MATLAB/Octave - Laser Range Finder Bricklet – Tinkerforge

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# MATLAB/Octave - Laser Range Finder Bricklet

Note

This Bricklet is currently in the prototype stage and the software/hardware as well as the documentation is in an incomplete state.

This is the description of the MATLAB/Octave API bindings for the Laser Range Finder Bricklet. General information and technical specifications for the Laser Range Finder 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.BrickletLaserRangeFinder;

        HOST = 'localhost';
        PORT = 4223;
        UID = 'XYZ'; % Change to your UID

        ipcon = IPConnection(); % Create IP connection
        lrf = BrickletLaserRangeFinder(UID, ipcon); % Create device object

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

        % Turn laser on and wait 250ms for very first measurement to be ready
        lrf.enableLaser();
        pause(0.25);

        % Get current distance (unit is cm)
        distance = lrf.getDistance();
        fprintf('Distance: %g cm\n', distance);

        input('Press any 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.BrickletLaserRangeFinder;

        HOST = 'localhost';
        PORT = 4223;
        UID = 'amb'; % Change to your UID

        ipcon = IPConnection(); % Create IP connection
        lrf = BrickletLaserRangeFinder(UID, ipcon); % Create device object

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

        % Turn laser on and wait 250ms for very first measurement to be ready
        lrf.enableLaser();
        pause(0.25);

        % Set Period for distance callback to 1s (1000ms)
        % Note: The callback is only called every second if the
        %       distance has changed since the last call!
        lrf.setDistanceCallbackPeriod(1000);

        % Register distance callback to function cb_distance
        set(lrf, 'DistanceCallback', @(h, e) cb_distance(e));

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

    % Callback function for distance callback (parameter has unit cm)
    function cb_distance(e)
        fprintf('Distance: %g cm\n', e.distance);
    end

### Threshold (MATLAB)

Download (matlab_example_threshold.m)

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

        HOST = 'localhost';
        PORT = 4223;
        UID = 'amb'; % Change to your UID

        ipcon = IPConnection(); % Create IP connection
        lrf = BrickletLaserRangeFinder(UID, ipcon); % Create device object

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

        % Turn laser on and wait 250ms for very first measurement to be ready
        lrf.enableLaser();
        pause(0.25);

        % Set threshold callbacks with a debounce time of 10 seconds (10000ms)
        lrf.setDebouncePeriod(10000);

        % Register threshold reached callback to function cb_reached
        set(lrf, 'DistanceReachedCallback', @(h, e) cb_reached(e));

        % Configure threshold for "greater than 20 cm"
        lrf.setDistanceCallbackThreshold('>', 20, 0);

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

    % Callback for distance greater than 20 cm
    function cb_reached(e)
        fprintf('Distance %g cm\n', e.distance);
    end

### Simple (Octave)

Download (octave_example_simple.m)

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    function octave_example_simple()
        more off;

        HOST = "localhost";
        PORT = 4223;
        UID = "amb"; % Change to your UID

        ipcon = java_new("com.tinkerforge.IPConnection"); % Create IP connection
        lrf = java_new("com.tinkerforge.BrickletLaserRangeFinder", UID, ipcon); % Create device object

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

        % Turn laser on and wait 250ms for very first measurement to be ready
        lrf.enableLaser();
        pause(0.25);

        % Get current distance (unit is cm)
        distance = lrf.getDistance();
        fprintf("Distance: %g cm\n", distance);

        input("Press any 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 = "amb"; % Change to your UID

        ipcon = java_new("com.tinkerforge.IPConnection"); % Create IP connection
        lrf = java_new("com.tinkerforge.BrickletLaserRangeFinder", UID, ipcon); % Create device object

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

        % Turn laser on and wait 250ms for very first measurement to be ready
        lrf.enableLaser();
        pause(0.25);

        % Set Period for distance callback to 1s (1000ms)
        % Note: The callback is only called every second if the
        %       distance has changed since the last call!
        lrf.setDistanceCallbackPeriod(1000);

        % Register distance callback to function cb_distance
        lrf.addDistanceCallback(@cb_distance);

