Arduino Buttons

Other Hardware 3rd Party Boards
3

1. This is the picture (Fig-1) of my NodeMCU (ESP8266-12E) with two onboard Blue LEDs which I have marked as Led1 and Led2.

nodeMCUPicLed
Figure-1:

2. Led1 is connected internally with GPIO-4/D4, and it blinks during sketch uploading. The Led1 also responds to blink program of Step-4.

3. Led2 is connected internally with GPIO-16/D0. The Led2 also responds to blink program of Step-4. Caution: Do not connect any circuit with GPIO-16/D0 during sketch uploading as it prevents the sketch from uploading!

4. Tset Sketch to blink Led1/Led2.

#define ledpin 16  //or 4

void setup()                                                                                                                  
{
  pinMode(ledpin, OUTPUT);
  Serial.begin(115200);
}

void loop()
{
  digitalWrite(ledpin, HIGH);
  delay(1000);
  digitalWrite(ledpin, LOW);
  delay(1000);
}