Blink for Node MCU; Blinking the builtin led on GPIO pin 2.

main.cpp

/**
 * Blink for Node MCU
 * also see https://arduino.stackexchange.com/questions/38477/does-the-node-mcu-v3-lolin-not-have-a-builtin-led
 *
 * Turns on an LED on for one second,
 * then off for one second, repeatedly.
 */
#include "Arduino.h"

// On a NodeMCU board the built-in led is on GPIO pin 2
#define LED_BUILTIN 2    

void setup()
{
  Serial.begin(14400);

  // initialize LED digital pin as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop()
{
  Serial.println("Node MCU blink!");
  // turn the LED on (the built-in led on a Node MCU board is active low)
  digitalWrite(LED_BUILTIN, LOW);
  // wait for a second
  delay(1000);
  // turn the LED off (the built-in led on a Node MCU board is active low)
  digitalWrite(LED_BUILTIN, HIGH);

   // wait for a second
  delay(1000);
}

I dont [sic]understand why but you should use GPIO 4 (?)

It's confusing with esp8266 modules because pin numbers on board don't map to GPIO - Pin D4 is actually GPIO2.

Lua must be using board pin numbers.

@flywire check the GPIO code. https://nodemcu.readthedocs.io/en/release/modules/gpio/
there's a little difference between IO index and ESP8266 pins

also, see my code for example :

switch_light = true
mytimer = tmr.create()
gpio.mode(0, gpio.OUTPUT)
gpio.mode(4, gpio.OUTPUT)
mytimer:register(10000, 
                 tmr.ALARM_AUTO, 
                 function(mytimer)
                    if (switch_light) then
                        gpio.write(0, gpio.LOW)
                        gpio.write(4, gpio.HIGH)
                        switch_light = false;
                    else
                        gpio.write(0, gpio.HIGH)
                        gpio.write(4, gpio.LOW)
                        switch_light = true;
                    end
                 end)
mytimer:interval(5000)
mytimer:start()