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avr-libc Reference Manual

1. Vector name Old vector Description Applicable for device name TIMER 1_ SIG_INPUT_ Timer Counter 9052333 AT90S4414 AT90S4433 CAPT vect CAPTUREI Capture Event 9054434 479058515 AT90S8535 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN 64 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 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 TIMERI SIG Timer Counter 1 ATtiny26 CMPA vect OUTPUT Compare Match COMPAREIA 1A TIMERI SIG_ Timer Counter1 ATtiny26 CMPB vect OUTPUT Compare Match COMPAREIB 1B TIMER SIG Timer Counter1 9052313 COMPI vect OUTPUT Compare Match COMPAREIA TIMER1_ SIG_ Timer Counter1 AT90S4414 AT90S4434 9058515 COMPA_vect OUTPUT_ Compare Match AT90S8535 AT90PWM3 AT90PWM2 COMPAREIA AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega
2. 304 9917 Which O flac touse W RR 304 9 9 18 How do I relocate code to a fixed 57 305 Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen CONTENTS 9 9 10 is generating nonsense ATmega128 keeps crashing Port F is completely 306 9 9 20 Why do all my foo bar strings eat up the SRAM 306 9 9 21 Why does the compiler compile an 8 bit operation that uses bitwise operators into 16 bit operation in assembly 307 9 9 22 How to detect RAM memory and variable overlap problems 308 9 9 23 Is it really impossible to program the ATtinyXX in 308 9 9 24 What is this clock skew detected messsage 309 9 9 25 Why are many interrupt flags cleared by writing alogical 1 309 9 9 26 Why have programmed fuses the bit value 0 310 9 9 27 Which AVR specific assembler operators are available 310 9 9 28 Why are interrupts re enabled in the middle of writing the stack Doni m 310 9 9 29 Why are there five different linker scripts 311 9 9 30 How to add a raw binary image to linker output 311 9 10 Installing the GNU Tool Chain 312 9 10 1 Required Tools 5 ee RR RR ERR 313 9 10 2 Optional Tools a ska se ees 313 9 10 3 GNU Binutils for the AVR target ooo 314 9104 GCC forthe AVR target 2 opoe 2 ove ak ke k wp SO 8 315 91
3. math library included avr libc If you use this on your linker command line clgrintt flt then the linker will look for a library called libprintf_flt a This is why naming your library is so important when you create it The linker will search libraries in the order that they appear on the command line Whichever function is found first that matches the undefined reference it will be linked in There are also command line switches that tell GCC which directory to look in 1 for the libraries that are specified to be linke in with 1 See the GNU Binutils manual for more information on the GNU linker ld program 9 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 be exacerbated when the application is an embedded system For example the C language Standard strangely does not specify a standard for declaring and defining Interrupt Service Rou tines ISRs Different compilers have different ways of defining registers some of which use non standard language constructs This chapter describes some methods and pointers on porting an AVR application built with the IAR compiler to the GNU toolchain AVR GCC Note that this may not be an exhaustive list 9 8 2 Registers
4. no outputs I _SFR_IO_ADDR _WD_CONTROL_REG r uint8_t _BV _WD_CHANGE_BIT BV WDE e Meg y 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 20 2 2 define wdt enable timeout wdt write timeout Enable the watchdog timer configuring it for expiry after t imeout which is 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 20 lt avr wdt h gt Watchdog timer handling 142 6 20 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 watchdog initiated device reset will occur 6 20 2 4 define WDTO 120MS 3 See WDT0_15MS 6 20 2 5 define WDTO 15MS 0 Symbolic constants for the watchdog timeout Since the watchdog timer is based on free running RC oscillator the times are approximate only and apply to 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 3 V while the newer devices g ATmegal28 ATmega8
5. could actually be the same register so take care to not clobber it TCCR1B TIMER1_CLOCKSOURCE Run device dependent timer 1 setup hook if present 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 int main void ioinrt 1 loop forever the interrupts are doing the rest for Note 7 sleep_mode return 0 6 30 3 Compiling and Linking This first thing that needs to be done is compile the source When compiling the compiler needs to know the processor type so the mmcu option is specified The s 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 167 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
6. 213 8 19 mernchr S Pile Reference 2 22 2 c o o n 213 8 19 1 Detailed Description 213 8 20 P S File 214 8 20 1 Detailed Description 214 8 21 memcmp S File Reference oco org 214 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen CONTENTS 822 8 23 8 24 8 25 8 26 8 27 8 28 8 29 8 30 8 31 8 32 8 34 8 21 1 Detailed Description 2 214 mememjp P S File Referenc 2 222 9 2 214 8 22 1 Detaled Description uz nea rie ee m 214 menicpys File Reference 202222224259 a SUS 214 8 23 1 Detailed Description 2 214 memcpy_B S Pile Reference 2 22 2222 52224 214 8 24 1 Detaled Description gt se csee 9 SSG SUR GE QU SUN 214 memmem S File Reference gt ooeec ccm RR 215 8 23 1 Detailed Description eoo RR Rm RR 215 memmove s File Referepee sod us 242 RR RE 215 8 26 1 Detailed Description 215 File Reference 2222222 1 2 55 215 9 27 1 Detailed Description gt se ecce e uf Rey y GK 215 memuchr P S File Referenc 2222122 c 9 x xc 215 5 28 1 Detailed Description 222 2 2 215 Imernset S File Referenc 2 22 2 215 8 29 1 Detailed Description lt e socs eas do ga oeae 215 panty bie Reference u oske s ok e o k 216 8 30 1 Detailed Descriptio
7. elpm BO Z WAN CU r __result r __addr32 I SFR IO ADDR RAMPZ ESOT result 8 31 2 6 define LPM classic Value extension_ uintl6 t addr16 uint8 t _ result asm lpm n t Its uintl16 t addr mov 0 r0 n t r result 2 addr16 ror result Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 8 31 pgmspace h File Reference 221 8 31 2 7 define LPM dword classic Value __extension__ uintl6 t _ addrl6 uintl6 t addr uint32 t result asm__ lpm mov A0 ro adiw r30 1 TA ANEU lpm mov BO ro TANNET adiw r30 1 NpnNEM N lpm NnNt N mov CO ro r30 1 n t lpm NnNE N mov DO ro MALE r result z addrl6 N 1 addrl6 N ro result N 8 31 2 8 define LPM dword enhanced addr Value __extension__ uintl6 t _ addr16 uintl6 t addr X uint32 t result N asm N N lpm 0 27 ANNET lpm B0 Z n t lpm 0 Z lpm DO Z UNDnNEN N r result z addrl16 N 1 addrl6 N result N 8 31 2 9 define LPM enhanced addr Value __extension__ Generated on Tue 15 14 56 11 2007 for a
8. 15 14 56 11 2007 for avr libe by Doxygen 9 9 Frequently Asked Questions 308 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 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
9. Pile Reference 222222226225 555 5505 205 551 Detailed Description 2 464 485 bs od xr ER RERO 205 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen CONTENTS vi 86 lt ctypeh File Reterence 22 2 205 8 6 1 Detailed Description gt e ecs pss 65 ren 205 87 delay h File Referenc 206 871 Detailed Description 222 2 206 8 8 delay basic h File Reference 206 8 8 1 Detailed Description 206 8 9 eprom Pile Reterence lt s ccc coreey pep 207 8 9 1 Detailed Description 207 5 10 emno b File Reference oo oc coco ee 208 8 10 1 Detailed Description 208 8 11 idevopen c File Referenc 208 8 11 1 Detailed Description 208 8 12 ns File Referente 2 9 eS 209 8 12 1 Detailed Description 209 815 ILS File Reference uuu ok 209 8 13 1 Detailed Description 209 8 14 ffsll S Pile Reterence oso mmm 209 8 14 1 Detailed Description 209 8 15 interrupt h File 209 8 15 1 Detailed Description 2 209 8 16 inttypes h Pile Reference 2222 2 2 209 8 16 1 Detailed Description 209 8 17 math Pile Reference 2 222 2 222 2 212 8 17 1 Detailed Description 212 8 18 memecepy S File Reference 213 8 18 1 Detailed Description
10. Clock prescaler setting enumerations clock prescale set x Set the clock prescaler register select bits selecting 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 16 Additional notes from lt avr sfr defs h gt The lt avr sfr defs h gt file is included by all of the lt avr 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 MEM8 0xC6 define TCNT3 _SFR_MEM16 0x94 define CANIDT _SFR_MEM32 0xF0 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 16 Additional notes from lt avr sfr defs h gt 132 If SFR ASM COMPAT is not defined C programs can use names like PORTA directly in expressions also on the left side of assignment operators and 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 ASM 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 automati
11. THE BEER WARE LICENSE Revision 42 lt joerg FreeBSD ORG gt wrote this file 5 long as you retain this notice you can do whatever you want with this stuff If we meet some day and you think this stuff is worth it you can buy me a beer in return Joerg Wunsch PTA a ee ee A STE Akt A ed Ea SS ar Simple AVR demonstration Controls LED that can be directly connected from OC1 OC1A to GND brightness of the LED is controlled with the After each period of the the value is either incremented or decremented that s all Id demo c v 1 6 2 3 2006 01 05 21 33 08 joerg wunsch Exp finclude lt inttypes h gt finclude lt avr io h gt include lt avr interrupt h gt include lt avr sleep h gt include iocompat h Note 1 enum UP DOWN ISR TIMER1_OVF_vect Note 2 static uintl6_t pwm Note 3 static uint8 t direction switch direction Note 4 x case UP if pwm TOP direction DOWN break case DOWN if pwm 0 direction UP break OCR pwm Note 5 x Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 166 void ioinit void Note 6 Timer 1 is 10 bit 8 bit PWM on some ATtinys x 1 TIMER1 INIT Start timer 1 NB TCCR1A and
12. Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 10 lt string h gt Strings 87 6 10 3 32 char strsep char xx 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 de lim or the terminating V0 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 sp to 707 Returns The strsep function returns a pointer to the original value of If sp is initially NULL strsep returns NULL 6 10 3 33 size_t strspn const char 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 10 3 34 char strstr const char s1 const char 52 Locate a substring The strstr function finds the first occurrence of the substring s2 in the string s1 The terminating 0 characters are not compared Returns The strstr functio
13. Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen INDEX 338 avr_stdlib 69 cli 114 atol S 198 EMPTY INTERRUPT 114 avr assert ISR 115 assert 13 ISR ALIAS 115 avr boot sei 115 boot is spm interrupt 90 SIGNAL 116 boot lock bits set 90 avr inttypes boot lock bits set safe 90 int farptr t 29 boot lock fuse bits get 91 PRId16 20 boot page erase 91 PRId32 20 boot page erase safe 91 PRId8 20 boot page fill 92 boot page fill safe 92 boot page write 92 boot page write safe 92 boot rww busy 93 boot rww enable 93 boot rww enable safe 93 boot spm busy 93 boot spm busy wait 93 boot spm interrupt disable 93 boot spm interrupt enable 93 BOOTLOADER SECTION 94 GET EXTENDED FUSE BITS 94 GET HIGH FUSE BITS 94 GET LOCK BITS 94 GET LOW FUSE BITS 94 avr_eeprom _EEGET 96 _EEPUT 96 __EEPROM_REG_LOCATIONS_ _ 95 EEMEM 96 eeprom_busy_wait 96 eeprom_is_ready 96 eeprom_read_block 96 eeprom_read_byte 96 eeprom_read_word 97 eeprom_write_block 97 eeprom_write_byte 97 eeprom_write_word 97 avr_errno EDOM 17 ERANGE 17 avr_interrupts PRIdFASTI6 20 PRIdFAST32 20 PRIdFASTS 20 PRIdLEASTI6 21 PRIdLEAST32 21 PRIdLEASTS 21 PRIdPTR 21 PRIi16 21 PRIi32 21 PRIi8 21 PRIiFAST16 21 PRIiFAST32 21 PRIiFASTS 21 PRIiLEASTI6 21 PRIiLEAST32 22 PRIiLEASTS 22 PRIiPTR 22 PRIo16 22 1032 22 PRI08 22 PRIoFASTI6 22 PRIoFAST32 22 PRIoFASTS 22 PRIoLE
14. PS File Reference 8 241 Detailed Description Defines define dest hi r25 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 25 memmem S File Reference 215 define dest 10 r24 define src hi r23 define src lo r22 define len hi r21 define len lo r20 8 25 memmenm S File Reference 8 25 1 Detailed Description 8 26 memmove S File Reference 8 26 1 Detailed Description Defines define dest hi r25 define dest lo 24 define src hi r23 define src lo r22 define len hi r21 define len lo r20 8 27 memrchrS File Reference 8 27 1 Detailed Description 8 28 memrchr P S File Reference 8 28 1 Detailed Description 829 memset S File Reference 8 29 1 Detailed Description Defines define dest hi r25 define dest lo r24 define val lo r22 define len_hi r21 define len_lo r20 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 30 parity h File Reference 216 8 30 parity h File Reference 8 301 Detailed Description Defines define parity_even_bit val 8 31 pemspace h File Reference 8 31 1 Detailed Description Defines define _ PGMSPACE_H_ 1 define __need_size_t define CONST attribute const Zdefine ATTR PROGMEM attribute progmem define PURE attribute pure define PROGMEM PROGMEM define PSTR s const PROGMEM char x s define LPM classi
15. S there s a comment in each generated assembler file that tells you the frame size for each generated function That s the amount of stack required for this function you have to add up that for all functions where you know that the calls could be nested Back to FAQ Index 9 9 23 Is it really impossible to program the ATtinyXX 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 it is possible anyway to use the general purpose registers as a RAM replacement since they are mapped into the data memory region Bruce D Lightner wrote an excellent description of how to do this and offers this together with a toolkit on his web page http lightner net avr ATtiny AvrGcc html Back to FAQ Index Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 309 9 9 24 What is this clock skew detected messsage It s known problem of the MS DOS FAT file system Since the FAT file system has only 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
16. const char size t size t strlcpy char const char size t size t strlen const char x PURE char strlwr char int strncasecmp const char const char size t ATTR PURE char strncat char const char size t int strncmp const char const char size_t ATTR PURE char strncpy char const char size 1 size t strnlen const char size t ATTR PURE char strpbrk const char s const char PURE char strrchr const char int PURE char strrev char char strsep char const char size t strspn const char xs const char xaccept ATTR PURE char strstr const char const char x ATTR PURE char strtok char const char char char strupr char 6 10 2 Define Documentation 6 10 2 1 define FFS x This macro finds the first least significant bit set in the input value This macro is very similar to the function ffs except that it evaluates its argument at compile time so it should only be applied to compile time constant expressions where it will reduce to a constant itself Application of this macro to expressions that are not constant at compile time is not recommended and might result in a huge amount of code generated Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 10 lt string h gt Strings 79 R
17. 16 File Reference 205 8 4 2 13 define boot rww enable alternate Value __asm__ __volatile__ sts 0 1 n t spminit word Oxffff n t hopxXnXEe i SFR MEM ADDR SPM REG r uint8 t BOOT RWW ENABLE HHS 8 5 16 File Reference 8 5 1 Detailed Description Functions static inline uint16 t crc16 update uint16 t crc uint8 t data static inline uint16 t crc xmodem update uint16 t crc uint8 t data static inline uint16 t crc ccitt update uint16 t ere uint8 t data static inline uint8 t crc ibutton update uint8 t crc uint8 t data 8 6 ctype h File Reference 8 6 1 Detailed Description 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 ATTR CONST int isalpha int ATTR CONST intisascii int c ATTR CONST intisblank int ATTR CONST intiscntrl int c ATTR CONST int isdigit int ATTR CONST int isgraph int ATTR CONST int islower int ATTR CONST Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 87 delay h File Reference 206 int isprint int ATTR CONST int ispunct int CONST in
18. 6 18 lt avr sleep h gt Power Management and Sleep Modes 136 6 18 lt avr sleep h gt Power Management and Sleep Modes 6 181 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 to sleep but all peripheral clocks are still running and then call sleep mode Unless it is the purpose to lock the CPU hard until 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 this combined macro might cause race conditions in some situations the individual steps of manipulating the sleep enable SE bit and actually issuing the SLEEP in struction are provided in the macros sleep enable sleep disable and sleep cpu This also allows for test and sleep scenarios that take care of not missing the interrupt that will awake the device from sleep Example finclude lt avr interrupt h gt include lt avr sl
19. 6 4 2 55 define PRIXLEAST32 IX uppercase hexadecimal printf format for uint least32 t 6 4 2 56 define PRIXLEAST32 Ix hexadecimal printf format for uint_least32_t 6 4 2 57 define PRIXLEASTS X uppercase hexadecimal printf format for least8 t Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 4 lt inttypes h gt Integer conversions 26 6 4 2 58 define PRIXLEASTS x hexadecimal printf format for uint_least8_t 6 4 2 59 define PRIXPTR PRIX16 uppercase hexadecimal printf format for uintptr_t 6 4 2 60 define PRIxPTR PRIx16 hexadecimal printf format for uintptr_t 6 4 2 61 define SCNd16 d decimal scanf format for int16 t 6 4 2 62 define SCNd32 decimal scanf format for int32_t 6 4 2 63 define SCNdFAST16 decimal scanf format for int_fast16_t 6 4 2 64 define SCNdFAST32 Id decimal scanf format for int_fast32_t 6 4 2 65 define SCNALEAST16 d decimal scanf format for int_least16_t 6 4 2 66 define SCNALEAST32 Id decimal scanf format for int_least32_t 6 4 2 67 define SCNdPTR SCNd16 decimal scanf format for intptr_t 6 4 2 68 define SCNil6 i generic integer scanf format for int16_t Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 4 lt inttypes h gt Integer conversions 27 6 4 2 69 define SCNi32 li generic Integer scanf format for int32_t 6 4 2 70 define SCNiFAST16 i generic in
20. 79 lt avr boot h gt Bootloader Support Utilities 88 GILL Detailed Description lt s ngs ne oA RR ERE 88 6 11 2 Define Documentation 90 lt avr eeprom h gt EEPROM handling 94 6 12 1 Detailed Description 94 6 12 2 Define Documentation 95 Generated Tue 15 14 56 11 2007 for avr libc Doxygen CONTENTS Hi 6 42 3 Function 96 6 13 lt aycintetupt Baz Eptemipls udo S s reke g Q S 97 6 13 1 Detailed Desenpt n uc cor RR Grad v RS 97 6 13 2 Define Doc mentati n 22 2222 2222 gt 114 6 14 lt avr pgmspace h gt Program Space Utilities 116 6 14 1 Detailed Description 116 6 142 Define Documentation e cs sis hee x omm ss 118 6 14 3 Typedef Documentation 120 6 14 4 Function 122 6 15 lt avr power h gt Power Reduction Management 128 6 16 Additional notes from lt avr sfr defs h gt 131 6 17 lt avr sfr defs h gt Special function registers 133 6 17 1 Detailed Description gt sce sos s e sae ee eA Res 133 6 17 2 Define Documentation lt 2 q 134 6 18 lt avr sleep h gt Power Management and Sleep Modes 136 6 18 1 Detailed Description 136 6 18 2 Define Docum
21. 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 PREFIX make make install 4 X oX X d X 9 10 7 GDB for the AVR target Gdb also uses the configure system so to build and install bunzip2 c gdb version tar bz2 tar xf cd gdb version mkdir obj avr cd obj avr configure prefix SPREFIX target avr make make install Ur Xr X Ur d X or 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 8 Simulavr Simulavr also uses the configure system so to build and install gunzip c simulavr version tar gz tar xf cd simulavr version mkdir obj avr cd obj avr configure prefix S PREFIX make make install Xr X X X d X 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 11 Using the GNU tools 318 9 10 9 AVaRice Note These install n
22. The strnepy P function returns a pointer to the destination string dest 6 14 4 21 size t strnlen P PGM P src size_t len Determine the length of a fixed size string The strnlen function is similar to strnlen except that src is a pointer to a string in program space Returns The strnlen P function returns strlen P src if that is less than len or len if there is no 0 character among the first 1 characters pointed to by src 6 14 4 22 char strpbrk P const char s P accept The strpbrk P function locates the first occurrence in the string s of any of the char acters in the flash string accept This function is similar to strpbrk except that accept is a pointer to a string in program space Returns The strpbrk PQ 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 14 4 23 PGM P strrchr P PGM 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 PO function returns a pointer to the matched character or NULL if the character is not found Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 15 lt avr power h gt Power Reduction Management 128 6 1
23. Variant of sscanf using a fmt string in program memory Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 8 lt stdio h gt Standard IO facilities 60 6 8 3 31 int ungetc int __ c FILE stream The ungetc function pushes the character c converted to an unsigned char back onto the input stream pointed to by stream The pushed back character will be returned by a subsequent read on the stream Currently only a single character can be pushed back onto the stream The ungetc function returns the character pushed back after the conversion or EOF 1 the operation fails If the value of the argument c character equals EOF the operation will fail and the stream will remain unchanged 6 8 3 32 int vfprintf FILE stream const char fmt 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 Variable argument list ap vfprintf returns the number of characters written to stream or EOF in case of an error Currently this will only happen if stream has not been opened with write intent The format string is composed of zero or more directives ordinary characters not which are copied unchanged to the output stream and conversion specifications each of which results in fetching zero or more subsequent arguments Each conversion specification is
24. 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 fdevopen int put char FILE int get FILE Define Documentation 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 8 lt stdio h gt Standard IO facilities 53 6 8 2 2 FDEV ERR 1 Return code for an error condition during device read be used in the get function of fdevopen 6 8 2 3 define FDEV SETUP READ _ SRD fdev setup stream with read intent 6 8 2 4 define FDEV SETUP RW SRD SWR fdev setup stream with read write intent 6 8 2 5 define FDEV SETUP WRITE SWR fdev setup stream with write intent 6 8 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 a
25. out SFR IO ADDR SREG intsav reti ioinit sbi SFR IO ADDR DDRD SQUARE 141 work _BV TOIF0 out SFR IO ADDR TIMSK work ldi work BV CS00 tmr0 1 out SFR IO ADDR TCCRO work ldi work 256 tmconst out SFR IO ADDR TCNTO work sei ret global vector default Note 10 vector default reti Generated Tue 15 14 56 11 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 267 Note 1 As in C programs this includes the central processor specific file containing the IO port definitions for the device Note that not all include files can be included into assembler sources Note 2 Assignment of registers to symbolic names used locally Another option would be to use a C preprocessor macro instead define work 16 Note 3 Our bit number for the square wave output Note that the right hand side consists of a CPP macro which will be substituted by its value 6 in this case before actually being passed to the assembler Note 4 The assembler uses integer operations in the host defined integer size 32 bits or longer when evaluating expressions This is in contrast to the C compiler that uses the C type int by default in order to calculate constant integer expressions In order to get 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
26. stdout amp mystdout printf Hello 1 return 0 This example uses the initializer form FDEV SETUP STREAMQ 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 device abstraction that is compatible with open but since this would have required to parse 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 UART interface might look like this int uart putchar char c FILE stream if uart_putchar r loop until bit is set UCSRA UDRE UDR return 0 Generated on Tue 15 14 56 11 2007 for avr libe
27. 6 13 lt avr interrupt h gt Interrupts 101 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 AT9082333 419054433 9054434 EEPROM AT9088535 ATmegal6 ATmegal6l READY ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 ATmega8515 AT mega8535 ATtinyl2 ATtiny13 ATtiny15 ATtiny26 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 EE_READY_ SIG_ EEPROM Ready AT90PWMS3 AT90PWM2 AT90PWMI vect EEPROM AT90CAN128 AT90CAN32 AT90CAN64 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 AT90USB82 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 419052323 INTERRUPTO 0 9052333 419052343 AT90S4414 AT9084433 419054434 419058515 9058535 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63
28. 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 10 3 22 size_t strlen const char src Calculate the length of a string The strlen function calculates the length of the string src not including the terminat ing 0 character Returns The strlen function returns the number of characters in src 6 10 3 23 char strlwr char x s Convert a string to lower case The striwr 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 10 3 24 int strncasecmp const char 51 const char s2 size_t len Compare two strings ignoring case The strncasecmp function is similar to strcasecmp except it only compares the first len characters of s1 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 10 lt string h gt Strings 85 Returns strncasecmp function returns an integer less than equal to or greater than Zero if 51 or the first 1en bytes thereof is found respectively to be less than to match or be greater than 52 consequence of the ordering used by strncasecmp is that if s1 is an initial substring of 52 then s1 is con
29. Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen INDEX 354 strstr P S 242 strtod avr stdlib 74 strtok r avr string 87 strtok r S 242 strtol avr stdlib 74 strtoul avr stdlib 75 strupr avr string 88 strupr S 242 supported devices 2 tan avr math 33 tanh avr math 33 timer enable int deprecated items 157 toascil ctype 16 tolower ctype 16 tools optional 313 tools required 313 toupper ctype 16 TW BUS ERROR util twi 151 TW MR ARB LOST util twi 151 TW MR DATA ACK util twi 151 TW MR DATA NACK util twi 151 TW MR SLA ACK util twi 151 TW MR SLA NACK util twi 151 TW MT ARB LOST util twi 151 TW MT DATA ACK util twi 151 TW MT DATA NACK util twi 151 TW MT SLA ACK util twi 152 TW MT SLA NACK util twi 152 TW NO INFO util twi 152 TW READ util twi 152 TW REP START util twi 152 TW SR ARB LOST GCALL ACK util twi 152 TW SR ARB LOST SLA ACK util twi 152 TW SR DATA ACK util twi 152 TW SR DATA NACK util twi 152 TW SR GCALL util twi 152 TW SR GCALL DATA ACK util twi 152 TW SR GCALL DATA NACK util_twi 153 TW SR SLA ACK util_twi 153 TW SR STOP util_twi 153 TW ST ARB LOST SLA ACK util twi 153 TW ST DATA ACK util twi 153 TW ST DATA NACK util_twi 153 TW ST LAST DATA util_twi 153 TW ST SLA ACK util_twi 153 TW START util twi 153 TW STATUS util twi 153 TW STATUS MASK util_twi 153 TW WRITE G
30. Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 6 lt setjmp h gt Non local goto 34 6 6 lt setjmp h gt Non local goto 6 6 1 Detailed Description While the C language has the dreaded goto statement it can only be used to jump to a label in the same local function In order to jump directly to another non local function the C library provides the setjmp and longjmp functions setjmp and longjmp are useful for dealing with errors and interrupts encountered in a low level subroutine of a program Note setjmp and longjmp make programs hard to understand and maintain If possi ble an alternative should be used longjmp can destroy changes made to global register variables see How to per manently bind a variable to a register For a very detailed discussion of setjmp longjmpQ see Chapter 7 of Advanced Pro gramming in the UNIX Environment by W Richard Stevens Example include setjmp h jmp buf env int main void if setjmp env handle error main processing loop which calls foo some where void foo void blah blah blah if err longjmp env 1 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 6 lt setjmp h gt Non local goto 35 Functions int setjmp jmp buf jmpb void longjmp jmp_buf __jmpb int ATTR NORETURN 6 6 2 Function Documentation 6 6 2 1 void longjmp jmp buf jmpb
31. INT64 MAX 40 INT64 MIN 40 int64 t 44 INTS8 C 40 INT8 MAX 40 INT8 MIN 40 int8 t 45 INT FAST16 MAX 40 INT FAST16 MIN 40 int fastl6 t 45 INT FAST32 MAX 40 INT FAST32 MIN 40 int fast32 t 45 INT FAST64 MAX 40 INT FAST64 MIN 41 int fast64 t 45 INT FAST8 MAX 41 INT FASTS MIN 41 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 341 int fast8 t 45 INT LEAST16 MAX 41 INT LEAST16 MIN 41 int 1 5 16 t 45 INT LEAST32 MAX 41 INT LEAST32 MIN 41 int least32 t 45 INT LEAST64 MAX 41 INT LEAST64 MIN 41 int least64 t 45 INT LEAST8 MAX 41 INT LEASTS8 MIN 41 int least8 t 45 INTMAX C 42 INTMAX MAX 42 MIN 42 intmax t 46 INTPTR MAX 42 INTPTR MIN 42 intptr t 46 PTRDIFF MAX 42 PTRDIFF MIN 42 SIG ATOMIC MAX 42 SIG ATOMIC MIN 42 SIZE MAX 42 JINT16 C 42 JINT16 MAX 43 int16 t 46 JINT32 C 43 JINT32 MAX 43 int32 t 46 JINT64 C 43 JINT64 MAX 43 11164 t 46 JINT8 C 43 INT8 MAX 43 int8 t 46 JINT FAST16 MAX 43 int fastl6 t 46 JINT FAST32 MAX 43 int fast32 t 46 JINT FAST64 MAX 43 int fast64 t 46 JINT FAST8 MAX 43 int fast8 t 47 JINT LEAST16 MAX 44 s CE u s e uint leastl6 t 47 JINT LEAST32 MAX 44 int least32 t 47 JINT LEAST64 MAX 44 int least64 t 47 INT LEAST8 MAX 44 int least8 t 47 JINTMAX C 44 JINTMAX MAX 44 intmax t 47 JINTPTR MAX 44 uintp
32. MCU_TARGET atmegal68 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 30 simple project 175 MCU_TARGET attiny26 MCU_TARGET attiny261 MCU_TARGET attiny44 MCU_TARGET attiny45 MCU_TARGET attiny461 MCU_TARGET attiny84 MCU_TARGET attiny85 MCU_TARGET attiny861 OPTIMIZE 02 DEFS LIBS You should not have to change anything below here CC avr gcc Override is only needed by avr lib build system override CFLAGS g Wall OPTIMIZE mmcu MCU TARGET DEFS override LDFLAGS W1l Map 5 PRG map OBJCOPY avr objcopy OBJDUMP avr objdump all PRG elf lst text eeprom 5 PRG elf 5 OBJ 5 CFLAGS LDFLAGS o 8 LIBS dependency demo o demo c iocompat h clean rm rf S PRG elf eps png pdf x bak rm rf x lst map EXTRA CLEAN FILES
33. 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 Wl u vfprintf lprintf flt 1m Limitations The specified width and precision can be at most 127 For floating point conversions trailing digits will be lost if a number close to DBL MAX is converted with a precision gt gt 0 6 8 3 33 int vfprintf P FILE stream const char fmt va list Variant of v printf that uses a fmt string that resides in program memory Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 8 lt stdio h gt Standard IO facilities 63 6 8 3 34 int vfscanf FILE stream const char __fmt va list Formatted input This function is the heart of the scanf family of functions Characters are read from st ream and processed in a way described by fmt Conver sion results will be assigned to the parameters passed via ap The format string 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 con
34. Thus if xnptr is not VO but xxendptr is 0 on return the entire string was valid The strtol function returns the result of the conversion unless the value would under flow or overflow If no conversion could be performed 0 is returned If an overflow or underflow occurs errno is set to ERANGE and the function return value is clamped to LONG MIN or LONG MAX respectively 6 9 4 28 unsigned long strtoul const char _ nptr char endptr int base The strtoul function converts the string in npt r to an unsigned long value The con version is done according to the given base which must be between 2 and 36 inclusive or be the special value 0 The string may begin with an arbitrary amount of white space as determined by iss pace followed by a single optional or sign If base is zero or 16 the string may then include a 0x prefix and the number will be read in base 16 otherwise a zero base is taken as 10 decimal unless the next character is 0 in which case it is taken as 8 octal The remainder of the string is converted to an unsigned long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 B represents 11 and so forth with 2 representing 35 If endptr is not NULL strtoul stores the address of the first invalid character i
35. 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 32 3 2 defines h This file just contains a few peripheral definitions The F_CPU macro defines the CPU clock frequency to be used in delay loops as well as in the UART baud rate calculation The macro UART BAUD defines the RS 232 baud rate Depending on the actual CPU frequency only a limited range of baud rates can be supported The remaining macros customize the IO port and pins used for the HD44780 LCD driver 6 32 3 3 hd44780 h This file describes the public interface of the low level LCD driver that interfaces to the HD44780 LCD controller Public functions are available to initialize the controller into 4 bit mode to wait for the controller s busy bit to be clear and to read or write one byte from or to the controller As there are two different forms of controller IO one to send 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 det
36. Why do some 16 bit timer registers sometimes get trashed How do I use a define d constant 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 What is this clock skew detected messsage Why are many interrupt flags cleared by writing a logical 1 Why have programmed fuses the bit value 0 Which AVR specific assembler operators are available Why are interrupts re enabled in the middle of writing the stack pointer Why are there five different linker scripts How to add a raw binary image to linker output Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 291 9 9 2 My program doesn t recognize a variable updated within an interrupt rou tine When u
37. avr_stdio 56 fflush avr_stdio 57 fread avr_stdio 57 free avr_stdlib 71 frexp avr math 31 fscanf avr_stdio 57 fscanf P avr_stdio 57 fwrite avr_stdio 58 GET EXTENDED FUSE BITS avr boot 94 GET HIGH FUSE BITS avr stdio 56 avr boot 94 ffs GET LOCK BITS avr string 78 avr boot 94 ffs S 209 GET LOW FUSE BITS ffsl avr boot 94 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen INDEX 346 getc 8 avr_stdio 54 avr_stdint 40 getchar INT8 MIN avr stdio 54 avr stdint 40 gets int8_t avr_stdio 58 avr_stdint 45 int_farptr_t inb avr_inttypes 29 deprecated_items 156 INT FASTI6 MAX inp avr stdint 40 deprecated items 156 installation 312 installation avarice 318 installation avr libc 316 installation avrdude 316 installation avrprog 316 installation binutils 314 installation gcc 315 Installation gdb 317 installation simulavr 317 6 avr_stdint 39 INT16 avr_stdint 39 6 avr_stdint 39 int16 t avr stdint 44 INT32 C avr stdint 39 INT32 MAX avr stdint 39 32 MIN avr stdint 39 int32 t avr stdint 44 INT64 C avr stdint 40 INT64 MAX avr stdint 40 INT64 MIN avr stdint 40 int64 t avr stdint 44 8 avr_stdint 40 INT FAST16 MIN avr stdint 40 int fastl16 t avr stdint 45 INT FAST32 MAX avr stdint 40 INT FAST32 MIN avr stdint 40 int fast32 t avr stdint 45 INT FAST6
38. binary conversion and up to 36 If radix is greater than 10 the next digit after 97 will be the letter a The ultoa function returns the pointer passed as s 6 9 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 10 lt string h gt Strings 77 Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix 15 greater than 10 the next digit after 9 will be the letter a The utoa function returns the pointer passed as s 6 9 5 Variable Documentation 6 9 5 1 char malloc heap end malloc tunable 6 9 5 2 char malloc heap start malloc tunable 6 9 5 3 size t malloc margin malloc tunable 6 10 lt string h gt Strings 6 10 1 Det
39. 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 local variable to hold temporary value Another use for local variable is return value The following function returns 16 bit value read from two successive port addresses uintl6 t inw uint8 t port uintl6_t result asm volatile in 0 1 n t in BO 1 1 r result I SFR IO ADDR port return result Note inw is supplied by avr libc 9 6 7 C Names Used in Assembler Code By default AVR GCC uses the same symbolic names of functions or variables in C and assembler code You can specify a different name for the assembler code by using a special form of the asm statement unsigned long value asm clock 3686400 This statement instructs the compiler to use the symbol name clock rather than value This makes sense only for external or static variables because local variables do 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 Tue May 15 14 56 11 2007 for avr libe by Doxygen 97 How to Build a Li
40. demo c The compilation will create a demo o file Next we link it into a binary called demo elf 5 avr gcc g mmcu atmega8 o demo elf demo o It is important to specify the MCU type when linking The compiler uses the mmcu option to choose start up files and run time libraries that get linked together If this option isn t specified the compiler defaults to the 8515 processor environment which is most certainly what you didn t want 6 30 4 Examining the Object File Now we have a binary file Can we do anything useful with it besides put it into the processor The GNU Binutils suite is made up of many useful tools for manipulating object files that get generated One tool is avr objdump which takes information from the object file and displays it in many useful ways Typing the command by itself will cause it to list out its options For instance to get a feel of the application s size the h option can be used The output of this option shows how much space is used in each of the sections the stab and stabstr sections hold the debugging information and won t make it into the ROM file An even more useful option is 5 This option disassembles the binary file and inter sperses the source code in the output This method is much better in my opinion than using the 5 with the compiler because this listing includes routines from the libraries and the vector table contents Also all the fix ups have been satisfied In othe
41. option avrdude is part of the FreeBSD ports system To install it simply do the following usr ports devel avrdude make install Once installed avrdude can program processors using the contents of the hex file specified on the command line In this example the file main hex is burned into the flash memory avrdude p 2313 e m flash i main hex avrdude AVR device initialized and ready to accept instructions avrdude Device signature 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 0x00 avrdude 1750 bytes of flash written avrdude verifying flash memory against main hex avrdude reading on chip flash data 1749 0x00 avrdude verifying avrdude 1750 bytes of flash verified avrdude done Thank you The p 2313 option lets avrdude know that we are operating on an 419052313 chip This option specifies the device id and is matched up with the device of the same id in avrdude s configuration file usr local etc avrdude conf list valid parts specify the v option The e option instructs avrdude to perform a chip erase before programming this is almost always necessary before programming the flash The m flash option indicates that we want to upload data into the flash memory while i main hex specifies the name of the input file The EEPROM is uploaded in the same
42. t like the ugly if above you can always use 145 55 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 3 combinations of SFR ASM COMPAT and SFR OFFSET are supported the SFR ADDR SPMCR macro can be used to get the address of the SPMCR register 0x57 or 0x68 depending on device Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 17 lt avr sfr defs h gt Special function registers 133 6 17 lt avr sfr defs h gt Special function registers 6 17 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 paradigms to perform this task There s a separate IO address space available as it is known from some high level CISC CPUs that 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
43. 34 loop until bit is clear avr sfr 135 loop until bit is set avr sfr 135 avr stdlib 71 M PI avr math 30 M SQRT2 avr math 30 malloc Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen INDEX 348 avr_stdlib 72 math h 212 memccpy avr_string 79 memccpy S 213 memchr avr_string 79 memchr S 213 memchr_P avr_pgmspace 122 memchr PS 214 memcmp avr string 79 memcmp S 214 memcmp P avr pgmspace 122 memcemp PS 214 memcpy avr string 80 memepy S 214 memocpy P avr pgmspace 122 memcpy_P S 214 memmem avr string 80 memmem S 215 memmem P avr pgmspace 122 memmove avr string 80 memmove s 215 memrchr avr string 81 memrchr S 215 deprecated items 157 parity h 216 parity even bit util parity 149 PGM P avr pgmspace 118 pgm read byte avr pgmspace 118 pgm read byte far avr pgmspace 118 pgm read byte near avr pgmspace 119 pgm read dword avr pgmspace 119 pgm read dword far avr pgmspace 119 pgm read dword near avr pgmspace 119 pgm read word avr pgmspace 119 pgm read word far avr pgmspace 120 pgm read word near avr pgmspace 120 PGM VOID P avr pgmspace 120 pgmspace h 216 ELPM classic sals ELPM dword enhanced 218 ELPM enhanced 219 ELPM word classic 219 ELPM word enhanced 220 LPM classic 220 LPM dword classic 220 avr pgmspace 122 LPM dword enhanced 221 memrchr PS 215 LPM enha
44. 4 uint8_t value uint8_t 1 bits __asm__ volatile r30 1 n t 141 r31 O0 n t mov r0 2 n t sts 0 1 n t POLO uet aue ut vu GEO Pg BO uuu a an an an an ana 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 Tue 15 14 56 11 2007 for avr libe by Doxygen 8 4 boot h File Reference 201 spm n t word Oxffff n t hopinXt N i SFR MEM ADDR SPM REG N r uint8 t BOOT LOCK BITS SET N r value MESO rad X 8 4 2 3 define boot page erase alternate address Value __asm__ __volatile__ movw r30 2 n t Sts 0 SlAn 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 vet PG PPT SF BO A 8 4 2 4 define boot page erase extended address Value __asm__ __volatile__ movw r30 A3 n t sts S03 ni t sts 0 2 n t spm n t i SFR MEM ADDR SPM REG i SFR MEM ADDR RAMPZ r uint8 t BOOT PAGE ERASE mu uint32 t address 130 PAPP Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 8 4 boot h File Reference 202 8 4 2 5 d
45. ATmega644P AT mega644 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega8HVA ATmegal6HVA ATmega406 AT90PWM1 AT90PWM2 AT90PWM3 AT90USB82 AT90USB162 AT90USB646 AT90USB647 9005 1286 AT90USB 1287 6 21 lt util crcl6 h gt CRC Computations 6 21 1 Detailed Description include util crcl6 h This header file provides a optimized inline functions for calculating cyclic redundancy checks CRC using common polynomials References 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 21 lt util erc16 h gt CRC Computations 144 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 typical application would look like Dallas iButton test vector uint8 t serno 0x02 Oxlc Oxb8 0x01 0 0 0 0xa2 int checkcrc void uint8 t cre 0 i for i 0 i lt sizeof serno sizeof serno 0 i crc _crc_ibutton_update cre serno i return crc must 0 Functions e static inline uintl6 t crc16 update uint16 t crc uint8 t data e static inline uintl6 t c
46. 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 language explicitly be specified using the assembler with cpp option 9 5 3 Example program The following annotated example features a simple 100 kHz square wave generator using an AT90S1200 clocked with a 10 7 MHz crystal Pin PD6 will be used for the square wave output include lt avr io h gt Note 1 work 16 Note 2 tmp 17 inttmp 19 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 266 intsav SQUARE PD6 Note 3 Note 4 tmconst 10700000 200000 fuzz 8 100 kHz gt 200000 edges s clocks in ISR until TCNTO is set section text global main Note 5 main rcall ioinit Ja rjmp 1b Note 6 global TIMERO OVF vect Note 7 TIMERO OVF vect ldi inttmp 256 tmconst fuzz out SFR IO ADDR TCNTO inttmp Note 8 in intsav SFR IO ADDR SREG Note 9 sbic SFR IO ADDR PORTD SQUARE rjmp 1f sbi SFR IO ADDR PORTD SQUARE rjmp 2f Ta cbi SFR IO ADDR PORTD SQUARE 2
47. String 5 and then you add your PROGMEM macro to end of the declaration char string_table PROGMEM toting i String s String 3 String 4 St tate 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 4 Data in Program Space 263 itself in the Program Space This DOES NOT put the actual strings themselves into Program Space At this point the strings are still in the Data Space which is probably not what you want In order to put the strings in Program Space you have to have explicit declarations for each string and put each string in Program Space char string 1 PROGMEM String 1 char string 2 PROGMEM String 2 char string 3 PROGMEM String 3 char string 4 PROGMEM String 4 char string 5 PROGMEM String 5 Then use the new symbols in your table like so PGM P string table PROGMEM string 1 string 2 string 3 string 4 string 5 Now this has effect of putting string_table Program Space where string table is array of pointers to characters strings where each pointer is pointer to the Program Space where each string is also stored The PGM P type above is also macro that defined as pointer to chara
48. 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 rO 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 290 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 EN coo 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 stuff about Can I use C on the AVR Shouldn t I initialize all my variables
49. The assert macro tests the given expression and if it is false the calling process is terminated A diagnostic message is written to stderr and the function abort is called effectively terminating the program If expression is true the assert macro does nothing The assert macro may be removed at compile time by defining NDEBUG as a macro e g by using the compiler option DNDEBUG 6 2 lt ctype h gt Character Operations 6 2 1 Detailed Description These functions perform various operations on characters include lt ctype h gt Character classification routines These functions perform character classification They return true or false status de pending whether the character passed to the function falls into the function s classifi cation i e isdigit returns true if its argument is any value 0 though 9 inclusive int isalnum int c ATTR_CONST int isalpha int c ATTR_CONST int isascii int c ATTR CONST int isblank int c ATTR CONST int iscntrl int ATTR CONST int isdigit int c ATTR CONST int isgraph int c ATTR CONST int islower int c ATTR_CONST int isprint int ATTR_CONST int ispunct int c ATTR CONST int isspace int c ATTR CONST int isupper int c ATTR_CONST int isxdigit int c ATTR_CONST Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 2 lt ctype h gt Character Operations 15 Character convertion r
50. address to read the high fuse bits using boot lock fuse bits get 6 11 2 21 define GET LOCK BITS 0x0001 address to read the lock bits using boot lock fuse bits get 6 11 2 22 define GET LOW FUSE BITS 0x0000 address to read the low fuse bits using boot lock fuse bits get 6 12 lt avr eeprom h gt EEPROM handling 6 12 1 Detailed Description include 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 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 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 Tue 15 14 56 11 2007 for avr libe by Doxygen 6 12 lt avr eeprom h gt handling 95 avr This header file declares inline functions that call the assembler subroutines di rectly This prevents that the compiler generates push pops for the call clobbered registers This way also a specific calling convention could be used for the eep rom routines e g by passing values in t
51. 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 gec 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 914 GNU Binutils The name GNU Binutils stands for Binary Utilities It contains the GNU assembler gas and the GNU linker 18 but also contains many other utilities that work with binary files that are created as part of the software development toolchain Again when these tools are built for the AVR target the actual program names are prefixed with avr For example the assembler program name for a native assembler is as even though in documentation the GNU assembler is commonly referred to as gas But when built for an AVR target it becomes avr as Below is a list of the programs that are included in Binutils avr as The Assembler Generated on Tue May 15 14 56 11 2007 for avr
52. 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 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C OxOD OxOE OxOF 0x10 0x11 0x12 0x13 0 14 0 15 0 16 0 17 0 18 0 19 0 1 0 1 0 1 0 1 Generated Tue 15 14 56 11 2007 for avr libc by Doxygen 9 4 Data in Program Space 261 0 1 0 1 0 20 0 21 0 22 0 23 0 24 0 25 0 26 0 27 0 28 0 29 0 2 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 0859 0x5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0 6 and later in your code you access this data 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 pgmspace h gt and put it after the declaration of the variable
53. error This will allow a 9600 Bd communication using the standard 1 MHz calibrated RC oscillator See also the Baud rate tables in the datasheets Note 5 The datasheet explains why a minimum TWBR value of 10 should be maintained when running in master mode Thus for system clocks below 3 6 MHz we cannot run the bus at the intented clock rate of 100 kHz but have to slow down accordingly Note 6 This function is used by the standard output facilities that are utilized in this example for debugging and demonstration purposes Note 7 In order to shorten the data to be sent over the TWI bus the 24Cxx EEPROMs support multiple data bytes transfered within single request maintaining an internal address counter that is updated after each data byte transfered successfully When reading data one request can read the entire device memory if desired the counter would wrap around and start back from 0 when reaching the end of the device Note 8 When reading the 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 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
