MATLAB/Octave - Dual Button Bricklet

This is the description of the MATLAB/Octave API bindings for the Dual Button Bricklet. General information and technical specifications for the Dual Button Bricklet are summarized in its hardware description.

An installation guide for the MATLAB/Octave API bindings is part of their general description.

Examples

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

Callback (MATLAB)

Download (matlab_example_callback.m)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
function matlab_example_callback()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletDualButton;

    HOST = 'localhost';
    PORT = 4223;
    UID = 'XYZ'; % Change XYZ to the UID of your Dual Button Bricklet

    ipcon = IPConnection(); % Create IP connection
    db = handle(BrickletDualButton(UID, ipcon), 'CallbackProperties'); % Create device object

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

    % Register state changed callback to function cb_state_changed
    set(db, 'StateChangedCallback', @(h, e) cb_state_changed(e));

    input('Press key to exit\n', 's');
    ipcon.disconnect();
end

% Callback function for state changed callback
function cb_state_changed(e)
    if e.buttonL == com.tinkerforge.BrickletDualButton.BUTTON_STATE_PRESSED
        fprintf('Left Button: Pressed\n');
    elseif e.buttonL == com.tinkerforge.BrickletDualButton.BUTTON_STATE_RELEASED
        fprintf('Left Button: Released\n');
    end

    if e.buttonR == com.tinkerforge.BrickletDualButton.BUTTON_STATE_PRESSED
        fprintf('Right Button: Pressed\n');
    elseif e.buttonR == com.tinkerforge.BrickletDualButton.BUTTON_STATE_RELEASED
        fprintf('Right Button: Released\n');
    end

    fprintf('\n');
end

Callback (Octave)

Download (octave_example_callback.m)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
function octave_example_callback()
    more off;

    HOST = "localhost";
    PORT = 4223;
    UID = "XYZ"; % Change XYZ to the UID of your Dual Button Bricklet

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    db = javaObject("com.tinkerforge.BrickletDualButton", UID, ipcon); % Create device object

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

    % Register state changed callback to function cb_state_changed
    db.addStateChangedCallback(@cb_state_changed);

    input("Press key to exit\n", "s");
    ipcon.disconnect();
end

% Callback function for state changed callback
function cb_state_changed(e)
    if java2int(e.buttonL) == 0
        fprintf("Left Button: Pressed\n");
    elseif java2int(e.buttonL) == 1
        fprintf("Left Button: Released\n");
    end

    if java2int(e.buttonR) == 0
        fprintf("Right Button: Pressed\n");
    elseif java2int(e.buttonR) == 1
        fprintf("Right Button: Released\n");
    end

    fprintf("\n");
end

function int = java2int(value)
    if compare_versions(version(), "3.8", "<=")
        int = value.intValue();
    else
        int = value;
    end
end

API

Generally, every method of the MATLAB 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 the MATLAB bindings are based on Java and 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 BrickletDualButton(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletDualButton;

dualButton = BrickletDualButton('YOUR_DEVICE_UID', ipcon);

In Octave:

dualButton = java_new("com.tinkerforge.BrickletDualButton", "YOUR_DEVICE_UID", ipcon);

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

public void setLEDState(short ledL, short ledR)

Sets the state of the LEDs. Possible states are:

  • 0 = AutoToggleOn: Enables auto toggle with initially enabled LED.
  • 1 = AutoToggleOff: Activates auto toggle with initially disabled LED.
  • 2 = On: Enables LED (auto toggle is disabled).
  • 3 = Off: Disables LED (auto toggle is disabled).

In auto toggle mode the LED is toggled automatically at each press of a button.

If you just want to set one of the LEDs and don't know the current state of the other LED, you can get the state with getLEDState() or you can use setSelectedLEDState().

The default value is (1, 1).

The following constants are available for this function:

  • BrickletDualButton.LED_STATE_AUTO_TOGGLE_ON = 0
  • BrickletDualButton.LED_STATE_AUTO_TOGGLE_OFF = 1
  • BrickletDualButton.LED_STATE_ON = 2
  • BrickletDualButton.LED_STATE_OFF = 3
public BrickletDualButton.LEDState getLEDState()

Returns the current state of the LEDs, as set by setLEDState().

