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avr-libc Reference Manual

1. mov BO ro n t r result r __addr32 I _SFR_IO_ADDR RAMPZ ro r30 r31 __result H 8 34 2 5 define ELPM _ _word_enhanced___ addr Value __extension__ uint32_t __addr32 uint32_t addr uint16_t __result __asm__ out 2 C1 n t movw r30 1 n t elpm AO Z n t elpm BO Z n t r __result r __addr32 I _SFR_IO_ADDR RAMPZ r30 r31 __result H 8 34 2 6 define LPM_classic__ addr Value __extension__ uint16_t __addr16 uint16_t addr uint8_t __result __asm__ lpm n t mov 90 ro n t r result z __addr16 ro __result H Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference 8 34 2 7 define Value __extension__ uint16_t _ uint32_t __result __asm__ lpm mov AO ro adiw r30 1 lpm mov BO ro adiw r30 1 lpm mov CO ro adiw r30 1 lpm mov DO ro r result z 1 __addr16 ro __result H 8 34 2 8 define Value __extension__ uint16_t uint32_t _asm_ _result lpm AO Z lpm BO Z lpm CO Z lpm DO Z r __result 1 __addr16 __result H 8 34 2 9 define Value __extension__ uint16_t _a
2. 9 17 Deprecated List Global SIGNAL p 139 Do not use SIGNAL p 139 in new code Use ISR p 136 instead Global ISR_ ALIAS p 136 For new code the use of ISR ISR_ ALIASOF is recommended Global timer enable int p 189 Global enable external int p 188 Global INTERRUPT p 188 Global inp p 188 Global outp p 189 Global inb p 188 Global outb p 189 Global sbi p 189 Global cbi p 187 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen Index PATH 347 PREFIX 347 prefix 347 lt alloca h gt Allocate space in the stack 15 lt assert h gt Diagnostics 15 lt avr boot h gt Bootloader Support Utilities 96 lt avr eeprom h gt dling 103 lt avr fuse h gt Fuse Support 107 lt avr interrupt h gt Interrupts 110 lt avr io h gt AVR device specific IO definitions 139 lt avr lock h gt Lockbit Support 140 lt avr pgmspace h gt Program Space Utilities 143 lt avr power h gt Power Reduction Management 156 lt avr sfr_defs h gt Special function registers 160 lt avr sleep h gt Power Management and Sleep Modes 162 lt avr version h gt avr libe version macros 164 lt avr wdt h gt Watchdog timer han dling 165 lt compat deprecated h gt Deprecated items 186 lt compat ina90 h gt Compatibility with IAR EWB 3 x 189 lt ctype h gt Character Operations 16 lt errno h gt System Errors 19 lt i
3. Note This type is not available when the compiler option mint8 is in effect 6 8 3 12 typedef int8 t int least8 t signed int with at least 8 bits 6 8 3 13 typedef int64_t intmax_t largest signed int available 6 8 3 14 typedef int16 tintptr t Signed pointer compatible type 6 8 3 15 typedef unsigned int uint16 t 16 bit unsigned type 6 8 3 16 typedef unsigned long int uint32 t 32 bit unsigned type 6 8 3 17 typedef unsigned long long int uint64 t 64 bit unsigned type Note This type is not available when the compiler option mint8 is in effect 6 8 3 18 typedef unsigned char uint8 t 8 bit unsigned type Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 53 6 8 3 19 typedef uint16_t uint fast16 t fastest unsigned int with at least 16 bits 6 8 3 20 typedef uint32 t uint fast32 t fastest unsigned int with at least 32 bits 6 8 3 21 typedef uint64_t uint fast64 t fastest unsigned int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect 6 8 3 22 typedef uint8 t uint fast8 t fastest unsigned int with at least 8 bits 6 8 3 23 typedef uint16_t uint least16 t unsigned int with at least 16 bits 6 8 3 24 typedef uint32_t uint_least32_t unsigned int with at least 32 bits 6 8 3 25 typedef uint64_t uint least64 t unsigned int with at least 64 bits Note This type is not available when
4. The linker will search libraries in the order that they appear on the command line Whichever function is found first that matches the undefined reference it will be linked in There are also command line switches that tell GCC which directory to look in L for the libraries that are specified to be linke in with 1 See the GNU Binutils manual for more information on the GNU linker ld program 9 8 Benchmarks The results below can only give a rough estimate of the resources necessary for using certain library functions There is a number of factors which can both increase or reduce the effort required e Expenses for preparation of operands and their stack are not considered e In the table the size includes all additional functions for example func tion to multiply two integers but they are only linked from the library e Expenses of time of performance of some functions essentially depend on parameters of a call for example qsort p 80 is recursive and sprintf p 66 receives parameters in a stack e Different versions of the compiler can give a significant difference in code size and execution time For example the dtostre p 78 function compiled with avr gcc 3 4 6 requires 930 bytes After transition to avr gcc 4 2 3 the size become 1088 bytes 9 8 1 lt A few of libc functions Avr gec version is 4 2 3 The size of function is given in view of all picked up functions By default Avr libe is com
5. include lt avr io h gt void my_init_portb void __attribute__ naked __attribute__ section init3 void my_init_portb void 1 PORTB Oxff DDRB Oxff Note Section init3 is used in this example as this ensures the inernal __zero_ reg__ has already been set up The code generated by the compiler might blindly rely on __zero_reg__ being really 0 9 4 Data in Program Space 9 4 1 Introduction So you have some constant data and you re running out of room to store it Many AVRs have limited amount of RAM in which to store data but may Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 4 Data in Program Space 287 have more Flash space available The AVR is a Harvard architecture processor where Flash is used for the program RAM is used for data and they each have separate address spaces It is a challenge to get constant data to be stored in the Program Space and to retrieve that data to use it in the AVR application The problem is exacerbated by the fact that the C Language was not designed for Harvard architectures it was designed for Von Neumann architectures where code and data exist in the same address space This means that any compiler for a Harvard architecture processor like the AVR has to use other means to operate with separate address spaces Some compilers use non standard C language keywords or they extend the stan dard syntax in ways that are non standard The AV
6. 2 00000 ffs S File Reference va vnr rn eee ftsl 5 File Reference 2 00000000004 ffsll S File Reference 1 0 0250p s eee fuse h File Reference 0 interrupt h File Reference 2000 inttypes h File Reference 0 0 io h File Reference _ ooann aaa lock h File Reference 4 a math h File Reference 0 0 0 memcecpy S File Reference _ 4 0 memchr S File Reference 0 memchr P S File Reference Les ki sarao aa E A ea memcmp S File Reference 0 memcmp P S File Reference acessadas acrem na a kre memcpy S File Reference 0 memcpy_ P S File Reference arv vr vr vnr rv memmem S File Reference 0 0 0 memmove S File Reference va vr vr arr rn nrk memrehr S File Reference 2 000000084 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen iii CONTENTS iv 8 31 8 32 8 33 8 34 8 35 8 36 8 37 8 38 8 39 8 40 8 41 8 42 8 43 8 44 8 45 8 46 8 47 8 48 8 49 8 50 8 51 8 52 8 53 8 54 8 55 8 56 8 57 8 58 8 59 8 60 8 61 memrchr P S File Reference 0 0 0 0 249 memset S File Reference v vr rv vnr vnr ran 249 parity h File Reference LL rv vr v vr vr knr vn 249 pgmspace h File Reference arr vr arva kn av 250 power h File Reference eva vn rar 00000004 257 setbaud h File Reference arv vr rv vr knr rv 258 setjmp h File
7. RS 232 header TXD of the RS 232 button SWO pin 1 down switches header button up SWI pin 2 switches header SW2 pin 3 switches header LEDO pin I LEDs header green clock out LEDI pin 2 LEDs header white 1 second LED2 pin 3 flash LEDs header Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 37 A more sophisticated project 214 1307099014 Figure 3 Wiring of the STK500 The following picture shows the alternate wiring where LED1 is connected but SW2 is not Figure 4 Wiring option 2 of the STK500 As an alternative this demo can also be run on the popular ATmega8 controller or its successor ATmega88 as well as the ATmega48 and ATmega168 variants of the latter These controllers do not have a port named A so their ADC inputs Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 37 A more sophisticated project 215 are located on port C instead thus the potentiometer needs to be attached to port C Likewise the OC1A output is not on port D pin 5 but on port B pin 1 PB1 Thus the above cabling scheme needs to be changed so that PB1 connects to the LEDO pin PD6 remains unconnected When using the STK500 use one of the jumper cables for this connection All other port D pins should be connected the same way as described for the ATmegal6 above When not using an STK500 starter kit attach the LEDs through some resistor to Vec low active LEDs and attach
8. See the Dallas Semiconductor app note 27 for 8051 assembler example and general CRC optimization suggestions The table on the last page of the app note is the key to understanding these implementations Jack Crenshaw s Implementing CRCs article in the January 1992 isue of Em bedded Systems Programming This may be difficult to find but it explains CRC s in very clear and concise terms Well worth the effort to obtain a copy A typical application would look like Dallas iButton test vector uint8_t serno 0x02 Oxic Oxb8 0x01 0 0 O Oxa2 int checkcrc void uint8_t crc 0 i for i 0 i lt sizeof serno sizeof serno 0 i cre _crc_ibutton_update crc serno i return crc must be 0 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 26 lt util crcl6 h gt CRC Computations 174 Functions e static inline uint16_t crc16 update uint16_t crc uint8 t data e static inline uintl6 t crc xmodem update uint16 t _crc uint8 t data e static inline uint16_t crc ccitt update uint16 t __ crc uint8 t data e static inline uint8_t crc ibutton update uint8 t cc uint8 t data 6 26 2 Function Documentation 6 26 2 1 static inline uint16_t crc16 update uint16 t _crc uint8 t data static Optimized CRC 16 calculation Polynomial x16 x15 x 2 1 0xa001 Initial value Oxffff This CRC is normally used in disk drive controllers The follo
9. e define boot page fill address data boot page fill normal address data define boot page erase address boot page erase normal address define boot page write address boot page write normal address e define boot rww enable boot rww enable e define boot lock bits set lock bits boot lock bits set lock bits Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 5 boot h File Reference define boot rww enable safe 8 5 2 Define Documentation 8 5 2 1 define boot lock bits set lock bits Value __extension__ uint8_t value uint8 t lock bits _ asm__ __volatile__ ldi r30 1 n t ldi r31 O n t mov r0 42 n t sts 0 1 n t spm n t i _SFR_MEM_ADDR __SPM_REG r uint8_t __BOOT_LOCK_BITS_SET r value ro p r30 A r31 H 8 5 2 2 define boot lock bits set alternate lock bits Value __extension__ uint8_t value uint8 t lock bits _ asm__ __volatile__ ldi r30 1 n t Idi r31 O n t mov r0 42 n t sts 0 1 n t spm n t word Oxffff n t nop n t i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT LOCK BITS SET r value ro r30 x r31 H Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen define boot page fill safe address data define boot page erase safe address define boot page write safe address define boot lock bits set safe lock bits JR EE EAR
10. e mno wrap For RJMP RCALL instructions don t allow the target address to wrap around for devices that have more than 8 KB of memory e gstabs Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 370 Generate stabs debugging symbols for assembler source lines This enables avr gdb to trace through assembler source files This option must not be used when assembling sources that have been generated by the C compiler these files already contain the appropriate line number information from the C source files e a cdhlmns file Turn on the assembler listing The sub options are c omit false conditionals e d omit debugging directives h include high level source e 1 include assembly m include macro expansions e n omit forms processing s include symbols file set the name of the listing file The various sub options can be combined into a single a option list file must be the last one in that case 9 12 2 2 Examples for assembler options passed through the C com piler Remember that assembler options can be passed from the C compiler frontend using Wa see above p 368 so in order to include the C source code into the assembler listing in file foo 1st when compiling foo c the following compiler command line can be used avr gcc c 0 foo c o foo o Wa ahls f00 1st In order to pass an assembler file through the C preprocessor first and have the assembler gener
11. e AVaRICE Open source code package Configure and build in a directory outside of the source code tree Set PATH in order x lt MikTex executables gt usr local bin usr bin bin lt install directory gt bin Set location of LibUSB headers and libraries export CPPFLAGS I startdir libusb win32 device bin libusb version include export CFLAGS I startdir libusb win32 device bin libusb version include export LDFLAGS static L startdir libusb win32 device bin libusb_version lib gcc Configure archivedir configure N prefix installdir datadir installdir doc mandir installdir man N infodir installdir info 2 gt amp 1 tee avarice configure log Make make all install 2 gt amp 1 tee avarice make log e SimulAVR Open source code package Configure and build in a directory outside of the source code tree Set PATH in order lt MikTex executables gt usr local bin usr bin Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 362 bin lt install directory gt bin Configure export LDFLAGS static archivedir configure N prefix installdir datadir installdir N disable tests disable versioned doc 2 gt amp 1 tee simulavr configure log Make make k all install 2 gt amp 1 tee simulavr make log make pdf install pdf 2 gt amp 1 tee simulavr pdf make log 9 12 U
12. mkdir obj avr cd obj avr configure prefix PREFIX make make install Note You might want to have already installed avr binutils p 348 avr gec p 350 and avr libc p 350 if you want to have the test programs built in the simulavr source 9 11 10 AVaRICE Note These install notes are not applicable to avarice 1 5 or older You probably don t want to use anything that old anyways since there have been many improvements and bug fixes since the 1 5 release AVaRICE also uses the configure system so to build and install gunzip c avarice lt version gt tar gz tar xf cd avarice lt version gt mkdir obj avr cd obj avr configure prefix PREFIX make make install 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 lt hdr_path gt with the path to the bfd h file on your system Replace lt lib_path gt with the path to 1ibbfd a on your system CPPFLAGS I lt hdr_path gt LDFLAGS L lt lib_path gt configure prefix PREFIX 9 11 11 Building and Installing under Windows Building and installing the toolchain under Windows requires more effort be cause all of the tools required for building and the programs themselves are Generated on Wed Jun 11 11 29 15 2008 for avr l
13. 6 10 4 30 char utoa unsigned int val char __s int __ radix Convert an unsigned integer to a string The function utoa p 84 converts the unsigned integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing sufficient storage in s Note The minimal size of the buffer s depends on the choice of radix For exam ple if the radix is 2 binary you need to supply a buffer with a minimal length of 8 x sizeof unsigned int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 29 will be the letter a Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 85 The utoa p 84 function returns the pointer passed as s 6 10 5 Variable Documentation 6 10 5 1 charx malloc heap end malloc p 80 tunable p 279 6 10 5 2 charx malloc heap start malloc p 80 tunable p 279 6 10 5 3 size_t _malloc_ margin malloc p 80 tunable p 279 6 11 lt string h gt Strings 6 11 1 Detailed Description include lt string h gt The string functions perform string operations on NU
14. 6 6 3 9 double exp double _ 2 The exp p 35 function returns the exponential value of __ x 6 6 3 10 double fabs double __ The fabs p 35 function computes the absolute value of a floating point number __z 6 6 3 11 double fdim double __ double 9 The fdim p 35 function returns mar x 90 If Tor __ yor both are NaN NaN is returned 6 6 3 12 double floor double ___2 The floor p 35 function returns the largest integral value less than or equal to __ x expressed as a floating point number Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 36 6 6 3 13 double fma double __ double _ _ y double 2 The fma p 36 function performs floating point multiply add This is the operation __ x y z but the intermediate result is not rounded to the destination type This can sometimes improve the precision of a calculation 6 6 3 14 double fmax double __ double 9 The fmax p 36 function returns the greater of the two values x and _ y If an argument is NaN the other argument is returned If both arguments are NaN NaN is returned 6 6 3 15 double fmin double __ double ___y The fmin p 36 function returns the lesser of the two values sand ___y If an argument is NaN the other argument is returned If both arguments are NaN NaN is returned 6 6 3 16 double fmod double __ double 9 The function fmod p 36 retur
15. Timer Counter0 AT90S2313 AT 9052323 AT90S2343 OVFO vect OVERFLOW Q Overflow ATtiny22 ATtiny26 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 124 Vector Old vector Description Applicable for device name name Timer Counter0 AT90S1200 AT9052333 AT90S4414 OVERFLOW Overflow AT9054433 AT90S4434 AT90S8515 AT9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 ATmega103 AT megal28 ATmegal284P ATmegal6 ATmegal61 ATmegal62 AT megal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 AT megal69P ATmega32 ATmega323 ATmega325 ATmega3250 AT mega3250P ATmega328P AT mega329 ATmega3290 AT mega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 ATmega6450 ATmega649 AT mega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 ATmegal6HVA ATtinyll ATtiny12 ATtiny15 ATtiny2313 ATtiny28 ATtiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMERI1 SIG Timer Counterl AT9052313 CAPTI_ INPUT_ Capture Event vect CAPTURE1 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 125 a Timer Counter AT90S2333 AT905
16. case UP if pwm TIMER1_TOP direction DOWN break case DOWN if pwm 0 direction UP break I OCR pum Note 5 void ioinit void Note 6 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 199 Timer 1 is 10 bit PWM 8 bit PWM on some ATtinys TCCR1A TIMER1_PWM_INIT Start timer 1 NB TCCR1A and TCCR1B could actually be the same register so take care to not clobber it TCCR1B TIMER1_CLOCKSOURCE Run any 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 OC1 as output DDROC BV 0C1 Enable timer 1 overflow interrupt TIMSK _BV TOIE1 sei I int main void 1 ioinit loop forever the interrupts are doing the rest for 33 Note 7 sleep mode return 0 I 6 36 3 Compiling and Linking This first thing that needs to be done is compile the source When compiling the compiler needs to know the processor type so the mmcu option is specified The 0s option will tell the compiler to optimize the code for efficient space usage at the possible expense of code execution speed The g is used to embed debug info The debug info is useful for disassemblies and doesn t end up in the hex files so I usually specify it Finally the c tells the compiler to com
17. e data switches to the data section initialized RAM variables e text switches to the text section code and ROM constants e set declares a symbol as a constant expression identical to equ e global or globl declares a public symbol that is visible to the linker e g function entry point global variable e extern declares a symbol to be externally defined this is effectively a comment only as gas treats all undefined symbols it encounters as globally undefined anyway Note that org is available in gas as well but is a fairly pointless pseudo op in an assembler 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 e 108 Takes the least significant 8 bits of a 16 bit integer e hi8 Takes the most significant 8 bits of a 16 bit integer e pm Takes a program memory ROM address and converts it into a RAM address 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 pa
18. mega3290P ATmega48P ATmega64 ATmega645 ATmega6450 AT mega649 ATmega6490 ATmega8 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 CAPT vect INPUT_ Capture Event AT90CAN64 ATmega128 AT CAPTURE3 megal284P ATmegal62 AT mega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 COMPA OUTPUT Compare AT90CAN64 ATmega128 AT vect COMPARE3A Match A megal284P ATmega162 AT mega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts COMPARE3B Match B TIMER3_ OVF vect SIG OVERFLOW3 Overflow SIG INPUT_ CAPTURE4 SIG OUTPUT_ TIMER4 CAPT vect TIMERA COMPA vect TIMERA COMPB vect TIMERA COMPC vect SIG INPUT CAPTURE5 SIG OUTPUT COMPARE5A TIMERS Capture Event TIMERS COMPA vect TIMERS COMPB vect TIMERS Compare Match A SIG_ COMPC_ OUTPUT_ vect COMPARE5C TIMERS SIG OVF_vect OVERFLOWS Compare Match C Overflow Timer
19. 236 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX boot lock bits set alternate 236 boot page erase alternate 236 boot 237 boot 237 boot 238 boot 238 boot boot 239 boot 239 boot 240 boot rww enable 240 boot rww enable alternate 240 boot is spm interrupt avr boot 98 boot lock bits set avr boot 98 boot lock bits set safe avr boot 99 boot lock fuse bits get avr boot 99 boot page erase avr boot 100 boot page erase safe avr boot 100 boot page fill avr boot 100 boot page fill safe avr boot 101 boot page write avr boot 101 boot page write safe avr boot 101 boot rww busy avr boot 101 boot rww enable avr boot 101 page erase extended page erase normal page fill alternate page fill extended fill normal 238 write alternate page page page write extended page write normal 389 boot rww enable safe avr boot 102 boot signature byte get avr boot 102 boot spm busy avr boot 102 boot spm busy wait avr boot 102 boot spm interrupt disable avr boot 103 boot spm interrupt enable avr boot 103 BOOTLOADER SECTION avr boot 103 bsearch avr stdlib 76 calloc avr stdlib 77 cbi deprecated items 187 ceil avr_math 34 clearerr avr stdio 61 cli avr interrupts 136 clock prescale set power h 257 Combining C and assembly source files 191 copysign avr math 34 cos avr_math 34 co
20. 6 10 4 27 long strtol const char x mnptr char xx endptr int base The strtol p 82 function converts the string in nptr to a long value The conversion is done according to the given base which must be between 2 and 36 inclusive or be the special value 0 The string may begin with an arbitrary amount of white space as determined by isspace p 19 followed by a single optional 2 or sign If base is zero or 16 the string may then include a 0x prefix and the number will be Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 83 read in base 16 otherwise a zero base is taken as 10 decimal unless the next character is 20 in which case it is taken as 8 octal The remainder of the string is converted to a long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 B represents 11 and so forth with Z representing 35 If endptr is not NULL strtol p 82 stores the address of the first invalid character in endptr If there were no digits at all however strtol p 82 stores the original value of nptr in endptr Thus if nptr is not 0 but endptr is 0 on return the entire string was valid The strtol p 82 function returns the result of the conversion unless the value would underflow or overflow If
21. 88 87 86 25 84 83 82 81 80 Tf Te 7d Tc 7b 00000026 26 28 2a 2c 2e 30 11 if cf d4 de cd 00000032 32 34 36 38 3a 3c 10 a0 bo e6 f1 02 0000003e 3e 40 05 od cO rjmp cO rjmp c0 rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp cO rjmp lt __ctors_end gt 24 eor be out e5 ldi e0 ldi bf out bf out 36 A 280 4278 276 274 1272 270 268 74 i 264 4 262 260 H 258 256 254 252 5 250 f 248 246 i ri ri 0x3f ri 63 r28 Ox5F 9 r29 0x04 4 lt __do_copy_data gt e0 ldi e6 ldi e0 ldi e2 ldi e0 ldi co rjmp lt do_copy_data 90 lpm 92 st X Ox3e r29 62 Ox3d r28 61 r17 0x00 0 r26 0x60 96 r27 0x00 0 r30 0x26 38 r31 0x01 1 4 0x42 lt do_copy_data_start gt _loop gt r0O Z ro 00000042 lt do_copy_data_start gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen debug_pubnames 00000035 00000000 00000000 000001ba 2 0 DEBUGGING 00000000 000001ef DEBUGGING 00000000 000002f4 DEBUGGING 00000000 000003c3 DEBUGGING 00000000 0000050c DEBUGGING 00000000 0000054c DEBUGGING 0x26 lt __ctors_end gt Oxtic Oxtic Oxtic Oxtic Oxtic Oxtic Oxtic lt __bad_interrupt gt lt __bad_interrupt
22. ACK returned 6 31 2 18 define TW SR DATA NACK 0x88 data received NACK returned Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 31 lt util twi h gt TWI bit mask definitions 185 6 31 2 19 define TW SR GCALL ACK 0x70 general call received ACK returned 6 31 2 20 define TW_SR_GCALL_DATA_ACK 0x90 general call data received ACK returned 6 31 2 21 define TW SR GCALL DATA NACK 0x98 general call data received NACK returned 6 31 2 22 define TW SR SLA _ ACK 0x60 SLA W received ACK returned 6 31 2 23 define TW SR STOP OxA0 stop or repeated start condition received while selected 6 31 2 24 define TW ST ARB LOST SLA _ ACK 0xBO arbitration lost in SLA RW SLA R received ACK returned 6 31 2 25 define TW ST DATA ACK 0xB8 data transmitted ACK received 6 31 2 26 define TW ST DATA NACK 0xCO data transmitted NACK received 6 31 2 27 define TW ST LAST DATA 0xC8 last data byte transmitted ACK received 6 31 2 28 define TW ST SLA ACK 0xA8 SLA R received ACK returned 6 31 2 29 define TW START 0x08 start condition transmitted Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 32 lt compat deprecated h gt Deprecated items 186 6 31 2 30 define TW STATUS TWSR amp TW STATUS MASK TWSR masked by TW STATUS MASK 6 31 2 31 define TW STATUS MASK Value _BV TWS7 _BV TWS6 I BV TWS5 _BV TWS4 _BV TWS3 The lower 3 bits of TWSR are reserved on the ATmegal63 T
23. AT90CAN32 AT90CAN64 ATmega128 AT megal284P ATmegal62 ATmega64 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P AT mega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT mega1281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmegal6 ATmega32 ATmega323 ATmega8 AT90PWM3 AT90PWM2 AT90PWM1 ATmegal68P AT mega3250 ATmega3250P AT mega328P ATmega3290 AT mega3290P ATmega48P AT mega6450 ATmega6490 AT mega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATtiny2313 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 134 USART Tx ATmegal6 ATmega32 ATmega323 Complete ATmega8 USART Tx AT90PWM3 AT90PWM2 Complete AT90PWMI ATmegal68P AT mega328P ATmega48P ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATtiny2313 USART USART Data AT90PWM3 AT90PWM2 UDRE_vect _ Register AT90PWM1 ATmegal6 AT Empty megal68P ATmega32 ATmega323 ATmega3250 ATmega3250P AT mega328P ATmega3290 AT mega3290P ATmega48P AT mega6450 ATmega6490 ATm
24. ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER2 SIG Timer Counter2 ATmegal68 ATmega48 ATmega88 COMPA OUTPUT Compare ATmega640 ATmega1280 AT vect COMPARE2A Match A megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMER2 Timer Counter2 ATmegal68 ATmega48 ATmega88 COMPB ATmega640 ATmega1280 AT vect megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 129 z E AT9058535 COMP vect OUTPUT AT90CAN128 AT90CAN32 COMPARE2 AT90CAN64 ATmegal03 AT megal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 AT megal65 ATmegal65P ATmegal69 ATmegal69P ATmega32 AT mega323 ATmega325 ATmega3250 ATmega3250P ATmega329 AT mega3290 ATmega3290P ATmega64 ATmega645 ATmega6450 AT mega649 ATmega6490 ATmega8 ATmega8535 TIMER2 SIG Timer Counter2 AT90S4434 AT9088535 OVF vect OVERFLOW2 Overflow AT90CAN128 AT90CAN32 AT90CAN64 ATmega103 AT megal28 ATmegal284P ATmegal6 ATmegal61 ATmegal62 AT megal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 AT megal69P ATmega32 ATmega323 ATmega325 ATmega3250 AT mega3250P ATmega328P AT mega329 ATmega3290 AT
25. Bootloader Support Utilities 97 The strupr p 96 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 p 96 function returns a pointer to the converted string The pointer is the same as that passed in since the operation is perform in place 6 12 lt avr boot h gt Bootloader Support Utilities 6 12 1 Detailed Description include lt avr io h gt include lt avr boot h gt The macros in this module provide a C language interface to the bootloader support functionality of certain AVR processors These macros are designed to work with all sizes of flash memory Global interrupts are not automatically disabled for these macros It is left up to the programmer to do this See the code example below Also see the processor datasheet for caveats on having global interrupts enabled during writing of the Flash Note Not all AVR processors provide bootloader support See your processor datasheet to see if it provides bootloader support Todo From email with Marek On smaller devices all except ATmega64 128 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 API Usage Example The following code shows typical usage of the boot API include lt inttypes h gt include lt avr
26. PRIxFAST32 avr inttypes 27 PRIXFASTS8 avr inttypes 27 PRIxFAST8 avr inttypes 27 PRIXLEAST16 avr inttypes 27 PRIxLEAST16 avr inttypes 27 PRIXLEAST32 avr inttypes 28 PRIxLEAST32 avr inttypes 28 PRIXLEASTS8 avr inttypes 28 PRIxLEAST8 avr inttypes 28 PRIXPTR avr inttypes 28 PRIxPTR avr inttypes 28 prog char avr pgmspace 147 prog intl6 t avr pgmspace 147 prog int32 t avr pgmspace 147 prog int64 t avr pgmspace 147 prog int8 t avr pgmspace 148 prog uchar avr pgmspace 148 prog uintl6 t avr pgmspace 148 prog uint32 t avr pgmspace 148 prog uint64 t avr pgmspace 148 prog uint8 t avr pgmspace 148 prog void avr pgmspace 148 PROGMEM avr pgmspace 147 PSTR avr pgmspace 147 PTRDIFF MAX avr stdint 48 PTRDIFF MIN avr stdint 48 putc avr stdio 60 putchar avr stdio 60 puts avr stdio 64 puts P avr stdio 64 qsort avr stdlib 80 quot div t 232 ldiv t 233 rand avr stdlib 80 RAND MAX avr stdlib 75 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 396 INDEX rand_r avr stdlib 80 random avr stdlib 80 RANDOM MAX avr stdlib 75 random r avr stdlib 81 realloc rem reti avr stdlib 81 div t 232 Idiv_t 233 avr interrupts 138 round sbi avr math 38 deprecated items 189 scanf avr stdio 65 scanf_P avr stdio 65 SCNd16 avr inttypes 28 SCNd32 avr inttypes 28 SCNdFAST
27. RAMEND for devices that do not allow for external RAM e E2END A constant describing the address of the last EEPROM cell FLASHEND A constant describing the last byte address in flash ROM e SPM PAGESIZE For devices with bootloader support the flash pagesize in bytes to be used for the SPM instruction 6 17 lt avr lock h gt Lockbit Support Introduction The Lockbit API allows a user to specify the lockbit settings for the specific AVR device they are compiling for These lockbit settings will be placed in a special section in the ELF output file after linking Programming tools can take advantage of the lockbit information embedded in the ELF file by extracting this information and determining if the lockbits need to be programmed after programming the Flash and EEPROM memories This also allows a single ELF file to contain all the information needed to program an AVR To use the Lockbit API include the lt avr io h p 247 gt header file which in turn automatically includes the individual I O header file and the lt avr lock h p 247 gt file These other two files provides everything necessary to set the AVR lockbits Lockbit API Each I O header file may define up to 3 macros that controls what kinds of lockbits are available to the user If LOCK BITS EXIST is defined then two lock bits are available to the user and 3 mode settings are defined for these two bits If BOOT LOCK BITS 0 EXIST is defined then
28. TIMERO_ TimerCounter0 ATmegal68 ATmega48 ATmega88 COMPA _ Compare ATmega640 ATmega1280 AT vect COMPAREOA Match A megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 AT tiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 123 k Timer Counter AT90PWM3 AT90PWM2 OUTPUT 0 Compare AT90PWM1 ATmegal284P AT COMPAREOB Match B megal68P ATmega328P AT SIG mega32HVB ATmega48P AT OUTPUT mega88P ATmegal68 ATmega48 COMPAREO ATmega88 ATmega640 AT B mega1280 ATmegal1281 AT mega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT megal6HVA ATtiny2313 AT tiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Timer Counter0 AT90PWM3 OUTPUT AT90PWM1 COMPAREOAI Match A SIG OUTPUT COMPAREO A TIMERO SIG Timer Counter0 AT90CAN128 AT90CAN32 COMP vect OUTPUT AT90CAN64 ATmega103 AT COMPAREO megal28 ATmegal6 ATmegal61 ATmegal62 ATmegal65 AT megal65P ATmegal69 ATmegal69P ATmega32 ATmega323 ATmega325 ATmega3250 ATmega3250P ATmega329 ATmega3290 AT mega3290P ATmega64 ATmega645 ATmega6450 ATmega649 AT mega6490 ATmega8515 ATmega8535 TIMERO SIG
29. The strrchr p 95 function returns a pointer to the matched character or NULL if the character is not found 6 11 3 31 char x strrev char s Reverse a string The strrev p 95 function reverses the order of the string Returns The strrev p 95 function returns a pointer to the beginning of the reversed string 6 11 3 32 char x strsep char xx sp const char x delim Parse a string into tokens The strsep p 95 function locates in the string referenced by sp the first occurrence of any character in the string delim or the terminating 0 char acter 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 xsp to 0 Returns The strsep p 95 function returns a pointer to the original value of sp If xsp is initially NULL strsep p 95 returns NULL Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 96 6 11 3 33 size_t strspn const char s const char accept The strspn p 96 function calculates the length of the initial segment of s which consists entirely of characters in accept Returns The strspn p 96 function returns the number of characters in the initial segm
30. avr watchdog 169 WDTO 85 avr watchdog 169 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 403
31. char x s const char x __fmt Variant of sprintf p 66 that uses a fmt string that resides in program memory 6 9 3 29 int sscanf const char x __ buf const char __ fmt The function sscanf performs formatted input reading the input data from the buffer pointed to by buf See vfscanf p 70 for details 6 9 3 30 int sscanf P const char __ buf const char __ fmt Variant of sscanf p 66 using a fmt string in program memory 6 9 3 31 int ungetc int c FILE stream The ungetc p 66 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 p 66 function returns the character pushed back after the con version or EOF if the operation fails If the value of the argument c character equals EOF the operation will fail and the stream will remain unchanged 6 9 3 32 int vfprintf FILE x stream const char x __ fmt va_list __ ap Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 67 vfprintf is the central facility of the printf family of functions It outputs values to stream under control of a format string passed in fmt The actual values to print are passed as a variable argument list ap vfprintf returns the
32. ctype 19 trunc avr_math 39 TW_BUS_ERROR util_ twi 183 TW MR ARB LOST til twi 183 TW MR DATA ACK til twi 183 TW MR DATA NACK util twi 183 TW MR SLA ACK s s 400 util_twi 183 TW MR SLA NACK til twi 183 TW MT ARB LOST til twi 183 TW MT DATA ACK til twi 183 TW MT DATA NACK util twi 184 TW MT SLA ACK util twi 184 TW MT SLA NACK util_ twi 184 TW NO INFO util_ twi 184 TW_READ util_ twi 184 TW_REP_ START util_ twi 184 TW SR ARB LOST GCALL ACK util twi 184 TW SR ARB LOST SLA ACK util_ twi 184 TW_SR_DATA ACK util_ twi 184 TW SR DATA NACK util twi 184 TW_SR_GCALL_ACK util_ twi 184 TW SR GCALL DATA ACK util_ twi 185 TW SR GCALL DATA NACK util_ twi 185 TW_SR_SLA_ACK util_ twi 185 TW_SR_STOP util_ twi 185 TW ST ARB LOST SLA ACK util_ twi 185 TW ST DATA ACK util_ twi 185 TW ST DATA NACK util_ twi 185 TW_ST_LAST DATA util_ twi 185 s s s Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX TW ST SLA ACK util twi 185 TW START util twi 185 TW_STATUS util_ twi 185 TW STATUS MASK util twi 186 TW WRITE util twi 186 twi h 269 UBRR VALUE util setbaud 181 UBRRH VALUE util setbaud 181 UBRRL VALUE util setbaud 181 UINT16_C avr stdint 48 UINT16 MAX avr stdint 48 uint16 t avr stdint 51 UINT32 C avr stdint 48 UINT32 MAX avr stdint 48 uint32 t avr stdint 51 UINT64 C avr stdint 48 UINT64 MAX avr stdin
33. e define SCNi32 li e define SCNiLEAST32 li e define SCNiFAST32 li e define SCNdPTR SCNd16 e define SCNiPTR SCNi16 e define SCNo16 o e define SCNoLEAST16 o e define SCNoFAST16 o e define SCNu16 u e define SCNuLEAST16 u e define SCNuFASTI16 u e define SCNx16 x e define SCNxLEASTI16 x e define SCNxFAST16 x e define SCNo32 lo e define SCNoLEAST32 lo e define SCNoFAST32 lo e define SCNu32 lu e define SCNuLEAST32 lu e define SCNuFAST32 lu e define SCNx32 lx e define SCNxLEAST32 Ix e define SCNxFAST32 lx e define SCNoPTR SCNo16 e define SCNuPTR SCNul6 e define SCNxPTR SCNx16 6 5 2 Define Documentation 6 5 2 1 define PRId16 d decimal printf format for int16 t 6 5 2 2 define PRId32 ld decimal printf format for int32 t 6 5 2 3 define PRId8 d decimal printf format for int8 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 24 6 5 2 4 define PRIdFAST16 d decimal printf format forint fastl6 t 6 5 2 5 define PRIdFAST32 Id decimal printf format for int fast32 t 6 5 2 6 define PRIdFASTS d decimal printf format for int fast8 t 6 5 2 7 define PRIGLEAST16 d decimal printf format for int leastl6 t 6 5 2 8 define PRIGLEAST32 Id decimal printf format for int least32 t 6 5 2 9 define PRIdLEASTS d decimal printf format for int least8
34. n t out KO L n t out __SREG__ __tmp_reg__ n t NY out 40 42 no outputs I _SFR_IO_ADDR _WD_CONTROL_REG r _BV _WD_CHANGE_BIT _BV WDE r uint8_t value amp 0x08 _WD_PS3_MASK 0x00 _BV WDE value amp 0x07 ro Enable the watchdog timer configuring it for expiry after timeout which is a combination of the WDPO through WDP2 bits to write into the WDTCR register For those devices that have a WDTCSR register it uses the combination of the WDPO through WDP3 bits See also the symbolic constants WDTO_15MS et al 6 24 2 3 define wdt reset asm volatile wdr Reset the watchdog timer When the watchdog timer is enabled a call to this instruction is required before the timer expires otherwise a watchdog initiated device reset will occur 6 24 2 4 define WDTO 120MS 3 See WDTO_15MS Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 24 lt avr wdt h gt Watchdog timer handling 168 6 24 2 5 define WDTO 15MS 0 Symbolic constants for the watchdog timeout Since the watchdog timer is based on a free running RC oscillator the times are approximate only and apply to a supply voltage of 5 V At lower supply voltages the times will increase For older devices the times will be as large as three times when operating at Vcc 3 V while the newer devices e g ATmegal28 ATmega8 only experience a negligible change Possible timeout va
35. pwm_incoming is used to communicate the most recent pulse width detected by the incoming PWM decoder up to the main loop The second variable actually only constitutes of a single bit intbits pwm_ received This bit will be set whenever the incoming PWM decoder has up dated pwm_incoming Both variables are marked volatile to ensure their readers will always pick up an updated value as both variables will be set by interrupt service routines The function ioinit initializes the microcontroller peripheral devices In particular it starts timer 0 to generate the outgoing PWM signal on OCOB Setting OCROA to 255 which is the TOP value of timer 0 is used to generate a timer 0 overflow A interrupt on the ATtiny13 This interrupt is used to inform the incoming PWM decoder that the counting direction of channel 0 is just changing from up to down Likewise an overflow interrupt will be generated whenever the countdown reached BOTTOM value 0 where the counter will again alter its counting direction to upwards This information is needed in Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 35 Combining C and assembly source files 193 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 set
36. rather than the function like fdev setup stream p 60 so all data ini tialization 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 p 59 and then destroying the object itself No call to fclose p 62 should be issued for these streams While calling fclose p 62 itself is harmless it will cause an undefined reference to free p 78 and thus cause the linker to link the malloc module into the application Notes Note 1 It might have been possible to implement a device abstraction that is com patible with fopen but since this would have required to parse a string and to take all the information needed either out of this string or out of an additional table that would need to be provided by the application this approach was not taken Note 2 This basically follows the Unix approach if a device such as a terminal needs special handling it is in the domain of the terminal device driver to provide this functionality Thus a simple function suitable as put for fdevopen p 62 that talks to a UART interface might look like this Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 57 int uart_putchar char c FILE stream if c n uart_putchar r loop_until_bit_is_set UCSRA UDRE UDR c return 0 Note 3 This implementation has been ch
37. terminating 0 character to the array pointed to by dest The strings may not overlap and the destination string dest must be large enough to receive the copy Returns The strepy p 91 function returns a pointer to the destination string dest Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 92 Note If the destination string of a strepy p 91 is not large enough that is if the programmer was stupid lazy and failed to check the size before copying then anything might happen Overflowing fixed length strings is a favourite cracker technique 6 11 3 19 size_t strcspn const char s const char reject The strespn p 92 function calculates the length of the initial segment of s which consists entirely of characters not in reject Returns The strcspn p 92 function returns the number of characters in the initial segment of s which are not in the string reject The terminating zero is not considered as a part of string 6 11 3 20 size_t strlcat char dst const char src size_t siz Concatenate two strings Appends src to string dst of size siz unlike strncat p 93 siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat p 92 function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 6 1
38. typedef int16 t PROGMEM prog int16 t typedef uint16 t PROGMEM prog uint16 t typedef int32 t PROGMEM prog int32 t typedef uint32 t PROGMEM prog uint32 t typedef int64 t PROGMEM prog int64 t typedef uint64 t PROGMEM prog uint64 t Functions e PGM VOID P memchr P PGM VOID P int val size_t len e int memcmp P const void x PGM VOID P size_t ATTR PURE e void x memcpy P void x PGM VOID P size_t e PGM VOID Pmemrchr P PGM VOID P int val size_t len int strcasecmp P const char x PGM P ATTR PURE char strcat P char x PGM P PGM Pstrchr P PGM P int __ val PGM Pstrchrnul P PGM P int __ val int stremp P const char PGM P ATTR PURE Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 145 e char strepy P char x PGM P e size_t strcspn_P const char x__s PGM_P __ reject _ ATTR_ PURE__ size_t strlcat__P char x PGM P size_t size tstrlepy P char x PGM P size_t size_t strlen P PGM P int strncasecmp P const char PGM P size_t ATTR PURE char x strncat P char x PGM P size_t int strncmp P const char x PGM P size_t ATTR PURE char strnepy P char x PGM P size_t size_t strnlen_ P PGM P size_t char strpbrk P const char x__s PGM_P accept ATTR PURE PGM Pstrrchr P PGM_P int val e char strsep P char __ sp PGM_P __ delim size_t strspn P const char x__s PGM_P
39. void e void srandom unsigned long __ seed e long random r unsigned long ___ ctx e char x itoa int __ val char __s int radix e define RANDOM MAX Ox7FFFFFFF Conversion functions for double arguments Note that these functions are not located in the default library libc a but in the mathematical library libm a So when linking the application the 1m option needs to be specified e char dtostre double val char s unsigned char ___ prec un signed char flags e char x dtostrf double val signed char width unsigned char __ prec char xs e define DTOSTR ALWAYS SIGN 0x01 e define DTOSTR PLUS SIGN 0x02 e define DTOSTR UPPERCASE 0x04 Defines e define RAND MAX Ox7FFF Typedefs e typedef int compar fn t const void const void Functions void abort void ATTR NORETURN__ int abs int __i long labs long __i void x bsearch const void key const void base size_t __ nmemb size_t size int x__ compar const void const void Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 75 e div_t div int num int __denom asm divmodhi4 e Idiv_t Idiv long num long denom asm divmodsi4 e void qsort void base size_t __nmemb size_t size compar fn t __ compar e long strtol const char x___nptr char x__endptr int base e unsigned long strtoul const char x nptr char xx endptr int __ ba
40. 11 3 Function Documentation 6 11 3 1 int ffs int val This function finds the first least significant bit set in the input value Returns The ffs p 87 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 p 86 macro instead 6 11 3 2 int ffsl long val Same as ffs p 87 for an argument of type long 6 11 3 3 int ffsll long long val Same as ffs p 87 for an argument of type long long 6 11 3 4 void x memccpy void x dest const void src int val size_t len Copy memory area The memccpy p 87 function copies no more than len bytes from memory area src to memory area dest stopping when the character val is found Returns The memccpy p 87 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 88 6 11 3 5 void memchr const void src int val size_t len Scan memory for a character The memchr p 88 function scans the first len bytes of the memory area pointed to by src for the character val The first byte to match val interpreted as an unsigned character stops the operation Returns The memchr p 88 function
41. 155 122 122 2 221 1184 1072 17 1313 1676 1564 36 1608 150 150 4 1172 220 220 9 3174 554 554 4 196 1553 38 20914 1216 1130 1674 3334 1540 1950 1950 3298 1570 942 830 29 1074 315 ri A 1040 1042 932 990 880 1104 1090 980 59 1846 1562 1542 1432 58 1610 3222 3084 2974 66 2513 1428 1354 1244 55 1339 1838 1704 1594 53 1334 1838 1704 1594 87 2878 3186 2934 2824 63 2187 1458 1472 1362 22 1237 874 764 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 149 A 118 Er 978 159 i 1438 DE r 134 je OG 200 ne 506 in 198 932 sa ae 898 rate 1086 59 1711 1498 58 1528 3040 66 2297 1354 55 1240 1704 53 1235 1704 87 2718 2918 63 1833 ig I 976 1388 ee 698 p 9 8 Benchmarks 316 9 8 2 Math functions The table contains the number of MCU clocks to calculate a function with a given argument s The main reason of a big difference between Avr2 and Avr4 is a hardware multiplication addsf3 1 234 13 108 saa gt NK I mulsf3 1 234 375 138 sa Eg 466 465 divsf3 1 234 5 678 atan 1234 5078 1665 max 1 251 1075 exp 12345 0 idexp 1 2345 6 fan 1995 nd E tanh 1 2549 3173 E trunc 1 2345 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen
42. 6 29 lt util parity h gt Parity bit generation 179 6 29 lt util parity h gt Parity bit generation 6 29 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 e define parity even bit val 6 29 2 Define Documentation 6 29 2 1 define parity even bit val Value __extension__ unsigned char __t __asm__ mov __tmp_reg__ 40 n t swap go n t eor 0 __tmp_reg__ n t mov __tmp_reg__ 40 n t Isr 70 n t Isr 70 n t eor 40 __tmp_reg__ Way __t 0 unsigned char val ro Ut 1 gt gt 1 amp 1 H Returns 1 if val has an odd number of bits set 6 30 lt util setbaud h gt Helper macros for baud rate cal culations 6 30 1 Detailed Description define F_CPU 11059200 define BAUD 38400 include lt util setbaud h gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 30 lt util setbaud h gt Helper macros for baud rate calculation 80 This header file requires that on entry values are already defined for F_ CPU and BAUD In addition the macro BAUD_ TOL will define the baud rate tolerance in percent that is acceptable during the calculations The value of BAUD_ TOL will default to 2 This header file defines macros suitable to setup the UART baud rate prescaler registers of an AVR All calculations are do
43. 6 5 2 27 define PRIOLEAST16 o octal printf format for uint_least16_t 6 5 2 28 define PRIoLEAST32 lo octal printf format for uint least32 t 6 5 2 29 define PRIOLEASTS8 o octal printf format for uint least8 t 6 5 2 30 define PRIoPTR PRIo16 octal printf format for uintptr_t 6 5 2 31 define PRIu16 u decimal printf format for uint16 t 6 5 2 32 define PRIu32 lu decimal printf format for uint32 t 6 5 2 33 define PRIu8 u decimal printf format for uint8 t 6 5 2 34 define PRIuFASTI16 u decimal printf format for uint_fast16_t 6 5 2 35 define PRIuFAST32 lu decimal printf format for uint fast32 t 6 5 2 36 define PRIuFASTS8 u decimal printf format for uint fast8 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 27 6 5 2 37 define PRIuLEASTI16 u decimal printf format for uint least16 t 6 5 2 38 define PRIuLEAST32 lu decimal printf format for uint least32 t 6 5 2 39 define PRIuLEAST8 u decimal printf format for uint least8 t 6 5 2 40 define PRIuPTR PRIu16 decimal printf format for uintptr_t 6 5 2 41 define PRIX16 X uppercase hexadecimal printf format for uint16 t 6 5 2 42 define PRIx16 x hexadecimal printf format for uint16 t 6 5 2 43 define PRIX32 IX uppercase hexadecimal printf format for uint32 t 6 5 2 44 define PRIx32 Ix hexadecimal printf format for
44. 77 define SCNoFAST16 o octal scanf format for uint_fast16_t 6 5 2 78 define SCNoFAST32 lo octal scanf format for uint fast32 t 6 5 2 79 define SCNoLEASTI16 o octal scanf format for uint_least16_t 6 5 2 80 define SCNoLEAST32 lo octal scanf format for uint least32 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 31 6 5 2 81 define SCNoPTR SCNo16 octal scanf format for uintptr_t 6 5 2 82 define SCNu16 u decimal scanf format for uint16 t 6 5 2 83 define SCNu32 lu decimal scanf format for uint32_t 6 5 2 84 define SCNuFASTI16 u decimal scanf format for uint fast16 t 6 5 2 85 define SCNuFAST32 lu decimal scanf format for uint fast32 t 6 5 2 86 define SCNuLEAST16 u decimal scanf format for uint leastl6 t 6 5 2 87 define SCNuLEAST32 lu decimal scanf format for uint least32 t 6 5 2 88 define SCNuPTR SCNu16 decimal scanf format for uintptr t 6 5 2 89 define SCNx16 x hexadecimal scanf format for uint16_t 6 5 2 90 define SCNx32 lx hexadecimal scanf format for uint32_t 6 5 2 91 define SCNxFAST16 x hexadecimal scanf format for uint fastl6 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 32 6 5 2 92 define SCNxFAST32 lx hexadecimal scanf format for uint fast32 t 6 5 2 93 define SCNxLEASTI16 x hexadecimal scanf form
45. 9 9 Porting From IAR to AVR GCC 317 9 9 Porting From IAR to AVR GCC 9 9 1 Introduction C language was designed to be a portable language There two main types of porting activities porting an application to a different platform OS and or pro cessor 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 Routines 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 applica tion built with the IAR compiler to the GNU toolchain AVR GCC Note that this may not be an exhaustive list 9 9 2 Registers IO header files contain identifiers for all the register names and bit names for a particular processor TAR has individual header files for each processor and they must be included when registers are being used in the code For example include lt iom169 h gt Note IAR does not always use the same register names or bit names that are used in the AVR datasheet AVR GCC also has individual IO header files for each processor However the actual processor type is specified as a command line flag to the compiler Using the mmcu processor flag This is usually done in the Makefile This allows you to spec
46. AT mega6490 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Analog Com AT90S1200 AT9052313 AT9052333 COMPARATQRparator AT9084414 AT90S4433 AT90S4434 AT9088515 AT90S8535 ATmegal6 ATmegal61 ATmegal62 AT megal63 ATmega32 ATmega323 ATmega8 ATmega8515 AT mega8535 ATtiny11 ATtiny12 ATtiny13 ATtinyl5 ATtiny2313 ATtiny26 ATtiny28 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 SIG CAN Transfer AT90CAN128 AT90CAN32 CAN Complete or AT90CAN64 INTERRUPT Error SIG_ ATtiny2313 EEPROM READY SIG EE je EEPROM AT9052333 AT9054433 AT9054434 EEPROM Ready AT90S58535 ATmegal6 ATmegal61 READY ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 ATmega8515 ATmega8535 ATtinyl2 ATtiny13 ATtiny15 ATtiny26 ATtiny43U AT tiny48 ATtiny24 ATtiny44 AT tiny84 ATtiny45 ATtiny25 AT tiny85 ATtiny261 ATtiny461 AT tiny861 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts A EEPROM EEPROM Ready READY 116 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 AT megal03 ATmegal28 ATmegal284P ATmegal65 ATmegal65P AT megal68P ATmegal69 ATmegal69P AT
47. ATtiny461 ATtiny861 pawratdadorenvele Gun 11 11 donebledbe f r lvnabdey Doxypeega169 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 power led disable power psc0 enable Disable the LCD module Enable the Power Stage Controller 0 module ATmegal69 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 AT90PWMI AT90PWM2 AT90PWM2B PERE JE ANE REZA 157 6 20 Additional notes from lt avr sfr defs h gt 158 Some of the newer AVRs contain a System Clock Prescale Register CLKPR that allows you to decrease the system clock frequency and the power consump tion when the need for processing power is low Below are two macros and an enumerated type that can be used to interface to the Clock Prescale Register Note Not all AVR devices have a Clock Prescale Register On those devices without a Clock Prescale Register these macros are not available typedef enum 1 clock_div_1 clock_div_2 clock_div_4 clock_div_8 clock_div_16 clock_div_32 clock_div_64 clock_div_128 clock_div_256 clock div t TE gt Hood Ao pe 2 7 8 o Clock prescaler setting enumerations clock_prescale_set x Set the clock prescaler register select bits selecting a system clock division setting They type of x is clock div t clock prescale get Gets and returns the clock prescaler register setting The return type is clock div t 6 20 Additional notes from lt avr sfr defs h gt
48. 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 37 A more sophisticated project 216 input value on PCO VAREF on the STK500 should be set to the same value as VCC When running in serial control mode the function of the watchdog timer can be demonstrated by typing an r This will make the demo application run in a tight loop without retriggering the watchdog so after some seconds the watchdog will reset the MCU This situation can be figured out on startup by reading the MCUCSR register The current value of the PWM is backed up in an EEPROM cell after about 3 seconds of idle time after the last change If that EEPROM cell contains a reasonable i e non erased value at startup it is taken as the initial value for the PWM This virtually preserves the last value across power cycles By not updating the EEPROM immmediately but only after a timeout EEPROM w
49. Memory Use the PROGMEM macro found in lt avr pgmspace h p 250 gt and put it after the declaration of the variable but before the initializer like so include lt avr pgmspace h gt unsigned char mydata 11 10 PROGMEM 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0xOF 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F 0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F 10x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x597 10x5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x637 10x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D 3 That s it Now your data is in the Program Space You can compile link and check the map file to verify that mydata is placed in the correct section Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 4 Data in Program Space 289 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 t
50. Note It has been ported to windows via MinGW or cygwin Linux and Solaris Other Unix systems should be trivial to port to avrdude is part of the FreeBSD ports system To install it simply do the following cd usr ports devel avrdude make install Note Installation into the default location usually requires root permissions However running the program only requires access permissions to the ap propriate ppi 4 device Building and installing on other systems should use the configure system as such gunzip c 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 9 11 8 GDB for the AVR target GDB also uses the configure system so to build and install bunzip2 c gdb lt version gt tar bz2 tar xf cd gdb lt version gt mkdir obj avr cd obj avr configure prefix PREFIX target avr make make install Note If you are planning on using avr gdb you will probably want to install either simulavr p 352 or avarice p 352 since avr gdb needs one of these to run as a a remote target backend Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 352 9 11 9 SimulAVR SimulAVR also uses the configure system so to build and install gunzip c simulavr lt version gt tar gz tar xf cd simulavr lt version gt
51. P PGM VOID P int __val size_t len u char strcat P char x PGM_P PGM_P strchr_P PGM_P int val PGM_P strchrnul_P PGM_P int __ val int stremp P const char x PGM_P ATTR PURE char strepy P char x PGM P int strcasecmp P const char x PGM P ATTR PURE char strcasestr P const char x PGM P ATTR PURE size_t strcspn P const char s PGM P __ reject ATTR PURE 5 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference 252 size_t strleat_P char x PGM P size_t size_t strlepy_ P char x PGM P size_t size_t strlen P PGM P size_t strnlen_P PGM_P size_t int strncmp P const char x PGM P size_t ATTR PURE int strncasecmp P const char PGM P size_t ATTR PURE char strncat P char x PGM P size_t e char strnepy P char x PGM P size_t e char strpbrk P const char s PGM P __ accept ATTR PURE e PGM Pstrrchr P PGM P int __ val e char strsep P char __ sp PGM_P __ delim e size_t strspn P const char x__s PGM_P accept ATTR PURE e char strstr P const char x PGM P ATTR PURE 8 34 2 Define Documentation 8 34 2 1 define ELPM classic _ addr Value __extension__ uint32_t __addr32 uint32_t addr uint8_t __result __asm__ out 2 AC1 n t mov r31 B1i n t mov r30 A1 n t elpm n t mov 40 ro n t r __resu
52. Reference 2 000004 258 sleep h File Reference 02 0 002004 258 stdint h File Reference LL arv rv vr vnr rn nr kn 259 stdio h File Reference evrnr eva rv 0000004 262 stdlib h File Reference 2 0 0 0 263 strcasecmp S File Reference rar vr vr rann av 266 strcaseemp P S File Reference 0 0 0 266 streasestr S File Reference 00 4 266 streat S File Reference 2 00200000004 266 streat FS File Reference aa 6 boba ka bee M 266 strchr S File Reference 02005020004 266 strchr_P 5 File Reference 0 0 266 strchrnul S File Reference _ 0 0 266 strchrnul P S File Reference o cocca aoad aiii a aT A 266 stremp S File Reference 0 0 266 stremp_ P S File Reference ee ass 4 ek ee sals 266 strepy S File Reference 0 266 strepy P S File Reference 0 0 0 266 strespn S File Reference 0 266 strespn P S File Reference a ab b bad kk wrr at k ri 266 string h File Reference 0 0 266 strleat S File Reference 00 0 269 strleat P S File Reference 0 05 4 6 6 gl a A s 269 strlepy S File Reference 00 0 269 strlepy P S File Reference 0 269 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen CONTENTS 9 8 62 strlen S File Reference 022 005 8 63 strlen P S File Reference sa s vuy rohaka ira EAE aaa 8 6
53. 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_I08 0x02 define EEAR _SFR_1016 0x21 define UDRO _SFR_MEM8 0xC6 define TCNT3 _SFR_MEM16 0x94 define CANIDT SFR MEM32 0xFO Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 20 Additional notes from lt avr sfr_ defs h gt 159 If _SFR_ASM_COMPAT is not defined C programs can use names like PORTA di rectly in C expressions also on the left side of assignment operators and GCC will do the right thing use short 1 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 addresses of the I O registers This is necessary when included in preprocessed assembler S source files so it is done automatically if __ASSEMBLER__ is defined By default all addresses are defined as if they were memory addresses used in 1ds 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 assembler source file define __SFR_OFFSET 0 This automatically subtra
54. The function isinf p 37 returns I if the argument _ lt is positive infinity l if __x is negative infinity and 0 otherwise 6 6 3 21 int isnan double _ The function isnan p 37 returns 1 if the argument __ x represents a not a number NaN object otherwise 0 6 6 3 22 double Idexp double g int exp The Idexp p 37 function multiplies a floating point number by an integral power of 2 The Idexp p 37 function returns the value of __ x times 2 raised to the power __ exp 6 6 3 23 double log double __ The log p 37 function returns the natural logarithm of argument __ z 6 6 3 24 double log10 double _z The log10 p 37 function returns the logarithm of argument ___x to base 10 6 6 3 25 long lrint double __ The lrint p 37 function rounds __ g to the nearest integer rounding the halfway cases to the even integer direction That is both 1 5 and 2 5 values are rounded to 2 This function is similar to rint function but it differs in type of return value and in that an overflow is possible Returns The rounded long integer value If __z is not a finite number or an overflow was this realization returns the LONG_MIN value 0x80000000 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 38 6 6 3 26 long lround double __ 2 The lround p 38 function rounds __ to the nearest integer but rounds halfway cases away fr
55. The routines feof p 63 or ferror p 63 must be used to distinguish between both situations 6 9 3 8 charx fgets char str int size FILE stream Read at most size 1 bytes from stream until a newline character was en countered and store the characters in the buffer pointed to by str Unless an error was encountered while reading the string will then be terminated with a NUL character If an error was encountered the function returns NULL and sets the error flag of stream which can be tested using ferror p 63 Otherwise a pointer to the string will be returned 6 9 3 9 int fprintf FILE stream const char x __ fmt The function fprintf performs formatted output to stream See vfprintf p 66 for details Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 64 6 9 3 10 int fprintf P FILE x stream const char _ fmt Variant of fprintf p 63 that uses a fmt string that resides in program memory 6 9 3 11 int fputc int c FILE x stream The function fputc sends the character c though given as type int to stream It returns the character or EOF in case an error occurred 6 9 3 12 int fputs const char str FILE x stream Write the string pointed to by str to stream stream Returns 0 on success and EOF on error 6 9 3 13 int fputs P const char str FILE stream Variant of fputs p 64 where str resides in progr
56. This must be applied to an output operand and the respective input operand list remains empty asm volatile mov __tmp_reg__ AO n t mov AO DO n t mov DO __tmp_reg__ n t mov __tmp_reg__ BO n t mov BO CO nyt mov ACO tmp reg n t r value If operands do not fit into a single register the compiler will automatically assign enough registers to hold the entire operand In the assembler code you 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 BO the next byte CO and so on This also implies that it is often neccessary to cast the type of an input operand to the desired size A final problem may arise while using pointer register pairs If you define an input operand e ptr and the compiler selects register Z r30 r31 then Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 306 AO refers to r30 and BO refers to r31 But both versions will fail during the assembly stage of the compiler if you explicitely need Z like in 1d r24 Z If you write ld r24 a0 with a lower case a following the percent sign then the compiler will create the proper assembler line 9 6 4 Clobbers As stated previously the last part of the asm statement the list of clobbers may be omitted including the colon seperator However if you
57. VALUE 181 USE_ 2X 181 util_ twi TW_BUS_ERROR 183 TW MR ARB LOST 183 TW MR DATA ACK 183 TW MR DATA NACK 183 TW MR SLA ACK 183 TW MR SLA NACK 183 TW MT ARB LOST 183 TW MT DATA ACK 183 TW MT DATA NACK 184 TW MT SLA ACK 184 TW MT SLA NACK 184 TW NO INFO 184 TW READ 184 TW REP START 184 402 TW SR ARB LOST GCALL_ ACK 184 TW SR ARB LOST SLA ACK 184 TW SR DATA ACK 184 TW SR DATA NACK 184 TW SR GCALL ACK 184 TW SR GCALL DATA ACK 185 TW SR GCALL DATA NACK 185 TW SR SLA ACK 185 TW SR STOP 185 TW ST ARB LOST SLA ACK 185 TW ST DATA ACK 185 TW ST DATA NACK 185 TW ST LAST DATA 185 TW ST SLA ACK 185 TW START 185 TW STATUS 185 TW STATUS MASK 186 TW WRITE 186 utoa avr stdlib 83 vfprintf avr stdio 66 vfprintf_P avr stdio 69 vfscanf avr stdio 69 vfscanf P avr stdio 72 vprintf avr stdio 72 vscanf avr stdio 72 vsnprintf avr stdio 72 vsnprintf_P avr stdio 72 vsprintf avr stdio 72 vsprintf_P avr stdio 72 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX wdt h 271 wdt_ disable avr watchdog 166 wdt_ enable avr watchdog 167 wdt reset avr watchdog 167 WDTO 120MS avr watchdog 167 WDTO 15MS avr watchdog 167 WDTO_15 avr watchdog 168 WDTO 250MS avr watchdog 168 WDTO 25 avr watchdog 168 WDTO 30MS avr watchdog 168 WDTO 45 avr watchdog 168 WDTO 500MS avr watchdog 168 WDTO 60MS
