MATLAB/Octave - Joystick Bricklet¶

This is the description of the MATLAB/Octave API bindings for the Joystick Bricklet. General information and technical specifications for the Joystick 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).

Simple (MATLAB)¶

Download (matlab_example_simple.m)

function matlab_example_simple()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletJoystick;

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

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

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

    % Get current position
    position = j.getPosition();

    fprintf('Position [X]: %i\n', position.x);
    fprintf('Position [Y]: %i\n', position.y);

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

Callback (MATLAB)¶

Download (matlab_example_callback.m)

function matlab_example_callback()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletJoystick;

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

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

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

    % Register pressed callback to function cb_pressed
    set(j, 'PressedCallback', @(h, e) cb_pressed(e));

    % Register released callback to function cb_released
    set(j, 'ReleasedCallback', @(h, e) cb_released(e));

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

% Callback function for pressed callback
function cb_pressed(e)
    fprintf('Pressed\n');
end

% Callback function for released callback
function cb_released(e)
    fprintf('Released\n');
end

Find Borders (MATLAB)¶

Download (matlab_example_find_borders.m)

function matlab_example_find_borders()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletJoystick;

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

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

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

    % Get threshold callbacks with a debounce time of 0.2 seconds (200ms)
    j.setDebouncePeriod(200);

    % Register position reached callback to function cb_position_reached
    set(j, 'PositionReachedCallback', @(h, e) cb_position_reached(e));

    % Configure threshold for position "outside of -99, -99 to 99, 99"
    j.setPositionCallbackThreshold('o', -99, 99, -99, 99);

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

% Callback function for position reached callback
function cb_position_reached(e)
    if e.y == 100
        fprintf('Top\n');
    elseif e.y == -100
        fprintf('Bottom\n');
    end
    if e.x == 100
        fprintf('Right\n');
    elseif e.x == -100
        fprintf('Left\n');
    end
    fprintf('\n');
end

Simple (Octave)¶

Download (octave_example_simple.m)

function octave_example_simple()
    more off;

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

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

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

    % Get current position
    position = j.getPosition();

    fprintf("Position [X]: %d\n", java2int(position.x));
    fprintf("Position [Y]: %d\n", java2int(position.y));

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

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

Callback (Octave)¶

Download (octave_example_callback.m)

function octave_example_callback()
    more off;

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

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

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

    % Register pressed callback to function cb_pressed
    j.addPressedCallback(@cb_pressed);

    % Register released callback to function cb_released
    j.addReleasedCallback(@cb_released);

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

% Callback function for pressed callback
function cb_pressed(e)
    fprintf("Pressed\n");
end

% Callback function for released callback
function cb_released(e)
    fprintf("Released\n");
end

Find Borders (Octave)¶

Download (octave_example_find_borders.m)

function octave_example_find_borders()
    more off;

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

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

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

    % Get threshold callbacks with a debounce time of 0.2 seconds (200ms)
    j.setDebouncePeriod(200);

    % Register position reached callback to function cb_position_reached
    j.addPositionReachedCallback(@cb_position_reached);

    % Configure threshold for position "outside of -99, -99 to 99, 99"
    j.setPositionCallbackThreshold("o", -99, 99, -99, 99);

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

% Callback function for position reached callback
function cb_position_reached(e)
    x = java2int(e.x);
    y = java2int(e.y);

    if y == 100
        fprintf("Top\n");
    elseif y == -100
        fprintf("Bottom\n");
    end
    if x == 100
        fprintf("Right\n");
    elseif x ==-100
        fprintf("Left\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¶

class BrickletJoystick(String uid, IPConnection ipcon)¶

Parameters:	uid – Type: String ipcon – Type: IPConnection
Returns:	joystick – Type: BrickletJoystick

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletJoystick;

joystick = BrickletJoystick('YOUR_DEVICE_UID', ipcon);

In Octave:

joystick = java_new("com.tinkerforge.BrickletJoystick", "YOUR_DEVICE_UID", ipcon);

This object can then be used after the IP Connection is connected.

BrickletJoystick.Position BrickletJoystick.getPosition()¶

Return Object:	x – Type: short, Range: [-100 to 100] y – Type: short, Range: [-100 to 100]

Returns the position of the joystick. The middle position of the joystick is x=0, y=0. The returned values are averaged and calibrated (see calibrate()).

