blink_blink_pullup.ino

const int BUTTON_PIN = 2;

// The setup function runs once when you press reset or power the board
void setup() {
  // Initialize button pin as a pull-up input.
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  // Initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

// The loop function runs over and over again forever
void loop() {
  // Get the digital state from the button pin
  // In pull-up inputs the button logic is inverted (HIGH is not pressed, LOW is pressed)
  int buttonState = digitalRead(BUTTON_PIN);
  // Turn on/off the LED depending on the button state
  if (buttonState == LOW) {
    digitalWrite(LED_BUILTIN, HIGH);
  } else {
    digitalWrite(LED_BUILTIN, LOW);
  }
}