Hi Eric! I'm not sure about what you mean by memory-mapped, but it's working just like eeprom variables using avr-libc. In this case I've created specific functions to read and write from external eeprom that use the variable address given by the compiler/linker. This address is the external eeprom address. I used 0x400000 as the start address just to not collide with the 0x800000 from internal eeprom.
Roy 2008/12/17 Weddington, Eric <ewedding...@cso.atmel.com>: > Hi Roy, > > You'll have to use a custom linker file. Start with the standard linker file > (*.x) and modify it to add your section for the external eeprom. See the GNU > ld user manual (part of GNU Binutils) for more information on the linker file > format. In your .eeprom_ext section in the linker file, you'll have a line > that will use wildcards to match all of the subsections, like so: > *(.eeprom_ext*) > The first * matches all files. The second * matches all endings after the > ".eeprom_ext", and it is this that will pull in all those sub-sections. > > Do you have your external EEPROM memory-mapped? > > Eric > >> -----Original Message----- >> From: >> avr-libc-dev-bounces+eweddington=cso.atmel....@nongnu.org >> [mailto:avr-libc-dev-bounces+eweddington=cso.atmel....@nongnu. >> org] On Behalf Of Roy Conrad >> Sent: Wednesday, December 17, 2008 11:41 AM >> To: avr-libc-dev@nongnu.org >> Subject: [avr-libc-dev] Problem using section attribute >> >> Hi! >> >> I'm using the section attribute on variables that are supposed to be >> stored in an external eeprom: >> >> #define EEPROMEXT __attribute__((section(".eeprom_ext"))) >> >> uint8_t EEPROMEXT outputs; >> >> In the Makefile I set the starting address for that section: >> >> LDFLAGS += -Wl,--section-start=.eeprom_ext=0x400000 >> >> Until now everithing is working ok. >> >> The problem arises when I define another variable in another >> unit (*.c file): >> >> uint8_t EEPROMEXT inputs; >> >> I have a *.map file with: >> >> .eeprom_ext 0x0000000000400000 0x166f >> .eeprom_ext 0x0000000000400000 0x166f main.o >> 0x0000000000400000 outputs >> >> .eeprom_ext.1 0x00000000008005fc 0x19c8 load address >> 0x000000000001e1f2 >> .eeprom_ext 0x00000000008005fc 0x19c8 sec.o >> 0x00000000008005fc inputs >> >> If I change units order the Makefile (sec.o main.o instead of main.o >> sec.o), inputs is assigned to .eeprom_ext and outputs to eeprom_ext.1. >> >> The address of .eeprom_ext.1 (0x00000000008005fc) is the same as the >> beginning of .bss section. >> >> I assume this is a linker issue. >> >> What should I change so that outputs and inputs variables stay in the >> same .eeprom_ext section, but being in different units (*.c files)? >> >> Thanks. >> >> Roy >> >> >> _______________________________________________ >> AVR-libc-dev mailing list >> AVR-libc-dev@nongnu.org >> http://lists.nongnu.org/mailman/listinfo/avr-libc-dev >> > _______________________________________________ AVR-libc-dev mailing list AVR-libc-dev@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-libc-dev
