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Version: 6

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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