#define DEBUG 0
bool oldval;
byte genPin = 2;

void setup() {
  if (DEBUG)
    Serial.begin(115200);
  pinMode(genPin, INPUT);
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  bool newval = digitalRead(genPin);
  if (oldval != newval) {
    oldval = newval;
    if (DEBUG)
      Serial.print(newval);
    digitalWrite(LED_BUILTIN, newval);
  }
}