54. 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 I trace an assembler file in avr gdb When using the g compiler option avr gcc only generates line number and other debug information for C and files that pass the compiler Functions that don t have line number information will be completely skipped by a single step command in gdb This includes functions linked from a standard library but by default also functions defined in an assembler source file since the g compiler switch does not apply to the assembler So in order to debug an assembler input file possibly one that has to be passed through the C preprocessor it s the assembler that needs to be told to include line number information into the output file Other debug information like data types and variable allocation cannot be generated since unlike a compiler the assembler basically doesn t know about this This is done using the GNU assembler option gstabs E
55. 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 A consequence of the ordering used by stremp P is that if 51 is an initial substring of s2 then s1 is considered to be less than s2 6 14 4 12 char P char dest P src The strepy function is similar to strcpy except that src is a pointer to a string in program space Returns The strepy P function returns a pointer to the destination string dest Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 125 6 14 4 13 size t strcspn P const char s PGM P reject The strcspn_P function calculates the length of the initial segment of s which consists entirely of characters not in reject This function is similar to strcspn except that reject is a pointer to a string in program space Returns The strcspn function returns the number of characters in the initial segment of s which are not in the string re ject The terminating zero is not considered as part of string 6 14 4 14 size t strlcat P char dst PGM P size t siz Concatenate two strings The strlcat PQ function is similar to strlcat except that the src string must be located in program space flash Appends src to
56. except that s2 is pointer to a string in program space 6 14 4 8 char 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 124 6 14 4 9 strchr P PGM Ps int val Locate character in program space string The strchr P function locates the first occurrence of val converted to a char in the string pointed to by s in program space The terminating null character is considered to be part of the string The strchr P function is similar to strchr except that s is pointer to a string in program space Returns The strchr P function returns a pointer to the matched character or NULL if the character is not found 6 14 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 14 4 11 int stremp P const char s1 P 52 The strcmp function is similar to stremp
57. lst PRG 1st lst elf S OBJDUMP h S lt gt SG Rules for building the text rom images text hex bin srec hex PRG hex bin PRG bin srec PRG srec hex elf j text j data O ihex lt 560 srec elf j text j data O srec lt 6 bin elf Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 176 j text j data O binary lt Q Rules for building the eeprom eeprom ehex ebin esrec ehex PRG eeprom hex PRG _eeprom bin esrec S PRG eeprom srec oe eeprom hex elf oe eeprom srec elf ur eeprom bin elf oe ur Every thing below here is used by the casual user FIG2DEV fig2dev 5 j eeprom c echo empty 6 not generated exit 0 OBJCOPY j eeprom c echo empty 506 not generated exit 0 OBJCOPY j eeprom c echo empty 86 not generated exit 0 rom images hange section lma eeprom 0 O ihex lt Q N hange section lma eeprom 0 O srec lt Q N hange section lma eeprom 0 O binary lt 8 N by avr libc s build system and can be ignored EXTRA CLEAN FILES x hex srec dox eps png pdf eps PRG eps png PRG png pdf pdf eps fig S FIG2DEV L eps lt pdf fig 5 2 L
58. lt errno h gt System Errors 16 lt inttypes h gt Integer Type conversions 17 lt math h gt Mathematics 29 lt setjmp h gt Non local goto 33 lt stdint h gt Standard Integer Types 35 lt stdio h gt Standard IO facilities 47 lt stdlib h gt General utilities 66 lt string h gt Strings 77 lt util crc16 h gt CRC Computations 143 lt util delay h gt Convenience functions for busy wait delay loops 147 lt util delay basic h gt Basic busy wait delay loops 148 lt util parity h gt Parity bit generation 149 lt util twi h gt TWI bit mask definitions 150 BV sfr 134 _EEGET avr_eeprom 96 _EEPUT avr_eeprom 96 _FDEV_EOF avr_stdio 52 _FDEV_ERR avr_stdio 52 _FDEV_SETUP_READ avr_stdio 52 _FDEV_SETUP_RW avr_stdio 52 _FDEV_SETUP_WRITE avr_stdio 52 _FFS avr_string 78 AVR_LIBC_DATE avr_version 139 AVR LIBC DATE STRING avr version 139 AVR MAJOR avr version 139 AVR LIBC MINOR avr version 139 AVR REVISION avr version 139 AVR LIBC VERSION STRING avr version 139 AVR VERSION avr version 139 EEPROM REG LOCATIONS avr eeprom 95 ELPM classic pgmspace h 218 ELPM dword enhanced pgmspace h 218 ELPM enhanced pgmspace h 219 ELPM word classic pgmspace h 219 INDEX 337 ELPM word enhanced pgmspace h 220 LPM classic pgmspace h 220 LPM d
59. or the first n bytes thereof is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strncasecmp_P is that if s1 is an initial substring of s2 then 51 is considered to be less than 52 6 14 4 18 char strncat P char dest P src size_t len Concatenate two strings The strncat_P function is similar to strncat except that the src string must be located in program space flash Returns The strncat_P function returns a pointer to the resulting string dest 6 14 4 19 int strncmp_P const char 57 PGM_P s2 size_t n The strncmp_P function is similar to stremp P except it only compares the first at most n characters of s1 and 52 Returns The strncmp_P function returns an integer less than equal to or greater than zero if sl or the first n bytes thereof is found respectively to be less than to match or be greater than s2 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 127 6 14 4 20 char strncpy_P char dest 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 15 less than that of n the remainder of dest will be padded with nulls Returns
60. pointer_ eeprom size_t 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 97 6 12 3 2 uint8 t eeprom read byte const uint8_t addr Read one byte from EEPROM address addr 6 12 3 3 uintl6 t eeprom read word const uint16 t addr Read one 16 bit word little endian from EEPROM address addr 6 12 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 12 3 5 void eeprom write byte uint8 t addr uint8 t value Write byte value to EEPROM address addr 6 12 3 6 void eeprom write word uint16 t addr uint16 t value Write a word value to EEPROM address addr 6 13 lt avr interrupt h gt Interrupts 6 13 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 on how to handle interrupt code Since the C language tries to stay away from machine dependent details each compiler writer is forced to design their method of support In the AV
61. 06 1 Detaled Description 22222222222 205 455 238 Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen CONTENTS x 8 67 8 68 8 69 8 70 8 71 8 72 8 73 8 74 8 75 8 76 8 77 8 78 8 79 5 File Reference 2 22 22 238 Detailed Descriptions 222 5259 6S ea EUR 238 sthepy PS Pile Referenc eios xu ea eie BAS S 239 8 66 1 Detailed Desenpfi n s ss s s as s Sek w wo a 239 strnlen S File 25 tes 239 8091 Detaled Description sos seas s e us s s guy s sten S 239 ES File Referente voc s ea S K Ue SG ERR 239 8 70 1 Detailed Description 239 strpbrk 5 File Reference oc eoo RR RR REOR 240 871 1 Detaled Description s s 5 5446 G mk 240 strpbik PS Fil Reference 2 2 2 2 22 22 240 5 72 1 Detailed Description 4 ouk eot oc RR 240 sieht Pile Referente ul eoe aus s xu e EGGE GEER 3 240 6 73 1 Detailed Description 222222225525 See se weak es 240 strrchr PS File Reference 242 8 74 1 Detailed Description 242 se se Reference loo c he e su s eae ee Y S Og s od 242 5 75 1 Detailed Description RR 242 stisep s File Reference 222222 2 2 2 2 222 2 242 6 70 1 Detailed Description ecce Gm eue sets 242 P S File Reference 645 242 8 77 1 Detailed Descrip
62. 128 Y pointer is used as 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 r0 temporary register be clobbered by any C code except interrupt handlers which save it may be used to remember something for a while within one piece of assembler code rl assumed to be always zero in any C code be used to remember something for a while within one piece of assembler code but must then be cleared after use clr r1 This includes any use of the mul s u instructions which return their result in rl r0 Interrupt handlers save and clear 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 enhanced core If too many those that don t fit are passed on the stack Return values 8 bit in 124 not 125 16 bit in r25 124 up to 32 bits in 122 125 up to 64 bits in r18 r25 8 bit return values are zero sign extended to 16 bits by the caller unsigned char is more efficient than signed char just clr r25 Argu ments to functions with variable argument lists printf etc are all passed on stack and char is extended to int G
63. 2 23 define TW SR STOP 0xA0 stop or repeated start condition received while selected 6 25 2 24 define TW ST LOST SLA ACK 0 0 arbitration lost in SLA RW SLA R received ACK returned 6 25 2 25 define TW ST DATA 0 8 data transmitted ACK received 6 25 2 26 define TW ST DATA 0 0 data transmitted NACK received 6 25 2 27 define TW ST LAST DATA 0xC8 last data byte transmitted ACK received 6 25 2 28 define TW ST SLA 0xA8 SLA R received ACK returned 6 25 2 29 define TW START 0x08 start condition transmitted 6 25 2 30 define TW STATUS TWSR amp TW STATUS MASK TWSR masked by TW STATUS MASK Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 26 lt compat deprecated h gt Deprecated items 154 6 25 2 31 define TW STATUS MASK Value BV TWS7 BV TWS6 BV TWS5 BV TWS4 N BV TWS3 The lower 3 bits of TWSR are reserved on the ATmegal63 The 2 LSB carry the prescaler bits on the newer ATmegas 6 25 2 32 define TW WRITE 0 SLA W address 6 26 lt compat deprecated h gt Deprecated items 6 26 1 Detailed Description This header file contains several items that used to be available in previous versions of this library but have eventually been deprecated over time include compat deprected h These items are supplied within that header file for backward compatibility reasons only so old source code that has been written for
64. 2223 define _ ELPM_enhanced_ addr Value __extension 2y SET ADNET r30 1 n t Z n t B0 Z n t 0 Z n t D0 2 result C addr32 SFR IO ADDR RAMPZ r31 8 uint32 t __addr32 asm ois out movw elpm nq r30 result 8 31 24 Value __extension result 24 SCIT TAANE 30 nti 0 7 n t __result C addr32 _SFR_IO_ADDR RAMPZ x r31 N 4772477727777 uint32_t __addr32 uintl6 t _ result asm out 2 mov r31 B1 mov r30 A1 elpm mov A0 ro in adiw 2 r307 p n t n t n t n t n t n t n t uint32 addr uint32 t addr Pea a an an an an an an an an an an an a ELPM word classic addr Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 31 pgmspace h File Reference 220 adc r0 zero reg n t out 2 r0 inc elpm MYNET mov B0 ro n t r result r addr32 I SFR IO ADDR RAMPZ 1x30 Trad result 8 31 2 5 define word enhanced _ Value __extension__ uint32_t __addr32 uintl6 t _ result a a a an a an uint32_t addr asm out 2 C1 movw r30 1 n t elpm A0 Z
65. 24 232 8 41 1 Detaled Description lt uo eot o Rok BR 232 stcat P S File Reference deco oom RE SER 233 5421 Detailed Description 222222225522 p eek 233 strebe S Fil Reference ossa 233 8 43 1 Detailed Description 233 strehr PS File Reference 233 8 44 1 Detailed Description 233 strehinul S File Reference osc u u a s s wasa c mmo Rs 233 6 45 1 Detailed Description ecc Rm eue e s 233 stchmul PS File Reference 22 2 22 eek k 49 59 233 8 46 1 Detailed Description 233 strcmp s File Referenc sos o s s zoo m RR RR 233 8 47 1 Detailed Description se csse kes sek ke 233 PS Pile Reference uoc loo TREES S 233 8 48 1 Detailed Description s sss soo RR RR RR Rn 233 siopy File Referente uso oto o e RR RERO 233 6 491 Detaled Description 222222222 233 step P S File Reference i si u e t comm o b RR 234 8 50 1 Detailed Description 234 sicspn s Pile Reference 222222222252 SSG EEG 234 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen CONTENTS ix 8 52 8 53 8 54 8 55 8 56 8 57 8 58 8 59 8 60 8 61 8 62 8 63 8 64 8 65 8 66 8 51 1 Detailed Description 2 234 strespn P S File Reference 22222225252 ks Kake Ka Rc 234 6 52 Detaled Description lt es zoe meos Skade 234 strap b File Re
66. 42 SIGNAL avr interrupts 116 sin avr math 33 sinh Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen INDEX 352 avr_math 33 SIZE MAX avr stdint 42 sleep h 224 sleep cpu avr sleep 138 sleep disable avr sleep 138 sleep enable avr sleep 138 sleep mode avr sleep 138 SLEEP MODE ADC avr sleep 137 SLEEP MODE EXT STANDBY avr sleep 137 SLEEP MODE IDLE avr sleep 137 SLEEP MODE PWR DOWN avr sleep 137 SLEEP MODE PWR SAVE avr sleep 137 SLEEP MODE STANDBY avr sleep 137 snprintf avr stdio 58 snprintf P avr stdio 59 sprintf avr stdio 59 sprintf P avr stdio 59 sqrt avr math 33 square avr math 33 srand avr stdlib 74 srandom avr stdlib 74 sscanf avr stdio 59 sscanf P avr stdio 59 stderr avr stdio 54 stdin avr stdio 54 stdint h 225 stdio h 228 stdlib h 230 stdout avr stdio 55 strcasecmp avr string 81 strcasecmp S 232 strcasecmp P avr pgmspace 123 strcasecmp P S 232 Strcasestr avr string 81 strcasestr S 232 strcasestr P avr pgmspace 123 strcat avr string 82 strcat S 232 strcat P avr pgmspace 123 streat_P S 233 strchr avr_string 82 strchr S 233 strchr_P avr_pgmspace 123 strchr_P S 233 strchrnul avr_string 82 strchrnul S 233 strchrnul P avr pgmspace 124 strchrnul P S 233 strcmp avr_string 82 stremp S 233 stremp P avr pgmspace 124 stremp P S 233 strepy avr string 83 strepy S
67. 5 3 9 double fabs double x The fabs function computes the absolute value of a floating point number x 6 5 3 10 double floor double x The floor function returns the largest integral value less than or equal to x expressed as floating point number 6 5 3 11 double fmod double _ x double y The function fmod returns the floating point remainder of x y 6 5 3 12 double frexp double _ value int x __exp The frexp function breaks a floating point number into a normalized fraction and an integral power of 2 It stores the integer in the int object pointed to by exp The frexp function returns the value x such that x is a double with magnitude in the interval 1 2 1 or zero and value equals x times 2 raised to the power exp If value is zero both parts of the result are zero 6 5 3 13 int isinf double x The function isinf returns 1 if the argument x is either positive or negative infinity otherwise 0 6 5 3 14 intisnan double x The function isnan returns if the argument x represents a not a number NaN object otherwise 0 6 5 3 15 double Idexp double __x int exp The Idexp function multiplies a floating point number by an integral power of 2 The Idexp function returns the value of x times 2 raised to the power exp If the resultant value would cause an overflow the global variable errno is set to ERANGE and the value NaN is returned 6 5 3 16 double log double x The log
68. 6 14 4 4 void memmem P const void sl size t len PGM VOID P s2 size t len2 The memmem function is similar to memmem except that 52 is pointer to a string in program space Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 123 6 1445 VOID P memrchr P VOID P src int val size_t len The memrchr 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 14 4 6 int strcasecmp P const char s1 P 52 Compare two strings ignoring case The strcasecmp 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 82 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 51 is found respectively to be less than to match or be greater than 52 A consequence of the ordering used by strcasecmp is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 6 14 4 7 char strcasestr P const char s1 PGM P 52 This funtion is similar to strcasestr
69. 73 RANDOM MAX avr stdlib 68 random r avr stdlib 73 realloc avr stdlib 73 rem div t 197 Idiv t 197 sbi Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 351 deprecated_items 157 scanf avr_stdio 58 scanf_P avr_stdio 58 SCNd16 avr_inttypes 25 SCNd32 avr_inttypes 26 SCNdFAST16 avr_inttypes 26 SCNdFAST32 avr_inttypes 26 SCNdLEAST16 avr_inttypes 26 SCNdLEAST32 avr_inttypes 26 SCNdPTR avr_inttypes 26 SCNi16 avr_inttypes 26 SCNi32 avr_inttypes 26 SCNiFAST 16 avr inttypes 26 SCNiFAST32 avr inttypes 26 SCNiLEAST16 avr inttypes 26 SCNiLEAST32 avr inttypes 27 SCNiPTR avr inttypes 27 SCNo16 avr inttypes 27 SCNo32 avr inttypes 27 SCNoFAST16 avr inttypes 27 SCNoFAST32 avr inttypes 27 SCNoLEAST16 avr_inttypes 27 SCNoLEAST32 avr_inttypes 27 SCNoPTR avr_inttypes 27 SCNu16 avr_inttypes 27 SCNu32 avr_inttypes 27 SCNuFAST16 avr inttypes 28 SCNuFAST32 avr inttypes 28 SCNuLEAST16 avr_inttypes 28 SCNuLEAST32 avr_inttypes 28 SCNuPTR avr_inttypes 28 SCNx16 avr_inttypes 28 SCNx32 avr_inttypes 28 SCNxFAST16 avr inttypes 28 SCNxFAST32 avr inttypes 28 SCNxLEAST16 avr_inttypes 28 SCNxLEAST32 avr_inttypes 28 SCNxPTR avr_inttypes 29 sei avr_interrupts 115 set_sleep_mode avr_sleep 138 setjmp longjmp 34 setjmp 35 setjmp h 223 SIG ATOMIC MAX avr stdint 42 SIG ATOMIC MIN avr stdint
70. 8 58 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 59 8 59 1 Defines strlen_ P S File Reference Detailed Description define src_hi r25 define src_lo r24 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 60 strlwr S File Reference 237 8 60 strlwr S File Reference 8 60 1 Detailed Description 8 61 strncasecmp S File Reference 8 61 1 Detailed Description 8 62 strncasecmp P S File Reference 8 62 1 Detailed Description 8 63 strncat S File Reference 8 63 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 64 strncat 5 File Reference 8 64 1 Detailed Description Defines define dest hi r25 define dest lo 24 define src hi r23 define src lo r22 define len hi r21 define len lo r20 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 65 strncmp S File Reference 238 8 65 strncmp S File Reference 8 65 1 Detailed Description Defines define 51 hi r25 define s1 lo r24 define s2 hi r23 define s2 lo 122 define len hi r21 define len lo r20 define
71. 855 4 Sek KAR s 150 6 25 2 Define Documentation 151 lt compat deprecated h gt Deprecated items 154 6 26 1 Detailed Description sa 54 ce ee eee ee L RR 154 6 26 2 Define Documentation 155 6 26 3 Function 157 lt compat ina90 h gt Compatibility with IAR EWB 3 x 157 Deni PROC 22222 ee ee mO G EE SEES vetus 158 6 28 1 Detailed Description 05 6254 158 Combining and assembly source files 159 JE EEE EO 222222222222 2 2 160 6 29 2 A code walkthrough 160 6 0 3 Te sourcecode 2e s reir etke ewe N 162 Ape Bes sa ard k ku e mene Bowe GR eddie BSR aS 162 TNS PURE 52222225 eee ek a 162 6 302 The a e w o m e wR G 165 6 30 3 Compiling and 166 6 304 Examining the Object File 2 167 6305 Linker Map Files e serves ees 171 6 30 0 Generating Intel Hex Files 173 6 30 7 Letting Make BuildtheProject 222 o se 174 6 30 8 Reference to the source code 176 more sophisticated project 177 6311 Hardware setup 45 osos orc Ge 177 6312 Functional VepvIeW lcg e ps Ged bee Ak 180 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen CONTENTS v 6 31 3 A code walkthrough
72. 90 lpm r0 Z 0 92 st X 00000010 lt do_copy_data_start gt 0 a0 36 cpi 26 0x60 96 25 bl OF ope 2 L i 4 do f7 brne 10 Oxc lt do copy data loop 00000016 lt do clear bss gt 6 10 0 ldi 17 0x00 0 8 a0 e6 ldi r26 0x60 96 a b0 eO ldi r27 0x00 O CUOI 0 rjmp 2 0x20 do clear bss start 0000001e do clear bss loop e 1d 92 St rl 00000020 do clear bss start 20 a3 36 cpi r26 0x63 99 22 bl 02 ope 127 219 24 7 brne 8 Oxle lt do clear bss loop 00000026 lt vector 8 enum UP DOWN ISR TIMER1 OVF vect Note 2 26 16 92 push 1 28 Of 92 push 2a Of b6 in rO Ox3f 63 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 169 26 OE 92 push 2e 11 24 eor rl rl 30 2f 93 push r18 32 3 df 93 push r19 34 8f 93 push r24 4c 50 54 56 58 SE 62 64 66 68 6a 6e TO 74 78 7a 80 84 86 8 static uintl6 t pwm Note 3 static uint8 t direction switch direction Note 4 36 3a 36 3e 40 42 46 4 80 91 60 00 145 r24 0 0060 88 23 r24 r24 39 0 breq 14 Ox4c lt SREG 81 30 cpi r24 0x01 1 59 0 breq 46 0x70 lt SREG 20 91 61 00 145 r18 0 0061 30 91 62 00 145 19 0 0062 21 60 rjmp 66 Ox8e lt SREG case UP if pwm 20
73. 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 31 3 4 Part 4 Auxiliary functions function handle mcucsr uses two attribute declarators to achieve specific goals First it will instruct the com piler to place the generated code into the init3 section of the output Thus it will be come part of the application initialization sequence This is done in order to fetch and clear the reason of the last hardware reset from MCUCSR as early as possible There is a short period of time where the next reset could already trigger before the current reason has been evaluated This also explains why the variable mcucsr that mirrors the register s value needs to be placed into the noinit section because otherwise the default initialization which happens after init3 would blank the value 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 31 Amore sophisticated project 183 handle_mcucsr is a function to the compiler the compiler will
74. ATmega2560 AT mega2561 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER3 SIG Timer Counter3 AT90CAN 128 AT90CAN32 AT90CAN 64 OVF vect OVERFLOW3 Overflow ATmegal28 ATmegal62 ATmega64 mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMERA SIG INPUT Timer Counter4 ATmega640 ATmegal280 ATmegal281 vect CAPTURE4 Capture Event ATmega2560 ATmega2561 TIMER4 SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPA vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARE4A TIMER4 SIG_ Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPB vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPAREAB B TIMER4 SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 vect OUTPUT Compare Match ATmega2560 ATmega2561 COMPARE4C C TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 OVF vect OVERFLOW4 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 TIMER5 SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 vect
75. 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 ATtiny461 AT tiny861 AT9OUSB162 9005 82 9005 1287 AT90USB 1286 9005 647 9005 646 Generated Tue 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 102 Vector name Old vector name Description Applicable for device INT1_vect SIG_ INTERRUPT1 External Interrupt Request 1 9052313 9052333 AT90S4414 9054433 AT90S4434 9058515 9058535 AT9OPWM3 AT90PWM2 AT90PWMI AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l 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 ATtiny461 AT tiny861 AT90USB162 9005 82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB6
76. AVR ATmega8HVA avr4 at90pwm 1 AVR ATOOPWMI avr4 at90pwm2 __AVR_AT9O0PWM2__ avr4 at90pwm3 __AVR_AT9OPWM3__ avr5 at90can32 AVR AT90CAN32 avr5 at90can64 AVR AT90CAN64 avr5 at90can128 AVR AT90CAN 128 avr5 at90usb82 AVR AT90USB82 _ avr5 at90usb162 AVR AT90USB162 avr5 at90usb646 AVR AT90USB646 avr5 at90usb647 AVR 9005 647 avr5 at90usb1286 AVR AT90USB1286 avr5 at90usb1287 AVR AT90USB1287 avr5 atmegal28 AVR ATmegal28 avr5 atmegal280 _AVR_ATmegal280__ avr5 atmegal281 AVR ATmegal281 avr5 atmegal6 AVR ATmegal16 avr5 atmegal61 __AVR_ATmegal61__ avr5 atmegal62 AVR ATmegal62 avr5 atmegal 3 AVR ATmegal63 avr5 atmegal64p AVR ATmegal64P _ avr5 atmegal65 AVR ATmegal65 avr5 atmegal65p AVR ATmegal65P avr5 atmegal68 __AVR_ATmegal68__ Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 11 Using the GNU tools 321 Architecture MCU name Macro 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 atmega329 AVR ATmega329 avr5 atmega329p _ AVR ATmega329P avr5 a
77. Asked Questions 307 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 if n uart_putchar Nr loop_until_bit_is_set USR UDRE UDR return 0 so it could be used for fdevopen too void debug P const char xaddr char while c read byte uart putchar c int main void ioinit initialize UART debug P PSTR foo was here n return 0 Note By convention the suffix P to the function name is used as an indication that this function is going to accept 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 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 To work around this use typecasts on the operands including literals to declare that the values are to be 8 bit operands Generated on Tue
78. 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 17 2 Define Documentation 6 17 2 1 define BV bit 1 lt lt bit Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 17 lt avr sfr defs h gt Special function registers 135 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 17 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 17 2 3 define bit is set sfr bit SFR BYTE sfr amp BV bit include lt avr io h gt Test whether bit bit in IO register sfr is set This will return a 0 if the bit is clear and non zero if the bit is set 6 17 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 sfr is clear 6 17 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 sfr is set Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen
79. COMP vect OUTPUT Compare Match ATmega103 ATmegal28 ATmegal6 COMPAREO megal61 ATmegal62 ATmegal65 AT 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 CounterO 9051200 419052333 AT90S4414 vect OVERFLOWO Overflow 9054433 419054434 41719058515 AT9088535 AT90PWM3 AT90PWM2 AT90PWMI 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 ATmega168 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtinyll ATtiny12 ATtiny15 ATtiny2313 ATtiny28 ATtiny261 ATtiny461 AT tiny861 AT9OUSB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER SIG INPUT Timer Counter I 9052313 CAPTI vect CAPTUREI Capture Event Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 107
80. 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 Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 20 lt avr wdt h gt Watchdog timer handling 140 6 19 2 7 define __ VERSION STRING GAVR VERSIONG String literal representation of the current library version 6 20 lt avr wdt h gt Watchdog timer handling 6 20 1 Detailed Description include lt avr wdt h gt This header file declares the interface to some inline macros handling the watchdog timer present in many AVR devices In order to prevent the watchdog timer configura tion from being accidentally altered by a crashing application a special timed sequence is required in order to change it The macros within this header file handle the required sequence automatically before changing any value Interrupts will be disabled during the manipulation Note Depending on the fuse configuration of the particular device further restrictions might apply in particular it might be disallowed to turn off the watchdog timer Note that for newer devices ATmega88 and newer effectively any AVR that has the op tion to also generate interrupts the wa
81. Rx Com AT90S2313 AT90S2333 419054414 vect RECV plete 9054433 AT90S4434 419058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART TX SIG UART UART Tx Com AT90S2313 AT90S2333 9054414 vect TRANS plete 9054433 419054434 41719058515 AT9088535 ATmegal03 ATmegal63 ATmega8515 UART SIG UART Data Reg AT90S2313 419052333 AT90S4414 UDRE vect DATA ister Empty 9054433 9054434 9058515 AT9088535 ATmegal03 ATmegal63 ATmega8515 USARTO SIG USARTO Rx ATmegal62 RXC_vect USARTO_ Complete RECV USARTO SIG USARTO Rx AT90CAN128 AT90CAN32 AT90CAN64 RX 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 112 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 AT
82. S File Reference 8 49 1 Detailed Description Defines define dest hi r25 define dest lo r24 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 50 strcpy_P S File Reference 234 define src_hi r23 define src_lo r22 8 50 strcpy 5 File Reference 8 50 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 8 51 strcspn S File Reference 8 51 1 Detailed Description 8 52 strcspn P S File Reference 8 52 1 Detailed Description 8 53 sSstring h File Reference 8 53 1 Detailed Description Defines fidefine 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 memcepy void const void int size t void memchr const void int size_t ATTR PURE int memcmp const void const void size_t ATTR PURE Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 53 string h File Reference 235 void memcpy void const void size_t void memmem const void size_t const void size_t ATTR PURE void memmove void const void size_t void memrchr const void int size_t ATTR PURE void memset void int size_t char strcat c
83. SLA NACK 0x48 define TW MR DATA ACK 0x50 define TW DATA NACK 0x58 define TW ST SLA 8 define TW ST LOST SLA OxBO define TW ST DATA ACK 0 8 define TW ST DATA 0xCO define TW ST LAST DATA 0xC8 define TW SR SLA ACK 0x60 define TW SR ARB LOST SLA 0x68 fdefine TW SR GCALL ACK 0x70 define TW SR LOST GCALL 0x78 define TW SR DATA ACK 0x80 fdefine TW SR DATA NACK 0x88 define TW SR GCALL DATA ACK 0x90 fdefine TW SR GCALL DATA NACK 0x98 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 25 lt util twi h gt TWI bit mask definitions 151 define TW_SR_STOP 0xA0 define TW_NO_INFO 0xF8 define TW_BUS_ERROR 0x00 define TW_STATUS_MASK define TW STATUS TWSR amp TW STATUS MASK R W bit in SLA R W address field define TW READ 1 define TW WRITE 0 6 25 2 Define Documentation 6 25 2 1 define TW BUS ERROR 0x00 illegal start or stop condition 6 25 2 define TW MR LOST 0x38 arbitration lost in SLA R or NACK 6 25 2 3 define TW MR DATA 0x50 data received ACK returned 6 25 2 4 define TW MR DATA NACK 0x58 data received NACK returned 6 25 2 5 didefine TW MR SLA 0x40 SLA R transmitted ACK received 6 25 2 6 define TW MR SLA 0x48 SLA R transmitted NACK received 6 25 27 define TW MT LOST 0x38 arbitration lost in SLA W or data 6 25 2 d
84. 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 terminating NUL character if precision is specified no more than the number specified are written If 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 terminating NUL character A is written No argument is converted The complete conversion specifica tion is 9696 eE The double argument is rounded and converted in the format d dddesdd where there is one digit before the decimal point charac ter and the number of digits after it is equal to the precision if the precision is missing it is taken as 6 if the precision is zero no decimal point character appears An E conversion uses the letter E rather than to introduce the exponent The exponent always contains two digits if the value is zero the exponent is 00 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 8 lt stdio h gt Standard IO facilities 62 fF The double argument is rounded and converted to decimal notation in the format 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 ch
85. Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 122 6 14 3 11 prog void Type of a void object located in flash ROM Does not make much sense by itself but can be used to declare a void object in flash ROM 6 14 4 Function Documentation 6 14 41 VOID P memchr P VOID P s int val size t len Scan flash memory for a character The memchr P function scans the first len bytes of the flash memory area pointed to by s for the character val The first byte to match val 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 14 4 2 int memcmp P const void s7 VOID P 52 size t len Compare memory areas memcmp function compares the first 1en bytes of the memory areas s1 and flash s2 The comparision is performed using unsigned char operations Returns The memcmp P function returns an integer less than equal to or greater than zero if the first Len bytes of s1 is found respectively to be less than to match or be greater than the first 1en bytes of s2 6 14 4 3 void memcpy_P void dest PGM VOID P src size_t n The memepy PO function is similar to memcpy except the src string resides in pro gram space Returns The memecpy function returns a pointer to dest
86. __c stdout The macro put char sends character c to stdout 6 8 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 8 2 18 define stdin __iob 0 Stream that will be used as an input stream by the simplified functions that don t take a stream argument The first stream opened with read intent using fdevopen will be assigned to stdin 6 8 2 19 define stdout __iob 1 Stream that will be used as an output stream by the simplified functions that don t take a stream argument The first stream opened with write intent using fdevopen will be assigned to both stdin and stderr 6 8 3 Function Documentation 6 8 3 1 void clearerr FILE _ stream Clear the error and end of file flags of st ream 6 8 3 2 intfclose FILE stream This function closes st ream and disallows and further IO to and from it When using fdevopen to setup the stream a call to fclose is needed in order to free the internal resources allocated If the stream has been set up using fdev setup stream or FDEV SETUP STREAMO use fdev close instead Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 8 lt stdio h gt Standard IO facilities 56 It currently alway
87. 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 Note 5 External functions need to be declared to be global main is the application entry point that will be jumped to from the ininitalization routine in crts1200 0 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 5 avr libc and assembler programs 268 Note 6 The main loop is just single jump back to itself Square wave generation itself is completely handled by the timer 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 is executed quite frequently Note 7 Interrupt functions can get the usual names that are also available to C programs The linker will then put them into the appropriate interrupt vector slots Note that they must be declared global in order to be acceptable for this purpose This will only work if lt avr io h gt has been included Note that the assembler or
88. although usually associated with presumably simple things like the famous Hello world program are actually fairly complex which causes their inclusion to eat up a fair amount of code space Also they are not fast due to the nature of interpreting the format string at run time Whenever possible resorting to the sometimes non standard predetermined conversion facilities that are offered by avr libc will usually cost much less in terms of speed and code size Tunable options for code size vs feature set order to allow programmers a code size vs functionality tradeoff the function vfprintf which is the heart of the printf family can be selected in different flavours using linker options See the documentation of vfprintf for a detailed description The same applies to vfscanf and the scanf family of functions Outline of the chosen API The standard streams stdin stdout and stderr provided but contrary to the C standard since avr libc has no knowledge about appli cable devices these streams are not already pre initialized at application startup Also since there is no notion of file whatsoever to avr libc there is no function fopen that could be used to associate a stream to some device See note 1 Instead the function fdevopen is provided to associate a stream to a device where the device needs to provide a function to send a character to receive a character or both There is no differentiation between
89. and required on some devices like ATmegal61 because of errata and add W1 Tdata 0x801100 to start the data section above the stack For more information on using sections see Memory Sections There is also an ex ample for Using Sections in C Code Note that in C code any such function would preferrably be placed into section init3 as the code in init2 ensures the internal regis ter zero reg isalready cleared Back to FAQ Index 9 9 6 What is all this BV stuff about When performing low level output work which is very central point in microcon troller programming it is quite common that particular bit needs to be set or cleared Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 9 9 Frequently Asked Questions 293 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 15 needed to convert a bit number usually within a byte register into a byte value that can be assigned directly to the register However sometimes the direct bit numbers are needed as well e g in an SBI instruction so the definitions cannot usefully be made as byte values in the first place So in order to access a particular bit number as byte value use BV macro Of course the implementation of this macro is just the usual bit shift which i
90. 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 GCC with the progmem attribute This macro was created as a convenience to the end user as we will see below The PROGMEM macro is defined in the avr pgmspace h system header file It is difficult to modify GCC to create new extensions to the C language syntax so instead avr libc has created macros to retrieve the data from the Program Space These macros are also found in the lt avr pgmspace h gt system header file 9 4 2 A Note On const Many users bring up the idea of using C s keyword const as a means of declaring data to be in Program Space Doing this would be an abuse of the intended meaning of the const keyword const is used to tell the compiler that the data is to be read only It is used to help make it easier for the compiler to make certain transformations or to help the compiler check for incorrect usage of those variables For example the const keyword is commonly used in many functions as a modifier on the parameter type This tells the compiler that the function will only use the parameter as read only and will not modify the contents of the parameter variable
91. avr interrupt h gt Interrupts 105 Vector name Old vector Description Applicable for device name SPM_ SIG_SPM_ Store Program AT90PWM3 AT90PWM2 AT90PWMI READY vect READY Memory Read AT90CAN 128 AT90CAN32 AT90CAN 64 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 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 TIMO SIG Timer Counter ATtiny13 ATtiny24 ATtiny44 ATtiny84 COMPA vect OUTPUT Compare Match ATtiny45 ATtiny25 ATtiny85 COMPAREOA TIMO SIG Timer Counter ATtiny13 ATtiny24 ATtiny44 ATtiny84 COMPB vect OUTPUT Compare Match ATtiny45 ATtiny25 ATtiny85 TIMO OVF SIG Timer CounterO ATtinyl3 ATtiny24 ATtiny44 ATtiny84 vect OVERFLOWO Overflow ATtiny45 ATtiny25 ATtiny85 TIMI SIG INPUT Timer Counter 1 ATtiny24 ATtiny44 ATtiny84 vect CAPTUREI Capture Event TIMI SIG Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 COMPA vect OUTPUT Compare Match ATtiny25 ATtiny85 COMPAREIA A TIMI SIG Timer Counter1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 COMPB vect OUTPUT Compare Mat
92. avr libc Related Pages Here is a list of all related documentation pages Toolchain Overview 245 Memory Areas and Using malloc 250 Memory Sections 255 Data in Program Space 259 avr libe and assembler programs 264 Inline Assembler Cookbook 270 How to Build a Library 282 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 avr libc Module Documentation 13 Porting From IAR to AVR GCC 285 Frequently Asked Questions 289 Installing the GNU Tool Chain 312 Using the GNU tools 318 Using the avrdude program 328 Release Numbering and Methodology 330 Acknowledgments 333 Todo List 334 Deprecated List 335 6 avr libc Module Documentation 6 1 lt assert h gt Diagnostics 6 1 1 Detailed Description finclude lt assert h gt This header file defines debugging aid As there is no standard error output stream available for many applications using this library the generation of 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 1 2 Define Documentation 6 1 2 1 define assert expression Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 2 lt ctype h gt Character Operations 14 Parameters expression Expression to test for
93. be achieved 6 24 lt util parity h gt Parity bit generation 6 24 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 6 24 2 Define Documentation 6 24 2 1 ftdefine 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 reg N mov tmp reg 0 n t N Isr 0 n t Isr 0 n t eor 0 tmp reg N ME N 0 unsigned char val N rO C_t 1 gt gt 1 amp 1 Returns 1 if val has odd number of bits set Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 25 lt util twi h gt TWI bit mask definitions 150 6 25 lt util twi h gt TWI bit mask definitions 6 25 1 Detailed Description include lt util twi h gt This header file contains bit mask definitions for use with the AVR TWI interface TWSR values Mnemonics TW_MT xxx master transmitter TW MR xxx master receiver TW_ST_xxx slave transmitter TW SR xxx slave receiver define TW START 0x08 define TW REP START 0x10 define TW MT SLA ACK 0x18 define TW MT SLA NACK 0x20 define TW MT DATA 0x28 define TW MT DATA NACK 0x30 define TW MT ARB LOST 0x38 define TW MR ARB LOST 0x38 define TW MR SLA 0x40 define TW MR
94. be re used within the source file references will pick the closest label with the same number and given direction Example myfunc push push push push push KKK H H ldi tdi rjmp 6 r16 start loop L lo8 sometable H hi8 sometable E jump to loop test at end 7 loop continues here H No Ho KK breq TE return from myfunc prematurely ine rl 2 brlo 1b jump back to top of loop H K 1 ret Back to FAQ Index 9 9 13 How do I pass an IO port as a parameter to a function Consider this example code include lt inttypes h gt include lt avr io h gt void set_bits_func_wrong volatile uint8_t port uint8_t mask Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 299 port mask void set bits func correct volatile uint8_t port uint8 t mask port mask define set_bits_macro port mask port mask int main void set_bits_func_wrong PORTB set bits func correct amp PORTB 0 55 set bits macro PORTB Oxf0 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 instructi
95. but before the initializer like so include lt avr pgmspace h gt unsigned char mydata 11 10 PROGMEM 0 00 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 0 14 0 15 0 16 0 17 0 18 0 19 0 1 0 1 0 1 0 1 0 1 0 1 0 20 0 21 0 22 0 23 0 24 0 25 0 26 0 27 0 28 0 29 0 2 0 2 0 2 0 2 0 2 0 2 0 30 0 31 0 32 0 33 0 34 0 35 0 36 0 37 0 38 0 39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0 46 0 47 0x48 0x49 0x4A 0x4B 0x4C Ox4D Ox4E 0x4F 0 50 0 51 0 52 0 53 0 54 0 55 0 56 0 57 0 58 0 59 Ox5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x63 0 64 0 65 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 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 T
96. can then extract this user data using fdev get udata and act appropriately For example a single put function could be used to talk to two different UARTS that way or the put and get functions could keep internal state between calls there Format strings in flash ROM All the printf and scanf family functions come in two flavours the standard name where the format string is expected to be in SRAM as well as a version with the suffix P where the format string is expected to reside in the flash ROM The macro PSTR explained in lt avr pgmspace h gt Program Space Utilities becomes very handy for declaring these format strings Running stdio without malloc By default fdevopen requires malloc As this is often not desired in the limited environment of a microcontroller an alternative option is provided to run completely without malloc The macro fdev setup stream is provided to prepare a user supplied FILE buffer for operation with stdio Example include lt stdio h gt static int uart putchar char c FILE stream static FILE mystdout FDEV SETUP STREAM uart putchar NULL FDEV SETUP WRITE static int uart putchar char c FILE stream Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 6 8 lt stdio h gt Standard IO facilities 50 if uart_putchar r stream loop until bit is set UCSRA UDRE UDR return 0 int main void init uart
97. char fmt va list ap int vfprintf P FILE stream const char fmt va list ap int fputc 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 const char fmt Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 8 lt stdio h gt Standard IO facilities 52 6 8 2 6 8 2 int sprintf_P char __s const char __fmt int snprintf char s size_t __n const char fmt int snprintf_P char __s size_t ___n const char 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 5 517 t n const char fmt va_list ap int vsnprintf_P char __s size_t __n const char fmt va_list ap int fprintf FILE __stream const char fmt int fprintf_P FILE stream const char __fmt int fputs const char str FILE stream int fputs_P const char str FILE __stream int puts const char __str int puts P const char __str 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
98. 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 9 4 10 dtostrf double val char __width char __prec char s The dtostrf function converts the double value passed in 1 into an ASCII repre sentationthat will be stored under s The caller is responsible for providing sufficient storage in s Conversion is done in the format d ddd The minimum field width of the Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 9 lt stdlib h gt General utilities 71 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 The dtostrf function returns the pointer to the converted string s 6 9 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 C context global destructors will be called before halting execution 6 9 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 x is NULL no ac
99. code executed after return from main 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 programs fini5 Unused User definable 4 Unused User definable fini3 Unused User definable fini2 Unused User definable finil Unused User definable 50110 Goes into infinite loop after program termination and completion of _exit code execution of code in the fini9 gt finil sections 9 3 8 Using Sections in Assembler Code Example Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 4 Data in Program Space 259 include lt avr io h gt section initl ax progbits 0 ORTE out SFR IO ADDR PORTB out SFR IO ADDR DDRB r0 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 C Code Example include lt avr io h gt void my_init_portb void __attribute__ naked __attribute__ section init3 void my_init_portb void PORTB Oxff DDR
100. 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 met by representing a logical 1 in the respec tive bit position When working with interrupt handlers this interrupt flag bit usually gets cleared automatically in the course of processing the interrupt sometimes by just calling the handler at all sometimes 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 res
101. followed by a larger gap so the en tire frame will repeat each 14 through 20 ms but this is ignored for the purpose of the demo so only a single input PWM channel is assumed The basic challenge is to use the cheapest controller available for the task an ATtiny13 that has only a single timer channel As this timer channel is required to run the out going PWM signal generation the incoming PWM decoding had to be adjusted to the constraints set by the outgoing PWM As PWM generation toggles the counting direction of timer 0 between up and down after each 256 timer cycles the current time cannot be deduced by reading TCNTO only but the current counting direction of the timer needs to be considered as well This requires servicing interrupts whenever the timer hits TOP 255 and BOTTOM 0 to learn about each 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 In order to verify parts of the algorithm and the unde
102. for avr libe by Doxygen CONTENTS ii 6 5 6 6 6 7 6 8 6 9 math h Mathematics 29 5651 Detaled Descripnion ex ea NU 29 652 Define Documentation 22 2 22222 30 65 5 Puncbos Documentation gt so ekke S pe 31 lt setjmp h gt Non local goto 34 661 Detailed Description 2 22 2222 34 662 Function 35 lt stdint h gt Standard Integer Types 36 67 1 Detaled Description 22 2 2222 2 2 36 67 2 Deine Documentation p s c o RR RE 39 6 7 3 Typedef Documentation 2 45 lt stdio h gt Standard TO facilites sss cog 48 56 8 1 Detailed Description gt o ce ecs s 9o eee 4 oA RU 48 652 Define Documentation e 24 4 969 x 3s 52 6 8 3 Function 55 lt stdlib h gt General utilities 66 6 9 1 Detailed Description lt o lt soose esa w k s aa 8 66 6 9 2 Define Documentation 68 693 Typedef Documentation 68 6 9 4 Function 68 6 9 5 Variable Documentation 77 sitting Ws 222222222222 25 222 77 6 10 1 Detailed Description sz RR km TI 6 10 2 Defne Documentation oe s ses oo RR RE RR 78 6 10 3 Function
103. function returns the natural logarithm of argument x If the argument is less than or equal 0 a domain error will occur Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 5 lt math h gt Mathematics 33 6 5 3 17 double 10210 double x The log 100 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 5 3 18 double modf double value double __iptr The modf function breaks the argument value into integral and fractional parts each of which has the same sign as the argument It stores the integral part as a double in the object pointed to by iptr The modf function returns the signed fractional part of value 6 5 3 19 double pow double double y The function pow returns the value of x to the exponent 6 5 3 20 double sin double x The sin function returns the sine of x measured in radians 6 5 3 21 double sinh double x sinh function returns the hyperbolic sine of x 6 5 3 22 double sqrt double x The sqrt function returns the non negative square root of x 6 5 3 23 double square double x The function square returns x x Note This function does not belong to the C standard definition 6 5 3 24 double tan double x The tan function returns the tangent of x measured in radians 6 5 3 25 double tanh double x The tanh function returns the hyperbolic tangent of x
