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1. 99 5 20 1 Detailed Description 2 99 320 3 Define Documentation 101 5203 Function Documentation lt lt e s e sac Rm 101 CRC Computations 22 108 51 1 Detailed Description gt o eves ok mm Rs 108 5 21 2 Function Documentation 109 lt util delay h gt Busy wait delay 111 5 22 1 Detailed D scription 111 5 22 2 Function Documentation o s s e sisare a 112 lt util parity h gt Parity bit 113 223 1 Detailed Description 2 22 2222 222259 113 3 23 2 Delfine DocumenGUOR ccu mt Rmo eye 113 lt util twi h gt TWI bit mask definitions 114 524 1 Detaled Description 222222 22 gt 114 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen CONTENTS iv 5 24 2 Define Documentation 115 325 i gt lou po a Oo 118 222 4 Detaled s s 24 ce ee X mete v RS 118 3 25 2 Define Documentation n rra pioa RR 131 5 26 lt avr sfr_defs h gt Special function 132 5 26 1 Detailed Description 2 2 Rm xo 132 526 2 Deine Documentation 2 2 2 2 25255 134 S7 Demo projets 222 cw room EROR Ew 135 25231 Detaled Description eie secr a w 135 228 Asimp
2. Vector name Old vector Description Applicable for device name USI_OVF_ SIG_USI_ USI Overflow ATtiny26 ATtiny45 vect OVERFLOW USI_START_ SIG_USI_ USI Start Condi ATmegal65 ATmegal69 ATmega325 vect START tion mega3250 ATmega329 ATmega3290 AT mega645 ATmega6450 ATmega649 AT mega6490 ATtiny2313 ATtiny45 USI_STRT_ SIG_USI_ USI Start ATtiny26 vect START WDT_ SIG_ Watchdog Timer ATtiny2313 OVERFLOW_ WATCHDOG_ Overflow vect TIMEOUT SIG_WDT_ OVERFLOW WDT_vect SIG_WDT Watchdog Time AT90PWM3 AT90PWM2 ATmegal68 SIG_ out Interrupt ATmega48 ATmega88 ATmega640 WATCHDOG_ megal280 ATmegal281 ATmega324 AT TIMEOUT megal64 ATmega644 ATtiny13 ATtiny45 Macros for writing interrupt handler functions define ISR vector define SIGNAL signame define EMPTY_INTERRUPT vector 5 25 2 Define Documentation 5 25 21 define EMPTY_INTERRUPT vector Value void vector void __attribute__ naked void vector void __asm__ __volatile__ reti 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 5 25 2 define ISR vector Value Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 26 lt avr sfr_defs h gt Speci
3. Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 199 Now every thing seems correct but it isn t really The assembler code modifies the variable that pt x points to The compiler will not recognize this and may keep its value in any of the other registers Not only does the compiler work with the wrong value but the assembler code does too The C program may have modified the value too but the compiler didn t update the memory location for optimization reasons The worst thing you can do in this case is uint8_t s asm volatile in 0 __5 __ ENG VE cli NND ld _ tmp reg 1 Wo NE inc tmp reg uA st al tmp reg ene out SREG 0 Wanye amp r s e ptr memory The special clobber memory informs the compiler that the assembler code may mod ify any memory location It forces the compiler to update all variables for which the contents are currently held in a register before executing the assembler code And of course everything has to be reloaded again after this code In most situations a much better solution would be to declare the pointer destination itself volatile volatile uint8 t ptr This way the compiler expects the value pointed to by ptr to be changed and will load it whenever used and store it whenever modified Situations in which you need clobbers are very rare In most cases there will be better ways Clobbered registers w
4. Evi while len gt 0 return total void error void status x n printf error twst exit 0 FILE mystdout FDEV SETUP STREAM uart putchar void main void uintl6_t Int Er uint8_t b 16 uint8_t x ioinit stdout amp mystdout for 0 lt 256 printf 04 a rv ee24xx_read_bytes a 16 b if ry lt 0 error if rv lt 16 8p NULL uint8 t buf FDEV SETUP WRITE Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 529 Example using the two wire interface TWI 158 printf warning short read d n rv rv for 0 lt printf 02x b x putchar n define EE WRITE addr str ee24xx write bytes addr sizeof str 1 str rv EE WRITE 55 The quick brown fox jumps over the lazy dog if rv 0 error printf Wrote d bytes n rv for 0 a lt 256 printf s 04x a rv ee24xx_read_bytes a 16 b if rv lt 0 error if rv lt 16 printf warning short read d n rv rv for x 0 X lt lt x printf 02x b x putchar n printf done n Note 1 The header file lt util twi h gt contains some macro definitions for symbolic con stants used in the TWI status register These definitions match the names used in the Atmel datasheet except that all names have been
5. 169 Tod AQIS cae ie Ges Bee e s x EORR Ee eS 169 7 32 My program doesn t recognize a variable updated within an i ee 171 7 3 3 I get undefined reference to for functions like sin 171 7 3 4 How to permanently bind a variable to a register 171 7 35 How to modify MCUCR or WDTCR 172 7 3 6 What is all this __BV stuff about 172 Duss Ne AVR 222242552222 v MES 173 7 38 Shouldn t I initialize all my variables 174 7 3 9 Why do some 16 bit timer registers sometimes get trashed 175 7 3 10 How do I use a define d constant in an asm statement 176 7 3 11 Why does the PC randomly jump around when single stepping through my program in 176 7 3 12 How do trace an assembler file in avr gdb 177 7 3 13 How do I pass an IO port as a parameter to a function 178 7 3 14 What registers are used by compiler 180 7 3 15 How do I put an array of strings completely in 182 7 3 16 How to use external 184 123 171 Whieh Bag to 222 2222 184 7 3 18 How do I relocate code to a fixed address 185 7 3 19 My is generating nonsense ATmegal28 keeps crashing Port F is completely broken 186 7 3 20 Why do all my foo bar strings eat up the SRAM 186 7 3 21 Why does the compiler comp
6. as RR eRe 210 Tl Thede Secdion e 210 112 The lata Section oe Le a y RR Ee eS 211 TG 222222222 SO Rok GS 211 TIA TNE Section cose os RR ee SR Re 211 KN The MOUNT eee 211 The IMIN Sections o cea bee heb RR bm 212 72212 Them Sections 6 22222 39 m betke 213 7 7 8 Using Sections in Assembler 214 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 1 AVR Libc 1 178 Using Sections in C Code 214 8 the GNU Tool Chain uuum po rg ee 215 Tol Tools amp 4 26 42 24 39 wes 216 4 8 2 Optional Took 22222222222 0 BARS Se eS 216 7 8 3 GNU Binutils for 217 7154 GCC forthe AVR target soo 252222 218 AVR DDG uc pa 218 Aes VISP ze 219 qam Ses e ESSE 219 7 88 GDB forthe AVR target o cc ce ek RE RR 220 T 22 eh m x n A eee ee 220 PAD 2 2 RS EROR BIER 220 T9 Using the ayrdude programi 222222222222 221 TID Usima the GNU m a ee vete 223 7 10 1 Options for compiler 223 7 10 2 Options for the assembler avr as 228 7 10 3 Controlling the linkeravr ld 230 TUA TIELE a ee 232 1 12 Deprecated List eee 232 1 AVRLibc 1 1 Introduction The latest version of this document is always available fr
7. Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h gt General utilities 88 5 18 3 37 vscanf const char fmt va list The function vscanf performs formatted input from stream st din taking a variable argument list as in vfscanf See vfscanf for details 5 18 3 38 int vsnprintf char s size t constchar __fmt va_list ap Like vsprintf but instead of assuming s to be of infinite size no more than n characters including the trailing NUL character will be converted to s Returns the number of characters that would have been written to s if there were enough space 5 18 3 39 int vsnprintf P char x s size t __n const char x fmt va list ap Variant of vsnprintf that uses a fmt string that resides in program memory 5 18 3 40 vsprintf char _ 5 const char fmt va list ap Like sprintf but takes a variable argument list for the arguments 5 18 3 41 int vsprintf P char x __s const char x _ fmt va_list ap Variant of vsprintf that uses a fmt string that resides in program memory 5 19 lt stdlib h gt General utilities 5 19 1 Detailed Description include lt stdlib h gt This file declares some basic C macros and functions as defined by the ISO standard plus some AVR specific extensions Data Structures struct div_t struct ldiv t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h gt Gene
8. standard streams stdin stdout and stderr are provided but contrary to the C standard since avr libc has no knowledge about appli cable devices these streams are not already pre initialized at application startup Also Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 5 18 lt stdio h gt Standard IO facilities 71 since there is no notion of file whatsoever to avr libc there is no function fopen that could be used to associate a stream to some device See note 1 Instead the function fdevopen is provided to associate a stream to a device where the device needs to provide a function to send a character to receive a character or both There is no differentiation between text and binary streams inside avr libc Character n is sent literally down to the device s put function If the device requires a carriage return character to be sent before the linefeed its put routine must implement this see note 2 As an alternative method to fdevopen the macro fdev_setup_stream might be used to setup a user supplied FILE structure It should be noted that the automatic conversion of a newline character into a carriage return newline sequence breaks binary transfers If binary transfers are desired no automatic conversion should be performed but instead any string that aims to issue a CR LF sequence must use r n explicitly For convenience the first call to fdevopen that opens
9. sz RR RR 23 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen CONTENTS ii 5 6 Additional notes from lt avr sfr_defs h gt 26 5 7 lt avr sleep h gt Power Management and Sleep Modes 28 a Detaled Descriphon s s sos sa ss Bde BAS es 28 3 52 Define Documento s srce e a pa a e a E a 28 5 7 3 Function Documentation 29 5 8 lt avr version h gt avr libc version macros 29 381 Detailed Descripfion e q o es ps ceea ee X RR e 29 5 8 2 Define Documentation 30 5 9 lt avr wdt h gt Watchdog timer handling 31 391 Detailed Descripfion s s lt sees mc e 4 RE RES 31 5 9 2 Define Documentation os o sasos eere 32 5 10 lt compat deprecated h gt Deprecated items 34 3 10 1 Detailed Description gt s lt e oo se csata CA Re 34 3 10 2 Define Documentation 222222 222 1 35 5 10 3 Function 36 5 11 lt compat ina90 h gt Compatibility with IAR EWB 3 x 37 2 12 lt ctypeh gt Character Operations 22 222 199 37 5 12 1 Detailed Description so RR Rm 37 5 12 2 Function Documentation 38 2 13 System 22 22 2205 39 513 1 Detailed Description e lox f ioni te nks 39 5 13 2 Define Documentation 22 22 2 22 40 5 14 lt inttypes h gt Integer Type conversions 40
10. Delay loop using 8 bit counter count so up to 256 iterations are possible The value 256 would have to be passed as 0 The loop executes three CPU cycles per iteration not including the overhead the compiler needs to setup the counter register Thus at a CPU speed of 1 MHz delays of up to 768 microseconds can be achieved 5 22 2 2 void delay loop 2 uintl6 t count Delay loop using a 16 bit counter count so up to 65536 iterations are possible The value 65536 would have to be passed as 0 The loop executes four CPU cycles per iteration not including the overhead the compiler requires to setup the counter register pair Thus at a CPU speed of 1 MHz delays of up to about 262 1 milliseconds be achieved Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 523 lt util parity h gt Parity bit generation 113 5 22 2 3 void delay ms double Perform a delay of __ms milliseconds using _delay_loop_2 The macro F_CPU is supposed to be defined to a constant defining the CPU clock frequency in Hertz The maximal possible delay is 262 14 ms F_CPU in MHz 5 22 2 4 void delay us double us Perform a delay of __us microseconds using delay loop 10 The macro CPU is supposed to be defined to a constant defining the CPU clock frequency in Hertz The maximal possible delay is 768 us F CPU in MHz 5 23 lt util parity h gt Parity bit generation 5 23 1 Detailed Desc
11. Perform a make distcheck and make sure it succeeds This will create the source tarball Tag the release cvs tag avr libe major minor patch release Upload the tarball to savannah Update the NEWS file and commit to cvs Add Changes since avr libc major minor patch Generate the latest documentation and upload to savannah Announce the release The following hypothetical diagram should help clarify version and branch relation ships Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 77 Memory Sections 210 HEAD 1 0 Branch 1 2 Branch cvs tag avr libc 1_0 branchpoint set version to 1 1 0 lt date gt cvs tag b avr libc 1 0 branch set version to 0 90 90 lt date gt set version to 1 0 cvs tag avr libc 1 0 release set version to 1 0 0 lt date gt i set version to 1 0 1 tag avr libc 1_0_1 release 1 cvs tag avr libc 1_2 branchpoint i set version to 1 3 0 lt date gt ci EA RD Ena set version to 1 1 90 lt date gt i set version to 1 2 cvs tag avr libc 1_2 release t cvs tag avr libc 2 0 branchpoint set version to 2 1 0 lt date gt t Figure 5 Release tree 7 7 Memory Sections Remarks Need to list all the sections which are available to the avr Weak Bindings FIXME need to discuss the weak directive The following describes the various sections available
12. if cre amp 0x01 crc crc gt gt 1 0x8C else crc gt gt 1 Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 522 lt util delay h gt Busy wait delay loops 111 return crc 5 21 24 static _ inline uintl6_t crc xmodem update uintl6 t _ crc uint8 t data static Optimized CRC XMODEM calculation Polynomial x 16 x 12 5 1 0x1021 Initial value 0 0 This is the CRC used by the Xmodem CRC protocol The following is the equivalent functionality written in C uintl6 t crc xmodem update uintl16 t crc uint8 t data int i crc crc uint16 t data lt lt 8 for i20 i 8 i if crc amp 0x8000 crc crc lt lt 1 0x1021 else crc lt lt 1 return crc 5 22 lt util delay h gt Busy wait delay loops 5 22 1 Detailed Description define F CPU 1000000UL 1 MHz tdefine CPU 14 7456E6 include util delay h Note As an alternative method it is possible to pass the F CPU macro down to the com piler from the Makefile Obviously in that case no define statement should be used The functions in this header file implement simple delay loops that perform a busy waiting They are typically used to facilitate short delays in the program execution Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 522 lt util delay h gt Busy wait delay loops 112 They are implemented as count down loops with a well known C
13. atmega8 atmega103 atmega128 atmega1280 atmega1281 atmega16 161 162 atmega 163 atmega 164 atmega 165 atmega 168 atmega 169 atmega32 atmega323 atmega324 atmega325 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 1 3 Supported Devices atmega3250 atmega329 atmega3290 atmega48 atmega64 atmega640 atmega644 atmega645 atmega6450 atmega649 atmega6490 atmega8515 atmega8535 atmega88 ATtiny Type Devices attiny11 1 attiny12 1 attiny 13 attiny15 1 attiny22 attiny25 attiny26 attiny28 1 attiny2313 attiny45 attiny85 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 2 avr libc Module Index Misc Devices at94K 2 at76c711 3 at43usb320 at43usb355 at86rf401 at90pwm2 at90pwm3 Note 1 Assembly only There is no direct support for these devices to be programmed in C since they do not have a RAM based stack Still it could be possible to program them see the FAQ for an option Note 2 The at94K devices are a combination of FPGA and AVR microcontroller TRoth 2002 11 12 Not sure of the level of support for these More information would be welcomed Note 3 The at76c711 is a USB to fast serial interface bridge chip using an AVR core 2 avr libc Module Index 21 avr libc Modules Here is a list of all modules lt asse
14. boot_spm_busy_wait eeprom_busy_wait boot_lock_bits_set lock_bits while 0 Same as boot_lock_bits_set except waits for eeprom and spm operations to complete before setting the lock bits 5 2 2 4 define boot lock fuse bits get address Value LL extension N uint8 t _ result N asm volatile X N idi r30 3 n t Idi r31 O n t sts 1 amp 2 n t lpm 0 Z n t i r _ result i SFR MEM ADDR SPM REG N r uint8 t BOOT LOCK BITS SET N M address X r30 U _ result Read the lock 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 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 22 lt avr boot h gt Bootloader Support Utilities 12 Note The lock and fuse bits returned are the physical values ie a bit returned as 0 means the corresponding fuse or lock bit is programmed 5 2 2 5 define boot page erase address __boot_page_erase_normal address Erase the flash page that contains address Note address is a byte address in flash not a word address 5 2 2 6 define boot_page_erase_safe address Value do boot spm busy wait N eeprom busy wait X boot page erase address X while 0 Same as boot page erase except it waits for eeprom and spm operations to complet
15. compiler Code for very time critical applications Special tweaks that cannot be done in Usually all but the first could probably be done easily using the inline assembler facility of the compiler Although avr libc is primarily targeted to support programming AVR microcontrollers using the C and C language there s limited support for direct assembler usage as well The benefits of it are Use of the C preprocessor and thus the ability to use the same symbolic constants that are available to programs as well as a flexible macro concept that can use any valid C identifier as a macro whereas the assembler s macro concept is basically targeted to use a macro in place of an assembler instruction Use of the runtime framework like automatically assigning interrupt vectors For devices that have RAM initializing the RAM variables can also be utilized 7 2 2 Invoking the compiler For the purpose described in this document the assembler and linker are usually not invoked manually but rather using the compiler frontend avr gcc that in turn will call the assembler and linker as required This approach has the following advantages e There is basically only one program to be called directly avr gcc regardless of the actual source language used The invokation of the C preprocessor will be automatic and will include the appropriate options to locate required include files in the filesystem The inv
16. int size t void memchr const void int size t PURE int memcmp const void const void size t ATTR_PURE void memcpy void const void size t void memmove void const void size_t void memset void int size t int strcasecmp const char const char __ ATTR_PURE char strcat char const char char strchr const char int PURE int strcmp const char const char x __ ATTR PURE char strcpy char const char size_t strlcat char const char size_t size t strlcpy char const char size t size t strlen const char x ATTR PURE char strlwr char int strncasecmp const char const char size t ATTR_PURE char strncat char const char size_t int strncmp const char const char size t PURE char strncpy char const char size_t size t strnlen const char size_t PURE char strrchr const char x int PURE char strrev char char strsep char const char char strstr const char const char x ATTR PURE char strtok char const char char char strupr char Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 20 lt string h gt Strings 101 5 20 2 Define Documentation 5 20 2 1 define FFS x This macro finds the first least significan
17. low 8 bits of addr _BV TWINT _BV TWEN clear interrupt to start transmission x while TWCR amp _BV TWINT 0 wait for transmission switch twst TW_STATUS case TW_MT_DATA_ACK break case TW_MT_DATA_NACK goto quit case TW_MT_ARB_LOST goto begin default goto error must send stop condition x for len gt 0 len TWDR xbuf TWCR _BV TWINT _BV TWEN start transmission x while TWCR amp _BV TWINT 0 x wait for transmission x switch twst TW_STATUS case TW_MT_DATA_NACK goto error device write protected Note 16 case TW MT DATA rvtt break default goto error quits TWCR BV TWINT _BV TWSTO _BV TWEN send stop condition x return rv error rv 1 goto quit Wrapper around ee24xx_write_page that repeats calling this function until either an error has been returned or all bytes have been written Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 29 Example using the two wire interface TWI 157 int ee24xx write bytes uintl6 t eeaddr int len int rv total total 0 do if DEBUG printf Calling ee24xx write page d d eeaddr len buf endif rv if DEBUG printf gt d n endif if ee24xx_write_page eeaddr len buf rv rv 1 return 1 eeaddr len buf rv total rv
18. simple project 145 noinit 0x00800063 PROVIDE __noinit_end 0x00800063 end 0x00800063 PROVIDE __heap_start eeprom 0x00810000 0 0 x eeprom x 0x00810000 eeprom end The last address in the text segment is location 0x 2 denoted by etext so the instructions use up 242 bytes of FLASH The data segment where initialized static variables are stored starts at location 0x 60 which is the first address after the register bank on a 2313 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 0 0 The next available address in the eeprom segment is also location 0 0 so there aren t any EEPROM variables 5 28 6 Intel Hex Files We have a binary of the application but how do we get it into the processor Most if not all programmers will not accept a GNU executable as an input file so we need to do a little more processing The next step is to extract portions of the binary and save the information into hex files The GNU utility that does this is called avr objcopy The ROM contents can be pulled from our project s binary and put into the file demo hex
19. 00 97 sbiw r24 0x00 O 19 f0 breq 6 0x54 lt __SREG__ 977 sbiw r24 0x01 1 31 f5 brne 76 Ox9e SREG 14 c0 rjmp 40 Ox7c SREG case UP if pwm 1023 80 91 61 00 lds r24 0x0061 90 91 62 00 lds r25 0x0062 01 96 adiw r24 0x01 1 90 93 62 00 sts 0x0062 r25 80 93 61 00 sts 0 0061 r24 80 91 61 00 145 r24 0 0061 90 91 62 00 145 r25 0x0062 8f 5f subi r24 OxFF 255 93 40 8 r25 0x03 7 3 a9 f4 brne 42 Ox9e _SREG__ direction DOWN 81 e0 ldi r24 0x01 1 80 93 60 00 sts 0x0060 r24 11 cO rjmp 34 Ox9e lt __SREG__ break case DOWN if pwm 0 80 91 61 00 145 r24 0x0061 90 91 62 00 145 r25 0x0062 01 97 sbiw r24 0x01 1 90 93 62 00 sts 0x0062 r25 80 93 61 00 sts 0 0061 r24 80 91 61 00 145 r24 0 0061 90 91 62 00 lds r25 0x0062 89 2b or 24 r25 4 brne 4 Ox9e SREG direction UP 10 92 60 00 sts 0x0060 r1 break OCR Note 4 Je a2 a6 a8 aa ac 80 91 61 00 145 r24 0x0061 90 91 62 00 145 r25 0x0062 9b bd out 0x2b r25 43 8a bd out 0x2a r24 42 91 r25 85 91 r24 0 15 gt 0x5f gt 0x3d gt 0 5 gt 0 5 gt 0 5 gt Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 simple project 143 ae 2f 91 pop r18 b0 Of 90 pop b2 Of be out Ox3f r0 63 b4 Of 90 pop b6 1f 90 pop rl ber 18 95 reti 000
20. 7 7 1 text Section The text section contains the actual machine instructions which make up your program This section is further subdivided by the initN and finiN sections dicussed below Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 77 Memory Sections 211 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 77 2 The Section This section contains static data which was defined in your code Things like the fol lowing would end up in data char err_str Your program has died horrible death struct point pt 1 1 It is possible to tell the linker the SRAM address of the beginning of the data section This is accomplished by adding W1 Tdata addr to the avr gcc command used to the link your program Not that addr must be offset by adding 0x800000 the to real SRAM address so that the linker knows that the address is in the SRAM memory space Thus if you want the data section to start at 0x1100 pass 0x801100 at the address to the linker offset explained Note When using malloc in the application which could even happen inside library calls additional adjus
21. ATTR CONST double frexp double value int exp double Idexp double x int exp CONST double exp double x ATTR CONST double cosh double x ATTR CONST double sinh double x ATTR CONST double tanh double x CONST double acos double x ATTR CONST double asin double x ATTR CONST double atan double x ATTR CONST double atan2 double y double x CONST double log double __x _ ATTR CONST double log10 double __x _ ATTR_CONST double pow double __x double y ATTR CONST int isnan double x _ ATTR_CONST int double __x _ ATTR_CONST double square double __x _ ATTR_CONST 5 15 2 Define Documentation 5 15 21 define 3 141592653589793238462643 The constant pi 5 15 2 22 define M SQRT2 1 4142135623730950488016887 The square root of 2 5 15 3 Function Documentation 5 15 3 1 double acos double __x The acos function computes the principal value of the arc cosine of x The returned value is in the range 0 pi radians A domain error occurs for arguments not in the range 1 1 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 15 lt math h gt Mathematics 54 5 15 3 2 double asin double x The asin function computes the principal value of the arc sine of x The returned value is in the range 0 pi radians A domain error occurs for
22. The ungetc function returns the character pushed back after the conversion or EOF if the operation fails If the value of the argument c character equals EOF the operation will fail and the stream will remain unchanged 5 18 3 32 int vfprintf FILE _ stream const char __ fmt va list vfprintf is the central facility of the print f family of functions It outputs values to stream under control of a format string passed in fmt The actual values to print are passed as a variable argument list ap vfprintf returns the number of characters written to stream or EOF in case of an error Currently this will only happen if st ream has not been opened with write intent The format string is composed of zero or more directives ordinary characters not which are copied unchanged to the output stream and conversion specifications each of which results in fetching zero or more subsequent arguments Each conversion specification is introduced by the character The arguments must properly correspond after type promotion with the conversion specifier After the the following appear in sequence Zero or more of the following flags The value should be converted to an alternate form For c d i s and u conversions this option has no effect For o conversions the precision of the number is increased to force the first character of the output string to a zero except if a zero value is printed with an explicit pre
23. _BV bit Modules Additional notes from lt avr sfr_defs h gt Bit manipulation e define_BV bit 1 lt lt bit IO register bit manipulation 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 define loop until bit is set sfr bit do while bit is clear sfr bit define loop until bit is clear sfr bit do while bit is set sfr bit 5 26 2 Define Documentation 5 26 2 1 define BV bit 1 lt lt bit include lt avr io h gt Converts a bit number into a byte value Note The bit shift is performed by the compiler which then inserts the result into the code Thus there is no run time overhead when using _BV 5 26 2 2 define bit_is_clear sfr bit _SFR_BYTE sfr amp _BV bit include lt avr io h gt Test whether bit bit in IO register sfr is clear This will return non zero if the bit is clear and a 0 if the bit is set Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 27 Demo projects 135 5 26 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 5 26 2 4 define loop_until_bit_is_clear sfr bit do while bit is set sfr bit include lt avr io h gt Wait until bit bit in IO register s fr is clear 5
24. avr stdint 69 UINT LEAST16 avr stdint 66 uint least16 t avr stdint 69 UINT LEAST32 MAX avr stdint 66 uint least32 t avr stdint 69 UINT LEAST64 MAX avr stdint 67 uint least64 t avr stdint 69 UINT LEAST8 MAX avr stdint 67 uint least8 t avr stdint 69 UINTMAX C avr stdint 67 UINTMAX MAX avr stdint 67 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 251 uintmax_t avr_stdint 69 UINTPTR_MAX avr_stdint 67 uintptr_t avr_stdint 69 ultoa avr_stdlib 98 ungetc avr_stdio 81 util_crc _crc16_update 109 _crc_ccitt_update 109 _crc_ibutton_update 109 _crc_xmodem_update 110 util_delay _delay_loop_1 112 _delay_loop_2 112 _delay_ms 112 _delay_us 112 util_parity parity_even_bit 113 util_twi TW_BUS_ERROR 114 TW_MR_ARB_LOST 114 TW_MR_DATA_ACK 115 TW_MR_DATA_NACK 115 TW MR SLA 115 TW MR SLA NACK 115 TW MT ARB LOST 115 TW MT DATA 115 TW MT DATA NACK 115 TW MT SLA ACK 115 TW MT SLA 115 TW NO INFO 115 TW READ 115 TW REP START 116 TW SR ARB LOST GCALL ACK 116 TW SR ARB LOST SLA ACK 116 TW SR DATA ACK 116 TW SR DATA NACK 116 TW SR GCALL ACK 116 TW SR GCALL DATA ACK 116 utoa TW SR GCALL DATA NACK 116 TW SR SLA ACK 116 TW SR STOP 116 TW ST ARB LOST SLA ACK 116 TW ST DATA ACK 117 TW ST DATA 117 TW ST LAST DATA 117 TW ST SLA AC
25. avr_inttypes 48 PRIXLEAST32 avr_inttypes 48 PRIxLEAST32 avr_inttypes 48 PRIXLEASTS8 avr inttypes 48 PRIxLEASTS8 avr inttypes 48 PRIXPTR avr inttypes 48 PRIxPTR avr inttypes 48 prog char avr pgmspace 22 prog intl6 t avr pgmspace 22 prog int32 t avr pgmspace 22 prog int64 t avr pgmspace 22 prog int8 t avr pgmspace 22 prog uchar avr pgmspace 22 prog uint16 t avr pgmspace 22 prog uint32 t avr pgmspace 22 prog uint64 t avr pgmspace 22 prog uint8 t avr pgmspace 22 prog void avr pgmspace 22 PROGMEM avr pgmspace 21 PSTR avr pgmspace 21 PTRDIFF MAX avr stdint 65 PTRDIFF MIN avr stdint 65 putc avr stdio 76 putchar avr stdio 77 puts avr stdio 80 puts P avr stdio 80 qsort avr stdlib 94 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 247 quot SCNiFAST16 div_t 161 avr_inttypes 49 ldiv t 161 SCNiFAST32 avr_inttypes 49 rand SCNiLEAST16 avr_stdlib 95 avr_inttypes 49 RAND_MAX SCNiLEAST32 avr_stdlib 90 avr_inttypes 49 rand_r SCNiPTR avr_stdlib 95 avr_inttypes 49 random SCNo16 avr stdlib 95 avr inttypes 50 RANDOM MAX SCNo32 avr stdlib 90 avr inttypes 50 random r SCNoFAST 16 avr_stdlib 95 avr_inttypes 50 realloc SCNoFAST32 avr_stdlib 95 avr_inttypes 50 rem SCNoLEAST16 div_t 161 avr_inttypes 50 Idiv_t 161 SCNoLEAST32 avr_inttypes 50 sbi SCNoPTR deprecated_items 36 avr_inttypes 50 sca
26. 2141 Detailed Description cc e espes specu era XR RR 40 5 14 2 Define Documentation 43 5 14 3 Typedef Documentation 2 52 3 15 Methemati s lt o ca ly a oo 52 2 15 1 Detuled Description zumo eee Se e Sob RR 52 3 15 2 Define Documentation s i mn Rmo 53 5 15 3 Function Documentation 53 5 16 Non local goto 222222222222 mx o 56 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen CONTENTS iii 5 20 32 222 5 22 5 24 5 16 1 Detailed Description 56 9 16 2 Funchon Documentation 222 22 222 25559 58 lt stdint h gt Standard Integer Types o oo csc ioaea re etis 58 5 17 1 Detaled Description lt s la emear rip eee a 58 5 17 2 Define Documentation s 2 29 o RR n Rx Rs 62 3 17 3 Typedef Documentation xx 67 lt stdio h gt Standard TO facilities o oo o sao orucu apeu iaa 70 5181 Detailed Description 2 m 2 4 70 5 18 2 Deine Documentation o s se e sea 22 2 75 5 15 3 Function Documentation s ce spe edate daps 77 lt stdlib h gt General utilities 88 5191 Detailed Description sos eR RR Rb 88 5 19 2 Defne Documentation suo o um Ro REGE 90 5 19 3 Typedef Docarnentalh H 222222222 g bees a eae es 91 5 19 4 Function Documentation 91 5 19 5 Variable Documentation 99 AWE Doe SERES S Ilo 9E
27. 8 MIN 8 MAX 1 define UINTS8 MAX CONCAT INT8 MAX U x 2U 1U define INTI6 MAX Ox7fff define INTI6 MIN 6 MAX 1 define UINTIG6 CONCAT INT16 MAX U 2U 1U define INT32 MAX Ox7fffffffL define INT32 MIN 32 MAX IL define UINT32 MAX CONCAT INT32 MAX U 2UL 1UL define INT64 MAX OXx7fffffffffffffffILL define INT64 MIN INT64 MAX ILL define UINT 4 CONCAT INT64 MAX U x 2ULL LULL Limits of minimum width integer types define INT LEAST8 MAX 8 MAX fdefine INT LEAST8 MIN INT8 MIN define UINT LEASTS MAX UINT8 MAX define INT LEASTI6 INTI6 MAX define INT LEASTI6 MIN INT16 MIN define UINT LEASTI6 MAX UINTI6 MAX fdefine INT LEAST32 MAX INT32 MAX define INT LEAST32 MIN INT32 MIN define UINT LEAST32 MAX UINT32 MAX define INT LEAST64 INT64 MAX define INT LEAST64 MIN INT64 MIN define UINT LEAST64 MAX UINT64 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Integer Types 60 Limits of fastest minimum width integer types define INT_FAST8_MAX INT8_MAX define INT_FAST8_MIN INT8_MIN define UINT FASTS MAX UINT8 MAX define INT FASTI6 MAX define INT FASTI6 MIN INT16 MIN define UINT FASTI6 MAX UINTI6 MAX define INT FAST32 MAX INT32 MAX define INT FAST32 MIN INT32 MIN define UINT FAST32 MAX UINT32 MAX define INT FAST64 MAX INT64 MAX define INT FAST
28. 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 devel opers can checkout the branch Note CVS tags do not allow the use of periods 7 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 6 Release Numbering and Methodology 209 7 6 2 2 Makinga release stable release will only be done on a branch not from the cvs HEAD The following steps should be taken when making a release 10 11 12 Make sure the source tree you are working from is on the correct branch cvs update r avr libe major minor branch Update the package version in configure in and commit it to cvs Update the gnu tool chain version requirements in the README and commit to CVS Update the ChangeLog file to note the release and commit to cvs on the branch Add Released avr libc lt this_release gt Update the NEWS file with pending release number and commit to cvs Change Changes since avr libc lt last_release gt to Changes in avr libc this relelase Bring the build system up to date by running bootstrap and configure
29. Device signature 0x1e9101 avrdude The command displays a list of valid commands avrdude gt gt gt 7 Valid commands dump dump memory dump lt memtype gt lt addr gt lt N Bytes gt read alias for dump write write memory write lt memtype gt lt addr gt bl lt b2 gt lt bN gt erase perform a chip erase sig display device signature bytes part display the current part information send send a raw command send bl lt b2 gt lt b3 gt lt b4 gt help help 2 help Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 223 quit oquit Use the part command to display valid memory types for use with the dump and write commands avrdude 7 10 Using the GNU tools This is a short summary of the AVR specific aspects of using the GNU tools Normally the generic documentation of these tools is fairly large and maintained in texinfo files Command line options are explained in detail in the manual page 7 10 1 Options for the C compiler avr gcc 7 10 1 4 Machine specific options for the AVR following machine specific options are recognized by the C compiler frontend mmcu architecture Compile code for architecture Currently known architectures are avrl Simple CPU core only assembler support avr2 Classic CPU core up to 8 KB of ROM avr3 Classic CPU core more than 8 KB of ROM avr
30. PRIdLEASTI6 43 PRIdLEAST32 43 PRIdLEASTS 44 PRIdPTR 44 PRIi16 44 PRIi32 44 PRIi8 44 PRIiFAST16 44 PRIiFAST32 44 PRIFASTS 44 PRILEASTI6 44 PRILEAST32 44 578 44 PRIiPTR 45 PRIo16 45 1032 45 108 45 PRIoFAST16 45 PRIoFAST32 45 PRIoFASTS 45 PRIoLEASTI6 45 PRIoLEAST32 45 PRIoLEASTS 45 PRIoPTR 45 PRIu16 46 PRIu32 46 8 46 PRIuFAST16 46 PRIuFAST32 46 PRIuFASTS 46 PRIuLEASTI6 46 PRIULEAST32 46 PRIuLEASTS 46 PRIuPTR 46 PRIX16 46 PRIx16 47 PRIX32 47 PRIx32 47 PRIX8 47 PRIx8 47 PRIXFAST16 47 PRIxFAST 16 47 PRIXFAST32 47 PRIxFAST32 47 PRIXFASTS 47 PRIxFASTS 47 PRIXLEAST16 48 PRIxLEAST16 48 PRIXLEAST32 48 PRIxLEAST32 48 PRIXLEASTS 48 PRIxLEASTS 48 PRIXPTR 48 PRIxPTR 48 SCNd16 48 SCNd32 48 SCNdFAST 16 48 SCNdFAST32 49 SCNdLEAST16 49 SCNdLEAST32 49 SCNdPTR 49 SCNi16 49 SCNi32 49 SCNiFAST16 49 SCNiFAST32 49 SCNiLEAST16 49 SCNiLEAST32 49 SCNiPTR 49 SCNo16 50 SCNo32 50 SCNoFAST 16 50 SCNoFAST32 50 SCNoLEAST16 50 SCNoLEAST32 50 SCNoPTR 50 SCNu16 50 SCNu32 50 SCNuFAST 16 50 SCNuFAST32 50 SCNuLEAST16 51 SCNuLEAST32 51 SCNuPTR 51 SCNx16 51 SCNx32 51 SCNxFAST 16 51 SCNxFAST32 51 SCNxLEAST16 51 SCNxLEAST32 51 SCNxPTR 51 uint_farptr_t 52 avr_math Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 237 acos 53 asin 53 atan 53 atan2 53 ceil 54 cos
31. SFR IO ADDR SREG Note 9 sbic _ IO ADDR PORTD SQUARE rjmp 1f sbi _ IO ADDR PORTD SQUARE rjmp 2f 45 chi _SFR_IO_ADDR PORTD SQUARE 23 out _SFR_IO_ADDR SREG intsav Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 7 2 avr libc and assembler programs 166 reti ioinit sbi _SFR_IO_ADDR DDRD SQUARE ldi work BV TOIEO out SFR IO ADDR TIMSK work ldi work _BV CS00 tmr0 1 out SFR IO ADDR ICCRO work ldi work 256 tmconst out _SFR_IO_ADDR TCNTO work sei ret global __vector_default Note 10 vector default reti end 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 Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 2 avr libc and assembler programs 167 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 us
32. SIG_ Timer Counter2 ATmegal68 ATmega48 ATmega88 COMPA_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal281 AT 2 mega324 ATmegal64 ATmega644 TIMER2_ SIG_ Timer Counter2 ATmegal68 ATmega48 ATmega88 AT COMPB_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal281 AT COMPARE2B mega324 ATmegal64 ATmega644 TIMER2_ SIG_ Timer Counter2 AT90S4434 AT90S8535 AT90CANI28 COMP vect OUTPUT Compare Match AT90CAN32 AT90CAN64 ATmegal03 COMPARE2 ATmegal28 ATmegal6 ATmegal61 megal62 ATmegal63 ATmegal65 AT megal69 ATmega32 ATmega323 AT mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT mega8 ATmega8535 TIMER2 SIG Timer Counter2 AT90S4434 9058535 AT90CANI28 OVF_vect OVERFLOW2 Overflow AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l megal62 ATmegal63 ATmegal65 AT megal69 ATmega32 ATmega323 AT mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT mega8 ATmega8535 ATmegal68 AT mega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega324 AT megal64 ATmega644 TIMER3 SIG INPUT Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA CAPT_vect CAPTURE3 Capture Event ATmegal28 ATmegal62 ATmega64 AT mega640 ATmegal280 ATmegal281 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPA_vect OUTPUT_ Compare Ma
33. UCSRA BV U2X UBRR F CPU 8 9600UL 1 9600 Bd else F CPU 16 9600UL 1 9600 Bd endif UCSRB _BV TXEN x tx enable x initialize clock 100 kHz clock TWPS 0 gt prescaler 1 if defined TWPSO has prescaler megal28 amp newer TWSR 0 endif if F_CPU lt 3600000UL TWBR 10 smallest TWBR value see note 5 x else TWBR F_CPU 10000001 16 2 endif Note 6 Send character down the UART Tx wait until tx holding register is empty int uart putchar char c FILE xunused if c An uart putchar Nr 0 loop until bit is set UCSRA UDRE UDR c return 0 Note 7 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 29 Example using the two wire interface TWI 152 Read len bytes from EEPROM starting at eeaddr into buf This requires two bus cycles during the first cycle the device will be selected master transmitter mode and the address transfered Address bits exceeding 256 are transfered in the 2 1 0 bits subaddress bits of the device selector The second bus cycle will reselect the device repeated start condition going into master receiver mode and transfer the data from the device to the TWI master Multiple bytes can be transfered by ACKing the client s transfer The last transfer will be NACKed which the client will
34. User definable init9 Jumps into main 777 finiN Sections These sections are used to define the exit code executed after return from main or a call to exit These all are subparts of the text section The finiN sections are executed in descending order from 9 to 0 finit9 Unused User definable This is effectively where _exit starts fini8 Unused User definable fini7 Unused User definable fini6 Unused for C programs but used for destructors in C programs Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 77 Memory Sections 214 fini5 Unused User definable fini4 Unused User definable fini3 Unused User definable fini2 Unused User definable finil Unused User definable fini0 Goes into an infinite loop after program termination and completion of any _exit code execution of code in the fini9 gt finil sections 7 7 8 Using Sections in Assembler Code Example include lt avr io h gt section init1 ax progbits ldi r0 Oxff out _ IO ADDR PORTB out IO ADDR DDRB Note The ax progbits tells the assembler that the section is allocatable a executable x and contains data progbits For more detailed information on the section directive see the gas user manual 77 9 Using Sections C Code Example include lt avr io h gt void my_init_portb void __attribute
35. Warning You must install avr binutils and make sure your path is set properly before in stalling avr gcc The steps to build avr gcc are essentially same as for binutils bunzip2 c gcc version tar bz2 tar xf cd gcc version mkdir obj avr cd obj avr configure prefix PREFIX target avr enable languages c c disable nls with dwarf2 make make install Ur Xr Xr ox or To save your self some download time you can alternatively download only the gcc core version tar bz2 and gcc c lt version gt tar bz2 parts of the gcc Also if you don t need C support you only need the core part and should only enable the C language support Note Early versions of these tools did not support C The stdc libs are not included with C for AVR due to the size limitations of the devices 7 8 5 AVRLibc Warning You must install avr binutils avr gcc and make sure your path is set properly before installing avr libc Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 8 Installing the GNU Tool Chain 219 Note If you have obtained the latest avr libc from cvs you will have to run the bootstrap script before using either of the build methods described below To build and install avr libc 5 gunzip c avr libc lt version gt tar gz tar xf 5 cd avr libc lt version gt 5 configure build config guess host avr make make install Note Other configure op
36. and the tail of the region that is no longer to be used is passed to the standard free function for insertion into the freelist Checks are first made whether the tail chunk is large enough to hold a chunk of its own at all otherwise realloc will simply do nothing and return the original region When growing the region it is first checked whether the existing allocation can be ex tended in place If so this is done and the original pointer is returned without copying any data contents As a side effect this check will also record the size of the largest chunk on the freelist If the region cannot be extended in place but the old chunk is at the top of heap and the above freelist walk did not reveal a large enough chunk on the freelist to satisfy the new request an attempt is made to quickly extend this topmost chunk and thus the heap so no need arises to copy over the existing data If there s no more space available in the heap same check is done as in malloc the entire request will fail Otherwise malloc will be called with the new request size the existing data will be copied over and free will be called on the old region Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 6 Release Numbering and Methodology 207 7 6 Release Numbering and Methodology 7 6 1 Release Version Numbering Scheme 7 6 1 1 Stable Versions A stable release will always have a minor number that is an even number This i
37. const void __ptr size_t size size t nmemb FILE x stream Write nmemb objects size bytes each to stream The first byte of the first object is referenced by pt r Returns the number of objects successfully written i e nmemb unless an output error occured 5 18 3 18 char gets char str Similar to fgets except that it will operate on stream st din and the trailing newline Gf any will not be stored in the string It is the caller s responsibility to provide enough storage to hold the characters read 5 18 3 19 int printf const char fmt Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 81 The function printf performs formatted output to stream stderr See vfprintf for details 5 18 3 20 int printf_P const char fmt Variant of printf that uses a fmt string that resides in program memory 5 18 3 21 int puts const char str Write the string pointed to by str and a trailing newline character to stdout 5 18 3 22 int puts P const char str Variant of puts where st r resides in program memory 5 18 3 23 int scanf const char fmt The function scanf performs formatted input from stream st din See vfscanf for details 5 18 3 24 int scanf_P const char Variant of scanf where fmt resides in program memory 5 18 3 25 int snprintf char __s size_t __n const char x __ fmt Lik
38. eeaddr x low 8 bits of addr _BV TWINT _BV TWEN clear interrupt to start transmission x while TWCR amp _BV TWINT 0 x wait for transmission x switch twst TW_STATUS case TW_MT_DATA_ACK break case TW_MT_DATA_NACK goto quit case TW_MT_ARB_LOST goto begin default goto error must send stop condition x Note 12 Next cycle s master receiver mode x BV TWINT _BV TWSTA _BV TWEN send rep start condition x while TWCR _BV TWINT 0 x wait for transmission x switch twst TW STATUS case TW_START but should not happen case TW_REP_START break case TW_MT_ARB_LOST goto begin default goto error send SLA R TWDR sla TW_READ _BV TWINT _BV TWEN x clear interrupt to start transmission x while TWCR amp _BV TWINT 0 wait for transmission switch twst TW_STATUS case TW_MR_SLA_ACK break Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 29 Example using the two wire interface TWI 154 case TW_MR_SLA_NACK goto quit case TW_MR_ARB_LOST goto begin default goto error for twcr _BV TWINT _BV TWEN _BV TWEA Note 13 x len gt 0 len if len 1 twcr _BV TWINT _BV TWEN send this time x TWCR twcr x clear int to start transmission x while TWCR am
