MATLAB/Octave - Rotary Encoder Bricklet

This is the description of the MATLAB/Octave API bindings for the Rotary Encoder Bricklet. General information and technical specifications for the Rotary Encoder 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.BrickletRotaryEncoder;

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

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

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

    % Get current count without reset
    count = re.getCount(false);
    fprintf('Count: %i\n', count);

    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.BrickletRotaryEncoder;

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

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

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

    % Register count callback to function cb_count
    set(re, 'CountCallback', @(h, e) cb_count(e));

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

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

% Callback function for count callback
function cb_count(e)
    fprintf('Count: %i\n', e.count);
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 Encoder Bricklet

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

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

    % Get current count without reset
    count = re.getCount(false);
    fprintf("Count: %d\n", count);

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

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

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

    % Register count callback to function cb_count
    re.addCountCallback(@cb_count);

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

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

% Callback function for count callback
function cb_count(e)
    fprintf("Count: %d\n", e.count);
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 BrickletRotaryEncoder(String uid, IPConnection ipcon)
Parameters:
  • uid – Type: String
  • ipcon – Type: IPConnection
Returns:
  • rotaryEncoder – Type: BrickletRotaryEncoder

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletRotaryEncoder;

rotaryEncoder = BrickletRotaryEncoder('YOUR_DEVICE_UID', ipcon);

In Octave:

rotaryEncoder = java_new("com.tinkerforge.BrickletRotaryEncoder", "YOUR_DEVICE_UID", ipcon);

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

int BrickletRotaryEncoder.getCount(boolean reset)
Parameters:
  • reset – Type: boolean
Returns:
  • count – Type: int, Range: [-231 to 231 - 1]

Returns the current count of the encoder. If you set reset to true, the count is set back to 0 directly after the current count is read.

The encoder has 24 steps per rotation

Turning the encoder to the left decrements the counter, so a negative count is possible.

boolean BrickletRotaryEncoder.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

short[] BrickletRotaryEncoder.getAPIVersion()
Returns:
  • apiVersion – Type: short[], Length: 3, Range: [0 to 255]

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.

boolean BrickletRotaryEncoder.getResponseExpected(short functionId)
Parameters:
  • functionId – Type: short, Range: See constants
Returns:
  • responseExpected – Type: boolean

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.

The following constants are available for this function:

For functionId:

  • BrickletRotaryEncoder.FUNCTION_SET_COUNT_CALLBACK_PERIOD = 2
  • BrickletRotaryEncoder.FUNCTION_SET_COUNT_CALLBACK_THRESHOLD = 4
  • BrickletRotaryEncoder.FUNCTION_SET_DEBOUNCE_PERIOD = 6
void BrickletRotaryEncoder.setResponseExpected(short functionId, boolean responseExpected)
Parameters:
  • functionId – Type: short, Range: See constants
  • responseExpected – Type: boolean

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 constants are available for this function:

For functionId:

  • BrickletRotaryEncoder.FUNCTION_SET_COUNT_CALLBACK_PERIOD = 2
  • BrickletRotaryEncoder.FUNCTION_SET_COUNT_CALLBACK_THRESHOLD = 4
  • BrickletRotaryEncoder.FUNCTION_SET_DEBOUNCE_PERIOD = 6
void BrickletRotaryEncoder.setResponseExpectedAll(boolean responseExpected)
Parameters:
  • responseExpected – Type: boolean

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

BrickletRotaryEncoder.Identity BrickletRotaryEncoder.getIdentity()
Return Object:
  • uid – Type: String, Length: up to 8
  • connectedUid – Type: String, Length: up to 8
  • position – Type: char
  • hardwareVersion – Type: short[], Length: 3, Range: [0 to 255]
  • firmwareVersion – Type: short[], Length: 3, 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' or 'd'.

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

Callback Configuration Functions

void BrickletRotaryEncoder.setCountCallbackPeriod(long period)
Parameters:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

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

The CountCallback callback is only triggered if the count has changed since the last triggering.

long BrickletRotaryEncoder.getCountCallbackPeriod()
Returns:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by setCountCallbackPeriod().

void BrickletRotaryEncoder.setCountCallbackThreshold(char option, int min, int max)
Parameters:
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: int, Range: [-231 to 231 - 1]
  • max – Type: int, Range: [-231 to 231 - 1]

Sets the thresholds for the CountReachedCallback callback.

The following options are possible:

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

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

The following constants are available for this function:

For option:

  • BrickletRotaryEncoder.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_GREATER = '>'
BrickletRotaryEncoder.CountCallbackThreshold BrickletRotaryEncoder.getCountCallbackThreshold()
Return Object:
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: int, Range: [-231 to 231 - 1]
  • max – Type: int, Range: [-231 to 231 - 1]

Returns the threshold as set by setCountCallbackThreshold().

The following constants are available for this function:

For option:

  • BrickletRotaryEncoder.THRESHOLD_OPTION_OFF = 'x'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletRotaryEncoder.THRESHOLD_OPTION_GREATER = '>'
void BrickletRotaryEncoder.setDebouncePeriod(long debounce)
Parameters:
  • debounce – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

Sets the period with which the threshold callback

is triggered, if the thresholds

keeps being reached.

long BrickletRotaryEncoder.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 BrickletRotaryEncoder.CountCallback
Event Object:
  • count – Type: int, Range: [-231 to 231 - 1]

This callback is triggered periodically with the period that is set by setCountCallbackPeriod(). The parameter is the count of the encoder.

The CountCallback callback is only triggered if the count 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 addCountCallback() function. An added callback function can be removed with the removeCountCallback() function.

callback BrickletRotaryEncoder.CountReachedCallback
Event Object:
  • count – Type: int, Range: [-231 to 231 - 1]

This callback is triggered when the threshold as set by setCountCallbackThreshold() is reached. The parameter is the count of the encoder.

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 addCountReachedCallback() function. An added callback function can be removed with the removeCountReachedCallback() function.

callback BrickletRotaryEncoder.PressedCallback
Event Object:
  • empty object

This callback is triggered when the button is pressed.

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 addPressedCallback() function. An added callback function can be removed with the removePressedCallback() function.

callback BrickletRotaryEncoder.ReleasedCallback
Event Object:
  • empty object

This callback is triggered when the button is released.

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 addReleasedCallback() function. An added callback function can be removed with the removeReleasedCallback() function.

Constants

int BrickletRotaryEncoder.DEVICE_IDENTIFIER

This constant is used to identify a Rotary Encoder Bricklet.

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

String BrickletRotaryEncoder.DEVICE_DISPLAY_NAME

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