LED BLINK

// LED Blink — wire a red LED + 220Ω resistor to pin 13 and GND.

const int LED_PIN = 13;

void setup() {
  pinMode(LED_PIN, OUTPUT);
  Serial.begin(9600);
  Serial.println("Blink started!");
}

void loop() {
  digitalWrite(LED_PIN, HIGH);  // turn LED on
  delay(1000);                   // wait 1 second
  digitalWrite(LED_PIN, LOW);   // turn LED off
  delay(1000);                   // wait 1 second
}