Two-way Control with Web and Button

By on January 30, 2017

Web site:

Project Summary:

This is the simplest application enabling the control of a GPIO line through a hardware button.

Full Project:

About the Application

You can expand the functionality of the prev app if you add a hardware button control. Pressing the button will also toggle the state of the GPIO line (LED, relay,…) which is reflected in the LED state displayed in the browser window.

What you need

Besides the hardware used in the prev app you will also need:

GitHub Repository

Name: tps-gpio-tutorials

Repository page:

Clone URL:

Updated At: Mon Oct 10 2016


Node.js Application

Add the following code to server.js:

  • server.js

var button = gpio.init("S11A");

var wasButtonPressed = false;


    // If button is just released...
    if(button.getValue() === 1 && wasButtonPressed === true){
        wasButtonPressed = false;

        // ...reads the LED state...
        var ledState = led.getValue();

        //...inverses it...
        if(ledState === 1){
            ledState = 0
            ledState = 1;


        //...and submits to the web app if connected
        if(clients !== undefined){
            clients.emit('tps:state:changed', ledState);
    }else if(button.getValue() === 0){
        // If button is pressed
        wasButtonPressed = true;




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