in dist
158. BLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR ONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF UBSTITUTE GOODS OR SERVICES LOSS OF USE NTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN ONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE DATA OR PROFITS OR BUSINESS Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 2 avr libc Module Index 2 avr libc Module Index 2 1 avr libc Modules 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 lt avr boot h gt Bootloader Support Utilities lt avr eeprom h gt EEPROM handling lt avr interrupt h gt Interrupts lt avr io h gt AVR device specific IO definitions lt avr pgmspace h gt Program Space Utilities lt avr power h gt Power Reduction Management lt avr sfr_defs h gt Special function registers Additional notes from lt avr sfr_defs h gt lt avr sleep h gt Power Management and Sleep Modes lt avr version h gt avr libc version
159. 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 Len bytes of 52 6 16 4 3 void memcpy_P void dest PGM_VOID_P src size_t n memcpy_PQ function is similar to memcpy except the src string resides in pro gram space Returns The memcpy_P function returns a pointer to dest 6 16 4 4 void x memmem P const void 51 size t len PGM_VOID_P s2 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pemspace h gt Program Space Utilities 132 6 16 4 5 PGM_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 16 4 6 int strcasecmp P const char s1 P 52 Compare two strings ignoring case T
160. 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 conversion These conversions will be available in the ex tended version provided by the library 1ibscanf flt a Note that these conver sions require a 40 byte conversion buffer so the extended version requires more stack space than the basic version irrespective of whether the actual call in progress actu ally uses this buffer or not To link a program against the extended version use the following compiler flags in the link stage Wl u vfscanf lscanf flt lm A third version is available for environments that are tight on space 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 In addition to the restrictions of the standard version this version implements no field width specification no conversion assignment suppression flag no n specification and no general format character matching at all All characters in mt that do not Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 70 comprise a conversion specification will
161. File Reference 8 25 1 Detailed Description Defines define dest hi r25 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 26 memcpy PS File Reference 231 define dest_lo r24 define src r23 define src lo r22 define len hi r21 define len lo r20 8 26 memcpy PS File Reference 8 26 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 define len hi r21 define len lo r20 8 27 memmem S File Reference 8 27 1 Detailed Description 828 memmove S File Reference 8 28 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 define len hi r21 define len lo r20 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 29 memrchr S File Reference 232 8 29 memrchr S File Reference 8 29 1 Detailed Description 8 30 memrchr_P S File Reference 8 30 1 Detailed Description 8 34 memset S File Reference 8 31 4 Detailed Description Defines define dest hi r25 define dest lo r24 define val lo r22 define len hi r21 define len lo r20 8 32 parity h File Reference 8 32 1 Detailed Description Defines define parity even bit val 8 33 pgmspace h File Reference 8 33 1 Detailed Description Defines define _ PGMSPACE H 1 define need size t define ATTR CONST attribute
162. Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 24 lt util crc16 h gt CRC Computations 158 uint16_t crc ccitt update uintl16 t crc uint8_t data data 108 crc data data lt lt 4 return uint16 lt lt 8 hi8 crc uint8_t data gt gt 4 uint16 t data 3 6 24 2 3 static inline uint8 t crc ibutton update uint8 t crc uint8 t _data static Optimized Dallas now Maxim iButton 8 bit CRC calculation Polynomial x 8 x 5 x 4 1 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 uint8 t data uint8_t i cre crc data for i 0 i lt 8 itt if cre amp 0x01 crc crc gt gt 1 0x8C else cre gt gt 1 return crc 6 24 2 4 static _ inline uint16_t _crc_xmodem_update uint16_t _ crc uint8 t data static Optimized CRC XMODEM calculation Polynomial x 16 x 12 x 5 1 0x1021 Initial value 0 0 This is the CRC used by the Xmodem CRC protocol The following is the equivalent functionality written in C Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 25 lt util delay h gt Convenience functions for busy wait delay loops 159 uintl6_t crc_xmodem_update uintl6_t crc uint8_t data int i A uintl1
163. IO facilities 61 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 stream This flag can only be cleared by call to clearerr 6 9 3 6 int fflush FILE x stream Flush stream This is a null operation provided for source code compatibility only as the standard IO implementation currently does not perform any buffering 6 9 37 int fgetc FILE x __ stream The function fgetc 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 char fgets char __str int __size FILE stream 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 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 9 int fprintf FILE x __ stream const char fmt The function fprintf performs formatted output to stream See vfprintf for details 6 9 3 10 int fprintf_P FILE stream const char fmt Variant of fprintf that uses a fmt st
164. Id32 1 define PRIGLEAST32 define PRIGFAST32 Id define PRIi32 li define PRIILEAST32 li define PRIiFAST32 li define PRIdPTR PRId16 define PRUPTR 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 22 define PRIu16 u define PRIULEAST16 u define PRIUFAST16 u define PRIx16 x define PRIXLEASTI16 x define PRIXFAST16 x define PRIX16 X define PRIXLEAST16 X define PRIXFAST16 X define PRIo32 lo define PRIOLEAST32 lo define PRIoFAST32 lo define PRIu32 lu define PRIULEAST32 lu define PRIuFAST32 lu define PRIx32 Ix define PRIXLEAST32 Ix define PRIXFAST32 Ix define PRIX32 IX define PRIXLEAST32 IX define PRIXFAST32 IX define PRIoPTR PRIo16 define PRIUPTR PRIul6 define PRIxPTR PRIx16 define PRIXPTR PRIX16 define SCNd16 d define SCNdLEAST16 d define SCNdFAST16 d define SCNi16 1 define SCNiLEAST16 i define SCNIFASTI6 i define SCNd32 Id define SCNdLEAST32 Id define SCNdFAST32 define SCNi32 li define SCNiLEAST32 li
165. LCD followed by three dots in one second spacing followed by a sequence that will clear the LCD Finally main Will be terminated and the library will add an infinite loop so only a CPU reset will be able to restart the application There are three commands recognized each determined by the first letter of the line entered converted to lower case The q quit command has the same effect of leaving the main loop The LCD command takes its second argument and sends it to the LCD The u UART command takes its second argument and sends it back to the UART connection Command recognition is done using sscanf where the first format in the format string just skips over the command itself as the assignment suppression modifier is given 6 36 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 36 Using the standard IO facilities 204 The remaining macros customize the IO port and pins used for the HD44780 LCD driver 6 36 3 3 hd44780 h This file describes the public interface of the low level LCD driver that interfaces to the HD44780 LCD controller Pub
166. LE 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 define FDEV ERR 1 define _FDEV_EOF 2 define FDEV_SETUP_STREAM put get rwflag define fdev_close define putc c stream fputc __c ___ define putchar __c fputc __c stdout define getc __stream fgetc __stream define getchar fgetc stdin stream Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 56 Functions int fclose FILE stream int vfprintf FILE _ stream const char fmt va_list int vfprintf P FILE stream const char fmt va_list __ap intfputc int __c FILE stream int printf const char fmt int printf P const char fmt int vprintf const char fmt va list ap int sprintf char s constchar fmt int sprintf P char __s const char x__fmt int snprintf char __s size_t __n const char __fmt 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 vsn
167. LLOC 2 stab 000007d4 00000000 00000000 00000188 2xx2 CONTENTS READONLY DEBUGGING 3 stabstr 000006ef 00000000 00000000 0000095 2 0 CONTENTS READONLY DEBUGGING Disassembly of section text 00000000 lt __vectors gt 22700 rjmp 36 0 26 lt __ctors_end gt 2 85 0 rjmp 266 Oxl0e lt __bad_interrupt gt 4 84 cO rjmp 264 0x10e lt __bad_interrupt gt 6 83 0 rjmp 262 Oxl0e lt __bad_interrupt gt 82 60 rjmp 260 Oxl0e lt __bad_interrupt gt 81 cO rjmp 258 Oxl0e bad interrupt c 80 0 rjmp 256 Oxl0e bad interrupt e 7f cO rjmp 254 Oxl0e bad interrupt 10 25 c0 rjmp 74 Ox5c vector 8 12 rjmp 250 0 10 lt __bad_interrupt gt Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 183 14 7 0 rjmp 248 0 0 lt __bad_interrupt gt 16 60 rjmp 246 0 10 lt __bad_interrupt gt 18 7a rjmp 244 0 10 lt __bad_interrupt gt lar 79 cU rjmp 242 0 10 bad interrupt lor 78 60 rjmp 240 0 10 bad interrupt le 77 0 rjmp 238 0 10 bad interrupt 20 76 cO rjmp 236 Oxl0e bad interrupt 22 TI OO rjmp 234 0 10 bad interrupt 24 74 cO rjmp 232 0 10 bad interrupt 00000026 ctors end 26 11 24 eor rl rl 28 1f be out 0x3f rl 63 2a cf e5 ldi r28 O0x5F 95 2c 4 eO ldi r29 0x04 4
168. MEM ADDR SPM REG N r uint8 t BOOT LOCK BITS SET x r value NEON TESIT X 8 5 2 3 define __boot_page_erase_alternate address Value __asm__ __volatile__ movw r30 2 n t sts 0 Sl An t spm n t word Oxffff n t nop n t i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE ERASE uint16_t address TESIS u PP A UEA u BO IAE 8 5 2 4 define __boot_page_erase_extended address Value __asm__ __volatile__ movw r30 A3 n t sts 1 C3 n 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 m uint32 t address 230 BA GO Vut Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 5 boot h File Reference 218 8 5 2 5 define _ boot_page erase normal address Value __asm__ __volatile__ movw r30 2 n t sts 0 1 n t spm n t SFR_MEM_ADDR __SPM_REG E uint8 t BOOT_PAGE_ERASE r uint16_t address 30 ya 8 5 2 6 define boot page fill alternate address data Value asm volatile movw r0 3 n t movw r30 2 n t sts 0 S INXNnNE spm n t word Oxffff n t nop n t Nele ZINE su 1 SFR_MEM_ADDR SPM_REG uint8_t BOOT_PAGE_FILL uint16 t address uint16_t data yo r30 r31
169. N 0x01 Bit value that can be passed in flags to dtostre Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 73 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 flags 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 typedefint compar fn t const void const void Comparision function type for qsort just for convenience 6 10 4 Function Documentation 6 10 4 1 inline void abort void The abort function causes abnormal program termination to occur In the limited AVR environment execution is effectively halted by entering an infinite loop 6 10 4 2 int abs int _ p 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 NULL Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 74 6 10 4 4 int atoi const char x s Co
170. NDBY avr_sleep 145 SLEEP_MODE_IDLE avr_sleep 145 SLEEP_MODE_PWR_DOWN avr_sleep 145 SLEEP_MODE_PWR_SAVE avr_sleep 145 SLEEP_MODE_STANDBY avr_sleep 145 snprintf avr_stdio 62 snprintf_P avr_stdio 62 sprintf avr_stdio 62 sprintf_P avr_stdio 62 sqrt avr_math 36 square avr_math 36 srand avr_stdlib 78 srandom avr_stdlib 78 sscanf avr_stdio 62 sscanf_P avr_stdio 63 stderr avr_stdio 58 stdin avr_stdio 58 stdint h 240 stdio h 243 stdlib h 245 stdout avr_stdio 58 strcasecmp avr_string 85 strcasecmp S 247 strcasecmp_P avr_pgmspace 131 strcasecmp_P S 247 strcasestr avr_string 85 strcasestr S 247 strcasestr_P avr_pgmspace 131 strcat avr_string 86 strcat S 247 strcat_P avr_pgmspace 131 strcat_P S 248 strchr avr_string 86 strchr S 248 strchr_P avr_pgmspace 131 strchr_P S 248 strchrnul avr_string 86 strchrnul S 248 strchrnul_P avr_pgmspace 132 strchrnul P S 248 strcmp avr_string 86 strcmp S 248 strcmp P avr pgmspace 132 strcmp P S 248 strcpy avr string 87 strcpy S 248 strcpy P avr pgmspace 132 strepy_P S 249 strcspn avr string 87 strcspn S 249 strcspn P avr pgmspace 132 strespn_P S 249 string h 249 strlcat avr string 87 strlcat S 251 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 381 strlcat_P avr_pgmspace 133 strlcat_ P S 251 strlcpy avr_string 88 strlcpy S 251 strlcp
171. Numerical representation of the release date 6 21 2 2 define AVR DATE STRING AVR LIBC RELDATE String literal representation of the release date 6 21 2 3 define LIBC MAJOR _ AVR_LIBC_MAJOR Library major version number 6 21 2 4 define AVR MINOR QGAVR LIBC MINORG Library minor version number 6 21 2 5 define REVISION AVR_LIBC_REVISION Library revision number 6 21 2 6 define __ LIBC VERSION GAVR LIBC VERSION NUMERIC UL 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 22 lt avr wdt h gt Watchdog timer handling 149 6 21 2 7 define __ AVR VERSION STRING GAVR VERSION String literal representation of the current library version 6 222 lt avr wdt h gt Watchdog timer handling 6 22 1 Detailed Description include lt avr wdt h gt This header file declares the interface to some inline macros handling the watchdog timer present in many AVR devices In order to prevent the watchdog timer configura tion from being accidentally altered by a crashing application a special timed sequence is requir
172. O facilities 200 6 336 Using the standard IO facilities This project illustrates how to use the standard IO facilities stdio provided by this library It assumes a basic knowledge of how the stdio subsystem is used in standard C applications and concentrates on the differences in this library s implementation that mainly result from the differences of the microcontroller environment compared to a hosted environment of a standard computer This demo is meant to supplement the documentation not to replace it 6 36 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 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 AO 1 LCD D4 Al 2 LCD D5 A2 3 LCD D6 A3 4 LCD D7 A4 5 LCD R W A5 6 LCDE A6 7 LCD RS A7 8 unused GND 9 GND VCC 10 Vcc Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 336 Using the standard IO facilities 201 Figure 5 Wiring
173. PB_vect OUTPUT_ Compare Match ATtiny25 ATtiny85 COMPAREIB B TIMI OVF SIG Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 vect OVERFLOWI Overflow ATtiny25 ATtiny85 TIMERO SIG INPUT ADC Conversion ATtiny261 ATtiny461 ATtiny861 CAPT vect CAPTUREO Complete TIMERO SIG TimerCounter0 ATmegal68 ATmega48 ATmega88 COMPA_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal281 COMPAREOA A ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 ATtiny261 ATtiny461 AT tiny861 ATOOUSBI62 9005 82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMERO SIG Timer Counter 0 AT90PWM3 AT90PWM2 AT90PWMI COMPB vect OUTPUT Compare Match ATmegal68 ATmega48 ATmega88 AT COMPAREOB B mega640 ATmegal280 ATmegal281 SIG ATmega2560 ATmega2561 ATmega324P OUTPUT ATmegal64P ATmega644P ATmega644 COMPAREO ATtiny2313 ATtiny261 ATtiny461 AT B tiny861 AT90USB162 9005 82 9005 1287 AT90USB 1286 9005 647 9005 646 Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 112 Vector name Old vector Description Applicable for device name 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 AT90CANGA
174. PESO Vests _ result 8 33 2 5 define ELPM word enhanced Value __extension__ uint32_t __addr32 uint32_t addr uint16_t __result asm N N out 2 C1 WAYNE M movw r30 1 n t elpm AO Z n t elpm BO Z n t r result r addre32 N I SFR IO ADDR RAMPZ N 0 r3 N result 8 33 2 6 define__LPM_classic__ addr Value Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 33 pgmspace h File Reference 237 extension_ uintl6 t _ addr16 uintl6 t addr uint8 t _ result asm Ipm n t mov 0 n t r result TZ 244416 Typ result rr rr rr ree 8 33 27 define _ LPM_dword_classic__ addr Value __extension__ V uintl6 t __addr16 uintl6 t addr N uint32 t _ result N asm N N lpm mov 0 ro X adiw r30 1 X lpm VANNES mov B0 ro TO NLY adiw r30 1 lpm n t mov CO ro N adiw r30 1 mn lpm n t N mov D0 ro r result z _ addr16 N 1 __addr16 yn N _ result 8 33 2 8 define _ LPM_dword_enhanced_ Value __extension__ uintl6 t _ addrl6 uint16_t addr uint32 t result N asm N N lpm SAO Z n t lpm BO Z n t
175. PM uint32 t address long Read a byte from the program space with a 32 bit far address Note The address is a byte address The address is in the program space Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pgmspace h gt Program Space Utilities 128 6 16 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 address The address is in the program space 6 16 2 5 define pgm read dword address short pgm read dword near address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 16 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 16 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 6 16 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
176. PTR PRIx16 hexadecimal printf format for uintptr t 6 5 2 61 define SCNd16 d decimal scanf format for int16 t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 29 6 5 2 62 define SCNd32 decimal scanf format for int32_t 6 5 2 63 define SCNdFAST16 decimal scanf format for int_fast16_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 decimal scanf format for int least32 t 6 5 2 67 ftdefine SCNdPTR SCNd16 decimal scanf format for intptr t 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 SCNiIFAST16 i generic integer scanf format for int_fast16_t 6 5 2 71 define SCNiIFAST32 li generic integer scanf format for int_fast32_t 6 5 2 72 define SCNILEASTIG i generic integer scanf format for int_least16_t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 30 6 5 2 73 define SCNILEAST32 li generic Integer scanf format for int_least32_t 6 5 2 74 ftdefine 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
177. RGET attiny84 MCU_TARGET attiny85 MCU_TARGET attiny861 OPTIMIZE 02 DEFS LIBS You should not have to change anything below here avr gcc Override is only needed by avr lib build system override CFLAGS g Wall OPTIMIZE mmcu MCU_TARGET DEFS override LDFLAGS Wl Map PRG map OBJCOPY avr objcopy OBJDUMP avr objdump all PRG elf lst text eeprom S PRG elf 5 OBJ 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 S PRG lst lst elf S OBJDUMP h S lt gt Rules for building the text rom images text hex bin srec hex bin PRG bin srec hex elf j text j data O ihex lt 560 srec elf j text j data O srec lt 6 oe bin elf j text j data O binary lt 50 Rules for building the eeprom rom images eeprom ehex ebin esrec Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 35 more sophisticated project 192 ehex PRG _eeprom hex S PRG _eeprom bin PRG _eeprom srec eeprom hex elf 5 OBJCOPY _eeprom ur OBJCOPY eeprom bin elf ur OBJCOPY j echo empty 8 not ge
178. T Complete mega8 TRANS SIG_UART_ TRANS USART_TX_ SIG_ USART Tx AT90PWM3 AT90PWM2 AT90PWMI vect USART_ Complete ATmega8535 ATmegal68 ATmega48 TRANS mega88 ATtiny2313 SIG_UART_ TRANS USART_ SIG_ USART Data AT90PWM3 AT90PWM2 AT90PWMI UDRE_vect USART_ Register Empty ATmegal6 ATmega32 ATmega323 AT DATA SIG_ mega3250 ATmega3290 ATmega3290P UART_DATA ATmega6450 ATmega6490 ATmega8 AT mega8535 ATmegal68 ATmega48 AT mega88 ATtiny2313 USL SIG_USI_ USI Overflow ATmegal65 ATmegal65P ATmegal69 OVERFLOW_ OVERFLOW ATmegal69P ATmega325 ATmega3250 vect ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega645 ATmega6450 ATmega649 ATmega6490 ATtiny2313 USI_OVF_ SIG_USI_ USI Overflow ATtiny26 ATtiny24 ATtiny44 ATtiny84 vect OVERFLOW ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 USI_START_ SIG_USI_ USI Start Condi ATmegal65 ATmegal65P ATmegal69 vect START tion ATmegal69P ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega645 ATmega6450 ATmega649 ATmega6490 ATtiny2313 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 USI STRT_ SIG_USI_ USI Start ATtiny26 vect START Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 120 Vector name Old vector Description Applicable for device name USI_STR_ SIG_USI_ USI START ATtiny24 ATtiny44 ATtiny8
179. T32 30 SCNuPTR 30 SCNx16 30 SCNx32 30 SCNxFASTI16 30 SCNxFAST32 30 SCNxLEASTI16 30 SCNxLEAST32 30 SCNxPTR 30 uint farptr t 31 avr math acos 33 asin 33 atan 33 atan2 33 ceil 33 copysign 33 cos 33 cosh 33 exp 33 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 367 fabs 34 fdim 34 floor 34 fma 34 fmax 34 fmin 34 fmod 34 frexp 34 hypot 34 INFINITY 32 isfinite 35 isinf 35 isnan 35 Idexp 35 log 35 log10 35 M_PI 32 5 2 32 modf 35 32 pow 36 signbit 36 sin 36 sinh 36 sqrt 36 square 36 36 tanh 36 trunc 36 avr_pgmspace memchr_P 130 memcmp_P 130 memcpy_P 130 memmem_P 130 memrchr_P 130 PGM_P 126 pgm_read_byte 126 pgm_read_byte_far 126 pgm_read_byte_near 126 pgm_read_dword 127 pgm_read_dword_far 127 pgm_read_dword_near 127 pgm_read_word 127 pgm_read_word_far 127 pgm_read_word_near 128 PGM_VOID_P 128 prog_char 128 prog_int16_t 128 prog_int32_t 128 prog 11164 t 128 prog_int8_t 129 prog_uchar 129 prog uintl6 t 129 prog uint32 t 129 prog uint64 t 129 prog uint8 t 129 prog void 129 PROGMEM 128 PSTR 128 strcasecmp P 131 strcasestr P 131 strcat P 131 strchr P 131 strchrnul P 132 strcmp P 132 strcpy P 132 strcspn P 132 stricat_P 133 P 133 strlen P 133 strncasecmp_P 133 strncat P 134 strncmp P 134 strncpy P 134 strnlen P 135 str
180. TMAX 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 INTI6 MAX define PTRDIFF MIN INT16 MIN define SIG ATOMIC MAX INT8 MAX define SIG ATOMIC MIN INT8 MIN define SIZE MAX CONCAT INT16 MAX U Macros for integer constants C implementations should define these macros only when _ STDC CONSTANT MACROS is defined before lt stdint h gt is included These definitions are valid for integer constants without suffix and for macros defined as integer constant without suffix define INT8_C value int8 t value define UINT8 C value uint8 0 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 define INTMAX_C value _ CONCAT value LL define UINTMAX_C value _ CONCAT value ULL Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 44 6 8 2 Define Documentation 6 8 2 1 INT16_C value value define constant of type int16_t 6 8 2 2 fidefine INT16_MAX 0x7fff largest positive value an int16_t
181. TTR PURE char strrchr const char x int PURE char strrev char char strsep char const char size t strspn const char s const char xaccept ATTR PURE char strstr const char const char x ATTR PURE char strtok_r char const char char char strupr char Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 57 strlcat S File Reference 252 8 57 8 57 1 8 58 8 58 1 8 59 8 59 1 8 60 8 60 1 8 61 8 61 1 Defines 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 define src_hi r25 define src_lo r24 8 62 8 62 1 Defines strlen_P S File Reference Detailed Description define src hi r25 define src_lo r24 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 63 strlwr S File Reference 253 8 63 strlwr S File Reference 8 63 1 Detailed Description 8 64 strncasecmp S File Reference 8 64 1 Detailed Description 8 65 strncasecmp P S File Reference 8 65 1 Detailed Description 8 66 strncat S File Reference 8 66 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src
182. The address is in the program space Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pgmspace h gt Program Space Utilities 129 6 16 2 9 define pgm_read_word_far address_long __KLPM_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 16 2 10 read word near address short _LPM_word uint16_ t address short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 16 2 11 define P const prog void Used to declare a generic pointer to an object in program space 6 16 2 12 define PROGMEM ATTR PROGMEM Attribute to use in order to declare an object being located in flash ROM 6 16 2 13 define PSTR s const PROGMEM char s Used to declare a static pointer to a string in program space 6 16 3 Typedef Documentation 6 16 3 1 prog char Type of a char object located in flash ROM 6 16 3 2 prog intl6 t Type of an int16 t object located in flash ROM 6 16 3 3 prog int32 t Type of an int32 t object located in flash ROM Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pgmspace h gt Program Space Utilities 130 6 16 3 4 prog int64 t Type of an int64 t object located in flash ROM Note
183. The linker will then go through the libraries in order to match the undefined references with function definitions that are found in the libraries If it finds the function that matches the call the linker will then link in the object module in which the function is located This part is important the linker links in THE ENTIRE OBJECT MODULE in which the function is located Remember the linker knows nothing about the functions internal to an object module other than symbol names such as function names The smallest unit the linker works with is object modules When there are no more undefined references the linker has linked everything and is done and outputs the final application 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 ex
184. The strupr function returns a pointer to the converted string The pointer is the same as that passed in since the operation is perform in place 6 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 C language interface to the bootloader support functionality of certain AVR processors These macros are designed to work with all sizes of flash memory Global interrupts are not automatically disabled for these macros It is left up to the programmer to do this See the code example below Also see the processor datasheet for caveats on having global interrupts enabled during writing of the Flash Note Not all AVR processors provide bootloader support See your processor datasheet to see if it provides bootloader support 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 94 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
185. To do the equivalent in AVR GCC do this void main void __attribute__ noreturn void main void Khan 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 8 7 Locking Registers The IAR compiler allows a user to lock general registers from r15 and down by using compiler options and this keyword syntax _ regvar __no_init volatile unsigned int filteredTimeSinceCommutation 814 This line locks r14 for use only when explicitly referenced in your code thorugh the var name filteredTimeSinceCommutation This means that the compiler cannot dispose of it at its own will To do this in AVR do this register unsigned char counter asm r3 Typically 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 GCC as it removes this register from the control of the compiler which may make code generation worse Use at your own risk 9 9 Frequently Asked Questions 9 91 FAQ Index 1 My program doesn t recognize a variable updated within an interrupt routine Generated on Mon Oct 29 20 02 34 2007
186. UTPUT_ Compare Match ATmegal28 ATmega64 ATmega640 COMPAREIC C ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB162 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 SIG_ Timer Counter1 ATtiny261 ATtiny461 ATtiny861 COMPD_vect OUTPUT_ Compare Match COMPAREOD D SIG_ Timer Counter1 9052333 AT90S4433 ATtiny15 COMP_vect OUTPUT_ Compare Match COMPAREIA TIMERI SIG Timer Counter1 AT908S2313 ATtiny26 OVFI vect OVERFLOWI Overflow TIMERI SIG Timer Counter1 AT90S2333 AT90S4414 AT90S4433 OVF_vect OVERFLOW 1 Overflow AT90S4434 9058515 419058535 AT90PWM3 AT90PWM2 AT90PWMI 90 128 AT90CAN32 ATOOCAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 15 ATtiny2313 ATtiny261 ATtiny461 tiny861 AT9OUSB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 115 Vector name Old vector name
187. X 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 10 9 SimulAVR SimulAVR also uses the configure system so to build and install gunzip c simulavr version tar gz tar xf simulavr lt version gt mkdir obj avr cd obj avr configure prefix PREFIX make make install A X X Xr X X XY Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 335 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 10 10 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 avarice lt version gt tar gz tar xf cd avarice lt version gt mkdir obj avr cd obj avr configure prefix S PREFIX make make install X X Xr X dX WH Note AVaRICE uses the BFD library for accessing various binary file formats You may need to tell the configure script where to find the lib and headers for the link to work This is usually done by invoking the configure script like this Replace hdr
188. _ COMP_0_vect SIG_ Analog Com COMPARATORD parator 0 AT90PWM3 AT90PWM2 AT90PWM1 ANALOG_ COMP_1_vect SIG_ COMPARATOR Analog Com parator 1 AT90PWM3 AT90PWM2 AT90PWM1 ANALOG_ COMP_2_vect SIG_ Analog Com COMPARATORE parator 2 AT90PWM3 AT90PWM2 AT90PWM1 ANALOG_ COMP_vect SIG_ COMPARATOR Analog Com parator AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P ATmega164P ATmega644P AT mega644 AT90USB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 ANA_ COMP_vect SIG_ COMPARATOR Analog Com parator AT90S1200 AT90S2313 AT90S4414 419054433 AT90S8515 419058535 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 AT mega8515 ATmega8535 ATtiny11 ATtiny12 ATtiny13 ATtiny15 ATtiny2313 ATtiny26 ATtiny28 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 861 AT90S2333 AT90S4434 CANIT_vect SIG_CAN_ INTERRUPTI CAN Transfer Complete or Error 90 128 AT90CAN32 AT90CAN64 Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxyge
189. _CPU 11059200 define BAUD 38400 include lt util setbaud h gt This header file requires that on entry values are already defined for F_CPU and BAUD In addition the macro BAUD_TOL will define the baud rate tolerance in percent that is acceptable during the calculations The value of BAUD_TOL will default to 2 This header file defines macros suitable to setup the UART baud rate prescaler registers of an AVR All calculations are done using the C 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 UBRRH_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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 28 lt util setbaud h gt Helper macros for baud rate calculations 163 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 lt avr io h gt define F_CPU 4000000 static void
190. _REG uint8 t BV SPMIE define spm interrupt disable SPM REG amp uint8_t _ BV SPMIB define boot is spm interrupt SPM REG amp uint8 t BV SPMIE define boot busy SPM REG amp uint8 t COMMON ASB define boot spm busy SPM REG amp uint8 t BV SPMEN fidefine boot spm busy wait do while boot busy define _ BOOT PAGE ERASE BV SPMEN BV PGERS define PAGE WRITE BV SPMEN BV PGWRT Zdefine PAGE 5 define RWW ENABLE BV SPMEN BV COMMON ASRE define _ BOOT LOCK BITS SET _BV SPMEN 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 define 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 BITS 0x0001 define GET EXTENDED FUSE BITS 0x0002 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen
191. _rww_busy isdigit 17 avr_boot 97 isgraph 17 boot_rww_enable islower 17 avr_boot 97 isprint 17 boot_rww_enable_safe ispunct 17 avr_boot 97 isspace 17 boot_spm_busy isupper 17 avr_boot 97 isxdigit 18 boot_spm_busy_wait toascii 18 avr_boot 97 tolower 18 boot_spm_interrupt_disable toupper 18 avr_boot 97 ctype h 220 boot_spm_interrupt_enable avr_boot 97 delay h 221 BOOTLOADER_SECTION delay_basic h 221 avr_boot 98 Demo projects 171 bsearch g deprecated_items avr_stdlib 73 calloc avr_stdlib 73 cbi 169 enable_external_int 169 inb 169 inp 169 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 372 INTERRUPT 170 outb 170 170 sbi 170 timer_enable_int 171 disassembling 181 div avr_stdlib 73 div_t 211 quot 211 rem 211 DTOSTR_ALWAYS_SIGN avr_stdlib 71 DTOSTR_PLUS_SIGN avr_stdlib 71 DTOSTR_UPPERCASE avr_stdlib 72 dtostre avr_stdlib 74 dtostrf avr_stdlib 74 EDOM avr_errno 19 EEMEM avr_eeprom 100 eeprom h 222 eeprom_busy_wait avr_eeprom 100 eeprom_is_ready avr_eeprom 100 eeprom_read_block avr_eeprom 100 eeprom_read_byte avr_eeprom 100 eeprom_read_word avr_eeprom 101 eeprom_write_block avr_eeprom 101 eeprom_write_byte avr_eeprom 101 eeprom_write_word avr_eeprom 101 EMPTY_INTERRUPT avr_interrupts 120 enable_external_int deprecated_items 169 EOF avr_stdio 56 ERANGE avr_errno 19 errno h 223 Example
192. _t strcspn P const char xs PGM_P reject ATTR_PURE Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pemspace h gt Program Space Utilities 127 size_t strlcat_P char P size_t size t strlcpy P char PGM_P size_t size_t strlen_P PGM_P ATTR CONST 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 strncpy_P char size_t size_t strnlen P size_t _ ATTR CONST char strpbrk_P const char xs PGM_P accept ATTR_PURE PGM_P strrchr_P PGM_P s int val ATTR CONST char strsep_P char x sp PGM_P delim size_t strspn_P const char s PGM P accept ATTR_PURE char strstr P const char PGM P ATTR PURE void memmem P const void size t VOID P size t ATTR PURE char strcasestr P const char P PURE 6 16 2 Define Documentation 6 16 2 1 define P const prog char Used to declare a variable that is a pointer to a string in program space 6 16 2 2 define read byte address short read byte near address short Read a byte from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 16 2 3 define read byte far address long EL
