#define LED_ONE PORTD ^= (1<<DDD5)
int period; // declare period as global variable

ISR(INT0_vect){ // interrupt service routine for pin change interrupt request 2
  LED_ONE;
  if (!(PIND & (1<<PD2))){         // if pin 2 is LOW, not pressed
	period = TCNT1*.0000625*1024; // convert clock ticks to milliseconds. 1/16M = 0.0000625 (time of a normal tick)
    Serial.println(period);
    
  }else{   
    TCNT1 = 0;                    // reset the timer to 0
    Serial.println("0");
  }
}

int main(void)
{
  // setup code that only runs once
  DDRD |= (1<<DDD5);      //Set PD 5 as output
  DDRD &= (~(1<<DDD2));   // set pin 2 as input
  PORTD |= (1<<PD2) ; //Enables pull-up resistors
  
  //EIMSK 00000001, External Interrupt Request 0 Enable
  EIMSK |= (1<<INT0);
  //EICRA 00000001, Any logical change on INT0 generates an interrupt request.
  EICRA |=  (1<<ISC00); 
  EICRA &=  (~(1<<ISC01)); // Push to lit
  
  sei();               // enable interrupts
  PORTD &= (~(1<<PD5));
  
  TCCR1A = 0b00000000; // set timer 1 to normal mode
  TCCR1B = 0b00000101; // and set prescaler to 1024
  
  Serial.begin(9600);  // initialize serial

  while(1){
    // code that loops forever
      
  } 
}