Java - Multi Touch Bricklet – Tinkerforge

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# Java - Multi Touch Bricklet

This is the description of the Java API bindings for the Multi Touch Bricklet. General information and technical specifications for the Multi Touch Bricklet are summarized in its hardware description.

An installation guide for the Java API bindings is part of their general description.

## Examples

The example code below is Public Domain (CC0 1.0).

### Simple

Download (ExampleSimple.java)

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    import com.tinkerforge.BrickletMultiTouch;
    import com.tinkerforge.IPConnection;

    public class ExampleSimple {
        private static final String HOST = "localhost";
        private static final int PORT = 4223;
        private static final String UID = "XYZ"; // Change to your UID

        // Note: To make the example code cleaner we do not handle exceptions. Exceptions you
        //       might normally want to catch are described in the documentation
        public static void main(String args[]) throws Exception {
            IPConnection ipcon = new IPConnection(); // Create IP connection
            BrickletMultiTouch mt = new BrickletMultiTouch(UID, ipcon); // Create device object

            ipcon.connect(HOST, PORT); // Connect to brickd
            // Don't use device before ipcon is connected

            // Get current touchState
            int touchState = mt.getTouchState(); // Can throw com.tinkerforge.TimeoutException

            String str = "";

            if((touchState & (1 << 12)) == (1 << 12)) {
                str += "In proximity, ";
            }

            if((touchState & 0xfff) == 0) {
                str += "No electrodes touched" + System.getProperty("line.separator");
            } else {
                str += "Electrodes ";
                for(int i = 0; i < 12; i++) {
                    if((touchState & (1 << i)) == (1 << i)) {
                        str += i + " ";
                    }
                }
                str += "touched" + System.getProperty("line.separator");
            }

            System.out.println(str);

            System.out.println("Press key to exit"); System.in.read();
            ipcon.disconnect();
        }
    }

### Callback

Download (ExampleCallback.java)

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    import com.tinkerforge.BrickletMultiTouch;
    import com.tinkerforge.IPConnection;

    public class ExampleCallback {
        private static final String HOST = "localhost";
        private static final int PORT = 4223;
        private static final String UID = "XYZ"; // Change to your UID

        // Note: To make the example code cleaner we do not handle exceptions. Exceptions you
        //       might normally want to catch are described in the documentation
        public static void main(String args[]) throws Exception {
            IPConnection ipcon = new IPConnection(); // Create IP connection
            BrickletMultiTouch mt = new BrickletMultiTouch(UID, ipcon); // Create device object

            ipcon.connect(HOST, PORT); // Connect to brickd
            // Don't use device before ipcon is connected

            // Add and implement touch state listener (called if touch state changes)
            mt.addTouchStateListener(new BrickletMultiTouch.TouchStateListener() {
                public void touchState(int touchState) {
                    String str = "";

                    if((touchState & (1 << 12)) == (1 << 12)) {
                        str += "In proximity, ";
                    }

                    if((touchState & 0xfff) == 0) {
                        str += "No electrodes touched" + System.getProperty("line.separator");
                    } else {
                        str += "Electrodes ";
                        for(int i = 0; i < 12; i++) {
                            if((touchState & (1 << i)) == (1 << i)) {
                                str += i + " ";
                            }
                        }
                        str += "touched" + System.getProperty("line.separator");
                    }

                    System.out.println(str);
                }
            });

            System.out.println("Press key to exit"); System.in.read();
            ipcon.disconnect();
        }
    }

## API

Generally, every method of the Java bindings that returns a value can throw a `TimeoutException`. This exception gets thrown if the device did not respond. If a cable based connection is used, it is unlikely that this exception gets thrown (assuming nobody unplugs the device). However, if a wireless connection is used, timeouts will occur if the distance to the device gets too big.

Beside the `TimeoutException` there is also a `NotConnectedException` that is thrown if a method needs to communicate with the device while the IP Connection is not connected.

Since Java does not support multiple return values and return by reference is not possible for primitive types, we use small classes that only consist of member variables. The member variables of the returned objects are described in the corresponding method descriptions.

The package for all Brick/Bricklet bindings and the IP Connection is `com.tinkerforge.*`

All methods listed below are thread-safe.

### Basic Functions

public class `BrickletMultiTouch`(String uid, IPConnection ipcon)

  Creates an object with the unique device ID `uid`:

      BrickletMultiTouch multiTouch = new BrickletMultiTouch("YOUR_DEVICE_UID", ipcon);

  This object can then be used after the IP Connection is connected (see examples above).

public int `getTouchState`()

  Returns the current touch state. The state is given as a bitfield.