193. ables first from the beginning of the internal RAM followed by bss The stack is started from the top of internal RAM growing downwards The so called heap available for the dynamic memory allocator will be placed beyond the end of bss Thus there s no risk that dynamic memory will ever collide with the RAM variables unless there were bugs in the implementation of the allocator There is still a risk that the heap and stack could collide if there are large requirements for either dynamic memory or stack space The former can even happen if the allocations aren t all that large but dynamic memory allocations get fragmented over time such that new requests don t quite fit into the holes of previously freed regions Large stack space requirements can arise in a C function containing large and or numerous local variables or when recursively calling function Note The pictures shown in this document represent typical situations where the RAM Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 267 locations refer to an ATmega128 The memory addresses used are not displayed in a linear scale e SP t RAMEND __brkval lt SP __malloc_margin on board RAM external RAM 0x0100 Ox10FF 0x1100 OxFFFF w heap start __heap_start C _ bss end data bss start data start Figure 6 RAM map of a device with internal R
194. ady Returns 1 if EEPROM is ready for a new read write operation 0 if not 6 13 3 Function Documentation 6 13 3 1 void eeprom_read_block void pointer_ram const void pointer_ eeprom size_t n Read a block of n bytes from EEPROM address pointer_eepromto pointer_ ram For constant n lt 256 bytes a library function is used For block sizes unknown at compile time or block sizes gt 256 an inline loop is expanded Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 102 6 13 3 2 uint8 t eeprom read byte const uint8 t addr Read one byte from EEPROM address addr 6 13 3 3 uint16 t eeprom read word const uint16 t x addr Read one 16 bit word little endian from EEPROM address addr 6 13 3 4 void eeprom write block const void pointer ram void pointer eeprom size t n Write a block of n bytes to EEPROM address pointer eepromfrom pointer ram 6 13 3 5 void eeprom write byte uint8 t x addr uint8 t value Write a byte value to EEPROM address addr 6 13 3 6 void eeprom write word uint16 t x addr uint16 t value Write a word value to EEPROM address addr 6 14 lt avr interrupt h gt Interrupts 6 14 1 Detailed Description Note This discussion of interrupts was originally taken from Rich Neswold s document See Acknowledgments Introduction to avr libc s interrupt handling It s nearly impossible to find compil ers that agree o
195. ainly what you didn t want 6 34 4 Examining the Object File Now we have a binary file Can we do anything useful with it besides put it into the processor The GNU Binutils suite is made up of many useful tools for manipulating object files that get generated One tool is avr objdump which takes information from the object file and displays it in many useful ways Typing the command by itself will cause it to list out its options For instance to get a feel of the application s size the h option can be used The output of this option shows how much space is used in each of the sections the stab and stabstr sections hold the debugging information and won t make it into the ROM file An even more useful option is S This option disassembles the binary file and inter sperses the source code in the output This method is much better in my opinion than using the S 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 00000114 00000000 00000000 00000074 2xx1 CONTENTS ALLOC LOAD READONLY CODE 1 bss 00000003 00800060 00000114 00000188 2xx0 A
196. ains why the variable mcucsr that mirrors the register s value needs to be placed into the noinit section because otherwise the default initialization which happens after init3 would blank the value again As the initialization code is not called using CALL RET instructions but rather con catenated together the compiler needs to be instructed to omit the entire function pro logue and epilogue This is performed by the naked attribute So while syntactically handle mcucsr is a function to the compiler the compiler will just emit the in structions for it without setting up any stack frame and not even a RET instruction at the end Function ioinit centralizes all hardware setup The very last part of that function demonstrates the use of the EEPROM variable ee pwm to obtain an EEPROM address that can in turn be applied as an argument to eeprom read word The following functions handle UART character and string output UART input is handled by an ISR There are two string output functions printstr and printstr p The latter function fetches the string from program memory Both functions translate a newline character into a carriage return newline sequence so a simple Nn 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
197. al281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 13 24 AT tiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 AT9OUSB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 PCINTI vect SIG PIN CHANGEI Pin Change Inter rupt Request 1 ATmegal62 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega406 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny24 ATtiny44 ATtiny84 9005 162 AT90USB82 PCINT2_vect SIG_PIN_ CHANGE2 Pin Change Inter rupt Request 2 ATmega3250 ATmega3290 ATmega3290P ATmega6450 ATmega6490 ATmegal68 ATmega48 ATmega88 ATmega640 AT mega1280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmega164P AT mega644P ATmega644 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 110 Vector name Old vector Description Applicable for device name PCINT3_vect SIG_PIN_ Pin Change Inter ATmega3250 ATmega3290 ATmega3290P CHANGE3 rupt Request 3 ATmega6450 ATmega6490 ATmega324P ATmega164P ATmega644P ATmega644 PCINT_vect SIG_PIN_ ATtiny2313 ATtiny261 ATtiny461 AT
198. ample malloc and free If someone is going to use malloc they will very likely be using free or at least should be using free In this case it makes more sense to aggregate those two functions in the same object module The second case is when you want to have an Interrupt Service Routine ISR in your library that you want to link in The problem in this case is that the linker looks for unresolved references and tries to resolve them with code in libraries A reference is the same as a function call But with ISRs there is no function call to initiate the ISR The ISR is placed in the Interrupt Vector Table IVT hence no call no reference and no linking in of the ISR In order to do this you have to trick the linker in a way Aggregate the ISR with another function in the same object module but have the other 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 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 7 How to Build a Library 300 The job of the librarian program is simple aggregate a list of object modules into a single library archiv
199. and how Makefile can be configured 6 34 1 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 1 can be omitted Normally for this experiment the external circuitry on RESET C3 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 178 R1 SCK 1
200. and returns the quotient and re mainder in a structure named 1div t that contains two long integer members named quot and rem Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 77 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 va1 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 malloc does not initialize the returned memory to zero bytes
201. ange 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 9 11 2 Options for the assembler avr as 9 11 2 1 Machine specific assembler options e mmcu architecture e mncu MCU name avr as understands the same mmcu options as avr gcc By default avr2 is assumed but this can be altered by using the appropriate arch pseudo instruction inside the assembler source file 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 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 352 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 a cdhI
202. ar operations Mnemonic Constraints Mnemonic Constraints adc rr add rr adiw rr andi asr r bclr I bld rl brbc Llabel brbs Llabel bset I bst rl cbi LI cbr d l com r cp Lr cpc LI cpi LI dec r elpm tz eor rr in rl inc r ld re ldd rb ldi d M 146 r label lpm 52 Isl r Isr r mov rr movw rr mul rr neg r or Lr ori out Lr pop r push r rol r ror r sbc rr sbci sbi LI sbic LI sbiw sbr sbrc rl sbrs rl ser d st e r std b r sts label r sub rr subi swap r Constraint characters may be prepended by a single constraint modifier Contraints without a modifier specify read only operands Modifiers are Modifier Specifies Write only operand usually used for all output operands Read write operand not supported by inline assembler amp Register should be used for output only Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 292 Output operands must be write only and the C expression result must be lvalue which means that the operands must be valid on the left side of 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
203. aracters inside the line buffer the input loop will be entered Charac ters will be read from the UART and processed accordingly If the UART signalled a framing error FE bit set typically caused by the terminal sending a line break con dition 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 Na 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 36 4 The source code The source code is installed under Sprefix share doc avr libc examples stdiodemo where prefix is a configuration option For Unix systems it is usually set to either usr local 6 37 Example using the two wire interface TWI Some newer devices of the ATmega series contain builtin support for interfacing the mi
204. arately if interrupts for this device are desired While some devices maintain their interrupt enable bit inside the device s register set external and timer interrupts have system wide configuration registers Example Enable timer 1 overflow interrupts timer_enable_int _BV TOIE1 Do some work Disable all timer interrupts timer_enable_int 0 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 30 lt compat deprecated h gt Deprecated items 170 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 t
205. as Rx s 230 memcpy RS File Reference 2e cmm em 255 231 8 26 1 Detailed Description m o RR 231 memmem S File Reference 2 2 2 2 2 231 8 27 1 Detailed Description oo 231 memmeorve S File REIEFENGE zm o o Rx x RR 231 8 28 1 Detailed Description 2 231 File Referente 222222222294 A RU RORORA 232 8 29 1 Detaled Description 44 es s es o RR cx RR 232 memrchr ES File Reference 2 232 5 30 1 Detaled 222 22 222 2 232 memset File Reference o os ee om 4 232 8 21 1 Detaled Description 22222222522 eS ee be eee as 232 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS viii 8 32 8 33 8 34 8 40 8 41 8 42 8 43 8 44 8 45 8 46 parity b File Referenc i 22 oea e RR ee Ra 232 321 Detaled DescHpEom usos m s Sa EUR X ER SUN 232 pemspace h File Reference oso o ewe Bed 232 5 33 1 Detailed Description luo o s w RU w wo a 232 8 33 2 Define Documentation 234 powerh Pile Reference s eo s mo e one o S EO S Row oe x 239 8 34 1 Detaled DesschpHon se cse 9X 9x RR 239 8 34 2 Define Documentation 239 seibaud h File Ci 2 22 e 240 8 35 1 Detaled Description 2 c o o ba S 240 setmp h File Reference ou s s v oom 22 2 2 7 240 8 36 1 Detailed Description osa e oc sap eos sp h s s 240 sleap h File Refe
206. avr libc Reference Manual 1 5 1 20071029 Generated by Doxygen 1 5 2 Mon Oct 29 20 02 34 2007 CONTENTS i Contents 1 AVR Libe 2 l l Introduction ek A ro o n m m Re n o E a 2 1 2 General information about this library 2 12 supported Devices 225222055524 OW RR Us 3 LA avrebbe LICENSE 222525225252 oe RR XU s 7 2 avr libc Module Index 9 21 svr hbeMaodule 202 2 2 225 4 4 9 3 avr ibc Data Structure Index 10 21 ayr Hbe Data Structures lt saa s k Rx oem t Sono Rs 10 4 File Index 11 1 File List co to loeo oom om e ee eS 11 5 avr libc Page Index 14 51 avr libe Related 2 2 14 6 avr libc Module Documentation 15 61 lt gt Allocate space in the stack 15 6 1 1 Detailed Description e s 4 2 2 whee xS 15 6 1 2 Function Documentation 22 22 2222 oo s 15 6 2 lt asserth gt Diagnostics o oe 0 o RES 16 6 21 Detailed Description 2 16 6 2 2 Define Documentation lt lt r ee a so derradan 16 6 3 Character Operations 222 2 2 17 6 3 1 Detailed Description 17 6 3 2 Function Documentation secos v s s s ks 17 64 Lemob SmE oepa danre 5 ERR RUE Q 19 6 4 44 Detailed Description 19 64 2 Define Documentation 20 6 5 lt inttypes h gt Integer Type conversions
207. avr5 atmega406 __AVR_ATmega406__ avr5 atmega64 __AVR_ATmega64__ avr5 atmega640 AVR_ATmega640__ avr5 atmega644 AVR ATmega644 avr5 atmega644p __AVR_ATmega644P__ avr5 atmega645 __AVR_ATmega645__ avr5 atmega6450 AVR ATmega6450 avr5 atmega649 AVR ATmega649 avr5 atmega6490 _ AVR ATmega6490 avr5 at94k AVR_AT94K avr6 atmega2560 _ AVR ATmega2560 avr6 atmega2561 __AVR_ATmega2561__ 1 avr25 architecture is new in GCC 4 2 morder1 morder2 Change the order of register assignment The default is 124 r25 r18 r19 120 r21 r22 r23 r30 r31 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 12 r0 r1 Order 1 uses r18 r19 120 r21 122 123 r24 r25 r30 r31 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 12 r0 r1 Order 2 uses 125 r24 123 122 121 r20 r19 r18 r30 r31 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 r2 r1 rO e mint8 Assume int to be an 8 bit integer Note that this is not really supported by avr libc so it should normally not be used The default is to use 16 bit integers e mno interrupts Generates code that changes the stack pointer without disabling interrupts Normally the state of the status register SREG is saved in a temporary register interrupts are disabled while changing the stack pointer and SREG is restored
208. bits_get address define boot page fill address data boot page fill normal address data define boot page erase address boot page erase normal address define boot page write address boot page write normal address define boot rww boot rww enable define boot lock bits set lock bits boot lock bits set lock bits define boot page fill safe address data define boot page erase safe address define boot page write safe address define boot rww enable safe define boot lock bits set safe lock bits 6 12 2 Define Documentation 6 12 2 1 define boot is spm interrupt SPM REG amp 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 Note Like any lock bits the Boot Loader Lock Bits once set cannot be cleared again except by a chip erase which will in turn also erase the boot loader itself Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 12 lt avr bo
209. brary 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 affer 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 308 9 9 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 possible to use r2 through r15 that way See C Names Used in Assembler Code for more details Back to FAQ Index 9 9 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 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
210. c by Doxygen 6 11 lt string h gt Strings 82 6 10 5 2 charx __malloc_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 attribute const int 51 long attribute const int ffsll long long attribute const void memccpy void const void int size t void memchr const void int size t PURE int memcmp const void const void size t ATTR_PURE void memcpy void const void size_t void 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 PURE char strchrnul const char int PURE Generated on Mon Oct 29 20 02 34 2007 for avr libc by Do
211. ce Detailed Description strupr S File Reference Detailed Description twi h File Reference Detailed Description Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen define TWIH 1 8 87 twi h File Reference 259 TWSR values Mnemonics TW MT xxx master transmitter TW MR xxx master receiver TW ST xxx slave transmitter TW SR xxx slave receiver define TW START 0x08 define TW REP START 0x10 define TW MT 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 fdefine TW MR ARB LOST 0x38 fdefine TW MR SLA ACK 0x40 fdefine TW MR SLA NACK 0x48 define TW MR DATA ACK 0x50 define TW MR DATA NACK 0x58 fdefine TW ST SLA 0xA8 define TW ST ARB LOST SLA ACK OxBO define TW ST 0xB8 fdefine TW ST DATA NACK 0xCO define TW ST LAST DATA 0xC8 define TW SR SLA ACK 0x60 define TW SR LOST SLA ACK 0x68 define TW SR GCALL 0x70 fdefine TW SR LOST GCALL 0x78 fdefine TW SR DATA ACK 0x80 define TW SR DATA NACK 0x88 define TW SR GCALL DATA ACK 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
212. ce compiler warnings if they are used in modules which are compiled in strict ANSI mode To avoid that you can write asm instead of asm and volatile instead of volatile These are equivalent aliases Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 296 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 N __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 may be translated to 1404 the next usage might create 1405 or whatever In any case the labels became unique too Another option is to use Unix assembler style numeric labels They are explained in How do I trace an assembler file in avr gdb The above example would then look like define loop until bit is clear port bit asm volatile 1 sbic 0 1 n t rime lb no outputs x I SFR IO ADDR port I bit 9 6 6 C Stub 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 y
213. ce is broken and never responds to a selection e g since it is no longer present at all this will cause an infinite loop Thus the maximal number of iterations made until the device is declared to be not responding at all and an error is returned will be limited to MAX_ITER Note 12 This is called master receiver mode the bus master still supplies the SCL clock but the device slave drives the SDA line with the appropriate data After 8 data bits the master responds with an ACK bit SDA driven low in order to request another data transfer 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 7 avr libc Data Structure Documentation 212 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 se
214. chr function scans the first len bytes of the memory area pointed to by src for the character val The first byte to match val interpreted as an unsigned character stops the operation Returns The memchr function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 11 lt string h gt Strings 85 6 11 3 6 int memcmp const void 57 const void 52 size_t len Compare memory areas memcmp function compares the first len bytes of the memory areas sl and 52 The comparision is performed using unsigned char operations Returns The memcmp function returns an integer less than equal to or greater than 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 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
215. const Zdefine ATTR PROGMEM attribute progmem define _ PURE attribute pure define PROGMEM PROGMEM define PSTR s const PROGMEM char s define _ LPM classic define _ LPM_enhanced_ addr Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 33 pgmspace h File Reference 233 define _ LPM_word_classic__ addr define _ LPM word enhanced addr define dword classic addr define _ LPM _ dword enhanced define __LPM addr LPM classic addr define _ LPM word addr LPM word classic addr define _ LPM_dword addr _ LPM dword classic define 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 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
216. created with no prologue or epilogue code The user code is responsible for preservation of the machine state including the SREG register as well as placing a reti at the end of the interrupt routine Use this attribute in the attributes parameter of the ISR macro 6 14 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 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 14 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 14 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 14 2 12 define SIGNAL vector include lt avr interrupt h gt
217. crocontroller to a two wire bus called TWI This is essentially the same called I2C by Philips but that term is avoided in Atmel s documentation due to patenting issues For the original Philips documentation see http www semiconductors philips com buses i2c index html 6 37 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 37 Example using the two wire interface TWD 208 using appropriate pullup resistors 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 they initiate a transfer as 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 t
218. d 9 11 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 1 Locate the archive library named libname a and use it to resolve currently unresolved symbols from it The library is searched along a path that con sists of builtin pathname entries that have been specified at compile time e g usr local avr lib on Unix systems possibly extended by pathname entries as specified by L options that must precede the 1 options on the command line Lpath Additional location to look for archive libraries requested by 1 options defsym symbol expr Define a global symbol symbol using expr as the value Print linker to stdout Map mapfile Print a linker map to mapfile c GOper Output a cross reference table to the map file in case is also present or to stdout section start sectionname org Start section sectionname at absolute address org Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 354 Tbss org Tdata org Ttext org Start the bss data or text section at org respectively 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
219. dding 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 3 Memory Sections 272 9 3 3 5 Section Uninitialized global or static variables end up the bss section 9 3 4 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 would normal bss data Only uninitialized variables can be placed in the noinit section Thus the following code will cause avr gcc to issue an error int bar __attribute__ section noinit Oxaa It is possible to tell the linker explicitly where to place the noinit section by adding W1 section start noinit 0x802000 to the avr gcc command line at the linking stage For example suppose you wish to place the noinit section at SRAM address 0x2000 5 avr gcc Wl section start noinit 0x802000 Note Because of the Harvard archi
220. de export LDFLAGS L libusb win32 device bin libusb_version lib gcc Configure configure N prefix installdir datadir installdir N sysconfdir installdir bin N enable doc N disable versioned doc N 2 gt amp 1 tee Spackage 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 mingw bin c cygwin bin lt install directory gt bin Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 343 Configure CFLAGS D_ USF_MINGW_ACCESS N LDFLAGS static Sarchivedir configure N prefix installdir target avr N with gmp usr local N with mpfr usr local N enable doc N 2 gt amp 1 tee insight configure log Make make all install 2 gt amp 1 tee Spackage make log SRecord Open source code package Configure and build at the top of the source code tree Set PATH in order MikTex executables gt usr local bin usr bin bin mingw bin c cygwi
221. der to not corrupt the ongoing transfer from the active master In this example upon detecting a lost arbitration condition the entire transfer is going to be restarted This will cause a new start condition to be initiated which will normally be delayed until the currently active master has released the bus Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 37 Example using the two wire interface TWI 211 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 devi
222. displays This is where the second parameter can be used the reference to the stream itself instead of keeping the state Inside a private variable of the function it can be kept inside a private object that is attached to the stream itself 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 be accessed inside 1cd_putchar using fdev_get_udata 6 36 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 36 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 r n Character input is organized as a line buffered operation that allows to minimally edit the current line until it is sent to the application when either a carriage return r or newline n character is received from the terminal The line editing functions implemented are b back space or N1 7 7 delete deletes the previ
223. dout are connected to a stream that will perform UART IO while stderr is arranged to output its data to the LCD text display Finally a main loop follows that accepts simple commands entered via the RS 232 connection and performs a few simple actions based on the commands First a prompt is sent out using printf P which takes a program space string The string is read into an internal buffer as one line of input using fgets While it would be also possible to use get s which implicitly reads from stdin gets has no control that the user s input does not overflow the input buffer provided so it should never be used at all If fgets fails to read anything the main loop is left Of course normally the main loop of a microcontroller application is supposed to never finish but again for demon strational purposes this explains the error handling of stdio fgets will return NULL in case of an input error or end of file condition on input Both these condi tions are in the domain of the function that is used to establish the stream uart_ putchar in this case In short this function returns EOF in case of a serial line 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 1 to the
224. dows 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 9 8 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 TAR declares an ISR like so pragma vector TIMERO_OVF_vect interrupt void MotorPWMBottom code In AVR GCC you declare an ISR like so ISR PCINT1_vect code Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 8 Porting From IAR to AVR GCC 303 AVR GCC uses the ISR macro to define an ISR This macro requries the header file 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
225. dress after the register bank on an ATmega8 processor The next available address in the data segment is also location 0x60 so the application has no initialized data The bss segment where uninitialized data is stored starts at location 0x60 The next available address in the bss segment is location 0x63 so the application uses 3 bytes of uninitialized data The eeprom segment where EEPROM variables are stored starts at location 0x0 The next available address in the eeprom segment is also location 0x0 so there aren t any EEPROM variables Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 189 6 34 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 5 avr objcopy j text j data ihex demo elf demo hex The resulting demo hex file contains 000000012C085C084C083C082C081C080C07FC050 000100025C07DC07CC07BC07AC079C078C077C065 1000200076C075C074C011241FBECFE5DAEODEBF1A 10003000CDBF10E0A0E6B0E0E4E1F1E002C0059041 100040000D92A036B107D9F
226. e Returns The strchr_P function returns a pointer to the matched character or NULL if the character is not found 6 16 4 10 PGM 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 ststrlen s if the character is not found 6 16 4 11 int strcmp P const char 57 P 52 The stremp_P function is similar to stremp except that 52 is pointer to a string in program space Returns The strcmp function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than 52 consequence of the ordering used by strcmp P is that if s1 is an initial substring of 52 then 51 is considered to be less than 52 6 16 4 12 char x strcpy_P 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pemspace h gt Program Space Utilities 134 6 16 4 13 size_t strcspn P const char s PGM P reject The strcspn_P
227. e except it waits for eeprom and spm operations to complete before writing the page 6 12 2 11 define boot rww SPM REG amp 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 N eeprom busy wait boot_rww_enable X while 0 Same as boot rww enable except waits for eeprom and spm operations to complete before enabling the RWW mameory 6 12 2 14 define boot spm busyO REG amp uint8 t BV SPMEN Check if the SPM instruction is busy 6 12 2 15 boot spm busy wait do while boot_spm_busy Wait while the SPM instruction is busy 6 12 2 16 boot interrupt disable SPM REG amp uint8_t _ BV SPMIE Disable the SPM interrupt Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 99 6 12 2 17 define_boot_spm_interrupt_enable _SPM_REG uint8_t _ BV SPMIE Enable the SPM interrupt 6 12 2 18 BOOTLOADER SECTION attribute _ section boot Used declare 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 1
228. e 130 memcpy_P S 230 memmem avr_string 84 memmem S 230 memmem_P Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 376 avr_pgmspace 130 memmove avr_string 84 memmove S 230 memrchr avr_string 85 memrchr S 231 memrchr_P avr_pgmspace 130 memrchr_P S 231 memset avr_string 85 memset S 231 modf avr_math 35 NAN avr_math 32 NONATOMIC_BLOCK util_atomic 154 NONATOMIC_FORCEOFF util_atomic 154 NONATOMIC_RESTORESTATE util_atomic 154 outb deprecated_items 170 outp deprecated_items 170 parity h 231 parity_even_bit util_parity 161 PGM_P avr_pgmspace 126 pgm_read_byte avr_pgmspace 126 pgm_read_byte_far avr_pgmspace 126 pgm_read_byte_near avr_pgmspace 126 pgm_read_dword avr_pgmspace 127 pgm_read_dword_far avr_pgmspace 127 pgm_read_dword_near avr_pgmspace 127 pgm_read_word avr_pgmspace 127 pgm_read_word_far avr_pgmspace 127 pgm_read_word_near avr_pgmspace 128 PGM_VOID_P avr_pgmspace 128 pgmspace h 231 ELPM_classic__ 233 ELPM_dword_enhanced__ 234 ELPM enhanced 234 ELPM word classic 234 ELPM word enhanced 235 LPM classic 235 LPM dword classic 236 LPM dword enhanced 236 LPM enhanced 237 LPM word classic 237 LPM word enhanced 237 pow avr math 36 power h 238 clock prescale set 238 PRId16 avr inttypes 22 PRId32 avr_inttypes 22 PRId8 avr_inttypes 22 PRIdFAST16 avr_inttypes 22 PRIdFAST32
229. e and create an index for the linker to use The name that you create for the library filename must follow a specific pattern lib lt name gt a The lt name gt part is the unique part of the filename that you create It makes it easier if the lt name gt part relates to what the library is about This lt name gt part must be prefixed by lib and it must a file extension of a for archive The reason for the special form of the filename is for how the library gets used by the toolchain as we will see later on Note The filename is case sensitive Use a lowercase lib prefix and a lowercase a as the file extension The command line is fairly simple avr as rcs lt library name gt lt list of object modules gt 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
230. e F CPU 100000001 Functions void delay us double _ us e void delay ms double ms 8 9 delay basic h File Reference 8 9 11 Detailed Description Defines define DELAY BASIC H 1 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 10 eeprom h File Reference 223 Functions void _delay_loop_1 uint8_t __count void _delay_loop_2 uintl6 t count 8 10 eeprom h File Reference 8 10 1 Detailed Description avr libc declarations define EEMEM attribute section eeprom define eeprom is ready define eeprom busy wait do while eeprom_is_ready uint8 t eeprom read byte const uint8 t addr uint16 t eeprom read word const uint16_t addr void eeprom read block void pointer ram const void xpointer eeprom size t n void eeprom write byte uint8 t addr uint8 t value void eeprom write word uint16 t uint16 t value void eeprom write block const void xpointer ram void xpointer eeprom size t n Defines define EEPROM H 1 define need size t define XCALL rcall define EEPROM REG LOCATIONS 1CIDIE define 8 2 STRI EXP define STRI EXP EXP define _REG_LOCATION_SUFFIX _STR2 __EEPROM_REG_ LOCATIONS define CR TAB n t IAR C compatibility defines e define _EEPUT addr val eeprom write byte uint8 t addr uint8 t val define _EEGET var addr var eeprom read byte uint8 t
