Re: [avr-libc-dev] Adding (some) Procyon AVRlibfunctionalitytoavr-libc

[Mike Perks]

Eric,
> Unfortunately, this is just a hisorical problem that we have to live with. 
> <snip> We just have to accept this fact and move on the best we can.
>   
Absolutely. At least Atmel seems to be getting better now.
> Would you be willing to describe in more detail about what you do to solve this problem? I think it would be good if we heard from others' experience. 
>   
Ruud and Frédéric described it pretty well. The idea (which is not new) 
is to virtualize a device definition. It will need iterating on and may 
or may be done automatically. I'm not tied to the process of getting 
there but I think virtualization is the only way to do go to make the 
library code easy to write and maintain. It could be something simple 
like this:

   #if defined(__AVR_ATmega128__) || defined(__AVR_ATmega644P__) ||
   defined(__AVR_ATmega328P__)
   #elif defined(__AVR_ATmega644__)
       #define SPCR    SPCR0
       #define SPDR    SPDR0
       #define SPSR    SPSR0
       #define SPE     SPE0
       #define SPIF    SPIF0
       #define MSTR    MSTR0
   #else
       #error "no SPI definition for MCU"
   #endif

where the port names are left asis for most of the devices and only the 
exceptions are dealt with or it could be something a little more complex 
where everything is virtualized:

   #define EEPROM_ADDR_REG   EEAR
   #define EEPROM_DATA_REG   EEDR
   #define EEPROM_CTL_REG    EECR

   #if defined(__AVR_ATmega128__)
       #define EEPROM_MASTER_WRITE  EEMWE
       #define EEPROM_WRITE         EEWE
   #elif defined(__AVR_ATmega644__) || defined(__AVR_ATmega644P__) ||
   defined(__AVR_ATmega328P__)
       #define EEPROM_MASTER_WRITE  EEMPE
       #define EEPROM_WRITE         EEPE
   #else
       #error "no EEPROM definition for MCU"
   #endif

   void eeprom_write_byte(uint16_t address, uint8_t byte)
   {
       /* wait until any other writes are complete */
       loop_until_bit_is_clear(EECR, EEPROM_WRITE);

       /* set up registers for write - master write enable is
   required    */
       EEPROM_ADDR_REG = address;
       EEPROM_DATA_REG = byte;
       EEPROM_CTL_REG |= _BV(EEPROM_MASTER_WRITE) | _BV(EEPROM_WRITE);
   }

Mike Perks
Oak Micros (oakmicros.com)