rpi_led_web_server.js

onst express = require('express')

var Gpio = require('onoff').Gpio; //include onoff to interact with the GPIO
var LED = new Gpio(21, 'out'); //use GPIO pin 4, and specify that it is output
var blinkInterval

function blinkLED() { //function to start blinking
  if (LED.readSync() === 0) { //check the pin state, if the state is 0 (or off)
    LED.writeSync(1); //set pin state to 1 (turn LED on)
  } else {
    LED.writeSync(0); //set pin state to 0 (turn LED off)
  }
}

function endBlink() { //function to stop blinking
  clearInterval(blinkInterval); // Stop blink intervals
  LED.writeSync(0); // Turn LED off
}

//setTimeout(endBlink, 9000); //stop blinking after 5 seconds

const app = express()

app.get('/', function(req, res){
  res.send("running")
});

app.get('/start', function(req, res){
  blinkInterval = setInterval(blinkLED, 250); //run the blinkLED function every 250ms
  res.send("starting")
});

app.get('/stop', function(req, res){
  endBlink()
  res.send("ended")
});

app.get('/shutdown', function(req, res){
  LED.unexport(); // Unexport GPIO to free resources
  res.send("shutdown")
});


app.listen(8888, '0.0.0.0', _ => { console.log("Listening port8888")})