@red-mobile/cordova-plugin-usb-serial

v2.0.0

Published

6 months ago

Cordova plugin to communicate with the android USB serial port

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okhiroyuki

serial arduino ecosystem:cordova cordova-android

cordova-plugin-usb-serial

Want a module for your Arduino board that provides:

Power
High-res Touch Interface
Storage
AND connectivity? (WiFi + 3G + Bluetooth)

Hey, why not just use your Android phone/tablet?

This Cordova/Phonegap plugin allows two-way serial communication using USB On-The-Go (OTG) from your Android device to your Arduino board or other USB-powered serial IO device.

And that means that ability to give your Arduino project a mobile app (web-view) interface as well as powering it using the rechargeable battery on your phone!

Install it

From the root folder of your cordova project, run :

cordova plugin add @red-mobile/cordova-plugin-usb-serial

unisntall it

cordova plugin remove @red-mobile/cordova-plugin-usb-serial

How to use it

Your first need to understand how to create and upload a simple Cordova Project. Here is some info on how to get started with Cordova on Android, and here is a simple Cordova plugin you can use to get familiar with the plugin system.

The plugin API for this behaves as follows:

Because you're polite, first request the permission to use the serial port to the system:

serial.requestPermission(function success(), function error());

You can now open the serial port:

serial.open(opts, function success(), function error());

opts is a JSON object with the following properties:

baudRate: defaults to 9600
dataBits: defaults to 8
stopBits: defaults to 1
parity: defaults to 0
dtr: defaults to false (it may be needed to be true for some arduino)
rts: defaults to false (it may be needed to be true for some modules, including the monkeyboard dab module)
sleepOnPause: defaults to true. If false, the the OTG port will remain open when the app goes to the background (or the screen turns off). Otherwise, the port with automatically close, and resume once the app is brought back to foreground.

You're now able to read and write:

serial.write(data, function success(), function error());
serial.read(function success(buffer), function error());

data is the string representation to be written to the serial port. buffer is a JavaScript ArrayBuffer containing the data that was just read.

Apart from using serial.write, you can also use serial.writeHex to have an easy way to work with RS232 protocol driven hardware from your javascript by using hex-strings.

In a nutshell, serial.writeHex('ff') would write just a single byte where serial.write('ff') would let java write 2 bytes to the serial port.

Apart from that, serial.writeHex works the same way as serial.write does.

Register a callback that will be invoked when the driver reads incoming data from your serial device. The success callback function will recieve an ArrayBuffer filled with the data read from serial:

serial.registerReadCallback(
  function success(data) {
    var view = new Uint8Array(data);
    console.log(view);
  },
  function error() {
    new Error("Failed to register read callback");
  },
);

And finally close the port:

serial.close(function success(), function error())

A Simple Example

A callback-ish example.

var errorCallback = function (message) {
  alert("Error: " + message);
};

serial.requestPermission(function (successMessage) {
  serial.open(
    { baudRate: 9600 },
    function (successMessage) {
      serial.write(
        "1",
        function (successMessage) {
          alert(successMessage);
        },
        errorCallback,
      );
    },
    errorCallback,
  );
}, errorCallback);

A Complete Example

Here is your index.html:

<!doctype html>
<html>
  <head>
    <meta
      http-equiv="Content-Security-Policy"
      content="default-src 'self' data: gap: https://ssl.gstatic.com 'unsafe-eval'; style-src 'self' 'unsafe-inline'; media-src *"
    />
    <meta name="format-detection" content="telephone=no" />
    <meta name="msapplication-tap-highlight" content="no" />
    <meta
      name="viewport"
      content="user-scalable=no, initial-scale=1, maximum-scale=1, minimum-scale=1, width=device-width"
    />
    <link rel="stylesheet" type="text/css" href="css/index.css" />
    <title>Hello World</title>
  </head>
  <body>
    <div class="app">
      <h1>Potentiometer value</h1>
      <p>Value <span id="pot">...</span></p>
      <p id="delta">...</p>
      <button id="on">On</button>
      <button id="off">Off</button>
    </div>
    <script type="text/javascript" src="cordova.js"></script>
    <script type="text/javascript" src="js/index.js"></script>
  </body>
</html>

