/* Program 6-1: Interrupts on an Arduino
 * 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 of pin#3
volatile byte count = LOW;

void setup() {
  pinMode(SW1, INPUT);  //pin as input
  Serial.begin(9600); 
  attachInterrupt(digitalPinToInterrupt(SW1), myISR, RISING);
}

void loop() {
   
}

//Interrupt Service Routine
//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      
}