Your first Arduino blink

Goal

Blink an LED connected to digital pin 13 (or any free pin with a resistor) every second.

Wiring

Arduino pin 13 ──[220 Ω]── LED (+) ── LED (-) ── GND

Sketch

const int ledPin = 13;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  digitalWrite(ledPin, HIGH);
  delay(1000);
  digitalWrite(ledPin, LOW);
  delay(1000);
}

Upload the sketch

1. Connect the board via USB
2. Select the correct board in Tools → Board
3. Select the port in Tools → Port
4. Click Upload

If upload fails, check the cable and drivers as described in the setup tutorial.

Variant: blink without an external resistor

Some boards have a built-in LED on pin 13. In that case you can skip external components and use the same code.

What you learn

• pinMode() configures input/output
• digitalWrite() sets HIGH/LOW
• delay() blocks execution (advanced tutorials use non-blocking timers)