If you want to get the position periodically, it is recommended to use the PositionCallback callback and set the period with setPositionCallbackPeriod().

boolean BrickletJoystick.isPressed()¶

Returns:	pressed – Type: boolean

Returns true if the button is pressed and false otherwise.

It is recommended to use the PressedCallback and ReleasedCallback callbacks to handle the button.

Advanced Functions¶

BrickletJoystick.AnalogValue BrickletJoystick.getAnalogValue()¶

Return Object:	x – Type: int, Range: [0 to 2¹² - 1] y – Type: int, Range: [0 to 2¹² - 1]

Returns the values as read by a 12-bit analog-to-digital converter.

Note

The values returned by getPosition() are averaged over several samples to yield less noise, while getAnalogValue() gives back raw unfiltered analog values. The only reason to use getAnalogValue() is, if you need the full resolution of the analog-to-digital converter.

If you want the analog values periodically, it is recommended to use the AnalogValueCallback callback and set the period with setAnalogValueCallbackPeriod().

void BrickletJoystick.calibrate()¶

Calibrates the middle position of the joystick. If your Joystick Bricklet does not return x=0 and y=0 in the middle position, call this function while the joystick is standing still in the middle position.

The resulting calibration will be saved on the EEPROM of the Joystick Bricklet, thus you only have to calibrate it once.

BrickletJoystick.Identity BrickletJoystick.getIdentity()¶

Return Object:

Return Object:	uid – Type: String, Length: up to 8 connectedUid – Type: String, Length: up to 8 position – Type: char, Range: ['a' to 'h', 'z'] hardwareVersion – Type: short[], Length: 3 1: major – Type: short, Range: [0 to 255] 2: minor – Type: short, Range: [0 to 255] 3: revision – Type: short, Range: [0 to 255] firmwareVersion – Type: short[], Length: 3 1: major – Type: short, Range: [0 to 255] 2: minor – Type: short, Range: [0 to 255] 3: revision – Type: short, Range: [0 to 255] deviceIdentifier – Type: int, Range: [0 to 2¹⁶ - 1]

uid – Type: String, Length: up to 8
connectedUid – Type: String, Length: up to 8
position – Type: char, Range: ['a' to 'h', 'z']
hardwareVersion – Type: short[], Length: 3

1: major – Type: short, Range: [0 to 255]
2: minor – Type: short, Range: [0 to 255]
3: revision – Type: short, Range: [0 to 255]

firmwareVersion – Type: short[], Length: 3

1: major – Type: short, Range: [0 to 255]
2: minor – Type: short, Range: [0 to 255]
3: revision – Type: short, Range: [0 to 255]

deviceIdentifier – Type: int, Range: [0 to 2¹⁶ - 1]

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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

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

Callback Configuration Functions¶

void BrickletJoystick.setPositionCallbackPeriod(long period)¶

Parameters:	period – Type: long, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Sets the period with which the PositionCallback callback is triggered periodically. A value of 0 turns the callback off.

The PositionCallback callback is only triggered if the position has changed since the last triggering.

long BrickletJoystick.getPositionCallbackPeriod()¶

Returns:	period – Type: long, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by setPositionCallbackPeriod().

void BrickletJoystick.setAnalogValueCallbackPeriod(long period)¶

Parameters:	period – Type: long, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Sets the period with which the AnalogValueCallback callback is triggered periodically. A value of 0 turns the callback off.

The AnalogValueCallback callback is only triggered if the analog values have changed since the last triggering.

long BrickletJoystick.getAnalogValueCallbackPeriod()¶

Returns:	period – Type: long, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by setAnalogValueCallbackPeriod().

void BrickletJoystick.setPositionCallbackThreshold(char option, short minX, short maxX, short minY, short maxY)¶

Parameters:	option – Type: char, Range: See constants, Default: 'x' minX – Type: short, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 maxX – Type: short, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 minY – Type: short, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 maxY – Type: short, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0

Sets the thresholds for the PositionReachedCallback callback.

