Hi Raphael!
Accesing via generic pointers would be amazing. If you had time, I would
love to see it implemeted.
The __eeprom keyword can wait, hehe!
Maybe I could help you with implementation of eeprom reads and writes. I
could start with device/lib/pic16/libsdcc/gptr/*.c which I think that I
understand, and send the patch to you so you can check if it's ok. I don't
know what to do in src/pic16/gen.c, though.
After reading the code in the repository, I think that code memory reads
via pointers are implemented but code memory writes are not, right?
Thank you very much.
On Sat, Apr 14, 2012 at 11:59 PM, Raphael Neider <rnei...@web.de> wrote:
> Hi,
>
> > I had always used a library with the following functions to read/write
> > eeprom memory:
> >
> > uint8_t eeprom_read(uint8_t address);
> > void eeprom_write(uint8_t address, uint8_t value);
> > uint8_t eeprom_write_and_verify(uint8_t address, uint8_t value);
> >
> > Reading the SDCC manual again, I started thinking that it may also be
> done
> > using pointers without needing this functions. Can it be done? If yes,
> how?
>
> It is planned (but obviously not yet implemented) to allow access to
> EEPROM via the generic pointer mechanism. EEPROM would be mapped into
> the generic address space at 0x40.0000..0x7F.FFFF; 0x00.0000-0x3F.FFFF
> is code/program memory, 0x40.0000-0x7F.FFFF is supposed to be EEPROM,
> and 0x80.0000-0xFF.FFFF is data memory. Once this feature is
> implemented, access to EEPROM is as simple as
>
> uint8_t __at(0x400000) eeprom_start;
> uint8_t * const eeprom = &eeprom_start;
>
> uint8_t eeprom_read(uint8_t address) {
> return eeprom[address];
> }
>
> void eeprom_write(uint8_t address, uint8_t value) {
> eeprom[address] = value;
> }
>
> uint8_t eeprom_write_and_verify(uint8_t address, uint8_t value) {
> volatile uint8_t *ee = (volatile uint8_t *)eeprom;
> ee[value] = value;
> return (ee[value] ^ value); /* or whatever is desired for verification */
> }
>
> If desired, I can try to implement this. Basically, adjustments need
> to be done in two places: device/lib/pic16/libsdcc/gptr/*.c must
> certainly be adjusted to actually implement EEPROM access, and
> src/pic16/gen.c must probably be adjusted to generate EEPROM access on
> certain pointer dereferences. One might want to introduce/enable some
> keyword (__eeprom?) to allocate objects in EEPROM space like
> __eeprom uint8_t in_eeprom; /* initialisers will be more difficult */
> but that may not be too urgent.
>
> Best regards
> Raphael
>
>
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