rpi-gpio

rpi-gpio.js

Control Raspberry Pi GPIO pins with node.js

Setup

See this guide on how to get node.js running on Raspberry Pi.

Usage

After loading the module, initialise a pin by calling setup. Each GPIO pin can be set as either an input or output, which lets you read and write to it respectively. The 'channel' must be specified, to indicate which pin to use. There are two different ways to reference a channel; either using the Raspberry Pi or the BCM naming schema (sadly, neither of which match the physical pins!). This module supports both schemas, with Raspberry Pi being the default. Please see this page for more details.

All functions within this module are asynchronous, so where necessary - for example in reading the value of a pin - a callback must be provided.

Query the value of a pin

var gpio = require('./rpi-gpio');

gpio.setup(7, gpio.DIR_IN);
gpio.read(7, function(value) {
    console.log('The value is ' + value);
});

Listen for changes on a pin

The GPIO module inherits from EventEmitter so any of the EventEmitter functions can be used. The example below shows how to listen for a change in value to a channel.

var gpio = require('./rpi-gpio');

gpio.setup(7, gpio.DIR_IN);
gpio.on('change', function(channel, value) {
	console.log('Channel ' + channel + ' value is now ' + value);
});

Voltage cycling a pin

This example shows how to set up a channel for output mode. After it is set up, it executes a callback which in turn calls another, causing the voltage to alternate up and down three times.

var gpio = require('./rpi-gpio');

var pin   = 7,
    delay = 2000,
    count = 0,
    max   = 3;

gpio.setup(pin, gpio.DIR_OUT, on);

function on() {
    if (count >= max) {
        process.exit(0);
        return;
    }

    setTimeout(function() {
        gpio.write(pin, 1, off);
        count += 1;
    }, delay);
}

function off() {
    setTimeout(function() {
        gpio.write(pin, 0, on);
    }, delay);
}

Querying a pin in BCM mode

This queries the same physical pin as in the previous examples.

var gpio = require('./rpi-gpio');

gpio.setMode(gpio.MODE_BCM);
gpio.setup(4, gpio.DIR_IN);

gpio.read(4, function(value) {
    console.log('The value is ' + value);
});