231. e PRIXLEASTI6 x define PRIxFAST16 x define PRIX16 X define PRIXLEASTI6 X define PRIXFASTIO 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 define PRIXFAST32 IX define PRIoPTR PRIo16 define PRIuPTR PRIu16 define PRIxPTR PRIx16 define PRIXPTR PRIX16 define SCNd16 d define SCNdLEAST16 d define SCNdFASTI6 d define SCNi16 i define SCNiLEAST16 i define SCNiFAST 16 i define SCNd32 Id define SCNdLEAST32 Id define SCNdFAST32 Id define SCNi32 li define SCNiLEAST32 li define SCNiFAST32 li define SCNdPTR SCNd16 define SCNiPTR SCNi16 define SCNo16 o define SCNoLEASTI6 o ftdefine SCNoFASTI6 o define SCNul6 u define SCNuLEAST16 u define SCNuFAST16 u define SCNx16 x define SCNxLEAST16 x define SCNxFAST16 x define SCNo32 define SCNoLEAST32 lo define SCNoFAST32 lo define SCNu32 lu define SCNuLEAST32 lu define SCNuFAST32 lu Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 18 io h File Reference 228 define SCNx32 Ix define SCNxLEAST32 Ix define SCNxFAST32 Ix define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR SCNx16 Typedefs Far pointers for memory access gt 64K typedef int3
232. e address space This means that any compiler for a Harvard Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 4 Data in Program Space 276 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 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 tax of 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 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 t
233. e are different read macros to read different sizes of data at the address given 9 4 4 Storing and Retrieving Strings the Program Space Now that you can successfully store and retrieve simple data from Program Space you want to store and retrive strings from Program Space And specifically you want to store and array of strings to Program Space So you start off with your array like so char xstring table String 10 String 2 Stiri 3 String 4 String S then you add your macro to of the declaration char string_table PROGMEM I String 2 String 3 String 4 Sting 5 Right WRONG Unfortunately with GCC attributes they affect only the declaration that they are at tached to So in this case we successfully put the string_table variable the array Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 4 Data in Program Space 279 itself in the Program Space This DOES NOT put the actual strings themselves into Program Space At this point the strings are still in the Data Space which is probably not what you want In order to put the strings in Program Space you have to have explicit declarations for each string and put each string in Program Space char string_1 PROGMEM String 1 char string_2 PROGMEM String 2 char string_3 PROGMEM String 3 char string_4 PROGMEM String 4 c
234. e end since they are to be used to resolve global symbols that are still unresolved at this point Specific linker flags can be passed from the C compiler command line using the W1 compiler option see above This option requires that there be no spaces in the appended linker option while some of the linker options above like Map or def sym would require a space In these situations the space can be replaced by an equal sign as well For example the following command line can be used to compile foo c into an executable and also produce a link map that contains a cross reference list in the file foo map avr gcc O o foo out Wl Map foo map Wl cref foo c Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 12 Using the avrdude program 355 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 5 avr gcc mmcu atmegal28 foo out Wl Tdata 0x802000 See the explanation of the data section for why 0x800000 needs to be added to the ac tual value Note that unless a minit stack option has been given when compiling the C source file that contains the function main the stack will still remain in inter nal RAM through the symbol __stack that is provided by the run time startup code This is probably a good idea an
235. e 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 compiler to the GNU toolchain AVR Note that this may not be an exhaustive list 9 8 2 Registers IO header files contain identifiers for all the register names and bit names for a par ticular processor IAR has individual header files for each processor and they must be included when registers are being used in the code For example include lt iom169 h gt Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 8 Porting From IAR to AVR GCC 302 Note IAR does not always use the same register names or bit names that are used in the AVR datasheet AVR also has individual IO header files for each processor However the actual processor type is specified as a command line flag to the compiler Using the mmcu lt processor gt flag This is usually done in the Makefile This allows you to specify only a single header file for any processor type include lt avr io h gt Note The forward slash in the lt avr io h gt file name that is used to separate subdirecto ries can be used on Win
236. e for this instruction and the right hand side of the expression is a constant value known at compile time The advantage of using the memory mapped paradigm in C programs is that it makes the programs more portable to other C compilers for the AVR platform Some people might also feel that this is more readable For example the following two statements would be equivalent Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 19 lt avr sfr_defs h gt Special function registers 143 outb DDRD inb DDRD amp LCDBITS DDRD amp LCDBITS The generated code is identical for both Without optimization the compiler strictly generates code following the memory mapped paradigm while with optimization turned on code is generated using the faster and smaller in out MCU instructions Note that special care must be taken when accessing some of the 16 bit timer IO reg isters where access from both the main program and within an interrupt context can happen See Why do some 16 bit timer registers sometimes get trashed Porting programs that use sbi cbi As described above access to the AVR single bit set and clear instructions are provided via the standard C bit manipulation commands The sbi and cbi commands are no longer directly supported sbi sfr bit can be replaced by sfr _BV bit ie sbi PORTB PB1 is now PORTB 1 This actually is more flexible than having sbi directly as the optimizer
237. e 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 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 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 uint 4 t PROGMEM prog uint64 t Functions PGM VOID P memchr PGM VOID P s int val size t len ATTR CONST int memcmp const void PGM VOID size t PURE void memcpy P void VOID size_t PGM VOID memrchr P PGM VOID P s int val size t len ATTR CONST int strcasecmp_P const char PGM_P ATTR PURE char strcat_P char PGM_P PGM P strchr P P s int val CONST PGM _P strchrnul_P s int val _ ATTR_CONST int stremp_P const char PGM_P __ATTR_PURE char strepy_P char x PGM_P size
238. e the stan dard string functions described in lt string h gt Strings If possible put your constant tables in the lower 64 KB and use pgm_read_byte_ near or pgm_read_word_near instead of pgm_read_byte_far or pgm_read_ word_far since it is more efficient that way and you can still use the upper 64K for executable code All functions that are suffixed with a _P require their ar guments to be in the lower 64 KB of the flash ROM as they do not use ELPM 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 s define read byte near address short LPM uint16 t address short define read word near address short LPM word uint16 t address short Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pemspace h gt Program Space Utilities 126 define pgm_read_dword_near address_short LPM dword uint16 t address short define read byte far address long ELPM uint32 t address long defin
239. e this function This function will convert accented letters into random characters 6 3 2 15 int tolower int _ c Converts the letter c to lower case if possible 6 3 2 16 int toupper int Converts the letter c to upper case if possible 64 lt errno h gt System Errors 6 4 1 Detailed Description include errno h 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 20 Defines define EDOM 33 define ERANGE 34 6 4 2 Define Documentation 6 4 2 1 define EDOM 33 Domain error 6 4 2 2 define 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 Currently the extensions include two additional integer types that could hold a far
240. e 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 If the get function pointer is provided the stream is opened with read intent The function passed as get shall take a pointer to FILE as its single argument and return one character from the device passed as an int type If an error occurs when trying to read from the device it shall return _FDEV_ERR If an end of file condition was reached while reading from the device FDEV EOF shall be returned If both functions are provided the stream is opened with read and write intent The first stream opened with read intent is assigned to st din and the first one opened with write intent is assigned to both stdout and stderr fdevopen uses calloc und thus malloc in order to allocate the storage for the new stream Note If the macro _ STDIO FDEVOPEN 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 69 lt stdio h gt Standard
241. ease under http sources redhat com binutils As gas comes from a Unix origin its pseudo op and overall assembler syntax is slightly different than the one being used by other assemblers Numeric constants follow the C notation prefix for hexadecimal constants expressions use a C like syntax Some common pseudo ops include byte allocates single byte constants e ascii allocates a non terminated string of characters asciz allocates a VO terminated string of characters C string data switches to the data section initialized RAM variables text switches to the text section code and ROM constants set declares a symbol as a constant expression identical to equ global or globl declares a public symbol that is visible to the linker e g function entry point global variable Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 286 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 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 specific operators available which are unfo
242. ect ISR attributes define ISR BLOCK define ISR NOBLOCK define ISR_NAKED define ISR_ALIASOF target_vector Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 17 inttypes h File Reference 226 8 17 inttypes h File Reference 8 17 1 Detailed Description Defines macros for printf and scanf format specifiers For C these are only included if _ STDC_LIMIT_MACROS is defined before including lt inttypes h gt define PRId8 define PRIGLEASTS8 d define PRIdFASTS d define PRIi8 i define PRIILEASTS i define 5 i define PRId16 d define PRIGLEAST16 d define PRIGFAST 16 d define PRIi16 i define PRILEAST16 i define PRIFASTI6 i define PRId32 define PRIGLEAST32 define PRIGFAST32 Id define PRIi32 li define PR iLEAST32 li define PRIiFAST32 li define PRIdPTR PRId16 define PRH16 define PRI08 o define PRIOLEASTS o define PRIoFASTS o define PRIu8 u define PRIULEASTS u define PRIUFASTS u define PRIx8 x define PRIXLEASTS x define PRIXFASTS x define PRIX8 X define PRIXLEASTS X define PRIXFASTS X define PRIo16 o define PRIOLEASTI6 o define PRIOFASTI6 o define PRIu16 u define PRIULEAST16 u define PRIUFASTI6 u define PRIx16 x Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 17 inttypes h File Reference defin
243. ed Back to FAQ Index 9 9 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 1i e they don t have an equal sign and an initialization expression to the right within the definition of the variable they go into the bss section of the file This section simply records the size of the variable but otherwise doesn t consume space neither within the object file nor within flash memory Of course being a variable it will consume space in the target s SRAM In contrast global and static variables that have an initializer go into the data section of the file This will cause them to consume space in the object file in order to record the initializing value and in the flash ROM of the target device The latter is needed since the flash ROM is the only way that the compiler can tell the target device the value this variable is going to be initialized to Generated on Mon Oct 29 20 02 34 2007 for avr
244. ed in order to change it The macros within this header file handle the required sequence automatically before changing any value Interrupts will be disabled during the manipulation Note Depending on the fuse configuration of the particular device further restrictions might apply in particular it might be disallowed to turn off the watchdog timer Note that for newer devices ATmega88 and newer effectively any AVR that has the op tion to also generate interrupts the watchdog timer remains active even after a system reset except a power on condition using the fastest prescaler value approximately 15 ms It is therefore required to turn off the watchdog early during program startup the datasheet recommends a sequence like the following include lt stdint h gt include lt avr wdt h gt uint8_t mcusr_mirror void get_mcusr void attribute naked attribute section init3 void get mcusr void mcusr_mirror MCUSR MCUSR 0 wdt_disable Saving the value of MCUSR in mcusr_mirror is only needed if the application later wants to examine the reset source but clearing in particular the watchdog reset flag before disabling the watchdog is required according to the datasheet Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 22 lt avr wdt h gt Watchdog timer handling 150 Defines define wdt reset volatile__ wdr define wdt_disable define wdt_enable
245. efine ISR_ALIAS vector target vector include lt avr interrupt h gt Aliases a given vector to another one in the same manner as the 5 ALIASOF at tribute for the ISR macro Unlike the ISR_ALIASOF attribute macro however this is compatible for all versions of GCC rather than just GCC version 4 2 onwards Note This macro creates a trampoline function for the aliased macro This will result in two cycle penalty for the aliased vector compared to the ISR the vector is aliased to due to the JMP RJMP opcode used Deprecated For new code the use of ISR ISR_ALIASOF is recommended Example ISR INTO PORTB 42 ISR_ALIAS INTI_vect INTO_vect 6 14 2 6 define ISR_ALIASOF target_vector include lt avr interrupt h gt 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 14 2 7 define ISR BLOCK include lt avr interrupt h gt Identical to an ISR with no attributes specified Global interrupts are initially disabled by the AVR hardware when entering the ISR without the compiler modifying this state Use this attribute in the attributes parameter of the ISR macro Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 123 6 14 2 define ISR NAKED include lt avr interrupt h gt ISR is
246. ega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 USARTO SIG USARTO Data AT90CANI28 AT90CAN32 AT90CAN64 UDRE vect UARTO Register Empty ATmegal28 ATmegal62 ATmegal65 DATA megal65P ATmegal69 ATmegal69P AT mega325 ATmega329 ATmega329P AT mega64 ATmega645 ATmega649 AT mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P AT megal64P ATmega644P ATmega644 USARTI SIG USARTI Rx ATmegal62 RXC vect USARTI Complete RECV USARTI SIG USARTI Rx AT90CANI28 AT90CAN32 AT90CAN64 vect UARTI Complete ATmegal28 ATmega64 ATmega640 RECV ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P ATmega164P ATmega644P AT mega644 9 162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 USARTI SIG USARTI Tx ATmegal62 vect USARTI Complete TRANS USARTI SIG USARTI Tx AT90CANI28 AT90CAN32 AT90CAN64 TX vect UARTI Complete ATmegal28 ATmega64 ATmega640 TRANS ATmegal280 ATmegal281 AT mega2560 ATmega2561 ATmega324P ATmega164P ATmega644P AT mega644 AT90USB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 USARTI SIG USARTI Data AT90CANI28 AT90CAN32 AT90CAN64 UDRE vect UARTI Register Empty ATmegal28 ATmegal62 ATmega64 AT DATA mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT9
247. egister 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 31226530 Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 290 Constraint Used for Range a Simple upper registers r16 to r23 b Base pointer registers 2 pairs d Upper register rl6tor31 e Pointer register pairs X y Z q Stack pointer register SPH SPL r Any register r0 to r31 t Temporary register r0 W Special upper register r24 r26 r28 r30 pairs x Pointer register pair X x 127 126 y Pointer register pair Y y 129 r28 7 Pointer register pair Z z 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
248. embler code string A good example is a simple statement to disable interrupts asm volatile cli Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 289 9 6 2 Assembler Code You can use the same assembler instruction mnemonics as you d use with any other assembler And you can write as many assembler statements into one code string as you like and your flash memory is able to hold Note The available assembler directives vary from one assembler to another To make it more readable you should put each statement on a seperate line asm volatile nopNnNt nop n t 40 linefeed 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 Stack pointer high byte at address 0x3E ASP Stack pointer low byte at address 0x3D __tmp_reg__ Register 0 used for temporary storage zero_reg Register rl always zero Register rO may be freely used by your assembler code and need not be restored at the end of your code It s a good idea to use tmp reg and zero reg instead of rO or r1 just in case a new compiler version changes the r
249. en 9 9 Frequently Asked Questions 321 9 9 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 ATmega128 to judge the effect of compiling the library itself using different optimization levels The following table lists the results The test case consisted of around 2 KB of strings to sort Test 1 used qsort using the standard library stremp test 2 used a function that sorted the strings by their size thus had two calls to strlen per invocation When comparing the resulting code size it should be noted that a floating point version of fvprintf was linked into the binary in order to print out the time elapsed which is entirely not affected by the different optimization levels and added about 2 5 KB to the code Optimization Size of text Time for test 1 Time for test 2 flags 03 6898 903 us 19 7 ms 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
250. enhanced core If too many those that don t fit are passed on the stack Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 318 Return values 8 bit in r24 not r25 16 bit in r25 r24 up to 32 bits in r22 r25 up to 64 bits in r18 r25 8 bit return values are zero sign extended to 16 bits by the caller unsigned char is more efficient than signed char just clr r25 Argu ments to functions with variable argument lists printf etc are all passed on stack and char is extended to int Warning There was no such alignment before 2000 07 01 including the old patches for gcc 2 95 2 Check your old assembler subroutines and adjust them accordingly Back to FAQ Index 9 9 15 How do I put an array of strings completely in ROM There are times when you may need an array of strings which will never be modified In this case you don t want to waste ram storing the constant strings The most obvious and incorrect thing to do is this include lt avr pgmspace h gt PGM_P array 2 PROGMEM 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 include avr pgmspace h const char foo PROGMEM Foo const char bar
251. entical to the contents of the old region even in case a new region had to be allocated It is acceptable to pass pt r as NULL in which case realloc will behave identical to malloc Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 79 If the new memory cannot be allocated realloc returns NULL and the region at pt r 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 xx __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 endpt If no conversion is performed zero is returned and the value of npt r is stored i
252. enting 35 If endptr is not NULL strtol stores the address of the first invalid character in xendptr If there were no digits at all however strtol stores the original value of in endptr Thus if xnptr is not NO but xxendptr is 710 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 MAX 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
253. er 6 36 3 6 Icd c The implementation of the higher level LCD driver This driver builds on top of the HD44780 low level LCD controller driver and offers a character IO interface suitable for direct use by the standard IO facilities Where the 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 n 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
254. er 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 case this chunk was only up to two bytes larger than the request the request will simply be altered internally to also account for these additional bytes since no separate freelist entry could be split off in that case If nothing could be found on the freelist heap extension is attempted This is where malloc margin will be considered if the heap is operating below the stack or where malloc heap end will be verified otherwise If the remaining memory is insufficient to satisfy the request NULL will eventually be returned to the caller When calling free a new f
255. erase address while 0 Same as boot_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 ftdefine boot page fill safe address data Value do boot spm busy wait X eeprom busy wait N boot page fill address data N while 0 Same as boot page fill except it waits for eeprom and spm operations to complete before filling the page 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 98 6 12 2 10 define boot_page_write_safe address Value do boot spm busy wait eeprom_busy_wait boot_page_write address X while 0 Same as boot page writ
256. erates push pops for the call clobbered registers This way also a specific calling convention could be used for the eep rom routines e g by passing values in __tmp_reg__ eeprom addresses in X and memory addresses Z registers Method is optimized for code size Presently supported are two locations of the EEPROM register set Ox1F 0x20 0x21 and 0x1C 0x1D 0x1E see _ EEPROM REG LOCATIONS As these functions modify IO registers they are known to be non reentrant If any of these functions are used from both standard and interrupt context the applica tions must ensure proper protection e g by disabling interrupts before accessing them libc declarations uint8 t eeprom_read_byte const uint8 t addr uint16 t eeprom read const uint16_t addr void eeprom read block void pointer ram const void xpointer eeprom size t n void eeprom write byte uint8 t addr uint8 t value void eeprom write word uint16 t uint16 t value void eeprom write block const void xpointer ram void xpointer eeprom size t n define EEMEM attribute section eeprom define eeprom is ready define busy wait do while eeprom_is_ready IAR C compatibility defines define EEPUT addr val eeprom write byte uint8 t uint8 t val define EEGET var addr var eeprom read byte uint8 t x addr Defines define _ EEPROM REG LOCATIONS 1CIDIE 6 13
257. ersion Conversions are introduced with the character Possible options can follow the a indicating that the conversion should be performed but the conversion result is to be discarded no parameters will be processed from ap e the character h indicating that the argument is a pointer to short int rather than int Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 69 lt stdio h gt Standard IO facilities 68 e the character 1 indicating that the argument is a pointer to long int rather than int for integer type conversions or a pointer to double for floating point conversions In addition a maximal field width may be specified as a nonzero positive decimal integer which will restrict the conversion to at most this many characters from the input stream This field width is limited to at most 127 characters which is also the default value except for the c conversion that defaults to 1 The following conversion flags are supported Matches a literal character This is not a conversion d Matches an optionally signed decimal integer the next pointer must be a pointer to int i Matches an optionally signed integer the next pointer must be a pointer to int The integer is read in base 16 if it begins with Ox or OX in base 8 if it begins with 0 and in base 10 otherwise Only characters that correspond to the base are used o Matches an octal integer the next pointer must be a
258. et by representing a logical in the respec tive bit position When working with interrupt handlers this interrupt flag bit usually gets cleared automatically in the course of processing the interrupt sometimes by just calling the handler at all sometimes e g for the U SJART by reading a particular hardware register that will normally happen anyway when processing the interrupt From the hardware s point of view an interrupt is asserted as long as the respective bit is set while global interrupts are enabled Thus it is essential to have the bit cleared before interrupts get re enabled again which usually happens when returning from an interrupt handler Only few subsystems require an explicit action to clear the interrupt request when using interrupt handlers The notable exception is the TWI interface where clearing the interrupt indicates to proceed with the TWI bus hardware handshake so it s never done Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 326 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 positio
259. etailed Description 24546 64 6 ee S OK 3 3 RR 255 strpbrk S File Reference coss o RARE 256 5 74 1 Detaled Description soo RR RR s amp 256 P S File Reference 222 292 x6 3 9 RR xx RR OR 256 6 75 1 Detaled Description uu od m bee as 256 sutchro File Reference o o oop s 24 045 Rt eek Re 256 8 76 1 Detaled Description 256 strehe PS File Reference lt lt a ado q ss oum ko 5 258 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS xi 8 77 1 Detailed Description 22 2 258 8 59 sinevo File BEeteren B s o oom s s S pus SE a X o 258 8 76 1 Detaled Description 222222225954 258 8 79 strsep S File Reference a e waq RR 258 8 79 1 Detailed Description 2 m Rs 258 90 strsep P S File Reference uuo omo Rem xo go 25558 258 8 90 1 Detailed Description lt se cs ees apee SUR 4 S 8 258 881 stspn S File Refeten e lt eo co emeret eeta 2 258 591 1 Detaled Description xoc ox ER Eee 258 592 strspn P S Pile Reference uso n xo so oem RR X o e 258 8 82 1 Detailed Description 258 5 83 strsteS Pile Reference u u cead w eR ot w kup w a a ERG s 258 8 83 1 Detailed Description gt e a s 6485 5 222524 258 8 84 s ste PS Pile Referente uuu cum q W QUQ we SW 258 8 84 1 Detailed Description oos RR 258 8 85 strtok rS File Reference 2 258 885 1 Detaled De
260. eturn a 0 if the bit is clear and non zero if the bit is set 6 19 2 4 define loop_until_bit_is_clear sfr bit do while bit is set sfr bit include lt avr io h gt Wait until bit bit in IO register s fr is clear 6 19 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 20 lt avr sleep h gt Power Management and Sleep Modes 145 6 20 lt avr sleep h gt Power Management and Sleep Modes 6 20 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 The simplest way is to optionally set the desired sleep mode using set_ sleep_mode it usually defaults to idle mode where the CPU is put on sleep but all peripheral clocks are still running and then call sleep_mode Unless it is the purpose to lock the CPU hard until a hardware reset interrupts need to be enabled at this point This macro automatically takes care to enable the sleep mode in the CPU before going to sleep and disable it again afterwards As t
261. eturns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 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 s1 const char 52 size t len Compare two strings ignoring case The strncasecmp function is similar to strcasecmp except it only compares the first len characters of s1 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 11 lt string h gt Strings 90 Returns The strncasecmp function returns an integer less than equal to or greater than Zero if s1 or the first 1en bytes thereof is found
262. exp double value int exp The frexp function breaks a floating point number into a normalized fraction and an integral power of 2 It stores the integer in the int object pointed to by exp The frexp function returns the value x such that x is a double with magnitude in the interval 1 2 1 or zero and value equals x times 2 raised to the power exp If value is zero both parts of the result are zero Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 6 lt math h gt Mathematics 36 6 6 3 18 double hypot double x double y The hypot function returns sqrt X x This is the length of the hypotenuse of a right triangle with sides of length x and y or the distance of the point x y from the origin Using this function instead of the direct formula is wise since the error is much smaller No underflow with small x and y No overflow if result is in range 6 6 3 19 _ ATTR CONST int isfinite double x The isfinite function returns a nonzero value if x is 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 x is either positive or negative infinity otherwise 0 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 The Idexp function multiplies a floating point number by an i
263. face 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 are applicable to your device Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 17 lt avr power h gt Power Reduction Management 139 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 AT90USB 1287 AT90PWM 1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 ATmega165 ATmega165P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmega169 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 ATmega164P 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 ATmegal281 ATmega2560 ATmega2561 9005 646 AT90USB647 AT9OUSB 128
264. ference 249 8 45 strcat_P S File Reference 8 45 1 Detailed Description Defines define dest_hi r25 define dest_lo r24 define src_hi r23 define src_lo r22 8 46 strchr S File Reference 8 46 1 Detailed Description 8 47 strchr P S File Reference 8 47 1 Detailed Description 8 48 strchrnul S File Reference 8 48 1 Detailed Description 8 49 strchrnul P S File Reference 8 49 1 Detailed Description 8 50 strcmp S File Reference 8 50 1 Detailed Description 8 51 strcmp P S File Reference 8 51 4 Detailed Description 8 52 sSstrcpy S File Reference 8 52 1 Detailed Description Defines define dest hi r25 define dest lo r24 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 53 strcpy_P S File Reference 250 define src_hi r23 define src_lo r22 8 53 strcpy_P S File Reference 8 531 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 8 54 strcspn S File Reference 8 54 1 Detailed Description 8 55 strcspn_P S File Reference 8 55 1 Detailed Description 8 56 string h File Reference 8 56 1 Detailed Description Defines define STRING H 1 define need NULL define need size t define PURE attribute pure define _FFS x Functions int ffs int attribute const int 51 long __attribute__ const int ffsll long long attribute const void me
265. fers hardware TWI support is the ATmega8 which comes with 512 bytes of EEPROM which is equivalent to an 24 04 device The ATmegal28 already comes with twice as much EEPROM as the 24C16 would offer One exception might be to use an externally connected EEPROM device that is removable e g SDRAM PC memory comes with an integrated TWI EEPROM that carries the RAM configuration information 6 37 3 The Source Code The source code is installed under Sprefix share doc avr libc examples twitest twitest c where prefix is a configuration option For Unix systems it is usually set to either Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 37 Example using the two wire interface TWI 209 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 24 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
266. fic 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 RA MEND for devices that do not allow for external RAM E2END A constant describing the address of the last EEPROM cell Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pgmspace h gt Program Space Utilities 125 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 16 lt avr pgmspace h gt Program Space Utilities 6 16 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 d device must support either the LPM or Note evice In order to use these functions the target ELPM instructions These functions are an attempt to provide some compatibility with header files that come with IAR C to make porting applications between different compilers easier This is not 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 us