104. install every thing under the usr ilocal directory In order to keep the AVR tools separate from the base system it is usually better to install everything into usr local avr If the usr local avr directory does not exist you should create it before trying to install anything You will need root access to install there If you don t have root access to the system you can alternatively install in your home directory for exam ple in SHOME 10cal avr Where you install is a completely arbitrary decision but should be consistent for all the tools You specify the installation directory by using the prefix dir option with the configure script It is important to install all the AVR tools in the same directory or some of the tools will not work correctly To ensure consistency and simplify the discussion we will use PREF IX to refer to whatever directory you wish to install in You can set this as an environment variable if you wish as such using a Bourne like shell PREFIX HOME local avr 5 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 10 Installing the GNU Tool Chain 313 you use prefix S PREFIX you must have SPREFIX bin in your exported such PATH SPATH SPREFIX bin 5 export PA
105. instead thus the potentiometer needs to be attached to port Likewise output is not on port D pin 5 but on port pin 1 PB1 Thus the above cabling scheme needs to be changed so that PB1 connects to the LED0 pin PD6 remains unconnected When using the STK500 use one of the jumper cables for this connection All other port D pins should be connected the same way as described for the ATmega16 above When not using an STK500 starter kit attach the LEDs through some resistor to Vcc low active LEDs and attach pushbuttons from the respective input pins to GND The internal pull up resistors are enabled for the pushbutton pins so no external resistors are needed Finally the demo has been ported to the ATtiny2313 as well As this AVR does not offer an ADC everything related to handling the ADC is disabled in the code for that MCU type Also port D of this controller type only features 6 pins so the 1 second flash LED had to be moved from PD6 to PD4 PD4 is used as the ADC control button on the other MCU types but that is not needed here OC1A is located at PB3 on this device The MCU TARGET macro in the Makefile needs to be adjusted appropriately for the alternative controller types The flash ROM and RAM consumption of this demo are way below the resources of even an ATmega48 and still well within the capabilities of an ATtiny2313 The major advantage of experimenting with the ATmega16 in addition that it shi
106. int ret Non local jump to a saved stack context finclude set jmp h longjmp restores the environment saved by the last call of setjmp with the corre sponding jmpb argument After longjmp is completed program execution contin ues as if the corresponding call of setjmp had just returned the value ret 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 6 2 2 intsetjmp jmp buf jmpb Save stack context for non local goto finclude lt setjmp h gt setjmp saves the stack context environment in jmpb for later use by longjmp The stack context will be invalidated if the function which called setjmp returns Parameters jmpb Variable of type jmp buf which holds the stack information such that the environment can be restored Returns setjmp returns O if returning directly and non zero when returning from longjmp using the saved context Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 7 lt stdint h gt Standard Integer Types 36 6 7 lt stdint h gt Standard Integer Types 6 7 1 Detailed Description include lt stdint h gt Use u intN t if you need exactly N bits Since these typedefs are mandated by the C99 standard th
107. integer members named quot and rem 6 9 4 16 charx long int char s int radix Convert a long integer to a string The function ltoa converts the long integer value from val into an ASCII represen tation that will be stored under s The caller is responsible for providing sufficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof long int 1 characters 1 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 minus sign will be prepended The ltoa function returns the pointer passed as s 6 9 4 17 void malloc size t size The malloc function allocates size bytes of memory If malloc fails a NULL pointer is returned Note that malloc does not initialize the returned memory to zero bytes See the chapter about malloc usage for implementation details 6 9 4 18 void qsort void base size t nmemb size t size compar fn t compar Generated on Tue May 15 14 56 11 200
108. 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 13 2 3 define ISR vector include lt avr interrupt h gt Introduces an interrupt handler function interrupt service routine that runs with global interrupts initially disabled vector must be one of the interrupt vector names that are valid for the particular MCU type 6 13 2 4 define ISR ALIAS vector target vector include lt avr interrupt h gt Defines vector to point to the same interrupt vector as target vector That way single interrupt vector implementation can be used to serve several interrupt sources Do not define a function body Note This requires a recent version of AVR GCC to work GCC 4 2 or patched GCC 4 1 x Example ISR INTO 42 ISR ALIAS INT1 INTO vect Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 116 6 13 2 5 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 13 2 6 define SIGNAL vector include lt avr interrupt h gt Introduces an interrupt handle
109. 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 conversions this option has no effect For 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 Ox or OX for X conversions prepended to it 0 zero Zero padding For all conversions the converted value is padded on the left with zeros rather than blanks If a precision is given with a numeric conversion d i 0 u i x and X the 0 flag is ignored A negative field width flag the converted value is to be left adjusted on the field boundary The converted value is padded on the right with blanks rather than on the left with blanks or zeros A overrides a 0 if both are given space A blank should be left before a positive number produced by a signed conversion d or i A sign must always be placed before a number produced by a signed conversion A overrides a space if both are used Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen lt stdio h gt Standard IO facilities 61 An optional decim
110. issues regarding debugging optimized code Wa assembler options W1 linker options Pass the listed options to the assembler or linker respectively 59 Generate debugging information that be used by avr gdb Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 11 Using the GNU tools 324 ffreestanding Assume freestanding environment as per the 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 void return type which makes some sense in microcontroller environment where the application cannot meaningfully provide 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 ffreestanding it will always call strlen at run time e funsigned char Make any unqualfied char type an unsigned char Without this option they default to a signed char e funsigned bitfields Make any unqualified bitfield type unsigned By default they are signed fshort enums A
111. 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 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 newline character into carriage return newline sequence so simple n can be used in the source code The function set pwm propagates the new PWM value to the PWM performing range checking When the value has been changed the new percentage will be an nounced on the serial link The current value is mirrored in the variable pwm so others can use it in calculations In order to allow for simple calculation of percentage value without requiring floating point mathematics the maximal value of the PWM is restricted to 1000 rather than 1023 so a simple division by 10 can be used Due to the nature of the human eye the difference in LED brightness between 1000 and 1023 is not noticable anyway 6 31 3 5 Part 5 main At the start of main a variable mode is declared to keep the current mode of operation An enumeration is used to impr
112. 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 251 locations refer to an ATmegal28 The memory addresses used are not displayed in linear scale 0x0100 Ox10FF 0 1100 OxFFFF on board RAM 5 t RAMEND brkval lt SP __malloc_margin wa __malloc_heap_start _ heap start bss end data bss start data start Figure 6 RAM map of a device with internal RAM external RAM On a simple device like a microcontroller it is a challenge to implement a dynamic memory allocator that is simple enough so the code size requirements will remain low yet powerful enough to avoid unnecessary memory fragmentation and to get it all done with reasonably few CPU cycles Microcontrollers are often low on space and also run at much lower speeds than the typical PC these days The memory allocator implemented in avr libc tries to cope with all of these con straints and offers some tuning options that can be used if there are more resources available than in the default configu
113. libe by Doxygen 91 Toolchain Overview 247 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 Tue May 15 14 56 11 2007 for avr libe by Doxygen 91 Toolchain Overview 248 9 1 5 avr libc GCC and Binutils provides a lot of the tools to develop software but there is one critical component that they do not provide a Standard C Library There are different open source projects that provide a Standard C Library depending upon your system time whether for a native compiler GNU Libc for some other embedded system newlib or for some versions of Linux uCLibc The open source AVR toolchain has its own Standard C Library project avr libc AVR Libc provides many of the same functions found in a regular Standard C Library and many additional library functions that is specific to an AVR Some of the Standard C Library functions that are comm
114. 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 1t 18 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 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 ISRO macro when declaring the interrupt function a
115. 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 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 the global CPU state Thus it is usually necessary to save at least the state of the flag bits in SREG Note that this serves as an example here only since actually all the following instructions would not modify SREG either but that s not commonly the case Also it must be made sure that registers used inside the interrupt routine do not conflict with those used outside In the case of a RAM less device like the 905 1200 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 Generated on Tu
116. lo r24 define val lo r22 define ret hir25 define ret lo r24 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 73 strrchr S File Reference 241 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 74 strrchr_P S File Reference 242 8 74 8 74 1 8 75 8 75 1 8 76 8 76 1 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 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 Reference Detailed Description strupr S File Reference Detailed Description twi h File Reference Detailed Description TWSR values Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen Mnemonics 8 84 twi h File Reference 243 TW MT xxx master transmitter TW MR xxx master receiver TW ST xxx slave transmitter TW SR xxx slave receiver define TW START 0x08 define TW START 0x10 define TW MT SLA ACK 0x18 define TW MT SLA NACK 0x20 define TW MT DATA ACK 0x28 define TW MT DATA NACK 0x30 define TW MT ARB LOST 0x38 define
117. 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 reasonable 1 non erased value at startup it is taken as the initial value for the PWM This virtually preserves the last value across power cycles By not updating the EEPROM immme diately but only after a timeout EEPROM wear is reduced considerably compared to immediately writing the value at each change 6 31 3 code walkthrough This section explains the ideas behind individual parts of the code The source code has been divided into numbered parts and the following subsections explain each of these parts 6 31 3 1 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 name
118. low CPU clock frequencies the U2X bit in the is set reducing the oversampling from 16x to 8x which allows for a 9600 Bd rate to be achieved with tolerable error using the default 1 MHz RC oscillator The public function uart putchar again has suitable arguments for direct use by the stdio stream interface It performs the n into r n translation by recursively calling itself when it sees a n character Just for demonstration purposes the a audible bell ASCII BEL character is implemented by sending a string to stderr so it will be displayed on the LCD The public function uart_getchar implements the line editor If there are char acters available in the line buffer variable rxp is not NULL the next character will be returned from the buffer without any UART interaction If there are no characters inside the line buffer the input loop will be entered Charac ters will be read from the UART and processed accordingly If the UART signalled a framing error FE bit set typically caused by the terminal sending a line break con dition 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
119. mode 6 18 2 4 define SLEEP MODE PWR DOWN BV SM1 Power Down Mode 6 18 2 5 define SLEEP MODE PWR SAVE BV SM0 BV SM1 Power Save Mode 6 18 2 6 define SLEEP MODE STANDBY _BV SM1 BV SM2 Standby Mode Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 19 lt avr version h gt avr libc version macros 138 6 18 3 Function Documentation 6 18 3 1 void set sleep mode uint8 t mode Select a sleep mode 6 18 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 18 3 3 void sleep disable void Clear the SE sleep enable bit 6 18 3 4 void sleep enable void Set the SE sleep enable bit 6 18 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 19 lt avr version h gt avr libc version macros 6 19 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 get
120. newly computed value is loaded into the PWM register Since in an interrupt routine it is safe to use a 16 bit assignment to the register e of an interrupt the assignment should only be performed with interrupts disabled if there s a chance that an interrupt routine could also access this register or another register that uses TEMP see the appropriate FAQ entry Note 6 This routine gets called after a reset It initializes the PWM and enables interrupts Note 7 The main loop of the program does nothing all the work is done by the interrupt routine The sleep mode puts the processor on sleep until the next interrupt to conserve power Of course that probably won t be noticable as we are still driving a LED it is merely mentioned here to demonstrate the basic principle Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 165 Note 8 Early devices saturate their outputs at rather low currents when sourcing cur rent so the LED can be connected directly the resulting current through the LED will be about 15 mA For modern parts at least for the ATmega 128 however Atmel has drastically increased the IO source capability so when operating at 5 V Vcc R2 is needed Its value should be about 150 Ohms When operating the circuit at 3 V it can still be omitted though 6 30 2 The Source Code Armene Se EG ot ges N oe ee SERE E
121. nop n t nop n t 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 a Stack pointer high byte at address 0 3 KSP Stack pointer low byte at address 0x3D tmp reg Register rO used for temporary storage zero reg Register r1 always zero Register rO may be freely used by your assembler code and need not be restored at the end of your code It s a good idea to use tmp reg and zero reg instead of r0 or r1 just in case a new compiler version changes the register usage definitions 9 6 3 Input and Output Operands Each input and output operand is described by a constraint string followed by a C expression in parantheses AVR GCC 3 3 knows the following constraint characters Note The most up to date and detailed information on contraints for the avr can be found in the gcc manual The x register is r27 r26 the y register is r29 r28 and the z register is r31l1 530 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 274 Constraint Used for Range a Simple upper
122. on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 272 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 Orefersto r value and lrefersto 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 registe
123. prescale set x Value CN uint8 t tmp _BV CLKPCE asm volatile 5 in tmp reg SREG n t N eli N sts 41 30 NHNET N sts 81 2 XNET N out SREG tmp reg no outputs x N Fg tmp M M SFR MEM ADDR CLKPR ro X 8 33 setjmp h File Reference 8 33 1 Detailed Description Defines define SETJMP H 1 define ATTR NORETURN aGattribute noreturn Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 34 sleep h File Reference 224 Functions int setjmp jmp buf __jmpb void longjmp jmp buf __jmpb int ATTR NORETURN 8 34 sleep h File Reference 8 34 1 Detailed Description 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 _BV SM0 define SLEEP MODE PWR DOWN _BV SM1 define SLEEP PWR SAVE BV SMO BV SMI define SLEEP MODE STANDBY 5 1 BV SM2 SLEEP MODE EXT STANDBY BV SMO BV SMI _ BV SM2 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 Defines define AVR SLEEP H 1 define SLEEP CONTROL REG MCUCR Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 35 std
124. previous library versions could easily be maintained until its end of life Use of any of these items in new code is strongly discouraged Allowing specific system wide interrupts In addition to globally enabling interrupts each device s particular interrupt needs to be enabled separately if interrupts for this device are desired While some devices maintain their interrupt enable bit inside the device s register set external and timer interrupts have system wide configuration registers Example Enable timer 1 overflow interrupts timer enable int BV TOIE1 Do some work Disable all timer interrupts timer enable int 0 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 26 lt compat deprecated h gt Deprecated items 155 Note Be careful when you use these functions If you already have a different interrupt enabled you could inadvertantly disable it by enabling another intterupt define enable_external_int mask __EICR mask define INTERRUPT signame define _ INTR_ATTRS used e static inline void timer enable int unsigned char ints Obsolete IO macros Back in a time when AVR GCC and avr libc could not handle IO port access in the di rect assignment form as they are handled now all IO port access had to be done through specific macros that eventually resulted in inline assembly instructions performing the desired action These macros became obsolete as reading
125. registers r16 to r23 b Base pointer registers Z pairs d Upper register rl6tor31 e Pointer register pairs X y Z G Floating point constant 0 0 I 6 bit positive integer 0 to 63 constant J 6 bit negative integer 63 to 0 constant K Integer constant 2 L Integer constant 0 1 Lower registers rO 0 15 8 bit integer constant 0 to 255 N Integer constant 1 O Integer constant 8 16 24 P Integer constant 1 q Stack pointer register SPH SPL r Any register r0 to r31 t Temporary register rO w Special upper register r24 r26 r28 r30 pairs x Pointer register pair X x 27 26 y Pointer register pair Y y 129 128 7 Pointer register pair Z z r31 r30 These definitions seem not to fit properly to the AVR instruction set The author s as sumption is that this part of the compiler has never been really finished in this version but that assumption may be wrong The selection of the proper contraint depends on the range of the constants or registers which must be acceptable to the AVR instruction they are used with The C compiler doesn t check any line of your assembler code But it is able to check the constraint against your C expression However if you specify the wrong constraints then the compiler may silently pass wrong code to the assem bler And of course the assembler will fail with some cryptic output or internal errors For example if you specify the constraint r and you are using this register wi
126. ret hi r25 define ret lo 124 8 66 strncmp P S File Reference 8 66 1 Detailed Description Defines define s1 hi r25 define s1 lo r24 define s2 hi r23 define s2 lo 122 define len hi r21 define len lo r20 define ret hi r25 define ret lo 124 8 67 strncpy S File Reference 8 67 1 Detailed Description Defines define dest hi r25 define dest lo 24 define src hi r23 define src lo r22 define len hi r21 define len lo r20 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 68 strncpy P S File Reference 239 8 68 strncpy PS File Reference 8 68 1 Detailed Description Defines define dest hir25 define dest_lo 24 define src r23 define src lo r22 define len hi r21 define len 10120 8 69 strnlen S File Reference 8 69 1 Detailed Description Defines define src hi r25 define src lo r24 define len hir23 define len lo r22 8 70 strnlen_P S File Reference 8 70 1 Detailed Description Defines define src hi r25 define src_lo r24 define len hir23 define len lo r22 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 71 strpbrk S File Reference 240 8 71 strpbrk S File Reference 8 71 1 Detailed Description 8 72 strpbrk_P S File Reference 8 72 1 Detailed Description 8 73 strrchr S File Reference 8 73 1 Detailed Description Defines define src hi r25 define src
127. 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 9 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 9 4 6 void bsearch const void __key const void base size_t nmemb size t size int const void const void compar The bsearch function searches an array of nmemb objects the initial member of which is pointed to by base for a member that matches the object pointed to by key The size of each member of the array is specified by size The contents of the array should be in ascending sorted order according to the compar ison function referenced by compar The compar routine is expected to have two Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 9 lt stdlib h gt General utilities 70 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 fo
128. 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 ap 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 stdlib h File Reference 8 37 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 char long int __val char __s int radix char utoa unsigned int val char s int radix char ultoa unsigned long int __val char __s int long random void void srandom unsigned long __ seed long random_r unsigned long ctx Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 37 stdlib h File Reference 231 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 S
129. 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 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 very different way of doing things than writing an application There are always exceptions to the rule There are generally two cases where you would want to have more than one function per object module The first is when you have very complementary functions that it doesn t make much sense to split them up For example malloc and free If someone is going to use malloc they will very likely be using free or at least should be using free In this 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 functi
130. srand 74 srandom 74 strtod 74 strtol 74 strtoul 75 ultoa 75 utoa 76 avr string _FFS 78 ffs 78 ffsl 79 ffsll 79 memcopy 79 memchr 79 memcmp 79 memcpy 80 memmem 80 memmove 80 memrchr 81 memset 81 strcasecmp 81 strcasestr 81 strcat 82 strchr 82 strchrnul 82 strcmp 82 strcpy 83 strcspn 83 stricat 83 strlcpy 84 strlen 84 striwr 84 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 343 strncasecmp 84 strncat 85 strncmp 85 strncpy 85 strnlen 85 strpbrk 86 strrchr 86 strrev 86 strsep 86 strspn 87 strstr 87 strtok 87 strupr 88 avr version AVR LIBC DATE 139 AVR LIBC DATE STRING 139 AVR MAJOR 139 AVR LIBC MINOR 139 AVR LIBC REVISION 139 AVR LIBC VERSION STRING 139 AVR LIBC VERSION _ 139 avr watchdog wdt disable 141 wdt enable 141 wdt reset 141 WDTO 120MS 142 WDTO 15MS 142 WDTO 165 142 WDTO 250MS 142 WDTO 25 142 WDTO 30MS 142 WDTO 45 142 WDTO 500MS 143 WDTO 60MS 143 WDTO 885 143 avrdude usage 328 avrprog usage 328 bit is clear sfr 135 bit is set avr sfr 135 boot h 199 boot lock bits set 200 boot lock bits set alternate 200 boot page erase alternate 201 boot page erase extended 201 boot page erase normal 201 boot page fill alternate 202 boot page fill extended 202 boot page fill normal 203 boot page write alternate 203 boot page write exte
131. text and binary streams inside avr libc Character Vn is sent literally down to the device s put function If the device requires a carriage return N r character to be sent before the linefeed its put routine must implement this see note 2 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 8 lt stdio h gt Standard IO facilities 49 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 newline character into carriage return newline sequence breaks binary transfers If binary transfers are desired no automatic conversion should be performed but instead any string that aims to issue 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
132. the ATmega8 48 88 168 use PB 1 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 pin varies between different AVRs and it is mandated by the AVR hardware SCK PB7 E 10 RESET MISO PB6 MOSI PB5 I XTAL2 PBA 18p OCI PB3 K XTAL1 PBZ AIN1 PB1 vec AINO PBO d ICP PD6 GND T1 PD5 TO PD4 INT1 PD3 INTO PD2 TXD PD1 RXD PDO AT90S2313P LED5MM R2 D1 ET D See note 8 NW GND PRPRFE REEREREE 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 or I 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 stateme
133. 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 include lt avr io h gt outb PORTA 0x33 or they can assign a value directly to the symbolic address PORTA 0x33 The compiler s choice of which method to use when actually accessing the IO port is completely independent of the way the programmer chooses to write the code So even if the programmer uses the memory mapped paradigm and writes PORTA 0x40 the compiler can optimize this into the use of an sbi instruction of course provided the target address is within the allowable range for this instruction and the right hand side of the expression is a constant value known at compile time The advantage of using the memory mapped paradigm in C programs is that it makes the programs more portable to other C compilers for the AVR platform Some people might also feel that this is more readable For example the following two statements would be equivalent Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 17 lt avr
134. value would cause underflow zero is returned and ERANGE 16 stored in errno FIXME HUGE VAL needs to be defined somewhere The bit pattern is Ox 7fffffff but what number would this be Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 9 lt stdlib h gt General utilities 75 6 9 4 27 long strtol const char __nptr char xx __endptr int base The strtol function converts the string in nptr to 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 zero base is taken as 10 decimal unless the next character 15 0 in which case it is taken as 8 octal The remainder of the string is converted to long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 represents 11 and so forth with Z representing 35 If endptr is not NULL strtol stores the address of the first invalid character in endptr If there were no digits at all however strtol stores the original value of in endptr
135. way the only difference is that you would use m eeprom instead of m flash To use interactive mode use the t option avrdude p 2313 t avrdude AVR device initialized and ready to accept instructions Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 13 Release Numbering Methodology 330 avrdude Device signature 0x1e9101 avrdude gt The command displays a list of valid commands avrdude gt gt gt gt 7 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 lt addr gt lt bl gt 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 lt bl gt lt b2 gt lt b3 gt lt b4 gt help help 2 help quit quit Use the part command to display valid memory types for use with the dump 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 minor number that is an even number This implies that you should be able to upgrade to 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 unde
136. 0 9 4 44 Storing and Retrieving Strings in the Program Space 262 SO Caved ny orat Bo mb ox SURUY E Xe Cs 264 avr libc and assembler programs 264 9X1 noden e e see S o t Ro erre ee 264 982 Invoking thecompiler 22222 2 mcs 265 953 Example program s cg oo ng Rm m RR RR BR Ro 265 9 5 4 Pseudo opsandoperators 269 Inline Assembler Cookbook 22 52 2255 ms 270 9 61 OLEG f Statement REESE ER b 271 962 Assembler Code 273 9 6 3 Input and Output 273 DD LIOBBOES ce kr ee SE SE RUE Y 277 9 6 5 Assembler Macros 279 9 6 0 C SOD FHBOUQOBS eo cse ek a 9 2 280 9 6 7 C Names Used m 281 02222 L eae oe SUE RUM S 282 How to Build a Library 222222222 ka was a w w AE ed kis N 282 dn oduGHoOH cecx e s e ea oo RR RR yw 5 282 9012 How the Linker Works ooo RR as 282 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen CONTENTS xiii 97 3 How to Design a 283 Us Cred nga LIDOT 22222598 Roe 09 x X93 X 88 e 283 EBEN xoc r3 oe BAR es 284 9 8 Porting From to AVR GCC 285 Infoduchon i sosser ae eek RR n RR RS 285 d 243054508 E ees Xe be SS SER Sen s 285 9 8 3 Inter
137. 007 for avr libc by Doxygen 6 7 lt stdint h gt Standard Integer Types 42 6 7 2 25 define INT LEAST64 MAX INT64 largest positive value an int least64 hold 6 7 2 26 define INT LEAST64 MIN INT64 MIN smallest negative value an int least64 hold 6 7 2 27 define INT LEAST8 MAX INT8 largest positive value an int least8 t can hold 6 7 2 28 define INT LEAST8 MIN INT8 MIN smallest negative value an int least8 t can hold 6 7 2 29 define INTMAX C value CONCAT value LL define a constant of type intmax t 6 7 2 30 define INTMAX MAX INT64 MAX largest positive value an intmax_t can hold 6 7 2 31 define INTMAX MIN INT64 MIN smallest negative value an intmax t can hold 6 7 2 32 define INTPTR INT16 largest positive value an intptr t can hold 6 7 2 33 define INTPTR MIN INT16 MIN smallest negative value an intptr t can hold 6 7 2 34 define PTRDIFF MAX INT16 MAX largest positive value a ptrdiff_t can hold 6 7 2 35 define PTRDIFF MIN INT16 MIN smallest negative value a ptrdiff_t can hold Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 7 lt stdint h gt Standard Integer Types 43 6 7 2 36 define SIG ATOMIC MAX INT8 MAX largest positive value a sig atomic t can hold 6 7 2 37 define SIG ATOMIC MIN INT8 MIN smallest negative value a sig atomic t can hold 6 7 2 38 define SIZE CONCAT INTI6 MAX U larg
138. 05 22 222222252225 om Ro 06 Y N 316 2 EO 2222356 ST SAS AE S eS 316 9 10 7 GDB forthe AVR target lt o oc piscate o Re 317 9 108 Sulla s sees ses Gled SG ees 317 5109 AVARO o ETE 318 Usmethe GNU mole veh ea 425 K q e OE s 318 9 11 1 Options for the compiler 318 9 11 2 Options for the assembler 324 9 11 3 Controlling the linker avr ld 326 912 Using the rdude program ra 29 328 9 13 Release Numbering and Methodology 330 9 13 1 Release Version Numbering 5 330 Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 1 AVR Libc 1 9 13 2 Releasing AVR Libe 331 9 14 Acknowledgments o p x EE Re xx Re 333 Pr ge oe p ushu ee Sun ae Ge 334 9 16 Deprecated List uu ao el Soe a Y 335 1 AVR Libc 1 1 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
139. 0PWM2 AT90PWM3 power_psc0_disable Disable the Power Stage Controller 0 module AT90PWMI AT90PWM2 AT90PWM3 power pscl enable Enable the Power Stage Controller I module AT90PWMI AT90PWM2 AT90PWM3 power psc disable Disable the Power Stage AT90PWMI ATOOPWM2 Generated on Tue May 15 14 56 11 2007 Gontvollihc byDeulgen AT90PWM3 power psc2 enable Enable the Power Stage Controller 2 module AT90PWMI AT90PWM2 AT90PWM3 power_psc2_disable Disable the Power Stage Controller 2 module AT90PWMI AT90PWM2 AT90PWM3 power spi enable Enable the Serial Peripheral Interface module ATmega640 ATmegal280 ATmegal281 ATmega2560 6 16 Additional notes from lt avr sfr defs h gt 131 Some of the newer AVRs contain System Clock Prescale Register CLKPR that allows you to decrease the system clock frequency and the power consumption when the need for processing power is low Below are two macros and an enumerated type that can be used to interface to the Clock Prescale Register Note Not all AVR devices have Clock Prescale Register On those devices without Clock Prescale Register these macros are not available typedef enum lock div 1 lock div 2 lock div 4 lock div 8 gt lock_div_16 4 lock div 32 5 lock div 64 6 lock div 128 7 clock div 256 8 clock div t Wl H IH CO NE FE CX nannananan e
140. 1 msg00044 html for 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 9 9 14 What registers are used by the C compiler Data types Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 9 9 Frequently Asked Questions 301 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 mint8 option see Options for the C compiler avr gcc to make int 8 bits but that is not supported by avr libc and violates C standards int must be at least 16 bits It may be removed in future release Call used registers r18 r27 r30 r31 May be allocated by gcc for local data You may use them freely in assembler subroutines Calling C subroutines can clobber any of them the caller is re sponsible for saving and restoring Call saved registers r2 r17 r28 r29 May be allocated by gcc for local data Calling C subroutines leaves them un changed Assembler subroutines are responsible for saving and restoring these registers if changed r29
141. 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 Inapractical application long delays like this one were better be handled by a hardware timer so the main CPU would be free for other tasks while waiting or could be put on sleep At the beginning of main after initializing the peripheral devices the default stdio streams stdin stdout and stderr are set up by using the existing static FILE stream objects While this is not mandatory the availability of stdin and stdout allows to use the shorthand functions e g printf instead of fprintf and stderr can mnemonically be referred to when sending out diagnostic messages Just for demonstration purposes stdin and stdout are connected to a stream that will perform UART IO while stderr is arranged to 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 gets 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 b
142. 16 decimal scanf format for uintptr_t 6 4 2 9 define SCNx16 x hexadecimal scanf format for uint16_t 6 4 2 90 define SCNx32 Ix hexadecimal scanf format for uint32_t Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 5 lt math h gt Mathematics 29 6 4 2 91 define SCNxFAST16 x hexadecimal scanf format for uint_fast16_t 6 4 2 92 define SCNxFAST32 Ix hexadecimal scanf format for uint_fast32_t 6 4 2 93 define SCNxLEAST16 x hexadecimal scanf format for uint_least16_t 6 4 2 94 define SCNxLEAST32 Ix hexadecimal scanf format for uint least32 t 6 4 2 95 define SCNxPTR SCNx16 hexadecimal scanf format for uintptr_t 6 4 3 Typedef Documentation 6 4 3 1 typedef int32 t int farptr t signed integer type that can hold a pointer gt 64 KB 6 4 3 2 typedef uint32 t uint farptr t unsigned integer type that can hold a pointer gt 64 KB 6 5 lt math h gt Mathematics 6 5 1 Detailed Description include lt math h gt This header file declares basic mathematics constants and functions Note In order to access the functions delcared herein it is usually also required to addi tionally link against the library 1ibm a See also the related FAQ entry Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 5 lt math h gt Mathematics 30 Defines define PI 3 141592653589793238462643 define M_SQRT2 1 4142135623730950488016887 Functions double
143. 16 t value void eeprom write block const void pointer ram void pointer eeprom size t n IAR C compatibility defines define _EEPUT addr val eeprom write byte uint8 t addr uint8 t val define _EEGET var addr var eeprom read byte uint8_t addr Defines define EEPROM H 1 define __need_size_t define XCALL rcall define EEPROM REG LOCATIONS 1CIDIE define STR2 EXP STRI EXP define STRI EXP EXP define REG LOCATION SUFFIX _STR2 __EEPROM_REG_ LOCATIONS define CR TAB n t Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 10 errno h File Reference 208 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 10 errno h File Reference 8 10 1 Detailed Description Defines define ERRNO 1 define EDOM 33 define ERANGE 34 Variables int errno 8 11 fdevopen c File Reference 8 11 1 Detailed Description Functions FILE x fdevopen int put char FILE int get FILE Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 12 5 5 File Reference 209 8 12 ffs S File Reference 8 12 1 Detailed Description 8 13 ffsl S File Reference 8 13 1 Detail
144. 16_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 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 uint 16 t typedef signed long int int32_t typedef unsigned long int uint32_t typedef signed long long int int64_t typedef unsigned long long int uint64_t Integer types capable of holding object pointers These allow you to declare variables of the same size as a pointer typedef int16 t intptr_t typedef uint16_t uintptr_t Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 7 lt stdint h gt Standard Integer Types 39 Minimum width integer types Integer types having at least the specified width typedef int8 t int least8 t typedef uint8 t uint least8 t typedef int16 t int least16 t typedef uint16 tuint leastl6 t typedef int32 t int least32 t typedef uint32 t least32 t typedef int64 t int least64 t typedef uint64 t least64 t Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8 t int fast8 t typedef uint8 t uint fast
145. 181 ola THE SOUICERGdE suus eee PSR K s 184 6 32 Using the standard IO facilities gt lt o lt c oc cactos aea 5 184 60321 Hardware coe moa a REG RR 184 6 32 2 Functional Overview s owe rya k us ske woe ke 186 6 32 3 A code walkthrough 186 5224 THE SOUREECOdE ou sss omo s ke Ke Se GA KG 191 6 33 Example using the two wire interface TWI 192 631 Introduction into TWL se ke ee ske RR 192 6 33 2 The TWI example project ico rr RR 192 6 33 3 The Source Code ok u s s ss xo Room e sk 193 7 avr ibc Data Structure Documentation 197 Tl du tSuatReferenoe 222222222222 See Q e X 3 38 197 7 1 1 Detaled Description 24222222 sk 197 7 1 2 197 72 div t Struct Reference 5222222 ooo RR 197 121 Detailed Description 22 2 197 7 2 2 Field Documentation 197 8 avr ibc File Documentation 198 81 assertd File Reference 2 2 ker Veske 198 811 Detailed Description 198 52 Pile Referente uuo sooo x 198 821 Detaled Description 52222 22 595522026553 198 Plen cou Rogo RU REY BUR ee RU 198 3 1 Detaled Description gt s ss or RR RR 198 4 boot Pile Reference 2 22 2 2 5224 199 841 Detailed Description 2 2 199 8 4 22 Define Documentation 200 3
146. 2007 for avr libc by Doxygen 6 7 lt stdint h gt Standard Integer Types 46 6 7 3 10 typedef int32_t int_least32_t signed int with at least 32 bits 6 7 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 7 3 12 typedef int8_t int_least8_t signed int with at least 8 bits 6 7 3 13 typedef int64_t intmax_t largest signed int available 6 7 3 14 typedef int16_t intptr_t Signed pointer compatible type 6 7 3 15 typedef unsigned int uint16_t 16 bit unsigned type 6 7 3 16 typedef unsigned long int uint32_t 32 bit unsigned type 6 7 3 17 typedef unsigned long long int uint64_t 64 bit unsigned type Note This type is not available when the compiler option mint8 is in effect 6 7 3 18 typedef unsigned char uint8_t 8 bit unsigned type Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 7 lt stdint h gt Standard Integer Types 47 6 7 3 19 typedef uint16_t uint_fast16_t fastest unsigned int with at least 16 bits 6 7 3 20 typedef uint32_t uint_fast32_t fastest unsigned int with at least 32 bits 6 7 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 7 3 22 typedef uint8_t uint_fast8_t fastest unsigned int with at least 8 bits 6 7 3 23 typedef uint16_t uint
147. 233 strepy P Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen INDEX 353 avr_pgmspace 124 strcpy_P S 234 strcspn avr_string 83 strcspn S 234 strcspn_P avr_pgmspace 124 strespn P S 234 string h 234 strlcat avr_string 83 strlcat S 236 strlcat_P avr pgmspace 125 strlcat P S 236 strlepy avr string 84 strlepy S 236 strlepy P avr pgmspace 125 strlepy P S 236 strlen avr string 84 strlen S 236 strlen P avr pgmspace 125 strlen P S 236 strlwr avr_string 84 strlwr S 237 strncasecmp avr_string 84 strncasecmp S 237 strncasecmp P avr pgmspace 125 strncasecmp P S 237 strncat avr string 85 strncat S 237 strncat P avr pgmspace 126 strncat P S 237 strncmp avr_string 85 strncmp S 238 strncmp P avr pgmspace 126 strncmp 5 238 strncpy avr string 85 strncpy S 238 strncpy P avr pgmspace 126 strnepy P S 239 strnlen avr string 85 strnlen S 239 strnlen P avr pgmspace 127 strnlen P S 239 strpbrk avr string 86 strpbrk S 240 strpbrk P avr pgmspace 127 strpbrk P S 240 strrchr avr string 86 strrchr S 240 strrchr P avr pgmspace 127 strrchr P S 242 strrev avr string 86 strrev S 242 strsep avr string 86 strsep S 242 strsep P avr pgmspace 127 strsep P S 242 strspn avr string 87 strspn S 242 strspn P avr pgmspace 128 strspn P S 242 strstr avr string 87 strstr S 242 strstr P avr pgmspace 128
148. 329 ATmega329P ATmega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 ATtiny261 ATtiny461 AT tiny861 AT9OUSB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 13 lt avr interrupt h gt Interrupts 108 Vector name Old vector Description Applicable for device name TIMER 1_ SIG_ Timer Counter1 AT90S4414 AT90S4434 9058515 COMPB vect OUTPUT Compare MatchB 419058535 AT90PWM3 AT90PWM2 COMPAREIB AT90PWMI 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 AT9OUSB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 9005 646 TIMER 1_ SIG_ Timer Counter1 AT90CAN128 AT90CAN32 AT90CAN64 COMPC_vect OUTPUT_ Compare Match A
149. 333 AVR_AT90S2333__ avr2 at90s2343 AVR_AT90S2343__ avr2 attiny22 __AVR_ATtiny22__ avr2 attiny26 __AVR_ATtiny26__ avr2 at90s4414 AVR 479054414 avr2 at90s4433 __AVR_AT90S4433__ avr2 at90s4434 AVR ATO908s4434 avra at90s8515 AVR 479058515 avr2 at90c8534 AVR AT90C8534 avr2 219058535 AVR 479058535 avr2 avr25 1 at86rf401 __AVR_AT86RF401__ avr2 avr25 1 attiny13 AVR AT nyl3 avr2 avr25 1 attiny2313 __AVR_ATtiny2313__ Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 11 Using the GNU tools 320 Architecture MCU name Macro avr2 avr25 1 attiny24 AVR AT ny24 avr2 avr25 1 attiny25 AVR AT ny25 avr2 avr25 1 attiny261 AVR AT ny261 avr2 avr25 1 attiny44 AVR AT ny44 avr2 avr25 1 attiny45 AVR ATtiny45 avr2 avr25 1 attiny461 AVR ATtiny461 avr2 avr25 1 attiny84 AVR ATtiny84 avr2 avr25 1 attiny85 AVR ATtiny85 avr2 avr25 1 attiny861 AVR ATtiny861 avr3 atmegal03 AVR ATmegal03 avr3 atmega603 AVR ATmega603 avr3 at43usb320 AVR AT43USB320 avr3 at43usb355 AVR AT43USB355 avr3 at76c711 __AVR_AT76C711__ avr4 atmega48 AVR ATmega48 avr4 atmega8 AVR ATmega8 avr4 atmega8515 AVR ATmega8515 avr4 atmega8535 AVR ATmega8535 avr4 atmega88 AVR ATmega88 avr4 atmega8hva
150. 4 xport mask fa 80 81 ld r24 Z fc 86 2b r24 r22 fe 80 83 st 2 r24 100 08 95 ret Notice that we are accessing the io port via the LD and ST instructions The port parameter must be volatile to avoid 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 Lig 88 b3 in r24 0x18 24 11 80 6f ori r24 OxFO 240 120 88 bb out 0 18 r24 24 Of course in a real application you might be doing a lot more in your function which uses a passed by reference io port address and thus the use of a function over a macro could save you some code space but still at a cost of execution speed Care should be taken when such an indirect port access is going to one of the 16 bit IO registers where the order of write access is critical like some timer registers All versions of avr gcc up to 3 3 will generate instructions that use the wrong access order in this situation since with normal memory operands where the order doesn t matter this sometimes yields shorter code See http mail nongnu org archive html avr libc dev 2003 0
151. 4 4 24 char strsep P char sp delim Parse a string into tokens strsep_P function locates in the string referenced by sp the first occurrence of any character in the string delim or the terminating VO character and replaces it with a V0 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 0 This function is similar to strsep except that delim is a pointer to a string in program space Returns The strsep_P function returns a pointer to the original value of If is initially NULL strsep P returns NULL 6 14 4 25 size t strspn P const char s PGM P accept The strspn P function calculates the length of the initial segment of s which con sists entirely of characters in accept This function is similar to strspn except that accept is a pointer to a string in program space Returns The strspn P function returns the number of characters in the initial segment of s which consist only of characters from accept The terminating zero is not considered as a part of string 6 14 4 26 char strstr P const char 57 P 52 Locate a substring strstr P function finds the first occurrence of the substring 52 in th
152. 4 MAX avr stdint 40 INT FAST64 MIN avr stdint 41 int fast64 t avr stdint 45 INT FAST8 avr stdint 41 INT FAST8 MIN avr stdint 41 int fast8 t avr stdint 45 INT LEAST16 avr stdint 41 INT LEAST16 MIN avr stdint 41 int least16 t avr stdint 45 INT LEAST32 MAX avr stdint 41 INT LEAST32 MIN avr stdint 41 int least32 t avr stdint 45 INT LEAST64 MAX avr stdint 41 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 347 INT LEAST64 MIN avr_stdint 41 int least64 t avr stdint 45 INT LEAST8 avr stdint 41 INT LEAST8 MIN avr stdint 41 int least8 t avr stdint 45 INTERRUPT deprecated items 156 interrupt h 209 INTMAX C avr stdint 42 INTMAX MAX avr stdint 42 INTMAX MIN avr stdint 42 intmax t avr stdint 46 MAX avr stdint 42 INTPTR MIN avr stdint 42 intptr t avr stdint 46 inttypes h 209 isalnum ctype 14 isalpha ctype 14 isascii ctype 15 isblank ctype 15 iscntrl ctype 15 isdigit ctype 15 isgraph ctype 15 isinf avr_math 32 islower ctype 15 isnan avr_math 32 isprint ctype 15 ispunct ctype 15 ISR avr_interrupts 115 ISR_ALIAS avr_interrupts 115 isspace ctype 15 isupper ctype 15 isxdigit ctype 16 itoa avr_stdlib 71 labs avr_stdlib 71 Idexp avr math 32 Idiv avr_stdlib 71 Idiv_t 197 quot 197 rem 197 log avr_math 32 log10 avr math 32 longjmp setjmp
153. 44P ATmega644 AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 USART2_ SIG_ USART2 Rx ATmega640 ATmegal280 ATmegal281 RX vect USART2 Complete ATmega2560 ATmega2561 RECV USART2_ SIG_ USART2 Tx ATmega640 ATmegal280 ATmegal281 TX vect USART2 Complete ATmega2560 ATmega2561 TRANS Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 113 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 ATmegal281 TX_vect USART3_ Complete ATmega2560 ATmega2561 TRANS USART3_ SIG_ USART3 Data ATmega640 ATmegal280 ATmegal28l UDRE vect USART3 register Empty ATmega2560 ATmega2561 DATA USART SIG USART Rx ATmegal6 ATmega32 ATmega323 AT vect USART Complete mega8 RECV SIG UART RECV USART RX SIG USART Rx AT90PWM3 2 AT90PWMI vect USART Complete ATmega3250 ATmega3290 ATmega3290P RECV SIG ATmega6450 ATmega6490 ATmega8535 UART RECV ATmegal68 ATmega48 ATmega88 tiny2313 USART SIG USART Tx ATmegal6 ATmega32 ATm
154. 46 INT2 vect SIG INTERRUPT2 External Interrupt Request 2 AT90PWMS3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN 64 ATmegal03 128 16 ATmegal6l 162 ATmega32 ATmega323 ATmega406 4 ATmega8515 ATmega8535 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P ATmega644 AT90USB162 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 INT3 vect SIG INTERRUPT3 External Interrupt Request 3 AT90PWMS3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN 64 ATmegal03 ATmegal28 ATmega406 ATmega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB162 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 AT90USB162 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 INT5_vect SIG_ INTERRUPT5 External Interrupt Request 5 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB162 9005 82 9005 1287 AT90USB 1286 9005 647 9005 646 Generated Tue 15 14 56 11 2007 for avr libc by Doxygen 6 13 l
155. 6 11 2007 for avr libe by Doxygen 1 3 Supported Devices atmega644p atmega645 atmega6450 atmega649 atmega6490 atmega8515 atmega8535 atmega88 ATtiny Type Devices attiny I I 1 attiny 12 1 attiny 13 attiny 15 1 attiny22 attiny24 attiny25 attiny26 attiny26 1 attiny28 1 attiny2313 attiny44 attiny45 attiny46 1 attiny84 attiny85 attiny861 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 1 3 Supported Devices 5 Misc Devices at94K 2 at76c711 3 at43usb320 at43usb355 at86rf401 at90can32 at90can64 at90can128 at90pwml at90pwm2 at90pwm3 at90usb82 at90usb162 at90usb646 at90usb647 at90usb1286 at90usb1287 atmega8hva atmegal6hva atmega406 Note 1 Assembly only There is no direct support for these devices to be programmed in C since they do not have a RAM based stack Still it could be possible to program them in C see the FAQ for an option Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 1 4 avr libc License 6 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 foll
156. 6 3 2 1 define EDOM 33 Domain error 6 3 2 2 define ERANGE 34 Range error 6 4 lt inttypes h gt Integer Type conversions 6 4 1 Detailed Description finclude 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 pointer i e a code pointer that can address more than 64 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 4 lt inttypes h gt Integer conversions 18 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 Nn smallval longval macros for printf and scanf format specifiers For C these are only included if STDC LIMIT MACROS is d
