HI-TECH Software Forums: Saving/Retrieving variables in EEPROM

The questions of how to write and read multibyte data objects to and from EEPROM are often asked in these forums. If using the HI-TECH compiler's 'eeprom' qualifier is not suitable for whatever reason, because we know that a data object has an address and a size, a general solution can be crafted similar to that demonstrated in this simple example:

Code:

#include <htc.h>
#include <stddef.h>

struct ee_map_s {
    char  sn[9];    /* Serial number string */
    long  l;
    float f;
    char  c;
};

#define EE_ADDR(member) (offsetof(struct ee_map_s, (member)))

void ee_read(unsigned char ee_addr, void *vp, unsigned char n)
{
    unsigned char *p = vp;

    while (n--) {
        *p++ = eeprom_read(ee_addr++);
    }
}

void ee_write(unsigned char ee_addr, void *vp, unsigned char n)
{
    unsigned char *p = vp;

    while (n--) {
        eeprom_write(ee_addr++, *p++);
    }
}

void main(void)
{
    float f = 1.234;
    long  l = 1234;

    ee_write(EE_ADDR(f), &f, sizeof f);
    ee_write(EE_ADDR(l), &l, sizeof l);

    ee_read(EE_ADDR(f), &f, sizeof f);

    for (;;);
}



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