void loop() {
digitalWrite(LED_BUILTIN, LOW); // Turn the LED on (Note that LOW is the voltage level
// but actually the LED is on; this is because
// it is active low on the ESP-01)
delay(1000); // Wait for a second
digitalWrite(LED_BUILTIN, HIGH); // Turn the LED off by making the voltage HIGH
delay(2000); // Wait for two seconds (to demonstrate the active low LED)
}