I started doing the Node.js and RPI tutorial from w3schools.com. I created a server to control an LED with a button on a prototype board or via http but the LED does not light up. It seems to me that there is a problem with the availability of the server to GPIO. I wrote a program that lights the LED without using a server and everything works. Can anyone help?
Node v17.3.0 Npm 8.3.0
https://www.w3schools.com/nodejs/nodejs_raspberrypi_webserver_websocket.asp
Code: test led
var Gpio = require('onoff').Gpio; //include onoff to interact with the GPIO
var LED = new Gpio(27, 'out'); //use GPIO pin 4 as output
var pushButton = new Gpio(17, 'in', 'both'); //use GPIO pin 17 as input, and 'b$
pushButton.watch(function (err, value) { //Watch for hardware interrupts on pus$
if (err) { //if an error
console.error('There was an error', err); //output error message to console
return;
}
LED.writeSync(value); //turn LED on or off depending on the button state (0 o$
});
function unexportOnClose() { //function to run when exiting program
LED.writeSync(0); // Turn LED off
LED.unexport(); // Unexport LED GPIO to free resources
pushButton.unexport(); // Unexport Button GPIO to free resources
};
process.on('SIGINT', unexportOnClose);
index.html
<!DOCTYPE html>
<html>
<body>
<h1>Control LED light</h1>
<p><input type="checkbox" id="light"></p>
<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.0.3/socket.io.js"></script> <!-- include socket.io client side script -->
<script>
var socket = io(); //load socket.io-client and connect to the host that serves the page
window.addEventListener("load", function(){ //when page loads
var lightbox = document.getElementById("light");
lightbox.addEventListener("change", function() { //add event listener for when checkbox changes
socket.emit("light", Number(this.checked)); //send button status to server (as 1 or 0)
});
});
socket.on('light', function (data) { //get button status from client
document.getElementById("light").checked = data; //change checkbox according to push button on Raspberry Pi
socket.emit("light", data); //send push button status to back to server
});
</script>
</body>
</html>
webserver.js
var http = require('http').createServer(handler); //require http server, and create server with function handler()
var fs = require('fs'); //require filesystem module
var io = require('socket.io')(http) //require socket.io module and pass the http object (server)
var Gpio = require('onoff').Gpio; //include onoff to interact with the GPIO
var LED = new Gpio(27, 'out'); //use GPIO pin 4 as output
var pushButton = new Gpio(17, 'in', 'both'); //use GPIO pin 17 as input, and 'both' button presses, and releases should be handled
http.listen(8080); //listen to port 8080
function handler (req, res) { //create server
fs.readFile(__dirname + '/public/index.html', function(err, data) { //read file index.html in public folder
if (err) {
res.writeHead(404, {'Content-Type': 'text/html'}); //display 404 on error
return res.end("404 Not Found");
}
res.writeHead(200, {'Content-Type': 'text/html'}); //write HTML
res.write(data); //write data from index.html
return res.end();
});
}
io.sockets.on('connection', function (socket) {// WebSocket Connection
var lightvalue = 0; //static variable for current status
pushButton.watch(function (err, value) { //Watch for hardware interrupts on pushButton
if (err) { //if an error
console.error('There was an error', err); //output error message to console
return;
}
lightvalue = value;
socket.emit('light', lightvalue); //send button status to client
});
socket.on('light', function(data) { //get light switch status from client
lightvalue = data;
if (lightvalue != LED.readSync()) { //only change LED if status has changed
LED.writeSync(lightvalue); //turn LED on or off
}
});
});
process.on('SIGINT', function () { //on ctrl+c
LED.writeSync(0); // Turn LED off
LED.unexport(); // Unexport LED GPIO to free resources
pushButton.unexport(); // Unexport Button GPIO to free resources
process.exit(); //exit completely
});