58. a release A stable release will only be done on a branch not from the cvs HEAD The following steps should be taken when making a release Make sure the source tree you are working from is on the correct branch cvs update r avr libe lt major gt lt minor gt branch Update the package version in configure ac and commit it to cvs Update the gnu tool chain version requirements in the README and commit to cvs Update the ChangeLog file to note the release and commit to cvs on the branch Add Released avr libe lt this release gt Update the NEWS file with pending release number and commit to cvs Change Changes since avr libe lt last release gt to Changes in avr libe lt this relelase gt Bring the build system up to date by running bootstrap and configure Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 14 Release Numbering and Methodology 378 7 Perform a make distcheck and make sure it succeeds This will create the source tarball 8 Tag the release cvs tag avr libe lt major gt lt minor gt lt patch gt release 9 Upload the tarball to savannah 10 Update the NEWS file and commit to cvs Add Changes since avr libe lt major gt lt minor gt 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 re lationships HEAD 1 0 Branch 1 2 B
59. a string in program space Returns The stremp P p 151 function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcmp P p 151 is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 6 18 4 12 char x strcpy_P char dest PGM_P src The strcpy_P p 151 function is similar to strepy p 91 except that src is a pointer to a string in program space Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 152 Returns The strepy P p 151 function returns a pointer to the destination string dest 6 18 4 13 size_t strcspn_P const char s PGM P reject The strcspn P p 152 function calculates the length of the initial segment of s which consists entirely of characters not in reject This function is similar to strespn p 92 except that reject is a pointer to a string in program space Returns The strespn_ P p 152 function returns the number of characters in the initial segment of s which are not in the string reject The terminating zero is not considered as a part of string 6 18 4 14 size_t strlcat_P char dst PGM P size_t siz Concatenate two strings The strlcat P p 152 function is similar to strlcat p 92 except that the src string must be located in prog
60. activated by the compiler as early as possible within the ISR to ensure minimal processing delay for nested interrupts This may be used to create nested ISRs however care should be taken to avoid stack overflows or to avoid infinitely entering the ISR for those cases where the AVR hardware does not clear the respective interrupt flag before entering the ISR Use this attribute in the attributes parameter of the ISR macro 6 15 2 10 define reti include lt avr interrupt h gt Returns from an interrupt routine enabling global interrupts This should be the last command executed before leaving an ISR defined with the ISR NAKED attribute This macro actually compiles into a single line of assembly so there is no function call overhead 6 15 2 11 define sei include lt avr interrupt h gt Enables interrupts by setting the global interrupt mask This function actually compiles into a single line of assembly so there is no function call overhead Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 16 lt avr io h gt AVR device specific IO definitions 139 6 15 2 12 define SIGNAL vector include lt avr interrupt h gt Introduces an interrupt handler function that runs with global interrupts ini tially disabled This is the same as the ISR macro without optional attributes Deprecated Do not use SIGNAL p 139 in new code Use ISR p 136 instead 6 16 lt avr io h gt AVR device speci
61. addr ELPM word classic addr 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference 251 e define pgm read byte address short pgm read byte near address short e define pgm read word address short pgm read word near address short u e define pgm read dword address short pgm_read_dword_ near address short e define PGM P const prog char x e 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 uint16 t typedef int32 t PROGMEM prog int32 t typedef uint32 t PROGMEM prog uint32 t typedef int64 t PROGMEM prog int64 t typedef uint64 t PROGMEM prog uint64 t Functions e PGM VOID P memchr P PGM VOID P int val size_t len u e int memcmp P const void x PGM VOID P size_t ATTR_ PURE _ void x memcpy P void x PGM VOID P size_t void x memmem P const void x size_t PGM VOID P size_t _ ATTR PURE e PGM VOID Pmemrchr
62. address r uint16 t data ro A r30 A r31 H 8 5 2 7 define boot page fill extended address data Value __extension__ _ asm__ __volatile__ movw r0 4 n t movw r30 A3 n t sts 1 C3 n t sts 0 2 n t spm n t clr ri n t i _SFR_MEM_ADDR __SPM_REG i _SFR_MEM_ADDR RAMPZ r uint8_t __BOOT_PAGE_FILL r U r U uint32 t address uint16 t data ro r30 r31 H Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen a7 A A FA ZA A ZA LAA A AAP AZ AZZ ZZ FA A AA LAA LA AAA ZA AZZ AZ 238 8 5 boot h File Reference 8 5 2 8 define boot page fill normal address data Value __extension__ _ asm__ __volatile__ movw r0 3 n t movw r30 2 n t sts 0 Zi n t spm n t clr ri n t i _SFR_MEM_ADDR __SPM_REG uint8_t __BOOT_PAGE_FILL i r r uint16_t address r uint16_t data ro A r30 x r31 H 8 5 2 9 define boot page write alternate address Value __extension__ _ asm__ __volatile__ movw r30 2 n t sts 0 1 n t spm n t word Oxffff n t nop n t i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE WRITE r uint16 t address r30 A r31 H 8 5 2 10 define boot page write extended address Value __extension__ _ asm__ __volatile__ movw r30 A3NnNt sts 1 C3 n t sts 0 2 n t spm n t Gen
63. are using registers which had not been passed as operands you need to inform the compiler about this The following example will do an atomic increment It increments an 8 bit value pointed to by a pointer variable in one go without being interrupted by an interrupt routine or another thread in a multithreaded environment Note that we must use a pointer because the incremented value needs to be stored before interrupts are enabled asm volatile cli n t ld r24 a0 n t inc r24 n t st a0 r24 n t Sei n t e ptr r24 The compiler might produce the following code cli ld r24 Z inc r24 st Z r24 sei One easy solution to avoid clobbering register r24 is to make use of the special temporary register __tmp_reg__ defined by the compiler Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 307 asm volatile Cli n t ld __tmp_reg__ kao n t inc __tmp_reg__ n t st a0 __tmp_reg__ nyt sei n t e ptr The compiler is prepared to reload this register next time it uses it Another problem with the above code is that it should not be called in code sections where interrupts are disabled and should be kept disabled because it will enable interrupts at the end We may store the current status but then we need another register Again we can solve this without clobbering a fixed but let the compiler select it T
64. as linker avr 1d and librarian avr ar and avr ranlib In addition you get tools which extract data from object files avr objcopy dissassemble object file information avr objdump and strip information from object files avr strip Before we can build the C compiler these tools need to be in place Download and unpack the source files bunzip2 c binutils lt version gt tar bz2 tar xf cd binutils lt version gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 349 Note Replace lt version gt with the version of the package you downloaded If you obtained a gzip compressed file gz use gunzip instead of bunzip2 It is usually a good idea to configure and build binutils in a subdirectory so as not to pollute the source with the compiled files This is recommended by the binutils developers mkdir obj avr cd obj avr The next step is to configure and build the tools This is done by supplying arguments to the configure script that enable the AVR specific options configure prefix PREFIX target avr disable nls If you don t specify the prefix option the tools will get installed in the usr local hierarchy i e the binaries will get installed in usr local bin the info pages get installed in usr local info etc Since these tools are changing frequently It is preferrable to put them in a location that is easily removed
65. at location 0x0 fini2 fini2 fini1 fini1 fini0 finiO 0x00000122 0x4 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _exit o finiO 0x00000126 etext data 0x00800060 0x0 load address 0x00000126 0x00800060 PROVIDE data start data data 0x00800060 0x0 demo o data 0x00800060 0x0 c avrdev avr libc avr libc avr lib avr4 atmega8 crtm8 o data 0x00800060 0x0 c avrdev avr libc avr libc avr lib avr4 exit o data 0x00800060 0x0 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _exit o data 0x00800060 0x0 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _copy_data o data 0x00800060 0x0 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _clear_bss o data rodata rodata gnu linkonce d Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 207 0x00800060 ALIGN 0x2 0x00800060 edata 0x00800060 PROVIDE __data_end bss 0x00800060 0x3 load address 0x00000126 0x00800060 PROVIDE __bss_start bss bss 0x00800060 0x3 demo o bss 0x00800063 0x0 c avrdev avr libc avr libc avr lib avr4 atmega8 crtm8 o bss 0x00800063 0x0 c avrdev avr libc avr libc avr lib avr4 exit o bss 0x00800063 0x0 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _exit o bss 0x00800063 0x0 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _copy_data o bss 0x00800063 0x0 c winavr bin lib gcc avr 4 3 0 avr4 libgcc a _clear_bss o bss COMMON 0x00800
66. avr eeprom h gt EEPROM handling 7 104 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen CONTENTS ii 6 14 lt avr fuse h gt Fuse Support 2 2004 107 6 15 lt avr interrupt h gt Interrupts 0 110 6 16 lt avr io h gt AVR device specific IO definitions 139 6 17 lt avr lock h gt Lockbit Support 0 140 6 18 lt avr pgmspace h gt Program Space Utilities 143 6 19 lt avr power h gt Power Reduction Management 156 6 20 Additional notes from lt avr sfr defs h5s 158 6 21 lt avr sfr defs h gt Special function registers 160 6 22 lt avr sleep h gt Power Management and Sleep Modes 162 6 23 lt avr version h gt avr libe version macros 164 6 24 lt avr wdt h gt Watchdog timer handling 165 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Blo dks art tente sk SG See ER Ne eru alene 169 6 26 lt util crcl6 h gt CRC Computations 173 6 27 lt util delay h gt Convenience functions for busy wait delay loops 176 6 28 lt util delay basic h gt Basic busy wait delay loops 178 6 29 lt util parity h gt Parity bit generation 179 6 30 lt util setbaud h gt Helper macros for baud rate calculations 179 6 31 lt util twi h gt TWI bit mask definitions 1
67. backup copy of avrdude config file in install directory if exists e Insight GDB Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 360 Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order lt MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin x lt install directory gt bin Configure CFLAGS D USE MINGW ACCESS LDFLAGS static archivedir configure prefix installdir target avr with gmp usr local with mpfr usr local enable doc 2 gt amp 1 tee insight configure log Make make all install 2 gt amp 1 tee package make log e SRecord Open source code package Configure and build at the top of the source code tree Set PATH in order x lt MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin lt install directory gt bin Configure configure prefix installdir infodir installdir info mandir installdir man 2 gt amp 1 tee package configure log Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 361 Make make all install 2 gt amp 1 tee package make log Build the tools below in Cygwin
68. be greater than s2 A consequence of the ordering used by strncasecmp p 93 is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 6 11 3 25 char x strncat char dest const char src size_t len Concatenate two strings The strncat p 93 function is similar to strcat p 90 except that only the first n characters of src are appended to dest Returns The strncat p 93 function returns a pointer to the resulting string dest Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 94 6 11 3 26 int strncmp const char s1 const char s2 size_t len Compare two strings The strncmp p 94 function is similar to stremp p 91 except it only compares the first at most n characters of sl and s2 Returns The strncmp p 94 function returns an integer less than equal to or greater than zero if sl or the first n bytes thereof is found respectively to be less than to match or be greater than s2 6 11 3 27 char strncpy char dest const char src size_t len Copy a string The strnepy p 94 function is similar to strepy p 91 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 strnep
69. binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution Neither the name of the copyright holders nor the names of contributors may be used to endorse or promote products derived from this software without specific prior written permission THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 2 avr libc Module Index POSSIBILITY OF SUCH DAMAGE 2 avr libc Module Index 2 1 avr libc Modules Here is a list of all modules lt alloca h gt Allocate space in the stack lt assert h gt Diagnostics lt ctype h gt Character Operations lt errno h gt System Errors lt inttypes h gt
70. bootloader temporary page buffer to flash page that contains address Note address is a byte address in flash not a word address 6 12 2 10 define boot page write safe address Value do boot_spm_busy_wait eeprom busy wait boot page write address while 0 AE she il Same as boot page write p 102 except it waits for eeprom and spm operations to complete before writing the page 6 12 2 11 define boot rww busy SPM REG amp uint8 t BV __COMMON_ASB Check if the RWW section is busy 6 12 2 12 define boot rww enable __ boot rww enable Enable the Read While Write memory section 6 12 2 13 define boot rww enable safe Value do boot_spm_busy_wait eeprom busy wait boot_rww_enable while 0 BRELA got Same as boot _rww_enable p 102 except waits for eeprom and spm op erations to complete before enabling the RWW mameory Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 103 6 12 2 14 define boot signature byte get addr Value __extension__ uint16_t __addri6 uint16_t addr uint8_t __result _ asm__ __volatile__ sts 1 2 n t lpm 70 z n t r __result i _SFR_MEM_ADDR __SPM_REG r uint8_t __BOOT_SIGROW_READ z __addr16 result Its H Read the Signature Row byte at address For some MCU types this function can also retr
71. busy wait func tions from lt util delay basic h p 242 gt They are meant as convenience functions where actual time values can be specified rather than a number of cycles to wait for The idea behind is that compile time constant expressions will be eliminated by compiler optimization so floating point expressions can be used to calculate the number of delay cycles needed based on the CPU frequency passed by the macro F_ CPU Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 27 lt util delay h gt Convenience functions for busy wait delay loops 177 Note In order for these functions to work as intended compiler optimizations must be enabled and the delay time must be an expression that is a known constant at compile time If these requirements are not met the resulting delay will be much longer and basically unpredictable and applications that otherwise do not use floating point calculations will experience severe code bloat by the floating point library routines linked into the application The functions available allow the specification of microsecond and millisecond delays directly using the application supplied macro F_CPU as the CPU clock frequency in Hertz Functions e void delay us double us e void delay ms double ms 6 27 2 Function Documentation 6 27 2 1 void delay ms double ms Perform a delay of __ms milliseconds using delay loop 20 p 178 The macro F CPU is supposed to be defined
72. const char _nptr char endptr int base e unsigned long strtoul const char x nptr char xx endptr int __ base e long atol const char ___s ATTR_PURE e int atoi const char __ s ATTR PURE e void exit int status ATTR_NORETURN__ e void x malloc size_t size ATTR_MALLOC_ _ e void free void x__ ptr e void x calloc size_t mnele size_t size ATTR_MALLOC_ _ e void x realloc void x___ ptr size_t size ATTR_MALLOC_ _ e double strtod const char x nptr char xx endptr e double atof const char x __nptr e int rand void e void srand unsigned int __ seed e int rand r unsigned long __ ctx Variables e size_t _malloc_ margin e char _ malloc_heap_ start e char _ malloc heap end Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 42 strcasecmp S File Reference 266 8 42 strcasecmp S File Reference 8 42 1 Detailed Description 8 43 strcasecmp P S File Reference 8 43 1 Detailed Description 8 44 strcasestr S File Reference 8 44 1 Detailed Description 8 45 strcat S File Reference 8 45 1 Detailed Description 8 46 strcat P S File Reference 8 46 1 Detailed Description 8 47 strchr S File Reference 8 47 1 Detailed Description 8 48 strchr P S File Reference 8 48 1 Detailed Description 8 49 strchrnul S File Reference 8 49 1 Detailed Description 8 50 strchrnul P S File Reference 8 50 1 Detailed Description 8 51 strcmp S File Reference 8 51 1 Detailed Description 8 52 strcmp P S F
73. constraint M the compiler will make sure that you don t pass anything Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 303 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 def initions in version 3 3 they aren t strict enough There is for example no constraint which restricts integer constants to the range 0 to 7 for bit set and bit clear operations Mnemonic Con Mnemonic Con LE ie IL pr eae mr Jam fer TT adiw pw iad frr andi am Jam pr bel bibe bset I b I com p cpse elpm bj 2 Q 9 Qu Q HI H H H er N a H Q B O ea gt m il H lela R E nn Per O KRR fpr Jss SSS subpar fs fam swap m hp mh mM Constraint characters may be prepended by a single constraint modifier Con traints without a modifier specify read only operands Modifiers are Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 304 Write only operand usually used for all output operands end waite operand amp Register should be used for output only Output operands must be write only and the C expression result must be an lvalue which means that the operands must be valid on the left side
74. creates a bit mask from a bit number It is then inverted to represent logical values for a fuse memory byte To combine the fuse bits macros together to represent a whole fuse byte use the bitwise AND operator like so Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 14 lt avr fuse h gt Fuse Support 109 FUSE_BOOTSZO amp FUSE_BOOTSZ1 amp FUSE_EESAVE amp FUSE_SPIEN amp FUSE_JTAGEN Each device I O header file also defines macros that provide default values for each fuse byte that is available LFUSE DEFAULT is defined for a Low Fuse byte HFUSE DEFAULT is defined for a High Fuse byte EFUSE DEFAULT is defined for an Extended Fuse byte If FUSE MEMORY SIZE gt 3 then the I O header file defines macros that provide default values for each fuse byte like so FUSE0_ DEFAULT FUSEL DEFAULT FUSE2 DEFAULT FUSE3_ DEFAULT FUSE4 DEFAULT API Usage Example Putting all of this together is easy include lt avr io h gt FUSES low LFUSE_DEFAULT high FUSE_BOOTSZO amp FUSE_BOOTSZ1 amp FUSE_EESAVE amp FUSE_SPIEN amp FUSE_JTAGEN extended EFUSE_DEFAULT 3 int main void return 0 Or include lt avr io h gt __fuse_t __fuse __attribute__ section fuse low LFUSE_DEFAULT high FUSE_BOOTSZO amp FUSE_BOOTSZ1 amp FUSE_EESAVE amp FUSE_SPIEN amp FUSE_JTAGEN extended EFUSE_DEFAULT F int main void return 0 However there are
75. data and bss 9 13 Using the avrdude program Note This section was contributed by Brian Dean bsd bsdhome com The avrdude program was previously called avrprog The name was changed to avoid confusion with the avrprog program that Atmel ships with AvrStudio avrdude is a program that is used to update or read the flash and EEPROM memories of Atmel AVR microcontrollers on FreeBSD Unix It supports the Atmel serial programming protocol using the PC s parallel port and can upload either a raw binary file or an Intel Hex format file It can also be used in an interactive mode to individually update EEPROM cells fuse bits and or lock bits if their access is supported by the Atmel serial programming protocol Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 13 Using the avrdude program 374 The main flash instruction memory of the AVR can also be programmed in interactive mode however this is not very useful because one can only turn bits off The only way to turn flash bits on is to erase the entire memory using avrdude s e option avrdude is part of the FreeBSD ports system To install it simply do the following cd usr ports devel avrdude make install Once installed avrdude can program processors using the contents of the hex file specified on the command line In this example the file main hex is burned into the flash memory avrdude p 2313 e m flash i main hex avrdude AVR dev
76. 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 p 247 gt Note The names of the interrupt vectors in AVR GCC has been changed to match the names of the vectors in IAR This significantly helps in porting applications from IAR to AVR GCC 9 9 4 Intrinsic Routines IAR has a number of intrinsic routine such as __enable_interrupts __disable_interrupts __watchdog_reset These intrinsic functions compile to specific AVR opcodes SEI CLI WDR Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 9 Porting From IAR to AVR GCC 319 There are equivalent macros that are used in AVR GCC however they are not located in a single include file AVR GCC has sei p 138 for __enable_interrupts and cli p 136 for __disable_interrupts Both of these macros are located in lt avr interrupts h gt AVR GCC has the macro wdt_reset p 167 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 p 271 gt 9 9 5 Flash Variables The C language was not designed for Harvard architecture processors with sep arate memory spaces This means that there are various non standard ways to define a variable whose data resides in the Program Memory Flash IAR uses a non s
77. doesn t contain an abstraction for actual files its origin as end of file is somewhat meaningless here 6 9 2 7 define fdev_close This macro frees up any library resources that might be associated with stream It should be called if stream is no longer needed right before the application is going to destroy the stream object itself Currently this macro evaluates to nothing but this might change in future versions of the library 6 9 2 8 define fdev get udata stream stream gt udata This macro retrieves a pointer to user defined data from a FILE stream object Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 60 6 9 2 9 define fdev set udata stream u do stream gt udata u while 0 This macro inserts a pointer to user defined data into a FILE stream object The user data can be useful for tracking state in the put and get functions supplied to the fdevopen p 62 function 6 9 2 10 define FDEV_SETUP_STREAM put get rwflag Initializer for a user supplied stdio stream This macro acts similar to fdev setup stream p 60 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 p 60 6 9 2 11 define fdev setup stream stream put get rwflag Setup a user supplied buffer as an stdio stream This macro takes a user supplied buffer stream and
78. enable boot h 240 boot rww enable alternate boot h 240 compar fn t pgmspace h 252 ELPM enhanced _ pgmspace h 253 ELPM word classic pgmspace h 253 ELPM word enhanced _ pgmspace h 254 LPM classic pgmspace h 254 LPM dword classic pgmspace h 254 LPM dword enhanced _ pgmspace h 255 LPM enhanced _ pgmspace h 255 LPM word classic pgmspace h 256 LPM word enhanced _ pgmspace h 256 boot lock bits set boot h 236 boot lock bits set alternate boot h 236 boot page erase alternate boot h 236 boot page erase extended boot h 237 boot page erase normal boot h 237 boot page fill alternate boot h 238 boot page fill extended boot h 238 boot page fill normal boot h 238 boot page write alternate avr stdlib 75 malloc heap end avr stdlib 84 malloc heap start avr stdlib 84 _ malloc margin avr stdlib 84 _crcl6_ update util ere 174 _crc_ccitt_ update util ere 174 ere ibutton update util ere 175 ere xmodem update util ere 175 delay loop 1 util delay basic 178 delay loop 2 util delay basic 178 delay ms util delay 177 delay us util delay 177 A more sophisticated project 212 A simple project 195 abort avr stdlib 75 abs avr stdlib 75 acos avr_math 34 Additional notes from lt avr sfr_ defs h gt 158 alloca alloca 15 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX asin avr_math 34 as
79. fuse bits get 6 13 lt avr eeprom h gt EEPROM handling 6 13 1 Detailed Description include lt avr eeprom h gt This header file declares the interface to some simple library routines suitable for handling the data EEPROM contained in the AVR microcontrollers The implementation uses a simple polled mode interface Applications that require interrupt controlled EEPROM access to ensure that no time will be wasted in spinloops will have to deploy their own implementation Note All of the read write functions first make sure the EEPROM is ready to be accessed Since this may cause long delays if a write operation is still pending time critical applications should first poll the EEPROM e g using eeprom is ready p 106 before attempting any actual I O But this functions are not wait until SELFPRGEN in SPMCSR becomes zero Do this manually if your softwate contains the Flash burning As these functions modify IO registers they are known to be non reentrant If any of these functions are used from both standard and interrupt context Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 105 the applications must ensure proper protection e g by disabling interrupts before accessing them All write functions force erase and write programming mode IAR C compatibility defines e define EEPUT addr val eeprom write byte uint8_t addr uint8 t val e define E
80. hrator 0 li Analog Com COMPARATORdarator 1 SIG Analog Com COMPARATOR rator 2 AT9052333 AT9054433 AT9054434 AT9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 ATmega103 AT megal28 ATmega1284P AT megal6 ATmegal63 ATmegal65 ATmegal65P ATmegal68P AT megal69 ATmegal69P ATmega32 ATmega323 ATmega325 AT mega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega48P AT mega64 ATmega645 ATmega6450 ATmega649 ATmega6490 AT mega8 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P AT mega644 ATtiny13 ATtiny15 ATtiny26 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 AT90PWM3 AT90PWM2 AT90PWM1 AT90PWM3 AT90PWM2 AT90PWM1 AT90PWM3 AT90PWM2 AT90PWM1 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 115 E Analog Com AT90CAN128 AT90CAN32 COMP vect COMPARATQRparator AT90CAN64 ATmega103 AT megal28 ATmegal284P ATmegal65 ATmegal65P ATmegal68P AT megal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega328P ATmega329 AT mega3290 ATmega3290P AT mega48P ATmega64 ATmega645 ATmega6450 ATmega649
81. in both directions reading and writing the slave device so the example will demonstrate the details of both Usually there is probably not much need to add more EEPROM to an ATmega system that way the smallest possible AVR device that offers hardware TWI support is the ATmega8 which comes with 512 bytes of EEPROM which is equivalent to an 24C04 device The ATmegal28 already comes with twice as much EEPROM as the 24C16 would offer One exception might be to use an externally connected EEPROM device that is removable e g SDRAM PC memory comes with an integrated TWI EEPROM that carries the RAM configuration information 6 39 3 The Source Code The source code is installed under prefix share doc avr libc examples twitest twitest c where prefix is a configuration option For Unix systems it is usually set to either usr or usr local Note 1 The header file lt util twi h p 269 gt contains some macro definitions for symbolic constants 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_ Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 229 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 thre
82. in this header file to actually put the device into sleep mode The simplest way is to optionally set the desired sleep mode using set sleep mode it usually defaults to idle mode where the CPU is put on sleep but all peripheral clocks are still running and then call sleep_mode This macro automatically sets the sleep enable bit goes to sleep and clears the sleep enable bit Example include lt avr sleep h gt set sleep mode cmode sleep mode Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 22 lt avr sleep h gt Power Management and Sleep Modes 163 Note that unless your purpose is to completely lock the CPU until a hardware reset interrupts need to be enabled before going to sleep As the sleep_mode macro might cause race conditions in some situations the individual steps of manipulating the sleep enable SE bit and actually issuing the SLEEP instruction are provided in the macros sleep_enable p 164 sleep_disable p 163 and sleep_cpu p 163 This also allows for test and sleep scenarios that take care of not missing the interrupt that will awake the device from sleep Example include lt avr interrupt h gt include lt avr sleep h gt set sleep mode cmode cli if some_condition 1 sleep_enable sei sleep_cpu sleep disable sei This sequence ensures an atomic test of some_condition with interrupts being disabled If the condition is met
83. interrupt h gt include lt avr pgmspace h gt void boot program page uint32_t page uint8_t buf Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities uint16_t i uint8_t sreg Disable interrupts sreg SREG cliQ eeprom busy wait boot page erase page boot spm busy wait Wait until the memory is erased for i 0 i lt SPM PAGESIZE i 2 1 Set up little endian word uint16_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 98 e define BOOTLOADER SECTION __attribute__ section bootloader e define boot spm interrupt enable SPM REG uint8 t BV SPMIE e define boot spm interrupt disable SPM REG amp uint8_t _BV SPMIE e define boot is spm interrupt __SPM_REG amp uint8 t BV SPMIE e define boot rww busy SPM REG amp uint8 t BV __ COMMON ASB e define boot spm busy SPM REG amp uint8 t BV __ SPM ENABLE e define boot spm busy wait do while boot spm busy e define GET LOW FUSE BITS 0x0000 Gener
84. is a 16 or more bit variable that is shared between the main execution path and an ISR While declaring such a variable as volatile ensures that the compiler will not optimize accesses Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks 170 to it away it does not guarantee atomic access to it Assuming the following example include lt inttypes h gt include lt avr interrupt h gt include lt avr io h gt volatile uint16_t ctr ISR TIMER1_OVF_vect ctr int main void ctr 0x200 start_timer while ctr 0 wait gt There is a chance where the main context will exit its wait loop when the variable ctr just reached the value OxFF This happens because the compiler cannot natively access a 16 bit variable atomically in an 8 bit CPU So the variable is for example at 0x100 the compiler then tests the low byte for 0 which succeeds It then proceeds to test the high byte but that moment the ISR triggers and the main context is interrupted The ISR will decrement the variable from 0x100 to OxFF and the main context proceeds It now tests the high byte of the variable which is now also 0 so it concludes the variable has reached 0 and terminates the loop Using the macros from this header file the above code can be rewritten like include lt inttypes h gt include lt avr interrupt h gt in
85. is not triggered for about 2 seconds it will issue a hardware reset Care needs to be taken that no code path blocks longer than this or it needs to frequently perform watchdog resets of its own An example of such a code path would be the string IO functions for an overly large string to print about 2000 characters at 9600 Bd they might block for too long The loop itself then acts on the interrupt indication bitfields as appropriate Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 219 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 approximately 100 Hz The CLOCKOUT pin will be toggled here so e g an oscilloscope can be used on that pin to measure the accuracy of our software clock Then the LED flasher for LED2 We are alive LED is built It will flash that LED for about 50 ms and pause it for another 950 ms Various actions depending on the operation mode follow Finally the 3 second backup timer is implemented that will write the PWM value back to EEPROM once it is not changing anymore The ADC interrupt will just adjust the PWM value only Finally the UART Rx interrupt will dispatch on the last character received from the UART All the string literals that are used as informational messages within main are placed in program memory p 143 so no SRAM needs to b
86. libc by Doxygen 9 1 Toolchain Overview 273 other programs seamlessly to create the final output The assembler and the linker are part of another open source project called GNU Binutils GCC knows how to drive the GNU assembler gas to assemble the output of the compiler GCC knows how to drive the GNU linker ld to link all of the object modules into a final executable The two projects GCC and Binutils are very much interrelated and many of the same volunteers work on both open source projects When GCC is built for the AVR target the actual program names are prefixed with avr So the actual executable name for AVR GCC is avr gcc The name avr gcc is used in documentation and discussion when referring to the program itself and not just the whole AVR GCC system See the GCC Web Site and GCC User Manual for more information about GCC 9 1 4 GNU Binutils The name GNU Binutils stands for Binary Utilities It contains the GNU assembler gas and the GNU linker ld but 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 th
87. no conversion could be performed 0 is returned If an overflow or underflow occurs errno is set to ERANGE p 19 and the function return value is clamped to LONG_MIN or LONG_MAX respectively 6 10 4 28 unsigned long strtoul const char x _ nptr char ___ endptr int base The strtoul p 83 function converts the string in nptr to an unsigned long value The conversion is done according to the given base which must be between 2 and 36 inclusive or be the special value 0 The string may begin with an arbitrary amount of white space as determined by isspace p 19 followed by a single optional 2 or sign If base is zero or 16 the string may then include a Ox prefix and the number will be read in base 16 otherwise a zero base is taken as 10 decimal unless the next character is 0 in which case it is taken as 8 octal The remainder of the string is converted to an unsigned long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 B represents 11 and so forth with Z representing 35 If endptr is not NULL strtoul p 83 stores the address of the first invalid character in endptr If there were no digits at all however strtoul p 83 stores the original value of nptr in endptr Thus if xnptr is not 0 but endptr is 0 on return the entire string was vali
88. one r value 3 A comma separated list of input operands Again our example uses one operand only I _SFR_IO_ADDR PORTD 4 Clobbered registers left empty in our example You can write assembler instructions in much the same way as you would write assembler 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 O refers to r value and 1 refers to I _SFR_IO_ADDR PORTD This may still look a little odd now but the syntax of an operand list will be explained soon Let us first examine the part of a compiler listing which may have been generated from our example Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 300 lds r24 value APP in r24 12 NOAPP sts value r24 The comments have been added by the compiler to inform the assembler that the included code was not generated by the compilation of C statements but by inline assembler statements The compiler se
89. or whatever In any case the labels became unique too Another option is to use Unix assembler style numeric labels They are ex plained in How do I trace an assembler file in avr gdb p 329 The above example would then look like Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 309 define loop until bit is clear port bit __asm__ __volatile__ 1 sbic 4 0 Vl n t rjmp 1b no outputs I _SFR_IO_ADDR port I bit 9 6 6 C Stub Functions Macro definitions will include the same assembler code whenever they are ref erenced This may not be acceptable for larger routines In this case you may define a C stub function containing nothing other than your assembler code void delay uint8_t ms uint16_t cnt asm volatile n L_dli n t mov AO ZA2 n t mov BO YB2 n L d12 n t sbiw A0 1 n t brne L_dl2 n t dec 41 n t brne L_dli n t kw cnt r ms r delay count 95 I The purpose of this function is to delay the program execution by a specified number of milliseconds using a counting loop The global 16 bit variable delay count must contain the CPU clock frequency in Hertz divided by 4000 and must have been set before calling this routine for the first time As described in the clobber p 306 section the routine uses a local variable to hold a temporary value Another u
90. perform output operations can be given as NULL Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 222 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 1cd_str stream provides a method to display character data on the LCD text display The function delay 1s suspends program execution for approximately one second This is done using the _delay_ms p 177 function from lt util delay h p 242 gt which in turn needs the F_CPU macro in order to adjust the cycle counts As the _delay_ms p 177 function has a limited range of allowable argument values depending on F_CPU a value of 10 ms has been chosen as the base delay which would be safe for CPU frequencies of up to about 26 MHz This function is then called 100 times to accomodate for the actual one second delay In a practical application long delays like this one were better be handled by a hardware timer so the main CPU would be free for other tasks while waiting or could be put on sleep At the beginning of main after initializing the peripheral devices the default stdio streams stdin stdout and stderr are set up by using the existing static FILE stream objects While this is not mandatory the availability of stdin and stdout allows to use the shorthand functions e g printf p 65 instead of fp
91. performs formatted output to stream stderr See vfprintf p 66 for details 6 9 3 20 int printf P const char _ fmt Variant of printf p 65 that uses a fmt string that resides in program memory 6 9 3 21 int puts const char x sir Write the string pointed to by str and a trailing newline character to stdout 6 9 3 22 int puts P const char str Variant of puts p 65 where str resides in program memory 6 9 3 23 int scanf const char __ fmt The function scanf performs formatted input from stream stdin See vfscanf p 70 for details 6 9 3 24 int scanf P const char _ fmt Variant of scanf p 65 where fmt resides in program memory 6 9 3 25 int snprintf char __s size_t __ n const char __fmt Like sprintf p 66 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 66 Returns the number of characters that would have been written to s if there were enough space 6 9 3 26 int snprintf P char _s size_t __n const char __ fmt Variant of snprintf p 65 that uses a fmt string that resides in program memory 6 9 3 27 int sprintf char __ s const char x __ fmt Variant of printf p 65 that sends the formatted characters to string s 6 9 3 28 int sprintf P
92. r22 r23 r24 r25 r30 r31 r26 r27 r28 r29 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 r2 r0 r1 Order 2 uses r25 r24 r23 r22 r21 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 r0 e mint8 Assume int to be an 8 bit integer Note that this is not really supported by avr libc so it should normally not be used The default is to use 16 bit integers e mno interrupts Generates code that changes the stack pointer without disabling interrupts Normally the state of the status register SREG is saved in a temporary register interrupts are disabled while changing the stack pointer and SREG is restored Specifying this option will define the preprocessor macro __NO_INTERRUPTS__ to the value 1 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 367 e mtiny stack Change only the low 8 bits of the stack pointer e mno tablejump Do not generate tablejump instructions By default jump tables can be used to optimize switch statements When turned off sequences of compare statements are used instead Jump tables are usually faster to execute on aver
93. returned By default all the conversions described above are available except the floating point conversions and the width is limited to 255 characters The float point conversion will be available in the extended version provided by the library libscanf_f1t a Also in this case the width is not limited exactly it is limited to 65535 characters To link a program against the extended version use the following compiler flags in the link stage Wl u vfscanf lscanf_flt lm A third version is available for environments that are tight on space In ad dition to the restrictions of the standard one this version implements no specification This version is provided in the library libscanf_min a and can be requested using the following options in the link stage Wl u vfscanf lscanf_min lm 6 9 3 35 int vfscanf_P FILE x stream const char _ fmt va list ap Variant of vfscanf p 70 using a fmt string in program memory 6 9 3 36 int vprintf const char fmt va list ap The function vprintf performs formatted output to stream stdout taking a variable argument list as in vfprintf p 66 See vfprintf p 66 for details Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 73 6 9 3 37 int vscanf const char x __ fmt va list ap The function vscanf performs formatted input from stream stdin taking a variable argument list as in vfscanf p 70 See
94. returned the value __ ret Note longjmp p 41 cannot cause 0 to be returned If longjmp p 41 is invoked with a second argument of 0 1 will be returned instead Parameters _ jmpb Information saved by a previous call to setjmp p 41 _ _ ret Value to return to the caller of setjmp p 41 Returns This function never returns 6 7 2 2 int setjmp jmp buf __jmpb Save stack context for non local goto include lt setjmp h gt setjmp p 41 saves the stack context environment in __ jmpb for later use by longjmp p 41 The stack context will be invalidated if the function which called setjmp p 41 returns Parameters _ jmpb Variable of type jmp_buf which holds the stack information such that the environment can be restored Returns setjmp p 41 returns 0 if returning directly and non zero when return ing from longjmp p 41 using the saved context Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 42 6 8 lt stdint h gt Standard Integer Types 6 8 1 Detailed Description include lt stdint h gt Use ulintN__t if you need exactly N bits Since these typedefs are mandated by the C99 standard they are preferred over rolling your own typedefs Exact width integer types Integer types having exactly the specified width typedef signed char int8 t typedef unsigned char uint8 t typedef signed int int16 t typedef unsigned i
95. returns a pointer to the last occurrence of the character val in the flash string s Returns The strrchr P p 155 function returns a pointer to the matched char acter or NULL if the character is not found 6 18 4 24 char x strsep P char sp PGM P delim Parse a string into tokens The strsep P p 155 function locates in the string referenced by sp the first occurrence of any character in the string delim or the terminating 0 character and replaces it with a 0 The location of the next character after the delimiter character or NULL if the end of the string was reached is stored in xsp An empty field i e one caused by two adjacent delimiter characters can be detected by comparing the location referenced by the pointer returned in sp to 0 This function is similar to strsep p 95 except that delim is a pointer to a string in program space Returns The strsep P p 155 function returns a pointer to the original value of sp If sp is initially NULL strsep P p 155 returns NULL 6 18 4 25 size_t strspn_P const char x s PGM P accept The strspn P p 155 function calculates the length of the initial segment of s which consists entirely of characters in accept This function is similar to strspn p 96 except that accept is a pointer to a string in program space Returns The strspn P p 155 function returns the number of characters in the initial segment of s
96. returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 11 3 6 int memcmp const void s1 const void s2 size_t len Compare memory areas The memcmp p 88 function compares the first len bytes of the memory areas sl and s2 The comparision is performed using unsigned char operations Returns The memcmp p 88 function returns an integer less than equal to or greater than zero if the first len bytes of s1 is found respectively to be less than to match or be greater than the first len bytes of s2 Note Be sure to store the result in a 16 bit variable since you may get incorrect results if you use an unsigned char or char due to truncation Warning This function is not mint8 compatible although if you only care about testing for equality this function should be safe to use 6 11 3 7 void x memcpy void x dest const void x src size_t len Copy a memory area The memcpy p 88 function copies len bytes from memory area src to mem ory area dest The memory areas may not overlap Use memmove p 89 if the memory areas do overlap Returns The memepy p 88 function returns a pointer to dest Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 89 6 11 3 8 void x memmem const void s1 size_t len1 const void x s2 size_t len2 The memmem p 89 function finds the start of the first occurrence of the substri
97. 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 35 3 The source code The source code is installed under prefix share doc avr libc examples asmdemo where prefix is a configuration option For Unix systems it is usually set to either usr or usr local Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 195 6 36 A simple project At this point you should have the GNU tools configured built and installed on your system In this chapter we present a simple example of using the GNU tools in an AVR project After reading this chapter you should have a better feel as to how the tools are used and how a Makefile can be configured 6 36 1 The Project This project will use the pulse width modulator PWM to ramp an LED on and off every two seconds An AT90S2313 processor will be used as the controller The circuit for this demonstration is shown in the schematic diagram p 195 If you have a development kit you should be able to use it rather than build the circuit for this project Note Meanwhile the AT9052313 became obsolete Either use its successor the pin compatible ATtiny2313 for the project or perhaps the ATmega8 or one of its successors ATmega
98. t BV SPMIE Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 5 boot h File Reference 235 define boot rww busy __SPM_REG amp uint8_t _BV __ COMMON_ASB define boot spm busy _ SPM REG amp uint8_t _BV __ SPM ENABLE u define boot spm busy wait dof while boot spm busy e define BOOT PAGE ERASE BV SPM ENABLE _ BV PGERS define BOOT PAGE WRITE BV SPM ENABLE _ BV PGWRT e define BOOT PAGE FILL BV SPM ENABLE e define BOOT RWW ENABLE BV SPM ENABLE BV COMMON ASRE define BOOT LOCK BITS SET BV SPM ENABLE BV BLBSET define boot page fill normal address data define boot page fill alternate address data define boot page fill extended address data define boot page erase normal address define boot page erase alternate address define boot page erase extended address define boot page write normal address define boot page write alternate address frdefine 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 frdefine GET LOW FUSE BITS 0x0000 define GET LOCK BITS 0x0001 define GET EXTENDED FUSE BITS 0x0002 define GET HIGH FUSE BITS 0x0003 define boot lock fuse bits get address frdefine BOOT SIGROW READ BV SPM ENABLE _BV SIGRD define boot signature byte get addr
99. 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 written left to right The public function lcd putchar takes arguments that make it suitable for being passed as a put function pointer to the stdio stream initialization func tions and macros fdevopen p 62 FDEV_SETUP_STREAM p 60 etc Thus it takes two arguments the character to display itself and a reference to the underlying stream object and it is expected to return 0 upon success This function remembers the last unprocessed newline character seen in the function local static variable n1_seen If a newline character is encountered it will simply set this variable to a true value and return to the caller As soon as the first non newline character is to be displayed with nl_seen still true the LCD controller is told to clear the display put the cursor home and restart at SRAM address 0 All other characters are sent to the display The single static function internal variable nl_seen works for t
100. that larger numbers behind the 0 option might automatically cause better optimization First there s no universal definition for better with optimization often being a speed vs code size tradeoff See the detailed discussion p 367 for which option affects which part of the code generation A test case was run on an ATmega128 to judge the effect of compiling the library itself using different optimization levels The following table lists the results The test case consisted of around 2 KB of strings to sort Test 1 used qsort p 80 using the standard library stremp p 91 test 2 used a function that sorted the strings by their size thus had two calls to strlen p 93 per invocation When comparing the resulting code size it should be noted that a floating point version of fvprintf was linked into the binary in order to print out the time elapsed which is entirely not affected by the different optimization levels and added about 2 5 KB to the code Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 338 Optimization Size of text Time for test Time for test flags HL 2 EE 6666 6618 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 th
101. the eeprom sec tion 6 13 2 4 define eeprom busy wait do while leeprom is ready Loops until the eeprom is no longer busy Returns Nothing 6 13 2 5 define eeprom is ready Returns 1 if EEPROM is ready for a new read write operation 0 if not 6 13 3 Function Documentation 6 13 3 1 static inline void eeprom read block void x ___ dst const void __sre size_t mn static Read a block of mn bytes from EEPROM address __ src to SRAM __ dst 6 13 3 2 static ATTR PURE _ inline uint8 t eeprom read byte const uint8 tx p static Read one byte from EEPROM address __p 6 13 3 3 static ATTR PURE _ inline uint32 t eeprom read dword const uint32 t p static Read one 32 bit double word little endian from EEPROM address __ p 6 13 3 4 static ATTR PURE inline uintl6 t eeprom read word const uint16 t __p static Read one 16 bit word little endian from EEPROM address p Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 14 lt avr fuse h gt Fuse Support 107 6 13 3 5 static inline void eeprom write block const void x _ src void x ___dst size_t mn static Write a block of mn bytes to EEPROM address dst from __ sre Note The argument order is mismatch with common functions like strepy p 91 6 13 3 6 static inline void eeprom write byte uint8 tr _p uint8 t value static Write a byte value to EEPROM address __p 6 13 3 7 st
102. the tools on an AVR microcontroller The more sophisticated demo project p 212 builds on top of that simple project and adds some controls to it It touches a number of avr libc s basic concepts on its way A comprehensive example on using the standard IO facilities p 219 intends to explain that complex topic using a practical microcontroller periph eral setup with one RS 232 connection and an HD44780 compatible industry standard LCD display The Example using the two wire interface TWI p 227 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 p 191 demo shows how C and assembly language source files can collaborate within one project While the overall project is managed by a C program part for easy maintenance time critical parts are written directly in manually optimized assembly language for shortest execution times possible Naturally this kind of project is very closely tied to the hardware design thus it is custom tailored to a particular controller type and peripheral setup As an alternative to the assembly language solution this project also offers a C only implementation deploying the exact same peripheral setup based on a more sophisticated and thus more expensive but pin compatible controller While the simple demo is meant to run on about any AVR setup possible where a LED could be c
103. the two BLBO lock bits are available to the user and 4 mode settings are defined for these two bits Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 17 lt avr lock h gt Lockbit Support 141 If BOOT LOCK BITS 1 EXIST is defined then the two BLB1 lock bits are available to the user and 4 mode settings are defined for these two bits If BOOT LOCK APPLICATION TABLE BITS EXIST is defined then two lock bits are available to set the locking mode for the Application Table Section which is used in the XMEGA family If BOOT LOCK APPLICATION BITS EXIST is defined then two lock bits are available to set the locking mode for the Application Section which is used in the XMEGA family If BOOT LOCK BOOT BITS EXIST is defined then two lock bits are available to set the locking mode for the Boot Loader Section which is used in the XMEGA family The AVR lockbit modes have inverted values logical 1 for an unprogrammed disabled bit and logical 0 for a programmed enabled bit The defined macros for each individual lock bit represent this in their definition by a bit wise inver sion of a mask For example the LB MODE 3 macro is defined as define LB MODE 3 OxFC To combine the lockbit mode macros together to represent a whole byte use the bitwise AND operator like so LB_MODE_3 amp BLBO_MODE_2 lt avr lock h p 247 gt also defines a macro that provides a default lockbit value LOCKBITS DEFAU
104. this function to your code to then disable the watchdog after a reset e g after a soft reset include lt avr wdt h gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 346 Function Pototype void wdt_init void __attribute__ naked __attribute__ section init3 Function Implementation void wdt_init void MCUSR 0 wdt disable return I Back to FAQ Index p 321 9 10 32 I am using floating point math Why is the compiled code so big Why does my code not work You are not linking in the math library from AVR LibC GCC has a library that is used for floating point operations but it is not optimized for the AVR and so it generates big code or it could be incorrect This can happen even when you are not using any floating point math functions from the Standard C library but you are just doing floating point math operations When you link in the math library from AVR LibC those routines get replaced by hand optimized AVR assembly and it produces much smaller code See I get undefined reference to for functions like sin p 323 for more details on how to link in the math library Back to FAQ Index p 321 9 11 Building and Installing the GNU Tool Chain This chapter shows how to build and install from source code a complete development environment for the AVR processors using the GNU toolset There are two main sect
105. 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 func tion CALCULATE Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 7 How to Build a Library 311 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 and practical knowledge that you will need to create and use your own libraries 9 7 2 How the Linker Works The compiler compiles a single high level language file C language for example into a sing
106. to a constant defining the CPU clock frequency in Hertz The maximal possible delay is 262 14 ms F_CPU in MHz When the user request delay which exceed the maximum possible one _ delay ms p 177 provides a decreased resolution functionality In this mode delay ms p 177 will work with a resolution of 1 10 ms providing delays up to 6 5535 seconds independent from CPU frequency The user will not be informed about decreased resolution 6 27 2 2 void delay us double us Perform a delay of __us microseconds using delay loop 10 p 178 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 If the user requests a delay greater than the maximal possible one delay us p 177 will automatically call delay ms p 177 instead The user will not be informed about this case Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 28 lt util delay basic h gt Basic busy wait delay loops 178 6 28 lt util delay basic h gt Basic busy wait delay loops 6 28 1 Detailed Description include lt util delay_basic h gt The functions in this header file implement simple delay loops that perform a busy waiting They are typically used to facilitate short delays in the program execution They are implemented as count down loops with a well known CPU cycle count per loop iteration As such no other processing ca
107. to assert this condition as some kind of out of band signalling on an RS 232 connection Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 223 When leaving the main loop a goodbye message is sent to standard error output i e to the LCD followed by three dots in one second spacing followed by a sequence that will clear the LCD Finally main will be terminated and the library will add an infinite loop so only a CPU reset will be able to restart the application There are three commands recognized each determined by the first letter of the line entered converted to lower case e The q quit command has the same effect of leaving the main loop e The 1 LCD command takes its second argument and sends it to the LCD e The u UART command takes its second argument and sends it back to the UART connection Command recognition is done using sscanf p 66 where the first format in the format string just skips over the command itself as the assignment sup pression modifier is given 6 38 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 por
108. to stdout e section start sectionname org Start section sectionname at absolute address org e Tbss org Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 372 e Tdata org e Ttext org Start the bss data or text section at org respectively e T scriptfile Use scriptfile as the linker script replacing the default linker script De fault linker scripts are stored in a system specific location e g under usr local avr lib ldscripts on Unix systems and consist of the AVR architecture name avr2 through avr5 with the suffix x appended They de scribe how the various memory sections p 282 will be linked together 9 12 3 2 Passing linker options from the C compiler By default all unknown non option arguments on the avr gcc command line i e all filename arguments that don t have a suffix that is handled by avr gcc are passed straight to the linker Thus all files ending in o object files and a object libraries are provided to the linker System libraries are usually not passed by their explicit filename but rather using the 1 option which uses an abbreviated form of the archive filename see above avr libc ships two system libraries libc a and libm a While the standard library libc a will always be searched for unresolved references when the linker is started using the C compiler frontend i e there s always at least one implied 1c option the mathematics li
109. unsigned long int __ val char __s int radix e long random void e void srandom unsigned long __ seed e long random r unsigned long ___ ctx Conversion functions for double arguments Note that these functions are not located in the default library libc a but in the mathematical library libm a So when linking the application the 1m option needs to be specified e define DTOSTR ALWAYS SIGN 0x01 e define DTOSTR PLUS SIGN 0x02 e define DTOSTR UPPERCASE 0x04 e char x dtostre double val char __s unsigned char ___ prec un signed char flags e char x dtostrf double __ val signed char ___ width unsigned char __ prec char __s Defines e define STDLIB H 1 e define need NULL e define need size_t e define need wchar t e define ptr t void e define RAND MAX 0x7FFF Typedefs e typedef int _ compar fn t const void const void Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 41 stdlib h File Reference 265 Functions e void abort void ATTR NORETURN__ e int abs int __i e long labs long __ i e void bsearch const void x key const void base size_t nmemb size_t _ size int x compar const void const void e div_t div int __num int __denom asm divmodhi4 e Idiv_t Idiv long num long _ _denom asm _divmodsi4 e void qsort void base size_t __nmemb size_t size __ compar_fn_t __compar e long strtol
110. used Then you would used it like so FLASH_DECLARE int mydata 9 9 6 Non Returning main To declare main to be a non returning function in IAR it is done like this __C_task void main void code I To do the equivalent in AVR GCC do this void main void __attribute__ noreturn void main void 1 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 attribute to specify that the main function is of type noreturn Then define main as normal Note that the return type for main is now void 9 9 7 Locking Registers The IAR compiler allows a user to lock general registers from r15 and down by using compiler options and this keyword syntax _ regvar __no_init volatile unsigned int filteredTimeSinceCommutation 014 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 321 This line locks r14 for use only when explicitly referenced in your code thorugh the var name filteredTimeSinceCommutation This means that the compiler cannot dispose of it at its own will To do this in AVR GCC do this register unsigned char counter asm r3 Typically it should be possible to use r2 through r15 that way Note Do not reserve r0 or rl as these are used internally by the compiler for a temporary register and for a zero value Locking regist
111. value U e define INT32 C value CONCAT value L e define UINT32 C value CONCAT value UL e define INT64 C value CONCAT value LL e define UINT64 C value CONCAT value ULL e define INTMAX C value CONCAT value LL e define UINTMAX C value CONCAT value ULL 6 8 2 Define Documentation 6 8 2 1 define INT16 C value value define a constant of type int16_t 6 8 2 2 define INT16 MAX Ox7fff largest positive value an int16 t can hold 6 8 2 3 define INT16 MIN INT16 MAX 1 smallest negative value an int16 t can hold Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 46 6 8 2 4 define INT32 C value CONCAT value L define a constant of type int32 t 6 8 2 5 define INT32 MAX Ox7frfffffL largest positive value an int32 t can hold 6 8 2 6 define INT32 MIN INT32_ MAX 11 smallest negative value an int32 t can hold 6 8 2 7 define INT64 C value CONCAT value LL define a constant of type int64_t 6 8 2 8 define INT64 MAX Ox7f fffffrfrfrAfLL largest positive value an int64 t can hold 6 8 2 9 define INT64 MIN INT64_ MAX 1LL smallest negative value an int64 t can hold 6 8 2 10 define INT8 C value int8 t value define a constant of type int8_t 6 8 2 11 define INT8 MAX O0x7f largest positive value an int8 t can hold 6 8 2 12 define INT8 MIN INT8 MAX 1 smallest negative val
112. 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 p 283 section in order to prevent it from being cleared upon application startup 6 37 3 3 Part 3 Interrupt service routines The ISR to handle timer 1 s overflow interrupt arranges for the software clock While timer 1 runs the PWM it calls its overflow handler rather frequently so the TMR1 SCALE value is used as a postscaler to reduce the internal software clock frequency further If the software clock triggers it sets the tmr_int bitfield and defers all further tasks to the main loop The ADC ISR just fetches the value from the ADC conversion disables the ADC interrupt again and announces the presence of the new value in the adc_int bitfield The interrupt is kept disabled while not needed because the ADC will also be triggered by executing the SLEEP instruction in idle mode which is the default sleep mode Another option would be to turn off the ADC completely here but that increases the ADC s startup time not that it would matter much for this application 6 37 3 4 Part 4 Auxiliary functions The function handle mcucsr uses two __attribute__ declarators to achieve specific goals First it will in struct the compiler to place the generated code into the init3 p 284 section of the output Thus it will be
113. vfscanf p 70 for details 6 9 3 38 int vsnprintf char x s size t mn constchar __ fmt va_list ap Like vsprintf p 73 but instead of assuming s to be of infinite size no more than n characters including the trailing NUL character will be converted to s Returns the number of characters that would have been written to s if there were enough space 6 9 3 39 int vsnprintf P char 8 size_t __n const char x __ fmt va_list ap Variant of vsnprintf p 73 that uses a fmt string that resides in program memory 6 9 3 40 int vsprintf char x __ s const char ___ fmt va_list ap Like sprintf p 66 but takes a variable argument list for the arguments 6 9 3 41 int vsprintf P char x _ s const char __ fmt va_list ap Variant of vsprintf p 73 that uses a fmt string that resides in program memory 6 10 lt stdlib h gt General utilities 6 10 1 Detailed Description include lt stdlib h gt This file declares some basic C macros and functions as defined by the ISO standard plus some AVR specific extensions Data Structures e struct div t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 74 e struct ldiv t Non standard i e non ISO C functions e char x Itoa long int val char __s int radix e char x utoa unsigned int val char s int __ radix e char x ultoa unsigned long int __ val char __s int radix e long random
