/***************************************************************************
 *   nvram parameter read/write                                            *
 *                                                                         *
 *   Copyright (C) 2011 - 2012 by Olaf Rempel                              *
 *   razzor AT kopf MINUS tisch DOT de                                     *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; version 2 of the License,               *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
#include <avr/eeprom.h>

#include <util/crc16.h>

#include "rgb16mpm.h"

static uint16_t nvram_write_pos;
struct _nvdata nvram_data;
static struct _nvdata nvram_eeprom EEMEM = NVRAM_DEFAULTS;
static struct _nvdata nvram_defaults PROGMEM = NVRAM_DEFAULTS;

/* store nvram data to eeprom */
ISR(EE_RDY_vect) {
    EECR &= ~(1<<EERIE);
    sei();

    if (nvram_write_pos < sizeof(struct _nvdata)) {
        /* not a function: shorter IRQ entry (fast IRQ re-enable) */
        EEARL = (nvram_write_pos & 0xFF);
        EEARH = (nvram_write_pos >> 8) & 0xFF;
        EEDR  = ((uint8_t *)&nvram_data)[nvram_write_pos++];
        cli();
        EECR |= (1<<EEMWE);
        EECR |= (1<<EEWE);
        sei();
        EECR |= (1<<EERIE);
    }
}

/* create crc and store nvram data to eeprom */
void eeprom_write(void)
{
    uint8_t i;
    uint16_t crc = 0x0000;
    uint8_t *tmp = (uint8_t *)&nvram_data;

    nvram_data.nvram_size = sizeof(struct _nvdata);

    for (i = 0; i < sizeof(struct _nvdata) -2; i++) {
        crc = _crc_ccitt_update(crc, *tmp++);
    }

    nvram_data.nvram_crc = crc;
    nvram_write_pos      = 0;

    EEARL = (nvram_write_pos & 0xFF);
    EEARH = (nvram_write_pos >> 8) & 0xFF;
    EEDR  = ((uint8_t *)&nvram_data)[nvram_write_pos++];
    cli();
    EECR |= (1<<EEMWE);
    EECR |= (1<<EEWE);
    sei();
    EECR |= (1<<EERIE);
}

/* read nvram from eeprom and check crc */
void eeprom_read(void)
{
    uint8_t i;
    uint16_t crc = 0x0000;
    uint8_t *tmp = (uint8_t *)&nvram_data;

    eeprom_read_block(&nvram_data, &nvram_eeprom, sizeof(struct _nvdata));

    for (i = 0; i < sizeof(struct _nvdata); i++) {
        crc = _crc_ccitt_update(crc, *tmp++);
    }

    /* if nvram content is invalid, overwrite with defaults */
    if ((nvram_data.nvram_size != sizeof(struct _nvdata)) || (crc != 0x0000)) {
        memcpy_P(&nvram_data, &nvram_defaults, sizeof(struct _nvdata));
        eeprom_write();
    }
}