267. fine PRIOLEAST32 lo octal printf format for uint_least32_t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 26 6 5 2 29 define PRIOLEASTS o octal printf format for uint_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 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 6 5 2 35 define PRIUFAST32 decimal printf format for fast32 t 6 5 2 36 define PRIUFASTS decimal printf format for uint_fast8_t 6 5 2 37 define PRIULEAST16 decimal printf format for uint_least16_t 6 5 2 38 define PRIULEAST32 decimal printf format for least32 t 6 5 2 39 define PRIULEASTS u decimal printf format for least8 t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 27 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 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
268. fine set_bits_macro port mask port mask int main void set_bits_func_wrong PORTB Oxaa set_bits_func_correct amp PORTB 0 55 set bits macro PORTB 0 0 return 0 The first function will generate object code which is not even close to what is intended The major problem arises when the function is called When the compiler sees this call it will actually pass the value of the PORTB 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 10a 6a ea ldi r22 170 106 88 r24 0 18 24 10 Oe 94 65 00 11 So the function once called only sees the value of the port register and knows nothing about which port it came from At this point whatever object code is generated for the function by the compiler is irrelevant The interested reader can examine the full disassembly to see that the function s body is completely fubar The second function shows how to pass by reference the memory mapped address of the io port to the function so that you can read and write to it in the function Here s the object code generated for the function call set_bits_func_correct amp PORTB 0x55 112 65 5 141 r22 0x55 j 85 114 88 e3 141 r24 0 38 56 116 90 e0 141 r25 0 00 270 118
269. ga324P ATmega644P ATmega644 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega8HVA AT megal6HVA ATmega406 AT90PWM1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 9005 82 9005 162 AT90USB646 AT90USB647 AT90USB 1286 AT90USB 1287 48 6 22 2 11 define WDTO_500MS 5 See WDTO_15MS 6 22 2 12 define WDTO_60MS 2 WDTO_15MS 6 22 2 13 define WDTO_8S 9 See WDTO_15MS Note This is only available on the ATtiny2313 ATtiny24 AT tiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmega48P ATmega88P ATmegal68P AT mega328P ATmegal64P ATmega324P ATmega644P ATmega644 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega8HVA AT megal6HVA ATmega406 ATOOPWM1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 16 9005 82 9005 162 AT90USB646 AT90USB647 9005 1286 9005 1287 48 6 23 lt util atomic h gt Atomicly and Non Atomically Executed Code Blocks 6 23 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
270. gen 13 Supported Devices 3 13 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 atmega103 atmega128 atmega1280 atmega1281 atmega16 atmegal61 atmega162 atmega 163 atmega164p atmega165 atmega165p atmegal68 atmegal68p atmega2560 atmega2561 atmega32 atmega323 atmega324p atmega325 atmega325p atmega3250 atmega3250p Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 13 Supported Devices 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 attiny261 attiny28 1 attiny2313 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 13 Supported Devices attiny43u attiny44 attiny45 attiny461 attiny48 attiny84 attiny85 attiny861 CAN AVR Devices at90can32 at90can64 at90can128 LCD AVR Devices atmega 169 atmega169p atmega329 atmega329p atmega3290 atmega3290p atmega649 atmega6490 Lighting AVR Devices e at90pwml Generated on Mon
271. gen 6 14 lt avr interrupt h gt Interrupts 111 Vector name Old vector Description Applicable for device name SPM_ SIG_SPM_ Store Program AT90PWM3 AT90PWM2 AT90PWMI READY vect READY Memory Read AT90CAN128 AT90CAN32 AT90CAN64 ATmegal28 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P AT mega406 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIM0_ SIG_ Timer Counter ATtiny13 ATtiny24 ATtiny44 ATtiny84 COMPA_vect OUTPUT_ Compare Match ATtiny45 ATtiny25 ATtiny85 A TIMO_ SIG_ Timer Counter ATtiny13 ATtiny24 ATtiny44 ATtiny84 COMPB_vect OUTPUT_ Compare Match ATtiny45 ATtiny25 ATtiny85 TIMO_OVF_ SIG_ Timer Counter0 13 ATtiny24 ATtiny44 ATtiny84 vect OVERFLOWO Overflow ATtiny45 ATtiny25 ATtiny85 SIG_INPUT Timer Counter1 ATtiny24 ATtiny44 ATtiny84 CAPT_vect CAPTURE1 Capture Event SIG_ Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 COMPA_vect OUTPUT_ Compare Match ATtiny25 ATtiny85 COMPAREIA A SIG_ Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 COM
272. generated assembler code Used for debugging avr gcc msize Dump the address size and relative cost of each statement into comments in the gen erated assembler code Used for debugging avr gcc mdeb Generate lots of debugging information to stderr Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 350 9 11 1 2 Selected general compiler options following general gcc options might be of some interest to AVR users On Optimization level n Increasing n is meant to optimize more an optimization level of 0 means no optimization at all which is the default if no O option is present The special option Os is meant to turn on all O2 optimizations that are not expected to increase code size Note that at O3 gcc attempts to inline all simple functions For the AVR target this will normally constitute a large pessimization due to the code increasement The only other optimization turned on with 03 is frename registers which could rather be enabled manually instead A simple O option is equivalent to 01 Note also that turning off 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
273. geting 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 GNU assembler gas to assemble the output of the compiler GCC knows how to drive the GNU linker Id to 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 als
274. 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 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 Id can only work with object modules to link them together Object modules are the smallest unit that the linker works with Typically on the linker command line you will specify a set of object modules that has been previously compiled and then a list of libraries including the Standard C Library The linker takes the set of object modules that you specify on the command line and links them together Afterwards there will probably be a set of undefined Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 7 How to Build a Library 299 references A reference is essentially a function call An undefined reference is a function call with no defined function to match the call
275. gt Character Operations 6 31 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 int isalnum int c ATTR_CONST int isalpha int c ATTR_CONST int isascii int c ATTR CONST int isblank int ATTR CONST intiscntrl int c ATTR CONST int isdigit int ATTR CONST int isgraph int ATTR CONST int islower int c CONST _ intisprint int ATTR CONST int ispunct int ATTR CONST int isspace int ATTR CONST int isupper int c ATTR CONST intisxdigit int ATTR CONST Character convertion routines If c is not an unsigned char value or EOF the behaviour of these functions is undefined inttoascii int c ATTR CONST int tolower int ATTR CONST int toupper int ATTR CONST 6 3 2 Function Documentation 6 3 2 1 intisalnum int c Checks for an alphanumeric character It is equivalent to isalpha c isdigit c Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 63 lt ctype h gt Character Operations 18 6 3 2 2 int isalpha int Checks for
276. gt General utilities 76 6 10 4 12 void free void ptr The free function causes the allocated memory referenced by pt r to be made avail able for future allocations If pt r is NULL no action occurs 6 10 4 13 charx itoa int char x s int radix Convert an integer to a string The function itoa converts the integer value from va1 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 9 will be the letter a If radix is 10 and val is negative a minus sign will be prepended The itoa function returns the pointer passed as s 6 10 4 14 long labs long The labs function computes the absolute value of the long integer i Note The abs and labs functions builtins of gcc 6 10 4 15 Idiv_tldiv long __num long denom Idiv function computes the value num denom
277. h 224 INTMAX_C avr_stdint 45 INTMAX MAX avr_stdint 45 INTMAX_MIN avr_stdint 45 intmax_t avr_stdint 49 INTPTR_MAX avr_stdint 45 INTPTR_MIN avr_stdint 45 intptr_t avr_stdint 49 inttypes h 225 io h 227 isalnum ctype 16 isalpha ctype 16 isascli ctype 17 isblank ctype 17 iscntrl Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 375 ctype 17 isdigit ctype 17 isfinite avr_math 35 isgraph ctype 17 isinf avr_math 35 islower ctype 17 isnan avr_math 35 isprint ctype 17 ispunct ctype 17 ISR avr_interrupts 120 ISR_ALIAS avr_interrupts 120 ISR_ALIASOF avr_interrupts 121 ISR_BLOCK avr_interrupts 121 ISR_NAKED avr_interrupts 121 ISR_NOBLOCK avr_interrupts 122 isspace ctype 17 isupper ctype 17 isxdigit ctype 18 itoa avr_stdlib 75 labs avr_stdlib 75 ldexp avr math 35 Idiv avr_stdlib 75 Idiv_t 212 quot 212 rem 212 log avr_math 35 log10 avr_math 35 longjmp setjmp 38 loop_until_bit_is_clear avr_sfr 143 loop_until_bit_is_set avr_sfr 143 Itoa avr_stdlib 75 M_PI avr_math 32 M_SQRT2 avr_math 32 malloc avr_stdlib 76 math h 227 memccpy avr string 83 memcopy S 228 memchr avr string 83 memchr S 229 memchr P avr pgmspace 130 memchr PS 229 memcmp avr_string 83 memcmp S 229 memcmp P avr pgmspace 130 memcemp PS 229 memcpy avr string 84 memcopy S 229 memcpy_P avr_pgmspac
278. h gt Compatibility with IAR EWB 3 x 171 lt ctype h gt Character Operations 16 lt errno h gt System Errors 18 lt inttypes h gt Integer Type conversions 19 lt math h gt Mathematics 31 lt setjmp h gt Non local goto 37 lt stdint h gt Standard Integer Types 39 lt stdio h gt Standard IO facilities 51 lt stdlib h gt General utilities 70 lt string h gt Strings 81 lt util atomic h gt Atomicly and Non Atomically Executed Code Blocks 151 lt util crc16 h gt CRC Computations 155 version Deprecated lt util delay h gt Convenience functions for busy wait delay loops 158 lt util delay_basic h gt Basic busy wait delay loops 159 lt util parity h gt Parity bit generation 160 lt util setbaud h gt Helper macros for baud rate calculations 161 lt util twi h gt TWI bit mask definitions 163 _BV avr_sfr 142 _EEGET avr_eeprom 100 _EEPUT avr_eeprom 100 _FDEV_EOF avr_stdio 56 _FDEV_ERR avr_stdio 56 _FDEV_SETUP_READ avr_stdio 56 _FDEV_SETUP_RW avr_stdio 56 _FDEV_SETUP_WRITE avr_stdio 56 _FFS avr_string 82 AVR_LIBC_DATE avr_version 147 AVR_LIBC_DATE_STRING__ avr_version 147 AVR_LIBC_MAJOR avr_version 147 AVR MINOR avr version 147 AVR REVISION avr version 147 AVR LIBC VERSION STRING avr version 147 AVR VERSION avr version 147 EEPROM REG LOCATIONS INDEX 364 avr_eeprom 99 ELPM classic pgms
279. h is less elegant but could be applied to all compiler versions Empty interruptservice 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_mode A handler for such an interrupt vector can be declared using the EMPTY macro EMPTY INTERRUPT vect Note There is no body to this macro 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 105 One solution to this could be to implement the entire ISR as manual assembly code in a separate assembly file See Combining C and assembly source files for an example of how to implement it that way Another solution is to still implement the ISR in C language but take over the com piler s job of generating the prologue and epilogue This can be done using the ISR_ NAKED attribute to the ISRO macro Note that the compiler does not generate any thing as pro
280. har string_5 PROGMEM String 5 Then use the new symbols in your table like so PGM_P string_table PROGMEM string_1 string_2 string_3 string_4 string_5 Now this has the effect of putting string_table in Program Space where string_table is 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 an automatic variable inside a function that is allocated on the stack you can do this void foo void char buffer 10 for unsigned char i 0 lt 5 itt strcpy_P buffer read word amp string table i Display buffer LCD return Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 280 the string_table array is stored in Program Space so we access it normally as if were stored Data Space then take the address of the location we want
281. hat 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 16 4223 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 function returns a pointer to the matched character or NULL if the character is not found Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 17 lt avr power h gt Power Reduction Management 137 6 16 4 24 char strsep_P char sp 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 or 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 16 4
282. he application will auto matically scale to new target softclock or master CPU frequencies without having to manually re calculate hardcoded constants 6 35 3 2 Part 2 Variable definitions The int flags structure demonstrates a way to allocate bit variables in memory Each of the interrupt service routines just sets one bit within that structure and the application s main loop then monitors the bits in order to act appropriately Like all variables that are used to communicate values between an interrupt service routine and the main application it is declared volatile The variable ee_pwm is not a variable in the classical C sense that could be used as an lvalue or within an expression to obtain its value Instead the attribute section eeprom marks it as belonging to the EEPROM section This section is merely used as a place holder so the compiler can arrange for each individual variable s location in EEPROM The compiler will also keep track of initial values assigned and usually the Makefile is arranged to extract these initial values into a separate load file Largedemo eeprom x in this case that can be used to initialize the EEPROM The actual EEPROM IO must be performed manually Similarly the variable mcucsr is kept in the noinit section in order to prevent it from being cleared upon application startup Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 35 more sophisticated project
283. he compiler to use the symbol name clock rather than value This makes sense only for external or static variables because local variables do not have symbolic names in the assembler code However local variables may be held in registers With AVR GCC you can specify the use of a specific register void Count void register unsigned char counter asm r3 some code asm volatile clr r3 more code Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 7 How to Build a Library 298 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 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
284. he 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 285 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 needs to be saved usually on the stack Note 10 As explained in Interrupts a global catch all interrupt handler that gets all unassigned interrupt vectors can be installed using the name __vector_default This must be global and obviously should end in a reti instruction By default a jump to location 0 would be implied instead 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 rel
285. he number of characters in src Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pemspace h gt Program Space Utilities 135 6 16 4 17 int strncasecmp_P const char s1 P s2 size_t n Compare two strings ignoring case The strncasecmp_P function is similar to strcasecmp_P except it only compares the first n characters of 51 Parameters sl A pointer to a string in the devices SRAM s2 A pointer to a string in the devices Flash n The maximum number of bytes to compare Returns The strncasecmp_P function returns an integer less than equal to or greater than zero if s1 or the first n bytes thereof is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strncasecmp_P is that if s1 is an initial substring of 52 then 51 is considered to be less than s2 6 16 4 18 char x strncat P char x 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 16 4 19 int strncmp P const char 81 P 52 size_t n The strncmp_P function is similar to stremp_P except it only compares the first at most n characters of 51 and 52 Returns The strncmp_P function returns an integer less than equal to or greater than
286. he 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 37 2 TWI example project The ATmega TWI hardware supports both master and slave operation This example will only demonstrate how to use an AVR microcontroller as TWI master The imple mentation is kept simple in order to concentrate on the steps that are required to talk to a TWI slave so all processing is done in polled mode waiting for the TWI interface to indicate that the next processing step is due by setting the TWINT interrupt bit If it is desired to have the entire TWI communication happen in background all this can 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 of
287. he strcasecmp_P function compares the two strings 51 and s2 ignoring the case of the characters Parameters sl 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 A consequence of the ordering used by strcasecmp is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 6 16 4 7 char x strcasestr P const char s1 P 52 This funtion is similar to strcasestr except that s2 is pointer to a string in program space 6 16 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pgmspace h gt Program Space Utilities 133 6 16 4 9 strchr P P s int val Locate character in program space string The strchr_P function locates the first occurrence of va1 converted to a char in the string pointed to by s in program space The terminating null character is 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 spac
288. his combined macro might cause race conditions in some situations the individual steps of manipulating the sleep enable SE bit and actually issuing the SLEEP in struction are provided in the macros sleep_enable sleep_disable and sleep cpu This also allows for test and sleep scenarios that take care of not missing the interrupt that will awake the device from sleep Example include lt avr interrupt h gt include lt avr sleep h gt cli if some_condition sleep_enable sei sleep cpu sleep disable sei This sequence ensures an atomic test of some_condition with interrupts being dis abled If the condition is met sleep mode will be prepared and the SLEEP instruction will be scheduled immediately after an SEI instruction As the intruction right after the SEI is guaranteed to be executed before an interrupt could trigger it is sure the device will really be put to sleep Sleep Functions void set sleep mode uint8 t mode void sleep mode void Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 20 lt avr sleep h gt Power Management and Sleep Modes 146 void sleep_enable void void sleep_disable void void sleep_cpu void Sleep Modes Note Some of these modes are not available on all devices See the datasheet for target device for the available sleep modes define SLEEP_MODE_IDLE 0 define SLEEP_MODE_ADC _BV
289. ibc 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 ox or 9 10 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 334 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 avrdude lt version gt tar gz tar xf cd avrdude lt version gt mkdir obj avr cd obj avr configure prefix S PREFIX make make install XY X Xr X d WH 9 10 8 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 cd obj avr configure prefix PREFIX target avr make make install 4 X o X X d
290. il_setbaud BAUD_TOL 163 UBRR_VALUE 163 UBRRH_VALUE 163 UBRRL_VALUE 163 USE_2X 163 util_twi TW_BUS_ERROR 165 TW_MR_ARB_LOST 165 TW DATA 165 TW DATA NACK 165 TW MR SLA ACK 165 TW MR SLA NACK 165 TW MT ARB LOST 165 TW MT DATA ACK 165 TW MT DATA NACK 165 TW MT SLA 165 TW MT SLA 165 TW NO INFO 165 TW READ 166 TW REP START 166 TW SR ARB LOST GCALL ACK 166 TW SR ARB LOST SLA ACK 166 TW SR DATA ACK 166 TW SR DATA NACK 166 TW SR GCALL ACK 166 TW SR GCALL DATA ACK 166 TW SR GCALL DATA NACK 166 TW SR SLA ACK 166 TW SR STOP 166 TW ST ARB LOST SLA ACK 167 TW ST DATA 167 TW ST NACK 167 TW ST LAST DATA 167 TW ST SLA 167 TW START 167 TW STATUS 167 TW STATUS MASK 167 TW WRITE 167 utoa avr stdlib 80 vfprintf avr stdio 63 vfprintf P avr stdio 66 vfscanf avr stdio 66 vfscanf P avr stdio 69 vprintf avr stdio 69 vscanf avr stdio 69 vsnprintf avr stdio 69 vsnprintf P avr stdio 69 vsprintf avr stdio 69 vsprintf P avr stdio 69 wdt h 259 _ write 259 wdt disable avr watchdog 149 wdt enable avr watchdog 149 wdt reset avr watchdog 149 WDTO_120MS avr_watchdog 150 WDTO 15MS avr watchdog 150 WDTO 15 avr watchdog 150 WDTO 250MS avr watchdog 150 WDTO 2S avr watchdog 150 WDTO 30MS avr watchdog 150 WDTO 45 avr watchdog 150 Generated
291. ill be called with the new request size the existing data will be Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 3 Memory Sections 271 copied over and free will be called on the old region 933 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 text Section The text section contains the actual machine instructions which make up your program This section is further subdivided by the initN and finiN sections dicussed below Note The avr size program part of binutils coming from a Unix background doesn t account for the data initialization space added to the text section so in order to know how much flash the final program will consume one needs to add the values for both text and data but not bss while the amount of pre allocated SRAM is the sum of data and bss 9 3 2 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 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 a
292. ill 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 12 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 are purely AVR specific like the entire program space string interface Unless otherwise noted functions of this library are not guaranteed to be reentrant In particular any functions that store local state are known to be non reentrant as well as functions that manipulate IO registers like the EEPROM access routines If these functions are used within both standard and interrupt contexts undefined behaviour will result Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxy
293. inct memory areas this is the safest way to avoid a stack heap collision Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 268 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 start is filled in by the linker to point just beyond bss heap end is set to 0 which makes malloc assume the heap is below the stack If the heap is going to be moved to external RAM _ malloc heap must be adjusted accordingly This can either be done at run time by writing directly to this variable or it can be done automatically at link time by adjusting the value of the symbol heap end The following example shows a linker command to relocate the entire data and bss segments and the heap to location 0x1100 in external RAM The heap will e
294. ine 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 fdev_setup_stream stream put get rwflag Setup a user supplied buffer as an stdio stream This macro takes a user supplied buffer st ream and sets it up as a stream that is valid for stdio operations similar to one that has been obtained dynamically from fdevopen The buffer to setup must be of type FILE The arguments put and get are identical to those that need to be passed to fdevopen The rwflag argument can take one of the values FDEV SETUP READ _FDEV_ SETUP WRITE or __FDEV_SETUP_RW for read write or read write intent respec tively Note No assignments to the standard streams will be performed by fdev_setup_stream If standard streams are to be used these need to be assigned by the user See also under Running stdio without malloc 6 9 2 12 define FILE struct file FILE is the opaque structure that is passed around between the various s
295. init4 defines the code which takes care of copying the contents of data from the flash to SRAM For all other devices this code as well as the code to zero out the bss section is loaded from libgcc a init5 Unused User definable 1016 Unused for C programs but used for constructors in C programs init7 Unused User definable init8 Unused User definable init9 Jumps into main Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 3 Memory Sections 274 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 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 fini 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 4 Data in Program Space 275 incl
296. 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 The string immedi ately following the 1 is the unique part of the library filename that the linker will link in For example if you use im this will expand to the library filename libm a Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 8 Porting From IAR to AVR GCC 301 which happens to be the math library included in avr libc If you use this on your linker command line lgrinutt flt then the linker will look for a library called libprint 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 18 program 9 8 Porting From to AVR GCC 9 8 1 Introduction C language was designed to be a portable language There two main types of port ing activities porting an application to a different platform OS and or processor and porting to a different compiler Porting to a different compiler can b
297. ion of channel 0 is just changing from up to down Likewise an overflow interrupt will be generated whenever the countdown reached BOTTOM value 0 where the counter will again alter its counting direction to upwards This informa tion is needed in order to know whether the current counter value of TCNTO is to be evaluated from bottom or top Further ioinit activates the pin change interrupt PCINTO on any edge of PB4 Finally PB1 OCOB will be activated as an output pin and global interrupts are being enabled In 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 33 2 2 project h order for the interrupt service routines to be as fast as possi ble some of the CPU registers are
298. irst resolving all include define etc directives The resulting program text will then be passed on to the assembler As the C preprocessor strips all C style comments preprocessed assembly source files can have both C style as well as assembly style comments At the top the IO register definition 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 ATtiny13 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 TOP as OCROA is set to 255 and timer 0 overflow timer 0 hits BOTTOM As dis cussed above these are kept as short as possible They only save SREG as the flags will be modified by the INC instruction increment the counter_hi variable which forms the high part of the current time counter the low part is formed by querying TCNTO directly and clear or set the variable flags respectively in order to note the current counting direction The RETI instruction terminates these interrupt service routines Total cycle count is 8 CPU cycles so together with the 4 CPU cycles needed for interrupt setup and the 2 cycles for the RJMP from the interrupt vector to the han dler these routines will require 14 out of each 256 CPU cycles or about 5 96 of the overall CPU time The pin change interrup
299. is fed into PB4 It will generate a pin change interrupt there on eache edge of the incoming signal The outgoing PWM is generated through OCOB of timer channel 0 PB 1 For demon stration purposes a LED should be connected to that pin like one of the LEDs of an 5 500 controllers run on their internal calibrated RC oscillators 1 2 on the Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 333 Combining C and assembly source files 175 tiny13 and 1 0 MHz on the ATtiny45 6 33 2 A code walkthrough 6 33 2 11 asmdemo c After the usual include files two variables are defined The first one pwm_incoming is used to communicate the most recent pulse width de tected by the incoming PWM decoder up to the main loop The second variable actually only constitutes of a single bit intbits pwm_ received This bit will be set whenever the incoming PWM decoder has updated pwm_incoming Both variables are marked volatile to ensure their readers will always pick up an up dated value as both variables will be set by interrupt service routines The function ioinit initializes the microcontroller peripheral devices In partic ular it starts timer 0 to generate the outgoing PWM signal on OCOB Setting OCROA to 255 which is the TOP value of timer 0 is used to generate a timer 0 overflow A interrupt on the ATtiny13 This interrupt is used to inform the incoming PWM decoder that the counting direct
300. is instructions without the SFR IO_REG_P test if you know that the register is in the I O space as with SREG for example If it isn t the assembler will complain I O address out of range 0 0x3f so this should be fairly safe If you do not define ___ SFR OFFSET so it will be 0x20 by default all special register addresses are defined as memory addresses so SREG is Ox5f and if code size and speed are not important and you don t like the ugly if above you can always use lds sts to access them But this will not work if SFR OFFSET 0x20 so use a different macro defined only if SFR OFFSET 0x20 for safety sts _SFR_ADDR SPMCR r24 In C programs all combinations of SFR 5 COMPAT and SFR OFFSET supported the SFR ADDR SPMCR macro be used to get the address of the SPMCR register 0x57 or 0x68 depending on device Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 19 lt avr sfr_defs h gt Special function registers 142 6 19 lt avr sfr_defs h gt Special function registers 6 19 1 Detailed Description When working with microcontrollers many of the tasks usually consist of controlling the peripherals that are connected to the device respectively programming the subsys tems that are contained in the controller which by itself communicate with the circuitry connected to the controller The AVR series of microcontrollers offers two different
301. ite_extended address Value __asm__ __volatile__ movw r30 A3 n t sts 1 C3 n t sts 0 2NnNt spm n t su i SFR_MEM_ADDR __SPM_REG i SFR_MEM_ADDR RAMPZ e r uint8 t BOOT PAGE WRITE uint32_t address 130 EI 8 5 2 11 define boot page write normal address Value __asm__ __volatile__ movw r30 2 n t sts 0 1 n t spm n t su i SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE WRITE r uint16_t address E30 32 8 5 2 12 define boot rww enable Value asm volatile sts 0 1 n t spmNn Nc i SFR MEM ADDR 5 REG r uint8 t BOOT RWW ENABLE coU E PEE V e Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 6 16 File Reference 221 8 5 2 13 define Value asm boot_rww_enable_alternate volatile sts 0 spm n t word Oxffff n t nop n t i _SFR_MEM_ADDR __SPM_REG uint8_t __BOOT_RWW_ENABLE 1NnNt 8 6 16 File Reference 8 6 1 Detailed Description Functions Static static static static inline uint16_t _crc16_update uint16_t __crc uint8_t _ data inline uint16_t_crc_xmodem_update uint16 t crc uint8 t data inline uint16_t crc ccitt update uint16 t crc uint8 t data i
302. jects are provided to illustrate several aspects of using the open source utilities for the AVR controller series It should be kept in mind that these de mos serve mainly educational purposes and are normally not directly suitable for use in any production environment Usually they have been kept as simple as sufficient to demonstrate one particular 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 32 Demo projects 173 to allow the reader to understand the basic concepts behind using the tools on an AVR microcontroller The more sophisticated demo project builds on top of that simple project and adds some controls to it It touches a number of avr libc s basic concepts on its way A comprehensive example on using the standard IO facilities intends to explain that complex topic using a practical microcontroller peripheral setup with one RS 232 con nection and an HD44780 compatible industry standard LCD display The Example using the two wire interface TWI project explains the use of the two wire hardware interface also known as I2C that is present on many AVR controllers Finally the Combining C and assembly source files demo shows how C and assem bly language source files can collaborate within one project While the overall p