The following constants are available for this function:

  • BrickletDualButton.LED_STATE_AUTO_TOGGLE_ON = 0
  • BrickletDualButton.LED_STATE_AUTO_TOGGLE_OFF = 1
  • BrickletDualButton.LED_STATE_ON = 2
  • BrickletDualButton.LED_STATE_OFF = 3

The returned object has the public member variables short ledL and short ledR.

public BrickletDualButton.ButtonState getButtonState()

Returns the current state for both buttons. Possible states are:

  • 0 = pressed
  • 1 = released

The following constants are available for this function:

  • BrickletDualButton.BUTTON_STATE_PRESSED = 0
  • BrickletDualButton.BUTTON_STATE_RELEASED = 1

The returned object has the public member variables short buttonL and short buttonR.

Advanced Functions

public void setSelectedLEDState(short led, short state)

Sets the state of the selected LED (0 or 1).

The other LED remains untouched.

The following constants are available for this function:

  • BrickletDualButton.LED_LEFT = 0
  • BrickletDualButton.LED_RIGHT = 1
  • BrickletDualButton.LED_STATE_AUTO_TOGGLE_ON = 0
  • BrickletDualButton.LED_STATE_AUTO_TOGGLE_OFF = 1
  • BrickletDualButton.LED_STATE_ON = 2
  • BrickletDualButton.LED_STATE_OFF = 3
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 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(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 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:

  • BrickletDualButton.FUNCTION_SET_LED_STATE = 1
  • BrickletDualButton.FUNCTION_SET_SELECTED_LED_STATE = 5
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletDualButton.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.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with "set" function of MATLAB. The parameters consist of the IP Connection object, the callback name and the callback function. For example, it looks like this in MATLAB:

function my_callback(e)
    fprintf('Parameter: %s\n', e.param);
end

set(device, 'ExampleCallback', @(h, e) my_callback(e));

Due to a difference in the Octave Java support the "set" function cannot be used in Octave. The registration is done with "add*Callback" functions of the device object. It looks like this in Octave:

function my_callback(e)
    fprintf("Parameter: %s\n", e.param);
end

device.addExampleCallback(@my_callback);

It is possible to add several callbacks and to remove them with the corresponding "remove*Callback" function.

The parameters of the callback are passed to the callback function as fields of the structure e, which is derived from the java.util.EventObject class. The available callback names with corresponding structure fields 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 callback BrickletDualButton.StateChangedCallback
Parameters:
  • buttonL -- short
  • buttonR -- short
  • ledL -- short
  • ledR -- short

This callback is called whenever a button is pressed.

Possible states for buttons are:

  • 0 = pressed
  • 1 = released

Possible states for LEDs are:

  • 0 = AutoToggleOn: Auto toggle enabled and LED on.
  • 1 = AutoToggleOff: Auto toggle enabled and LED off.
  • 2 = On: LED on (auto toggle is disabled).
  • 3 = Off: LED off (auto toggle is disabled).

The following constants are available for this function:

  • BrickletDualButton.BUTTON_STATE_PRESSED = 0
  • BrickletDualButton.BUTTON_STATE_RELEASED = 1
  • BrickletDualButton.LED_STATE_AUTO_TOGGLE_ON = 0
  • BrickletDualButton.LED_STATE_AUTO_TOGGLE_OFF = 1
  • BrickletDualButton.LED_STATE_ON = 2
  • BrickletDualButton.LED_STATE_OFF = 3

In MATLAB the set() function can be used to register a callback function to this callback.

In Octave a callback function can be added to this callback using the addStateChangedCallback() function. An added callback function can be removed with the removeStateChangedCallback() function.

Constants

public static final int BrickletDualButton.DEVICE_IDENTIFIER

This constant is used to identify a Dual Button 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 static final String BrickletDualButton.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Dual Button Bricklet.