157. 7 for avr libc by Doxygen 6 9 lt stdlib h gt General utilities 73 The qsort function is a modified partition exchange sort or quicksort qsort function sorts an array of nmemb objects the initial member of which is pointed to by base The size of each object is specified by size The contents of the array base are sorted in ascending order according to a comparison function pointed to by compar which requires two arguments pointing to the objects being compared The comparison function must return an integer less than equal to or greater than zero if the first argument is considered to be respectively less than equal to or greater than the second 6 9 4 19 int rand void The rand function computes 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 value of 1 In compliance with the C standard these functions operate on int arguments Since the underlying algorithm already uses 32 bit calculations this causes a loss of preci sion See random for an alternate set of functions that retains full 32 bit precision 6 9 4 20 int rand unsigned long ctx Variant o
158. 8 x define PRIX8 X define PRIXLEASTS X define PRIXFASTS X define PRIo16 o define PRIOLEAST16 define PRIOFAST16 o define PRIu16 define PRIULEAST16 u define PRIUFAST16 define PRIx16 x define PRIXLEAST16 x define PRIxFAST16 x define PRIX16 X define PRIXLEASTI6 X define PRIXFAST16 X Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 16 inttypes h File Reference 211 define PRIo32 lo define PRIOLEAST32 lo define PRIOFAST32 lo define PRIu32 lu define PRIULEAST32 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 PRIul6 define PRIxPTR PRIx16 define PRIXPTR PRIX16 define SCNd16 d define SCNdLEAST16 d define SCNdFAST16 d define SCNi16 1 define SCNILEASTI6 i define SCNiFAST16 i define SCNd32 Id define SCNdLEAST32 Id define SCNdFAST32 define SCNi32 li define SCNiLEAST32 li define SCNiFAST32 li define SCNdPTR SCNd16 define SCNiPTR SCNi16 define SCNo16 define SCNoLEAST16 o define SCNoFAST16 o define SCNu16 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 Gene
159. 8 t typedef int16 t int fastl6 t typedef uint16 tuint fastl t typedef int32 t int fast32 t typedef uint32 t uint_fast32_t typedef int64 t int fast64 t typedef uint64 t uint fast64 t Greatest width integer types Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category typedef int64 t intmax t typedef uint64 t uintmax t 6 7 2 Define Documentation 6 7 2 1 define INT16 C value value define a constant of type int16 t 6 7 2 2 fidefine INT16 MAX Ox7fff largest positive value an int16 t can hold Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 7 lt stdint h gt Standard Integer Types 40 6 7 2 3 define INT16 MIN INT16 MAX 1 smallest negative value an int 16 t can hold 6 7 2 4 INT32 C value CONCAT value L define a constant of type int32 t 6 7 2 5 define INT32 MAX 0x7fffffffL largest positive value an int32 t can hold 6 7 2 6 define INT32 MIN INT32 MAX 1L smallest negative value an int32 t can hold 6 7 27 define INT64 C value CONCAT value LL define a constant of type int64 t 6 7 2 8 define INT64 MAX Ox fffffffffffffffLL largest positive value an int64 t can hold 6 7 2 9 define INT64 MIN INT64 MAX ILL smallest negative value an int64 t can hold 6 7 2 10 define INT8 C value int8 t value define a constant of type int8 t 6 7 2 11 define INT8
160. 9 8 85 2 Define Documentation 8 85 2 1 define wdt write value Value asm volatile N tmp reg SREG n t cli iaie wdr Ant N out 0 951 Nnlt x out SREG tmp reg Nnlt N out 0 2 no outputs N I SFR IO ADDR WD CONTROL REG r BV WD CHANGE BIT BV WDE r uint8_t value amp 0x08 _WD_PS3_MASK 0 00 N BV WDE value amp 0x07 7 ro CM Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 9 avr libc Page Documentation 245 9 avr libc Page Documentation 91 Toolchain Overview 9 1 1 Introduction Welcome to the open source software development toolset for the Atmel AVR There is not a single tool that provides everything needed to develop software for the AVR It takes many tools working together Collectively the group of tools are called a toolset or commonly 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 GUI front end and not know what goes on underneath the hood You may be coming from 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 Hop
161. 91 61 00 145 r18 0x0061 30 91 62 00 145 19 0x0062 2 5 subi r18 OxFF 255 4f sbci r19 OxFF 255 30 93 62 00 sts 0x0062 r19 20 93 61 00 sts 0 0061 r18 83 0 ldi r24 0x03 3 2f 3f cpi r18 OxFF 255 38 07 19 r24 99 4 brne 38 Ox8e lt __SREG__ direction DOWN 81 e0 141 r24 0x01 1 80 93 60 00 sts 0x0060 r24 Of cO rjmp 30 Ox8e lt SREG break case DOWN if pwm 0 20 91 61 00 145 r18 0x0061 30 91 62 00 145 19 0x0062 21 50 subi r18 0x01 1 30 40 sbci r19 0x00 O 30 93 62 00 sts 0x0062 r19 20 93 61 00 sts 0 0061 r18 2l d ep 118 31 05 epo 119 x1 11 f4 brne 4 Ox8e SREG direction UP 10 92 60 00 sts 0x0060 r1 break OCR pwm Note 5 8e 90 92 94 3b bd out 0 25 19 43 2 bd out 0 2 18 42 8f 91 r24 91 r19 0xd gt 0x31 gt 0x4f gt 0x4f gt 0x4f gt 0x4f gt Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 30 simple project 170 96 2 91 pop r18 98 0 90 pop 0 out Ox3f r0 63 9 0 90 pop 9e 1f 90 pop rl 18 95 reti 000000a2 lt ioinit gt void ioinit void Note 6 a2 83 e8 141 r24 0x83 131 a4 8 out Ox2f r24 47 Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys 1 TIMER1 INIT Start timer 1 x NB TCCR1A and cou
162. AST16_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 UINT FAST32 MAX UINT32 MAX define INT FAST64 MAX INT64 MAX define INT FAST64 MIN INT64 MIN define UINT FAST64 MAX UINT64 Limits of integer types capable of holding object pointers define INTPTR MAX INT16 MAX define INTPTR MIN INT16 MIN define UINTPTR MAX UINTI6 MAX Limits of greatest width integer types define INTMAX MAX INT64 MAX define INTMAX MIN INT64 MIN define UINTMAX MAX UINT64 MAX Limits of other integer types C implementations should define these macros only when STDC LIMIT MACROS is defined before lt stdint h gt is included define PTRDIFF MAX 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 7 lt stdint h gt Standard Integer Types 38 Macros for integer constants C implementations should define these macros only when STDC CONSTANT MACROS is defined before lt stdint h gt is included These definitions are valid for integer constants without suffix and for macros defined as integer constant without suffix define INT8 C value int8_t value define UINT8 C value uint8 t CONCAT value U define INT
163. ASTI6 22 PRIOLEAST32 22 PRIoLEASTS 23 PRIoPTR 23 PRIu16 23 PRIu32 23 8 23 PRIuFASTI6 23 PRIUFAST32 23 PRIuFASTS 23 PRIuLEASTI6 23 PRIULEAST32 23 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 339 PRIuLEASTS 23 PRIuPTR 24 PRIX16 24 PRIx16 24 PRIX32 24 PRIx32 24 PRIX8 24 PRIX8 24 PRIXFAST16 24 PRIXFAST 16 24 PRIXFAST32 24 PRIxFAST22 24 PRIXFASTS 25 PRIxFASTS 25 PRIXLEAST 16 25 PRIXLEAST 16 25 PRIXLEAST32 25 PRIXLEAST32 25 PRIXLEASTS 25 PRIxLEASTS 25 PRIXPTR 25 PRIxPTR 25 SCNd16 25 SCNd32 26 SCNdFASTI6 26 SCNdFAST32 26 SCNdLEASTI6 26 SCNdLEAST32 26 SCNdPTR 26 SCNil6 26 SCNi32 26 SCNiFAST 16 26 SCNiFAST32 26 SCNiLEAST 16 26 SCNiLEAST32 27 SCNiPTR 27 SCNo16 27 SCNo32 27 SCNoFAST 16 27 SCNoFAST32 27 SCNoLEAST 16 27 SCNoLEAST32 27 SCNoPTR 27 SCNul6 27 SCNu32 27 SCNuFAST 16 28 SCNuFAST32 28 SCNuLEAST16 28 SCNuLEAST32 28 SCNuPTR 28 SCNx16 28 SCNx32 28 SCNXxFAST 16 28 SCNxFAST32 28 SCNxLEAST16 28 SCNxLEAST32 28 SCNxPTR 29 uint farptr t 29 avr math acos 30 asin 30 atan 30 atan2 31 ceil 31 cos 31 cosh 31 exp 31 fabs 31 floor 31 fmod 31 frexp 31 isinf 32 isnan 32 Idexp 32 log 32 log 10 32 M PI 30 M SQRT2 30 modf 32 pow 32 sin 33 sinh 33 sqrt 33 square 33 tan 33 tanh 33 avr pgmspace memchr P 122 memcemp P 122 memopy P 122 memmem P 122 me
164. Asked Questions 294 Some of the supplied include files are not C safe i they need to be wrapped into extern C gt 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 in space and runtime sensitive environments like microcon trollers extra care should be taken to avoid unwanted side effects of the calling conventions like implied copy constructors that could be called upon function invo cation etc These things could easily add up into a considerable amount of time and program memory wasted Thus casual inspection of the generated assembler code using the S compiler option seems to be warranted Back to FAQ Index 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 gener
165. B 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 same address space This means that any compiler for a Harvard Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 4 Data in Program Space 260 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
166. BUS ERROR 151 TW LOST 151 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 356 utoa TW MR DATA ACK 151 TW MR DATA 151 TW MR SLA ACK 151 TW MR SLA 151 TW MT ARB LOST 151 TW MT DATA ACK 151 TW MT DATA 151 TW MT SLA 152 TW MT SLA NACK 152 TW NO INFO 152 TW READ 152 TW REP START 152 TW SR ARB LOST GCALL ACK 152 TW SR ARB LOST SLA ACK 152 TW SR DATA ACK 152 TW SR DATA 152 TW SR GCALL ACK 152 TW SR GCALL DATA 152 TW SR GCALL DATA NACK 153 TW SR SLA ACK 153 TW SR STOP 153 TW ST ARB LOST SLA ACK 153 TW ST 153 TW ST DATA NACK 153 TW ST LAST DATA 153 TW ST SLA ACK 153 TW START 153 TW STATUS 153 TW STATUS MASK 153 TW WRITE 154 avr stdlib 76 vfprintf avr stdio 59 vfprintf P avr stdio 62 vfscanf avr stdio 62 vfscanf P avr stdio 65 vprintf stdio 65 vscanf stdio 65 vsnprintf avr stdio 65 vsnprintf P avr stdio 65 vsprintf avr stdio 65 vsprintf P avr stdio 65 wdt h 244 wdt write 244 wdt disable avr watchdog 141 wdt enable avr watchdog 141 wdt reset avr watchdog 141 WDTO 120 5 avr watchdog 142 WDTO 15 5 avr watchdog 142 WDTO 15 avr watchdog 142 WDTO 250MS avr watchdog 142 WDTO 25 avr watchdog 142 WDTO 30MS avr watchdog 142 WDTO 45 avr watch
167. 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 ioml69 h gt Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 8 Porting From to AVR 286 Note IAR does not always use the same register names or bit names that are used in the AVR datasheet 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 Windows distributions of the toolchain and is the recommended method of including this file The compiler knows the processor type and through the single header file above it can pullin 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 reg
168. MAX 0x7f largest positive value an int8 t can hold 6 7 2 12 define INT8 MIN INT8 MAX 1 smallest negative value an int8 t can hold 6 7 2 13 define INT FAST16 MAX INT16 MAX largest positive value an int fast16 t can hold Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 7 lt stdint h gt Standard Integer Types 41 6 7 2 14 define INT FAST16_MIN INT16 MIN smallest negative value an int fast16 t can hold 6 7 2 15 define INT FAST32 MAX INT32 largest positive value an int fast32 t can hold 6 7 2 16 define INT FAST32 MIN INT32 MIN smallest negative value an int fast32 t can hold 6 7 2 17 define INT FAST64 MAX INT64 MAX largest positive value an int fast64 t can hold 6 7 2 18 define INT FAST64 MIN INT64 MIN smallest negative value an int fast64 t can hold 6 7 2 19 define INT FAST8 MAX INT8 MAX largest positive value an int fast8 t can hold 6 7 2 20 define INT FAST8 MIN INT8 MIN smallest negative value an int fast8 t can hold 6 7 2 21 define INT LEASTI6 MAX INT16 MAX largest positive value an int least16 t can hold 6 7 2 22 INT LEASTI6 MIN INT16 MIN smallest negative value an int least16 t can hold 6 7 2 23 define INT LEAST32 INT32 largest positive value an int least32 t can hold 6 7 2 24 define INT LEAST32 MIN INT32 MIN smallest negative value an int least32 t can hold Generated on Tue May 15 14 56 11 2
169. May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 117 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 __ _ __ define PSTR s const PROGMEM char x s define pgm read byte near address short LPM uint16 t address short define pgm read word near address short LPM word uint16 t address short define pgm read dword near address short LPM dword uint16 t address_short define pgm read byte far address long ELPM uint32 t address long define pgm read word far address long ELPM word uint32 t address_long define pgm_read_dword_far address_long __ELPM_dword uint32_ t address_long define pgm_read_byte address_short pgm_read_byte_near address_short define pgm_read_word address_short pgm_read_word_near address_short define pgm_read_dword address_short pgm_read_dword_near address_short define PGM_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
170. OMMON ASB Check if the RWW section is busy 6 11 2 12 boot rww enable boot rww enable Enable the Read While Write memory section 6 11 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 enable except waits for eeprom and spm operations to complete before enabling the RWW mameory 6 11 2 14 define boot spm busyO SPM REG amp uint8 t BV SPMEN Check if the SPM instruction is busy 6 11 2 15 zdefine boot spm busy wait do while boot spm busy Wait while the SPM instruction is busy 6 11 2 16 boot spm interrupt disable SPM REG amp uint8_t _ BV SPMIE Disable the SPM interrupt Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 12 lt avr eeprom h gt EEPROM handling 94 6 11 2 17 define boot spm interrupt enable SPM REG uint8 t BV SPMIE Enable the SPM interrupt 6 11 2 18 define BOOTLOADER SECTION A2Gattribute _ 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 11 2 19 define GET EXTENDED FUSE BITS 0x0002 address to read the extended fuse bits using boot lock fuse bits get 6 11 2 20 define GET HIGH FUSE BITS 0x0003
171. OT PAGE FILL uint16 t address uint16 t data y r30 r31 8 4 2 9 define Value boot_page_write_alternate address __asm__ __volatile__ movw r30 2 n t sts 0 1 n t spm n t word Oxffff n t nop n t 1 yn yn SFR MEM ADDR SPM REG uint16 t address uint8 t BOOT PAGE WRITE 30 f r31 POLE LEG LA A PS FRP AN Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 8 4 boot h File Reference 204 8 4 2 10 define boot page write extended address Value __asm__ __volatile__ movw r30 A3 n t sts 1 C3 n t sts 0 2 n t spm n t in i SFR MEM ADDR SPM REG SFR MEM ADDR RAMPZ r uint8 t PAGE WRITE Wa uint32 t address r30 6 31 8 4 2 11 define boot page write normal address Value __asm__ __volatile__ movw r30 2 n t sts 0 1 n t som n t non i SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE WRITE r uintl6 t address 230 W ae ih 8 4 2 12 define boot rww_enable0 Value __asm__ volatile sts 0 1 n t spmNn Nc i SFR MEM ADDR SPM REG r uint8 t BOOT RWW ENABLE qu p cut cur ch quo QA uo V AC a AS ow Eua Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 5
172. OUTPUT Compare Match ATmega2560 ATmega2561 COMPARESC C TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 OVF vect OVERFLOWS Overflow ATmega2560 ATmega2561 TWI vect SIG 2WIRE 2 wire Serial In AT90CANI28 AT90CAN32 AT90CAN64 SERIAL terface ATmegal28 ATmegal6 ATmegal63 ATmega32 ATmega323 ATmega406 ATmega64 ATmega8 8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal28l ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 111 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 ATmegal6l vect UARTO Complete RECV UARTO TX SIG UARTO Tx ATmegal6l vect UARTO Complete TRANS UARTO SIG UARTO Data ATmegal61 UDRE vect UARTO Register Empty DATA UARTI RX SIG UARTI Rx ATmegal6l vect UARTI Complete RECV UARTI TX SIG UARTI Tx ATmegal6l vect UARTI Complete TRANS UARTI SIG UARTI Data ATmegal61 UDRE vect UARTI Register Empty DATA UART RX SIG UART UART
173. 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 118 Functions PGM VOID P memchr P PGM VOID P s int val size_t len ATTR CONST int memcmp P const void PGM VOID size_t PURE void memcpy P void PGM VOID size t PGM VOID P memrchr P PGM VOID P s int val size t len ATTR CONST int strcasecmp P const char PGM ATTR PURE char strcat P char PGM P PGM P strchr P PGM Ps int val CONST PGM P strchrnul P Ps int val ATTR CONST int stremp P const char PGM P PURE char strepy P char PGM P size t strcspn P const char s PGM P reject PURE size t strlcat P char P size t size t strlcpy P char PGM P size t size t strlen P PGM P CONST int strncasecmp P const char x P size_t PURE char strncat P char PGM P size t int strncmp P const char PGM P size_t PURE char strnepy P char size t size t strnlen P PGM P size t ATTR CONST char strpbrk P const char s PGM P ac
174. PT 156 outb 156 outp 157 sbi 157 timer_enable_int 157 disassembling 167 div avr_stdlib 70 div_t 197 quot 197 rem 197 DTOSTR_ALWAYS_SIGN avr_stdlib 68 DTOSTR_PLUS_SIGN avr_stdlib 68 DTOSTR_UPPERCASE avr_stdlib 68 dtostre avr_stdlib 70 dtostrf avr_stdlib 70 EDOM avr errno 17 EEMEM avr eeprom 96 eeprom h 207 eeprom busy wait avr eeprom 96 eeprom is ready avr eeprom 96 eeprom read block avr eeprom 96 eeprom read byte avr eeprom 96 eeprom read word avr eeprom 97 eeprom write block avr eeprom 97 eeprom write byte avr eeprom 97 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen INDEX eeprom Write word avr string 79 avr eeprom 97 ffsl S 209 EMPTY INTERRUPT ffsll avr interrupts 114 avr string 79 enable external int ffsll S 209 deprecated items 155 fgetc EOF avr stdio 56 avr stdio 53 fgets ERANGE avr stdio 56 avr errno 17 FILE errno h 208 avr stdio 54 Example using the two wire interface floor TWD 192 avr math 31 exit fmod avr stdlib 70 avr math 31 exp fprintf avr math 31 avr stdio 57 fprintf P fabs avr stdio 57 avr math 31 fputc FAQ 289 avr stdio 57 fclose fputs avr stdio 35 stdio 97 fdev_close fputs P stdio 53 fdev get udata avr stdio 53 fdev set udata stdio 53 FDEV SETUP STREAM avr stdio 53 fdev setup stream stdio 53 fdevopen avr_stdio 55 fdevopen c 208 feof avr_stdio 56 ferror
175. R 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 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 8 Porting From to AVR 288 Note See the GCC User Manual for more information 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 read macros defined in lt avr pgmspace h gt All P
176. R 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 Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 13 lt avr interrupt h gt Interrupts 98 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 finclude avr interrupt h ISR ADC vect user code here Refer to the chapter explaining assembler programming for an explanation about inter rupt routines written solely in assembler language Catch all interrupt vector If an unexpected interrupt occurs interrupt is enabled and no handler is insta
177. RUS SO NW 248 918 GDB Isght DDD o RE X IG 248 MLE regirse ue de v pre gue SE de edens 249 OLA LET s ek kup ee 249 22222222222254 sekk aed ee 249 9 1 12 Toolchain Distributions Distros 249 ULIS Open Source ose 250 9 2 Memory Areas and Using 250 921 IDUQQUGHO0W 22 99 RRE a E EO US S 250 922 Internal vs extemal RAM 2 4 2253 rad es RR 251 923 252 9 2 4 Implementation d tails 253 93 Memory s on esee Ge vy Se Qw ah N 255 Te fe c vasset gue SPT SEE AS 255 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen CONTENTS xii 9 4 9 5 9 6 9 7 852 Te dal S6ohoH 22529 ke er Ei N 255 933 The WES GECUOM culos 229 5 SE 256 954 The Secon ouem eco ke RR E RES 256 932 The On 2 los o a a OR SANG 256 9 3 6 The Sections s ve creeer ob o m x Skee 256 937 The hmN SecHols 4 o GEN GE Roo 258 9 3 8 Using Sections in Assembler 258 9 39 Using Sections MO Code 0 605 5 ee a ku N U N 259 Data in Program Space 22 222 22 BR A ee a 259 941 cono Reo Re RE EE 259 9 4 2 Note On const 260 9 4 3 Storing and Retrieving Data in the Program Space 26
178. TERRUPTION ONTRACT STRICT LIABILITY INDIRECT INCLUDING OR TORT POHNAH DP POSSIBILITY OF SUCH DAMAGE 2 avr libc Module Index 21 avr libc Modules Here is a list of all modules 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 pgmspace h gt Program Space Utilities IS PROVIDED BY THE COPYRIG INCLUDING MPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR IN NO EVENT SHALL THE CO INCIDENTAL BUT NOT LIMITED TO LOSS OF US HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WH INC RISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE BUT A PARTICU OR CONTRI EXEMPLARY PYRIGHT OWNER SPECIAL E DATA OR PROFITS OR HT HOLDERS AND CONTRIBUI NOT LIMITED TO 5 AS IS THE LAR PURPOSE BUTORS BE OR PROCUREMENT OF BUSINESS ETHER IN LUDING NEGLIGENCE OR OT HERWISE EVEN IF ADVISED OF THE 13 14 17 17 29 34 36 48 66 at 88 94 97 116 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 3
179. TH 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 1 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 2 Optional Tools You can develop programs for AVR devices without the following tools They may or may not be of use for you uisp http savannah gnu org projects uisp Installation avrdude http savannah nongnu org projects avrdude Installation Usage Notes Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 10 Installing the GNU Tool Chain 314 GDB http sources redhat com gdb Installation Simulavr http savannah gnu org projects simulavr Installation AVaRice http avarice sourceforge net Installation 9 10 3 GNU Binutils for the AVR target The binutils package provides all the low level utilities needed in building and ma nipulating object files Once installed your environment will have an AVR assembler avr as linker avr 1d and librarian avr ar and avr ranlib In addi tion you get tools which extract data from object files avr objcopy dissassem ble object file information avr objdum
180. TK500 development kit The UART port needs to be connected to the RS 232 spare port by a jumper cable that connects PDO to RxD and PD1 to TxD The RS 232 channel is set up as standard input st din and standard output st dout respectively In order to have a different device available for a standard error channel stderr an industry standard LCD display with an HD44780 compatible LCD controller has been chosen This display needs to be connected to port A of the STK500 in the following way Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 332 Using the standard IO facilities 185 Port Header Function A0 1 LCD D4 Al 2 LCD D5 A2 3 LCD D6 A3 4 LCD D7 A4 5 LCD R W 5 6 LCD E A6 7 LCD RS 7 8 unused GND 9 GND VCC 10 Vcc Figure 5 Wiring of the STK500 LCD controller is used 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 progra
181. TW MR ARB LOST 0x38 define TW MR SLA ACK 0x40 define TW MR SLA NACK 0x48 define TW DATA ACK 0x50 define TW DATA NACK 0x58 define TW ST SLA ACK 0 8 define TW ST ARB LOST SLA OxBO define TW ST DATA ACK OxB8 define TW ST DATA 0xCO define TW ST LAST DATA 0xC8 define TW SR SLA ACK 0x60 define TW SR ARB LOST SLA ACK 0x68 define TW SR GCALL ACK 0x70 define TW SR ARB LOST GCALL ACK 0x78 define TW SR DATA ACK 0x80 define TW SR DATA NACK 0x88 define TW SR GCALL DATA ACK 0x90 fdefine TW SR GCALL DATA NACK 0x98 define TW SR STOP OxAO define TW NO INFO OxF8 define TW BUS ERROR 0x00 define TW STATUS 5 fdefine TW STATUS TWSR amp TW STATUS MASK R W bit in SLA R W address field define TW READ 1 define TW WRITE 0 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 85 wdt h File Reference 244 Defines 8 85 8 85 1 define UTIL TWIH 1 wdt h File Reference Detailed Description Defines define wdt_reset 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 156 define WDTO 28 7 define WDTO 458 define WDTO 85
182. Tmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 AT megal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 9005 1286 AT90USB647 AT90USB646 TIMER3 vect SIG INPUT CAPTURE3 Timer Counter3 Capture Event AT90CAN128 AT90CAN32 AT90CAN64 ATmegal28 ATmegal62 ATmega64 AT mega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT90USB1287 9005 1286 AT90USB647 AT90USB646 TIMER3_ vect SIG_ OUTPUT_ COMPARE3A Timer Counter3 Compare Match A AT90CAN128 AT90CAN32 AT90CAN64 ATmega128 ATmega162 ATmega64 AT mega640 ATmega1280 ATmega1281 AT mega2560 ATmega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 110 Vector name Old vector Description Applicable for device name TIMER3 SIG Timer Counter3 AT90CAN 128 AT90CAN32 AT90CAN 64 COMPB vect OUTPUT Compare Match ATmegal28 ATmegal62 ATmega64 COMPARE3B B mega640 ATmegal280 ATmegal281 mega2560 ATmega2561 AT90USB1287 AT90USB 1286 AT90USB647 AT90USB646 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CAN 64 vect OUTPUT Compare Match ATmegal28 ATmega64 ATmega640 AT COMPARE3C C megal280 ATmegal281
183. Tmegal28 ATmega64 ATmega640 COMPAREIC C ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB162 9005 82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMERI SIG Timer Counter1 ATtiny261 ATtiny461 ATtiny861 COMPD vect OUTPUT Compare Match COMPAREOD D SIG Timer Counter I AT9082333 9054433 ATtiny 15 COMP vect OUTPUT Compare Match 1 TIMERI SIG Timer Counter 1 AT9082313 ATtiny26 OVFI vect OVERFLOW I Overflow TIMER SIG Timer Counter I 9052333 AT90S4414 479054433 OVF vect OVERFLOW I Overflow AT90S4434 9058515 AT90S8535 AT9OPWM3 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 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 13 lt avr interrupt h gt Interrupts 109 Vector name Old vector name Description A
184. U Debugger GDB is a command line debugger that can be used with the rest of the AVR toolchain Insight is GDB plus a GUI written in Tcl Tk Both GDB and Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 91 Toolchain Overview 249 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 19 AVaRICE AVaRICE 15 back end program to GDB and interfaces to the Atmel JTAG In Circuit Emulator ICE to provide emulation capabilities 9 1 10 SimulAVR SimulAVR is an AVR simulator used as a back end with AVR GDB Unfortunately this project is currently unmaintained and could use some help 9 1 11 Utilities There are also other optional utilities available that may be useful to add to your toolset SRecord is a collection of powerful tools for manipulating EPROM load files It reads and writes numerous EPROM file formats and can perform many different ma nipulations MF ile is a simple Makefile generator is meant as an aid to quickly customize 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 a
185. USI USI START ATtiny24 ATtiny44 ATtiny84 vect START WATCHDOG SIG Watchdog Time ATtiny24 ATtiny44 ATtiny84 vect WATCHDOG out TIMEOUT WDT SIG Watchdog Timer ATtiny2313 OVERFLOW WATCHDOG Overflow vect TIMEOUT SIG WDT OVERFLOW vect SIG WDT Watchdog Time AT90PWM3 AT90PWM2 AT90PWMI SIG out Interrupt ATmega406 ATmegal68 ATmega48 WATCHDOG ATmega88 ATmega640 ATmegal280 TIMEOUT ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtinyl3 ATtiny45 tiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 AT90USBI62 AT90USB82 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 define SIGNAL vector define EMPTY INTERRUPT vector define ISR_ALIAS vector target vector 6 13 2 Define Documentation 6 13 2 1 define cli finclude avr interrupt h Disables all interrupts by clearing the global interrupt mask This function actually compiles into a single line of assembly so there is no function call overhead Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 115 6 13 2 2 define EMPTY INTERRUPT vector include lt avr
186. WI project explains the use of the two wire hardware interface also known as I2C that is present on many AVR controllers Finally the Combining C and assembly source files demo shows how C and assem bly language source files can collaborate within one project While the overall project is managed by 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 C only implementation de ploying the exact same peripheral setup based on 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 LED could be connected to the OCR1 A output the large and stdio demos are mainly targeted to the Atmel STK500 starter kit and the TWI example requires controller where some 24Cxx two wire EEPPROM can be connected to For the STK500 demos the default CPU either 419058515 or ATmega8515 should be removed from its socket and the ATmegal6 that ships with the kit should be inserted into socket SCKT3100A3 The ATmega16 offers an on board ADC that is used in the large demo and all AVRs with an ADC feature a differ
187. 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 asm volatile mov X tmp reg A0 n t mov 0 0 n t mov D0 __tmp_reg__ n t mov __tmp_reg__ BO n t Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 277 mov 0 0 mov C0 __tmp_reg__ n t r value 0 value If operands do not fit into a single register 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 also implies that it is often neccessary to cast the type of an input operand to the desired size final problem may arise While using pointer register pairs If you define an input operand e ptr and the compiler selects register Z 130 r31 then A0 refers to lt 30 and BO refers to r31 But both versions will fail during the assembly stage of the compiler if you explicitely need 7 like in ld r24 Z If you write ld r24 0 with lower case following the percent sign then the compile
188. _least16_t unsigned int with at least 16 bits 6 7 3 24 typedef uint32_t uint_least32_t unsigned int with at least 32 bits 6 7 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 6 7 3 26 typedef uint8_t uint_least8_t unsigned int with at least 8 bits 6 7 3 27 typedef uint64_t uintmax_t largest unsigned int available Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 8 lt stdio h gt Standard IO facilities 48 6 7 3 28 typedef uint16 t uintptr t Unsigned pointer compatible type 6 8 lt stdio h gt Standard IO facilities 6 8 1 Detailed Description finclude lt stdio h gt Introduction to the Standard IO facilities This file declares the standard IO facili ties that are implemented in avr libc Due to the nature of the underlying hardware only a limited subset of standard IO is implemented There is no actual file 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
189. acceptable to pass pt r as NULL in which case realloc will behave identical to malloc If the new memory cannot be allocated realloc returns NULL and the region at pt r will not be changed 6 9 4 24 void srand unsigned int __seed Pseudo random number generator seeding see rand 6 9 4 25 void srandom unsigned long __seed Pseudo random number generator seeding see random 6 9 4 26 double strtod const char __nptr char endptr 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 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 endpt r is not NULL a pointer to the character after the last character used in the conversion is stored in the location referenced by endpt r If no conversion is performed zero is returned and the value of npt is stored in the location referenced by endpt If the correct value would cause overflow plus or minus HUGE VAL is returned ac cording to the sign of the value and ERANGE is stored in errno If the correct
190. ail 6 32 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 from the controller needs to be handled as two nibble IOs The functions hd44780 outnibble and Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 32 Using the standard IO facilities 189 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 signa
191. ailed 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 10 lt string h gt Strings 78 int memcmp const void const void size_t __ _ void memcpy void const void size_t void memmem const void size_t const void size_t ATTR PURE void memmove void const void size_t void memrchr const void int size_t ATTR PURE void memset void int size t int strcasecmp const char const char x ATTR_PURE char strcasestr const char const char x ATTR PURE char strcat char const char char strchr const char int ATTR PURE char strchrnul const char int PURE int strcmp const char const char ATTR PURE char strepy char const char size t strcspn const char s const char reject ATTR PURE size t strlcat char
192. ain 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 previous write request it will simply leave its bus interface drivers at high impedance and does not respond to 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 NACK to its selection request Thus the select process is simply started over effectively causing a repeated start condition until the device will eventually respond This polling procedure is recommended in the 24Cxx datasheet in order to minimize the busy wait time when writing Note that in case a device is broken and never responds to a selection e g since it is no longer present at all this will cause an infinite loop Thus the maximal number of iterations made until the device is declared to be not responding at all 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 33 Example using the two wire interface TWD 196 respo
193. al all integer type variables are set to 0 all pointers to a NULL pointer and all floating point variables to 0 0 As long as these variables are not initialized 1 e they don t have an equal sign and an initialization expression to the right within the definition of the variable they go into the bss section of the file This section simply records the size of the variable but otherwise doesn t consume space neither within the object file nor within flash memory Of course being a variable it will consume space in the target s SRAM In contrast global and static variables that have an initializer go into the data section of the file This will cause them to consume space in the object file in order to record the initializing value and in the flash ROM of the target device The latter is needed since the flash ROM is the only way that the compiler can tell the target device the value this variable is going to be initialized to Now if some programmer wants to make doubly sure their variables really get a 0 at program startup and adds an initializer just containing 0 on the right hand side they waste space While this waste of space applies to virtually any platform C is Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 295 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
194. al digit string specifying a minimum field width If the con verted value has fewer characters than the field width it will be padded with spaces on the left or right if the left adjustm ment flag has been given to fill out the field width An optional precision in the form of 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 0 u x and X conversions or the maximum number of characters to be printed from string for 5 conversions An optional 1 length modifier that specifies that the argument for the d i o u x or X conversion is long int rather than int 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 and 1 unsigned octal unsigned decimal 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 p The void argument is taken as an unsigned integer and converted similarly as a 3 x command would do c The int argument is converted to an unsigned char and the resulting character is written s
195. ameter 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 instructive to look at the resulting disassembly from the compiler 9 5 avr libc and assembler programs 9 5 1 Introduction There might be several reasons to write code for AVR microcontrollers using plain assembler source code Among them are Code for devices that do not have RAM and are thus not supported by the compiler Code for very time critical applications Special tweaks that cannot be done in Usually all but the first could probably be done easily using the inline assembler facility of the compiler Although avr libc is primarily targeted to support programming AVR microcontrollers
196. and writing IO ports can be done by simply using the IO port name in an expression and all bit manipulation including those on IO ports can be done using generic C bit manipulation operators The macros in this group simulate the historical behaviour While they are supposed to be applied to IO ports the emulation actually uses standard C methods so they could be applied to arbitrary memory locations as well define inp port port define outp val port port val define inb port port define outb port val port val define sbi port bit port 1 lt lt bit define cbi port bit port amp 1 lt lt bit 6 26 2 Define Documentation 6 26 2 1 define cbi port bit port amp 1 lt lt bit Deprecated Clear bit in IO port port Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 26 lt compat deprecated h gt Deprecated items 156 6 26 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 26 2 3 define inb port port Deprecated Read a value from an IO port port 6 26 2 4 define inp port
197. ap file is useful for monitoring the sizes of your code and data It also shows where modules are loaded and which modules were loaded from libraries It is yet another view of your application To get a map file I usually add Wl Map demo map to my link command Relink the application using the following command to generate demo map a portion of which is shown below avr gcc g mmcu atmega8 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 0 vectors vectors progmem gcc progmem 0x00000000 ALIGN 0 2 0 00000000 __trampolines_start trampolines trampolines 0x00000000 0 0 linker stubs trampolinesx 0x00000000 trampolines end jumptables jumptables lowtext lowtext 0x00000000 ctors start Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 172 text segment where program instructions are stored starts at location 0 0 fini2 fini2 finil finil finiO finiO 0x000000ce etext data 0x00800060 0x0 load address 0x000000ce 0x00800060 PROVIDE data start data data 0x00800060 0 0 demo o data 0x00800060 0 0 c winavr bin lib gcc avr 4 1 2 avr4Nlibgcc a copy data o data 0x00800060 0 0 c winavr bin lib gcc avr 4 1 2 avr4Nlibgcc a _clear_bss o datax rodata rodata gnu
198. aracter appears If decimal point appears at least one digit appears before it gG The double argument is converted in style or or F or E for conver sions The precision specifies the number of significant digits If the precision is missing 6 digits are given if the precision is zero it is treated as 1 Style 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 5 Similar to the s format except the pointer is expected to point to a program memory ROM string instead of a RAM string In no case does a non existent or small field width cause truncation of a numeric field if the result of a conversion is wider than the field width the field is expanded to contain the conversion result Since the full implementation of all the mentioned features becomes fairly large three different flavours of vfprintf can be selected using linker options The default vf printf implements all the mentioned functionality except floating point conversions A minimized version of vfprintf is available that only implements the very basic in teger and string conversion facilities but none of the additional options that can be specified using conversion flags these flags are parsed correctly from the format spec ification but then simply ignored
199. aracter 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 other characters are sent to the display The single static function internal variable n1 seen works for this purpose If mul tiple LCDs should be controlled using the same set of driver functions that would not work anymore as a way is needed to distinguish between the various displays This is where the second parameter can be used the reference to the stream itself instead of keeping the state inside a private variable of the function it can be kept inside a private object that is attached to the stream itself A reference to that private object can be at tached to the stream e g inside the function 1cd init that then also needs to be passed a reference to the stream using fdev set udata and can be accessed inside putchar using fdev get udata 6 32 3 7 uart h Public interface definition for the RS 232 UART driver much like in lcd h except there is now also a character
200. assed 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 100 Vector name Old name vector Description Applicable for device ADC_vect SIG_ADC ADC Conversion Complete 9052333 AT90S4433 9054434 9058535 AT9OPWM3 AT90PWM2 AT90PWMI 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 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_ COMP 0 vect SIG Analo
201. at 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 8 3 35 int vfscanf P FILE stream const char _ fmt va list Variant of vfscanf using fmt string in program memory 6 8 3 36 int vprintf const char _ fmt va list The function vprintf performs formatted output to stream stdout taking vari able argument list as in vfprintf See vfprintf for details 6 8 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 8 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 9 lt stdlib h gt General utilities 66 6 8 3 39 int vsnprintf_P char _ 5 size_t__n const char __ fmt va_list ap Variant of vsnprintf that uses a fmt string that resides in program memory 6 8 3 40 int vsprintf char _ 5 const char fmt va_list ap Like sprintf but takes a variable argument list for the argum
202. avr libc Data Structure Index 8 lt avr power h gt Power Reduction Management 128 lt avr sfr defs h gt Special function registers 133 Additional notes from lt avr sfr defs h gt 131 lt avr sleep h gt Power Management and Sleep Modes 136 lt avr version h gt avr libc version macros 138 lt avr wdt h gt Watchdog timer handling 140 util crc16 h CRC Computations 143 lt util delay h gt Convenience functions for busy wait delay loops 147 lt util delay_basic h gt Basic busy wait delay loops 148 lt util parity h gt Parity bit generation 149 lt util twi h gt TWI bit mask definitions 150 lt compat deprecated h gt Deprecated items 154 lt compat ina90 h gt Compatibility with EWB 3 x 157 Demo projects 158 Combining C and assembly source files 159 A simple project 162 A more sophisticated project 177 Using the standard IO facilities 184 Example using the two wire interface TWI 192 3 avr libc Data Structure Index 3 1 avr libc Data Structures Here are the data structures with brief descriptions div_t 197 Idiv_t 197 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 4 avr libc File Index 4 avr libc File Index 4 1 avr libc File List is a list of all documented files with brief descriptions assert h atoi S atol S boot h crc16 h ctype h delay h delay basic h eeprom h errno h fdevopen c ffs S ffsl S ffsll S interrupt h inttypes h math h memccpy S memch
203. avr libc Reference Manual 1 4 6 Generated by Doxygen 1 4 7 Tue May 15 14 56 11 2007 CONTENTS Contents 1 AVR Libe IntodHOOOl 2 5 59 SAR m n m Rc m on no Reo OR AG 1 2 General information about this library 12 Supported Deyts 29 poco o coy QUNKU spess AE LA AvrDbebac Hs saved deres eR XS 2 avr libc Module Index 2 avr hbeModules 7 3 avr libc Data Structure Index 34 avr libe Data Structures gt eac aoe sa coo RS 4 avr libc File Index 4 1 File List 0 noo om o moto oom MY 5 5 avr libc Page Index 34 ave lbe Related 22 222 6 avr libc Module Documentation 6 1 6 2 6 3 6 4 assert ho Diagnostics 2 22 2249 ac RR REG S 6 11 Detailed Description gt sce ec e esas eee Ix REO 612 Defne Documentation 2 24 ewros s eaka eee eS lt ctype b gt Character Operations 4 gt 621 Detailed Description 2222 2229 cR RR 622 Function Documentation 222 2 Seno oo System EMOS sss REESE 63 1 Detailed Description 6 3 2 Define Documentation lt gt eros s a s a kokk koke g lt inttypes h gt Integer Type conversions 6 4 44 Detailed Description 6 4 2 Define Documentation 643 Typedet Documentation 2 29 Se Re ee RR os Generated on Tue May 15 14 56 11 2007
204. 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 32 4 The source code The source code is installed under Sprefix share doc avr libc examples stdiodemo where prefix isa configuration option For Unix systems it is usually set to either usror usr local Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 33 Example using the two wire interface TWD 192 6 33 Example using the two wire interface Some newer devices of the ATmega series contain builtin support for interfacing the microcontroller to a two wire bus called TWI This is essentially the same called I2C by Philips but that term is avoided Atmel s documentation due to patenting issues For the original Philips documentation see http www semiconductors philips com buses i2c index html 6 33 1 Introduction into TWI The two wire interface consists of two signal lines named SDA serial data and SCL serial clock plus ground line of course All devices participating in the bus are connected together using open dra
205. 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 8 lt stdio h gt Standard IO facilities 65 By default all the conversions described above are available except the floating point conversions and the conversion These conversions will be available in the 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 lscanf 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 fmt that do not comprise conversion specification will simply be ignored including white space th
206. 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 push r28 push r29 in r28 SP L _ r29 SP H sbiw r28 20 in tmp reg SREG Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 311 GLa out SPH r29 out SREG tmp reg out SP h 28 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 enabl
207. braries Back to FAQ Index 9 9 4 How to permanently bind a variable to a register This can be done with Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 292 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 ldi r16 BV SRE _BV SRW out SFR IO ADDR MCUCR r16 end xram S Assemble it link the resulting xram o with other files in your program and this piece of code will be inserted in initialization code which is run right after reset See the linker script for comments about the new initN sections which one to use etc The advantage of this method is that you can insert any initialization code you want just remember that this is very early startup no stack and 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
208. brary 282 The assembler instruction clr r3 will clear the variable counter AVR GCC will not completely reserve the specified register If the optimizer recognizes that the vari able will not be referenced any longer the register may be re used But the compiler is not able to check wether this register usage conflicts with any predefined register If you reserve too many registers in this way the compiler may even run out of registers during code generation In order to change the name of a function you need a prototype declaration because the compiler will not accept the asm keyword in the function definition extern long Calc void asm CALCULATE Calling the function Calc will create assembler instructions to call the function CALCULATE 9 6 8 Links For a more thorough discussion of inline assembly usage see the gcc user manual The latest version of the gcc manual is always available here http gcc gnu org onlinedocs 9 7 How to Build a Library 9 7 1 Introduction So you keep reusing the same functions that you created over and over Tired of 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 an
209. by Doxygen 6 8 lt stdio h gt Standard IO facilities 51 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 FILE struct file define stdin _ iob 0 define stdout __iob 1 define stderr __iob 2 define EOF 1 define fdev_set_udata stream u do stream udata u while 0 define fdev_get_udata stream stream udata define fdev_setup_stream stream put get rwflag define FDEV SETUP READ SRD define FDEV SETUP WRITE SWR define FDEV SETUP RW SRD SWR define FDEV ERR 1 define FDEV EOF 2 define FDEV SETUP STREAM put get rwflag define fdev close define putc c stream fputc stream define putchar __c fputc c stdout define getc __stream fgetc __stream define getchar fgetc stdin Functions int fclose FILE stream int vfprintf FILE stream const
210. c define LPM enhanced addr define LPM word classic addr define LPM word enhanced addr define _ LPM dword classic addr define LPM dword enhanced addr define LPM addr LPM classic addr define LPM word addr word classic addr define LPM dword addr dword classic addr 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 addr define ELPM word enhanced addr define ELPM dword classic addr define ELPM dword enhanced addr define ELPM addr ELPM classic addr define ELPM word addr ELPM word classic addr Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 31 pgmspace h File Reference 217 define ELPM dword addr ELPM dword classic addr define pgm read byte far address long ELPM uint32 t address long define pgm read word far address long ELPM word uint32 t address long define pgm_read_dword_far address_long ELPM dword uint32 t address long define read byte address short pgm read byte near address short define read word address short pgm read word near address short
211. cally if ASSEMBLER is defined By default all addresses are defined as if they were memory addresses used in lds sts 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 OFFSET definition is no longer necessary and can be removed Real example this code could be used in boot loader that is portable between devices with SPMCR at different addresses lt avr ioml63 h gt define SPMCR SFR 08 0 37 lt avr ioml28 h gt define SPMCR SFR MEM8 0x68 dif SFR IO REG P SPMCR out SFR IO ADDR SPMCR r24 felse sts _SFR_MEM_ADDR SPMCR r24 fendif You use the in out cbi sbi sbic sbis instructions without the SFR IO REG P test if you know that the register is in the I O space as with SREG for example If it isn t the assembler will complain I O address out of range 0 0x3f so this should be fairly safe If you do not define SFR OFFSET so it will be 0x20 by default all special register addresses are defined as memory addresses so SREG is Ox5f and if code size and speed are not important and you don
212. cept ATTR PURE PGM P strrchr P PGM Ps int val ATTR CONST char strsep P char sp 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 PGM P PURE 6 14 2 Define Documentation 6 14 2 1 define P const prog char Used to declare a variable that is a pointer to a string in program space 6 14 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 119 6 14 2 3 ftdefine pgm read byte far address long ELPM uint32 t address long Read a byte from the program space with a 32 bit far address Note The address is a byte address The address is in the program space 6 14 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 14 2 5 define pgm read dword address short pgm read dword near addres
