int ledPin = D2;

void setup()
{
 // We want to tell the Argon that we'll use
 // D2 as an output pin.    
    pinMode( ledPin, OUTPUT );
}

void loop() {
  // First... On
  digitalWrite(ledPin, HIGH);   // Turn ON the LED pins
  delay(1000);               // Wait for 1000mS = 1 second

  // Now... Off
  digitalWrite(ledPin, LOW);   // Turn OFF the LED pins
  delay(1000);               // Wait for 1000mS = 1 second
  // rinse + repeat

}