C# - Multi Touch Bricklet

This is the description of the C# 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 C# API bindings is part of their general description.

Examples

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

Simple

Download (ExampleSimple.cs)

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using System;
using Tinkerforge;

class Example
{
    private static string HOST = "localhost";
    private static int PORT = 4223;
    private static string UID = "XYZ"; // Change XYZ to the UID of your Multi Touch Bricklet

    static void Main()
    {
        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 touch state
        int state = mt.GetTouchState();
        string str = "";

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

        if((state & 0xfff) == 0) {
            str += "No electrodes touched";
        } else {
            str += "Electrodes ";
            for(int i = 0; i < 12; i++) {
                if((state & (1 << i)) == (1 << i)) {
                    str += i + " ";
                }
            }
            str += "touched";
        }

        Console.WriteLine(str);

        Console.WriteLine("Press enter to exit");
        Console.ReadLine();
        ipcon.Disconnect();
    }
}

Callback

Download (ExampleCallback.cs)

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using System;
using Tinkerforge;

class Example
{
    private static string HOST = "localhost";
    private static int PORT = 4223;
    private static string UID = "XYZ"; // Change XYZ to the UID of your Multi Touch Bricklet

    // Callback function for touch state callback
    static void TouchStateCB(BrickletMultiTouch sender, int state)
    {
        string str = "";

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

        if((state & 0xfff) == 0) {
            str += "No electrodes touched";
        } else {
            str += "Electrodes ";
            for(int i = 0; i < 12; i++) {
                if((state & (1 << i)) == (1 << i)) {
                    str += i + " ";
                }
            }
            str += "touched";
        }

        Console.WriteLine(str);
    }

    static void Main()
    {
        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

        // Register touch state callback to function TouchStateCB
        mt.TouchStateCallback += TouchStateCB;

        Console.WriteLine("Press enter to exit");
        Console.ReadLine();
        ipcon.Disconnect();
    }
}

API

Generally, every method of the C# bindings that returns a value can throw a Tinkerforge.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 plugs the device out). However, if a wireless connection is used, timeouts will occur if the distance to the device gets too big.

Since C# does not support multiple return values directly, we use the out keyword to return multiple values from a method.

The namespace for all Brick/Bricklet bindings and the IPConnection is 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 TouchStateCallback callback.

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(byte 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 byte GetElectrodeSensitivity()

Returns the current sensitivity, as set by SetElectrodeSensitivity().

Advanced Functions

public byte[] 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 bool GetResponseExpected(byte 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 callback 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(byte functionId, bool 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 callback configuration functions (default value: true). For getter functions it is always 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.

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(bool responseExpected)

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

public void GetIdentity(out string uid, out string connectedUid, out char position, out byte[] hardwareVersion, out byte[] firmwareVersion, out int deviceIdentifier)

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.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done by appending your callback handler to the corresponding event:

void MyCallback(BrickletMultiTouch sender, int value)
{
    System.Console.WriteLine("Value: " + value);
}

multiTouch.ExampleCallback += MyCallback;

The available events are described below.

Note

Using callbacks 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 event TouchStateCallback(BrickletMultiTouch sender, int state)

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

This callback is triggered every time the touch state changes.

Constants

public int DEVICE_IDENTIFIER

This constant is used to identify a Multi Touch Bricklet.

The GetIdentity() function and the EnumerateCallback callback of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

public string DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Multi Touch Bricklet.