Imagecraft c compiler and development environment for the atmel avr

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ICCV8 for AVR – C Compiler for Atmel AVRAccessing EEPROMThe EEPROM can be accessed at runtime using library functions. Use #include before calling these functions.IMPORTANT: These functions do not work for the XMega. XMega support will beprovided in a later release. EEPROM_READ(int location, object)This macro calls the EEPROMReadBytes function (see below) to read in the dataobject from the EEPROM location(s). The int “object” can be any program variable,including structures and arrays. For example,int i;EEPROM_READ(0x1, i); // read 2 bytes into i EEPROM_WRITE(int location, object)This macro calls the EEPROMWriteBytes function (see the next section) to writethe data object to the EEPROM location(s). The int “object” can be any programvariable, including structures and arrays. For example,int i;EEPROM_WRITE(0x1, i); // write 2 bytes to 0x1There are actually 3 sets of macros and functions: Most classic and mega AVRs AVRs with 256 bytes of EEPROM MegaAVRs with extended IOThe IDE predefines certain macros (e.g., ATMega168), so that the right macros andfunctions are used when you #include the eeprom.h header file. Thus, you mayuse the names given here for these macros and functions.Initializing EEPROMEEPROM can be initialized in your program source file by allocation of a globalvariable to a special area called eeprom. In C source, this can be done usingpragmas. See Program Areas for a discussion of the different program areas. Theresulting file is .eep. For example,#pragma data:eepromint foo = 0x1234;char table[] = { 0, 1, 2, 3, 4, 5 };136
ICCV8 for AVR – C Compiler for Atmel AVR#pragma data:data...int i;EEPROM_READ((int)&foo, i); // i now has 0x1234The second pragma is necessary to reset the data area name back to the defaultdata.Note that to work around the hardware bug in the older AVRs, location 0 is not usedfor the initialized EEPROM data for some of these older devices (mostly the pre-MegaAT90S series).Note that when using this in an external declaration (e.g. accessing foo in anotherfile), you do not use the pragma. For example, in another file:extern int foo;int i;EEPROM_READ((int)&foo, i);Internal FunctionsThe following functions can be used directly if needed, but the macros describedabove should suffice for most if not all situations. unsigned char EEPROMread(int location)Reads a byte from the specified EEPROM location. int EEPROMwrite(int location, unsigned char byte)Writes byte to the specified EEPROM location. Returns 0 if successful. void EEPROMReadBytes(int location, void *ptr, int size)Reads size bytes starting from the EEPROM location into a buffer pointed toby ptr. void EEPROMWriteBytes(int location, void *ptr, int size)Writes size bytes to EEPROM starting with location with content from a bufferpointed to by ptr.“Real Time” EEPROM AccessThe preceding macros and functions wait until the any pending EEPROM write isfinished before their access. The files rteeprom.h and rteeprom.c in thec:\iccv8avr\examples.avr directory contain source code for routines that readand write to EEPROM that do not wait. This is particularly useful for a real-time137
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