main.cpp

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


int main()
{
    PORTD.DIRSET = (1<<PIN0_bm);

    for(;;)
    {
        PORTD.OUTSET = (1<<PIN0_bm);
        _delay_ms(250);

        PORTD.OUTCLR = (1<<PIN0_bm);
        _delay_ms(250);
    }
}