Wiring
Check pinout, power supply, common GND and voltage levels before connecting the module.
Full code
const int ledPin = 13;
unsigned long previousMillis = 0;
const unsigned long interval = 1000;
bool ledState = LOW;
void setup() {
pinMode(ledPin, OUTPUT);
}
void loop() {
unsigned long now = millis();
if (now - previousMillis >= interval) {
previousMillis = now;
ledState = !ledState;
digitalWrite(ledPin, ledState);
}
}How it works
This lesson matches the page title and gives a clean starting point for this exact example.
Common mistakes
Check board selection, wiring, libraries, power supply and serial monitor baud rate.