const int interruptPin=2;
volatile int counter=0;

void ISR_function() {
  counter++;
}
void setup() {
  pinMode(interruptPin,INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(interruptPin),ISR_function,FALLING);
  Serial.begin(9600);
}

void loop() {
  Serial.println("Counter:"+String(counter));
  delay(1000);
  
}