39. 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 5 5 4 10 char x strncat P char dest src size_t len Concatenate two strings The strncat_P function is similar to strncat except that the src string must be located in program space flash Returns strncat_P function returns a pointer to the resulting string dest Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 6 Additional notes from lt avr sfr_defs h gt 26 5 5 4 11 intstrncmp P const char s1 P 52 size_t n The function is similar to strcmp P except it only compares the first at most characters of 51 and s2 Returns The strncmp_P function returns an integer less than equal to or greater than zero if sl or the first n bytes thereof is found respectively to be less than to match or be greater than s2 5 5 4 12 char x strncpy P char dest P src size_t n The strncpy_P function is similar to strcpy P except that not more than n bytes of src are copied Thus if there is no null byte among the first n bytes of src the result will not be null terminated In the case where the length of src is less than that of n the remainder of dest will be padded with nulls Returns The strncpy_P function returns a pointer to the destinat
40. 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 24 series has been chosen where xx can be one of 01 02 04 08 or 16 which are available from various vendors The choice was almost arbitrary mainly triggered by the fact that an EEPROM device is being talked to in both directions reading and writing the slave device so the example will demonstrate the details of both Usually there is probably not much need to add more EEPROM to an ATmega system that way the smallest possible AVR device that offers hardware TWI support is the ATmega8 which comes with 512 bytes of EEPROM which is equivalent to an 24C04 device The ATmegal28 already comes with twice as much EEPROM as the 24C16 would offer One exception might be to use an externally connected EEPROM device that is removable g SDRAM PC memory comes with an integrated TWI EEPROM that carries the RAM configuration information 5 29 3 The Source Code 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 th
41. lt stdint h gt Standard Integer Types 65 5 17 2 28 define INT LEAST8 MIN INT8 MIN smallest negative value an int least8 t can hold 5 17 2 29 define INTMAX_C value CONCAT value LL define a constant of type intmax t 5 17 2 30 INTMAX MAX INT64 MAX largest positive value an intmax t can hold 5 17 2 31 INTMAX MIN INT64 MIN smallest negative value an intmax t can hold 5 17 2 32 define INTPTR MAX INT16 MAX largest positive value an intptr t can hold 5 17 2 33 define INTPTR MIN 6 MIN smallest negative value an intptr t can hold 5 17 2 34 define PTRDIFF MAX 6 MAX largest positive value a ptrdiff t can hold 5 17 2 35 itdefine PTRDIFF MIN INT16 MIN smallest negative value a ptrdiff t can hold 5 17 2 36 define SIG ATOMIC MAX INT8 largest positive value a sig atomic t can hold 5 17 2 37 SIG ATOMIC MIN INT8 MIN smallest negative value a sig atomic t can hold 5 17 2 38 define SIZE MAX CONCAT INTI6 MAX U largest value a size t can hold Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Integer Types 66 5 17 2 39 define UINT16_C value CONCAT value U define a constant of type uint16_t 5 17 2 40 define UINT16_MAX __CONCAT INT16_MAX U 2U 10 largest value an uint16_t can hold 5 17 2 41 define UINT32_C value _CONCAT value UL define a constant of type uin
42. of the device In order to use these functions the target device must support either the LPM or ELPM instructions Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 5 lt avr pgmspace h gt Program Space String Utilities 19 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 stan dard string functions described in lt string h gt Strings If possible put your constant tables in the lower 64K and use pgm_read_byte_ near or pgm_read_word_near instead of pgm_read_byte_far or pgm_read_ word_far since it is more efficient that way and you can still use the upper 64K for executable code Defines define PROGMEM __ATTR_PROGMEM__ define PSTR s const PROGMEM char x s define pgm_read_byte_near address_short __ LPM uint16 t address short define pgm_read_word_near address_short LPM word uint16 t address_short define pgm_read_dword_near address_short LPM dword uint16 t address_short define pgm_read_byte_far address_long _ ELPM uint32 t address long define pgm_read_word_far address_long __ELPM_word uint32_ t address_long define pgm_read_dword_far address_lon
43. 1 r result SFR IO ADDR port return result Note inw is supplied by avr libc 7 4 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 vari able will not be referenced any longer the register may be re used But the compiler Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 5 Using malloc 202 is not able to check wether this register usage conflicts with any predefined register If you reserve too many registers in this way the compiler may even run out of registers during code generation In order to change the name of a function you need a prototy
44. 141 r24 lo8 pm somefunc ldi r25 hi8 pm somefunc call something This passes the address of function somefunc as the first parameter to function something 7 3 Frequently Asked Questions 7 31 FAQ Index 1 My program doesn t recognize a variable updated within an interrupt routine Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 170 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 I get undefined reference to for functions like sin How to permanently bind a variable to a register How to modify MCUCR or WDTCR early What is all this BV stuff about Can I use C on the AVR Shouldn t I initialize all my variables Why do some 16 bit timer registers sometimes get trashed How do I use a define d constant an asm statement Why does the PC randomly jump around when single stepping through my pro gram in avr gdb How do I trace an assembler file in avr gdb How do I pass an IO port as a parameter to a function What registers are used by the C compiler How do I put an array of strings completely in ROM How to use external RAM Which O flag to use How do I relocate code to a fixed address My UART is generating nonsense My ATmega128 keeps crashing Port F is completely broken Why do all my foo bar strings eat up the SRAM Why does the compiler compile an 8 bit operation that uses bitwise oper
45. 2 15 define INT FAST32 MAX INT32 MAX largest positive value an int fast32 t can hold 5 17 2 16 define INT FAST32 MIN INT32 MIN smallest negative value an int fast32 t can hold Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Integer Types 64 5 17 2 17 define INT FAST64 MAX INT64 MAX largest positive value an int fast64 t can hold 5 17 2 18 define INT FAST64 MIN INT64 MIN smallest negative value an int fast 4 t can hold 5 17 2 19 define INT FAST8 MAX INT8 MAX largest positive value an int fast8 t can hold 5 17 2 20 define INT FAST8 MIN INT8 MIN smallest negative value an int fast8 t can hold 5 17 2 21 INT LEASTI6 MAX INTI6 MAX largest positive value an int least16 t can hold 5 17 2 22 itdefine INT LEAST16 MIN INT16 MIN smallest negative value an int least16 t can hold 5 17 2 23 define INT LEAST32 MAX INT32 MAX largest positive value an int least32 t can hold 5 17 2 24 define INT LEAST32 MIN INT32 MIN smallest negative value an int least32 t can hold 5 17 2 25 itdefine INT LEAST64 MAX INT64 MAX largest positive value an int least64 t can hold 5 17 2 26 define INT LEAST64 MIN INT64 MIN smallest negative value an int 1625464 t can hold 5 17 2 27 INT LEAST8 MAX INT8 MAX largest positive value an int least8 t can hold Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17
46. 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 122 Vector name Old vector name Description Applicable for device INTO_vect SIG_ INTERRUPTO External Interrupt 0 AT90S 1200 9052333 AT90S2313 AT90S2343 9054433 419054434 41719058515 AT90S8535 AT90PWMS3 AT9OPWM2 AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 16 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtinyll ATtinyl2 AT tiny13 ATtiny15 ATtiny22 ATtiny2313 ATtiny26 ATtiny28 ATtiny45 9052323 9054414 vect SIG_ INTERRUPT1 External Interrupt Request 1 9052313 9052333 9054433 AT90S4434 9058515 AT90S8535 AT90PWMS3 AT9IOPWM2 AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 16 ATmegal61 ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega64 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny2313 ATtiny28 9054414 INT2_vect SIG_ INTERRUPT2 External Interrupt Request 2 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64
47. 24 2 24 define TW ST LOST SLA 0xB0 arbitration lost in SLA RW SLA R received ACK returned 5 24 2 25 define TW ST DATA 0xB8 data transmitted ACK received 5 24 2 26 define TW ST DATA 0 0 data transmitted NACK received 5 24 2 27 define TW ST LAST DATA 0xC8 last data byte transmitted ACK received 5 24 2 28 define TW ST SLA 0xA8 SLA R received ACK returned Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 118 5 24 2 29 define TW START 0x08 start condition transmitted 5 24 2 30 define STATUS TWSR amp TW STATUS MASK TWSR masked by TW STATUS MASK 5 24 2 31 define TW STATUS MASK Value BV TWS7 BV TWS6 BV TWS5 54 BV TWS3 The lower 3 bits of TWSR are reserved on the ATmegal63 The 2 LSB carry the prescaler bits on the newer ATmegas 5 24 2 32 define TW WRITE 0 SLA W address 5 25 lt avr interrupt h gt Interrupts 5 25 1 Detailed Description Note This discussion of interrupts was originally taken from Rich Neswold s document See Acknowledgments Introduction to avr libe s interrupt handling It s nearly impossible to find compil ers that agree on how to handle interrupt code Since the C language tries to stay away from machine dependent details each compiler writer is forced to design their method of support In the AVR GCC environment the vector t
48. 5 15 3 18 double modf double __value double __iptr Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 16 lt setjmp h gt Non local goto 56 The modf function breaks the argument value into integral and fractional parts each of which has the same sign as the argument It stores the integral part as a double in the object pointed to by iptr The modf function returns the signed fractional part of value 5 15 3 19 double pow double __x double y The function pow returns the value of x to the exponent y 5 15 3 20 double sin double x The sin function returns the sine of x measured in radians 5 15 3 21 double sinh double x The sinh function returns the hyperbolic sine of x 5 15 3 22 double sqrt double x The sqrt function returns the non negative square root of x 5 15 3 23 double square double __x The function square returns x Note This function does not belong to the C standard definition 5 15 3 24 double tan double x The tan function returns the tangent of x measured in radians 5 15 3 25 double tanh double x The tanh function returns the hyperbolic tangent of x 5 16 lt setjmp h gt Non local goto 5 16 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 Generated on Sat Nov 19 23 00 48 2005 for a
49. 5 32 1 define REG LOCATIONS 1CIDIE In order to be able to work without a requiring a multilib approach for dealing with controllers having the EEPROM registers at different positions in memory space the eeprom functions evaluate _ LOCATIONS It is assumed to be defined by the device io header and contains 6 uppercase hex digits encoding the ad dresses of EECR EEDR and EEAR First two letters EECR address Second two letters EEDR address Last two letters EEAR address The default ICIDIE corre sponds to the register location that is valid for most controllers The value of this define symbol is used for appending it to the base name of the assembler functions 5 3 2 2 define EEGET var addr var eeprom read byte uint8 t x addr Read a byte from EEPROM Compatibility define for IAR C 5 3 2 3 define EEPUT addr val eeprom write byte uint8 t addr uint8 t val Write a byte to EEPROM Compatibility define for IAR C 5 3 2 4 define EEMEM attribute section eeprom Attribute expression causing a variable to be allocated within the eeprom section 5 3 2 5 fidefine eeprom busy wait do 1 while is ready Loops until the eeprom is no longer busy Returns Nothing Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 4 lt avr io h gt AVR device specific IO definitions 17 5 3 2 6 define eeprom_is_ready Returns 1 if EEPROM
50. 75 define SCNo16 o octal scanf format for uint16_t 5 14 2 76 define SCNo32 lo octal scanf format for uint32_t 5 14 2 77 define SCNoFASTI6 o octal scanf format for uint_fast16_t 5 14 2 78 define SCNoFAST32 lo octal scanf format for uint_fast32_t 5 14 2 79 define SCNoLEAST16 o octal scanf format for uint_least16_t 5 14 2 80 define SCNoLEAST32 lo octal scanf format for uint_least32_t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt inttypes h gt Integer Type conversions 51 5 14 2 81 ftdefine SCNoPTR SCNo16 octal scanf format for uintptr_t 5 14 2 82 define SCNu16 decimal scanf format for uint16_t 5 14 2 83 define SCNu32 lu decimal scanf format for uint32_t 5 14 2 84 define SCNuFASTI6 decimal scanf format for uint_fast16_t 5 14 2 85 define SCNuFAST32 lu decimal scanf format for uint_fast32_t 5 14 2 86 define SCNuLEASTIG u decimal scanf format for uint_least16_t 5 14 2 87 define SCNuLEAST32 lu decimal scanf format for uint_least32_t 5 14 2 88 define SCNuPTR SCNu16 decimal scanf format for uintptr_t 5 14 2 89 define SCNx16 x hexadecimal scanf format for uint16_t 5 14 2 90 define SCNx32 Ix hexadecimal scanf format for uint32_t 5 14 2 91 define SCNxFAST16 x hexadecimal scanf format for uint_fast16_t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 15 lt math h gt Mathematic
51. Capture AT9OPWM3 AT90PWM2 vect CAPTURE Event PSCI EC SIG PSCI End Cycle AT90PWM3 AT90PWM2 vect END_CYCLE PSC2_ SIG_PSC2_ PSC2 Capture AT90PWM3 AT90PWM2 CAPT_vect CAPTURE Event PSC2_EC_ SIG_PSC2_ PSC2 End Cycle AT90PWM3 AT90PWM2 vect END_CYCLE Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 124 Vector name Old vector Description Applicable for device name SPI STC vect SIG SPI Serial Transfer AT90S2333 AT90S4414 479054433 Complete AT90S4434 479058515 419058535 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 SPM RDY SIG SPM Store Program ATmegal6 ATmegal62 ATmega32 AT vect READY Memory Ready mega323 ATmega8 ATmega8515 AT mega8535 SPM_ SIG_SPM_ Store Program AT90PWM3 AT90PWM2 AT90CANI28 READY vect READY Memory Read AT90CAN32 AT90CAN64 ATmegal28 ATmegal65 ATmegal69 ATmega325 mega3250 ATmega329 ATmega3290 AT mega64 ATmega645 ATmega6450 AT mega649 ATmega6490 ATmegal68 AT mega48 ATmega88 ATmega
52. Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 521 lt utiV crc16 h gt CRC Computations 109 See the Dallas Semiconductor app note 27 for 8051 assembler example and general CRC optimization suggestions The table on the last page of the app note is the key to understanding these implementations Jack Crenshaw s Implementing CRCs article in the January 1992 isue of Embedded Systems Programming This may be difficult to find but it explains CRC s in very clear and concise terms Well worth the effort to obtain a copy A typical application would look like Dallas iButton test vector uint8 t serno 0x02 Oxlc 0xb8 0x01 0 0 0 Oxa2 int checkcrc void uint8 t cre 0 i for i 0 i lt sizeof serno sizeof serno 0 i crc _crc_ibutton_update crc serno i return crc must be 0 Functions e static inline uintl6 t crc16 update uint16 t __crc uint8 t data e static inline uintl6 t crc xmodem update uint16 t crc uint8 t data e static inline uintl6 t crc ccitt update uint16 t crc uint8 t data e static _ inline uint8 t crc ibutton update uint8 t crc uint8 t data 5 21 2 Function Documentation 5 21 2 1 static _ inline uint16 t crc16 update uint16 t _ crc uint8_t _ static Optimized CRC 16 calculation Polynomial x 16 x 15 x 2 1 0xa001 Initial value Oxffff This CRC is normally used in disk drive cont
53. Space String Utilities 18 register names common to all AVR devices are defined directly within lt avr io h gt but most of the details come from the respective include file Note that this file always includes include lt avr sfr_defs h gt See lt avr sfr_defs h gt Special function registers for the details Included are definitions of the IO register set and their respective bit values as specified in the Atmel documentation Note that Atmel is not very consistent in its naming conventions so even identical functions sometimes get different names on different devices Also included are the specific names useable for interrupt function definitions as docu mented here Finally the following macros are defined RAMEND A constant describing the last on chip RAM location XRAMEND A constant describing the last possible location in RAM This is equal to RA MEND for devices that do not allow for external RAM E2END A constant describing the address of the last EEPROM cell FLASHEND A constant describing the last byte address in flash ROM SPM_PAGESIZE For devices with bootloader support the flash pagesize in bytes to be used for the SPM instruction 5 5 lt avr pgmspace h gt Program Space String Utilities 5 51 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
54. a stream for reading will cause the resulting stream to be aliased to stdin Likewise the first call to fdevopen that opens a stream for writing will cause the resulting stream to be aliased to both stdout and stderr Thus if the open was done with both read and write intent all three standard streams will be identical Note that these aliases are indistinguishable from each other thus calling fclose on such a stream will also effectively close all of its aliases note 3 It is possible to tie additional user data to a stream using fdev_set_udata The back end put and get functions can then extract this user data using fdev_get_udata and act appropriately For example a single put function could be used to talk to two different UARTs that way or the put and get functions could keep internal state between calls there Format strings in flash ROM All the printf and scanf family functions come in two flavours the standard name where the format string is expected to be in SRAM as well as a version with the suffix _P where the format string is expected to reside in the flash ROM The macro PSTR explained in lt avr pgmspace h gt Program Space String Utilities becomes very handy for declaring these format strings Running stdio without malloc default fdevopen as well as the floating point versions of the printf and scanf family require malloc As this is often not desired in the limited environment of a microcont
55. arguments not in the range 1 1 5 15 3 3 double atan double x The atan function computes the principal value of the arc tangent of x The returned value is in the range 0 pi radians A domain error occurs for arguments not in the range 1 1 5 15 3 4 double atan2 double __y double The atan2 function computes the principal value of the arc tangent of y x using the signs of both arguments to determine the quadrant of the return value The returned value is in the range pi pi radians If both x and y are zero the global variable errno is set to EDOM 5 15 3 5 double ceil double x The ceil function returns the smallest integral value greater than or equal to x ex pressed as a floating point number 5 15 3 6 double cos double x The cos function returns the cosine of x measured in radians 5 15 3 7 double cosh double x The cosh function returns the hyperbolic cosine of x 5 15 3 8 double exp double x The exp function returns the exponential value of x 5 15 3 9 double fabs double x The fabs function computes the absolute value of a floating point number x 5 15 3 10 double floor double x The floor function returns the largest integral value less than or equal to x expressed as a floating point number Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 15 lt math h gt Mathematics 55 5 15 3 11 double fmod double _ double y Th
56. at90s8535 AVR 479058535 avr2 at86rf401 AVR AT86RF401 avr2 attiny 13 AVR AT nyl3 avr2 attiny2313 __AVR_ATtiny2313__ avr3 atmega 103 __AVR_ATmegal03__ avr3 atmega603 __AVR_ATmega603__ avr3 at43usb320 AVR AT43USB320 avr3 at43usb355 AVR AT43USB355 avr3 at76c711 __AVR_AT76C711__ avr4 atmega48 __AVR_ATmega48__ avr4 atmega8 __AVR_ATmega8__ avr4 atmega8515 _ AVR_ATmega8515__ avr4 atmega8535 AVR_ATmega8535__ avr4 atmega88 AVR ATmega88 avr4 at90pwm2 _ AVR_AT90PWM2__ avr4 at90pwm3 AVR AT90PWM3 avr5 at90can32 AVR AT90CAN32 avr5 at90can64 __AVR_AT90CAN64__ avr5 at90canl28 AVR ATO0CANI28 avr5 atmega 128 AVR ATmegal28 avr5 atmegal280 AVR ATmegal280 avr5 atmegal281 ATmegal281 avr5 atmega16 __AVR_ATmegal6__ avr5 atmegal61 AVR ATmegal6l Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 225 Architecture MCU name Macro avr5 atmegal62 AVR ATmegal62 avr5 atmega 163 AVR ATmegal63 avr5 atmegal64 _ AVR ATmegal64 avr5 atmega 165 AVR ATmegal65 avr5 atmega 168 __AVR_ATmegal68__ avr5 atmegal69 AVR_ATmegal69__ avr5 atmega32 AVR ATmega32 avr5 atmega323 AVR ATmega323 avr5 atmega324 AVR ATmega324 avr5 atmega325 AVR ATmega325 avr5 atmega3250 AVR ATmega3250 avr5 atmega329 ATmega320 avr5 atmega3290 _ AVR
57. avr libc Data Structure Index 3 1 avr libc Data Structures Here are the data structures with brief descriptions div_t 161 Idiv_t 162 4 avr libc Page Index 41 avr libc Related Pages Here is a list of all related documentation pages Acknowledgments 163 avr libc and assembler programs 164 Frequently Asked Questions 169 Inline Asm 190 Using malloc 202 Release Numbering and Methodology 207 Memory Sections 210 Installing the GNU Tool Chain 215 Using the avrdude program 221 Using the GNU tools 223 Todo List 232 Deprecated List 232 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 avr libc Module Documentation 8 5 avr libc Module Documentation 5 1 lt assert h gt Diagnostics 5 1 4 Detailed Description finclude assert h This header file defines a debugging aid As there is no standard error output stream available for many applications using this library the generation of a printable error message is not enabled by default These messages will only be generated if the application defines the macro ASSERT USE STDERR before including the assert h gt header file By default only abort will be called to halt the application Defines define assert expression 5 1 22 Define Documentation 5 1 2 1 define assert expression Parameters expression Expression to test for The assert macro tests the given expression and if it is false the calling process is terminated A diagn
58. be small enough to recharge the line capacity in short enough time compared to the desired maximal clock fre quency yet large enough so all drivers will not be overloaded There are formulas in the datasheet that help selecting the pullups Devices can either act as a master to the bus i e they initiate a transfer or as a slave they only act when being called by a master The bus is multi master capable and a particular device implementation can act as either master or slave at different times Devices are addressed using a 7 bit address coordinated by Philips transfered as the first byte after the so called start condition The LSB of that byte is R W i e it determines whether the request to the slave is to read or write data during the next cycles There is also an option to have devices using 10 bit addresses but that is not covered by this example 5 29 2 TWI example project The ATmega TWI hardware supports both master and slave operation This example will only demonstrate how to use an AVR microcontroller as TWI master The imple mentation is kept simple in order to concentrate on the steps that are required to talk to a TWI slave so all processing is done in polled mode waiting for the TWI interface to Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 29 Example using the two wire interface TWI 149 indicate that the next processing step is due by setting the TWINT interrupt bit If it
59. bug then the default action is to reset the device by jumping to the reset vector You can override this by supplying a function named vector default which should be defined with ISR as such include lt avr interrupt h gt ISR __vector_default user code here Nested interrupts AVR hardware clears the global interrupt flag in SREG be fore entering an interrupt vector Thus normally interrupts will remain disabled inside the handler until the handler exits where the RETI instruction that is emitted by the compiler as part of the normal function epilogue for an interrupt handler will even tually re enable further interrupts For that reason interrupt handlers normally do not nest For most interrupt handlers this is the desired behaviour for some it is even required in order to prevent infinitely recursive interrupts like UART interrupts or level triggered external interrupts In rare circumstances though it might be desired to re enable the global interrupt flag as early as possible in the interrupt handler in order to not defer any other interrupt more than absolutely needed This could be done using an sei instruction right at the beginning of the interrupt handler but this still leaves few instructions inside the compiler generated function prologue to run with global in terrupts disabled The compiler can be instructed to insert an SEI instruction right at the beginning of an interrupt handler by declaring
60. by simply using the IO port name in an expression and all bit manipulation including those on IO ports can be done using generic C bit manipulation operators The macros in this group simulate the historical behaviour While they are supposed to be applied to IO ports the emulation actually uses standard C methods so they could be applied to arbitrary memory locations as well define inp port port define outp port val port val e define sbi port bit port 1 lt lt bit define cbi port bit port amp 1 lt lt bit 5 10 2 Define Documentation 5 10 2 1 define cbi port bit port amp 1 lt lt bit Deprecated Clear bit in IO port port 5 10 2 2 define enable external int mask __EICR mask Deprecated This macro gives access to the GIMSK register or EIMSK register if using an AVR Mega device or GICR register for others Although this macro is essentially the same as assigning to the register it does adapt slightly to the type of device being used This macro is unavailable if none of the registers listed above are defined Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 10 lt compat deprecated h gt Deprecated items 36 5 10 2 3 define inp port port Deprecated Read a value from an IO port port 5 10 2 4 define INTERRUPT signame Value void signame void __attribute__ interrupt void signame void Deprecated Intr
61. by the prefix WDTO_ followed by the time Example that would select a watchdog timer expiry of approximately 500 ms enable WDTO 500 5 5 9 2 6 define WDTO 1S 6 See WDTO_15MS 5 9 2 7 define WDTO 250MS 4 See WDTO 15MS 5 9 2 8 define WDTO 28 7 See WDTO 15MS 5 9 2 9 define WDTO 30MS 1 See WDTO 15MS 5 9 2 10 ftdefine WDTO 45 8 See WDTO_15MS Note This is only available on the ATtiny2313 ATtiny25 AT tiny45 ATtiny85 ATmega48 ATmega88 ATmegal64 ATmegal68 ATmega324 ATmega644 ATmega640 ATmegal280 ATmegal281 AT9OPWM2 and the AT90PWM3 5 9 2 11 define WDTO 500MS 5 See WDTO 15MS Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 10 lt compat deprecated h gt Deprecated items 34 5 9 2 12 define WDTO_60MS 2 WDTO_15MS 5 9 2 13 define WDTO 85 9 See WDTO_15MS Note This is only available on the ATtiny2313 25 AT tiny45 ATtiny85 ATmega48 ATmega88 ATmegal64 ATmegal68 ATmega324 ATmega644 ATmega640 ATmegal280 ATmegal281 AT90PWM2 and the AT90PWM3 5 10 lt compat deprecated h gt Deprecated items 5 10 1 Detailed Description This header file contains several items that used to be available in previous versions of this library but have eventually been deprecated over time include lt compat deprected h gt These items are supplied within that header file for backward compatibility reasons only so old source code that has been written fo
62. characters C string Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 169 data switches to the data section initialized RAM variables text switches to the text section code and ROM constants set declares a symbol as a constant expression identical to equ global or globl declares a public symbol that is visible to the linker e g function entry point global variable extern declares a symbol to be externally defined this is effectively a comment only as gas treats all undefined symbols it encounters as globally undefined any way Note that org is available in gas as well but is a fairly pointless pseudo op in an as sembler environment that uses relocatable object files as it is the linker that determines the final position of some object in ROM or RAM Along with the architecture independent standard operators there are some AVR specific operators available which are unfortunately not yet described in the official documentation The most notable operators are 108 Takes the least significant 8 bits of a 16 bit integer hi8 Takes the most significant 8 bits of a 16 bit integer pm Takes a program memory ROM address and converts it into a RAM ad dress This implies a division by 2 as the AVR handles ROM addresses as 16 bit words e g in an IJMP or ICALL instruction can also handle relocatable symbols on the right hand side Example
63. currently no support for libstdc the standard support library needed for a complete C implementation This imposes a number of restrictions on the C programs that can be compiled Among them are Obviously none of the C related standard functions classes and template classes are available The operators new and delete are not implemented attempting to use them will cause the linker to complain about undefined external references This could perhaps be fixed Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 174 Some of the supplied include files are not C safe i e they need to be wrapped into extern C This could certainly be fixed too Exceptions are not supported Since exceptions are enabled by default in the C frontend they explicitly need to be turned off using no exceptions in the compiler options Failing this the linker will complain about an undefined external referenceto personality 510 Constructors and destructors are supported though including global ones When programming C in space and runtime sensitive environments like microcon trollers extra care should be taken to avoid unwanted side effects of the C calling conventions like implied copy constructors that could be called upon function invo cation etc These things could easily add up into a considerable amount of time and program memory wasted Thus
64. date code YY YYMMDD appended This file will also be included by lt avr io h gt That way portable tests can be imple mented using lt avr io h gt that can be used in code that wants to remain backwards compatible to library versions prior to the date when the library version API had been added as referenced but undefined C preprocessor macros automatically evaluate to 0 Defines e define _ AVR VERSION STRING 1 4 0 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 8 lt avr version h gt avr libc version macros 30 e define _ AVR_LIBC_VERSION__ 10400UL e define _ AVR_LIBC_DATE_STRING__ 20051119 e define 20051119UL e define _ MAJOR 1 e define _ LIBC MINOR 4 define _ AVR REVISION 0 5 8 Define Documentation 5 8 2 1 define AVR DATE 20051119UL Numerical representation of the release date 5 8 2 2 define DATE STRING 20051119 String literal representation of the release date 5 8 2 3 define AVR MAJOR 1 Library major version number 5 8 2 4 define _ LIBC MINOR 4 Library minor version number 5 8 2 5 fidefine REVISION 0 Library revision number 5 8 2 6 define VERSION 1040001 Numerical representation of the current library version In the numerical representation the major number is multiplied by 10000 the minor
65. decimal point appears only if it is followed by at least one digit S Similar to the s format except the pointer is expected to point to a program memory ROM string instead of a RAM string In no case does a non existent or small field width cause truncation of a numeric field if the result of a conversion is wider than the field width the field is expanded to contain the conversion result Since the full implementation of all the mentioned features becomes fairly large three different flavours of vfprintf can be selected using linker options The default vf printf implements all the mentioned functionality except floating point conversions A minimized version of vfprintf is available that only implements the very basic in teger and string conversion facilities but none of the additional options that can be specified using conversion flags these flags are parsed correctly from the format spec ification but then simply ignored This version can be requested using the following compiler options Wl u vfprintf lprintf min If the full functionality including the floating point conversions is required the follow ing options should be used Wl wvfprintf lprinttf flt lm Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 85 Limitations The specified width and precision can be at most 127 For floating point conversions trailing digits w
66. device to respond for selection Should be large enough to allow for a pending write to complete but low enough to properly abort an infinite loop in case a slave is broken or not present at all With 100 kHz TWI clock transfering the start condition and SLA R W packet takes about 10 ts longest write period is supposed to not exceed 10 ms Thus normal operation should not require more than 100 iterations to get the device to respond to a selection define MAX_ITER 200 Number of bytes that can be written row see comments for ee24xx_write_page below Some vendor s devices would accept 16 but 8 seems to be the lowest common denominator Note that the page size must be a power of two this simplifies the page boundary calculations below define PAGE_SIZE 8 Saved status register for error messages only We need to Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 29 Example using the two wire interface TWI 151 save it in a variable since the datasheet only guarantees the TWSR register to have valid contents while the TWINT bit in TWCR is set x uint8 t twst Do all the startup time peripheral initializations UART for our debug test output and TWI clock void ioinit void if F_CPU lt 1000000UL Note 4 Slow system clock double Baud rate to improve rate error
67. drivers at high impedance and does not respond to a selection in any way at all The master selecting the device will see the high level at SDA after transfering the SLA R W packet as a NACK to its selection request Thus the select process is simply started over effectively causing a repeated start condition until the device will eventually respond This polling procedure is recommended in the 24Cxx datasheet in order to minimize the busy wait time when writing Note that in case a device is broken and never responds to a selection e g since it is no longer present at all this will cause an infinite loop Thus the maximal number of iterations made until the device is declared to be not responding at all and an error is returned will be limited to MAX_ITER Note 12 This is called master receiver mode the bus master still supplies the SCL clock but the device slave drives the SDA line with the appropriate data After 8 data bits the master responds with an ACK bit SDA driven low in order to request another data transfer Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 6 avr libc Data Structure Documentation 161 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 n
68. external memory interface early during the device initialization so the initialization of these variable will take place Refer to How to modify MCUCR or WDTCR early for a description how to do this using few lines of assembler code or to the chapter about memory sections for an example written in C The explanation of malloc contains a discussion about the use of internal RAM vs external RAM in particular with respect to the various possible locations of the heap area reserved for malloc It also explains the linker command line options that are required to move the memory regions away from their respective standard locations in internal RAM Finally if the application simply wants to use the additional RAM for private data storage kept outside the domain of compiler g through a char variable initialized directly to a particular address it would be sufficient to defer the initializa tion of the external RAM interface to the beginning of main so no tweaking of the init3 section is necessary The same applies if only the heap is going to be located there since the application start up code does not affect the heap It is not recommended to locate the stack in external RAM In general accessing exter nal RAM is slower than internal RAM and errata of some AVR devices even prevent this configuration from working properly at all Back to FAQ Index 7 3 17 Which O flag to use There s acommon misconception th
69. in preprocessed assem bler S source files so it is done automatically if ASSEMBLER is defined By default all addresses are defined as if they were memory addresses used in 1ds st s instructions To use these addresses in in out instructions you must subtract 0x20 from them For more backwards compatibility insert the following at the start of your old assem bler source file define _ SFR OFFSET 0 This automatically subtracts 0x20 from I O space addresses but it s a hack so it is recommended to change your source wrap such addresses in macros defined here as shown below After this is done the___SFR_OFF SET definition is no longer necessary and can be removed Real example this code could be used in a boot loader that is portable between devices with SPMCR at different addresses lt avr ioml63 h gt define SPMCR _SFR_I08 0x37 lt avr iom128 h gt define SPMCR _SFR_MEM8 0x68 dif SFR IO REG P SPMCR out SFR IO ADDR SPMCR r24 else sts _SFR_MEM_ADDR SPMCR r24 endif You can use the in out cbi sbi sbic 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 s
70. int64 t intmax t e typedef uint64 t uintmax t 5 17 2 Define Documentation 5 17 21 define 6 C value value define a constant of type int16 t 5 17 2 2 ftdefine INTI6 MAX 0x7fff largest positive value an int16 t can hold 5 17 2 3 INTI6 MIN 16 MAX 1 smallest negative value an int16 t can hold 5 17 2 4 define INT32_C value _CONCAT value L define a constant of type int32_t 5 17 2 5 define INT32 MAX Ox7fffffffL largest positive value an int32 t can hold Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Integer Types 63 5 17 2 6 define INT32 MIN INT32 MAX IL smallest negative value an int32 t can hold 5 17 27 define INT64_C value CONCAT value LL define a constant of type int64_t 5 17 2 define INT64_MAX OXx 7fffffffffffffffLL largest positive value an int64_t can hold 5 17 2 9 define INT64 MIN INT64 MAX ILL smallest negative value an int64 t can hold 5 17 2 10 define INT8 C value int8 t value define a constant of type int8 t 5 17 2 11 define INT8 MAX 0x7f largest positive value an int8 t can hold 5 17 212 ftdefine INT8 MIN INT8 MAX 1 smallest negative value an int8 t can hold 5 17 2 13 define INT FASTI6 MAX INTI6 MAX largest positive value an int fast16 t can hold 5 17 2 14 define INT FAST16 MIN INT16 MIN smallest negative value an int fast16 t can hold 5 17
71. isblank loop_until_bit_is_set ctype 38 avr_sfr 134 iscntrl Itoa ctype 38 avr_stdlib 94 isdigit ctype 38 M_PI isgraph avr_math 53 ctype 38 M_SQRT2 isinf avr_math 53 avr_math 54 malloc islower avr_stdlib 94 ctype 38 isnan avr_string 101 avr_math 55 memchr isprint avr_string 101 ctype 38 memcmp ispunct avr string 101 ctype 38 memcpy ISR avr string 102 avr interrupts 130 P isspace avr pgmspace 23 ctype 38 memmove isupper avr string 102 ctype 38 memset isxdigit avr string 102 ctype 39 modf itoa avr math 55 avr stdlib 93 labs avr stdlib 93 ldexp avr math 55 Idiv avr_stdlib 94 Idiv_t 161 quot 161 rem 161 outp deprecated_items 36 parity_even_bit util_parity 113 PGM_P avr_pgmspace 19 pgm_read_byte avr_pgmspace 19 pgm_read_byte_far Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 245 avr_pgmspace 20 pgm_read_byte_near avr_pgmspace 20 pgm_read_dword avr_pgmspace 20 pgm_read_dword_far avr_pgmspace 20 pgm_read_dword_near avr_pgmspace 20 pgm_read_word avr_pgmspace 21 pgm_read_word_far avr_pgmspace 21 pgm_read_word_near avr_pgmspace 21 PGM_VOID_P avr_pgmspace 21 pow avr_math 55 PRId16 avr_inttypes 43 PRId32 avr_inttypes 43 PRId8 avr inttypes 43 PRIdFAST 16 avr_inttypes 43 PRIdFAST32 avr_inttypes 43 PRIdFAST8 avr_inttypes 43 PRIdLEAST16 avr_inttypes 43 PRI
72. it makes the programs more portable to other C compilers for the AVR platform Some people might also feel that this is more readable For example the following two statements would be equivalent outb DDRD inb DDRD amp LCDBITS DDRD amp LCDBITS The generated code is identical for both Without optimization the compiler strictly generates code following the memory mapped paradigm while with optimization turned on code is generated using the faster and smaller in out MCU instructions Note that special care must be taken when accessing some of the 16 bit timer IO reg isters where access from both the main program and within an interrupt context can happen See Why do some 16 bit timer registers sometimes get trashed Porting programs that use sbi cbi As described above access to the AVR single bit set and clear instructions are provided via the standard C bit manipulation commands The sbi and cbi commands are no longer directly supported sbi sfr bit can be replaced by sfr _BV bit ie sbi PORTB PB1 is now PORTB _BV PB1 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 26 lt avr sfr_defs h gt Special function registers 134 This actually is more flexible than having sbi directly as the optimizer will use a hard ware sbi if appropriate or a read or write if not You do not need to keep track of which registers sbi cbi will operate on Likewise cbi sfr bit is now sfr amp
73. much lower speeds than the typical PC these days The memory allocator implemented in avr libc tries to cope with all of these con straints and offers some tuning options that can be used if there are more resources available than in the default configuration 7 5 2 Internal vs external RAM Obviously the constraints are much harder to satisfy in the default configuration where only internal RAM is available Extreme care must be taken to avoid a stack heap collision both by making sure functions aren t nesting too deeply and don t require too much stack space for local variables as well as by being cautious with allocating too much dynamic memory If external RAM is available it is strongly recommended to move the heap into the ex ternal RAM regardless of whether or not the variables from the data and bss sections are also going to be located there The stack should always be kept in internal RAM Some devices even require this and in general internal RAM can be accessed faster since no extra wait states are required When using dynamic memory allocation and stack and heap are separated in distinct memory areas this is the safest way to avoid a stack heap collision Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 5 Using malloc 204 7 5 3 for malloc There are a number of variables that can be tuned to adapt the behavior of malloc to the expected requirements and constraints of the
74. number by 100 and all three parts are then added It is intented to provide a monoton ically increasing numerical value that can easily be used in numerical checks 5 8 2 7 define VERSION STRING 1 4 0 String literal representation of the current library version Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 9 lt avr wdt h gt Watchdog timer handling 3l 5 9 lt avr wdt h gt Watchdog timer handling 5 9 1 Detailed Description finclude avr wdt h This header file declares the interface to some inline macros handling the watchdog timer present in many AVR devices In order to prevent the watchdog timer configura tion from being accidentally altered by a crashing application a special timed sequence is required in order to change it The macros within this header file handle the required sequence automatically before changing any value Interrupts will be disabled during the manipulation Note Depending on the fuse configuration of the particular device further restrictions might apply in particular it might be disallowed to turn off the watchdog timer Note that for newer devices ATmega88 and newer effectively any AVR that has the op tion to also generate interrupts the watchdog timer remains active even after a system reset except a power on condition using the fastest prescaler value approximately 15 ms It is therefore required to turn off the watchdog early during progr
75. 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 ilocal hierarchy i e the binaries will get installed in usr local bin the info pages get installed in usr local info etc Since these tools are chang ing frequently It is preferrable to put them in a location that is easily removed When configure is run it generates a lot of messages while it determines what is available on your operating system When it finishes it will have created several Makefiles that are custom tailored to your platform At this point you can build the project Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 8 Installing the GNU Tool Chain 218 5 make Note BSD users should note that the project s Makefile uses GNU make syntax This means FreeBSD users may need to build the tools by using gmake If the tools compiled cleanly you re ready to install them If you specified a destination that isn t owned by your account you ll need root access to install them To install 5 make install You should now have the programs from binutils installed into SPREFIX bin Don t forget to set your PATH environment variable before going to build avr gcc 7 8 4 GCC for the AVR target