114. would suffice For example pin change interrupts arriving from two different ports could logically signal an event that is indepen dent from the actual port and thus interrupt vector where it happened Shar ing interrupt vector code can be accomplished using the ISR ALIASOF p 137 attribute to the ISR macro ISR PCINTO_vect Code to handle the event ISR PCINT1_vect ISR_ALIASOF PCINTO_vect Note There is no body to the aliased ISR Note that the ISR ALIASOF p 137 feature requires GCC 4 2 or above or a patched version of GCC 4 1 x See the documentation of the ISR_ ALIAS p 136 macro for an implementation which is less elegant but could be applied to all compiler versions Empty interrupt service routines In rare circumstances in interrupt vec tor does not need any code to be implemented at all The vector must be de clared anyway so when the interrupt triggers it won t execute the BADISR _ vect code which by default restarts the application This could for example be the case for interrupts that are solely enabled for the purpose of getting the controller out of sleep mode Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 113 A handler for such an interrupt vector can be declared using the EMPTY INTERRUPT p 136 macro EMPTY INTERRUPT ADC vect Note There is no body to this macro Manually defined ISRs In some circumst
115. 0 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT megal6HVA ATtiny13 ATtiny43U ATtiny48 ATtiny45 ATtiny25 AT tiny85 ATtiny261 ATtiny461 AT tiny861 AT90USB162 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 e define sei e define cli Macros for writing interrupt handler functions define ISR vector attributes define SIGNAL vector frdefine EMPTY INTERRUPT vector define ISR ALIAS vector target vector define reti 7 define BADISR_vect ISR attributes define ISR BLOCK define ISR NOBLOCK define ISR NAKED define ISR ALIASOF target vector 6 15 2 Define Documentation 6 15 2 1 define BADISR vect include lt avr interrupt h gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 136 This is a vector which is aliased to vector default the vector executed when an ISR fires with no accompanying ISR handler This may be used along with the ISR p 136 macro to create a catch all for undefined but used ISRs for debugging purposes 6 15 2 2 define cli include lt avr interrupt h gt Disables all interrupts by clearing the global interrupt mask This function actually compiles into a single line of assembly so there is no function call overhead 6 15 2 3 define E
116. 063 PROVIDE bss end 0x00000126 __data_load_start LOADADDR data 0x00000126 _ data_load_end data load start SIZEOF data noinit 0x00800063 0x0 0x00800063 PROVIDE __noinit_start noinit 0x00800063 PROVIDE __noinit_end 0x00800063 end 0x00800063 PROVIDE __heap_start eeprom 0x00810000 0x0 eeprom 0x00810000 _ eeprom_end The last address in the text segment is location 0x114 denoted by _etext so the instructions use up 276 bytes of FLASH The data segment where initialized static variables are stored starts at lo cation 0x60 which is the first address after the register bank on an ATmega8 processor The next available address in the data segment is also location 0x60 so the application has no initialized data The bss segment where uninitialized data is stored starts at location 0x60 The next available address in the bss segment is location 0x63 so the application uses 3 bytes of uninitialized data The eeprom segment where EEPROM variables are stored starts at location 0x0 The next available address in the eeprom segment is also location 0x0 so there aren t any EEPROM variables Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 208 6 36 6 Generating Intel Hex Files We have a binary of the application but how do we get it into the processor Most if not all programmers will not accept a GNU executable as an inp
117. 1 ATtiny461 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmega48P ATmega88P ATmegal68P ATmega328P ATmegal64P ATmega324P ATmega644P AT mega644 ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 ATmega8HVA ATmegal6HVA ATmega32HVB ATmega406 ATmega1284P AT90PWM1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 AT90USB82 AT90USB162 AT90USB646 AT90USB647 AT90USB1286 AT90USB1287 ATtiny48 ATtiny88 6 25 lt util atomic h gt Atomically and Non Atomically Ex ecuted Code Blocks 6 25 1 Detailed Description include lt util atomic h gt Note The macros in this header file require the ISO IEC 9899 1999 ISO C99 feature of for loop variables that are declared inside the for loop itself For that reason this header file can only be used if the standard level of the compiler option std is set to either c99 or gnu99 The macros in this header file deal with code blocks that are guaranteed to be excuted Atomically or Non Atmomically The term Atomic in this context refers to the unability of the respective code to be interrupted These macros operate via automatic manipulation of the Global Interrupt Status 1 bit of the SREG register Exit paths from both block types are all managed automatically without the need for special considerations i e the interrupt status will be restored to the same value it has been when entering the respective block A typical example that requires atomic access
118. 1 functions setjmp p 41 and longjmp p 41 are useful for dealing with errors and interrupts encountered in a low level subroutine of a program Note setjmp p 41 and longjmp p 41 make programs hard to understand and maintain If possible an alternative should be used longjmp p 41 can destroy changes made to global register variables see How to permanently bind a variable to a register p 323 For a very detailed discussion of setjmp p 41 longjmp see Chapter 7 of Advanced Programming in the UNIX Environment by W Richard Stevens Example include lt setjmp h gt jmp_buf env int main void if setjmp env 1 handle error I while 1 main processing loop which calls foo some where void foo void blah blah blah if err longjmp env 1 Functions e int setjmp jmp buf __jmpb e void longjmp jmp_buf __jmpb int ret ATTR NORETURN _ Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 7 lt setjmp h gt Non local goto 41 6 7 2 Function Documentation 6 7 2 1 void longjmp jmp buf jmpb int __ ret Non local jump to a saved stack context include lt setjmp h gt longjmp p 41 restores the environment saved by the last call of setjmp p 41 with the corresponding jmpb argument After longjmp p 41 is completed program execution continues as if the corresponding call of setjmp p 41 had just
119. 1 3 21 size_t strlcpy char dst const char src size_t siz Copy a string Copy src to string dst of size siz At most siz 1 characters will be copied Always NULL terminates unless siz 0 Returns The strlepy p 92 function returns strlen src If retval gt siz trun cation occurred Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 93 6 11 3 22 size_t strlen const char src Calculate the length of a string The strlen p 93 function calculates the length of the string src not includ ing the terminating 0 character Returns The strlen p 93 function returns the number of characters in src 6 11 3 23 char x strlwr char s Convert a string to lower case The strlwr p 93 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 p 93 function returns a pointer to the converted string 6 11 3 24 int strncasecmp const char s1 const char s2 size_t len Compare two strings ignoring case The strncasecmp p 93 function is similar to strcasecmp p 90 except it only compares the first len characters of s1 Returns The strncasecmp p 93 function returns an integer less than equal to or greater than zero if s1 or the first len bytes thereof is found respectively to be less than to match or
120. 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 326 e 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 e Some of the supplied include files are not C safe i e they need to be wrapped into extern C This could certainly be fixed too e Exceptions are not supported Since exceptions are enabled by de fault in the C frontend they explicitly need to be turned off using fno exceptions in the compiler options Failing this the linker will complain about an undefined external reference to __gxx_personality_ sjo Constructors and destructors are supported though including global ones When programming C in space and runtime sensitive environments like mi crocontrollers extra care should be taken to avoid unwanted side effects of the C calling conventions like implied copy constructors that could be called upon function invocation etc These things could easily add up into a consid erable 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 p 321 9 10 8 Shouldn t I initialize all my variables Global and static variables are guaranteed to be initialized to 0 by the C stan dard avr gcc does this by placing the appropriate code into secti
121. 16 avr inttypes 28 SCNdFAST32 avr inttypes 28 SCNdLEAST16 SCNdLEAST32 SCNdPTR SCNi16 SCNiLEAST16 avr inttypes 29 SCNiLEAST32 avr inttypes 29 SCNiPTR avr inttypes 29 SCNo16 avr inttypes 29 SCNo32 avr inttypes 29 SCNoFAST16 avr inttypes 30 SCNoFAST32 avr inttypes 30 SCNoLEAST16 avr inttypes 30 SCNoLEAST32 avr inttypes 30 SCNoPTR avr inttypes 30 SCNul6 avr inttypes 30 SCNu32 avr inttypes 30 SCNuFAST16 avr inttypes 30 SCNuFAST32 avr inttypes 30 SCNuLEAST16 avr inttypes 30 SCNuLEAST32 avr inttypes 30 avr inttypes 28 avr inttypes 29 avr inttypes 29 SCNuPTR SCNx16 SCNx32 SCNxFAST16 avr inttypes 31 avr inttypes 31 avr inttypes 31 avr inttypes 29 SCNi32 avr inttypes 29 SCNiFAST16 avr inttypes 29 SCNiFAST32 avr inttypes 29 avr inttypes 31 SCNxFAST32 avr inttypes 31 SCNxLEAST16 avr inttypes 31 SCNxLEAST32 avr inttypes 31 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 397 INDEX SCNxPTR avr inttypes 31 sei avr interrupts 138 setbaud h 258 setjmp longjmp 40 setjmp 40 setjmp h 258 SIG ATOMIC MAX avr stdint 48 SIG ATOMIC MIN avr stdint 48 SIGNAL avr interrupts 138 signbit avr math 38 sin avr math 38 sinh avr math 38 SIZE MAX avr stdint 48 sleep h 258 sleep cpu avr sleep 163 sleep dis
122. 1U largest value an uint16 t can hold 6 8 2 41 define UINT32 C value CONCAT value UL define a constant of type uint32 t 6 8 2 42 define UINT32 MAX CONCAT INT32 MAX U 2UL 1UL largest value an uint32 t can hold 6 8 2 43 define UINT64 C value CONCAT value ULL define a constant of type uint64 t 6 8 2 44 define UINT64 MAX CONCAT INT64 MAX U 2ULL 1ULL largest value an uint64 t can hold 6 8 2 45 define UINT8 C value uint8 t CONCAT value U define a constant of type uint8_t 6 8 2 46 define UINT8 MAX __CONCAT INT8_ MAX U x 2U 1U largest value an uint8 t can hold Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 50 6 8 2 47 define UINT_FAST16_ MAX UINT16_ MAX largest value an uint fastl6 t can hold 6 8 2 48 define UINT FAST32 MAX UINT32 MAX largest value an uint fast32 t can hold 6 8 2 49 define UINT FAST64 MAX UINT64 MAX largest value an uint fast64 t can hold 6 8 2 50 define UINT FAST8 MAX UINTS8 MAX largest value an uint fast8 t can hold 6 8 2 51 define UINT LEASTI6 MAX UINT16 MAX largest value an uint least16 t can hold 6 8 2 52 define UINT LEAST32 MAX UINT32 MAX largest value an uint least32 t can hold 6 8 2 53 define UINT LEAST64 MAX UINT64 MAX largest value an uint least64 t can hold 6 8 2 54 define UINT LEAST8 MAX UINT8 MAX largest value an uint least8 t can hold
123. 2 MIN INT32 MIN e define UINT LEAST32 MAX UINT32 MAX e define INT LEAST64 MAX INT64 MAX e define INT LEAST64 MIN INT64 MIN e 4define UINT LEAST64 MAX UINT64 MAX Limits of fastest minimum width integer types e 4define INT FASTS MAX INTS MAX Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 39 stdint h File Reference 260 e define INT_FAST8 MIN INT8_MIN e 4define UINT FAST8 MAX UINT8_MAX e 4define INT FAST16 MAX INT16_MAX e define INT FAST16 MIN INT16_ MIN e 4define UINT FASTIG MAX UINT16 MAX e define INT FAST32 MAX INT32_ MAX e define INT FAST32 MIN INT32 MIN e define UINT FAST32 MAX UINT32 MAX e define INT FAST64 MAX INT64 MAX e define INT FAST64 MIN INT64 MIN e define UINT FAST64 MAX UINT64 MAX Limits of integer types capable of holding object pointers e define INTPTR MAX INT16 MAX e define INTPTR MIN INT16 MIN e define UINTPTR MAX UINTI6 MAX Limits of greatest width integer types e define INTMAX MAX INT64 MAX e define INTMAX MIN INT64_ MIN e 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 p 259 gt is included e define PTRDIFF MAX INT16_MAX e define PTRDIFF MIN INT16 MIN e define SIG ATOMIC MAX INT8 MAX e define SIGT ATOMIC MIN INT8 MIN e define SIZE MAX __CONCAT INT16_ MAX U Macros for integ
124. 4 strlwr S File Reference 0 8 65 strncasecmp S File Reference _ 0 0 0 8 66 strncasecmp P S File Reference 8 67 strncat S File Reference _ oaoa 8 68 strncat P S File Reference a soru aa aa i a 8 69 strnemp S File Reference oaaae 8 70 strnemp P S File Reference 22 ov arv vr vr rea 8 71 strnepyS File Reference ervvr vr vr vr vr avs 8 72 strnepy P S File Reference 0 000 0 8 73 strnlen S File Reference 0 2 000 8 74 strnlen P S File Reference 2 2 v rav rv vr vr rv 8 75 strpbrk S File Reference rar rv rv rv ras 8 76 strpbrk P S File Reference 0 0 0 0 8 77 strrchr S File Reference 522 00 8 78 strrchr P S File Reference 2 e var rv rv vr rea 8 79 strrev S File Reference vr rv vr rv vnr vr aan 8 80 strsep S File Reference 00 0 000004 8 81 strsep PS File Reference aaa raea tal ge eg rv vr vr ra 8 82 strspn S File Reference rv rv rv vnr rea 8 83 strspn P S File Reference t t A rv rv rv vr re 8 84 strstr S File Reference vnua vnr rv rn vever 8 85 strstr P S File Reference ines aoun aaa i A 8 86 strtok r S File Reference 0 0 0 8 87 strupr S File Reference 0 8 88 twi h File Reference 8 89 wdt h File Reference uoaa avr libc Page Documentation 9 1 Toolchain Overview 0 0 vr vr vr eee eee Gene
125. 4414 AT90S4433 CAPT _ vect i Capture Event AT90S4434 AT90S8515 AT90S8535 CAPTURE1 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 AT megal03 ATmegal28 ATmegal284P ATmegal6 ATmegal61 AT megal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P AT megal69 ATmegal69P ATmega32 ATmega323 ATmega325 AT mega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega48P AT mega64 ATmega645 ATmega6450 ATmega649 ATmega6490 AT mega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 AT mega48 ATmega88 ATmega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 ATtiny2313 ATtiny48 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMERI1 SIG_ Timer Counter1 ATtiny26 CMPA vect OUTPUT Compare COMPARE1A Match 1A TIMERI1 SIG Timer Counter1 ATtiny26 CMPB_vect OUTPUT_ Compare COMPAREI1B Match 1B TIMERI1 SIG Timer Counterl AT9052313 COMP1_ OUTPUT Compare vect COMPARE1A Match Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 126 AT9058535 AT90PWM216 COMPARELA Match A AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 ATmega103 AT megal28 ATmegal284P ATmegal6 ATmegal61 ATmegal62 AT megal63 ATmegal65 ATmegal65P ATmega
126. 48 88 168 which have become quite popular since the original demo project had been established For all these more modern devices it is no longer necessary to use an external crystal for clock ing as they ship with the internal 1 MHz oscillator enabled so C1 C2 and Q1 can be omitted Normally for this experiment the external circuitry on RESET R1 C3 can be omitted as well leaving only the AVR the LED the bypass capacitor C4 and perhaps R2 For the ATmega8 48 88 168 use PB1 pin 15 at the DIP 28 package to connect the LED to Addition ally this demo has been ported to many different other AVRs The location of the respective OC pin varies between different AVRs and it is mandated by the AVR hardware Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 196 NN IC1 R1 id SCK PB7 22 E ts RESET mIso PB6 8 20K n 5 c2 E 2 4 E MOSI PB5 LED5MM a f 26 a dHe zraz ane Fer in OCI PB3 25 DA s XTALI PB2 14 see note 8 WA 18pf 20 AIN1 PB1 23 4 vec GND im AINO PBO 12 ua g rcp pps 4 T1 PD5 2 T0 PD4 H8 INT1 PD3 GND INTO PD2 P TxD PD1 3 RXD PDO 2 AT90S2313P Figure 1 Schematic of circuit for demo project The source code is given in demo c p 198 For the sake of this example create a file called demo c containing this source code Some of the more important pa
127. 5 __AVR_ENHANCED___ 5 __ AVR_HAV 1 New in GCC 4 2 2 Unofficial patch for GCC 4 1 3 New in GCC 4 2 3 4 New in GCC 4 3 5 Obsolete By default code is generated for the avr2 architecture Note that when only using mmcu architecture but no mmcu MCU type in cluding the file lt avr io h p 247 gt cannot work since it cannot decide which device s definitions to select e mmcu MCU type The following MCU types are currently understood by avr gcc The table matches them against the corresponding avr gcc architecture name and shows the preprocessor symbol declared by the mmcu option Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 364 AVR ATIOPWMBB AVR ATOOPWMS16 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 365 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 366 atmega2560 _ ATmega2560_ atmega2561 AVR ATmega2561 atxmega64al AVR ATxmega64Al atxmegal28al AVR ATxmegal28A1 1 avr25 architecture is new in GCC 4 2 2 avr35 architecture is new in GCC 4 2 3 e morderi e morder2 Change the order of register assignment The default is r24 r25 r18 r19 r20 r21 r22 r23 r30 r31 126 r27 r28 r29 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 r2 r0 r1 Order 1 uses r18 r19 r20 r21
128. 5 option Next are the two interrupt service routines for timer 0 compare A match timer 0 hits TOP as OCROA is set to 255 and timer 0 overflow timer 0 hits BOT TOM As discussed above these are kept as short as possible They only save SREG as the flags will be modified by the INC instruction increment the counter_hi variable which forms the high part of the current time counter the low part is formed by querying TCNTO directly and clear or set the variable flags respectively in order to note the current counting direction The RETI instruction terminates these interrupt service routines Total cycle count is 8 CPU cycles so together with the 4 CPU cycles needed for interrupt setup and the 2 cycles for the RJMP from the interrupt vector to the handler these rou tines 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
129. 560 AT mega2561 ATmega324P AT megal64P ATmega644P AT mega644 ATtiny13 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 ATtiny45 ATtiny25 AT tiny85 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 ATmegal62 ATmegal65 AT megal65P ATmegal68P ATmega169 ATmegal69P ATmega325 AT mega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega406 ATmega48P AT mega645 ATmega6450 ATmega649 ATmega6490 ATmega88P AT megal68 ATmega48 ATmega88 AT mega640 ATmega1280 ATmegal1281 ATmega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 ATtiny43U ATtiny48 ATtiny24 ATtiny44 ATtiny84 AT90USB162 AT90USB82 ATmega3250 ATmega3250P AT mega328P ATmega3290 AT mega3290P ATmega48P AT mega6450 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 ATtiny48 ATmega3250 ATmega3250P mega3290 ATmega3290P mega6450 ATmega6490 mega324P ATmegal64P mega644P ATmega644 ATtiny48 ATtiny2313 ATtiny261 ATtiny461 ATtiny861 avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 121 Vector Old vector Description Applicable for device a NEVNTE l PSCO_ SIG_ PSCO Capture AT90PWM3 AT90PWM2 CAPT vect PSCO_ Event AT90PWM1 CAPTURE PSCO_ SIG PSCO End Cy AT90PWM3 PSC1_ SIG_ PSC1 Capture AT90PWM3 AT90
130. 6 8 2 55 define UINTMAX C value CONCAT value ULL define a constant of type uintmax_t 6 8 2 56 define UINTMAX MAX UINT64 MAX largest value an uintmax t can hold 6 8 2 57 define UINTPTR MAX UINT16 MAX largest value an uintptr_t can hold Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 51 6 8 3 Typedef Documentation 6 8 3 1 typedef signed int int16 t 16 bit signed type 6 8 3 2 typedef signed long int int32 t 32 bit signed type 6 8 3 3 typedef signed long long int int64 t 64 bit signed type Note This type is not available when the compiler option mint8 is in effect 6 8 3 4 typedef signed char int8 t 8 bit signed type 6 8 3 5 typedef int16 t int fast16 t fastest signed int with at least 16 bits 6 8 3 6 typedef int32_t int fast32 t fastest signed int with at least 32 bits 6 8 3 7 typedef int64_t int fast64 t fastest signed int with at least 64 bits Note This type is not available when the compiler option mint8 is in effect 6 8 3 8 typedef int8 tint fast8 t fastest signed int with at least 8 bits 6 8 3 9 typedef int16_t int least16 t signed int with at least 16 bits Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 52 6 8 3 10 typedef int32_t int least32 t signed int with at least 32 bits 6 8 3 11 typedef int64 t int least64 t signed int with at least 64 bits
131. 7 attiny13 attiny15 1 p 7 attiny22 attiny24 attiny25 attiny26 attiny261 attiny28 1 p 7 attiny2313 attiny43u attiny44 attiny45 attiny461 attiny48 attiny84 attiny85 attiny861 attiny88 Automotive AVR Devices e atmega32cl Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 1 3 Supported Devices e atmega32m1 e attiny167 CAN AVR Devices e at90can32 e at90can64 e at90can128 LCD AVR Devices atmegal69 atmegal69p atmega329 atmega329p atmega3290 e atmega3290p e atmega649 e atmega6490 Lighting AVR Devices e at90pwml e at90pwm2 at90pwm2b at90pwm216 at90pwm3 at90pwm3b at90pwm316 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 1 3 Supported Devices Smart Battery AVR Devices atmega8hva atmegal6hva atmega32hvb atmega406 USB AVR Devices at90usb82 at90usb162 at90usb646 at90usb647 e at90usb1286 e at90usb1287 e atmega32u4 XMEGA Devices e atxmegal28al e atxmega64al Miscellaneous Devices at94K 2 p 7 at76c711 3 p 7 at43usb320 at43usb355 at86rf401 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 1 3 Supported Devices 7 Classic AVR Devices at90s1200 1 p 7 at90s2313 at90s2323 at90s2333 at90s2343 at90s4414 at90s4433 at90s4434 at90s8515 at90c8534 at90s8535 Note 1 Assembly only There is no direct
132. 7 sei f0 78 94 sei f2 08 95 ret 000000f4 lt main gt int main void f4 83 e8 ldi r24 0x83 131 f6 8f bd out Ox2f r24 47 Start timer 1 NB TCCR1A and TCCR1B could actually be the same register so take care to not clobber it TCCR1B TIMER1_CLOCKSOURCE 8 8e b5 in r24 Ox2e 46 fa 81 60 ori r24 0x01 1 fc 8e bd out Ox2e r24 46 if defined TIMER1_SETUP_HOOK TIMER1_SETUP_HOOK endif Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 204 6 36 A simple project 205 Set PWM value to 0 OCR 0 fe 1b bc out 0x2b ri 43 100 1a bc out Ox2a ri 42 Enable OC1 as output DDROC BV OC1 102 82 e0 ldi r24 0x02 2 104 87 bb out 0x17 r24 23 Enable timer 1 overflow interrupt TIMSK _BV TOIE1 106 84 e0 ldi r24 0x04 4 108 89 bf out 0x39 r24 57 sei 10a 78 94 sei ioinit loop forever the interrupts are doing the rest for Note 7 sleep_mode 10c 85 b7 in r24 0x35 53 10e 80 68 ori r24 0x80 128 110 85 bf out 0x35 r24 53 112 88 95 sleep 114 85 b7 in r24 0x35 53 116 8f 77 andi r24 Ox7F 127 118 85 bf out 0x35 r24 53 dia 8 cf rjmp 16 Ox10c lt main 0x18 gt 0000011c lt __bad_interrupt gt 11c 71 cf rjmp 286 0x0 lt __vectors gt 0000011e lt exit gt 11e f8 94 cli 120 00 cO rjmp 0 0x122 lt _exit gt 00000122 lt _exit g
133. 82 6 32 lt compat deprecated h gt Deprecated items 186 6 33 lt compat ina90 h gt Compatibility with IAR EWB 3 x 189 6 34 Demo projects 190 6 35 Combining C and assembly source files 191 6 36 A simple project eiaa Liun i a a a a i e y a a a L a a A 195 6 37 A more sophisticated project ooo 212 6 38 Using the standard IO facilities 219 6 39 Example using the two wire interface TWI 227 7 avr libc Data Structure Documentation 232 7 1 div_t Struct Reference vvr rav rv 0 000000 232 Ta ldiv_t Struct Reference sans vasse ka d ka 233 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen CONTENTS 8 avr libc File Documentation 8 1 8 2 8 3 8 4 8 5 8 6 8 7 8 8 8 9 8 10 8 11 8 12 8 13 8 14 8 15 8 16 8 17 8 18 8 19 8 20 8 21 8 22 8 23 8 24 8 25 8 26 8 27 8 28 8 29 8 30 assert h File Reference arv v a atoi S File Reference rv vr vnr kv atol S File Reference 2 20 rv rv vr rv ee atomic h File Reference 0 2 0 000 boot h File Reference av av vr vnr rn kr crc16 h File Reference 20 0 ctype h File Reference 2 2 0 4 delay h File Reference 02 00 an av delay basic h File Reference 0 0 00 0 errno h File Reference avv rv rv vnr vn knr vn fdevopen c File Reference
134. AX 49 int least32 t 52 INT LEAST64 MAX 49 int least64 t 52 INT LEAST8 MAX 49 int least8 t 53 INTMAX_C 50 INTMAX MAX 50 Gras eve ele ere Ee eee ee Che eves ie ae eee ee Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX uintmax t 53 UINTPTR MAX 50 uintptr t 53 avr stdio _FDEV_ EOF 58 _FDEV_ERR 58 _FDEV_SETUP_READ 58 _FDEV_SETUP_RW 58 _FDEV_SETUP_WRITE 58 clearerr 61 EOF 58 fclose 61 fdev close 59 fdev get udata 59 fdev set udata 59 FDEV SETUP STREAM 59 fdev setup stream 59 fdevopen 61 feof 62 ferror 62 flush 62 fgetc 62 fgets 63 FILE 60 fprintf 63 fprintf P 63 fputc 63 fputs 63 fputs P 63 fread 63 fscanf 64 fscanf P 64 fwrite 64 getc 60 getchar 60 gets 64 printf 64 printf P 64 putc 60 putchar 60 puts 64 puts P 64 scanf 65 scanf_P 65 snprintf 65 snprintf_P 65 387 sprintf 65 sprintf P 65 sscanf 65 sscanf_P 65 stderr 60 stdin 60 stdout 61 ungetc 66 vfprintf 66 vfprintf_ P 69 vfscanf 69 viscanf_P 72 vprintf 72 vscanf 72 vsnprintf 72 vsnprintf_P 72 vsprintf 72 vsprintf_ P 72 avr stdlib _ compar fn t 75 malloc heap end 84 malloc heap start 84 __malloc_ margin 84 abort 75 abs 75 atof 75 atoi 76 atol 76 bsearch 76 calloc 77 div 77 DTOSTR ALWAYS SIGN 75 DTOSTR_PLUS_ SIGN 75 DTOSTR_UPPERCASE 75 dtostre 77 dtostrf 77 ex
135. Counter3 AT90CAN128 Timer Counter4 Timer Counter4 Compare COMPAREAA Match A SIG_ Timer Counter4 OUTPUT Compare SIG_ Timer Counter4 OUTPUT_ Compare COMPAREAC Match C TIMERA SIG_ Timer Counter4 OV RELOW ovo Timer Counter5 Timer Counter5 SIG_ Timer Counter5 OUTPUT_ Compare COMPARESB Match B Timer Counter5 Timer Counter5 130 AT90CAN32 AT90CAN64 ATmega128 AT megal284P ATmegal62 AT mega64 ATmega640 ATmegal280 ATmega1281 ATmega2560 ATmega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 AT90CAN32 AT90CAN64 ATmegal 28 AT mega64 ATmega640 ATmegal280 ATmega1281 ATmega2560 ATmega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 AT90CAN32 AT90CAN64 ATmega128 AT megal284P ATmega162 AT mega64 ATmega640 ATmegal280 ATmega1281 ATmega2560 ATmega2561 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 ATmega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 AT
136. D Change Changes since avr libe lt last release gt to Changes in avr libe lt this relelase gt 3 Set the branch point tag setting lt major gt and lt minor gt accordingly cvs tag avr libe lt major gt lt minor gt branchpoint 4 Create the branch cvs tag b avr libe 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 14 Release Numbering and Methodology 377 Update the NEWS file and commit to cvs HEAD Add Changes since avr libe lt this release gt 7 Check out a new tree for the branch evs co r avr libc lt major gt _ lt minor gt branch 8 Update the package version in configure ac and commit configure ac to cvs branch Change the patch number to 90 to denote that this now a branch leading up to a release Be sure to leave the lt date gt part of the version 9 Bring the build system up to date by running bootstrap and configure 10 Perform a make distcheck and make sure it 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 developers can checkout the branch Note CVS tags do not allow the use of periods 9 14 2 2 Making
137. E stream int fputs P const char str FILE stream int puts const char x 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 x stream char gets char x str size_t fread void __ ptr size_t size size_t nmemb FILE x _ stream void clearerr FILE _ stream int feof FILE stream int ferror FILE x stream int vfscanf FILE x stream const char fmt va list ap int vfscanf P FILE _ stream const char __ fmt va list ap int fscanf FILE stream const char x fmt int fscanf P FILE stream const char fmt int scanf const char x fmt int scanf P const char fmt int vscanf const char x__ fmt va_list ap int sscanf const char ___buf const char ___fmt int sscanf P const char __ buf const char fmt int flush FILE stream stdlib h File Reference 8 41 1 Detailed Description Data Structures struct div t struct Idiv_t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 41 stdlib h File Reference 264 Non standard i e non ISO C functions e define RANDOM MAX 0x7FFFFFFF e char x itoa int __ val char __s int radix e char x Itoa long int val char s int radix e char x utoa unsigned int val char s int __ radix e char x ultoa
138. EGET var addr var eeprom read byte const uint8 t addr Defines e define EEMEM __ attribute _ section eeprom e define eeprom is ready e define eeprom busy wait do while leeprom is ready Functions e static ATTR PURE inline uint8 t eeprom read byte const uint8 t __p u u e static ATTR_PURE inline uint16 t eeprom read word const uint16 t p u u u e static ATTR_PURE inline uint32 t eeprom read dword const uint32_t __p e static inline void eeprom_read_ block void dst const void src size_t _n e static inline void eeprom write byte uint8 t x p uint8 t value E u u e static inline void eeprom write word uint16 t __p uint16 t __ value u u e static inline void eeprom write dword uint32_t __p uint32_t _ value e static inline void eeprom write block const void sre void dst size tn 6 13 2 Define Documentation 6 13 2 1 define _EEGET var addr var eeprom read byte const uint8_t addr Read a byte from EEPROM Compatibility define for IAR C Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 106 6 13 2 2 define EEPUT addr val eeprom write byte uint8 t addr uint8 t val Write a byte to EEPROM Compatibility define for IAR C 6 13 2 3 define EEMEM __ attribute section eeprom Attribute expression causing a variable to be allocated within
139. FDEV_SETUP_RW __SRD __SWR e define FDEV ERR 1 e define FDEV EOF 2 e define FDEV SETUP STREAM put get rwflag e define fdev close e define putc __c __ stream fputc __c stream e define putchar c fputc __c stdout e define getc _ stream fgete stream e define getchar fgetc stdin e define SEEK SET 0 e define SEEK CUR 1 e define SEEK END 2 Functions int fclose FILE stream int vfprintf FILE stream const char ___ fmt va_list ap ap int vfprintf P FILE stream const char __ fmt va_list int fputc int c FILE x stream int printf const char x fmt int printf P const char __fmt int vprintf const char fmt va_list ap int sprintf char x_ s const char fmt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 41 8 41 stdlib h File Reference 263 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 charx s 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 x fmt va_list ap int fprintf FILE x stream const char x__fmt int fprintf P FILE stream const char __ fmt int fputs const char ___ str FIL
140. 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 fuse h gt Fuse Support lt avr interrupt h gt Interrupts lt avr io h gt AVR device specific IO definitions lt avr lock h gt Lockbit Support lt avr pgmspace h gt Program Space Utilities lt avr power h gt Power Reduction Management lt avr sfr defs h gt Special function registers Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 15 16 17 19 20 32 39 42 54 73 85 97 104 107 110 139 140 143 156 160 3 avr libc Data Structure Index Additional notes from lt avr sfr defs h gt lt avr sleep h gt Power Management and Sleep Modes lt avr version h gt avr libc version macros lt avr wdt h gt Watchdog timer handling 10 158 162 164 165 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks lt util crc16 h gt CRC Computations 169 173 lt util delay h gt Convenience functions for busy wait delay loops lt util delay basic h gt Basic busy wait delay loops lt util parity h gt Parity bit generation lt util setbaud h gt Helper macros for baud rate calculations lt util twi h gt T
141. LL 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 p 143 Defines e define _FFS x Functions e int ffs int val int ffsl long __ val int ffsll long long val void x memccpy void const void x int size_t void x memchr const void x int size_t ATTR PURE int memcmp const void x const void x size_t ATTR PURE void x memcpy void const void x size_t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 86 void x memmem const void x size_t const void x size_t ATTR PURE__ void x memmove void const void x size_t void x memrchr const void x int size_t ATTR PURE void x memset void x int size_t int strcasecmp const char const char ATTR PURE char strcasestr const char x const char ATTR PURE char strcat char const char char strchr const char int ATTR PURE char strchrnul const char int ATTR PURE int stremp const char x const char ATTR PURE char strcpy char const char size_t strcspn const char x s const char x reject ATTR PURE size_t strlcat char const char x size_t size_t strlcpy char x const char size_t size_t strlen const char ATTR PURE char strlwr char x int strncasecmp const c
142. LT which is defined to be OxFF See the AVR device specific datasheet for more details about these lock bits and the available mode settings A convenience macro LOCKMEM is defined as a GCC attribute for a custom named section of lock A convenience macro LOCKBITS is defined that declares a variable lock of type unsigned char with the attribute defined by LOCKMEM This variable allows the end user to easily set the lockbit data Note If a device specific I O header file has previously defined LOCKMEM then LOCKMEM is not redefined If a device specific I O header file has previ ously defined LOCKBITS then LOCKBITS is not redefined LOCKBITS is currently known to be defined in the I O header files for the XMEGA devices API Usage Example Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 17 lt avr lock h gt Lockbit Support 142 Putting all of this together is easy include lt avr io h gt LOCKBITS LB_MODE_1 amp BLBO_MODE_3 amp BLB1_MODE_4 int main void return 0 Or include lt avr io h gt unsigned char __lock __attribute__ section lock LB MODE 1 amp BLBO_MODE_3 amp BLB1_MODE_4 int main void return 0 However there are a number of caveats that you need to be aware of to use this API properly Be sure to include lt avr io h p 247 gt to get all of the definitions for the API The LOCKBITS macro defines a global variable to store t
143. MAX e define INT FAST32 MAX INT32 MAX e define INT FAST32 MIN INT32_ MIN e define UINT FAST32 MAX UINT32 MAX e define INT FAST64 MAX INT64 MAX e define INT FAST64 MIN INT64 MIN e define UINT FAST64 MAX UINT64 MAX Limits of integer types capable of holding object pointers e define INTPTR MAX INTI6 MAX e define INTPTR MIN INT16 MIN e define UINTPTR MAX UINTI6 MAX Limits of greatest width integer types e define INTMAX MAX INT64 MAX e define INTMAX MIN INT64 MIN e define UINTMAX MAX UINT64 MAX Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 45 Limits of other integer types C implementations should define these macros only when __ STDC LIMIT MACROS is defined before lt stdint h p 259 gt is included e define PTRDIFF MAX INT16_ MAX e define PTRDIFF MIN INT16_ MIN e define SIG ATOMIC MAX INT8_MAX e define SIG ATOMIC MIN INT8_ MIN e 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 p 259 gt is included These definitions are valid for integer constants without suffix and for macros defined as integer constant without suffix e define INT8 C value int8 t value e define UINT8 C value uint8 t CONCAT value U e define INT16 C value value e define UINT16 C value CONCAT
144. MPAT 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 6 21 lt avr sfr_defs h gt Special function registers 6 21 1 Detailed Description When working with microcontrollers many tasks usually consist of controlling internal peripherals or external peripherals that are connected to the device The entire IO address space is made available as memory mapped IO i e it can be accessed using all the MCU instructions that are applicable to normal data memory For most AVR devices the IO register space is mapped into the data memory address space with an offset of 0x20 since the bottom of this space is reserved for direct access to the MCU registers Actual SRAM is available only behind the IO register area starting at some specific address depending on the device For example the user can access memory mapped IO registers as if they were globally defined variables like this PORTA 0x33 unsigned char foo PINA The compiler will choose the correct instruction sequence to generate based on the address of the register being accessed The advantage of using the memory mapped registers in C programs is that it makes the programs more portable to other C compilers for the AVR platform Note that special care must be taken when accessing some of the 16 bit timer IO registers where access from both the main program and within an interrupt cont
145. MPTY INTERRUPT vector include lt avr interrupt h gt Defines an empty interrupt handler function This will not generate any prolog or epilog code and will only return from the ISR Do not define a function body as this will define it for you Example EMPTY INTERRUPT ADC vect 6 15 2 4 define ISR vector attributes include lt avr interrupt h gt Introduces an interrupt handler function interrupt service routine that runs with global interrupts initially disabled by default with no attributes specified The attributes are optional and alter the behaviour and resultant generated code of the interrupt routine Multiple attributes may be used for a single function with a space seperating each attribute Valid attributes are ISR_BLOCK ISR_NOBLOCK ISR_NAKED and ISR ALIASOF vect p 137 vector must be one of the interrupt vector names that are valid for the partic ular MCU type 6 15 2 5 define ISR ALIAS vector target vector include lt avr interrupt h gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 137 Aliases a given vector to another one in the same manner as the ISR_ ALIASOF attribute for the ISR p 136 macro Unlike the ISR_ALIASOF attribute macro however this is compatible for all versions of GCC rather than just GCC version 4 2 onwards Note This macro creates a trampoline function for the aliased macro This will result in a two cy
146. 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 p 161 6 21 2 2 define bit is clear sfr bit _ SFR BYTE sfr amp _ BV bit finclude 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 22 lt avr sleep h gt Power Management and Sleep Modes 162 6 21 2 3 define bit is set sfr bit SFR BYTE sfr amp BV bit include lt avr io h gt Test whether bit bit in IO register sfr is set This will return a 0 if the bit is clear and non zero if the bit is set 6 21 2 4 define loop until bit is clear sfr bit do while bit is set sfr bit finclude lt avr io h gt Wait until bit bit in IO register sfr is clear 6 21 2 5 define loop_until bit is set sfr bit do while bit is clear sfr bit include lt avr io h gt Wait until bit bit in IO register sfr is set 6 22 lt avr sleep h gt Power Management and Sleep Modes 6 22 1 Detailed Description include lt avr sleep h gt Use of the SLEEP instruction can allow an application to reduce its power com sumption 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
147. O driver for the internal UART e uart h Interface declarations for the UART driver 6 38 3 A code walkthrough 6 38 3 1 stdiodemo c As usual include files go first While conventionally system header files those in angular brackets lt gt go before application specific header files in double quotes defines h comes as the first 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 simplicity and with a reasonable optimization level in effect it will inline that function That needs to be kept in mind when debugging because the inlining might cause the debugger to jump around wildly at a first glance when single stepping The definitions of uart_str and 1cd_str set up two stdio streams The ini tialization is done using the FDEV_SETUP_STREAM p 60 initializer template macro so a static object can be constructed that can be used for IO purposes This initializer macro takes three arguments two function macros to connect the corresponding output and input functions respectively the third one de scribes the intent of the stream read write or both Those functions that are not required by the specified intent like the input function for 1cd_str which is specified to only
148. P buf p 82 69 al ldd r22 Y 33 0x21 84 7a al ldd r23 Y 34 0x22 86 ce 01 movw r24 r28 88 01 96 adiw r24 0x01 v 8a Oc dO reall 24 Oxa4 This will finally copy the ROM string into the local buffer buf Variable p located at Y 33 is read and passed together with the address of buf Y 1 to strepy P This will copy the string from ROM to buf Note that when using a compile time constant index omitting the first step reading the pointer from ROM via memcpy P usually remains unnoticed since the compiler would then optimize the code for accessing array at compile time Back to FAQ Index p 321 9 10 16 How to use external RAM Well there is no universal answer to this question it depends on what the external RAM is going to be used for Basically the bit SRE SRAM enable in the MCUCR register needs to be set in order to enable the external memory interface Depending on the device to be used and the application details further registers affecting the external memory operation like XMCRA and XMCRB and or further bits in MCUCR might be configured Refer to the datasheet for details If the external RAM is going to be used to store the variables from the C program i e the data and or bss segment in that memory area it is essential to set up Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 337 the external memory interface early during the device i
149. PE a GE PE OE EE AE CE BE e EE sk 236 8 5 boot h File Reference 8 5 2 3 define boot page erase alternate address Value __extension__ _ asm__ __volatile__ movw r30 2Nnlt sts 0 1 n t spm n t word Oxffff n t nop n t i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE ERASE r uint16 t address r30 r31 H 8 5 2 4 define boot page erase extended address Value __extension__ _ asm__ __volatile__ movw r30 ZA3 n t sts 1 C3 n t sts 0 2 n t spm n t i _SFR_MEM_ADDR __SPM_REG i _SFR_MEM_ADDR RAMPZ r uint8 t BOOT PAGE ERASE r uint32_t address 730 r31 H 8 5 2 5 define __boot_page_erase_normal address Value __extension__ _ asm__ __volatile__ movw r30 2 n t sts 0 1 n t spm n t i SFR MEM ADDR SPM REG Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen DO LO LO LO BOBO GO GL LO PO PO POE PO GSO ZA A A A A AA AA ZA ZZ sz KISS 237 8 5 boot h File Reference r uint8 t BOOT PAGE ERASE nr uint16_t address r30 r31 H 8 5 2 6 define boot page fill alternate address data Value __extension__ _ asm__ __volatile__ movw r0 3 n t movw r30 2 n t sts 0 1 n t spm n t word Oxffff n t nop n t clr ri n t i _SFR_MEM_ADDR __SPM_REG r uint8_t __BOOT_PAGE_FILL r uint16 t
150. PWM2 CAPT vect PSCI_ Event AT90PWM1 CAPTURE PSCI_ SIG PSC1 End Cy AT90PWM3 a ATJOPWMI PSC2 SIG_ PSC2 Capture AT90PWM3 AT90PWM2 CAPT vect PSC2_ Event AT90PWM1 CAPTURE PSC2_ PSC2 End Cy AT90PWM3 AT90PWM2 SPI STC SIG SPI Serial Transfer AT9052333 AT9054414 AT90S4433 vect Complete AT90S4434 AT90S8515 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 AT megal03 ATmegal28 ATmegal284P ATmegal6 ATmegal61 AT megal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P AT megal69 ATmegal69P ATmega32 ATmega323 ATmega325 AT mega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 ATmega6450 ATmega649 AT mega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 mega2561 ATmega324P megal64P ATmega644P mega644 ATmegal6HVA tiny48 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 SPM SIG Store Program ATmegal6 ATmegal62 ATmega32 RDY _ vect SPM_ ATmega323 ATmega8 ATmega8515 READY ATmega8535 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 122 Store Program AT90PWM3 AT90PWM2 Memory Read AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 AT megal28 ATmegal284P ATmegal65 ATmegal65P ATme
151. R toolset takes a different approach GCC has a special keyword __attribute__ that is used to attach different attributes to things such as function declarations variables and types This keyword is followed by an attribute specification in double parentheses In AVR GCC there is a special attribute called progmem This attribute is use on data declarations and tells the compiler to place the data in the Program Memory Flash AVR Libc provides a simple macro PROGMEM that is defined as the attribute syntax of GCC with the progmem attribute This macro was created as a con venience to the end user as we will see below The PROGMEM macro is defined in the lt avr pgmspace h p 250 gt system header file It is difficult to modify GCC to create new extensions to the C language syntax so instead avr libc has created macros to retrieve the data from the Program Space These macros are also found in the lt avr pgmspace h p 250 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
152. RAM is what is available for stack If your application uses malloc p 80 which e g also can happen inside printf p 65 the heap for dynamic memory is also located there See Memory Areas and Using malloc p 277 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 gener ated assembler code avr gcc S there s a comment in each generated assembler file that tells you the frame size for each generated function That s the amount of stack required for this function you have to add up that for all functions where you know that the calls could be nested Back to FAQ Index p 321 9 10 23 Is it really impossible to program the ATtinyXX in C While some small AVRs are not directly supported by the C compiler since they do not have a RAM based stack and some do not even have RAM at all 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 ATtinyAvrGcc html Back to FAQ Index p 321 9 10 24 What is this clock skew detected messsage It s a known problem of the MS DOS FAT file system Since the FAT file sys
153. RGET atmega324p MCU_TARGET atmega325 MCU_TARGET atmega3250 MCU_TARGET atmega329 MCU_TARGET atmega3290 MCU_TARGET atmega48 MCU_TARGET atmega64 MCU_TARGET atmega640 MCU_TARGET atmega644 MCU_TARGET atmega644p MCU_TARGET atmega645 MCU_TARGET atmega6450 MCU_TARGET atmega649 MCU_TARGET atmega6490 MCU_TARGET atmega8 MCU_TARGET atmega8515 MCU_TARGET atmega8535 MCU_TARGET atmega88 MCU_TARGET attiny2313 MCU_TARGET attiny24 MCU_TARGET attiny25 MCU_TARGET attiny26 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 210 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 override LDFLAGS g Wall OPTIMIZE mmcu MCU_TARGET DEFS W1 Map PRG map OBJCOPY avr objcopy OBJDUMP avr objdump all PRG elf 1st text eeprom PRG elf 0BJ CC CFLAGS LDFLAGS o LIBS dependency demo o demo c iocompat h clean rm rf o PRG elf eps png pdf bak rm rf 1st map EXTRA_CLEAN_FILES lst PRG 1st hist A elf OBJDUMP h S lt gt Rules for building the text rom images text hex bin srec he
154. ROMs support multiple data bytes transfered within a single request maintaining an internal address counter that is updated after each data byte transfered suc cessfully When reading data one request can read the entire device memory if desired the counter would wrap around and start back from 0 when reaching the end of the device Note 8 When reading the EEPROM a first device selection must be made with write intent R W bit set to 0 indicating a write operation in order to transfer the EEPROM address to start reading from This is called master transmitter mode Each completion of a particular step in TWI communication is indicated by an asserted TWINT bit in TWCR An interrupt would be generated if allowed After performing any actions that are needed for the next communication step the interrupt condition must be manually cleared by setting the TWINT bit Unlike with many other interrupt sources this would even be required when using a true interrupt routine since as soon as TWINT is re asserted the next bus transaction will start Note 9 Since the TWI bus is multi master capable there is potential for a bus con tention 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 ma
155. ROS is defined before lt stdint h p 259 gt is included e define INT8 MAX Oxrf e define INT8 MIN INT8 MAX 1 e define UINT8 MAX __CONCAT INT8_MAX U x 2U 1U e define INT16 MAX Ox fff e define INT16 MIN INT16_MAX 1 e define UINT16 MAX __ CONCAT INT16 MAX U 2U 1U e define INT32 MAX Ox fffffffL e define INT32 MIN INT32 MAX 1L e define UINT32 MAX __CONCAT INT32_MAX U 2UL 1UL e define INT64 MAX Ox7 ALL e define INT64_ MIN INT64_MAX 1LL e define UINT64 MAX __CONCAT INT64_MAX U 2ULL 1ULL Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 44 Limits of minimum width integer types e define INT_LEAST8_MAX INT8_MAX e define INT_LEAST8_MIN INT8_MIN e define UINT_LEAST8_ MAX UINT8_MAX e define INT LEASTI6 MAX INT16_MAX e define INT LEAST16 MIN INT16 MIN e define UINT_LEAST16_ MAX UINT16 MAX e define INT_LEAST32_ MAX INT32_ MAX e define INT LEAST32 MIN INT32_ MIN e define UINT LEAST32 MAX UINT32 MAX e define INT LEAST64 MAX INT64 MAX e define INT LEAST64 MIN INT64 MIN e define UINT LEAST64 MAX UINT64 MAX Limits of fastest minimum width integer types e define INT FAST8 MAX INTS MAX e define INT FAST8 MIN INTS8_ MIN e define UINT FAST8 MAX UINT8 MAX e define INT FASTI6 MAX INT16_ MAX e define INT FAST16 MIN INT16 MIN e define UINT_FAST16_ MAX UINT16_
156. S8 X e define PRIo16 o e define PRIoLEASTI1G o e define PRIOFAST16 o e define PRIu16 u e define PRIuLEASTI16 u e define PRIuFASTI16 u e define PRIx16 x e define PRIxXLEAST16 x e define PRIxFAST16 x e define PRIX16 X e define PRIXLEAST16 X e define PRIXFAST16 X e define PRIo32 lo e define PRIOLEAST32 lo e define PRIoFAST32 lo e define PRIu32 lu e define PRIULEAST32 lu e define PRIuFAST32 lu e define PRIx32 lx e define PRIxLEAST32 Ix e define PRIxFAST32 lx e define PRIX32 IX e define PRIXLEAST32 IX e define PRIXFAST32 1X e define PRIOPTR PRIo16 e define PRIuPTR PRIul6 e define PRIxPTR PRIx16 e define PRIXPTR PRIX16 e define SCNd16 d e define SCNdLEAST16 d e define SCNdFAST16 d e define SCNi16 i e define SCNiLEAST16 i e define SCNiFAST16 i e define SCNd32 Id e define SCNdLEAST32 ld e define SCNdFAST32 Id e define SCNi32 li e define SCNiLEAST32 li e define SCNiFAST32 li e define SCNdPTR SCNd16 e define SCNIPTR SCNi16 e define SCNo16 o e define SCNoLEAST16 o e define SCNoFAST16 o e define SCNu16 u e define SCNuLEAST16 u Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 18 io h File Reference 247 e define SCNuFAST16 u e define SCNx16 x e define SCNxLEASTI16 x e define SCNxFAST16 x e define SCNo32 lo e de
157. SLEEP ENABLE MASK BV SE Functions void sleep enable void void sleep _ disable void void sleep cpu void void sleep mode void Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 39 stdint h File Reference 259 8 39 stdint h File Reference 8 39 1 Detailed Description Defines e define USING MINTS 0 e define CONCATenate left right left right e define CONCAT left right _ CONCATenate left right Limits of specified width integer types C implementations should define these macros only when STDC LIMIT MACROS is defined before lt stdint h p 259 gt is included e define INT8 MAX Ox7f e define INT8 MIN INT8 MAX 1 e define UINT8 MAX __CONCAT INT8 MAX U x 2U 1U e define INT16 MAX Ox7fff e define INT16 MIN INT16 MAX 1 e define UINT16 MAX __CONCAT INT16_MAX U x 2U 1U e define INT32 MAX Ox7fffffifL e define INT32 MIN INT32 MAX 1L e define UINT32 MAX __CONCAT INT32_MAX U 2UL 1UL e define INT64 MAX Ox7 AALL e define INT64 MIN INT64_ MAX ILL e define UINT64 MAX CONCAT INT64 MAX U x 2ULL 1ULL Limits of minimum width integer types e define INT LEAST8 MAX INT8 MAX e define INT LEAST8 MIN INT8 MIN e define UINT LEAST8 MAX UINTS MAX e define INT LEAST16 MAX INT16 MAX e define INT LEAST16 MIN INT16 MIN e define UINT LEASTI6 MAX UINTI6 MAX e define INT LEAST32 MAX INT32 MAX e define INT LEAST3
158. Standard IO facilities 55 carriage return r character to be sent before the linefeed its put routine must implement this see note 2 p 56 As an alternative method to fdevopen p 62 the macro fdev setup stream p 60 might be used to setup a user supplied FILE structure It should be noted that the automatic conversion of a newline character into a carriage return newline sequence breaks binary transfers If binary transfers are desired no automatic conversion should be performed but instead any string that aims to issue a CR LF sequence must use r n explicitly For convenience the first call to fdevopen p 62 that opens a stream for reading will cause the resulting stream to be aliased to stdin Likewise the first call to fdevopen p 62 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 p 62 on such a stream will also effectively close all of its aliases note 3 p 57 It is possible to tie additional user data to a stream using fdev set udata p 60 The backend put and get functions can then extract this user data using fdev get udata p 59 and act appropriately For example a single put function could be used to talk to two different UARTs that way or
159. T90USB1286 AT90USB647 AT90USB646 TIMERI1 SIG Timer Counterl AT90CAN128 AT90CAN32 COMPC OUTPUT Compare AT90CAN64 ATmega128 AT vect COMPAREIC Match C mega64 ATmega640 ATmegal280 ATmegal281 ATmega2561 AT90USB82 AT90USB1286 AT90USB646 ATmega2560 AT90USB162 AT90USB1287 AT90USB647 TIMERI1 SIG Timer Counter1 ATtiny261 ATtiny461 ATtiny861 COMPD OUTPUT Compare vect COMPAREOD Match D TIMERI1 SIG Timer Counter1 AT90S2333 AT90S4433 ATtiny15 COMP vect OUTPUT Compare COMPAREILA Match TIMERI1 SIG Timer Counterl AT90S2313 ATtiny26 ov v r ovmievowl ovrtov Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 128 AT9084434 AT90S8515 AT90S8535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 AT megal03 ATmegal28 ATmegal284P ATmegal6 ATmegal61 AT megal62 ATmegal63 ATmegal65 ATmegal65P ATmegal68P AT megal69 ATmegal69P ATmega32 ATmega323 ATmega325 AT mega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 ATmega6450 ATmega649 AT mega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 AT mega640 ATmega1280 ATmegal1281 ATmega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT megal6HVA ATtiny15 ATtiny2313 ATtiny48
160. WI bit mask definitions lt compat deprecated h gt Deprecated items lt compat ina90 h gt Compatibility with IAR EWB 3 x Demo projects Combining C and assembly source files A simple project A more sophisticated project Using the standard IO facilities Example using the two wire interface TWI 3 avr libc Data Structure Index 3 1 avr libc Data Structures Here are the data structures with brief descriptions div_t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 176 178 179 179 182 186 189 190 191 195 212 219 227 232 4 avr libc File Index Idiv_t 4 avr libc File Index 4 1 avr libc File List Here is a list of all documented files with brief descriptions assert h atoi S atol S atomic h boot h crc16 h ctype h delay h delay basic h errno h fdevopen c ffs S ffsl S ffsll S fuse h interrupt h inttypes h io h lock h math h Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 11 233 233 234 234 234 234 241 241 242 242 243 243 244 244 244 244 244 245 247 247 247 4 1 avr libc File List 12 memccpy S 249 memchr S 249 memchr_P S 249 memcmp S 249 memcmp P S 249 memcpy S 249 memcpy P S 249 memmem S 249 memmove S 249 memrchr S 249 memrchr_P S 249 memset S 249 parity h 249 pgmspace h 250 power h 257 setbaud h 258 setjmp h 258 sleep h 258 stdint h 259 stdio h 262 s
161. When configure is run it generates a lot of messages while it determines what is available on your operating system When it finishes it will have created several Makefiles that are custom tailored to your platform At this point you can build the project make Note BSD users should note that the project s Makefile uses GNU make syntax This means FreeBSD users may need to build the tools by using gmake If the tools compiled cleanly you re ready to install them If you specified a destination that isn t owned by your account you ll need root access to install them To install make install You should now have the programs from binutils installed into PREFIX bin Don t forget to set your PATH p 347 environment variable before going to build avr gec Note The official version of binutils might lack support for recent AVR devices A patch that adds more AVR types can be found at http www freebsd org cgi cvsweb cgi ports devel avr binutils files patch newdevices Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 350 9 11 5 GCC for the AVR target Warning You must install avr binutils p 348 and make sure your path is set p 347 properly before installing avr gcc The steps to build avr gcc are essentially same as for binutils p 348 bunzip2 c gcc lt version gt tar bz2 tar xf cd gcc lt version gt mkdir obj avr cd
162. X16 uppercase hexadecimal printf format for uintptr_t 6 5 2 60 define PRIxPTR PRIx16 hexadecimal printf format for uintptr_t 6 5 2 61 define SCNd16 d decimal scanf format for int16_t 6 5 2 62 define SCNd32 Id decimal scanf format for int32 t 6 5 2 63 define SCNdFASTI16 d decimal scanf format for int fastl6 t 6 5 2 64 define SCNdFAST32 Id decimal scanf format for int fast32 t 6 5 2 65 define SCNdLEASTI16 d decimal scanf format for int least16 t 6 5 2 66 define SCNdLEAST32 Ild decimal scanf format for int least32 t 6 5 2 67 define SCNdPTR SCNd16 decimal scanf format for intptr_t 6 5 2 68 define SCNi16 i generic integer scanf format for int16 t 6 5 2 69 define SCNi32 li generic integer scanf format for int32 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 30 6 5 2 70 define SCNiFAST16 i generic integer scanf format for int_fast16_t 6 5 2 71 define SCNiFAST32 li generic integer scanf format for int fast32 t 6 5 2 72 define SCNiLEAST16 i generic integer scanf format for int least16 t 6 5 2 73 define SCNiLEAST32 li generic integer scanf format for int least32 t 6 5 2 74 define SCNiPTR SCNi16 generic integer scanf format for intptr_t 6 5 2 75 define SCNo16 o octal scanf format for uint16 t 6 5 2 76 define SCNo32 lo octal scanf format for uint32_t 6 5 2
163. _ BV 161 bit is clear 161 bit is set 161 loop until bit is clear 162 loop until bit is set 162 avr sleep sleep cpu 163 sleep disable 163 sleep enable 163 avr stdint INT16 GC 45 INT16 MAX 45 INT16 MIN 45 int16 t 50 INT32 GC 45 INT32 MAX 45 INT32 MIN 45 int32 t 50 INT64 OC 45 INT64 MAX 45 INT64 MIN 45 int64 t 50 INT8_C 45 INT8_MAX 46 INT8_MIN 46 int8_t 50 INT_FAST16_MAX 46 INT FAST16 MIN 46 int fastl6 t 50 INT FAST32 MAX 46 INT FAST32 MIN 46 int fast32 t 50 INT FAST64 MAX 46 INT FAST64 MIN 46 int fast64 t 50 INT FAST8 MAX 46 INT FASTS8 MIN 46 nt fast8 t 51 INT LEAST16 MAX 46 INT LEAST16 MIN 47 int_least16_t 51 INT LEAST32 MAX 47 INT LEAST32 MIN 47 int least32 t 51 INT LEAST64 MAX 47 INT LEAST64 MIN 47 m 386 int least64 t 51 INT LEAST8 MAX 47 INT _LEAST8_ MIN 47 int least8 t 51 INTMAX_C 47 INTMAX_MAX 47 INTMAX_MIN 47 intmax_t 51 INTPTR_MAX 47 INTPTR_ MIN 48 intptr_t 51 PTRDIFF MAX 48 PTRDIFF MIN 48 SIG ATOMIC MAX 48 SIG ATOMIC MIN 48 SIZE MAX 48 INT16 C 48 INT16 MAX 48 int16 t 51 INT32 C 48 INT32 MAX 48 int32 t 51 INT64 C 48 INT64 MAX 49 int64 t 52 INT8_C 49 INT8_MAX 49 int8 t 52 INT FAST16 MAX 49 int fastl6 t 52 INT FAST32 MAX 49 int fast32 t 52 INT FAST64 MAX 49 int fast64 t 52 INT FAST8 MAX 49 int fast8 t 52 INT LEAST16 MAX 49 int leastl6 t 52 INT LEAST32 M
164. _ADDR PORTD SQUARE out _SFR_IO_ADDR SREG intsav reti Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 294 ioinit sbi _SFR_IO_ADDR DDRD SQUARE ldi work _BV TOIEO out _SFR_IO_ADDR TIMSK work ldi work _BV CS00 tmrO CK 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 end Note 1 As in C programs this includes the central processor specific file containing the IO port definitions for the device Note that not all include files can be included into assembler sources Note 2 Assignment of registers to symbolic names used locally Another option would be to use a C preprocessor macro instead define work 16 Note 3 Our bit number for the square wave output Note that the right hand side consists of a CPP macro which will be substituted by its value 6 in this case before actually being passed to the assembler Note 4 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 295 The assembler uses integer operations in the host defined integer size 32 bits or longer when evaluating expressions This is in contrast to the C compiler that uses the C type int by default in order to calculate constant integer expressions In order to get a 100 kHz output we need to toggle the PD6 line 200000 times per se
165. __ 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 in particular clearing the watchdog reset flag before disabling the watchdog is required according to the datasheet Defines e define wdt reset asm volatile wdr e define wdt enable value e define wdt disable e define WDTO_15MS 0 e define WDTO 30MS 1 e define WDTO 60MS 2 e define WDTO_120MS 3 e define WDTO 250MS 4 e define WDTO 500MS 5 e define WDTO 1S 6 e define WDTO_2S 7 e define WDTO_4S 8 e define WDTO 8S 9 6 24 2 Define Documentation 6 24 2 1 define wdt disable Value Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 24 lt avr wdt h gt Watchdog timer handling 167 __asm__ __volatile__ in __tmp_reg__ __SREG__ n t cli n t out 4 0 i 1 n t out 40 __zero_reg__ n t out __SREG__ __tmp_reg__ n t no outputs I _SFR_IO_ADDR _WD_CONTROL_REG r uint8 t BV WD CHANGE BIT _BV WDE ro Disable the watchdog timer if possible This attempts to turn off the Enable bit in the watchdog control register See the datasheet for details 6 24 2 2 define wdt_enable value Value __asm__ __volatile__ in __tmp_reg__ __SREG__ n t cli n t wdr
166. a number of caveats that you need to be aware of to use this API properly Be sure to include lt avr io h p 247 gt to get all of the definitions for the API The FUSES macro defines a global variable to store the fuse data This variable Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 110 is assigned to its own linker section Assign the desired fuse values immediately in the variable initialization The fuse section in the ELF file will get its values from the initial variable assignment ONLY This means that you can NOT assign values to this variable in functions and the new values will not be put into the ELF fuse section The global variable is declared in the FUSES macro has two leading underscores which means that it is reserved for the implementation meaning the library so it will not conflict with a user named variable You must initialize ALL fields in the fuse t structure This is because the fuse bits in all bytes default to a logical 1 meaning unprogrammed Normal uninitialized data defaults to all locgial zeros So it is vital that all fuse bytes are initialized even with default data If they are not then the fuse bits may not programmed to the desired settings Be sure to have the mmcu device flag in your compile command line and your linker command line to have the correct device selected and to have the correct I O header file included when you incl
167. able avr sleep 163 sleep enable avr sleep 163 snprintf avr stdio 65 snprintf_P avr stdio 65 sprintf avr stdio 65 sprintf P avr stdio 65 sqrt avr_math 38 square avr math 38 srand avr stdlib 81 srandom avr stdlib 81 sscanf avr stdio 65 sscanf P avr stdio 65 stderr avr stdio 60 stdin avr stdio 60 stdint h 259 stdio h 262 stdlib h 263 stdout avr stdio 61 strcasecmp avr_ string 89 strcasecmp S 266 strcasecmp_ P avr pgmspace 150 strcasecmp P S 266 strcasestr avr_ string 89 strcasestr S 266 strcasestr_ P avr pgmspace 150 strcat avr string 89 strcat 5 266 strcat_P avr pgmspace 150 strcat P S 266 strchr avr_ string 90 strchr S 266 strchr P avr pgmspace 150 strchr P S 266 strchrnul avr string 90 strchrnul S 266 strchrnul P avr pgmspace 151 strchrnul P S 266 strcmp avr_ string 90 stremp S 266 stremp P Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 398 INDEX avr pgmspace 151 stremp P S 266 strepy avr string 91 strepy S 266 strepy P avr pgmspace 151 strepy P S 266 strespn avr string 91 strespn S 266 strespn P avr pgmspace 152 strespn P S 266 string h 266 strlcat avr string 91 strleat S 269 strleat P avr pgmspace 152 strleat P S 269 strlepy avr_ string 92 strlepy S 269 strlepy P avr pgmspace 152 strlepy P S 269 strlen avr string 92 strlen S 269 strlen P a
168. accept ATTR PURE e char strstr P const char x PGM P ATTR PURE void x memmem _P const void x size_t PGM VOID P size_t _ ATTR PURE e char strcasestr P const char x PGM P ATTR PURE 6 18 2 Define Documentation 6 18 2 1 define PGM P const prog char Used to declare a variable that is a pointer to a string in program space 6 18 2 2 define pgm read byte address short pgm read byte mnear 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 18 2 3 define pgm read byte far address long __ ELPM uint32 t address long Read a byte from the program space with a 32 bit far address Note The address is a byte address The address is in the program space Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 146 6 18 2 4 define pgm read byte near address short __ LPM uint16 t address short Read a byte from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 18 2 5 define pgm read dword address short pgm read dword mnear address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 18 2 6 define pgm read dword fa
169. ag 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 A xbn script is for linking with N flag mix text and data on same page Back to FAQ Index p 321 9 10 30 How to add a raw binary image to linker output The GNU linker avr 1d cannot handle binary data directly However there s a companion tool called avr objcopy This is already known from the output side it s used to extract the contents of the linked ELF file into an Intel Hex load file avr objcopy can create a relocatable object file from arbitrary binary input like avr objcopy I binary 0 elf32 avr foo bin foo o This will create a file named foo o with the contents of foo bin The contents will default to section data and two symbols will be created named _binary_ foo_bin_start_ and _binary_foo_bin_end_ These symbols can be referred to inside a C source to access these data 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 345 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 0 elf32 avr foo bin Note that all this could be conveniently wired into a Makefile so whenever f
