#define LED_PIN 4  // GPIO 4 connected to external LED

void setup() {
  pinMode(LED_PIN, OUTPUT);  // Set GPIO 4 as output
}

void loop() {
  digitalWrite(LED_PIN, HIGH);  // Turn the LED ON
  delay(1000);                  // Wait 1 second
  digitalWrite(LED_PIN, LOW);   // Turn the LED OFF
  delay(1000);                  // Wait 1 second
}