76. point Specific linker flags can be passed from the C compiler command line using W1 compiler option see above This option requires that there be no spaces in the appended linker option while some of the linker options above like Map or def sym would require a space In these situations the space can be replaced by an equal sign as well For example the following command line can be used to compile foo c into an executable and also produce a link map that contains a cross reference list in the file foo map avr gcc O o foo out Wl Map foo map Wl cref foo c Alternatively a comma as a placeholder will be replaced by a space before passing the option to the linker So for a device with external SRAM the following command line would cause the linker to place the data segment at address 0x2000 in the SRAM avr gcc mmcu atmegal28 o foo out Wl Tdata 0x802000 See the explanation of the data section for why 0x800000 needs to be added to the ac tual value Note that unless a minit stack option has been given when compiling the C source file that contains the function main the stack will still remain in inter nal RAM through the symbol __ stack that is provided by the run time startup code This is probably a good idea 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
77. prefixed with TW Note 2 The clock is used in timer calculations done by the compiler for the UART baud rate and the TWI clock rate Note 3 The address assigned for the 24Cxx EEPROM consists of 1010 in the upper four bits The following three bits are normally available as slave sub addresses allowing to operate more than one device of the same type on a single bus where the actual sub address used for each device is configured by hardware strapping However since the next data packet following the device selection only allows for 8 bits that are used as an EEPROM address devices that require more than 8 address bits 24C04 and above Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 529 Example using the two wire interface TWI 159 steal subaddress bits and use them for the EEPROM cell address bits 9 to 11 as re quired This example simply assumes all subaddress bits 0 for the smaller devices so the E1 and E2 inputs of the 24Cxx must be grounded Note 4 For slow clocks enable the 2 x U S ART clock multiplier to improve the baud rate error This will allow a 9600 Bd communication using the standard 1 MHz calibrated RC oscillator See also the Baud rate tables in the datasheets Note 5 The datasheet explains why a minimum TWBR value of 10 should be maintained when running in master mode Thus for system clocks below 3 6 MHz we cannot run the bus at the intented clock rate of 1
78. 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 The dtostrf function returns the pointer to the converted string s 5 19 4 11 void exit int status The exit function terminates the application Since there is no environment to re turn to status is ignored and code execution will eventually reach an infinite loop thereby effectively halting all code processing In a C context global destructors will be called before halting execution 5 19 4 12 void free void ptr The free function causes the allocated memory referenced by pt to be made avail able for future allocations If pt is NULL no action occurs 5 19 4 13 charx itoa int __val char x s int radix Convert an integer to a string The function itoa converts the integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing sufficient storage in s Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h gt General utilities 94 Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof int 1 characters i e one character for e
79. the FreeBSD http www freebsd org ports tree and for pro viding the basics for the demo project Brian Dean bsd bsdhome com for developing avrdude an alternative to uisp and for contributing documentation which describes how to use it Avr dude was previously called avrprog Eric Weddington eric evcohs com for maintaining the WinAVR pack age and thus making the continued improvements to the Opensource AVR toolchain available to many users Rich Neswold for writing the original avr tools document which he graciously allowed to be merged into this document and his improvements to the demo project Theodore A Roth for having been a long time maintainer of many of the tools AVR Libc the AVR port of GDB AVaRICE uisp avrdude All the people who currently maintain the tools and or have submitted sugges tions patches and bug reports See the AUTHORS files of the various tools And lastly all the users who use the software If nobody used the software we would probably not be very motivated to continue to develop it Keep those bug reports coming Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 2 avr libc and assembler programs 164 7 22 avr libc and assembler programs 7 2 Introduction There might be several reasons to write code for AVR microcontrollers using plain assembler source code Among them are Code for devices that do not have RAM and are thus not supported by the
80. using the following command avr objcopy j text j data O ihex demo elf demo hex The resulting demo hex file contains 1000000012C06DC06CC06BCO6ACO69CO068CO67COF8 1000100011 065 064 063 062 061 060 05 021 100020005ECO5DC05CC011241FBECFE5D4E0DEBF 62 0003000CDBF4FC01F920F920FB60F9211242F9376 00040008F939F93809160009927009719F00197F3 000500031F514C0809161009091620001969093F7 000600062008093610080916100909162008F5FD7 100070009340A9F481E08093600011C080916100F9 10008000909162000197909362008093610080914B Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 simple project 146 10009000610090916200892 11 4109260008091 0 1000A0006100909162009BBD8ABD9F918F912F91BD 1000B0000F900FBE0F901F90189583E88FBD81E0C1 1000C0008EBDIBBClABC82E087BB84E089BF7894DC 1000D0000895CFE5DA4EODEBFCDBFEFDFFFCF90CFF7 00000001FF The option indicates that we want the information from the text and data segment extracted If we specify the EEPROM segment we can generate a hex file that can be used to program the EEPROM avr objcopy j eeprom change section Ima eeprom 0 O ihex demo elf demo eeprom hex The resulting demo eeprom hex file contains 00000001FF which is an empty hex file which is expected since we didn t define any EEPROM variables 5 28 7 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 proje
81. 00 kHz but have to slow down accordingly Note 6 This function is used by the standard output facilities that are utilized in this example for debugging and demonstration purposes Note 7 In order to shorten the data to be sent over the TWI bus the 24Cxx EEPROMs support multiple data bytes transfered within a single request maintaining an internal address counter that is updated after each data byte transfered successfully When reading data one request can read the entire device memory if desired the counter would wrap around and start back from 0 when reaching the end of the device Note 8 When reading the EEPROM a first device selection must be made with write intent R W bit set to 0 indicating a write operation in order to transfer the EEPROM ad dress to start reading from This is called master transmitter mode Each completion of a particular step in TWI communication is indicated by an asserted TWINT bit in TWCR An interrupt would be generated if allowed After performing any actions that are needed for the next communication step the interrupt condition must be man ually cleared by setting the TWINT bit Unlike with many other interrupt sources this would even be required when using a true interrupt routine since as soon as TWINT is re asserted the next bus transaction will start Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 29 Example using the two wire interface TWI 160 Note
82. 000 lt ioinit gt void ioinit void x Note 5 tmrl is 10 bit PWM x TCCRIA BV PWM10 _BV PWM11 _BV 11 ba 83 e8 141 r24 0x83 131 bc 8f bd out 0x2f r24 47 tmrl running on full MCU clock x TCCRIB BV CS10 be 81 eO c0 8e bd out 0x2e set PWM value to 0 OCR 0 C2 1b be out 0x2b c4 la be out 0 2 enable and PB2 as DDROC BV 0 1 c6 82 e0 c8 87 bb out 0x17 enable interrupts TIMSK TOIE1 84 0 ec 89 bf out 0x39 sei ce 78 94 sei d0 08 95 ret 00000082 main int main void d2 cf 5 1 r28 0 d4 d4 eO ldi r29 0 d6 de bf out 0x3e d8 cd bf out 0x3d ioinit da ef df rcall 34 cE rjmp 2 2 000000de lt __bad_interrupt gt de 90 cf rjmp 224 141 r24 0x01 1 r24 46 a gd 42 output x ldi r24 0x02 2 r24 23 ldi r24 0x04 4 p24 3 5T XSF 3 95 x04 4 29 77 62 28 7 61 lt ioinit gt Oxdc lt main 0xa gt 0 0 lt __heap_end gt Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 simple project 144 5 28 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 w
83. 0x55 ES 114 88 e3 141 r24 0x38 56 116 90 0 141 r25 0 00 4 50 1185 94 7c 00 call Oxf8 You can clearly see that 0 0038 is correctly passed for the address of the 10 port Looking at the disassembled object code for the body of the function we can see that the function is indeed performing the operation we intended void set bits func correct volatile uint8 t xport uint8 t mask 8 fc 01 movw r30 r24 port mask Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 180 fa 80 81 1 r24 7 FG 86 2b or r24 r22 fe 80 83 st 2 r24 100 08 95 ret Notice that we are accessing the io port via the LD and ST instructions The port parameter must be volatile to avoid a compiler warning Note Because of the nature of the IN and OUT assembly instructions they can not be used inside the function when passing the port in this way Readers interested in the details should consult the Instruction Set data sheet Finally we come to the macro version of the operation In this contrived example the macro is the most efficient method with respect to both execution speed and code size set bits macro PORTB 0 0 IIg 88 in r24 0x18 24 11 80 6f ori r24 OxF0 240 120 88 bb out 0x18 r24 24 Of course in a real application you might be doing a lot more in your function which uses a passed by reference io port address and thus the use of a functi
84. 14 2 10 define PRIdPTR PRId16 decimal printf format for intptr_t 5 14 2 11 PRIi16 i integer printf format for int16_t 5 14 2 12 define PRIi32 li integer printf format for int32_t 5 14 2 13 ffdefine PRIi8 i integer printf format for int8_t 5 14 2 14 define PRIiFASTI6 i integer printf format for int_fast16_t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 45 5 14 2 15 define PRIiFAST32 Ii integer printf format for int fast32 t 5 14 2 16 define PRIiFASTS i integer printf format for int fast8 t 5 14 2 17 ftdefine PRIILEASTI6 i integer printf format for int leastl6 t 5 14 2 18 define PRIILEAST32 li integer printf format for int least32 t 5 14 2 19 define PRIiLEASTS i integer printf format for int least8 t 5 14 2 20 define PRIiPTR PRIi16 integer printf format for intptr t 5 14 2 21 define PRIo16 o octal printf format for uint16 t 5 14 2 22 define PRIo32 lo octal printf format for uint32 t 5 14 2 23 define PRIo8 o octal printf format for uint8 t 5 14 2 24 define PRIoFAST16 o octal printf format for uint fast16 t 5 14 2 25 define PRIoFAST32 lo octal printf format for uint_fast32_t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 46 5 14 2 26 define PRIoFASTS o octal
85. 26 2 5 loop until bit is set sfr bit do while bit_is_clear sfr bit include lt avr io h gt Wait until bit bit in IO register s fr is set 5 27 Demo projects 5 27 1 Detailed Description Various small demo projects are provided to illustrate several aspects of using the open source utilities for the AVR controller series It should be kept in mind that these de mos serve mainly educational purposes and are normally not directly suitable for use in any production environment Usually they have been kept as simple as sufficient to demonstrate one particular feature The simple project is somewhat like the Hello world application for a microcon troller about the most simple project that can be done It is explained in good detail to allow the reader to understand the basic concepts behind using the tools on an AVR microcontroller The Example using the two wire interface TWT project explains the use of the two wire hardware interface also known as I2C that is present on many AVR controllers Modules e A simple project Example using the two wire interface TWI Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 simple project 136 5 28 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
86. 28 AT90CAN32 AT90CANGA COMP_vect COMPARATOR parator ATmegal03 ATmegal28 ATmegal65 megal69 ATmega325 ATmega3250 AT mega329 ATmega3290 ATmega64 AT mega645 ATmega6450 ATmega649 AT mega6490 ATmegal68 ATmega48 AT mega88 ATmega640 ATmegal280 AT megal281 ATmega324 ATmegal64 AT mega644 ANA SIG Analog Com 9051200 AT90S2313 AT908S2333 COMP vect COMPARATOR parator AT90S4414 419054433 419054434 AT90S8515 419058535 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 AT mega8515 ATmega8535 ATtinyll ATtiny12 ATtiny13 ATtiny15 ATtiny2313 ATtiny26 ATtiny28 ATtiny45 CANIT vect SIG CAN Transfer AT90CAN128 AT90CAN32 AT90CAN64 INTERRUPTI Complete or Error EEPROM SIG ATtiny2313 READY vect EEPROM READY SIG EE READY EE RDY vect SIG EEPROM Ready 9052333 AT90S4433 AT90S4434 EEPROM_ AT9088535 ATmegal6 ATmegal6l READY ATmegal62 ATmegal63 ATmega32 ATmega323 ATmega8 ATmega8515 AT mega8535 ATtiny12 ATtiny13 ATtiny15 ATtiny26 ATtiny45 EE_READY_ SIG_ EEPROM Ready AT90PWM3 AT90PWM2 AT90CANI28 vect EEPROM AT90CAN32 AT90CANO4 ATmegal03 READY ATmegal28 ATmegal65 ATmegal69 AT mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT megal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 Generated on Sat Nov 19 23 00 48
87. 4 Enhanced CPU core up to 8 KB of ROM avr5 Enhanced CPU core more than 8 KB of ROM By default code is generated for the avr2 architecture Note that when only using mmcu architecture but no mmcu MCU type including the file lt avr io h gt cannot work since it cannot decide which device s definitions to select e 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 Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 224 Architecture MCU name Macro avrl at90s1200 AVR AT9081200 avrl attinyll _ ATtinyll avrl attiny 12 __AVR_ATtiny12__ avrl attiny 15 __AVR_ATtiny15__ avrl attiny28 __AVR_ATtiny28__ avr2 at90s2313 __AVR_AT90S2313__ avr2 at90s2323 AVR 479052323 avr2 at90s2333 __AVR_AT90S2333__ avr2 at90s2343 AVR 479052343 avr2 attiny22 __AVR_ATtiny22__ avr2 attiny25 __AVR_ATtiny25__ avr2 attiny26 __AVR_ATtiny26__ 2 attiny45 __AVR_ATtiny45__ avr2 attiny85 __AVR_ATtiny85__ avr2 at90s4414 AVR 479054414 avr2 at90s4433 AVR 479054433 avr2 at90s4434 AVR 479054434 avr2 219058515 __AVR_AT90S8515__ avr2 at90c8534 AVR AT90C8534 avr2
88. 479052313 define PB3 define OCR OCR1 define DDROC DDRB elif defined __AVR_AT90S2333__ defined __AVR_AT90S4433__ define 1 define DDROC DDRB define OCR OCRI elif defined AVR 479054414 defined AVR AT90S8515 defined AVR AT90S4434 defined AVR ATmegal63 9 efine PD5 efine DDROC DDRD efine OCR OCRIA f defined __AVR_ATmega8__ efine 1 efine DDROC DDRB efine OCR OCRIA efine 10 WGM10 efine PWM11 WGM11 f defined __AVR_ATmega32__ defined __AVR_ATmegal6__ efine PD5 efine DDROC DDRD e e e f e e e e e e r i defined _ AVR 479058535 Fh Fh Fh H o E ine OCR OCRIA fine 10 WGM10 fine 11 WGM11 defined __AVR_ATmega64__ defined AVR ATmegal28 fine 5 fine DDROC DDRB fine OCR OCRIA fine 10 WGM10 fine 11 WGM11 h Fh H oO db de SE db db dE db db db db db de Je de de db OSE db dE SE db dk ror Don t know what kind of MCU you are compiling for fif defined COMI11 define 11 11 elif defined 1 1 define 11 1 1 else error need either COMIA1 or 11 endif enum UP DOWN volatile uint16_t x Note 1 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 simple project 139 vola
89. 5 for avr libe by Doxygen 5 19 lt stdlib h gt General utilities 97 The expected form of the string is an optional plus or minus sign followed by a sequence of digits optionally containing a decimal point character op tionally followed by an exponent An exponent consists of an E or e followed by an optional plus or minus sign followed by a sequence of digits Leading white space characters in the string are skipped The strtod function returns the converted value if any If endptr is not NULL a pointer to the character after the last character used in the conversion is stored in the location referenced by endpt r If no conversion is performed zero is returned and the value of is stored in the location referenced by endpt If the correct value would cause overflow plus or minus HUGE_VAL is returned ac cording to the sign of the value and ERANGE is stored in errno If the correct value would cause underflow zero is returned and ERANGE is stored in errno FIXME HUGE VAL needs to be defined somewhere The bit pattern is Ox7fffffff but what number would this be 5 19 4 27 long strtol const char __nptr char __endptr int __base strtol function converts the string in nptr to a long value The conversion is done according to the given base which must be between 2 and 36 inclusive or be the special value 0 The string may begin with an ar
90. 54 cosh 54 exp 54 fabs 54 floor 54 fmod 54 frexp 54 isinf 54 isnan 55 1 55 log 55 log 10 55 M_PI 53 M 5 2 53 modf 55 pow 55 sin 55 sinh 55 sqrt 56 square 56 tan 56 tanh 56 avr_pgmspace memcpy_P 23 PGM_P 19 pgm_read_byte 19 pgm_read_byte_far 20 pgm_read_byte_near 20 pgm_read_dword 20 pgm_read_dword_far 20 pgm_read_dword_near 20 pgm_read_word 21 pgm_read_word_far 21 pgm_read_word_near 21 PGM_VOID_P 21 prog_char 22 prog_int16_t 22 prog_int32_t 22 prog_int64_t 22 prog_int8_t 22 prog_uchar 22 prog_uint16_t 22 prog_uint32_t 22 prog_uint64_t 22 prog_uint8_t 22 prog_void 22 PROGMEM 21 PSTR 21 strcasecmp_P 23 strcat_P 23 strcmp P 23 strcpy P 23 strlcat P 24 strlcpy P 24 strlen P 24 strncasecmp P 24 strncat P 25 strncmp_P 25 strncpy P 25 strnlen P 26 avr sfr _BV 133 bit is clear 133 bit is set 133 loop until bit is clear 134 loop until bit is set 134 avr sleep set sleep mode 29 sleep mode 29 SLEEP MODE ADC 28 SLEEP MODE EXT STANDBY 28 SLEEP MODE IDLE 28 SLEEP MODE PWR DOWN 28 SLEEP MODE PWR SAVE 28 SLEEP MODE STANDBY 28 avr stdint INT16 C 62 INT16 MAX 62 INTI16 MIN 62 int16 t 67 INT32 C 62 INT32 MAX 62 INT32 MIN 62 int32 t 67 INT64 C 62 INT64 MAX 62 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 238 INT64_MIN 63 int64_t 67 INT8
91. 64 MIN INT64 MIN define UINT FAST64 MAX UINT64 Limits of integer types capable of holding object pointers define INTPTR MAX INTIG6 MAX e define INTPTR MIN INT16 MIN e define UINTPTR MAX UINTI6 MAX Limits of greatest width integer types define INTMAX MAX INT64 MAX define INTMAX MIN INT64 MIN define UINTMAX MAX UINT64 Limits of other integer types define PTRDIFF MAX INTI6 MAX e define PTRDIFF MIN INT16 MIN define SIG ATOMIC MAX INT8 MAX e define SIG ATOMIC MIN INT8 MIN define SIZE MAX CONCAT INT16 MAX U Macros for integer constants C implementations should define these macros only when STDC CONSTANT MACROS is defined before lt stdint h gt is included These definitions are valid for integer constants without suffix and for macros defined as integer constant without suffix Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 5 17 lt stdint h gt Standard Integer Types 61 define INT8_C value int8 t value define UINT8_C value uint8_t _ CONCAT value U define INT16 C value value define UINT16_C value _ CONCAT value U define INT32_C value _ CONCAT value L define UINT32_C value _ CONCAT value UL define INT64_C value _ CONCAT value LL define UINT64_C value _ CONCAT value ULL define INTMAX_C value _ CONCAT value LL define UINTMAX_C value _ CONCAT value ULL Exact width integer types Integer t
92. 640 AT megal280 ATmegal281 ATmega324 AT megal64 ATmega644 TIMO SIG Timer Counter ATtiny13 ATtiny45 COMPA vect OUTPUT Compare Match COMPAREOA A TIMO SIG Timer Counter ATtiny13 ATtiny45 COMPB vect OUTPUT Compare Match COMPAREOB B TIMO OVF SIG Timer Counter0 ATtiny13 ATtiny45 vect OVERFLOWO Overflow TIM1_ SIG_ Timer Counter1 ATtiny45 COMPA_vect OUTPUT_ Compare Match COMPAREIA 1A SIG_ Timer Counter1 ATtiny45 COMPB_vect OUTPUT_ Compare Match COMPAREIB B OVF SIG Timer Counter1 ATtiny45 vect OVERFLOWI Overflow TIMERO SIG TimerCounter0 ATmegal68 ATmega48 ATmega88 COMPA_vect OUTPUT_ Compare Match mega640 ATmegal280 ATmegal281 AT COMPAREOA A mega324 ATmegal64 ATmega644 AT tiny2313 TIMERO SIG Timer Counter 0 AT90PWM3 AT9OPWM2 ATmegal68 COMPB_vect OUTPUT_ Compare Match ATmega48 ATmega88 ATmega640 COMPAREOB megal280 ATmegal281 ATmega324 SIG_ megal64 ATmega644 ATtiny2313 OUTPUT_ COMPAREO B Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 125 Vector name Old vector Description Applicable for device name TIMERO_ SIG_ Timer Counter0 AT90PWM3 AT90PWM2 COMP A OUTPUT Compare Match vect COMPAREOA A SIG OUTPUT COMPAREO A TIMERO SIG Timer Counter0 AT90CAN128 AT90CAN32 AT90CANGA COMP_vect OUTP
93. 7 Dump the address size and relative cost of each statement into comments in the gen erated assembler code Used for debugging avr gcc e mdeb Generate lots of debugging information to stderr 7 10 1 2 Selected general compiler options following general gcc options might be of some interest to AVR users On Optimization level n Increasing is meant to optimize more an optimization level of 0 means no optimization at all which is the default if no O option is present The special option Os is meant to turn on all O2 optimizations that are not expected to increase code size Note that at O3 gcc attempts to inline all simple functions For the AVR target this will normally constitute a large pessimization due to the code increasement The only other optimization turned on with 03 is frename registers which could rather be enabled manually instead A simple O option is equivalent to 01 Note also that turning off all optimizations will prevent some warnings from being issued since the generation of those warnings depends on code analysis steps that are only performed when optimizing unreachable code unused variables See also the appropriate FAQ entry for issues regarding debugging optimized code e Wa assembler options e W1l linker options Pass the listed options to the assembler or linker respectively 4 4 Generate debugging information that can be used by avr gdb ffree
94. 7 EOF 75 fclose 77 fdev_close 75 fdev_get_udata 75 fdev_set_udata 75 FDEV_SETUP_STREAM 75 fdev_setup_stream 76 fdevopen 78 feof 78 ferror 78 Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen vsprintf_P 88 INDEX 239 fflush 78 __malloc_heap_end 99 fgetc 79 __malloc_heap_start 99 fgets 79 __malloc_margin 99 FILE 76 abort 90 fprintf 79 abs 90 fprintf_P 79 atof 91 fputc 79 atoi 91 fputs 79 atol 91 fputs_P 79 bsearch 91 fread 79 calloc 92 fscanf 80 div 92 fscanf_P 80 DTOSTR_ALWAYS_SIGN 90 fwrite 80 DTOSTR_PLUS_SIGN 90 getc 76 DTOSTR_UPPERCASE 90 getchar 76 dtostre 92 gets 80 dtostrf 92 printf 80 exit 93 printf_P 80 free 93 putc 76 itoa 93 putchar 77 labs 93 puts 80 Idiv 94 puts_P 80 Itoa 94 scanf 81 malloc 94 scanf_P 81 qsort 94 snprintf 81 rand 95 snprintf_P 81 RAND_MAX 90 sprintf 81 rand 95 sprintf P 81 random 95 sscanf 81 MAX 90 sscanf_P 81 random_r 95 stderr 77 realloc 95 stdin 77 srand 96 stdout 77 srandom 96 ungetc 81 strtod 96 vfprintf 82 strtol 96 vfprintf_P 84 strtoul 97 vfscanf 84 ultoa 98 vfscanf_P 87 utoa 98 vprintf 87 avr_string vscanf 87 _FFS 100 vsnprintf 87 ffs 100 vsnprintf_P 87 ffsl 101 vsprintf 88 ffsll 101 memccpy 101 avr_stdlib memchr 101 compar fn t 90 memcmp 101 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 240 me
95. 9 Since the TWI bus is multi master capable there is potential for a bus contention when one master starts to access the bus Normally the TWI bus interface unit will detect this situation and will not initiate a start condition while the bus is busy However in case two masters were starting at exactly the same time the way bus arbitration works there is always a chance that one master could lose arbitration of the bus during any transmit operation A master that has lost arbitration is required by the protocol to immediately cease talking on the bus in particular it must not initiate a stop condition in order to not corrupt the ongoing transfer from the active master In this example upon detecting a lost arbitration condition the entire transfer is going to be restarted This will cause a new start condition to be initiated which will normally be delayed until the currently active master has released the bus Note 10 Next the device slave is going to be reselected using a so called repeated start con dition which is meant to guarantee that the bus arbitration will remain at the current master using the same slave address SLA but this time with read intent R W bit set to 1 in order to request the device slave to start transfering data from the slave to the master in the next packet Note 11 If the EEPROM device is still busy writing one or more cells after a previous write request it will simply leave its bus interface
96. ATmegal03 ATmegal28 ATmegal6 ATmegal61 megal62 ATmega32 ATmega323 AT mega64 ATmega8515 ATmega8535 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 INT3 vect SIG INTERRUPT3 External Interrupt Request 3 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmega64 ATmega640 AT mega1280 ATmegal281 INT4_vect SIG_ INTERRUPT4 External Interrupt Request 4 AT90CANI28 AT90CAN32 AT90CANGA4 ATmegal03 ATmegal28 ATmega64 mega640 ATmegal 280 ATmegal281 5 vect SIG_ INTERRUPT5 External Interrupt Request 5 AT90CANI28 AT90CAN32 AT90CANGA4 ATmegal03 ATmegal28 ATmega64 mega640 ATmegal 280 ATmegal281 INT6_vect SIG_ INTERRUPT6 External Interrupt Request 6 AT90CANI28 AT90CAN32 AT90CANGA4 ATmegal03 ATmegal28 ATmega64 mega640 ATmega1280 ATmegal281 INT7 vect SIG INTERRUPT7 External Interrupt Request 7 AT90CANI28 AT90CAN32 ATOOCAN64 ATmegal03 ATmegal28 ATmega64 AT mega640 ATmega1280 ATmegal281 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 123 Vector name Old vector Description Applicable for device name IO PINS vect SIG PIN External Interrupt ATtinyll ATtiny12 ATtiny15 ATtiny26 SIG PIN Re
97. ATmegal280 ATmegal281 CAPT vect 5 Capture Event TIMERS_ SIG_ Timer Counter5 ATmega640 ATmegal280 ATmegal281 COMPA vect OUTPUT Compare Match COMPARESA A TIMERS SIG Timer Counter5 ATmega640 ATmega1280 ATmegal281 COMPB vect OUTPUT Compare Match COMPARESB B TIMERS SIG Timer Counter5 ATmega640 ATmega1280 ATmegal281 COMPC vect OUTPUT Compare Match COMPARESC C TIMERS SIG Timer Counter5 ATmega640 ATmegal280 ATmegal281 OVF vect OVERFLOW5 Overflow TWI_vect SIG_2WIRE_ 2 wire Serial In AT90CANI28 AT90CAN32 AT90CANGA SERIAL terface ATmegal28 ATmegal6 ATmegal63 mega32 ATmega323 ATmega64 AT mega8 ATmega8535 ATmegal68 AT mega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega324 megal64 ATmega644 TXDONE_ SIG_ Transmission AT86RF401 vect TXDONE Done Bit Timer Flag 2 Interrupt TXEMPTY_ SIG_TXBE Transmit Buffer AT86RF401 vect Empty Bit Itmer Flag 0 Interrupt UARTO_RX_ SIG_ UARTO Rx ATmegal61 vect UARTO_ Complete RECV UARTO_TX_ SIG_ UARTO Tx ATmegal61 vect UARTO_ Complete TRANS UARTO_ SIG_ UARTO Data ATmegal61 UDRE_vect UARTO_ Register Empty DATA UARTI_RX_ SIG_ UARTI Rx ATmegal61 vect UARTI Complete RECV Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 129 Vector name Old vector Description Applicable for device name UAR
98. B 3 x 36 lt ctype h gt Character Operations 37 lt ermo h gt System Errors 39 lt inttypes h gt Integer Type conversions 40 lt math h gt Mathematics 52 lt setjmp h gt Non local goto 56 lt stdint h gt Standard Integer Types 58 lt stdio h gt Standard IO facilities 70 lt stdlib h gt General utilities 88 lt string h gt Strings 99 lt util crc16 h gt CRC Computations 108 lt util delay h gt Busy wait delay loops 111 lt util parity h gt Parity bit generation 112 lt util twi h gt TWI bit mask definitions 113 _BV avr_sfr 133 _EEGET avr_eeprom 15 _EEPUT avr_eeprom 15 _FDEV_EOF avr_stdio 74 _FDEV_ERR avr_stdio 74 _FDEV_SETUP_READ avr_stdio 75 _FDEV_SETUP_RW avr_stdio 75 _FDEV_SETUP_WRITE avr_stdio 75 _FFS avr_string 100 AVR_LIBC_DATE avr_version 29 AVR LIBC DATE STRING avr version 20 AVR LIBC MAJOR avr version 30 AVR LIBC MINOR avr version 30 AVR LIBC REVISION avr version 30 AVR VERSION STRING avr version 30 AVR VERSION avr version 30 EEPROM REG LOCATIONS avr eeprom 15 compar fn t avr stdlib 90 malloc heap end avr stdlib 99 malloc heap start avr stdlib 99 malloc margin avr stdlib 99 crc16 update util crc 109 INDEX 235 _crc_ccitt_update util_crc 109 _crc_ibutton_update util_crc 109 _crc_xmodem_update util_crc 110 _delay_loop_1 util_delay 112 _delay_loop_2 u
99. D5 TO PD4 omen INT1 PD3 INTO PD2 TXD PD1 RXD PDO AT90S2313P PPP PEPE KEEBRERE Figure 1 Schematic of circuit for demo project The source code is given in demo c For the sake of this example create a file called demo c containing this source code Some of the more important parts of the code are Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 5 28 simple project 137 Note 1 The PWM is being used in 10 bit mode so we need a 16 bit variable to remember the current value Note 2 ISRQ is a macro that marks the function as an interrupt routine In this case the function will get called when the timer overflows Setting up interrupts is explained in greater detail in lt avr interrupt h gt Interrupts Note 3 This section determines the new value of the PWM Note 4 Here s where the newly computed value is loaded into the PWM register Since we are in an interrupt routine it is safe to use a 16 bit assignment to the register Outside of an interrupt the assignment should only be performed with interrupts disabled if there s a chance that an interrupt routine could also access this register or another register that uses TEMP see the appropriate FAQ entry Note 5 This routine gets called after a reset It initializes the PWM and enables interrupts Note 6 The main loop of the program does nothing all the work is done by the interrupt routine If thi
100. K 117 TW START 117 TW STATUS 117 TW STATUS MASK 117 TW WRITE 117 avr stdlib 98 vfprintf avr stdio 82 vfprintf P avr stdio 84 vfscanf avr stdio 84 vfscanf P avr stdio 87 vprintf avr stdio 87 vscanf avr stdio 87 vsnprintf avr stdio 87 vsnprintf P avr stdio 87 vsprintf avr stdio 88 vsprintf P avr stdio 88 wdt disable avr watchdog 31 wdt enable avr watchdog 32 wdt reset avr watchdog 32 WDTO 120MS avr watchdog 32 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 252 WDTO_15MS avr_watchdog 32 WDTO IS avr watchdog 32 WDTO 250MS avr watchdog 33 WDTO 2S avr watchdog 33 WDTO 30MS avr watchdog 33 WDTO 45 avr watchdog 33 WDTO 500MS avr watchdog 33 WDTO_60MS avr_watchdog 33 WDTO_8S avr_watchdog 33 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen
101. MIN avr_stdint 62 avr_stdint 64 INT32_MAX int_fast8_t avr_stdint 62 avr_stdint 68 INT32_MIN INT_LEAST16_MAX avr_stdint 62 avr_stdint 64 int32_t INT_LEAST16_MIN avr_stdint 67 avr_stdint 64 INT64_C int least16 t avr stdint 62 avr stdint 68 INT64 MAX INT LEAST32 MAX avr stdint 62 avr stdint 64 INT64 MIN INT LEAST32 MIN avr stdint 63 avr stdint 64 int64 t int least32 t avr stdint 67 avr stdint 68 8 INT LEAST64 avr stdint 63 avr stdint 64 INT8 MAX INT LEAST64 MIN avr stdint 63 avr stdint 64 8 MIN int least64 t avr stdint 63 avr stdint 68 int8 t INT LEAST8 MAX avr stdint 67 avr stdint 64 int farptr t INT LEAST8 MIN avr inttypes 52 INT FASTI6 MAX avr stdint 63 INT FAST16 MIN avr stdint 63 int fastl6 t avr stdint 67 INT FAST32 MAX avr stdint 63 INT FAST32 MIN avr stdint 63 int fast32 t avr stdint 67 INT FAST64 MAX avr stdint 63 INT FAST64 MIN avr stdint 63 avr stdint 64 int least8 t avr stdint 68 INTERRUPT deprecated items 35 INTMAX C avr stdint 64 INTMAX MAX avr stdint 64 MIN avr stdint 65 intmax t avr stdint 68 MAX avr stdint 65 INTPTR MIN avr stdint 65 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 244 intptr_t log avr_stdint 68 avr_math 55 isalnum log10 ctype 37 avr_math 55 isalpha longjmp ctype 37 setimp 57 isascii loop_until_bit_is_clear ctype 38 avr_sfr 134
102. Note 1 It might have been possible to implement a device abstraction that is compatible with fopen but since this would have required to parse a string and to take all the information needed either out of this string or out of an additional table that would need to be provided by the application this approach was not taken Note 2 This basically follows the Unix approach if a device such as a terminal needs special handling it is in the domain of the terminal device driver to provide this functionality Thus a simple function suitable as put for fdevopen that talks to a UART interface might look like this Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 73 int uart_putchar char FILE xstream if uart_putchar r loop_until_bit_is_set UCSRA UDRE UDR return 0 Note 3 This implementation has been chosen because the cost of maintaining an alias is considerably smaller than the cost of maintaining full copies of each stream Yet providing an implementation that offers the complete set of standard streams was deemed to be useful Not only that writing printf instead of fprintf mystream saves typing work but since avr gcc needs to re sort to pass all arguments of variadic functions on the stack as opposed to passing them in registers for functions that take a fixed number of parameters the ability to pass
103. PU cycle count per loop iteration As such no other processing can occur simultaneously It should be kept in mind that the functions described here do not disable interrupts In general for long delays the use of hardware timers is much preferrable as they free the CPU and allow for concurrent processing of other events while the timer is running However in particular for very short delays the overhead of setting up a hardware timer is too much compared to the overall delay time Two inline functions are provided for the actual delay algorithms Two wrapper functions allow the specification of microsecond and millisecond delays directly using the application supplied macro CPU as the CPU clock frequency in Hertz These functions operate on double typed arguments however when optimiza tion is turned on the entire floating point calculation will be done at compile time Note When using delay us and delay ms the expressions passed as arguments to these functions shall be compile time constants otherwise the floating point cal culations to setup the loops will be done at run time thereby drastically increasing both the resulting code size as well as the time required to setup the loops Functions e void delay loop 1 uint8 t count e void delay loop 2 uint16 t count e void delay us double us e void delay ms double ms 5 22 2 Function Documentation 5 22 21 void delay loop 1 uint8 t count
104. SPM REG amp uint8 t BV COMMON ASB Check if the RWW section is busy 5 2 2 12 define boot rww enable boot rww enable Enable the Read While Write memory section 5 2 2 13 define boot rww enable safe Value do boot spm busy wait N eeprom busy wait boot_rww_enable while 0 Same as boot_rww_enable except waits for eeprom and spm operations to complete before enabling the RWW mameory Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 22 lt avr boot h gt Bootloader Support Utilities 14 5 2 214 define boot_spm_busy _SPM_REG amp uint8 t BV SPMEN Check if the SPM instruction is busy 5 2 215 define boot_spm_busy_wait do while boot_spm_busy Wait while the SPM instruction is busy 5 2 216 define boot_spm_interrupt_disable _SPM_REG amp uint8_t _ BV SPMIE Disable the SPM interrupt 5 2 2 17 define boot spm interrupt enable _SPM_REG uint8 t BV SPMIE Enable the SPM interrupt 5 2 2 18 define BOOTLOADER SECTION attribute section boot Used to declare a function or variable to be placed into a new section called boot loader This section and its contents can then be relocated to any address such as the bootloader NRWW area at link time 5 2 2 19 define GET EXTENDED FUSE BITS 0x0002 address to read the extended fuse bits using boot lock fuse bits get 5 2 2 20 define GET HIGH FUSE BI
105. T1_TX_ SIG_ UARTI Tx ATmegal61 vect UARTI Complete TRANS UARTI SIG UARTI Data ATmegal61 UDRE vect UARTI Register Empty DATA UART RX SIG UART UART Rx Com AT90S2313 AT90S2333 419054414 vect RECV plete 9054433 419054434 419058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_TX_ SIG_UART_ UART Tx Com AT90S2313 9052333 9054414 vect TRANS plete 9054433 AT90S4434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 UART_ SIG_UART_ Data Reg AT90S2313 419052333 AT90S4414 UDRE_vect DATA ister Empty AT90S4433 9054434 9058515 AT90S8535 ATmegal03 ATmegal63 ATmega8515 USARTO SIG USARTO Rx ATmegal62 vect USARTO Complete RECV USARTO SIG USARTO Rx AT90CANI28 AT90CAN32 AT90CANGA RX_vect UARTO_ Complete ATmegal28 ATmegal65 ATmegal69 AT RECV mega325 ATmega329 ATmega64 AT mega645 ATmega649 ATmega640 AT megal280 ATmegal281 ATmega324 AT megal64 ATmega644 USARTO SIG USARTO Tx ATmegal62 TXC vect USARTO Complete TRANS USARTO SIG USARTO Tx AT90CANI28 AT90CAN32 AT90CAN64 TX vect UARTO Complete ATmegal28 ATmegal65 ATmegal69 AT TRANS mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 USARTO SIG USARTO Data AT90CANI28 AT90CAN32 AT90CANGA UDRE vect UARTO Register Empty ATm
106. TS 0 0003 address to read the high fuse bits using boot lock fuse bits get 5 2 2 21 define GET LOCK BITS 0x0001 address to read the lock bits using boot lock fuse bits get 5 2 2 22 define GET LOW FUSE BITS 0x0000 address to read the low fuse bits using boot lock fuse bits get Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 3 lt avr eeprom h gt EEPROM handling 15 5 3 lt avr eeprom h gt EEPROM handling 5 31 Detailed Description include lt avr eeprom h gt This header file declares the interface to some simple library routines suitable for han dling the data EEPROM contained in the AVR microcontrollers The implementation uses 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 avr All of the read write functions first make sure the EEPROM is ready to be ac cessed Since this may cause long delays if a write operation is still pending time critical applications should first poll the EEPROM e g using eeprom_is_ready before attempting any actual I O This header file declares inline functions that call the assembler subroutines di rectly This prevents that the compiler generates push pops for the call clobbered registers This way also a specific calling convention could be used for the eep rom routines e g by passing v
107. UPTR PRII16 define PRIo8 o define PRIOLEASTS o define PRIOFASTS o define PRIu8 u define PRIULEASTS u define PRIUFASTS u define PRIx8 x define PRIXLEASTS x define PRIXFASTS8 x define PRIX8 X Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 42 define PRIXLEASTS X define PRIXFASTS X define PRIo16 o define PRIOLEAST16 define PRIOFAST16 define PRIu16 u define PRIULEAST16 u define PRIUFAST16 u define PRIx16 x define PRIxLEAST16 x define PRIxFAST16 x define PRIX16 X define PRIXLEAST16 X define PRIXFAST16 X define PRIo32 lo define PRIOLEAST32 lo define PRIoFAST32 lo define PRIu32 lu define PRIULEAST32 lu define PRIuFAST32 lu define PRIx32 Ix define PRIXLEAST322 Ix define PRIXFAST32 Ix define PRIX32 IX define PRIXLEAST32 IX define PRIXFAST32 IX define PRIoPTR PRIo16 define PRIuPTR PRIul6 define PRIxPTR PRIx16 define PRIXPTR PRIX16 define SCNd16 d define SCNdLEAST16 d define SCNdFAST16 d define SCNi16 i define SCNILEASTI6 i define SCNIFASTI6 i define SCNd32 Id define SCNdLEAST32 Id define SCNdFAST32 define SCNi32 li define SCNiLEAST32 li define SCNIFAST32 li define SCNdPTR SCNd16 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integ
108. UT_ Compare Match ATmegal03 ATmegal28 ATmegal6 AT megal61 ATmegal62 ATmegal65 megal69 ATmega32 ATmega323 mega325 ATmega3250 ATmega329 AT mega3290 ATmega64 ATmega645 AT mega6450 ATmega649 ATmega6490 AT mega8515 ATmega8535 TIMERO_ SIG_ Timer Counter0 AT90S2313 AT90S2323 AT90S2343 AT OVFO_vect OVERFLOWO Overflow tiny22 ATtiny26 TIMERO_ SIG_ Timer Counter0 AT90S1200 419052333 AT90S4414 OVF_vect OVERFLOWO Overflow 9054433 9054434 9058515 AT90S8535 AT90PWMS3 9 2 AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 16 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtinyll ATtiny12 ATtiny15 ATtiny2313 ATtiny28 TIMERI SIG INPUT Timer Counter1 AT90S2313 CAPTI_vect CAPTURE1 Capture Event TIMER 1 SIG_INPUT_ Timer Counter AT90S2333 AT90S4414 479054433 CAPT_vect CAPTURE Capture Event AT90S4434 479058515 419058535 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmeg
109. _ATmega3290__ avr5 atmega64 AVR ATmega64 avr5 atmega640 ATmega640 avr5 atmega644 AVR ATmega644 avr5 atmega645 AVR ATmega645 avr5 atmega6450 _ AVR ATmega6450 avr5 atmega649 AVR ATmega649 avr5 atmega6490 ATmega6490 avr5 at94k AVR_AT94K e morder1 e morder2 Change the order of register assignment The default is 124 r25 r18 r19 120 r21 r22 r23 r30 r31 r26 127 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 12 r0 r1 Order 1 uses r18 r19 120 r21 122 r23 r24 r25 r30 r31 r26 r27 r28 r29 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 12 rO r1 Order 2 uses 125 r24 123 122 121 r20 r19 r18 r30 r31 r26 r27 128 129 r17 r16 r15 r14 r13 r12 r11 r10 r9 r8 r7 r6 r5 r4 r3 r2 r1 rO e mint8 Assume int to be an 8 bit integer Note that this is not really supported by avr libc so it should normally not be used The default is to use 16 bit integers e mno interrupts Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 226 Generates code that changes the stack pointer without disabling interrupts Normally the state of the status register SREG is saved in a temporary register interrupts are disabled while changing the stack pointer and SREG is restored e mcall prologues Use subroutines for function prologue e
110. _C 63 INT8_MAX 63 INT8_MIN 63 int8_t 67 INT_FAST16_MAX 63 INT_FAST16_MIN 63 int_fast16_t 67 INT_FAST32_MAX 63 INT_FAST32_MIN 63 int_fast32_t 67 INT_FAST64_MAX 63 INT_FAST64_MIN 63 int_fast64_t 68 INT_FAST8_MAX 63 INT_FAST8_MIN 64 int_fast8_t 68 INT_LEAST16_MAX 64 INT LEASTI6 MIN 64 int 1 5 16 t 68 INT LEAST32 MAX 64 INT LEAST32 MIN 64 int least32 t 68 INT LEAST64 MAX 64 INT LEAST64 MIN 64 int least64 t 68 INT LEAST8 MAX 64 INT LEASTS MIN 64 int least8 t 68 INTMAX C 64 INTMAX MAX 64 MIN 65 intmax_t 68 INTPTR_MAX 65 INTPTR_MIN 65 intptr_t 68 PTRDIFF_MAX 65 PTRDIFF_MIN 65 SIG_ATOMIC_MAX 65 SIG_ATOMIC_MIN 65 SIZE_MAX 65 UINT16_C 65 UINT16_MAX 65 uint16_t 68 UINT32_C 65 E JINT32_MAX 66 int32_t 68 JINT64_C 66 INT64_MAX 66 int64_t 68 JINT8_C 66 JINT8_MAX 66 int8_t 69 JINT_FAST16_MAX 66 int_fast16_t 69 JINT_FAST32_MAX 66 int_fast32_t 69 JINT_FAST64_MAX 66 int_fast64_t 69 JINT_FAST8_MAX 66 int_fast8_t 69 JINT_LEAST16_MAX 66 int_least16_t 69 INT_LEAST32_MAX 66 int_least32_t 69 JINT_LEAST64_MAX 67 int_least64_t 69 JINT_LEAST8_MAX 67 int_least8_t 69 JINTMAX_C 67 67 intmax_t 69 JINTPTR_MAX 67 uintptr_t 69 CEOS SCaACLkCE CECE E avr_stdio _FDEV_EOF 74 _FDEV_ERR 74 _FDEV_SETUP_READ 75 _FDEV_SETUP_RW 75 _FDEV_SETUP_WRITE 75 clearerr 7
111. _MT_DATA_ACK util_twi 115 TW_MT_DATA_NACK util_twi 115 TW_MT_SLA_ACK util_twi 115 TW_MT_SLA_NACK util_twi 115 TW_NO_INFO util_twi 115 TW_READ util_twi 115 TW_REP_START util_twi 116 TW_SR_ARB_LOST_GCALL_ACK util_twi 116 TW_SR_ARB_LOST_SLA_ACK util_twi 116 TW_SR_DATA_ACK util_twi 116 TW_SR_DATA_NACK Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 250 util_twi 116 TW_SR_GCALL_ACK util_twi 116 TW_SR_GCALL_DATA_ACK util_twi 116 TW_SR_GCALL_DATA_NACK util_twi 116 TW_SR_SLA_ACK util_twi 116 TW_SR_STOP util_twi 116 TW_ST_ARB_LOST_SLA_ACK util_twi 116 TW_ST_DATA_ACK util_twi 117 TW_ST_DATA_NACK util_twi 117 TW_ST_LAST_DATA util_twi 117 TW_ST_SLA_ACK util_twi 117 TW_START util_twi 117 TW_STATUS util_twi 117 TW_STATUS_MASK util_twi 117 TW_WRITE util_twi 117 UINT16_C avr_stdint 65 UINT16_MAX avr_stdint 65 uint16_t avr_stdint 68 UINT32_C avr_stdint 65 UINT32_MAX avr_stdint 66 uint32_t avr_stdint 68 UINT64_C avr_stdint 66 UINT64_MAX avr_stdint 66 uint64_t avr_stdint 68 UINT8_C avr_stdint 66 UINT8_MAX avr_stdint 66 uint8_t avr_stdint 69 uint_farptr_t avr_inttypes 52 UINT FASTI6 MAX avr stdint 66 uint fastl6 t avr stdint 69 UINT FAST32 MAX avr stdint 66 uint fast32 t avr stdint 69 UINT FAST64 MAX avr stdint 66 uint fast64 t avr stdint 69 UINT FAST8 MAX avr stdint 66 uint fast8 t
112. __ naked __attribute__ section init3 void my_init_portb void PORTB Oxff DDRB Oxff Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 8 Installing the GNU Tool Chain 215 Note Section init3 is used in this example as this ensures the inernal__ zero_reg_ _ has already been set up The code generated by the compiler might blindly rely on zero reg beingreally 0 7 8 Installing the GNU Tool Chain Note This discussion was taken directly from Rich Neswold s document See Acknowl edgments This discussion is Unix specific FIXME troth 2002 08 13 we need a volunteer to add windows specific notes to these instructions This chapter shows how to build and install a complete development environment for the AVR processors using the GNU toolset The default behaviour for most of these tools is to install every thing under the usr ilocal directory In order to keep the AVR tools separate from the base system it is usually better to install everything into usr local avr If the usr local avr directory does not exist you should create it before trying to install anything You will need root access to install there If you don t have root access to the system you can alternatively install in your home directory for exam ple in SHOME 10cal avr Where you install is a completely arbitrary decision but should be consistent for all the tools You specify the installat
113. a The memcpy function copies len bytes from memory area src to memory area dest The memory areas may not overlap Use memmove if the memory areas do overlap Returns memcpy function returns a pointer to dest Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 20 lt string h gt Strings 103 5 20 3 8 void x memmove void dest const void src size_t len Copy memory area The memmove function copies len bytes from memory area src to memory area dest The memory areas may overlap Returns memmove function returns a pointer to dest 5 20 3 9 void x memset void dest int val size_t len Fill memory with a constant byte The memset function fills the first len bytes of the memory area pointed to by dest with the constant byte val Returns The memset function returns a pointer to the memory area dest 5 20 3 10 strcasecmp const char s1 const char 52 Compare two strings ignoring case The strcasecmp function compares the two strings s1 and 82 ignoring the case of the characters Returns The strcasecmp function returns an integer less than equal to or greater than zero if sl is found respectively to be less than to match or be greater than 52 5 20 3 11 char x strcat char dest const char src Concatenate two strings The strcat function appends the src string to the dest string overwriting the 0 char acter at the end of
