#define LED_EXTERN 2

void setup()
{
	pinMode(LED_BUILTIN, OUTPUT);
	pinMode(LED_EXTERN, OUTPUT);
	digitalWrite(LED_EXTERN, LOW);
}

void loop()
{
	digitalWrite(LED_BUILTIN, HIGH);
	digitalWrite(LED_EXTERN, HIGH);
	delay(1000); // Wait for 1000 millisecond(s)
	digitalWrite(LED_BUILTIN, LOW);
	digitalWrite(LED_EXTERN, LOW);
	delay(1000); // Wait for 1000 millisecond(s)
}