170. age but in particular for switch statements where most of the jumps would go to the default label they might waste a bit of flash memory e mshort calls Use rjmp rcall limited range on gt 8K devices On avr2 and avr4 architec tures less than 8 KB or flash memory this is always the case On avr3 and avr5 architectures calls and jumps to targets outside the current function will by default use jmp call instructions that can cover the entire address range but that require more flash ROM and execution time e mrtl Dump the internal compilation result called RTL into comments in the gen erated assembler code Used for debugging avr gcc e msize Dump the address size and relative cost of each statement into comments in the generated assembler code Used for debugging avr gcc e mdeb Generate lots of debugging information to stderr 9 12 1 2 Selected general compiler options The following general gcc options might be of some interest to AVR users e 0n 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 0 option is Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 368 present The special option Os is meant to turn on all 02 optimizations that are not expected to increase code size Note that at 03 gcc attempts to inline all simple functions For the AVR tar get this w
171. ailed Description 8 68 strncat P S File Reference 8 68 1 Detailed Description 8 69 strncmp S File Reference 8 69 1 Detailed Description 8 70 strncmp P S File Reference 8 70 1 Detailed Description 8 71 strncpy S File Reference 8 88 twi h File Reference 270 TWSR values Mnemonics TW MT xxx master transmitter TW MR zx master receiver TW ST xxx slave transmitter TW_SR_ aaz slave receiver e define TW START 0x08 e 4define TW REP START 0x10 e 4define TW MT SLA ACK 0x18 e define TW MT SLA NACK 0x20 e 4define TW MT DATA ACK 0x28 e 4define TW MT DATA NACK 0x30 e 4define TW_MT_ARB_LOST 0x38 e 4define TW_MR_ARB_ LOST 0x38 e define TW MR SLA ACK 0x40 e jedefine TW MR SLA NACK 0x48 e 4define TW MR DATA _ ACK 0x50 e 4define TW MR DATA NACK 0x58 e 4define TW ST SLA ACK 0xA8 e 4define TW ST ARB LOST SLA ACK 0xB0 e 4define TW ST DAT ACK 0xB8 e 4define TW ST DATA NACK 0xC0 e 4define TW ST LAST DATA 0xC8 e 4define TW SR SLA ACK 0x60 e 4define TW_SR_ARB_LOST_SLA_ ACK 0x68 e 4define TW_SR_GCALL_ ACK 0x70 e 4define TW SR ARB LOST GCALL ACK 0x78 e 4define TW SR DAT ACK 0x80 e define TW SR DATA NACK 0x88 e 4define TW SR GOALL DATA ACK 0x90 e define TW SR GOALL DATA NACK 0x98 e 4define TW SR STOP 0xA0 e define TW NO INFO 0xF8 e 4define TW BUS ERROR 0x00 e 4define TW STATUS MASK e idefine TW_STATUS TWSR amp TW_STATUS_MASK R W bit in SLA R W address field e defin
172. alked to see if it could satisfy the request If there s a chunk available on the freelist that will fit the request exactly it will be taken disconnected from the freelist and returned to the caller If no exact match could be found the closest match that would just satisfy the request will be used The chunk will normally be split up into one to be returned to the caller and another smaller one that will remain on the freelist In case this chunk was only up to two bytes larger than the request the request will simply be altered internally to also account for these additional bytes since no separate freelist entry could be split off in that case If nothing could be found on the freelist heap extension is attempted This is where __malloc_margin will be considered if the heap is operating below the stack or where __malloc_heap_end will be verified otherwise If the remaining memory is insufficient to satisfy the request NULL will eventu ally be returned to the caller When calling free p 78 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 p 81 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 ta
173. am memory 6 9 3 14 size_t fread void x __ ptr size_t _ size size_t nmemb FILE x stream Read nmemb objects size bytes each from stream to the buffer pointed to by ptr Returns the number of objects successfully read i e nmemb unless an input error occured or end of file was encountered feof p 63 and ferror p 63 must be used to distinguish between these two conditions 6 9 3 15 int fscanf FILE stream const char x _ fmt The function fscanf performs formatted input reading the input data from stream See vfscanf p 70 for details 6 9 3 16 int fscanf P FILE x stream const char _ fmt Variant of fscanf p 64 using a fmt string in program memory 6 9 3 17 size_t fwrite const void x __ ptr size_t size size_t __nmemb FILE stream Write nmemb objects size bytes each to stream The first byte of the first object is referenced by ptr Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 65 Returns the number of objects successfully written i e nmemb unless an output error occured 6 9 3 18 char gets char x str Similar to fgets p 63 except that it will operate on stream stdin and the trailing newline if any will not be stored in the string It is the caller s responsibility to provide enough storage to hold the characters read 6 9 3 19 int printf const char __ fmt The function printf
174. ances the compiler generated pro logue and epilogue of the ISR might not be optimal for the job and a manually defined ISR could be considered particularly to speedup the interrupt handling One solution to this could be to implement the entire ISR as manual assembly code in a separate assembly file See Combining C and assembly source files p 191 for an example of how to implement it that way Another solution is to still implement the ISR in C language but take over the compiler s job of generating the prologue and epilogue This can be done using the ISR_ NAKED attribute to the ISR p 136 macro Note that the compiler does not generate anything as prologue or epilogue so the final reti p 138 must be provided by the actual implementation SREG must be manually saved if the ISR code modifies it and the compiler implied assumption of __zero_ reg__ always being 0 could be wrong e g when interrupting right after of a MUL instruction ISR TIMER1_OVF_vect ISR_NAKED PORTB BV 0 results in SBI which does not affect SREG reti Choosing the vector Interrupt vector names The interrupt is chosen by supplying one of the symbols in following table There are currently two different styles present for naming the vectors One form uses names starting with SIG_ followed by a relatively verbose but arbitrarily chosen name describing the interrupt vector This has been the only available style in avr libc up to ver
175. andler exits where the RETI in struction that is emitted by the compiler as part of the normal function epilogue for an interrupt handler will eventually re enable further interrupts For that reason interrupt handlers normally do not nest For most interrupt handlers this is the desired behaviour for some it is even required in order to prevent infinitely recursive interrupts like UART interrupts or level triggered external interrupts In rare circumstances though it might be desired to re enable the global interrupt flag as early as possible in the interrupt handler in order to Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 112 not defer any other interrupt more than absolutely needed This could be done using an sei p 138 instruction right at the beginning of the interrupt han dler but this still leaves few instructions inside the compiler generated function prologue to run with global interrupts disabled The compiler can be instructed to insert an SEI instruction right at the beginning of an interrupt handler by declaring the handler the following way ISR XXX_vect ISR_NOBLOCK where XXX_vect is the name of a valid interrupt vector for the MCU type in question as explained below Two vectors sharing the same code In some circumstances the actions to be taken upon two different interrupts might be completely identical so a single implementation for the ISR
176. aracters hh indicating that the argument is a pointer to char rather than int e the character 1 indicating that the argument is a pointer to long int rather than int for integer type conversions or a pointer to double for floating point conversions In addition a maximal field width may be specified as a nonzero positive decimal integer which will restrict the conversion to at most this many characters from the input stream This field width is limited to at most 255 characters which is also the default value except for the c conversion that defaults to 1 The following conversion flags are supported Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 lt stdio h gt Standard IO facilities 71 6 9 Matches a literal character This is not a conversion d Matches an optionally signed decimal integer the next pointer must be a pointer to int i Matches an optionally signed integer the next pointer must be a pointer to int The integer is read in base 16 if it begins with Ox or OX in base 8 if it begins with 0 and in base 10 otherwise Only characters that correspond to the base are used o Matches an octal integer the next pointer must be a pointer to unsigned int u Matches an optionally signed decimal integer the next pointer must be a pointer to unsigned int x Matches an optionally signed hexadecimal integer the next pointer must be a pointer to unsigned int f Matches an optionally sign
177. aries as well as the application start up code crt XXX o and linker script Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 293 Note that the invokation of the C preprocessor will be automatic when the filename provided for the assembler file ends in S the capital letter s This would even apply to operating systems that use case insensitive filesystems since the actual decision is made based on the case of the filename suffix given on the command line not based on the actual filename from the file system Alternatively the language can explicitly be specified using the x assembler with cpp option 9 5 3 Example program The following annotated example features a simple 100 kHz square wave gen erator using an AT9051200 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 intsav 0 SQUARE PD6 Note 3 Note 4 tmconst 10700000 200000 100 kHz gt 200000 edges s fuzz 8 clocks in ISR until TCNTO is set section text global main Note 5 main rcall ioinit 1 rjmp ib 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 1 cbi _SFR_IO
178. ary functions that are commonly used on a PC environment have limitations or additional issues that a user needs to be aware of when used on an embedded system AVR Libc also contains the most documentation about the whole AVR toolchain Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 1 Toolchain Overview 275 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 1 7 AVRDUDE After creating your software you ll want to program your device You can do this by using the program AVRDUDE which can interface with various hardware devices to program your processor AVRDUDE is a very flexible package All the information about AVR processors and various hardware programmers is stored in a text database This database can be modified b
179. aste a lot of SRAM In Program Space String Utilities p 143 a method is described how such constant data can be moved out to flash ROM However a constant string located in flash ROM is no longer a valid argument to pass to a function that expects a const char x type string since the AVR processor needs the special instruction LPM to access these strings Thus separate functions are needed that take this into account Many of the standard C library functions have equivalents available where one of the string arguments can be located in flash ROM Private functions in the applications need to handle this too For example the following can be used to implement simple debugging messages that will be sent through a UART include lt inttypes h gt include lt avr io h gt include lt avr pgmspace h gt int uart_putchar char c Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 340 if c Np uart_putchar r loop_until_bit_is_set USR UDRE UDR c return 0 so it could be used for fdevopen too void debug_P const char addr char c while c pgm read byte addr uart_putchar c int main void 1 ioinit initialize UART debug_P PSTR foo was here n return 0 Note By convention the suffix P to the function name is used as an indication that this function is going to accept a program space string Note also the u
180. at for uint_least16_t 6 5 2 94 define SCNxLEAST32 lx hexadecimal scanf format for uint least32 t 6 5 2 95 define SCNxPTR SCNx16 hexadecimal scanf format for uintptr_t 6 5 3 Typedef Documentation 6 5 3 1 typedef int32_t int farptr t signed integer type that can hold a pointer gt 64 KB 6 5 3 2 typedef uint32_t uint farptr t unsigned integer type that can hold a pointer gt 64 KB 6 6 lt math h gt Mathematics 6 6 1 Detailed Description include lt math h gt This header file declares basic mathematics constants and functions Notes e In order to access the functions delcared herein it is usually also re quired to additionally link against the library libm a See also the related FAQ entry p 323 e Math functions do not raise exceptions and do not change the errno variable Therefore the majority of them are declared with const at tribute for better optimization by GCC Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 33 Defines e define M_ PI 3 141592653589793238462643 e define M SQRT2 1 4142135623730950488016887 e define NAN __ builtin_nan e define INFINITY __ builtin_inf Functions double cos double __ x double fabs double __ x double fmod double ___x double ___y double modf double ___x double __iptr double sin double ___x double sqrt double __ x double tan double __x double floor double __ x double ceil do
181. ate 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 specify ing a file name with the suffix S upper case letter S will make the compiler automatically assume x assembler with cpp while using s would pass the file directly to the assembler no preprocessing done Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 371 9 12 3 Controlling the linker avr ld 9 12 3 1 Selected linker options While there are no machine specific op tions for avr ld a number of the standard options might be of interest to AVR users e 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 consists of builtin pathname entries that have been specified at compile time e g usr local avr 1ib on Unix systems possibly extended by pathname entries as specified by L options that must precede the 1 options on the command line e Lpath Additional location to look for archive libraries requested by 1 options e defsym symbol ezpr Define a global symbol symbol using ezpr as the value e M Print a linker map to stdout e Map mapfile Print a linker map to mapfile e cref Output a cross reference table to the map file in case Map is also present or
182. ated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 99 e define GET LOCK BITS 0x0001 e define GET EXTENDED FUSE BITS 0x0002 e define GET HIGH FUSE BITS 0x0003 e define boot lock fuse bits get address e define boot signature byte get addr e define boot page fill address data boot page fill normal address data e define boot page erase address boot page erase normal address e define boot page write address boot page write normal address u e define boot rww enable __boot_rww_enable define boot lock bits set lock bits boot lock bits set lock bits e define boot page fill safe address data e define boot page erase safe address e define boot page write safe address e define boot rww enable safe e define boot lock bits set safe lock bits 6 12 2 Define Documentation 6 12 2 1 define boot is spm interrupt SPM REG amp uint8 t BV SPMIE Check if the SPM interrupt is enabled 6 12 2 2 define boot lock bits set lock bits boot lock bits set lock bits Set the bootloader lock bits Parameters lock bits A mask of which Boot Loader Lock Bits to set Note In this context a set bit will be written to a zero value Note also that only BLBxx bits can be programmed by this command For example to disallow the SPM instruction from writing to the Boot Loader memory section of flash yo
183. atic inline void eeprom write dword uint32_t x __ P uint32_t value static Write a 32 bit double word value to EEPROM address __p 6 13 3 8 static inline void eeprom write word uint16_t x __p uintl6 t _ _ value static Write a word value to EEPROM address __p 6 14 lt avr fuse h gt Fuse Support Introduction The Fuse API allows a user to specify the fuse settings for the specific AVR device they are compiling for These fuse settings will be placed in a special section in the ELF output file after linking Programming tools can take advantage of the fuse information embedded in the ELF file by extracting this information and determining if the fuses need to be programmed before programming the Flash and EEPROM memories This also allows a single ELF file to contain all the information needed to program an AVR To use the Fuse API include the lt avr io h p 247 gt header file which in turn automatically includes the individual I O header file and the lt avr fuse h p 244 gt file These other two files provides everything necessary to set the AVR fuses Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 14 lt avr fuse h gt Fuse Support 108 Fuse API Each I O header file must define the FUSE MEMORY SIZE macro which is defined to the number of fuse bytes that exist in the AVR device A new type __fuse_t is defined as a structure The number of fields in this structure are determined by the
184. atic uint8 t direction switch direction Note 4 6c 80 91 60 00 lds r24 0x0060 70 88 23 and r24 r24 72 ci 4 brne 48 Oxa4 lt __vector_8 0x48 gt case UP if pwm TIMER1_TOP 74 20 91 61 00 lds r18 0x0061 78 30 91 62 00 lds r19 0x0062 7c 2f 5f subi r18 OxFF 255 Te 3f 4f sbci r19 OxFF 255 80 30 93 62 00 sts 0x0062 r19 84 20 93 61 00 sts 0x0061 r18 88 83 e0 ldi r24 0x03 3 8a 2f 3f cpi r18 OxFF 255 8c 38 07 cpc r19 r24 8e 09 f1 breq 66 Oxd2 lt __vector_8 0x76 gt if pwm 0 direction UP Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 90 92 94 96 98 9a 9c 9e a0 a2 I break OCR pwm Note 5 3b 2a 8f 3f 2f of Of Of 1f 18 bd out 0x2b r19 43 bd out Ox2a r18 42 91 pop r24 91 pop r19 91 pop r18 90 pop ro be out 0x3f rO 63 90 pop ro 90 pop ri 95 reti ISR TIMER1 OVF vect Note 2 a4 a6 a8 ac bo b2 b6 ba be c2 c6 c8 ca cc do d2 d4 d8 0000 static uint16_t pum Note 3 static uint8_t direction switch direction Note 4 81 29 20 30 ef 20 30 21 30 30 20 21 31 11 10 df 30 cpi r24 Ox01 1 fO breq 10 Oxb2 lt __vector_8 0x56 gt 91 61 00 lds r18 0x0061 91 62 00 lds r19 0x0062 cf rjmp 34 0x90 lt __vector_8 0x34 gt if pwm TIMER1_TOP dire
185. ating the specified interrupt condition has been met by representing a logi cal 1 in the respective bit position When working with interrupt handlers this interrupt flag bit usually gets cleared automatically in the course of processing the interrupt sometimes by just calling the handler at all sometimes e g for the U SJART by reading a particular hardware register that will normally happen anyway when processing the interrupt From the hardware s point of view an interrupt is asserted as long as the respec tive 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 inter rupts e g an external edge triggered one it can be necessary to explicitly clear the respective hardware interrupt bit by software This is usually done by writing a logical 1 into this bit position This seems to be illogical at first the bit position already carries a logical 1 when reading it so w
186. atter function fetches the string from program mem ory p 143 Both functions translate a newline character into a carriage re turn newline sequence so a simple n can be used in the source code The function set_pwm propagates the new PWM value to the PWM perform ing range checking When the value has been changed the new percentage will be announced on the serial link The current value is mirrored in the variable pwm so others can use it in calculations In order to allow for a simple calcu lation of a percentage value without requiring floating point mathematics the maximal value of the PWM is restricted to 1000 rather than 1023 so a simple division by 10 can be used Due to the nature of the human eye the difference in LED brightness between 1000 and 1023 is not noticable anyway 6 37 3 5 Part 5 main At the start ofmain a variable mode is declared to keep the current mode of operation An enumeration is used to improve the readability By default the compiler would allocate a variable of type int for an enumeration The packed attribute declarator instructs the compiler to use the smallest possible integer type which would be an 8 bit type here After some initialization actions the application s main loop follows In an embedded application this is normally an infinite loop as there is nothing an application could exit into anyway At the beginning of the loop the watchdog timer will be retriggered If that timer
187. avoid this confusion is to only use non local labels when declaring a new function and restrict anything else to local labels Local labels consist just of a number only References to these labels consist of the number followed by the letter b for a backward reference or f for a forward reference These local labels may be re used within the source file references will pick the closest label with the same number and given direction Example myfunc push r16 push ri7 push r18 push YL push YH eor r16 r16 start loop ldi YL 108 sometable ldi YH hi8 sometable rjmp 2f jump to loop test at end li ld ri7 Y loop continues here breq 1f return from myfunc prematurely inc r16 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 331 2 cmp r16 r18 brlo 1b jump back to top of loop T pop YH pop YL pop r18 pop ri7 pop r16 ret Back to FAQ Index p 321 9 10 13 How do I pass an IO port as a parameter to a function Consider this example code include lt inttypes h gt include lt avr io h gt void set_bits_func_wrong volatile uint8_t port uint8_t mask 1 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 Oxaa set_bits_func_correct amp PORTB 0x55 set bits macro PORTB Oxf0 retu
188. avr libc Reference Manual 1 6 2 Generated by Doxygen 1 5 2 Wed Jun 11 11 29 15 2008 CONTENTS i Contents 1 AVR Libc 1 1 1 Totroduetion pt Gakk Wk aS eg dr ee ae ee 1 1 2 General information about this library 2 1 3 Supported Devices 2 00000020004 2 1 4 awvr libc License 0 8 2 avr libc Module Index 9 2 1 vr libe Modules recs ane goa Be s l Pa dada aoa SG 9 3 avr libc Data Structure Index 10 3 1 avr libe Data Structures ooo 10 4 avr libc File Index 11 4 1 avr libc File List 2 2 ee ee 11 5 avr libc Page Index 14 5 1 avr libc Related Pages 2 0 14 6 avr libc Module Documentation 15 6 1 lt alloca h gt Allocate space in the stack 15 6 2 lt assert h gt Diagnostics er vr vr vr vr vr ravn 16 6 3 lt ctype h gt Character Operations 17 6 4 lt errno h gt System Errors 2 var vr rv vr rea 19 6 5 lt inttypes h gt Integer Type conversions 20 6 6 lt math h gt Mathematics evvr rv r vr rv ravn 32 6 7 lt setjmp h gt Non local goto 008 39 6 8 lt stdint h gt Standard Integer Types 7 7 42 6 9 lt stdio h gt Standard IO facilities 54 6 10 lt stdlib h gt General utilities ooa aaa 73 6 11 lt string hes Strings nas BRAGE BA ee Sea 85 6 12 lt avr boot h gt Bootloader Support Utilities 97 6 13 lt
189. been chosen This display needs to be connected to port A of the STK500 in the following way wooo fi 0 1 2 3 4 5 6 7 GND Figure 5 Wiring of the STK500 The LCD controller is used in 4 bit mode including polling the busy flag so the R W line from the LCD controller needs to be connected Note that the LCD controller has yet another supply pin that is used to adjust the LCD s contrast V5 Typically 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 221 Port A has been chosen as 7 pins on a single port are needed to connect the LCD yet all other ports are already partially in use port B has the pins for in system programming ISP port C has the ports for JTAG can be used for debugging and port D is used for the UART connection 6 38 2 Functional overview The project consists of the following files e stdiodemo c This is the main example file e defines h Contains some global defines like the LCD wiring e hd44780 c Implementation of an HD44780 LCD display driver e hd44780 h Interface declarations for the HD44780 driver e 1cd c Implementation of LCD character IO on top of the HD44780 driver e 1cd h Interface declarations for the LCD driver e uart c Implementation of a character I
190. bjcopy j eeprom change section lma eeprom 0 0 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 objcopy command that used to generate the empty EEPROM files now aborts because of the empty input section eeprom so these empty files are not generated It also signals an error to the Makefile which will be caught there and makes it print a message about the empty file not being generated Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 209 6 36 7 Letting Make Build the Project Rather than type these commands over and over they can all be placed in a make file To build the demo project using make save the following in a file called Makefile Note This Makefile can only be used as input for 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 atmega128 MCU_TARGET atmega1280 MCU_TARGET atmega1281 MCU_TARGET atmega1284p MCU_TARGET atmega16 MCU_TARGET atmega163 MCU_TARGET atmega164p MCU_TARGET atmega165 MCU_TARGET atmega165p MCU_TARGET atmega168 MCU_TARGET atmega169 MCU_TARGET atmega169p MCU_TARGET atmega2560 MCU_TARGET atmega2561 MCU_TARGET atmega32 MCU_TA
191. blanks or zeros A overrides a 0 if both are given 2 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 e An optional decimal digit string specifying a minimum field width If the converted value has fewer characters than the field width it will be padded with spaces on the left or right if the left adjustment flag has been given to fill out the field width e An optional precision in the form of a period followed by an optional digit string If the digit string is omitted the precision is taken as zero This gives the minimum number of digits to appear for d i o u x and X conversions or the maximum number of characters to be printed from a string for s conversions Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 68 e An optional 1 or h length modifier that specifies that the argument for the d i 0 u x or X conversion is a long int rather than int The h is ignored as short int is equivalent to int e A character that specifies the type of conversion to be applied The conversion specifiers and their meanings are e diouxX The int or appropriate variant argument is converted to signed decimal d and i unsigned octal 0 unsigned decimal u or unsigned hexadecima
192. brary 1ibm a needs to be explicitly requested using 1m See also the entry in the FAQ p 323 explaining this Conventionally Makefiles use the make macro LDLIBS to keep track of 1 and possibly L options that should only be appended to the C compiler command line when linking the final binary In contrast the macro LDFLAGS is used to store other command line options to the C compiler that should be passed as options during the linking stage The difference is that options are placed early on the command line while libraries are put at the end since they are to be used to resolve global symbols that are still unresolved at this point Specific linker flags can be passed from the C compiler command line using the W1 compiler option see above p 368 This option requires that there be no spaces in the appended linker option while some of the linker options above like Map or defsym would require a space In these situations the space can be replaced by an equal sign as well For example the following command line can be used to compile foo c into an executable and also produce a link map that contains a cross reference list in the file foo map avr gcc 0 o foo out Wl Map foo map Wl cref foo c Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 13 Using the avrdude program 373 Alternatively a comma as a placeholder will be replaced by a space before passing the option to the linker So for a device with ex
193. c uint8 t data e static inline uint8_t crc ibutton update uint8 t cc uint8 t data 8 7 ctype h File Reference 8 7 1 Detailed Description Defines e defne CTYPE H 1 Functions Character classification routines These functions perform character classification They return true or false status depending whether the character passed to the function falls into the functions classification i e isdigit p 18 returns true if its argument is any value 0 though 9 inclusive If the input is not an unsigned char value all of this function return false e int isalnum int _c e int isalpha int __c e int isascii int c e int isblank int __c Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 8 delay h File Reference 242 e int iscntrl int __c e int isdigit int _c e int isgraph int c e int islower int _ _c e int isprint int c e int ispunct aut o e int isspace int c e int isupper int __c e int isxdigit int c Character convertion routines This realization permits all possible values of integer argument The toascit p 19 function clears all highest bits The tolower p 19 and toupper p 19 functions return an input argument as is if it is not an unsigned char value e int toascii int _c e int tolower int _c e int toupper int _c 8 8 delay h File Reference 8 8 1 Detailed Description Defines e define UTIL DELAY H 1 e define F CPU 1000000UL Funct
194. ccess from within an interrupt context could clobber the TEMP register data of an in progress transaction that has just started elsewhere To protect interrupt routines against other interrupt routines it s usually best to use the ISR p 136 macro when declaring the interrupt function and to ensure that interrupts are still disabled when accessing those 16 bit timer registers Within the main program access to those registers could be encapsulated in calls to the cli p 136 and sei p 138 macros If the status of the global Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 328 interrupt flag before accessing one of those registers is uncertain something like the following example code can be used uint16_t read_timer1 void 1 uint8_t sreg uint16_t val sreg SREG cliQ val TCNT1 SREG sreg return val Back to FAQ Index p 321 9 10 10 How do I use a define d constant in an asm statement So you tried this asm volatile sbi 0x18 0x07 Which works When you do the same thing but replace the address of the port by its macro name like this asm volatile sbi PORTB 0x07 you get a compilation error Error constant value required PORTB is a precompiler definition included in the processor specific file included in avr io h p 247 As you may know the precompiler will not touch strings and PORTB instead of 0x18 gets passed to th
195. ce Utilities 143 avr objdump s j lock lt ELF file gt 6 18 lt avr pgmspace h gt Program Space Utilities 6 18 1 Detailed Description include lt avr io h gt include lt avr pgmspace h gt The functions in this module provide interfaces for a program to access data stored in program space flash memory of the device In order to use these functions the target device must support either the LPM or ELPM instructions Note These functions are an attempt to provide some compatibility with header files that come with IAR C to make porting applications between different compilers easier This is not 100 compatibility though GCC does not have full support for multiple address spaces yet If you are working with strings which are completely based in ram use the standard string functions described in lt string h gt Strings p 85 If possible put your constant tables in the lower 64 KB and use pgm read byte mnear p 146 or pgm read word near p 147 in stead of pgm read byte far p 145 or pgm read word far p 147 since it is more efficient that way and you can still use the upper 64K for executable code All functions that are suffixed with a P require their arguments to be in the lower 64 KB of the flash ROM as they do not use ELPM instructions This is normally not a big concern as the linker setup arranges any program space constants declared using the macros from this header file so they are placed
196. ce into 4 bit mode which would not be done automatically after a power on reset 6 38 3 5 Icd h This function declares the public interface of the higher level character IO LCD driver 6 38 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 moving the cursor this high level driver allows to just write a character to the LCD in the assumption this will somehow show up on the display Control characters can be handled at this level and used to perform specific actions on the LCD Currently there is only one control character that is being Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 225 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
197. ce the symbolic names by their right hand side definitions before calling the assembler 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 p 323 Even in case the C code never has a need to access these variables declaring the register binding that way causes the compiler to not use these registers in C code at all The flags variable needs to be in the range of r16 through r31 as it is the target of a load immediate or SER instruction that is not applicable to the entire register file 6 35 2 3 isrs S This file is a preprocessed assembly source file The C pre processor will be run by the compiler front end first resolving all include define etc directives The resulting program text will then be passed on to the assembler Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 35 Combining C and assembly source files 194 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 p 247 and the project declaration file project h are included The remainder of the file is condi tionally assembled only if the target MCU type is an ATtiny13 so it will be completely ignored for the ATtiny4
198. choice e Install Mik Tex Version 2 5 lt http miktex org gt Download and install e Install Ghostscript Version 8 54 lt http www cs wisc edu ghost gt Download and install e Set the TEMP and TMP environment variables to c temp or to the short filename version This helps to avoid NTVDM errors during building 9 11 13 Building the Toolchain for Windows All directories in the PATH enviornment variable should be specified using their short filename 8 3 version This will also help to avoid NTVDM errors during building These short filenames can be specific to each machine Build the tools below in MSYS e Binutils Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 357 Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order x lt MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin lt install directory gt bin Configure CFLAGS D USE MINGW ACCESS archivedir configure N prefix installdir target avr N disable nls enable doc N datadir installdir doc binutils with gmp usr local N with mpfr usr local 2 gt amp 1 tee binutils configure log Make make all html install install html 2 gt amp 1 tee binutils make log Manually cha
199. ck space or they will risk colliding with the data segment The default value of __malloc_margin is set to 32 9 2 4 Implementation details Dynamic memory allocation requests will be returned with a two byte header prepended that records the size of the allocation This is later used by free p 78 The returned address points just beyond that header Thus if the application accidentally writes before the returned memory region the internal consistency of the memory allocator is compromised The implementation maintains a simple freelist that accounts for memory blocks that have been returned in previous calls to free p 78 Note that all of this Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 281 memory is considered to be successfully added to the heap already so no further checks against stack heap collisions are done when recycling memory from the freelist The freelist itself is not maintained as a separate data structure but rather by modifying the contents of the freed memory to contain pointers chaining the pieces together That way no additional memory is reqired to maintain this list except for a variable that keeps track of the lowest memory segment available for reallocation Since both a chain pointer and the size of the chunk need to be recorded in each chunk the minimum chunk size on the freelist is four bytes When allocating memory first the freelist is w
200. cle penalty for the aliased vector compared to the ISR the vector is aliased to due to the JMP RJMP opcode used Deprecated For new code the use of ISR ISR_ALIASOF is recommended Example ISR INTO_vect 1 PORTB 42 I ISR ALIAS INT1 vect INTO vect 6 15 2 6 define ISR ALIASOF target vector include lt avr interrupt h gt The ISR is linked to another ISR specified by the vect parameter This is compatible with GCC 4 2 and greater only Use this attribute in the attributes parameter of the ISR macro 6 15 2 7 define ISR BLOCK include lt avr interrupt h gt Identical to an ISR with no attributes specified Global interrupts are initially disabled by the AVR hardware when entering the ISR without the compiler modifying this state Use this attribute in the attributes parameter of the ISR macro Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 138 6 15 2 8 define ISR NAKED include lt avr interrupt h gt ISR is created with no prologue or epilogue code The user code is responsible for preservation of the machine state including the SREG register as well as placing a reti p 138 at the end of the interrupt routine Use this attribute in the attributes parameter of the ISR macro 6 15 2 9 define ISR NOBLOCK include lt avr interrupt h gt ISR runs with global interrupts initially enabled The interrupt enable flag is
201. close avr stdio 59 fdev get udata avr stdio 59 fdev set udata avr stdio 59 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX FDEV SETUP STREAM avr stdio 59 fdev setup stream avr stdio 59 fdevopen avr stdio 61 fdevopen c 243 fdim avr math 35 feof avr stdio 62 ferror avr stdio 62 filush avr stdio 62 ffs avr_ string 86 ffs S 244 ffs avr string 86 ffsl S 244 ffsll avr_ string 87 ftsll S 244 fgetc avr stdio 62 fgets avr stdio 63 FILE avr stdio 60 floor avr math 35 fma avr math 35 fmax avr math 35 fmin avr math 35 fmod avr math 35 fprintf avr stdio 63 fprintf P avr stdio 63 fputc avr stdio 63 391 fputs avr stdio 63 fputs P avr stdio 63 fread avr stdio 63 free avr stdlib 78 frexp avr math 35 fscanf avr stdio 64 fscanf P avr stdio 64 fuse h 244 fwrite avr stdio 64 GET EXTENDED FUSE BITS avr boot 103 GET HIGH FUSE BITS avr boot 103 GET LOCK BITS avr boot 103 GET LOW FUSE BITS avr boot 103 getc avr stdio 60 getchar avr stdio 60 gets avr stdio 64 hypot avr math 36 inb deprecated items 188 INFINITY avr math 33 inp deprecated items 188 installation 346 installation avarice 352 installation avr libc 350 installation avrdude 351 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX installation avrprog 351 installation binutils 348 instal
202. clude lt avr io h gt include lt util atomic h gt volatile uint16_t ctr ISR TIMER1_OVF_vect 1 ctr int main void Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks 171 ctr 0x200 start_timer sei uint16_t ctr_copy do ATOMIC_BLOCK ATOMIC_FORCEON ctr_copy ctr while ctr_copy 0 This will install the appropriate interrupt protection before accessing vari able ctr so it is guaranteed to be consistently tested If the global inter rupt state were uncertain before entering the ATOMIC BLOCK it should be executed with the parameter ATOMIC RESTORESTATE rather than ATOMIC_FORCEON Defines e define ATOMIC BLOCK type e define NONATOMIC BLOCK type e define ATOMIC RESTORESTATE e define ATOMIC FORCEON e define NONATOMIC RESTORESTATE e define NONATOMIC_FORCEOFF 6 25 2 Define Documentation 6 25 2 1 define ATOMIC BLOCK type Creates a block of code that is guaranteed to be executed atomically Upon entering the block the Global Interrupt Status flag in SREG is disabled and re enabled upon exiting the block from any exit path Two possible macro parameters are permitted ATOMIC RESTORESTATE and ATOMIC FORCEON 6 25 2 2 define ATOMIC FORCEON This is a possible parameter for ATOMIC BLOCK When used it will cause the ATOMIC_ BLOCK to force the state of the SREG register on ex
203. 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 37 A more sophisticated project 218 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 concatenated together the compiler needs to be instructed to omit the entire function prologue and epilogue This is performed by the naked attribute So while syntactically handle_mcucsr is a function to the compiler the compiler will just emit the instructions for it without setting up any stack frame and not even a RET instruction at the end Function ioinit centralizes all hardware setup The very last part of that function demonstrates the use of the EEPROM variable ee_pwm to obtain an EEPROM address that can in turn be applied as an argument to eeprom_ read_word p 106 The following functions handle UART character and string output UART in put is handled by an ISR There are two string output functions printstr and printstr_p The l
204. cond Since we use timer 0 without any prescaling options in order to get the desired frequency and accuracy we already run into serious timing con siderations 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 inter rupt 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 en try point that will be jumped to from the ininitalization routine in crts1200 0 Note 6 The main loop is just a single jump back to itself Square wave generation itself is completely handled by the timer 0 overflow interrupt service A sleep instruc tion 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 p 114 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 p 247 gt has been included Note that the as
205. ction DOWN break case DOWN if pum 0 91 61 00 lds r18 0x0061 91 62 00 lds r19 0x0062 50 subi r18 0x01 1 40 sbci r19 0x00 0 93 62 00 sts 0x0062 r19 93 61 00 sts 0x0061 r18 15 cp r18 ri 05 cpc r19 ri 7 brne 60 0x90 lt __vector_8 0x34 gt direction UP 92 60 00 sts 0x0060 ri cf rjmp 66 0x90 lt __vector_8 0x34 gt switch direction Note 4 81 80 db 00da OCR case UP if pwm TIMER1_TOP direction DOWN e0 ldi r24 0x01 1 93 60 00 sts 0x0060 r24 cf rjmp 74 0x90 lt __vector_8 0x34 gt lt ioinit gt pwm Note 5 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 203 6 36 A simple project void ioinit void Note 6 da 83 e8 ldi r24 0x83 131 dc 8f bd out Ox2f r24 47 Start timer 1 NB TCCR1A and TCCR1B could actually be the same register so take care to not clobber it TCCR1B TIMER1_CLOCKSOURCE de 8e b5 in r24 Ox2e 46 e0 81 60 ori r24 0x01 1 e2 8e bd out 0x2e r24 46 if defined TIMER1_SETUP_HOOK TIMER1_SETUP_HOOK endif Set PWM value to 0 OCR 0 e4 1b bc out 0x2b ri 43 e6 1a bc out Ox2a ri 42 Enable OC1 as output DDROC BV 0C1 e8 82 e0 ldi r24 0x02 2 ea 87 bb out 0x17 r24 23 Enable timer 1 overflow interrupt TIMSK _BV TOIE1 ec 84 e0 ldi r24 0x04 4 ee 89 bf out 0x39 r24 5
206. ction 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 301 To make it more readable you should put each statement on a seperate line asm volatile nop n t nop n t nop n t nop n t 22 The linefeed and tab characters will make the assembler listing generated by the compiler 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 Status register at address 0x3F Stack pointer high byte at address Ox3E Stack pointer low byte at address __tmp_reg__ Register r0 used for temporary rage E Register rT always zero Register rO may be freely used by your assembler code and need not be restored at the end of your code It s a good idea to use __tmp_reg__ and __zero_reg_ _ instead of rO or r1 just in case a new compiler version changes the register usage definitions 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 i
207. ction on the enhanced core If too many those that don t fit are passed on the stack Return values 8 bit in r24 not r25 16 bit in r25 r24 up to 32 bits in r22 r25 up to 64 bits in r18 r25 8 bit return values are zero sign extended to 16 bits by the called function unsigned char is more efficient than signed char just clr r25 Arguments to functions with variable argument lists printf etc are all passed on stack and char is extended to int Warning There was no such alignment before 2000 07 01 including the old patches for gcc 2 95 2 Check your old assembler subroutines and adjust them accordingly Back to FAQ Index p 321 9 10 15 How do I put an array of strings completely in ROM There are times when you may need an array of strings which will never be modified In this case you don t want to waste ram storing the constant strings The most obvious and incorrect thing to do is this include lt avr pgmspace h gt PGM_P array 2 PROGMEM 1 Foo Bar 3 int main void Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 335 char buf 32 strepy P buf array 1 return 0 The result is not what you want though What you end up with is the ar ray stored in ROM while the individual strings end up in RAM in the data section To work around this you need to do something like this include lt avr pgmspace h gt const char
208. cts 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 a boot loader that is portable between devices with SPMCR at different addresses lt avr iom163 h gt define SPMCR _SFR_I08 0x37 lt avr iom128 h gt define SPMCR _SFR_MEM8 0x68 if _SFR_IO_REG_P SPMCR out _SFR_IO_ADDR SPMCR r24 else sts _SFR_MEM_ADDR SPMCR r24 endif You can use the in out cbi sbi sbic sbis instructions without the _SFR_ IO_REG_P test if you know that the register is in the I O space as with SREG for example If it isn t the assembler will complain I O address out of range 0 0x3f so this should be fairly safe If you do not define __SFR_OFFSET so it will be 0x20 by default all special register addresses are defined as memory addresses so SREG is Ox5f and if code size and speed are not important and you don t like the ugly if above you can always use lds sts to access them But this will not work if __SFR_ OFFSET 0x20 so use a different macro defined only if __SFR_OFFSET 0x20 for safety sts _SFR_ADDR SPMCR r24 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 21 lt avr sfr defs h gt Special function registers 160 In C programs all 3 combinations of _SFR_ASM_CO
209. d The strtoul p 83 function return either the result of the conversion or if there was a leading minus sign the negation of the result of the conversion unless the original non negated value would overflow in the latter case str toul p 83 returns ULONG_ MAX and errno is set to ERANGE p 19 If no conversion could be performed 0 is returned Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 84 6 10 4 29 char ultoa unsigned long int val char 8 int _ radix Convert an unsigned long integer to a string The function ultoa p 84 converts the unsigned long integer value from val into an ASCII representation that will be stored under s The caller is respon sible for providing sufficient storage in s Note The minimal size of the buffer s depends on the choice of radix For exam ple if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof unsigned long int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 29 will be the letter a The ultoa p 84 function returns the pointer passed as s
210. d and restored The extra code needed to do this is enabled by tagging the interrupt function with __attribute__ signal These details seem to make interrupt routines a little messy but all these details are handled by the Interrupt API An interrupt routine is defined with ISR p 136 This macro register and mark the routine as an interrupt handler for the specified peripheral The following is an example definition of a handler for the ADC interrupt include lt avr interrupt h gt ISR ADC_vect user code here Refer to the chapter explaining assembler programming p 296 for an ex planation about interrupt routines written solely in assembler language Catch all interrupt vector If an unexpected interrupt occurs interrupt is enabled and no handler is installed which usually indicates a bug then the default action is to reset the device by jumping to the reset vector You can override this by supplying a function named BADISR_vect which should be defined with ISR p 136 as such The name BADISR_vect is actually an alias for vector default The latter must be used inside assembly code in case lt avr interrupt h p 244 gt is not included include lt avr interrupt h gt ISR BADISR_vect user code here Nested interrupts The AVR hardware clears the global interrupt flag in SREG before entering an interrupt vector Thus normally interrupts will re main disabled inside the handler until the h
211. d on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 3 Memory Sections 284 9 3 6 The initN Sections These sections are used to define the startup code from reset up through the start of main These all are subparts of the text section p 282 The purpose of these sections is to allow for more specific placement of code within your program Note Sometimes it is convenient to think of the initN and finiN sections as functions but in reality they are just symbolic names which tell the linker where to stick a chunk of code which is not a function Notice that the examples for asm p 286 and C p 286 can not be called as functions and should not be jumped into The initN sections are executed in order from 0 to 9 initO Weakly bound to init If user defines init it will be jumped into immediately after a reset init1 Unused User definable init2 In C programs weakly bound to initialize the stack and to clear zero reg r1 init3 Unused User definable init For devices with gt 64 KB of ROM init4 defines the code which takes care of copying the contents of data from the flash to SRAM For all other devices this code as well as the code to zero out the bss section is loaded from libgcc a init5 Unused User definable init6 Unused for C programs but used for constructors in C programs Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 3 Memor
212. ddr16 uint16_t addr n t n t n t n t n t n t n t n t n t n t n t _addri6 uint16_t addr n t n t n t n t _addr16 uint16_t addr z __addr16 255 LPM dword classic addr OPO LO LO LO LO LO LO PO PO BODO JAH TS A OG LPM dword enhanced _ addr FA A A A ZAZA AP A ZAZA ZZ LPM enhanced addr Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference uint8_t __result __asm__ lpm 40 z n t r __result z __addr16 __result H Its 8 34 2 10 7define LPM word classic addr Value __extension__ uint16_t __addr16 uint16_t addr uint16_t __result __asm__ lpm n t mov ZAO ro n t adiw r30 1 n t lpm n t mov BO ro n t r result z __addr16 1 __addr16 ro result H 8 34 2 11 define LPM word enhanced addr Value __extension__ uint16_t __addr16 uint16_t addr uint16_t __result __asm__ lpm AO Z n t lpm BO Z n t r result z addr16 1 __addr16 result H Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen LOL LO LO AO E POP GOO GO PO GO GOP LOLOL AO GO AO GO LEE GO SO 256 8 35 power h File Reference 257 8 35 power h File Reference 8 35 1 Detailed Descripti
213. dint 47 INTMAX MIN avr stdint 47 intmax t avr stdint 51 INTPTR MAX avr stdint 47 INTPTR MIN avr stdint 48 intptr_t avr stdint 51 inttypes h 245 io h 247 isalnum ctype 17 isalpha ctype 17 isascii ctype 17 isblank ctype 17 iscntrl ctype 18 isdigit ctype 18 isfinite avr_math 36 isgraph ctype 18 isinf avr math 36 islower ctype 18 isnan avr math 36 isprint ctype 18 ispunct ctype 18 ISR avr interrupts 136 ISR ALIAS avr interrupts 136 ISR ALIASOF avr interrupts 137 ISR BLOCK avr interrupts 137 ISR NAKED avr interrupts 137 ISR NOBLOCK avr interrupts 138 isspace ctype 18 isupper ctype 18 isxdigit ctype 18 itoa avr stdlib 78 labs avr stdlib 78 ldexp avr math 36 Idiv avr stdlib 79 ldiv t 233 quot 233 rem 233 lock h 247 log avr math 36 log10 avr math 37 longjmp setjmp 40 loop until bit is clear avr s r 162 loop until bit is set avr s r 162 lrint avr math 37 lround avr math 37 Itoa avr stdlib 79 M PI avr math 33 M SQRT2 avr math 33 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 393 INDEX malloc avr stdlib 79 math h 247 memccpy avr string 87 memccpy S 249 memchr avr string 87 memchr S 249 memchr P avr pgmspace 149 memchr P S 249 memcmp avr_ string 87 memcmp S 249 memcmp_ P avr pgmspace 149 memcmp P S 249 memcpy avr string 88 memepy S 249
214. displays a list of valid commands avrdude gt gt gt gt Valid commands dump dump memory dump lt memtype gt lt addr gt lt N Bytes gt read alias for dump write write memory write lt memtype gt lt addr gt lt b1 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 bi gt lt b2 gt lt b3 gt lt b4 gt help help help quit quit Use the part command to display valid memory types for use with the dump and write commands avrdude gt 9 14 Release Numbering and Methodology 9 14 1 Release Version Numbering Scheme 9 14 1 1 Stable Versions A stable release will always have a minor number that is an even number This implies that you should be able to upgrade to a new version of the library with the same major and minor numbers without fear that any of the APIs have changed The only changes that should be made to a stable branch are bug fixes and under some circumstances additional functionality e g adding support for a new device If major version number has changed this implies that the required versions of gcc and binutils have changed Consult the README file in the toplevel directory of the AVR Libc source for which versions are required 9 14 1 2 Development Versions The major version number of a develop ment series is always the same as the last stabl
215. dth typedef int8 tint least8 t typedef uint8 t uint least8 t typedef int16 tint Teast16 t typedef uint16 t uint least 6 t typedef int32 tint least32 t typedef uint32 t uint least32 t typedef int64 tint least64 t typedef uint64 t uint least64 t Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8 tint fast8 t typedef uint8 t uint fast8 t typedef int16 tint fast16 t typedef uint16 t uint fastI6 t typedef int32 tint fast32 t typedef uint32 t uint fast32 t typedef int64 tint fast64 t typedef uint64_t uint_fast64_t Greatest width integer types Types designating integer data capable of representing any value of any inte ger type in the corresponding signed or unsigned category e typedef int64 tintmax t e typedef uint64 t uintmax t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 40 stdio h File Reference 8 40 stdio h File Reference 8 40 1 Detailed Description Defines e define STDIO_H_ 1 e define need NULL e define need size_t e define FILE struct file e define stdin __iob 0 e define stdout __iob 1 e define stderr __iob 2 e define EOF 1 262 e define fdev set udata stream u do stream udata u while 0 e define fdev get udata stream stream udata e define fdev setup _ stream stream put get rwflag e define FDEV SETUP READ __ SRD e define FDEV SETUP WRITE __SWR e define
216. e define EMPTY INTERRUPT vector e define ISR ALIAS vector target vector e define reti Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 17 inttypes h File Reference 245 e define BADISR_vect ISR attributes e define ISR BLOCK e define ISR NOBLOCK e define ISR NAKED e define ISR ALIASOF target vector 8 17 inttypes h File Reference 8 17 1 Detailed Description Defines macros for printf and scanf format specifiers For C these are only included if STDC LIMIT MACROS is defined before including lt inttypes h p 245 gt e define PRId8 d e define PRIdLEASTS d e define PRIdFASTS d e define PRIi8 i e define PRIiLEASTB8 i e define PRIiFASTB8 i e define PRId16 d e define PRIGLEAST16 d e define PRIGFAST16 d e define PRIi16 i e define PRIILEAST16 i e define PRIiFAST16 i e define PRId32 Id e define PRIdLEAST32 Id e define PRIGFAST32 Id e define PRIi32 li e define PRIiLEAST32 li e define PRIiFAST32 li e define PRIdPTR PRId16 e define PRIiPTR PRIi16 e define PRIo8 o e define PRIoLEASTS8 o e define PRIOFASTS8 o e define PRIu8 u e define PRIULEASTS u e define PRIUFASTS u e define PRIx8 x e define PRIxLEASTS x e define PRIxFASTS x Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 17 inttypes h File Reference 246 e define PRIX8 X e define PRIXLEASTS8 X e define PRIXFAST
217. e define PRIOLEASTS8 o e define PRIOFASTS8 o e define PRIu8 u e define PRIULEASTS u Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions e define PRIUFASTS u e define PRIx8 x e define PRIxLEASTS x e define PRIxFASTS x e define PRIX8 X e define PRIXLEASTS8 X e define PRIXFASTS X e define PRIo16 o e define PRIOLEAST16 o e define PRIoFASTI16 o e define PRIu16 u e define PRIULEAST16 u e define PRIuFASTI16 u e define PRIx16 x e define PRIxLEAST16 x e define PRIxFAST16 x e define PRIX16 X e define PRIXLEAST16 X e define PRIXFAST16 X e define PRI032 lo e define PRIOLEAST32 lo e define PRIOFAST32 lo e define PRIu32 lu e define PRIULEAST32 lu e define PRIuFAST32 lu e define PRIx32 lx e define PRIxLEAST32 lx e define PRIxFAST32 Ix e define PRIX32 IX e define PRIXLEAST32 1X e define PRIXFAST32 IX e define PRIoPTR PRIo16 e define PRIuPTR PRlu16 e define PRIxPTR PRIx16 e define PRIXPTR PRIX16 e define SCNd16 d e define SCNdLEAST16 d e define SCNdFAST16 d e define SCNi16 i e define SCNILEASTI16 i e define SCNiFAST16 i e define SCNd32 Id e define SCNdLEAST32 Id Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 22 6 5 lt inttypes h gt Integer Type conversions 23 e define SCNdFAST32 Id
218. e TW READ 1 e define TW WRITE 0 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 89 wdt h File Reference 271 8 89 wdt h File Reference 8 89 1 Detailed Description Defines e define wdt reset asm volatile wdr e define WD PS3 MASK 0x00 e define WD CONTROL REG WDTCR e define WD CHANGE BIT WDCE e define wdt enable value e define wdt disable e define WDTO_15MS 0 e define WDTO 30MS 1 e define WDTO 60MS 2 e define WDTO_120MS 3 e define WDTO 250MS 4 e define WDTO 500MS 5 e define WDTO 1S 6 e define WDTO_2S 7 e define WDTO_4S 8 e define WDTO 8S 9 9 avr libc Page Documentation 9 1 Toolchain Overview 9 1 1 Introduction Welcome to the open source software development toolset for the Atmel AVR There is not a single tool that provides everything needed to develop software for the AVR It takes many tools working together Collectively the group of tools are called a toolset or commonly a toolchain as the tools are chained together to produce the final executable application for the AVR microcontroller The following sections provide an overview of all of these tools You may be used to cross compilers that provide everything with a GUI front end and not know what goes on underneath the hood You may be coming from a desktop or server computer background and not used to embedded systems Or you may be just learning about the most common software development toolchain availab
219. e allocated for them This is done by using the PSTR macro and passing the string to printstr_p 6 37 4 The source code The source code is installed under prefix share doc avr libc examples largedemo largedemo c where prefix is a configuration option For Unix systems it is usually set to either usr or usr local 6 38 Using the standard IO facilities This project illustrates how to use the standard IO facilities stdio provided by this library It assumes a basic knowledge of how the stdio subsystem is used in standard C applications and concentrates on the differences in this library s implementation that mainly result from the differences of the microcontroller environment compared to a hosted environment of a standard computer This demo is meant to supplement the documentation p 54 not to replace it 6 38 1 Hardware setup The demo is set up in a way so it can be run on the ATmegal6 that ships with the STK500 development kit The UART port needs to be connected to the RS 232 spare port by a jumper cable that connects PDO to RxD and PD1 to TxD The RS 232 channel is set up as standard input stdin and standard Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 220 output stdout respectively In order to have a different device available for a standard error channel stderr an industry standard LCD display with an HD44780 compatible LCD controller has
220. e assembler One way to avoid this problem is asm volatile sbi 0 0x07 I _SFR_IO_ADDR PORTB Note For C programs rather use the standard C bit operators instead so the above would be expressed as PORTB 1 lt lt 7 The optimizer will take care to transform this into a single SBI instruction assuming the operands allow for this Back to FAQ Index p 321 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 329 9 10 11 Why does the PC randomly jump around when single stepping through my program in avr gdb When compiling a program with both optimization 0 and debug information g which is fortunately possible in avr gcc the code watched in the debugger is optimized 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 execution 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 rjmp instruction which will need one additional word of ROM Anot
221. e 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 subaddress 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 required This example simply assumes all subaddress bits are 0 for the smaller devices so the EO El and E2 inputs of the 24Cxx must be grounded Note 4 For slow clocks enable the 2 x U SJART clock multiplier to improve the baud rate error This will allow a 9600 Bd communication using the standard 1 MHz calibrated RC oscillator See also the Baud rate tables in the datasheets Note 5 The datasheet explains why a minimum TWBR value of 10 should be maintained when running in master mode Thus for system clocks below 3 6 MHz we cannot run the bus at the intented clock rate of 100 kHz but have to slow down accordingly Note 6 This function is used by the standard output facilities that are utilized in this example for debugging and demonstration purposes Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 230 Note 7 In order to shorten the data to be sent over the TWI bus the 24Cxx EEP
222. e large requirements for either dynamic memory or stack space The former can even happen if the allocations aren t all that large but dynamic memory allocations get fragmented over time such that new requests don t quite fit into the holes of previously freed regions Large stack space requirements can arise in a C function containing large and or numerous local variables or when recursively calling function Note The pictures shown in this document represent typical situations where the RAM locations refer to an ATmegal28 The memory addresses used are not displayed in a linear scale Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 278 Ox10FF 0x1100 OxFFFF 8 on board RAM gt SP t RAMEND __brkval lt SP __malloc_margin Ko __malloc_heap_start __heap_start __bss_end data end 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 dy namic memory allocator that is simple enough so the code size reguirements will remain low yet powerful enough to avoid unnecessary memory ragmentation 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 constraints a
223. e last few percent of speed benefit rom using 03 Back to FAG Index p 321 9 10 18 How do I relocate code to a fixed address First the code should be put into a new named section p 282 This is done with a section attribute __attribute__ section bootloader In this example bootloader is the name of the new section This attribute needs to be placed after the prototype of any function to force the function into the new section void boot void __attribute__ section bootloader To relocate the section to a fixed address the linker flag section start is used This option can be passed to the linker using the W1 compiler option p 368 Wl section start bootloader 0x1E000 The name after section start is the name of the section to be relocated The number after the section name is the beginning address of the named section Back to FAQ Index p 321 9 10 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 339 e All devices that have an internal RC oscillator ship with the fuse enabled that causes the device to run off this osc
224. e programs that are included in Binutils avr as The Assembler avr ld The Linker avr ar Create modify and extract from libraries archives avr ranlib Generate index to library archive contents avr objcopy Copy and translate object files to different formats avr objdump Display information from object files including disassembly Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 1 Toolchain Overview 274 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 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 de pending 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 libe 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 Libr
225. e release The minor version number of a development series is always an odd number and is 1 more than the last stable release The patch version number of a development series is always 0 until a new branch is cut at which point the patch number is changed to 90 to denote the branch is approaching a release and the date appended to the version to denote that it Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 14 Release Numbering and Methodology 376 is still in development All versions in development in cvs will also always have the date appended as a fourth version number The format of the date will be YYYYMMDD So the development version number will look like this 1 1 0 20030825 While a pre release version number on a branch destined to become either 1 2 or 2 0 will look like this 1 1 90 20030828 9 14 2 Releasing AVR Libc The information in this section is only relevant to AVR Libc developers and can be ignored by end users Note In what follows I assume you know how to use cvs and how to checkout multiple source trees in a single directory without having them clobber each other If you don t know how to do this you probably shouldn t be making releases or cutting branches 9 14 2 1 Creating a cvs branch The following steps should be taken to cut a branch in cvs 1 Check out a fresh source tree from cvs HEAD 2 Update the NEWS file with pending release number and commit to cvs HEA