114. a649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny2313 TIMERI SIG Timer Counter1 ATtiny26 CMPA_vect OUTPUT_ Compare Match COMPAREIA 1A Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 126 Vector name Old vector Description Applicable for device name TIMERI SIG_ Timer Counter1 ATtiny26 CMPB_vect OUTPUT_ Compare Match COMPAREIB 1B TIMER 1_ SIG_ Timer Counter1 AT90S2313 vect OUTPUT_ Compare Match COMPAREIA SIG Timer Counter1 AT90S4414 419054434 419058515 _vect OUTPUT_ Compare Match AT90S8535 AT9OPWM3 9 2 COMPAREIA A AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal6 ATmegal61 ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny2313 SIG Timer Counter1 AT90S4414 419054434 9058515 COMPB_vect OUTPUT_ Compare MatchB AT90S8535 AT90PWM3 AT90PWM2 COMPAREIB AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal6 ATmegal61 ATmegal62 ATmega
115. able is predefined to point to interrupt rou tines with predetermined names By using the appropriate name your routine will be called when the corresponding interrupt occurs The device library provides a set of default interrupt routines which will get used if you don t define your own Patching into the vector table is only one part of the problem The compiler uses by convention a set of registers when it s normally executing compiler generated code It s important that these registers as well as the status register get saved and restored The extra code needed to do this is enabled by tagging the interrupt function with attribute signal Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 119 These details seem to make interrupt routines a little messy but all these details are handled by the Interrupt API An interrupt routine is defined with ISR This macro register and mark the routine as an interrupt handler for the specified peripheral The following is an example definition of a handler for the ADC interrupt include lt avr interrupt h gt ISR ADC_vect user code here Refer to the chapter explaining assembler programming for an explanation about inter rupt routines written solely in assembler language Catch all interrupt vector If an unexpected interrupt occurs interrupt is enabled and no handler is installed which usually indicates a
116. ach bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 9 will be the letter a If radix is 10 and val is negative a minus sign will be prepended The itoa function returns the pointer passed as s 5 19 4 14 long labs long The labs function computes the absolute value of the long integer i Note The abs and labs functions are builtins of gcc 5 19 4 15 Idiv_t Idiv long __num long denom The ldiv function computes the value num denom and returns the quotient and re mainder in a structure named 1div_t that contains two long integer members named quot and rem 5 19 4 16 char long int __val char x __s int _ radix Convert a long integer to a string The function Itoa converts the long integer value from val into an ASCII represen tation that will be stored under s The caller is responsible for providing sufficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof long int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix wi
117. ack pointer high byte at address 0 3 _ _ Stack pointer low byte at address 0x3D tmp reg Register rO used for temporary storage zero reg Register r1 always zero Register rO may be freely used by your assembler code and need not be restored at the end of your code It s a good idea to use tmp reg and zero reg instead of rO or r1 just in case a new compiler version changes the register usage definitions 7 4 3 Input and Output Operands Each input and output operand is described by a constraint string followed by a C expression in parantheses AVR GCC 3 3 knows the following constraint characters Note The most up to date and detailed information on contraints for the avr can be found in the gcc manual The x register is r27 r26 the y register is r29 r28 and the z register is r31 r30 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 194 Constraint Used for Range a Simple upper registers r16 to r23 b Base pointer registers 2 pairs d Upper register rl6tor31 e Pointer register pairs y Z G Floating point constant 0 0 I 6 bit positive integer 0 to 63 constant J 6 bit negative integer 63 to 0 constant K Integer constant 2 L Integer constant 0 1 Lower registers r0 to r15 M 8 bit integer constant 0 to 255 N Integer constant 1 O Integer constant 8 16 24 Integer con
118. ad in a multithreaded environment Note that we must use a pointer because the incremented value needs to be stored before interrupts are enabled Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 198 asm volatile oli ld r24 0 inc r24 n t st a0 r24 mane sei ptr r24 The compiler might produce the following code eli ld r24 7 inc r24 st 7 r24 sei One easy solution to avoid clobbering register r24 is to make use of the special tem porary register tmp reg defined by the compiler asm volatile cli ld _tmp_reg__ a0 inc __tmp_reg__ st a0 __tmp_reg__ sel ptr n t n t n t n t n t The compiler is prepared to reload this register next time it uses it Another problem with the above code is that it should not be called in code sections where interrupts are disabled and should be kept disabled because it will enable interrupts at the end We may store the current status but then we need another register Again we can solve this without clobbering a fixed but let the compiler select it This could be done with the help of a local variable uint8_t s asm volatile in 0 cli _ SREG__ ld _tmp_reg__ 1 inc tmp_reg__ st Sal __tmp_reg__ out SREG 0 amp r s e ptr NN mt MATINET n t
119. address The address is in the program space 5 5 2 7 define pgm read dword near address short LPM dword uint16 t address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 5 5 2 8 define pgm read word address short pgm read word near address short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 5 5 2 9 define read word far address long ELPM_word uint32_ t address_long Read a word from the program space with a 32 bit far address Note The address is a byte address The address is in the program space Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 5 lt avr pgmspace h gt Program Space String Utilities 22 5 5 2 10 define read word near address short LPM_word uint16_ t address short Read a word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 5 5 211 define VOID P const prog void Used to declare a generic pointer to an object in program space 5 5 2 12 define PROGMEM ATTR PROGMEM Attribute to use in order to declare an object being located in flash ROM 5 5 2 13 define PSTR s const PROGMEM char s Used to declare a static pointer to a string in prog
120. al function registers 132 void vector void __attribute__ signal void vector void include lt avr interrupt h gt Introduces an interrupt handler function interrupt service routine that runs with global interrupts initially disabled vector must be one of the interrupt vector names that are valid for the particular MCU type 5 25 2 3 define SIGNAL signame Value void signame void __attribute__ signal void signame void include lt avr interrupt h gt Introduces an interrupt handler function that runs with global interrupts initially dis abled This is the same as the ISR macro Note Do not use anymore in new code it will be deprecated in a future release 5 26 lt avr sfr_defs h gt Special function registers 5 26 1 Detailed Description When working with microcontrollers many of the tasks usually consist of controlling the peripherals that are connected to the device respectively programming the subsys tems that are contained in the controller which by itself communicate with the circuitry connected to the controller The AVR series of microcontrollers offers two different paradigms to perform this task There s a separate IO address space available as it is known from some high level CISC CPUs that be addressed with specific IO instructions that are applicable to some or all of the IO address space in out sbi etc The entire IO address space is also made available as m
121. alues in __tmp_reg__ eeprom addresses in X and memory addresses in Z registers Method is optimized for code size Presently supported are two locations of the EEPROM register set 0x 1F 0x20 0x21 and 0x1C 0x1D 0x1E see _ REG LOCATIONS __ As these functions modify IO registers they are known to be non reentrant If any of these functions are used from both standard and interrupt context the applica tions must ensure proper protection e g by disabling interrupts before accessing them libc declarations define EEMEM attribute section eeprom define eeprom is ready define busy wait do while is ready uint8 t eeprom read byte const uint8 t addr uint16 t eeprom read word const uint16_t addr void eeprom read block void pointer ram const void xpointer eeprom size t n void eeprom write byte uint8 t addr uint8 t value void eeprom write word uint16 t uint16 t value void eeprom write block const void xpointer ram void xpointer eeprom size t n Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 3 lt avr eeprom h gt EEPROM handling 16 compatibility defines e define _EEPUT addr val eeprom write byte uint8 t uint8_ t val define EEGET var addr var eeprom read byte uint8 t x addr Defines e define _ EEPROM REG LOCATIONS 1C1D1E 5 3 2 Define Documentation
122. am startup the datasheet recommends a sequence like the following include lt stdint h gt include lt avr wdt h gt uint8_t mcusr_mirror void get_mcusr void attribute naked attribute section init3 void get mcusr void mcusr_mirror MCUSR MCUSR 0 wdt disable Saving the value of MCUSR in mcusr_mirror is only needed if the application later wants to examine the reset source but clearing in particular the watchdog reset flag before disabling the watchdog is required according to the datasheet Defines e define wdt_reset volatile__ wdr define wdt_disable define wdt_enable timeout _wdt_write timeout Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 9 lt avr wdt h gt Watchdog timer handling 32 define WDTO_15MS 0 define WDTO_30MS 1 define WDTO_60MS 2 define WDTO_120MS 3 define WDTO_250MS 4 define WDTO_500MS 5 define WDTO 156 define WDTO_2S 7 define WDTO_4S 8 define WDTO 88 9 5 9 2 Define Documentation 5 9 2 1 define wdt_disable Value __asm__ _ volatile__ in tmp_reg__ SREG Maker X cli nNE X out 0 SLE n t out 0 __zero_reg__ n t out SREG__ __tmp_reg__ n t no outputs I _SFR_IO_ADDR _WD_CONTROL_REG r uint8 t _BV _WD_CHANGE_BIT BV WDE ro Disable the watchdog timer if possible This atte
123. amp constraint modifier to your output operand The following example demonstrates this problem asm volatile in 0 1 mne out 1 2 n t amp r input I SFR IO ADDR port r output this example an input value is read from a port and then an output value is written to the same port If the compiler would have choosen the same register for input and out put then the output value would have been destroyed on the first assembler instruction Fortunately this example uses the amp constraint modifier to instruct the compiler not to select any register for the output value which is used for any of the input operands Back to swapping Here is the code to swap high and low byte of a 16 bit value asm volatile mov tmp reg 0 n t mov 0 BO n t mov B0 tmp_reg__ n t r value 0 value First you will notice the usage of register __tmp_reg__ which we listed among other special registers in the Assembler Code section You can use this register without saving its contents Completely new are those letters and B in A0 and B0 In fact they refer to two different 8 bit registers both containing a part of value Another example to swap bytes of a 32 bit value asm volatile mov __tmp_reg__ 5 0 n t mov 0 0 NN p mov D0 tmp reg n t mov tmp reg BO n t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline A
124. application Any changes to these tunables should be made before the very first call to malloc Note that some library functions might also use dynamic memory notably those from the lt stdio h gt Stan dard IO facilities so make sure the changes will be done early enough in the startup sequence The variables malloc heap start and malloc heap end be used to restrict the malloc function to a certain memory region These variables are stati cally initialized to point to__ heap start and heap end respectively where heap start is filled in by the linker to point just beyond bss and heap end is set to 0 which makes malloc assume the heap is below the stack If the heap is going to be moved to external RAM malloc heap must be adjusted accordingly This can either be done at run time by writing directly to this variable or it can be done automatically at link time by adjusting the value of the symbol heap end The following example shows a linker command to relocate the entire data and bss segments and the heap to location 0x1100 in external RAM The heap will extend up to address Oxffff avr gcc Wl Tdata 0x801100 defsym end 0x80ffff Note See explanation for offset 0x800000 See the chapter about using gcc for the w1 options on board RAM external RAM 0x0100 Ox10FF 0x1100 OxFFFF SP 1 malloc heap end heap end RAMEND brkval malloc heap start
125. archive library named libname a and use it to resolve currently unresolved symbols from it The library is searched along a path that con sists of builtin pathname entries that have been specified at compile time e g usr local avr lib on Unix systems possibly extended by pathname entries as specified by L options that must precede the 1 options on the command line e Lpath Additional location to look for archive libraries requested by 1 options defsym symbol expr Define a global symbol symbol using expr as the value Print a linker map to stdout Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 231 Map mapfile Print a linker map to mapfile cref Output a cross reference table to the map file in case is also present or to stdout e section start sectionname org Start section sectionname at absolute address org Tbss org e Tdata org text org Start the bss data or text section at org respectively e T scriptfile Use scriptfile as the linker script replacing the default linker script De fault linker scripts are stored in system specific location e g under usr local avr lib ldscripts on Unix systems and consist of the AVR architecture name avr2 through avr5 with the suffix x appended They describe how the various memory sections will be linked together 7 10 3 2 Passing linker options from th
126. are not available in the C language Because of a lack of documentation especially for the AVR version of the compiler it may take some time to figure out the implementation details by studying the compiler and assembler source code There are also a few sample programs available in the net Hopefully this document will help to increase their number It s assumed that you are familiar with writing AVR assembler programs because this is not an AVR assembler programming tutorial It s not a C language tutorial either Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 191 Note that this document does not cover file written completely in assembler language refer to avr libc and assembler programs for this Copyright C 2001 2002 by egnite Software GmbH Permission is granted to copy and distribute verbatim copies of this manual provided that the copyright notice and this permission notice are preserved on all copies Permis sion is granted to copy and distribute modified versions of this manual provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one This document describes version 3 3 of the compiler There may be some parts which hadn t been completely understood by the author himself and not all samples had been tested so far Because the author is German and not familiar with the English language there are definitely some typo
127. at larger numbers behind the option might auto matically cause better optimization First there s no universal definition for better with optimization often being a speed vs code size tradeoff See the detailed discus sion for which option affects which part of the code generation A test case was run on an ATmega128 to judge the effect of compiling the library itself using different optimization levels The following table lists the results The test case consisted of around 2 KB of strings to sort Test 1 used qsort using the standard library strcmp test 2 used a function that sorted the strings by their size thus had Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 185 two calls to strlen per invocation When comparing the resulting code size it should be noted that a floating point version of fvprintf was linked into the binary in order to print out the time elapsed which is entirely not affected by the different optimization levels and added about 2 5 KB to the code Optimization Size of text Time for test 1 Time for test 2 flags 6898 903 us 19 7 ms 02 6666 972 us 20 1 ms Os 6618 955 us 20 1 ms Os 6474 972 us 20 1 ms mcall prologues The difference between 955 us and 972 us was just a single timer tick so take this with a grain of salt So generally it seems Os mcall prologues is the most universa
128. at the src string must be located in program space flash Appends src to string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Returns The strlcat_P function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 5 lt avr pgmspace h gt Program Space String Utilities 25 5 5 4 7 size tstrlcpy P char dst size_t siz Copy a string from progmem to RAM Copy src to string dst of size siz At most siz 1 characters will be copied Always NULL terminates unless siz 0 Returns The strlcpy_P function returns strlen src If retval gt siz truncation occurred 5 5 4 8 size tstrlen P P src The function is similar to strlen except that src is a pointer to a string in program space Returns The strlen function returns the number of characters in src 5 5 4 9 intstrncasecmp P const char x 57 P s2 size Compare two strings ignoring case The strncasecmp function is similar to strcasecmp P except it only compares the first n characters of s1 Parameters 51 A pointer to a string in the devices SRAM 82 A pointer to a string in the devices Flash n The maximum number of bytes to compare Returns The strcasecmp
129. ators into a 16 bit operation in assembly How to detect RAM memory and variable overlap problems Is it really impossible to program the ATtinyXX in What is this clock skew detected messsage Why are many interrupt flags cleared by writing a logical 1 Why have programmed fuses the bit value 0 Which AVR specific assembler operators are available Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 171 7 3 2 My program doesn t recognize a variable updated within an interrupt rou tine When using the optimizer in a loop like the following one uint8_t flag ISR SOME_vect flag 1 while flag 0 the compiler will typically access flag only once and optimize further accesses com pletely away since its code path analysis shows that nothing inside the loop could change the value of 1ag anyway To tell the compiler that this variable could be changed outside the scope of its code path analysis e g from within an interrupt routine the variable needs to be declared like volatile uint8 t flag Back to FAQ Index 7 3 3 I get undefined reference to for functions like sin In order to access the mathematical functions that are declared in lt math h gt the linker needs to be told to also link the mathematical library 1ibm a Typically system libraries like 1ibm a are given to the final C compiler command line that performs the li
130. avr libc Reference Manual 1 4 0 Generated by Doxygen 1 4 1 Sat Nov 19 23 00 48 2005 CONTENTS i Contents 1 AVR Libc 1 lt lt eo oda kAd 2 22 eae eRe m xke A AA 1 1 2 General information about this library 2 12 supported Devies 22222522229 RES 2 2 avr libc Module Index 5 21 ayrlibe Modules 464054 4608 Rb Be RE EP SE e 5 3 avr libc Data Structure Index 7 3 1 avrlib Data os s cs caw e 22 22 42 y 4 avr libc Page Index 41 ave libe Related P ges gt ooo onu oc com mg Re 7 5 avr ibc Module Documentation 8 S l lt assert h Diagnostics 2 222622 oem 2 2 4 8 X11 ss so e e meam Re c Ro RR RA 8 512 Demme Documentation p eR 8 5 22 avr boot h Bootloader Support Utilities 8 521 Detailed Description RR 8 5 22 Dehne Documentation 22222522222 225445552 10 5 3 lt avr eeprom h gt EEPROM handling 15 531 Detailed Description lt 229 ok koc BR R 15 5 3 2 Define Documentation 16 5 3 3 Function Documentation lt s ss es o 0 ew ow n 17 5 4 lt avr io h gt AVR device specific IO definitions 17 5 5 lt avr pgmspace h gt Program Space String Utilities 18 Sal Detaled WDeseripnan lt s erue ke SE BAERS 18 552 Deine Documentation 222222222225 RE RR 20 5 5 3 Typedef Documentation 22 5 5 4 Function Documentation
131. bitrary amount of white space as determined by iss pace followed by a single optional or sign If base is zero or 16 the string may then include a 0x prefix and the number will be read in base 16 otherwise a zero base is taken as 10 decimal unless the next character is 0 in which case it is taken as 8 octal The remainder of the string is converted to a long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 represents 11 and so forth with Z representing 35 If endptr is not NULL strtol stores the address of the first invalid character in xendptr If there were digits at all however strtol stores the original value of nptr in endptr Thus if npt r is not NO but xxendptr is 0 on return the entire string was valid The strtol function returns the result of the conversion unless the value would under flow or overflow If no conversion could be performed 0 is returned If an overflow or underflow occurs errno is set to ERANGE and the function return value is clamped to LONG MIN or LONG respectively Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h gt General utilities 98 5 19 4 28 unsigned long strtoul const char __nptr char __endptr int __ base The strtoul fu
132. bitration lost in SLA W or data 5 24 2 8 define TW MT DATA 0x28 data transmitted ACK received 5 24 2 9 define TW MT DATA NACK 0x30 data transmitted NACK received 5 24 2 10 define TW MT SLA ACK 0x18 SLA W transmitted ACK received 5 24 2 11 TW_MT_SLA_NACK 0x20 SLA W transmitted NACK received 5 24 2 12 ftdefine TW NO INFO 0xF8 no state information available 5 24 2 13 define TW READ 1 SLA R address 5 24 214 define TW REP START 0x10 repeated start condition transmitted 5 24 2 15 define TW SR LOST GCALL 0x78 arbitration lost in SLA RW general call received ACK returned 5 24 2 16 define TW SR LOST SLA 0x68 arbitration lost in SLA RW SLA W received ACK returned 5 24 2 17 define TW SR DATA 0x80 data received ACK returned Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 524 lt util twi h gt TWI bit mask definitions 117 5 24 2 18 define TW_SR_DATA_NACK 0x88 data received NACK returned 5 24 2 19 define TW_SR_GCALL_ACK 0x70 general call received ACK returned 5 24 2 20 define TW SR GCALL DATA 0x90 general call data received ACK returned 5 24 2 21 define TW SR GCALL DATA NACK 0x98 general call data received NACK returned 5 24 2 22 TW SR 51 ACK 0x60 SLA W received ACK returned 5 24 2 23 define TW SR STOP 0xA0 stop or repeated start condition received while selected 5
133. boot page erase page boot spm busy wait Wait until the memory is erased for i20 i SPM PAGESIZE i 2 Set up little endian word uint16_t w buf w xbuf lt lt 8 boot_page_fill page i w boot_page_write page Store buffer in flash page boot spm busy wait Wait until the memory is written Reenable RWW section again We need this if we want to jump back to the application after bootloading boot rww enable Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 2 lt avr boot h gt Bootloader Support Utilities 10 Re enable interrupts if they were ever enabled SREG sreg Defines define BOOTLOADER_SECTION __attribute__ section bootloader define boot_spm_interrupt_enable __SPM_REG uint8 t BV SPMIE define boot spm interrupt disable _SPM_REG amp uint8 t BV SPMIE define boot is spm interrupt REG amp uint8 t BV SPMIE define boot rww busy SPM REG amp uint8 0 COMMON ASB define boot spm busy SPM REG amp uint8 t BV SPMEN define boot spm busy do while boot busy define GET LOW FUSE BITS 0x0000 define GET LOCK BITS 0x0001 define GET EXTENDED FUSE BITS 0x0002 define GET HIGH FUSE BITS 0x0003 define boot lock fuse bits get address define boot page fill address data boot page fill normal address data define boot page
134. c by Doxygen 5 14 lt gt Integer Type conversions 49 5 14 2 59 define PRIXPTR PRIX16 uppercase hexadecimal printf format for uintptr_t 5 14 2 60 PRIxPTR PRIx16 hexadecimal printf format for uintptr_t 5 14 2 61 define SCNd16 d decimal scanf format for int16 t 5 14 2 62 define SCNd32 Id decimal scanf format for int32 t 5 14 2 63 define SCNdFASTI6 decimal scanf format for int fastl6 t 5 14 2 64 ftdefine SCNdFAST32 Id decimal scanf format for int fast32 t 5 14 2 65 define SCNdLEASTIG d decimal scanf format for int leastl6 t 5 14 2 66 define SCNdLEAST32 Id decimal scanf format for int_least32_t 5 14 2 67 define SCNdPTR SCNd16 decimal scanf format for intptr_t 5 14 2 68 define SCNi16 i generic integer scanf format for int16_t 5 14 2 69 define SCNi32 li generic integer scanf format for int32_t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 50 5 14 2 70 define SCNiFASTI6 i generic integer scanf format for int_fast16_t 5 14 2 71 define SCNiIFAST32 li generic integer scanf format for int_fast32_t 5 14 2 72 define SCNILEASTI6 i generic integer scanf format for int_least16_t 5 14 2 73 define SCNILEAST32 li generic integer scanf format for int_least32_t 5 14 2 74 define SCNIPTR SCNi16 generic integer scanf format for intptr_t 5 14 2
135. c memory will ever collide with the RAM variables unless there were bugs in the implementation of the allocator There is still a risk that the heap and stack could collide if there are large requirements for either dynamic memory or stack space The former can even happen if the allocations aren t all that large but dynamic memory allocations get fragmented over time such that new requests don t quite fit into the holes of previously freed regions Large stack space requirements can arise in a C function containing large and or numerous local variables or when recursively calling function Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 5 Using malloc 203 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 on board RAM 0x0100 Ox10FF 0x1100 OxFFFF external RAM 1 SP RAMEND brkval lt SP malloc margin gt malloc heap start __heap_start _ bss end data 055 start data start Figure 2 RAM map of a device with internal RAM Finally there s a challenge to make the memory allocator simple enough so the code size requirements will remain low yet powerful enough to avoid unnecessary memory fragmentation and to get it all done with reasonably few CPU cycles since microcon trollers aren t only often low on space but also run at
136. casual inspection of the generated assembler code using the S compiler option seems to be warranted Back to FAQ Index 7 3 8 Shouldn t I initialize all my variables Global and static variables are guaranteed to be initialized to 0 by the C standard avr gcc does this by placing the appropriate code into section init4 see The initN Sections With respect to the standard this sentence is somewhat simplified because the standard allows for machines where the actual bit pattern used differs from all bits being 0 but for the AVR target in general all integer type variables are set to 0 all pointers to a NULL pointer and all floating point variables to 0 0 As long as these variables are not initialized 1 e they don t have an equal sign and an initialization expression to the right within the definition of the variable they go into the bss section of the file This section simply records the size of the variable but otherwise doesn t consume space neither within the object file nor within flash memory Of course being a variable it will consume space in the target s SRAM In contrast global and static variables that have an initializer go into the data section of the file This will cause them to consume space in the object file in order to record the initializing value and in the flash ROM of the target device The latter is needed since the flash ROM is the only way that the compiler can tell the target device the val
137. cision of zero For x and X conversions a non zero result has the string 0 or OX for X conversions prepended to it Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 83 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 u i x and X the 0 flag is ignored A negative field width flag the converted value is to be left adjusted on the field boundary The converted value is padded on the right with blanks rather than on the left with blanks or zeros A overrides a 0 if both are given space A blank should be left before a positive number produced by a signed conversion d or i A sign must always be placed before a number produced by a signed conversion A overrides a space if both are used An optional decimal digit string specifying a minimum field width If the con verted value has fewer characters than the field width it will be padded with spaces on the left or right if the left adjust173 ment flag has been given to fill out the field width 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 nu
138. const char __fmt va list ap int vsprintf P char __s const char __fmt va_list ap int vsnprintf char x__s size_t __n const char __fmt va_list ap int vsnprintf P char __s size_t __n const char __fmt va_list ap int fprintf FILE stream const char fmt int fprintf _P FILE stream const char fmt int fputs const char str FILE stream int fputs_P const char str FILE stream int puts const char str int puts P const char str size t fwrite const void ptr size_t _ size size t nmemb FILE stream int fgetc FILE stream int ungetc int __c FILE stream char fgets char str int size FILE stream char gets char str size_t fread void size t size size t nmemb FILE stream void clearerr FILE stream int feof FILE stream int ferror FILE stream int vfscanf FILE stream const char fmt va list int vfscanf P FILE stream const char fmt va list int fscanf FILE stream const char fmt int fscanf P FILE stream const char fmt int scanf const char fmt int scanf P const char fmt int vscanf const char fmt va_list int sscanf const char buf const char fmt int sscanf_P const char buf const char fmt int fflush FILE xstream FILE fdevopen int put char FILE x int get FILE Ge
139. ct 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 atmega8 OPTIMIZE 02 DEFS LIBS You should not have to change anything below here CG avr gcc Override is only needed by avr lib build system override CFLAGS g Wall 5 mmcu MCU_TARGET DEFS override LDFLAGS W1 Map PRG map OBJCOPY avr objcopy OBJDUMP avr objdump all PRG elf lst text eeprom Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 simple project 147 S PRG elf OBJ 5 CFLAGS LDFLAGS 58 LIBS clean rm rf x o PRG elf eps png pdf x bak rm rf x lst map EXTRA_CLEAN_FILES lst PRG 1st 1st elf OBJDUMP h S lt gt 60 Rules for building the text rom images eeprom 0 O eeprom 0 O eeprom 0 O text hex bin srec hex PRG hex bin PRG bin srec PRG srec hex elf j text j data O ihex lt 8 srec elf j text j data O srec lt 6 bin elf j text j data O binary lt 50 Rules for building the eeprom rom images eeprom ehex ebin esrec ehex PRG eeprom hex PRG _eeprom bin esrec PRG eeprom srec eeprom hex elf 5 j eeprom change section 1ma ee
140. dLEAST32 avr_inttypes 43 PRIdLEASTS avr inttypes 44 PRIdPTR avr inttypes 44 PRIi16 avr inttypes 44 PRIi32 avr inttypes 44 PRIi8 avr_inttypes 44 PRIiFAST16 avr_inttypes 44 PRIiFAST32 avr_inttypes 44 PRIiFAST8 avr_inttypes 44 PRIiLEAST16 avr_inttypes 44 PRIiLEAST32 avr_inttypes 44 PRIiLEAST8 avr_inttypes 44 PRIiPTR avr_inttypes 45 printf avr_stdio 80 printf_P avr_stdio 80 PRIo16 avr_inttypes 45 PRIo32 avr inttypes 45 PRIo8 avr inttypes 45 PRIoFASTI6 avr inttypes 45 PRIoFAST32 avr inttypes 45 PRIoFASTS avr inttypes 45 PRIoLEASTI6 avr inttypes 45 PRIoLEAST32 avr inttypes 45 PRIoLEASTS avr inttypes 45 PRIoPTR avr inttypes 45 PRIu16 avr inttypes 46 PRIu32 avr inttypes 46 PRIu8 avr inttypes 46 PRIUFAST16 avr_inttypes 46 PRIuFAST32 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 246 avr_inttypes 46 PRIuFAST8 avr_inttypes 46 PRIuLEAST16 avr_inttypes 46 PRIuLEAST32 avr_inttypes 46 PRIuLEASTS avr inttypes 46 PRIuPTR avr inttypes 46 PRIX16 avr_inttypes 46 PRIx16 avr_inttypes 47 PRIX32 avr_inttypes 47 PRIx32 avr_inttypes 47 PRIX8 avr_inttypes 47 PRIx8 avr_inttypes 47 PRIXFAST16 avr_inttypes 47 PRIxFAST 16 avr_inttypes 47 PRIXFAST32 avr_inttypes 47 PRIxFAST32 avr_inttypes 47 PRIXFAST8 avr_inttypes 47 PRIxFAST8 avr_inttypes 47 PRIXLEAST16 avr_inttypes 48 PRIxLEAST16
141. de 5 18 3 4 int feof FILE stream Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 79 Test the end of file flag of st ream This flag can only be cleared by a call to clearerr 5 18 3 5 int ferror FILE stream Test the error flag of st ream This flag can only be cleared by a call to clearerr 5 18 3 6 int fflush FILE x stream Flush stream This is a null operation provided for source code compatibility only as the standard IO implementation currently does not perform any buffering 5 18 3 7 int fgetc FILE stream The function fgetc reads a character from st ream It returns the character or EOF in case end of file was encountered or an error occurred The routines feof or ferror must be used to distinguish between both situations 5 18 3 8 char fgets char __str int size FILE x __stream Read at most size 1 bytes from st ream until a newline character was encoun tered and store the characters in the buffer pointed to by str Unless an error was encountered while reading the string will then be terminated with a NUL character If an error was encountered the function returns NULL and sets the error flag of stream which can be tested using ferror Otherwise a pointer to the string will be returned 5 18 3 9 int fprintf FILE __ stream const char fmt The function fprintf performs formatted output
142. de macro expansions n omit forms processing s include symbols file set the name of the listing file The various sub options be combined into a single a option list file must be the last one in that case Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 230 7 10 2 2 Examples for assembler options passed through the compiler member that assembler options can be passed from the C compiler frontend using Wa see above so in order to include the C source code into the assembler listing in file foo 1st when compiling foo c the following compiler command line can be used 5 avr gcc c foo c o foo o Wa ahls foo lst In order to pass an assembler file through the C preprocessor first and have the assem bler generate line number debugging information for it the following command can be used avr gcc c x assembler with cpp o foo o foo S Wa gstabs Note that on Unix systems that have case distinguishing file systems specifying a file name with the suffix S upper case letter S will make the compiler automatically assume x assembler with cpp while using s would pass the file directly to the assembler no preprocessing done 7 10 3 Controlling the linker avr ld 7 10 3 1 Selected linker options While there are no machine specific options for avr ld a number of the standard options might be of interest to AVR users lname Locate the
143. dest and then adds a terminating 70 character The strings may not overlap and the dest string must have enough space for the result Returns The strcat function returns a pointer to the resulting string dest Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 20 lt string h gt Strings 104 5 20 3 12 char x strchr const char src int val Locate character in string The strchr function returns a pointer to the first occurrence of the character val in the string src Here character means byte these functions do not work with wide or multi byte characters Returns The strchr function returns a pointer to the matched character or NULL if the character is not found 5 20 3 13 int strcmp const char x 57 const char 52 Compare two strings The strcmp function compares the two strings sl and 52 Returns The stremp function returns an integer less than equal to or greater than zero if sl is found respectively to be less than to match or be greater than s2 5 20 3 14 char strcpy char dest const char src Copy a string The strcpy function copies the string pointed to by src including the terminating 0 character to the array pointed to by dest The strings may not overlap and the destination string dest must be large enough to receive the copy Returns The strcpy function returns a pointer to the destination string dest Note If the destinatio
144. ds int must be at least 16 bits It may be removed in a future release Call used registers r18 r27 30 31 May be allocated by gcc for local data You may use them freely in assembler subroutines Calling C subroutines can clobber any of them the caller is re sponsible for saving and restoring Call saved registers r2 r17 r28 r29 May be allocated by gcc for local data Calling C subroutines leaves them un changed Assembler subroutines are responsible for saving and restoring these registers if changed r29 r28 Y pointer is used as a frame pointer points to local data on stack if necessary Fixed registers r0 r1 Never allocated by gcc for local data but often used for fixed purposes rO temporary register be clobbered by any code except interrupt handlers which save it may be used to remember something for a while within one piece of assembler code rl assumed to be always zero in any code may be used to remember something for a while within one piece of assembler code but must then be cleared after use r1 This includes any use of the mul s u instructions which return their result in rl r0 Interrupt handlers save and clear r1 on entry and restore r1 on exit in case it was non zero Function call conventions Arguments allocated left to right r25 to r8 All arguments are aligned to start in even numbered registers odd sized arguments including char have one fr
145. e 23 SLEEP MODE PWR DOWN strcpy avr sleep 28 avr string 103 SLEEP MODE PWR SAVE strcpy P avr sleep 28 avr pgmspace 23 SLEEP MODE STANDBY strlcat avr_sleep 28 avr_string 104 snprintf strlcat P avr stdio 81 avr pgmspace 24 snprintf P strlcpy avr_stdio 81 avr_string 104 sprintf strlcpy_P avr_stdio 81 avr_pgmspace 24 sprintf_P strlen avr_stdio 81 avr_string 104 sqrt strlen_P Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 249 avr_pgmspace 24 strlwr avr_string 104 strncasecmp avr_string 105 strncasecmp_P avr_pgmspace 24 strncat avr_string 105 strncat_P avr_pgmspace 25 strncmp avr_string 105 strncmp P avr pgmspace 25 strncpy avr_string 105 strncpy_P avr_pgmspace 25 strnlen avr_string 106 strnlen_P avr_pgmspace 26 strrchr avr_string 106 strrev avr_string 106 strsep avr_string 106 strstr avr_string 107 strtod avr_stdlib 96 strtok_r avr_string 107 strtol avr_stdlib 96 strtoul avr_stdlib 97 strupr avr_string 107 supported devices 2 tan avr_math 56 tanh avr_math 56 timer_enable_int deprecated_items 36 toascii ctype 39 tolower ctype 39 tools optional 215 tools required 215 toupper ctype 39 TW_BUS_ERROR util_twi 114 TW_MR_ARB_LOST util_twi 114 TW_MR_DATA_ACK util_twi 115 TW_MR_DATA_NACK util_twi 115 TW_MR_SLA_ACK util_twi 115 TW_MR_SLA_NACK util_twi 115 TW_MT_ARB_LOST util_twi 115 TW
146. e before erasing the page 5 2 2 7 define boot page fill address data boot page fill normal address data Fill the bootloader temporary page buffer for flash address with data word Note The address is a byte address The data is a word The AVR writes data to the buffer a word at a time but addresses the buffer per byte So increment your address by 2 between calls and send 2 data bytes in a word format The LSB of the data is written to the lower address the MSB of the data is written to the higher address 5 2 2 8 define boot page fill safe address data Value do boot spm busy wait N eeprom busy wait boot_page_fill address data while 0 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 2 lt avr boot h gt Bootloader Support Utilities 13 Same as boot_page_fill except it waits for eeprom and spm operations to complete before filling the page 5 2 2 9 define boot_page_write address __boot_page_write_normal address Write the bootloader temporary page buffer to flash page that contains address Note address is a byte address in flash not a word address 5 2 210 define boot page write safe address Value do boot spm busy wait eeprom_busy_wait boot_page_write address while 0 Same as boot_page_write except it waits for eeprom spm operations to complete before writing the page 5 2 211 define boot rww busy
147. e this is going to waste a lot of SRAM In Program Space String Utilities a method is described how such constant data can be moved out to flash ROM How ever a constant string located in flash ROM is no longer a valid argument to pass to a function that expects const char x type string since the AVR processor needs the special instruction LPM to access these strings Thus separate functions are needed that take this into account Many of the standard C library functions have equivalents available where one of the string arguments can be located in flash ROM Private func tions in the applications need to handle this too For example the following can be used to implement simple debugging messages that will be sent through a UART Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 187 include lt inttypes h gt include lt avr io h gt include lt avr pgmspace h gt int uart_putchar char c if Mn uart putchar Nr loop until bit is set USR UDRE UDR return 0 so it could be used for fdevopen too void debug_P const char addr char Gs while c pgm_read_byte addr uart_putchar c int main void ioinit initialize UART x 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
148. e C compiler By default all unknown non option arguments on the avr gcc command line 1 e all filename arguments that don t have a suffix that is handled by avr gcc are passed straight to the linker Thus all files ending in o object files and a object libraries are provided to the linker System libraries are usually not passed by their explicit filename but rather using the 1 option which uses an abbreviated form of the archive filename see above avr libc ships two system libraries 1ibc a and libm a While the standard library libc a will always be searched for unresolved references when the linker is started using the C compiler frontend i e there s always at least one implied 1c option the mathematics library 1ibm a needs to be explicitly requested using 1m See also the entry in the FAQ explaining this Conventionally Makefiles use the make macro LDLIBS to keep track of 1 and possibly L options that should only be appended to the C compiler command line Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 11 Todo List 232 when linking the final binary In contrast the macro LDF LAGS 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
149. e TW ST 8 fdefine TW ST ARB LOST SLA ACK OxBO define TW ST DATA ACK 0xB8 fdefine TW ST DATA NACK 0xCO define TW ST LAST DATA 0xC8 define TW SR SLA ACK 0x60 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 524 lt util twi h gt TWI bit mask definitions 115 define TW SR LOST SLA ACK 0x68 fdefine TW SR GCALL 0x70 define TW SR LOST 0x78 define TW SR 0x80 define TW SR 0x88 define TW SR DATA ACK 0x90 fdefine TW SR GCALL DATA NACK 0x98 define TW SR STOP OxAO define TW INFO OxF8 fdefine TW BUS ERROR 0x00 define TW STATUS 5 define TW STATUS TWSR amp TW STATUS MASK R W bit in SLA R W address field define TW READ 1 define TW WRITE 0 5 24 2 Define Documentation 5 24 21 define TW BUS ERROR 0x00 illegal start or stop condition 5 24 2 define TW MR LOST 0x38 arbitration lost in SLA R or NACK 5 24 2 3 define TW MR DATA 0x50 data received ACK returned 5 24 2 4 ftdefine TW MR DATA NACK 0x58 data received NACK returned 5 24 2 5 didefine TW MR SLA 0x40 SLA R transmitted ACK received 5 24 2 6 define TW MR SLA 0x48 SLA R transmitted NACK received Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 524 lt util twi h gt TWI bit mask definitions 116 5 24 27 define TW MT LOST 0x38 ar
150. e function fmod returns the floating point remainder of x y 5 15 3 12 double frexp double __value int exp The frexp function breaks a floating point number into a normalized fraction and an integral power of 2 It stores the integer in the int object pointed to by exp The frexp function returns the value x such that x is a double with magnitude in the interval 1 2 1 or zero and value equals x times 2 raised to the power exp If value is zero both parts of the result are zero 5 15 3 13 int isinf double x The function isinf returns 1 if the argument x is either positive or negative infinity otherwise 0 5 15 3 14 int isnan double x The function isnan returns 1 if the argument x represents a not a number NaN object otherwise 0 5 15 3 15 double Idexp double __x int exp The Idexp function multiplies a floating point number by an integral power of 2 The Idexp function returns the value of x times 2 raised to the power exp If the resultant value would cause an overflow the global variable errno is set to ERANGE and the value NaN is returned 5 15 3 16 double log double _ x The log function returns the natural logarithm of argument x If the argument is less than or equal 0 a domain error will occur 5 15 3 17 double 10210 double x 102100 function returns the logarithm of argument x to base 10 If the argument is less than or equal 0 a domain error will occur
