ATMega328P PCINT example

pcint_example.c

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/atomic.h>
#include <util/delay.h>
#include <stdbool.h>

/*
 * A global flag used to communicate between the Interrupt Service Routine
 * and the main program.  It has to be declared volatile or the compiler
 *  might optimize it out.
 */
volatile bool update = false;

/**
 * set update on a high edge
 */
ISR(PCINT0_vect) {
	if (PINB & _BV(PB0)) update = true;
	_delay_ms(500); // Giant friggin' debounce delay
}

int main(void) {

	/**
	 * Using PB1 as LED output
	 */
	DDRB = 0x02;
	PORTB = 0x00;

	/**
	 * Pin Change Interrupt enable on PCINT0 (PB0)
	 */
	PCICR |= _BV(PCIE0);
	PCMSK0 |= _BV(PCINT0);

	// Turn interrupts on.
	sei();

	for(;;) {

		// This turns interrupts off for the code inside it.  Probably
		// not needed here but it's good to know about.
		ATOMIC_BLOCK(ATOMIC_FORCEON) {

			// If the ISR has indicated we need to update the state
			// then run this block.
			if (update) {

				// Toggle the pins on PORTB on/off.
				PORTB ^= 0x02;

				/*
				 * We reset the update flag to false to indicate that
				 * we are done.  This ensures that this block will not
				 * be executed until update is set to true again, which
				 * is only done by the interrupt service routine.
				 */
				update = false;
			}

		}

	}

}

great