/* 14 august 2014
 * Oleg Terentiev t.oleg@ymail.com
 *       *------*
 * rst  -|      |-  V+
 *  PB3 -|      |- PB2
 *  PB4 -|      |- PB1 plus 1 minute
 * gnd  -|      |- PB0 plus 5 minutes
 *       *------*
 * PB3, PB4 - both connect to buzzer
 * PB[0,1] - buttons-to-GND
 */

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

FUSES =
    {
        .low  = LFUSE_DEFAULT,
        .high = HFUSE_DEFAULT
    }; /* hfuse=0xff, lfuse=0x6A */

#define T1MIN (10*2)
#define T5MIN (T1MIN*2)

#define NOPRESS 0b11
#define T1PRESS 0b01
#define T5PRESS 0b10
#define ALLPRESS 0b00
#define FALSE 0
#define TRUE (!FALSE)

int16_t time    __attribute__ ((section (".noinit")));

int16_t timestored    __attribute__ ((section (".noinit")));

uint8_t buttons __attribute__ ((section (".noinit")));

void beep_low (uint8_t time);
void beep_mid (uint8_t time);
void beep_high(uint8_t time);

int main (void)
{
uint8_t tmp;
    ACSR |= 1<<ACD; // disable comparator
    cli();
    /* ADCSRA &= ~(1<<ADEN); // default by reset */
    wdt_enable(WDTO_500MS);

    if ( bit_is_set(MCUSR, WDRF)) { // reset by WDT
        // tune I/O
        DDRB =  0b00011100;
        PORTB = 0b00000111;
        asm("nop");

        buttons = PINB & 0x03;
        switch (buttons) {

        case ALLPRESS: // long beep, reset time
            time = -1;
            timestored = -1;
            beep_low(400);
            set_sleep_mode(SLEEP_MODE_PWR_DOWN);
            sleep_enable();
            sleep_cpu();
            break;

        case T1PRESS: // beep, add time, sleep
            timestored = timestored + T1MIN;
            time = timestored;
            beep_mid(100);
            set_sleep_mode(SLEEP_MODE_PWR_DOWN);
            sleep_enable();
            sleep_cpu();
            break;

        case T5PRESS: // beep, add time, sleep
            timestored = timestored + T5MIN;
            time = timestored;
            beep_high(200);
            set_sleep_mode(SLEEP_MODE_PWR_DOWN);
            sleep_enable();
            sleep_cpu();
            break;

        case NOPRESS:
            if (time > 0) {
                time--;
            } else  if ( time == 0 ) { // it is TIME! beep for 1 minute!
                //wdt_disable(); // no working!

                wdt_enable(WDTO_2S);

                tmp = 1; /* seconds */
                while ( tmp > 0 ){
                    PORTB =  (0<<PB2);
                    beep_high(250);
                    _delay_ms(1000);
                    wdt_reset();
                    PORTB =  (1<<PB2);
                    _delay_ms(1500);
                    wdt_reset();
                    PORTB =  (0<<PB2);
                    _delay_ms(1000);
                    PORTB =  (1<<PB2);
                    wdt_reset();
                    beep_low(250);
                    wdt_reset();
                    tmp--;
                }

                time = timestored;
                wdt_enable(WDTO_500MS);
            }
            set_sleep_mode(SLEEP_MODE_PWR_DOWN);
            sleep_enable();
            sleep_cpu();
            break;
        default:
            beep_high(200);
            beep_high(200);
            beep_high(200);
            break;
        }

    } else { // no WDT reset
        // first ON, no calibration
        time = -1;
        timestored = -1;
        set_sleep_mode(SLEEP_MODE_PWR_DOWN);
        sleep_enable();
        sleep_cpu();
    }
}

void beep_low(uint8_t time) /* in milliseconds. 500 Hz */
{
uint8_t tmp;
    tmp = time>>2;
    while ( --tmp > 0){
        PORTB |=  (1<<PB3);
        PORTB &= ~(1<<PB4);
        _delay_us(2000);
        PORTB &= ~(1<<PB3);
        PORTB |=  (1<<PB4);
        _delay_us(2000);
    }
}

void beep_mid(uint8_t time) /* in milliseconds. 1 kHz */
{
uint8_t tmp;
    tmp = time>>1;
    while ( --tmp > 0){
        PORTB |=  (1<<PB3);
        PORTB &= ~(1<<PB4);
        _delay_us(1000);
        PORTB &= ~(1<<PB3);
        PORTB |=  (1<<PB4);
        _delay_us(1000);
    }
}

void beep_high(uint8_t time) /* in milliseconds. 2 kHz */
{
uint8_t tmp;
    tmp = time;
    while ( --tmp > 0){
        PORTB |=  (1<<PB3);
        PORTB &= ~(1<<PB4);
        _delay_us(500);
        PORTB &= ~(1<<PB3);
        PORTB |=  (1<<PB4);
        _delay_us(500);
    }
}