#include <avr/io.h>
#include <avr/sleep.h>
#include <util/atomic.h>

static uint32_t seconds;

uint32_t getSeconds() {
    ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
        return seconds;
    }
}
// EMPTY_INTERRUPT(TIMER2_OVF_vect);
ISR(TIMER2_OVF_vect) {
    seconds++;
}

int main() {
    set_sleep_mode(SLEEP_MODE_PWR_SAVE);
    // set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    //  async
    TIMSK2 = 0;
    ASSR = _BV(AS2);

    // Prescaler 1024
    // TCCR2B = _BV(CS22) | _BV(CS21) | _BV(CS20);
    // Prescaler 128
    TCCR2B = _BV(CS22) | _BV(CS20);

    TCCR2A = 0;

    // Wait until OSC is running
    while (ASSR != _BV(AS2)) {
    }

    // clear interrupt flags
    TIFR2 = (1 << TOV2);

    // Enable only Overflow
    TIMSK2 = _BV(TOIE2);

    DDRB |= _BV(PB5);
    sei();
    while (true) {
        sleep_mode();
        PINB |= _BV(PB5);
    }
    return 0;
}