/* Program 6-2: Counting Interrupts while the main program toggles an LED continuously
 * SW1 is connected to pin 3 (interrupt 2) of Arduino
* count up every time SW1 interrupts the main program 
*/
const byte SW1 = 3;   //SW1 is connected to interrupt pin#3
volatile byte count = LOW;

void setup() {
  pinMode(13, OUTPUT);    /* set pin 13 as output */
  pinMode(SW1, INPUT);  //pin as input
  Serial.begin(9600); 
  attachInterrupt(digitalPinToInterrupt(SW1), myISR, RISING);
}
//main loop toggles LED continuously  
void loop() {
    digitalWrite(13,HIGH);  /* turn on the LED */
    delay(500);             /* delay 500 ms */
    digitalWrite(13,LOW);   /* turn off the LED */
    delay(500);             /* delay 500 ms */
}

//Interrupt Service Routine(ISR)
//Count up every time SW1 interrupts the main program
void myISR() {
  count++;              //count up upon pressing SW1
  Serial.println(count);     // Display count on Serial Monitor      
}