Arduino communication with nodeJs

Way to show how Node.Js can communicate with Arduino Uno.

Node Js communication with Arduino via serialport

Node js code

Sample to start this topic is Node.js server communicating with Arduino via serialport.

npm install express --save
npm install serialport --save

Sample app.js:

const express = require('express');
const app = express();
var SerialPort = require("serialport");

var port = 3000;

var arduinoCOMPort = "COM3";

var arduinoSerialPort = new SerialPort(arduinoCOMPort, {  
 baudrate: 9600
});

arduinoSerialPort.on('open',function() {
  console.log('Serial Port ' + arduinoCOMPort + ' is opened.');
});

app.get('/', function (req, res) {

    return res.send('Working');
 
})

app.get('/:action', function (req, res) {
    
   var action = req.params.action || req.param('action');
    
    if(action == 'led'){
        arduinoSerialPort.write("w");
        return res.send('Led light is on!');
    } 
    if(action == 'off') {
        arduinoSerialPort.write("t");
        return res.send("Led light is off!");
    }
    
    return res.send('Action: ' + action);
 
});

app.listen(port, function () {
  console.log('Example app listening on port http://0.0.0.0:' + port + '!');
});

Starting sample express server:

node app.js

Arduino code

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.

  Serial.begin(9600); // Begen listening on port 9600 for serial
  
  pinMode(LED_BUILTIN, OUTPUT);

  digitalWrite(LED_BUILTIN, LOW);
}

// the loop function runs over and over again forever
void loop() {

   if(Serial.available() > 0) // Read from serial port
    {
      char ReaderFromNode; // Store current character
      ReaderFromNode = (char) Serial.read();
      convertToState(ReaderFromNode); // Convert character to state  
    }
  delay(1000); 
}

void convertToState(char chr) {
  if(chr=='o'){
    digitalWrite(LED_BUILTIN, HIGH);
    delay(100); 
  }
  if(chr=='f'){
    digitalWrite(LED_BUILTIN, LOW);
    delay(100); 
  }
}

Starting Up

1. Connect the arduino to your machine.
2. Start the server

Control the build in led via node js express server.

To turn on the led:

http://0.0.0.0:3000/led

To turn off the led:

http://0.0.0.0:3000/off