213. ch ATtiny25 ATtiny85 COMPAREIB B OVF SIG Timer Counter 1 ATtiny24 ATtiny44 ATtiny84 ATtiny45 vect OVERFLOWI Overflow ATtiny25 ATtiny85 TIMERO SIG INPUT ADC Conversion ATtiny261 ATtiny461 ATtiny861 CAPT vect CAPTUREO Complete TIMERO SIG TimerCounterO ATmegal68 ATmega48 ATmega88 AT COMPA vect OUTPUT Compare Match mega640 ATmegal280 ATmegal281 COMPAREOA A ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtiny2313 ATtiny261 ATtiny461 AT tiny861 ATOOUSBI62 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 SIG Timer Counter 0 AT90PWM3 2 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 B tiny861 AT9OUSB162 9005 82 9005 1287 AT90USB 1286 9005 647 9005 646 Generated Tue 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 106 Vector name Old vector Description Applicable for device name TIMERO_ SIG_ Timer Counter0 AT90PWM3 AT90PWM2 AT90PWMI COMP A OUTPUT Compare Match vect COMPAREOA A SIG OUTPUT COMPAREO A TIMERO SIG Timer CounterO AT90CAN128 AT90CAN32 AT90CAN 64
214. cos double x _ ATTR_CONST double fabs double _ x _ ATTR_CONST double fmod double _ x double _ y ATTR CONST double modf double __ value double double sin double __x 5 double sqrt double _ x ATTR CONST double tan double x ATTR CONST double floor double __ x ATTR CONST double double x ATTR CONST double frexp double value int exp double Idexp double _ int exp CONST double exp double _ x ATTR CONST double cosh double x ATTR CONST double sinh double x ATTR CONST double tanh double x 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 ATTR CONST double log10 double x ATTR CONST double pow double x double ATTR CONST int isnan double x ATTR CONST int double _ x ATTR CONST double square double _ x ATTR CONST 6 5 2 Define Documentation 6 5 2 1 define 3 141592653589793238462643 The constant pi 6 5 2 2 define M_SQRT2 1 4142135623730950488016887 The square root of 2 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 5 lt math h gt Mathematics 31 6 5 3 Function Documentation 6 5 3 1 double acos double x The acos function computes the principal val
215. crocontroller peripheral devices In partic it starts timer 0 to generate the outgoing PWM signal OCOB Setting OCROA to 255 which is the TOP value of timer is used to generate a timer overflow A interrupt on the ATtiny13 This interrupt is used to inform the incoming PWM decoder that the counting direction of channel 0 is just changing from up to down Likewise an overflow interrupt will be generated whenever the countdown reached BOTTOM value 0 where the counter will again alter its counting direction to upwards This informa tion is needed in order to know whether the current counter value of TCNTO is to be evaluated from bottom or top Further ioinit activates the pin change interrupt PCINTO on any edge of PB4 Finally PB1 OCOB will be activated as an output pin and global interrupts are being enabled In 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 29 Combining and assembly so
216. cter in the Program Space Retrieving the strings 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 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 food void char buffer 10 for unsigned char 0 lt 5 i _ buffer read amp string_table i Display buffer LCD return Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 5 avr libc and assembler programs 264 Here the string table array is stored in Program Space so we access it normally as if were stored in Data Space then take the address of the location we want to access and use the address as a parameter to read word We use the read word macro to read the string pointer out of the string table array Remember that a pointer is 16 bits or word size This pointer is an address in Program Space of the string that we want to copy This pointer is used as a parameter to the function strcpy P The function st rcpy_P is just like the regular st rcpy function except that it copies a string from Program Space the second par
217. ctual files its origin as end of file is somewhat meaningless here 6 8 2 7 define 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 8 2 8 define get udata stream stream udata This macro retrieves a pointer to user defined data from a FILE stream object 6 8 2 9 define fdev set udata stream u do stream udata u while 0 This macro inserts a pointer to user defined data into a FILE stream object The user data can be useful for tracking state in the put and get functions supplied to the fdevopen function Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 8 lt stdio h gt Standard IO facilities 54 6 8 2 10 define FDEV SETUP STREAM put get rwflag Initializer for 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 8 2 11 define setup stream stream put get rwflag Setup a user supplied buffer as an stdio stream This macro takes a user supplied buffer st ream and sets it up as a stream that is valid for stdio operat
218. d by the initN and finiN sections dicussed below Note The avr size program part of binutils coming from 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 a horrible death struct point pt 1 1 It is possible to tell the linker the SRAM address of the beginning of the data section This is accomplished by adding Wl Tdata addr to the avr gcc command used to the link your program Not that addr must be offset by adding 0x800000 the to real SRAM address so that the linker knows that the address is in the SRAM memory space Thus if you want the data section to start at 0x1100 pass 0x801100 at the address to the linker offset explained Note When using malloc in the application which could even happen inside library calls additional adjustments are required Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 3 Memory Sections 256 9 3 3 5 Section Uninitialized global or static variables end the bss section 9 3 4 eepr
219. d on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 14 Acknowledements 333 9 Upload the tarball to savannah 10 Update the NEWS file and commit to cvs Add Changes since avr libc major minor lt patch gt 11 Generate the latest documentation and upload to savannah 12 Announce the release The following hypothetical diagram should help clarify version and branch relation ships HEAD 1 0 Branch 1 2 Branch cvs tag avr libc 1 0 branchpoint set version to 1 1 0 lt date gt cvs tag b avr libc 1 0 branch set version to 0 90 90 lt date gt 1 set version to 1 0 cvs tag avr libc 1_0 release set version to 1 0 0 lt date gt h set version to 1 0 1 5 tag M tag avr libc l 2 branchpoint i set version to 1 3 0 lt date gt duse hoc autc EE o panah set version to 1 1 90 lt date gt set version to 1 2 cvs tag avr libc 1 2 release cvs tag avr libc 2 0 branchpoint set version to 2 1 0 lt date gt 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 a terrific free set of tools to develop AVR Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 9 15 Todo List 334 projects We all owe thanks to The GCC Team which produced a very capable set of development tools for an amazing
220. d 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 Tue 15 14 56 11 2007 for avr libe by Doxygen 9 7 How to Build Library 283 references A reference is essentially a function call An undefined reference is a function call with no defined function to match the call The linker will then go through the libraries in order to match the undefined references with function definitions that are found in the libraries If 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
221. def uint8 t uint fast8 t typedef int16 t int fast16 t typedef uint16 t fastl6 t typedef int32 t int fast32 t typedef uint32 t fast32 t typedef int64 t int fast64 t typedef uint64 t fast64 t Greatest width integer 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 Defines define USING MINT8 0 define _ CONCATenate left right left right define CONCAT left right _ CONCATenate left right 8 36 stdio h File Reference 8 36 1 Detailed Description Defines define STDIO 1 define need NULL define need size t define FILE struct file define stdin _ 10b 0 define stdout __iob 1 define stderr __iob 2 define EOF 1 define fdev_set_udata stream u do stream udata u while 0 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 36 stdio h File Reference 229 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 stream fputc stream define putchar __c fputc c stdout define getc __stream fgetc __str
222. define boot page write address boot page write normal address define boot rww enable __boot_rww_enable define boot lock bits set lock bits boot lock bits set lock bits define boot page fill safe address data define boot page erase safe address define boot page write safe address define boot rww enable safe define boot lock bits set safe lock bits 6 11 2 Define Documentation 6 11 2 1 fdefine boot is spm interrupt SPM REG amp uint8 t BV SPMIE Check if the SPM interrupt is enabled 6 11 2 2 define boot lock bits set lock bits boot lock bits set lock bits Set the bootloader lock bits Parameters lock bits 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 11 lt avr boot h gt Bootloader Support Utilities 91 6 11 2 3 define boot lock bits set safe lock bits Value do N boot spm busy wait N eeprom busy wait boo
223. 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 Functions PGM VOID P memchr PGM VOID P s int val size t len ATTR CONST int memcmp P const void PGM VOID size_t PURE void memcpy P void VOID size_t void memmem P const void size t VOID P size_t ATTR PURE PGM VOID memrchr PGM VOID P s int val size t len ATTR CONST char strcat P char PGM P PGM P strchr P PGM Ps int val CONST PGM P strchrnul P Ps int val ATTR CONST int stremp P const char PGM P PURE char strepy P char PGM P int strcasecmp P const char PGM P ATTR PURE Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 31 pgmspace h File Reference 218 char strcasestr P const char PGM P PURE size_t strespn P const char s PGM P reject PURE si
224. dition on stream Most conversions skip leading white space before starting the actual conversion Conversions are introduced with the character Possible options can follow the x indicating that the conversion should be performed but the conversion result is to be discarded no parameters will be processed from ap the character h indicating that the argument is a pointer to short int rather than int 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 Matches an octal integer the next pointer must be a pointer to unsigned i
225. dog 142 WDTO 500MS avr watchdog 143 WDTO 60MS avr watchdog 143 WDTO 8S avr watchdog 143 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen
226. e 15 14 56 11 2007 for avr libe by Doxygen 9 5 avr libc and assembler programs 269 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 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 reti instruction By default jump to location 0 would be implied instead 9 5 4 Pseudo ops and operators The available pseudo ops in the assembler are described in the GNU assembler gas manual The manual can be found online as part of the current binutils release under http sources redhat com binutils As gas comes from a Unix origin its pseudo op and overall assembler syntax is slightly different than the one being used by other assemblers Numeric constants follow the C notation prefix 0x for hexadecimal constants expressions use C like syntax Some common pseudo ops include byte allocates single byte constants 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 constant
227. e 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 SREG VELL ld tmp reg al inc tmp reg st Sal tmp reg out SREG 0 amp r 8 an e ptr TINE TANGI Generated Tue 15 14 56 11 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 279 Now every thing seems correct but it isn t really The assembler code modifies the variable that pt x points to The compiler will not recognize this and may keep its value in any of the other registers Not only does the compiler work with the wrong value but the assembler code does too The program may have modified the value too but the compiler didn t update the memory location for optimization reasons worst thing you can do in this case is uint8 t s asm volatile in 0 __5 __ NANET cli NINE ld tmp reg al T NE inc tmp reg Tne st al __tmp_reg__ Tyne out SREG 0 MATINET amp 5 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 c
228. e line number information from the C source files a cdhlmns file Turn on the assembler listing The sub options are omit false conditionals domit debugging directives h include high level source 1 include assembly e m include macro expansions n omit forms processing s include symbols file set the name of the listing file The various sub options can be combined into a single a option list file must be the last one in that case Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 11 Using the GNU tools 326 9 11 2 2 Examples for assembler options passed through the compiler member that assembler options can be passed from the C compiler frontend using Wa see above so in order to include the C source code into the assembler listing in file foo 1st when compiling foo c the following compiler command line can be used 5 avr gcc c foo c o foo o Wa ahls foo lst In order to pass an assembler file through the C preprocessor first and have the assem bler generate line number debugging information for it the following command can be used avr gcc c x assembler with cpp o foo o foo S Wa gstabs Note that on Unix systems that have case distinguishing file systems specifying a file name with the suffix S upper case letter S will make the compiler automatically assume x assembler with cpp while using s would pass the file directly to the assemble
229. e main application it is declared volatile The variable pwm is not a variable in the classical C sense that could be used as Ivalue or within an expression to obtain its value Instead the attribute section eeprom marks it as belonging to the EEPROM section This section is merely used as a place holder so the compiler can arrange for each individual variable s location in EEPROM The compiler will also keep track of initial values assigned and usually the Makefile is arranged to extract these initial values into a separate load file Largedemo eeprom x in this case that can be used to initialize the EEPROM The actual EEPROM IO must be performed manually Similarly the variable mcucsr is kept in the noinit section in order to prevent it from being cleared upon application startup 6 31 3 3 Part 3 Interrupt service routines ISR to handle timer 175 overflow interrupt arranges for the software clock While timer 1 runs the PWM it calls its overflow handler rather frequently so the TMR1 SCALE value is used as a postscaler to reduce the internal software clock frequency further If the software clock triggers it sets the tmr int bitfield and defers all further tasks to the main loop The ADC ISR just fetches the value from the ADC conversion disables the ADC interrupt again and announces the presence of the new value in the adc int bitfield The interrupt is kept disabled while not needed because the
230. e return Vr horizontal tab 717 and vertical tab Cw 6 2 2 12 intisupper int Checks for an uppercase letter 6 2 2 13 intisxdigit int c Checks for a hexadecimal digits i e 0 12345678 9 6 2 2 14 int toascii int Converts c to a 7 bit unsigned char value that fits into the ASCII character set by clearing the high order bits Warning Many people will be unhappy if you use this function This function will convert accented letters into random characters 6 2 2 15 int tolower int Converts the letter c to lower case if possible 6 2 2 16 int toupper int Converts the letter c to upper case if possible Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 3 lt errno h gt System Errors 17 6 3 lt gt System Errors 6 3 1 Detailed Description include lt errno h gt Some functions in the library set the global variable errno when an error occurs The file lt errno h gt provides symbolic names for various error codes Warning The errno global variable is not safe to use in a threaded or multi task system A race condition can occur if a task is interrupted between the call which sets error and when the task examines errno If another task changes errno during this time the result will be incorrect for the interrupted task Defines define EDOM 33 define ERANGE 34 6 3 2 Define Documentation
231. e string 51 The terminating 0 characters not compared The strstr P function is similar to strstr except that s2 is pointer to a string in program space Returns The strstr P function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of zero length the function returns s1 6 15 lt avr power h gt Power Reduction Management finclude lt avr power h gt Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 15 lt avr power h gt Power Reduction Management 129 Many AVRs contain a Power Reduction Register PRR or Registers PRRx that allow you to reduce power consumption by disabling or enabling various on board peripher als as needed There are many macros in this header file that provide an easy interface to enable or disable on board peripherals to reduce power See the table below Note Not all AVR devices have a Power Reduction Register for example the AT megal28 On those devices without a Power Reduction Register these macros are not available Not all AVR devices contain the same peripherals for example the LCD inter face or they will be named differently for example USART and USARTO Please consult your device s datasheet or the header file to find out which macros are applicable to your device Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 15 lt avr power h gt Power Reduct
232. e used at all If fgets fails to read anything the main loop is left Of course normally the main loop of a microcontroller application is supposed to never finish but again for demon strational purposes this explains the error handling of stdio fgets will return NULL in case of an input error or end of file condition on input Both these condi tions are in the domain of the function that is used to establish the stream uart putchar in this case In short this function returns EOF in case of a serial line break condition extended start condition has been recognized on the serial line Common PC terminal programs allow to assert this condition as some kind of out of band signalling on an RS 232 connection When leaving the main loop a goodbye message is sent to standard error output i e to the LCD followed by three dots in one second spacing followed by 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 32 Using the standard IO facilities 188 The u
233. e x CONST double log double x ATTR CONST double log10 double x ATTR CONST double pow double x double y CONST int isnan double x ATTR CONST int double x ATTR CONST double square double x ATTR CONST 8 18 memccpy S File Reference 8 18 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 8 19 memchrS File Reference 8 19 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 20 memchr PS File Reference 214 8 20 memchr P S File Reference 8 20 1 Detailed Description 8 21 memcmp S File Reference 8 21 1 Detailed Description Defines define s1_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 22 memcmp P S File Reference 8 22 1 Detailed Description 8 22 memcpy S File Reference 8 23 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src r23 define src lo r22 define len hi r21 define len lo r20 8 24
234. eam 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 const char fmt int sprintf_P char s const char fmt intsnprintf char s size t fmt intsnprintf P char s size t n const char fmt int vsprintf char 5 const char fmt va list ap int vsprintf P char s const char fmt va list ap int vsnprintf 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 37 stdlib h File Reference 230 8 37 int fgetc FILE __stream int ungetc int c FILE stream char fgets char str int
235. ed before and finally writes the low part of the stack pointer At the first glance there s a race between restoring SREG and writing SPL However after enabling interrupts either explicitly by setting the I flag or by restoring it as part of the entire SREG the AVR hardware executes at least the next instruction still with interrupts disabled so the write to SPL is guaranteed to be executed with interrupts disabled still Thus the emitted sequence ensures interrupts will be disabled only for the minimum time required to guarantee the integrity of this operation 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 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
236. ed Description 8 14 ffsll S File Reference 8 14 1 Detailed Description 8 15 interrupt h File Reference 8 15 1 Detailed Description et 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 define SIGNAL vector define EMPTY INTERRUPT vector define ISR ALIAS vector target vector 8 16 inttypes h File Reference 8 16 1 Detailed Description 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 16 inttypes h File Reference 210 define PRIdLEASTS define PRIdFASTS d define PRIIS i define PRILEASTS 1 define PRUFASTS8 1 define PRId16 d define PRIGLEAST16 d define PRIdFAST16 d define PRI16 i define PRILEASTI6 i define PRHFAST16 1 define PRId32 Id define PRIGLEAST32 define PRIdFAST32 Id define 2 li define PRULEAST32 li define PRHFAST32 li define PRIdPTR PRId16 define PRUPTR PRII16 define PRIo8 o define PRIOLEASTS o define PRIOFASTS o define PRIu8 define PRIULEASTS define PRIUFASTS define PRIx8 x define PRIXLEASTS x define PRIXFASTS
237. ed on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 8 lt stdio h gt Standard IO facilities 59 6 8 3 22 int puts P const char str Variant of puts where str resides in program memory 6 8 3 23 int scanf const char fmt The function scanf performs formatted input from stream stdin See vfscanf for details 6 8 3 24 int scanf const char fmt Variant of scanf where fmt resides in program memory 6 8 3 25 int snprintf char s size t __n const char fmt Like sprintf but instead of assuming s to be of infinite size no more than n characters including the trailing NUL character will be converted to s Returns the number of characters that would have been written to s if there were enough space 6 8 3 26 int snprintf P char s size t mn const char fmt Variant of snprintf that uses a fmt string that resides in program memory 6 8 3 27 int sprintf char s const char Variant of printf that sends the formatted characters to string s 6 8 3 28 int sprintf P char _ 5 const char _ fit Variant of sprintf that uses fmt string that resides in program memory 6 8 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 8 3 30 int sscanf_P const char _ buf const char __ fmt
238. ed work is distributed under the terms of a permission notice identical to this one This document describes version 3 3 of the compiler There may be some parts which hadn t been completely understood by the author himself and not all samples had been tested so far Because the author is German and not familiar with the English language there are definitely some typos and syntax errors in the text As a programmer the author knows that a wrong documentation sometimes might be worse than none Any way he decided to offer his little knowledge to the public in the hope to get enough response to improve this document Feel free to contact the author via e mail For the latest release check http www ethernut de Herne 17th of May 2002 Harald Kipp harald kipp at egnite de Note As of 26th of July 2002 this document has been merged into the documentation for avr libc The latest version is now available at http savannah nongnu org projects avr libc 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 SFR IO ADDR PORTD Each asm statement is devided by colons into up to four parts 1 The assembler instructions defined as a single string constant 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
239. eep h gt 11 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 Modes Note Some of these modes are not available on all devices See the datasheet for target device for the available sleep modes Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 18 lt avr sleep h gt Power Management and Sleep Modes 137 define SLEEP MODE IDLE 0 define SLEEP MODE BV SMO define SLEEP MODE PWR DOWN _BV SM1 define SLEEP MODE PWR SAVE BV SMO BV SMI define SLEEP MODE STANDBY 5 1 BV SM2 define SLEEP MODE EXT STANDBY BV SMO BV SMI _ BV SM2 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 6 18 2 Define Documentation 6 18 2 1 define SLEEP MODE BV SM0 ADC Noise Reduction Mode 6 18 2 2 define SLEEP MODE EXT STANDBY _BV SM0 BV SM1 BV SM2 Extended Standby Mode 6 18 2 3 define SLEEP MODE IDLE 0 Idle
240. efine TW MT DATA 0x28 data transmitted ACK received Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 625 lt util twi h gt TWI bit mask definitions 152 6 25 2 9 define TW MT DATA 0x30 data transmitted NACK received 6 25 2 10 define TW MT SLA ACK 0x18 SLA W transmitted ACK received 6 25 2 11 TW MT SLA 0x20 SLA W transmitted NACK received 6 25 2 12 define TW NO INFO 0 8 no state information available 6 25 2 13 define TW READ 1 SLA R address 6 25 2 14 define TW REP START 0x10 repeated start condition transmitted 6 25 2 15 define TW SR LOST GCALL 0x78 arbitration lost in SLA RW general call received ACK returned 6 25 2 16 define TW SR LOST SLA 0x68 arbitration lost in SLA RW SLA W received ACK returned 6 25 2 17 define TW SR DATA 0x80 data received ACK returned 6 25 2 18 define TW SR DATA NACK 0x88 data received NACK returned 6 25 2 19 define TW SR GCALL 0x70 general call received ACK returned Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 625 lt util twi h gt TWI bit mask definitions 153 6 25 2 20 define TW SR GCALL DATA 0x90 general call data received ACK returned 6 25 2 21 define TW SR GCALL DATA NACK 0x98 general call data received NACK returned 6 25 2 22 TW SR SLA 0x60 SLA W received ACK returned 6 25
241. efine boot page erase normal address Value __asm__ __volatile__ movw r30 2 n t sts 0 1 n t spom n t SFR MEM ADDR SPM REG C uint8 t BOOT PAGE ERASE r uintl6 t address 230 cau 8 4 2 6 define boot page fill alternate address data Value asm volatile movw r0 3 n t movw r30 2 n t sts 0 HI1NANET spm n t word Oxffff n t nop n t Tolr in i SFR ADDR SPM REG uint8 t BOOT PAGE FILL uint16 t address uint16_t data yo r30 r31 p y 8 4 2 7 define boot page fill extended address data Value __asm__ __volatile__ movw r0 4 n t movw r30 A3 n t sts 1 SC3 n t PEPE EP LL POP AP LP PSP FS PP PN IE Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 4 boot h File Reference 203 sts 0 2 n t spom n t elr 1 non d yn y y Xm SFR MEM ADDR SPM REG SFR MEM ADDR RAMPZ2 uint8 t BOOT PAGE FILL uint32 t address uint16 t data 0 130 r31 8 4 2 8 define Value EE A EA PE a a A boot page fill normal address data asm volatile movw r0 3 n t movw r30 2 n t sts 0 1 n t som n t 1 rinit SFR_MEM_ADDR SPM REG uint8 t BO
242. efined before in cluding lt inttypes h gt define PRId8 d define PRIdLEASTS define PRIdFASTS d define PRIIS 1 define PRIILEASTS i define PRIIFASTS 1 define PRId16 d define PRIGLEAST16 d define PRIdFAST16 define PRIII6 i define PRILEASTI6 i define PRIiFAST 16 i define PRId32 Id define PRIGLEAST32 define PRIdFAST32 Id define PRIi32 li define PRULEAST32 li define PRHFAST32 li define PRIdPTR PRId16 define PRUPTR PRH16 define PRIo8 o define PRIOLEASTS define PRIOFASTS o define PRIu8 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 4 lt inttypes h gt Integer conversions 19 define PRIULEASTS define PRIUFASTS define PRIx8 x define PRIXLEASTS x define PRIXFASTS8 x define PRIX8 X define PRIXLEASTS X define PRIXFASTS X define PRIo16 o define PRIOLEAST16 define PRIOFAST16 define PRIu16 define PRIULEAST16 u define PRIUFAST16 u define PRIx16 x define PRIXLEAST16 x define PRIxFAST16 x define PRIX16 X define PRIXLEASTI6 X define PRIXFAST16 X define PRIo32 lo define PRIoLEAST32 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 def
243. efully 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 complete Unix like operating system which is free software the GNU system GNU is a recursive acronym for SGNU s Not Unix T it is pronounced guh noo approximately like canoe One of the main projects of the GNU system is the GNU Compiler Collection or GCC and its sister project GNU Binutils These two open source projects provide a foun dation for a software development toolchain Note that these projects were designed to originally run on Unix like systems 9 1 3 stands for GNU Compiler Collection is highly flexible compiler system It has different compiler front ends for different languages It has many back ends that generate assembly code for many different processors and host operating systems All share 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 c
244. ega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 ATtinyl3 ATtiny24 AT tiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 AT90USB162 9005 82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 PCINTI vect SIG PIN CHANGEI Pin Change Inter rupt Request 1 ATmegal62 ATmegal65 ATmegal65P ATmega169 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 megal280 ATmegal281 ATmega2560 AT mega2561 ATmega324P ATmegal 64P AT mega644P ATmega644 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 13 lt avr interrupt h gt Interrupts 104 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 CHANGE tin
245. ega323 AT TXC vect USART Complete mega8 TRANS SIG UART TRANS USART TX SIG USART Tx AT90PWM3 AT90PWM2 AT90PWMI vect USART Complete ATmega8535 ATmegal68 ATmega48 AT TRANS mega88 ATtiny2313 SIG UART TRANS USART SIG USART Data AT90PWM3 AT9OPWM2 AT90PWMI UDRE vect USART Register Empty ATmegal6 ATmega32 ATmega323 AT DATA SIG mega3250 ATmega3290 ATmega3290P UART DATA ATmega6450 ATmega6490 ATmega8 AT mega8535 ATmegal68 ATmega48 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 Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 13 lt avr interrupt h gt Interrupts 114 Vector name Old vector Description Applicable for device name USI STR SIG
246. en disconnected from the freelist and returned to the caller If no exact match could be found the closest match that would just satisfy the request will be used The chunk will normally be split up into one to be returned to the caller and another smaller one that will remain on the freelist In case this chunk was only up to two bytes larger than the request the request will simply be altered internally to also account for these additional bytes since no separate freelist entry could be split off in that case If nothing could be found on the freelist heap extension is attempted This is where malloc margin will be considered if the heap is operating below the stack or where malloc heap end will be verified otherwise If the remaining memory is insufficient to satisfy the request NULL will eventually be returned to the caller When calling free a new freelist entry will be prepared An attempt is then made to aggregate the new entry with possible adjacent entries yielding a single larger entry available for further allocations That way the potential for heap fragmentation is hopefully reduced 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 ta
247. enerated on Tue 15 14 56 11 2007 for avr libe by Doxygen INDEX 355 util twi 154 twi h 242 UINT16_C avr_stdint 42 UINT16_MAX avr_stdint 43 uint16 t avr stdint 46 UINT32 C avr stdint 43 UINT32 MAX avr stdint 43 uint32 t avr stdint 46 UINT64 C avr stdint 43 UINT64 MAX avr stdint 43 uint64 t avr stdint 46 UINT8 C avr stdint 43 UINTS MAX avr stdint 43 uint8 t avr stdint 46 uint farptr t avr inttypes 20 UINT FAST16 avr stdint 43 uint fastl6 t avr stdint 46 UINT FAST32 avr stdint 43 uint fast32 t avr stdint 46 UINT FAST64 MAX avr stdint 43 uint fast64 t avr stdint 46 UINT FAST8 MAX avr stdint 43 uint fast8 t avr stdint 47 UINT LEASTI6 MAX avr stdint 44 uint leastl6 t avr stdint 47 UINT LEAST32 MAX avr stdint 44 uint least32 t avr stdint 47 UINT LEAST64 avr stdint 44 uint least64 t avr stdint 47 UINT LEAST8 avr stdint 44 uint least8 t avr stdint 47 UINTMAX C avr stdint 44 UINTMAX MAX avr stdint 44 uintmax t avr stdint 47 UINTPTR MAX avr stdint 44 uintptr t avr stdint 47 ultoa avr stdlib 75 ungetc avr stdio 59 Using the standard IO facilities 184 util crc erc16 update 144 ccitt update 145 crc ibutton update 145 crc xmodem update 146 util delay delay ms 147 delay us 148 util delay basic delay loop 1 148 delay loop 2 148 util parity parity even bit 149 util twi TW
248. enerated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 31 Amore sophisticated project 178 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 Port Header Color Function Connect to DO 1 brown RxD RXD of the RS 232 header D1 2 grey TxD TXD of the RS 232 header D2 3 black button SWO pin I down switches header D3 4 red button up SWI pin 2 switches header D4 5 green button SW2 pin 3 ADC switches header D5 6 blue LED LEDO pin 1 LEDs header D6 7 green clock out LEDI pin 2 LEDs header D7 8 white 1 second LED2 pin 3 flash LEDs header GND 9 unused VCC 10 unused Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 31 Amore sophisticated project 179 Figure 3 Wiring of the STK500 The following picture shows the alternate wiring where LED1 is connected but SW2 is not 111099 l I Gh 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 31 Amore sophisticated project 180 port
249. enerated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 302 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 incorrect thing to do is this include lt avr pgmspace h gt PGM_P array 2 PROGMEM FOO Bar int main void char buf 32 strcpy P buf array 1 return 0 The result is not what you want though What you end up with is the array stored in ROM while the individual strings end up in RAM in the data section To work around this you need to do something like this finclude avr pgmspace h const char foo PROGMEM Foo const char bar PROGMEM Bar PGM P array 2 PROGMEM 00 bar int main void char buf 32 PGM_P p int memcpy P amp p amp array i sizeof PGM_P strcpy_P buf p return 0 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 9 Frequently Asked Questions 303 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 word 0
250. ent pinout than the industry standard com patible devices In order to fully utilize the large demo a female 10 pin header with cable connecting to a 10 kOhm potentiometer will be useful For the stdio demo an industry standard HD44780 compatible LCD display of at least 16x1 characters will be needed Among other things the LCD4Linux project page Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 29 Combining assembly source files 159 describes many things around these displays including common pinouts Modules Combining and assembly source files simple project more sophisticated project Using the standard IO facilities e Example using the two wire interface TWD 6 29 Combining C and assembly source files For time or space critical applications it can often be desirable to combine C code for easy maintenance and assembly code for maximal speed or minimal code size together This demo provides an example of how to do that The objective of the demo is to decode radio controlled model PWM signals and con trol an output PWM based on the current input signal s value The incoming PWM pulses follow a standard encoding scheme where a pulse width of 920 microseconds denotes one end of the scale represented as 0 pulse width on output and 2120 microseconds mark the other end 100 output PWM Normally multiple channels would be encoded that way in subsequent pulses
251. entation lt sa se sacs x w ew p 137 6 18 3 Function 138 6 19 lt avr version h gt avr libe version Macros 138 6 19 1 Detailed Description su 240 s aca s mmm BA es 138 5 15 2 Define Documentation s ss e scese niteni 139 6 20 lt avr wdt h gt Watchdog timer handling 140 6 20 1 Detailed Description soo RR xk 140 6202 Define Documentation p c sss aru o XU ke 141 6 21 lt util crcl6 h gt CRC Computations 143 621 1 Detaled Description se oe RE sa w sos q S 143 6212 Function Documentation 144 6 22 lt util delay h gt Convenience functions for busy wait delay loops 147 622 1 Detailed Description lt o cerea sety 147 6 22 2 Function 147 6 23 util delay basic h gt Basic busy wait delay loops 148 Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen CONTENTS iv 6 24 6 25 6 26 6 27 6 28 6 29 6 30 6 23 1 Detailed Description 148 623 2 Function Documentation gt s ss 85 o eae ters 148 lt util parity h gt Panty bit 149 6 24 1 Detailed Description 22 222 22 gt 149 6 24 2 Define Documentation 149 lt util twi h gt TWI bit mask definitions 150 52531 Detailed Description o o o es s s
252. ents 6 8 3 41 int vsprintf_P char _ 5 const char fmt va_list ap Variant of vsprintf that uses fmt string that resides in program memory 6 9 lt stdlib h gt General utilities 6 9 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 define RANDOM MAX 0x7 FFFFFFF char long int val char s int radix char utoa unsigned int val char __s int __radix char ultoa unsigned long int __val char __s int __radix long random void void srandom unsigned long __ seed long random_r unsigned long char itoa int __ val char __s int radix Conversion functions for double arguments Note that these functions are not located in the default library 1ibc a but in the mathematical library 1 ibm a So when linking the application the 1m option needs to be specified Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 9 lt stdlib h gt General utilities 67 define DTOSTR ALWAYS SIGN 0x01 define DTOSTR PLUS SIGN 0x02 define DTOSTR UPPERCASE 0x04 char dtostre double val char s unsigned char prec unsigned char flags char dtostrf double __ val char width char __ prec char 5 Defines define RAND MAX 0x7FFF T
253. es twitest twitest c where prefix isa configuration option For Unix systems it is usually set to either usror usr local Note 1 The header file lt util twi h gt contains some macro definitions for symbolic con stants used in the TWI status register These definitions match the names used in the Atmel datasheet except that all names have been prefixed with TW Note 2 The clock is used in timer calculations done by the compiler for the UART baud rate and the TWI clock rate Note 3 The address assigned for the 24Cxx EEPROM consists of 1010 in the upper four bits The following three bits are normally available as slave sub addresses allowing to operate more than one device of the same type on a single bus where the actual sub address used for each device is configured by hardware strapping However since the next data packet following the device selection only allows for 8 bits that are used as an EEPROM address devices that require more than 8 address bits 24C04 and above steal subaddress bits and use them for the EEPROM cell address bits 9 to 11 as re quired This example simply assumes all subaddress bits are 0 for the smaller devices so the EO E1 and E2 inputs of the 24Cxx must be grounded Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 33 Example using the two wire interface TWD 194 Note 4 For slow clocks enable the 2 x U SJART clock multiplier to improve the rate
254. escription Defines define str hi r25 define str lo r24 define num hi hi r25 define num hi lo r24 define num lo hi r23 define num lo lo r22 define tmp r17 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 4 boot h File Reference 199 8 4 8 4 1 boot h File Reference Detailed Description Defines define AVR BOOT H 1 define BOOTLOADER SECTION attribute section bootloader Zdefine COMMON ASB RWWSB Zdefine COMMON ASRE RWWSRE define BLB12 5 define BLB11 4 define BLB02 3 define BLB01 2 define boot spm interrupt enable __ _ uint8 t BV SPMIE define boot spm interrupt disable _5 amp uint8 0 BV SPMIE 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 amp uint8 t BV SPMEN define boot spm busy wait do while boot spm busy define PAGE ERASE _BV SPMEN BV PGERS define BOOT PAGE WRITE BV SPMEN BV PGWRT define BOOT PAGE FILL BV SPMEN define RWW ENABLE 5 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 define boot page erase normal address fdefine boot
255. est value a size t can hold 6 7 2 39 define UINT16 C value CONCAT value U define a constant of type uint16 t 6 7 2 40 define UINT16 MAX CONCAT INTI6 MAX U 20 1U largest value an uint16 t can hold 6 7 2 41 define UINT32 C value UL define a constant of type uint32 t 6 7 2 42 ftdefine UINT32 MAX CONCAT INT32 U 2UL 1UL largest value an uint32 t can hold 6 7 2 43 define UINT64 C value ULL define a constant of type uint64 t 6 7 2 44 ftdefine UINT64 MAX CONCAT INT64 U 2ULL 1ULL largest value an uint64 t can hold 6 7 2 45 define UINT8_C value uint8 t CONCAT value U define a constant of type uint8 t 6 7 2 46 define UINTS MAX CONCAT INTS8 MAX U 2U 10 largest value an uint8 t can hold Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 7 lt stdint h gt Standard Integer Types 44 6 7 2 47 define UINT FASTI6 MAX UINT16_MAX largest value an uint_fast16_t can hold 6 7 2 48 define UINT FAST32 MAX UINT32 largest value an uint_fast32_t can hold 6 7 2 49 define UINT FAST64 MAX UINT64 MAX largest value an uint fast64 t can hold 6 7 2 50 define UINT FAST8 MAX UINT8 MAX largest value an uint fast8 t can hold 6 7 2 51 define UINT LEASTI16 MAX UINTI6 largest value an uint least16 t can hold 6 7 2 52 define UINT LEAST32 MAX UINT32 largest val
256. eturns The _FFSQ macro returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 6 10 3 Function Documentation 6 10 3 1 int ffs int val const This function finds the first least significant bit set in the input value Returns The ffs function returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 Note For expressions that are constant at compile time consider using the FFS macro instead 6 10 3 2 int ffsl long const Same as ffs for an argument of type long 6 10 3 3 int ffsll long long const Same as ffs for an argument of type long long 6 10 3 4 void x memccpy void dest const void src int val size t len Copy memory area The memccpy function copies no more than len bytes from memory area src to mem 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 10 3 5 void memchr const void src int val size t len Scan memory for a character The memchr function scans the first len bytes of the memory area pointed to by src for the character val The first byte to match val interpreted as an unsigned character stops the operation Genera
257. ey are preferred over rolling your own typedefs Limits of specified width integer types C implementations should define these macros only when STDC LIMIT MACROS is defined before lt stdint h gt is included define INT8 MAX Ox7f define INT8 MIN 8 MAX 1 define UINT8 MAX CONCAT INT8 MAX U 2U 1U define INT16 MAX Ox7fff define INTI6 MIN 6 MAX 1 define UINT16 MAX CONCAT INT16 MAX U 2U 1U define INT32 MAX Ox7fffffffL define INT32 MIN INT32 MAX IL define UINT32 MAX CONCAT INT32 MAX U 2UL 100 define INT64 MAX 0x7ffffffffFfffffffLL define INT64 MIN INT64 MAX ILL define UINT64 MAX CONCAT INT64 MAX U x 2ULL 1ULL Limits of minimum width integer types define INT LEAST8 MAX 8 MAX fdefine INT LEAST8 MIN INT8 MIN define UINT LEAST8 MAX UINT8 MAX define INT LEASTI6 MAX INTI6 MAX define INT LEASTI6 MIN INT16 MIN define UINT LEASTI6 UINTI6 MAX define INT LEAST32 MAX INT32 MAX define INT LEAST32 MIN INT32 MIN define UINT LEAST32 MAX UINT32 MAX define INT LEAST64 INT64 MAX define INT LEAST64 MIN INT64 MIN define UINT LEAST64 MAX UINT64 MAX Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 7 lt stdint h gt Standard Integer Types 37 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_F
258. f 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 9 4 21 long random void The random function computes a sequence of pseudo random integers in the range of 0 to RANDOM 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 9 4 22 long random unsigned long c x 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 9 lt stdlib h gt General utilities 74 6 9 4 23 void realloc void size_t size The realloc function tries to change the size of the region allocated at pt r to the new size value It returns a pointer to the new region The returned pointer might be the same as the old pointer or a pointer to a completely different region The contents of the returned region up to either the old or the new size value whatever is less will be identical to the contents of the old region even in case a new region had to be allocated It is
259. ference 222222222222 2885554 234 5 53 1 Detailed Descriptio lt e so esre ee ee Rs 234 strleat S Pile Reference 2222 222 2 skr se S 236 8541 Detaled Description ee csse aep SUR GE 236 PS File Referent havs L u s a a Sk XS 236 8 55 1 Detaled Description lt s sos o RR RR RR 236 slep Pile Referente uuo dom ouo q 4 E ARR 236 8 56 1 Detailed Description 236 strlepy P S File Reference oc ciaccera tewi i emea 236 8 57 1 Detailed Description 2 229 RR 8 XA 236 sen S File Pene uy us Ee ee BE Eee SAGE wake S 236 5 58 1 Detailed Description lt s rcc 6654 022 RR 236 strlen PS File Referenc 2 h q s e k Q 236 8 59 1 Detaled Description 2 22222 2 2 2 2 236 File Reference 2 2 2 m m RR RR RT 237 8 60 1 Detailed Description 237 stmcasecmp o Pile Reference 2 22 2252 ems 237 8 61 1 Detaled Description sps ecic 583 5 9 2 sg gt 237 strncasecmp PS File Reference 237 62 1 Detailed Description 22 2 2 2 2 237 simcabs Pile Referente 222 2 o m 555558556 237 8 63 1 Detailed Description 237 strncat_PS File Reference 237 8 64 1 Detaled Description sss c oc ER 237 strnemp S Pile Referente 22222525 255 2525 Se WU Susu S 238 5 65 1 Detailed Description suo omm 55 238 strnemp PS File Referenc 238 8
260. fine DTOSTR ALWAYS SIGN 0x01 Bit value that be passed in flags to dtostre 6 9 2 2 define DTOSTR PLUS SIGN 0x02 Bit value that can be passed in flags to dtostre 6 9 2 3 define DTOSTR_UPPERCASE 0x04 Bit value that can be passed in flags to dtostre 6 9 2 4 define RAND MAX 0x7FFF Highest number that can be generated by rand 6 9 2 5 define RANDOM MAX 0x7FFFFFFF Highest number that can be generated by random 6 9 3 Typedef Documentation 6 9 31 typedef int compar fn t const void const void Comparision function type for qsort just for convenience 6 9 4 Function Documentation 6 9 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 9 4 2 int abs int 1 The abs function computes the absolute value of the integer i Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 9 lt stdlib h gt General utilities 69 Note The abs and labs functions are builtins of gcc 6 9 43 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 x NULL 6 9 4 4 int atoi const char x s Convert a string to an integer The atoi function converts the initial portion of the string pointed to by
261. fine 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 byte address The data is 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 11 2 8 define boot page fill safe address data Value do boot spm busy wait N eeprom busy wait X 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 11 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 11 lt avr boot h gt Bootloader Support Utilities 93 6 11 2 10 boot page write safe address Value do boot spm busy wait eeprom busy wait boot page write address X while 0 Same as boot page write except it waits for eeprom and spm operations to complete before writing the page 6 11 2 11 define boot rww busy SPM REG amp uint8 t BV _ C
262. for ATmega128 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 single one but obviously only for one compilation unit i single source file That way any string literal will be valid argument to any function that expects const char argument Of course this is going to waste lot of SRAM In Program Space String Utilities method is described how such constant data can be moved out to flash ROM How ever constant string located in flash ROM is no longer valid argument to pass to function that expects a const char type string since the AVR processor needs the special instruction LPM to access these strings Thus separate functions are needed Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently
263. 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 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 few sample programs available in the net Hopefully this document will help to increase their number It s assumed that you are familiar with writing AVR assembler programs because this is not an AVR assembler programming tutorial It s not C language tutorial either Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 9 6 Inline Assembler Cookbook 271 Note that this document does not cover file written completely in assembler language refer to avr libc and assembler programs for this Copyright C 2001 2002 by egnite Software GmbH Permission is granted to copy and distribute verbatim copies of this manual provided that the copyright notice and this permission notice are preserved on all copies Permis sion is granted to copy and distribute modified versions of this manual provided that the entire resulting deriv
264. g Com COMPARATORD parator 0 AT90PWM3 AT90PWM2 AT90PWM1 ANALOG COMP 1 vect SIG COMPARATOR Analog Com parator 1 AT90PWM3 AT90PWM2 ATOOPWM1 ANALOG COMP 2 vect SIG Analog Com COMPARATOR parator 2 AT90PWM3 AT90PWM2 ATOOPWM1 ANALOG vect SIG COMPARATOR Analog Com parator AT90CANI28 AT90CAN32 AT90CAN64 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 ATmegal64P ATmega644P AT mega644 AT90USB162 9005 82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 ANA COMP vect SIG COMPARATOR Analog Com parator 9051200 419052313 AT90S4414 419054433 AT90S8515 419058535 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 mega8515 ATmega8535 ATtinyll ATtiny12 ATtiny13 ATtiny15 ATtiny2313 ATtiny26 ATtiny28 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 79052333 AT9084434 CANIT vect SIG CAN INTERRUPTI CAN Transfer Complete or Error 90 128 AT90CAN32 AT90CAN64 Generated Tue 15 14 56 11 2007 for avr libc by Doxygen
265. g the EEPROM registers at different positions in memory space the eeprom functions evaluate _ REG LOCATIONS It is assumed to be Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 12 lt avr eeprom h gt handling 96 defined by the device io header contains 6 uppercase 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 IC1DIE 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 12 2 2 define _EEGET var addr var eeprom read byte uint8 t x addr Read a byte from EEPROM Compatibility define for IAR C 6 12 2 3 define EEPUT addr val eeprom write byte uint8 t addr uint8 t val Write a byte to EEPROM Compatibility define for IAR C 6 12 2 4 define EEMEM attribute section eeprom Attribute expression causing a variable to be allocated within the eeprom section 6 12 2 5 define eeprom busy wait do while eeprom is ready Loops until the eeprom is no longer busy Returns Nothing 6 12 2 6 define eeprom is ready Returns 1 if EEPROM is ready for a new read write operation 0 if not 6 12 3 Function Documentation 6 12 3 1 void eeprom read block void pointer ram const void
