eeprom.c

/*
 * Example of how to use the avr-libc EEPROM functions;
 * http://www.nongnu.org/avr-libc/user-manual/group__avr__eeprom.html
 *
*/

#define F_CPU 32000000
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/eeprom.h>
#include <util/delay.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "usart.h"
#include "clock.h"

#define EXPECTED_MAGIC 27
#define STRING_LEN 13

uint8_t eeprom_magic_byte EEMEM = 0;
uint16_t eeprom_big EEMEM = 0;
uint32_t eeprom_bigger EEMEM = 0;
char eeprom_string[STRING_LEN] EEMEM = "";

uint8_t magic_byte = 0;
uint16_t big = 0;
uint32_t bigger = 0;
char string[STRING_LEN] = "";

int main(void) {
  sysclk_init();
  sei();

  // configure the usart1 (attached to USB) for 9600,8,N,1 to
  // show debugging info, see usart examples for explanation
  usart_init(1, 128, 128);
  usart_conf(1, 9600, 8, none, 1, 0, NULL);
  usart_map_stdio(1);
  usart_run(1);

  // wait for EEPROM to be ready
  eeprom_busy_wait();

  // Delay to give time for you to open a terminal and see the output
  _delay_ms(2000);

  // read magic byte from EEPROM to see if we've ever run before
  magic_byte = eeprom_read_byte(&eeprom_magic_byte); // single byte

  if (magic_byte != EXPECTED_MAGIC) {
    puts("No magic found, setting values to defaults.\r");
    puts("Reset your Kakapo to run again.\r");

    magic_byte = EXPECTED_MAGIC;
    big = 12345;
    bigger = 1234567890UL;
    strncpy(string, "Hello World!\0", STRING_LEN);

    // update values to EEPROM
    // the _update_ functions will test whether the existing EEPROM value is the same
    // before writing to save flash wear, there are also _write_ functions which do not
    eeprom_update_byte(&eeprom_magic_byte, magic_byte);
    eeprom_update_word(&eeprom_big, big);
    eeprom_update_dword(&eeprom_bigger, bigger);
    eeprom_update_block((void*)&string, (void*)&eeprom_string, STRING_LEN);
  } else {
    puts("Magic found, reading values from EEPROM;\r");

    big = eeprom_read_word(&eeprom_big); // word
    bigger = eeprom_read_dword(&eeprom_bigger); // long integer
    eeprom_read_block((void*)&string, (void*)&eeprom_string, STRING_LEN); // char array

    _delay_ms(100);
    printf("magic_byte = %u\r\n", magic_byte);
    printf("big = %u\r\n", big);
    printf("bigger = %lu\r\n", bigger);
    printf("string = %s\r\n", string);
  }

  puts("========================\r\n");
  _delay_ms(100); // let the characters go out the usart

  return 0;
}

Makefile

# Where is the toolchain unpacked?
TOOLBASE  ?= /usr/local/share/avr8-gnu-toolchain-linux_x86_64
# What MCU do we have on this board?
MCU       ?= atxmega64d4
# Port that Kakapo popped up on
PORT      ?= /dev/ttyUSB1
# Application name 
APP       = eeprom
# If using libkakapo, uncomment
LIBKAKAPO = -lkakapo
#Tools we'll need
CC        = $(TOOLBASE)/bin/avr-gcc
AVRDUDE   = /usr/bin/avrdude 
OBJCOPY   = $(TOOLBASE)/bin/avr-objcopy
CFLAGS    = -Os --std=c99 -funroll-loops -funsigned-char -funsigned-bitfields -fpack-struct
CFLAGS   += -fshort-enums -Wstrict-prototypes -Wall -mcall-prologues -I. -I../../
CFLAGS   += -mmcu=$(MCU)
INCLUDE   = -L../../
OBJ       = $(patsubst %.c,%.o,$(wildcard *.c))

build: $(APP).hex

eeprom: $(APP).eep
	$(AVRDUDE) -p $(MCU) -c avr109 -P $(PORT) -b 115200 -U eeprom:w:$(APP).eep

program: $(APP).hex
	$(AVRDUDE) -p $(MCU) -c avr109 -P $(PORT) -b 115200 -U flash:w:$(APP).hex -e

$(APP).hex: $(APP).elf
	$(OBJCOPY) -O ihex -R .eeprom $< $@ 

$(APP).eep : $(APP).elf
	$(OBJCOPY) -j .eeprom --set-section-flags=.eeprom="alloc,load" \
	--change-section-lma .eeprom=0 -O ihex $< $@

$(APP).elf: $(OBJ)
	$(CC) $(CFLAGS) $(INCLUDE) $^ -o $@ $(LIBKAKAPO)

%.o: %.c %.h Makefile
	$(CC) -c $(CFLAGS) $< -o $@

clean:
	rm -f $(OBJ) $(APP).hex $(APP).elf $(APP).eep