303. l As this timer channel is required to run the out going PWM signal generation the incoming PWM decoding had to be adjusted to the constraints set by the outgoing PWM As PWM generation toggles the counting direction of timer 0 between up and down after each 256 timer cycles the current time cannot be deduced by reading TCNTO only but the current counting direction of the timer needs to be considered as well This requires servicing interrupts whenever the timer hits TOP 255 and BOTTOM 0 to learn about each change of the counting direction For PWM generation it is usually desired to run it at the highest possible speed so filtering the PWM frequency from the modulated output signal is made easy Thus the PWM timer runs at full CPU speed This causes the overflow and compare match interrupts to be triggered each 256 CPU clocks so they must run with the minimal number of processor cycles possible in order to not impose a too high CPU load by these interrupt service routines This is the main reason to implement the entire interrupt handling in fine tuned assembly code rather than in C In order to verify parts of the algorithm and the underlying hardware the demo has been set up in a way so the pin compatible but more expensive ATtiny45 or its siblings ATtiny25 and ATtiny85 could be used as well In that case no separate assembly code is required as two timer channels are avaible 6 33 1 Hardware setup The incoming PWM pulse train
304. l not be crashed For default version the width field and the pad to left symbol minus option will work in this case e The hh length modifier is ignored char argument is promouted to int More exactly this realization does not check the number of h symbols e 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 stream const char x fmt va list Variant of vfprintf that uses a fmt string that resides in program memory 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 st ream and processed in a way described by fmt Conver sion results will be assigned to the parameters passed via ap The format string 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 conv
305. l used registers r18 r27 r30 r31 May be allocated by gcc for local data You may use them freely in assembler subroutines Calling C subroutines can clobber any of them the caller is re sponsible for saving and restoring Call saved registers r2 r17 r28 r29 May be allocated by gcc for local data Calling C subroutines leaves them un changed Assembler subroutines are responsible for saving and restoring these registers if changed r29 r28 Y pointer is used as a frame pointer points to local data on stack if necessary Fixed registers r0 r1 Never allocated by gcc for local data but often used for fixed purposes rO temporary register can be clobbered by any C code except interrupt handlers which save it may be used to remember something for a while within one piece of assembler code rl assumed to be always zero in any C code may 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 the mul s u instructions which return their result in rl r0 Interrupt handlers save and clear rl 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
306. lection is always considered to be the EEPROM address for the next operation This packet is exactly the same as the one above sent before starting to read the device In case a master transmitter mode transfer is going to send more than one data packet all following packets will be considered data bytes to write at the indicated address The internal address pointer will be incremented after each write operation Note 16 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 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 7 2 ldiv t Struct Reference 213 7 1 2 0 intdiv 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 ldiv 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_
307. ler operators are available Why are interrupts re enabled in the middle of writing the stack pointer Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 307 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 9 9 2 My program doesn t recognize a variable updated within an interrupt rou tine When using the optimizer in a loop like the following one uint8_t flag ISR SOME_vect flag 1 while flag 0 the compiler will typically access 1 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 flag anyway To tell the compiler that this variable could be changed outside the scope of its code path analysis e g from within an interrupt routine the variable needs to be declared like volatile uint8_t flag Back to FAQ Index 9 9 3 I get undefined reference to for functions like sin In order to access the mathematical functions that are declared in lt math h gt the linker needs to be told to also link the mathematical library 1ibm a Typically system libraries like 1ibm a are given to the final C compiler command line that performs the linking step by adding a flag 1m at the end That is the initial lib and the filename suffix from the li
308. letter A in either upper or lower case represents 10 B represents 11 and so forth with 2 representing 35 If endptr is not NULL strtoul stores the address of the first invalid character in xendptr If there were digits at all however strtoul stores the original value of in endptr Thus if npt r is not NO but xxendptr is 710 return the entire string was valid The strtoul function return either the result of the conversion or if there was a lead ing minus sign the negation of the result of the conversion unless the original non negated value would overflow in the latter case strtoul returns ULONG MAX and errno is set to ERANGE If no conversion could be performed 0 is returned 6 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 81 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 characters i e one character for each bit plus one for the string terminator U
309. libc by Doxygen 9 9 Frequently Asked Questions 311 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 compilers might not do that optimization and as the C standard guarantees the initialization it is safe to rely on it Back to FAQ Index 9 9 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
310. lic functions are available to initialize the controller into 4 bit mode to wait for the controller s busy bit to be clear and to read or write one byte from or to the controller As there are two different forms of controller IO one to send a command or 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 36 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 hd44780_pulse_e function asserts a short pulse to the controller s E en able pin Since reading back the data asserted by the LCD controller needs to be performed while E is active this function reads and returns the input data if the param eter readback is true When called with a compile time constant parameter that is false the compiler will completely eliminate the unused readback operation as well as the return value as part of its optimizations As the controller is used in 4 bit interface mode all byte IO to
311. ll be needed Among other things the LCD4Linux project page describes many things around these displays including common pinouts Modules Combining C and assembly source files A simple project A more sophisticated project Using the standard IO facilities Example using the two wire interface TWI Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 333 Combining C and assembly source files 174 633 Combining C and assembly source files For time or space critical applications it can often be desirable to combine C code for easy maintenance and assembly code for maximal speed or minimal code size together This demo provides an example of how to do that The objective of the demo is to decode radio controlled model PWM signals and trol an output PWM based on the current input signal s value The incoming PWM pulses follow a standard encoding scheme where a pulse width of 920 microseconds denotes one end of the scale represented as 0 pulse width on output and 2120 microseconds mark the other end 100 output PWM Normally multiple channels would be encoded that way in subsequent pulses followed by a larger gap so the en tire frame will repeat each 14 through 20 ms but this is ignored for the purpose of the demo so only a single input PWM channel is assumed The basic challenge is to use the cheapest controller available for the task an ATtiny13 that has only a single timer channe
312. ll fail and the stream will remain unchanged 6 9 3 32 int vfprintf FILE stream const char va_list vfprintf is the central facility of the print f family of functions It outputs values to stream under control of a format string passed in fmt The actual values to print are passed as a variable argument list ap vfprintf returns the number of characters written to stream or EOF in case of an error Currently this will only happen if st ream has not been opened with write intent The format string is composed of zero or more directives ordinary characters not which are copied unchanged to the output stream and conversion specifications each of which results in fetching zero or more subsequent arguments Each conversion specification is introduced by the character The arguments must properly correspond after type promotion with the conversion specifier After the the following appear in sequence Zero or more of the following flags The value should be converted to an alternate form For c d i s and u conversions this option has no effect For o conversions the precision of the number is increased to force the first character of the output string to a zero except if a zero value is printed with an explicit precision of zero For x and X conversions a non zero result has the string or OX for X conversions prepended to it Generated on Mon Oct 29 20 02 34 200
313. lo r22 define len hi r21 define len lo r20 8 67 strncat 5 File Reference 8 67 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 define len hi r21 define len lo r20 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 68 strncmp S File Reference 254 8 68 strncmp S File Reference 8 68 1 Detailed Description Defines define s1 hi r25 define s1 lo r24 define s2_hi r23 define s2_lo r22 define len_hi r21 define len_lo r20 define ret_hi r25 define ret_lo 124 8 69 strncmp P S File Reference 8 69 1 Detailed Description Defines define 51 hi r25 define s1 lo r24 define 52 hi r23 define s2 lo 122 define len hi r21 define len lo r20 define ret hi r25 define ret lo 124 8 70 strncpy S File Reference 8 70 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 define len hi r21 define len lo r20 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 71 strncpy_P S File Reference 255 8 71 strncpy_P S File Reference 8 711 Detailed Description Defines define dest_hi r25 define dest_lo r24 define src_hi r23 define src_lo r22 define len_hi r21 define len_lo r20 8 72 strnlen S File Reference 8 72 1 Detailed Description Defines define src hi r25 define
314. logue 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 available for the AVR that use a similar naming con vention The historical naming style might become deprecated in a future release so it is not recommended for new projects Note The ISR macro cannot
315. lt Returns The strcat function returns a pointer to the resulting string dest 6 11 3 15 char x strchr const char src int val Locate character in string The strchr function returns a pointer to the first occurrence of the character val in the string 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 tstrlen s if the character is not found Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 11 lt string h gt Strings 88 6 11 3 17 int strcmp const char x 81 const char 52 Compare two strings The strcmp function compares the two strings s1 and s2 Returns The stremp 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 51 is considered to be less than 52 6 11 3
316. lways contains 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 1ags 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 va1 into an ASCII repre sentationthat will be stored under s The caller is responsible for providing sufficient storage in s Conversion is done in the format d ddd The minimum field width of the output string including the and the possible sign for negative values is given in width and prec determines the number of digits after the decimal sign width is signed value negative for left adjustment The dtostrf function returns the pointer to the converted string s 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 In a C context global destructors will be called before halting execution Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h
317. macros 15 16 17 19 20 32 38 40 52 71 82 93 99 102 124 125 137 142 140 145 147 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 3 avr libc Data Structure Index 10 lt avr wdt h gt Watchdog timer handling 149 lt util atomic h gt Atomicly and Non Atomically Executed Code Blocks 152 util crc16 h CRC Computations 156 lt util delay h gt Convenience functions for busy wait delay loops 159 lt util delay_basic h gt Basic busy wait delay loops 160 lt util parity h gt Parity bit generation 161 lt util setbaud h gt Helper macros for baud rate calculations 162 lt util twi h gt TWI bit mask definitions 164 lt compat deprecated h gt Deprecated items 169 lt compat ina90 h gt Compatibility with IAR EWB 3 x 172 Demo projects 172 Combining C and assembly source files 174 A simple project 177 A more sophisticated project 192 Using the standard IO facilities 200 Example using the two wire interface TWI 207 3 avr libc Data Structure Index 3 1 avr libc Data Structures Here are the data structures with brief descriptions div t 212 Idiv t 213 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 4 avr libc File Index 11 4 avr libc File Index 41 avr libc File List Here is a list of all documented files with brief descriptions assert h 213 atoi S 214 atol S 214 atomic h 214 boot h 215 16 221 ctype h 221 dela
318. 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 21 Introduction Many of the devices that are possible targets of avr libc have a minimal amount of RAM The smallest parts supported by the C environment come with 128 bytes of RAM This needs to be shared between initialized and uninitialized variables sections data and bss the dynamic memory allocator and the stack that is used for calling subroutines and storing local automatic variables Also unlike larger architectures there is no hardware supported memory management which could help in separating the mentioned RAM regions from being overwritten by each other The standard RAM layout is to place data vari
319. mccpy void const void int size t void memchr const void int size t PURE int memcmp const void const void size t ATTR_PURE Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 56 string h File Reference 251 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 ATTR_ PURE char strchrnul const char int PURE int strcmp const char const char x ATTR PURE char strcpy char const char int strcasecmp const char const char x ATTR_PURE char strcasestr const char const char ATTR PURE size t strcspn 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 PURE char strpbrk const char s const char xaccept A
320. med 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_set_udata The back end put and get functions can then extract this user data using fdev_get_udata and act appropriately For example a single put function could be used to talk to two different UARTs that way or the put and get functions could keep internal state between calls there Format strings in flash ROM All the printf and scanf family functions come in two flavours the standard name where the format string is expected to be in SRAM as well as a version with the suffix _P where the format string is expected to reside in the flash ROM The macro PSTR explained in lt avr pgmspace h gt Program Space Utilities becomes very handy for declaring these format strings Running stdio without malloc By default fdevopen requires malloc
321. 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 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 or
322. mns file Turn on the assembler listing The sub options are c omit false conditionals d omit debugging directives h include high level source 1 include assembly m include macro expansions n omit forms processing s include symbols file set 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 11 2 2 Examples for assembler options passed through the C compiler Re member that assembler options can be passed from the C compiler frontend using Wa see above so in order to include the C source code into the assembler listing in file foo 1st when compiling foo c the following compiler command line can be used avr gcc c 0 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 5 avr gcc c x assembler with cpp o foo o foo S Wa gstabs Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 11 Using the GNU tools 353 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 11 3 Controlling the linker avr l
323. my link command Relink the application using the following command to generate demo map a portion of which is shown below avr gcc g mmcu atmega8 Wl Map demo map o demo elf demo o Some points of interest in the demo map file are rela plt rela plt text 0x00000000 vectors vectors 0x00000000 0x00000000 0x00000000 x vectors x progmem gccx progmemx 0x00000026 0x00000026 trampolines trampolines 0x00000026 x trampolinesx 0x00000026 jumptables jumptablesx lowtext lowtextx 0x00000026 0 114 0 26 0 0 home joerg src 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 0 0 fini2 fini2 finil finil finiO finiO 0x00000112 xi finio 0x00000114 data 0x00800060 0x00800060 x data data 0x00800060 data 0x00800060 data 0x00800060 data 0x00800060 data 0x00800060 0x2 0x0 0 0 0 0 0 0 0 0 0 0 usr local lib gcc avr 4 2 2 avr4 libgcc a _exit o etext load address 0x00000114 PROVIDE data start demo o home joerg src avr libc avr lib avr4 atmega8 crtm8 o home joerg src avr libc avr lib avr4 exit o usr local lib gcc avr 4 2 2 avr4 libgcc a _exit o usr local lib gcc avr 4 2 2 avr4 libgcc a _copy_data
324. n 6 14 lt avr interrupt h gt Interrupts 107 Vector name Old vector Description Applicable for device name EEPROM_ SIG_ ATtiny2313 READY vect EEPROM READY SIG EE READY EE RDY vect SIG EEPROM Ready 9052333 AT90S4433 AT90S4434 AT90S8535 ATmegal6 ATmegal6l READY ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 ATmega8515 AT mega8535 ATtiny12 ATtiny13 ATtiny15 ATtiny26 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 EE_READY_ SIG_ EEPROM Ready AT90PWM3 AT90PWM2 AT90PWMI vect EEPROM_ AT90CAN128 AT90CAN32 AT90CANGA READY ATmegal03 ATmegal28 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega406 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 EXT INTO SIG External Interrupt ATtiny24 ATtiny44 ATtiny84 vect INTERRUPTO Request 0 INTO vect SIG External Interrupt AT90S1200 419052313 AT90S2323 INTERRUPTO 0 9052333 AT90S2343 AT90S4414 AT90S4433 419054434 419058515 AT90S8535 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6
325. n already carries a logical 1 when reading it so why does writing a logical to it clear the interrupt bit The solution is simple writing a logical to it requires only a single OUT instruction and it is clear that only this single interrupt request bit will be cleared There is no need to perform a read modify write cycle like an SBI instruction since all bits in these control registers are interrupt bits and writing a logical 0 to the remaining bits as it is done by the simple OUT instruction will not alter them so there is no risk of any race condition that might accidentally clear another interrupt request bit So instead of writing TIFR _BV TOVO wrong x simply use TIFR _BV TOVO Back to FAQ Index 9 9 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 9 27 Which AVR specific assembler operators are available See Pseudo ops and operators Back to FAQ Index 9 9 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently A
326. n bin lt install directory gt bin Configure configure N prefix installdir N infodir installdir info mandir installdir man 2 gt amp 1 tee Spackage configure log Make make all install 2 gt amp 1 tee Spackage make log Build the tools below in Cygwin AVaRICE Open source code package Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 344 Configure and build in a directory outside of the source code tree Set PATH in order lt MikTex executables gt usr local bin usr bin bin lt 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 N prefix installdir N datadir installdir doc N mandir installdir man N infodir installdir info N 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 lt MikTex executables gt usr local bin usr bin bin lt install directory gt bin
327. n how to handle interrupt code Since the C language tries to stay away from machine dependent details each compiler writer is forced to design their method of support In the AVR GCC environment the vector table is predefined to point to interrupt rou tines with predetermined names By using the appropriate name your routine will be called when the corresponding interrupt occurs The device library provides a set of default interrupt routines which will get used if you don t define your own Patching into the vector table is only one part of the problem The compiler uses by convention a set of registers when it s normally executing compiler generated code It s important that these registers as well as the status register get saved and restored The extra code needed to do this is enabled by tagging the interrupt function with attribute signal Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 103 These details seem to make interrupt routines a little messy but all these details are handled by the Interrupt API An interrupt routine is defined with ISR This macro register and mark the routine as an interrupt handler for the specified peripheral The following is an example definition of a handler for the ADC interrupt include lt avr interrupt h gt ISR ADC_vect user code here Refer to the chapter explaining assembler programming for an e
328. n the location referenced by endpt If the correct value would cause overflow plus or minus HUGE_VAL is returned ac cording to the sign of the value and ERANGE is stored in errno If the correct value would cause underflow zero is returned and ERANGE is stored in errno FIXME HUGE VAL needs to be defined somewhere The bit pattern is Ox7fffffff but what number would this be 6 10 4 27 long strtol const char __nptr char __endptr int __base 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 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 80 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 B represents 11 and so forth with 2 repres
329. n 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 wdt_disable return Back to FAQ Index 9 10 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 10 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 specify the installation directory by using the prefix dir option with the configure script It is important to install all
330. ncepts of an AVR microcontroller 6 35 1 Hardware setup The demo is set up in way so it can be run on the ATmega16 that ships with the STK500 development kit The only external part needed is a potentiometer attached to the ADC It is connected to a 10 ribbon cable for port both ends of the poten tiometer to pins 9 GND and 10 VCO and the wiper to pin 1 port A0 A bypass capacitor from pin 1 to pin 9 like 47 is recommendable 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 35 more sophisticated project 194 Port Header Color Function Connect to DO 1 brown RxD RXD of the RS 232 header 2 grey TxD TXD of the RS 232 header D2 3 black button SWO pin 1 down switches header D3 4 red button up SWI pin 2 switches header D4 5 green button SW2 pin 3 ADC switches header D5 6 blue LED LEDO pin 1 LEDs header D6 7 green clock out LED 1 pin 2 LEDs header D7 8 white 1 second LED 3 flash LEDs header GND 9 unused VCC 10 unused
331. nd 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 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 9 9 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 doe
332. ne INT64_MIN CINT64_MAX ILL define UINT64_MAX __CONCAT INT64_MAX U 2ULL 1ULL Limits of minimum width integer types define INT_LEAST8_MAX INT8_MAX define INT_LEAST8_MIN INT8_MIN define UINT_LEAST8_MAX UINT8_MAX define INT_LEAST16_MAX INT16_MAX define INT_LEAST16_MIN INT16_MIN define UINT_LEAST16_MAX UINT16_MAX define INT_LEAST32_MAX INT32_MAX define INT_LEAST32_MIN INT32_MIN define UINT_LEAST32_MAX UINT32_MAX define INT_LEAST64_MAX INT64_MAX define INT_LEAST64_MIN INT64_MIN define UINT_LEAST64_MAX UINT64_MAX Limits of fastest minimum width integer types define INT_FAST8_MAX INT8_MAX define INT_FAST8_MIN INT8_MIN define UINT_FAST8_MAX UINT8 MAX define INT_FAST16_MAX INT16_MAX define INT_FAST16_MIN INT16_MIN define UINT_FAST16_MAX UINT16_MAX define INT FAST32 MAX INT32 MAX define INT FAST32 MIN INT32 MIN define FAST32 MAX UINT32 define INT FAST64 MAX INT64 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 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 g
333. ne NONATOMIC FORCEOFF 6 23 2 Define Documentation 6 23 2 1 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 23 2 2 ftdefine ATOMIC FORCEON Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 23 lt util atomic h gt Atomicly and Non Atomically Executed Code Blocks 155 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 23 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
334. 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 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 n t 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 inst
335. nerated srec elf j echo empty 5068 not generated echo empty not generated eeprom c eeprom change section lma exit 0 eeprom change section 1ma exit 0 hange section lma exit 0 eeprom 0 O eeprom 0 O eeprom 0 O Every thing below here is used by avr libc s build system and by the casual user FIG2DEV EXTRA CLEAN FILES dox eps png pdf eps PRG eps png PRG png pdf PRG pdf eps fig 5 FIG2DEV pdf fig 5 FIG2DEV png fig 5 FIG2DEV L eps L pdf L png fig2dev hex bin srec lt Se lt Se lt 6 34 8 Reference to the source code The source code is installed under Sprefix share doc avr libc examples demo ihex lt 8 srec lt 8 binary lt can be ignored where prefix is a configuration option For Unix systems it is usually set to either usr or usr local 6 35 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 35 more sophisticated project 193 Understanding this project assumes the simple project has been understood in full as well as being acquainted with the basic hardware co
336. next data packet following the device selection only allows for 8 bits that are used as an EEPROM address devices that require more than 8 address bits 24C04 and above steal subaddress bits and use them for the EEPROM cell address bits 9 to 11 as re quired This example simply assumes all subaddress bits are 0 for the smaller devices so the 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 37 Example using the two wire interface TWD 210 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 EEPROMS 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
337. nline uint8 t crc ibutton update uint8 t _ crc uint8 t data 8 7 ctype h File Reference 8 7 1 Detailed Description Defines define CTYPEH 1 define ATTR CONST _ attribute const Functions Character classification routines These functions perform character classification They return true or false status depending whether the character passed to the function falls into the function s classification i e isdigit returns true if its argument is any value 0 though 9 inclusive intisalnum int c CONST Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 8 delay h File Reference 222 int isalpha int c ATTR_CONST__ int isascii int c ATTR CONST int isblank int ATTR CONST intiscntrl int ATTR CONST intisdigit int _ ATTR CONST intisgraph int CONST int islower int c CONST int isprint int CONST int ispunct int ATTR CONST __ int isspace int ATTR CONST __ int isupper int _ ATTR_CONST__ intisxdigit int ATTR_CONST__ Character convertion routines If c is not an unsigned char value or EOF the behaviour of these functions is undefined inttoascii int ATTR CONST e int tolower int ATTR CONST e int toupper int c ATTR CONST __ 8 8 delay h File Reference 8 8 1 Detailed Description Defines define UTIL DELAY H 1 defin
338. nt h gt Standard Integer Types 48 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 an uint fast32 t can hold 6 8 2 49 define UINT FAST64 MAX UINT64 MAX 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 6 8 2 51 define UINT LEASTI16 MAX UINTI6 largest value an uint least16 t can hold 6 8 2 52 define UNT LEAST32 MAX UINT32 largest value an uint least32 t can hold 6 8 2 53 define UNT 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 _ CONCAT value ULL define a constant of type uintmax t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 49 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 31 typedef signed int 16 t 16 bit signed type 6 8 3 2 typedef signed long int int32
339. nt has been merged into the documentation for avr libc The latest version is now available at http savannah nongnu org projects avr libc 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 288 I SFR IO ADDR PORTD 4 Clobbered registers left empty in our example You can write assembler instructions in much the same way as you would write assem bler programs However registers and constants are used in a different way if they refer to expressions of your C program The connection between registers and C operands is specified in the second and third part of the asm instruction the list of input and output operands respectively The general form is asm code output operand list input operand list clobber list In the code section operands are referenced by a percent sign followed by a single digit 0 refers to the first 1 to the second operand and so forth From the above example Orefers to r
340. ntegral power of 2 The 1 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 If the argument is less than or equal 0 a domain error will occur 6 6 3 24 double log10 double x log10 function returns the logarithm of argument x to base 10 If the argument is less than or equal 0 a domain error will occur 6 6 3 25 double modf double value double The modf function breaks the argument value into integral and fractional parts each of which has the same sign as the argument It stores the integral part as a double in the object pointed to by iptr The modf function returns the signed fractional part of value Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 6 lt math h gt Mathematics 37 Note This implementation skips writing by zero pointer 6 6 3 26 double pow double double y The function pow returns the value of x to the exponent y 6 6 3 27 int signbit double x The signbit function returns a nonzero value if the value of x has its sign bit set This is not the same as x lt 0 0 because IEEE 754 floating point allows zero to be signed The comparison 0 0 lt 0 0 is false but signbit 0 0 will return a nonzero value Note This implementation returns 1 if sign bit is set 6 6 3 28 double sin double
341. nter Do you have MinGW installed Press y and press enter Where is your MinGW installation Type in c mingw without quotes and press enter Do you wish for me to add mount bindings for c mingw to mingw Press y and press enter It will display some messages the screen then it will display Press any key to continue Press any key Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 337 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 lt http downloads sourceforge net mingw msys autoconf 2 59 tar bz2 use_ mirror internap gt Extract to c msys 1 0 automake 1 8 2 automake 1 8 1 9 is needed to build avr libc in MinGW http downloads so
342. nter register and memcpy_P is called strcpy_P buf p 62 69 1 ldd r22 Y 33 E 84 7a al idd r23 Y 34 F 86 ce 01 movw r24 r28 88 01 96 adiw r24 0 01 8a Oc reall 24 0 21 0 22 4 Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 320 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 compile time Back to FAQ Index 9 9 16 How to use external RAM Well there is no universal answer to this question it depends on what the external RAM is going to be used for Basically the bit SRE SRAM enable in the MCUCR register needs to be set in order to enable the external memory interface Depending on the device to be used and the application details further registers affecting the external memory operation like XMCRA and XMCRB and or further bits in MCUCR might be configured Refer to the datasheet for details If the external RAM is going to be used to store the variables from the C program i e the data and or bss segment in that memory area it is essential to set
