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

#define LED_PIN 5
#define BUTTON_PIN 2

int main ()
{
	DDRC = 1 << LED_PIN;		//PC5 as an output
	DDRD &= ~(1 << BUTTON_PIN);		//PD2 as input
	PORTD = 1 << BUTTON_PIN;		//pull-up activated

	EICRA = (1 << ISC01);		//make INT0 falling edge triggered
	EIMSK = (1 << INT0);	//enable external interrupt 0
	sei ();			//enable interrupts

	while (1)			//wait here
	{
		// No code
	}

	return 0;
	
}

ISR (INT0_vect)			//ISR for external interrupt 0
{
	PORTC ^= (1 << LED_PIN);		//toggle PORTB.5
}