266. hanges will be done early enough in the startup sequence The variables malloc heap start and malloc heap end can be used to restrict the malloc function to a certain memory region These variables are stati cally initialized to point to__ heap start and heap end respectively where heap start is filled in by the linker to point just beyond bss and heap end is set to 0 which makes malloc assume the heap is below the stack If the heap is going to be moved to external RAM malloc heap end must be adjusted accordingly This can either be done at run time by writing directly to this variable or it can be done automatically at link time by adjusting the value of the symbol heap end The following example shows a linker command to relocate the entire data and bss segments and the heap to location 0x1100 in external RAM The heap will extend up to address Oxffff avr gcc Wl Tdata 0x801100 defsym J heap end 0x80ffff Note See explanation for offset 0x800000 See the chapter about using gcc for the W1 options 0x0100 Ox10FF 0x1100 OxFFFF on board RAM external RAM SP d 1 malloc heap heap end RAMEND __brkval __malloc_heap_start heap start im bss end data bss start data start Figure 7 Internal RAM stack only external RAM variables and heap If dynamic memory should be placed in external RAM while keeping the variables in Gene
267. har const char char strchr const char int ATTR PURE char strchrnul const char int ATTR PURE int strcmp const char const char ATTR PURE char strepy char const char int strcasecmp const char const char ATTR PURE char strcasestr const char const char x 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 1 int strncasecmp const char const char size t ATTR PURE size t strnlen const char size t ATTR PURE char strpbrk const char s const char __ _ char strrchr const char int ATTR 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 char const char char char strupr char Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 54 strlcat S File Reference 236 8 54 8 54 1 8 55 8 55 1 8 56 8 56 1 8 57 8 57 1 8 58
268. he gcc core lt version gt 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 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 newdevices 9 10 5 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 libc from cvs you will have to run the bootstrap script before using either of the build methods described below To build and install avr libc gunzip c avr libc version tar gz tar xf cd avr libc version configure prefix PREFIX build config guess host avr make make install X Xr XY 9 10 6 Avrdude Note It has been ported to windows via MinGW or cygwin Linux and Solaris Other Unix systems should be trivial to port to avrdude is part of the FreeBSD ports system To install it simply do the following cd usr ports devel avrdude make install Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 10 Installing the GNU Tool Chain 317
269. he 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 Tue 15 14 56 11 2007 for avr libe by Doxygen 9 4 Data in Program Space 262 byte 11131 then take the address of the data byte amp mydata il jl then use the appropriate pgm read macro and the address of your data becomes the parameter to that macro byte read byte amp mydata i j1 The read macros take an address that points to the Program Space and re trieves the data that is stored at that address This is why you take the address of the offset into the array This address becomes the parameter to the macro so it can gen erate the correct code to retrieve the data from the Program Space There are different read macros to read different sizes of data at the address given 9 4 4 Storing and Retrieving Strings in the Program Space Now that you can successfully store and retrieve simple data from Program Space you want to store and retrive strings from Program Space And specifically you want to store and array of strings to Program Space So you start off with your array like so char xstring table String Lr String 2 Totripg 3 String 4
270. il chunk is large enough to hold 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 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 large enough chunk on the freelist to satisfy the new request an attempt is made to quickly extend this topmost chunk and thus the heap so no need arises to copy over the existing data If there s no more space available in the heap same check is done as in malloc the entire request will fail Otherwise malloc will be called with the new request size the existing data will be Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 3 Memory Sections 255 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 The text Section The text section contains the actual machine instructions which make up your program This section is further subdivide
271. ile Reference 226 define INT FAST1I6 MAX INT16_MAX define INT FAST16 MIN INT16 MIN define UINT FASTI6 MAX UINTI6 MAX define INT FAST32 MAX INT32 MAX define INT FAST32 MIN INT32 MIN define UINT FAST32 MAX UINT32 MAX define INT FAST64 MAX INT64 define INT FAST64 MIN INT64 MIN define UINT FAST64 MAX UINT64 Limits of integer types capable of holding object pointers define INTPTR MAX INT16 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 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 e 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 8 t value Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 35 stdint h File Reference 227 define UINT8 C value u
272. in C code at all The flags variable needs to be in the range of r16 through r31 as it is the target of a load immediate or SER instruction that is not applicable to the entire register file 6 29 2 3 isrs S This file is a preprocessed assembly source file The C preprocessor will be run by the compiler front end first resolving all finclude define etc directives The resulting program text will then be passed on to the assembler As the C preprocessor strips all C style comments preprocessed assembly source files can have both C style as well as assembly style comments At the top the IO register definition file avr io h and the project declaration file project hare included The remainder of the file is conditionally assembled only if the target MCU type is an ATtiny 13 so it will be completely ignored for the ATtiny45 option Next are the two interrupt service routines for timer 0 compare A match timer 0 hits as OCROA is set to 255 and timer 0 overflow timer 0 hits BOTTOM 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 the
273. in driver circuitry so the wires must be terminated using appropriate pullup resistors The pullups must be small enough to recharge the line capacity in short enough time compared to the desired maximal clock fre quency yet large enough so all drivers will not be overloaded There are formulas in the datasheet that help selecting the pullups Devices can either act as master to the bus 1 e they initiate transfer or as slave they only act when being called by master The bus is multi master capable and 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 1 it determines whether the request to the slave is to read or write data during the next cycles There is also an option to have devices using 10 bit addresses but that is not covered by this example 6 33 2 The 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 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 ha
274. ine 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 SCNiFAST16 i define SCNd32 Id Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 4 lt inttypes h gt Integer conversions 20 define SCNdLEAST32 Id define SCNdFAST32 Id define SCNi32 li define SCNiLEAST32 li define SCNiFAST32 li define SCNdPTR SCNd16 define SCNiPTR SCNi16 define SCNo16 define SCNoLEASTI6 o define SCNoFASTI16 o define SCNul6 define SCNuLEASTI6 define SCNuFASTI6 u define SCNx16 x define SCNxLEASTI6 x define SCNxFAST16 x define SCNo32 lo define SCNoLEAST32 lo define SCNoFAST32 lo define SCNu32 lu define SCNuLEAST32 lu define SCNuFAST32 define SCNx32 Ix define SCNxLEAST32 Ix define SCNxFAST32 Ix define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR SCNx16 Far pointers for memory access gt 64K typedef int32_t int_farptr_t typedef uint32_t uint_farptr_t 6 4 2 Define Documentation 6 4 2 1 define PRId16 decimal printf format for int16 t 6 4 2 2 define PRId32 Id decimal printf format for int32 t Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 4 lt inttypes h gt Integer conversions 21 6 4 2 3 define PRId8 d deci
275. ing 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 An Wt N rjmp L N no outputs x N I SFR IO ADDR port I bit When used for the first time L may be translated to L 1404 the next usage might create 1405 or whatever In any case the labels became unique too Another option is to use Unix assembler style numeric labels They are explained in How do I trace an assembler file in avr gdb The above example would then look like define loop until bit is clear port bit asm volatile 1 sbic 0 1 n t ramp 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 your assembler code void delay uint8 t ms uintl6 t cnt asm volatile An L 11 n t mov A0 A2 n t mov BO B2 An L 12 n t sbiw A0 1 AnNt brne L dl2 Nnlt dec 1 n t brne L 11 Nnlt amp w cnt r ms r delay count Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 281 The purpose of this function is to delay the program execution by a specified number of milliseconds using
276. ing interrupts Normally the state of the status register SREG is saved in temporary register interrupts are disabled while changing the stack pointer and SREG is restored e mcall prologues Use subroutines for function prologue epilogue For complex functions that use many registers that needs to be saved restored on function entry exit this saves some space at the cost of a slightly increased execution time 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 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 On avr2 and avr4 architec tures less than 8 KB or flash memory this is always the case On avr3 and avr5 architectures calls and jumps to targets outside the current function will by default use jmp ca11 instructions that can cover the entire address range but that require more flash ROM and execution time
277. ing 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 11 Upload the snapshot tarball to savannah 12 Announce the branch and the branch tag to the avr libc dev list so other devel opers can checkout the branch Note CVS tags do not allow the use of periods C 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 1 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 2 Update the package version in configure ac and commit it to cvs 3 Update the gnu tool chain version requirements in the README and commit to CVS 4 Update the ChangeLog file to note the release and commit to on the branch Add Released avr libc lt this_release gt 5 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 lt this_relelase gt 6 Bring the build system up to date by running bootstrap and configure 7 Perform a make distcheck and make sure it succeeds This will create the source tarball 8 Tag the release cvs tag avr libc lt major gt _ lt minor gt _ lt patch gt release Generate
278. ing the case of the characters Returns The strcasecmp function returns an integer less than equal to or greater than zero if 51 is found respectively to be less than to match or be greater than 52 A consequence of the ordering used by strcasecmp is that if 51 is an initial substring of s2 then s1 is considered to be less than s2 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 10 lt string h gt Strings 82 6 10 3 13 char 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 10 3 14 char strcat char dest const char src Concatenate two strings The strcat function appends the src string to the dest string overwriting the 0 char acter at the end of dest and then adds a terminating 70 character The strings may not overlap and the dest string must have enough space for the result Returns The strcat function returns a pointer to the resulting string dest 6 10 3 15 char strchr const char src int val Locate character in string The strchr functi
279. input function available As the RS 232 input is line buffered in this example the macro BUFSIZE deter mines the size of that buffer 6 32 3 8 uart c This implements an stdio compatible RS 232 driver using AVR s standard UART or USART in asynchronous operation mode Both char acter output as well as character input operations are implemented Character output takes care of converting the internal newline Nn into its external representation carriage return line feed V r n Character input is organized as a line buffered operation that allows to minimally edit the current line until it is sent to the application when either a carriage return Nr or newline n character is received from the terminal The line editing functions implemented are Vb back space or N1 7 7 delete deletes the previous character u control U ASCII NAK deletes the entire input buffer w control W ASCII ETB deletes the previous input word delimited by white space Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 32 Using the standard IO facilities 191 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
280. 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 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 WATA t out 1 2 n t amp r input I SFR IO ADDR port r output this example input value is read from port then an output value is written to the same port If the compiler would have choosen the same register for input and out put then the output value would have been destroyed on the first assembler instruction Fortunately this example uses the 6 constraint modifier to instruct the compiler not to select any register for the output value which is used for any of the input operands Back to swapping Here is the code to swap high and low byte of a 16 bit value asm volatile mov tmp reg A0 n t mov A0 BO Inter mov B0 tmp reg n t r value 0 value First you will notice the usage of register tmp reg which we listed among other special registers in the Assembler Code section
281. int library routines linked into the application The functions available allow the specification of microsecond and millisecond delays directly using the application supplied macro F CPU as the CPU clock frequency in Hertz Functions void delay us double us void delay ms double ms 6 22 2 Function Documentation 6 22 2 1 void delay ms double ms Perform a delay of ms milliseconds using delay loop 20 Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 23 lt util delay_basic h gt Basic busy wait delay loops 148 The macro F_CPU is supposed to be defined to a constant defining the CPU clock frequency in Hertz The maximal possible delay is 262 14 ms F CPU in MHz 6 22 2 2 void _delay_us double us Perform a delay of us microseconds using delay loop 10 The macro F_CPU is supposed to be defined to a constant defining the CPU clock frequency in Hertz The maximal possible delay is 768 us F_CPU in MHz 6 23 lt util delay_basic h gt Basic busy wait delay loops 6 23 1 Detailed Description include lt util delay basic h The functions in this header file implement simple delay loops that perform a busy waiting They are typically used to facilitate short delays in the program execution They are implemented as count down loops with a well known CPU cycle count per loop iteration As such no other processing can occur simultaneously It should be kept in mind that the f
282. int h File Reference 225 8 35 stdint h File Reference 8 35 1 Detailed Description 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 8 MAX 1 define UINT8 __CONCAT INT8_MAX U 2U 1U define INT16 MAX Ox7fff define INT16 MIN INT16 MAX 1 define UINT16 MAX CONCAT INT16 MAX U 2U 1U define INT32 MAX Ox7fffffffL define INT32_MIN 32 MAX 1L define UINT32 2 U 2UL 1UL define INT64 MAX 0x7ffffffffFfffffffLL define INT64_MIN INT64 MAX ILL define UINT64 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 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 define INT LEAST64 INT64 MAX define INT LEAST64 MIN INT64 MIN define UINT LEAST64 MAX UINT64 Limits of fastest minimum width integer types define INT FAST8 MAX INT8 MAX define INT FAST8 MIN INT8 MIN define UINT FASTS MAX UINT8 MAX Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 35 stdint h F
283. int8 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 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 uint 16 t typedef signed long int int32 t typedef unsigned long int uint32 t typedef signed long long int int64 t typedef unsigned long long int uint64 t Integer types capable of holding object pointers These allow you to declare variables of the same size as a pointer typedef int16 t intptr t typedef uint16 t uintptr t Minimum width integer types Integer types having at least the specified width typedef int8 t int least8 t typedef uint8 t uint least8 t typedef int16 t int leastl6 t typedef uint16 tuint leastl6 t typedef int32 t int least32 t typedef uint32 t least32 t typedef int64 t int least64 t typedef uint64 t least64 t Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 36 stdio h File Reference 228 Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8 t int fast8 t type
284. ion void boot void attribute section bootloader To relocate the section to a fixed address the linker flag section start is used This option can be passed to the linker using the W1 compiler option Wl section start bootloader 0x1E000 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 306 The name after section start 15 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 ATmega128 keeps crashing Port F is completely broken Well certain odd problems arise out of the situation that the AVR devices as shipped by Atmel often come with a default fuse bit configuration that doesn t match the user s expectations Here is a list of things to care for All devices that have an internal RC oscillator ship with the fuse enabled that causes the device to run off this oscillator instead of an external crystal This often remains unnoticed until the first attempt is made to use something critical in timing like UART communication ATmegal28 ships with the fuse enabled that turns this device into AT mega103 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
285. ion Management 130 Power Macro Description Applicable for device power adc enable Enable the Analog to Digital Converter module ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB646 AT90USB647 9005 1286 AT90USB1287 AT90PWMI AT90PWNA2 AT90PWM3 ATmegal65 ATmegal65P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmega168 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 power adc disable Disable the Analog to Digital Converter module ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 9005 646 AT90USB647 9005 1286 AT90USB1287 AT90PWMI AT9OPWM2 AT90PWM3 ATmegal65 ATmegal65P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmega168 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 power led enable Enable the LCD module ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 power lcd disable Disable the LCD module ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 power pscO enable Enable the Power Stage Controller 0 module AT90PWMI AT9
286. ions 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 8 2 12 define FILE struct file FILE is the opaque structure that is passed around between the various standard IO functions 6 8 2 13 getc stream fgetc stream The macro get c used to be a fast macro implementation with a functionality iden tical to fgetc For space constraints in avr libc it is just an alias for fgetc 6 8 2 14 define getchar void fgetc stdin The macro get char reads a character from st din Return values and error handling is identical to fgetc 6 8 2 15 define putc c stream fputc c stream Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 68 lt stdio h gt Standard IO facilities 55 The macro putc 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 8 2 16 define putchar __c fputc
287. is in the program space 6 14 2 11 define PGM VOID P const prog void Used to declare a generic pointer to an object in program space 6 14 2 12 define PROGMEM ATTR PROGMEM Attribute to use in order to declare an object being located in flash ROM 6 14 2 13 define PSTR s const PROGMEM char 6 Used to declare a static pointer to a string in program space 6 14 3 Typedef Documentation 6 14 3 1 prog char Type of a char object located in flash ROM Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 121 6 14 3 2 prog intl6 t Type of an int16 t object located in flash ROM 6 14 3 3 prog int32 t Type of an int32 t object located in flash ROM 6 14 3 4 prog int64 t Type of an int64 t object located in flash ROM Note This type is not available when the compiler option mint8 is in effect 6 14 3 5 prog int8 t Type of an int8 t object located in flash ROM 6 14 3 6 prog uchar Type of an unsigned char object located in flash ROM 6 14 3 7 prog uintl6 t Type of an uint16 t object located in flash ROM 6 14 3 8 prog uint32 t Type of an uint32 t object located in flash ROM 6 14 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 14 3 10 prog uint8 t Type of an uint8 t object located in flash ROM Generated on
288. isters and names of the bits found in the AVR datasheet There may be some descrepencies between the register names found in the IO header files and the 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 you declare an ISR like so ISR PCINT1_vect Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 8 Porting From to AVR 287 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 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 to AVR 9 8 4 Intrinsic Routines has 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 AV
289. ity 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 Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 28 Demo projects 158 6 28 Demo projects 6 28 1 Detailed Description Various small demo projects are provided to illustrate several aspects of using the open source utilities for the AVR controller series It should be kept in mind that these de mos serve mainly educational purposes and are normally not directly suitable for use in any production environment Usually they have been kept as simple as sufficient to demonstrate one particular feature The simple project is somewhat like the Hello world application for microcon troller about the most simple project that can be done It is explained in good detail to allow the reader to understand the basic concepts behind using the tools on an AVR microcontroller The more sophisticated demo project builds on top of that simple project and adds some controls to it It touches a number of avr libc s basic concepts on its way comprehensive example on using the standard IO facilities intends to explain that complex topic using 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 T
290. l stack that is provided by the run time startup code This is probably a good idea anyway since internal RAM access is faster and even required for some early devices that had hardware bugs preventing them from using a stack in external RAM Note also that the heap for malloc will still be placed after all the variables in the data section so in this situation no stack heap collision can occur 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 12 Using the avrdude program 329 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
291. l AVR ARCH 1 AVR ASM ONLY AVR 2 BYTE PC 2 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 11 Using the GNU tools 319 Architecture Macros avr2 AVR ARCH 2 AVR 2 BYTE PC 2 avr25 1 AVR ARCH 25 AVR HAVE MOVW 1 AVR HAVE LPMX AVR 2 BYTE P avr3 AVR ARCH 3 AVR MEGA AVR 2 BYTE PC 2 avr4 AVR ARCH 4 AVR ENHANCED AVR HAVE MOVW 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 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 Architecture MCU name Macro 1 at90s1200 __AVR_AT90S1200__ avr 1 attiny 11 __AVR_ATtiny11__ attiny 12 __AVR_ATtiny12__ avri attiny15 AVR ATt nyl5 avri attiny28 AVR AT ny28 avr2 at90s2313 __AVR_AT908S2313__ avr2 at90s2323 __ _ 9052323__ avr2 at90s2
292. l 1 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 7 avr libc Data Structure Documentation 197 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 7 1 2 2 int div_t rem The Remainder The documentation for this struct was generated from the following file stdlib h 7 2 Idiv t Struct Reference 7 2 Detailed Description Result type for function Idiv Data Fields long quot long rem 7 2 2 Field Documentation 7 2 2 1 long Idiv_t quot The Quotient Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 avr libc File Documentation 198 7 2 2 1 long Idiv_t rem The Remainder The documentation for this struct was generated from the following file stdlib h S avr libc File Documentation 81 assert h File Reference 8 1 1 Detailed Description Defines define assert expression 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 D
293. l cleard and examining the BUSY flag within the status byte This function needs to be called before performing any controller IO Finally hd44780_init initializes the LCD controller into 4 bit mode based on the initialization sequence mandated by the datasheet As the BUSY flag cannot be examined yet at this point this is the only part of this code where timed delays are used While the controller can perform a power on reset when certain constraints on the power supply rise time are met always calling the software initialization routine at startup ensures the controller will be in a known state This function also puts the interface into 4 bit mode which would not be done automatically after a power on reset 6 32 3 5 Icd h This function declares the public interface of the higher level char acter IO LCD driver 6 32 3 6 Icd c The implementation of the higher level LCD driver This driver 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 pe
294. ld actually be the same register take care to not clobber it TCCRIB TIMER1_CLOCKSOURCE a6 8e b5 in r24 0 2 46 a8 81 60 ori r24 0x01 1 aa 8e bd out 0 2 r24 46 Run device dependent timer 1 setup hook if present if defined TIMER1 SETUP HOOK TIMER1 SETUP HOOK endif Set PWM value to 0 OCR 0 ac db out 0 2 r1 43 la bc out 0 2 r1 42 Enable as output DDROC BV OC1 b0 82 eO ldi r24 0x02 2 b2 87 bb out xl7 r24 3 23 Enable timer 1 overflow interrupt TIMSK TOIE1 b4 84 eO ldi r24 0x04 4 b6 89 bf out 0x39 r24 57 sei b8 78 94 sei ba 08 95 ret 000000bc main int main void so Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 171 b s 2 dt reall 28 Oxa2 lt ioinit gt ioinit loop forever the interrupts are doing the rest x for Note 7 x sleep mode be 85 b7 in 224 0x35 13 53 0 80 68 ori r24 0x80 128 c2 x 185 bf out 0x35 r24 53 c4 88 95 sleep GOS 285 457 in 124 0x35 4 53 c8 8f 77 andi r24 Ox7F 127 ca 85 bf out 0x35 r24 53 CEN E8 GB rjmp 16 Oxbe lt main 0x2 gt 6 30 5 Linker Map Files avr objdump is very useful but sometimes it s necessary to see information about the link that can only be generated by the linker map file contains this information m
295. linkonce d 0x00800060 ALIGN 0 2 0 00800060 edata 0 00800060 PROVIDE end bss 0x00800060 0x3 0x00800060 PROVIDE _ bss start bss bss 0x00800060 0x3 demo o bss 0x00800063 0 0 c winavr bin lib gcc avr 4 1 2 avr4Nlibgcc a copy data o bss 0x00800063 0 0 c winavr bin lib gcc avr 4 1 2 avr4Nlibgcc a clear bss o bssx COMMON 0x00800063 PROVIDE 55 end 0x000000ce data load start LOADADDR data 0x000000ce data load end data load start SIZEOF data noinit 0x00800063 0x0 0x00800063 PROVIDE noinit start noinitx 0x00800063 PROVIDE noinit end 0x00800063 end 0x00800063 PROVIDE start eeprom 0x00810000 0x0 0 00810000 eeprom 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 0 60 which is the first address after the register bank on an AT mega8 processor The next available address in the data segment is also location 0x 60 so the application has no initialized data Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 30 simple project 173 bss segment where uninitialized data is stored starts at location 0 60 The next available address in the bss segment is location 0x63 so the application uses 3 b
296. lled 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 function named vector default which should be defined with ISR as such include lt avr interrupt h gt ISR vector default user code here Nested interrupts The 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 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 inte
297. llocate to an enum type only as many bytes as it needs for the declared range of possible values Specifically the enum type will be equivalent to the smallest integer type which has enough room fpack struct Pack all structure members together without holes 9 11 2 Options for the assembler avr as 9 11 2 1 Machine specific assembler options e mmcu architecture mmcu MCU name avr as understands the same mmcu options as avr gcc By default avr2 is assumed but this can be altered by using the appropriate arch pseudo instruction inside the assembler source file Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 11 Using the GNU tools 325 e mall 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 warning when trying to skip 2 word instruction with CPSE SBIC SBIS SBRC SBRS instruction Early AVR devices suffered from hardware bug where these instructions could not be properly skipped mno wrap For RIMP RCALL instructions don t allow the target address to wrap around for de vices that have more than 8 KB of memory gstabs Generate stabs debugging symbols for assembler source lines This enables avr gdb to trace through assembler source files This option must not be used when assembling sources that have been generated by the C compiler these files already contain the appropriat
298. lop it Keep those bug reports coming 9 15 Todo List Group avr_boot From email with Marek On smaller devices all except AT mega64 128 SPM REG is in the I O space accessible with the shorter in and out instructions since the boot loader has a limited size this could be an important optimization Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 16 Deprecated List 335 9 16 Deprecated List Global SIGNAL Do not use SIGNAL O in new code Use ISR instead Global enable external int Global INTERRUPT Global timer enable int Global inp Global outp Global inb Global outb Global sbi Global cbi Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen Index PATH 312 PREFIX 312 prefix 312 lt assert h gt Diagnostics 13 lt avr boot h gt Bootloader Support Utili ties 88 lt avr eeprom h gt EEPROM handling 94 lt avr interrupt h gt Interrupts 97 lt avr pgmspace h gt Program Space Util ities 116 lt avr power h gt Power Reduction Man agement 128 lt avr sfr defs h gt Special function regis ters 133 lt avr sleep h gt Power Management and Sleep Modes 136 lt avr version h gt avr libe version macros 138 lt avr wdt h gt Watchdog timer handling 140 lt compat deprecated h gt Deprecated items 154 lt compat ina90 h gt Compatibility with EWB 3 x 157 lt ctype h gt Character Operations 14
299. m Read at most size 1 bytes from stream until 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 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 8 3 9 int fprintf FILE _ stream const char The function fprintf performs formatted output to stream See vfprintf for details 6 8 3 10 int fprintf P FILE stream const char fmt Variant of fprintf that uses a fmt string that resides in program memory 6 8 3 11 int fpute int _ c FILE stream The function fputc sends the character c though given as type int to stream It returns the character or EOF in case an error occurred 6 8 3 12 int fputs const char s r FILE stream Write the string pointed to by str to stream st ream Returns 0 on success and EOF on error 6 8 3 13 int fputs_P const char str FILE stream Variant of fputs where st r resides in program memory Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 8 lt stdio h gt Standard IO facilities 58 6 8 3 14 size_t fread void ptr size t size size_t nmemb FILE stream Read nmemb objects size bytes each from stream to the buffer pointed t
300. mal printf format for int8 t 6 4 2 4 define PRIdFASTI6 decimal printf format for int_fast16_t 6 4 2 5 define PRIdFAST32 Id decimal printf format for int_fast32_t 6 4 2 6 define PRIdFASTS decimal printf format for int fast8 t 6 4 2 7 define PRIGLEAST16 decimal printf format for int least16 t 6 4 2 8 define PRIGLEAST32 Id decimal printf format for int_least32_t 6 4 2 9 define PRIdLEASTS d decimal printf format for int_least8_t 6 4 2 10 define PRIdPTR PRId16 decimal printf format for intptr_t 6 4 2 11 ftdefine PRIi16 i integer printf format for int16 t 6 4 2 12 define PRIi32 li integer printf format for int32 t 6 4 2 13 define PRIiS i integer printf format for int8 t Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 4 lt inttypes h gt Integer conversions 22 6 4 2 14 define PRIiFAST16 i integer printf format for int_fast16_t 6 4 2 15 define PRIiFAST32 li integer printf format for int_fast32_t 6 4 2 16 define PRIiFASTS i integer printf format for int_fast8_t 6 4 2 17 define PRIILEAST16 i integer printf format for int_least16_t 6 4 2 18 define PRIILEAST32 li integer printf format for int least32 t 6 4 2 19 define PRIiLEASTS i integer printf format for int least8 t 6 4 2 20 define PRIiPTR PRIi16 integer printf format for intptr t 6 4 2 21 define PRIo16 octal printf format for ui
301. mega649 ATmega6490 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P ATmega644 USARTO SIG USARTO Data AT90CAN128 AT90CAN32 AT90CAN64 UDRE vect UARTO Register Empty ATmegal28 ATmegal62 ATmegal65 AT 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 vect USARTI Complete RECV USARTI SIG USARTI Rx AT90CANI28 AT90CAN32 AT90CAN64 RX vect UARTI Complete ATmegal28 ATmega64 ATmega640 RECV ATmega1 280 ATmegal 281 AT mega2560 ATmega2561 ATmega324P ATmegal64P ATmega644P AT mega644 AT90USB162 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 USARTI SIG_ USARTI Tx ATmegal62 TXC_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 ATmegal64P ATmega644P AT mega644 AT90USB162 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 USARTI SIG USARTI Data AT90CAN128 AT90CAN32 AT90CAN64 UDRE vect UARTI Register Empty ATmegal28 ATmegal62 ATmega64 DATA mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega6
302. mmand line options to the C compiler that should be passed as options during the linking stage The difference is that options are placed early on the command line while libraries are put at the end since they are to be used to resolve global symbols that are still unresolved at this point Specific linker flags can be passed from the C compiler command line using the W1 compiler option see above This option requires that there be no spaces in the appended linker option while some of the linker options above like Map or def sym would require 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 link map that contains cross reference list in the file foo map 5 avr gcc 0 o foo out Wl Map foo map Wl cref foo c Alternatively a comma as a placeholder will be replaced by a space before passing the option to the linker So for a device with external SRAM the following command line would cause the linker to place the data segment at address 0x2000 in the SRAM avr gcc mmcu atmegal28 o foo out Wl Tdata 0x802000 See the explanation of the data section for why 0x800000 needs to be added to the 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 symbo
303. mming ISP port C has the ports for JTAG can be used for debugging and port D is used for the UART connection Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 32 Using the standard IO facilities 186 6 32 2 Functional overview The project consists of the following files stdiodemo c This is the main example file defines h Contains some global defines like the LCD wiring hd44780 c Implementation of an HD44780 LCD display driver hd44780 h Interface declarations for the HD44780 driver 1cd c Implementation of LCD character IO on top of the HD44780 driver e 1cd h Interface declarations for the LCD driver uart c Implementation of a character IO driver for the internal UART uart h Interface declarations for the UART driver 6 32 3 A code walkthrough 6 32 3 1 stdiodemo c As usual include files go first While conventionally system header files those in angular brackets 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 mi
304. mp reg eeprom addresses in X and memory addresses in Z registers Method is optimized for code size Presently supported are two locations of the EEPROM register set Ox 1F 0x20 0x21 and 0x1C 0x1D 0x1E see _ EEPROM REG LOCATIONS _ As these functions modify IO registers they are known to be non reentrant If any of these functions are used from both standard and interrupt context the applica tions must ensure proper protection e g by disabling interrupts before accessing them libc declarations define EEMEM attribute section eeprom define eeprom is ready define eeprom busy wait do while 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 pointer eeprom size t n void eeprom write byte uint8 t addr uint8 t value void eeprom write word uint16 t addr uint16 t value void eeprom write block const void pointer ram void pointer eeprom size t n 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 addr Defines fidefine _ EEPROM REG LOCATIONS 1C1D1E 6 12 2 Define Documentation 6 12 21 define EEPROM REG LOCATIONS 1C1D1E In o rder to be able to work without a requiring a multilib approach for dealing with controllers havin
305. mrchr P 122 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 340 PGM P 118 read byte 118 read byte far 118 read byte near 119 pgm read dword 119 pgm read dword far 119 pgm read dword near 119 pgm read word 119 read word far 120 pgm read word near 120 PGM VOID P 120 prog char 120 prog int16 t 120 prog int32 t 121 prog int64 t 121 prog int8 t 121 prog uchar 121 prog uint16 t 121 prog uint32 t 121 prog uint64 t 121 prog uint8 t 121 prog void 121 PROGMEM 120 PSTR 120 strcasecmp P 123 strcasestr P 123 strcat P 123 strchr P 123 strchrnul P 124 strcmp P 124 strepy P 124 strcspn P 124 strlcat P 125 strlepy P 125 strlen P 125 strncasecmp P 125 strncat P 126 strnemp P 126 strncpy P 126 strnlen P 127 strpbrk P 127 strrchr P 127 strsep P 127 strspn P 128 strstr P 128 avr sfr _ 134 bit is clear 135 bit is set 135 loop until bit is clear 135 loop until bit is set 135 avr sleep set sleep mode 138 sleep cpu 138 sleep disable 138 sleep enable 138 sleep mode 138 SLEEP MODE 137 SLEEP MODE EXT STANDBY 137 SLEEP MODE IDLE 137 SLEEP MODE PWR DOWN 137 SLEEP MODE PWR SAVE 137 SLEEP MODE STANDBY 137 avr stdint 6 C 39 INT16 MAX 39 INT16 MIN 39 int16 t 44 INT32 C 39 INT32 MAX 39 INT32 MIN 39 int32 t 44 INT64 C 40
306. must be man ually cleared by setting the TWINT bit Unlike with many other interrupt sources this would even be required when using a true interrupt routine since as soon as TWINT is re asserted the next bus transaction will start Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 33 Example using the two wire interface TWD 195 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 master that has lost arbitration is required by the protocol to immediately cease talking on the bus in particular it must not initiate a stop condition in order to not corrupt the ongoing transfer from the active master In this example upon detecting lost arbitration condition the entire transfer is going to be restarted This will cause new start condition to be initiated which will normally be delayed until the currently active master has released the bus Note 10 Next the device slave is going to be reselected using so called repeated start con dition which is meant to guarantee that the bus arbitration will rem
307. n 2 s N 216 pemspace h File Relerenee o voe mm morem Reus 216 8311 Detaled Description esis 5 09 4kx9 216 8 31 2 Define Documentation 06 5 5 cmm o Rm Rs 218 powerh File Reference gc RE we WU Ua s 223 5321 Detaled Description c se csse s 845 S446 see ed 223 8 32 2 Define Documentation 223 setimp Ii File Reterence 2222 222 s waq w SS hope bk EGG 223 8 33 1 Detaled Description gt lt as cs s p eG 6x SO 223 sleep Pile Referenc o 222522525 ske SS S EA GAGE 224 8341 Detailed Description oso mk 224 stdint h Reference 2 2 2 224 225 8 23 1 Detaled Description s s scone mi YEAR 225 Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen CONTENTS viii 8 40 8 41 8 42 8 43 844 8 45 8 46 8 47 8 48 8 49 8 50 8 51 stdio h Pile Reference gt gt oct Rm REN BEER 228 5 90 1 Detailed Description xo rco m o 86 F9 XO EUR 228 stdhb h File Reference 22222222222 ea eip Re te S 230 8 37 1 Detailed Desenption gt se A Uw w wo s SG 230 streasecmp S File Referenc tey 232 6 38 1 Detailed Description 2 22 2222 2225222 232 strcasecmp P S File Reference 2 2 2299 2255 232 8 39 1 Detaled Description 232 streas stt S File Referenc o ccoo coc o RR RR a 232 8 40 1 Detailed Description 2 2 sirs 232 streat S File Reference a oom ee
308. n 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 0 on return the entire string was valid Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 9 lt stdlib h gt General utilities 76 The strtoul function return either the result of the conversion or if there was 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 9 4 29 char ultoa unsigned long int val char s int __radix Convert an unsigned long integer to a string The function ultoa converts the unsigned long integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing suf ficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof unsigned long int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2
309. n 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 EOF is returned if an input failure occurs
310. n 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 10 3 35 char strtok char string const char delim char 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 11 lt avr boot h gt Bootloader Support Utilities 88 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 10 3 36 char 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 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 11 lt avr boo
311. nced 221 memset LPM word classic 222 LPM word enhanced 222 memrchr P avr string 81 memset S 215 pow modf avr math 32 outb deprecated items 156 outp avr math 32 power h 223 clock prescale set PRId16 avr inttypes 20 PRId32 223 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen INDEX 349 avr_inttypes 20 PRId8 avr_inttypes 20 PRIdFAST 16 avr_inttypes 20 PRIdFAST32 avr_inttypes 20 PRIdFAST8 avr_inttypes 20 PRIdLEAST16 avr_inttypes 21 PRIdLEAST32 avr_inttypes 21 PRIdLEAST8 avr_inttypes 21 PRIdPTR avr_inttypes 21 PRIi16 avr inttypes 21 PRIi32 avr inttypes 21 PRIi8 avr_inttypes 21 PRIiFAST16 avr_inttypes 21 PRIiFAST32 avr inttypes 21 PRIiFASTS avr inttypes 21 PRIiLEASTI6 avr inttypes 21 PRIiLEAST32 avr inttypes 22 PRIiLEAST8 avr inttypes 22 PRIiPTR avr inttypes 22 printf avr stdio 58 printf P avr stdio 58 PRIo16 avr inttypes 22 PRIo32 avr inttypes 22 PRIo8 avr inttypes 22 PRIoFASTI6 avr inttypes 22 PRIoFAST32 avr inttypes 22 PRIoFASTS avr inttypes 22 PRIoLEASTI6 avr inttypes 22 PRIoLEAST32 avr inttypes 22 PRIoLEASTS avr inttypes 23 PRIoPTR avr inttypes 23 PRIu16 avr inttypes 23 PRIu32 avr inttypes 23 PRIu8 avr inttypes 23 PRIUFAST16 avr_inttypes 23 PRIuFAST32 avr inttypes 23 PRIuFASTS avr inttypes 23 PRIuLEASTI6 avr inttypes 23 PRIuLEAST32 av
312. nd 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 uintl6 t read timerl void uint8_t sreg uintl6 t val sreg SREG cli val TCNT1 SREG sreg return val Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 296 Back to FAQ Index 9 9 10 How do I use define d constant in an asm statement So you tried this asm volatile sbi 0 18 0 07 Which works When you do the same thing but replace the address of the port by its macro name like this asm volatile sbi PORTB 0x07 you get a compilation error Error constant value required PORTB is precompiler definition included in the processor specific file included in avr io h you may know the precompiler will not touch strings and PORTB instead of 0 18 gets passed to the assembler One way to avoid this problem is asm volatile sbi 0 0x07 SFR IO ADDR PORTB Note For C programs rather use the standard C bit operators instead so the above would be expressed as PORTB 1 lt lt 7 The optimizer will take care to trans form this into a single SBI instruc
313. nd when debugging because the inlining might cause the debug ger to jump around wildly at a first glance when single stepping The definitions of uart str and lcd str set up two stdio streams The initial ization is done using the FDEV SETUP STREAM initializer template macro so static object can be constructed that can be used for IO purposes This initializer macro takes three arguments two function macros to connect the corresponding output and input functions respectively the third one describes the intent of the stream read write or both Those functions that are not required by the specified intent like the input function for 1 str which is specified to only perform output operations can be given as NULL The stream uart str corresponds to input and output operations performed over the RS 232 connection to a terminal e g from to a PC running a terminal program while the 1 str stream provides a method to display character data 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 332 Using the standard IO facilities 187 which turn needs F_CPU macro order adjust the cycle counts the delay ms function has a limited range of allowable argument values depending on F CPU a value of
314. nded 203 boot page write normal 204 boot rww enable 204 boot rww enable alternate 204 boot is spm interrupt avr boot 90 boot lock bits set avr boot 90 boot lock bits set safe avr boot 90 boot lock fuse bits get avr boot 91 boot page erase avr boot 91 boot page erase safe avr boot 91 boot page fill avr boot 92 boot page fill safe avr boot 92 boot page write avr boot 92 boot page write safe avr boot 92 boot rww busy avr boot 93 boot rww enable avr boot 93 boot rww enable safe avr boot 93 boot spm busy avr boot 93 boot spm busy wait avr boot 93 boot spm interrupt disable avr boot 93 boot spm interrupt enable avr boot 93 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 344 BOOTLOADER_SECTION avr_boot 94 bsearch avr_stdlib 69 calloc avr_stdlib 69 cbi deprecated_items 155 ceil avr math 31 clearerr avr_stdio 55 cli avr_interrupts 114 clock_prescale_set power h 223 Combining C and assembly source files 159 Cos avr math 31 cosh avr math 31 crc16 h 205 ctype isalnum 14 isalpha 14 isascii 15 isblank 15 iscntrl 15 isdigit 15 isgraph 15 islower 15 isprint 15 ispunct 15 isspace 15 isupper 15 isxdigit 16 toascii 16 tolower 16 toupper 16 ctype h 205 delay h 206 delay_basic h 206 Demo projects 158 deprecated_items cbi 155 enable_external_int 155 inb 156 inp 156 INTERRU
315. nds 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 TWEA bit in TWCR when starting the current transfer Note 13 The control word sent out in order to initiate the transfer of the next data packet is initially set up to assert the TWEA bit During the last loop iteration TWEA is de asserted so the client will get informed that no further transfer is desired Note 14 Except in the case of lost arbitration all bus transactions must properly be terminated by the master initiating a stop condition Note 15 Writing to the EEPROM device is simpler than reading since only a master transmitter mode transfer is needed Note that the first packet after the SLA W selection is always considered to be the EEPROM address for the next operation This packet is exactly the same as 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 leve
316. nrtl Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 11 Using the GNU tools 323 Dump the internal compilation result called RTL into comments in the 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 9 11 1 2 Selected general compiler options The following general gcc options might be of some interest to AVR users On Optimization level n Increasing n is meant to optimize more an optimization level of 0 means no optimization at all which is the default if no O option is present The special option Os is meant to turn on all O2 optimizations that are not expected to increase code size Note that at 03 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
317. nt u Matches an optionally signed decimal integer the next pointer must be a pointer to unsigned int Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen lt stdio h gt Standard IO facilities 64 x Matches an optionally signed hexadecimal integer the next pointer must be a pointerto unsigned int f Matches an optionally signed floating point number the next pointer must be a pointer to float e g 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 first use an explicit space in the format Matches a nonempty sequence of characters from the specified set of accepted characters the next pointer must be a pointer to char and there must be enough room for all the characters in the string plus a terminating NUL character The usual skip of leading white space is suppressed The string is to be made up of characters in or not in a particular set the set is defined by the characters between the ope
