/*
 * Simple minute timer. Toggles the output LED every minute.
 *
 * Copyright 2007, Jon McClintock.
 *
 * This software is licensed under the CC-GNU GPL. 
 */

#define F_CPU 4915200UL

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <util/delay.h>

#define BUTTON_LINE     2
#define LED_LINE        1
#define OUTPUT_LINE     0

#define TIMER0_TCCR0B 0x05        // ck/1024 = 4800 ticks/sec
#define TIMER0_VALUE  0x56        // 160 ticks to overflow: 30 overflows/sec 

#define TIMER1_TCCR1  0x8F        // ck/16384 = 300 ticks/sec
#define TIMER1_VALUE  0x60        // 150 ticks to overflow:  2 overflows/sec
#define TIMER1_COMP   150         // 150 ticks to overflow:  2 overflows/sec

volatile int count;

int main(void)
{
    // Set the data direction bits on port B
    DDRB  = _BV(LED_LINE) | _BV(OUTPUT_LINE);
    PORTB = _BV(LED_LINE);

    count = 0;

    TCNT1 = 0;
    OCR1A = TIMER1_COMP;
    OCR1C = TIMER1_COMP;
    TIMSK |= _BV(OCIE1A);
    TCCR1 = TIMER1_TCCR1;

    TCNT0  = TIMER0_VALUE;
    TIMSK |= _BV(TOIE0);
    TCCR0B = TIMER0_TCCR0B;

    sei();

    while(1) {
        sleep_mode();
    }

    return 0;
}

ISR(SIG_OVERFLOW0)
{
    TCNT0  = TIMER0_VALUE;
}

ISR(SIG_OUTPUT_COMPARE1A)
{
    count++;
    if ( count == 120 ) {
        PORTB = PORTB ^ _BV(LED_LINE);
        count = 0;
    }
}