226. e size 20 push r28 push r29 in r28 __SP_L__ in r29 __SP_H__ sbiw r28 20 in __tmp_reg__ __SREG__ cli out __SP_H__ r29 out __SREG__ __tmp_reg__ out __SP_L__ r28 prologue end size 10 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 344 It reads the current stack pointer value decrements it by the required amount of bytes then disables interrupts writes back the high part of the stack pointer writes back the saved SREG which will eventually re enable interrupts if they have been enabled before and finally writes the low part of the stack pointer At the first glance there s a race between restoring SREG and writing SPL However after enabling interrupts either explicitly by setting the I flag or by restoring it as part of the entire SREG the AVR hardware executes at least the next instruction still with interrupts disabled so the write to SPL is guaranteed to be executed with interrupts disabled still Thus the emitted sequence ensures interrupts will be disabled only for the minimum time required to guarantee the integrity of this operation Back to FAQ Index p 321 9 10 29 Why are there five different linker scripts From a comment in the source code Which one of the five linker script files is actually used depends on command line options given to ld A x script file is the default script xr script is for linking without relocation r fl
227. e strcat P p 150 function is similar to strcat p 90 except that the src string must be located in program space flash Returns The strcat p 90 function returns a pointer to the resulting string dest Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 151 6 18 4 9 PGM_P strchr_P PGM P s int val Locate character in program space string The strchr_P p 151 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 p 151 function is similar to strchr p 90 except that s is pointer to a string in program space Returns The strchr P p 151 function returns a pointer to the matched char acter or NULL if the character is not found 6 18 4 10 PGM P strchrnul P PGM Ps int c The strchrnul P p 151 function is like strchr P p 151 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 p 151 function returns a pointer to the matched character or a pointer to the null byte at the end of s i e s strlen s if the character is not found 6 18 4 11 int stremp_P const char x s1 PGM_P s2 The stremp_ P p 151 function is similar to stremp p 91 except that s2 is pointer to
228. ear is reduced considerably compared to immediately writing the value at each change 6 37 3 A code walkthrough This section explains the ideas behind individual parts of the code The source code p 219 has been divided into numbered parts and the following subsec tions explain each of these parts 6 37 3 1 Part 1 Macro definitions A number of preprocessor macros are defined to improve readability and or portability of the application The first macros describe the IO pins our LEDs and pushbuttons are con nected to This provides some kind of mini HAL hardware abstraction layer so should some of the connections be changed they don t need to be changed inside the code but only on top Note that the location of the PWM output itself is mandated by the hardware so it cannot be easily changed As the ATmega48 88 168 controllers belong to a more recent generation of AVRs a number of register and bit names have been changed there so they are mapped back to their ATmega8 16 equivalents to keep the actual program code portable The name F_CPU is the conventional name to describe the CPU clock frequency of the controller This demo project just uses the internal calibrated 1 MHz RC oscillator that is enabled by default Note that when using the lt util delay h p 242 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 u
229. eclare an object being located in flash ROM 6 18 2 13 define PSTR s const PROGMEM char s Used to declare a static pointer to a string in program space 6 18 3 Typedef Documentation 6 18 3 1 prog char Type of a char object located in flash ROM 6 18 3 2 prog int16 t Type of an int16 t object located in flash ROM 6 18 3 3 prog int32 t Type of an int32 t object located in flash ROM Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 148 6 18 3 4 prog int64 t Type of an int64 t object located in flash ROM Note This type is not available when the compiler option mint8 is in effect 6 18 3 5 prog int8 t Type of an int8 t object located in flash ROM 6 18 3 6 prog uchar Type of an unsigned char object located in flash ROM 6 18 3 7 prog uint16 t Type of an uint16 t object located in flash ROM 6 18 3 8 prog uint32 t Type of an uint32 t object located in flash ROM 6 18 3 9 prog uint64 t Type of an uint64 t object located in flash ROM Note This type is not available when the compiler option mint8 is in effect 6 18 3 10 prog uint8 t Type of an uint8 t object located in flash ROM 6 18 3 11 prog void Type of a void object located in flash ROM Does not make much sense by itself but can be used to declare a void x object in flash ROM Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18
230. ed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 4 Data in Program Space 290 and then you add your PROGMEM macro to the end of the declaration char string_table PROGMEM String 1 String 2 String 3 String 4 String 5 3 Right WRONG Unfortunately with GCC attributes they affect only the declaration that they are attached to So in this case we successfully put the string_table variable the array itself in the Program Space This DOES NOT put the actual strings themselves into Program Space At this point the strings are still in the Data Space which is probably not what you want In order to put the strings in Program Space you have to have explicit decla rations 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 33 Now this has the effect of putting string_table in Program Space where string_table is an array of pointers to characters strings where each pointer is a pointer to the Program Space where each string is also stored The PGM_P type above is also a macro that defined as a pointer to a character in the Program Space Retrieving the strings are a di
231. ed floating point number the next pointer must be a pointer to float e g F E G Equivalent to f s Matches a sequence of non white space characters the next pointer must be a pointer to char and the array must be large enough to accept all the sequence and the terminating NUL character The input string stops at white space or at the maximum field width whichever occurs first c Matches a sequence of width count characters default 1 the next pointer must be a pointer to char and there must be enough room for all the characters no terminating NUL is added The usual skip of leading white space is suppressed To skip white space first use an explicit space in the format Matches a nonempty sequence of characters from the specified set of accepted characters the next pointer must be a pointer to char and there must be enough room for all the characters in the string plus a terminating NUL character The usual skip of leading white space is suppressed The string is to be made up of characters in or not in a particular set the set is defined by the characters between the open bracket character and a close bracket character The set excludes those characters if the first character after the open bracket is a circumflex 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 betwee
232. ed 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 control an output PWM based on the current input signal s value The incoming PWM pulses follow a standard encoding scheme where a pulse width of 920 microseconds denotes one end of the scale represented as 0 pulse width on output and 2120 microseconds mark the other end 100 output PWM Normally multiple channels would be encoded that way in subsequent pulses followed by a larger gap so the entire 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 outgoing 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 con sidered as well This requires servicing interrupts whenever the timer hits TOP 255 and BOTTOM 0 to learn about each change of the counting direction Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 35 Combin
233. eebsd org ports tree and for providing the basics for the demo project p 195 Brian Dean bsd bsdhome com for developing avrdude an alternative to uisp and for contributing documentation p 373 which describes how to use it Avrdude was previously called avrprog Eric Weddington eweddington cso atmel com for maintaining the WinAVR package and thus making the continued improvements to the open source AVR toolchain available to many users Rich Neswold for writing the original avr tools document which he gra ciously allowed to be merged into this document and his improvements to the demo project p 195 Theodore A Roth for having been a long time maintainer of many of the tools AVR Libc the AVR port of GDB AVaRICE uisp avrdude All the people who currently maintain the tools and or have submitted suggestions patches and bug reports See the AUTHORS files of the various tools And lastly all the users who use the software If nobody used the software we would probably not be very motivated to continue to develop it Keep those bug reports coming Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 16 Todo List 380 9 16 Todo List Group avr_ boot p 97 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
234. een inspired by other standards like IEEE Std 1003 1 1988 POSIX 1 while other extensions are purely AVR specific like the entire program space string interface Unless otherwise noted functions of this library are not guaranteed to be reen trant In particular any functions that store local state are known to be non reentrant as well as functions that manipulate IO registers like the EEPROM access routines If these functions are used within both standard and interrupt contexts undefined behaviour will result 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 com piler assembler to support these devices at library compile time megaAVR Devices atmega103 atmegal28 atmegal280 atmegal281 atmegal284p Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 1 3 Supported Devices atmegal6 atmegal61 atmegal62 atmegal63 atmegal64p atmegal65 atmegal65p atmega168 atmegal68p atmega2560 atmega2561 atmega32 atmega323 atmega324p atmega325 atmega325p atmega3250 atmega3250p atmega328p atmega48 atmega48p atmega64 atmega640 atmega644 atmega644p atmega645 atmega6450 atmega8 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 1 3 Supported Devices atmega88 atmega88p atmega8515 atmega8535 tiny AVR Devices attiny11 1 p 7 attiny12 1 p
235. ega8 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 ATtiny2313 Je SIG USI USI Overflow ATmegal65 ATmegal65P AT OVERFLOW OVERFLOW megal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega329 ATmega3290 AT mega3290P ATmega645 AT mega6450 ATmega649 ATmega6490 ATtiny2313 USI_ SIG USI USI Overflow ATtiny26 ATtiny43U ATtiny24 AT OVF vect OVERFLOW tiny44 ATtiny84 ATtiny45 AT tiny25 ATtiny85 ATtiny261 AT tiny461 ATtiny861 SIG USI USI Start Con ATmegal65 ATmegal65P AT START dition megal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P ATmega329 ATmega3290 AT mega3290P ATmega645 AT mega6450 ATmega649 ATmega6490 ATtiny2313 ATtiny43U ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 USI SIG USI USI Start ATtiny26 ET USI STR SIG USI USI START ATtiny24 ATtiny44 ATtiny84 KNE WATCHDOG SIG_ Watchdog ATtiny24 ATtiny44 ATtiny84 vect WATCHDOG Time out TIMEOUT WDT SIG_ Watchdog ATtiny2313 OVERFLOW WATCHDOG Timer Over TIMEOUT flow SIG_ WDT_ OVERFLOW Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 135 Watchdog AT90PWM3 AT90PWM2 Timeout Inter AT9OPWM1 ATmegal284P AT WATCHDOG rupt megal68P ATmega328P AT TIMEOUT mega32HVB ATmega406 AT mega48P ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 AT mega256
236. en inside library calls additional adjustments p 279 are required 9 3 3 The bss Section Uninitialized global or static variables end up in the bss section 9 3 4 The eeprom Section This is where eeprom variables are stored 9 3 5 The noinit Section This sections is a part of the bss section What makes the noinit section special is that variables which are defined as such int foo __attribute__ section noinit will not be initialized to zero during startup as would normal bss data Only uninitialized variables can be placed in the noinit section Thus the following code will cause avr gcc to issue an error int bar __attribute__ section noinit Oxaa It is possible to tell the linker explicitly where to place the noinit section by adding W1 section start noinit 0x802000 to the avr gcc command line at the linking stage For example suppose you wish to place the noinit section at SRAM address 0x2000 avr gcc Wl section start noinit 0x802000 Note Because of the Harvard architecture of the AVR devices you must manually add 0x800000 to the address you pass to the linker as the start of the section Otherwise 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 Generate
237. ent flavours of vfprintf p 66 can be selected using linker options The default vfprintf p 66 implements all the mentioned functionality except floating point conversions A minimized version of vfprintf p 66 is available that only implements the very basic integer and string conversion facilities but only the additional option can be specified using conversion flags these flags are parsed correctly from the format specification but then simply ignored This version can be requested using the following compiler options p 368 Wl u vfprintf lprintf min If the full functionality including the floating point conversions is required the following options should be used Wl u vfprintf lprintf flt lm Limitations e The specified width and precision can be at most 255 Notes e For floating point conversions if you link default or minimized version of vfprintf p 66 the symbol will be output and double argu ment will be skiped So you output below will not be crashed For default version the width field and the pad to left symbol minus option will work in this case e The hh length modifier is ignored char argument is promouted to int More exactly this realization does not check the number of h symbols e But the 11 length modifier will to abort the output as this realization does not operate long long arguments Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt std
238. ent of s which consist only of characters from accept The terminating zero is not considered as a part of string 6 11 3 34 char x strstr const char s1 const char s2 Locate a substring The strstr p 96 function finds the first occurrence of the substring s2 in the string si The terminating 0 characters are not compared Returns The strstr p 96 function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of zero length the function returns s1 6 11 3 35 char x strtok r char string const char delim char xx last Parses the string s into tokens strtok r parses the string s into tokens The first call to strtok r should have string as its first argument Subsequent calls should have the first argument set to NULL If a token ends with a delimiter this delimiting character is overwritten with a 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 charx pointer It must be the same while parsing the same string strtok_r is a reentrant version of strtok Returns The strtok r p 96 function returns a pointer to the next token or NULL when no more tokens are found 6 11 3 36 char x strupr char x s Convert a string to upper case Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 12 lt avr boot h gt
239. ept that it copies a string from Program Space the second parameter to a buffer in the Data Space the first parameter There are many string functions available that work with strings located in Program Space All of these special string functions have a suffix of _P in the function name and are declared in the lt avr pgmspace h p 250 gt header file 9 4 5 Caveats The macros and functions used to retrieve data from the Program Space have to generate 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 minimize 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 292 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 e Code for devices that do not have RAM and are thus not supported by the C compiler e Code for very time critical applications e Special tweaks that cannot be done in C Usually all but the firs
240. er usr or usr local Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 37 A more sophisticated project 212 6 37 A more sophisticated project This project extends the basic idea of the simple project p 195 to control a LED with a PWM output but adds methods to adjust the LED brightness It employs a lot of the basic concepts of avr libc to achieve that goal Understanding this project assumes the simple project has been understood in full as well as being acquainted with the basic hardware concepts of an AVR microcontroller 6 37 1 Hardware setup The demo is set up in a way so it can be run on the ATmegal6 that ships with the STK500 development kit The only external part needed is a potentiometer attached to the ADC It is connected to a 10 pin ribbon cable for port A both ends of the potentiometer to pins 9 GND and 10 VCC and the wiper to pin 1 port A0 A bypass capacitor from pin 1 to pin 9 like 47 nF is recommendable 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 37 A more sophisticated project 213 this demo The second option for the yellow green cable is shown in parenthesis in the table Alternatively the squid cable from the JTAG ICE kit can be used if available cader so of the
241. er constants C implementations should define these macros only when STDC_ CONSTANT_ MACROS is defined before lt stdint h p 259 gt is included These definitions are valid for integer constants without suffix and for macros defined as integer constant without suffix e define INT8 C value int8 t value e define UINT8 C value uint8 t CONCAT value U e define INT16 C value value e define UINT16 C value CONCAT value U e define INT32 C value CONCAT value L e define UINT32 C value CONCAT value UL e define INT64 C value CONCAT value LL e define UINT64 C value CONCAT value ULL e define INTMAX C value CONCAT value LL e define UINTMAX C value CONCAT value ULL Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 39 stdint h File Reference 261 Typedefs Exact width integer types Integer types having exactly the specified width typedef signed char int8 t typedef unsigned char uint8 t typedef signed int int16 t typedef unsigned int uint16 t typedef signed long int int32 t typedef unsigned long int uint32 t typedef signed long long int int64 t typedef unsigned long long int uint64_t Integer types capable of holding object pointers These allow you to declare variables of the same size as a pointer e typedef int16 tintptr t e typedef uint16 t uintptr t Minimum width integer types Integer types having at least the specified wi
242. er s The caller is responsible for providing sufficient storage in s Conversion is done in the format d ddd The minimum field width of the output string including the and the possible sign for negative values is given in width and prec determines the number of digits after the decimal sign width is signed value negative for left adjustment The dtostrf p 78 function returns the pointer to the converted string s 6 10 4 11 void exit int status The exit p 78 function terminates the application Since there is no en vironment to return to status is ignored and code execution will eventually reach an infinite loop thereby effectively halting all code processing Before entering the infinite loop interrupts are globally disabled In a C context global destructors will be called before halting execution 6 10 4 12 void free void __ ptr The free p 78 function causes the allocated memory referenced by ptr to be made available for future allocations If ptr is NULL no action occurs Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 79 6 10 4 13 charx itoa int __ val char s int radix Convert an integer to a string The function itoa p 79 converts the integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing sufficient storage in s Note The minimal size of the buffe
243. erated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen POLO LO LO LO AO BO GO GE LO PO PO PE GO GSO FA A A A AAA ZA A ZAZA ZZ KISS 239 8 5 boot h File Reference i _SFR_MEM_ADDR __SPM_REG i _SFR_MEM_ADDR RAMPZ r uint8 t BOOT PAGE WRITE r uint32_t address r30 r31 H 8 5 2 11 define boot page write normal address Value __extension__ _ asm__ __volatile__ movw r30 2 n t sts 0 1 n t spm n t i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT PAGE WRITE r uint16 t address r30 5 r31 H Its ZA A A A AA A ZA ZA ZZ 8 5 2 12 define boot rww enable Value __extension__ _ asm__ __volatile__ sts 0 Zi n t spm n t i _SFR_MEM_ADDR __SPM_REG r uint8_t __BOOT_RWW_ENABLE H 8 5 2 13 define boot rww enable alternate Value __extension__ asm__ __volatile__ Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen Its LO POG 240 8 6 crcl6 h File Reference 241 sts 0 1 n t spm n t N word Oxffff n t nop n t N i _SFR_MEM_ADDR __SPM_REG r uint8_t __BOOT_RWW_ENABLE H 8 6 crc16 h File Reference 8 6 1 Detailed Description Functions e static inline uint16_t crc16 update uint16 t cc uint8 t data e static inline uint16_t crc xmodem update uint16 t _crc uint8 t data e static inline uint16_t crc ccitt update uint16 t c
244. erating nonsense My ATmega128 keeps crash ing Port F is completely broken p 338 Why do all my foo bar strings eat up the SRAM p 339 Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit operation in assembly p 340 How to detect RAM memory and variable overlap problems p 341 Is it really impossible to program the ATtinyXX in C p 341 What is this clock skew detected messsage p 341 Why are many interrupt flags cleared by writing a logical 1 p 342 Why have programmed fuses the bit value 0 p 343 Which AVR specific assembler operators are available p 343 Why are interrupts re enabled in the middle of writing the stack pointer p 343 Why are there five different linker scripts p 344 How to add a raw binary image to linker output p 344 How do I perform a software reset of the AVR p 345 I am using floating point math Why is the compiled code so big Why does my code not work p 346 9 10 2 My program doesn t recognize a variable updated within an interrupt routine When using the optimizer in a loop like the following one uint8_t flag ISR SOME_vect flag 1 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 323 while flag 0 the compiler will typically access flag only once and optimize further accesses completely away since its code path analysis sho
245. eration that allows to mini mally edit the current line until it is sent to the application when either a carriage return r or newline n character is received from the terminal The line editing functions implemented are e b back space or 177 delete deletes the previous character e u control U ASCII NAK deletes the entire input buffer e w control W ASCII ETB deletes the previous input word delimited by white space e r control R ASCII DC2 sends a r 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 re quired 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 p 223 At low CPU clock frequencies the U2X bit in the UART is set re ducing 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 a
246. ers is not recommended in AVR GCC as it removes this reg ister from the control of the compiler which may make code generation worse Use at your own risk 9 10 Frequently Asked Questions 9 10 1 FAQ Index 1 My program doesn t recognize a variable updated within an in terrupt routine p 322 2 I get undefined reference to for functions like sin p 323 How to permanently bind a variable to a register p 323 How to modify MCUCR or WDTCR early p 324 What is all this _BV stuff about p 325 Can I use C on the AVR p 325 Shouldn t I initialize all my variables p 326 9 Nn oo A Q Why do some 16 bit timer registers sometimes get trashed p 327 9 How do I use a define d constant in an asm statement p 328 10 Why does the PC randomly jump around when single stepping through my program in avr gdb p 329 11 How do I trace an assembler file in avr gdb p 329 12 How do I pass an IO port as a parameter to a function p 331 13 What registers are used by the C compiler p 333 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 322 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 How do I put an array of strings completely in ROM p 334 How to use external RAM p 336 Which O flag to use p 337 How do I relocate code to a fixed address p 338 My UART is gen
247. essor 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 330 Example avr as mmcu atmegal28 gstabs o foo o foo s When the assembler is not called directly but through the C compiler fron tend 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 Oth erwise the assembler code that results from the C compilation stage will also get line number information which confuses the debugger Note You can also use Wa gstabs since the compiler will add the extra for you Example EXTRA_OPTS Wall mmcu atmega128 x assembler with cpp avr gcc Wa gstabs EXTRA_OPTS c o foo o foo S Also note that the debugger might get confused when entering a piece of code that has a non local label before since it then takes this label as the name of a new function that appears to have been entered Thus the best practice to
248. everything in before you start installing anything For example if you use prefix PREFIX you must have PREFIX bin in your exported PATH As such PATH PATH PREFIX bin export PATH Warning If you have CC set to anything other than avr gcc in your environment this will cause the configure script to fail It is best to not have CC set at all Note It is usually the best to use the latest released version of each of the tools 9 11 2 Required Tools e GNU Binutils http sources redhat com binutils Installation p 348 e GCC http gcc gnu org Installation p 350 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 348 e AVR Libc http savannah gnu org projects avr libc Installation p 350 9 11 3 Optional Tools You can develop programs for AVR devices without the following tools They may or may not be of use for you e AVRDUDE http savannah nongnu org projects avrdude Installation p 351 Usage Notes p 373 e GDB http sources redhat com gdb Installation p 351 e SimulAVR http savannah gnu org projects simulavr Installation p 352 e AVaRICE http avarice sourceforge net Installation p 352 9 11 4 GNU Binutils for the AVR target The binutils package provides all the low level utilities needed in building and manipulating object files Once installed your environment will have an AVR assembler avr
249. ext can happen See Why do some 16 bit timer registers sometimes get trashed p 327 Porting programs that use the deprecated sbi cbi macros Access to the AVR single bit set and clear instructions are provided via the standard C bit manipulation commands The sbi and cbi macros are no longer directly supported sbi sfr bit can be replaced by sfr _ BV bit p 161 i e sbi PORTB PB1 p 189 is now PORTB _BV PB1 p 161 This actually is more flexible than having sbi directly as the optimizer will use a hardware sbi if appropriate or a read or write operation if not appropriate You do not need to keep track of which registers sbi cbi will operate on Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 21 lt avr sfr defs h gt Special function registers 161 Likewise cbi sfr bit is now sfr amp _ BV bit p 161 Modules e Additional notes from lt avr sfr_ defs h gt Bit manipulation e define BV bit 1 lt lt bit IO register bit manipulation e define bit is set sfr bit _SFR_BYTE sfr amp _BV bit e define bit is clear sfr bit _SFR_BYTE sfr amp BV bit e define loop until bit is set sfr bit do while bit is clear sfr bit e define loop until bit is clear sfr bit do while bit is set sfr bit 6 21 2 Define Documentation 6 21 2 1 7zHdefine__BV bit 1 lt lt bit include lt avr io h gt Converts a bit number into a byte value
250. farptr_t 31 avr_ math acos 34 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 384 INDEX 385 asin 34 PGM P 145 atan 34 pgm_read_ byte 145 atan2 34 pgm read byte far 145 ceil 34 pgm read byte near 145 copysign 34 pgm read dword 146 cos 34 pgm read dword far 146 cosh 34 pgm read dword near 146 exp 34 pgm read word 146 fabs 35 pgm read word far 146 fdim 35 pgm read word near 147 floor 35 PGM VOID P 147 fma 35 prog char 147 fmax 35 prog intl6 t 147 fmin 35 prog int32 t 147 fmod 35 prog int64 t 147 frexp 35 prog int8 t 148 hypot 36 prog uchar 148 INFINITY 33 prog uint16 t 148 isfinite 36 prog uint32 t 148 isinf 36 prog uint64 t 148 isnan 36 prog uint8 t 148 Idexp 36 prog void 148 log 36 PROGMEM 147 log10 37 PSTR 147 lrint 37 strcasecmp P 150 lround 37 strcasestr_ P 150 M_PI 33 strcat_P 150 M_SQRT2 33 strchr_P 150 modf 37 strchrnul_P 151 NAN 33 stremp P 151 pow 37 strepy P 151 round 38 strespn P 152 signbit 38 strleat P 152 sin 38 strlepy P 152 sinh 38 strlen_P 152 sqrt 38 strncasecmp P 153 square 38 strncat P 153 tan 38 strnemp P 153 tanh 39 strnepy P 154 trunc 39 strnlen P 154 avr pgmspace strpbrk P 154 memchr_P 149 strrchr_P 155 memcmp_ P 149 strsep_ P 155 memcpy P 149 strspn_P 155 memmem P 149 strstr P 155 memrchr P 149 avr sfr Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX
251. fferent matter You probably don t want to pull the string out of Program Space byte by byte using the pgm_read_byte p 145 macro There are other functions declared in the lt avr pgmspace h p 250 gt header file that work with strings that are stored in the Program Space Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 4 Data in Program Space 291 For example if you want to copy the string from Program Space to a buffer in RAM like an automatic variable inside a function that is allocated on the stack you can do this void foo void char buffer 10 for unsigned char i 0 i lt 5 i 1 strcpy_P buffer PGM_P pgm_read_word amp string_table i Display buffer on LCD return Here the string_table array is stored in Program Space so we access it nor mally as if were stored in Data Space then take the address of the location we want to access and use the address as a parameter to pgm_read_word We use the pgm_read_word macro to read the string pointer out of the string_table array Remember that a pointer is 16 bits or word size The pgm_read_word macro will return a 16 bit unsigned integer We then have to typecast it as a true pointer to program memory PGM_P This pointer is an address in Program Space pointing to the string that we want to copy This pointer is then used as a parameter to the function strcpy_P The function strcpy_P is just like the regular strcpy function exc
252. fic IO definitions include lt avr io h gt This header file includes the apropriate IO definitions for the device that has been specified by the mmcu compiler command line switch This is done by diverting to the appropriate file lt avr ioX XXX h gt which should never be included directly Some register names common to all AVR devices are defined directly within lt avr common h gt which is included in lt avr io h p 247 gt but most of the details come from the respective include file Note that this file always includes the following files include lt avr sfr_defs h gt include lt avr portpins h gt include lt avr common h gt include lt avr version h gt See lt avr sfr defs h gt Special function registers p 160 for more details about that header file Included are definitions of the IO register set and their respective bit values as specified in the Atmel documentation Note that inconsistencies in naming con ventions so even identical functions sometimes get different names on different devices Also included are the specific names useable for interrupt function definitions as documented here p 114 Finally the following macros are defined e RAMEND A constant describing the last on chip RAM location Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 17 lt avr lock h gt Lockbit Support 140 e XRAMEND A constant describing the last possible location in RAM This is equal to
253. fine SCNoLEAST32 lo e define SCNoFAST32 lo e define SCNu32 lu e define SCNuLEAST32 lu e define SCNuFAST32 lu e define SCNx32 Ix e define SCNxLEAST32 Ix e define SCNxFAST32 lx e define SCNoPTR SCNo16 e define SCNuPTR SCNu16 e define SCNxPTR SCNx16 Typedefs Far pointers for memory access gt 64K e typedef int32 tint farptr t e typedef uint32_t uint farptr t 8 18 io h File Reference 8 18 1 Detailed Description 8 19 lock h File Reference 8 19 1 Detailed Description Defines e define AVR LOCK H 1 e define LOCKMEM __ attribute _ section lock e define LOCKBITS unsigned char lock LOCKMEM e define LOCKBITS DEFAULT 0xFF 8 20 math h File Reference 8 20 1 Detailed Description Defines e define M_ PI 3 141592653589793238462643 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 20 math h File Reference 248 define M SQRT2 1 4142135623730950488016887 define NAN __ builtin_nan define INFINITY __ builtin_inf Functions double cos double __ x double fabs double __ x double fmod double ___x double ___y double modf double ___x double iptr double sin double __x double sqrt double __ x double tan double __x double floor double __ x double ceil double __ x double frexp double ___x int __pexp double Idexp double ___x int ___exp double exp double __x double cosh double __ x double sinh double __x double tan
254. foo PROGMEM const char bar PROGMEM LI Foo Bar LI PGM_P array 2 PROGMEM 1 foo bar Fs int main void char buf 32 PGM_P p int i memcpy P amp p amp arrayli sizeof PGM_P strcpy_P buf p return 0 Looking at the disassembly of the resulting object file we see that array is in flash as such 00000026 lt array gt 26 2e 00 word 0x002e 7777 28 2a 00 word 0x002a 7777 0000002a lt bar gt 2a 42 61 72 00 Bar 0000002e lt foo gt 2e 46 6f 6f 00 Foo foo is at addr 0x002e bar is at addr 0x002a array is at addr 0x0026 Then in main we see this memcpy_P amp p amp array i sizeof PGM P Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 336 70 66 Of add r22 r22 72 77 1f adc r23 r23 T4 6a 5d subi r22 OxDA 218 76 TL 4f sbci r23 OxFF 255 78 42 e0 ldi r20 0x02 2 Ta 50 e0 ldi r21 0x00 0 Tc ce 01 movw r24 r28 Te 81 96 adiw r24 0x21 33 80 08 do reall 16 0x92 This code reads the pointer to the desired string from the ROM table array into a register pair The value of i in r22 r23 is doubled to accomodate for the word offset required to access array then the address of array 0x26 is added by subtracting the negated address Oxffda The address of variable p is computed by adding its offset within the stack frame 33 to the Y pointer register and memcpy_P is called strcpy_
255. functions as a modi fier on the parameter type This tells the compiler that the function will only use the parameter as read only and will not modify the contents of the parameter variable const was intended for uses such as this not as a means to identify where the data should be stored If it were used as a means to define data storage then it Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 4 Data in Program Space 288 loses its correct meaning changes its semantics in other situations such as in the function parameter 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 1 10x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 Ox0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 10x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F 0x30 0x31 10x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 10x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 10x5A 0x5B 0x5C 0x5D 0x5E 0x5F 0x60 0x61 0x62 0x637 10x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6D 3 and later in your code you access this data in a function and store a single byte into a variable like so byte mydatalilljl Now you want to store your data in Program
256. ga649 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 USARTI SIG USARTI1 Rx ATmegal62 RXC vect USARTI1 Complete RECV USARTI SIG USARTI AT90CAN128 Fe RX vect Ma Complete AT90CAN64 ATmega128 T megal284P ATmega64 re ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 USARTI SIG USARTI1 Tx ATmegal62 TXC vect USARTI1 Complete TRANS Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts USARTI TX vect USART2_ SIG_ RX vect USART2 RECV USART2_ SIG TX vect USART2 TRANS USART2 SIG UDRE vect USART2 DATA U T USART3_ SIG_ X vect USART3 TRANS USART3 SIG UDRE_vect USART3 DATA SIG U SART3 SIG RX vect USART3_ RECV U Data Register USART2 Rx Complete USART2 Tx Complete USART2 Data register Empty USART3 Rx Complete USART3 Tx Complete USART3 Data register Empty USART Rx Complete USART Rx Complete 133 AT90CAN128 AT90CAN32 AT90CAN64 ATmega128 AT megal284P ATmega64 ATmega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 AT90CAN128
257. ga8515 UART UART Data AT90S2313 AT9052333 AT90S4414 UDRE_ vect Register AT90S4433 AT90S4434 AT90S8515 AT9088535 ATmega103 ATmega163 ATmega8515 ARTO SIG UARTO T ATmegal61 TX vect UARTO Complete RANS Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 132 Vector Old vector Description Applicable for device name name USARTO SIG USARTO Rx ATmegal62 RXC vect USARTO Complete RECV USARTO SIG __ USARTO Rx AT90CAN128 FE RX vect Complete AT90CAN64 ATmega128 T megal284P ATmegal65 ie megal65P ATmegal69 ATmegal69P ATmega325 ATmega329 ATmega64 ATmega645 ATmega649 AT mega640 ATmega1280 ATmegal1281 ATmega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 USARTO SIG USARTO Tx ATmegal62 TXC_vect USARTO_ Complete TRANS USARTO SIG USARTO Tx AT90CAN128 AT90CAN32 TX vect aa Complete AT90CAN64 ATmega128 AT megal284P ATmegal65 AT megal65P ATmegal69 ATmegal69P ATmega325 ATmega3250 AT mega3250P ATmega329 AT mega3290 ATmega3290P AT mega64 ATmega645 ATmega6450 ATmega649 ATmega6490 AT mega640 ATmega1280 ATmegal281 ATmega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT90CAN128 AT90CAN32 Data Register AT90CAN64 ATmega128 AT megal284P ATmegal62 ATmegal65 ATmegal65P ATmegal69 AT megal69P ATmega325 ATmega329 ATmega64 ATmega645 ATme
258. gal62 ATmega32 ATmega323 ATmega32HVB ATmega406 AT mega64 ATmega8515 ATmega8535 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 ATmegal6HVA AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 AT mega103 ATmega128 AT mega32HVB ATmega406 AT mega64 ATmega640 ATmegal280 ATmegal281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 119 INT4 vect Z AT90CAN128 AT90CAN32 INTERRUPT4 rupt Request 4 AT90CAN64 ATmega103 AT megal28 ATmega64 ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 INT5 vect SIG External Inter AT90CAN128 AT90CAN32 INTERRUPTS rupt Request 5 AT90CAN64 ATmega103 AT megal28 ATmega64 ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 INT6_vect SIG_ External Inter AT90CAN128 AT90CAN32 INTERRUPT 6 rupt Request 6 AT90CAN64 ATmega103 AT megal28 ATmega64 ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 INT7_vect SIG_ External I
259. gal68P AT megal69 ATmegal69P ATmega325 ATmega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega406 AT mega48P ATmega64 ATmega645 ATmega6450 ATmega649 AT mega6490 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TIMO SIG Timer Counter ATtiny13 ATtiny43U ATtiny24 AT COMPA OUTPUT Compare tiny44 ATtiny84 ATtiny45 AT vect COMPAREOA Match A tiny25 ATtiny85 TIMO SIG Timer Counter ATtiny13 ATtiny43U ATtiny24 AT COMPB OUTPUT Compare tiny44 ATtiny84 ATtiny45 AT vect COMPAREOB Match B tiny25 ATtiny85 TIMO SIG Timer Counter0 ATtiny13 ATtiny43U ATtiny24 AT OVF _vect OVERFLOW Q Overflow tiny44 ATtiny84 ATtiny45 AT tiny25 ATtiny85 TIM1 SIG_ Timer Counterl ATtiny24 ATtiny44 ATtiny84 CAPT vect INPUT_ Capture Event CAPTURE1 TIM1 SIG_ Timer Counterl ATtiny24 ATtiny44 ATtiny84 AT COMPA _ OUTPUT_ Compare tiny45 ATtiny25 ATtiny85 vect COMPARELA Match A TIM1 SIG_ Timer Counterl ATtiny24 ATtiny44 ATtiny84 AT COMPB_ OUTPUT Compare tiny45 ATtiny25 ATtiny85 vect COMPAREIB Match B TIM1 SIG Timer Counterl ATtiny24 ATtiny44 ATtiny84 AT TIMERO SIG ADC Conver ATtiny261 ATtiny461 ATtiny861 CAPT vect INPUT sion Complete CAPTUREO
260. gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt Ox5c lt __vector_8 gt Oxtic Oxtic Oxtic Oxtic Oxtic Oxtic Oxtic Oxtic Oxtic Oxtic 5 lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt lt __bad_interrupt gt 2 0 2 0 2 0 2 2 2 0 201 6 36 A simple project 202 42 a0 36 cpi r26 0x60 96 44 bi 07 cpc r27 ri7 46 d9 f7 brne 10 Ox3e lt do_copy_data_loop gt 00000048 lt __do_clear_bss gt 48 10 e0 1di r17 0x00 0 4a a0 e6 ldi r26 0x60 96 4c bO e0 ldi r27 0x00 0 4e 01 c0 rjmp 2 0x52 lt do_clear_bss_start gt 00000050 lt do_clear_bss_loop gt 50 1d 92 st X ri 00000052 lt do clear bss start gt 52 a3 36 cpi r26 0x63 99 54 bi 07 cpc r27 ri7 56 el f7 brne 8 0x50 lt do_clear_bss_loop gt 58 4d do reall 154 Oxf4 lt main gt 5a 61 cO rjmp 194 Oxile lt exit gt 0000005c lt __vector_8 gt include iocompat h Note 1 enum UP DOWN ISR TIMER1_OVF_vect Note 2 5c 1f 92 push ri 5e Of 92 push ro 60 Of b6 in rO Ox3f 63 62 Of 92 push ro 64 11 24 eor ri ri 66 2f 93 push r18 68 3f 93 push r19 6a 8f 93 push r24 static uint16 t pwm Note 3 st
261. gure 7 Internal RAM stack only external RAM variables and heap Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 280 If dynamic memory should be placed in external RAM while keeping the vari ables in internal RAM something like the following could be used Note that for demonstration purposes the assignment of the various regions has not been made adjacent in this example so there are holes below and above the heap in external RAM that remain completely unaccessible by regular variables or dynamic memory allocations shown in light bisque color in the picture below avr gcc Wl defsym __heap_start 0x802000 defsym __heap_end 0x803fff grama RAM 0x0100 Ox10FF 0x1100 0x2000 Ox3FFF OxFFFF on board RAM ie a S _ malloc heap end __heap_end e _ brkval __bss_end _ malloc heap start __heap_start _ data end __bss_start data start Figure 8 Internal RAM variables and stack external RAM heap If __malloc_heap_end is 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 sta
262. h double __ x double acos double ___x double asin double __ x double atan double ___x double atan2 double __ y double ___x double log double __ x double log10 double __x double pow double __x double ___y int isnan double __ x int isinf double __x double square double __x static double copysign double __x double __y double fdim double ___ x double __y double fma double __x double __ y double __z double fmax double __x double y double fmin double ___x double __y int signbit double __x double trunc double __x static int isfinite double __x double hypot double __ x double ___y double round double __ x long lround double __x long lrint double __x Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 21 memccpy S File Reference 249 8 21 memccpy S File Reference 8 21 1 Detailed Description 8 22 memchr S File Reference 8 22 1 Detailed Description 8 23 memchr P S File Reference 8 23 1 Detailed Description 8 24 memcmp S File Reference 8 24 1 Detailed Description 8 25 memcmp P S File Reference 8 25 1 Detailed Description 8 26 memcpy S File Reference 8 26 1 Detailed Description 8 27 memcpy P S File Reference 8 27 1 Detailed Description 8 28 memmem S File Reference 8 28 1 Detailed Description 8 29 memmove S File Reference 8 29 1 Detailed Description 8 30 memrchr S File Reference 8 30 1 Detailed Description 8 31 memrchr_P S File Reference 8 31 1 Deta
263. har x const char size_t int strnemp const char const char x size_t ATTR_PURE char strnepy char x const char x size_t int strncasecmp const char x const char size_t ATTR PURE size_t strnlen const char size_t ATTR PURE e char strpbrk const char x s const char x accept _ ATTR PURE e char x strrchr const char x int ATTR PURE char strrev char x char strsep char xx const char Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 57 string h File Reference 268 e size_t strspn const char x s const char x accept ATTR PURE__ e char x strstr const char x const char ATTR PURE e char strtok r char x const char char xx e char x strupr char Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 58 strlcat S File Reference 269 8 58 stricat S File Reference 8 58 1 Detailed Description 8 59 stricat P S File Reference 8 59 1 Detailed Description 8 60 strlepy S File Reference 8 60 1 Detailed Description 8 61 strlepy P S File Reference 8 61 1 Detailed Description 8 62 strlen S File Reference 8 62 1 Detailed Description 8 63 strlen P S File Reference 8 63 1 Detailed Description 8 64 strlwr S File Reference 8 64 1 Detailed Description 8 65 strncasecmp S File Reference 8 65 1 Detailed Description 8 66 strncasecmp P S File Reference 8 66 1 Detailed Description 8 67 strncat S File Reference 8 67 1 Det
264. har x const char size_t ATTR PURE char x strncat char x const char x size t int strnemp const char x const char x size t ATTR PURE char x strnepy char x const char x size_t size_t strnlen const char x size_t ATTR PURE char x strpbrk const char x s const char x accept _ ATTR PURE__ char strrchr const char int ATTR PURE char strrev char char strsep char xx const char size_t strspn const char x s const char x accept ATTR PURE char strstr const char const char ATTR PURE e char x strtok r char x const char char xx e char strupr char 6 11 2 Define Documentation 6 11 2 1 define FFS x This macro finds the first least significant bit set in the input value This macro is very similar to the function ffs p 87 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 Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 87 Returns The FFS p 86 macro returns the position of the first least signifi cant bit set in the word val or 0 if no bits are set The least significant bit is position 1 6
265. he data is actually located It is likely that you will be retrieving some garbage The problem is that AVR GCC does not intrinsically know that the data resides in the Program Space The solution is fairly simple The rule of thumb for accessing data stored in the Program Space is to access the data as you normally would as if the variable is stored in Data Space like so byte mydatalilljl then take the address of the data byte amp mydata il j then use the appropriate pgm_read_ macro and the address of your data be comes the parameter to that macro byte pgm read byte amp mydatalil jl The pgm read macros take an address that points to the Program Space and retrieves 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 generate the correct code to retrieve the data from the Program Space There are different pgm 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 specifi cally you want to store and array of strings to Program Space So you start off with your array like so char string_table String 1 String 2 String 3 String 4 String 5 3 Generated on W
266. he 2 LSB carry the prescaler bits on the newer ATmegas 6 31 2 32 define TW WRITE 0 SLA W address 6 32 lt compat deprecated h gt Deprecated items 6 32 1 Detailed Description This header file contains several items that used to be available in previous versions of this library but have eventually been deprecated over time include lt compat deprected h gt These items are supplied within that header file for backward compatibility rea sons only so old source code that has been written for previous library versions could easily be maintained until its end of life Use of any of these items in new code is strongly discouraged Allowing specific system wide interrupts In addition to globally enabling interrupts each device s particular interrupt needs to be enabled separately if interrupts for this device are desired 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 32 lt compat deprecated h gt Deprecated items 187 Do some work Disable all timer interrupts timer_enable_int 0 Note Be careful when you use these functions If you already have a different interrupt enabled you could inadvertantly disable it by enabling another intterupt e s
267. he lockbit data This variable is assigned to its own linker section Assign the desired lockbit values immediately in the variable initialization The lock section in the ELF file will get its values from the initial variable assignment ONLY This means that you can NOT assign values to this variable in functions and the new values will not be put into the ELF lock section The global variable is declared in the LOCKBITS macro has two leading un derscores which means that it is reserved for the implementation meaning the library so it will not conflict with a user named variable You must initialize the lockbit variable to some meaningful value even if it is the default value This is because the lockbits default to a logical 1 meaning unprogrammed Normal uninitialized data defaults to all locgial zeros So it is vital that all lockbits are initialized even with default data If they are not then the lockbits may not programmed to the desired settings and can possibly put your device into an unrecoverable state Be sure to have the mmcu device flag in your compile command line and your linker command line to have the correct device selected and to have the correct I O header file included when you include lt avr io h p 247 gt You can print out the contents of the lock section in the ELF file by using this command line Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Spa
268. he new memory cannot be allocated realloc p 81 returns NULL and the region at ptr will not be changed 6 10 4 24 void srand unsigned int __ seed Pseudo random number generator seeding see rand p 80 6 10 4 25 void srandom unsigned long __ seed Pseudo random number generator seeding see random p 81 6 10 4 26 double strtod const char nptr char x endptr The strtod p 82 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 optionally followed by an exponent An exponent consists of an E or e followed by an optional plus or minus sign followed by a sequence of digits Leading white space characters in the string are skipped The strtod p 82 function returns the converted value if any If endptr is not NULL a pointer to the character after the last character used in the conversion is stored in the location referenced by endptr If no conversion is performed zero is returned and the value of nptr is stored in the location referenced by endptr If the correct value would cause overflow plus or minus INFINITY is returned according to the sign of the value and ERANGE is stored in errno If the correct value would cause underflow zero is returned and ERANGE is stored in errno
269. her side effect of optimzation is that variable usage is restricted to the area of code where it is actually used So if a variable was placed in a register at the beginning of some function this same register can be re used later on if the compiler notices that the first variable is no longer used inside that function even though the variable is still in lexical scope When trying to examine the variable in avr gdb the displayed result will then look garbled So in order to avoid these side effects optimization can be turned off while debugging However some of these optimizations might also have the side effect of uncovering bugs that would otherwise not be obvious so it must be noted that turning off optimization can easily change the bug pattern In most cases you are better off leaving optimizations enabled while debugging Back to FAQ Index p 321 9 10 12 How do I trace an assembler file in avr gdb When using the g compiler option avr gcc only generates line number and other debug information for C and C files that pass the compiler Functions that don t have line number information will be completely skipped by a single step command in gdb This includes functions linked from a standard library but by default also functions defined in an assembler source file since the g compiler switch does not apply to the assembler So in order to debug an assembler input file possibly one that has to be passed through the C preproc
270. his could be done with the help of a local C variable uint8_t s asm volatile in 40 __SREG__ n t cli n t Id __tmp_reg__ al n t inc __tmp_reg__ n t st fal __tmp_reg__ n t out __SREG__ 0 n t amp r s e ptr I Now every thing seems correct but it isn t really The assembler code modifies the variable that ptr points to The compiler will not recognize this and may keep its value in any of the other registers Not only does the compiler work with the wrong value but the assembler code does too The C program may have modified the value too but the compiler didn t update the memory location for optimization reasons The worst thing you can do in this case is 1 uint8_t s asm volatile in 40 __SREG__ n t cli n t ld __tmp_reg__ al n t inc __tmp_reg__ n t st Zal __tmp_reg__ n t out __SREG__ 0 n t amp r s e ptr memory Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 308 The special clobber memory informs the compiler that the assembler code may modify any memory location It forces the compiler to update all variables for which the contents are currently held in a register before executing the assembler code And of course everything has to be reloaded again after this code In most situations a much better solution would be to declare the pointer destination itself v
271. his purpose If multiple 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 attached 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 p 60 and can be accessed inside lcd_putchar using fdev get udata p 59 6 38 3 7 uart h Public interface definition for the RS 232 UART driver much like in led h p 224 except there is now also a character input function available As the RS 232 input is line buffered in this example the macro RX_BUFSIZE determines the size of that buffer Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 226 6 38 3 8 uart c This implements an stdio compatible RS 232 driver using an AVR s standard UART or USART in asynchronous operation mode Both character output as well as character input operations are implemented Char acter output takes care of converting the internal newline n into its external representation carriage return line feed r n Character input is organized as a line buffered op
272. hy does writing a logical 1 to it clear the interrupt bit The solution is simple writing a logical 1 to it requires only a single OUT instruc Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 343 tion and it is clear that only this single interrupt request bit will be cleared There is no need to perform a read modify write cycle like an SBI instruction since all bits in these control registers are interrupt bits and writing a logical 0 to the remaining bits as it is done by the simple OUT instruction will not alter them so there is no risk of any race condition that might accidentally clear another interrupt request bit So instead of writing TIFR _BV TOVO wrong simply use TIFR _BV TOVO Back to FAQ Index p 321 9 10 26 Why have programmed fuses the bit value 0 Basically fuses are just a bit in a special EEPROM area For technical reasons erased E E PROM cells have all bits set to the value 1 so unprogrammed fuses also have a logical 1 Conversely programmed fuse cells read out as bit value 0 Back to FAQ Index p 321 9 10 27 Which AVR specific assembler operators are available See Pseudo ops and operators p 296 Back to FAQ Index p 321 9 10 28 Why are interrupts re enabled in the middle of writing the stack pointer When setting up space for local variables on the stack the compiler generates code like this prologue fram
273. ibc by Doxygen 9 11 Building and Installing the GNU Tool Chain 353 mainly designed for running under a POSIX environment such as Unix and Linux Windows does not natively provide such an environment There are two projects available that provide such an environment Cygwin and MinGW MSYS There are advantages and disadvantages to both Cygwin provides a very complete POSIX environment that allows one to build many Linux based tools from source with very little or no source modifications How ever POSIX functionality is provided in the form of a DLL that is linked to the application This DLL has to be redistributed with your application and there are issues if the Cygwin DLL already exists on the installation system and different versions of the DLL On the other hand MinGW MSYS can compile code as native Win32 applications However this means that programs de signed for Unix and Linux i e that use POSIX functionality will not compile as MinGW MSYS does not provide that POSIX layer for you Therefore most programs that compile on both types of host systems usually must provide some sort of abstraction layer to allow an application to be built cross platform MinGW MSYS does provide somewhat of a POSIX environment that allows you to build Unix and Linux applications as they woud normally do with a configure step and a make step Cygwin also provides such an environment This means that building the AVR toolchain is very similar to how it i
274. ice initialized and ready to accept instructions avrdude Device signature 0x1e9101 avrdude erasing chip avrdude done avrdude reading input file main hex avrdude input file main hex auto detected as Intel Hex avrdude writing flash 1749 0x00 avrdude 1750 bytes of flash written avrdude verifying flash memory against main hex avrdude reading on chip flash data 1749 0x00 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 AT9052313 chip This option specifies the device id and is matched up with the device of the same id in avrdude s configuration file usr local etc avrdude conf To list valid parts specify the v option The e option instructs avrdude to perform a chip erase before programming this is almost always necessary before programming the flash The m flash option indicates that we want to upload data into the flash memory while i main hex specifies the name of the input file The EEPROM is uploaded in the same way the only difference is that you would use m eeprom instead of m flash To use interactive mode use the t option avrdude p 2313 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 14 Release Numbering and Methodology 375 avrdude AVR device initialized and ready to accept instructions avrdude Device signature 0x1e9101 avrdude gt The 7 command
275. ieve the factory stored oscillator calibration bytes Parameter address can be 0 0x1f as documented by the datasheet Note The values are MCU type dependent 6 12 2 15 define boot spm busy __SPM_REG amp uint8_ t BV SPM ENABLE Check if the SPM instruction is busy 6 12 2 16 define boot spm busy wait do while boot spm busy Wait while the SPM instruction is busy 6 12 2 17 define boot spm interrupt disable SPM REG amp uint8 t BV SPMIE Disable the SPM interrupt 6 12 2 18 define boot spm interrupt enable SPM REG uint8 t BV SPMIE Enable the SPM interrupt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 13 lt avr eeprom h gt EEPROM handling 104 6 12 2 19 define BOOTLOADER SECTION __ attribute section bootloader Used to declare a function or variable to be placed into a new section called bootloader This section and its contents can then be relocated to any address such as the bootloader NRWW area at link time 6 12 2 20 define GET EXTENDED FUSE BITS 0x0002 address to read the extended fuse bits using boot lock fuse bits get 6 12 2 21 define GET HIGH FUSE BITS 0x0003 address to read the high fuse bits using boot lock fuse bits get 6 12 2 22 define GET LOCK BITS 0x0001 address to read the lock bits using boot lock fuse bits get 6 12 2 23 define GET LOW FUSE BITS 0x0000 address to read the low fuse bits using boot lock
276. ify 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 p 247 gt file name that is used to sep arate subdirectories can be used on Windows distributions of the toolchain and is the recommended method of including this file The compiler knows the processor type and through the single header file above it can pull in and include the correct individual IO header file This has the advantage that you only have to specify one generic header file and you can easily port your application to another processor type without having to change every file to include the new IO header file Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 9 Porting From IAR to AVR GCC 318 The AVR toolchain tries to adhere to the exact names of the registers and names of the bits found in the AVR datasheet There may be some descrepencies between the register names found in the IAR IO header files and the AVR GCC IO header files 9 9 3 Interrupt Service Routines ISRs As mentioned above the C language Standard strangely does not specify a standard way of declaring and defining an ISR Hence every compiler seems to have their own special way of doing so IAR declares an ISR like so pragma vector TIMERO_OVF_vect __interrupt void MotorPWMBottom code I In AVR GCC you declare an ISR like so ISR PCINT1_vect 1 code AVR GCC uses the ISR macro to
277. il of the region that is no longer to be used is passed to the standard free p 78 function for insertion into the freelist Checks are first made whether the tail chunk is large enough to hold a chunk of its own at all otherwise realloc p 81 will simply do nothing and return the original region When growing the region it is first checked whether the existing allocation can be extended in place If so this is done and the original pointer is returned without copying any data contents As a side effect this check will also record the size of the largest chunk on the freelist If the region cannot be extended in place but the old chunk is at the top of heap and the above freelist walk did not reveal a large enough chunk on the freelist to satisfy the new request an attempt is made to quickly extend this topmost chunk and thus the heap so no need arises to copy over the existing Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 3 Memory Sections 282 data If there s no more space available in the heap same check is done as in malloc p 80 the entire request will fail Otherwise malloc p 80 will be called with the new request size the existing data will be copied over and free p 78 will be called on the old region 9 3 Memory Sections Remarks Need to list all the sections which are available to the avr Weak Bindings FIXME need to discuss the weak directive The following desc
278. ile Reference 8 52 1 Detailed Description 8 53 strepy S File Reference 8 53 1 Detailed Description 8 54 strcpy P S File Reference 8 54 1 Detailed Description 8 55 strcspn S File Reference 8 57 A string h File Reference 267 7 define need NULL 7 define need size_t define ATTR PURE attribute pure define FFS x Functions int ffs int __ val int ffsl long __ val int ffsll long long _ val void x memccpy void const void x int size_t void x memchr const void x int size_t ATTR PURE int memcmp const void x const void x size_t ATTR PURE void x memcpy void const void x size_t void x memmem const void x size_t const void x size_t ATTR PURE__ void x memmove void const void x size_t void x memrchr const void x int size_t ATTR_PURE void x memset void x int size_t char strcat char const char char strchr const char int ATTR_PURE char strchrnul const char int ATTR_PURE int stremp const char x const char ATTR_PURE char strepy char const char int strcasecmp const char const char ATTR PURE char x strcasestr const char x const char ATTR PURE size_t strcspn const char x s const char x reject ATTR PURE size_t strlcat char const char x size_t size_t strlcpy char x const char x size_t size_t strlen const char ATTR PURE char strlwr char char strncat c
279. iled Description 8 32 memset S File Reference 8 32 1 Detailed Description 8 33 parity h File Reference 8 33 1 Detailed Description Defines 8 34 pgmspace h File Reference 250 8 34 pgmspace h File Reference 8 34 1 Detailed Description Defines define define define PGMSPACE H 1 need size t ATTR PROGMEM _ attribute progmem define define PROGMEM ATTR PROGMEM ATTR PURE _ __attribute__ __pure__ define PSTR s const PROGMEM char s define _ define define _ define fedefine _ define define _ define define _ define pgm_read_byte_near address_short LPM uint16 t address short define LPM classic addr LPM enhanced addr LPM word classic addr LPM word enhanced _ addr LPM dword classic addr LPM dword enhanced _ addr LPM addr LPM classic __ addr _LPM_word addr LPM_word_classic___ addr _LPM_dword addr LPM_dword_classic___ addr pgm read word mnear address short LPM word uint16 t address short define pgm read dword near address_ short LPM dword uint16 t address short define define _ define define define _ define define define _ELPM classic addr ELPM enhanced addr ELPM word classic addr ELPM word enhanced _ addr ELPM dword classic addr ELPM dword enhanced addr ELPM addr ELPM classic addr ELPM word
280. ill normally constitute a large pessimization due to the code increase ment The only other optimization turned on with 03 is frename registers which could rather be enabled manually instead A simple 0 option is equivalent to 01 Note also that turning off all optimizations will prevent some warnings from be ing 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 p 329 for issues regarding debugging optimized code e Wa assembler options e W1 linker options Pass the listed options to the assembler or linker respectively e g Generate debugging information that can be used by avr gdb e ffreestanding Assume a freestanding environment as per the C standard This turns off automatic builtin functions though they can still be reached by prepending __ builtin to the actual function name It also makes the compiler not complain when main is declared with a void return type which makes some sense in a microcontroller environment where the application cannot meaningfully provide a return value to its environment in most cases main won t even return anyway However this also turns off all optimizations normally done by the compiler which assume that functions known by a certain name behave as described by the standard E g applying the function strlen p 93 to a literal stri