Here is the index.js file:

var app = {
  initialize: function () {
    document.addEventListener("deviceready", this.onDeviceReady, false);
  },
  onDeviceReady: function () {
    var potText = document.getElementById("pot");
    var delta = document.getElementById("delta");
    var on = document.getElementById("on");
    var off = document.getElementById("off");
    var open = false;
    var str = "";
    var lastRead = new Date();

    var errorCallback = function (message) {
      alert("Error: " + message);
    };
    // request permission first
    serial.requestPermission(
      // if user grants permission
      function (successMessage) {
        // open serial port
        serial.open(
          { baudRate: 9600 },
          // if port is succesfuly opened
          function (successMessage) {
            open = true;
            // register the read callback
            serial.registerReadCallback(
              function success(data) {
                // decode the received message
                var view = new Uint8Array(data);
                if (view.length >= 1) {
                  for (var i = 0; i < view.length; i++) {
                    // if we received a \n, the message is complete, display it
                    if (view[i] == 13) {
                      // check if the read rate correspond to the arduino serial print rate
                      var now = new Date();
                      delta.innerText = now - lastRead;
                      lastRead = now;
                      // display the message
                      var value = parseInt(str);
                      pot.innerText = value;
                      str = "";
                    }
                    // if not, concatenate with the begening of the message
                    else {
                      var temp_str = String.fromCharCode(view[i]);
                      var str_esc = escape(temp_str);
                      str += unescape(str_esc);
                    }
                  }
                }
              },
              // error attaching the callback
              errorCallback,
            );
          },
          // error opening the port
          errorCallback,
        );
      },
      // user does not grant permission
      errorCallback,
    );

    on.onclick = function () {
      console.log("click");
      if (open) serial.write("1");
    };
    off.onclick = function () {
      if (open) serial.write("0");
    };
  },
};

app.initialize();

And here is your Arduino project .ino file, with a potentiometer on A0 and a led on 13:

#define POT A0
#define LED 13

unsigned long previousMillis;
int interval = 50;

void setup() {
    Serial.begin(9600);
    pinMode(POT, INPUT);
    pinMode(LED, OUTPUT);
}

void loop() {
    if (Serial.available() > 0) {
        char i = Serial.read();
        switch (i) {
            case '0':
                digitalWrite(LED, LOW);
                break;
            case '1':
                digitalWrite(LED, HIGH);
                break;
        }
    }
    if (millis() - previousMillis >= interval) {
        previousMillis = millis();
        int value = analogRead(POT);
        Serial.println(value);
    }
}

Your Device is not (yet) known?

Thanks to usb-serial-for-android library, you can communicate with CDC, FTDI, Arduino and other devices.

Your device might not be listed over at https://github.com/mik3y/usb-serial-for-android . If you know your devices VID (Vendor ID) and PID (Product ID) you could however try

serial.requestPermission({vid: '1d50', pid: '607d'}, function success(), function error()); //hex strings
or
serial.requestPermission({vid: 7504, pid: 24701}, function success(), function error()); //integers

You can also choose the driver to use. Options are:

CdcAcmSerialDriver
Ch34xSerialDriver
Cp21xxSerialDriver
FtdiSerialDriver
ProlificSerialDriver

It defaults to CdcAcmSerialDriver if empty or not one of these (please feel free to add a PR to support more).

serial.requestPermission({
        vid: '1d50',
        pid: '607d',
        driver: 'FtdiSerialDriver' // or any other
    },
    function success(),
    function error()
);

You can find your devices VID and PID on linux or android using "lsusb" (returning VID:PID in hex) or by looking at your dmesg log.

Change log

2015.10: Ed. Lafargue: Implemented "sleepOnPause" flag in the 'open' options to prevent closing the OTG port when app goes to background.

2014.08: Zevero: Option to find device by VID and PID, that let you use "unrecognized" devices.

2014.07: Hendrik Maus: Implemented writeHex for working with RS232 protocol, i.e. javascript can now pass "ff", java turns it into a 1 byte array and writes to the serial port - naturally, java, and the existing write method here, would create a 2 byte array from the input string.

2014.04: Derek K: Implemented registerReadCallback for evented reading and Android onPause/onResume

2014.03: Ed. Lafargue: Implemented read(). The success callback returns a Javascript ArrayBuffer which is the best way to handle binary data in Javascript. It is straightforward to convert this to a string if required - a utility function could be implemented in this plugin.

2013.11: Xavier Seignard: First implementation

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