Code:
#include <avr/eeprom.h>

float afloat;
const float float_ee __attribute__ ((section (".eeprom")));

void write_float (const float * pfloat)
{
	eeprom_write_block (pfloat, &float_ee, sizeof (float));
}

void foo ()
{
	write_float (&afloat);
}
Je nach gcc-Version hat's unterschiedliche Makros wie EEMEM.