  Bits 0 to 11 represent the 12 electrodes and bit 12 represents the proximity.

  If an electrode is touched, the corresponding bit is true. If a hand or similar is in proximity to the electrodes, bit 12 is true.

  Example: The state 4103 = 0x1007 = 0b1000000000111 means that electrodes 0, 1 and 2 are touched and that something is in the proximity of the electrodes.

  The proximity is activated with a distance of 1-2cm. An electrode is already counted as touched if a finger is nearly touching the electrode. This means that you can put a piece of paper or foil or similar on top of a electrode to build a touch panel with a professional look.

public void `recalibrate`()

  Recalibrates the electrodes. Call this function whenever you changed or moved you electrodes.

public void `setElectrodeConfig`(int enabledElectrodes)

  Enables/disables electrodes with a bitfield (see `getTouchState()`).

  True enables the electrode, false disables the electrode. A disabled electrode will always return false as its state. If you don't need all electrodes you can disable the electrodes that are not needed.

  It is recommended that you disable the proximity bit (bit 12) if the proximity feature is not needed. This will reduce the amount of traffic that is produced by the `TouchStateListener` listener.

  Disabling electrodes will also reduce power consumption.

  Default: 8191 = 0x1FFF = 0b1111111111111 (all electrodes enabled)

public int `getElectrodeConfig`()

  Returns the electrode configuration, as set by `setElectrodeConfig()`.

public void `setElectrodeSensitivity`(short sensitivity)

  Sets the sensitivity of the electrodes. An electrode with a high sensitivity will register a touch earlier then an electrode with a low sensitivity.

  If you build a big electrode you might need to decrease the sensitivity, since the area that can be charged will get bigger. If you want to be able to activate an electrode from further away you need to increase the sensitivity.

  After a new sensitivity is set, you likely want to call `recalibrate()` to calibrate the electrodes with the newly defined sensitivity.

  The valid sensitivity value range is 5-201.

  The default sensitivity value is 181.

public short `getElectrodeSensitivity`()

  Returns the current sensitivity, as set by `setElectrodeSensitivity()`.

### Advanced Functions

public short[] `getAPIVersion`()

  Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

public boolean `getResponseExpected`(short functionId)

  Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

  For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For listener configuration functions it is enabled by default too, but can be disabled by `setResponseExpected()`. For setter functions it is disabled by default and can be enabled.

  Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

  See `setResponseExpected()` for the list of function ID constants available for this function.

public void `setResponseExpected`(short functionId, boolean responseExpected)

  Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and listener configuration functions (default value: true). For getter functions it is always enabled and listeners it is always disabled.

  Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

  The following function ID constants are available for this function:

  - BrickletMultiTouch.FUNCTION_RECALIBRATE = 2
  - BrickletMultiTouch.FUNCTION_SET_ELECTRODE_CONFIG = 3
  - BrickletMultiTouch.FUNCTION_SET_ELECTRODE_SENSITIVITY = 6

public void `setResponseExpectedAll`(boolean responseExpected)

  Changes the response expected flag for all setter and listener configuration functions of this device at once.

public BrickletMultiTouch.Identity `getIdentity`()

  Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

  The position can be 'a', 'b', 'c' or 'd'.

  The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

  The returned object has the public member variables `String uid`, `String connectedUid`, `char position`, `short[] hardwareVersion`, `short[] firmwareVersion` and `int deviceIdentifier`.

### Listeners

Listeners can be registered to receive time critical or recurring data from the device. The registration is done with "add*Listener" functions of the device object.

The parameter is a listener class object, for example:

    device.addExampleListener(new BrickletMultiTouch.ExampleListener() {
        public void property(int value) {
            System.out.println("Value: " + value);
        }
    });

The available listener classes with inherent methods to be overwritten are described below. It is possible to add several listeners and to remove them with the corresponding "remove*Listener" function.

Note

Using listeners for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

public class `BrickletMultiTouch.TouchStateListener`()

  This listener can be added with the `addTouchStateListener()` function. An added listener can be removed with the `removeTouchStateListener()` function.

  public void `touchState`(int state)

    Returns the current touch state, see `getTouchState()` for information about the state.

    This listener is triggered every time the touch state changes.

### Constants

public static final int `BrickletMultiTouch.DEVICE_IDENTIFIER`

  This constant is used to identify a Multi Touch Bricklet.

  The `getIdentity()` function and the `EnumerateListener` listener of the IP Connection have a `deviceIdentifier` parameter to specify the Brick's or Bricklet's type.

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