Controlling LED with firmdata

Aim

Caution: Methods described in this section only applies to LinkIt smart 7688 Duo. LinkIt smart 7688 is not allowed to use.

Preface: LinkIt Smart 7688 has two chips, one is the MPU (7688) capable to run linux; the other one is the Arduino MCU. For Node.js developers, it is desired to run Node.js app on the MPU. Arduino MCU is directly controlled by this app. As as result, we are going to use Node.js firmdata package to communciate between MPU and Arduino MCU.

Prerequisites

Control LED requires

• LED x 1
• Resistor x 1
• A few DuPont wires

Please install circuit first:

Steps

MCU side

• Open your Arduino IDE.
• Copy contents in this URL: https://gist.github.com/edgarsilva/e73c15a019396d6aaef2
• Burn into Arduino

MPU side

• ssh into your LinkIt smart 7688 Duo.

• Generate a folder named app.

        > mkdir app && cd app
  

• Install firmata

  Notice! Because there are some compilation procedures during npm install, which will cause too long running time on LinkIt smart 7688 Duo, it is not recommended to use npm install method for firmata package.

  So we will first generate a testfirmdata folder on host side (your computer).

        mkdir testfirmata && cd testfirmata
  

  Then execute:

        npm init
  

  Install firmata:

        npm install firmata --save
  

  Because of a dependent package inside firmata, it will generate the compilation spec file according on your computer's spec during installation on your computer. However, the MIPS compilation spec file has already been installed on LinkIt Smart 7688 Duo, so we must erase this package manually:

        rm -rf ./node_modules/firmata/node_modules/serialport/
  

  Package firmata folder:

        tar -cvf ./firmata.tar ./node_modules/firmata
  

  Transfer the tar file into your LinkIt smart 7688 Duo board.

        scp ./firmata.tar [email protected]:/root/app/node_modules/
  

  (If something like can not find node_modules folder appears, please return to /app folder on your board and make a folder named node_modules: mkdir node_modules)

• Go back to your board's terminal.

• Back to /testfirmata:
• Enter node_modules folder: cd node_modules
• Unpack the tar file: tar -xvf ./firmata
• Back to /testfirmata：cd ..

• generate a app.js file:

        vim app.js
  

• Paste the following content:

console.log('WWW blink start ...');

var ledPin = 13;
var firmata = require('firmata');

var board = new firmata.Board("/dev/ttyS0", function(err) {
    if (err) {
        console.log(err);
        board.reset();
        return;
    }

    console.log('connected...');
    console.log('board.firmware: ', board.firmware);

    board.pinMode(ledPin, board.MODES.OUTPUT);

    var url = require('url');
    var http = require('http');

    http.createServer(function(request, response) {
        var params = url.parse(request.url, true).query;
        try {
            if (params.value.toLowerCase() == 'high') {
                board.digitalWrite(ledPin, board.HIGH);
            } else if (params.value.toLowerCase() == 'low'){
                board.digitalWrite(ledPin, board.LOW);
            }
        } catch(e) {

        }
        response.writeHead(200);
        response.write("The value written was: " + params.value);
        response.end();
    }.bind(this)).listen(8080);

    console.log('Listening on port 8080 ...');
});

• Execute app.js.

        node app
  

• Press ESC, then enter wq! to save and leave.

• Open your browser:

  • http://mylinkit.local?value=high (led-on)
  • http://mylinkit.local?value=low (led-off)