firmata4j

firmata4j is a client library of Firmata written in Java. The library allows controlling Arduino (or another board) which runs Firmata protocol from your java program.

Capabilities

• Interaction with a board and its pins in object-oriented style
• Abstraction over details of the protocol
• Provides an UI component that visualize the current state of every pin and allows changing a mode and state of each of those
• Allows communicating with I2C devices

Installation

Maven

Add the following dependency to pom.xml of your project:

<dependency>
    <groupId>com.github.kurbatov</groupId>
    <artifactId>firmata4j</artifactId>
    <version>2.3.4.1</version>
</dependency>

Usage

General scenario of usage is following:

IODevice device = new FirmataDevice("/dev/ttyUSB0"); // construct the Firmata device instance using the name of a port
// subscribe to events using device.addEventListener(...);
// and/or device.getPin(n).addEventListener(...);
device.start(); // initiate communication to the device
device.ensureInitializationIsDone(); // wait for initialization is done
// do actual work here
device.stop(); // stop communication to the device

The "actual work" consists in sending commands to the board. Registered listeners process events of the device asynchronously. You can add and remove listeners along the way.

You can subscribe to events of the device or its pin.

device.addEventListener(new IODeviceEventListener() {
    @Override
    public void onStart(IOEvent event) {
        // since this moment we are sure that the device is initialized
        // so we can hide initialization spinners and begin doing cool stuff
        System.out.println("Device is ready");
    }

    @Override
    public void onStop(IOEvent event) {
        // since this moment we are sure that the device is properly shut down
        System.out.println("Device has been stopped");
    }

    @Override
    public void onPinChange(IOEvent event) {
        // here we react to changes of pins' state
        Pin pin = event.getPin();
        System.out.println(
                String.format(
                    "Pin %d got a value of %d",
                    pin.getIndex(),
                    pin.getValue())
            );
    }

    @Override
    public void onMessageReceive(IOEvent event, String message) {
        // here we react to receiving a text message from the device
        System.out.println(message);
    }
});

To obtain more fine grained control you can subscribe to events of a particular pin.

Pin pin = device.getPin(2);
pin.addEventListener(new PinEventListener() {
    @Override
    public void onModeChange(IOEvent event) {
        System.out.println("Mode of the pin has been changed");
    }

    @Override
    public void onValueChange(IOEvent event) {
        System.out.println("Value of the pin has been changed");
    }
});

You can change the mode and value of a pin:

pin.setMode(Pin.Mode.OUTPUT); // our listeners will get event about this change
pin.setValue(1); // and then about this change

You can get visual representation of device's pins using JPinboard Swing component.

JPinboard pinboard = new JPinboard(device);
JFrame frame = new JFrame("Pinboard Example");
frame.add(pinboard);
frame.pack();
frame.setVisible(true);

JPinboard allows setting the pin's mode by choosing one from a context menu of the pin. State of the output pin can be changed by double clicking on it.

An example of JPinboard usage can be found in org.firmata4j.Example class.

I2C

firmata4j supports working with I2C devices. You can obtain a reference to an I2C device in this way:

IODevice device = new FirmataDevice(port);
...
byte i2cAddress = 0x3C;
I2CDevice i2cDevice = device.getI2CDevice(i2cAddress);

You may find convenient writing a wrapper for I2CDevice class to facilitate communication with I2C device. Consider I2CExample and SSD1306 classes as an example of that approach.

Versions

firmata4j sticks to Firmata protocol versions. The first available version of firmata4j is 2.3.1.

firmata4j-2.3.x will work well with Fimata v. 2.3.x. Actually it should work with Firmata v. 2.x.x but not necessarily support all of the protocol features. The first digits of versions must be equal because those stand for incompatible changes of the protocol.

Uploading Firmata To Arduino

Arduino IDE is shipped with an implementation of Firmata protocol. You can upload it as follows:

• Plug your Arduino to the computer
• Launch Arduino IDE
• Select File -> Examples -> Firmata -> StandardFirmata in IDE's menu
• Select your board in Tools -> Board
• Select the port in Tools -> Port (it is already selected if you have uploaded something to your Arduino)
• Click on Upload button

Arduino IDE may contain an outdated version of Firmata. You can update it using the guide on this page.

Contributing

Contributions are welcome. If you discover a bug or would like to propose a new feature, please, open a new issue.

If you have an improvement to share, please, do the following:

1. Fork this repository
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Adds some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

License

firmata4j is distributed under the terms of the MIT License. See the LICENSE file.