318. nt 16 t 6 4 2 22 define PRIo32 lo octal printf format for uint32 t 6 4 2 23 define PRIo8 octal printf format for uint8 t 6 4 2 24 define PRIOFAST16 octal printf format for uint fast16 t Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 4 lt inttypes h gt Integer conversions 23 6 4 2 25 define PRIoFAST32 lo octal printf format for uint fast32 t 6 4 2 26 define PRIoFASTS o octal printf format for uint fast8 t 6 4 2 27 tdefine PRIOLEAST16 octal printf format for uint least16 t 6 4 2 28 define PRIOLEAST32 lo octal printf format for uint least32 t 6 4 2 29 define PRIOLEASTS o octal printf format for uint least8 t 6 4 2 30 define PRIOPTR PRIo16 octal printf format for uintptr_t 6 4 2 31 define PRIul6 decimal printf format for uint 16 t 6 4 2 32 define PRIu32 lu decimal printf format for uint32_t 6 4 2 33 define PRIu8 u decimal printf format for uint8_t 6 4 2 34 define PRIUFASTI6 decimal printf format for uint_fast16_t 6 4 2 35 define PRIUFAST32 decimal printf format for uint_fast32_t Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 4 lt inttypes h gt Integer conversions 24 6 4 2 36 define PRIUFASTS decimal printf format for uint_fast8_t 6 4 2 37 define PRIULEAST16 decimal printf format for uint_least16_t 6 4 2 38 define PRIULEAST32 l
319. nt is assigned to st din and the first one opened with write intent is assigned to both stdout and stderr fdevopen uses calloc und thus malloc in order to allocate the storage for the new stream Note If the macro __ STDIO_FDEVOPEN_COMPAT_12 is declared before including lt stdio h gt a 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 8 3 4 intfeof FILE stream Test the end of file flag of st ream This flag can only be cleared by a call to clearerr 6 8 3 5 int ferror FILE stream Test the error flag of st ream This flag can only be cleared by a call to clearerr Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 8 lt stdio h gt Standard IO facilities 57 6 8 3 6 int fflush FILE stream Flush stream This is null operation provided for source code compatibility only as the standard IO implementation currently does not perform any buffering 6 8 3 7 int fgetc FILE 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 8 3 8 char fgets char x str int size FILE strea
320. nt 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 5 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 174 which will be caught there and makes it print a message about the empty file not being generated 6 30 7 Letting Make Build the Project Rather than type these commands over and over they can all be placed in make file To build the demo project using make save the following in a file called Makefile Note This Makefile can only be used as input for the GNU version of make PRG demo OBJ demo o 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 atmegal65 MCU_TARGET atmegal65p
321. nts so the actual program itself can operate on a common set of symbolic names The macros defined by that file are OCR the name of the OCR register used to control the PWM usually either or OCR1A Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 164 DDROC the name of the DDR data direction register for the OC output the pin number of the 1 output within its port the TOP value of the timer used for the PWM 1023 for 10 bit PWMs 255 for devices that can only handle an 8 bit PWM TIMI 1 INIT the initialization bits to be set into control register in order to setup 10 bit or 8 bit phase and frequency correct PWM mode CLOCKSOURCE the clock bits to set in the respective control regis ter to start the PWM timer usually the timer runs at full CPU clock for 10 bit PWMs while it runs on a prescaled clock for 8 bit PWMs Note 2 ISRO is macro that marks the function as an interrupt routine In this case the function will get called when timer I overflows Setting up interrupts is explained in greater detail in lt avr interrupt h gt Interrupts Note 3 The PWM is being used 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 we are Outsid where the
322. number of platforms and processors Denis Chertykov denisc overta ru for making the AVR specific changes to the GNU tools Denis Chertykov and Marek Michalkiewicz marekm linux org pl for devel oping the standard libraries and startup code for AVR GCC Uros Platise for developing the AVR programmer tool uisp Joerg Wunsch joerg amp FreeBSD ORG for adding all the AVR development tools to the FreeBSD http www freebsd org ports tree and for providing the basics for the demo project Brian Dean bsd bsdhome com for developing avrdude an alternative to uisp and for contributing documentation which describes how to use it Avr dude was previously called avrprog Weddington eric Gevcohs com for maintaining the WinAVR package and thus making the continued improvements to the Opensource AVR toolchain available to many users Rich Neswold for writing the original avr tools document which he graciously allowed to be merged into this document and his improvements to the demo project Theodore Roth for having been long time maintainer of many of the tools AVR Libc the AVR port of GDB AVaRICE 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 deve
323. o by ptr Returns the number of objects successfully read i 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 8 3 15 int fscanf FILE _ stream const char fmt The function fscanf performs formatted input reading the input data from stream See vfscanf for details 6 8 3 16 int fscanf P FILE _ stream const char fmt Variant of fscanf using a fmt string in program memory 6 8 3 17 size_t fwrite const void pir size t size size t nmemb FILE x stream Write nmemb objects size bytes each to stream The first byte of the first object is referenced by pt r Returns the number of objects successfully written i e nmemb unless an output error occured 6 8 3 18 char gets char str Similar to fgets except that it will operate on stream st din and the trailing newline Gf any will not be stored in the string It is the caller s responsibility to provide enough storage to hold the characters read 6 8 3 19 int printf const char fmt The function printf performs formatted output to stream stderr See vfprintf for details 6 8 3 20 int printf const char fmt Variant of printf that uses a fmt string that resides in program memory 6 8 3 21 int puts const char str Write the string pointed to by str and a trailing newline character to stdout Generat
324. o 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 C compiler g through a char variable initialized directly to particular address it would be sufficient to defer the initializa tion of the external RAM interface to the beginning of main so no tweaking of the init3 section is necessary The same applies if only the heap is going to be located there since the application start up code does not affect the heap It is not recommended to locate the stack in external RAM In general accessing exter nal RAM is slower than internal RAM and errata of some AVR devices even prevent this configuration from working properly at all Back to FAQ Index 9 9 17 Which O flag to use There s acommon misconception that larger numbers behind the O option might auto matically cause better optimization First there s no universal definition for better Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 9 Frequently Asked Questions 305 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 ATmega128 to judge the effect of compiling the library itself using differen
325. o 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 char width char __prec char __s Defines define STDLIB H 1 define need NULL define need size t define need wchar t define _ ptr t void fidefine RAND MAX Ox7FFF Typedefs typedef int compar fn t const void const void Functions e inline void abort void NORETURN int abs int i 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 _ divmodhi4 ATTR CONST e div t ldiv dong __num long denom asm divmodsi4 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 endptr int base long atol const char xs PURE Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 38 strcasecmp S File Reference 232 int atoi const char xs ATTR PURE void exit int status ATTR NORETURN void mall
326. oc size_t size ATTR 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 unsigned long ctx Variables size t malloc margin char _ malloc heap start char heap end 8 38 strcasecmp S File Reference 8 38 1 Detailed Description 8 39 strcasecmp P S File Reference 8 39 1 Detailed Description 8 40 strcasestr S File Reference 8 40 1 Detailed Description 8 41 strcat S File Reference 8 41 1 Detailed Description Defines define dest hi r25 define dest lo r24 define src hi r23 define src lo r22 Generat ed on Tue 15 14 56 11 2007 for avr libe by Doxygen 8 42 strcat_P S File Reference 233 8 42 strcat_P S File Reference 8 42 1 Detailed Description Defines define dest hi r25 define dest lo 24 define src r23 define src lo r22 8 43 strchr S File Reference 8 43 1 Detailed Description 8 44 strchr P S File Reference 8 44 1 Detailed Description 8 45 strchrnul S File Reference 8 45 1 Detailed Description 8 46 strchrnul P S File Reference 8 46 1 Detailed Description 8 47 strcmp S File Reference 8 47 1 Detailed Description 8 48 strcmp P S File Reference 8 48 1 Detailed Description 8 49 strcpy
327. om Section This is where eeprom variables are stored 9 3 5 The noinit Section This sections is 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 Wl section start noinit 0x802000 to the avr gcc command line at the linking stage For example suppose you wish to place the noinit section at SRAM address 0x2000 Wl section start noinit 0x802000 Note Because of the Harvard architecture of the AVR devices you must manually add 0x800000 to the address you pass to the linker as the start of the section Oth erwise the linker thinks you want to put the noinit section into the text section instead of data bss and will complain Alternatively you can write your own linker script to automate this FIXME need an example or ref to dox for writing linker scripts 9 3 6 initN Sections These sections used to define the startup code from reset up through the start of main These all are subparts of the text section The purpo
328. ompiler runs on Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 91 Toolchain Overview 246 target system 15 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 is built to execute on host system such as FreeBSD Linux or Windows and it is built to generate code for the AVR microcontroller target then it is a cross compiler and this version of GCC is commonly known as AVR GCC In documentation or discussion AVR GCC is used when referring to GCC targeting specifically the AVR or something that is AVR specific about GCC The term GCC is usually used to refer to something generic about GCC or about GCC as a whole GCC is different from most other compilers GCC focuses on translating a high level language to the target assembly only AVR GCC has three available compilers for the AVR C language C and Ada The compiler itself does not assemble or link the final code GCC is also known as a driver program in that it knows about and drives other programs seamlessly to create the final output The assembler
329. on 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 OxAA 170 10c 88 b3 in r24 0x18 24 10e 0e 94 65 00 call So the function once called only sees 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 0 55 112 65 e5 141 r22 0x55 85 114 88 e3 141 r24 0 38 56 116 90 eO 141 r25 0 00 2 0 118 0e 94 7c 00 11 Oxf8 You can clearly see that 0x0038 is correctly passed for the address of the io port Looking at the disassembled object code for the body of the function we can see that the function is indeed performing the operation we intended void Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 300 set bits func correct volatile uint8_t port uint8_t mask 8 fc 01 movw r30 r2
330. on e g under usr local avr lib ldscripts on Unix systems and consist of the AVR architecture name avr2 through avr5 with the suffix x appended They describe how the various memory sections will be linked together 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 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 1ibm 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 12 Using the avrdude program 328 when linking the final binary In contrast the macro LDFLAGS is used to store other co
331. on call But with ISRs there is no function call to initiate the ISR The ISR is placed in the Interrupt Vector Table 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 7 How to Build a Library 284 The job of the librarian program is simple aggregate a list of object modules into a single library archive and create an index for the linker to use The name that you create for the library filename must follow a specific pattern lib lt name gt a The lt name gt part 15 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 have a file extension of a for archive The reason for the special form of the filename is for how the library gets used by the toolchain as we
332. on 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 254 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 separate data structure but rather by modifying the contents of the freed memory to contain pointers chaining the pieces together That way no additional memory is reqired to maintain this list except for variable that keeps track of the lowest memory segment available for reallocation Since both 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 chunk available on the freelist that will fit the request exactly it will be tak
333. on 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 10 3 16 char 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 st strlen s if the character is not found Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 10 lt string h gt Strings 83 6 10 3 17 stremp const char 81 const char s2 Compare two strings The stremp function compares the two strings 51 and 52 Returns The strcmp function returns an integer less than equal to or greater than zero if 51 is found respectively to be less than to match or be greater than 52 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 10 3 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
334. on 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 10 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 10 3 30 char strrchr const char 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 10 3 31 char strrev char s Reverse a string The strrev function reverses the order of the string Returns The strrev function returns a pointer to the beginning of the reversed string
335. 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 20 2 6 define WDTO 1S 6 See WDTO 15MS 6 20 2 7 define WDTO 250MS 4 See WDTO 15MS 6 20 2 8 define WDTO 287 See WDTO 15MS 6 20 2 9 define WDTO 30MS 1 See WDTO 15MS 6 20 2 10 define WDTO 458 See WDTO 15MS Note This is only available on the ATtiny2313 ATtiny24 AT tiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 621 lt util erc16 h gt CRC Computations 143 ATmega48 ATmega88 ATmegal68 ATmega164P ATmega324P ATmega644P AT mega644 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 mega8HVA ATmegal6HVA ATmega406 AT90PWM1 AT90PWM2 AT90PWM3 AT90USB82 AT90USB162 AT90USB646 AT90USB647 AT90USB1286 9005 1287 6 20 2 11 define WDTO 500MS 5 See WDTO 15MS 6 20 2 12 define WDTO 60MS 2 WDTO 15MS 6 20 2 13 define WDTO 859 See WDTO 15MS Note This is only available on the ATtiny2313 ATtiny24 AT tiny44 ATtiny84 ATtiny25 45 ATtiny85 ATtiny261 461 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmegal64P ATmega324P
336. only used on a PC environment have limitations or additional issues that a user needs to be aware of when used on an embedded system AV R Libc also contains the most documentation about the whole AVR toolchain 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 for your application See the GNU Make User Manual for more information 9 17 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 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 GN
337. otes 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 PREFIX make make install X Xr X dX X 89 Note AVaRice uses the bfd library for accessing various binary file formats You may need to tell the configure script where to find the lib and headers for the link to work This is usually done by invoking the configure script like this Replace hdr path with the path to the bfd h file on your system Replace lt 1ib path with the path to 1ibbfd a on your system CPPFLAGS I hdr path LDFLAGS L lib path configure prefix PREFIX 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 following machine specific options are recognized by the C compiler frontend mmcu architecture Compile code for architecture Currently known architectures are Architecture Macros avr
338. ou know how to use cvs and how to checkout multiple source trees in a single directory without having them clobber each other If you don t know how to do this you probably shouldn t be making releases or cutting branches 9 13 2 1 Creating a cvs branch The following steps should be taken to cut a branch 1 Check out a fresh source tree from cvs HEAD 2 Update the NEWS file with pending release number and commit to cvs HEAD Change Changes since avr libc lt last_release gt to Changes avr libc lt this relelase gt 3 Set the branch point tag setting lt major gt and lt minor gt accordingly cvs tag avr libc lt major gt _ lt minor gt branchpoint 4 Create the branch cvs tag b avr libc lt major gt _ lt minor gt branch 5 Update the package version in configure ac and commit configure ac to cvs HEAD Change minor number to next odd value 6 Update the NEWS file and commit to cvs HEAD Add Changes since avr libc this release gt Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 9 13 Release Numbering and Methodology 332 10 Check out a new tree for the branch cvs co r avr libe lt major gt lt minor gt 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 branch leading up to release Be sure to leave the lt date gt part of the version Br
339. outines If c is not an unsigned char value or EOF the behaviour of these functions is undefined int toascii int CONST int tolower int CONST int toupper int ATTR CONST 6 2 2 Function Documentation 6 2 2 1 int isalnum int c Checks for an alphanumeric character It is equivalent to isalpha c isdigit c 6 2 2 2 int isalpha int Checks for an alphabetic character It is equivalent to isupper c islower c 6 2 2 3 int isascii int Checks whether c is a 7 bit unsigned char value that fits into the ASCII character set 6 2 2 4 int isblank int c Checks for a blank character that is a space or a tab 6 2 2 5 int iscntr int _ c Checks for a control character 6 2 2 6 int isdigit int Checks for a digit 0 through 9 6 2 2 7 int isgraph int Checks for any printable character except space 6 2 2 8 int islower int Checks for a lower case character Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 2 lt gt Character Operations 16 6 2 2 0 int isprint int Checks for printable character including space 6 2 2 10 intispunct int c Checks for any printable character which is not a space or an alphanumeric character 6 2 2 11 intisspace int Checks for white space characters For the avr libc library these are space form feed newline n carriag
340. ove the readability By default the compiler would allocate 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 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 example of such code path would be the string IO functions for an overly large string to print about 2000 characters at 9600 Bd they might block for too long The loop itself then acts on the interrupt indication bitfields as appropriate and will eventually put the CPU on sleep at its end to conserve power The first interrupt bit that is handled is the software timer at a frequency of approx imately 100 Hz The CLOCKOUT pin will be toggled here so 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 follo
341. owing license conditions are met Portions of avr libc are Copyright c 1999 2007 Keith Gudger Bjoern Haase Steinar Haugen Peter Jansen Reinhard Jessich Magnus Johansson Artur Lipowski Marek Michalkiewicz Colin O Flynn Bob Paddock Reiner Patommel Michael Rickman Theodore A Roth Juergen Schilling Philip Soeberg Anatoly Sokolov Nils Kristian Strom Michael Stumpf Stefan Swanepoel Eric B Weddington Joerg Wunsch Dmitry Xmelkov The Regents of the University of California All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution Neither the name of the copyright holders nor the names of Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 2 avr libc Module Index contributors may be used to endorse or promote products derived from this software without specific prior written permission HIS SOFTWARE ND ANY EXPRESS OR IMPLIED WARRANTIES DISCLAIMED IABLE FOR DIRECT ONSEQUENTIAL DAMAGES UBSTITUTE GOODS OR SERVICES N
342. p 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 c binutils lt version gt tar bz2 tar xf cd binutils lt version gt Note Replace lt version gt with the version of the package you downloaded If you obtained a gzip compressed file gz use gunzip instead of bunzip2 It is usually a good idea to configure and build binutils in a subdirectory so as not to pollute the source with the compiled files This is recommended by the binutils developers 5 mkdir obj avr 5 obj avr The next step is to configure and build the tools This is done by supplying arguments to the configure script that enable the AVR specific options configure prefix SPREFIX target avr disable nls Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 10 Installing the GNU Tool Chain 315 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 location that is easily removed When configure is run it generates 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
343. 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 0 0000 define LOCK BITS 0x0001 define GET EXTENDED FUSE BITS 0x0002 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 4 boot h File Reference 200 define GET HIGH FUSE BITS 0 0003 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 4 2 Define Documentation 8 4 2 1 define boot lock bits set lock bits Value uint8_t value uint8_t lock_bits __asm__ __volatile__ idi 30 T n t vidi r3l O n t mov r0 2 n t sts 0 1 n t spom n t i SFR MEM ADDR SPM REG r int8 t BOOT LOCK BITS SET r value 730 731 8 4 2 2 define boot lock bits set alternate lock bits Value
344. pdf lt png fig FIG2DEV L png lt 6 30 8 Reference to the source code The source code is installed under Sprefix share doc avr libc examples demo where prefix is a configuration option For Unix systems it is usually set to either usr usr local Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 31 Amore sophisticated project 177 6 31 more sophisticated project This project extends the basic idea of the simple project to control LED witha PWM output but adds methods to adjust the LED brightness It employs a lot of the basic concepts of avr libc to achieve that goal Understanding this project assumes the simple project has been understood in full as well as being acquainted with the basic hardware concepts of an AVR microcontroller 6 31 1 Hardware setup The demo is set up in a way so it can be run on the ATmegal6 that ships with the STK500 development kit The only external part needed is a potentiometer attached to the ADC It is connected to a 10 pin ribbon cable for port A both ends of the poten tiometer to pins 9 GND and 10 VCC and the wiper to pin 1 port A bypass capacitor from pin 1 to pin 9 like 47 nF is recommendable m 1 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 G
345. pective bit is set while global interrupts are enabled Thus it is essential to have the bit cleared before interrupts get re enabled again which usually happens when returning from an interrupt handler Only few subsystems require an explicit action to clear the interrupt request when using interrupt handlers The notable exception is the TWI interface where clearing the interrupt indicates to proceed with the TWI bus hardware handshake so it s never done automatically However if no normal interrupt handlers are to be used or in order to make extra sure any pending interrupt gets cleared before re activating global interrupts g an external edge triggered one it can be necessary to explicitly clear the respective Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 9 Frequently Asked Questions 310 hardware interrupt bit by software This is usually done by writing a logical 1 into this bit position This seems to be illogical at first the bit position already carries a logical 1 when reading it so why does writing a logical I to it clear the interrupt bit The solution is simple writing logical 1 to it requires only single OUT instruction and it is clear that only this single interrupt request bit will be cleared There is no need to perform read modify write cycle like an SBI instruction since all bits in these control registers are interrupt bits and writing logical 0 to the remaining
346. 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 10 3 19 size_t strcspn const char s const char reject The strcspn function calculates the length of the initial segment of s which consists entirely of characters not in re ject Returns The strcspn function returns the number of characters in the initial segment of s which are not in the string reject The terminating zero is not considered as a part of string 6 10 3 20 size t strlcat char dst const char 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 10 lt string h gt Strings 84 Returns The strlcat function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 6 10 3 21 size_t strlcpy char dst const char src size_t siz Copy a string
347. port Deprecated Read a value from an IO port port 6 26 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 initially en abled This allows interrupt handlers to be interrupted As this macro has been used by too many unsuspecting people in the past it has been deprecated and will be removed in a future version of the library Users who want to legitimately re enable interrupts in their interrupt handlers as quickly as possible are encouraged to explicitly declare their handlers as described above Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 27 lt compat ina90 h gt Compatibility with EWB 3 157 6 26 2 6 define outb port val port val Deprecated Write val to IO port port 6 26 2 7 define outp val port port val Deprecated Write val to IO port port 6 26 2 8 define sbi port bit port 1 lt lt bit Deprecated Set bit in IO port port 6 26 3 Function Documentation 6 26 3 1 static _ inline void timer enable int unsigned char ints static Deprecated This function modifies the timsk register The value you pass via ints is device specific 6 27 lt compat ina90 h gt Compatibility with EWB 3 x include lt compat ina90 h gt This is an attempt to provide some compatibil
348. pplicable for device TIMER2_ COMPA vect SIG_ OUTPUT_ COMPARE2A Timer Counter2 Compare Match A ATmegal68 ATmega48 ATmega88 mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 9005 1286 AT90USB647 AT90USB646 TIMER2 COMPB vect SIG OUTPUT COMPARE2B Timer Counter2 Compare Match A ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P ATmega644P AT mega644 AT90USB1287 9005 1286 AT90USB647 AT90USB646 TIMER2 COMP vect SIG OUTPUT COMPARE2 Timer Counter2 Compare Match 9054434 9058535 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmega128 ATmegal6 ATmegal61 megal62 ATmegal63 ATmegal65 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 AT90S8535 AT90CAN128 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 8 A
349. pplication 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 Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 2 Memory Areas and Using malloc 250 9 1 13 Open Source of these tools from the original source code in the multitude of projects to the various distros are put together by many many volunteers All of these projects could always use more help from other people who are willing to volunteer some of their time There are many different ways to help for people with varying skill levels abilities and available time You can help to answer questions in mailing lists such as the avr gcc list or on forums at the AVR Freaks website This helps many people new to the open source AVR tools If you think you found a bug in any of the tools it is always a big help to submit a good bug report to the proper project good bug report always helps other voluntee
350. ps together with an STK500 anyway is that it can be debugged online via JTAG Likewise the ATmega48 88 168 and ATtiny23 13 devices be debugged through debug Wire 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 31 2 Functional overview PD6 will be toggled with each internal clock tick approx 10 ms PD7 will flash once per second PDO and PD1 are configured as UART IO and can be used to connect the demo kit to a PC 9600 Bd 8N1 frame format The demo application talks to the serial port and it can be controlled from the serial port PD2 through PD4 are configured as inputs and control the application unless control has been taken over by the serial port Shorting PD2 to GND will decrease the current PWM value shorting PD3 to GND will increase it While PD4 is shorted to GND one ADC conversion for channel 0 ADC input is on 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 31 Amore sophisticated project 181 Whenrunning 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
351. r sbrc r I sbrs r I 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 Modifier Specifies Write only operand usually used for all output operands Read write operand not supported by inline assembler amp Register should be used for output only Output operands must be write only and the C expression result must be an lvalue which means that the operands must be valid on the left side of assignments Note that the compiler will not check if the operands are of reasonable type for the kind of operation used in the assembler instructions Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 6 Inline Assembler Cookbook 276 Input operands are you guessed it read only But what if you need the same operand for input and output As stated above read write operands are not supported in inline assembler code But there is another solution For input operators it is possible to use a single digit in the constraint string Using digit n tells the compiler to use the same register as for the n th operand starting with zero Here is an example asm volatile swap 0 r value 0 value This statement will swap the nibbles of an 8 bit variable named value Constraint 0 tells the compiler to use the same
352. r no preprocessing done 9 11 3 Controlling the linker avr ld 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 lname Locate the archive library named libname a and use it to resolve currently unresolved symbols from it The library is searched along a path that con sists of builtin pathname entries that have been specified at compile time e g usr local avr lib on Unix systems possibly extended by pathname entries as specified by L options that must precede the 1 options on the command line Lpath Additional location to look for archive libraries requested by 1 options defsym symbol expr Define a global symbol symbol using expr as the value Print linker to stdout Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 11 Using the GNU tools 327 Map mapfile Print a linker map to mapfile cref 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 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 locati
353. r 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 assembler code string A good example is a simple statement to disable interrupts asm volatile cli Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 273 9 6 2 Assembler Code You can use the same assembler instruction mnemonics as you d use with any other AVR assembler And you can write as many assembler statements into one code string as you like and your flash memory is able to hold Note The available assembler directives vary from one assembler to another To make it more readable you should put each statement on seperate line asm volatile nop n t
354. r S memchr_P S memcmp S 198 198 198 199 205 205 206 206 207 208 208 209 209 209 209 209 212 213 213 214 214 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 41 avr libc File List 10 memcmp_P S 214 memcpy S 214 memcpy_P S 214 memmem S 215 memmove S 215 memrchr S 215 memrchr P S 215 memset S 215 parity h 216 pgmspace h 216 power h 223 setjmp h 223 sleep h 224 stdint h 225 stdio h 228 stdlib h 230 strcasecmp S 232 strcasecmp P S 232 strcasestr S 232 strcat S 232 strcat P S 233 strchr S 233 strchr P S 233 strchrnul S 233 strchrnul P S 233 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 41 avr libc File List 11 strcmp S 233 stremp P S 233 strcpy S 233 strepy P S 234 strespn S 234 strespn P S 234 string h 234 strlcat S 236 strlcat P S 236 strlepy S 236 strlepy P S 236 strlen S 236 strlen_P S 236 strlwr S 237 strncasecmp S 237 strncasecmp_P S 237 strncat S 237 strncat_P S 237 strncmp S 238 strnemp P S 238 strncpy S 238 strnepy P S 239 strnlen S 239 strnlen P S 239 strpbrk S 240 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 5 avr libc Page Index 12 strpbrk_P S 240 strrchr S 240 strrchr_P S 242 strrev S 242 strsep S 242 strsep P S 242 strspn S 242 strspn P S 242 strstr S 242 strstr P S 242 strtok r S 242 strupr S 242 util twi h 242 wdt h 244 5 avr libc Page Index 5 1
355. r function that runs with global interrupts initially dis abled This is the same as the ISR macro Deprecated Do not use SIGNAL in new code Use ISR instead 6 14 lt avr pgmspace h gt Program Space Utilities 6 14 1 Detailed Description include lt avr io h gt include avr pgmspace h The functions in this module provide interfaces for a program to access data stored in program space flash memory of the device In order to use these functions the target device must support either the LPM or ELPM instructions Note These functions are an attempt to provide some compatibility with header files that come with IAR C to make porting applications between different compilers easier This is not 100 compatibility though does not have full support for multiple address spaces yet If you are working with strings which are completely based in ram use the stan dard string functions described in lt string h gt Strings If possible put your constant tables in the lower 64 KB and use pgm read byte near or pgm read word near instead of pgm read byte far or pgm read word far since it is more efficient that way and you can still use the upper 64K for executable code 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 Generated on Tue
356. r inttypes 23 PRIuLEASTS avr inttypes 23 PRIuPTR avr inttypes 24 PRIX16 avr inttypes 24 PRIx16 avr inttypes 24 PRIX32 avr inttypes 24 PRIx32 avr_inttypes 24 PRIX8 avr_inttypes 24 PRIx8 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen INDEX 350 avr_inttypes 24 PRIXFAST16 avr inttypes 24 PRIxFAST 16 avr inttypes 24 PRIXFAST32 avr inttypes 24 PRIxFAST32 avr_inttypes 24 PRIXFAST8 avr_inttypes 25 PRIXFAST8 avr inttypes 25 PRIXLEAST16 avr inttypes 25 PRIxLEAST16 avr_inttypes 25 PRIXLEAST32 avr_inttypes 25 PRIxLEAST32 avr inttypes 25 PRIXLEAST8 avr inttypes 25 PRIxLEASTS avr inttypes 25 PRIXPTR avr inttypes 25 PRIxPTR avr inttypes 25 prog char avr pgmspace 120 prog intl6 t avr pgmspace 120 prog int32 t avr pgmspace 121 prog int64 t avr pgmspace 121 prog int8 t avr pgmspace 121 prog uchar avr pgmspace 121 prog uint16 t avr pgmspace 121 prog uint32 t avr pgmspace 121 prog uint64 t avr pgmspace 121 prog uint8 t avr pgmspace 121 prog void avr pgmspace 121 PROGMEM avr pgmspace 120 PSTR avr pgmspace 120 PTRDIFF MAX avr stdint 42 PTRDIFF MIN avr stdint 42 putc avr stdio 54 putchar avr stdio 54 puts avr stdio 58 puts P avr stdio 58 qsort avr stdlib 72 quot div t 197 ldiv t 197 rand avr stdlib 72 RAND MAX avr stdlib 68 rand r avr stdlib 73 random avr stdlib
357. r some circumstances additional functionality e g adding support for new device If major version number has changed this implies that the required versions of gcc and binutils have changed Consult the README file in the toplevel directory of the AVR Libc source for which versions are required 9 13 1 2 Development Versions The major version number of development se ries is always the same as the last stable release The minor version number of development series is always an odd number and is 1 more than the last stable release The patch version number of development series is always 0 until 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 13 Release Numbering and Methodology 331 versions in development in cvs will also always have the date appended as fourth version number The format of the date will be YYYYMMDD So the development version number will look like this 1 1 0 20030825 While pre release version number on branch destined to become either 1 2 or 2 0 will look like this 1 1 90 20030828 9 13 2 Releasing AVR Libc information in this section is only relevant to Libc developers be ignored by end users Note In what follows I assume y
358. r 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 Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 6 Inline Assembler Cookbook 278 asm volatile n t ld r24 0 ine r24 MANE st a0 r24 n t sei ANEI e ptr r24 compiler might produce the following code eli ld r24 2 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 ld _tmp_reg__ a0 inc __tmp_reg__ st a0 __tmp_reg__ sel e ptr n t n t n t nye nye 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 b
359. r 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 000000ce 00000000 00000000 00000074 2 1 CONTENTS ALLOC LOAD READONLY CODE 1 bes 00000003 00800060 00800060 00000142 2xx0 Generated Tue 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 168 ALLOC 2 debug aranges 00000020 00000000 00000000 00000142 2xx0 CONTENTS READONLY DEBUGGING 3 debug pubnames 00000035 00000000 00000000 00000162 2xx0 CONTENTS READONLY DEBUGGING 4 debug info 000000db 00000000 00000000 00000197 2x x 0 CONTENTS READONLY DEBUGGING 5 debug abbrev 00000098 00000000 00000000 00000272 2xx0 CONTENTS READONLY DEBUGGING 6 debug line 00000121 00000000 00000000 0000030a 2x0 CONTENTS READONLY DEBUGGING 7 debug frame 00000040 00000000 00000000 0000042c 2xx2 CONTENTS READONLY DEBUGGING 8 debug str 000000be 00000000 00000000 0000046c 2xx0 CONTENTS READONLY DEBUGGING Disassembly of section text 00000000 ctors end 0 10 e0 Idi r7 0x00 0 2 a0 e6 ldi r26 0x60 96 4 bO eO ldi r27 0x00 0 6 ee ec ldi r30 OxCE 206 8 0 531 0x00 7 0 02 0 rjmp 4 0x10 do copy start 0000000 do copy data loop er 05
360. rated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 253 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 Ox10FF 0x1100 0 200 OxFFFF on board RAM SP 4 __malloc_heap_end heap end RAMEND __brkval bss end malloc heap start _ heap start data bss start data start Figure 8 Internal RAM variables and stack external RAM heap If malloc heap 1 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 Implementati
361. rated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 17 math h File Reference 212 define SCNuLEAST32 lu define SCNuFAST32 lu define SCNx32 Ix define SCNxLEAST32 Ix define SCNxFAST32 Ix define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR SCNx16 Far pointers for memory access gt 64K typedef int32_t int_farptr_t typedef uint32_t uint_farptr_t 8 17 math h File Reference 8 17 1 Detailed Description Defines define PI 3 141592653589793238462643 define M_SQRT2 1 4142135623730950488016887 Functions double cos double x ATTR CONST double fabs double __x _ ATTR CONST double fmod double _ x double y ATTR_CONST double modf double __ value double iptr double sin double __x CONST double sqrt double _ x ATTR CONST double tan double x ATTR CONST double floor double _ x _ ATTR CONST double double _ x ATTR CONST double frexp double value int exp double Idexp double int exp CONST double exp double _ x ATTR CONST double cosh double x ATTR CONST double sinh double _ x _ ATTR CONST double tanh double x ATTR CONST double acos double x ATTR CONST double asin double x _ ATTR CONST Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 18 memccpy S File Reference double atan double x ATTR CONST double atan2 double __y doubl
362. ration 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 distinct memory areas this is the safest way to avoid a stack heap collision Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 252 9 2 3 Tunables for malloc There are 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 c
363. rc xmodem update uint16 t crc uint8 t data e static inline uintl6 t crc ccitt update uint16 t crc uint8 t data e static inline uint8 t crc ibutton update uint8 t crc uint8 t data 6 21 2 Function Documentation 6 21 2 1 static inline 16 t crc16 update uint16 t _ crc uint8 t data static Optimized CRC 16 calculation Polynomial x 16 x 15 x 2 1 0xa001 Initial value Oxffff This CRC is normally used in disk drive controllers The following is the equivalent functionality written in C uintl6 t crcl6 update uintl6 t crc uint8 t a int i cre Generated Tue 15 14 56 11 2007 for avr libc by Doxygen 6 21 lt util erc16 h gt CRC Computations 145 for i 0 i lt 8 i if cre amp 1 crc crc gt gt 1 0 001 crc crc gt gt 1 return crc 6 21 2 2 static inline uintl16 t crc ccitt update uint16 t crc uint8_t_ 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
364. relocatable object file from arbitrary binary input like avr objcopy I binary O elf32 avr foo bin foo o This will create a file named with the contents of foo bin The contents will default to section data and two symbols will be created named binary foo bin start and binary foo bin end These symbols can be referred to inside a C source to access these data Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 10 Installing the GNU Tool Chain 312 If the 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 9 10 Installing the GNU Tool Chain Note This discussion was taken directly from Rich Neswold s document See Acknowl edgments This discussion is Unix specific FIXME troth 2002 08 13 we need volunteer to add windows specific notes to these instructions This chapter shows how to build and install complete development environment for the AVR processors using the GNU toolset The default behaviour for most of these tools is to
365. rform 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 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 32 Using the standard IO facilities 190 written left to right The public function 1 putchar takes arguments that make it suitable for be ing passed as a put function pointer to the stdio stream initialization functions and macros devopen FDEV SETUP STREAM etc Thus it takes two argu ments the ch
366. rlying hardware the demo has been set up in a way so the pin compatible but more expensive ATtiny45 or its siblings Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 29 Combining and assembly source files 160 25 85 could be used as well In that case no separate assembly code is required as two timer channels are avaible 6 29 1 Hardware setup The incoming PWM pulse train is fed into PB4 It will generate a pin change interrupt there on eache edge of the incoming signal The outgoing PWM is generated through OCOB of timer channel 0 PB 1 For demon stration purposes 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 tiny13 and 1 0 MHz on the ATtiny45 6 29 2 A code walkthrough 6 29 2 1 asmdemo c After the usual include files two variables are defined The first one pwm_incoming is used to communicate the most recent pulse width de tected by the incoming PWM decoder up to the main loop The second variable actually only constitutes of a single bit intbits pwm received This bit will be set whenever the incoming PWM decoder has updated pwm incoming Both variables are marked volatile to ensure their readers will always pick up an up dated value as both variables will be set by interrupt service routines The function ioinit initializes the mi
367. rogram Memory handling macros are defined there There is also way to create method to define variables in Program Memory that is common between the two compilers and AVR GCC Create header file that has these definitions fif defined ICCAVR IAR C Compiler define FLASH DECLARE x flash x fendif if defined GNUC GNU Compiler define FLASH DECLARE x x __attribute__ __progmem_ fendif This code snippet checks for the compiler or for the compiler and defines macro FLASH DECLARE x that will declare 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 289 To do the equivalent in AVR GCC do this void main void attribute noreturn void main void bf sas 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
368. rrupt handler by declaring the handler the following way void void attribute interrupt void XXX vect void Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 13 lt avr interrupt h gt Interrupts 99 where XXX_vect is the name of a valid interrupt vector for the MCU type in question as explained below 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 libe 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 ISR macro cannot really spell check the argument p
369. rs to analyze the problem and to get it fixed for future versions of the software You can also help to fix bugs in various software projects or to add desirable new features Volunteers are always welcome 9 2 Memory Areas and Using malloc 9 2 1 Introduction Many of the devices that are possible targets of avr libc have a minimal amount of RAM The smallest parts supported by the C environment come with 128 bytes of RAM This needs to be shared between initialized and uninitialized variables sections data and bss the dynamic memory allocator and the stack that is used for calling subroutines and storing local automatic variables Also unlike larger architectures there is no hardware supported memory management which could help in separating the mentioned RAM regions from being overwritten by each other The standard RAM layout is to place data variables first from the beginning of the internal RAM followed by bss The stack is started from the top of internal RAM growing downwards The so called heap available for the dynamic memory allocator will be placed beyond the end of bss Thus there s no risk that dynamic memory will ever collide with the RAM variables unless there were bugs in the implementation of the allocator There is still a risk that the heap and stack could collide if there are large requirements for either dynamic memory or stack space The former can even happen if the allocations aren t all that
370. rupt Service Routines ISRs 286 9 84 22 287 9853 Flash Varable gt u a cua RR UA UM kone 287 9 8 6 Non Returning main 288 987 Locking Registers 5 66a e ws san rm s 289 99 Frequently Asked Questions 2 289 FAO Shae ee oso Xo See SE RD 289 9 9 2 program doesn t recognize a variable updated within an inierupt poA o llus RA ek Gs 291 9 9 3 I get undefined reference to for functions like sin0 291 9 9 4 How to permanently bind a variable toa register 291 9 9 5 How to modify MCUCR or WDTCR 292 9 9 6 Whatisallthis BVO stuff about LL 292 997 CanluseCiHRontbe AVR 2 52 454 6544 bee aes 293 9 9 8 Shouldn t I initialize all 294 9 9 9 Why do some 16 bit timer registers sometimes get trashed 295 9 9 10 How do I use a define d constant in an asm statement 296 9 9 11 Why does the PC randomly jump around when single stepping through my program in 296 9 9 12 How do I trace an assembler file 016 297 9 9 13 How do I pass an IO port as a parameter to a function 298 9 9 14 What registers are used by C compiler 300 9 9 15 How do I put an array of strings completely in 302 9 9 16 How 1
371. s set declares a symbol as a constant expression identical to equ global or globl declares a public symbol that is visible to the linker g function entry point global variable extern declares a symbol to be externally defined this is effectively a comment only as gas treats all undefined symbols it encounters as globally undefined any way Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 6 Inline Assembler Cookbook 270 Note that org is available in gas as well but is fairly pointless pseudo op in an as sembler environment that uses relocatable object files as it is the linker that determines the final position of some object in ROM or RAM Along with the architecture independent standard operators there are some AVR specific operators available which are unfortunately not yet described in the official documentation The most notable operators are 108 Takes the least significant 8 bits of 16 bit integer hi8 Takes the most significant 8 bits of a 16 bit integer pm Takes program memory ROM address and converts it into RAM ad dress This implies a division by 2 as the AVR handles ROM addresses as 16 bit words e g in an IJMP or ICALL instruction and can also handle relocatable symbols on the right hand side Example ldi r24 108 pm somefunc ldi r25 hi8 pm somefunc call something This passes the address of function somefunc as the first parameter to
372. s the date code YYYYMMDD 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 19 lt avr version h gt avr libc version macros 139 Defines fidefine AVR VERSION STRING GAVR LIBC VERSIONG define __AVR_LIBC_VERSION__ AVR_LIBC_VERSION_ NUMERIC UL define _ AVR DATE STRING AVR_LIBC_RELDATE define AVR DATE AVR_LIBC_RELDATE UL define AVR LIBC MAJOR AVR LIBC MAJORG define AVR LIBC MINOR AVR_LIBC_MINOR define AVR REVISION AVR_LIBC_REVISION 6 19 2 Define Documentation 6 19 21 ftdefine AVR DATE AVR RELDATEGUL Numerical representation of the release date 6 19 2 2 define AVR DATE STRING AVR LIBC RELDATE String literal representation of the release date 6 19 2 3 define _AVR_LIBC_MAJOR__ AVR_LIBC_MAJOR Library major version number 6 19 2 4 define _AVR_LIBC_MINOR__ AVR_LIBC_MINOR Library minor version number 6 19 2 5 define AVR LIBC REVISION GAVR LIBC REVISIONG Library revision number 6 19 2 6 define __ LIBC VERSION
373. s 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 05001 toggle OC2 output on compare match COM2x 0b01 and clear timer on compare match CTC2 1 Make OC2 PD7 an output TCCR2 _BV COM20 _BV CTC2 _BV CS20 DDRD _BV PD7 Back to FAQ Index 9 9 7 Can I use C on the AVR Basically yes C is supported assuming your compiler has been configured and compiled to support it of course Source files ending in cc cpp or C will automati cally cause the compiler frontend to invoke the C compiler Alternatively the C compiler could be explicitly called by the name avr c However there s currently no support for libstdc the standard support library needed for a complete C implementation This imposes a number of restrictions on the C programs that can be compiled Among them are Obviously none of the C related standard functions classes and template classes are available The operators new and delete are not implemented attempting to use them will cause the linker to complain about undefined external references This could perhaps be fixed Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 9 Frequently