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

    % Callback function for distance callback (parameter has unit cm)
    function cb_distance(e)
        fprintf("Distance: %g cm\n", e.distance);
    end

### Threshold (Octave)

Download (octave_example_threshold.m)

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    function octave_example_threshold()
        more off;

        HOST = "localhost";
        PORT = 4223;
        UID = "amb"; % Change to your UID

        ipcon = java_new("com.tinkerforge.IPConnection"); % Create IP connection
        lrf = java_new("com.tinkerforge.BrickletLaserRangeFinder", UID, ipcon); % Create device object

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

        % Turn laser on and wait 250ms for very first measurement to be ready
        lrf.enableLaser();
        pause(0.25);

        % Set threshold callbacks with a debounce time of 10 seconds (10000ms)
        lrf.setDebouncePeriod(10000);

        % Configure threshold for "greater than 20 cm"
        lrf.setDistanceCallbackThreshold(lrf.THRESHOLD_OPTION_GREATER, 20, 0);

        % Register threshold reached callback to function cb_reached
        lrf.addDistanceReachedCallback(@cb_reached);

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

    % Callback function for distance callback (parameter has unit cm)
    function cb_reached(e)
        fprintf("Distance %g cm\n", e.distance);
    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 `BrickletLaserRangeFinder`(String uid, IPConnection ipcon)

  Creates an object with the unique device ID `uid`.

  In MATLAB:

      import com.tinkerforge.BrickletLaserRangeFinder;

      laserRangeFinder = BrickletLaserRangeFinder('YOUR_DEVICE_UID', ipcon);

  In Octave:

      laserRangeFinder = java_new("com.tinkerforge.BrickletLaserRangeFinder", "YOUR_DEVICE_UID", ipcon);

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

public int `getDistance`()

  Returns the measured distance. The value has a range of 0 to 4000 and is given in cm.

  The Laser Range Finder Bricklet knows different modes. Distances are only measured in the distance measurement mode, see `setMode()`. Also the laser has to be enabled, see `enableLaser()`.

  If you want to get the distance periodically, it is recommended to use the callback `DistanceCallback` and set the period with `setDistanceCallbackPeriod()`.

public short `getVelocity`()

  Returns the measured velocity. The value has a range of 0 to 12700 and is given in 1/100 m/s.

  The Laser Range Finder Bricklet knows different modes. Velocity is only measured in the velocity measurement modes, see `setMode()`. Also the laser has to be enabled, see `enableLaser()`.

  If you want to get the velocity periodically, it is recommended to use the callback `VelocityCallback` and set the period with `setVelocityCallbackPeriod()`.

public void `setMode`(short mode)

  The LIDAR has five different modes. One mode is for distance measurements and four modes are for velocity measurements with different ranges.

  The following modes are available:

  - 0: Distance is measured with resolution 1.0 cm and range 0-400 cm
  - 1: Velocity is measured with resolution 0.1 m/s and range is 0-12.7 m/s
  - 2: Velocity is measured with resolution 0.25 m/s and range is 0-31.75 m/s
  - 3: Velocity is measured with resolution 0.5 m/s and range is 0-63.5 m/s
  - 4: Velocity is measured with resolution 1.0 m/s and range is 0-127 m/s

  The default mode is 0 (distance is measured).

  The following constants are available for this function:

  - BrickletLaserRangeFinder.MODE_DISTANCE = 0
  - BrickletLaserRangeFinder.MODE_VELOCITY_MAX_13MS = 1
  - BrickletLaserRangeFinder.MODE_VELOCITY_MAX_32MS = 2
  - BrickletLaserRangeFinder.MODE_VELOCITY_MAX_64MS = 3
  - BrickletLaserRangeFinder.MODE_VELOCITY_MAX_127MS = 4

public short `getMode`()

  Returns the mode as set by `setMode()`.

