Zanim kupisz Atmegę

/*
 * randomrussian.c
 *
 * Created: 05.07.2017 17:50:26
 * Author : hkk
 */

#include <avr/io.h>

#define LED (1<<PB5)
#define INP (1<<PD0)

int main(void) {

    DDRB |= LED;
    DDRD &= ~INP;

    while(1) {
        if (PIND & INP) PORTB |= LED;
        else PORTB &= ~LED;
    }
}

/* http://russianrandom.blox.pl/html */