MATLAB/Octave - Rotary Poti Bricklet

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

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

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

    ipcon = IPConnection(); % Create IP connection
    rp = handle(BrickletRotaryPoti(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 = rp.getPosition();
    fprintf('Position: %i\n', position); % Range: -150 to 150

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

Callback (MATLAB)

Download (matlab_example_callback.m)

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

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

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

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

    % Register position callback to function cb_position
    set(rp, 'PositionCallback', @(h, e) cb_position(e));

    % Set period for position callback to 0.05s (50ms)
    % Note: The position callback is only called every 0.05 seconds
    %       if the position has changed since the last call!
    rp.setPositionCallbackPeriod(50);

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

% Callback function for position callback
function cb_position(e)
    fprintf('Position: %i\n', e.position); % Range: -150 to 150
end

Simple (Octave)

Download (octave_example_simple.m)

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function octave_example_simple()
    more off;

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

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

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

    % Get current position
    position = rp.getPosition();
    fprintf("Position: %d\n", java2int(position)); % Range: -150 to 150

    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)

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function octave_example_callback()
    more off;

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

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

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

    % Register position callback to function cb_position
    rp.addPositionCallback(@cb_position);

    % Set period for position callback to 0.05s (50ms)
    % Note: The position callback is only called every 0.05 seconds
    %       if the position has changed since the last call!
    rp.setPositionCallbackPeriod(50);

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

% Callback function for position callback
function cb_position(e)
    fprintf("Position: %d\n", java2int(e.position)); % Range: -150 to 150
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 BrickletRotaryPoti(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletRotaryPoti;

rotaryPoti = BrickletRotaryPoti('YOUR_DEVICE_UID', ipcon);

In Octave:

rotaryPoti = java_new("com.tinkerforge.BrickletRotaryPoti", "YOUR_DEVICE_UID", ipcon);

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

public short getPosition()

Returns the position of the rotary potentiometer. The value is in degree and between -150° (turned left) and 150° (turned right).

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

Advanced Functions

public int getAnalogValue()

Returns the value as read by a 12-bit analog-to-digital converter. The value is between 0 and 4095.

Note

The value returned by getPosition() is 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 value periodically, it is recommended to use the AnalogValueCallback callback and set the period with setAnalogValueCallbackPeriod().

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:

  • BrickletRotaryPoti.FUNCTION_SET_POSITION_CALLBACK_PERIOD = 3
  • BrickletRotaryPoti.FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 5
  • BrickletRotaryPoti.FUNCTION_SET_POSITION_CALLBACK_THRESHOLD = 7
  • BrickletRotaryPoti.FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 9
  • BrickletRotaryPoti.FUNCTION_SET_DEBOUNCE_PERIOD = 11
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletRotaryPoti.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.

Callback Configuration Functions

public void setPositionCallbackPeriod(long period)

Sets the period in ms 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.

The default value is 0.

public long getPositionCallbackPeriod()

Returns the period as set by setPositionCallbackPeriod().

public void setAnalogValueCallbackPeriod(long period)

Sets the period in ms 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 value has changed since the last triggering.

The default value is 0.

public long getAnalogValueCallbackPeriod()

Returns the period as set by setAnalogValueCallbackPeriod().

public void setPositionCallbackThreshold(char option, short min, short max)

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 value (max is ignored)
'>' Callback is triggered when the position is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following constants are available for this function:

  • BrickletRotaryPoti.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryPoti.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryPoti.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryPoti.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryPoti.THRESHOLD_OPTION_GREATER = '>'
public BrickletRotaryPoti.PositionCallbackThreshold getPositionCallbackThreshold()

Returns the threshold as set by setPositionCallbackThreshold().

The following constants are available for this function:

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

The returned object has the public member variables char option, short min and short max.

public void setAnalogValueCallbackThreshold(char option, int min, int max)

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 value is outside the min and max values
'i' Callback is triggered when the analog value is inside the min and max values
'<' Callback is triggered when the analog value is smaller than the min value (max is ignored)
'>' Callback is triggered when the analog value is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following constants are available for this function:

  • BrickletRotaryPoti.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryPoti.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryPoti.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryPoti.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryPoti.THRESHOLD_OPTION_GREATER = '>'
public BrickletRotaryPoti.AnalogValueCallbackThreshold getAnalogValueCallbackThreshold()

Returns the threshold as set by setAnalogValueCallbackThreshold().

The following constants are available for this function:

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

The returned object has the public member variables char option, int min and int max.

public void setDebouncePeriod(long debounce)

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

public long getDebouncePeriod()

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.

public callback BrickletRotaryPoti.PositionCallback
Parameters:position -- short

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

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

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 addPositionCallback() function. An added callback function can be removed with the removePositionCallback() function.

public callback BrickletRotaryPoti.AnalogValueCallback
Parameters:value -- int

This callback is triggered periodically with the period that is set by setAnalogValueCallbackPeriod(). The parameter is the analog value of the rotary potentiometer.

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

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 addAnalogValueCallback() function. An added callback function can be removed with the removeAnalogValueCallback() function.

public callback BrickletRotaryPoti.PositionReachedCallback
Parameters:position -- short

This callback is triggered when the threshold as set by setPositionCallbackThreshold() is reached. The parameter is the position of the rotary potentiometer.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by setDebouncePeriod().

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 addPositionReachedCallback() function. An added callback function can be removed with the removePositionReachedCallback() function.

public callback BrickletRotaryPoti.AnalogValueReachedCallback
Parameters:value -- int

This callback is triggered when the threshold as set by setAnalogValueCallbackThreshold() is reached. The parameter is the analog value of the rotary potentiometer.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by setDebouncePeriod().

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 addAnalogValueReachedCallback() function. An added callback function can be removed with the removeAnalogValueReachedCallback() function.

Constants

public static final int BrickletRotaryPoti.DEVICE_IDENTIFIER

This constant is used to identify a Rotary Poti 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 BrickletRotaryPoti.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Rotary Poti Bricklet.