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

ISR(TIMER0_OVF)
{
    PORTB ^= 1;
}

int main(void)
{
    DDRB |= (1 << PB1); // set PB1 as output
    PORTB |= (1 << PB1); // led on
    TIMSK0 |= (1 << TOIE0); // enable timer overflow interrupt
    TCCR0B |= (1 << CS00) | (1 << CS02);  //set prescaler to 1024

    sei();
    while(1)
    {
    }

    return 0;
}