343. nul_P S File Reference 22222222 22 22 22 2 249 8491 Detailed Description 2 2 2 22 2 2 2 22 52 249 stromp s Pile Reference 2 6 cu cere s was RR RIS 249 8 50 1 Detaled Description ecce ERES 249 sremp P S Pile Reference 2 4 06 6 4 cmo RR E 249 8 51 1 Detailed Description 249 sttcpy o File Reference c occ ee h W S N 249 6 52 1 Detailed Description gt e e ecce 54855 ROG y sea Res 249 stepy FS File Reference uu lux EE ee E ud eS 250 8 53 1 Detaled 222 22 22 250 strospn S File Reference oomo oos q Q rms 250 8 54 1 Detailed Description gt e sro ea so s er aotar 250 strespn PS File Reference Lus so dorade aira om s p e 250 5 55 1 Detailed Description 2 250 stime h File 22 22 2222 02 250 8 56 1 Detaled Description 22 2 22 222 250 stilcatS File Reference oo onu sa s s b ee ee NUS N 252 8 57 1 Detaled Description Rm RB 252 stricat ES File Reference zs eR SE RR 252 8 8 1 Detailed Description 252 stiicpy o File Reference 2 Rok RR 252 3 59 1 Detaled Description cc o RR c REG 252 P S File Reference 2 goe lt oma m doy S A eS 252 5 60 1 Detailed Description 222 22 2 2 2 2 252 5 File Reference wu olm w 225 252 8 61 1 Detailed Description gt soe saone mn 252 Generated on Mon Oct 29 20
344. number for the square wave output Note that the right hand side consists of a CPP macro which will be substituted by its value 6 in this case before actually being passed to the assembler Note 4 The assembler uses integer operations in the host defined integer size 32 bits or longer when evaluating expressions This is in contrast to the C compiler that uses the C type int by default in order to calculate constant integer expressions In order to get a 100 kHz output we need to toggle the PD6 line 200000 times per second Since we use timer 0 without any prescaling options in order to get the de sired frequency and accuracy we already run into serious timing considerations while accepting and processing the timer overflow interrupt the timer already continues to count When pre loading the TCCNTO register we therefore have to account for the number of clock cycles required for interrupt acknowledge and for the instructions to reload TCCNTO 4 clock cycles for 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 284 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 s1200 o Note 6 The main loop is jus
345. nvert a string to an integer The atoi function converts the initial portion of the string pointed to by s to integer representation In contrast to int strtol s char NULL 10 this function does not detect overflow errno is not changed and the result value is not predictable uses smaller memory flash and stack and works more quickly 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 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 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 that order and should return an integer less than equal to or greater than zero if the key object is found
346. o be applied to IO ports the emulation actually uses standard C methods so they could be applied to arbitrary memory locations as well define inp port port define outp val port port val define inb port port define outb port val port val define sbi port bit port 1 lt lt bit define cbi port bit port amp 1 lt lt bit 6 30 2 Define Documentation 6 30 2 1 define cbi port bit port amp 1 lt lt bit Deprecated Clear bit in IO port port 6 30 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 30 2 3 define inb port port Deprecated Read a value from an IO port port Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 30 lt compat deprecated h gt Deprecated items 171 6 30 2 4 define inp port port Deprecated Read a value from an IO port port 6 30 2 5 define INTERRUPT signame Value void signame void __attribute__ interrupt __INTR_ATTRS void signame void Deprecated Introduces an interrupt handler function that runs with global interrupts ini
347. o but the compiler didn t update the memory location for optimization reasons The worst thing you can do this case is uint8_t s asm volatile in 0 SREG ADNET cli NND ld _ tmp reg 1 Wo NE inc tmp reg uA st al tmp reg ene out SREG 0 WAYNE 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 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 produ
348. o 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 the 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 0 00 0 01 0 02 0 03 0 04 0 05 0 06 0 07 0 08 0 09 0 0 0 0 0 0 0 0 0 0 0 0 0 10 0 11 0 12 0 13 0 14 0 15 0 16 0 17 0 18 0 19 0 1 0 1 0 1 0 1 Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 4 Data in Program Space 277 0x1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0 28 0 29 0 2 0 2 0 2 0 2 0 2 0 2 0 30 0 31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C
349. o 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 header file here The main reason is that this file defines the value of F_CPU which needs to be known before including lt utils delay h gt The function ioinit summarizes all hardware initialization tasks As this function is declared to be module internal only 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 1cd_st r which is specified to only perform output operations can be given as NULL The stream uart_str corresponds to input and output operations performed
350. o 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 1 Toolchain Overview 263 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 object files including disassembly avr size List section sizes and total size avr nm List symbols from object files avr strings List printable strings from files avr strip Discard symbols from files avr readelf Display the contents of ELF format files avr addr2line Convert addresses to file and line avr c filt Filter to demangle encoded C symbols Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 1 Toolchain Overview 264 9 1 5 avr libc GCC and Binutils provides a lot of the tools to develop software but there is one cri
351. o oo Pe Q N Ree 213 Tl Detaled Descriphon lt s ooe ears o Sox 213 722 Field Documentation lt s a m sa s s k om eg 213 8 avr libc File Documentation 213 File Referenoe eo uoo ae p e Q x RUE Ee Xs 213 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS 8 1 1 Detailed Description 82 dns Pile Referente uos os NUS 821 Detaled Description 222 22 222 5 3 mols File Reference 22222222222 2 8 3 1 Detailed Description 84 atomic h File 22 2 8 4 1 Detailed Description 85 booth File Reference 2 8 5 1 Detailed Description cs seo ses ess 8 5 2 Define Documentation 8 6 r l6 h File Reference o s a s esa Re 8 6 1 Detailed Description 2 57 ctype Pile Reference s cacce entesa ka sn 871 Detailed Description 222 288 5554 8 8 delayh Fil Reference 8 8 1 Detailed Description 8 9 delay_basic h File Reference 8 9 1 Detailed Description 2 8 10 eeprom h File Reference 2 8 10 1 Detailed Description 8 11 File Reference scs cesc mx n 4 8 11 1 Detailed Description 8 12 idevopen c File Referenc 8 12 1 Detaled Description 2 5456 re 8 13 15 5 Pile Reference gt o 2 a a e a ee 8 13 1 Detailed Description
352. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 39 stdio h File Reference 244 typedef int8_t int_least8_t typedef uint8_t uint_least8_t typedef int16_t int_least16_t typedef uint16_t uint_least16_t typedef int32_t int_least32_t typedef uint32_t uint_least32_t typedef int64_t int_least64_t typedef uint64_t uint_least64_t Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8_t int_fast8_t typedef uint8_t uint_fast8_t typedef int16_t int_fast16_t typedef uint16_t uint_fast16_t typedef int32_t int_fast32_t typedef uint32_t uint_fast32_t typedef int64_t int_fast64_t typedef uint64_t uint_fast64_t Greatest width integer types Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category typedef int64_t intmax_t typedef uint64_t uintmax_t 8 39 stdio h File Reference 8 39 1 Detailed Description Defines define STDIO 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 s
353. on include lt stdio h gt Introduction to the Standard IO facilities This file declares the standard IO facili ties that are implemented in avr 1libc Due to the nature of the underlying hardware only a limited subset of standard IO is implemented There is no actual file implementa tion available so only device IO can be performed Since there s no operating system the application needs to provide enough details about their devices in order to make them usable by the standard IO facilities Due to space constraints some functionality has not been implemented at all like some of the printf conversions that have been left out Nevertheless potential users of this implementation should be warned the printf and scanf families of functions although usually associated with presumably simple things like the famous Hello world program are actually fairly complex which causes their inclusion to eat up a fair amount of code space Also they are not fast due to the nature of interpreting the format string at run time Whenever possible resorting to the sometimes non standard predetermined conversion facilities that are offered by avr libc will usually cost much less in terms of speed and code size Tunable options for code size vs 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
354. on Controls a LED that can be directly connected from OC1 OC1A to GND The brightness of the LED is controlled with the PWM After each period of the PWM the PWM value is either incremented or decremented that s all SId demo c v 1 9 2006 01 05 21 30 10 joerg_wunsch Exp 5 include lt inttypes h gt include lt avr io h gt include lt avr interrupt h gt include lt avr sleep h gt include iocompat h Note 1 enum UP DOWN ISR TIMERI_OVF_vect Note 2 static uint16_t pwm x Note 3 static uint8_t direction switch direction Note 4 case UP if pwm direction DOWN break case DOWN if pwm 0 direction UP break OCR pwm x Note 5 x void ioinit void Note 6 Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys TCCRIA TIMER1_PWM_INIT x Start timer 1 x TCCRIA TCCRIB could actually be the same register so take care to not clobber it TCCR1B TIMERI_CLOCKSOURCE x Run device dependent timer 1 setup hook if present Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 181 x if defined TIMER1 SETUP HOOK TIMER1 SETUP HOOK endif Set PWM value to 0 OCR 0 Enable as output DDROC _BV OC1 Enable timer 1 overflow interrupt TIMSK TOIE1 sei
355. on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 385 WDTO_500MS avr_watchdog 151 WDTO_60MS avr_watchdog 151 WDTO_8S avr_watchdog 151 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen
356. onstant at compile time is not recommended and might result in a huge amount of code generated Returns The _FFS macro returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 6 11 3 Function Documentation 6 11 3 1 int ffs int val const This function finds the first least significant bit set in the input value Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 11 lt string h gt Strings 84 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 ffs long const Same as ffs for an argument of type long 6 11 3 3 int ffsll long Jong const 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 no 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 x memchr const void x src int val size t len Scan memory for a character The mem
357. org cgi cvsweb cgi ports devel avr binutils files patch ne 9 10 5 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 333 bunzip2 gcc lt version gt tar bz2 tar xf cd gcc lt version gt mkdir obj avr cd obj avr configure prefix SPREFIX target avr enable languages c c N disable nls disable libssp with dwarf2 make make install X Xr Xo To save your self some download time you can alternatively download only the gcc core version tar bz2 and gcc c lt version gt tar bz2 parts of the gcc Also if you don t need C support you only need the core part and should only enable the C language support Note Early versions of these tools did not support C The stdc libs are not included with C for AVR due to the size limitations of the devices The official version of GCC might lack support for recent AVR devices A patch that adds more AVR types can be found at http www freebsd org cgi cvsweb cgi ports devel avr gcc files patch newdevi 9 10 6 AVR Libc Warning You must install avr binutils avr gcc and make sure your path is set properly before installing avr libc Note If you have obtained the latest avr l
358. ormation about Variable Attributes avr libc provides a convenience macro for the Variable Attribute include lt avr pgmspace h gt 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 avr pgmspace h All Program Memory handling macros are defined there There is also a way to create a method to define variables in Program Memory that is common between the two compilers IAR and AVR GCC Create a header file that has these definitions fif defined ICCAVR IAR C Compiler define FLASH DECLARE x flash x endif if defined __GNUC__ GNU Compiler define FLASH DECLARE x x attribute__ _progmem__ endif This code snippet checks for the IAR compiler or for the GCC compiler and defines a macro FLASH_DECLARE x that will declare a variable in Program Memory using the appropriate method based on the compiler that is being used Then you would used it like so FLASH_DECLARE int mydata 9 8 6 Non Returning main To declare main to be a non returning function in it is done like this C task void main void code Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 305
359. ot h gt Bootloader Support Utilities 96 6 12 2 3 define boot lock bits set safe lock bits Value do boot spm busy wait N eeprom busy wait boot_lock_bits_set lock_bits while 0 Same as boot_lock_bits_set except waits for eeprom spm operations to complete before setting the lock bits 6 12 2 4 define boot lock fuse bits get address result Value __extension__ uint8_t __result __asm__ __volatile__ Idi r30 3 n t ldi r31 O n t sts 1 2 n t lpm 0 Z n t io ex result N i SFR MEM ADDR __SPM_REG N UINES_t BOOT LOCK BITS SET N M address N rO r30 r31 N N N 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 ie a bit returned as 0 means the corresponding fuse or lock bit is programmed 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 97 6 12 2 6 define boot page erase safe address Value do boot spm busy wait eeprom_busy_wait boot_page_
360. ouble _ x ATTR CONST ATTR CONST double copysign double x double y double double x double y CONST double fma double x double y double z CONST double fmax double x double y CONST double fmin double x double y CONST int signbit double x _ CONST double double x ATTR CONST ATTR CONST int isfinite double x double hypot double x double y 8 20 memccpy S File Reference 8 20 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 define val lo r20 define len hi r19 define len lo r18 define ret hi r25 define ret lo r24 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 821 memchr S File Reference 230 8 21 memchr S File Reference 8 21 1 Detailed Description Defines define src hi r25 define src_lo r24 define val lo r22 define len hi r21 define len lo r20 define ret hi r25 define ret lo r24 8 22 memchr PS File Reference 8 22 1 Detailed Description 8 23 memcmp S File Reference 8 23 1 Detailed Description Defines define 51 hi r25 define 51 lo 124 define s2 hi r23 define s2 lo 122 define len hi r21 define len lo r20 define ret hi r25 define ret lo r24 8 24 memcmp 5 File Reference 8 24 1 Detailed Description 8 25 memcpy S
361. our assembler code void delay uint8 t ms uint16_t cnt asm volatile An L_dli n t mov 0 2 n t mov B0 B2 Nn IL 412 n t sbiw A0 1 n t brne L_dl2 n t dec 81 n t brne L_dli n t amp w cnt r ms r delay_count Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 297 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 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 t
362. ous character u control U ASCII NAK deletes the entire input buffer Aw control W ASCII ETB deletes the previous input word delimited by white space r control R ASCII DC2 sends a Vr then reprints the buffer refresh t tabulator will be replaced by a single space The function uart_init takes care of all hardware initialization that is required to put the UART into a mode with 8 data bits no parity one stop bit commonly referred to as 8N1 at the baud rate configured in defines h At low CPU clock frequencies the U2X bit in the UART is set reducing the oversampling from 16x to 8x which allows for a 9600 Bd rate to be achieved with tolerable error using the default 1 MHz RC oscillator The public function uart_putchar again has suitable arguments for direct use by the stdio stream interface It performs the n into r n translation by recursively Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 37 Example using the two wire interface TWD 207 calling itself when it sees a Nn 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 ch
363. ovide a foun dation for a software development toolchain Note that these projects were designed to originally run on Unix like systems 9 1 3 GCC stands for GNU Compiler Collection GCC is highly flexible compiler system It has different compiler front ends for different languages It has many back ends that generate assembly code for many different processors and host operating systems All share a common middle end containing the generic parts of the compiler including a lot of optimizations In GCC a host system is the system processor OS that the compiler runs on A Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 1 Toolchain Overview 262 target system is the system that the compiler compiles code for And a system is the system that the compiler is built from source code on If a compiler has the same system for host 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 tar
364. p Variant of vsprintf that uses a fmt string that resides in program memory Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 71 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 __ 5 int radix char utoa unsigned int val char x__s int radix char ultoa unsigned long int __ val char _ 5 int long random void void srandom unsigned long __ seed long random_r unsigned long ctx char itoa int __ val char __s int radix define RANDOM_MAX Ox7FFFFFFF Conversion functions for double arguments Note that these functions are not located in the default library 1ibc a but in the mathematical library 1ibm a So when linking the application the 1m option needs to be specified e char dtostre double val char s unsigned char __ prec unsigned char flags e char dtostrf double __val signed char __ width unsigned char prec char S define DTOSTR_ALWAYS_SIGN 0x01 define DTOSTR_PLUS_SIGN 0x02 define DTOSTR_UPPERCASE 0x04 Defines define RAND MAX Ox7FFF Generated on Mon Oct 29 20 02 34 2
365. p If malloc heap endis 0 the allocator attempts to detect the bottom of stack in order to prevent a stack heap collision when extending the actual size of the heap to gain more space for dynamic memory It will not try to go beyond the current stack limit decreased by malloc margin bytes Thus all possible stack frames of interrupt routines that could interrupt the current function plus all further nested function calls must not require more stack space or they will risk colliding with the data segment The default value of malloc 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 address points just beyond that header Thus if the application accidentally writes before the returned memory region the internal consistency of the memory al locator is compromised The implementation maintains a simple freelist that accounts for memory blocks that have been returned in previous calls to free Note that all of this memory is considered Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 270 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 rath
366. pace h 233 ELPM dword enhanced pgmspace h 234 ELPM enhanced pgmspace h 234 ELPM word classic pgmspace h 234 ELPM word enhanced pgmspace h 235 LPM classic pgmspace h 235 LPM dword classic pgmspace h 236 LPM dword enhanced pgmspace h 236 LPM enhanced pgmspace h 237 LPM word classic pgmspace h 237 LPM word enhanced pgmspace h 237 boot lock bits set boot h 215 boot lock bits set alternate boot h 215 boot page erase alternate boot h 216 boot page erase extended boot h 216 boot page erase normal boot h 216 boot page fill alternate boot h 217 boot page fill extended boot h 217 boot page fill normal boot h 218 boot page write alternate boot h 218 boot page write extended boot h 218 boot page write normal boot h 219 boot rww enable boot h 219 boot rww enable alternate boot h 219 compar fn t avr stdlib 72 malloc heap end avr stdlib 80 malloc heap start avr stdlib 80 malloc margin avr stdlib 81 crc16 update util crc 156 ccitt update util crc 156 crc ibutton update util crc 157 crc xmodem update util crc 157 delay loop 1 util delay basic 160 delay loop 2 util delay basic 160 delay ms util delay 159 delay us util delay 159 wdt write wdt h 259 A more sophisticated project 191 A simple project 176 abort avr stdlib 72 abs avr stdlib 72 acos avr math 33 Addi
367. paradigms to perform this task There s a separate IO address space available as it is known from some high level CISC CPUs that can be addressed with specific IO instructions that are applicable to some or all of the IO address space in out sbi etc The entire IO address space is also made available as memory mapped IO i e it can be accessed using all the MCU instructions that are applicable to normal data memory The IO register space is mapped into the data memory 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 either address 0x60 or 0x100 depending on the device AVR Libc supports both these paradigms While by default the implementation uses memory mapped IO access this is hidden from the programmer So the programmer can access IO registers either with a special function like outb include lt avr io h gt outb PORTA 0x33 or they can assign a value directly to the symbolic address PORTA 0x33 The compiler s choice of which method to use when actually accessing the IO port is completely independent of the way the programmer chooses to write the code So even if the programmer uses the memory mapped paradigm and writes PORTA 0 40 the compiler can optimize this into the use of an sbi instruction of course provided the target address is within the allowable rang
368. pbrk P 135 strrchr P 135 strsep P 135 strspn P 136 strstr P 136 avr sfr BV 142 bit is clear 143 bit is set 143 loop until bit is clear 143 loop until bit is set 143 avr sleep set sleep mode 146 sleep cpu 146 sleep disable 146 sleep enable 146 sleep mode 146 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 368 SLEEP_MODE_ADC 145 SLEEP_MODE_EXT_STANDBY 145 SLEEP_MODE_IDLE 145 SLEEP_MODE_PWR_DOWN 145 SLEEP_MODE_PWR_SAVE 145 SLEEP_MODE_STANDBY 145 avr_stdint 6 43 6 MAX 43 INT16 MIN 43 int16 t 48 INT32 C 43 INT32 MAX 43 INT32 MIN 43 int32 t 48 INT64 C 43 INT64 MAX 43 INT64 MIN 43 int64 t 48 INT8_C 43 INT8 MAX 43 INT8 MIN 43 int8 t 48 INT FAST16 MAX 44 INT FASTI16 MIN 44 int fastl6 t 48 INT FAST32 MAX 44 INT FAST32 MIN 44 int_fast32_t 48 INT FAST64 MAX 44 INT FAST64 MIN 44 int fast64 t 48 INT FAST8 MAX 44 INT FASTS MIN 44 int fast8 t 48 INT LEAST16 MAX 44 INT LEASTI16 MIN 44 int 1 5 16 t 49 INT LEAST32 MAX 44 INT LEAST32 MIN 45 int least32 t 49 INT LEAST64 MAX 45 INT LEAST64 MIN 45 int least64 t 49 INT LEAST8 MAX 45 INT LEASTS MIN 45 int least8 t 49 INTMAX C 45 INTMAX MAX 45 MIN 45 intmax t 49 INTPTR MAX 45 MIN 45 intptr_t 49 PTRDIFF_MAX 45 PTRDIFF_MIN 46 SIG_ATOMIC_MAX 46 SIG_ATOMIC_MIN 46 SIZE_MAX
369. ple at 0 100 the compiler then tests the low byte for 0 which succeeds It then proceeds to test the high byte but that moment the ISR triggers and the main context is interrupted The ISR will decrement the variable from 0x100 to OxFF and the main context proceeds It now tests the high byte of the variable which is now also 0 so it concludes the variable has reached 0 and terminates the loop Using the macros from this header file the above code can be rewritten like include inttypes h include lt avr interrupt h gt include lt avr io h gt include lt util atomic h gt volatile uint16_t ctr ISR TIMER1_OVF_vect GEr 5 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 23 lt util atomic h gt Atomicly and Non Atomically Executed Code Blocks 154 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 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 defi
370. pointer to unsigned int u Matches an optionally signed decimal integer the next pointer must be a pointer to unsigned int x Matches an optionally signed hexadecimal integer the next pointer must be a pointer to unsigned int f Matches an optionally signed floating point number the next pointer must be a pointer to float 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 leading white space is suppressed To skip white space f irst use an explicit space in the format Matches a nonempty sequence of characters from the specified set of accepted characters the next pointer must be a pointer to char and there must be enough room for all the characters in the string plus a terminating NUL character The usual skip of leading white space is suppressed The string is to be made up Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 69 of characters in or not in a particular set the
371. positive value an int fast64 t can hold 6 8 2 18 ftdefine 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 MAX 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 46 6 8 2 23 define INT LEAST32_MAX 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 1625464 t can hold 6 8 2 27 define INT LEAST8 MAX INT8 MAX largest positive value an int least8 t can hold 6 8 2 28 define INT LEAST8 MIN INT8 MIN smallest negative value an int least8 t can hold 6 8 2 29 define INTMAX_C value _ CONCAT 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 negati
372. printf char __s size_t __n const char __fmt va_list ap int vsnprintf P char __s size_t __n const char __fmt va_list ap int fprintf FILE stream const char fmt int fprintf 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 __c FILE stream char fgets char str int size FILE stream char gets char str size_t fread void size t size size t nmemb FILE stream void clearerr FILE stream int feof FILE stream int ferror FILE stream int vfscanf FILE stream const char fmt va list int vfscanf P FILE stream const char fmt va list int fscanf FILE stream const char fmt int fscanf P FILE stream const char fmt int scanf const char fmt int scanf P const char fmt int vscanf const char fmt va_list int sscanf const char buf const char fmt int sscanf_P const char buf const char fmt int fflush FILE xstream FILE x fdevopen int put char FILE int xget FILE Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facili
373. r manently bind a variable to a register For a very detailed discussion of setimp longjmp see Chapter 7 of Advanced Pro gramming in the UNIX Environment by W Richard Stevens Example include setjmp h jmp buf env int main void if setjmp env handle error main processing loop which calls some where void foo void blah blah blah iss if err Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 7 lt setjmp h gt Non local goto 39 longjmp env 1 Functions int setimp imp_buf __jmpb e void longjmp jmp_buf __jmpb int ret ATTR NORETURN 6 7 2 Function Documentation 6 7 2 1 void longjmp jmp buf __jmpb int ret Non local jump to a saved stack context finclude lt setjmp h gt longjmp restores the environment saved by the last call of setjmp with the corre sponding jmpb argument After longjmp is completed program execution contin ues as if the corresponding call of setjmp had just returned the value ret Note longjmp cannot cause 0 to be returned If longjmp is invoked with a second argument of 0 1 will be returned instead Parameters jmpb Information saved by a previous call to setjmp ret Value to return to the caller of setjmp Returns This function never returns 6 7 2 2 intsetjmp jmp buf jmpb Save stack context for non local goto include lt setjmp h gt setjmp
374. r to the memory area dest 6 11 3 12 int strcasecmp const char s1 const char 52 Compare 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 consequence of the ordering used by strcasecmp is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 11 lt string h gt Strings 87 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 51 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 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 resu
375. r x PGM_P int strcasecmp_P const char PGM_P _ATTR_PURE char strcasestr P const char x PGM_P __ATTR_PURE size_t strcspn_P const char s PGM_P reject _ ATTR_PURE size_t strlcat_P char x size_t size_t strlcpy_P char PGM_P size_t size_t strlen_P PGM_P __ATTR_CONST size_t strnlen_P size_t _ ATTR_CONST int strnemp_P const char PGM_P size_t _ ATTR_PURE int strncasecmp_P const char x PGM_P size_t _ ATTR_PURE char strncat_P char PGM_P size_t char strncpy_P char size_t char strpbrk_P const char xs PGM_P accept ATTR_PURE PGM_P strrchr_P PGM_P s int val ATTR CONST char strsep P char sp PGM_P delim size_t strspn_P const char s PGM P accept ATTR_PURE char strstr P const char PGM P ATTR PURE 8 33 2 Define Documentation 8 33 21 define ELPM classic addr Value extension N uint32 t _ addr32 uint32 t addr uint8 t _ result N asm N N out 2 SUI N now r31 SBI Age b PGM VOID memrchr PGM VOID P s int val size t len ATTR Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 33 pgmspace h File Reference 235 mov r30 1 elpm mov y EO result 8 33 22 define Value L extension n t 0 ro n t n t result
376. r24 7 inc r24 st 7 r24 sei One easy solution to avoid clobbering register r24 is to make use of the special tem porary register tmp reg defined by the compiler asm volatile cli ld _tmp_reg__ a0 inc __tmp_reg__ st a0 __tmp_reg__ sel e ptr n t n t n t n t n t The compiler is prepared to reload this register next time it uses it Another problem with the above code is that it should not be called in code sections where interrupts are disabled and should be kept disabled because it will enable interrupts at the end We may store the current status but then we need another register Again we can solve this without clobbering a fixed but let the compiler select it This could be done with the help of a local C variable uint8_t s asm volatile in 0 sli ld _tmp_reg__ 1 inc tmp_reg__ st Sal __tmp_reg__ out __SREG__ 0 amp r s an e ptr LA ob Es mne wha MATINET Generated Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 295 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 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 to
377. rball to savannah 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 9 13 Release Numbering and Methodology 359 9 13 2 2 Making release 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 a make distcheck and make sure it succeeds This will create the source tarball Tag the release cvs tag avr libe major minor patch release Upload the tarball to savannah Update the NEWS file and commit to cvs Add Changes since avr libc major minor
378. rcmp 86 strepy 87 BADISR_vect strespn 87 avr_interrupts 120 strlcat 87 BAUD_TOL strlcpy 88 util_setbaud 163 strlen 88 bit_is_clear strlwr 88 avr_sfr 143 strncasecmp 88 bit_is_set strncat 89 avr_sfr 143 strncmp 89 boot h 214 strncpy 89 boot lock bits set 215 strnlen 89 boot lock bits set alternate 215 strpbrk 90 boot page erase alternate 216 strrchr 90 boot page erase extended 216 strrev 90 boot page erase normal 216 strsep 90 boot page fill alternate 217 strspn 91 boot page fill extended 217 strstr 91 boot page fill normal 218 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 371 boot_page_write_alternate 218 cbi boot_page_write_extended 218 deprecated_items 169 boot_page_write_normal 219 ceil boot rww enable 219 avr math 33 boot rww enable alternate 219 clearerr boot is spm interrupt avr stdio 58 avr boot 94 cli boot lock bits set avr interrupts 120 avr boot 94 clock prescale set boot lock bits set safe power h 238 avr boot 94 Combining C and assembly source files boot lock fuse bits get 173 avr boot 95 copysign boot page erase avr math 33 avr boot 95 COS boot page erase safe avr math 33 avr boot 95 cosh boot page fill avr math 33 avr boot 96 crc16 h 220 boot page fill safe ctype avr boot 96 isalnum 16 boot page write isalpha 16 avr boot 96 isascii 17 boot_page_write_safe isblank 17 avr_boot 96 iscntrl 17 boot