151. e further data int ee24xx write page uintl6 t eeaddr int len uint8 t buf uint8_t sla 0 int rv 0 uintl6 t endaddr if eeaddr len eeaddr PAGE SIZE 1 endaddr eeaddr len else endaddr eeaddr PAGE_SIZE 1 1 len endaddr eeaddr patch high bits of EEPROM address into SLA x sla SLA 24CXX eeaddr gt gt 8 amp 0x07 lt lt 1 restart if n gt MAX_ITER return 1 begin x Note 15 _BV TWINT _BV TWSTA _BV TWEN x send start condition while TWCR amp _BV TWINT 0 wait for transmission switch twst TW_STATUS case TW_REP_START OK but should not happen case TW_START break case TW_MT_ARB_LOST goto begin default return 1 error not in start condition NB do not send stop condition send SLA W TWDR sla TW_WRITE TWCR _BV TWINT _BV TWEN clear interrupt to start transmission x while TWCR _BV TWINT 0 x wait for transmission x switch twst TW_STATUS case TW_MT_SLA_ACK break case TW_MT_SLA_NACK nack during select device busy writing goto restart case TW_MT_ARB_LOST re arbitrate Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 529 Example using the two wire interface TWI 156 goto begin default goto error must send stop condition x TWDR eeaddr
152. e s timestamp and it seems that some MS DOS derivative Win9x perhaps rounds up the current time to the next sec ond when calculating the timestamp of an updated file in case the current time cannot Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 189 be represented in FAT s terms this causes a situation where make sees a file coming from the future Since all make decisions are based on file timestamps and their dependencies make warns about this situation Solution don t use inferior file systems operating systems Neither Unix file systems nor HPFS aka NTFS do experience that problem Workaround after saving the file wait a second before starting make Or simply ignore the warning If you are paranoid execute a make clean all to make sure everything gets rebuilt In networked environments where the files are accessed from a file server this message can also happen if the file server s clock differs too much from the network client s clock In this case the solution is to use a proper time keeping protocol on both sys tems like NTP As a workaround synchronize the client s clock frequently with the server s clock Back to FAQ Index 7 3 25 Why are many interrupt flags cleared by writing a logical 1 Usually each interrupt has its own interrupt flag bit in some control register indicating the specified interrupt condition has been met by represen
153. e sprintf but instead of assuming s to be of infinite size more than n characters including the trailing NUL character will be converted to s Returns the number of characters that would have been written to s if there were enough space 5 18 3 26 int snprintf_P char __s size_t const char __ fmt Variant of snprintf that uses fmt string that resides in program memory 5 18 3 27 int sprintf char __s const char fmt Variant of printf that sends the formatted characters to string s 5 18 3 28 int sprintf_P char __s const char __ fmt Variant of sprintf that uses a fmt string that resides in program memory Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 82 5 18 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 for details 5 18 3 30 int sscanf_P const char x _ buf const char Variant of sscanf using a fmt string in program memory 5 18 3 31 int ungetc int c FILE stream The ungetc function pushes the character c converted to an unsigned char back onto the input stream pointed to by st ream The pushed back character will be returned by a subsequent read on the stream Currently only a single character can be pushed back onto the stream
154. ects will have several modules and will typically need to break up the building of the project into several compiles and one link avr gcc g Os mmcu at90s2333 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 at90s2333 o demo elf demo o It is important to specify the MCU type when linking The compiler uses the mmcu option to choose start up files and run time libraries that get linked together If this option isn t specified the compiler defaults to the 8515 processor environment which is most certainly what you didn t want 528 4 Examining the Object File Now we have a binary file Can we do anything useful with it besides put it into the processor The GNU Binutils suite is made up of many useful tools for manipulating object files that get generated One tool is avr objdump which takes information from the object file and displays it in many useful ways Typing the command by itself will cause it to list out its options For instance to get a feel of the application s size the h option can be used The output of this option shows how much space is used in each of the sections the stab and stabstr sections hold the debugging information and won t make it into the ROM file An even more useful option is 5 This option disassembles the binary file and inter sperses the source code in the output This method is much better in my opinion than usin
155. ee register above them This allows making better use of the movw instruction on the enhanced core If too many those that don t fit are passed on the stack Return values 8 bit in r24 not r25 16 bit in r25 124 up to 32 bits in 122 125 up to 64 bits in r18 r25 8 bit return values are zero sign extended to 16 bits by the caller unsigned char is more efficient than signed char just clr r25 Argu ments to functions with variable argument lists printf etc are all passed on stack and char is extended to int Warning There was no such alignment before 2000 07 01 including the old patches for gcc 2 95 2 Check your old assembler subroutines and adjust them accordingly Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 182 Back to FAQ Index 7 3 15 How do I put an array of strings completely in ROM There are times when you may need an array of strings which will never be modified In this case you don t want to waste ram storing the constant strings The most obvious and incorrect thing to do is this include lt avr pgmspace h gt PGM_P array 2 PROGMEM Poo Bar int main void char 32 stropy P buf array 1 return 0 The result is not want you want though What you end up with is the array stored in ROM while the individual strings end up in RAM in the data section To work around this you need to do something like t
156. egal28 ATmegal62 ATmegal65 DATA megal69 ATmega325 ATmega329 AT mega64 ATmega645 ATmega649 AT mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 USARTI SIG USARTI Rx ATmegal62 RXC vect USARTI Complete RECV USARTI SIG USARTI Rx AT90CANI28 AT90CAN32 AT90CANGA RX_vect UARTI Complete ATmegal28 ATmega64 ATmega640 AT RECV megal280 ATmegal281 ATmega324 AT megal64 ATmega644 USARTI SIG USARTI Tx ATmegal62 TXC vect USARTI Complete TRANS Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 130 vect Vector name Old vector Description Applicable for device name USARTI SIG USARTI Tx AT90CANI28 AT90CAN32 AT90CAN64 TX vect UARTI Complete ATmegal28 ATmega64 ATmega640 AT TRANS megal280 ATmegal281 ATmega324 AT megal64 ATmega644 USARTI SIG USARTI Data AT90CANI28 AT90CAN32 AT90CANGA UDRE vect UARTI Register Empty ATmegal28 ATmegal62 ATmega64 AT DATA mega640 ATmegal280 ATmegal281 AT mega324 ATmegal64 ATmega644 USART2_ SIG_ USART2 Rx ATmega640 ATmegal280 ATmega1281 RX_vect USART2_ Complete RECV USART2 SIG USART2 Tx ATmega640 ATmegal280 ATmegal281 TX vect USART2 Complete TRANS USART2_ SIG_ USART2 Data ATmega640 ATmegal280 ATmegal281 UDRE vect USART2 regist
157. emory mapped IO i e it can be accessed using all the MCU instructions that are applicable to normal data memory The IO register space is mapped into the data memory address space with an offset of 0x20 since the bottom of this space is reserved for direct access to the MCU registers Actual SRAM is available only behind the IO register area starting at either address 0x60 or Ox100 depending on the device Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 526 lt avr sfr_defs h gt Special function registers 133 AVR Libc supports both these paradigms While by default the implementation uses memory mapped IO access this is hidden from the programmer So the programmer can access IO registers either with a special function like out b include lt avr io h gt outb PORTA 0x33 or they can assign a value directly to the symbolic address PORTA 0x33 The compiler s choice of which method to use when actually accessing the IO port is completely independent of the way the programmer chooses to write the code So even if the programmer uses the memory mapped paradigm and writes PORTA 0x40 the compiler can optimize this into the use of an sbi instruction of course provided the target address is within the allowable range for this instruction and the right hand side of the expression is a constant value known at compile time The advantage of using the memory mapped paradigm in C programs is that
158. er Empty DATA USART3 SIG USART3 Rx ATmega640 ATmegal280 ATmegal281 RX_vect USART3 Complete RECV USART3 SIG USART3 Tx ATmega640 ATmegal280 ATmegal281 TX vect USART3 Complete TRANS USART3 SIG USART3 Data ATmega640 ATmegal280 ATmegal281 UDRE vect USART3 register Empty DATA USART SIG USART Rx ATmegal6 ATmega32 ATmega323 AT RXC vect USART Complete mega8 RECV SIG_ UART_RECV USART_RX_ SIG_ USART Rx AT90PWM3 AT90PWM2 ATmega3250 vect USART_ Complete ATmega3290 ATmega6450 ATmega6490 SIG_ ATmega8535 ATmegal68 ATmega48 UART_RECV mega88 ATtiny2313 USART_ SIG_ USART Tx ATmegal6 ATmega32 ATmega323 TXC_vect USART_ Complete mega8 TRANS SIG_UART_ TRANS USART_TX_ SIG_ USART Tx AT90PWM3 AT90PWM2 ATmega8535 vect USART_ Complete ATmegal68 ATmega48 ATmega88 AT TRANS tiny2313 SIG_UART_ TRANS USART_ SIG_ USART Data AT90PWM3 AT90PWM2 ATmegal6 AT UDRE_vect USART_ Register Empty mega32 ATmega323 ATmega3250 DATA SIG_ mega3290 ATmega6450 ATmega6490 AT UART_DATA mega8 ATmega8535 ATmegal68 mega48 ATmega88 ATtiny2313 USI_ SIG USI USI Overflow ATmegal65 ATmegal69 ATmega325 AT OVERFLOW OVERFLOW mega3250 ATmega329 ATmega3290 AT mega645 ATmega6450 ATmega649 AT mega6490 ATtiny2313 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 131
159. er Type conversions 43 define SCNiPTR SCNi16 define SCNo16 o define SCNoLEASTI6 o define SCNoFAST16 o define SCNul6 u define SCNuLEASTI6 u define SCNuFAST16 u define SCNx16 x define SCNxLEASTI6 x define SCNxFAST16 x define SCNo32 lo define SCNoLEAST32 lo define SCNoFAST32 lo define SCNu32 lu define SCNuLEAST32 lu define SCNuFAST32 lu define SCNx32 Ix define SCNxLEAST32 Ix define SCNxFAST32 Ix define SCNoPTR SCNo16 define SCNuPTR SCNu16 define SCNxPTR SCNx16 Far pointers for memory access gt 64K typedef int32_t int_farptr_t typedef uint32_t uint_farptr_t 5 14 2 Define Documentation 5 14 21 define PRId16 d decimal printf format for int16_t 5 14 2 22 define PRId32 1d decimal printf format for int32_t 5 14 2 3 define PRId8 d decimal printf format for int8_t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 44 5 14 2 4 define PRIGFAST16 decimal printf format for int_fast16_t 5 14 2 5 define PRIdFAST32 Id decimal printf format for int_fast32_t 5 14 2 6 define PRIdFASTS decimal printf format for int_fast8_t 5 14 27 define PRIGLEAST16 d decimal printf format for int_least16_t 5 14 2 define PRI4LEAST32 Id decimal printf format for int_least32_t 5 14 2 9 define PRIGLEASTS8 d decimal printf format for int_least8_t 5
160. er representation It is equivalent to strtol nptr char NULL 10 except that atol does not detect errors 5 19 4 6 void bsearch const void const void size_t __nmemb size t size int const void const void __ compar The bsearch function searches an array of nmemb objects the initial member of which is pointed to by base for a member that matches the object pointed to by key The size of each member of the array is specified by size The contents of the array should be in ascending sorted order according to the compar ison function referenced by compar The compar routine is expected to have two arguments which point to the key object and to an array member in that order and should return an integer less than equal to or greater than zero if the key object is found respectively to be less than to match or be greater than the array member The bsearch function returns a pointer to a matching member of the array or a null pointer if no match is found If two members compare as equal which member is matched is unspecified 5 19 4 7 void calloc size t __nele size_t __size Allocate nele elements of size each Identical to calling malloc using nele size as argument except the allocated memory will be cleared to zero 5 19 4 8 div div int __num int __denom The div function computes the value num denom and returns the quotient and re mainder in a structure
161. erase address boot page erase normal address define boot page write address boot page write normal address define boot rww enable boot rww enable define boot lock bits set lock bits boot lock bits set lock bits define boot page fill safe address data define boot page erase safe address define boot page write safe address define boot rww enable safe define boot lock bits set safe lock bits 5 2 2 Define Documentation 5 2 21 define boot_is_spm_interrupt _SPM_REG amp uint8 t BV SPMIE Check if the SPM interrupt is enabled 5 2 2 2 define boot lock bits set lock bits boot lock bits set lock bits Set the bootloader lock bits Parameters lock bits mask of which Boot Loader Lock Bits to set Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 22 lt avr boot h gt Bootloader Support Utilities 11 Note In this context a set bit will be written to a zero value Note also that only BLBxx bits can be programmed by this command For example to disallow the SPM instruction from writing to the Boot Loader memory section of flash you would use this macro as such boot_lock_bits_set 12 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 5 2 2 3 define boot_lock_bits_set_safe lock_bits Value do
162. es the C type int by default in order to calculate constant integer expressions In order to get a 100 kHz output we need to toggle the PD6 line 200000 times per second Since we use timer 0 without any prescaling options in order to get the de sired frequency and accuracy we already run into serious timing considerations while accepting and processing the timer overflow interrupt the timer already continues to count When pre loading the TCCNTO register we therefore have to account for the number of clock cycles required for interrupt acknowledge and for the instructions to reload TCCNTO 4 clock cycles for interrupt acknowledge 2 cycles for the jump from the interrupt vector 2 cycles for the 2 instructions that reload TCCNTO This is what the constant fuzz is for Note 5 External functions need to be declared to be global main is the application entry point that will be jumped to from the ininitalization routine in crts1200 0 Note 6 The main loop is just a single jump back to itself Square wave generation itself is completely handled by the timer 0 overflow interrupt service A sleep instruction using idle mode could be used as well but probably would not conserve much energy anyway since the interrupt service is executed quite frequently Note 7 Interrupt functions can get the usual names that are also available to C programs The linker will then put them into the appropriate interrupt vector slots Note that they m
163. ext data packet is initially set up to assert the TWEA bit During the last loop iteration TWEA is de asserted so the client will get informed that no further transfer is desired Note 14 Except in the case of lost arbitration all bus transactions must properly be terminated by the master initiating a stop condition Note 15 Writing to the EEPROM device is simpler than reading since only a master transmitter mode transfer is needed Note that the first packet after the SLA W selection is always considered to be the EEPROM address for the next operation This packet is exactly the same as the one above sent before starting to read the device In case a master transmitter mode transfer is going to send more than one data packet all following packets will be considered data bytes to write at the indicated address The internal address pointer will be incremented after each write operation Note 16 24Cxx devices can become write protected by strapping their WC pin to logic high Leaving it unconnected is explicitly allowed and constitutes logic low 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 avr libc Data Structure Documentation 6 1 div t Struct Reference 6 1 1 Detailed Description Result type for function div Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 6 2 Idi
164. for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 84 A is written No argument is converted The complete conversion specification is 9696 eE The double argument is rounded and converted in the format d ddde177dd where there is 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 to introduce the exponent The exponent always contains two digits if the value is zero the exponent is 00 F The double argument is rounded and converted to decimal notation in the format ddd ddd where the number of digits after the decimal point character is equal to the precision specification If the precision is missing it is taken as 6 if the precision is explicitly zero no decimal point character appears If a decimal point appears at least one digit appears before it gG The double argument is converted in style or e or F or E for conver sions The precision specifies the number of significant digits If the precision is missing 6 digits are given if the precision is zero it is treated as 1 Style e is used if the exponent from its conversion is less than 4 or greater than or equal to the precision Trailing zeros are removed from the fractional part of the result a
165. further nested function calls must not require more stack space or they will risk colliding with the data segment The default value of malloc margin is set to 32 7 5 4 Implementation details Dynamic memory allocation requests will be returned with a two byte header prepended that records the size of the allocation This is later used by free The returned address points just beyond that header Thus if the application accidentally writes before the returned memory region the internal consistency of the memory al locator is compromised The implementation maintains a simple freelist that accounts for memory blocks that have been returned in previous calls to free Note that all of this memory is considered to be successfully added to the heap already so no further checks against stack heap collisions are done when recycling memory from the freelist Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 5 Using malloc 206 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 me
166. g __ELPM_dword uint32_ t address_long define pgm_read_byte address_short pgm_read_byte_near address_short define pgm_read_word address_short pgm_read_word_near address_short define pgm_read_dword address_short pgm_read_dword_near address_short define PGM_P const prog_char define PGM_VOID_P const prog_void Typedefs typedef void PROGMEM prog_void typedef char PROGMEM prog_char typedef unsigned char PROGMEM prog_uchar typedef int8 t PROGMEM prog int8 t typedef uint8 t PROGMEM prog uint8 t typedef int16 t PROGMEM prog int16 t typedef uint16 t PROGMEM prog uintl6 t typedef int32 t PROGMEM prog int32 t typedef uint32 t PROGMEM prog uint32 t typedef int 4 t PROGMEM prog int64 t typedef uint6 4 t PROGMEM prog uint64 t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 5 lt avr pgmspace h gt Program Space String Utilities 20 Functions void memcpy_P void PGM_VOID_P size_t int strcasecmp_P const char PGM_P _ ATTR PURE char strcat_P char PGM_P int stremp_P const char PGM_P _ ATTR_PURE char strepy_P char PGM_P size_t strlcat_P char P size_t size t strlcpy P char PGM_P size_t size t strlen_P PGM_P CONST int strncasecmp_P const char x PGM_P size_t _ ATTR_PURE char strncat_P char PGM P size_t int strnemp_P const char PGM_P size_t _ ATTR_PURE char strncpy_P char size_t size_
167. g the 5 with the compiler because this listing includes routines from the libraries and the vector table contents Also all the fix ups have been satisfied In other words the listing generated by this option reflects the actual code that the processor will run avr objdump h 5 demo elf gt demo lst Here s the output as saved in the demo 1st file Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 simple project demo elf file format elf32 avr Sections Idx Name Size VMA LMA File off Algn 0 text 000000 0 00000000 00000000 00000094 2xx0 CONTENTS ALLOC LOAD READONLY CODE 1 data 00000000 00800060 000000 0 00000174 2xx0 CONTENTS ALLOC LOAD DATA 2 bss 00000003 00800060 00800060 00000174 2xx0 ALLOC 3 noinit 00000000 00800063 00800063 00000174 2xx0 CONTENTS 4 eeprom 00000000 00810000 00810000 00000174 2xx0 CONTENTS 5 stab 00000768 00000000 00000000 00000174 2xx2 CONTENTS READONLY DEBUGGING 6 stabstr 000007da 00000000 00000000 000008dc 2x0 CONTENTS READONLY DEBUGGING Disassembly of section text 00000000 vectors 02 12 60 rjmp 36 0x26 ctors end 2 6d cO rjmp 218 Oxde bad interrupt 4 6c cO rjmp 216 Oxde bad interrupt 6 6b cO rjmp 214 Oxde bad interrupt 8 6a cO rjmp 212 Oxde bad interrupt a 69 cO rjmp 210 Oxde bad interrupt 68 0 rjmp 208 Oxde lt bad interrupt 67 cO rjmp 206 Oxde lt bad inter
168. ger Types 69 5 17 3 15 typedef unsigned int uint16_t 16 bit unsigned type 5 17 3 16 typedef unsigned long int uint32_t 32 bit unsigned type 5 17 3 17 typedef unsigned long long int uint64_t 64 bit unsigned type 5 17 3 18 typedef unsigned char uint8_t 8 bit unsigned type 5 17 3 19 typedef uint16_t uint_fast16_t fastest unsigned int with at least 16 bits 5 17 3 20 typedef uint32 t uint fast32 t fastest unsigned int with at least 32 bits 5 17 3 21 typedef uint64 t uint fast64 t fastest unsigned int with at least 64 bits 5 17 3 22 typedef uint8 t uint fast8 t fastest unsigned int with at least 8 bits 5 17 3 23 typedef uint16_t uint_least16_t unsigned int with at least 16 bits 5 17 3 24 typedef uint32 t uint_least32_t unsigned int with at least 32 bits 5 17 3 25 typedef uint64_t uint_least64_t unsigned int with at least 64 bits Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 70 5 17 3 26 typedef uint8_t uint_least8_t unsigned int with at least 8 bits 5 17 3 27 typedef uint64_t uintmax_t largest unsigned int available 5 17 3 28 typedef uint16_t uintptr_t Unsigned pointer compatible type 5 18 lt stdio h gt Standard IO facilities 5 18 1 Detailed Description include lt stdio h gt Introduction to the Standard IO facilities This file declares the standard IO facili ties that are implemented in avr 1libc D
169. gt General utilities 90 ldiv t ldiv long num long __denom __asm__ __divmodsi4 __ATTR_ CONST void qsort void base size_t __nmemb size t size compar fn t compar long strtol const char nptr char endptr int base unsigned long strtoul const char nptr char __endptr int base __inline__ long atol const char __nptr PURE __inline__ int atoi const char __nptr _ ATTR_PURE void exit int status ATTR NORETURN void malloc size t size ATTR MALLOC void free void ptr void calloc size nele size t size ATTR MALLOC void realloc void ptr size t size MALLOC double strtod const char nptr char endptr double const char nptr int rand void void srand unsigned int seed int rand unsigned long ctx Variables e size t malloc margin e char x malloc heap start e char x malloc heap end 5 19 2 Define Documentation 5 19 2 1 ftdefine DTOSTR_ALWAYS_SIGN 0x01 Bit value that can be passed in flags to dtostre 5 19 2 22 define DTOSTR_PLUS_SIGN 0x02 Bit value that can be passed in flags to dtostre 5 19 2 3 define DTOSTR_UPPERCASE 0x04 Bit value that can be passed in flags to dtostre 5 19 2 4 define RAND MAX 0x7FFF Highest number that can be generated by rand Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h gt Ge
170. han 64 KB as well as standard names for all printf and scanf formatting options that are supported by the lt stdio h gt Standard IO facilities As the library does not support the full range of conversion specifiers from ISO 9899 1999 only those conversions that are actually implemented will be listed here The idea behind these conversion macros is that for each of the types defined by lt stdint h gt a macro will be supplied that portably allows formatting an object of that type in printf or scanf operations Example Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 41 include lt inttypes h gt uint8_t smallval int32_t longval printf The hexadecimal value of smallval is PRIx8 the decimal value of longval is PRId32 n smallval longval macros for printf and scanf format specifiers For C these are only included if STDC LIMIT MACROS is defined before in cluding lt inttypes h gt define PRId8 d define PRIGLEASTS8 define PRIdFASTS d define i define PRULEASTS8 i define PRIIFASTS 1 define PRId16 d define PRIGLEAST16 d define PRIGFAST16 d define PRIi16 i define PRILEASTI6 i define PRHFAST16 i define PRId32 ld define PRIGLEAST32 Id define PRIdFAST32 Id define PRIi32 li define PRULEAST32 li define PRIiFAST32 li define PRIdPTR PRId16 define PR
171. haracter is not found 5 20 3 25 char strrev char string Reverse a string The strrev function reverses the order of the string Returns The strrev function returns a pointer to the beginning of the reversed string 5 20 3 26 char strsep char x string const char delim Parse a string into tokens The strsep function locates in the string referenced by string 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 string An empty field i e one caused by two adjacent delimiter characters can be detected by comparing the location referenced by the pointer returned in string to 7107 Returns The strtok_r function returns a pointer to the original value of string If xstringp is initially NULL strsep returns NULL 5 20 3 27 char x strstr const char 57 const char 52 Locate a substring The strstr function finds the first occurrence of the substring s2 in the string 51 The terminating 0 characters are not compared Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 521 lt utiV crc16 h gt CRC Computations 108 Returns The strstr function returns a pointer to the beginning of the substring or NULL if the substring is not found If s2 points to a string of
172. haracters 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 circum flex To include a close bracket in the set make it the first character after the open bracket or the circumflex any other position will end the set The hyphen character is also special when placed between two other characters it adds all intervening characters to the set To include a hyphen make it the last character before the final close bracke
173. have a better feel as to how the tools are used and how a Makefile can be configured 5 28 1 The Project This project will use the pulse width modulator PWM to ramp an LED on and off every two seconds An AT90S2313 processor will be used as the controller The circuit for this demonstration is shown in the schematic diagram If you have a development kit you should be able to use it rather than build the circuit for this project Note Meanwhile the AT90S2313 became obsolete Either use its successor the pin compatible ATtiny2313 for the project or perhaps the ATmega8 or one of its successors ATmega48 88 168 which have become quite popular since the orig inal demo project had been established For all these more modern devices it is no longer necessary to use an external crystal for clocking as they ship with the internal 1 MHz oscillator enabled so C2 and 1 can be omitted Normally for this experiment the external circuitry on RESET 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 15 at the DIP 28 package to connect the LED to VCC SCK PB7 rz ts O RESET uISO PB6 20K m 3 2 5 a UB MOSI PB5 XTAL2 PB4 18 OCI PB3 pore 2 XTAL1 BBZ 18pf 5 20 vec AIN1 PB1 AINO PBO LED5MM R2 D1 D See note 7 Na GND GND ICP PD6 GND T1 P
174. he AVR device specific IO definitions reflect these names in definitions for numerical constants a way is needed to convert a bit number usually within a byte register into a byte value that can be assigned directly to the register However sometimes the direct bit numbers are needed as well e g in an SBI instruction so the definitions cannot usefully be made as byte values in the first place So in order to access a particular bit number as a byte value use the _BV macro Of course the implementation of this macro is just the usual bit shift which is done by the compiler anyway thus doesn t impose any run time penalty so the following applies _BV 3 gt 1 lt lt 3 gt 0x08 However using the macro often makes the program better readable BV stands for bit value in case someone might ask you Example clock timer 2 with full IO clock CS2x 05001 toggle OC2 output on compare match COM2x 0b01 and clear timer on compare match CTC2 1 Make OC2 PD7 an output TCCR2 _BV COM20 _BV CTC2 _BV CS20 DDRD _BV PD7 Back to FAQ Index 7 37 Can I use C on the AVR Basically yes C is supported assuming your compiler has been configured and compiled to support it of course Source files ending in cc cpp or C will automati cally cause the compiler frontend to invoke the C compiler Alternatively the C compiler could be explicitly called by the name avr c However there s
175. he library 1ibscanf flt a Note that either of these conversions requires the availability of a buffer that needs to be obtained at run time using malloc If this buffer cannot be obtained the operation is aborted returning the value EOF To link a program against the extended version use the following compiler flags in the link stage Wl u vfscanf lscanf flt im A third version is available for environments that are tight on space This version is provided in the library 1ibscanf min a and can be requested using the following options in the link stage Wl u vfscanf l1scanf min lm In addition to the restrictions of the standard version this version implements no field width specification no conversion assignment suppression flag no n specification and no general format character matching at all characters mt that do not comprise a conversion specification will simply be ignored including white space that is normally used to consume any amount of white space in the input stream However the usual skip of initial white space in the formats that support it is implemented 5 18 3 35 int vfscanf P FILE stream const char fmt va list Variant of vfscanf using a mt string in program memory 5 18 3 36 int vprintf const char fmt va list The function vprintf performs formatted output to stream stdout taking a vari able argument list as in vfprintf See vfprintf for details
176. heap start bss end data end bss start data start Figure 3 Internal RAM stack only external RAM variables and heap If dynamic memory should be placed in external RAM while keeping the variables in internal RAM something like the following could be used Note that for demonstration Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 5 Using malloc 205 purposes the assignment of the various regions has not been made adjacent in this example so there are holes below and above the heap in external RAM that remain completely unaccessible by regular variables or dynamic memory allocations shown in light bisque color in the picture below avr gcc Wl defsym heap start 0x802000 defsym heap end 0x803fff external RAM S s In 2 on board zx amp SP 1 malloc heap end heap end RAMEND brkval bss end malloc heap start heap start data bss start data start Figure 4 Internal RAM variables and stack external RAM heap If 11 heap endis 0 the allocator attempts to detect the bottom of stack in order to prevent a stack heap collision when extending the actual size of the heap to gain more space for dynamic memory It will not try to go beyond the current stack limit decreased by malloc margin bytes Thus all possible stack frames of interrupt routines that could interrupt the current function plus all
177. here modules are loaded and which modules were loaded from libraries It is yet another view of your application To get a map file I usually add Wl Map demo map to my link command Relink the application using the following command to generate demo map a portion of which is shown below avr gcc g mmcu at90s2313 Wl Map demo map o demo elf demo o Some points of interest in the demo map file are rela plt rela plt text 0x00000000 x vectors vectors 0x00000000 0x00000000 0x00000000 0x00000026 0 0 0 26 junk AVR avr libc 1 4 avr lib avr4 atmega8 crtm8 o _ vectors vector default ctors start The text segment where program instructions are stored starts at location 0 0 x fini2 finil x fini0 0x000000e0 data 0x00800060 0x00800060 x data x gnu linkonce dx 0x00800060 0x00800060 0x00800060 bss 0x00800060 0x00800060 x bss COMMON COMMON 0x00800060 0x00800060 0x00800061 0x00800063 0x000000e0 0x000000e0 noinit 0x00800063 0x00800063 0x0 0x3 0x3 0x0 etext load address 0x000000e0 PROVIDE __data_start ALIGN 0x2 _edata PROVIDE __data_end PROVIDE __bss_start demo o direction pwm PROVIDE __bss_end _ data load start LOADADDR data data load end data load start SIZEOF data PROVIDE noinit start Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28
178. his finclude avr pgmspace h const char foo PROGMEM Foo const char bar PROGMEM Bar PGM P array 2 PROGMEM foo bar int main void char buf 32 PGM_P p int i memcpy P amp p amp array i sizeof PGM P strcpy P buf p return 0 Looking at the disassembly of the resulting object file we see that array is in flash as such 00000026 array Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 183 26 2 00 word 0x002e 28 2 00 word Ox002a 0000002a bar 2 42 61 72 00 Bar 0000002e lt foo gt 2e 46 6f 6f 00 Foo foo is at addr 0x002e bar is at addr 0 002 array is at addr 0x0026 Then in main we see this memcpy P amp p amp array i sizeof PGM_P 70 66 Of add r22 r22 TAR 77 lf adc t23 x23 74 6a 5d subi r22 OxDA 218 76 TE AE sbci r23 OxFF 255 78 42 0 141 r20 0 02 2 7a 50 0 ldi r21 0 00 520 Tos ce 01 movw r24 r28 7e 81 96 adiw r24 0 21 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 reg
179. hose used outside In the case of aRAM less device like the AT90S1200 this can only be done by agreeing on a set of registers to be used exclusively inside the interrupt routine there would not be any other chance to save a register anywhere If the interrupt routine is to be linked together with C modules care must be taken to follow the register usage guidelines imposed by the C compiler Also any register modified inside the interrupt sevice needs to be saved usually on the stack Note 10 As explained in Interrupts a global catch all interrupt handler that gets all unassigned interrupt vectors 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 7 2 4 Pseudo ops and operators The available pseudo ops in the assembler are described in the GNU assembler gas manual The manual can be found online as part of the current binutils release under http sources redhat com binutils As gas comes from a Unix origin its pseudo op and overall assembler syntax is slightly different than the one being used by other assemblers Numeric constants follow the C notation prefix for hexadecimal constants expressions use a C like syntax Some common pseudo ops include byte allocates single byte constants e ascii allocates a non terminated string of characters e asciz allocates a VO terminated string of
180. ile an 8 bit operation that uses bitwise operators into 16 bit operation in assembly 187 7 3 22 How to detect RAM memory and variable overlap problems 188 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen CONTENTS vi 7 3 23 Is it really impossible to program the ATtinyXX C 188 7 3 24 What is this clock skew detected messsage 188 7 3 25 Why are many interrupt flags cleared by writing alogical 1 189 7 3 26 Why have programmed fuses the bit value 0 190 7 3 27 Which AVR specific assembler operators are available 190 pra o Mp rr 190 GOC gen Sistement ccoo xoxo x ER Rs 191 742 AssemblerCode 2 6 5 0 6456495 Bee REX RS 193 7 43 Inputand Output 2 193 M MC 197 745 Assembler Macros 0 lt 6 00 aaa m Rs 199 146 C Stub Functions cus RR GR RE S 200 7 4 7 Names Used in Assembler 201 Tob C3 eae OS EMS Sled de s 202 T2 cn A RR SR m 202 Tl o e e od ee a mm o e ea 202 7 82 Internal vs extemal RAM 2 60 555 cri rS 203 7 5 3 Tunables for 204 754 Implementation details 205 7 6 Release Numbering and Methodology 207 7 6 1 Release Version Numbering Scheme 207 162 Releasing AVR Libe crut e 207 14 Memory Secuons
181. ill be lost if a number close to DBL_MAX is converted with a precision gt 0 5 18 3 33 vfprintf P FILE __ stream const char __fmt va_list Variant of vfprintf that uses fmt string that resides in program memory 5 18 3 34 int vfscanf FILE __ stream const char fmt va list Formatted input This function is the heart of the scanf family of functions Characters are read from st ream and processed in a way described by fmt Conver sion results will be assigned to the parameters passed via ap The format string fmt is scanned for conversion specifications Anything that doesn t comprise a conversion specification is taken as text that is matched literally against the input White space in the format string will match any white space in the data including none all other characters match only itself Processing is aborted as soon as the data and format string no longer match or there is an error or end of file 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 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 character 1 indicating that the argument is a pointer to long i
182. ill 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 7 4 5 Assembler Macros In order to reuse your assembler language parts it is useful to define them as macros and put them into include files AVR Libc comes with a bunch of them which could be found in the directory avr include Using such include files may produce compiler warnings if they are used in modules which are compiled in strict ANSI mode To avoid that you can write asm instead of asm and volatile instead of volatile These are equivalent aliases Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 200 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 N L sbic 0 1 An Wt N rjmp L N no outputs x N I SFR IO ADDR port I brt When used for the first time L_ may be translated to L_1404 the next usage might create 1405 or whatever In any case the labels became unique too Another option is to use Unix assembler style numeric labels They are explained in How do I trace an assembler file in avr gdb The above examp
183. ink this stuff is worth it you can buy me a beer in return Joerg Wunsch Id twitest c v 1 6 2005 11 05 22 32 46 joerg wunsch Exp Simple demo program that talks to 24Cxx ISC EEPROM using the builtin TWI interface of ATmega device include lt inttypes h gt include lt stdio h gt include lt stdlib h gt include lt avr io h gt include lt util twi h gt Note 1 define DEBUG 1 System clock Hz define F_CPU 14745600UL Note 2 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 529 Example using the two wire interface TWI 150 Compatibility defines This should work ATmega8 ATmegal6 ATmegal63 ATmega323 ATmegal28 IOW on all devices that provide a builtin interface On the 128 it defaults to USART 1 ifndef UCSRB ifdef UCSRIA ATmegal28 define UCSRA UCSRIA define UCSRB UCSRIB define UBRR UBRRIL define UDR UDRI else x ATmega8 define UCSRA USR define UCSRB UCR endif endif ifndef UBRR define UBRR UBRRL endif Note 3 address for 24Cxx EEPROM 1010 E2 El EO R W 24C01 24C02 101 0 E2 El A8 R W 24C04 x 1010 E2 A9 A8 R W 24C08 x 1 0 1 0 10 A9 A8 R W 24C16 x define SLA 24CXX 0xa0 E2 E1 00 0 Maximal number of iterations to wait for a
184. inserted in initialization code which is run right after reset See the linker script for comments about the new initN sections which one to use etc The advantage of this method is that you can insert any initialization code you want just remember that this is very early startup no stack and no zero reg yet and no program memory space is wasted if this feature is not used There should be no need to modify linker scripts anymore except for some very spe cial cases It is best to leave stack at its default value end of internal SRAM faster and required on some devices like ATmegal61 because of errata and add W1 Tdata 0x801100 to start the data section above the stack For more information on using sections see Memory Sections There is also an ex ample for Using Sections in C Code Note that in C code any such function would preferrably be placed into section init3 as the code in init2 ensures the internal regis ter zero reg is already cleared Back to FAQ Index 7 3 6 What is all this BV stuff about When performing low level output work which is a very central point in microcon troller programming it is quite common that a particular bit needs to be set or cleared Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 173 in some IO register While the device documentation provides mnemonic names for the various bits in the IO registers and t
185. int32_t 5 14 2 44 define PRIx32 Ix hexadecimal printf format for uint32_t 5 14 2 45 define PRIX8 X uppercase hexadecimal printf format for uint8_t 5 14 2 46 define PRIx8 x hexadecimal printf format for uint8_t 5 14 2 47 define PRIXFASTI6 X uppercase hexadecimal printf format for uint_fast16_t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 48 5 14 2 48 define PRIxFASTI16 hexadecimal printf format for uint_fast16_t 5 14 2 49 define PRIXFAST32 IX uppercase hexadecimal printf format for fast32 t 5 14 2 50 define PRIXFAST32 Ix hexadecimal printf format for uint fast32 t 5 14 2 51 define PRIXFASTS X uppercase hexadecimal printf format for uint fast8 t 5 14 2 52 define PRIxFASTS x hexadecimal printf format for fast8 t 5 14 2 53 define PRIXLEASTIG X uppercase hexadecimal printf format for uint_least16_t 5 14 2 54 define PRIXLEASTI6 x hexadecimal printf format for uint_least16_t 5 14 2 55 define PRIXLEAST32 IX uppercase hexadecimal printf format for uint least32 t 5 14 2 56 define PRIXLEAST32 Ix hexadecimal printf format for least32 t 5 14 2 57 define PRIXLEASTS X uppercase hexadecimal printf format for least8 t 5 14 2 58 define PRIXLEASTS hexadecimal printf format for uint_least8_t Generated on Sat Nov 19 23 00 48 2005 for avr lib
186. ion directory by using the prefix dir option with the configure script It is important to install all the AVR tools in the same directory or some of the tools will not work correctly To ensure consistency and simplify the discussion we will use SPREF IX to refer to whatever directory you wish to install in You can set this as an environment variable if you wish as such using a Bourne like shell PREFIX HOME local avr 5 export PREFIX Note Be sure that you have your PATH environment variable set to search the direc tory you install everything in before you start installing anything For example if you use prefix PREFIX you must have PREFIX bin in your exported PATH As such PATH PATH PREFIX bin 5 export PATH Warning If you have CC set to anything other than avr gcc in your environment this will cause the configure script to fail It is best to not have CC set at all Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 8 Installing the GNU Tool Chain 216 Note It is usually the best to use the latest released version of each of the tools 7 8 Required Tools GNU Binutils http sources redhat com binutils Installation httpiJ oce onth ora Installation AVR Libc http savannah gnu org projects avr libc Installation 7 8 2 Optional Tools You can develop programs for AVR devices without the following tools They may or may not be of use for you
187. ion string dest 5 5 4 13 size_t strnlen_P P src size_t len Determine the length of a fixed size string The strnlen_P function is similar to strnlen except that src is a pointer to a string in program space Returns The strnlen_P function returns strlen_P src if that is less than len or len if there is no 0 character among the first 1 characters pointed to by src 5 6 Additional notes from lt avr sfr_defs h gt The lt avr sfr_defs h gt file is included by all of the lt avr ioXxxXx h gt files which use macros defined here to make the special function register definitions look like C variables or simple constants depending on the SFR ASM COMPAT define Some examples from avr iom128 h to show how to define such macros define PORTA SFR 108 0 1 define TCNT1 SFR 1016 0 2 define PORTF SFR 8 0x61 define TCNT3 _SFR_MEM16 0x88 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 6 Additional notes from lt avr sfr_defs h gt 27 If SFR ASM COMPAT is not defined C programs can use names like PORTA directly in C expressions also on the left side of assignment operators and GCC will do the right thing use short I O instructions if possible The SFR OFFSET definition is not used in any way in this case Define SFR 5 COMPAT as 1 to make these names work as simple constants ad dresses of the I O registers This is necessary when included
