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Re: [avr-gcc-list] Macro to read /write long to eeprom

From: Royce Pereira
Subject: Re: [avr-gcc-list] Macro to read /write long to eeprom
Date: Wed, 10 Aug 2005 01:06:23 +0530
User-agent: Opera M2/8.02 (Win32, build 7680)


On Wed, 10 Aug 2005 00:41:20 +0530, Dave Hansen <address@hidden> wrote:

From: "Royce Pereira" <address@hidden>

Is there a macro to read or write a long word (32 bits) to eeprom?
For the last hour I've been trying to write one unsuccessfully.

Not directly, but you can do something like

   #include <avr/eeprom.h>

   inline void eeprom_write_long(long *dest, long val)
      eeprom_write_block(&val, dest, sizeof(val));

   inline long eeprom_read_long(long *src)
      long retval;

      eeprom_read_block(&retval, src, sizeof(retval));
      return retval;

WARNING: untested code, but it should be close. Note that (IMHO) eeprom_write_block's parameters are backwards, but that's what's been provided.
Actually I managed something with the existing word rd/wr macros. But I've yet to see how the code size compares with the read/write block method..

uint32_t eeprom_read_long( uint16_t *loc)
            uint32_t num;
            num = eeprom_read_word((uint16_t *)(loc+1));
            num <<=16;
            num |= eeprom_read_word((uint16_t *)loc);
            return num;
void eeprom_write_long(uint16_t *loc, uint32_t val)
            eeprom_write_word(loc, val & 0xffff);
            eeprom_write_word(++loc, val >>16);


Thanks, all,

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