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

volatile uint8_t button_reset_counter;
volatile uint8_t button_press_count;

// decrease reset_counter until 0
ISR(TIMER2_OVF_vect)
{
    button_reset_counter -= button_reset_counter == 0 ? 0 : 1;
}

// update press_counter on interrupt if reset == 0
ISR(PCINT2_vect){
    if (button_reset_counter == 0){
        button_press_count++;
        button_reset_counter = 20;
        
        if(button_press_count % 2 == 0){
            PORTD &= ~(1<<5);
        }else{
            PORTD |= (1<<5);
        }
    }
}

int main(void) {
    // C7 as input for external interrupt
	DDRC &= ~_BV(DDC7);
	PORTC |= _BV(PORTC7);
    
    // D5 as output
    DDRD = _BV(PD5);
    PORTD = _BV(PD5);


    // TIMER 2 setup
    TCCR2B |= _BV(CS22) | _BV(CS21) | _BV(CS20);
    TIMSK2 |= _BV(TOIE2);


cli();
    // rising edge interrupt on INT2
    EICRA |= _BV(ISC20);
    EIMSK |= _BV(INT2);
    
    // enable external interrupt for pin 23 - PC7
    PCMSK2 |= _BV(PCINT23);
    PCICR   |= _BV(PCIE2);

 sei();

	for(;;){}

	return 0;
}