Node.js Raspberry Pi GPIO – LED and Pushbutton

Welcome to The Coding College! In this tutorial, we will combine an LED and a pushbutton to create an interactive project using Node.js and the GPIO pins of a Raspberry Pi. This project introduces the concept of reading input signals (pushbutton) and controlling outputs (LED).

What You’ll Learn

  • How to connect and program a pushbutton to work with GPIO pins.
  • How to use a button press to control an LED.
  • Best practices for Node.js GPIO projects.

Prerequisites

  1. Raspberry Pi with an operating system installed (e.g., Raspberry Pi OS).
  2. Node.js installed on your Raspberry Pi. If not, check out our Node.js Setup Guide.
  3. Basic knowledge of electronics and JavaScript.

Hardware Requirements

  • 1 x Raspberry Pi (any model with GPIO pins).
  • 1 x LED.
  • 1 x Resistor (330Ω recommended for the LED).
  • 1 x Pushbutton.
  • 1 x Resistor (10kΩ for the pushbutton).
  • Jumper wires.
  • Breadboard.

Circuit Setup

LED Connection

  1. Connect the positive leg of the LED to GPIO17 (Pin 11) via a 330Ω resistor.
  2. Connect the negative leg of the LED to GND (Pin 6).

Pushbutton Connection

  1. Connect one terminal of the button to GPIO27 (Pin 13).
  2. Connect the other terminal to GND (Pin 6).
  3. Add a 10kΩ pull-up resistor between GPIO27 and 3.3V to prevent floating signals.

Refer to the GPIO Pinout Diagram for accurate pin connections.

Installing Required Libraries

Install the onoff library for GPIO control:

npm install onoff

Node.js Code

  • Open a terminal and create a new file:
nano led_button.js
  • Add the following code: 
const Gpio = require('onoff').Gpio; // Import onoff library

// Initialize GPIO pins
const led = new Gpio(17, 'out'); // GPIO17 as output for LED
const button = new Gpio(27, 'in', 'both'); // GPIO27 as input for the button

// Button press handler
button.watch((err, value) => {
    if (err) {
        console.error('Error reading button:', err.message);
        return;
    }
    led.writeSync(value); // Turn LED on/off based on button state
    console.log(`Button pressed: ${value}`);
});

// Graceful shutdown
process.on('SIGINT', () => {
    led.writeSync(0); // Turn off LED
    led.unexport();   // Free GPIO resources
    button.unexport();
    console.log('Exiting...');
    process.exit();
});
  • Save and exit: Press Ctrl + O, Enter, and Ctrl + X.

Running the Code

Run the script with sudo for GPIO access:

sudo node led_button.js

Expected Behavior

  • When you press the button, the LED turns on.
  • When you release the button, the LED turns off.

Understanding the Code

  1. GPIO Initialization:
    • led: Configured as an output pin to control the LED.
    • button: Configured as an input pin with the both edge to detect button presses and releases.
  2. button.watch(): Listens for state changes on the button pin (pressed/released) and executes a callback function.
  3. Graceful Shutdown: Ensures that GPIO resources are freed when the program exits.

Enhancements

  1. Toggle LED State: Modify the code so the LED toggles on/off with each button press.
  2. Debouncing: Add software debouncing to prevent false triggers caused by noise.
  3. Multiple Buttons: Control multiple LEDs with different buttons.

Best Practices

  • Pull-Up/Down Resistors: Always use resistors to prevent floating GPIO pins.
  • Proper Shutdown: Free GPIO resources to avoid errors in future executions.
  • Avoid Overloading GPIO Pins: Use external components for high-power devices.

Conclusion

This project demonstrates how to combine inputs and outputs on a Raspberry Pi using Node.js. By integrating a pushbutton and an LED, you’ve taken your first step into creating interactive hardware projects.

For more coding tutorials and hardware projects, visit The Coding College.

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