374. s 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 the application will auto matically scale to new target softclock or master CPU frequencies without having to manually re calculate hardcoded constants 6 31 3 2 Part 2 Variable definitions The int flags structure demonstrates a way to allocate bit variables in memory Each of the interrupt service routines just sets Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 6 31 Amore sophisticated project 182 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 th
375. s returns 0 for success 6 8 33 FILE fdevopen int char FILE put int FILE get This function is a replacement for fopen It opens stream for device where the actual device implementation needs to be provided by the application If successful pointer to the structure for the opened stream is returned Reasons for possible failure currently include that neither the put nor the get argument have been provided thus attempting to open stream with no intent at all or that insufficient dynamic memory is available to establish new stream If the put function pointer is provided the stream is opened with write intent The function passed as put shall take two arguments the first character to write to the device and the second a pointer to FILE and shall return 0 if the output was successful and 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 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 inte
376. s 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 14 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 14 2 7 define pgm read dword near address short LPM dword uint16 t address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 120 6 14 2 8 define pgm_read_word address_short pgm_read_word_ near address_short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 14 2 9 define pgm_read_word_far address_long ELPM word uint32 t address_long Read a word from the program space with a 32 bit far address Note The address is a byte address The address is in the program space 6 14 2 10 read word near address short LPM word uint16 address short Read word from the program space with 16 bit near address Note The address is byte address The address
377. se crc lt lt 1 return crc Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 22 lt util delay h gt Convenience functions for busy wait delay loops 147 6 222 lt util delay h gt Convenience functions for busy wait delay loops 6 22 1 Detailed Description define F_CPU 1000000UL 1 MHz define CPU 14 7456E6 include lt util delay h gt 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 de fine statement should be used The functions in this header file are wrappers around the basic busy wait functions from lt util delay basic h gt They are meant as convenience functions where actual time values can be specified rather than 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 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 po
378. se interrupt service routines Total cycle count is 8 CPU cycles so together with the 4 CPU cycles needed Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 30 simple project 162 for interrupt setup and the 2 cycles for the RJMP from the interrupt vector to the han dler these routines will require 14 out of each 256 CPU cycles or about 5 of the overall CPU time The pin change interrupt PCINTO will be handled in the final part of this file The basic algorithm is to quickly evaluate the current system time by fetching the current timer value of TCNTO and combining it with the overflow part in counter_hi If the counter is currently counting down rather than up the value fetched from TCNTO must be negated Finally if this pin change interrupt was triggered by a rising edge the time computed will be recorded as the start time only Then at the falling edge 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 disabled so no new measurement can be performed until the upper layer had a chance to process the current value 6 29 3 The source code The source code is installed under Sprefix share doc avr libc examples asmdemo where prefix isa configuration option For Unix systems it is usually se
379. se of these sections is to allow for more specific placement of code within your program Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 3 Memory Sections 257 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 chunk of code which is not a function Notice that the examples for asm and C can not be called as functions and should not be jumped into The initN sections are executed in order from 0 to 9 init0 Weakly bound to __init If user defines init it will be jumped into immedi ately after a reset initi Unused User definable init2 In C programs weakly bound to initialize the stack and to clear zero reg r1 init3 Unused User definable init4 For devices with gt 64 KB of ROM init4 defines the code which takes care of copying the contents of data from the flash to SRAM For all other devices this code as well as the code to zero out the bss section is loaded from libgec a 10145 Unused User definable init6 Unused for C programs but used for constructors in programs init7 Unused User definable 1018 Unused User definable init9 Jumps into main Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 3 Memory Sections 258 9 3 7 The finiN Sections These sections are used to define the exit
380. sfr defs h gt Special function registers 134 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 is now PORTB 1 This actually is more flexible than having sbi directly as the optimizer will use a hard ware sbi if appropriate or a read or write if not You do not need to keep track of which registers sbi cbi will operate on Likewise cbi sfr bit is now sfr amp _BV bit Modules Additional notes from lt avr sfr_defs h gt Bit manipulation define BV bit I 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 I SFR
381. sidered to be less than s2 6 10 3 25 char strncat char dest const char src size_t len Concatenate two strings The strncat function is similar to strcat except that only the first characters of src are appended to dest Returns The strncat function returns a pointer to the resulting string dest 6 10 3 26 strncmp const char 81 const char 52 size_t len Compare two strings The strncmp function is similar to stremp except it only compares the first at most n characters of s1 and 52 Returns The strncmp function returns an integer less than equal to or greater than zero if sl or the first bytes thereof is found respectively to be less than to match or be greater than s2 6 10 3 27 char strnepy 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 Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 10 lt string h gt Strings 86 6 10 3 28 size_t strnlen const char src size t len Determine the length of a fixed size string The strnlen functi
382. sing the optimizer in a loop like the following one uint8 t flag ISR SOME vect flag 1 while flag 0 the compiler will typically access flag only once and optimize further accesses com pletely away since its code path analysis shows that nothing inside the loop could change the value of 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 Libm a Typically system libraries like 1ibm a are given to the final C compiler command line that performs the linking step by adding a flag 1m at the end That is the initial lib and the filename suffix from the library are written immediately after a flag So for a 1ibfoo a library 1foo needs to be provided This will make the linker search the library in a path known to the system An alternative would be to specify the full path to the 1ibm a file at the same place on the command line i e after all the object files However since this re quires knowledge of where the build system will exactly find those library files this is deprecated for system li
383. space string interface Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 1 3 Supported Devices 2 Unless otherwise noted functions of this library are not guarenteed to be reentrant In particular any functions that store local state are known to be non reentrant as well as functions that manipulate IO registers like the EEPROM access routines If these functions are used within both standard and interrupt context undefined behaviour will result 1 3 Supported Devices The following is a list of AVR devices currently supported by the library Note that actual support for some newer devices depends on the ability of the compiler assembler to support these devices at library compile time AT90S Type Devices 319051200 1 at90s2313 at90s2323 at90s2333 at90s2343 at90s4414 at90s4433 at90s4434 at90s8515 at90c8534 at90s8535 ATmega Type Devices atmega8 atmega103 atmegal28 atmega1280 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 1 3 Supported Devices atmega1281 atmegal6 atmegal61 atmega162 atmega163 atmegal64p atmega 165 165 atmega 168 atmega 169 atmega169p atmega2560 atmega2561 atmega32 atmega323 atmega324p atmega325 atmega325p atmega3250 atmega3250p atmega329 atmega329p atmega3290 atmega3290p atmega48 atmega64 atmega640 atmega644 Generated on Tue May 15 14 5
384. stions 304 Note that when using a compile time constant index omitting the first step reading the pointer from ROM via memcpy_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 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 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 program 1 the data and or bss segment that memory area it is essential to set up the external memory interface early during the device initialization so the initialization of these variable will take place Refer to How to modify MCUCR or WDTCR early for a description how to do this using few lines of assembler code or to the chapter about memory sections for an example written in C The explanation of malloc contains 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 als
385. string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 6 14 4 15 size t strlcpy P char dst PGM 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 strlepy function returns strlen src If retval gt siz truncation occurred 6 14 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 the number of characters in src Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 14 lt avr pgmspace h gt Program Space Utilities 126 6 14 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 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
386. t avr interrupt h gt Interrupts 103 Vector name Old name vector Description Applicable for device INT6_vect SIG_ INTERRUPT6 External Interrupt Request 6 AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB162 9005 82 9005 1287 AT90USB 1286 AT90USB647 AT90USB646 INT7_vect SIG_ INTERRUPT7 External Interrupt Request 7 AT90CAN128 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 AT mega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 AT mega2561 AT90USB162 9005 82 9005 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 OVERFLOW I CAN Overrun Timer AT90CAN128 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 ATmegal281 ATm
387. t h gt Bootloader Support Utilities 6 11 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 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 11 lt avr boot h gt Support Utilities 89 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 buf uintl6 t i uint8 t sreg Disable interrupts sreg SREG cli eeprom busy wait boot page erase page boot spm busy wait Wai
388. t isspace int CONST int isupper int CONST int isxdigit int ATTR CONST Character convertion routines If c is not an unsigned char value or EOF the behaviour of these functions is undefined int toascii int CONST int tolower int CONST int toupper int ATTR CONST Defines define 1 define CONST attribute const 8 7 delay h File Reference 8 7 1 Detailed Description Defines define UTIL DELAY H 1 define F CPU 100000001 Functions void delay us double us void delay ms double ms 8 8 delay basic h File Reference 8 8 1 Detailed Description Defines define UTIL DELAY BASIC H 1 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 8 9 eeprom h File Reference 207 Functions 8 9 8 9 1 void delay loop 1 uint8_t __count void delay loop 2 uint16_t count eeprom h File Reference Detailed Description avr libe 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 pointer eeprom size t n void eeprom write byte uint8 t addr uint8 t value void eeprom write word uint16 t addr uint
389. t optimization levels The following table lists the results The test case consisted of around 2 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 42 flags 6898 903 us 19 7 ms 02 6666 972 us 20 1 ms Os 6618 955 us 20 1 ms Os 6474 972 us 20 1 ms mcall prologues The difference between 955 us and 972 us was just a single timer tick so take this with a grain of salt So generally it seems Os mcall prologues is the most universal best opti mization level Only applications that need to get the last few percent of speed benefit from using 03 Back to FAQ Index 9 9 18 How do I relocate code to fixed address First the code should be put into new named section This is done with 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 sect
390. t to either usror usr local 6 30 simple project At this point you should have the GNU tools configured built and installed on your system In this chapter we present simple example of using the GNU tools in an AVR project After reading this chapter you should have a better feel as to how the tools are used and how Makefile can be configured 6 30 1 The Project This project will use the pulse width modulator PWM to ramp an LED on and off every two seconds AT90S2313 processor will be used as the controller The circuit for this demonstration is shown in the schematic diagram If you have development kit you should be able to use it rather than build the circuit for this project Note Meanwhile the 419052313 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 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 30 simple project 163 longer necessary to use external crystal for clocking as they ship with the inter nal 1 MHz oscillator enabled so C1 C2 and 1 can be omitted Normally for this experiment the external circuitry on RESET R1 C3 can be omitted as well leaving only the AVR the LED the bypass capacitor C4 and perhaps R2 For
391. t 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 REG amp uint8 t BV SPMIE define boot rww busy SPM REG amp uint8 t COMMON ASB Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 11 lt avr boot h gt Bootloader Support Utilities 90 define boot spm busy SPM REG amp uint8_t _BV SPMEN define boot_spm_busy_wait dot while boot spm busy define GET_LOW_FUSE_BITS 0x0000 define GET_LOCK_BITS 0x0001 define GET EXTENDED FUSE BITS 0 0002 define GET HIGH FUSE BITS 0x0003 define boot lock fuse bits get address define boot page fill address data boot page fill normal address data define boot page erase address boot page erase normal address
392. t_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 11 2 4 boot lock fuse bits get address result Value __extension__ uint8_t __result __asm__ __volatile__ 141 r30 3 n t Idi r31 O n t sts 1 2 n t lpm 0 Z n t gt ex result i _SFR_MEM_ADDR __SPM_REG N r uint8 t BOOT LOCK BITS SET N M address N 4 VANT 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 11 2 5 define boot page erase address boot page erase normal address Erase the flash page that contains address Note address is byte address in flash not word address Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 11 lt avr boot h gt Bootloader Support Utilities 92 6 11 2 6 define boot page erase safe address Value do N boot_spm_busy_wait eeprom busy wait boot page erase address while 0 Same as boot page erase except it waits for eeprom and spm operations to complete before erasing the page 6 11 2 7 de
393. 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 5 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 patch that adds more AVR types can be found at http www freebsd org cgi cvsweb cgi ports devel avr binutils files patch newdevices 9 10 4 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 5 bunzip2 gcc version tar bz2 tar xf gcc version 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 10 Installing the GNU Tool Chain 316 To save your self some download time you can alternatively download only t
394. tchdog 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 stdint h include avr wdt h 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 Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 20 lt avr wdt h gt Watchdog timer handling 141 Defines define wdt reset volatile wdr 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 156 define WDTO 2S 7 define WDTO 458 define WDTO 859 6 20 2 Define Documentation 6 20 2 1 define wdt disable Value asm volatile N in tmp reg SREG n t aJi n t out 0 1 n t N out 0 reg n t X out SREG__ __tmp_reg__ n t
395. ted on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 10 lt string h gt Strings 80 Returns The memchr function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 10 3 6 int memcmp const void 57 const void 52 size_t len Compare memory areas The memcmp function compares the first len bytes of the memory areas s1 and 52 The comparision is performed using unsigned char operations Returns memcmp function returns an integer less than equal to or greater than zero if the first len bytes of s1 is found respectively to be less than to match or be greater than the first len bytes of s2 Note Be sure to store the result in a 16 bit variable since you may get incorrect results if you use an unsigned char or char due to truncation Warning This function is not mint8 compatible although if you only care about testing for equality this function should be safe to use 6 10 3 7 void memcpy void dest const void src size_t len Copy a memory area The memcpy function copies len bytes from memory area src to memory area dest The memory areas may not overlap Use memmove if the memory areas do overlap Returns The memcpy function returns a pointer to dest 6 10 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 subs
396. teger scanf format for int fast16 t 6 4 2 71 define SCNiFAST32 li generic integer scanf format for int fast32 t 6 4 2 72 define SCNILEASTIG i generic integer scanf format for int_least16_t 6 4 2 73 define SCNiLEAST32 Ti generic integer scanf format for int least32 1 6 4 2 74 define SCNiPTR SCNi16 generic integer scanf format for intptr_t 6 4 2 75 define SCNo16 octal scanf format for uint16 t 6 4 2 76 define SCNo32 lo octal scanf format for uint32 t 6 4 2 77 define SCNoFAST16 octal scanf format for uint fast16 t 6 4 2 78 define SCNoFAST32 lo octal scanf format for uint_fast32_t 6 4 2 79 define SCNoLEAST16 octal scanf format for uint_least16_t Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 4 lt inttypes h gt Integer conversions 28 6 4 2 80 define SCNoLEAST32 lo octal scanf format for uint_least32_t 6 4 2 1 define SCNoPTR SCNo16 octal scanf format for uintptr_t 6 4 2 82 define SCNu16 decimal scanf format for uint16_t 6 4 2 83 define SCNu32 lu decimal scanf format for uint32_t 6 4 2 84 define SCNuFAST16 u decimal scanf format for uint_fast16_t 6 4 2 85 define SCNuFAST32 lu decimal scanf format for uint fast32 t 6 4 2 86 define SCNULEAST16 decimal scanf format for uint_least16_t 6 4 2 87 define SCNULEAST32 lu decimal scanf format for uint_least32_t 6 4 2 88 define SCNuPTR SCNu
397. th an ori instruction in your assembler code then the compiler may select any register This will fail if the compiler chooses r2 to r15 It will never choose r0 or r1 because these are uses for special purposes That s why the correct constraint in that case is d On the other hand if you use the constraint M the compiler will make sure that you don t pass anything else but an 8 bit value Later on we will see how to pass multibyte expression results to the assembler code The following table shows all AVR assembler mnemonics which require 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 275 constants to the range 0 to 7 for bit set and bit clear operations Mnemonic Constraints Mnemonic Constraints rr add rr adiw rr andi belr I bld r I brbc Llabel brbs Llabel bset I bst r I cbi LI cbr d I com r cp Lr cpc 1 LI dec r elpm tz eor rr in r I inc r ld re Idd r b ldi d M 146 r label 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 sb
398. the equivalent functionality written in C uintl6 t crc ccitt update uintl16 t crc uint8 t data data 108 crc data data lt lt 4 return uintl6 t data lt lt 8 hi8 uint8_t data gt gt 4 uintl6 t data lt lt 3 6 21 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 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 21 lt util erc16 h gt CRC Computations 146 See http www maxim ic com appnotes cfm appnote_number 27 The following is the equivalent functionality written in C uint8 t crc ibutton update uint8 t crc uint8 t data uint8 t i crc crc data for i 0 lt B i if crc amp 0x01 crc crc gt gt 1 0x8C else crc gt gt 1 return crc 6 21 2 4 static inline uintl6_t _ xmodem update uintl6 t _ crc uint8 t data static Optimized CRC XMODEM calculation Polynomial x 16 x 12 x 5 1 0x1021 Initial value OxO This is the CRC used by the Xmodem CRC protocol The following is the equivalent functionality written in C uintl6 t crc xmodem update uintl6 t crc uint8 t data int i crc crc uintl6 t data lt lt 8 for i 0 i lt 8 i 1 amp 0 8000 crc crc lt lt 1 0x1021 el
399. this document provides enough information to get a new AVR developer up to speed quickly using the freely available development tools binutils gcc avr libc and many others If you find yourself stuck on a problem which this document doesn t quite address you may wish to post a message to the avr gcc mailing list Most of the developers of the AVR binutils and gcc ports in addition to the devleopers of avr libc subscribe to the list so you will usually be able to get your problem resolved You can subscribe to the list at http lists nongnu org mailman listinfo avr gec list Before posting to the list you might want to try reading the Frequently Asked Questions chapter of this document Note If you think you ve found a bug or have a suggestion for an improvement ei ther in this documentation or in the library itself please use the bug tracker at https savannah nongnu org bugs group avr libc to ensure the issue won t be forgotten 1 2 General information about this library In general it has been the goal to stick as best as possible to established standards while implementing this library Commonly this refers to the 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
400. tion 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 O and debug information 9 which is fortunately possible in avr gcc the code watched in the debugger is opti mized code While it is not guaranteed very often this code runs with the exact same optimizations as it would run without the g switch This can have unwanted side effects Since the compiler is free to reorder code ex ecution as long as the semantics do not change code is often rearranged in order to make it possible to use a single branch instruction for conditional operations Branch instructions can only cover a short range for the target PC 63 through 64 words from the current PC If a branch instruction cannot be used directly the compiler needs to work around it by combining a skip instruction together with a relative jump r jmp instruction which will need one additional word of ROM Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 297 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
401. tion 2 242 Strspn S Reference scs RR Re RR RS 242 8 76 1 Detailed Description 22 2222 2 2 2222 25525 242 sirspn_PS 2222 22222252 22992 242 8 79 1 Detaled Desenption ss sos oo RR RR RR 242 situs Pile Reterence uos oo oos gor so 242 6 80 1 Detailed Description gt s soe co oz x o 242 strstr P S PyeRefer n e k s k o 242 8 81 1 Detailed Description 2 2 242 stok ks File Reference 0 2222 xS Rum RU Rs 242 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen CONTENTS xi 8 82 1 Detailed Description 242 33 siupro Pile Rererence 222222222555 242 8 83 1 Detailed Description cs m zu mes exte 242 8 84 frit Pile Reletente cu noo SE AGE S 56 242 8 84 1 Detailed Description 242 8 65 woth Pile Reference 22222222225 eoe mom DOE 244 8 83 1 Detaled Description 24546 9 5 5446 526 244 8 85 2 Define Documentation 244 9 avr libc Page Documentation 245 91 Toolehain Overview e osons ee e m e 2 245 den s 222822 c RR REG 245 912 FSP Smt 22222522225 245 L3 OEC Boat tee ene eee ta BUS 245 DILA GNU Bimmer eo ee 246 EE c upon eee ee ko SUS 248 416 Building Software lt a 22122024 sa Fase tes 248 ANRDUDE icra kered ke SE
402. tion occurs 6 9 4 13 charx itoa int _ yal char x __s int radix Convert an integer to a string The function itoa converts the integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing sufficient storage in 5 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 minus sign will be prepended The itoa function returns the pointer passed as s 6 9 4 14 long labs long The labs function computes the absolute value of the long integer i Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 9 lt stdlib h gt General utilities 72 Note The abs and labs functions are builtins of gcc 6 9 4 15 div tldiv ong num long denom The Idiv function computes the value num denom and returns the quotient and re mainder in a structure named 1div t that contains two long
403. tmega3290 AVR ATmega3290 avr5 atmega3290p AVR ATmega3290P 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 atmega2560 __ _ 2560__ atmega2561 __AVR_ATmega2561__ 1 avr25 architecture is new in GCC 4 2 morderl 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 10 r1 Order 1 uses r18 r19 r20 r21 122 r23 r24 r25 r30 r31 r26 r27 128 129 r17 116 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 12 r0 r1 Order 2 uses 125 r24 r23 122 121 r20 r19 r18 r30 r31 r26 r27 r28 r29 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 r2 r1 rO Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 9 11 Using the GNU tools 322 e mint8 Assume int to be an 8 bit integer Note that this is not really supported by avr libc so it should normally not be used The default is to use 16 bit integers mno interrupts Generates code that changes the stack pointer without disabl
404. tr t 47 ere se ECCECE avr_stdio FDEV EOF 52 FDEV ERR 52 FDEV SETUP READ 52 FDEV SETUP RW 52 FDEV SETUP WRITE 52 clearerr 55 EOF 53 fclose 55 fdev close 53 fdev get udata 53 fdev set udata 53 FDEV SETUP STREAM 53 fdev setup stream 53 fdevopen 55 feof 56 ferror 56 fflush 56 fgetc 56 fgets 56 FILE 54 fprintf 57 fprintf P 57 fputc 57 fputs 57 fputs P 57 fread 57 fscanf 57 fscanf P 57 fwrite 58 getc 54 getchar 54 gets 58 printf 58 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen INDEX 342 printf_P 58 putc 54 putchar 54 puts 58 puts_P 58 scanf 58 scanf_P 58 snprintf 58 snprintf_P 59 sprintf 59 sprintf_P 59 sscanf 59 sscanf_P 59 stderr 54 stdin 54 stdout 55 ungetc 59 vfprintf 59 vfprintf_P 62 vfscanf 62 vfscanf_P 65 vprintf 65 vscanf 65 vsnprintf 65 vsnprintf_P 65 vsprintf 65 vsprintf_P 65 avr_stdlib compar fn t 68 malloc heap end 76 malloc heap start 76 malloc margin 77 abort 68 abs 68 atof 68 atoi 69 atol 69 bsearch 69 calloc 69 div 70 DTOSTR ALWAYS SIGN 68 DTOSTR PLUS SIGN 68 DTOSTR UPPERCASE 68 dtostre 70 dtostrf 70 exit 70 free 71 itoa 71 labs 71 ldiv 71 71 malloc 72 qsort 72 rand 72 RAND MAX 68 rand r 73 random 73 RANDOM MAX 68 random r 73 realloc 73
405. tring s2 of length 1en2 in the memory area s1 of length 1en1 Returns The memmem function returns a pointer to the beginning of the substring or NULL if the substring is not found If 1en2 is zero the function returns s1 Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 10 lt string h gt Strings 81 6 10 3 9 void x memmove void gt dest const void src size_t len Copy memory area The memmove function copies len bytes from memory area src to memory area dest The memory areas may overlap Returns The memmove function returns a pointer to dest 6 10 3 10 void memrchr const void src int val size_t len The memrchr function is like the memchr function except that it searches back wards from the end of the len bytes pointed to by src instead of forwards from the front Glibc GNU extension Returns The memrchr function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 10 3 11 void memset void dest int val size_t len Fill memory with a constant byte The memset function fills the first len bytes of the memory area pointed to by dest with the constant byte val Returns The memset function returns a pointer to the memory area dest 6 10 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 ignor
406. u decimal printf format for uint_least32_t 6 4 2 39 define PRIULEASTS decimal printf format for uint_least8_t 6 4 2 40 define PRIUPTR PRIul6 decimal printf format for uintptr_t 6 4 2 41 define PRIX16 X uppercase hexadecimal printf format for uint16_t 6 4 2 42 define PRIx16 x hexadecimal printf format for uint16 t 6 4 2 43 define PRIX32 IX uppercase hexadecimal printf format for uint32 t 6 4 2 44 define PRIx32 Ix hexadecimal printf format for uint32 t 6 4 2 45 ftdefine PRIX8 X uppercase hexadecimal printf format for uint8 t 6 4 2 46 define PRIx8 hexadecimal printf format for uint8 t Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 4 lt inttypes h gt Integer conversions 25 6 4 2 47 define PRIXFAST16 X uppercase hexadecimal printf format for uint_fast16_t 6 4 2 48 define PRIxFAST16 x hexadecimal printf format for uint_fast16_t 6 4 2 49 define PRIXFAST32 uppercase hexadecimal printf format for uint_fast32_t 6 4 2 50 define PRIXFAST32 Ix hexadecimal printf format for uint_fast32_t 6 4 2 51 define PRIXFASTS X uppercase hexadecimal printf format for uint fast8 t 6 4 2 52 define PRIxFASTS hexadecimal printf format for uint fast8 t 6 4 2 53 define PRIXLEAST16 X uppercase hexadecimal printf format for uint least16 t 6 4 2 54 define PRIXLEAST16 hexadecimal printf format for uint least16 1
407. ue an uint least32 t can hold 6 7 2 53 define UINT LEAST64 MAX UINT64 MAX largest value an uint least64 t can hold 6 7 2 54 define UINT LEAST8 MAX UINT8 MAX largest value an uint least8 t can hold 6 7 2 55 define UINTMAX C value CONCAT value ULL define a constant of type uintmax t 6 7 2 56 define UINTMAX MAX UINT64 MAX largest value an uintmax t can hold 6 7 2 57 define UINTPTR MAX UINT16 MAX largest value an uintptr t can hold Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 7 lt stdint h gt Standard Integer Types 45 6 7 3 Typedef Documentation 6 7 3 1 typedef signed int int16 t 16 bit signed type 6 7 3 2 typedef signed long int int32 t 32 bit signed type 6 7 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 7 3 4 typedef signed char int8 t 8 bit signed type 6 7 3 5 typedef int16 t int fast16 t fastest signed int with at least 16 bits 6 7 3 6 typedef int32 t int fast32 t fastest signed int with at least 32 bits 6 7 37 typedef int64 t int fast64 t fastest signed int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect 6 7 3 8 typedef int8 tint fast8 t fastest signed int with at least 8 bits 6 7 3 9 typedef int16 t int least16 t signed int with at least 16 bits Generated on Tue May 15 14 56 11
408. ue of the arc cosine of x The returned value is in the range 0 pi radians domain error occurs for arguments not in the range 1 1 6 5 5 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 0 pi radians domain error occurs for arguments not in the range 1 1 6 5 3 3 double atan double x The atan function computes the principal value of the arc tangent of x The returned value is in the range 0 pi radians domain error occurs for arguments not in the range 1 1 6 5 3 4 double atan2 double y double x 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 If both x and y are zero the global variable errno is set to EDOM 6 5 3 5 double double x The ceil function returns the smallest integral value greater than or equal to x ex pressed as a floating point number 6 5 3 6 double cos double x The cos function returns the cosine of x measured in radians 6 5 3 7 double cosh double x The cosh function returns the hyperbolic cosine of x 6 5 3 8 double exp double x The exp function returns the exponential value of x Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 5 lt math h gt Mathematics 32 6
409. unctions described here do not disable interrupts In general for long delays the use of hardware timers is much preferrable as they free the CPU and allow for concurrent processing of other events while the timer is running However in particular for very short delays the overhead of setting up a hardware timer is too much compared to the overall delay time Two inline functions are provided for the actual delay algorithms Functions e void delay loop 1 uint8 t count void delay loop 2 uint16 t count 6 23 2 Function Documentation 6 23 2 1 void delay loop 1 uint8 t count Delay loop using an 8 bit counter count so up to 256 iterations are possible The value 256 would have to be passed as 0 The loop executes three CPU cycles per iteration not including the overhead the compiler needs to setup the counter register Thus at a CPU speed of 1 MHz delays of up to 768 microseconds can be achieved Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 6 24 lt util parity h gt Parity bit generation 149 6 23 2 2 void _delay_loop_2 uint16_t count Delay loop using a 16 bit counter count so up to 65536 iterations are possible The value 65536 would have to be passed as 0 The loop executes four CPU cycles per iteration not including the overhead the compiler requires to setup the counter register pair Thus at a CPU speed of 1 MHz delays of up to about 262 1 milliseconds can
410. und 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 9 4 7 void calloc size t mnele size_t size Allocate nele elements of size each Identical to calling malloc using nele size argument except the allocated memory will be cleared to zero 6 9 4 8 div t div int __ num int denom The div function computes the value num denom and returns the quotient and re mainder in structure named div t that contains two int members named quot and rem 6 9 4 9 char dtostre double val char s unsigned char prec unsigned char flags The dtostre function converts the double value passed in val into an ASCII repre sentation that will be stored under s The caller is responsible for providing sufficient storage in s Conversion is done in the format d ddde dd where there is one digit before the decimal point character and the number of digits after it is equal to the precision prec if the precision is zero no decimal point character appears If 1ags has the DTOSTRE UPPERCASE bit set the letter E rather than e will be used to introduce the exponent The exponent always contains two digits if the value is zero the exponent is 00 If 1ags has the DTOSTRE ALWAYS SIGN bit set a space
411. urce files 161 Function main first initializes the hardware by calling ioinit and then waits until some incoming PWM value is available If it is the output PWM will be adjusted by computing the relative value of the incoming PWM Finally the pin change interrupt is re enabled and the CPU is put to sleep 6 29 2 2 project h In order for the interrupt service routines to be as fast as possi ble some of the CPU registers are set aside completely for use by these routines so the compiler would not use them for C code This is arranged for in project h The file is divided into one section that will be used by the assembly source code and another one to be used by C code The assembly part is distinguished by the prepro cessing macro __ASSEMBLER__ which will be automatically set by the compiler front end when preprocessing an assembly language file and it contains just macros that give symbolic names to a number of CPU registers The preprocessor will then replace the symbolic names by their right hand side definitions before calling the as sembler In C code the compiler needs to see variable declarations for these objects This is done by using declarations that bind a variable permanently to a CPU register see How to permanently bind a variable to a register Even in case the C code never has a need to access these variables declaring the register binding that way causes the compiler to not use these registers
412. urrently held in register before executing the assembler code And of course everything has to be reloaded again after this code In most situations 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 produce compiler warnings if they are used in modules which are compiled in strict ANSI mode To avoid that you can write asm instead of asm and volatile instead of volatile These are equivalent aliases Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 280 Another problem with reused macros arises if you are using labels In such cases you may make use of the special pattern which is replaced by unique number on each asm statement follow
413. using the C and C language there s limited support for direct assembler usage as well The benefits of it are Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 5 avr libc and assembler programs 265 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 identifier as a macro whereas the assembler s macro concept is basically targeted to use macro in place of an assembler instruction Use of the runtime framework like automatically assigning interrupt vectors For devices that have RAM initializing the RAM variables can also be utilized 9 5 2 Invoking the compiler For the purpose described in this document the assembler and linker are usually not invoked manually but rather using the C compiler frontend avr gcc that in turn will call the assembler and linker as required This approach has the following advantages 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 crt XXX o and linker script
414. ve 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 variety of slave devices available that can be connected to TWI bus For the purpose of this example an EEPROM device out of the industry standard 24Cxx series has been chosen where xx can be one of 01 02 04 08 or 16 which are available from various vendors The choice was almost arbitrary mainly triggered by the fact that an EEPROM device is being talked to in both directions reading and writing the slave device so the example will demonstrate the details of both Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 33 Example using the two wire interface TWI 193 Usually there is probably not much need to add more EEPROM to an ATmega system that way the smallest possible device that offers hardware support is the ATmega8 which comes with 512 bytes of which is equivalent to an 24C04 device 128 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 g SDRAM PC memory comes with an integrated TWI EEPROM that carries the RAM configuration information 6 33 3 Source Code The source code is installed under Sprefix share doc avr libc exampl
415. vr libc by Doxygen 8 31 pgmspace h File Reference 222 uintl6 t _ addrl6 uintl6 t addr uint8 t result asm lpm 0 Z n t r result z addr16 result tt 8 31 2 10 define word classic Value __extension__ X uintl6 t addrl6 uintl6 t addr N uintl6 t _ result N asm N N lpm NnNE N mov A0 ro n t adiw r30 1 n t lpm UNDNE N mov B0 ro TANT r _ result z addrl16 N 1 __addr16 ny N result i 8 31 2 11 define LPM word enhanced addr Value __extension__ uintl6 t _ addr16 uintl6 t addr uintl6 t result X asm N N lpm 0 27 n t lpm B0 Z nyt r result z __ 16 N 1 __addr16 result N Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 8 32 power h File Reference 223 8 32 power h File Reference 8 32 1 Detailed Description Defines define AVR POWER 1 define clock_prescale_set x define clock_prescale_get clock_div_t CLKPR amp uint8_ t 1 lt lt CLKPS0 1 lt lt CLKPS1 1 lt lt CLKPS2 1 lt lt CLKPS3 Enumerations enum clock div t clock div 1 0 clock div 2 1 clock div 4 2 clock div 8 3 clock div 16 4 clock div 32 5 clock div 64 6 clock div 128 7 clock div 256 8 8 32 2 Define Documentation 8 32 2 1 define clock
416. w Finally the 3 second backup timer is implemented that will write the PWM Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 32 Using the standard IO facilities 184 value back to EEPROM once it Is not changing anymore The ADC interrupt will just adjust the PWM value only Finally the UART Rx interrupt will dispatch on the last character received from the UART All the string literals that are used as informational messages within main are placed in program memory so no SRAM needs to be allocated for them This is done by using the PSTR macro and passing the string to printstr_p 6 31 4 The source code The source code is installed under Sprefix share doc avr libc examples largedemo largedemo c where prefix isa configuration option For Unix systems it is usually set to either usror usr local 6 32 Using the standard IO facilities This project illustrates how to use the standard IO facilities stdio provided by this library It assumes basic knowledge of how the stdio subsystem is used in standard 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 32 1 Hardware setup The demo is set up in a way so it can be run on the ATmegal6 that ships with the S
417. will see later on Note The filename is case sensitive Use lowercase lib prefix and lowercase a as the file extension The command line is fairly simple avr as rcs library name gt list of object modules The command switch tells the program to insert the object modules into the archive with replacement The c command line switch tells the program to create the archive And the s command line switch tells the program to write an object file index into the archive or update an existing one This last switch is very important as it helps the linker to find what it needs to do its job Note The command line switches are case sensitive There are uppercase switches that have completely different actions MFile and the WinAVR distribution contain a Makefile Template that includes the necessary command lines to build a library You will have to manually modify the template to switch it over to build a library instead of an application See the GNU Binutils manual for more information on the ar program 9 7 5 Using a Library To use a library use the 1 switch on your linker command line 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 E this will expand to the library filename libm a Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 9 8 Porting From IAR to AVR GCC 285 which happens to
418. word classic pgmspace h 220 LPM dword enhanced pgmspace h 221 LPM enhanced pgmspace h 221 LPM word classic pgmspace h 222 LPM word enhanced pgmspace h 222 boot lock bits set boot h 200 boot lock bits set alternate boot h 200 boot page erase alternate boot h 201 boot page erase extended boot h 201 boot page erase normal boot h 201 boot page fill alternate boot h 202 boot page fill extended boot h 202 boot page fill normal boot h 203 boot page write alternate boot h 203 boot page write extended boot h 203 boot page write normal boot h 204 boot rww enable boot h 204 boot rww enable alternate boot h 204 compar fn t avr stdlib 68 malloc heap end avr stdlib 76 malloc heap start avr stdlib 76 malloc margin avr stdlib 77 erc16 update util crc 144 _crc_ccitt_update util crc 145 crc ibutton update util crc 145 crc xmodem update util crc 146 delay loop 1 util delay basic 148 delay loop 2 util delay basic 148 delay ms util delay 147 delay us util delay 148 wdt write wdt h 244 more sophisticated project 177 simple project 162 abort avr stdlib 68 abs avr stdlib 68 acos avr_math 30 Additional notes from lt avr sfr_defs h gt 131 asin avr math 30 assert avr assert 13 assert h 198 atan avr math 30 atan2 avr math 31 atof avr stdlib 68 atoi avr stdlib 69 atoi S 198 atol
419. x002e 7 28 2 00 word 0x002a 7 0000002a lt bar gt 2a 42 61 72 00 Bar 0000002e lt foo gt 2e 46 6 6 00 Foo foo is at addr 0x002e bar is at addr 0x002a array is at addr 0x0026 Then in main we see this memcpy P amp p amp array i sizeof 70 66 Of add r22 922 72 TY VE adc 23 23 74 6a 5d subi r22 OxDA 272218 76 7f 4f sbci r23 OxFF 4 1255 78 42 0 ldi r20 0x02 3 72 7a 50 ldi r21 0x00 4 5 76 ce 01 movw r24 r28 81 96 adiw r24 0 21 HEG 80 08 rcall 16 pr 0x92 This code reads the pointer to the desired string from the ROM table array into a register pair The value of i in 122 123 is doubled to accomodate for the word offset required to access array then the address of array 0x26 is added by subtracting the negated address Oxffda The address of variable p is computed by adding its offset within the stack frame 33 to the Y pointer register and memcpy P is called strcpy P buf p 82 69 1 14 r22 33 0 21 84 Ja al ldd r23 Y 34 0x22 86 ce 01 movw r24 r28 88 01 96 adiw r24 0x01 2 8a Oc reall 24 Oxa4 This will finally copy the ROM string into the local buffer buf Variable p located at Y 33 is read and passed together with the address of buf Y 1 to strepy P This will copy the string from ROM to buf Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 9 9 Frequently Asked Que
420. xample avr as mmcu atmegal28 gstabs o foo o foo s When the assembler is not called directly but through the C compiler frontend either implicitly by passing a source file ending in S or explicitly using x assembler with cpp the compiler frontend needs to be told to pass the gstabs option down to the assembler This is done using Wa gstabs Please take care to only pass this option when compiling an assembler input file Otherwise the assembler code that results from the C compilation stage will also get line number information which confuses the debugger Note You can also use Wa gstabs since the compiler will add the extra for you Example Generated on Tue May 15 14 56 11 2007 for avr libc by Doxygen 9 9 Frequently Asked Questions 298 5 EXTRA OPTS Wall mmcu atmegal28 x assembler with cpp 5 avr gcc Wa gstabs EXTRA OPTS c o foo o foo S Also note that the debugger might get confused when entering a piece of code that has a non local label before since it then takes this label as the name of a new function that appears to have been entered Thus the best practice to avoid this confusion is to only use non local labels when declaring a new function and restrict anything else to local labels Local labels consist just of a number only References to these labels consist of the number followed by the letter b for a backward reference or f for a forward reference These local labels may
421. y861 SIG PCINT PSCO SIG PSCO PSCO Capture AT90PWM3 AT90PWM2 AT90PWMI CAPT vect CAPTURE Event PSCO EC SIG PSCO 5 0 End Cycle AT90PWM3 AT90PWM2 AT90PWMI vect END CYCLE PSCI SIG PSCI PSCI Capture AT90PWM3 AT90PWM2 AT90PWMI vect CAPTURE Event PSCI EC SIG PSCI 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 AT90PWMG AT90PWM2 AT90PWMI vect END CYCLE SPI STC vect SIG SPI Serial Transfer AT90S2333 AT90S4414 419054433 Complete AT9084434 419058515 419058535 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN 128 AT90CAN32 AT90CAN 64 ATmegal03 ATmegal28 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 AT90USB82 AT90USB 1287 AT90USB 1286 AT90USB647 AT90USB646 SPM RDY SIG SPM Store Program ATmegal6 ATmegal62 ATmega32 vect READY Memory Ready mega323 ATmega8 ATmega8515 mega8535 Generated on Tue May 15 14 56 11 2007 for avr libe by Doxygen 6 13 lt
422. ypedefs typedef int __ compar fn t const void const void Functions inline void abort void _ ATTR_NORETURN__ int abs int 1 CONST long labs long 1 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 divmodhi4 _ ATTR CONST t ldiv 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 x endptr int base long atol const char xs ATTR PURE int atoi const char xs ATTR PURE void exit int status _ ATTR_NORETURN__ void x malloc size_t size ATTR MALLOC void free void __ void calloc size t nele size t size ATTR MALLOC void realloc void ptr size_t size _ ATTR_MALLOC__ double strtod const char nptr char __endptr double const char nptr int rand void void srand unsigned int __seed int rand unsigned long Generated on Tue 15 14 56 11 2007 for avr libe by Doxygen 6 9 lt stdlib h gt General utilities 68 Variables e size t malloc margin char _ malloc heap start char _ malloc_heap_end 6 9 2 Define Documentation 6 9 2 1 de
423. ytes 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 0 0 so there aren t any EEPROM variables 6 30 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 The ROM contents can be pulled from our project s binary and put into the file demo hex using the following command avr objcopy j text j data O ihex demo elf demo hex The resulting demo hex file contains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he j option indicates that we wa
424. ze_t strlcat P char PGM P size t size t strlcpy P char PGM P size t size t strlen P PGM P CONST size t strnlen P PGM P size 09 ATTR CONST int strncmp P const char PGM P size_t PURE int strncasecmp P const char PGM P size_t PURE char strncat P char PGM P size t char strnepy P char size t char strpbrk P const char s PGM P accept ATTR PURE PGM P strrchr P PGM Ps int val ATTR CONST char strsep P char sp delim size_t strspn_P const char s PGM P accept ATTR PURE char strstr P const char PGM P ATTR PURE 8 31 2 Define Documentation 8 31 2 1 define ELPM classic addr Value extension N uint32 t __addr32 uint32 t addr uint8 t _ result N asm N N out 2 SUI N mov r31 B1 n t N mov r30 A1 n t elpm n t now 30 r result r addr32 I _SFR_IO_ADDR RAMPZ 0 result N 8 31 2 2 define dword enhanced Value __extension__ uint32_t __addr32 uint32_t addr uint32_t result X Generated on Tue 15 14 56 11 2007 for avr libc by Doxygen 8 31 pemspace h File Reference 219 asm out movw elpm elpm elpm elpm ly pn 730 result 8 31

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