MATLAB/Octave - Line Bricklet

This is the description of the MATLAB/Octave API bindings for the Line Bricklet. General information and technical specifications for the Line 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.BrickletLine;

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

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

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

    % Get current reflectivity
    reflectivity = l.getReflectivity();
    fprintf('Reflectivity: %i\n', reflectivity);

    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.BrickletLine;

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

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

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

    % Register reflectivity callback to function cb_reflectivity
    set(l, 'ReflectivityCallback', @(h, e) cb_reflectivity(e));

    % Set period for reflectivity callback to 1s (1000ms)
    % Note: The reflectivity callback is only called every second
    %       if the reflectivity has changed since the last call!
    l.setReflectivityCallbackPeriod(1000);

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

% Callback function for reflectivity callback
function cb_reflectivity(e)
    fprintf('Reflectivity: %i\n', e.reflectivity);
end

Threshold (MATLAB)

Download (matlab_example_threshold.m)

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function matlab_example_threshold()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletLine;

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

    ipcon = IPConnection(); % Create IP connection
    l = handle(BrickletLine(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 1 second (1000ms)
    l.setDebouncePeriod(1000);

    % Register reflectivity reached callback to function cb_reflectivity_reached
    set(l, 'ReflectivityReachedCallback', @(h, e) cb_reflectivity_reached(e));

    % Configure threshold for reflectivity "greater than 2000"
    l.setReflectivityCallbackThreshold('>', 2000, 0);

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

% Callback function for reflectivity reached callback
function cb_reflectivity_reached(e)
    fprintf('Reflectivity: %i\n', e.reflectivity);
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 Line Bricklet

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

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

    % Get current reflectivity
    reflectivity = l.getReflectivity();
    fprintf("Reflectivity: %d\n", reflectivity);

    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 Line Bricklet

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

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

    % Register reflectivity callback to function cb_reflectivity
    l.addReflectivityCallback(@cb_reflectivity);

    % Set period for reflectivity callback to 1s (1000ms)
    % Note: The reflectivity callback is only called every second
    %       if the reflectivity has changed since the last call!
    l.setReflectivityCallbackPeriod(1000);

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

% Callback function for reflectivity callback
function cb_reflectivity(e)
    fprintf("Reflectivity: %d\n", e.reflectivity);
end

Threshold (Octave)

Download (octave_example_threshold.m)

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function octave_example_threshold()
    more off;

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

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    l = javaObject("com.tinkerforge.BrickletLine", 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 1 second (1000ms)
    l.setDebouncePeriod(1000);

    % Register reflectivity reached callback to function cb_reflectivity_reached
    l.addReflectivityReachedCallback(@cb_reflectivity_reached);

    % Configure threshold for reflectivity "greater than 2000"
    l.setReflectivityCallbackThreshold(">", 2000, 0);

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

% Callback function for reflectivity reached callback
function cb_reflectivity_reached(e)
    fprintf("Reflectivity: %d\n", e.reflectivity);
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 BrickletLine(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletLine;

line = BrickletLine('YOUR_DEVICE_UID', ipcon);

In Octave:

line = java_new("com.tinkerforge.BrickletLine", "YOUR_DEVICE_UID", ipcon);

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

public int getReflectivity()

Returns the currently measured reflectivity. The reflectivity is a value between 0 (not reflective) and 4095 (very reflective).

Usually black has a low reflectivity while white has a high reflectivity.

If you want to get the reflectivity periodically, it is recommended to use the ReflectivityCallback callback and set the period with setReflectivityCallbackPeriod().

Advanced Functions

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:

  • BrickletLine.FUNCTION_SET_REFLECTIVITY_CALLBACK_PERIOD = 2
  • BrickletLine.FUNCTION_SET_REFLECTIVITY_CALLBACK_THRESHOLD = 4
  • BrickletLine.FUNCTION_SET_DEBOUNCE_PERIOD = 6
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletLine.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 setReflectivityCallbackPeriod(long period)

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

The ReflectivityCallback callback is only triggered if the reflectivity has changed since the last triggering.

The default value is 0.

public long getReflectivityCallbackPeriod()

Returns the period as set by setReflectivityCallbackPeriod().

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

Sets the thresholds for the ReflectivityReachedCallback callback.

The following options are possible:

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

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

The following constants are available for this function:

  • BrickletLine.THRESHOLD_OPTION_OFF = 'x'
  • BrickletLine.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLine.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLine.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLine.THRESHOLD_OPTION_GREATER = '>'
public BrickletLine.ReflectivityCallbackThreshold getReflectivityCallbackThreshold()

Returns the threshold as set by setReflectivityCallbackThreshold().

The following constants are available for this function:

  • BrickletLine.THRESHOLD_OPTION_OFF = 'x'
  • BrickletLine.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLine.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLine.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLine.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 callback

is triggered, if the threshold

keeps 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 BrickletLine.ReflectivityCallback
Parameters:reflectivity -- int

This callback is triggered periodically with the period that is set by setReflectivityCallbackPeriod(). The parameter is the reflectivity of the sensor.

The ReflectivityCallback callback is only triggered if the reflectivity 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 addReflectivityCallback() function. An added callback function can be removed with the removeReflectivityCallback() function.

public callback BrickletLine.ReflectivityReachedCallback
Parameters:reflectivity -- int

This callback is triggered when the threshold as set by setReflectivityCallbackThreshold() is reached. The parameter is the reflectivity of the sensor.

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 addReflectivityReachedCallback() function. An added callback function can be removed with the removeReflectivityReachedCallback() function.

Constants

public static final int BrickletLine.DEVICE_IDENTIFIER

This constant is used to identify a Line 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 BrickletLine.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Line Bricklet.