281. illator instead of an external crystal This often remains unnoticed until the first attempt is made to use something critical in timing like UART communication e The ATmegal28 ships with the fuse enabled that turns this device into ATmegal03 compatibility mode This means that some ports are not fully usable and in particular that the internal SRAM is located at lower addresses Since by default the stack is located at the top of internal SRAM a program compiled for an ATmega128 running on such a device will immediately crash upon the first function call or rather upon the first function return e Devices with a JTAG interface have the JTAGEN fuse programmed by de fault This will make the respective port pins that are used for the JTAG interface unavailable for regular IO Back to FAQ Index p 321 9 10 20 Why do all my foo bar strings eat up the SRAM By default all strings are handled as all other initialized variables they occupy RAM even though the compiler might warn you when it detects write attempts to these RAM locations and occupy the same amount of flash ROM so they can be initialized to the actual string by startup code The compiler can op timize multiple identical strings into a single one but obviously only for one compilation unit i e a single C source file That way any string literal will be a valid argument to any C function that expects a const char argument Of course this is going to w
282. in SLA R W address field e define TW READ 1 e define TW WRITE 0 6 31 2 Define Documentation 6 31 2 1 define TW BUS ERROR 0x00 illegal start or stop condition 6 31 2 2 define TW MR ARB LOST 0x38 arbitration lost in SLA R or NACK 6 31 2 3 define TW MR DATA ACK 0x50 data received ACK returned 6 31 2 4 define TW MR DATA NACK 0x58 data received NACK returned 6 31 2 5 define TW MR SLA ACK 0x40 SLA R transmitted ACK received 6 31 2 6 define TW MR SLA NACK 0x48 SLA R transmitted NACK received 6 31 2 7 define TW MT ARB LOST 0x38 arbitration lost in SLA W or data Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 31 lt util twi h gt TWI bit mask definitions 184 6 31 2 8 define TW MT DATA ACK 0x28 data transmitted ACK received 6 31 2 9 define TW MT DATA NACK 0x30 data transmitted NACK received 6 31 2 10 define TW MT SLA ACK 0x18 SLA W transmitted ACK received 6 31 2 11 define TW MT SLA NACK 0x20 SLA W transmitted NACK received 6 31 2 12 define TW NO INFO OxF8 no state information available 6 31 2 13 define TW READ 1 SLA R address 6 31 2 14 define TW REP START 0x10 repeated start condition transmitted 6 31 2 15 define TW SR ARB LOST GCALL ACK 0x78 arbitration lost in SLA RW general call received ACK returned 6 31 2 16 define TW SR ARB LOST SLA ACK 0x68 arbitration lost in SLA RW SLA W received ACK returned 6 31 2 17 define TW SR DATA _ ACK 0x80 data received
283. ine boot page erase address __boot_page_ erase normal address Erase the flash page that contains address Note address is a byte address in flash not a word address 6 12 2 6 define boot page erase safe address Value do boot spm busy wait eeprom busy wait boot page erase address while 0 E aii a Same as boot page erase p 101 except it waits for eeprom and spm operations to complete before erasing the page 6 12 2 7 define boot page fill address data boot page fill normal address data Fill the bootloader temporary page buffer for flash address with data word Note The address is a byte address The data is a word The AVR writes data to the buffer a word at a time but addresses the buffer per byte So increment your address by 2 between calls and send 2 data bytes in a word format The LSB of the data is written to the lower address the MSB of the data is written to the higher address 6 12 2 8 define boot page fill safe address data Value do boot spm busy wait eeprom busy wait boot_page_fill address data while 0 Same as boot page fill p 101 except it waits for eeprom and spm oper ations to complete before filling the page Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 102 6 12 2 9 define boot page write address boot page write normal address Write the
284. ing C and assembly source files 192 For PWM generation it is usually desired to run it at the highest possible speed so filtering the PWM frequency from the modulated output signal is made easy Thus the PWM timer runs at full CPU speed This causes the overflow and compare match interrupts to be triggered each 256 CPU clocks so they must run with the minimal number of processor cycles possible in order to not impose a too high CPU load by these interrupt service routines This is the main reason to implement the entire interrupt handling in fine tuned assembly code rather than in C In order to verify parts of the algorithm and the underlying hardware the demo has been set up in a way so the pin compatible but more expensive ATtiny45 or its siblings ATtiny25 and ATtiny85 could be used as well In that case no separate assembly code is required as two timer channels are avaible 6 35 1 Hardware setup The incoming PWM pulse train is fed into PB4 It will generate a pin change interrupt there on eache edge of the incoming signal The outgoing PWM is generated through OCOB of timer channel 0 PB1 For demonstration purposes a LED should be connected to that pin like one of the LEDs of an STK500 The controllers run on their internal calibrated RC oscillators 1 2 MHz on the ATtiny13 and 1 0 MHz on the ATtiny45 6 35 2 A code walkthrough 6 35 2 1 asmdemo c After the usual include files two variables are defined The first one
285. ing literal representation of the current library version 6 24 lt avr wdt h gt Watchdog timer handling 6 24 1 Detailed Description include lt avr wdt h gt This header file declares the interface to some inline macros handling the watch dog timer present in many AVR devices In order to prevent the watchdog timer configuration 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 In terrupts will be disabled during the manipulation Note Depending on the fuse configuration of the particular device further re strictions might apply in particular it might be disallowed to turn off the watchdog timer Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 24 lt avr wdt h gt Watchdog timer handling 166 Note that for newer devices ATmega88 and newer effectively any AVR that has the option to also generate interrupts the watchdog timer remains active even after a system reset except a power on condition using the fastest prescaler value approximately 15 ms It is therefore required to turn off the watchdog early during program startup the datasheet recommends a sequence like the following include lt stdint h gt include lt avr wdt h gt uint8_t mcusr_mirror _attribute_ section noinit void get_mcusr void __attribute
286. int __ Checks for a control character 6 3 2 6 int isdigit int __ c Checks for a digit 0 through 9 6 3 2 7 int isgraph int __c Checks for any printable character except space 6 3 2 8 int islower int c Checks for a lower case character 6 3 2 9 int isprint int __ Checks for any printable character including space Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 4 lt errno h gt System Errors 19 6 3 2 10 int ispunct int __c Checks for any printable character which is not a space or an alphanumeric character 6 3 2 11 int isspace int __c Checks for white space characters For the avr libc library these are space form feed f newline n carriage return r horizontal tab t and vertical tab Vw 6 3 2 12 int isupper int __c Checks for an uppercase letter 6 3 2 13 int isxdigit int __ c Checks for a hexadecimal digits i e one of 0123456789abcdefAB CDEF 6 3 2 14 int toascii int c Converts c to a 7 bit unsigned char value that fits into the ASCII character set by clearing the high order bits Warning Many people will be unhappy if you use this function This function will convert accented letters into random characters 6 3 2 15 int tolower int c Converts the letter c to lower case if possible 6 3 2 16 int toupper int __c Converts the letter c to upper case if possible 6 4 lt errno h gt System Er
287. int mask _ EICR mask Deprecated This macro gives access to the GIMSK register or EIMSK register if using an AVR Mega device or GICR register for others Although this macro is essentially the same as assigning to the register it does adapt slightly to the type of device being used This macro is unavailable if none of the registers listed above are defined 6 32 2 3 define inb port port Deprecated Read a value from an IO port port 6 32 2 4 define inp port port Deprecated Read a value from an IO port port 6 32 2 5 define INTERRUPT signame Value void signame void __attribute__ interrupt __INTR_ATTRS void signame void jas Deprecated Introduces an interrupt handler function that runs with global interrupts ini tially enabled 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 p 112 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 33 lt compat ina90 h gt Compatibility with IAR EWB 3 x 189 6 32 2 6 define outb port val port val Deprecated Write val to IO port port 6 32 2 7 define outp val port port val Dep
288. iny12 ATtiny13 ATtinyl5 ATtiny22 ATtiny2313 ATtiny26 ATtiny28 ATtiny43U ATtiny48 ATtiny45 ATtiny25 ATtiny85 ATtiny261 ATtiny461 ATtiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 118 Vector Old vector Description Applicable for device name name INT1_vect SIG_ INTERRUPT INT2 vect SIG_ INTERRUPT4 INT3 vect SIG_ INTERRUPT External Inter rupt Request 1 External Inter rupt Request 2 External Inter rupt Request 3 AT9052313 AT9052333 AT90S4414 AT9084433 AT90S4434 AT90S8515 AT9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 ATmega103 AT megal28 ATmega1284P AT megal6 ATmegal61 ATmegal62 ATmegal63 ATmegal68P AT mega32 ATmega323 ATmega328P ATmega32HVB ATmega406 AT mega48P ATmega64 ATmega8 AT mega8515 ATmega8535 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 AT tiny28 ATtiny48 ATtiny261 AT tiny461 ATtiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 AT90PWM3 AT90PWM2 AT90PWMI AT90CAN128 AT90CAN32 AT90CAN64 AT megal03 ATmegal28 ATmegal284P ATmegal6 ATmegal61 AT me
289. io h gt Standard IO facilities 70 e The variable width or precision field an asterisk x symbol is not realized and will to abort the output 6 9 3 33 int vfprintf P FILE __ stream const char x __ fmt va list ap Variant of vfprintf p 66 that uses a fmt string that resides in program memory 6 9 3 34 int vfscanf FILE stream const char fmt va_list ap Formatted input This function is the heart of the scanf family of functions Characters are read from stream and processed in a way described by fmt Conversion results will be assigned to the parameters passed via ap The format string fmt is scanned for conversion specifications Anything that doesn t comprise a conversion specification is taken as text that is matched literally against the input White space in the format string will match any white space in the data including none all other characters match only itself Processing is aborted as soon as the data and format string no longer match or there is an error or end of file condition on stream Most conversions skip leading white space before starting the actual conversion Conversions are introduced with the character Possible options can follow the e a x indicating that the conversion should be performed but the conversion result is to be discarded no parameters will be processed from ap e the character h indicating that the argument is a pointer to short int rather than int e the 2 ch
290. iodemo where prefix is a configuration option For Unix systems it is usually set to either usr or usr local 6 39 Example using the two wire interface TWI Some newer devices of the ATmega series contain builtin support for interfacing the microcontroller to a two wire bus called TWI This is essentially the same called I2C by Philips but that term is avoided in Atmel s documentation due to patenting issues For the original Philips documentation see http www semiconductors philips com buses i2c index html 6 39 1 Introduction into TWI The two wire interface consists of two signal lines named SDA serial data and SCL serial clock plus a ground line of course All devices participating in the bus are connected together using open drain driver circuitry so the wires must be terminated 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 frequency yet large enough so all drivers will not be overloaded There are formulas in the datasheet that help selecting the pullups Devices can either act as a master to the bus i e they initiate a transfer or as a slave they only act when being called by a master The bus is multi master capable and a particular device implementation can act as either master or slave at different times Devices are addressed using a 7 bit address coordinated by Philips transfered as
291. ion and won t make it into the ROM file An even more useful option is S This option disassembles the binary file and intersperses the source code in the output This method is much better in my opinion than using the S with the compiler because this listing includes routines from the libraries and the vector table contents Also all the fix ups have been satisfied In other words the listing generated by this option reflects the actual code that the processor will run avr objdump h S demo elf gt demo lst Here s the output as saved in the demo 1st file demo elf file format elf32 avr Sections Idx Name Size VMA LMA File off Algn 0 text 00000126 00000000 00000000 00000074 2 1 CONTENTS ALLOC LOAD READONLY CODE 1 bss 00000003 00800060 00000126 0000019a 2 0 ALLOC 2 debug_aranges 00000020 00000000 00000000 0000019a 2 0 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 8 CONTENTS READONLY DEBUGGING CONTE debug_info 00000 CONTE debug_abbrev 00000 CONTE debug_line 00000 CONTE debug_frame 00000 CONTE debug_str 00000 CONTE NTS READONLY 105 00000000 NTS READONLY Ocf 00000000 NTS READONLY 147 00000000 NTS READONLY 040 00000000 NTS READONLY Oab 00000000 NTS READONLY Disassembly of section text 00000000 lt __vectors gt 0 10 12 14 16 18 la ic le 20 22 24 CA MAA PN 12 8c 8b 8a 89
292. ion 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 p 259 gt a macro will be supplied that portably allows formatting an object of that type in printf p 65 or scanf p 65 operations Example Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 21 include lt inttypes h gt uint8_t smallval int32_t longval printf The hexadecimal value of smallval is PRIx8 the decimal value of longval is PRId32 n smallval longval Far pointers for memory access gt 64K e typedef int32 tint farptr t e typedef uint32_t uint farptr t macros for printf and scanf format specifiers For C these are only included if STDC LIMIT MACROS is defined before including lt inttypes h p 245 gt e define PRId8 d e define PRIdLEASTS d e define PRIdFASTS8 d e define PRIi8 i e define PRIILEASTS i e define PRIiFASTS i e define PRId16 d e define PRIGLEAST16 d e define PRIdFAST16 d e define PRIi16 i e define PRIiLEASTI16 i e define PRIiFAST16 i e define PRId32 Id e define PRIdLEAST32 Id e define PRIdFAST32 Id e define PRIi32 li e define PRIiLEAST32 li e define PRIiFAST32 li e define PRIdPTR PRId16 e define PRIiPTR PRIi16 e define PRIo8 o
293. ions e void delay us double us e void delay ms double ms 8 9 delay basic h File Reference 8 9 1 Detailed Description Defines e define UTIL DELAY BASIC H 1 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 10 errno h File Reference 243 Functions e void delay loop 1 uint8 t count e void delay loop 2 uint16 t count 8 10 errno h File Reference 8 10 1 Detailed Description Defines e defne ERRNO H 1 e define EDOM 33 e define ERANGE 34 Variables e int errno 8 11 fdevopen c File Reference 8 11 1 Detailed Description Functions e FILE x fdevopen int put char FILE x int get FILE Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 12 ffs S File Reference 244 8 12 ffs S File Reference 8 12 1 Detailed Description 8 13 ffsl S File Reference 8 13 1 Detailed Description 8 14 ffsll S File Reference 8 14 1 Detailed Description 8 15 fuse h File Reference 8 15 1 Detailed Description Defines e define AVR FUSE H 1 e define FUSEMEM __attribute___ section fuse e define FUSES __ fuse t __ fuse FUSEMEM 8 16 interrupt h File Reference 8 16 1 Detailed Description af Defines Global manipulation of the interrupt flag The global interrupt flag is maintained in the I bit of the status register SREG e define sei e define cli Macros for writing interrupt handler functions e define ISR vector attributes e define SIGNAL vector
294. ions one for Linux FreeBSD and other Unix like operating systems and another section for Windows 9 11 1 Building and Installing under Linux FreeBSD and Others The default behaviour for most of these tools is to install every thing under the usr local directory In order to keep the AVR tools separate from the base system it is usually better to install everything into usr local avr If the Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 347 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 example in HOME local avr Where you install is a completely arbitrary decision but should be consistent for all the tools You specify the installation directory by using the prefix dir option with the configure script It is important to install all the AVR tools in the same directory or some of the tools will not work correctly To ensure consistency and simplify the discussion we will use PREFIX to refer to whatever directory you wish to install in You can set this as an environment variable if you wish as such using a Bourne like shell PREFIX HOME local avr export PREFIX Note Be sure that you have your PATH environment variable set to search the directory you install
295. ise the entire toolchain are normally distributed as source code It is left up to the user to build the tool application from its source code This can be a very daunting task to any potential user of these tools Luckily there are people who help out in this area Volunteers take the time to build the application from source code on particular host platforms and sometimes packaging the tools for convenient installation by the end user These packages contain the binary executables of the tools pre made and ready to use These packages are known as distributions of the AVR toolchain or by a more shortened name distros AVR toolchain distros are available on FreeBSD Windows Mac OS X and certain flavors of Linux 9 1 13 Open Source All of these tools from the original source code in the multitude of projects to the various distros are put together by many many volunteers All of these projects could always use more help from other people who are willing to vol unteer some of their time There are many different ways to help for people with varying skill levels abilities and available time You can help to answer questions in mailing lists such as the avr gcc list or on forums at the AVR Freaks website This helps many people new to the open source AVR tools If you think you found a bug in any of the tools it is always a big help to submit a good bug report to the proper project A good bug report always helps other volu
296. isplay Press any key to continue Press any key e Edit c msys 1 0 msys bat Change line should be line 41 if EXIST rxvt exe goto startrxvt to rem if EXIST rxvt exe goto startrxvt to remark out this line Doing this will cause MSYS to always use the bash shell and not the rxvt shell Note The order of the next three is important Install MSYS Developer toolkit before the autotools e MSYS Developer Toolkit version 1 0 1 This is needed to build avr libc in MinGW lt http downloads sourceforge net mingw msysDTK 1 0 1 exe use_ mirror internap gt Single file installer executable Install e autoconf 2 59 from the MSYS Developer Toolkit release autoconf 2 59 2 60 is needed to build avr libc in MinGW lt http downloads sourceforge net mingw msys autoconf 2 59 tar bz2 use_ mirror internap gt Extract to c msys 1 0 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 355 e automake 1 8 2 automake 1 8 1 9 is needed to build avr libc in MinGW lt http downloads sourceforge net mingw msys automake 1 8 2 tar bz2 use_ mirror internap gt Extract to c msys 1 0 e Install Cygwin Install everything all users UNIX line endings This will take a long time A fat internet pipe is highly recommended It is also recommended that you download all to a directory first and then install fro
297. it 78 free 78 itoa 78 labs 78 Idiv 79 ltoa 79 malloc 79 qsort 80 rand 80 RAND_ MAX 75 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX rand r 80 random 80 RANDOM MAX 75 random r 81 realloc 81 srand 81 srandom 81 strtod 81 strtol 82 strtoul 82 ultoa 83 utoa 83 avr string FFS 86 ffs 86 ffsl 86 ffsll 87 memccpy 87 memchr 87 memcmp 87 memcpy 88 memmem 88 memmove 88 memrchr 88 memset 89 strcasecmp 89 strcasestr 89 strcat 89 strchr 90 strchrnul 90 strcmp 90 strepy 91 strcspn 91 strlcat 91 strlcpy 92 strlen 92 strlwr 92 strncasecmp 92 strncat 93 strnemp 93 strncpy 93 strnlen 93 strpbrk 94 strrchr 94 strrev 94 strsep 95 388 strspn 95 strstr 95 strtok_r 95 strupr 96 avr version AVR LIBC DATE 164 AVR LIBC DATE STRING 164 AVR LIBC MAJOR 164 AVR LIBC MINOR 165 AVR LIBC REVISION __ 165 AVR LIBC VERSION STRING ___ 165 AVR LIBC VERSION 165 avr watchdog wdt disable 166 wdt enable 167 wdt reset 167 WDTO 120MS 167 WDTO 15MS 167 WDTO 15 168 WDTO_250MS 168 WDTO 25 168 WDTO 30MS 168 WDTO_4S 168 WDTO_500MS 168 WDTO_60MS 169 WDTO_85 169 avrdude usage 373 AVI prog usage 373 BADISR_ vect avr interrupts 135 BAUD TOL util setbaud 181 bit is clear avr s r 161 bit is set avr s r 161 boot h 234 boot lock bits set
298. it enabling Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks 172 the Global Interrupt Status flag bit This saves on flash space as the previous value of the SREG register does not need to be saved at the start of the block Care should be taken that ATOMIC FORCEON is only used when it is known that interrupts are enabled before the block s execution or when the side effects of enabling global interrupts at the block s completion are known and under stood 6 25 2 3 define ATOMIC RESTORESTATE This is a possible parameter for ATOMIC_ BLOCK When used it will cause the ATOMIC_BLOCK to restore the previous state of the SREG register saved before the Global Interrupt Status flag bit was disabled The net effect of this is to make the ATOMIC BLOCK s contents guaranteed atomic without changing the state of the Global Interrupt Status flag when execution of the block completes 6 25 2 4 define NONATOMIC BLOCK type Creates a block of code that is executed non atomically Upon entering the block the Global Interrupt Status flag in SREG is enabled and disabled upon exiting the block from any exit path This is useful when nested inside ATOMIC_ BLOCK sections allowing for non atomic execution of small blocks of code while maintaining the atomic access of the other sections of the parent ATOMIC _ BLOCK Two possible macro parameters are permit
299. itions 182 6 31 lt util twi h gt TWI bit mask definitions 6 31 1 Detailed Description include lt util twi h gt This header file contains bit mask definitions for use with the AVR TWI inter face TWSR values Mnemonics TW MT xxx master transmitter TW MR xxx master receiver TW ST xxx slave transmitter TW SR xxx slave receiver e idefine TW START 0x08 e define TW REP START 0x10 e define TW MT SLA ACK 0x18 e define TW MT SLA NACK 0x20 e define TW MT DATA ACK 0x28 e define TW MT DATA NACK 0x30 e define TW MT ARB LOST 0x38 e define TW MR ARB LOST 0x38 e define TW MR SLA ACK 0x40 e define TW MR SLA NACK 0x48 e define TW MR DATA ACK 0x50 e define TW MR DATA NACK 0x58 e define TW ST SLA ACK 0xA8 e define TW ST ARB LOST SLA ACK 0xB0 e define TW ST DATA ACK 0xB8 e define TW ST DATA NACK 0xC0 e define TW ST LAST DATA 0xC8 e define TW SR SLA ACK 0x60 e define TW SR ARB LOST SLA ACK 0x68 e define TW SR GCALL ACK 0x70 e define TW SR ARB LOST GCALL ACK 0x78 e define TW SR DATA ACK 0x80 e define TW SR DATA NACK 0x88 e define TW SR GCALL DATA ACK 0x90 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 31 lt util twi h gt TWI bit mask definitions 183 e define TW_SR_GCALL_DATA_NACK 0x98 e define TW SR STOP 0xA0 e define TW NO INFO 0xF8 e define TW BUS ERROR 0x00 e define TW STATUS MASK e define TW STATUS TWSR amp TW STATUS MASK R W bit
300. l x and X notation The letters abcdef are used for x conversions the letters ABCDEF are used for X conversions The pre cision if any gives the minimum number of digits that must appear if the converted value requires fewer digits it is padded on the left with zeros e p The void argument is taken as an unsigned integer and converted similarly as a 4 x command would do e c The int argument is converted to an unsigned char and the result ing character is written e s The char argument is expected to be a pointer to an array of character type pointer to a string Characters from the array are written up to but not including a terminating NUL character if a precision is specified no more than the number specified are written If a precision is given no null character need be present if the precision is not specified or is greater than the size of the array the array must contain a terminating NUL character e A is written No argument is converted The complete conversion specification is e eE The double argument is rounded and converted in the format d ddde dd where there is one digit before the decimal point char acter 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 e to introduce the exponent The exponent always contains
301. l 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 Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 19 lt avr power h gt Power Reduction Management Power Macro power adc enable power adc disable Description Enable the Analog to Digital Converter module Disable the Analog to Digital Converter module Applicable for device ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 AT90USB646 AT90USB647 AT90USB1286 AT90USB1287 AT90PWM1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 ATmegal65 ATmegal65P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmega169 ATmega169P ATmega329 ATmega3290 ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmegal68 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 ATmega640 ATmega1280 ATmegal281 ATmega2560 ATmega2561 AT90USB646 AT90USB647 AT90USB1286 AT90USB1287 AT90PWM1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 ATmegal65 ATmegal65P ATmega325 ATmega3250 ATmega645 ATmega6450 ATmega169 ATmegal69P ATmega329 ATmega3290 ATmega649 ATmega6490 ATmegal64P ATmega324P ATmega644 ATmega48 ATmega88 ATmegal68 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261
302. l68P ATmegal69 AT megal69P ATmega32 ATmega323 ATmega325 ATmega3250 AT mega3250P ATmega328P AT mega329 ATmega3290 AT mega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 ATmega6450 ATmega649 AT mega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 AT tiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 127 AT9058535 AT90PWM216 COMPAREIB MatchB AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 ATmega103 AT megal28 ATmegal284P ATmegal6 ATmegal61 ATmegal62 AT megal63 ATmegal65 ATmegal65P ATmegal68P ATmegal69 AT megal69P ATmega32 ATmega323 ATmega325 ATmega3250 AT mega3250P ATmega328P AT mega329 ATmega3290 AT mega3290P ATmega32HVB AT mega48P ATmega64 ATmega645 ATmega6450 ATmega649 AT mega6490 ATmega8 ATmega8515 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 ATmegal6HVA ATtiny2313 AT tiny48 ATtiny261 ATtiny461 AT tiny861 AT90USB162 AT90USB82 AT90USB1287 A
303. lation gcc 350 Installation gdb 351 installation simulavr 352 INT16_C avr stdint 45 INT16 MAX avr stdint 45 INT16 MIN avr stdint 45 int16 t avr stdint 50 INT32 C avr stdint 45 INT32 MAX avr stdint 45 INT32 MIN avr stdint 45 int32 t avr stdint 50 INT64 C avr stdint 45 INT64 MAX avr stdint 45 INT64 MIN avr stdint 45 int64 t avr stdint 50 INT8_C avr stdint 45 INT8 MAX avr stdint 46 INT8 MIN avr stdint 46 int8 t avr stdint 50 int farptr t avr inttypes 31 INT FASTI6 MAX avr stdint 46 INT FAST16 MIN avr stdint 46 int fastl6 t avr stdint 50 INT FAST32 MAX 392 avr stdint 46 INT FAST32 MIN avr stdint 46 int fast32 t avr stdint 50 INT FAST64 MAX avr stdint 46 INT FAST64 MIN avr stdint 46 int fast64 t avr stdint 50 INT FASTS8 MAX avr stdint 46 INT FAST8 MIN avr stdint 46 int fast8 t avr stdint 51 INT LEAST16 MAX avr stdint 46 INT LEAST16 MIN avr stdint 47 int leastl6 t avr stdint 51 INT LEAST32 MAX avr stdint 47 INT LEAST32 MIN avr stdint 47 int least32 t avr stdint 51 INT LEAST64 MAX avr stdint 47 INT LEAST64 MIN avr stdint 47 int least64 t avr stdint 51 INT _LEAST8 MAX avr stdint 47 INT _LEAST8 MIN avr stdint 47 int least8 t avr stdint 51 INTERRUPT deprecated items 188 interrupt h 244 INTMAX C avr stdint 47 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX INTMAX MAX avr st
304. le an input value is read from a port and then an output value is written to the same port If the compiler would have choosen the same register for input and output then the output value would have been destroyed on the first assembler instruction Fortunately this example uses the amp constraint modifier to instruct the compiler not to select any register for the output value which is used for any of the input operands Back to swapping Here is the code to swap high and low byte of a 16 bit value asm volatile mov __tmp_reg__ AO n t mov AO BO n t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 305 mov BO __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 p 300 section You can use this register without saving its contents Completely new are those letters A and B in A0 and BO In fact they refer to two different 8 bit registers both containing a part of value Another example to swap bytes of a 32 bit value asm volatile mov __tmp_reg__ AO n t mov ZAO DO n t mov ADO __tmp_reg__ n t mov __tmp_reg__ BO n t mov BO CO n t mov ACO __tmp_reg__ n t r value 0 value 5 Instead of listing the same operand as both input and output operand it can also be declared as a read write operand
305. le object module file The linker ld can only work with object modules to link them together Object modules are the smallest unit that the linker works with Typically on the linker command line you will specify a set of object modules that has been previously compiled and then a list of libraries including the Standard C Library The linker takes the set of object modules that you specify on the command line and links them together Afterwards there will probably be a set of undefined references A reference is essentially a function call An 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 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 7 How to Build a Library 312 9 7 3 How to Design a Librar
306. le on Unix and Linux systems Hopefully the following overview will be helpful in putting everything in perspective Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 1 Toolchain Overview 272 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 mod ify and redistribute computer programs The FSF promotes the development and use of free software particularly the GNU operating system used widely in its GNU Linux variant The FSF remains the primary sponsor of the GNU project The GNU Project was launched in 1984 to develop a complete Unix like op erating system which is free software the GNU system GNU is a recursive acronym for GNU s Not Unix it is pronounced guh noo approximately like canoe One of the main projects of the GNU system is the GNU Compiler Collection or GCC and its sister project GNU Binutils These two open source projects provide a foundation for a software development toolchain Note that these projects were designed to originally run on Unix like systems 9 1 3 GCC GCC stands for GNU Compiler Collection GCC is highly flexible compiler system It has different compiler front ends for different languages It has many back ends that generate assembly code for many different processors and host operating systems All share a common middle end containing the generic pa
307. lected register r24 for storage of the value read from PORTD The compiler could have selected any other register though It may not explicitely load or store the value and it may even decide not to include your assembler code at all All these decisions are part of the compiler s optimization strategy For example if you never use the variable value in the remaining part of the C program the compiler will most likely remove your code unless you switched off optimization To avoid this you can add the volatile attribute to the asm statement asm volatile in 0 1 r value I _SFR_IO_ADDR PORTD Alternatively operands can be given names The name is prepended in brackets to the constraints in the operand list and references to the named operand use the bracketed name instead of a number after the sign Thus the above example could also be written as asm in retval port retval r value port I _SFR_IO_ADDR PORTD The last part of the asm instruction the clobber list is mainly used to tell the compiler about modifications done by the assembler code This part may be omitted all other parts are required but may be left empty If your assembler routine won t use any input or output operand two colons must still follow the assembler code string A good example is a simple statement to disable interrupts asm volatile cli 9 6 2 Assembler Code You can use the same assembler instru
308. lse but signbit 0 0 will return a nonzero value Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 7 lt setjmp h gt Non local goto 39 Note This implementation returns 1 if sign bit is set 6 6 3 31 double sin double __ The sin p 39 function returns the sine of __ measured in radians 6 6 3 32 double sinh double __ 2 The sinh p 39 function returns the hyperbolic sine of __ 2 6 6 3 33 double sqrt double ___2 The sqrt p 39 function returns the non negative square root of z 6 6 3 34 double square double __ The function square p 39 returns r x Note This function does not belong to the C standard definition 6 6 3 35 double tan double x The tan p 39 function returns the tangent of x measured in radians 6 6 3 36 double tanh double __ The tanh p 39 function returns the hyperbolic tangent of __ x 6 6 3 37 double trunc double ___2 The trunc p 39 function rounds __x to the nearest integer not larger in absolute value 6 7 lt setjmp h gt Non local goto 6 7 1 Detailed Description While the C language has the dreaded 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 p 41 and Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 7 lt setjmp h gt Non local goto 40 longjmp p 4
309. lt r __addr32 I _SFR_IO_ADDR RAMPZ ro r r30 7 r31 __result H FA A A A ZA AA 4 8 34 2 2 define ELPM dword enhanced addr Value __extension__ uint32_t __addr32 uint32_t addr Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 34 pgmspace h File Reference uint32 t result __asm__ out 2 YCL n t movu r30 1 n t elpm AO Z n t elpm BO Z n t elpm CO Z n t elpm DO Z n t r __result r __addr32 I _SFR_IO_ADDR RAMPZ r30 r31 __result H 8 34 2 3 define ELPM enhanced addr Value __extension__ uint32_t __addr32 uint32_t addr uint8_t __result __asm__ out 2 YCL n t movw r30 1 n t elpm 0 Z n t r __result r __addr32 I _SFR_IO_ADDR RAMPZ r30 r31 __result H 8 34 2 4 define ELPM word classic addr Value __extension__ uint32_t __addr32 uint32_t addr uint16_t __result __asm__ out 2 C1 n t mov r31 Bi n t mov r30 ZA1 n t elpm n t mov ZAO ro n t in ro 2 n t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 253 8 34 pgmspace h File Reference 254 adiw r30 1 n t adc r0 __zero_reg__ n t out 2 ro n t elpm n t
310. lt avr pgmspace h gt Program Space Utilities 149 6 18 4 Function Documentation 6 18 4 1 PGM VOID P memchr P PGM VOID Ps int val size t len Scan flash memory for a character The memchr P p 149 function scans the first len bytes of the flash mem ory 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 p 149 function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 18 4 2 int memcmp P const void x s1 PGM VOID P s2 size t len Compare memory areas The memcmp P p 149 function compares the first len bytes of the mem ory areas s1 and flash s2 The comparision is performed using unsigned char operations Returns The memcmp P p 149 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 6 18 4 3 void x memcpy P void x dest PGM VOID P src size_t n The memcpy_P p 149 function is similar to memepy p 88 except the src string resides in program space Returns The memcpy P p 149 function returns a pointer to dest 6 18 4 4 void x memmem P const void s1 size_t len1 PGM VOID P s2 size_t len2 The memmem P p 149 function is similar to memmem p 89 except that s2 is pointer
311. lues 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 wdt_enable WDTO_500MS 6 24 2 6 define WDTO_1S 6 See WDTO_15MS 6 24 2 7 define WDTO 250MS 4 See WDTO_15MS 6 24 2 8 define WDTO 2857 See WDTO_15MS 6 24 2 9 define WDTO 30MS 1 See WDTO_15MS 6 24 2 10 define WDTO_ 4S 8 See WDTO_15MS Note This is only available on the ATtiny2313 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny261 ATtiny461 ATtiny861 ATmega48 ATmega88 ATmegal68 ATmega48P ATmega88P ATmegal68P ATmega328P ATmegal64P ATmega324P ATmega644P AT mega644 ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 ATmega8HVA ATmegal6HVA ATmega32HVB ATmega406 ATmega1284P AT90PWM1 AT90PWM2 AT90PWM2B AT90PWM3 AT90PWM3B AT90PWM216 AT90PWM316 AT90USB82 AT90USB162 AT90USB646 AT90USB647 AT90USB1286 AT90USB1287 ATtiny48 ATtiny88 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 25 lt util atomic h gt Atomically and Non Atomically Executed Code Blocks 169 6 24 2 11 define WDTO 500MS 5 See WDTO_15MS 6 24 2 12 define WDTO 60MS 2 WDTO_15MS 6 24 2 13 define WDTO_ 8S 9 See WDTO_15MS Note This is only available on the ATtiny2313 ATtiny24 ATtiny44 ATtiny84 ATtiny25 ATtiny45 ATtiny85 ATtiny26
312. m that directory to your machine Note MPFR requires GMP so build it first e Build GMP for MinGW Version 4 2 1 lt http gmplib org gt Build script configure 2 gt amp 1 make 2 gt amp 1 make check 2 gt amp 1 make install 2 gt amp 1 tee gmp configure log tee gmp make log tee gmp make check log tee gmp make install log GMP headers will be installed under usr local include and library installed under usr local lib e Build MPFR for MinGW Version 2 2 1 lt http www mpfr org gt Build script configure with gmp usr local 2 gt amp 1 tee mpfr configure log make 2 gt amp 1 tee mpfr make log make check 2 gt amp 1 tee mpfr make check log make install 2 gt amp 1 tee mpfr make install log MPFR headers will be installed under usr local include and library installed under usr local lib Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 356 e Install Doxygen Version 1 4 7 lt http www stack nl dimitri doxygen gt Download and install e Install NetPBM Version 10 27 0 From the GNUWin32 project lt http gnuwin32 sourceforge net packages html gt Download and install e Install fig2dev Version 3 2 Patchlevel 5 alpha7 From WinFig 1 71 lt http www schmidt web berlin de winfig gt Unzip the download file and install in a location of your
313. mat 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 In order to allow program mers a code size vs functionality tradeoff the function vfprintf p 66 which is the heart of the printf family can be selected in different flavours using linker options See the documentation of vfprintf p 66 for a detailed description The same applies to vfscanf p 70 and the scanf family of functions Outline of the chosen API The standard streams stdin stdout and stderr are provided but contrary to the C standard since avr libc has no knowledge about applicable 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 p 56 Instead the function fdevopen p 62 is provided to associate a stream to a device where the device needs to provide a function to send a character to receive a character or both There is no differentiation between text and binary streams inside avr libc Character Yn is sent literally down to the device s put function If the device requires a Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt
314. maxim ic com appnotes cfm appnote_number 27 The following is the equivalent functionality written in C uint8_t _crc_ibutton_update uint8_t crc uint8_t data uint8_t i cre crc data for i 0 i lt 8 i if crc amp 0x01 crc cre gt gt 1 0x8C else cre gt gt 1 return crc Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 27 lt util delay h gt Convenience functions for busy wait delay loops 176 6 26 2 4 static inline uintl6_t crc xmodem update uint16 t __ crc uint8_t data static Optimized CRC XMODEM calculation Polynomial x 16 x12 x 5 1 0x1021 Initial value 0x0 This is the CRC used by the Xmodem CRC protocol The following is the equivalent functionality written in C uint16_t crc_xmodem_update uint16_t crc uint8_t data int i cre cre 7 uint16 t data lt lt 8 for i 0 i lt 8 i if cre amp 0x8000 crc cre lt lt 1 7 0x1021 else cre lt lt 1 return crc 6 27 lt util delay h gt Convenience functions for busy wait delay loops 6 27 1 Detailed Description define F CPU 1000000UL 1 MHz define F 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 compiler from the Makefile Obviously in that case no define statement should be used The functions in this header file are wrappers around the basic
315. mega325 ATmega3250 AT mega3250P ATmega328P AT mega329 ATmega3290 AT mega3290P ATmega32HVB AT mega406 ATmega48P ATmega64 ATmega645 ATmega6450 AT mega649 ATmega6490 ATmega88P ATmegal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2560 AT mega2561 ATmega324P AT megal64P ATmega644P ATmega644 ATmegal6HVA AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 EXT SIG_ External Inter ATtiny24 ATtiny44 ATtiny84 INTO vect INTERRUPTO rupt Request 0 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts External Inter rupt 0 117 AT90S1200 AT9052313 AT9052323 AT9052333 AT9052343 AT90S4414 AT9054433 AT90S4434 AT90S8515 AT9058535 AT90PWM216 AT90PWM2B AT90PWM316 AT90PWM3B AT90PWM3 AT90PWM2 AT90PWM1 AT90CAN128 AT90CAN32 AT90CAN64 ATmega103 AT megal28 ATmegal1284P AT megal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 AT megal65P ATmegal68P AT megal69 ATmegal69P ATmega32 ATmega323 ATmega325 AT mega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega406 ATmega48P AT mega64 ATmega645 ATmega6450 ATmega649 ATmega6490 AT mega8 ATmega8515 ATmega8535 ATmega88P ATmegal68 AT mega48 ATmega88 ATmega640 ATmegal280 ATmegal281 AT mega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 AT megal6HVA ATtinyll ATt
316. mega640 ATmega1280 AT megal281 ATmega2560 ATmega2561 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 131 TWI_vect E 2 wire Serial AT90CAN128 AT90CAN32 Interface AT90CAN64 ATmega128 AT megal284P ATmegal6 ATmegal63 ATmegal68P ATmega32 AT mega323 ATmega328P AT mega32HVB ATmega406 AT mega48P ATmega64 ATmega8 ATmega8535 ATmega88P AT megal68 ATmega48 ATmega88 AT mega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 AT mega324P ATmegal64P AT mega644P ATmega644 ATtiny48 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 TXDONE SIG Transmission AT86RF401 vect TXDONE Done Bit Timer Flag 2 Interrupt TXEMPTY SIG TXBE Transmit AT86RF401 vect Buffer Empty Bit Itmer Flag 0 Interrupt UARTO SIG UARTO x ATmegal61 RX vect UARTO Complete RECV U x T UARTO SIG UARTO Data ATmegal61 UDRE_vect UARTO Register DATA Empty UARTI SIG UARTI x ATmegal61 RX vect UARTI1 Complete RECV UARTI SIG UARTI Tx ATmegal61 TX vect UART1_ Complete TRANS UARTI SIG UARTI1 Data ATmegal61 UDRE_vect UARTI_ Register DATA Empty SIG UA UART RT R AT9052313 AT9052333 AT90S4414 U Complete AT9084433 AT90S4434 AT90S8515 AT9088535 ATmega103 ATmega163 ATmega8515 UART ae UART Tx AT9052313 AT9052333 AT90S4414 TX vect Complete AT9084433 AT90S4434 AT90S8515 AT9088535 ATmega103 ATmega163 ATme
317. memcpy P avr pgmspace 149 memcpy P S 249 memmem avr_ string 88 memmem S 249 memmem_P avr pgmspace 149 memmove avr string 88 memmove S 249 memrchr avr_ string 88 memrchr S 249 memrchr_ P avr pgmspace 149 memrchr P S 249 memset avr string 89 memset S 249 modf avr_math 37 NAN avr_ math 33 Generated on Wed Jun 11 394 NONATOMIC_ BLOCK util_ atomic 172 NONATOMIC_FORCEOFF util_ atomic 172 NONATOMIC RESTORESTATE util atomic 172 outb deprecated items 188 outp deprecated items 189 parity h 249 parity even bit util_ parity 179 PGM_P avr pgmspace 145 pgm read byte avr pgmspace 145 pgm read byte far avr pgmspace 145 pgm read byte near avr pgmspace 145 pgm read dword avr pgmspace 146 pgm read dword far avr pgmspace 146 pgm read dword near avr pgmspace 146 pgm read word avr pgmspace 146 pgm read word far avr pgmspace 146 pgm read word near avr pgmspace 147 PGM VOD P avr pgmspace 147 pgmspace h 250 ELPM classic _ 252 ELPM dword enhanced 252 ELPM enhanced 253 ELPM word classic 253 ELPM word enhanced __ 254 LPM classic _ 254 11 29 15 2008 for avr libc by Doxygen INDEX LPM_dword_classic___ 254 LPM_dword_enhanced__ 255 LPM enhanced 255 LPM word classic 256 LPM word enhanced gt 256 pow avr math 37 power h 257 clock prescale set 257 PRId16 avr inttypes 23 PRId32 avr inttypes 23 PRId8 avr i
318. ml doc enable pdf doc enable man doc mandir installdir man datadir installdir 2 gt amp 1 tee package configure log Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 359 Make make all install 2 gt amp 1 tee package make log Manually change location of man page documentation Move the examples to the top level of the install tree Convert line endings in examples to Windows line endings Convert line endings in header files to Windows line endings e AVRDUDE Open source code package Configure and build at the top of the source code tree Set PATH in order x lt MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin lt install directory gt bin Set location of LibUSB headers and libraries export CPPFLAGS I libusb win32 device bin libusb version include export CFLAGS I libusb win32 device bin libusb version include export LDFLAGS L libusb win32 device bin libusb version lib gcc Configure configure prefix installdir datadir installdir N sysconfdir installdir bin enable doc N disable versioned doc 2 gt amp 1 tee package configure log Make make k all install 2 gt amp 1 tee package make log Convert line endings in avrdude config file to Windows line endings Delete
319. n be used in code that wants to remain backwards compatible to library versions prior to the date when the library version API had been added as referenced but undefined C preprocessor macros automatically evaluate to 0 Defines e define AVR_LIBC_ VERSION STRING __ 1 6 2 e define AVR LIBC VERSION _ 10602UL 7 e define AVR LIBC DATE STRING _ 20080403 e define AVR LIBC DATE 20080403UL e define AVR LIBC MAJOR 1 e define AVR LIBC MINOR __ 6 e define _ AVR_LIBC_REVISION__ 2 6 23 2 Define Documentation 6 23 2 1 define AVR LIBC DATE 20080403UL Numerical representation of the release date 6 23 2 2 define AVR LIBC DATE STRING _ 20080403 String literal representation of the release date Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 24 lt avr wdt h gt Watchdog timer handling 165 6 23 2 3 define _AVR_LIBC_MAJOR__ 1 Library major version number 6 23 2 4 define AVR LIBC MINOR 6 Library minor version number 6 23 2 5 define AVR LIBC REVISION 2 Library revision number 6 23 2 6 define AVR LIBC VERSION _ 10602UL Numerical representation of the current library version In the numerical representation the major number is multiplied by 10000 the minor number by 100 and all three parts are then added It is intented to provide a monotonically increasing numerical value that can easily be used in numerical checks 6 23 2 7 define AVR LIBC VERSION STRING 1 6 2 Str
320. n occur simul taneously It should be kept in mind that the functions described here do not disable interrupts In general for long delays the use of hardware timers is much preferrable as they free the CPU and allow for concurrent processing of other events while the timer is running However in particular for very short delays the overhead of setting up a hardware timer is too much compared to the overall delay time Two inline functions are provided for the actual delay algorithms Functions e void delay loop 1 uint8 t count e void delay loop 2 uint16 t count 6 28 2 Function Documentation 6 28 2 1 void delay loop 1 uint8 t count Delay loop using an 8 bit counter count so up to 256 iterations are possible The value 256 would have to be passed as 0 The loop executes three CPU cycles per iteration not including the overhead the compiler needs to setup the counter register Thus at a CPU speed of 1 MHz delays of up to 768 microseconds can be achieved 6 28 2 2 void delay loop 2 uint16_t count Delay loop using a 16 bit counter __count so up to 65536 iterations are possible The value 65536 would have to be passed as 0 The loop executes four CPU cycles per iteration not including the overhead the compiler requires to setup the counter register pair Thus at a CPU speed of 1 MHz delays of up to about 262 1 milliseconds can be achieved Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen
321. n 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 10 9 means the set of everything except close bracket zero through nine and hyphen Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 72 The string ends with the appearance of a character not in the or with a circumflex in set or when the field width runs out Note that usage of this conversion enlarges the stack expense e p Matches a pointer value as printed by p in printf p 65 the next pointer must be a pointer to void e 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 x flag These functions return the number of input items assigned which can be fewer than provided for or even zero in the event of a matching failure Zero indicates that while there was input available no conversions were assigned typically this is due to an invalid input character such as an alphabetic character for a d conversion The value EOF is returned if an input failure occurs before any conversion such as an end of file occurs If an error or end of file occurs after conversion has begun the number of conversions which were successfully completed is
322. nated 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 level i e no write protection In case of a write protected device all data transfer attempts will be NACKed by the device Note that some devices might not implement this 7 avr libc Data Structure Documentation 7 1 div t Struct Reference 7 1 1 Detailed Description Result type for function div p 77 Data Fields e int quot e int rem 7 1 2 Field Documentation 7 1 2 1 int div t quot The Quotient Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 7 2 1div_t Struct Reference 233 7 1 2 2 int div_t rem The Remainder The documentation for this struct was generated from the following file e stdlib h 7 2 Idi
323. nctions are provided the stream is opened with read and write intent The first stream opened with read intent is assigned to stdin and the first one opened with write intent is assigned to both stdout and stderr fdevopen p 62 uses calloc p 77 und thus malloc p 80 in order to allocate the storage for the new stream Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 63 Note If the macro STDIO FDEVOPEN COMPAT 12 is declared before including lt stdio h p 262 gt a function prototype for fdevopen p 62 will be chosen that is backwards compatible with avr libc version 1 2 and before This is solely intented for providing a simple migration path without the need to immediately change all source code Do not use for new code 6 9 3 4 int feof FILE stream Test the end of file flag of stream This flag can only be cleared by a call to clearerr p 62 6 9 3 5 int ferror FILE stream Test the error flag of stream This flag can only be cleared by a call to clear err p 62 6 9 3 6 int flush FILE stream Flush stream This is a null operation provided for source code compatibility only as the standard IO implementation currently does not perform any buffering 6 9 3 7 int fgetc FILE stream The function fgetc reads a character from stream It returns the character or EOF in case end of file was encountered or an error occurred
324. nctions might also use dynamic memory notably those from the lt stdio h gt Standard IO facilities p 54 so make sure the changes will be done early enough in the startup sequence The variables __malloc_heap_start and __malloc_heap_end can be used to restrict the malloc p 80 function to a certain memory region These vari ables are statically initialized to point to __heap_start and __heap_end re spectively where __heap_start is filled in by the linker to point just beyond bss and __heap_end is set to 0 which makes malloc p 80 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 W1 Tdata 0x801100 defsym __heap_end Ox80ffff Note See explanation p 283 for offset 0x800000 See the chapter about using gcc p 368 for the W1 options 0x0100 Ox10FF 0x1100 OxFFFF on board RAM external RAM sp E __malloc_heap_end heap end RAMEND __brkval __malloc_heap_start __heap_start b __bss_end __data_end bss start data start Fi
325. nd offers some tuning options that can be used if there are more resources available than in the default configuration 9 2 2 Internal vs external RAM Obviously the constraints are much harder to satisfy in the default configuration where only internal RAM is available Extreme care must be taken to avoid a stack heap collision both by making sure functions aren t nesting too deeply and don t require too much stack space for local variables as well as by being cautious with allocating too much dynamic memory If external RAM is available it is strongly recommended to move the heap into the external 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 Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 279 9 2 3 Tunables for malloc There are a number of variables that can be tuned to adapt the behavior of malloc p 80 to the expected requirements and constraints of the applica tion Any changes to these tunables should be made before the very first call to malloc p 80 Note that some library fu
326. nder in a structure named div t p 232 that contains two int members named quot and rem Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 78 6 10 4 9 char dtostre double val char 8 unsigned char __ prec unsigned char flags The dtostre p 78 function converts the double value passed in val into an ASCII representation that will be stored under s The caller is responsible for providing sufficient storage in s Conversion is done in the format d ddde dd where there is one digit before the decimal point character and the number of digits after it is equal to the precision prec if the precision is zero no decimal point character appears If flags 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 flags has the DTOSTRE ALWAYS SIGN bit set a space character will be placed into the leading position for positive numbers If flags has the DTOSTRE PLUS SIGN bit set a plus sign will be used instead of a space character in this case The dtostre p 78 function returns the pointer to the converted string s 6 10 4 10 char dtostrf double val signed char __ width un signed char __ prec char ___8 The dtostrf p 78 function converts the double value passed in val into an ASCII representationthat will be stored und
327. ndom void The random p 81 function computes a sequence of pseudo random inte gers in the range of 0 to RANDOM_MAX as defined by the header file lt stdlib h p 263 gt The srandom p 82 function sets its argument seed as the seed for a new sequence of pseudo random numbers to be returned by rand p 80 These sequences are repeatable by calling srandom p 82 with the same seed value If no seed value is provided the functions are automatically seeded with a value of 1 6 10 4 22 long random r unsigned long __ ct Variant of random p 81 that stores the context in the user supplied variable located at ctx instead of a static library variable so the function becomes re entrant 6 10 4 23 void realloc void __ ptr size_t size The realloc p 81 function tries to change the size of the region allocated at ptr 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 82 It is acceptable to pass ptr as NULL in which case realloc p 81 will behave identical to malloc p 80 If t
328. ne using the C preprocessor Includ ing this header file causes no other side effects so it is possible to include this file more than once supposedly with different values for the BAUD parameter possibly even within the same function Assuming that the requested BAUD is valid for the given F_CPU then the macro UBRR_ VALUE is set to the required prescaler value Two additional macros are provided for the low and high bytes of the prescaler respectively UBRRL VALUE is set to the lower byte of the UBRR VALUE and UBRRH VALUE is set to the upper byte An additional macro USE_ 2X will be defined Its value is set to 1 if the desired BAUD rate within the given tolerance could only be achieved by setting the U2X bit in the UART configuration It will be defined to 0 if U2X is not needed Example usage include lt avr io h gt define F_CPU 4000000 static void uart _9600 void define BAUD 9600 include lt util setbaud h gt UBRRH UBRRH_VALUE UBRRL UBRRL_VALUE if USE 2X UCSRA 1 lt lt U2X else UCSRA amp 1 lt lt U2X endif static void uart_38400 void undef BAUD avoid compiler warning define BAUD 38400 include lt util setbaud h gt UBRRH UBRRH_VALUE UBRRL UBRRL_VALUE if USE_2X UCSRA 1 lt lt U2X else UCSRA amp 1 lt lt U2X endif Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 30 lt util setbaud h gt Helper macros fo
329. nformation on contraints for the avr can be found in the gcc manual The x register is r27 r26 the y register is r29 r28 and the z register is r31 r30 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 302 Constraint Simple upper registers r16 to r23 Base pointer registers y Z pairs Special upper register Sa r26 r28 r30 pairs 6 bit postive integer 0 to 63 a a 6 bit Va integer 63 to 0 prali ka Treger constant 0 C gt 4 2 x ae address m on Y or Z pointer with displacement GCC gt 4 3 x 6 to 5 Integer constant The selection of the proper contraint depends on the range of the constants or registers which must be acceptable to the AVR instruction they are used with The C compiler doesn t check any line of your assembler code But it is able to check the constraint against your C expression However if you specify the wrong constraints then the compiler may silently pass wrong code to the assembler And of course the assembler will fail with some cryptic output or internal errors For ce ee if you specify the constraint r and you are using this register with an ori instruction in your assembler EN 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
330. ng s2 of length len2 in the memory area s1 of length lent Returns The memmem p 89 function returns a pointer to the beginning of the substring or NULL if the substring is not found If len2 is zero the function returns s1 6 11 3 9 void x memmove void dest const void src size_t len Copy memory area The memmove p 89 function copies len bytes from memory area src to memory area dest The memory areas may overlap Returns The memmove p 89 function returns a pointer to dest 6 11 3 10 void x memrchr const void src int val size_t len The memrchr p 89 function is like the memchr p 88 function except that it searches backwards from the end of the len bytes pointed to by src instead of forwards from the front Glibc GNU extension Returns The memrchr p 89 function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 11 3 11 void x memset void dest int val size_t len Fill memory with a constant byte The memset p 89 function fills the first len bytes of the memory area pointed to by dest with the constant byte val Returns The memset p 89 function returns a pointer to the memory area dest Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 90 6 11 3 12 int strcasecmp const char s1 const char s2 Compare two strings ignoring case The strcasecmp p 90 f
331. ng 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 p 93 at run time e funsigned char Make any ungualfied char type an unsigned char Without this option they default to a signed char Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 369 e funsigned bitfields Make any unqualified bitfield type unsigned By default they are signed e fshort enums Allocate to an enum type only as many bytes as it needs for the declared range of possible values Specifically the enum type will be equivalent to the smallest integer type which has enough room e fpack struct Pack all structure members together without holes 9 12 2 Options for the assembler avr as 9 12 2 1 Machine specific assembler options e mmcu architecture e mmcu MCU name avr as understands the same mmcu options as avr gcc p 362 By default avr2 is assumed but this can be altered by using the appropriate arch pseudo instruction inside the assembler source file 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 a warning when trying to skip a 2 word instruction with a CPSE SBIC SBIS SBRC SBRS instruction Early AVR devices suffered from a hardware bug where these instructions could not be properly skipped
332. nge documentation location e GCC Open source code pacakge and patch as necessary Configure and build in a directory outside of the source code tree Set PATH in order x lt MikTex executables gt usr local bin usr bin bin mingw bin c cygwin bin lt install directory gt bin Configure Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 358 CFLAGS D__USE_MINGW_ACCESS gcc version configure prefix installdir target target enable languages c c with dwarf2 enable win32 registry WinAVR release disable nls with gmp usr local with mpfr usr local enable doc disable libssp 2 gt amp 1 tee package configure log Make make all html install 2 gt amp 1 tee package make log Manually copy the HTML documentation from the source code tree to the installation tree e avr libc Open source code package Configure and build at the top of the source code tree Set PATH in order x usr local bin mingw bin bin x lt MikTex executables gt lt install directory gt bin lt Doxygen executables gt lt NetPBM executables gt lt fig2dev executables gt lt Ghostscript executables gt c cygwin bin Configure configure host avr prefix installdir enable doc disable versioned doc enable ht
333. nitialization p 284 so the initialization of these variable will take place Refer to How to modify MCUCR or WDTCR early p 324 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 p 286 The explanation of malloc p 80 contains a discussion p 278 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 p 80 It also ex plains the linker command line options that are required to move the memory regions away from their respective standard locations in internal RAM Finally if the application simply wants to use the additional RAM for private data storage kept outside the domain of the C compiler e g through a char variable initialized directly to a particular address it would be sufficient to defer the initialization 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 external 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 p 321 9 10 17 Which O flag to use There s a common misconception
334. no is not changed and the result value is not predictable uses smaller memory flash and stack and works more quickly 6 10 4 6 void bsearch const void key const void base size_t mnmemb size_t size int const void const void x __ compar The bsearch p 77 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 comparison function referenced by compar The compar routine is expected to have two arguments which point to the key object and to an array member in that order and should return an integer less than equal to or greater than zero if the key object is found respectively to be less than to match or be greater than the array member The bsearch p 77 function returns a pointer to a matching member of the array or a null pointer if no match is found If two members compare as equal which member is matched is unspecified 6 10 4 7 void calloc size_t nele size_t size Allocate nele elements of size each Identical to calling malloc p 80 using nele size as argument except the allocated memory will be cleared to zero 6 10 4 8 div t div int mnum int denom The div p 77 function computes the value num denom and returns the quo tient and remai
335. nput data if the parameter readback is true When called with a compile time con stant parameter that is false the compiler will completely eliminate the unused readback operation as well as the return value as part of its optimizations As the controller is used in 4 bit interface mode all byte IO to from the controller needs to be handled as two nibble IOs The functions hd44780_ outnibble and hd44780_innibble implement this They do not belong to the public interface so they are declared static Building upon these the public functions hd44780 outbyte and hd44780_ inbyte transfer one byte to from the controller The function hd44780_wait_ready waits for the controller to become ready by continuously polling the controller s status which is read by performing a byte read with the RS signal cleard and examining the BUSY flag within the status byte This function needs to be called before performing any controller IO Finally hd44780_init initializes the LCD controller into 4 bit mode based on the initialization sequence mandated by the datasheet As the BUSY flag cannot be examined yet at this point this is the only part of this code where timed delays are used While the controller can perform a power on reset when certain constraints on the power supply rise time are met always calling the software initialization routine at startup ensures the controller will be in a known state This function also puts the interfa
