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Version: BSP 6.x.y

Node.js and Node-RED on Linux

Introduction

info

For Torizon users, you may want to check Node.js on Torizon and Node-RED on Torizon.

This Article explains how to install Node.js, npm, and Node-RED to a Linux Image, then Blink a LED using the GPIOs.

Node.js Setup

While Building a Linux Image

Node.js can be added to an OpenEmbedded Linux build for inclusion into the image's rootfs. After establishing the image build configuration, additionally, append the following line to the oe-core/build/conf/local.conf file:

local.conf
CORE_IMAGE_EXTRA_INSTALL += "nodejs"

You may also include NPM:

local.conf
CORE_IMAGE_EXTRA_INSTALL += "nodejs nodejs-npm"

You may find the page TipsAndTricks/NPM from the Yocto Project Wiki useful.

Performance & Suitability

Since Node.js is a server-side interpreter for the Javascript language, it is expected to perform slower than a compiled language such as C/C++. However, because of its event-driven paradigm, it may well suit web I/O intensive tasks, such as implementing a web server.

Still, Node.js can also be viable for tasks that aren't very CPU intensive, which may be a fast development solution since Javascript is a high level programming language.

Node-RED Setup

Installing Node-RED

Install Node-RED with the following command:

# npm install -g node-red --unsafe-perm

Running Node-RED

Start Node-RED by running the following command on the terminal:

# node-red

Examples

GPIO - Blinking LED


var fs = require('fs');

var export_path = '/sys/class/gpio/export';
var blink_period = 500; //in milisseconds

var gpio_53 = new NewGpio(53, 'out', 0);
function NewGpio (id, direction, state) {
this.number = id;
this.path = '/sys/class/gpio/gpio' + id + '/';
this.direction = direction;
this.value = state;
}

function export_pin (pin, callback){
//callback has error as argument, or null if no error
console.log('first');
console.log(pin);
fs.stat(pin.path, function(err, stats) {
console.log('second_not_exp');
console.log(pin);
if (!err) callback(null, pin);//if gpio already exported
else{//if gpio not exported yet
//export it
fs.writeFile(export_path, pin.number, function (err) {
console.log('second_exp');
console.log(pin);
if (err) callback(err, null);
else callback(null, pin);
});
}
});
}

function configure_pin(pin, callback){
//callback has error as argument, or null if no error
console.log('third');
console.log(pin);
fs.writeFile(pin.path + 'direction', pin.direction, function (err) {
if (err) callback(err, null);
else callback(null, pin);
});
}

function blink(pin){
console.log('fourth');
console.log(pin);
fs.writeFile(pin.path + 'value', pin.value, function (err) {
if (err) throw err;
pin.value ? pin.value = 0 : pin.value = 1;
});
}

//here the code execution starts
export_pin( gpio_53, function (err, pin) {
if (err) throw err;
configure_pin(pin, function (err, pin) {
if (err) throw err;
setInterval(function(){
blink(pin);
}, blink_period);//call blink periodically
});
});



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