The following options are possible:

Option	Description
'x'	Callback is turned off
'o'	Callback is triggered when the position is outside the min and max values
'i'	Callback is triggered when the position is inside the min and max values
'<'	Callback is triggered when the position is smaller than the min values (max is ignored)
'>'	Callback is triggered when the position is greater than the min values (max is ignored)

The following constants are available for this function:

For option:

BrickletJoystick.THRESHOLD_OPTION_OFF = 'x'
BrickletJoystick.THRESHOLD_OPTION_OUTSIDE = 'o'
BrickletJoystick.THRESHOLD_OPTION_INSIDE = 'i'
BrickletJoystick.THRESHOLD_OPTION_SMALLER = '<'
BrickletJoystick.THRESHOLD_OPTION_GREATER = '>'

BrickletJoystick.PositionCallbackThreshold BrickletJoystick.getPositionCallbackThreshold()¶

Return Object:	option – Type: char, Range: See constants, Default: 'x' minX – Type: short, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 maxX – Type: short, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 minY – Type: short, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0 maxY – Type: short, Range: [-2¹⁵ to 2¹⁵ - 1], Default: 0

Returns the threshold as set by setPositionCallbackThreshold().

The following constants are available for this function:

For option:

BrickletJoystick.THRESHOLD_OPTION_OFF = 'x'
BrickletJoystick.THRESHOLD_OPTION_OUTSIDE = 'o'
BrickletJoystick.THRESHOLD_OPTION_INSIDE = 'i'
BrickletJoystick.THRESHOLD_OPTION_SMALLER = '<'
BrickletJoystick.THRESHOLD_OPTION_GREATER = '>'

void BrickletJoystick.setAnalogValueCallbackThreshold(char option, int minX, int maxX, int minY, int maxY)¶

Parameters:	option – Type: char, Range: See constants, Default: 'x' minX – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0 maxX – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0 minY – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0 maxY – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0

Sets the thresholds for the AnalogValueReachedCallback callback.

The following options are possible:

Option	Description
'x'	Callback is turned off
'o'	Callback is triggered when the analog values are outside the min and max values
'i'	Callback is triggered when the analog values are inside the min and max values
'<'	Callback is triggered when the analog values are smaller than the min values (max is ignored)
'>'	Callback is triggered when the analog values are greater than the min values (max is ignored)

The following constants are available for this function:

For option:

BrickletJoystick.THRESHOLD_OPTION_OFF = 'x'
BrickletJoystick.THRESHOLD_OPTION_OUTSIDE = 'o'
BrickletJoystick.THRESHOLD_OPTION_INSIDE = 'i'
BrickletJoystick.THRESHOLD_OPTION_SMALLER = '<'
BrickletJoystick.THRESHOLD_OPTION_GREATER = '>'

BrickletJoystick.AnalogValueCallbackThreshold BrickletJoystick.getAnalogValueCallbackThreshold()¶

Return Object:	option – Type: char, Range: See constants, Default: 'x' minX – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0 maxX – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0 minY – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0 maxY – Type: int, Range: [0 to 2¹⁶ - 1], Default: 0

Returns the threshold as set by setAnalogValueCallbackThreshold().

The following constants are available for this function:

For option:

BrickletJoystick.THRESHOLD_OPTION_OFF = 'x'
BrickletJoystick.THRESHOLD_OPTION_OUTSIDE = 'o'
BrickletJoystick.THRESHOLD_OPTION_INSIDE = 'i'
BrickletJoystick.THRESHOLD_OPTION_SMALLER = '<'
BrickletJoystick.THRESHOLD_OPTION_GREATER = '>'

void BrickletJoystick.setDebouncePeriod(long debounce)¶

Parameters:	debounce – Type: long, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100

Sets the period with which the threshold callbacks

PositionReachedCallback,
AnalogValueReachedCallback

are triggered, if the thresholds

setPositionCallbackThreshold(),
setAnalogValueCallbackThreshold()

keep being reached.

long BrickletJoystick.getDebouncePeriod()¶

Returns:	debounce – Type: long, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100

Returns the debounce period as set by setDebouncePeriod().

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.

callback BrickletJoystick.PositionCallback¶

Event Object:	x – Type: short, Range: [-100 to 100] y – Type: short, Range: [-100 to 100]

This callback is triggered periodically with the period that is set by setPositionCallbackPeriod(). The parameter is the position of the joystick.

The PositionCallback callback is only triggered if the position has changed since the last triggering.