379. 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 Vector name Old vector Description Applicable for device name Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 106 Vector name Old name vector Description Applicable for device ADC_vect SIG_ADC ADC Conversion Complete AT90S2333 419054433 AT90S4434 AT90S8535 AT90PWMS3 9 2 AT90PWM1 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny13 ATtiny15 ATtiny26 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 AT tiny861 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 ANALOG
380. reelist entry will be prepared An attempt is then made to aggregate the new entry with possible adjacent entries yielding a single larger entry available for further allocations That way the potential for heap fragmentation is hopefully reduced A call to realloc first determines whether the operation is about to grow or shrink the current allocation When shrinking the case is easy the existing chunk is split and the tail of the region that is no longer to be used is passed to the standard free function for insertion into the freelist Checks are first made whether the tail chunk is large enough to hold a chunk of its own at all otherwise realloc will simply do nothing and return the original region When growing the region it is first checked whether the existing allocation can be ex tended in place If so this is done and the original pointer is returned without copying any data contents As a side effect this check will also record the size of the largest chunk on the freelist If the region cannot be extended in place but the old chunk is at the top of heap and the above freelist walk did not reveal a large enough chunk on the freelist to satisfy the new request an attempt is made to quickly extend this topmost chunk and thus the heap so no need arises to copy over the existing data If there s no more space available the heap same check is done as in malloc the entire request will fail Otherwise malloc w
381. 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 cli and sei macros If the status of the global interrupt flag before accessing one of those registers is uncertain something like the following example code can be used uint16_t read timerl void uint8_t sreg uintl6 t val sreg SREG cli Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 312 val TCNT1 SREG sreg return val Back to FAQ Index 9 9 10 How do I use a define d constant in asm statement So you tried this asm volatile sbi 0x18 0x07 Which works When you do the same thing but replace the address of the port by its macro name like this asm volatile sbi PORTB 0x07 you get compilation error Error constant value required PORTB is a precompiler definition included in the proces
382. registers 142 6 19 1 Detailed Description lt 24 0 6 24 sa s 142 6 19 2 Define Documentation 143 lt avr sleep h gt Power Management and Sleep 145 6 20 1 Detailed Descriphon lt s cs s c saca sus 145 620 2 Define Documentation lt c sesepi tanfu ik 146 6 20 3 Function Documentation 147 lt avr version h gt avr libc version macros 147 62L1 Detailed Descripiien sz oc km xem f 9339 9 xo RR Rs 147 6212 Define Documentation es esre este ieste 148 lt avr wdt h gt Watchdog timer handling 149 622 1 Detailed Descripfion sp es ce cpa gd ee es siks 149 6 22 2 Define Documentation 150 lt util atomic h gt Atomicly and Non Atomically Executed Code Blocks 152 6 23 1 Detailed Description 152 6 23 2 Define Documentangn lt 2 2244 8 6 heey a wae es 154 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS iv 6 24 6 25 6 26 6 27 6 28 6 29 6 31 6 32 6 34 lt util crc16 h gt CRC Computations 156 6241 Detailed Description lt o e s sss xxx tars 156 6 24 2 Function Documentation 157 lt util delay h gt Convenience functions for busy wait delay loops 159 6 25 1 Detailed Description 2 2 159 6 25 2 Function Documentation 160
383. rence 222222225 Xo Ro Uy Y A NU s 240 8 37 1 Detaled Description 4 622444885 i ia eae es 240 stdint h ong a ee a o RES 241 8 38 1 Detailed Description 22s mms 241 sta File Referees sous ook Y he ew 244 8 39 1 Detailed Description 65666546 RR RR 244 Pile Reference lt cer o s RR Rx Rex N 246 6 401 Detaled Description 22 mc Rom 246 sicasecmp s File Referente ico os RS osx D 248 8 41 1 Detailed Description 248 streasecmp_ P5 248 5421 Detaled Description 22 2222 2 2 2222 25525 248 sticasestr s File Reference 2 2 2 2 2222 2 248 5431 Detailed Descripti n 22 2 22 252 2 248 Pile 222222225299 Oe 248 8 44 1 Detailed Description 248 strcat_PS File Referenc soo ao 5 4 865 25 66 o a ko k HS a 249 5 45 1 Detailed Description 249 sichrs File Referente 022502255222 EIE E EARS 249 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS ix 8 47 8 48 8 49 8 50 8 51 8 52 8 53 8 54 8 55 8 56 8 57 8 58 8 59 8 60 8 61 8 46 1 Detailed Description 249 schr PS File Reference 222222252222 25 52 555 249 8 47 1 Detaled Description lt s oe ec cce ms oem RR 249 File Referente 2 2 5222 9 5284 w wo s O 3 249 8 48 1 Detailed Description 249 strchr
384. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 75 6 10 4 8 div tdiv 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 dtostre double val char __s unsigned char __prec unsigned char __flags The dtostre function converts the double value passed in va1 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 a
385. ring that resides in program memory 6 9 3 11 int fputc int _ c FILE stream The function fput c sends the character c though given as type int to stream It returns the character or EOF in case an error occurred Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 69 lt stdio h gt Standard IO facilities 62 6 9 3 12 int fputs const char str FILE stream Write the string pointed to by str to stream stream Returns 0 on success and EOF on error 6 9 3 13 int fputs_P const char __str FILE stream Variant of fputs where st r 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 stream 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 int fscanf FILE _ stream const char fmt The function f scanf performs formatted input reading the input data from st ream See vfscanf for details 6 9 3 16 int fscanf_P FILE _ stream const char _ 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 stream Write nmemb objects size bytes each to stream The first byte of the first
386. roject is managed by a C program part for easy maintenance time critical parts are written directly in manually optimized assembly language for shortest execution times possi ble Naturally this kind of project is very closely tied to the hardware design thus it is custom tailored to a particular controller type and peripheral setup As an alternative to the assembly language solution this project also offers a C only implementation de ploying the exact same peripheral setup based on a more sophisticated and thus more expensive but pin compatible controller While the simple demo is meant to run on about any AVR setup possible where a LED could be connected to OCR1 A output the large and stdio demos are mainly targeted to the Atmel STK500 starter kit and the TWI example requires a controller where some 24Cxx two wire EEPPROM can be connected to For the STK500 demos the default CPU either an AT90S8515 or an ATmega8515 should be removed from its socket and the ATmegal6 that ships with the kit should be inserted into socket SCKT3100A3 The 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 wi
387. rolling the linkeravr ld 353 9 12 Using the avrdude program lt s zz Rm m mg es 355 9 13 Release Numbering and Methodology 357 9 13 1 Release Version Numbering Scheme 357 9 13 2 Releasing AVR Libo 357 9 14 Acknowledgments nox X RR 360 915 Todo Lif l us s was a eA em Eee QU N 361 9 16 Deprecated List 222222252254 EG QO Rs eS 361 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 1 AVR Libc 2 1 AVR Libe 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 libc subscribe to the list so you w
388. rrupt routine could also access this register or another register that uses TEMP see the appropriate FAQ entry Note 6 This routine gets called after a reset It initializes the PWM and enables interrupts Note 7 The main loop of the program does nothing all the work is done by the interrupt routine The sleep_mode puts the processor on sleep until the next interrupt to conserve power 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 modem parts at least for the ATmega 128 however Atmel has drastically increased the IO source capability so when operating at 5 Vcc R2 is needed Its value should be about 150 Ohms When operating the circuit at 3 V it can still be omitted though 6 34 2 The Source Code THE BEER WARE LICENSE Revision 42 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 180 lt joerg FreeBSD ORG gt wrote this file 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 Deer in return Joerg Wunsch Simple AVR demonstrati
389. rtunately not yet described in the official documentation The most notable operators are lo8 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 IJMP or ICALL instruction and can also handle relocatable symbols on the right hand side Example 141 r24 lo8 pm somefunc 141 r25 hi8 pm somefunc call something This passes the address of function somefunc the first parameter to function something 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 language code into C programs This cool feature may be used for manually optimizing time critical parts of the software or to use specific processor instruction which are not available in the C language Because of a lack of documentation especially for the AVR version of the compiler it may take some time to figure out the implementation details by studying the compiler and assembler source code There are also a few sample programs available in the net Hopefully this document will help to increase their number Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 287 It s assumed
390. ruction 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 is the code to swap high and low byte of a 16 bit value asm volatile mov tmp_reg__ 0 n t mov 0 BO mov B0 tmp reg n t r value O value First you will notice the usage of register __tmp_reg__ which we listed among other special registers in the Assembler Code section You can use this register without saving its contents Completely new are those letters A and B in SAO and BO In fact they refer to two different 8 bit registers both containing a part of value Another example to swap bytes of a 32 bit value Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 293 asm volatile mov tmp_reg__ A0 n t mov 0 0 n t mov D0 tmp reg n t mov tmp reg BO n t mov BO CO TAXE mov 0 tmp reg n t r value 0 value If operands do not fit into a single register the compiler will automatically assign enough registers to hold the entire operand In the assembler code you use A0 to refer to the lowest byte of the first operand A1 to the lowest byte of the second operand and so on The next byte of the first operand will be B0 the next byte CO and so on This al
391. s having at least the specified width typedef int8_t int_least8_t typedef uint8_t uint_least8_t typedef int16_t int_least16_t typedef uint16_t uint_least16_t typedef int32_t int_least32_t typedef uint32_t uint_least32_t typedef int64_t int_least64_t typedef uint64_t uint_least64_t Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8_t int_fast8_t typedef uint8_t uint_fast8_t typedef int16 t int_fast16_t typedef uint16_t uint_fast16_t typedef int32_t int_fast32_t typedef uint32_t uint_fast32_t typedef int64_t int_fast64_t typedef uint64_t uint_fast64_t Greatest width integer types Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category typedef int64_t intmax_t typedef uint64_t uintmax_t Limits of specified width integer types C implementations should define these macros only when STDC LIMIT MACROS is defined before lt stdint h gt is included define INT8_MAX 0x7f define INT8_MIN INT8_MAX 1 define UINT8_MAX L_CONCAT INT8_MAX U 2U 1U Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 42 define INT16_MAX 0x7fff define INT16_MIN INT16_MAX 1 define UINT16_MAX __CONCAT INT16_MAX U 2U 1U define INT32 MAX Ox7fffffffL define INT32 MIN CINT32 MAX IL define
392. s 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 310 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 not C safe i e they need to be wrapped into extern C lt This could certainly be fixed too Exceptions are not supported Since exceptions are enabled by default in the C frontend they explicitly need to be turned off using no exceptions in the compiler options Failing this the linker will complain about an undefined external reference to personality 510 Constructors and destructors are supported though including global ones When programming C in space and runtime sensitive environments like microcon trollers extra care should be taken to avoid unwanted side effects of the C calling conventions like implied copy constructors that could be called upon function invo cation etc These things could easily add up into a considerable amount of time and program memory wasted Thus casual inspection of the generated assembler code using the 5 compiler option seems to be warrant
393. s 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 5 avr as mmcu atmegal28 gstabs foo o foo s When the assembler is not called directly but through the C compiler frontend either implicitly by passing a source file ending in S or explicitly using assembler with cpp the compiler frontend needs to be told to pass the gstabs option down to the assembler This is done using Wa gstabs Please take care to only pass this option when compiling an assembler input file Otherwise the assembler code that results from the C compilation stage will also get line number information which confuses the debugger Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 314 Note You can also use Wa gstabs since the compiler will add the extra for you Example 5 EXTRA_OPTS Wall mmcu atmegal28 x assembler with cpp avr gcc Wa gstabs EXTRA_OPTS c o foo o foo S Also note that the debugger might get confused when entering a piece of code that has a non local
394. s over and over they can all be placed a make file To build the demo project using make save the following file called Makefile Note This Makefile can only be used as input for the GNU version of make PRG demo OBJ demo o MCU_TARGET at90s2313 MCU_TARGET at90s2333 MCU_TARGET at90s4414 MCU_TARGET at90s4433 MCU_TARGET at90s4434 MCU_TARGET at90s8515 MCU_TARGET at90s8535 MCU_TARGET atmegal28 MCU_TARGET atmegal280 MCU_TARGET atmegal281 MCU_TARGET atmegal6 MCU_TARGET atmegal63 MCU_TARGET atmegal64p MCU_TARGET atmega165 MCU_TARGET atmegal65p MCU_TARGET atmega168 MCU_TARGET atmegal69 MCU_TARGET atmegal69p 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 191 MCU_TA
395. scription 222 222 2 258 5 86 struprS File Reference 2 2 258 8 86 1 Detailed Description 258 Bayt wih Pile Reene 222522 e Z Qua e Rue BARES 258 8 87 1 Detailed Description 22 2 2 2 2 258 8 88 wdth File Reference 2 2 22 260 8 88 1 Detailed Description sso RR 260 8 95 3 DefneDocumentalo H 24654665 85 2 sade ko 260 9 avr libc Page Documentation 261 91 Paaleh in sn eoo soe moo dun omo UR o4 P ER SOROR Oa 261 OLI o dinDGduchH l2 2 2 danak 261 91 2 PSEPand ONU he RR RR eR ER 261 OCC o ermes eee ox x Y es 261 414 ONU EIUS zem da zg ES EE 5 262 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen CONTENTS xii 9 2 93 9 4 a 913 eee 264 9 16 Building Sofware sea g po xx eR eo 264 AE S oie uem evum X eerte e in 264 914 GDBilInugh DDD 99 c9 9 RR 264 919 22 222222252225 265 SuaBlAVES 52223555 ee Gk 265 22oxeo Yo oe e 265 9 1 12 Toolchain Distributions Distros 265 Ze 266 Memory Areas and Using 266 921 A 266 922 Internal vs extemal RAM 267 923 Tomables 268 O24 Implementatiomn detis 222222222
396. 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 p Matches a pointer value as printed by p in printf the next pointer must be a pointer to void n Nothing is expected instead the number of characters consumed thus far from the input is stored through the next pointer which must be a pointer to int This is not a conversion although it can be suppressed with the flag These functions return the number of input items assigned which can be fewer than provided for or even zero in the event of a matching failure Zero indicates that while there was input available no conversions were assigned typically this is due to an invalid input character such as an alphabetic character for a d conversion The value
397. simplified functions that don t take 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 69 lt stdio h gt Standard IO facilities 60 6 9 3 2 int fclose FILE _ stream This function closes stream and disallows and further IO to and from it When using fdevopen to setup the stream a call to fclose is needed in order to free the internal resources allocated If the stream has been set up using fdev_setup_stream or FDEV_SETUP_ STREAM use fdev_close instead It currently always returns 0 for success 6 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 structure for the opened stream is returned Reasons for a possible failure currently include that neither the put nor the get argument have been provided thus attempting to open a stream with no IO intent at all or that insufficient dynamic memory is available to establish a new stream If the put function pointer is provided the stream is opened with write intent The function passed as put shall tak
398. simply be ignored including white space that is normally used to consume any amount of white space in the input stream However the usual skip of initial white space in the formats that support it is implemented 6 9 3 35 int vfscanf_P FILE x stream const char x va_list Variant of vfscanf using a fmt 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 va_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 va_list ap Like vsprintf but instead of assuming s to be of infinite size no more than n characters including the trailing NUL character will be converted to s Returns the number of characters that would have been written to s if there were enough space 6 9 3 39 int vsnprintf_P char s size t __n const char __ fmt va_list ap Variant of vsnprintf that uses fmt string that resides in program memory 6 9 3 40 int vsprintf char __s const char fmt va_list ap Like sprintf but takes a variable argument list for the arguments 6 9 3 41 int vsprintf_P char _ 5 const char va_list a
399. sing a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 9 will be the letter a The ultoa function returns the pointer passed as s 6 10 4 30 char utoa unsigned int val char __s int radix Convert an unsigned integer to a string The function utoa converts the unsigned integer value from val into an ASCII repre sentation that will be stored under s The caller is responsible for providing sufficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof unsigned int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 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 Generated on Mon Oct 29 20 02 34 2007 for avr lib
400. sing the C compiler frontend avr gcc that in turn will call the assembler and linker as required This approach has the following advantages There is basically only one program to be called directly avr gcc regardless of the actual source language used The invokation of the C preprocessor will be automatic and will include the appropriate options to locate required include files in the filesystem The invokation of the linker will be automatic and will include the appropri ate options to locate additional libraries as well as the application start up code crtXXX and linker script Note that the invokation of the C preprocessor will be automatic when the filename provided for the assembler file ends in S the capital letter s This would even apply to operating systems that use case insensitive filesystems since the actual decision is made based on the case of the filename suffix given on the command line not based on the actual filename from the file system Alternatively the language explicitly be specified using the x 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 282 include lt avr io h gt work tmp
401. sked Questions 327 push r28 push r29 r28 SP L in r29 SP sbiw r28 20 in tmp reg SREG cli out SPH r29 out SREG tmp reg out r28 prologue end size 10 x It reads the current stack pointer value decrements it by the required amount of bytes then disables interrupts writes back the high part of the stack pointer writes back the saved SREG which will eventually re enable interrupts if they have been enabled before and finally writes the low part of the stack pointer At the first glance there s a race between restoring SREG and writing SPL However after enabling interrupts either explicitly by setting the 1 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 9 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 do create constructors Ur flag A xn script is for linking with n flag mix
402. so implies that it is often neccessary to cast the type of an input operand to the desired size A final problem may arise while using pointer register pairs If you define an input operand e ptr and the compiler selects register Z 130 131 then refers to r30 and BO refers to r31 But both versions will fail during the assembly stage of the compiler if you explicitely need 7 like in 1 r24 z If you write r24 0 with a lower case a following the percent sign then the compiler will create the proper assembler line 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 294 asm volatile oli 14 r24 0 inc r24 n t st a0 r24 mane sei ptr r24 The compiler might produce the following code eli ld
403. so 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 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 the 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 266 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
404. sor specific file included in avr io h As you may know the precompiler will not touch strings and PORTB instead of 0x18 gets passed to the assembler One way to avoid this problem is asm volatile sbi 0 0x07 I SFR IO ADDR PORTB Note For C programs rather use the standard C bit operators instead so the above would be expressed as PORTB 1 7 The optimizer will take care to trans form this into a single SBI instruction assuming the operands allow for this Back to FAQ Index 9 9 11 Why does the PC randomly jump around when single stepping through my program in avr gdb When compiling a program with both optimization and debug information 9 which is fortunately possible in avr gcc the code watched in the debugger is opti mized code While it is not guaranteed very often this code runs with the exact same optimizations as it would run without the g switch This can have unwanted side effects Since the compiler is free to reorder code ex ecution as long as the semantics do not change code is often rearranged in order to Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 313 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 arou
405. src lo r24 define len_hi r23 define len_lo r22 8 73 strnlen_P S File Reference 8 73 1 Detailed Description Defines define src_hi r25 define src_lo r24 define len hi r23 define len_lo r22 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 74 strpbrk S File Reference 256 8 74 strpbrk S File Reference 8 74 1 Detailed Description 8 75 strpbrk_P S File Reference 8 75 1 Detailed Description 8 76 strrchr S File Reference 8 76 1 Detailed Description Defines define src hi r25 define src_lo r24 define val_lo r22 define ret hi r25 define ret lo r24 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 76 strrchr S File Reference 257 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 77 strrchr_P S File Reference 258 8 77 8 77 1 8 78 8 78 1 8 79 8 79 1 8 80 8 80 1 8 81 8 81 1 8 82 8 82 1 8 83 8 83 1 8 84 8 84 1 8 85 8 85 1 8 86 8 86 1 8 87 8 87 1 Defines strrchr_P S File Reference Detailed Description strrev S File Reference Detailed Description strsep S File Reference Detailed Description strsep_P S File Reference Detailed Description strspn S File Reference Detailed Description strspn P S File Reference Detailed Description strstr S File Reference Detailed Description strstr P S File Reference Detailed Description strtok r S File Referen
406. stalling the GNU Tool Chain 331 AVRDUDE http savannah nongnu org projects avrdude Installation Usage Notes http sources redhat com gdb Installation SimulAVR http savannah gnu org projects simulavr Installation AVaRICE http avarice sourceforge net Installation 9 10 4 GNU Binutils for the AVR target The binutils package provides all the low level utilities needed in building and ma nipulating object files Once installed your environment will have an AVR assembler avr as linker avr 13G and librarian avr ar and avr ranlib In addi tion you get tools which extract data from object files avr objcopy dissassem ble object file information avr 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 5 bunzip2 binutils lt version gt tar bz2 tar xf cd binutils lt version gt Note Replace lt version gt with the version of the package you downloaded If you obtained 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 332
407. structive 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 281 Although avr libc is primarily targeted to support programming AVR microcontrollers using the C and C language there s limited support for direct assembler usage as well The benefits of it are Use of the C preprocessor and thus the ability to use the same symbolic constants that are available to C programs as well as a flexible macro concept that can use any valid C identifier as a macro whereas the assembler s macro concept is basically targeted to use a macro in place of an assembler instruction Use of the runtime framework like automatically assigning interrupt vectors For devices that have RAM initializing the RAM variables can also be utilized 9 5 2 Invoking the compiler For the purpose described in this document the assembler and linker are usually not invoked manually but rather u
408. 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 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 50 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_least8_t signed int with at least 8 bits 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 uint
409. t is included Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 38 stdint h File Reference 243 define PTRDIFF_MAX INT16_MAX define PTRDIFF_MIN INT16_MIN define SIG ATOMIC MAX INT8 MAX SIG ATOMIC MIN INT8 MIN define SIZE MAX CONCAT INTI6 MAX U Macros for integer constants C implementations should define these macros only when STDC CONSTANT MACROS is defined before lt stdint h gt is included These definitions are valid for integer constants without suffix and for macros de fined as integer constant without suffix define INT8_C value int8 t value define UINT8_C value uint8 t CONCAT value U define INT16 C value value define UINT16_C value CONCAT value U define INT32_C value _ CONCAT value L define UINT32_C value _ CONCAT value UL define INT64_C value _ CONCAT value LL define UINT64_C value _ CONCAT value ULL define INTMAX_C value _ CONCAT value LL define UINTMAX_C value _ CONCAT value ULL 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
410. 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 assert expression Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 2 atoi S File Reference 214 8 2 atoi S File Reference 8 2 1 Detailed Description Defines define str_hi r25 define str_lo r24 define num hi r25 define num_lo r24 define tmp r18 8 3 atol S File Reference 8 3 1 Detailed Description Defines define str hi r25 define str lo r24 define num hi hi r25 fidefine num hi lo r24 define num lo hi 123 define num lo r22 define tmp r17 8 4 atomic h File Reference 8 4 1 Detailed Description Defines 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 5 boot h File Reference 215 8 5 8 5 1 boot h File Reference Detailed Description Defines define AVR_BOOT_H_ 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
411. t PCINTO will be handled in the final part of this file The basic algorithm is to quickly evaluate the current system time by fetching the current timer value of TCNTO and combining it with the overflow part in counter hi If the counter is currently counting down rather than up the value fetched from TCNTO must be negated Finally if this pin change interrupt was triggered by a rising edge the time computed will be recorded as the start time only Then at the falling edge this start time will be subracted from the current time to compute the actual pulse width seen left in pwm 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 34 simple project 177 disabled so no new measurement can be performed until the upper layer had a chance to process the current value 6 33 3 source code The source code is installed under Sprefix share doc avr libc examples asmdemo where prefix is a configuration option For Unix systems it is usually set to either usror usr local 6 34 A 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
412. t a single jump back to itself Square wave generation itself is completely handled by the timer 0 overflow interrupt service sleep instruction using idle mode could be used as well but probably would not conserve much energy anyway since the interrupt service 15 executed quite frequently Note 7 Interrupt functions can get the usual names that are also available to C programs The linker will then put them into the appropriate interrupt vector slots Note that they must be declared global in order to be acceptable for this purpose This will only work if lt avr io h gt has been included Note that the assembler or linker have no chance to check the correct spelling of an interrupt function so it should be double checked When analyzing the resulting object file using avr objdump or avr nm a name like vector N should appear with N being a small integer number Note 8 As explained in the section about special function registers the actual IO port address should be obtained using the macro SFR IO ADDR The 905 1200 does not have RAM thus the memory mapped 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 t
413. t 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 Solution don t use inferior file systems operating systems Neither Unix file systems nor HPFS aka NTFS do experience that problem Workaround after saving the file wait a second before starting make Or simply ignore the warning If you are paranoid execute a make clean all to make sure everything gets rebuilt In networked environments where the files are accessed from a file server this message can also happen if the file server s clock differs too much from the network client s clock In this case the solution is to use a proper time keeping protocol on both sys tems like NTP As a workaround synchronize the client s clock frequently with the server s clock Back to FAQ Index 9 9 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 m
414. t util delay_basic h gt Basic busy wait delay loops 6 26 1 Detailed Description include lt util delay_basic h gt The functions in this header file implement simple delay loops that perform a busy waiting They are typically used to facilitate short delays in the program execution They are implemented as count down loops with a well known CPU cycle count per Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 27 lt util parity h gt Parity bit generation 161 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 1l uint8_t __count void _delay_loop_2 uint16_t __count 6 26 2 Function Documentation 6 26 2 1 void _delay_loop_1 uint8_t count Delay loop using 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 regis
415. tandard IO functions 6 9 2 13 define getc __stream fgetc __stream The macro getc 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 59 6 9 2 14 ftdefine getchar void fgetc stdin The macro getchar reads a character from stdin 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 c 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 closing the previous st derr since this would also close stdout 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 astream argument The first stream opened with read intent using fdevopen will be assigned to stdin 6 9 2 19 Zdefine stdout iob 1 Stream that will be used as an output stream by the
