/*Timer overflow interrupt*/

int main() {
    // Set PB0 as output
    DDRB |= (1 << PB0);

    // Configure Timer1, NORMAL_MODE:
    TCCR1A = 0;
    TCCR1B = (1 << CS12)|(1<<CS00);       // Prescaler = 1024
    TCNT1 = 0;      
    TIMSK1 = (1 << TOIE1);//timer1, overflow interrupt:
    sei();

    while (1) {
        // 
    }
}

ISR(TIMER1_OVF_vect) {
    PORTB ^= (1 << PB0);
}