Here's a beginner-friendly intro to using GPIO pins on a Raspberry Pi with Node.js — perfect if you want to control hardware like LEDs, buttons, sensors, and more using JavaScript! 🚀

🧠 What is GPIO?

GPIO stands for General Purpose Input/Output.
Raspberry Pi’s GPIO pins allow you to send output (e.g. turn on an LED) or read input (e.g. check if a button is pressed).

✅ Node.js + GPIO = JavaScript Hardware Control

To interact with GPIO pins in Node.js, the most popular libraries are:

• onoff – simple GPIO read/write

• rpi-gpio – similar, slightly older

• pigpio – for precise PWM, servo, ultrasonic sensors, etc.

⚙️ Basic Circuit Example

Let’s start with a basic setup:

Hardware:

• LED connected to GPIO17 (Pin 11)

• 330Ω resistor

• GND (Pin 6)

📦 Step 1: Install Dependencies

bash
npm init -ynpm install onoff

💡 Step 2: Blink an LED (GPIO Output)

js
const Gpio = require('onoff').Gpio;const led = new Gpio(17, 'out'); // GPIO17setInterval(() => {  led.writeSync(led.readSync() ^ 1); // Toggle LED}, 500);// Cleanup on Ctrl+Cprocess.on('SIGINT', () => {  led.writeSync(0);  led.unexport();  console.log('LED turned off');  process.exit();});

Run with:

bash
sudo node led-blink.js

🔘 Step 3: Read a Button (GPIO Input)

Wire a push button to GPIO27 (Pin 13) and GND (Pin 6).

js
// button.jsconst Gpio = require('onoff').Gpio;const button = new Gpio(27, 'in', 'both');button.watch((err, value) => {  if (err) throw err;  console.log('Button state:', value);});process.on('SIGINT', () => {  button.unexport();  console.log('Button program stopped');  process.exit();});

🧠 GPIO Modes

• 'out' → output (LEDs, relays, etc.)

• 'in' → input (buttons, switches, etc.)

• 'both' → detect rising and falling edges (good for buttons)

🚨 Safety Tips

• Always use resistors to limit current.

• Don’t connect high-voltage devices directly.

• GPIO pins are 3.3V — sending 5V can damage your Pi.

🌟 What’s Next?

You can build cool stuff like:

• LED chasers / flowing lights

• Motion sensors

• Web-controlled relays

• Real-time dashboards with Express or Socket.io