void setup() {
  pinMode(D2, OUTPUT);     }
void loop() {
  digitalWrite(D2, LOW);   // Turn the LED on (Note that LOW is the voltage level
  delay(1000);                      // Wait for a second
  digitalWrite(D2, HIGH);  // Turn the LED off by making the voltage HIGH
  delay(2000);                      // Wait for two seconds (to demonstrate the active low LED)
}