188. is ready for a new read write operation 0 if not 5 3 3 Function Documentation 5 3 31 void eeprom read block void pointer ram const void pointer_ eeprom size_t n Read a block of n bytes from EEPROM address pointer eepromto pointer ram For constant n lt 256 bytes a library function is used For block sizes unknown at compile time or block sizes gt 256 an inline loop is expanded 5 3 3 2 uint8 t eeprom read byte const uint8_t x addr Read one byte from EEPROM address addr 5 3 3 3 uint16 t eeprom read word const uint16_t addr Read one 16 bit word little endian from EEPROM address addr 5 3 3 4 void eeprom write block const void pointer ram void pointer eeprom size t n Write a block of n bytes to EEPROM address pointer eepromfrom pointer ram 5 3 3 5 void eeprom write byte uint8 t addr uint8 t value Write a byte value to EEPROM address addr 5 3 3 6 void eeprom write word uint16 t x addr uint16_t value Write a word value to EEPROM address addr 5 4 lt avr io h gt AVR device specific IO definitions include lt avr io h gt This header file includes the apropriate IO definitions for the device that has been spec ified by the mmcu compiler command line switch This is done by diverting to the appropriate file lt avr ioXXXX h gt which should never be included directly Some Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 5 lt avr pgmspace h gt Program
189. ister and is called strcpy P buf p 82 69 al lada r22 Y433 0x21 84 7a al 14 r23 Y 34 0x22 86 ce 01 movw r24 r28 88 01 96 adiw r24 0x01 I 8a Oc reall 24 Oxa4 This will finally copy the ROM string into the local buffer buf Variable p located at Y 33 is read and passed together with the address of buf Y 1 to strepy_P This will copy the string from ROM to buf Note that when using a compile time constant index omitting the first step reading the pointer from ROM via P usually remains unnoticed since the compiler would then optimize the code for accessing array at compile time Back to FAQ Index Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 184 7 3 16 How to use external RAM Well there is no universal answer to this question it depends on what the external RAM is going to be used for Basically the bit SRE SRAM enable in the MCUCR register needs to be set in order to enable the external memory interface Depending on the device to be used and the application details further registers affecting the external memory operation like XMCRA and XMCRB and or further bits in MCUCR might be configured Refer to the datasheet for details If the external RAM is going to be used to store the variables from the C program 1 the data and or bss segment that memory area it is essential to set up the
190. l best opti mization level Only applications that need to get the last few percent of speed benefit from using 03 Back to FAQ Index 7 3 18 How do I relocate code to a fixed address First the code should be put into a new named section This is done with a section attribute attribute section bootloader In this example bootloader is the name of the new section This attribute needs to be placed after the prototype of any function to force the function into the new section void boot void attribute section bootloader To relocate the section to a fixed address the linker flag section start is used This option can be passed to the linker using the W1 compiler option Wl section start bootloader 0x1E000 The name after section start is the name of the section to be relocated The number after the section name is the beginning address of the named section Back to FAQ Index Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 186 7 3 19 My UART is generating nonsense My ATmega128 keeps crashing Port F is completely broken Well certain odd problems arise out of the situation that the AVR devices as shipped by Atmel often come with a default fuse bit configuration that doesn t match the user s expectations Here is a list of things to care for All devices that have an internal RC oscillator ship with the fuse enabled that causes
191. l63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny2313 TIMERI SIG Timer Counter1 AT90CAN128 AT90CAN32 AT90CANGA COMPC_vect OUTPUT_ Compare Match ATmegal28 ATmega64 ATmega640 AT COMPAREIC C mega1280 ATmegal281 TIMER 1 SIG_ Timer Counter1 AT90S2333 AT90S4433 ATtiny15 COMP_vect OUTPUT_ Compare Match COMPAREIA TIMERI SIG Timer Counter1 AT908S2313 ATtiny26 OVFI vect OVERFLOWI Overflow Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 127 Vector name Old vector Description Applicable for device name TIMER 1_ SIG_ Timer Counter1 AT90S2333 AT90S4414 479054433 OVF_vect OVERFLOW1 Overflow AT90S4434 479058515 419058535 AT90PWM3 AT90PWM2 AT90CANI28 AT90CAN32 AT90CAN64 ATmegal03 ATmegal28 ATmegal6 ATmegal6l ATmegal62 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 ATmega8 ATmega8515 ATmega8535 ATmegal68 ATmega48 ATmega88 AT mega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny15 ATtiny2313 TIMER2_
192. le projeti lt es a a ee TR RS 136 2481 TheBrojec 26k om on RR B b 9 ob ea 136 5 28 2 Ibe Source Code s 5 654 c eR RR REG x 137 5 25 3 Compiling and LinkoE uo 6 4 6k wee RR RD 140 226 4 Examining the Object Pile 24 4 sss 6 bees a evades 140 5 28 3 Linker Map Files s oe cuo ee eB a 144 5 28 6 Intel Hex Files sca cmo m o 145 5 26 7 Make Build the Project se 6622502 64 146 5 29 Example using the two wire interface TWI 148 5 29 1 Introduction mio TWI 2 148 2349 The TWlexample project 22222 22 22 25 148 zo bil gt Code e 149 6 avr ibc Data Structure Documentation 161 6l div tStruct Reference sso ce ce oot ee Re GO ee 161 611 Detailed Description lt s e m eos v ER eS 161 61 22 Field Documentation 2 5 0 bee o o m REA 162 56 2 ldiv t Struct Reference uos o ooo oo og oko upa 162 21 Detailed Descriphon 2 22 2222 RYE Sox omms 162 622 Field Documentation s sa e458 544524 25 eee 162 7 avr libc Page Documentation 163 TIL Acknowledgments poo ven sone er 0 163 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen CONTENTS 72 Ta avr libc and assembler programs 164 T4 o mere 164 422 Invokmethe compiler se s 2 ne ee x mew RR 164 22 222222 222222 0 4 gt 165 7 2 4 Pseudo ops and operators 168 Frequently Asked Questions 2
193. le would then look like define loop_until_bit_is_clear port bit __asm__ __volatile_ 1 sbic 0 1 n t N rjmp 1 no outputs x N I SFR IO ADDR port I bit X 7 4 6 CStub Functions Macro definitions will include the same assembler code whenever they are referenced This may not be acceptable for larger routines In this case you may define a C stub function containing nothing other than your assembler code void delay uint8 t ms uintl6 t cnt asm volatile An L_dli n t mov A0 A2 n t mov B0 B2 Xn IL 412 n t sbiw 0 1 n t brne L 12 n t dec 1 n t brne L 11 n t amp w cnt r ms r delay count Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 201 The purpose of this function is to delay the program execution by a specified number of milliseconds using a counting loop The global 16 bit variable delay_count must contain the CPU clock frequency in Hertz divided by 4000 and must have been set before calling this routine for the first time As described in the clobber section the routine uses a local variable to hold a temporary value Another use for a local variable is a return value The following function returns a 16 bit value read from two successive port addresses uint16_t inw uint8 t port uintl6 t result asm volatile in 200 41 Manje in BO 1
194. levant 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 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 6 Release Numbering and Methodology 208 7 6 2 1 Creating a cvs branch following steps should be taken to cut a branch in Cvs 1 Check out a fresh source tree from cvs HEAD 2 Update the NEWS file with pending release number and commit to cvs HEAD Change Changes since avr libc lt last_release gt to Changes in avr libc this relelase 3 Set the branch point tag setting lt major gt and lt minor gt accordingly cvs tag avr libe major minor branchpoint 4 Create the branch cvs tag b avr libe major minor branch 5 Update the package version in configure ac and commit configure ac to cvs HEAD Change minor number to next odd value 6 Update the NEWS file and commit to cvs HEAD Add Changes since avr libc this release 7 Check out a new tree for the branch CO r avr libe major minor branch 8 Update the package version in configure ac and commit configure ac to cvs branch Change the patch number to 90 to denote that this now a branch leading up to a release
195. ll Xr Xo X X x or Note If you are planning on using avr gdb you will probably want to install either simulavr or avarice since avr gdb needs one of these to run as a a remote target backend 7 8 9 Simulavr Simulavr also uses the configure system so to build and install gunzip c simulavr version tar gz tar xf cd simulavr version mkdir obj avr cd obj avr configure prefix PREFIX make make install X X X X d WH Note You might want to have already installed avr binutils avr gcc and avr libc if you want to have the test programs built in the simulavr source 7 8 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 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 9 Using the avrdude program 221 AVaRice also uses the configure system so to build and install 5 gunzip c avarice lt version gt tar gz tar xf avarice lt version gt 5 mkdir obj avr 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 t
196. ll require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 5 19 lt stdlib h gt General utilities 95 Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 9 will be the letter a If radix is 10 and val is negative a minus sign will be prepended The ltoa function returns the pointer passed as s 5 19 4 17 void malloc size_t __ size The malloc function allocates size bytes of memory If malloc fails a NULL pointer is returned Note that malloc does not initialize the returned memory to zero bytes See the chapter about malloc usage for implementation details 5 19 4 18 void qsort void size_t __nmemb size_t __size compar fnt compar The qsort function is a modified partition exchange sort or quicksort The qsort function sorts an array of nmemb objects the initial member of which is pointed to by base The size of each object is specified by size The contents of the array base are sorted in ascending order according to a comparison function pointed to by compar which requires two arguments pointing to the objects being compared The comparison function must return an integer less than equal to or greater than zero if the first argument is considered to be re
197. loc 5 18 2 12 define FILE struct file FILE is the opaque structure that is passed around between the various standard IO functions 5 18 2 13 getc __stream fgetc __stream The macro getc used to be a fast macro implementation with a functionality iden tical to fgetc For space constraints in avr libc it is just an alias for fgetc Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 77 5 18 2 14 define getchar void fgetc stdin The macro get char reads a character from stdin Return values and error handling is identical to fgetc 5 18 2 15 putc c stream stream The macro put c used to be a fast macro implementation with a functionality iden tical to fputc For space constraints in avr libc it is just an alias for fputc 5 18 2 16 define putchar c fputc stdout The macro put char sends character c to stdout 5 18 2 17 define stderr iob 2 Stream destined for error output Unless specifically assigned identical to stdout If stderr should point to another stream the result of another fdevopen must be explicitly assigned to it without closing the previous st derr since this would also close stdout 5 18 2 18 define stdin iob 0 Stream that will be used as an input stream by the simplified functions that don t take astream argument The first stream opened with read inten
198. lution is simple writing a logical to it requires only a single OUT instruction and it is clear that only this single interrupt request bit will be cleared There is no need to perform a read modify write cycle like an SBI instruction since all bits in these Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 190 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 7 3 26 Why have programmed fuses the bit value 0 Basically fuses are just a bit in a special EEPROM area For technical reasons erased E E PROM cells have all bits set to the value 1 so unprogrammed fuses also have a logical 1 Conversely programmed fuse cells read out as bit value 0 Back to FAQ Index 7 3 27 Which AVR specific assembler operators are available See Pseudo ops and operators Back to FAQ Index 7 4 Inline Asm AVR GCC Inline Assembler Cookbook About this Document The GNU C compiler for Atmel AVR RISC processors offers to embed assembly language code into C programs This cool feature may be used for manually optimizing time critical parts of the software or to use specific processor instruction which
199. m characters 5 12 2 15 int tolower int Converts the letter c to lower case if possible 5 12 2 16 int toupper int Converts the letter c to upper case if possible 5 13 lt errno h gt System Errors 5 13 1 Detailed Description include lt errno h gt Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 40 Some functions in the library set the global variable errno when an error occurs The file lt errno h gt provides symbolic names for various error codes Warning The errno global variable is not safe to use in a threaded or multi task system A race condition can occur if a task is interrupted between the call which sets error and when the task examines errno If another task changes errno during this time the result will be incorrect for the interrupted task Defines define EDOM 33 define ERANGE 34 5 13 2 Define Documentation 5 13 21 ftdefine EDOM 33 Domain error 5 13 2 2 define ERANGE 34 Range error 5 14 lt inttypes h gt Integer Type conversions 5 14 1 Detailed Description include lt inttypes h gt This header file includes the exact width integer definitions from lt stdint h gt and extends them with additional facilities provided by the implementation Currently the extensions include two additional integer types that could hold a far pointer i e a code pointer that can address more t
200. mber of characters to be printed from a string for s conversions An optional 1 length modifier that specifies that the argument for the d i o u X or X conversion isa long int rather than int A character that specifies the type of conversion to be applied The conversion specifiers and their meanings are diouxX The int or appropriate variant argument is converted to signed decimal d and i unsigned octal unsigned decimal u or unsigned hexadecimal x and X notation The letters abcdef are used for x conversions the letters ABCDEF are used for X conversions The precision if any gives the minimum number of digits that must appear if the converted value requires fewer digits it is padded on the left with zeros e p The void xargumentis taken as an unsigned integer and converted similarly as a x command would do c The int argument is converted to an unsigned char and the resulting character is written s The char x argument is expected to be a pointer to an array of character type pointer to a string Characters from the array are written up to but not including a terminating NUL character if a precision is specified no more than 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 Generated on Sat Nov 19 23 00 48 2005
201. mbining a skip instruction together with a relative jump r jmp instruction which will need one additional word of ROM Another side effect of optimzation is that variable usage is restricted to the area of code where it is actually used So if a variable was placed in a register at the beginning of Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 177 some function this same register can be re used later on if the compiler notices that the first variable is no longer used inside that function even though the variable is still in lexical scope When trying to examine the variable in avr gdb the displayed result will then look garbled So in order to avoid these side effects optimization can be turned off while debugging However some of these optimizations might also have the side effect of uncovering bugs that would otherwise not be obvious so it must be noted that turning off opti mization can easily change the bug pattern In most cases you are better off leaving optimizations enabled while debugging Back to FAQ Index 7 3 12 How do trace an assembler file in avr gdb When using the g compiler option avr gcc only generates line number and other debug information for C and C files that pass the compiler Functions that don t have line number information will be completely skipped by a single st ep command in gdb This includes functions linked from a standard library b
202. mcpy 102 memmove 102 memset 102 strcasecmp 102 strcat 103 strchr 103 stremp 103 strepy 103 strlcat 104 strlcpy 104 strlen 104 strlwr 104 strncasecmp 105 strncat 105 strncmp 105 strncpy 105 strnlen 106 strrchr 106 strrev 106 strsep 106 strstr 107 strtok 107 strupr 107 avr version AVR LIBC DATE 29 AVR LIBC DATE STRING 29 AVR LIBC MAJOR 30 AVR LIBC MINOR 30 AVR LIBC REVISION 30 AVR LIBC VERSION STRING 30 AVR LIBC VERSION avr watchdog wdt disable 31 wdt enable 32 wdt reset 32 WDTO 120MS 32 WDTO 15MS 32 WDTO 15 32 WDTO 250MS 33 WDTO 285 33 WDTO 30MS 33 WDTO 45 33 WDTO 500MS 33 WDTO 60MS 33 30 gt WDTO_8S 33 avrdude usage 220 avrprog usage 220 bit_is_clear avr_sfr 133 bit_is_set avr_sfr 133 boot_is_spm_interrupt avr_boot 10 boot_lock_bits_set avr_boot 10 boot_lock_bits_set_safe avr_boot 10 boot_lock_fuse_bits_get avr_boot 10 boot_page_erase avr_boot 11 boot_page_erase_safe avr_boot 11 boot_page_fill avr_boot 11 boot_page_fill_safe avr_boot 12 boot_page_write avr_boot 12 boot_page_write_safe avr_boot 12 boot_rww_busy avr_boot 12 boot_rww_enable avr_boot 13 boot_rww_enable_safe avr_boot 13 boot_spm_busy avr_boot 13 boot_spm_busy_wait avr_boot 13 boot_spm_interrupt_disable avr_boot 13 boot_spm_interrupt_enable avr_boot 13 BOOTLOADER_SECTION avr_boot 13 b
203. mory first the freelist is walked to see if it could satisfy the request If there s a chunk available on the freelist that will fit the request exactly it will be taken disconnected from the freelist and returned to the caller If no exact match could be found the closest match that would just satisfy the request will be used The chunk will normally be split up into one to be returned to the caller and another smaller one that will remain on the freelist In case this chunk was only up to two bytes larger than the request the request will simply be altered internally to also account for these additional bytes since no separate freelist entry could be split off in that case If nothing could be found on the freelist heap extension is attempted This is where malloc margin will be considered if the heap is operating below the stack or where malloc heap end will be verified otherwise If the remaining memory is insufficient to satisfy the request NULL will eventually be returned to the caller When calling free a new freelist entry will be prepared An attempt is then made to aggregate the new entry with possible adjacent entries yielding a single larger entry available for further allocations That way the potential for heap fragmentation is hopefully reduced A call to realloc first determines whether the operation is about to grow or shrink the current allocation When shrinking the case is easy the existing chunk is split
204. mplies 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 7 6 1 2 Development Versions major version number of a development series is always the same as the last stable release The minor version number of a development series is always an odd number and is 1 more than the last stable release The patch version number of a development series is always 0 until a new branch is cut at which point the patch number is changed to 90 to denote the branch is approaching a release and the date appended to the version to denote that it is still in development All versions in development in cvs will also always have the date appended as a fourth version number The format of the date will be YY YYMMDD So the development version number will look like this 1 1 0 20030825 While a pre release version number on a branch destined to become either 1 2 or 2 0 will look like this 1 1 90 20030828 7 6 2 Releasing AVR Libc The information in this section is only re
205. mpts to turn off the Enable bit in the watchdog control register See the datasheet for details 5 9 2 2 define wdt_enable timeout _wdt_write timeout Enable the watchdog timer configuring it for expiry after t imeout which is a com bination of the WDPO through WDP2 bits to write into the WDTCR register For those devices that have a WDTCSR register it uses the combination of the WDPO through WDP3 bits See also the symbolic constants WOTO_15MS et al 5 9 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 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 9 lt avr wdt h gt Watchdog timer handling 33 5 9 2 4 define WDTO 120MS 3 See WDTO 15MS 5 9 2 5 define WDTO 15MS 0 Symbolic constants for the watchdog timeout Since the watchdog timer is based on a free running RC oscillator the times are approximate only and apply to a supply voltage of 5 V At lower supply voltages the times will increase For older devices the times will be as large as three times when operating at Vcc 3 V while the newer devices e g ATmegal28 ATmega8 only experience a negligible change Possible timeout values are 15 ms 30 ms 60 ms 120 ms 250 ms 500 ms 1 s 2 s Some devices also allow for 4 s and 8 s Symbolic constants are formed
206. n 5 20 lt string h gt Strings 102 Returns The memccpy function returns a pointer to the next character in dest after val or NULL if val was not found in the first len characters of src 5 20 3 5 void memchr const void src int val size t len Scan memory for a character The memchr function scans the first len bytes of the memory area pointed to by src for the character val The first byte to match val interpreted as an unsigned character stops the operation Returns The memchr function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area 5 20 3 6 int memcmp const void 57 const void 52 size t len Compare memory areas The memcmp function compares the first len bytes of the memory areas sl and 52 The comparision is performed using unsigned char operations Returns memcmp function returns an integer less than equal to or greater than zero if the first len bytes of 51 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 5 20 3 7 void memcpy void dest const void src size t len Copy a memory are
207. n add the volatile attribute to the asm statement asm volatile in 0 1 r value I SFR IO ADDR PORTD The last part of the asm instruction the clobber list is mainly used to tell the compiler about modifications done by the assembler code This part may be omitted all other parts are required but may be left empty If your assembler routine won t use any input or output operand two colons must still follow the assembler code string A good example is a simple statement to disable interrupts asm volatile cli Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 193 7 4 2 Assembler Code You can use the same assembler instruction mnemonics as you d use with any other AVR assembler And you can write as many assembler statements into one code string as you like and your flash memory is able to hold Note The available assembler directives vary from one assembler to another To make it more readable you should put each statement on a seperate line asm volatile nop n t nop n t nop n t nop n t linefeed and tab characters will make the assembler listing generated by the com piler more readable It may look a bit odd for the first time but that s the way the compiler creates it s own assembler code You may also make use of some special registers Symbol Register SREG Status register at address Ox3F SP H St
208. n error Error constant value required PORTB is a precompiler definition included in the processor specific file included in avr io h As you may know the precompiler will not touch strings and PORTB instead of 0x18 gets passed to the assembler One way to avoid this problem is asm volatile sbi 0 0x07 I _SFR_IO_ADDR PORTB Note For C programs rather use the standard C bit operators instead so the above would be expressed as PORTB 1 7 The optimizer will take care to trans form this into a single SBI instruction assuming the operands allow for this Back to FAQ Index 7 311 Why does the PC randomly jump around when single stepping through my program in avr gdb When compiling a program with both optimization and debug information 9 which is fortunately possible in avr gcc the code watched in the debugger is opti mized code While it is not guaranteed very often this code runs with the exact same optimizations as it would run without the g switch This can have unwanted side effects Since the compiler is free to reorder code ex ecution as long as the semantics do not change code is often rearranged in order to make it possible to use a single branch instruction for conditional operations Branch instructions can only cover a short range for the target PC 63 through 64 words from the current PC If a branch instruction cannot be used directly the compiler needs to work around it by co
209. n string of a strcpy is not large enough that is if the programmer was stupid lazy and failed to check the size before copying then anything might happen Overflowing fixed length strings is a favourite cracker technique 5 20 3 15 size t strlcat char dst const char src size t siz Concatenate two strings Appends src to string dst of size siz unlike strncat siz is the full size of dst not space left At most siz 1 characters will be copied Always NULL terminates unless siz lt strlen dst Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 20 lt string h gt Strings 105 Returns The strlcat function returns strlen src MIN siz strlen initial dst If retval gt siz truncation occurred 5 20 3 16 size t strlcpy char dst const char src size_t siz Copy a string Copy src to string dst of size siz At most siz 1 characters will be copied Always NULL terminates unless siz 0 Returns The strlcpy function returns strlen src If retval gt siz truncation occurred 5 20 3 17 size_t strlen const char x src Calculate the length of a string The strlen function calculates the length of the string src not including the terminat ing 70 character Returns The strlen function returns the number of characters in src 5 20 3 18 char x strlwr char string Convert a string to lower case The strlwr function will convert a string to lower case Only
210. named div t that contains two int members named quot and rem 5 19 4 9 dtostre double val char s unsigned char prec unsigned char flags The dtostre function converts the double value passed in val into an ASCII repre sentation that will be stored under s The caller is responsible for providing sufficient storage in s Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h gt General utilities 93 Conversion is done in the format d ddde177dd where there is one digit be fore the decimal point character and the number of digits after it is equal to the preci sion 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 function returns the pointer to the converted string s 5 19 4 10 char dtostrf double __val char __width char __prec char __s The dtostrf function converts the double value passed in val into an ASCII repre sentationthat will be stored under s The caller is responsible for providing
211. nction converts the string in npt r to an unsigned long value The con version is done according to the given base which must be between 2 and 36 inclusive or be the special value 0 The string may begin with an arbitrary amount of white space as determined by iss pace followed by a single optional or sign If base is zero or 16 the string may then include a 0x prefix and the number will be read in base 16 otherwise a zero base is taken as 10 decimal unless the next character is 0 in which case it is taken as 8 octal The remainder of the string is converted to an unsigned long value in the obvious manner stopping at the first character which is not a valid digit in the given base In bases above 10 the letter A in either upper or lower case represents 10 B represents 11 and so forth with 2 representing 35 If endptr is not NULL strtoul stores the address of the first invalid character in xendptr If there were digits at all however strtoul stores the original value of nptr in endptr Thus if xnptr is not NO but xxendptr is 0 on return the entire string was valid The strtoul function return either the result of the conversion or if there was a lead ing minus sign the negation of the result of the conversion unless the original non negated value would overflow in the latter case strtoul returns ULONG MAX and errno is set to ERANGE If no conve
212. ndom with the same seed value If no seed value is provided the functions are automatically seeded with a value of 1 5 19 4 22 long random_r unsigned long ctx Variant of random that stores the context in the user supplied variable located at ct x instead of a static library variable so the function becomes re entrant 5 19 4 23 void realloc void __ptr size_t size The realloc function tries to change the size of the region allocated at pt r to the new size value It returns a pointer to the new region The returned pointer might be the same as the old pointer or a pointer to a completely different region The contents of the returned region up to either the old or the new size value whatever is less will be identical to the contents of the old region even in case a new region had to be allocated It is acceptable to pass ptr as NULL in which case realloc will behave identical to malloc If the new memory cannot be allocated realloc returns NULL and the region at pt r will not be changed 5 19 4 24 void srand unsigned int __seed Pseudo random number generator seeding see rand 5 19 4 25 void srandom unsigned long __seed Pseudo random number generator seeding see random 5 19 4 26 double strtod const char x __nptr char xx __endptr The strtod function converts the initial portion of the string pointed to by nptr to double representation Generated on Sat Nov 19 23 00 48 200
213. neral utilities 91 5 19 2 5 define RANDOM MAX 0x7FFFFFFF Highest number that can be generated by random 5 19 3 Typedef Documentation 5 19 3 1 typedef int __compar_fn_t const void const void Comparision function type for qsort just for convenience 5 19 4 Function Documentation 5 1941 inline void abort void The abort function causes abnormal program termination to occur In the limited AVR environment execution is effectively halted by entering an infinite loop 5 19 4 2 int abs int 1 The abs function computes the absolute value of the integer i Note The abs and labs functions are builtins of gcc 5 19 4 3 double atof const char __nptr The atof function converts the initial portion of the string pointed to by nptr to double representation It is equivalent to calling strtod nptr char xx NULL 5 19 4 4 int atoi const char string Convert a string to an integer The atoi function converts the initial portion of the string pointed to by nptr to integer representation It is equivalent to int strtol nptr char NULL 10 except that atoi does not detect errors Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h gt General utilities 92 5 19 4 5 long int atol const char string Convert a string to a long integer The atol function converts the initial portion of the string pointed to by st ringp to integ
214. nerated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 75 5 18 2 Define Documentation 5 18 21 define FDEV EOF 2 Return code for an end of file condition during device read To be used in the get function of fdevopen 5 18 2 2 define FDEV ERR 1 Return code for an error condition during device read To be used in the get function of fdevopen 5 18 2 3 define FDEV SETUP READ _ SRD fdev_setup_stream with read intent 5 18 2 4 define FDEV SETUP RW SRD SWR fdev setup stream with read write intent 5 18 2 5 ftdefine FDEV SETUP WRITE SWR setup stream with write intent 5 18 2 6 define EOF 1 EOF declares the value that is returned by various standard IO functions in case of an error Since the AVR platform currently doesn t contain an abstraction for actual files its origin as end of file is somewhat meaningless here 5 18 2 7 define fdev close This macro frees up any library resources that might be associated with stream It should be called if st ream is no longer needed right before the application is going to destroy the st ream object itself Currently this macro evaluates to nothing but this might change in future versions of the library 5 18 2 8 get udata stream stream udata This macro retrieves a pointer to user defined data from a FILE stream object Generated on Sa
215. nf SCNul6 avr stdio 81 avr inttypes 50 scanf P SCNu32 avr_stdio 81 avr_inttypes 50 SCNd16 SCNuFAST16 avr_inttypes 48 avr_inttypes 50 SCNd32 SCNuFAST32 avr_inttypes 48 avr_inttypes 50 SCNdFAST16 SCNuLEASTI16 avr inttypes 48 avr inttypes 51 SCNdFAST32 SCNuLEAST32 avr inttypes 49 avr inttypes 51 SCNdLEAST16 SCNuPTR avr_inttypes 49 avr_inttypes 51 SCNdLEAST32 SCNx16 avr_inttypes 49 avr_inttypes 51 SCNdPTR SCNx32 avr_inttypes 49 avr_inttypes 51 SCNi16 SCNxFAST 16 avr_inttypes 49 avr_inttypes 51 SCNi32 SCNxFAST32 avr inttypes 49 avr inttypes 51 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 248 SCNxLEAST16 avr_math 56 avr_inttypes 51 square SCNxLEAST32 avr_math 56 avr_inttypes 51 srand SCNxPTR avr_stdlib 96 avr_inttypes 51 srandom set_sleep_mode avr_stdlib 96 avr_sleep 29 sscanf setjmp avr_stdio 81 longjmp 57 sscanf_P setjmp 58 avr_stdio 81 SIG_ATOMIC_MAX stderr avr_stdint 65 avr_stdio 77 SIG_ATOMIC_MIN stdin avr_stdint 65 avr_stdio 77 SIGNAL stdout avr_interrupts 131 avr_stdio 77 sin strcasecmp avr_math 55 avr_string 102 sinh strcasecmp_P avr_math 55 avr_pgmspace 23 SIZE_MAX strcat avr_stdint 65 avr_string 103 sleep_mode strcat_P avr_sleep 29 avr_pgmspace 23 SLEEP_MODE_ADC strchr avr_sleep 28 avr_string 103 SLEEP_MODE_EXT_STANDBY strcmp avr_sleep 28 avr_string 103 SLEEP MODE IDLE strcmp P avr sleep 28 avr pgmspac
216. nking step by adding a flag 1m at the end That is the initial lib and the filename suffix from the library are written immediately after a flag So for a libfoo a library 1foo needs to be provided This will make the linker search the library in a path known to the system An alternative would be to specify the full path to the 1ibm a file at the same place on the command line i e after all the object files However since this re quires knowledge of where the build system will exactly find those library files this is deprecated for system libraries Back to FAQ Index 7 3 4 How to permanently bind a variable to a register This can be done with Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 172 register unsigned char counter asm r3 Typically it should be possible to use r2 through r15 that way See C Names Used in Assembler Code for more details Back to FAQ Index 7 3 5 How to modify MCUCR or WDTCR early The method of early initialization MCUCR WDTCR or anything else is different and more flexible in the current version Basically write a small assembler file which looks like this begin xram S include lt avr io h gt section 1 ax progbits idi r16 BV SRE _BV SRW out _SFR_IO_ADDR MCUCR r16 end xram S Assemble it link the resulting xram o with other files in your program and this piece of code will be
217. nnection between registers and C operands is specified in the second and third part of the asm instruction the list of input and output operands respectively The general form is asm code output operand list input operand list clobber list In the code section operands are referenced by a percent sign followed by a single digit 0 refers to the first 1 to the second operand and so forth From the above example Orefers to r value and 1 refers to I SFR IO ADDR PORTD This may still look a little odd now but the syntax of an operand list will be explained soon Let us first examine the part of a compiler listing which may have been generated from our example lds r24 value x in r24 12 NOAPP x sts value r24 The comments have been added by the compiler to inform the assembler that the in cluded code was not generated by the compilation of C statements but by inline as sembler statements The compiler selected register r24 for storage of the value read from PORTD The compiler could have selected any other register though It may not explicitely load or store the value and it may even decide not to include your assembler code at all All these decisions are part of the compiler s optimization strategy For example if you never use the variable value in the remaining part of the C program the compiler will most likely remove your code unless you switched off optimization To avoid this you ca
218. nt rather than int for integer type conversions or a pointer to double for floating point conversions In addition a maximal field width may be specified as a nonzero positive decimal integer which will restrict the conversion to at most this many characters from the input stream This field width is limited to at most 127 characters which is also the default value except for the c conversion that defaults to 1 The following conversion flags are supported Matches aliteral character This is not a conversion d Matches an optionally signed decimal integer the next pointer must be a pointer to int Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 86 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 signed floating point number the next pointer must be a pointer to float e g E G Equivalent to f s Matches a sequence of non white space c
219. ntisascii int c Checks whether c is a 7 bit unsigned char value that fits into the ASCII character set 5 12 2 4 int isblank int c Checks for a blank character that is a space or a tab 5 12 2 5 intiscntrl int c Checks for a control character 5 12 2 6 int isdigit int Checks for a digit 0 through 9 5 12 2 7 intisgraph int Checks for any printable character except space 5 12 2 8 int islower int Checks for a lower case character Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 13 lt errno h gt System Errors 39 5 12 2 9 int isprint int Checks for any printable character including space 5 12 2 10 int ispunct int Checks for any printable character which is not a space or an alphanumeric character 5 12 2 11 int isspace int 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 Cw 5 12 2 12 int isupper int Checks for an uppercase letter 5 12 2 13 int isxdigit int Checks for a hexadecimal digits ie one of 0123456789abcdefABCDEF 5 12 2 14 int toascii int Converts c to a 7 bit unsigned char value that fits into the ASCII character set by clearing the high order bits Warning Many people will be unhappy if you use this function This function will convert accented letters into rando
220. o SREG is Ox5f and if code size and speed are not important and you don t like the ugly if above you can always use lds sts to access them But this will not work if SFR OFFSET 0x20 so use a different macro defined only if SFR OFFSET 0x20 for safety sts _SFR_ADDR SPMCR r24 In programs all combinations of SFR 5 COMPAT and SFR OFFSET supported the SFR ADDR SPMCR macro be used to get the address of the SPMCR register 0x57 or 0x68 depending on device Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 7 lt avr sleep h gt Power Management and Sleep Modes 28 5 7 lt avr sleep h gt Power Management and Sleep Modes 5 7 Detailed Description include lt avr sleep h gt Use of the SLEEP instruction can allow your application to reduce it s 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 Sleep Modes Note Some of these modes are not available on all devices See the datasheet for target device for the available sleep modes define SLEEP_MODE_IDLE 0 define SLEEP_MODE_ADC _BV SMO define SLEEP_MODE_PWR_DOWN _BV SM1 define SLEEP_MODE_PWR_SAVE _BV SMO __BV SM1 define SLEEP MODE STANDBY BV SMI BV SM2 define SLEEP MODE EXT STANDBY BV SMO BV SMD BV SM2 Sleep Functions e void set
221. o 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 functions are provided the stream is opened with read and write intent The first stream opened with read intent is assigned to st din and the first one opened with write intent is assigned to both stdout and stderr fdevopen uses calloc und thus malloc in order to allocate the storage for the new stream Note If the macro __ STDIO FDEVOPEN COMPAT 12 is declared before including lt stdio h gt a function prototype for fdevopen will be chosen that is backwards compatible with avr libc version 1 2 and before This is solely intented for pro viding a simple migration path without the need to immediately change all source code Do not use for new co
222. o the bfd h file on your system Replace 1ib path gt with the path to 1ibbfd a on your system 5 CPPFLAGS I hdr path LDFLAGS L lib path configure prefix PREFIX 7 9 Using the avrdude program Note This section was contributed by Brian Dean bsd bsdhome com 1 The avrdude program was previously called avrprog The name was changed to avoid confusion with the avrprog program that Atmel ships with AvrStudio avrdude is a program that is used to update or read the flash and EEPROM memories of Atmel AVR microcontrollers on FreeBSD Unix It supports the Atmel serial pro gramming protocol using the PC s parallel port and can upload either a raw binary file or an Intel Hex format file It can also be used in an interactive mode to individually update EEPROM cells fuse bits and or lock bits if their access is supported by the Atmel serial programming protocol The main flash instruction memory of the AVR can also be programmed in interactive mode however this is not very useful because one can only turn bits off The only way to turn flash bits on is to erase the entire memory using avrdude s e option avrdude is part of the FreeBSD ports system To install it simply do the following 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 a
223. oduces an interrupt handler function that runs with global interrupts initially en abled This allows interrupt handlers to be interrupted As this macro has been used by too many unsuspecting people in the past it has been deprecated and will be removed in a future version of the library Users who want to legitimately re enable interrupts in their interrupt handlers as quickly as possible are encouraged to explicitly declare their handlers as described above 5 10 2 5 define outp port val port val Deprecated Write val to IO port port 5 10 2 6 define sbi port bit port 1 lt lt bit Deprecated Set bit inIO port port 5 10 3 Function Documentation 5 10 3 1 static inline void timer enable int unsigned char ints static Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 11 lt compat ina90 h gt Compatibility with EWB 3 x 37 Deprecated This function modifies the timsk register The value you pass via ints is device specific 5 11 lt compat ina90 h gt Compatibility with EWB 3 x include lt compat ina90 h gt This is an attempt to provide some compatibility with header files that come with IAR C to make porting applications between different compilers easier No 100 compat ibility though Note For actual documentation please see the manual 5 12 lt ctype h gt Character Operations 5 12 1 Detailed Description These functions perform various ope
224. of SRAM is what is available for stack If your application uses malloc which e g also can happen inside printf the heap for dynamic memory is also located there See Using malloc The amount of stack required for your application cannot be determined that easily For example if you recursively call a function and forget to break that recursion the amount of stack required is infinite You can look at the generated assembler code avr gcc 5 there s a comment in each generated assembler file 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 7 3 23 Is it really impossible to program the ATtinyXX in C While some small are not directly supported by the C compiler since they do not have a RAM based stack and some do not even have RAM at all itis possible anyway to use the general purpose registers as a RAM replacement since they are mapped into the data memory region Bruce D Lightner wrote an excellent description of how to do this and offers this together with a toolkit on his web page http lightner net avr ATtinyAvrGcc html Back to FAQ Index 7 3 24 What is this clock skew detected messsage It s a known problem of the MS DOS FAT file system Since the FAT file system has only a granularity of 2 seconds for maintaining a fil
225. of the names below in a call to ISR a function will be created that while possibly being usable as an interrupt function is not actually wired into the interrupt vector table The compiler will generate a warning if it detects a sus piciously looking name of a ISR function i e one that after macro replacement does not start with vector Vector name Old vector Description Applicable for device name vect SIG ADC ADC Conversion AT90S2333 9054433 419054434 Complete AT9088535 AT90PWMS3 AT90PWMO AT90CAN128 AT90CAN32 AT90CANGA ATmegal03 ATmegal28 ATmegal6 ATmegal63 ATmegal65 ATmegal69 ATmega32 ATmega323 ATmega325 ATmega3250 ATmega329 ATmega3290 ATmega64 ATmega645 ATmega6450 ATmega649 ATmega6490 8 ATmega8535 ATmegal68 ATmega48 ATmega88 ATmega640 ATmegal280 ATmegal281 ATmega324 ATmegal64 ATmega644 ATtiny13 ATtiny15 ATtiny26 ATtiny45 ANALOG_ SIG_ Analog Com AT90PWM3 AT90PWM2 COMP_0_vect COMPARATOR Q parator 0 ANALOG_ SIG_ Analog Com AT90PWM3 AT90PWM2 COMP_1_vect COMPARATORI parator 1 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 121 Vector name Old vector Description Applicable for device name ANALOG_ SIG_ Analog Com AT90PWM3 AT90PWM2 COMP_2_vect COMPARATORE parator 2 ANALOG_ SIG_ Analog Com AT90CANI
