void setup() {
 Serial.begin(115200);
 pinMode(LED_BUILTIN, OUTPUT);     // Initialize the LED_BUILTIN pin as an output
}

// the loop function runs over and over again forever
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 acive low on the ESP-01)
 Serial.println("LED On!");
 delay(1000);                      // Wait for a second
 digitalWrite(LED_BUILTIN, HIGH);  // Turn the LED off by making the voltage HIGH
 Serial.println("LED Off!");
 delay(2000);                      // Wait for two seconds (to demonstrate the active low LED)
}