336. ns Building and Installing the GNU Tool Chain Using the GNU tools Using the avrdude program Release Numbering and Methodology Acknowledgments Todo List Deprecated List 6 avr libc Module Documentation 6 1 lt alloca h gt Allocate space in the stack 6 1 1 Detailed Description Functions e void x alloca size_t _ size 6 1 2 Function Documentation 6 1 2 1 void alloca size_t size Allocate size bytes of space in the stack frame of the caller Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 15 282 286 292 298 311 314 317 321 346 362 373 375 379 380 380 6 2 lt assert h gt Diagnostics 16 This temporary space is automatically freed when the function that called al loca p 15 returns to its caller Avr libc defines the alloca p 15 as a macro which is translated into the inlined __builtin_alloca function The fact that the code is inlined means that it is impossible to take the address of this function or to change its behaviour by linking with a different library Returns alloca p 15 returns a pointer to the beginning of the allocated space If the allocation causes stack overflow program behaviour is undefined Warning Avoid use alloca p 15 inside the list of arguments of a function call 6 2 lt assert h gt Diagnostics 6 2 1 Detailed Description include lt assert h gt This header file defines a debugging aid As the
337. ns the floating point remainder of x BREE 6 6 3 17 double frexp double __ x int x __ pep The frexp p 36 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 __ pezp If __ x is anormal float point number the frexp p 36 function returns the value v such that v has a magnitude in the interval 1 2 1 or zero and __ lt equals v times 2 raised to the power __ perp If __ amp is zero both parts of the result are zero If is not a finite number the frexp p 36 returns ___ as is and stores 0 by _ pexp Note This implementation permits a zero pointer as a directive to skip a storing the exponent 6 6 3 18 double hypot double __ double __y The hypot p 36 function returns sqrt __ax__ yx__y This is the length of the hypotenuse of a right triangle with sides of length __z and __y or the distance of the point __ 2 __ y from the origin Using this Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 37 function instead of the direct formula is wise since the error is much smaller No underflow with small xand __y No overflow if result is in range 6 6 3 19 static int isfinite double static The isfinite p 37 function returns a nonzero value if 2 is finite not plus or minus infinity and not NaN 6 6 3 20 int isinf double 7
338. nside the interrupt routine there would not be any other chance to save a register anywhere If the interrupt routine is to be linked together with C modules care must be taken to follow the register usage guidelines p 333 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 p 110 a global catch all interrupt handler that gets all unassigned interrupt vectors can be installed using the name __vector_ default This must be global and obviously should end in a reti instruction By default a jump to location 0 would be implied instead 9 5 4 Pseudo ops and operators The available pseudo ops in the assembler are described in the GNU assembler gas manual The manual can be found online as part of the current binutils 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 con Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 297 stants follow the C notation prefix Ox for hexadecimal constants expressions use a C like syntax Some common pseudo ops include e byte allocates single byte constants e ascii allocates a non terminated string of characters e asciz allocates a 0 terminated string of characters C string
339. nt ferror FILE x stream e int vfscanf FILE stream const char x__fmt va list ap e int vfscanf P FILE stream const char __ fmt va list ap e int fscanf FILE stream const charx fmt e int fscanf P FILE stream const char _fmt e int scanf const char x _ fmt e int scanf P const char __ fmt e int vscanf const char x fmt va_list ap e int sscanf const char x buf const char ___fmt e int sscanf P const char __ buf const char __ fmt e int flush FILE stream e FILE x fdevopen int put char FILE x int get FILE Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 59 6 9 2 Define Documentation 6 9 2 1 define FDEV EOF 2 Return code for an end of file condition during device read To be used in the get function of fdevopen p 62 6 9 2 2 define FDEV ERR 1 Return code for an error condition during device read To be used in the get function of fdevopen p 62 6 9 2 3 define FDEV SETUP READ _ SRD fdev setup stream p 60 with read intent 6 9 2 4 define FDEV SETUP RW SRD SWR fdev setup stream p 60 with read write intent 6 9 2 5 define FDEV SETUP WRITE SWR fdev setup stream p 60 with write intent 6 9 2 6 define EOF 1 EOF declares the value that is returned by various standard IO functions in case of an error Since the AVR platform currently
340. nt uint16_t typedef signed long int int32_t typedef unsigned long int uint32 t typedef signed long long int int64 t typedef unsigned long long int uint64 t Integer types capable of holding object pointers These allow you to declare variables of the same size as a pointer e typedef int16 tintptr t e typedef uint16 t uintptr_t Minimum width integer types Integer types having at least the specified width typedef int8 tint least8 t typedef uint8_t uint least8 t typedef int16 tint least16 t typedef uint16_t uint least16 t typedef int32_ tint least32 t typedef uint32_t uint least32 t typedef int64 tint least64 t typedef uint64_t uint least64 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 43 Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8 tint fast8 t typedef uint8 t uint fast8 t typedef int16 tint fast16 t typedef uint16 t uint fast16 t typedef int32_ tint fast32 t typedef uint32_t uint fast32 t typedef int64 tint fast64 t typedef uint64_t uint fast64 t Greatest width integer types Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category e typedef int64_t intmax_t e typedef uint64_t uintmax_t Limits of specified width integer types C implementations should define these macros only when STDC LIMIT MAC
341. nt vfprintf FILE __ stream const charx fmt va_list ap e int vfprintf P FILE stream const char __ fmt va_list ap e int fputc int c FILE x stream e int printf const char x fmt e int printf P const char __ fmt e int vprintf const char fmt va_list ap e int sprintf char s const char x fmt e int sprintf P char __s const char ___ fmt e int snprintf char __s size_t __n const char __fmt e int snprintf P char __s size_t __n const char __fmt e int vsprintf char x_ s const char ___fmt va_list ap e int vsprintf P char __s const char __ fmt va_list ap e int vsnprintf char __s size_t __n const char __fmt va list ap e int vsnprintf P char __s size_t __n const char ___ fmt va_list ap e int fprintf FILE stream const char ___fmt e int fprintf P FILE stream const char __ fmt e int fputs const char str FILE x stream e int fputs P const char __ str FILE __ stream e int puts const char __ str e int puts P const char __ str e size_t fwrite const void __ ptr size_t size size_t __nmemb FILE _ stream e int fgetc FILE stream e int ungetc int __c FILE stream e char x fgets char str int size FILE x stream e char x gets char x str e size_t fread void __ ptr size_t size size_t __nmemb FILE x _ stream e void clearerr FILE __ stream e int feof FILE stream e i
342. ntaining 0 on the right hand side they waste space While this waste of space applies to virtually any platform C is implemented on it s usually not noticeable on larger machines like PCs while the waste of flash ROM storage can be very painful on a small microcontroller like the AVR So in general variables should only be explicitly initialized if the initial value is non zero Note Recent versions of GCC are now smart enough to detect this situation and revert variables that are explicitly initialized to 0 to the bss section Still other compilers might not do that optimization and as the C standard guarantees the initialization it is safe to rely on it Back to FAQ Index p 321 9 10 9 Why do some 16 bit timer registers sometimes get trashed Some of the timer related 16 bit IO registers use a temporary register called TEMP in the Atmel datasheet to guarantee an atomic access to the register despite the fact that two separate 8 bit IO transfers are required to actually move the data Typically this includes access to the current timer counter value register TCNTn the input capture register ICRn and write access to the output compare registers OCRnM Refer to the actual datasheet for each device s set of registers that involves the TEMP register When accessing one of the registers that use TEMP from the main application and possibly any other one from within an interrupt routine care must be taken that no a
343. nteers 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 2 Memory Areas and Using malloc 277 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 p 282 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 man agement 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 ar
344. nter AT90CAN128 AT90CAN32 INTERRUPTT rupt Request 7 AT90CAN64 ATmega103 AT megal28 ATmega64 ATmega640 ATmega1280 ATmega1281 ATmega2560 ATmega2561 AT90USB162 AT90USB82 AT90USB1287 AT90USB1286 AT90USB647 AT90USB646 IO PINS SIG PIN External Inter ATtinyll ATtinyl2 ATtiny15 AT vect SIG PIN rupt Request 0 tiny26 CHANGE LCD vect SIG LCD LCD Start of ATmegal69 ATmegal69P AT Frame mega329 ATmega3290 AT mega3290P ATmega649 AT mega6490 LOWLEVEL SIG PIN Low level In ATtiny28 IO PINS put on Port vect B OVRIT SIG_ CAN Timer AT90CAN128 AT90CAN32 vect CAN Overrun AT90CAN64 OVERFLOW Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts PCINTO vect PCINT1 vect PCINT2_ vect PCINT3_ vect Generated on Wed Jun 11 11 29 15 2008 for CHANGEO SIG_PIN_ CHANGEI SIG PIN CHANGE2 SIG PIN CHANGE3 SIG PIN CHANGE SIG PCINT Pin Change Interrupt Request 0 Pin Change Interrupt Request 1 Pin Change Interrupt Request 2 Pin Change Interrupt Request 3 120 ATmegal62 ATmegal65 AT megal65P ATmegal68P ATmega169 ATmegal69P ATmega325 AT mega3250 ATmega3250P AT mega328P ATmega329 ATmega3290 ATmega3290P ATmega32HVB ATmega406 ATmega48P AT mega645 ATmega6450 ATmega649 ATmega6490 ATmega88P AT megal68 ATmega48 ATmega88 ATmega640 ATmega1280 AT megal281 ATmega2
345. nttypes 23 PRIdFAST16 avr inttypes 23 PRIdFAST32 avr inttypes 23 PRIdFAST8 avr inttypes 23 PRIdLEAST16 avr inttypes 23 PRIdLEAST32 avr inttypes 23 PRIdLEASTS8 avr inttypes 23 PRIdPTR avr inttypes 23 PRIi16 avr inttypes 24 PRIi32 avr inttypes 24 PRIi8 avr inttypes 24 PRIiFAST16 avr inttypes 24 PRIiFAST32 avr inttypes 24 PRIiFAST8 avr inttypes 24 PRIiLEAST16 avr inttypes 24 PRIiLEAST32 avr inttypes 24 PRIiLEASTS8 avr inttypes 24 PRIiPTR avr inttypes 24 printf avr stdio 64 printf P avr stdio 64 PRIo16 avr inttypes 24 PR1032 avr inttypes 25 PRI08 avr inttypes 25 PRIoFAST16 avr inttypes 25 PRIoFAST32 avr inttypes 25 PRIoFAST8 avr inttypes 25 PRIoLEAST16 avr inttypes 25 PRIoLEAST32 avr inttypes 25 PRIoLEAST8 avr inttypes 25 PRIoPTR avr inttypes 25 PRIu16 avr inttypes 25 PRIu32 avr inttypes 25 PRIu8 avr inttypes 26 PRIuFAST16 avr inttypes 26 PRIuFAST32 avr inttypes 26 PRIuFAST8 avr inttypes 26 PRIuLEAST16 avr inttypes 26 PRIuLEAST32 avr inttypes 26 PRIuLEASTS8 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 395 INDEX avr inttypes 26 PRIuPTR avr inttypes 26 PRIX16 avr inttypes 26 PRIx16 avr inttypes 26 PRIX32 avr inttypes 26 PRIx32 avr inttypes 27 PRIX8 avr inttypes 27 PRIx8 avr inttypes 27 PRIXFAST16 avr inttypes 27 PRIxFAST16 avr inttypes 27 PRIXFAST32 avr inttypes 27
346. nttypes h gt Integer Type conver sions 20 lt math h gt Mathematics 32 lt setjmp h gt Non local goto 39 lt stdint h gt Standard Integer Types 41 lt stdio h gt Standard IO facilities 53 lt stdlib h gt General utilities 73 lt string h gt Strings 84 EEPROM han lt util atomic h gt Atomically and Non Atomically Executed Code Blocks 169 lt util crcl6 h gt CRC Computations 173 lt util delay h gt tions for loops 176 lt util delay_basic h gt Basic busy wait delay loops 178 lt util parity h gt Parity bit genera tion 179 lt util setbaud h gt Helper macros for baud rate calculations 179 lt util twi h gt TWI bit mask defini tions 182 Convenience func busy wait delay _BV avr s r 161 EEGET avr_ eeprom 105 _EEPUT avr_ eeprom 105 FDEV EOF avr stdio 58 FDEV ERR avr stdio 58 FDEV SETUP READ avr stdio 58 FDEV SETUP RW avr stdio 58 FDEV SETUP WRITE avr stdio 58 FFS avr string 86 AVR LIBC DATE avr version 164 AVR LIBC DATE STRING avr version 164 AVR LIBC MAJOR avr version 164 AVR LIBC MINOR _ avr version 165 INDEX AVR LIBC REVISION _ avr_ version 165 AVR LIBC VERSION STRING _ avr version 165 AVR LIBC VERSION _ avr version 165 ELPM classic pgmspace h 252 ELPM dword enhanced 382 boot h 239 boot page write extended boot h 239 boot page write normal boot h 240 boot rww
347. 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 spec ifications each of which results in fetching zero or more subsequent arguments Each conversion specification is introduced by the character The arguments must properly correspond after type promotion with the conversion specifier After the the following appear in sequence e Zero or more of the following flags The value should be converted to an alternate form For c d i s and u conversions this option has no effect For o conversions the precision of the number is increased to force the first character of the output string to a zero except if a zero value is printed with an explicit precision of zero For x and X conversions a non zero result has the string 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
348. number of fuse bytes in the FUSE_ MEMORY SIZE macro If FUSE MEMORY SIZE 1 there is only a single field byte of type unsigned char If FUSE MEMORY SIZE 2 there are two fields low and high of type unsigned char If FUSE MEMORY SIZE 3 there are three fields low high and ex tended of type unsigned char If FUSE MEMORY SIZE gt 3 there is a single field byte which is an array of unsigned char with the size of the array being FUSE MEMORY SIZE A convenience macro FUSEMEM is defined as a GCC attribute for a custom named section of fuse A convenience macro FUSES is defined that declares a variable __ fuse of type __fuse_t with the attribute defined by FUSEMEM This variable allows the end user to easily set the fuse data Note If a device specific I O header file has previously defined FUSEMEM then FUSEMEM is not redefined If a device specific I O header file has previ ously defined FUSES then FUSES is not redefined Each AVR device I O header file has a set of defined macros which specify the actual fuse bits available on that device The AVR fuses have inverted values logical 1 for an unprogrammed disabled bit and logical 0 for a programmed enabled bit The defined macros for each individual fuse bit represent this in their definition by a bit wise inversion of a mask For example the FUSE EESAVE fuse in the ATmega128 is defined as define FUSE_EESAVE _BV 3 Note The _ BV macro
349. obj avr configure prefix PREFIX target avr enable languages c c disable nls disable libssp with dwarf2 make make install To save your self some download time you can alternatively download only the gcc core 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 The stdc libs are not included with C for AVR due to the size limi tations 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 11 6 AVR Libc Warning You must install avr binutils p 348 avr gcc p 350 and make sure your path is set p 347 properly before installing avr libe 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 libe gunzip c avr libc lt version gt tar gz tar xf cd avr libc lt version gt configure prefix PREFIX build config guess host avr make make install Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 351 9 11 7 AVRDUDE
350. of assign ments Note that the compiler will not check if the operands are of reasonable type for the kind of operation used in the assembler instructions Input operands are you guessed it read only But what if you need the same operand for input and output As stated above read write operands are not supported in inline assembler code But there is another solution For input operators it is possible to use a single digit in the constraint string Using digit n tells the compiler to use the same register as for the n th operand starting with zero Here is an example asm volatile swap 0 r value 0 value This statement will swap the nibbles of an 8 bit variable named value Con straint 0 tells the compiler to use the same input register as for the first operand Note however that this doesn t automatically imply the reverse case The compiler may choose the same registers for input and output even if not told to do so This is not a problem in most cases but may be fatal if the output operator is modified by the assembler code before the input operator is used In the situation where your code depends on different registers used for input and output operands you must add the amp constraint modifier to your output operand The following example demonstrates this problem asm volatile in 0 1 n t out 1 s 92 n t amp r input I _SFR_IO_ADDR port r output In this examp
351. olatile 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 Another problem with reused macros arises if you are using labels In such cases you may make use of the special pattern which is replaced by a unique number on each asm statement The following code had been taken from avr include iomacros h define loop_until_bit_is_clear port bit __asm__ __volatile__ L Y sbic 0 1 n t rjmp L_ no outputs 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 L_1405
352. om zero instead of to the nearest even integer This function is similar to round p 38 function but it differs in type of return value and in that an overflow is possible Returns The rounded long integer value If __ zx is not a finite number or an overflow was this realization returns the LONG_MIN value 0x80000000 6 6 3 27 double modf double __ double __iptr The modf p 38 function breaks the argument _ lt into integral and frac tional 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 pir The modf p 38 function returns the signed fractional part of __ x Note This implementation skips writing by zero pointer 6 6 3 28 double pow double z double ___y The function pow p 38 returns the value of __ x to the exponent __y 6 6 3 29 double round double ma The round p 38 function rounds m to the nearest integer but rounds halfway cases away from zero instead of to the nearest even integer Overflow is impossible Returns The rounded value If xisan integral or infinite x itself is returned If __x is NaN then NaN is returned 6 6 3 30 int signbit double _ The signbit p 38 function returns a nonzero value if the value of __ x has its sign bit set This is not the same as x lt 0 0 because IEEE 754 floating point allows zero to be signed The comparison 0 0 lt 0 0 is fa
353. on Defines e defne AVR POWER H 1 e define clock prescale set x e 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 CLKPS 3 Enumerations e 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 35 2 Define Documentation 8 35 2 1 define clock prescale set x Value uint8_t tmp _BV CLKPCE _ asm__ __volatile__ in __tmp_reg__ __SREG__ n t cli n t sts 1 s 0 n t Sts 1 s 2 n t out __SREG__ __tmp_reg__ no outputs d tmp M _SFR_MEM_ADDR CLKPR nd x ro Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 36 setbaud h File Reference 258 8 36 setbaud h File Reference 8 36 1 Detailed Description Defines e define BAUD_TOL 2 e define UBRR_ VALUE e define UBRRL VALUE e define UBRRH_ VALUE e define USE 2X 0 8 37 setjmp h File Reference 8 37 1 Detailed Description Defines e define _SETJMP_H_ 1 e define ATTR_NORETURN__ __attribute__ __ noreturn__ Functions e int setjmp jmp buf __jmpb e void longjmp jmp_buf __jmpb int ret ATTR NORETURN _ 8 38 sleep h File Reference 8 38 1 Detailed Description Defines e define AVR SLEEP H 1 e define SLEEP CONTROL REG MCUCR e define
354. on init4 see The initN Sections p 284 With respect to the standard this sentence is somewhat simplified because the standard allows for machines where the ac tual bit pattern used differs from all bits being 0 but for the AVR target in general all integer type variables are set to 0 all pointers to a NULL pointer and all floating point variables to 0 0 As long as these variables are not initialized i 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 p 283 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 327 In contrast global and static variables that have an initializer go into the data p 282 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 co
355. 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 91 Returns The strchr p 90 function returns a pointer to the matched character or NULL if the character is not found 6 11 3 16 char x strchrnul const char x s int c The strchrnul p 91 function is like strchr p 90 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 91 function returns a pointer to the matched charac ter or a pointer to the null byte at the end of s i e ststrlen s if the character is not found 6 11 3 17 int stremp const char s1 const char s2 Compare two strings The stremp p 91 function compares the two strings s1 and s2 Returns The stremp p 91 function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcmp p 91 is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 6 11 3 18 char x strcpy char x dest const char src Copy a string The strepy p 91 function copies the string pointed to by src including the
356. onnected to the OCRI1 A output the large p 212 and stdio p 219 demos are mainly targeted to the Atmel STK500 starter kit and the TWI p 227 example requires a controller where some 24Cxx two wire EEPPROM can be connected to For the STK500 demos the default CPU either an AT9058515 or an ATmega8515 should be removed from its Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 35 Combining C and assembly source files 191 socket and the ATmegal6 that ships with the kit should be inserted into socket SCKT3100A3 The ATmegal6 offers an on board ADC that is used in the large p 212 demo and all AVRs with an ADC feature a different pinout than the industry standard compatible devices In order to fully utilize the large p 212 demo a female 10 pin header with cable connecting to a 10 kOhm potentiometer will be useful For the stdio p 219 demo an industry standard HD44780 compatible LCD display of at least 16x1 characters will be needed Among other things the LCD4Linux project page describes many things around these displays including common pinouts Modules Combining C and assembly source files A simple project A more sophisticated project Using the standard IO facilities Example using the two wire interface TWI 6 35 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 spe
357. oo bin changes it will trigger the recreation of foo o and a subsequent relink of the final ELF file Back to FAQ Index p 321 9 10 31 How do I perform a software reset of the AVR The canonical way to perform a software reset of the AVR is to use the watchdog timer Enable the watchdog timer to the shortest timeout setting then go into an infinite do nothing loop The watchdog will then reset the processor The reason why this is preferrable over jumping to the reset vector is that when the watchdog resets the AVR the registers will be reset to their known default settings Whereas jumping to the reset vector will leave the registers in their previous state which is generally not a good idea CAUTION Older AVRs will have the watchdog timer disabled on a reset For these older AVRs doing a soft reset by enabling the watchdog is easy as the watchdog will then be disabled after the reset On newer AVRs once the watchdog is enabled then it stays enabled even after a reset For these newer AVRs a function needs to be added to the init3 section i e during the startup code before main to disable the watchdog early enough so it does not continually reset the AVR Here is some example code that creates a macro that can be called to perform a soft reset include lt avr wdt h gt define soft_reset do 1 wdt_enable WDTO_15MS for 1 I I while 0 For newer AVRs such as the ATmega1281 also add
358. osen 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 p 65 instead of fprintf mystream saves typing work but since avr gcc needs to resort to pass all arguments of variadic functions on the stack as opposed to passing them in registers for functions that take a fixed number of parameters the ability to pass one parameter less by implying stdin will also save some execution time Defines e define FILE struct file e define stdin __iob 0 e define stdout __iob 1 e define stderr __iob 2 e define EOF 1 e define fdev set udata stream u do stream udata u while 0 define fdev get udata stream stream udata define fdev setup streamf 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 frdefine FDEV SETUP STREAM put get rwflag frdefine fdev close define putc __c stream fputc __c stream define putchar c fputc __c stdout define getc _ stream fgete stream define getchar fgetc stdin Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 58 Functions e int fclose FILE x _ stream e i
359. pile and stop don t link This demo is small enough that we could compile and link in one step However real world projects will have several modules and will typically need to break up the building of the project into several compiles Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 200 and one link avr gcc g Os mmcu atmega8 c demo c The compilation will create a demo o file Next we link it into a binary called demo elf 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 to gether If this option isn t specified the compiler defaults to the 8515 processor environment which is most certainly what you didn t want 6 36 4 Examining 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 informat
360. piled with mcall prologues option In brackets the size without taking into account modules of a prologue and an epilogue is resulted Both of the size can coincide if function does not cause a prologue epilogue Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 8 Benchmarks Ae atoi 12345 atol 12345 dtostre 3 2345 s 6 oa 2345 15 6 im 12345 s Itoa 12345L s 10 realloc void 0 1 qsort a 5 sizeof s cmp sprintf min d 12345 sprintf s d 12345 sprintf fit Ne ae sscanf min 12345 d amp i sscanf 12345 d amp i sscanf point color a z s sscanf fit 1 2345 Ze amp x strtod 1 2345 amp p strtol 12345 amp p 0 Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks Flash bytes Stack bytes MCU clocks 22 2
361. 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 ATmegal6 in addition that it ships together with an STK500 anyway is that it can be debugged online via JTAG Likewise the ATmega48 88 168 and ATtiny2313 devices can be debugged through debugWire using the Atmel JTAG ICE mkII or the low cost AVR Dragon Note that in the explanation below all port pin names are applicable to the ATmegal6 setup 6 37 2 Functional overview PD6 will be toggled with each internal clock tick approx 10 ms PD7 will flash once per second PDO and PD1 are configured as UART IO and can be used to connect the demo kit to a PC 9600
362. r address long __ ELPM_ dword uint32 t address long Read a double word from the program space with a 32 bit far address Note The address is a byte address The address is in the program space 6 18 2 7 define pgm read dword near address short LPM dword uint16 t address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 18 2 8 define pgm read word address short pgm read word mnear address short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 147 6 18 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 18 2 10 define pgm read word mnear address short __ LPM word uint16 t address short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 6 18 2 11 define PGM VOID P const prog void Used to declare a generic pointer to an object in program space 6 18 2 12 define PROGMEM ATTR_PROGMEM_ _ Attribute to use in order to d
363. r baud rate calculation 81 In this example two functions are defined to setup the UART to run at 9600 Bd and 38400 Bd respectively Using a CPU clock of 4 MHz 9600 Bd can be achieved with an acceptable tolerance without setting U2X prescaler 25 while 38400 Bd require U2X to be set prescaler 12 Defines e define BAUD_TOL 2 e define UBRR_ VALUE e define UBRRL_ VALUE e define UBRRH_ VALUE e define USE 2X 0 6 30 2 Define Documentation 6 30 2 1 define BAUD TOL 2 Input and output macro for lt util setbaud h p 258 gt Define the acceptable baud rate tolerance in percent If not set on entry it will be set to its default value of 2 6 30 2 2 define UBRR VALUE Output macro from lt util setbaud h p 258 gt Contains the calculated baud rate prescaler value for the UBRR register 6 30 2 3 define UBRRH VALUE Output macro from lt util setbaud h p 258 gt Contains the upper byte of the calculated prescaler value UBRR_ VALUE 6 30 2 4 define UBRRL VALUE Output macro from lt util setbaud h p 258 gt Contains the lower byte of the calculated prescaler value UBRR_ VALUE 6 30 2 5 define USE 2X 0 Output bacro from lt util setbaud h p 258 gt Contains the value 1 if the desired baud rate tolerance could only be achieved by setting the U2X bit in the UART configuration Contains 0 otherwise Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 31 lt util twi h gt TWI bit mask defin
364. r s depends on the choice of radix For exam ple 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 29 will be the letter a If radix is 10 and val is negative a minus sign will be prepended The itoa p 79 function returns the pointer passed as s 6 10 4 14 long labs long __i The labs p 79 function computes the absolute value of the long integer i Note The abs p 76 and labs p 79 functions are builtins of gcc 6 10 4 15 ldiv_t ldiv long _ num long denom The Idiv p 79 function computes the value num denom and returns the quo tient and remainder in a structure named ldiv_t p 233 that contains two long integer members named quot and rem 6 10 4 16 char Itoa long int __ val char __s int radix Convert a long integer to a string The function Itoa p 79 converts the long integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing sufficient storage in s Generated on Wed Jun 11 11 29 15 2008 for avr libc by Dox
365. r15 can be used for argument passing by the compiler in case many or long arguments are being passed to callees If this is not the case throughout the entire application these registers could be used for register variables as well Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 324 Extreme care should be taken that the entire application is compiled with a con sistent set of register allocated variables including possibly used library func tions See C Names Used in Assembler Code p 310 for more details Back to FAQ Index p 321 9 10 5 How to modify MCUCR or WDTCR early The method of early initialization MCUCR WDTCR or anything else is different and more flexible in the current version Basically write a small assembler file which looks like this begin xram S include lt avr io h gt section init1 ax progbits 1di r16 _BV SRE _BV SRW out _SFR_IO_ADDR MCUCR r16 33 end xram S Assemble it link the resulting xram o with other files in your program and this piece of code will be inserted in initialization code which is run right after reset See the linker script for comments about the new initN sections which one to use etc The advantage of this method is that you can insert any initialization code you want just remember that this is very early startup no stack and no __ zero_reg__ yet and no program memory space is wasted if this fea
366. ram space flash Appends src to string dst of size siz unlike strncat p 93 siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat P p 152 function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 6 18 4 15 size_t strlepy_P char x 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 P p 152 function returns strlen src If retval gt siz truncation occurred Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 153 6 18 4 16 size_t strlen P PGM_P src The strlen P p 153 function is similar to strlen p 93 except that src is a pointer to a string in program space Returns The strlen p 93 function returns the number of characters in src 6 18 4 17 int strncasecmp P const char s1 PGM_P s2 size_t n Compare two strings ignoring case The strncasecmp P p 153 function is similar to strcasecmp_P p 150 except it only compares the first n characters of s1 Parameters s1 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
367. rameter to function something Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 298 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 instruc tion which are not available in the C language Because of a lack of documentation especially for the AVR version of the com piler it may take some time to figure out the implementation details by studying the compiler and assembler source code There are also a few sample programs available in the net Hopefully this document will help to increase their number It s assumed that you are familiar with writing AVR assembler programs be cause this is not an AVR assembler programming tutorial It s not a C language tutorial either Note that this document does not cover file written completely in assembler language refer to avr libc and assembler programs p 292 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 Permission is granted to copy and distribute modified versions of this manual provided that the entire
368. ranch cvs tag se ee eee EE 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 t set version to 1 0 cvs tag avr libc 1_0 release set version to 1 0 0 lt date gt i set version to 1 0 1 a cvs tag avr libc 1_0_1 releas 1 cvs tag avr libc 1_2 branchpoint set version to 1 3 0 lt date gt cvs tag b avr libc 1_2 branch set version to 1 1 90 lt date gt set version to 1 2 cvs tag avr libc 1_2 release cvs tag avr libc 2 0 branchpoint set version to 2 1 0 lt date gt Figure 9 Release tree Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 15 Acknowledgments 379 9 15 Acknowledgments This document tries to tie together the labors of a large group of people With out these individuals efforts we wouldn t have a terrific free set of tools to develop AVR projects We all owe thanks to The GCC Team which produced a very capable set of development tools for an amazing number of platforms and processors Denis Chertykov denisc overta ru for making the AVR specific changes to the GNU tools Denis Chertykov and Marek Michalkiewicz marekm linux org p1 for developing the standard libraries and startup code for AVR GCC Uros Platise for developing the AVR programmer tool uisp Joerg Wunsch joergeFreeBSD ORG for adding all the AVR development tools to the FreeBSD http www fr
369. rated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 1 AVR Libc 1 9 2 Memory Areas and Using malloc 0 277 9 3 Memory Sections ear vnr rn nrk eee 282 9 4 Data in Program Space 0 2 00000 286 9 5 avr libc and assembler programs 292 9 6 Inline Assembler Cookbook 298 9 7 Howto Build a Library 4 311 9 8 Benchmarks 4 d ds bad LAA ak EJ ea E lve eb G dd 314 9 9 Porting From IAR to AVR GCC 317 9 10 Frequently Asked Questions 2 0004 321 9 11 Building and Installing the GNU Tool Chain 346 9 12 Using the GNU tools aoaaa en 362 9 13 Using the avrdude program saoao 373 9 14 Release Numbering and Methodology 375 9 15 Acknowledgments 0 000000 E 379 9 16 Todo List 4 dni ee ee Saa FE SE ea 380 9 17 Deprecated List 2 2 0 2 2 vr 0000002 eee eee 380 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 ba sic startup code needed by most applications There is a wealth of information in this document which goes beyond simply describing the interfaces and routines provided by the library We hope
370. re characters available in the line buffer variable rxp is not NULL the next char acter 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 Characters 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 condition 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 condition on input DOR bit set an error condition will be returned as _FDEV_ERR Line editing characters are handled inside the loop potentially modifying the buffer status If characters are attempted to be entered beyond the size of the Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 227 line buffer their reception is refused and a a character is sent to the terminal If a r or n character is seen the variable rxp receive pointer is set to the beginning of the buffer the loop is left and the first character of the buffer will be returned to the application If no other characters have been entered this will just be the newline character and the buffer is marked as being exhausted immediately again 6 38 4 The source code The source code is installed under prefix share doc avr libc examples std
371. re is no standard error output stream available for many applications using this library the generation of a printable error message is not enabled by default These messages will only be generated if the application defines the macro __ASSERT_USE_STDERR before including the lt assert h p 233 gt header file By default only abort p 76 will be called to halt the application Defines e define assert expression 6 2 2 Define Documentation 6 2 2 1 define assert expression Parameters expression Expression to test for Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 3 lt ctype h gt Character Operations 17 The assert p 16 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 p 76 is called effectively terminating the program If expression is true the assert p 16 macro does nothing The assert p 16 macro may be removed at compile time by defining NDE BUG as a macro e g by using the compiler option DNDEBUG 6 3 lt ctype h gt Character Operations 6 3 1 Detailed Description These functions perform various operations on characters include lt ctype h gt Character classification routines These functions perform character classification They return true or false status depending whether the character passed to the function falls into the function s classifica
372. recated Write val to IO port port 6 32 2 8 define sbi port bit port 1 lt lt bit Deprecated Set bit in IO port port 6 32 3 Function Documentation 6 32 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 33 lt compat ina90 h gt Compatibility with IAR EWB 3 x include lt compat ina90 h gt This is an attempt to provide some compatibility with header files that come with IAR C to make porting applications between different compilers easier No 100 compatibility though Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 34 Demo projects 190 Note For actual documentation please see the IAR manual 6 34 Demo projects 6 34 1 Detailed Description Various small demo projects are provided to illustrate several aspects of using the opensource utilities for the AVR controller series It should be kept in mind that these demos 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 p 195 is somewhat like the Hello world application for a microcontroller 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
373. resulting derived work is distributed under the terms of a permission notice identical to this one This document describes version 3 3 of the compiler There may be some parts which hadn t been completely understood by the author himself and not all samples had been tested so far Because the author is German and not familiar with the English language there are definitely some typos and syntax errors in the text As a programmer the author knows that a wrong documentation sometimes might be worse than none Anyway he decided to offer his little knowledge to the public in the hope to get enough response to improve this document Feel free to contact the author via e mail For the latest release check http www ethernut de Herne 17th of May 2002 Harald Kipp harald kipp at egnite de Note As of 26th of July 2002 this document has been merged into the documentation for avr libc The latest version is now available at http savannah nongnu org projects avr libc Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 299 9 6 1 GCC asm Statement Let s start with a simple example of reading a value from port D asm in 0 1 r value I _SFR_IO_ADDR PORTD Each asm statement is devided by colons into up to four parts 1 The assembler instructions defined as a single string constant in 70 Vl 2 A list of output operands separated by commas Our example uses just
374. ribes the various sections available 9 3 1 The text Section The text section contains the actual machine instructions which make up your program This section is further subdivided by the initN and finiN sections dicussed below Note The avr size program part of binutils coming from a Unix background doesn t account for the data initialization space added to the text section so in order to know how much flash the final program will consume one needs to add the 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 The data Section This section contains static data which was defined in your code Things like the following 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 3 Memory Sections 283 start at 0x1100 pass 0x801100 at the address to the linker offset explained p 283 Note When using malloc p 80 in the application which could even happ
375. right after the interrupt vectors and in front of any executable code However it can become a problem if there are too many of these constants or for bootloaders on devices with more than 64 KB of ROM All these functions will not work in that situation Defines define PROGMEM __ATTR_ PROGMEM_ _ define PSTR s const PROGMEM char s define pgm_read_byte_near address_short LPM uint16 t address short define pgm read word mnear address short LPM word uint16 t address short define pgm read dword near address_ short LPM dword uint16 t address short Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 144 e define pgm read byte far address long __ELPM uint32_ t address long e define pgm read word far address long ELPM word uint32 t address long e define pgm read dword far address long __ELPM dword uint32 t address long e define pgm read byte address short pgm read byte near address short e define pgm read word address short pgm read word near address short e define pgm read dword address short pgm read dword near address short e define PGM P const prog char x e 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
376. rintf p 63 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 p 65 which takes a program space string p 143 The string is read into an internal buffer as one line of input using fgets p 63 While it would be also possible to use gets p 65 which implicitly reads from stdin gets p 65 has no control that the user s input does not overflow the input buffer provided so it should never be used at all If fgets p 63 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 demonstrational purposes this explains the error handling of stdio fgets p 63 will return NULL in case of an input error or end of file condition on input Both these conditions 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
377. rn 0 The first function will generate object code which is not even close to what is intended The major problem arises when the function is called When the compiler sees this call it will actually pass the value of the PORTB register using an IN instruction instead of passing the address of PORTB e g memory mapped io addr of 0x38 io port 0x18 for the megal28 This is seen clearly when looking at the disassembly of the call set_bits_func_wrong PORTB Oxaa 10a 6a ea ldi r22 OxAA 5 170 10c 88 b3 in r24 0x18 24 10e Oe 94 65 00 call Oxca Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 332 So the function once called only sees the value of the port register and knows nothing about which port it came from At this point whatever object code is generated for the function by the compiler is irrelevant The interested reader can examine the full disassembly to see that the function s body is completely fubar The second function shows how to pass by reference the memory mapped address of the io port to the function so that you can read and write to it in the function Here s the object code generated for the function call set_bits_func_correct amp PORTB 0x55 112 65 e5 ldi r22 0x55 85 114 88 e3 ldi r24 0x38 56 116 90 eo ldi r25 0x00 0 118 0e 94 7c 00 call Oxf8 You can clearly see that 0x0038 is correctly passed for the address of the io po
378. rned value is in the range 0 pi radians A domain error occurs for arguments not in the range 1 1 6 6 3 2 double asin double __ The asin p 34 function computes the principal value of the arc sine of __a The returned value is in the range pi 2 pi 2 radians A domain error occurs for arguments not in the range 1 1 6 6 3 3 double atan double __ 2 The atan p 34 function computes the principal value of the arc tangent of __ x The returned value is in the range pi 2 pi 2 radians 6 6 3 4 double atan2 double y double___2 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 35 The atan2 p 34 function computes the principal value of the arc tangent of __y __ using the signs of both arguments to determine the quadrant of the return value The returned value is in the range pi pi radians 6 6 3 5 double ceil double __z The ceil p 35 function returns the smallest integral value greater than or equal to x expressed as a floating point number 6 6 3 6 static double copysign double __ double y static The copysign p 35 function returns __ but with the sign of __ y They work even if or __y are NaN or zero 6 6 3 7 double cos double __ The cos p 35 function returns the cosine of __ x measured in radians 6 6 3 8 double cosh double __ The cosh p 35 function returns the hyperbolic cosine of __ x
379. rors 6 4 1 Detailed Description include lt errno h gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 20 Some functions in the library set the global variable errno when an error occurs The file lt errno h p 243 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 inter rupted task Defines e define EDOM 33 e define ERANGE 34 6 4 2 Define Documentation 6 4 2 1 define EDOM 33 Domain error 6 4 2 2 define ERANGE 34 Range error 6 5 lt inttypes h gt Integer Type conversions 6 5 1 Detailed Description include lt inttypes h gt This header file includes the exact width integer definitions from lt stdint h p 259 gt and extends them with additional facilities provided by the imple mentation Currently the extensions include two additional integer types that could hold a far pointer i e a code pointer that can address more than 64 KB as well as standard names for all printf and scanf formatting options that are supported by the lt stdio h gt Standard IO facilities p 54 As the library does not support the full range of convers
380. rt Looking at the disassembled object code for the body of the function we can see that the function is indeed performing the operation we intended void set_bits_func_correct volatile uint8_t port uint8_t mask 1 f8 fc 01 movw r30 r24 port mask fa 80 81 ld r24 Z fc 86 2b or r24 r22 fe 80 83 st Z r24 100 08 95 ret Notice that we are accessing the io port via the LD and ST instructions The port parameter must be volatile to avoid a compiler warning Note Because of the nature of the IN and OUT assembly instructions they can not be used inside the function when passing the port in this way Readers interested in the details should consult the Instruction Set data sheet Finally we come to the macro version of the operation In this contrived ex ample the macro is the most efficient method with respect to both execution speed and code size set bits macro PORTB Oxf0 lic 88 b3 in r24 0x18 24 ile 80 6f ori r24 OxFO 240 120 88 bb out 0x18 r24 24 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 333 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
381. rts of the code are Note 1 As the AVR microcontroller series has been developed during the past years new features have been added over time Even though the basic concepts of the timer counter1 are still the same as they used to be back in early 2001 when this simple demo was written initially the names of registers and bits have been changed slightly to reflect the new features Also the port and pin mapping of the output compare match 1A or 1 for older devices pin which is used to control the LED varies between different AVRs The file iocompat h tries to abstract between all this differences using some preprocessor ifdef statements so the actual program itself can operate on a common set of symbolic names The macros defined by that file are e OCR the name of the OCR register used to control the PWM usually either OCRI or OCRIA e DDROC the name of the DDR data direction register for the OC output e OC1 the pin number of the OC1 A output within its port e TIMER1_TOP the TOP value of the timer used for the PWM 1023 for 10 bit PWMs 255 for devices that can only handle an 8 bit PWM e TIMER1_PWM_INIT the initialization bits to be set into control register 1A in order to setup 10 bit or 8 bit phase and frequency correct PWM mode Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 197 e TIMER1_CLOCKSOURCE the clock bits to set in the respective control register to start the PWM timer
382. rts of the compiler including a lot of optimizations In GCC a host system is the system processor OS that the compiler runs on A target system is the system that the compiler compiles code for And a build system is the system that the compiler is built from source code on If a compiler has the same system for host and for target it is known as a native compiler If a compiler has different systems for host and target it is known asa cross compiler And if all three build host and target systems are different it is known as a Canadian cross compiler but we won t discuss that here When GCC is built to execute on a host system such as FreeBSD Linux or Windows and it is built to generate code for the AVR microcontroller target then it is a cross compiler and this version of GCC is commonly known as AVR GCC In documentation or discussion AVR GCC is used when referring to GCC targeting specifically the AVR or something that is AVR specific about GCC The term GCC is usually used to refer to something generic about GCC or about GCC as a whole GCC is different from most other compilers GCC focuses on translating a high level language to the target assembly only AVR GCC has three available compilers for the AVR C language C and Ada The compiler itself does not assemble or link the final code GCC is also known as a driver program in that it knows about and drives Generated on Wed Jun 11 11 29 15 2008 for avr
383. s r2 r17 r28 r29 May be allocated by gcc for local data Calling C subroutines leaves them unchanged Assembler subroutines are responsible for saving and restoring these registers if changed r29 r28 Y pointer is used as a frame pointer points to local data on stack if necessary The requirement for the callee to save preserve the contents of these registers even applies in situations where the compiler assigns them for argument passing e Fixed registers r0 r1 Never allocated by gcc for local data but often used for fixed purposes Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 334 r0 temporary register can be clobbered by any C code except interrupt han dlers which save it may be used to remember something for a while within one piece of assembler code rl assumed to be always zero in any C code may be used to remember some thing for a while within one piece of assembler code but must then be cleared after use clr r1 This includes any use of the f mul s u instructions which return their result in rl r0 Interrupt handlers save and clear r1 on entry and restore rl on exit in case it was non zero e 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 instru
384. s built in Linux described above The main differences are in what the PATH environ ment variable gets set to pathname differences and the tools that are required to build the projects under Windows We ll take a look at the tools next 9 11 12 Tools Required for Building the Toolchain for Windows These are the tools that are currently used to build WinAVR 20070525 or later This list may change either the version of the tools or the tools themselves as improvements are made e MinGW MSYS lt http downloads sourceforge net mingw MinGW 5 1 3 exe use_ mirror superb east gt Put MinGW 5 1 3 exe in it s own directory for example C MinGWSetup Run MinGW 5 1 3 exe Select Download and install Select Current package Select type of install Full e Install MSYS 1 0 10 exe package lt http prdownloads sf net mingw MSYS 1 0 10 exe download gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 11 Building and Installing the GNU Tool Chain 354 Default selections Batch file will ask Woo Do you wish to continue with the post install Press y and press enter Do you have MinGW installed Press y and press enter Where is your MinGW installation Type in c mingw without quotes and press enter Do you wish for me to add mount bindings for c mingw to mingw Press y and press enter It will display some messages on the screen then it will d
385. se long atol const char ___s ATTR_PURE int atoi const char __ s ATTR PURE void exit int status ATTR NORETURN void x malloc size_t size ATTR MALLOC _ void free void x__ ptr void calloc size_t __ nele size_t size ATTR MALLOC _ void realloc void pir size_t size ATTR MALLOC double strtod const char x nptr char xx___endptr double atof const char ___nptr int rand void void srand unsigned int _ seed int rand r unsigned long ___ ctx Variables e size_t _malloc_ margin e char malloc_heap_ start e char _ malloc_heap_ end 6 10 2 Define Documentation 6 10 2 1 define DTOSTR ALWAYS SIGN 0x01 Bit value that can be passed in flags to dtostre p 78 6 10 2 2 define DTOSTR PLUS SIGN 0x02 Bit value that can be passed in flags to dtostre p 78 6 10 2 3 define DTOSTR UPPERCASE 0x04 Bit value that can be passed in flags to dtostre p 78 6 10 2 4 define RAND MAX Ox7FFF Highest number that can be generated by rand p 80 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 76 6 10 2 5 define RANDOM MAX 0x7FFFFFFF Highest number that can be generated by random p 81 6 10 3 Typedef Documentation 6 10 3 1 typedef int x compar fn t const void x const void x Comparision function type for qsort p 80 just for convenience 6 10 4 Function Documentation 6 10 4 1 void abor
386. se for a local variable is a return value The following function returns a 16 bit value read from two successive port addresses uint16_t inw uint8_t port 1 uint16_t result asm volatile in KAO 1 n t in BO 1 1 r result I _SFR_IO_ADDR port Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 6 Inline Assembler Cookbook 310 return result Note inw is supplied by avr libe 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 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 variable will not be referenced any longer the register may be re used But the compiler is not able to check wether
387. se of the PSTR p 147 macro Back to FAQ Index p 321 9 10 21 Why does the compiler compile an 8 bit operation that uses bitwise operators into a 16 bit operation in assembly Bitwise operations in Standard C will automatically promote their operands to an int which is by default 16 bits in avr gec To work around this use typecasts on the operands including literals to declare that the values are to be 8 bit operands This may be especially important when clearing a bit var amp mask wrong way The bitwise not operator will also promote the value in mask to an int To keep it an 8 bit value typecast before the not operator var amp unsigned char mask Back to FAQ Index p 321 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 341 9 10 22 How to detect RAM memory and variable overlap prob lems 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 allo cated 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 S
388. se the preprocessor and the compiler s constant expression computation to calculate the value of timer 1 s 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 automatically scale to new target softclock or master CPU frequencies without having to manually re calculate hardcoded constants Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 37 A more sophisticated project 217 6 37 3 2 Part 2 Variable definitions The intflags structure demon strates a way to allocate bit variables in memory Each of the interrupt service routines just sets one bit within that structure and the application s main loop then monitors the bits in order to act appropriately Like all variables that are used to communicate values between an interrupt service routine and the main application it is declared volatile p 322 The variable ee_pwm is not a variable in the classical C sense that could be used as an lvalue or within an expression to obtain its value Instead the _ attribute__ section eeprom marks it as belonging to the EEPROM section p 283 This section is merely used as a placeholder 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
389. sembler or linker have no chance to check the correct spelling of an interrupt function so it should be double checked When analyzing the resulting object file using avr objdump or avr nm a name like __vector_W should appear with N being a small integer number Note 8 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 5 avr libc and assembler programs 296 As explained in the section about special function registers p 158 the ac tual IO port address should be obtained using the macro _SFR_IO_ADDR The AT9081200 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 instruc tions 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 AT9051200 this can only be done by agreeing on a set of registers to be used exclusively i
390. sert avr_ assert 16 assert h 233 atan avr_math 34 atan2 avr math 34 atof avr stdlib 75 atoi avr stdlib 76 atoi S 234 atol avr stdlib 76 atol S 234 atomic h 234 ATOMIC BLOCK util atomic 171 ATOMIC FORCEON util atomic 171 ATOMIC RESTORESTATE util atomic 172 avr assert assert 16 avr boot boot is spm interrupt 98 boot lock bits set 98 boot lock bits set safe 99 boot lock fuse bits get 99 boot page erase 100 boot page erase safe 100 boot page fill 100 boot page fill safe 101 boot page write 101 boot page write safe 101 boot rww busy 101 boot rww enable 101 boot rww enable safe 102 boot signature byte get 102 boot spm busy 102 boot spm busy wait 102 boot spm interrupt disable 103 383 boot spm interrupt enable 103 BOOTLOADER SECTION 103 GET EXTENDED FUSE BITS 103 GET HIGH FUSE BITS 103 GET LOCK BITS 103 GET LOW FUSE BITS 103 avr eeprom _EEGET 105 _EEPUT 105 EEMEM 105 eeprom busy wait 105 eeprom is ready 105 eeprom read block 105 eeprom read byte 106 eeprom read dword 106 eeprom read word 106 eeprom write block 106 eeprom write byte 106 eeprom write dword 106 eeprom write word 106 avr_ errno EDOM 19 ERANGE 19 avr_ interrupts BADISR_vect 135 cli 136 EMPTY INTERRUPT 136 ISR 136 ISR ALIAS 136 ISR ALIASOF 137 ISR BLOCK 137 ISR NAKED 137 ISR NOBLOCK 138 reti 138 sei 138 SIGNAL 138 a
391. sets it up as a stream that is valid for stdio operations similar to one that has been obtained dynamically from fdevopen p 62 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 p 62 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 respectively Note No assignments to the standard streams will be performed by fdev setup stream p 60 If standard streams are to be used these need to be assigned by the user See also under Running stdio without malloc p 55 6 9 2 12 define FILE struct file FILE is the opaque structure that is passed around between the various standard IO functions 6 9 2 13 define getc _ stream fgetc _ stream Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 61 The macro getc used to be a fast macro implementation with a functionality identical to fgetc p 63 For space constraints in avr libc it is just an alias for fgetc 6 9 2 14 define getchar void fgetc stdin The macro getchar reads a character from stdin Return values and error handling is identical to fgetc p 63 6 9 2 15 define putc __c stream fputc __c stream The macro putc used to be a fast macro implementation with a functionality identical to fputc p 64 For space con
392. sh avr_math 34 crc16 h 241 ctype isalnum 17 isalpha 17 isascii 17 isblank 17 iscntrl 18 isdigit 18 isgraph 18 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX islower 18 isprint 18 ispunct 18 isspace 18 isupper 18 isxdigit 18 toascii 18 tolower 19 toupper 19 ctype h 241 delay h 242 delay basic h 242 Demo projects 190 deprecated items cbi 187 enable external int 187 inb 188 inp 188 INTERRUPT 188 outb 188 outp 189 sbi 189 timer enable int 189 disassembling 200 div avr_stdlib 77 div t 232 quot 232 rem 232 DTOSTR ALWAYS SIGN avr stdlib 75 DTOSTR PLUS SIGN avr stdlib 75 DTOSTR_UPPERCASE avr stdlib 75 dtostre avr stdlib 77 dtostrf avr stdlib 77 EDOM avr errno 19 EEMEM avr eeprom 105 eeprom busy wait avr_ eeprom 105 eeprom_is_ ready avr_ eeprom 105 eeprom read block avr eeprom 105 eeprom read byte avr eeprom 106 eeprom read dword avr eeprom 106 eeprom read word avr eeprom 106 eeprom write block avr eeprom 106 eeprom write byte avr eeprom 106 eeprom write dword avr eeprom 106 eeprom write word avr eeprom 106 EMPTY INTERRUPT avr interrupts 136 enable external int deprecated items 187 EOF avr stdio 58 ERANGE avr errno 19 errno h 243 390 Example using the two wire interface TWI 227 exit avr stdlib 78 exp avr math 34 fabs avr math 35 FAQ 321 fclose avr stdio 61 fdev
393. sing the GNU tools This is a short summary of the AVR specific aspects of using the GNU tools Normally the generic documentation of these tools is fairly large and maintained in texinfo files Command line options are explained in detail in the manual page 9 12 1 Options for the C compiler avr gcc 9 12 1 1 Machine specific options for the AVR The following machine specific options are recognized by the C compiler frontend In addition to the preprocessor macros indicated in the tables below the preprocessor will define the macros AVR and AVR to the value 1 when compiling for an AVR target The macro AVR will be defined as well when using the standard levels gnu89 default and gnu99 but not with c89 and c99 e mmcu architecture Compile code for architecture Currently known architectures are Architecture Macros AVR_ARCH__ 1__AVR_ASM_ONLY AVR_2_BYTE_PC__ 2 AVR ARCH 2 AVR 2 BYTE PC 2 AVR_ARCH__ 25_ AVR HAVE MOVW 1 AVR HAVE LPMX__ 1 AVR ARCH 3 AVR MEGA 5 AVR HAVE JMP CALL 4 AV AVR ARCH 31 AVR MEGA AVR HAVE RAMPZ 4 AVR HAV AVR ARCH 0 35 AVR MEGA 5 AVR HAVE JMP CALL 4 __ AV Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 12 Using the GNU tools 363 Macros AVR_ARCH__ 4__AVR_ENHANCED__ B AVR HAVE MOW Nm AV AVR ARCH 5 AVR MEGA B AVR ENHANCED B AVR_HAV AVR ARCH 51 AVR MEGA AVR_ENHANCED AVR_HAVE_M AVR_ARCH__ 6__AVR_MEGA___
394. sion 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 convention Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 114 The historical naming style might become deprecated in a future release so it is not recommended for new projects Note The ISR p 136 macro cannot really spell check the argument passed to them Thus by misspelling one of the names below in a call to ISR p 136 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 suspiciously looking name of a ISR p 136 function ie one that after macro replacement does not start with vector Vector Old vector Description Applicable for device name name ADC vect SIG ADC ADC Conver sion Complete ANALOG COMP 0 vect ANALOG COMP 1 vect ANALOG COMP 2 vect SIG_ Analog Com contpanan OR
395. sleep mode will be prepared and the SLEEP instruction will be scheduled immediately after an SEI instruction As the intruction right after the SEI is guaranteed to be executed before an interrupt could trigger it is sure the device will really be put to sleep Functions e void sleep enable void e void sleep disable void e void sleep cpu void 6 22 2 Function Documentation 6 22 2 1 void sleep cpu void Put the device into sleep mode The SE bit must be set beforehand and it is recommended to clear it afterwards 6 22 2 2 void sleep disable void Clear the SE sleep enable bit Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 23 lt avr version h gt avr libc version macros 164 6 22 2 3 void sleep enable void Set the SE sleep enable bit 6 23 lt avr version h gt avr libc version macros 6 23 1 Detailed Description include lt avr version h gt This header file defines macros that contain version numbers and strings de scribing 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 de velopment versions which use an odd minor number the string representation additionally gets the date code YYYYMMDD appended This file will also be included by lt avr io h p 247 gt That way portable tests can be implemented using lt avr io h p 247 gt that ca