226. okation of the linker will be automatic and will include the appropri ate options to locate additional libraries as well as the application start up code crtXXX o and linker script Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 2 avr libc and assembler programs 165 Note that the invokation of the C preprocessor will be automatic when the filename provided for the assembler file ends in S the capital letter s This would even apply to operating systems that use case insensitive filesystems since the actual decision is made based on the case of the filename suffix given on the command line not based on the actual filename from the file system Alternatively the language explicitly be specified using the assembler with cpp option 7 2 3 Example program The following annotated example features a simple 100 kHz square wave generator using an AT90S1200 clocked with a 10 7 MHz crystal Pin PD6 will be used for the square wave output include 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 T3 rjmp 1b Note 6 global TIMERO_OVF_vect Note 7 TIMERO_OVF_vect 141 inttmp 256 tmconst fuzz out _SFR_IO_ADDR TCNTO inttmp Note 8 in intsav
227. om http savannah nongnu org projects avr libc The AVR Libc package provides a subset of the standard C library for Atmel AVR 8 bit RISC microcontrollers In addition the library provides the basic startup code needed by most applications There is a wealth of information in this document which goes beyond simply describ ing the interfaces and routines provided by the library We hope that this document provides enough information to get a new AVR developer up to speed quickly using the freely available development tools binutils gcc avr libc and many others If you find yourself stuck on a problem which this document doesn t quite address you Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 12 General information about this library 2 may wish to post a message to the avr gcc mailing list Most of the developers of the AVR binutils and gcc ports in addition to the devleopers of avr libc subscribe to the list so you will usually be able to get your problem resolved You can subscribe to the list at http 1ists nongnu org mailman listinfo avr gcc list Before posting to the list you might want to try reading the Frequently Asked Ques tions chapter of this document Note If you think you ve found a bug or have a suggestion for an improvement ei ther in this documentation or in the library itself please use the bug tracker at https savannah nongnu org bugs group avr libc to ensure the issue won t be forgo
228. on over a macro could save you some code space but still at a cost of execution speed Care should be taken when such an indirect port access is going to one of the 16 bit IO registers where the order of write access is critical like some timer registers All versions of avr gcc up to 3 3 will generate instructions that use the wrong access order in this situation since with normal memory operands where the order doesn t matter this sometimes yields shorter code Seehttp mail nongnu org archive html avr libc dev 2003 01 msg00044 html for a possible workaround avr gcc versions after 3 3 have been fixed in a way where this optimization will be disabled if the respective pointer variable is declared to be volatile so the correct behaviour for 16 bit IO ports can be forced that way Back to FAQ Index 7 3 14 What registers are used by the compiler Data types char is 8 bits int is 16 bits long is 32 bits Long long is 64 bits float and double are 32 bits this is the only supported floating point format pointers are 16 bits function pointers are word addresses to allow addressing the whole Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 181 128K program memory space on the ATmega devices with gt 64 KB of flash ROM There is a mint 8 option see Options for the C compiler avr gcc to make int 8 bits but that is not supported by avr libc and violates standar
229. onding call of setjmp had just returned the value __ret Note longjmp cannot cause 0 to be returned If longjmp is invoked with a second argument of 0 1 will be returned instead Parameters jmpb Information saved by a previous call to setjmp ret Value to return to the caller of setjmp Returns This function never returns 5 16 2 2 int setjmp jmp buf Save stack context for non local goto include lt setjmp h gt setjmp saves the stack context environment __jmpb for later use by longjmp The stack context will be invalidated if the function which called setjmp returns Parameters jmpb Variable of type jmp_buf which holds the stack information such that the environment can be restored Returns setjmp returns O if returning directly and non zero when returning from longjmp using the saved context 5 17 lt stdint h gt Standard Integer Types 5 17 1 Detailed Description include stdint h Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Integer Types 59 Use u intN t if you need exactly N bits Since these typedefs are mandated by the C99 standard they are preferred over rolling your own typedefs Limits of specified width integer types C implementations should define these macros only when STDC LIMIT MACROS is defined before lt stdint h gt is included define INT8 MAX Ox7f define
230. one parameter less by implying st din will also save some execution time Defines define FILE struct file define stdin __iob 0 define stdout __iob 1 define stderr __iob 2 define EOF 1 define fdev_set_udata stream u do stream udata u while 0 define fdev_get_udata stream stream udata define fdev_setup_stream stream put get rwflag define FDEV SETUP READ SRD define FDEV SETUP WRITE SWR define FDEV SETUP RW SRD SWR define FDEV ERR 1 define _FDEV_EOF 2 fdefine FDEV SETUP 5 get rwflag define fdev_close define putc __c __ stream fputc __c define putchar __c fputc __c stdout define getc __stream fgetc __stream define getchar fgetc stdin stream Pi Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 74 Functions int fclose FILE __stream int vfprintf FILE __stream const char fmt va_list __ap int vfprintf P FILE stream const char fmt va list ap intfputc int __c FILE stream int printf const char fmt int printf P const char fmt int vprintf const char fmt va list ap int sprintf char s constchar fmt int sprintf P char __s const char x__fmt int snprintf char __s size_t __n const char __fmt int snprintf_P char __s size_t __n const char x__fmt int vsprintf char __s
231. only Output operands must be write only and the C expression result must be an lvalue which means that the operands must be valid on the left side of assignments Note that the compiler will not check if the operands are of reasonable type for the kind of operation used in the assembler instructions Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 196 Input operands are you guessed it read only But what if you need the same operand for input and output As stated above read write operands are not supported in inline assembler code But there is another solution For input operators it is possible to use a single digit in the constraint string Using digit n tells the compiler to use the same register as for the n th operand starting with zero Here is an example asm volatile swap 0 r value 0 value This statement will swap the nibbles of an 8 bit variable named value Constraint 0 tells the compiler to use the same input register as for the 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
232. ostic message is written to stderr and the function abort is called effectively terminating the program If expression is true the assert macro does nothing The assert macro may be removed at compile time by defining NDEBUG as a macro e g by using the compiler option DNDEBUG 5 2 lt avr boot h gt Bootloader Support Utilities 5 2 1 Detailed Description include lt avr io h gt include lt avr boot h gt Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 22 lt avr boot h gt Bootloader Support Utilities 9 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 Note Not all AVR processors provide bootloader support See your processor datasheet to see if it provides bootloader support Todo From email with Marek On smaller devices all except ATmega64 128 5 REG is in the I O space accessible with the shorter in and out instructions since the boot loader has a limited size this could be an important optimization API Usage Example The following code shows typical usage of the boot API include lt inttypes h gt include lt avr interrupt h gt include lt avr pgmspace h gt void boot program page uint32 t page uint8 t buf intli6o t i uint8 t sreg Disable interrupts sreg SREG cli eeprom busy wait
233. p _BV TWINT 0 x wait for transmission x switch twst TW STATUS case TW_MR_DATA_NACK len 0 force end of loop FALLTHROUGH x case TW MR DATA xbuf rvtt break default goto error quit Note 14 _BV TWINT _BV TWSTO _BV TWEN send stop condition x return rv error rv 1 goto quit Write len bytes into EEPROM starting at eeaddr from buf This is a bit simpler than the previous function since both the address and the data bytes will be transfered in master transmitter mode thus no reselection of the device is necessary However the EEPROMs are only capable of writing one page simultaneously so care must be taken to not cross a page boundary within one write cycle The amount of data one page consists of varies from manufacturer to manufacturer some vendors only use 8 byte pages for the smaller devices and 16 byte pages for the larger devices while other vendors generally use 16 byte pages We thus use the smallest common denominator of 8 bytes per page declared by the X Xo Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 29 Example using the two wire interface TWI 155 macro PAGE_SIZE above The function simply returns after writing page returning the actual number of data byte written It is up to the caller to re invoke it in order to writ
234. pe declaration because the compiler will not accept the asm keyword in the function definition extern long Calc void asm CALCULATE Calling the function Calc will create assembler instructions to call the function CALCULATE 7 4 8 Links For a more thorough discussion of inline assembly usage see the gcc user manual The latest version of the gcc manual is always available here http gcc gnu org onlinedocs 7 5 Using malloc 7 5 1 Introduction On a simple device like a microcontroller implementing dynamic memory allocation is quite a challenge Many of the devices that are possible targets of avr libc have a minimal amount of RAM The smallest parts supported by the C environment come with 128 bytes of RAM This needs to be shared between initialized and uninitialized variables sections data and bss the dynamic memory allocator and the stack that is used for calling subroutines and storing local automatic variables Also unlike larger architectures there is no hardware supported memory management which could help in separating the mentioned RAM regions from being overwritten by each other The standard RAM layout is to place data variables first from the beginning of the internal RAM followed by bss The stack is started from the top of internal RAM growing downwards The so called heap available for the dynamic memory allocator will be placed beyond the end of bss Thus there s no risk that dynami
235. pilogue For complex functions that use many registers that needs to be saved restored on function entry exit this saves some space at the cost of a slightly increased execution time e minit stack nnnn Set the initial stack pointer to nnnn By default the stack pointer is initialized to the symbol __stack which is set to RAMEND by the run time initialization code e mtiny stack Change only the low 8 bits of the stack pointer e mno tablejump Do not generate tablejump instructions By default jump tables can be used to op timize switch statements When turned off sequences of compare statements are used instead Jump tables are usually faster to execute on average but in particular for switch statements where most of the jumps would go to the default label they might waste a bit of flash memory short calls Use rjmp rcall limited range on gt 8K devices avr2 and avr4 architec tures less than 8 KB or flash memory this is always the case On avr3 and avr5 architectures calls and jumps to targets outside the current function will by default use jmp call instructions that can cover the entire address range but that require more flash ROM and execution time nrtl Dump the internal compilation result called RTL into comments in the generated assembler code Used for debugging avr gcc e msize Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 22
236. printf format for fast8 t 5 14 2 27 PRIOLEASTI6 octal printf format for least16 t 5 14 2 28 ftdefine PRIOLEAST32 lo octal printf format for least32 t 5 14 2 29 define PRIOLEASTS o octal printf format for least8 t 5 14 2 30 PRIoPTR PRIo16 octal printf format for uintptr t 5 14 2 31 define PRIu16 u decimal printf format for uint16 t 5 14 2 32 define PRIu32 lu decimal printf format for uint32 t 5 14 2 33 define PRIu8 decimal printf format for uint8 t 5 14 2 34 define PRIuFASTI6 decimal printf format for uint_fast16_t 5 14 2 35 define PRIUFAST32 lu decimal printf format for fast32 t 5 14 2 36 define PRIuFASTS decimal printf format for uint_fast8_t Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 14 lt gt Integer Type conversions 47 5 14 2 37 PRIULEAST16 u decimal printf format for leastl16 t 5 14 2 38 ffdefine PRIULEAST32 lu decimal printf format for least32 t 5 14 2 39 define PRIULEASTS decimal printf format for uint_least8_t 5 14 2 40 define PRIuPTR PRIu16 decimal printf format for uintptr_t 5 14 2 41 PRIX16 X uppercase hexadecimal printf format for uint16_t 5 14 2 42 define PRIx16 hexadecimal printf format for uint16_t 5 14 2 43 define PRIX32 IX uppercase hexadecimal printf format for u
237. prom srec elf 5 j eeprom change section 1ma eeprom bin elf 5 j eeprom change section 1ma Every thing below here is used by the casual user FIG2DEV EXTRA CLEAN FILES dox eps png pdf eps PRG eps png PRG png fig2dev x bin x srec by avr libc s build system and ihex lt Q srec Q binary 56 can be ignored Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 529 Example using the two wire interface TWI 148 pdf pdf fig 5 FIG2DEV L eps lt 56 amp pdf fig FIG2DEV L pdf lt 560 fig FIG2DEV L png lt SG 5 29 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 5 29 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 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
238. py char dest const char src size_t len Copy a string The strncpy function is similar to strcpy except that not more than n bytes of src are copied Thus if there is no null byte among the first n bytes of src the result will not be null terminated In the case where the length of src is less than that of n the remainder of dest will be padded with nulls Returns The strncpy function returns a pointer to the destination string dest 5 20 3 23 size t strnlen const char x src size t len Determine the length of a fixed size string The strnlen function returns the number of characters in the string pointed to by src not including the terminating 70 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 15 less than len or len if there is no 0 character among the first len characters pointed to by src Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 20 lt string h gt Strings 107 5 20 3 24 char x strrchr const char x src int val Locate character in string The strrchr function returns a pointer to the last occurrence of the character val in the string src Here character means byte these functions do not work with wide or multi byte characters Returns The strrchr function returns a pointer to the matched character or NULL if the c
239. quest 0 CHANGE LCD vect SIG LCD LCD Stat of ATmegal69 ATmega329 ATmega3290 Frame ATmega649 ATmega6490 LOWLEVEL SIG PIN Low level Input ATtiny28 IO PINS vect on Port B OVRIT vect SIG CAN CAN Timer AT90CANI28 AT90CAN32 AT90CAN64 OVERFLOWI Overrun PCINTO vect SIG PIN Pin Change Inter ATmegal62 ATmegal65 ATmegal69 AT CHANGEO rupt Request 0 mega325 ATmega3250 ATmega329 AT mega3290 ATmega645 ATmega6450 AT mega649 ATmega6490 ATmegal68 AT mega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega324 AT megal64 ATmega644 ATtiny13 ATtiny45 PCINTI vect SIG PIN Pin Change Inter ATmegal62 ATmegal65 ATmegal69 AT CHANGEI rupt Request 1 mega325 ATmega3250 ATmega329 AT mega3290 ATmega645 ATmega6450 AT mega649 ATmega6490 ATmegal68 AT mega48 ATmega88 ATmega640 AT megal280 ATmegal281 ATmega324 AT megal64 ATmega644 PCINT2_vect SIG_PIN_ Pin Change Inter ATmega3250 ATmega3290 ATmega6450 CHANGE2 rupt Request 2 ATmega6490 ATmegal68 ATmega48 AT mega88 ATmega640 ATmegal280 AT megal281 ATmega324 ATmegal64 AT mega644 PCINT3_vect SIG_PIN_ Pin Change Inter ATmega3250 ATmega3290 ATmega6450 CHANGE3 rupt Request 3 ATmega6490 ATmega324 ATmegal64 ATmega644 PCINT_vect SIG_PIN_ ATtiny2313 CHANGE SIG_PCINT PSCO SIG PSCO PSCO Capture AT90PWM3 AT90PWM2 CAPT vect CAPTURE Event PSCO EC SIG PSCO 5 0 End Cycle AT90PWM3 AT90PWM2 vect END CYCLE PSCI SIG PSCI PSCI
240. r previous library versions could easily be maintained until its end of life Use of any of these items in new code is strongly discouraged Allowing specific system wide interrupts In addition to globally enabling interrupts each device s particular interrupt needs to be enabled separately if interrupts for this device are desired While some devices maintain their interrupt enable bit inside the device s register set external and timer interrupts have system wide configuration registers Example Enable timer 1 overflow interrupts timer enable int BV TOIE1 Do some work Disable all timer interrupts timer enable int 0 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 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 10 lt compat deprecated h gt Deprecated items 35 define enable_external_int mask __EICR mask define INTERRUPT signame e static inline void timer enable int unsigned char ints Obsolete IO macros Back in a time when AVR GCC and avr libc could not handle IO port access in the di rect assignment form as they are handled now all IO port access had to be done through specific macros that eventually resulted in inline assembly instructions performing the desired action These macros became obsolete as reading and writing IO ports can be done
241. ral utilities 89 Non standard i e non ISO functions define RANDOM_MAX Ox7FFFFFFF char itoa int __ val char __s int radix char Itoa long int __val char __s int radix char unsigned int __val char __s int radix char ultoa unsigned long int __ val char __s int __radix long random void void srandom unsigned long __ seed long random_r unsigned long ctx Conversion functions for double arguments Note that these functions are not located in the default library 1ibc a but in the mathematical library 1ibm a So when linking the application the 1m option needs to be specified define DTOSTR_ALWAYS_SIGN 0x01 define DTOSTR_PLUS_SIGN 0x02 define DTOSTR_UPPERCASE 0x04 e char dtostre double val char __s unsigned char __ prec unsigned char flags e char dtostrf double __ val char width char __prec char __s Defines define RAND_MAX 0x7FFF Typedefs e typedef int x __compar_fn_t const void const void Functions e inline void abort void _ ATTR_NORETURN_ e int abs int _i CONST e long labs long 1 ATTR CONST e void bsearch const void key const void base size_t __nmemb size_t size int __compar const void const void e div t div int _ num int _ denom divmodhi4 ATTR CONST Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h
242. ram space 5 5 3 Typedef Documentation 5 5 3 1 prog char Type of a char object located in flash ROM 5 5 3 2 prog intl6 t Type of an int16 t object located in flash ROM 5 5 3 3 prog int32 t Type of an int32 t object located in flash ROM 5 5 3 4 prog int64 t Type of an int64 t object located in flash ROM 5 5 3 5 prog int8 t Type of an int8 t object located in flash ROM 5 5 3 6 prog uchar Type of an unsigned char object located in flash ROM Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 5 lt avr pgmspace h gt Program Space String Utilities 23 5 5 3 7 prog uintl6 t Type of an uintl6 t object located in flash ROM 5 5 3 8 prog uint32 t Type of an uint32 t object located in flash ROM 5 5 3 9 prog uint64 t Type of an uint64 t object located in flash ROM 5 5 3 10 prog uint8 t Type of an uint8 t object located in flash ROM 5 5 3 11 prog void Type of a void object located in flash ROM Does not make much sense by itself but can be used to declare a void object in flash ROM 5 5 4 Function Documentation 5 5 4 1 void x memcpy_P void dest VOID P src size_t n The memcpy_P function is similar to memcpy except the src string resides in pro gram space Returns The memopy function returns a pointer to dest 5 5 4 2 int strcasecmp P const char 57 52 Compare two strings ignoring case The strcasecmp function compare
243. rations on characters include lt ctype h gt Character classification routines These functions perform character classification They return true or false status de pending whether the character passed to the function falls into the function s classifi cation i e isdigit returns true if its argument is any value 0 though 9 inclusive int isalnum int c ATTR_CONST int isalpha int c ATTR_CONST int isascii int c ATTR CONST int isblank int ATTR CONST intiscntrl int c ATTR CONST int isdigit int ATTR CONST int isgraph int ATTR CONST int islower int c ATTR CONST intisprint int ATTR CONST int ispunct int __c ATTR CONST int isspace int ATTR CONST int isupper int ATTR CONST int isxdigit int ATTR CONST Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 12 lt ctype h gt Character Operations 38 Character convertion routines If c is not an unsigned char value or EOF the behaviour of these functions is undefined e int toascii int c ATTR_CONST int tolower int c ATTR CONST e int toupper int c ATTR CONST 5 12 2 Function Documentation 5 12 2 1 intisalnum int c Checks for an alphanumeric character It is equivalent to isalpha c isdigit c 5 12 2 2 int isalpha int Checks for an alphabetic character It is equivalent to isupper c islower c 5 12 2 3 i
244. ription finclude lt util parity h gt This header file contains optimized assembler code to calculate the parity bit for a byte Defines define parity even bit val 5 23 2 Define Documentation 5 23 2 1 define parity even bit val Value extension N unsigned char t N asm N mov tmp reg 0 n t N swap 0 n t N eor 0 tmp reg n t N mov tmp reg 0 n t N Isr 0 n t lsr 0 n t N eor 0 tmp reg N 2 t 0 unsigned char val ro Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 524 lt util twi h gt TWI bit mask definitions 114 UL x 1 gt 1 13 Returns lif val has an odd number of bits set 5 24 lt util twi h gt TWI bit mask definitions 5 24 1 Detailed Description include lt util twi h gt This header file contains bit mask definitions for use with the AVR TWI interface TWSR values Mnemonics TW MT xxx master transmitter TW MR xxx master receiver TW ST xxx slave transmitter TW SR xxx slave receiver define TW START 0x08 define TW START 0x10 fdefine TW MT SLA 0x18 define TW MT SLA NACK 0x20 define TW MT DATA ACK 0x28 define TW MT DATA NACK 0x30 define TW MT ARB LOST 0x38 define TW LOST 0x38 define TW SLA 0x40 define TW SLA 0x48 define TW DATA ACK 0x50 define TW DATA 0x58 defin
245. roller an alternative option is provided to run completely without malloc The macro fdev_setup_stream is provided to prepare a user supplied FILE buffer for operation with stdio If floating point operation is desired a user supplied buffer can as well be passed for the internal buffering for the floating point numbers and processing of scanf data Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 72 Example include lt stdio h gt static int uart putchar char c FILE xstream static FILE mystdout FDEV SETUP STREAM uart putchar NULL FDEV SETUP WRITE static int uart putchar char c FILE xstream if c uart_putchar r loop_until_bit_is_set UCSRA UDRE UDR return 0 int main void init_uart stdout amp mystdout printf Hello world n return 0 This example uses the initializer form FDEV SETUP STREAMYO rather than the function like fdev_setup_stream so all data initialization happens during C start up If streams initialized that way are no longer needed they can be destroyed by first calling the macro fdev_close and then destroying the object itself No call to fclose should be issued for these streams While calling fclose itself is harmless it will cause an undefined reference to free and thus cause the linker to link the malloc module into the application Notes
246. rollers 5 21 2 2 static inline uint16 t crc ccitt update uint16 t crc uint8 t static Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 521 lt utiV crc16 h gt CRC Computations 110 Optimized CRC CCITT calculation Polynomial x 16 x 12 5 1 0x8408 Initial value Oxffff This is the CRC used by PPP and IrDA See RFC1171 PPP protocol and IrDA IrLAP 1 1 Note Although the CCITT polynomial is the same as that used by the Xmodem protocol they are quite different The difference is in how the bits are shifted through the alorgithm Xmodem shifts the MSB of the CRC and the input first while CCITT shifts the LSB of the CRC and the input first The following is the equivalent functionality written in C uint16_t crc ccitt update uintl16 t crc uint8 t data data 108 crc data data lt lt 4 return uintl6_t data lt lt 8 hi8 crc uint8 t data gt gt 4 uint16 lt lt 3 5 21 2 3 static inline uint8 t crc ibutton update uint8 t crc uint8 t _data static Optimized Dallas now Maxim iButton 8 bit CRC calculation Polynomial x 8 x 5 x 4 1 0x8C Initial value 0 0 See http www maxim ic com appnotes cfm appnote number 27 The following is the equivalent functionality written in C uint8 t Crco ibutton update uint8 t crc uint8 t data uint8 t i crc crc data for 0 lt 8 irt
247. rsion could be performed 0 is returned 5 19 4 29 char ultoa unsigned long int __val char x s int radix Convert an unsigned long integer to a string The function ultoa converts the unsigned long integer value from val into an ASCII representation that will be stored under s The caller is responsible for providing suf ficient storage in s Note The minimal size of the buffer s depends on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof unsigned long int 1 characters i e one character for each bit plus one for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 97 will be the letter a Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 20 lt string h gt Strings 99 The ultoa function returns the pointer passed as s 5 19 4 30 char utoa unsigned int val char __s int radix Convert an unsigned integer to a string The function utoa converts the unsigned integer value from val into an ASCII repre sentation that will be stored under s The caller is responsible for providing sufficient storage s Note The minimal size of the buffer s depend
248. rt h gt Diagnostics avr boot h gt Bootloader Support Utilities lt avr eeprom h gt EEPROM handling lt avr io h gt AVR device specific IO definitions lt avr pgmspace h gt Program Space String Utilities 15 17 18 Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 2 1 avr libc Modules 6 lt avr sleep h gt Power Management and Sleep Modes 28 lt avr version h gt avr libc version macros 29 lt avr wdt h gt Watchdog timer handling 31 lt compat deprecated h gt Deprecated items 34 lt compat ina90 h gt Compatibility with IAR EWB 3 x 37 lt ctype h gt Character Operations 37 lt errno h gt System Errors 39 lt inttypes h gt Integer Type conversions 40 lt math h gt Mathematics 52 lt setjmp h gt Non local goto 56 lt stdint h gt Standard Integer Types 58 lt stdio h gt Standard IO facilities 70 lt stdlib h gt General utilities 88 lt string h gt Strings 99 lt util crc16 h gt CRC Computations 108 lt util delay h gt Busy wait delay loops 111 lt util parity h gt Parity bit generation 113 lt util twi h gt TWI bit mask definitions 114 lt avr interrupt h gt Interrupts 118 lt avr sfr_defs h gt Special function registers 132 Additional notes from lt avr sfr_defs h gt 26 Demo projects 135 A simple project 136 Example using the two wire interface TWI 148 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 3 avr libc Data Structure Index 7 3
249. rupt T0 11 60 rjmp 34 0x34 vector 8 12255 60 rjmp 202 Oxde lt interrupt 14 64 cO rjmp 200 Oxde lt interrupt 16 63 cO rjmp 198 Oxde bad interrupt 18 62 cO rjmp 196 Oxde lt __bad_interrupt gt la 61 0 rjmp 194 Oxde lt __bad_interrupt gt lg 65060 rjmp 192 Oxde lt __bad_interrupt gt le 5f rjmp 190 Oxde bad interrupt 20 c0 rjmp 188 Oxde lt interrupt 22 90 GU rjmp 186 Oxde lt interrupt 24 5c cO rjmp 184 Oxde lt interrupt 00000026 ctors end 26 11 24 eor rl rl 28 1f be Out 0x3f nil 63 2as Gf 5 ldi r28 Ox5F 95 2c 4 eO ldi r29 0x04 4 2e de bf out 0x3e r29 62 30 cd bf out 0x3d r28 61 32 4f cO rjmp 158 Oxd2 main 00000034 vector 8 volatile uintl16 t x Note 1 volatile uint8 t direction ISR TIMER1 OVF Note 2 x 34 92 push r1 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 A simple project 142 36 38 IdE 3e 40 42 switch direction x Note 3 44 48 4a 4 4 50 522 54 IG 5e 62 66 6a 6e 70 72 74 Los 7 80 84 86 8a 8e 92 96 98 Sat 05 92 push r0 Of 56 im f0 0x3f 63 Of 92 push r0 11 24 eor rl rl 2f 93 push r18 8f 93 push r24 9f 93 push r25 80 91 60 00 145 r24 0x0060 99 27 eor r25 r25
250. s 52 5 14 2 92 define SCNxFAST32 Ix hexadecimal scanf format for uint_fast32_t 5 14 2 93 define SCNxLEAST16 x hexadecimal scanf format for uint_least16_t 5 14 2 94 define SCNxLEAST32 Ix hexadecimal scanf format for uint_least32_t 5 14 2 95 define SCNxPTR SCNx16 hexadecimal scanf format for uintptr_t 5 14 3 Typedef Documentation 5 14 3 1 typedef int32_t int_farptr_t signed integer type that can hold a pointer gt 64 KB 5 14 3 2 typedef uint32_t uint_farptr_t unsigned integer type that can hold a pointer gt 64 KB 5 15 lt math h gt Mathematics 5 15 1 Detailed Description include lt math h gt This header file declares basic mathematics constants and functions Note In order to access the functions delcared herein it is usually also required to addi tionally link against the library 1ibm a See also the related FAQ entry Defines define PI 3 141592653589793238462643 define M SORT2 1 4142135623730950488016887 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 15 lt math h gt Mathematics 53 Functions double cos double x ATTR CONST double fabs double __x CONST double fmod double __x double __y CONST double modf double __ value double iptr double sin double __x CONST double sqrt double x ATTR CONST double tan double x ATTR CONST double floor double __ x _ ATTR CONST double double x
251. s and syntax errors in the text As a programmer the author knows that a wrong documentation sometimes might be worse than none Any way he decided to offer his little knowledge to the public in the hope to get enough response to improve this document Feel free to contact the author via e mail For the latest release check http www ethernut de Herne 17th of May 2002 Harald Kipp harald kipp at egnite de Note As of 26th of July 2002 this document has been merged into the documentation for avr libc The latest version is now available at http savannah nongnu org projects avr libc 741 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 0 1 2 A list of output operands separated by commas Our example uses just one r value 3 A comma separated list of input operands Again our example uses one operand only I SFR IO ADDR PORTD Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 192 4 Clobbered registers left empty in our example You can write assembler instructions in much the same way as you would write assem bler programs However registers and constants are used in a different way if they refer to expressions of your C program The co
252. s func correct volatile uint8 t xport uint8 t mask xport mask define set bits macro port mask port mask int main void set_bits_func_wrong PORTB set_bits_func_correct amp PORTB 0x55 set bits macro PORTB 0 0 return 0 The first function will generate object code which is not even close to what is intended The major problem arises when the function is called When the compiler sees this call it will actually pass the value of the PORTB register using an IN instruction instead of passing the address of PORTB e g memory mapped io addr of 0x38 io port 0x18 for the mega128 This is seen clearly when looking at the disassembly of the call set bits func wrong PORTB 10a 6a ea 141 r22 170 10c 88 b3 in r24 0x18 224 10e 0e 94 65 00 call So the function once called only sees the value of the port register and knows nothing about which port it came from At this point whatever object code is generated for the function by the compiler is irrelevant The interested reader can examine the full disassembly to see that the function s body is completely fubar The second function shows how to pass by reference the memory mapped address of the io port to the function so that you can read and write to it in the function Here s the object code generated for the function call set_bits_func_correct amp PORTB 0x55 112 65 5 idi r22
253. s on the choice of radix For example if the radix is 2 binary you need to supply a buffer with a minimal length of 8 sizeof unsigned int 1 characters i e one character for each bit plus for the string terminator Using a larger radix will require a smaller minimal buffer size Warning If the buffer is too small you risk a buffer overflow Conversion is done using the radix as base which may be a number between 2 binary conversion and up to 36 If radix is greater than 10 the next digit after 9 will be the letter a The utoa function returns the pointer passed as s 5 19 5 Variable Documentation 5 19 5 1 charx malloc heap end malloc tunable 5 19 5 2 charx malloc heap start malloc tunable 5 19 5 3 size t malloc margin malloc tunable 5 200 lt string h gt Strings 5 20 1 Detailed Description finclude string h Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 20 lt string h gt Strings 100 The string functions perform string operations on NULL terminated strings Note If the strings you are working on resident in program space flash you will need to use the string functions described in lt avr pgmspace h gt Program Space String Utilities Defines define _FFS x Functions int ffs int attribute const int 51 long attribute const int ffsll long long attribute const void memccpy void const void
254. s the two strings 51 and s2 ignoring the case of the characters Parameters 81 A pointer to a string in the devices SRAM s2 A pointer to a string in the devices Flash Returns The strcasecmp_P function returns an integer less than equal to or greater than zero if sl is found respectively to be less than to match or be greater than 52 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 5 lt avr pgmspace h gt Program Space String Utilities 24 5 5 4 3 char x strcat_P char x dest PGM P src The strcat_P function is similar to strcat except that the src string must be located in program space flash Returns The strcat function returns a pointer to the resulting string dest 5 5 4 4 int stremp_P const char s1 P 52 The stremp_P function is similar to stremp except that s2 is pointer to a string in program space Returns The strcmp P function returns an integer less than equal to or greater than zero if sl is found respectively to be less than to match or be greater than s2 5 5 4 5 char x P char dest P src The strcpy_P function is similar to strcpy except that src is a pointer to a string in program space Returns The strcpy P function returns a pointer to the destination string dest 5 5 4 6 size tstrlcat P char dst PGM_P size_t siz Concatenate two strings The strlcat_P function is similar to strlcat except th
255. s was a real product we d probably put a SLEEP instruction in this loop to conserve power I Note 7 Early AVR devices saturate their outputs at rather low currents when sourcing cur rent so the LED can be connected directly the resulting current through the LED will be about 15 mA For modern parts at least for the ATmega 128 however Atmel has drastically increased the IO source capability so when operating at 5 V Vcc R2 is needed Its value should be about 150 Ohms When operating the circuit at 3 V it can still be omitted though 5 28 2 The Source Code t ntc Leer iL toe m tatu 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 1 1 to GND The brightness of the LED is Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 528 simple project 138 controlled with the PWM After each period of the PWM the PWM value is either incremented or decremented that s all SId demo c v 1 6 2005 11 04 22 55 15 joerg_wunsch Exp include lt inttypes h gt include lt avr io h gt include lt avr interrupt h gt if defined AVR
256. search avr_stdlib 91 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 241 calloc avr_stdlib 92 cbi deprecated_items 35 ceil avr_math 54 clearerr avr_stdio 77 cos avr_math 54 cosh avr_math 54 ctype isalnum 37 isalpha 37 isascii 38 isblank 38 iscntrl 38 isdigit 38 isgraph 38 islower 38 isprint 38 ispunct 38 isspace 38 isupper 38 isxdigit 39 toascii 39 tolower 39 toupper 39 Demo projects 134 deprecated_items cbi 35 enable_external_int 35 inp 35 INTERRUPT 35 outp 36 sbi 36 timer_enable_int 36 disassembling 139 div avr_stdlib 92 div_t 160 quot 161 rem 161 DTOSTR_ALWAYS_SIGN avr_stdlib 90 DTOSTR_PLUS_SIGN avr_stdlib 90 DTOSTR_UPPERCASE avr_stdlib 90 dtostre avr_stdlib 92 dtostrf avr_stdlib 92 EDOM avr_errno 40 EEMEM avr_eeprom 16 eeprom_busy_wait avr_eeprom 16 eeprom_is_ready avr_eeprom 16 eeprom_read_block avr_eeprom 16 eeprom_read_byte avr_eeprom 16 eeprom_read_word avr_eeprom 16 eeprom_write_block avr_eeprom 16 eeprom_write_byte avr_eeprom 16 eeprom_write_word avr_eeprom 17 EMPTY_INTERRUPT avr_interrupts 130 enable_external_int deprecated_items 35 EOF avr_stdio 75 ERANGE avr_errno 40 Example using the two wire interface TWI 147 exit avr_stdlib 93 exp avr_math 54 fabs Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX 242 avr_math 54 fp
257. sleep mode uint8 t mode void sleep mode void 5 7 2 Define Documentation 5 7 21 define SLEEP MODE BV SMO0 ADC Noise Reduction Mode 5 7 2 2 define SLEEP MODE EXT STANDBY BV SM0 BV SMI BV SM2 Extended Standby Mode 5 7 2 3 define SLEEP MODE IDLE 0 Idle mode Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 8 lt avr version h gt avr libc version macros 29 5 7 2 4 define SLEEP MODE PWR DOWN _BV SM1 Power Down Mode 5 7 2 5 iidefine SLEEP MODE PWR SAVE BV SM0 _BV SM1 Power Save Mode 5 7 2 6 define SLEEP MODE STANDBY BV SM1 BV SM2 Standby Mode 57 3 Function Documentation 5 7 3 1 void set sleep mode uint8 t mode Select a sleep mode 5 7 3 2 void sleep mode void Put the device in sleep mode How the device is brought out of sleep mode depends on the specific mode selected with the set sleep mode function See the data sheet for your device for more details 5 8 lt avr version h gt avr libc version macros 5 8 Detailed Description include avr version h This header file defines macros that contain version numbers and strings describing the current version of avr libc The version number itself basically consists of three pieces that are separated by a dot the major number the minor number and the revision number For development versions which use an odd minor number the string representation additionally gets the
258. sm 197 mov BO 0 ANNAT mov C0 __tmp_reg__ n t r value 0 value If operands do not fit into a single register the compiler will automatically assign enough registers to hold the entire operand In the assembler code you use 0 to refer to the lowest byte of the first operand A1 to the lowest byte of the second operand and so on The next byte of the first operand will be B0 the next byte CO and so on This also implies that it is often neccessary to cast the type of an input operand to the desired size A final problem may arise while using pointer register pairs If you define an input operand e ptr and the compiler selects register Z 130 r31 then SAO refers to r30 and BO refers to r31 But both versions will fail during the assembly stage of the compiler if you explicitely need 7 like in ld r24 2 If you write r24 0 with a lower case a following the percent sign then the compiler will create the proper assembler line 7 4 4 Clobbers As stated previously the last part of the asm statement the list of clobbers may be omitted including the colon seperator However if you are using registers which had not been passed as operands you need to inform the compiler about this The following example will do an atomic increment It increments an 8 bit value pointed to by a pointer variable in one go without being interrupted by an interrupt routine or another thre
259. so note that the debugger might get confused when entering a piece of code that has non local label before since it then takes this label as the name of a new function that appears to have been entered Thus the best practice to avoid this confusion is to only use non local labels when declaring a new function and restrict anything else to local labels Local labels consist just of a number only References to these labels consist of the number followed by the letter b for a backward reference or f for a forward reference These local labels may be re used within the source file references will pick the closest label with the same number and given direction Example myfunc push push push push push KKK RAK eor idi idi rjmp 6 r16 start loop L lo8 sometable hi8 sometable f jump to loop test at end 7 Y loop continues here HNK KA breq Jf return from myfunc prematurely inc r16 23 cmp brlo 1b jump back to top of loop H K Ex ret HH H KK Back to FAQ Index 7 3 13 How do I pass an IO port as a parameter to a function Consider this example code include lt inttypes h gt include lt avr io h gt void set_bits_func_wrong volatile uint8_t port uint8_t mask port mask void Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 179 set bit
260. space string Note also the use of the PSTRQ macro Back to FAQ Index 7 3 21 Why does the compiler compile an 8 bit operation that uses bitwise oper ators into a 16 bit operation in assembly Bitwise operations in Standard C will automatically promote their operands to an int which is by default 16 bits in avr gcc To work around this use typecasts on the operands including literals to declare that the values are to be 8 bit operands This may be especially important when clearing a bit var amp mask wrong way The bitwise not operator will also promote the value in mask to an int To keep it an 8 bit value typecast before the not operator Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 188 var amp unsigned char mask Back to FAQ Index 7 3 22 How to detect RAM memory and variable overlap problems You can simply run avr nm on your output ELF file Run it with the n option and it will sort the symbols numerically by default they are sorted alphabetically Look for the symbol _end that s the first address in RAM that is not allocated by a variable avr gcc internally adds 0x800000 to all data bss variable addresses so please ignore this offset Then the run time initialization code initializes the stack pointer by default to point to the last avaialable address in internal SRAM Thus the region between _end and the end
261. spectively less than equal to or greater than the second 5 19 4 19 int rand void The rand function computes a sequence of pseudo random integers in the range of 0 to RAND MAX as defined by the header file lt stdlib h gt The srand function sets its argument seed as the seed for a new sequence of pseudo random numbers to be returned by rand These sequences are repeatable by calling srand with the same seed value If no seed value is provided the functions are automatically seeded with a value of 1 In compliance with the C standard these functions operate on int arguments Since the underlying algorithm already uses 32 bit calculations this causes a loss of preci sion See random for an alternate set of functions that retains full 32 bit precision 5 19 4 20 int rand unsigned long ctx Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 19 lt stdlib h gt General utilities 96 Variant of rand that stores the context in the user supplied variable located at ct x instead of a static library variable so the function becomes re entrant 5 19 4 21 long random void The random function computes a sequence of pseudo random integers in the range of 0 to RANDOM_MAX as defined by the header file lt stdlib h gt The srandom function sets its argument seed as the seed for a new sequence of pseudo random numbers to be returned by rand These sequences are repeatable by calling sra
262. standing 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 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 228 is declared with a void return type which makes some sense in a microcontroller environment where the application cannot meaningfully provide a return value to its environment in most cases main won t even return anyway However this also turns off all optimizations normally done by the compiler which assume that functions known by a certain name behave as described by the standard E g applying the function strlen to a literal string will normally cause the compiler to immediately replace that call by the actual length of the string while with f freestanding it will always call strlen at run time e funsigned char Make any unqualfied char type an unsigned char Without this option they default to a signed char e funsigned bitfields Make any unqualified bitfield type unsigned By default they are signed fshort enums Allocate to an enum type only as many bytes as it needs for the declared range of possible values Specifically the enum type will be equivalent to the smallest integer type which has enough room fpack struct Pack all structure members together wi