416. tecture 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 used to define the startup code from reset up through the start of main These all are subparts of the text section The purpose of these sections is to allow for more specific placement of code within your program Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 3 Memory Sections 273 Note Sometimes it is convenient to think of the initN and finiN sections as functions but in reality they are just symbolic names which tell the linker where to stick a chunk of code which is not a function Notice that the examples for asm and C can not be called as functions and should not be jumped into initN sections are executed order from 0 to 9 init0 Weakly bound to __init If user defines _ init it will be jumped into immedi ately after a reset initi Unused User definable init2 In C programs weakly bound to initialize the stack and to clear zero reg r1 init3 Unused User definable init4 For devices with gt 64 KB of ROM
417. ter Thus at a CPU speed of 1 MHz delays of up to 768 microseconds can be achieved 6 26 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 be achieved 6 27 lt util parity h gt Parity bit generation 6 27 1 Detailed Description include lt util parity h gt This header file contains optimized assembler code to calculate the parity bit for a byte Defines define parity_even_bit val Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 28 lt util setbaud h gt Helper macros for baud rate calculations 162 6 27 2 Define Documentation 6 27 2 1 define parity even bit val Value extension N unsigned char t N asm X mov tmp reg 0 n t N swap 0 n t N eor 0 tmp reg n t N mov tmp reg 0 n t N lsr 0 n t N lar 0 mne N eor 0 tmp reg x MS n GC E 0 unsigned char val X N 1 gt gt 1 amp 1 N Returns lif val has an odd number of bits set 6 28 lt util setbaud h gt Helper macros for baud rate calculations 6 28 1 Detailed Description define F
418. ters at 9600 Bd they might block for too long The loop itself then acts on the interrupt indication bitfields as appropriate and will eventually put the CPU on sleep at its end to conserve power The first interrupt bit that is handled is the software timer at a frequency of approx imately 100 Hz The CLOCKOUT pin Will be toggled here so e g an oscilloscope can be used on that pin to measure the accuracy of our software clock Then the LED flasher for LED2 We are alive LED is built It will flash that LED for about 50 ms and pause it for another 950 ms Various actions depending on the operation mode follow Finally the 3 second backup timer is implemented that will write the PWM value back to EEPROM once it is not changing anymore The ADC interrupt will just adjust the PWM value only Finally the UART Rx interrupt will dispatch on the last character received from the UART All the string literals that are used as informational messages within main are placed in program memory so no SRAM needs to be allocated for them This is done by using the PSTR macro and passing the string to printstr_p 6 35 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 336 Using the standard I
419. text and data on same page xbn script is for linking with N flag mix text and data on same page Back to FAQ Index 9 9 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 328 This will create a file named with the contents of foo The contents will default to section data and two symbols will be created named binary foo bin start and binary foo bin end These symbols can be referred to inside a C source to access these data Ifthe goal is to have those data go to flash ROM similar to having used the PROGMEM attribute in C source code the sections have to be renamed while copying and it s also useful to set the section flags avr objcopy rename section data progmem data contents alloc load readonly data I binary O elf3 Note that all this could be conveniently wired into a Makefile so whenever foo bin changes it will trigger the recreation of and a subsequent relink of the final ELF file Back to FAQ Index
420. tf 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 6 5 2 13 ffdefine PRIi8 i integer printf format for int8 t 6 5 2 14 define PRIiFASTI16 i integer printf format for int fastl16 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 leastl6 t Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 25 6 5 2 18 define PRIILEAST32 li integer printf format for int_least32_t 6 5 2 19 define PRIILEASTS 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 o octal printf format for uint16_t 6 5 2 22 define PRIo32 lo octal printf format for uint32_t 6 5 2 23 define PRIo8 octal printf format for uint8_t 6 5 2 24 define PRIoFASTI16 o octal printf format for uint_fast16_t 6 5 2 25 define PRIoFAST32 10 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 PRIOLEAST16 o octal printf format for uint_least16_t 6 5 2 28 de
421. th 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 16 Deprecated List Global SIGNAL Do not use SIGNAL 0 in new code Use ISR instead Global ISR ALIAS For new code the use of ISR ISR_ALIASOF is recom mended Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 16 Deprecated List 362 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 Oct 29 20 02 34 2007 for avr libc by Doxygen Index PATH 329 PREFIX 328 prefix 328 lt alloca h gt Allocate space in the stack 14 lt assert h gt Diagnostics 15 lt avr boot h gt Bootloader Support Utili ties 92 lt avr eeprom h gt EEPROM handling 98 lt avr interrupt h gt Interrupts 101 lt avr io h gt AVR device specific IO defi nitions 123 lt avr pgmspace h gt Program Space Util ities 124 lt avr power h gt Power Reduction Man agement 136 lt avr sfr_defs h gt Special function regis ters 141 lt avr sleep h gt Power Management and Sleep Modes 144 lt avr version h gt avr libc macros 146 avr wdt h Watchdog timer handling 148 lt compat deprecated h gt items 168 lt compat ina90
422. 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 ISR XXX_vect ISR_NOBLOCK Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 14 lt avr interrupt h gt Interrupts 104 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 ISR macro ISR PCINTO_vect Code to handle the event ISR PCINTI_vect ISR ALIASOF PCINTO vect Note There is no body to the aliased ISR Note that the ISR_ALIASOF feature requires GCC 4 2 or above or a patched version of GCC 4 1 x See the documentation of the 5 ALIAS macro for an implementa tion whic
423. 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 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 9 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
424. 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 9 1 2 FSF and GNU According to its website the Free Software Foundation FSF established in 1985 is dedicated to promoting computer users rights to use study copy modify and redis tribute computer programs The FSF promotes the development and use of free soft ware particularly the GNU operating system used widely in its GNU Linux variant The FSF remains the primary sponsor of the GNU project The GNU Project was launched in 1984 to develop a complete Unix like operating system which is free software the GNU system GNU is a recursive acronym for GNU s Not Unix it is pronounced guh noo approximately like canoe One of the main projects of the GNU system is the GNU Compiler Collection or GCC and its sister project GNU Binutils These two open source projects pr
425. 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 323 function that expects a const char x type string since the AVR processor needs the special instruction LPM to access these strings Thus separate functions are needed that take this into account Many of the standard C library functions have equivalents available where one of the string arguments can be located in flash ROM Private func tions in the applications need to handle this too For example the following can be used to implement simple debugging messages that will be sent through a UART include lt inttypes h gt include lt avr io h gt include lt avr pgmspace h gt int uart_putchar char c if c uart_putchar r 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 oc int main void ioinit initialize UART debug_P PSTR foo was here n return 0 Note By convention the suffix _P to the function name is used as an indication that this function is going to accept
426. tially en abled This allows interrupt handlers to be interrupted As this macro has been used by too many unsuspecting people in the past it has been deprecated and will be removed in a future version of the library Users who want to legitimately re enable interrupts in their interrupt handlers as quickly as possible are encouraged to explicitly declare their handlers as described above 6 30 2 6 define outb port val port val Deprecated Write val to IO port port 6 30 2 7 define outp val port port val Deprecated Write val to IO port port Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 31 lt compat ina90 h gt Compatibility with EWB 3 x 172 6 30 2 8 define sbi port bit port 1 lt lt bit Deprecated Set bit in IO port port 6 30 3 Function Documentation 6 30 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 31 lt compat ina90 h gt Compatibility with EWB 3 x include lt compat ina90 h gt 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 manual 6 32 Demo projects 6 32 1 Detailed Description Various small demo pro
427. tic _ inline uintl t crc ccitt update uint16 t crc uint8 t data e static _ inline uint8 t crc ibutton update uint8 t crc uint8 t data Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 624 lt utiV crc16 h gt CRC Computations 157 6 24 2 Function Documentation 6 24 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 uintl16 t crcl16 update uintl16 t crc uint8 t a int i cre a for i 0 i lt 8 i if cre amp 1 crc crc gt gt 1 0xA001 crc cre gt gt 1 return crc 6 24 2 2 static inline uintl16 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
428. tical 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 AVR 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 projects that are used to build software for the AVR there is another piece of software that ties it all together Make GNU Make is a program that makes things and mainly software Make interprets and executes a Makefile that is written for a project A Makefile contains dependency rules showing which output files are dependent upon which input files and instructions on how to build output files from input files Some distributions of the toolchains and other AVR tools such as MFile contain a Makefile template written for the AVR toolchain and AVR applications that you can copy and modify
429. ties 57 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 fidefine FDEV SETUP READ SRD setup stream with read intent 6 9 2 4 define FDEV SETUP RW SRD SWR fdev setup stream with read write intent 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 fdev close This macro frees up any library resources that might be associated with stream It should be called if st ream is no longer needed right before the application is going to destroy the st ream object itself Currently this macro evaluates to nothing but this might change in future versions of the library 6 9 2 8 define get udata stream stream udata This macro retrieves a pointer to user defined data from a FILE stream object Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 69 lt stdio h gt Standard IO facilities 58 6 9 2 9 def
430. tion avrprog 332 installation binutils 330 installation gcc 331 Installation gdb 333 installation simulavr 333 INT16_C avr_stdint 43 6 avr_stdint 43 6 avr_stdint 43 int16_t avr_stdint 48 INT32_C avr_stdint 43 INT32_MAX avr_stdint 43 INT32_MIN avr_stdint 43 int32_t avr_stdint 48 INT64_C avr_stdint 43 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 374 INT64_MAX INT_LEAST32_MAX avr_stdint 43 avr_stdint 44 INT64_MIN INT_LEAST32_MIN avr_stdint 43 avr_stdint 45 int64_t int_least32_t avr_stdint 48 avr_stdint 49 INT8_C INT_LEAST64_MAX avr_stdint 43 avr_stdint 45 INT8_MAX INT_LEAST64_MIN avr_stdint 43 avr_stdint 45 INT8_MIN int_least64_t avr_stdint 43 avr_stdint 49 int8_t INT LEAST8 avr stdint 48 avr stdint 45 int farptr t INT LEAST8 MIN avr inttypes 31 INT FASTI6 MAX avr stdint 44 INT FAST16 MIN avr stdint 44 int fastl6 t avr stdint 48 INT FAST32 MAX avr stdint 44 INT FAST32 MIN avr stdint 44 int fast32 t avr stdint 48 INT FAST64 MAX avr stdint 44 INT FAST64 MIN avr stdint 44 int fast64 t avr stdint 48 INT FASTS MAX avr stdint 44 INT FASTS8 MIN avr stdint 44 int fast8 t avr stdint 48 INT 5 6 avr_stdint 44 INT_LEAST16_MIN avr_stdint 44 int_least16_t avr_stdint 49 avr_stdint 45 int_least8_t avr_stdint 49 INTERRUPT deprecated_items 170 interrupt
431. tional notes from lt avr sfr_defs h gt 139 alloca alloca 14 asin avr math 33 assert avr assert 15 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 365 assert h 212 atan avr_math 33 atan2 avr math 33 atof avr stdlib 72 atoi avr_stdlib 72 atoi S 213 atol avr_stdlib 73 atol S 213 atomic h 213 ATOMIC_BLOCK util_atomic 153 ATOMIC_FORCEON util_atomic 153 ATOMIC_RESTORESTATE util_atomic 154 avr_assert assert 15 avr_boot boot_is_spm_interrupt 94 boot_lock_bits_set 94 boot_lock_bits_set_safe 94 boot_lock_fuse_bits_get 95 boot_page_erase 95 boot_page_erase_safe 95 boot_page_fill 96 boot_page_fill_safe 96 boot_page_write 96 boot_page_write_safe 96 boot_rww_busy 97 boot_rww_enable 97 boot_rww_enable_safe 97 boot_spm_busy 97 boot_spm_busy_wait 97 boot_spm_interrupt_disable 97 boot_spm_interrupt_enable 97 BOOTLOADER_SECTION 98 GET EXTENDED FUSE BITS 98 GET HIGH FUSE BITS 98 GET LOCK BITS 98 GET LOW FUSE BITS 98 avr eeprom EEGET 100 _EEPUT 100 EEPROM REG LOCATIONS 99 EEMEM 100 eeprom busy wait 100 eeprom is ready 100 eeprom read block 100 eeprom read byte 100 eeprom read word 101 eeprom write block 101 eeprom write byte 101 eeprom write word 101 avr errno EDOM 19 ERANGE 19 avr interrupts BADISR vect 120 cli 120 EMPTY INTERRUPT 120 ISR 120 ISR ALIAS 120 5 ALIASOF 1
432. 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 Example clock timer 2 with full IO clock CS2x 0b001 toggle OC2 output on compare match COM2x 0601 and clear timer on compare match CTC2 1 Make OC2 PD7 an output TCCR2 BV COM20 BV CTC2 _BV CS20 DDRD _BV PD7 Back to FAQ Index 9 9 7 Can I use C the AVR Basically yes C is supported assuming your compiler has been configured and compiled to support it of course Source files ending in cc cpp or C will automati cally cause the compiler frontend to invoke the C compiler Alternatively the C compiler could be explicitly called by the name avr c However there s currently no support for libstdc the standard support library needed for a complete C implementation Thi
433. to the application The functions available allow the specification of microsecond and millisecond delays Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 26 lt util delay_basic h gt Basic busy wait delay loops 160 directly using the application supplied macro as the CPU clock frequency Hertz Functions void delay us double _ us void delay ms double ms 6 25 2 Function Documentation 6 25 2 1 void delay ms double _ ms Perform a delay of __ms milliseconds using delay loop 20 The macro 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 25 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 26 l
434. tream udata define fdev_setup_stream stream put get rwflag Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 8 39 stdio h File Reference 245 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 __ stream define putchar __c fputc __c stdout define getc __stream fgetc __stream define getchar fgetc stdin define SEEK_SET 0 define SEEK_CUR 1 define SEEK_END 2 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 fmt int vprintf const char fmt va list ap int sprintf char s constchar fmt intsprintf 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 __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
435. trstr function finds the first occurrence of the substring s2 in the string s1 The terminating 0 characters are not compared Returns The strstr function returns a pointer to the beginning of the substring or NULL if the substring is 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 93 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 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
436. uart_9600 void define BAUD 9600 include lt util setbaud h gt UBRRH UBRRH_VALUE UBRRL UBRRL_VALUE if 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 if USE_2X UCSRA 1 lt lt U2X else UCSRA amp lt 1 lt lt U2X endif In this example two functions are defined to setup the UART to run at 9600 Bd and 38400 Bd respectively Using a CPU clock of 4 MHz 9600 Bd can be achieved with an acceptable tolerance without setting U2X prescaler 25 while 38400 Bd require U2X to be set prescaler 12 Defines define BAUD_TOL 2 define UBRR_VALUE define UBRRL_VALUE define UBRRH_VALUE define USE_2X 0 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 29 lt util twi h gt TWI bit mask definitions 164 6 28 2 Define Documentation 6 28 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 28 2 2 define VALUE Output macro from lt util setbaud h gt Contains the calculated baud rate prescaler value for the UBRR register 6 28 2 3 define UBRRH VALUE Output macro from lt util setbaud h gt
437. uble frexp double _ value int exp double ldexp double _ x int exp _ ATTR_CONST double exp double x _ATTR_CONST double cosh double x ATTR CONST double sinh double x ATTR CONST double tanh double _ x CONST double acos double x ATTR CONST double asin double x ATTR CONST double atan double x ATTR CONST double atan2 double __y double x CONST double log double _ x ATTR CONST double log10 double _ x CONST double pow double x double ATTR CONST int isnan double x ATTR CONST int isinf double x CONST double square double _ x ATTR CONST ATTR CONST double copysign double x double y double double x double y CONST double fma double x double y double z CONST double fmax double x double y CONST double fmin double x double y ATTR CONST int signbit double x CONST double double x CONST ATTR CONST int isfinite double x double hypot double x double y 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 square root of 2 6 6 2 4 define NAN __builtin_nan NAN constant Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6
438. ude lt avr io h gt section initl 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 progbits For more detailed information on the section directive see the gas user manual 9 3 9 Using Sections in C Code Example include lt avr io h gt void my_init_portb void __attribute__ naked N __attribute__ section init3 void my_init_portb void i PORTB Oxff DDRB Oxff Note Section init3 is used in this example as this ensures the inernal zero reg _ has already been set up The code generated by the compiler might blindly rely on zero reg being really 0 9 4 Data in Program Space 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 sam
439. umber 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 13 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 All versions in development in cvs will also always have the date appended as a fourth version number The format of the date will be YY YYMMDD So the development version number will look like this 1 1 0 20030825 While a pre release version number on a branch destined to become either 1 2 or 2 0 will look like this 1 1 90 20030828 9 13 2 Releasing AVR Libc The information in this section is only relevant to AVR Libc developers and be ignored by end users Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 13 Release Numbering and Methodology 358 Note 9 13 bran 1 22 10 11 12 In what follows I assume you know how to use cvs and how to checkout multiple source trees in a single
440. umerated type that can be used to interface to the Clock Prescale Register Note Not all AVR devices have a Clock Prescale Register On those devices without a Clock Prescale Register these macros are not available typedef enum lock_div_1 lock_div_2 lock_div_4 lock_div_8 lock_div_16 4 lock div 32 5 lock div 64 6 lock div 128 7 clock div 256 8 clock div t II Clock prescaler setting enumerations clock_prescale_set x Set the clock prescaler register select bits selecting a system clock division setting They type of x is clock_div_t clock_prescale_get Gets and returns the clock prescaler register setting The return type is clock_div_t 6 18 Additional notes from lt avr sfr_defs h gt The avr sfr defs h file is included by all of lt avr ioXxxx 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 Oct 29 20 02 34 2007 for avr libc by Doxygen 6 18 Additional notes from lt avr sfr_defs h gt 141 If SFR ASM COMPAT is not defined C programs can use
441. unction returns the hyperbolic cosine of x Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 6 lt math h gt Mathematics 35 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 The fabs function computes the absolute value of a floating point number x 6 6 3 11 double fdim double x double y The fdim function returns max x y 0 If x or y or both are NaN NaN is returned 6 6 3 12 double floor double x The floor function returns the largest integral value less than or equal to x expressed as a floating point number 6 6 3 13 double fma double x double y double z The fma function performs floating point multiply add This is the operation y 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 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 fr
442. urceforge net mingw msys automake 1 8 2 tar bz2 use mirror internap gt Extract to c msys 1 0 Install Cygwin Install everything all users UNIX line endings This will take a 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 338 Note MPFR requires GMP so build it first Build GMP for MinGW Version 4 2 1 lt http omplib org gt Build script configure 2 gt amp 1 make 2 gt amp 1 make check 2 gt amp 1 make install 2 gt amp 1 tee gmp configure log tee gmp make log tee gmp make check log tee gmp make install log GMP headers will be installed under usr local include and library installed under usr local lib 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 stack nl dimitri doxygen gt Download and install Install NetPBM
443. ure 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 N prefix installdir N enable doc N disable versioned doc N enable html doc N enable pdf doc N enable man doc N mandir installdir man datadir installdir N 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 AVRDUDE Open source code package Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 10 Building and Installing the GNU Tool Chain 342 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 lt install directory gt bin Set location of LibUSB headers and libraries export CPPFLAGS I libusb win32 device bin libusb_version include export CFLAGS I libusb win32 device bin libusb_version inclu
444. using the two wire interface TWD 206 exit avr_stdlib 74 exp avr_math 33 fabs avr_math 34 FAQ 304 fclose avr_stdio 58 fdev_close avr_stdio 56 fdev_get_udata avr_stdio 56 fdev_set_udata avr_stdio 56 FDEV_SETUP_STREAM avr_stdio 57 fdev_setup_stream avr_stdio 57 fdevopen avr_stdio 59 fdevopen c 223 fdim avr_math 34 feof avr_stdio 59 ferror avr_stdio 60 fflush avr_stdio 60 ffs avr_string 82 ffs S 224 ffsl avr_string 83 ffsl S 224 ffsll Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 373 avr_string 83 ffsll S 224 fgetc avr_stdio 60 fgets avr_stdio 60 FILE avr_stdio 57 floor avr_math 34 fma avr_math 34 fmax avr_math 34 fmin avr_math 34 fmod avr_math 34 fprintf avr_stdio 60 fprintf_P avr_stdio 60 fputc avr_stdio 60 fputs avr_stdio 60 fputs_P avr_stdio 61 fread avr_stdio 61 free avr_stdlib 74 frexp avr math 34 fscanf avr_stdio 61 fscanf_P avr_stdio 61 fwrite avr_stdio 61 GET_EXTENDED_FUSE_BITS avr_boot 98 GET_HIGH_FUSE_BITS avr_boot 98 GET_LOCK_BITS avr_boot 98 GET_LOW_FUSE_BITS avr_boot 98 getc avr_stdio 57 getchar avr_stdio 57 gets avr_stdio 61 hypot avr_math 34 inb deprecated_items 169 INFINITY avr_math 32 inp deprecated_items 169 installation 328 installation avarice 334 installation avr libc 332 installation avrdude 332 installa
445. ution 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 forced that way Back to FAQ Index Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 317 9 9 14 What registers are used by the C compiler Data types char is 8 bits int is 16 bits Long is 32 bits Long long is 64 bits float and double are 32 bits this is the only supported floating point format pointers are 16 bits function pointers are word addresses to allow addressing the whole 128K program memory space on the ATmega devices with gt 64 KB of flash ROM There is a 8 option see Options for the C compiler avr gcc to make int 8 bits but that is not supported by avr libc and violates C standards int must be at least 16 bits It may be removed in a future release Cal
446. ve value an intmax t can hold 6 8 2 32 define INTPTR MAX INTI6 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 47 6 8 2 34 define PTRDIFF_MAX INT16_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 CONCAT INTI6 MAX U largest value a size t can hold 6 8 2 39 define UINT16_C value U define a constant of type uint16 t 6 8 2 40 define UNTI6 MAX CONCAT INTI6 MAX U x 20 10 largest value an uint16 t can hold 6 8 2 41 define UINT32 CONCAT value UL define a constant of type uint32 t 6 8 2 42 define UINT32 CONCAT INT32 U 2UL 1UL largest value an uint32 t can hold 6 8 2 43 define UINT64 CONCAT value ULL define a constant of type uint64 t 6 8 4144 define UINT64_MAX _ CONCAT INT64_MAX U 2ULL 1ULL largest value an uint64 t can hold Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 8 lt stdi
447. will use a hard ware sbi if appropriate or a read or write if not You do not need to keep track of which registers sbi cbi will operate on Likewise cbi sfr bit is now sfr amp _BV bit Modules Additional notes from lt avr sfr_defs h gt Bit manipulation define BV bit 1 lt lt bit IO register bit manipulation define bit is set sfr bit SFR BYTE sfr amp BV bit define bit is clear sfr bit SFR BYTE sfr amp BV 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 19 2 Define Documentation 6 19 2 1 define _BV bit 1 lt lt bit Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 19 lt avr sfr_defs h gt Special function registers 144 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 19 2 2 define bit_is_clear sfr bit _SFR_BYTE sfr amp _BV bit include lt avr io h gt Test whether bit bit in IO register sfr is clear This will return non zero if the bit is clear and a 0 if the bit is set 6 19 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 r
448. with lt avr io h gt Note The names of the interrupt vectors in AVR GCC has been changed to match the names of the vectors in IAR This significantly helps in porting applications from IAR to AVR GCC 9 8 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 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 8 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 int mydata AVR GCC uses Variable Attributes to achieve the same effect int mydata _ attribute progmem Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 8 Porting From IAR to AVR GCC 304 Note See the GCC User Manual for more inf
449. xplanation about inter rupt routines written solely in assembler language Catch all interrupt vector IFf 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 ISRO 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 triggered external interrupts In rare circumstances though it might be desired to re enable the global interrupt flag as early as possible in the interrupt handler in order to not defer any other interrupt more
450. xtend up to address Oxffff avr gcc Wl Tdata 0x801100 defsym end 0x80ffff Note See explanation for offset 0x800000 See the chapter about using gcc for the w1 options 0x0100 on board RAM SP t maroc heap end RAMEND __brkval __malloc_heap_start heap start bss end data bss start data start external RAM Ox10FF 0x1100 OxFFFF 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 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 269 internal RAM something like the following could be used Note that for demonstration purposes the assignment of the various regions has not been made adjacent in this example so there are holes below and above the heap in external RAM that remain completely unaccessible by regular variables or dynamic memory allocations shown in light bisque color in the picture below avr gcc Wl defsym heap start 0x802000 defsym heap end 0x803fff external RAM 0x0100 0x1 0FF 0x1100 0x2000 Ox3FFF OxFFFF on board RAM et oA malloc heap heap end ot _ brkval bss end malloc heap start heap start data end bss start data start Figure 8 Internal RAM variables and stack external RAM hea
451. xygen 6 11 lt string h gt Strings 83 int strcmp const char const char x ATTR PURE char strcpy char const char size t strcspn const char s const char xreject ATTR PURE size t strlcat char const char size t size t strlcpy char const char size t size t strlen const char PURE char strlwr char int strncasecmp const char const char size t ATTR_PURE char strncat char const char size_t int strncmp const char const char size t ATTR_PURE char strncpy char const char size_t size t strnlen const char size_t PURE char strpbrk const char s const char xaccept PURE char strrchr const char int PURE char strrev char x char strsep char const char size t strspn const char s const char xaccept 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 c
452. y h 222 delay_basic h 222 eeprom h 223 errno h 224 fdevopen c 224 ffs S 225 ffsl S 225 ffsll S 225 interrupt h 225 inttypes h 226 io h 228 math h 228 memccpy S 229 memchr S 230 memchr_P S 230 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 41 avr libc File List 12 memcmp S 230 memcmp_P S 230 memcpy S 230 memcpy_P S 231 memmem S 231 memmove S 231 memrchr S 232 memrchr_P S 232 memset S 232 parity h 232 pgmspace h 232 power h 239 setbaud h 240 setjmp h 240 sleep h 240 stdint h 241 stdio h 244 stdlib h 246 strcasecmp S 248 strcasecmp_P S 248 strcasestr S 248 strcat S 248 strcat_P S 249 strchr S 249 strchr_P S 249 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 41 avr libc File List 13 strchrnul S 249 strchrnul_P S 249 stremp S 249 stremp_P S 249 strcpy S 249 strepy_P S 250 strespn S 250 strcspn_ P S 250 string h 250 strlcat S 252 strlcat_ P S 252 strlcpy S 252 stricpy_P S 252 strlen S 252 strlen_P S 252 strlwr S 253 strncasecmp S 253 strncasecmp_P S 253 strncat S 253 strncat_P S 253 strncmp S 254 strncmp P S 254 strncpy S 254 strncpy P S 255 strnlen S 255 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 5 avr libc Page Index 14 strnlen_P S 255 strpbrk S 256 strpbrk_P S 256 strrchr S 256 strrchr_P S 258 strrev S 258 strsep S 258 strsep_P S 258 strspn S 258 strspn_P S 258 strstr S 258 strstr_P S 258 strtok_r S 258 strupr S
453. y_P avr_pgmspace 133 strlcpy_P S 251 strlen avr_string 88 strlen S 251 strlen_P avr_pgmspace 133 strlen_P S 251 strlwr avr_string 88 strlwr S 252 strncasecmp avr_string 88 strncasecmp S 252 strncasecmp_P avr_pgmspace 133 strncasecmp_P S 252 strncat avr_string 89 strncat S 252 strncat_P avr_pgmspace 134 strncat_P S 252 strncmp avr_string 89 strncmp S 253 strncmp P avr pgmspace 134 strncmp P S 253 strncpy avr string 89 strncpy S 253 strncpy_P avr_pgmspace 134 strncpy_P S 254 strnlen avr_string 89 strnlen S 254 strnlen_P avr_pgmspace 135 strnlen_P S 254 strpbrk avr_string 90 strpbrk S 255 strpbrk_P avr_pgmspace 135 strpbrk_P S 255 strrchr avr_string 90 strrchr S 255 strrchr_P avr_pgmspace 135 strrchr_P S 257 strrev avr_string 90 strrev S 257 strsep avr_string 90 strsep S 257 strsep_P avr_pgmspace 135 strsep_P S 257 strspn avr_string 91 strspn S 257 strspn_P avr_pgmspace 136 strspn_P S 257 strstr avr_string 91 strstr S 257 strstr_P avr_pgmspace 136 strstr_P S 257 strtod avr_stdlib 78 strtok_r avr_string 91 strtok_r S 257 strtol avr_stdlib 78 strtoul avr_stdlib 79 strupr avr_string 92 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen INDEX 382 strupr S 257 supported devices 2 tan avr math 36 tanh avr math 36 timer enable int deprecated items 171 toascii ctype 1
454. yway 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 9 12 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 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
455. zero if sl or the first n bytes thereof is found respectively to be less than to match or be greater than s2 Generated on Mon Oct 29 20 02 34 2007 for avr libc by Doxygen 6 16 lt avr pemspace h gt Program Space Utilities 136 6 16 4 20 char strncpy_P char 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 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 16 4 21 size t strnlen_P PGM P src size_t len Determine the length of a fixed size string The strnlen_P 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 16 4 22 char x strpbrk_P const char s 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 t

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