396. sorted in ascending order according to a compar ison function pointed to by compar which requires two arguments pointing to the objects being compared The comparison function must return an integer less than equal to or greater than zero if the first argument is considered to be respectively less than equal to or greater than the second 6 10 4 19 int rand void The rand p 80 function computes a sequence of pseudo random integers in the range of 0 to RAND MAX as defined by the header file lt stdlib h p 263 gt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 81 The srand p 82 function sets its argument seed as the seed for a new sequence of pseudo random numbers to be returned by rand p 80 These sequences are repeatable by calling srand p 82 with the same seed value If no seed value is provided the functions are automatically seeded with a value of 1 In compliance with the C standard these functions operate on int arguments Since the underlying algorithm already uses 32 bit calculations this causes a loss of precision See random p 81 for an alternate set of functions that retains full 32 bit precision 6 10 4 20 int rand r unsigned long __ ct Variant of rand p 80 that stores the context in the user supplied variable located at ctx instead of a static library variable so the function becomes re entrant 6 10 4 21 long ra
397. 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 strnepy P p 154 function returns a pointer to the destination string dest 6 18 4 21 size_t strnlen_P PGM P src size_t len Determine the length of a fixed size string The strnlen P p 154 function is similar to strnlen p 94 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 len characters pointed to by src 6 18 4 22 char x strpbrk P const char s PGM P accept The strpbrk P p 154 function locates the first occurrence in the string s of any of the characters in the flash string accept This function is similar to strpbrk p 94 except that accept is a pointer to a string in program space Returns The strpbrk P p 154 function returns a pointer to the character in s that matches one of the characters in accept or NULL if no such character Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 155 is found The terminating zero is not considered as a part of string if one or both args are empty the result will NULL 6 18 4 23 PGM_P strrchr_ P PGM Ps int val Locate character in string The strrchr P p 155 function
398. ster could lose arbitration of the bus during any transmit operation A master that has lost arbitration is required by the protocol to immediately cease talking on the bus in particular it must not initiate a stop condition in order to not corrupt the ongoing transfer from the active master In this exam ple upon detecting a lost arbitration condition the entire transfer is going to be restarted This will cause a new start condition to be initiated which will normally be delayed until the currently active master has released the bus Note 10 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 231 Next the device slave is going to be reselected using a so called repeated start condition which is meant to guarantee that the bus arbitration will remain at the current master using the same slave address SLA but this time with read intent R W bit set to 1 in order to request the device slave to start transfering data from the slave to the master in the next packet Note 11 If the EEPROM device is still busy writing one or more cells after a previous write request it will simply leave its bus interface drivers at high impedance and does not respond to a selection in any way at all The master selecting the device will see the high level at SDA after transfering the SLA R W packet as a NACK to its selection request Thus the select process is simply started over effecti
399. straints in avr libc it is just an alias for fputc 6 9 2 16 define putchar c fputc __c stdout The macro putchar sends character c to stdout 6 9 2 17 define stderr iob 2 Stream destined for error output Unless specifically assigned identical to stdout If stderr should point to another stream the result of another fdevopen p 62 must be explicitly assigned to it without closing the previous stderr since this would also close stdout 6 9 2 18 define stdin _iob 0 Stream that will be used as an input stream by the simplified functions that don t take a stream argument The first stream opened with read intent using fdevopen p 62 will be assigned to stdin 6 9 2 19 define stdout iob 1 Stream that will be used as an output stream by the simplified functions that don t take a stream argument The first stream opened with write intent using fdevopen p 62 will be assigned to both stdin and stderr Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 62 6 9 3 Function Documentation 6 9 3 1 void clearerr FILE stream Clear the error and end of file flags of stream 6 9 3 2 int fclose FILE stream This function closes stream and disallows and further IO to and from it When using fdevopen p 62 to setup the stream a call to fclose p 62 is needed in order to free the internal resources allocated If the s
400. strncasecmp P p 153 function returns an integer less than equal to or greater than zero if s1 or the first n bytes thereof is found respectively to be less than to match or be greater than s2 A conse quence of the ordering used by strncasecmp P p 153 is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 6 18 4 18 char x strncat P char dest PGM P src size_t len Concatenate two strings The strncat P p 153 function is similar to strncat p 93 except that the src string must be located in program space flash Returns The strncat P p 153 function returns a pointer to the resulting string dest Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 154 6 18 4 19 int strncmp_P const char x s1 PGM P s2 size_t n The strnecmp P p 154 function is similar to strcmp P p 151 except it only compares the first at most n characters of sl and s2 Returns The strnecmp _ P p 154 function returns an integer less than equal to or greater than zero if sl or the first n bytes thereof is found respectively to be less than to match or be greater than s2 6 18 4 20 char x strncpy_P char dest PGM P src size tn The strnepy P p 154 function is similar to strepy P p 151 except that not more than n bytes of src are copied Thus if there is no null byte among the first n bytes of
401. support for these devices to be pro grammed in C since they do not have a RAM based stack Still it could be possible to program them in C see the FAQ p 341 for an option Note 2 The at94K devices are a combination of FPGA and AVR microcon troller 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 1 4 avr libc License 8 1 4 avr libc License avr libc can be freely used and redistributed provided the following license conditions are met Portions of avr libc are Copyright c 1999 2007 Keith Gudger Bjoern Haase Steinar Haugen Peter Jansen Reinhard Jessich Magnus Johansson Artur Lipowski Marek Michalkiewicz Colin O Flynn Bob Paddock Reiner Patommel Michael Rickman Theodore A Roth Juergen Schilling Philip Soeberg Anatoly Sokolov Nils Kristian Strom Michael Stumpf Stefan Swanepoel Eric B Weddington Joerg Wunsch Dmitry Xmelkov The Regents of the University of California All rights reserved Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaimer Redistributions in
402. t 122 f8 94 cli 124 ff cf rjmp 2 0x124 lt __stop_program gt 00000124 lt __stop_program gt 6 36 5 Linker Map Files avr objdump is very useful but sometimes it s necessary to see information about the link that can only be generated by the linker A map file contains this information A map file is useful for monitoring the sizes of your code and data It also shows where modules are loaded and which modules were loaded from libraries It is yet another view of your application To get a map file I usually add W1 Map demo map to my link command Relink the application using the following command to generate demo map a portion of Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 206 which is shown below avr gcc g mmcu atmega8 W1 Map demo map o demo elf demo o Some points of interest in the demo map file are rela plt rela plt text 0x00000000 0x126 vectors vectors 0x00000000 0x26 c avrdev avr libc avr libc avr lib avr4 atmega8 crtm8 o 0x00000000 __vectors 0x00000000 __vector_default vectors progmem gcc progmem 0x00000026 ALIGN 0x2 0x00000026 _ trampolines_start trampolines trampolines 0x00000026 0x0 linker stubs trampolines 0x00000026 _ trampolines_end jumptables jumptables lowtext lowtext 0x00000026 __ctors_start The text segment where program instructions are stored starts
403. t 6 5 2 10 define PRIdPTR PRId16 decimal printf format for intptr_t 6 5 2 11 define PRIi16 i integer printf format for int16_t 6 5 2 12 define PRIi32 li integer printf format for int32 t 6 5 2 13 define PRIi8 i integer printf format for int8 t 6 5 2 14 define PRIiFAST16 i integer printf format for int fast16_t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 25 6 5 2 15 define PRIiFAST32 li integer printf format for int fast32 t 6 5 2 16 define PRIiFASTS i integer printf format for int fast8 t 6 5 2 17 define PRIiLEAST16 i integer printf format for int_least16_t 6 5 2 18 define PRIiLEAST32 li integer printf format for int least32 t 6 5 2 19 define PRIiLEASTS i integer printf format for int least8 t 6 5 2 20 define PRIiPTR PRIi16 integer printf format for intptr_t 6 5 2 21 define PRIo16 o octal printf format for uint16 t 6 5 2 22 define PRIo32 lo octal printf format for uint32 t 6 5 2 23 define PRIo8 o octal printf format for uint8 t 6 5 2 24 define PRIoFAST16 o octal printf format for uint_fast16_t 6 5 2 25 define PRIoFAST32 lo octal printf format for uint fast32 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 26 6 5 2 26 define PRIoFASTS8 o octal printf format for uint fast8 t
404. t 49 uint64 t avr stdint 52 UINT8_C avr stdint 49 UINT8 MAX avr stdint 49 uint8 t avr stdint 52 uint_farptr_t avr inttypes 31 UINT FAST16 MAX avr stdint 49 401 uint fastl6 t avr stdint 52 UINT FAST32 MAX avr stdint 49 uint fast32 t avr stdint 52 UINT FAST64 MAX avr stdint 49 uint fast64 t avr stdint 52 UINT_FAST8 MAX avr stdint 49 uint fast8 t avr stdint 52 UINT LEASTI6 MAX avr stdint 49 uint leastl6 t avr stdint 52 UINT LEAST32 MAX avr stdint 49 uint least32 t avr stdint 52 UINT LEAST64 MAX avr stdint 49 uint least64 t avr stdint 52 UINT LEASTS MAX avr stdint 49 uint least8 t avr stdint 53 UINTMAX C avr stdint 50 UINTMAX MAX avr stdint 50 uintmax_t avr stdint 53 UINTPTR MAX avr stdint 50 uintptr_t avr stdint 53 ultoa avr stdlib 83 ungetc avr stdio 66 USE_ 2X util_ setbaud 181 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX Using the standard IO facilities 219 util_ atomic ATOMIC_ BLOCK 171 ATOMIC FORCEON 171 ATOMIC RESTORESTATE 172 NONATOMIC BLOCK 172 NONATOMIC FORCEOFF 172 NONATOMIC RESTORESTATE 172 util_ cre ercl6 update 174 ere ceitt update 174 ere ibutton update 175 ere xmodem update 175 util delay delay ms 177 delay us 177 util delay basic delay loop 1 178 delay loop 2 178 util_ parity parity even bit 179 util_ setbaud BAUD_ TOL 181 UBRR_ VALUE 181 UBRRH_ VALUE 181 UBRRL_
405. t void The abort p 76 function causes abnormal program termination to occur This realization disables interrupts and jumps to _ exit function with argument equal to 1 In the limited AVR environment execution is effectively halted by entering an infinite loop 6 10 4 2 int abs int The abs p 76 function computes the absolute value of the integer i Note The abs p 76 and labs p 79 functions are builtins of gcc 6 10 4 3 double atof const char nptr The atof p 76 function converts the initial portion of the string pointed to by nptr to double representation It is equivalent to calling strtod nptr char 0 6 10 4 4 int atoi const char s Convert a string to an integer The atoi p 76 function converts the initial portion of the string pointed to by s to integer representation In contrast to int strtol s char NULL 10 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 10 lt stdlib h gt General utilities 77 this function does not detect overflow errno is not changed and the result value is not predictable uses smaller memory flash and stack and works more quickly 6 10 4 5 long atol const char s Convert a string to a long integer The atol p 77 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 err
406. t and pins used for the HD44780 LCD driver 6 38 3 3 hd44780 h This file describes the public interface of the low level LCD driver that interfaces to the HD44780 LCD controller Public functions are available to initialize the controller into 4 bit mode to wait for the controller s busy bit to be clear and to read or write one byte from or to the controller As there are two different forms of controller IO one to send a command or receive the controller status RS signal clear and one to send or receive data to from the controller s SRAM RS asserted macros are provided that build on the mentioned function primitives Finally macros are provided for all the controller commands to allow them to be used symbolically The HD44780 datasheet explains these basic functions of the controller in more detail 6 38 3 4 hd44780 c This is the implementation of the low level HD44780 LCD controller driver Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 38 Using the standard IO facilities 224 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 p 223 The hd44780_pulse_e function asserts a short pulse to the controller s E enable 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 i
407. t could probably be done easily using the inline assem bler p 298 facility of the compiler Although avr libe is primarily targeted to support programming AVR micro controllers using the C and C language there s limited support for direct assembler usage as well The benefits of it are e Use of the C preprocessor and thus the ability to use the same symbolic constants that are available to C programs as well as a flexible macro concept that can use any valid C identifier as a macro whereas the as sembler s macro concept is basically targeted to use a macro in place of an assembler instruction e Use of the runtime framework like automatically assigning interrupt vec tors For devices that have RAM initializing the RAM variables p 284 can also be utilized 9 5 2 Invoking the compiler For the purpose described in this document the assembler and linker are usually not invoked manually but rather using the C compiler frontend avr gcc that in turn will call the assembler and linker as required This approach has the following advantages e There is basically only one program to be called directly avr gcc regard less of the actual source language used e The invokation of the C preprocessor will be automatic and will include the appropriate options to locate required include files in the filesystem e The invokation of the linker will be automatic and will include the ap propriate options to locate additional libr
408. t of object modules gt The r command switch tells the program to insert the object modules into the archive with replacement The c command line switch tells the program to create the archive And the s command line switch tells the program to write an object file index into the archive or update an existing one This last switch is very important as it helps the linker to find what it needs to do its job Note The command line switches are case sensitive There are uppercase switches that have completely different actions MFile and the WinAVR distribution contain a Makefile Template that in cludes 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 immediately following the 1 is the unique part of the library filename that the linker will link in For example if you use 1m this will expand to the library filename libm a which happens to be the math library included in avr libc If you use this on your linker command line iprintf_f1t then the linker will look for a library called Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 8 Benchmarks 314 libprintf_flt a This is why naming your library is so important when you create it
409. tandard Integer Types 48 6 8 2 26 define INT LEAST64 MIN INT64_ MIN smallest negative value an int least64 t can hold 6 8 2 27 define INT LEASTS MAX INT8_ MAX largest positive value an int least8 t can hold 6 8 2 28 define INT LEAST8 MIN INT8 MIN smallest negative value an int least8 t can hold 6 8 2 29 define INTMAX C value CONCAT value LL define a constant of type intmax_t 6 8 2 30 define INTMAX MAX INT64 MAX largest positive value an intmax t can hold 6 8 2 31 define INTMAX MIN INT64 MIN smallest negative value an intmax t can hold 6 8 2 32 define INTPTR MAX INT16 MAX largest positive value an intptr t can hold 6 8 2 33 define INTPTR_ MIN INT16 MIN smallest negative value an intptr t can hold 6 8 2 34 define PTRDIFF MAX INT16 MAX largest positive value a ptrdiff_t can hold 6 8 2 35 define PTRDIFF MIN INT16 MIN smallest negative value a ptrdiff_t can hold 6 8 2 36 define SIG ATOMIC MAX INT8 MAX largest positive value a sig atomic t can hold Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 49 6 8 2 37 define SIG ATOMIC MIN INT8 MIN smallest negative value a sig atomic t can hold 6 8 2 38 define SIZE MAX CONCAT INT16 MAX U largest value a size t can hold 6 8 2 39 define UINT16 C value CONCAT value U define a constant of type uint16 t 6 8 2 40 define UINT16 MAX CONCAT INT16 MAX U x 2U
410. tandard keyword to declare a variable in Program Memory _ flash int mydata AVR GCC uses Variable Attributes to achieve the same effect int mydata __attribute__ progmem Note See the GCC User Manual for more information about Variable Attributes avr libc provides a convenience macro for the Variable Attribute 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 p 250 gt This is the canonical method for defining a variable in Program Space To read back flash data use the pgm read x macros defined in lt avr pgmspace h p 250 gt All Program Memory handling macros are de fined there There is also a way to create a method to define variables in Program Memory that is common between the two compilers IAR and AVR GCC Create a header file that has these definitions Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 9 Porting From IAR to AVR GCC 320 if defined __ICCAVR__ IAR C Compiler define FLASH_DECLARE x __flash x endif if defined __GNUC__ GNU Compiler define FLASH_DECLARE x x __attribute__ __progmem__ endif This code snippet checks for the IAR compiler or for the GCC compiler and defines a macro FLASH_DECLARE x that will declare a variable in Program Memory using the appropriate method based on the compiler that is being
411. tatic inline voidtimer enable int unsigned char ints e define enable external int mask EICR mask e define INTERRUPT signame e define INTR_ATTRS used Obsolete IO macros Back in a time when AVR GCC and avr libe could not handle IO port access in the direct assignment form as they are handled now all IO port access had to be done through specific macros that eventually resulted in inline assembly instructions performing the desired action These macros became obsolete as reading and writing IO ports can be done by simply using the IO port name in an expression and all bit manipulation including those on IO ports can be done using generic C bit manipulation operators The macros in this group simulate the historical behaviour While they are supposed to be applied to IO ports the emulation actually uses standard C methods so they could be applied to arbitrary memory locations as well e 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 32 2 Define Documentation 6 32 2 1 define cbi port bit port amp 1 lt lt bit Deprecated Clear bit in IO port port Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 32 lt compat deprecated h gt Deprecated items 188 6 32 2 2 define enable external
412. tdlib h 263 strcasecmp S 266 strcasecmp P S 266 strcasestr S 266 strcat S 266 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 4 1 avr libc File List 13 strcat_P S 266 strchr S 266 strchr P S 266 strchrnul S 266 strchrnul P S 266 strcmp S 266 stremp P S 266 strepy S 266 strepy P S 266 strcspn S 266 strespn P S 266 string h 266 strlcat S 269 strleat P S 269 strlepy S 269 strlepy P S 269 strlen S 269 strlen P S 269 striwr S 269 strncasecmp S 269 strncasecmp P S 269 strncat S 269 strncat_P S 269 strncmp S 269 strnemp P S 269 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 5 avr libc Page Index strnepy S strnepy P S strnlen S strnlen P S strpbrk S strpbrk P S strrchr S strrchr_ P S strrev S strsep S strsep P S strspn S strspn P S strstr S strstr P S strtok r S strupr S util twi h wdt h 5 avr libc Page Index 5 1 avr libc Related Pages Here is a list of all related documentation pages Toolchain Overview Memory Areas and Using malloc Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 14 269 269 269 269 269 269 269 269 269 269 269 269 269 269 269 269 269 269 271 271 277 6 avr libc Module Documentation Memory Sections Data in Program Space avr libc and assembler programs Inline Assembler Cookbook How to Build a Library Benchmarks Porting From IAR to AVR GCC Frequently Asked Questio
413. ted NONATOMIC RESTORESTATE and NONATOMIC_FORCEOFF 6 25 2 5 define NONATOMIC FORCEOFF This is a possible parameter for NONATOMIC_BLOCK When used it will cause the NONATOMIC BLOCK to force the state of the SREG register on exit disabling the Global Interrupt Status flag bit This saves on flash space as the previous value of the SREG register does not need to be saved at the start of the block Care should be taken that NONATOMIC FORCEOFF is only used when it is known that interrupts are disabled before the block s execution or when the side effects of disabling global interrupts at the block s completion are known and understood 6 25 2 6 define NONATOMIC RESTORESTATE This is a possible parameter for NONATOMIC_ BLOCK When used it will cause the NONATOMIC_ BLOCK to restore the previous state of the SREG register saved before the Global Interrupt Status flag bit was enabled The Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 26 lt util crcl6 h gt CRC Computations 173 net effect of this is to make the NONATOMIC_BLOCK s contents guaranteed non atomic without changing the state of the Global Interrupt Status flag when execution of the block completes 6 26 lt util crcl6 h gt CRC Computations 6 26 1 Detailed Description include lt util crc16 h gt This header file provides a optimized inline functions for calculating cyclic re dundancy checks CRC using common polynomials References
414. tem has only a granularity of 2 seconds for maintaining a file s timestamp and it seems that some MS DOS derivative Win9x perhaps rounds up the current time to the next second when calculating the timestamp of an updated file in case the current time cannot be represented in FAT s terms this causes a Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 342 situation where make sees a file coming from the future Since all make decisions are based on file timestamps and their dependencies make warns about this situation Solution don t use inferior file systems operating systems Neither Unix file systems nor HPFS aka NTFS do experience that problem Workaround after saving the file wait a second before starting make Or simply ignore the warning If you are paranoid execute a make clean all to make sure everything gets rebuilt In networked environments where the files are accessed from a file server this message can also happen if the file server s clock differs too much from the network client s clock In this case the solution is to use a proper time keeping protocol on both systems like NTP As a workaround synchronize the client s clock frequently with the server s clock Back to FAQ Index p 321 9 10 25 Why are many interrupt flags cleared by writing a logical 1 Usually each interrupt has its own interrupt flag bit in some control register indic
415. ternal SRAM the following command line would cause the linker to place the data segment at address 0x2000 in the SRAM avr gcc mmcu atmega128 o foo out Wl Tdata 0x802000 See the explanation of the data section p 282 for why 0x800000 needs to be added to the actual value Note that the stack will still remain in internal RAM through the symbol __stack that is provided by the run time startup code This is probably a good idea anyway since internal RAM access is faster and even required for some early devices that had hardware bugs preventing them from using a stack in external RAM Note also that the heap for malloc p 80 will still be placed after all the variables in the data section so in this situation no stack heap collision can occur In order to relocate the stack from its default location at the top of interns RAM the value of the symbol __stack can be changed on the linker command line As the linker is typically called from the compiler frontend this can be achieved using a compiler option like W1 defsym __stack 0x8003ff The above will make the code use stack space from RAM address 0x3ff down wards The amount of stack space available then depends on the bottom address of internal RAM for a particular device It is the responsibility of the applica tion to ensure the stack does not grow out of bounds as well as to arrange for the stack to not collide with variable allocations made by the compiler sections
416. that this document provides enough information to get a new AVR developer up to speed quickly using the freely available development tools binutils gcc avr libe 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 addi tion to the devleopers of avr libc subscribe to the list so you will usually Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 1 2 General information about this library 2 be able to get your problem resolved You can subscribe to the list at http lists nongnu org mailman listinfo avr gcc list Before post ing to the list you might want to try reading the Frequently Asked Ques tions p 321 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 stan dards while implementing this library Commonly this refers to the C library as described by the ANSI X3 159 1989 and ISO IEC 9899 1990 ANSI C standard as well as parts of their successor ISO IEC 9899 1999 C99 Some additions have b
417. 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 The job of the librarian program is simple aggregate a list of object modules into a single library archive and create an index for the linker to use The name that you create for the library filename must follow a specific pattern libname a The name part is the unique part of the filename that you create It makes it easier if the name part relates to what the library is about This name part must be prefixed by lib and it must have a file extension of a for archive The reason for the special form of the filename is for how the library gets used by the toolchain as we will see later on Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 7 How to Build a Library 313 Note The filename is case sensitive Use a lowercase lib prefix and a lowercase a as the file extension The command line is fairly simple avr ar rcs lt library name gt lt lis
418. the compiler option mint8 is in effect 6 8 3 26 typedef uint8 t uint least8 t unsigned int with at least 8 bits 6 8 3 27 typedef uint64 t uintmax t largest unsigned int available Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 54 6 8 3 28 typedef uint16_t uintptr_t Unsigned pointer compatible type 6 9 lt stdio h gt Standard IO facilities 6 9 1 Detailed Description include lt stdio h gt Introduction to the Standard IO facilities This file declares the standard IO facilities that are implemented in avr 1ibc Due to the nature of the under lying hardware only a limited subset of standard IO is implemented There is no actual file implementation 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 po tential users of this implementation should be warned the printf and scanf families of functions although usually associated with presumably simple things like the famous Hello world program are actually fairly complex which causes their inclusion to eat up a fair amount of code space Also they are not fast due to the nature of interpreting the for
419. the first byte after the so called start condition The LSB of that byte is R W i e it determines whether the request to the slave is to read or write data during the next cycles There is also an option to have devices using 10 bit addresses but that is not covered by this example Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 39 Example using the two wire interface TWI 228 6 39 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 implementation is kept simple in order to concentrate on the steps that are required to talk to a TWI slave so all processing is done in polled mode waiting for the TWI interface to indicate that the next processing step is due by setting the TWINT interrupt bit If it is desired to have the entire TWI communication happen in background all this can be implemented in an interrupt controlled way where only the start condition needs to be triggered from outside the interrupt routine There is a variety of slave devices available that can be connected to a TWI bus For the purpose of this example an EEPROM device out of the industry standard 24C aa series has been chosen where xz 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
420. 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 p 143 becomes very handy for declaring these format strings Running stdio without malloc p 80 By default fdevopen p 62 requires malloc p 80 As this is often not desired in the limited environment of a microcontroller an alternative option is provided to run completely without malloc p 80 The macro fdev setup stream p 60 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 56 _FDEV_SETUP_WRITE static int uart_putchar char c FILE stream if c n uart_putchar r stream loop_until_bit_is_set UCSRA UDRE UDR c return 0 int main void init_uart stdout amp mystdout printf Hello world n return 0 This example uses the initializer form FDEV_SETUP_STREAM p 60
421. ther low currents when sourc ing current 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 198 ATmega 128 however Atmel has drastically increased the IO source ca pability 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 36 2 The Source Code FF amp HF GR THE BEER WARE LICENSE Revision 42 lt joerg FreeBSD ORG gt wrote this file As long as you retain this notice you can do whatever you want with this stuff If we meet some day and you think this stuff is worth it you can buy me a beer in return Joerg Wunsch Simple AVR demonstration Controls a LED that can be directly connected from 0C1 0C1A to GND The brightness of the LED is controlled with the PWM After each period of the PWM the PWM value is either incremented or decremented that s all Id demo c v 1 9 2006 01 05 21 30 10 joerg_wunsch Exp include lt inttypes h gt include lt avr io h gt include lt avr interrupt h gt include lt avr sleep h gt include iocompat h Note 1 enum UP DOWN ISR TIMER1_OVF_vect Note 2 static uint16_t pum Note 3 static uint8_t direction switch direction Note 4
422. tion i e isdigit p 18 returns true if its argument is any value 0 though 9 inclusive If the input is not an unsigned char value all of this function return false e int isalnum int __c e int isalpha int _c e int isascii int c e int isblank int __c e int iscntrl int c e int isdigit int _c e int isgraph int __c e int islower int c e int isprint int _c e int ispunct int _c e int isspace int _c e int isupper int __c e int isxdigit int _c Character convertion routines This realization permits all possible values of integer argument The toascii p 19 function clears all highest bits The tolower p 19 and toupper p 19 functions return an input argument as is if it is not an unsigned char value Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 3 lt ctype h gt Character Operations 18 e int toascii int _c e int tolower int _c e int toupper int __c 6 3 2 Function Documentation 6 3 2 1 int isalnum int __ c Checks for an alphanumeric character It is equivalent to isalpha c isdigit c 6 3 2 2 int isalpha int __ Checks for an alphabetic character It is equivalent to isupper c islower c 6 3 2 3 int isascii int __ c Checks whether c is a 7 bit unsigned char value that fits into the ASCII character set 6 3 2 4 int isblank int __c Checks for a blank character that is a space or a tab 6 3 2 5 int iscntrl
423. to a string in program space Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 18 lt avr pgmspace h gt Program Space Utilities 150 6 18 4 5 PGM VOID P memrchr P PGM VOID P sre int val size t len The memrchr P p 150 function is like the memchr P p 149 func tion except that it searches backwards from the end of the len bytes pointed to by src instead of forwards from the front Glibc GNU extension Returns The memrchr P p 150 function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 6 18 4 6 int strcasecmp P const char s1 PGM_P s2 Compare two strings ignoring case The strcasecmp P p 150 function compares the two strings s1 and s2 ignoring the case of the characters Parameters s1 A pointer to a string in the devices SRAM s2 A pointer to a string in the devices Flash Returns The strcasecmp P p 150 function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcasecmp P p 150 is that if s1 is an initial substring of s2 then si is considered to be less than s2 6 18 4 7 char strcasestr P const char x s1 PGM P s2 This funtion is similar to strcasestr p 90 except that s2 is pointer to a string in program space 6 18 4 8 char strcat P char x dest PGM P src Th
424. tream has been set up using fdev setup stream p 60 or FDEV SETUP STREAM p 60 use fdev close p 59 instead It currently always returns 0 for success 6 9 3 3 FILE fdevopen int char FILE x put int FILE x get This function is a replacement for fopen It opens a stream for a device where the actual device implementation needs to be provided by the application If successful a pointer to the structure for the opened stream is returned Reasons for a possible failure currently include that neither the put nor the get argument have been provided thus attempting to open a stream with no IO intent at all or that insufficient dynamic memory is available to establish a new stream If the put function pointer is provided the stream is opened with write intent The function passed as put shall take two arguments the first a character to write to the device and the second a pointer to FILE and shall return 0 if the output was successful and a nonzero value if the character could not be sent to the device If the get function pointer is provided the stream is opened with read intent The function passed as get shall take a pointer to FILE as its single argument and return one character from the device passed as an int type If an error occurs when trying to read from the device it shall return _FDEV_ERR If an end of file condition was reached while reading from the device FDEV EOF shall be returned If both fu
425. ture is not used There should be no need to modify linker scripts anymore except for some very special cases It is best to leave __stack at its default value end of internal SRAM faster and required on some devices like ATmega161 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 p 282 There is also an example for Using Sections in C Code p 286 Note that in C code any such function would preferrably be placed into section init3 as the code in init2 ensures the internal register __zero_reg__ is already cleared Back to FAQ Index p 321 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 10 Frequently Asked Questions 325 9 10 6 What is all this _BV stuff about When performing low level output work which is a very central point in mi crocontroller programming it is quite common that a particular bit needs to be set or cleared in some IO register While the device documentation pro vides mnemonic names for the various bits in the IO registers and the AVR device specific IO definitions p 139 reflect these names in definitions for numerical constants a way is needed to convert a bit number usually within a byte register into a byte value that can be assigned directly to the register However sometimes the direct bit numbers are needed as well e g in an SBI instruction so the definitions cannot
426. two digits if the value is zero the exponent is 00 e fF The double argument is rounded and converted to decimal notation in the format ddd ddd where the number of digits after the decimal point character is equal to the precision specification If the precision is missing it is taken as 6 if the precision is explicitly zero no decimal point character appears If a decimal point appears at least one digit appears before it Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 9 lt stdio h gt Standard IO facilities 69 e gG The double argument is converted in style f or e or F or E for G conversions The precision specifies the number of significant digits If the precision is missing 6 digits are given if the precision is zero it is treated as 1 Style e is used if the exponent from its conversion is less than 4 or greater than or equal to the precision Trailing zeros are removed from the fractional part of the result a decimal point appears only if it is followed by at least one digit e S Similar to the s format except the pointer is expected to point to a program memory ROM string instead of a RAM string In no case does a non existent or small field width cause truncation of a numeric field if the result of a conversion is wider than the field width the field is expanded to contain the conversion result Since the full implementation of all the mentioned features becomes fairly large three differ
427. u would use this macro as such boot_lock_bits_set _BV BLB11 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 100 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 6 12 2 3 define boot lock bits set safe lock bits Value do boot_spm_busy_wait eeprom busy wait boot lock bits set lock bits while 0 EE Same as boot lock bits set p 99 except waits for eeprom and spm operations to complete before setting the lock bits 6 12 2 4 define boot lock fuse bits get address Value __extension__ uint8_t __result _ asm__ __volatile__ Idi r30 3 n t Idi r31 O n t sts 1 2 n t lpm 40 Z n t r result i _SFR_MEM_ADDR __SPM_REG r uint8 t BOOT LOCK BITS SET M address ro r30 r31 __result H PE Lp E E EE E a GE AE A 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 i e a bit returned as 0 means the corresponding fuse or lock bit is programmed Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 12 lt avr boot h gt Bootloader Support Utilities 101 6 12 2 5 def
428. uble __x double frexp double ___x int __pexp double Idexp double ___x int __exp double exp double __ x double cosh double __x double sinh double __ x double tanh double __ x double acos double ___x double asin double __x double atan double __ x double atan2 double __ y double ___x double log double __x double log10 double __x double pow double __ x double ___y int isnan double __x int isinf double __ x double square double __x static double copysign double __x double __y double fdim double ___ x double __y double fma double __ x double __ y double __z double fmax double x double y double fmin double ___x double __y int signbit double __x double trunc double __x static int isfinite double _ x double hypot double __ x double ___y Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 6 lt math h gt Mathematics 34 e double round double __x e long lround double __ x e long Irint double __x 6 6 2 Define Documentation 6 6 2 1 define INFINITY __ builtin inf INFINITY constant 6 6 2 2 define M PI 3 141592653589793238462643 The constant pi 6 6 2 3 define M SQRT2 1 4142135623730950488016887 The square root of 2 6 6 2 4 define NAN __ builtin_ nan NAN constant 6 6 3 Function Documentation 6 6 3 1 double acos double ___ The acos p 34 function computes the principal value of the arc cosine of __z The retu
429. ude lt avr io h p 247 gt You can print out the contents of the fuse section in the ELF file by using this command line avr objdump s j fuse lt ELF file gt The section contents shows the address on the left then the data going from lower address to a higher address left to right 6 15 lt avr interrupt h gt Interrupts 6 15 1 Detailed Description Note This discussion of interrupts was originally taken from Rich Neswold s doc ument See Acknowledgments p 379 Introduction to avr libc s interrupt handling It s nearly impossible to find compilers that agree on how to handle interrupt code Since the C language tries to stay away from machine dependent details each compiler writer is forced to design their method of support In the AVR GCC environment the vector table is predefined to point to in terrupt routines 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 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 15 lt avr interrupt h gt Interrupts 111 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 save
430. ue an int8 t can hold 6 8 2 13 define INT_FAST16_MAX INT16_MAX largest positive value an int fast16 t can hold 6 8 2 14 define INT FAST16 MIN INT16 MIN smallest negative value an int fast16 t can hold Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt Standard Integer Types 47 6 8 2 15 define INT FAST32 MAX INT32 MAX largest positive value an int fast32 t can hold 6 8 2 16 define INT FAST32 MIN INT32 MIN smallest negative value an int fast32 t can hold 6 8 2 17 define INT FAST64 MAX INT64 MAX largest positive value an int fast64 t can hold 6 8 2 18 define INT FAST64 MIN INT64 MIN smallest negative value an int fast64 t can hold 6 8 2 19 define INT FAST8 MAX INT8_ MAX largest positive value an int fast8 t can hold 6 8 2 20 define INT FAST8 MIN INT8 MIN smallest negative value an int fast8 t can hold 6 8 2 21 define INT LEASTI6 MAX INT1I6 MAX largest positive value an int least16 t can hold 6 8 2 22 define INT LEAST16 MIN INT16 MIN smallest negative value an int least16 t can hold 6 8 2 23 define INT LEAST32 MAX INT32 MAX largest positive value an int least32 t can hold 6 8 2 24 define INT LEAST32 MIN INT32 MIN smallest negative value an int least32 t can hold 6 8 2 25 define INT LEAST64 MAX INT64 MAX largest positive value an int least64 t can hold Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 8 lt stdint h gt S
431. uint32 t 6 5 2 45 define PRIX8 X uppercase hexadecimal printf format for uint8 t 6 5 2 46 define PRIx8 x hexadecimal printf format for uint8 t 6 5 2 47 define PRIXFAST16 X uppercase hexadecimal printf format for uint fast16 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 28 6 5 2 48 define PRIxFAST16 x hexadecimal printf format for uint_fast16_t 6 5 2 49 define PRIXFAST32 1X uppercase hexadecimal printf format for uint fast32 t 6 5 2 50 define PRIxFAST32 lx hexadecimal printf format for uint fast32 t 6 5 2 51 define PRIXFASTS8 X uppercase hexadecimal printf format for uint fast8 t 6 5 2 52 define PRIxFASTS x hexadecimal printf format for uint fast8 t 6 5 2 53 define PRIXLEAST16 X uppercase hexadecimal printf format for uint_least16_t 6 5 2 54 define PRIxLEASTI16 x hexadecimal printf format for uint least16 t 6 5 2 55 define PRIXLEAST32 IX uppercase hexadecimal printf format for uint least32 t 6 5 2 56 define PRIxLEAST32 lx hexadecimal printf format for uint least32 t 6 5 2 57 define PRIXLEASTS8 X uppercase hexadecimal printf format for uint least8 t 6 5 2 58 define PRIxLEASTS x hexadecimal printf format for uint least8 t Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 5 lt inttypes h gt Integer Type conversions 29 6 5 2 59 define PRIXPTR PRI
432. unction compares the two strings s1 and s2 ignoring the case of the characters Returns The strcasecmp p 90 function returns an integer less than equal to or greater than zero if s1 is found respectively to be less than to match or be greater than s2 A consequence of the ordering used by strcasecmp p 90 is that if s1 is an initial substring of s2 then s1 is considered to be less than s2 6 11 3 13 char x strcasestr const char s1 const char x s2 The strcasestr p 90 function finds the first occurrence of the substring s2 in the string s1 This is like strstr p 96 except that it ignores case of alphabetic symbols in searching for the substring Glibc GNU extension Returns The strcasestr p 90 function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of zero length the function returns s1 6 11 3 14 char x strcat char x dest const char src Concatenate two strings The strcat p 90 function appends the src string to the dest string over writing the 0 character at the end of dest and then adds a terminating 0 character The strings may not overlap and the dest string must have enough space for the result Returns The strcat p 90 function returns a pointer to the resulting string dest 6 11 3 15 char x strchr const char src int val Locate character in string The strchr p 90 functi
433. up the C code contains an ISR for PCINTO At each pin change interrupt it will first be analyzed whether the interrupt was caused by a rising or a falling edge In case of the rising edge timer 1 will be started with a prescaler of 16 after clearing the current timer value Then at the falling edge the current timer value will be recorded and timer 1 stopped the pin change interrupt will be suspended and the upper layer will be notified that the incoming PWM measurement data is available Function main first initializes the hardware by calling ioinit and then waits until some incoming PWM value is available If it is the output PWM will be adjusted by computing the relative value of the incoming PWM Finally the pin change interrupt is re enabled and the CPU is put to sleep 6 35 2 2 project h In order for the interrupt service routines to be as fast as possible some of the CPU registers are set aside completely for use by these routines so the compiler would not use them for C code This is arranged for in project h The file is divided into one section that will be used by the assembly source code and another one to be used by C code The assembly part is distinguished by the preprocessing 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 repla
434. usefully be made as byte values in the first place So in order to access a particular bit number as a byte value use the _BV p 161 macro Of course the implementation of this macro is just the usual bit shift which is done by the compiler anyway thus doesn t impose any run time penalty so the following applies _BV 3 gt 1 lt lt 3 gt 0x08 However using the macro often makes the program better readable BV stands for bit value in case someone might ask you Example clock timer 2 with full IO clock CS2z 0b001 toggle OC2 output on compare match COM2x 0b01 and clear timer on compare match CTC2 1 Make OC2 PD7 an output TCCR2 _BV COM20 BV CTC2 _BV CS20 DDRD _BV PD7 Back to FAQ Index p 321 9 10 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 automatically 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 e Obviously none of the C related standard functions classes and tem plate classes are available Generated on Wed Jun
435. usually the timer runs at full CPU clock for 10 bit PWMs while it runs on a prescaled clock for 8 bit PWMs Note 2 ISR p 136 is a macro that marks the function as an interrupt routine In this case the function will get called when timer 1 overflows Setting up interrupts is explained in greater detail in lt avr interrupt h gt Inter rupts p 110 Note 3 The PWM is being used in 10 bit mode so we need a 16 bit variable to remember the current value Note 4 This section determines the new value of the PWM Note 5 Here s where the newly computed value is loaded into the PWM register Since we are in an interrupt routine it is safe to use a 16 bit assignment to the register Outside of an interrupt the assignment should only be performed with interrupts disabled if there s a chance that an interrupt routine could also access this register or another register that uses TEMP see the appropriate FAQ entry p 327 Note 6 This routine gets called after a reset It initializes the PWM and enables interrupts Note 7 The main loop of the program does nothing all the work is done by the interrupt routine The sleep_mode puts the processor on sleep until the next interrupt to conserve power Of course that probably won t be noticable as we are still driving a LED it is merely mentioned here to demonstrate the basic principle Note 8 Early AVR devices saturate their outputs at ra
436. ut file so we need to do a little more processing The next step is to extract portions of the binary and save the information into hex files The GNU utility that does this is called avr objcopy The ROM contents can be pulled from our project s binary and put into the file demo hex using the following command avr objcopy j text j data 0 ihex demo elf demo hex The resulting demo hex file contains 100000001 2CO8CCO8BCO8AC089C088C087C086CO1F 1000100025C084C083C082C081C080C07FCO7EC034 100020007DC07CC07BC011241FBECFE5D4EODEBF05 10003000CDBF10EOAOE6BOEOEG6E2F1E002C005903E 100040000D92A036B107D9F710E0A0E6B0E001C0EC 100050001D92A336B107E1F74DD061C01F920F92F8 100060000FB60F9211242F933F938F9380916000CE 100070008823C1F420916100309162002F5F3F4FCF 10008000309362002093610083E02F3F380709F12D 100090003BBD2ABD8F913F912F910F900FBEOF90C6 1000A0001F901895813029F02091610030916200F5 LOOOBOOOEFCF2091610030916200215030403093A9 1000C0006200209361002115310511F71092600044 1000D000DFCF81E080936000DBCF83E88FBD8EB5FA 1000E00081608EBD1BBC1ABC82E087BB84E089BFE7 1000F0007894089583E88FBD8EB581608EBD1BBC5A 100100001ABC82E087BB84E089BF789485B7 806899 1001100085BF889585B78F7785BFF8CF71CFF89465 0601200000COF894FFCFBF 00000001FF The j option indicates that we want the information from the text and data segment extracted If we specify the EEPROM segment we can generate a hex file that can be used to program the EEPROM avr o
437. v_t Struct Reference 7 2 1 Detailed Description Result type for function Idiv p 79 Data Fields e long quot e long rem 7 2 2 Field Documentation 7 2 2 1 long ldiv t quot The Quotient 7 2 2 2 long Idiv_t rem The Remainder The documentation for this struct was generated from the following file e stdlib h 8 avr libc File Documentation 8 1 assert h File Reference 8 1 1 Detailed Description Defines e define assert expression Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 8 2 atoi S File Reference 234 8 2 atoi S File Reference 8 2 1 Detailed Description 8 3 atol S File Reference 8 3 1 Detailed Description 8 4 atomic h File Reference 8 4 1 Detailed Description Defines e define UTIL ATOMIC H 1 e define ATOMIC BLOCK type e define NONATOMIC_ BLOCK type e define ATOMIC RESTORESTATE e define ATOMIC FORCEON e define NONATOMIC RESTORESTATE e define NONATOMIC_FORCEOFF 8 5 boot h File Reference 8 5 1 Detailed Description Defines e define AVR BOOT H 1 e define BOOTLOADER SECTION __attribute__ section bootloader e define COMMON ASB RWWSB e define COMMON ASRE RWWSRE e define BLB12 5 e define BLB11 4 e define BLBO2 3 e define BLBO1 2 e define boot spm interrupt enable __SPM_REG uint8 t BV SPMIE e define boot spm interrupt disable SPM REG amp uint8 t BV SPMIE e define boot is spm interrupt SPM REG amp uint8
438. vely 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 responds with an ACK bit SDA driven low in order to request another data transfer from the slave or it can leave the SDA line high NACK indicating to the slave that it is going to stop the transfer now Assertion of ACK is handled by setting the TWEA bit in TWCR when starting the current transfer Note 13 The control word sent out in order to initiate the transfer of the next data packet is initially set up to assert the TWEA bit During the last loop iteration TWEA is de asserted so the client will get informed that no further transfer is desired Note 14 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 7 avr libc Data Structure Documentation 232 Except in the case of lost arbitration all bus transactions must properly be termi
439. vr inttypes int farptr t 31 PRId16 23 PRId32 23 PRId8 23 PRIdFAST16 23 PRIdFAST32 23 PRIdFASTS 23 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen INDEX PRIdLEAST 16 23 PRIdLEAST32 23 PRIdLEASTS 23 PRIdPTR 23 PRIi16 24 PRIi32 24 PRIS 24 PRIFAST16 24 PRIiFAST32 24 PRIFASTS 24 PRILEAST16 24 PRILEAST32 24 PRILEASTS 24 PRIPTR 24 PRIo16 24 PRI032 25 PRIo8 25 PRIoFAST16 25 PRIoFAST32 25 PRIoFASTS 25 PRIoLEAST16 25 PRIoLEAST32 25 PRIoLEASTS 25 PRIoPTR 25 PRIul6 25 PR1u32 25 PRIu8 26 PRIuFAST16 26 PRIuFAST32 26 PRIuFASTS 26 PRIuLEAST 16 26 PRIuLEAST32 26 PRIuLEASTS 26 PRIuPTR 26 PRIX16 26 PRIx16 26 PRIX32 26 PRIx32 27 PRIX8 27 PRIx8 27 PRIXFASTI16 27 PRIxFAST16 27 PRIXFAST32 27 PRIxFAST32 27 PRIXFASTS 27 PRIxFASTS 27 PRIXLEAST16 27 PRIxLEAST16 27 PRIXLEAST32 28 PRIxLEAST32 28 PRIXLEASTS 28 PRIxLEASTS8 28 PRIXPTR 28 PRIxPTR 28 SCNd16 28 SCNd32 28 SCNdFAST16 28 SCNdFAST32 28 SCNdLEAST16 28 SCNdLEAST32 29 SCNdPTR 29 SCNi16 29 SCNi32 29 SCNiFAST16 29 SCNiFAST32 29 SCNiLEAST16 29 SCNiLEAST32 29 SCNiPTR 29 SCNo16 29 SCNo32 29 SCNoFAST16 30 SCNoFAST32 30 SCNoLEAST16 30 SCNoLEAST32 30 SCNoPTR 30 SCNu16 30 SCNu32 30 SCNuFAST16 30 SCNuFAST32 30 SCNuLEAST16 30 SCNuLEAST32 30 SCNuPTR 31 SCNx16 31 SCNx32 31 SCNxFAST16 31 SCNxFAST32 31 SCNxLEAST16 31 SCNxLEAST32 31 SCNxPTR 31 uint_
440. vr pgmspace 152 strlen_ P S 269 strlwr avr string 92 strlwr S 269 strncasecmp avr string 92 strncasecmp S 269 strncaseemp P avr pgmspace 153 strncasecemp P S 269 strncat avr string 93 strncat S 269 strncat_P avr pgmspace 153 strncat P S 269 strncmp avr_ string 93 strnemp S 269 strnemp P avr pgmspace 153 strnemp P S 269 strncpy avr_ string 93 strnepy S 269 strnepy P avr pgmspace 154 strnepy P S 269 strnlen avr string 93 strnlen S 269 strnlen P avr pgmspace 154 strnlen P S 269 strpbrk avr string 94 strpbrk S 269 strpbrk_P avr pgmspace 154 strpbrk P S 269 strrchr avr_ string 94 strrchr S 269 strrchr_P avr pgmspace 155 strrchr P S 269 strrev avr string 94 strrev S 269 strsep avr string 95 strsep S 269 strsep P avr pgmspace 155 strsep P S 269 strspn avr string 95 strspn S 269 strspn P avr pgmspace 155 Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 399 INDEX strspn_ P S 269 strstr avr string 95 strstr S 269 strstr P avr pgmspace 155 strstr P S 269 strtod avr stdlib 81 strtok r avr string 95 strtok r S 269 strtol avr stdlib 82 strtoul avr stdlib 82 strupr avr string 96 strupr S 269 supported devices 2 tan avr math 38 tanh avr math 39 timer enable int deprecated items 189 toascii ctype 18 tolower ctype 19 tools optional 348 tools required 347 toupper
441. where the order of write access is critical like some timer registers All versions of avr gcc up to 3 3 will generate instructions that use the wrong access order in this situation since with normal memory operands where the order doesn t matter this sometimes yields shorter code See http mail nongnu org archive html avr libc dev 2003 01 msg00044 html for a possible workaround avr gcc versions after 3 3 have been fixed in a way where this optimization will be disabled if the respective pointer variable is declared to be volatile so the correct behaviour for 16 bit IO ports can be forced that way Back to FAQ Index p 321 9 10 14 What registers are used by the C compiler e Data types char is 8 bits int is 16 bits long is 32 bits long long is 64 bits float and double are 32 bits this is the only supported floating point format pointers are 16 bits function pointers are word addresses to allow ad dressing up to 128K program memory space There is a mint8 option see Options for the C compiler avr gcc p 362 to make int 8 bits but that is not supported by avr libc and violates C standards int must be at least 16 bits It may be removed in a future release e 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 responsible for saving and restoring e Call saved register
442. which consist only of characters from accept The terminating zero is not considered as a part of string Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 19 lt avr power h gt Power Reduction Management 156 6 18 4 26 char x strstr P const char x s1 PGM_P s2 Locate a substring The strstr P p 156 function finds the first occurrence of the substring s2 in the string s1 The terminating 0 characters are not compared The strstr P p 156 function is similar to strstr p 96 except that s2 is pointer to a string in program space Returns The strstr P p 156 function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of zero length the function returns s1 6 19 lt avr power h gt Power Reduction Management include lt avr power h gt Many AVRs contain a Power Reduction Register PRR or Registers PRRx that allow you to reduce power consumption by disabling or enabling various on board peripherals 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 ATmegal28 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 interface or they wil
443. wing is the equivalent functionality written in C uint16_t crc16_update uint16_t crc uint8_t a 1 int i crc a for i 0 i lt 8 i if crc amp 1 crc crc gt gt 1 OxA001 else crc cre gt gt 1 return crc 6 26 2 2 static inline uintl6 t crc ccitt update uint16 t __ crc uint8 t data static Optimized CRC CCITT calculation Polynomial x 16 x12 x 5 1 0x8408 Initial value Oxffff Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 26 lt util crcl6 h gt CRC Computations 175 This is the CRC used by PPP and IrDA See RFC1171 PPP protocol and IrDA IrLAP 1 1 Note Although the CCITT polynomial is the same as that used by the Xmodem protocol they are quite different The difference is in how the bits are shifted through the alorgithm Xmodem shifts the MSB of the CRC and the input first while CCITT shifts the LSB of the CRC and the input first The following is the equivalent functionality written in C uint16_t crc_ccitt_update uint16_t crc uint8_t data 1 data 108 crc data data lt lt 4 return uint16_t data lt lt 8 hi8 crc 7 uint8_t data gt gt 4 uint16_t data lt lt 3 6 26 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 0x0 See http www
444. ws 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 p 321 9 10 3 I get undefined reference to for functions like sin In order to access the mathematical functions that are declared in lt math h p 247 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 com mand 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 l flag So for a libfoo a library 1foo needs to be provided This will make the linker search the library in a path known to the system An alternative would be to specify the full path to the libm a file at the same place on the command line i e after all the object files x o However since this requires knowledge of where the build system will exactly find those library files this is deprecated for system libraries Back to FAQ Index p 321 9 10 4 How to permanently bind a variable to a register This can be done with register unsigned char counter asm r3 Typically it should be save to use r2 through r7 that way Registers r8 through
445. x PRG hex bin PRG bin srec PRG srec 4 hex elf OBJCOPY j text j data 0 ihex lt 0 srec elf OBJCOPY j text j data 0 srec lt bin elf OBJCOPY j text j data 0 binary lt Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 36 A simple project 211 Rules for building the eeprom rom images eeprom ehex ebin esrec ehex PRG _eeprom hex ebin PRG _eeprom bin esrec PRG _eeprom srec _eeprom hex elf OBJCOPY j eeprom change section lma eeprom 0 0 ihex lt II echo empty not generated exit 0 _eeprom srec elf OBJCOPY j eeprom change section lma eeprom 0 0 srec lt II echo empty not generated exit 0 _eeprom bin elf OBJCOPY j eeprom change section lma eeprom 0 0 binary lt II echo empty not generated exit 0 Every thing below here is used by avr libc s build system and can be ignored by the casual user FIG2DEV fig2dev EXTRA CLEAN FILES hex bin srec dox eps png pdf eps PRG eps png PRG png pdf PRG pdf h eps fig FIG2DEV L eps lt pdf fig FIG2DEV L pdf lt png fig FIG2DEV L png lt 6 36 8 Reference to the source code The source code is installed under prefix share doc avr libc examples demo where prefix is a configuration option For Unix systems it is usually set to eith
446. y How the linker behaves is very important in designing a library Ideally you want to design a library where only the functions that are called are the only functions to be linked into the final application This helps keep the code size to a minimum In order to do this with the way the linker works is to only write one function per code module This will compile to one function per object module This is usually a very different way of doing things than writing an application There are always exceptions to the rule There are generally two cases where you would want to have more than one function per object module The first is when you have very complementary functions that it doesn t make much sense to split them up For example malloc p 80 and free p 78 If someone is going to use malloc p 80 they will very likely be using free p 78 or at least should be using free p 78 In this case it makes more sense to aggregate those two functions in the same object module The second case is when you want to have an Interrupt Service Routine ISR in your library that you want to link in The problem in this case is that the linker looks for unresolved references and tries to resolve them with code in libraries A reference is the same as a function call But with ISRs there is no function call to initiate the ISR The ISR is placed in the Interrupt Vector Table IVT hence no call no reference and no linking in of
447. y p 94 function returns a pointer to the destination string dest 6 11 3 28 size_t strnlen const char src size_t len Determine the length of a fixed size string The strnlen function returns the number of characters in the string pointed to by src not including the terminating 0 character but at most len In doing this strnlen looks only at the first len characters at src and never beyond src len Returns The strnlen function returns strlen src if that is less than len or len if there is no 0 character among the first len characters pointed to by src 6 11 3 29 char x strpbrk const char s const char accept The strpbrk p 94 function locates the first occurrence in the string s of any of the characters in the string accept Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 6 11 lt string h gt Strings 95 Returns The strpbrk p 94 function returns a pointer to the character in s that matches one of the characters in accept or NULL if no such character is found The terminating zero is not considered as a part of string if one or both args are empty the result will NULL 6 11 3 30 char x strrchr const char src int val Locate character in string The strrchr p 95 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
448. y Sections 285 init7 Unused User definable init8 Unused User definable init9 Jumps into main 9 3 7 The finiN Sections These sections are used to define the exit code executed after return from main or a call to exit p 78 These all are subparts of the text section p 282 The finiN sections are executed in descending order from 9 to 0 finit9 Unused User definable This is effectively where _ exit starts fini8 Unused User definable fini7 Unused User definable fini6 Unused for C programs but used for destructors in C programs fini5 Unused User definable fini4 Unused User definable fini3 Unused User definable fini2 Unused User definable finil Unused User definable Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 4 Data in Program Space 286 finiO Goes into an infinite loop after program termination and completion of any _exit code execution of code in the fini9 gt finil sections 9 3 8 Using Sections in Assembler Code Example include lt avr io h gt section init1 ax progbits ldi rO Oxff out SFR IO ADDR PORTB ro out _SFR_IO_ADDR DDRB ro Note The ax progbits tells the assembler that the section is allocatable a executable x and contains data progbits For more detailed information on the section directive see the gas user manual 9 3 9 Using Sections in C Code Example
449. y any user to add new hardware or to add an AVR processor if it is not already listed 9 1 8 GDB Insight DDD The GNU Debugger GDB is a command line debugger that can be used with the rest of the AVR toolchain Insight is GDB plus a GUI written in Tel Tk Both GDB and Insight are configured for the AVR and the main executables are prefixed with the target name avr gdb and avr insight There is also a text mode GUI for GDB avr gdbtui DDD Data Display Debugger is another popular GUI front end to GDB available on Unix and Linux systems 9 1 9 AVaRICE AVaRICE is a back end program to AVR GDB and interfaces to the Atmel JTAG In Circuit Emulator ICE to provide emulation capabilities 9 1 10 SimulAVR SimulAVR is an AVR simulator used as a back end with AVR GDB Unfortu nately this project is currently unmaintained and could use some help Generated on Wed Jun 11 11 29 15 2008 for avr libc by Doxygen 9 1 Toolchain Overview 276 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 manipulations MFile is a simple Makefile generator is meant as an aid to quickly customize a Makefile to use for your AVR application 9 1 12 Toolchain Distributions Distros All of the various open source projects that compr
450. ygen 6 10 lt stdlib h gt General utilities 80 Note The minimal size of the buffer s depends on the choice of radix For exam ple if the radix is 2 binary you need to supply a buffer with a minimal length of 8 x sizeof long int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 9 will be the letter a If radix is 10 and val is negative a minus sign will be prepended The Itoa p 79 function returns the pointer passed as s 6 10 4 17 void malloc size_t size The malloc p 80 function allocates size bytes of memory If malloc p 80 fails a NULL pointer is returned Note that malloc p 80 does not initialize the returned memory to zero bytes See the chapter about malloc usage p 277 for implementation details 6 10 4 18 void qsort void x base size_t __nmemb size t size compar_fn_t __ compar The qsort p 80 function is a modified partition exchange sort or quicksort The qsort p 80 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

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