263. stant 1 q Stack pointer register SPH SPL r Any register r0 to r31 t Temporary register r0 w Special upper register r24 r26 r28 r30 pairs X Pointer register pair X 127 126 y Pointer register pair Y y 129 r28 7 Pointer register pair Z z r31 130 These definitions seem not to fit properly to the AVR instruction set The author s as sumption is that this part of the compiler has never been really finished in this version but that assumption may be wrong The selection of the proper contraint depends on the range of the constants or registers which must be acceptable to the AVR instruction they are used with The C compiler doesn t check any line of your assembler code But it is able to check the constraint against your C expression However if you specify the wrong constraints then the compiler may silently pass wrong code to the assem bler And of course the assembler will fail with some cryptic output or internal errors For example if you specify the constraint r and you are using this register with an ori instruction in your assembler code then the compiler may select any register This will fail if the compiler chooses r2 to r15 It will never choose r0 or r1 because these are uses for special purposes That s why the correct constraint in that case is d On the other hand if you use the constraint M the compiler will make sure that you don t pass anything else but an 8 bit value Later on we
264. t For instance 0 9 means the set of every thing except close bracket zero through nine and hyphen The string ends with the appearance of a character not in the or with a circumflex in set or when the field width runs out p Matches a pointer value as printed by p in printf the next pointer must be a pointer to void Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 87 n Nothing is expected instead the number of characters consumed thus far from the input is stored through the next pointer which must be a pointer to int This is not a conversion although it can be suppressed with the flag These functions return the number of input items assigned which can be fewer than provided for or even zero in the event of a matching failure Zero indicates that while there was input available no conversions were assigned typically this is due to an invalid input character such as an alphabetic character for a d conversion The value EOF is returned if an input failure occurs before any conversion such as an end of file occurs If an error or end of file occurs after conversion has begun the number of conversions which were successfully completed is returned By default all the conversions described above are available except the floating point conversions and the conversion These conversions will be available in the ex tended version provided by t
265. t bit set in the input value This macro is very similar to the function ffs except that it evaluates its argument at compile time so it should only be applied to compile time constant expressions where it will reduce to a constant itself Application of this macro to expressions that are not constant at compile time is not recommended and might result in a huge amount of code generated Returns The _FFS macro returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 5 20 3 Function Documentation 5 20 3 1 int ffs int val const This function finds the first least significant bit set in the input value Returns The ffs function returns the position of the first least significant bit set in the word val or 0 if no bits are set The least significant bit is position 1 Note For expressions that are constant at compile time consider using the FFS macro instead 5 20 3 2 int ffsl long val const Same as ffs for an argument of type long 5 20 3 3 int ffsll long long val const Same as ffs for an argument of type long long 5 20 3 4 void x memccpy void dest const void src int val size t len Copy memory area The memccpy function copies no more than len bytes from memory area src to mem ory area dest stopping when the character val is found Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxyge
266. t Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 76 5 18 2 9 define fdev set udata stream u do stream udata u while 0 This macro inserts a pointer to user defined data into a FILE stream object The user data can be useful for tracking state in the put and get functions supplied to the fdevopen function 5 18 2 10 define FDEV_SETUP_STREAM put get rwflag Initializer for a user supplied stdio stream This macro acts similar to fdev_setup_stream but it is to be used as the initializer of a variable of type FILE The remaining arguments are to be used as explained in fdev_setup_stream 5 18 2 11 setup stream stream put get rwflag Setup a user supplied buffer as an stdio stream This macro takes a user supplied buffer st ream and sets it up as a stream that is valid for stdio operations similar to one that has been obtained dynamically from fdevopen The buffer to setup must be of type FILE The arguments put and get are identical to those that need to be passed to fdevopen The rwflag argument can take one of the values FDEV SETUP READ FDEV SETUP WRITE or FDEV SETUP RW for read write or read write intent respec tively Note No assignments to the standard streams will be performed by fdev setup stream If standard streams are to be used these need to be assigned by the user See also under Running stdio without mal
267. t strnlen_P PGM_P size_t _ ATTR CONST 5 5 2 Define Documentation 5 5 2 1 define const prog char Used to declare a variable that is a pointer to a string in program space 5 5 2 2 define read byte address short pgm_read_byte_near address_ short Read a byte from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 5 5 2 3 define 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 5 5 2 4 fidefine pgm read byte near address short LPM uint16 t address short Read a byte from the program space with a 16 bit near address Note The address is a byte address The address is in the program space Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 5 lt avr pgmspace h gt Program Space String Utilities 21 5 5 2 5 define pgm_read_dword address_short pgm read dword near address short Read a double word from the program space with a 16 bit near address Note The address is a byte address The address is in the program space 5 5 2 6 define read dword far address long ELPM_dword uint32_ t address long Read a double word from the program space with a 32 bit far address Note The address is a byte
268. t using fdevopen will be assigned to stdin 5 18 2 19 define stdout iob 1 Stream that will be used as an output stream by the simplified functions that don t take a stream argument The first stream opened with write intent using fdevopen will be assigned to both stdin and stderr 5 18 3 Function Documentation 5 18 3 1 void clearerr FILE stream Clear the error and end of file flags of st ream Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 78 5 18 3 2 int fclose FILE __ stream This function closes st ream and disallows and further IO to and from it When using fdevopen to setup the stream a call to fclose is needed in order to free the internal resources allocated If the stream has been set up using fdev_setup_stream or FDEV_SETUP_ STREAM use fdev_close instead It currently always returns 0 for success 5 18 3 3 FILE fdevopen int x char FILE put int xX 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 t
269. t32_t 5 17 2 42 define UINT32 MAX CONCAT INT32 U 2UL 100 largest value an uint32_t can hold 5 17 2 43 UINT64_C value __ CONCAT value ULL define a constant of type uint64_t 5 17 2 44 define UINT6 4 MAX CONCAT INT64 U 2ULL 1ULL largest value an uint64_t can hold 5 17 2 45 define UINT8_C value uint8_t _CONCAT value U define a constant of type uint8_t 5 17 2 46 define UINT8_MAX _CONCAT INT8_MAX U x 20 10 largest value an uint8_t can hold 5 17 2 47 ttdefine UINT_FAST16_MAX UINT16_MAX largest value an uint_fast16_t can hold 5 17 2 48 define UINT FAST32 MAX UINT32 MAX largest value an uint_fast32_t can hold 5 17 2 49 UINT FAST64 MAX UINT64 largest value an uint fast64 t can hold Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Integer Types 67 5 17 2 50 define UINT FAST8 MAX UINT8 MAX largest value an uint fast8 t can hold 5 17 2 51 UINT LEASTI6 MAX UINTI6 MAX largest value an uint leastl6 t can hold 5 17 2 52 itdefine UINT LEAST32 MAX UINT32 largest value an uint least32 t can hold 5 17 2 53 define UINT LEAST64 MAX UINT64 largest value an uint least64 t can hold 5 17 2 54 define UINT LEAST8 MAX UINT8 MAX largest value an uint least8 t can hold 5 17 2 55 define UINTMAX_C value CONCAT value ULL define a constant of type
270. take as an indication to not initiate further transfers int ee24xx read bytes uintl6 t eeaddr int len uint8_t buf uint8_t sla twcr n 0 int rv 0 X top ce a x patch high bits of EEPROM address into SLA x sla SLA 24CXX eeaddr gt gt 8 amp 0x07 lt lt 1 Note 8 x First cycle master transmitter mode restart if n gt MAX_ITER return 1 begin _BV TWINT _BV TWSTA _BV TWEN x send start condition while TWCR amp _BV TWINT 0 x wait for transmission x switch twst TW_STATUS case TW_REP_START but should not happen case TW_START break case TW_MT_ARB_LOST Note 9 goto begin default return 1 x error not in start condition NB do not send stop condition Note 10 send SLA W x TWDR sla TW_WRITE _BV TWINT _BV TWEN clear interrupt to start transmission x while TWCR _BV TWINT 0 wait for transmission switch twst TW_STATUS case TW_MT_SLA_ACK break Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 529 Example using the two wire interface TWI 153 case TW MT SLA nack during select device busy writing x Note 11 goto restart case TW MT ARB LOST re arbitrate goto begin default goto error must send stop condition x TWDR
271. tch ATmegal28 ATmegal62 ATmega64 COMPARE3A A mega640 ATmegal280 ATmegal281 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPB_vect OUTPUT_ Compare Match ATmegal28 ATmegal62 ATmega64 COMPARE3B B mega640 ATmegal280 ATmegal281 TIMER3 SIG Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA COMPC_vect OUTPUT_ Compare Match ATmegal28 ATmega64 ATmega640 megal280 ATmegal281 Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 525 lt avr interrupt h gt Interrupts 128 Vector name Old vector Description Applicable for device name TIMER3_ SIG_ Timer Counter3 AT90CAN128 AT90CAN32 AT90CANGA OVF_vect OVERFLOW3 Overflow ATmegal28 ATmegal62 ATmega64 AT mega640 ATmegal280 ATmegal281 TIMERA SIG INPUT Timer Counter4 ATmega640 ATmega1280 ATmegal281 CAPT vect CAPTUREA Capture Event TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 COMPA vect OUTPUT Compare Match COMPARE4A TIMER4 SIG_ Timer Counter4 ATmega640 ATmegal280 ATmega1281 COMPB vect OUTPUT Compare Match COMPAREAB B TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmegal281 vect OUTPUT Compare Match COMPARE4C C TIMERA SIG Timer Counter4 ATmega640 ATmegal280 ATmega1281 OVF vect OVERFLOW4 Overflow TIMERS SIG INPUT Timer Counter5 ATmega640
272. ters OCRnM Refer to the actual datasheet for each device s set of registers that involves the TEMP register When accessing one of the registers that use TEMP from the main application and possibly any other one from within an interrupt routine care must be taken that no access from within an interrupt context could clobber the TEMP register data of an in progress transaction that has just started elsewhere To protect interrupt routines against other interrupt routines it s usually best to use the ISR macro when declaring the interrupt function and to ensure that interrupts are still disabled when accessing those 16 bit timer registers Within the main program access to those registers could be encapsulated in calls to the cli and sei macros If the status of the global interrupt flag before accessing one of those registers is uncertain something like the following example code can be used uintl16 t read timerl void uint8_t sreg uint16_t val sreg SREG cli val TCNT1 SREG sreg return val Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 7 3 Frequently Asked Questions 176 Back to FAQ Index 7 3 10 How do I use a define d constant 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 compilatio
273. the device to run off this oscillator instead of an external crystal This often remains unnoticed until the first attempt is made to use something critical in timing like UART communication The ATmegal28 ships with the fuse enabled that turns this device into AT mega103 compatibility mode This means that some ports are not fully usable and in particular that the internal SRAM is located at lower addresses Since by default the stack is located at the top of internal SRAM a program compiled for ATmega128 running on such a device will immediately crash upon the first function call or rather upon the first function return Devices with a JTAG interface have the JTAGEN fuse programmed by default This will make the respective port pins that are used for the JTAG interface un available for regular IO Back to FAQ Index 7 3 20 Why do all my foo bar strings eat up the SRAM By default all strings are handled as all other initialized variables they occupy RAM even though the compiler might warn you when it detects write attempts to these RAM locations and occupy the same amount of flash ROM so they can be initialized to the actual string by startup code The compiler can optimize multiple identical strings into a single one but obviously only for one compilation unit i e a single C source file That way any string literal will be a valid argument to any C function that expects a const char argument Of cours
274. the handler the following way void XXX_vect void __attribute__ interrupt void XXX_vect void Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 525 lt avr interrupt h gt Interrupts 120 where XXX_vect is the name of a valid interrupt vector for the MCU type in question as explained below Chosing the vector Interrupt vector names interrupt is chosen by supplying one of the symbols in following table There are currently two different styles present for naming the vectors One form uses names starting with SIG_ followed by a relatively verbose but arbitrarily chosen name describing the interrupt vector This has been the only available style in avr libc up to version 1 2 x Starting with avr libc version 1 4 0 a second style of interrupt vector names has been added where a short phrase for the vector description is followed by vect The short phrase matches the vector name as described in the datasheet of the respective device and in Atmel s XML files with spaces replaced by an underscore and other non alphanumeric characters dropped Using the suffix vect is intented to improve portability to other C compilers available for the AVR that use a similar naming con vention The historical naming style might become deprecated in a future release so it is not recommended for new projects Note The ISR macro cannot really spell check the argument passed to them Thus by misspelling one
275. the upper case alphabetic characters A Z are converted Non alphabetic characters will not be changed Returns The strlwr function returns a pointer to the converted string 5 20 3 19 int strncasecmp const char s1 const char 52 size t len Compare two strings ignoring case The strncasecmp function is similar to strcasecmp except it only compares the first n characters of s1 Returns The strncasecmp function returns an integer less than equal to or greater than zero if 61 or the first n bytes thereof is found respectively to be less than to match or be greater than s2 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 20 lt string h gt Strings 106 5 20 3 20 char x strncat char dest const char x src size_t len Concatenate two strings The strncat function is similar to strcat except that only the first n characters of src are appended to dest Returns strncat function returns a pointer to the resulting string dest 5 20 3 21 int strncmp const char 57 const char 52 size_t len Compare two strings The strncmp function is similar to stremp except it only compares the first at most characters of sl and 52 Returns The strncmp function returns an integer less than equal to or greater than zero if sl or the first n bytes thereof is found respectively to be less than to match or be greater than s2 5 20 3 22 char strnc
276. thout holes 7 10 2 Options for the assembler avr as 7 10 2 1 Machine specific assembler options e mmcu architecture mncu MCU name avr as understands the same mmcu options as avr gcc By default avr2 is assumed but this can be altered by using the appropriate arch pseudo instruction inside the assembler source file e mmall opcodes Turns off opcode checking for the actual MCU type and allows any possible AVR opcode to be assembled Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 10 Using the GNU tools 229 e mno skip bug Don t emit a warning when trying to skip 2 word instruction with a CPSE SBIC SBIS SBRC SBRS instruction Early AVR devices suffered from a hardware bug where these instructions could not be properly skipped e mno wrap For RIMP RCALL instructions don t allow the target address to wrap around for de vices that have more than 8 KB of memory e gstabs Generate stabs debugging symbols for assembler source lines This enables avr gdb to trace through assembler source files This option must not be used when assembling sources that have been generated by the C compiler these files already contain the appropriate line number information from the C source files e a cdhlmns file Turn on the assembler listing The sub options are e omit false conditionals domit debugging directives h include high level source 1 include assembly e m inclu
277. til_delay 112 _delay_ms util_delay 112 _delay_us util_delay 112 A simple project 135 abort avr_stdlib 90 abs avr_stdlib 90 acos avr_math 53 Additional notes from lt avr sfr_defs h gt 26 asin avr_math 53 assert avr_assert 7 atan avr_math 53 atan2 avr_math 53 atof avr_stdlib 91 atoi avr_stdlib 91 atol avr_stdlib 91 avr_assert assert 7 avr_boot boot_is_spm_interrupt 10 boot_lock_bits_set 10 boot_lock_bits_set_safe 10 boot_lock_fuse_bits_get 10 boot_page_erase 11 boot_page_erase_safe 11 boot_page_fill 11 boot_page_fill_safe 12 boot_page_write 12 boot_page_write_safe 12 boot_rww_busy 12 boot_rww_enable 13 boot_rww_enable_safe 13 boot_spm_busy 13 boot_spm_busy_wait 13 boot_spm_interrupt_disable 13 boot_spm_interrupt_enable 13 BOOTLOADER_SECTION 13 GET_EXTENDED_FUSE_BITS 13 GET_HIGH_FUSE_BITS 14 GET_LOCK_BITS 14 GET_LOW_FUSE_BITS 14 avr_eeprom _EEGET 15 _EEPUT 15 EEPROM REG LOCATIONS 15 16 eeprom_busy_wait 16 eeprom_is_ready 16 eeprom_read_block 16 eeprom_read_byte 16 eeprom_read_word 16 eeprom_write_block 16 eeprom_write_byte 16 eeprom_write_word 17 avr_errno EDOM 40 ERANGE 40 avr_interrupts EMPTY_INTERRUPT 130 ISR 130 SIGNAL 131 avr_inttypes int_farptr_t 52 PRId16 43 PRId32 43 PRId8 43 PRIdFAST16 43 PRIdFAST32 43 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen INDEX PRIdFASTS 43
278. tile uint8_t direction ISR TIMER1 OVF vect Note 2 switch direction x Note 3 case UP if pwm 1023 direction DOWN break case DOWN if pwm 0 direction UP break OCR Note 4 void ioinit void x Note 5 tmrl is 10 bit PWM TCCRIA PWM10 BV PWM11 _BV XCOM11 tmrl running on full MCU clock x TCCRIB _BV CS10 set PWM value to 0 OCR 0 enable 1 and PB2 as output DDROC _BV OC1 enable interrupts TIMSK TOIE1 sei int main void loop forever the interrupts are doing the rest for Note 6 x return 0 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 28 simple project 140 5 28 3 Compiling and Linking This first thing that needs to be done is compile the source When compiling the compiler needs to know the processor type so the mmcu option is specified The Os option will tell the compiler to optimize the code for efficient space usage at the possible expense of code execution speed The g is used to embed debug info The debug info is useful for disassemblies and doesn t end up in the hex files so I usually specify it Finally the tells the compiler to compile and stop don t link This demo is small enough that we could compile and link in one step However real world proj
279. ting a logical in the respec tive bit position When working with interrupt handlers this interrupt flag bit usually gets cleared automatically in the course of processing the interrupt sometimes by just calling the handler at all sometimes g for the U SJART by reading a particular hardware register that will normally happen anyway when processing the interrupt From the hardware s point of view an interrupt is asserted as long as the respective bit is set while global interrupts are enabled Thus it is essential to have the bit cleared before interrupts get re enabled again which usually happens when returning from an interrupt handler Only few subsystems require an explicit action to clear the interrupt request when using interrupt handlers The notable exception is the TWI interface where clearing the interrupt indicates to proceed with the TWI bus hardware handshake so it s never done automatically However if no normal interrupt handlers are to be used or in order to make extra sure any pending interrupt gets cleared before re activating global interrupts e g an external edge triggered one it can be necessary to explicitly clear the respective hardware interrupt bit by software This is usually done by writing a logical 1 into this bit position This seems to be illogical at first the bit position already carries a logical 1 when reading it so why does writing a logical 1 to it clear the interrupt bit The so
280. tions might follow notably prefix in order to change the direc tory prefix for the installed files from its default usr local 7 8 6 UISP Uisp also uses the configure system so to build and install gunzip c uisp lt version gt tar gz tar xf cd uisp lt version gt mkdir obj avr cd obj avr configure prefix PREFIX make make install X Xr Xr X d Xr 7 8 7 Avrdude Note It has been ported to windows via cygwin and linux Other unix systems should be trivial to port to avrdude is part of the FreeBSD ports system To install it simply do the following usr ports devel avrdude make install Note Installation into the default location usually requires root permissions However running the program only requires access permissions to the appropriate ppi 4 device Building and installing on other systems should use the configure system as such Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 7 8 Installing the GNU Tool Chain 220 gunzip avrdude lt version gt tar gz tar xf cd avrdude lt version gt mkdir obj avr obj avr configure prefix PREFIX make make install Xr Xr o X Xr Xr XY 7 8 8 GDB for the AVR target Gdb also uses the configure system so to build and install bunzip2 c gdb version tar bz2 tar xf cd gdb version mkdir obj avr cd obj avr configure prefix PREFIX target avr make make insta
281. tments are required 77 3 The bss Section Uninitialized global or static variables end up in the bss section 77 4 eeprom Section This is where eeprom variables are stored 7 7 5 The noinit Section This sections is a part of the bss section What makes the noinit section special is that variables which are defined as such int foo __attribute__ section noinit Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 77 Memory Sections 212 will not be initialized to zero during startup as would normal bss data Only uninitialized variables can be placed in the noinit section Thus the following code will cause avr gcc to issue an error int bar __attribute__ section noinit Oxaa It is possible to tell the linker explicitly where to place the noinit section by adding W1 section start noinit 0x802000 to the avr gcc command line at the linking stage For example suppose you wish to place the noinit section at SRAM address 0x2000 5 avr gcc Wl section start noinit 0x802000 Note Because of the Harvard architecture of the AVR devices you must manually add 0 800000 to the address you pass to the linker as the start of the section Oth erwise the linker thinks you want to put the noinit section into the text section instead of data bss and will complain Alternatively you can write your own linker script to automate this FIXME need an example or ref
282. to dox for writing linker scripts 7 7 6 initN Sections These sections are used to define the startup code from reset up through the start of main These all are subparts of the text section The purpose of these sections is to allow for more specific placement of code within your program Note Sometimes it is convenient to think of the initN and finiN sections as functions but in reality they are just symbolic names which tell the linker where to stick a chunk of code which is not a function Notice that the examples for asm and C can not be called as functions and should not be jumped into The initN sections are executed in order from 0 to 9 init0 Weakly bound to __init If user defines init it will be jumped into immedi ately after a reset initi Unused User definable Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 77 Memory Sections 213 init2 In C programs weakly bound to initialize the stack and to clear zero reg r1 init3 Unused User definable init4 For devices with gt 64 KB of init4 defines the code which takes care of copying the contents of data from the flash to SRAM For all other devices this code as well as the code to zero out the bss section is loaded from libgcc a init5 Unused User definable init6 Unused for C programs but used for constructors in C programs init7 Unused User definable 11168 Unused
283. to stream See vfprintf for details 5 18 3 10 int fprintf_P FILE x stream const char fmt Variant of fprintf that uses a fmt string that resides in program memory 5 18 3 11 intfputc int FILE stream The function fputc sends the character c though given as type int to stream It returns the character or EOF in case an error occurred Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 18 lt stdio h gt Standard IO facilities 80 5 18 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 5 18 3 13 intfputs P const char __str FILE stream Variant of fputs where st r resides in program memory 5 18 3 14 size t fread void __ptr size t __size size_t __nmemb FILE x _ stream Read nmemb objects size bytes each from st ream to the buffer pointed to by ptr Returns the number of objects successfully read i e nmemb unless an input error occured or end of file was encountered feof and ferror must be used to distinguish between these two conditions 5 18 3 15 int fscanf FILE stream const char x fmt The function f scanf performs formatted input reading the input data from st ream See vfscanf for details 5 18 3 16 int fscanf_P FILE stream const char x fmt Variant of fscanf using a mt string in program memory 5 18 3 17 size t fwrite
284. tten 1 2 General information about this library In general it has been the goal to stick as best as possible to established standards while implementing this library Commonly this refers to the C library as described by the ANSI X3 159 1989 and ISO IEC 9899 1990 ANSI C standard as well as parts of their successor ISO IEC 9899 1999 C99 Some additions have been inspired by other standards like IEEE Std 1003 1 1988 POSIX 1 while other extensions purely AVR specific like the entire program space string interface Unless otherwise noted functions of this library are not guarenteed to be reentrant In particular any functions that store local state are known to be non reentrant as well as functions that manipulate IO registers like the EEPROM access routines If these functions are used within both standard and interrupt context undefined behaviour will result 1 3 Supported Devices The following is a list of AVR devices currently supported by the library Note that actual support for some newer devices depends on the ability of the compiler assembler to support these devices at library compile time AT90S Type Devices 219051200 1 at90s2313 at90s2323 at90s2333 at90s2343 Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 1 3 Supported Devices at90s4414 at90s4433 at90s4434 219058515 at90c8534 at90s8535 at90can32 at90can64 at90can128 ATmega Type Devices
285. ue 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 initializer just containing 0 on the right hand side they waste space While this waste of space applies to virtually any platform C is Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 175 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 standard guarantees the initialization it is safe to rely on it Back to FAQ Index 7 3 9 Why do some 16 bit timer registers sometimes get trashed Some of the timer related 16 bit IO registers use a temporary register called TEMP in the Atmel datasheet to guarantee an atomic access to the register despite the fact that two separate 8 bit IO transfers are required to actually move the data Typically this includes access to the current timer counter value register TCNTn the input capture register ICRn and write access to the output compare regis
286. ue to the nature of the underlying hardware only a limited subset of standard IO is implemented There is no actual file implementa tion available so only device IO can be performed Since there s no operating system the application needs to provide enough details about their devices in order to make them usable by the standard IO facilities Due to space constraints some functionality has not been implemented at all like some of the printf conversions that have been left out Nevertheless potential users of this implementation should be warned the printf and scanf families of functions although usually associated with presumably simple things like the famous Hello world program are actually fairly complex which causes their inclusion to eat up a fair amount of code space Also they are not fast due to the nature of interpreting the format string at run time Whenever possible resorting to the sometimes non standard predetermined conversion facilities that are offered by avr libc will usually cost much less in terms of speed and code size Tunable options for code size vs feature set order to allow programmers a code size vs functionality tradeoff the function vfprintf which is the heart of the printf family can be selected in different flavours using linker options See the documentation of vfprintf for a detailed description The same applies to vfscanf and the scanf family of functions Outline of the chosen API
287. uintmax t 5 17 2 56 define UINTMAX MAX UINT64 largest value an uintmax t can hold 5 17 2 57 UINTPTR MAX UINTI6 MAX largest value an uintptr t can hold 5 17 3 Typedef Documentation 5 17 3 1 typedef signed int int16_t 16 bit signed type 5 17 3 2 typedef signed long int int32_t 32 bit signed type 5 17 3 3 typedef signed long long int int64 t 64 bit signed type Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Integer Types 68 5 17 3 4 typedef signed char int8_t 8 bit signed type 5 17 3 5 typedef int16_t int_fast16_t fastest signed int with at least 16 bits 5 17 3 6 typedef int32_t int_fast32_t fastest signed int with at least 32 bits 5 17 3 7 typedef int64 t int fast64 t fastest signed int with at least 64 bits 5 17 3 8 typedef int8 t int fast8 t fastest signed int with at least 8 bits 5 17 3 9 typedef int16 t int least16 t signed int with at least 16 bits 5 17 3 10 typedef int32 t int least32 t signed int with at least 32 bits 5 17 3 11 typedef int64 t int least64 t signed int with at least 64 bits 5 17 3 12 typedef int8 t int least8 t signed int with at least 8 bits 5 17 3 13 typedef int64 t intmax t largest signed int available 5 17 3 14 typedef int16 tintptr t Signed pointer compatible type Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Inte
288. uisp http savannah gnu org projects uisp Installation avrdude http savannah nongnu org projects avrdude Installation Usage Notes GDB http sources redhat com gdb Installation Simulavr http savannah gnu org projects simulavr Installation Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 8 Installing the GNU Tool Chain 217 AVaRice http avarice sourceforge net Installation 7 8 3 GNU Binutils for the AVR target The binutils package provides all the low level utilities needed in building and ma nipulating object files Once installed your environment will have an AVR assembler avr as linker avr 13G and librarian avr ar and avr ranlib In addi tion you get tools which extract data from object files avr objcopy dissassem ble object file information avr objdump and strip information from object files avr strip Before we can build the compiler these tools need to be in place Download and unpack the source files 5 bunzip2 binutils lt version gt tar bz2 tar xf cd binutils lt version gt Note Replace with the version of the package you downloaded Note If you obtained gzip compressed file gz use gunzip instead of bunzip2 It is usually a good idea to configure and build binutils in a subdirectory so as not to pollute the source with the compiled files This is recommended by the binutils developers 5 mkdir obj avr 5
289. ust be declared global in order to be acceptable for this purpose This will only work if lt avr io h gt has been included Note that the assembler or linker have no chance to check the correct spelling of an interrupt function so it should be double checked When analyzing the resulting object file using avr objdump or avr nm a name like vector N should appear with N being a small integer number Note 8 As explained in the section about special function registers the actual IO port address should be obtained using the macro SFR IO ADDR The 905 1200 does not have RAM thus the memory mapped approach to access the IO registers is not available It would be slower than using in out instructions anyway Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 2 avr libc and assembler programs 168 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 t
290. ut by default also functions defined in an assembler source file since the g compiler switch does not apply to the assembler So in order to debug an assembler input file possibly one that has to be passed through the C preprocessor it s the assembler that needs to be told to include line number information into the output file Other debug information like data types and variable allocation cannot be generated since unlike a compiler the assembler basically doesn t know about this This is done using the GNU assembler option gstabs Example 5 avr as mmcu atmegal28 gstabs o foo o foo s When the assembler is not called directly but through the C compiler frontend either implicitly by passing a source file ending in S or explicitly using assembler with cpp the compiler frontend needs to be told to pass the gstabs option down to the assembler This is done using Wa gstabs Please take care to only pass this option when compiling an assembler input file Otherwise the assembler code that results from the C compilation stage will also get line number information which confuses the debugger Note You can also use Wa gstabs since the compiler will add the extra for you Example EXTRA OPTS Wall mmcu atmegal28 x assembler with cpp avr gcc Wa gstabs EXTRA_OPTS c o foo o foo S Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 3 Frequently Asked Questions 178 Al
291. uts_P FAQ 168 avr_stdio 79 fclose fread avr_stdio 77 avr_stdio 79 fdev_close free avr_stdio 75 avr_stdlib 93 fdev_get_udata frexp avr_stdio 75 avr_math 54 fdev_set_udata fscanf avr_stdio 75 avr_stdio 80 FDEV_SETUP_STREAM fscanf_P avr_stdio 75 avr_stdio 80 fdev_setup_stream fwrite avr_stdio 76 fdevopen avr_stdio 78 feof avr_stdio 78 ferror avr_stdio 78 fflush avr_stdio 78 ffs avr_string 100 ffsl avr_string 101 ffsll avr_string 101 fgetc avr_stdio 79 fgets avr_stdio 79 FILE avr_stdio 76 floor avr_math 54 fmod avr_math 54 fprintf avr_stdio 79 fprintf_P avr_stdio 79 fputc avr stdio 79 fputs avr stdio 79 avr stdio 80 GET EXTENDED FUSE BITS avr boot 13 HIGH FUSE BITS avr boot 14 GET LOCK BITS avr boot 14 GET LOW FUSE BITS avr boot 14 getc avr stdio 76 getchar avr stdio 76 gets avr stdio 80 inp deprecated items 35 installation 214 installation avarice 219 installation avr libc 217 installation avrdude 218 installation avrprog 218 installation binutils 216 installation gcc 217 Installation gdb 219 installation simulavr 219 installation uisp 218 INT16 C avr stdint 62 6 avr_stdint 62 Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen INDEX 243 INT16_MIN int_fast64_t avr_stdint 62 avr_stdint 68 intl6_t INT_FAST8_MAX avr_stdint 67 avr_stdint 63 INT32_C INT_FAST8_
292. v_t Struct Reference 162 Data Fields int quot intrem 6 1 2 Field Documentation 6 1 2 1 int div_t quot The Quotient 6 1 2 2 int div_t rem The Remainder The documentation for this struct was generated from the following file stdlib h 6 2 1div_t Struct Reference 6 2 1 Detailed Description Result type for function Idiv Data Fields long quot e long rem 6 2 2 Field Documentation 6 2 2 1 long Idiv_t quot The Quotient 6 2 2 2 long Idiv_t rem The Remainder The documentation for this struct was generated from the following file stdlib h Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 avr libc Page Documentation 163 7 avr libc Page Documentation 7 1 Acknowledgments This document tries to tie together the labors of a large group of people Without these individuals efforts we wouldn t have terrific free set of tools to develop AVR projects We all owe thanks to The GCC Team which produced a very capable set of development tools for an amazing number of platforms and processors Denis Chertykov denisc overta ru for making the AVR specific changes to the GNU tools Denis Chertykov and Marek Michalkiewicz marekm linux org pl for developing the standard libraries and startup code for AVR GCC Uros Platise for developing the AVR programmer tool uisp Joerg Wunsch joerg FreeBSD ORG for adding all the AVR development tools to
293. vr libc by Doxygen 5 16 lt setjmp h gt Non local goto 57 function the C library provides the setjmp and longjmp functions setjmp and longjmp are useful for dealing with errors and interrupts encountered in a low level subroutine of a program Note setjmp and longjmp make programs hard to understand and maintain If possi ble an alternative should be used longjmp can destroy changes made to global register variables see How to per manently bind a variable to a register For a very detailed discussion of setimp longjmp see Chapter 7 of Advanced Pro gramming in the UNIX Environment by W Richard Stevens Example include setjmp h jmp buf env int main void if setjmp env handle error main processing loop which calls foo some where void foo void blah blah blah if err longjmp env 1 Functions int setimp jmp buf __jmpb void longjmp jmp_buf __jmpb int ATTR NORETURN Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 5 17 lt stdint h gt Standard Integer Types 58 5 16 2 Function Documentation 5 16 2 1 void longjmp jmp buf __jmpb int ret Non local jump to a saved stack context include lt setjmp h gt longjmp restores the environment saved by the last call of setjmp with the corre sponding __jmpb argument After longjmp is completed program execution contin ues as if the corresp
294. vrdude 2313 m flash main hex Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 9 Using the avrdude program 222 avrdude AVR device initialized and ready to accept instructions avrdude Device signature 0 1 9101 avrdude erasing chip avrdude done avrdude reading input file main hex avrdude input file main hex auto detected as Intel Hex avrdude writing flash 1749 0x00 avrdude 1750 bytes of flash written avrdude verifying flash memory against main hex avrdude reading on chip flash data 1749 0x00 avrdude verifying avrdude 1750 bytes of flash verified avrdude done Thank you The 2313 option lets avrdude know that we are operating on an 419052313 chip This option specifies the device id and is matched up with the device of the same id in avrdude s configuration file usr local etc avrdude conf To list valid parts specify the option The option instructs avrdude to perform a chip erase before programming this is almost always necessary before programming the flash The m flash option indicates that we want to upload data into the flash memory while i main hex specifies the name of the input file The EEPROM is uploaded in the same way the only difference is that you would use m eeprom instead of m flash To use interactive mode use the t option avrdude p 2313 t avrdude AVR device initialized and ready to accept instructions avrdude
295. will see how to pass multibyte expression results to the assembler code The following table shows all AVR assembler mnemonics which require operands and the related contraints Because of the improper constraint definitions in version 3 3 they aren t strict enough There is for example no constraint which restricts integer Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 4 Inline Asm 195 constants to the range 0 to 7 for bit set and bit clear operations Mnemonic Constraints Mnemonic Constraints adc rr add rr adiw rr andi asr r bclr I bid rl brbc Llabel brbs Llabel bset I bst rl cbi LI cbr d l com r cp Lr LI cpi d M cpse rr dec r elpm tz eor rr in rl inc r ld re Idd rb ldi d M 146 r label lpm 52 Isl r Isr r mov rr movw rr mul rr neg r or Lr ori out Lr pop r push r rol r ror sbc rr sbci sbi sbic LI sbiw sbr sbrc rl sbrs rl ser d st e r std b r sts label r sub rr subi swap Constraint characters may be prepended by a single constraint modifier Contraints without a modifier specify read only operands Modifiers are Modifier Specifies Write only operand usually used for all output operands Read write operand not supported by inline assembler amp Register should be used for output
296. will still be placed after all the variables in the data section so in this situation no stack heap collision can occur 7 11 Todo List Group avr_boot From email with Marek On smaller devices all except AT mega64 128 SPM_REG is in the I O space accessible with the shorter in and out instructions since the boot loader has a limited size this could be an important optimization 7 12 Deprecated List Global enable_external_int mask Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen 7 12 Deprecated List 233 Global INTERRUPT signame Global timer_enable_int unsigned char ints Global inp port Global outp port val Global sbi port bit Global cbi port bit Generated on Sat Nov 19 23 00 48 2005 for avr libc by Doxygen Index PATH 214 PREFIX 214 prefix 214 lt assert h gt Diagnostics 7 lt avr boot h gt Bootloader Support Utili ties 8 lt avr eeprom h gt EEPROM handling 14 lt avr interrupt h gt Interrupts 118 lt avr io h gt AVR device specific IO defi nitions 17 lt avr pgmspace h gt Program 5 String Utilities 18 lt avr sfr_defs h gt Special function regis ters 131 lt avr sleep h gt Power Management and Sleep Modes 27 lt avr version h gt avr libc version macros 29 avr wdt h Watchdog timer handling 30 lt compat deprecated h gt Deprecated items 33 lt compat ina90 h gt Compatibility with IAR EW
297. ypes having exactly the specified width typedef signed char int8_t typedef unsigned char uint8_t typedef signed int int16 t typedef unsigned int uint16_t typedef signed long int int32_t typedef unsigned long int uint32_t typedef signed long long int int64_t typedef unsigned long long int uint64_t Integer types capable of holding object pointers These allow you to declare variables of the same size as a pointer typedef int16_t intptr_t typedef uint16_t uintptr_t Minimum width integer types Integer types having at least the specified width typedef int8_t int_least8_t typedef uint8_t uint_least8_t typedef int16 t int_least16_t typedef uint16_t uint_least16_t typedef int32_t int_least32_t typedef uint32_t uint_least32_t typedef int64_t int_least64_t typedef uint64_t uint_least64_t Generated on Sat Nov 19 23 00 48 2005 for avr libe by Doxygen 5 17 lt stdint h gt Standard Integer Types 62 Fastest minimum width integer types Integer types being usually fastest having at least the specified width typedef int8 t int fast8 t typedef uint8 t uint fast8 t typedef int16 t int fast16 t typedef uint16 t fastl6 t typedef int32 t int fast32 t typedef uint32 t uint_fast32_t typedef int64 t int fast 4 t typedef uint64 t uint_fast64_t Greatest width integer types Types designating integer data capable of representing any value of any integer type in the corresponding signed or unsigned category typedef
298. zero length the function returns s1 5 20 3 28 char x strtok_r char x string const char delim char xx last Parses the string s into tokens strtok_r parses the string s into tokens The first call to strtok_r should have string as its first argument Subsequent calls should have the first argument set to NULL If a token ends with a delimiter this delimiting character is overwritten with a 70 and a pointer to the next character is saved for the next call to strtok_r The delimiter string delim may be different for each call last is a user allocated pointer It must be the same while parsing the same string strtok_r is a reentrant version of strtok Returns The strtok_r function returns a pointer to the next token or NULL when no more tokens are found 5 20 3 29 char x strupr char x string Convert a string to upper case The strupr function will convert a string to upper case Only the lower case alphabetic characters a z are converted Non alphabetic characters will not be changed Returns The strupr function returns a pointer to the converted string The pointer is the same as that passed in since the operation is perform in place 5 21 lt util crcl6 h gt CRC Computations 5 21 1 Detailed Description include lt util crc16 h gt This header file provides a optimized inline functions for calculating cyclic redundancy checks CRC using common polynomials References Generated on

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