#define LED_BUILTIN 2 // define the GPIO 2 as LED_BUILTIN
void setup() {
pinMode(LED_BUILTIN, OUTPUT); // initialize GPIO pin 2 LED_BUILTIN as an output.
}
void loop() {
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on
delay(100); // wait for a second
digitalWrite(LED_BUILTIN, LOW); // turn the LED off
delay(100); // wait for a second
}