  The following constants are available for this function:

  - BrickletLaserRangeFinder.MODE_DISTANCE = 0
  - BrickletLaserRangeFinder.MODE_VELOCITY_MAX_13MS = 1
  - BrickletLaserRangeFinder.MODE_VELOCITY_MAX_32MS = 2
  - BrickletLaserRangeFinder.MODE_VELOCITY_MAX_64MS = 3
  - BrickletLaserRangeFinder.MODE_VELOCITY_MAX_127MS = 4

public void `enableLaser`()

  Activates the laser of the LIDAR.

  We recommend that you wait 250ms after enabling the laser before the first call of `getDistance()` to ensure stable measurements.

public void `disableLaser`()

  Deactivates the laser of the LIDAR.

public boolean `isLaserEnabled`()

  Returns true if the laser is enabled, false otherwise.

### Advanced Functions

public void `setMovingAverage`(short distanceAverageLength, short velocityAverageLength)

  Sets the length of a moving averaging for the distance and velocity.

  Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.

  The range for the averaging is 0-30.

  The default value is 10.

public BrickletLaserRangeFinder.MovingAverage `getMovingAverage`()

  Returns the length moving average as set by `setMovingAverage()`.

  The returned object has the public member variables `short distanceAverageLength` and `short velocityAverageLength`.

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 and callbacks it is always disabled.

  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:

  - BrickletLaserRangeFinder.FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 3
  - BrickletLaserRangeFinder.FUNCTION_SET_VELOCITY_CALLBACK_PERIOD = 5
  - BrickletLaserRangeFinder.FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 7
  - BrickletLaserRangeFinder.FUNCTION_SET_VELOCITY_CALLBACK_THRESHOLD = 9
  - BrickletLaserRangeFinder.FUNCTION_SET_DEBOUNCE_PERIOD = 11
  - BrickletLaserRangeFinder.FUNCTION_SET_MOVING_AVERAGE = 13
  - BrickletLaserRangeFinder.FUNCTION_SET_MODE = 15
  - BrickletLaserRangeFinder.FUNCTION_ENABLE_LASER = 17
  - BrickletLaserRangeFinder.FUNCTION_DISABLE_LASER = 18

public void `setResponseExpectedAll`(boolean responseExpected)

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

public BrickletLaserRangeFinder.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 `setDistanceCallbackPeriod`(long period)

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

  `DistanceCallback` is only triggered if the distance value has changed since the last triggering.

  The default value is 0.

public long `getDistanceCallbackPeriod`()

  Returns the period as set by `setDistanceCallbackPeriod()`.

public void `setVelocityCallbackPeriod`(long period)

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

  `VelocityCallback` is only triggered if the velocity value has changed since the last triggering.

  The default value is 0.

public long `getVelocityCallbackPeriod`()

  Returns the period as set by `setVelocityCallbackPeriod()`.

public void `setDistanceCallbackThreshold`(char option, int min, int max)

  Sets the thresholds for the `DistanceReachedCallback` callback.

  The following options are possible:

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

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

public BrickletLaserRangeFinder.DistanceCallbackThreshold `getDistanceCallbackThreshold`()

  Returns the threshold as set by `setDistanceCallbackThreshold()`.

  The following constants are available for this function:

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

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

public void `setVelocityCallbackThreshold`(char option, short min, short max)

  Sets the thresholds for the `VelocityReachedCallback` callback.

  The following options are possible:

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

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

  The following constants are available for this function:

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

public BrickletLaserRangeFinder.VelocityCallbackThreshold `getVelocityCallbackThreshold`()

  Returns the threshold as set by `setVelocityCallbackThreshold()`.

  The following constants are available for this function:

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

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

public void `setDebouncePeriod`(long debounce)

  Sets the period in ms with which the threshold callbacks

  - `DistanceReachedCallback`,
  - `VelocityReachedCallback`,

  are triggered, if the thresholds

  - `setDistanceCallbackThreshold()`,
  - `setVelocityCallbackThreshold()`,

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

    set(device, 'ExampleCallback', @(h, e) cb_example(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 cb_example(e)
        fprintf("Parameter: %s\n", e.param);
    end

    device.addExampleCallback(@cb_example);

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 `BrickletLaserRangeFinder.DistanceCallback`

  Parameters: | distance -- int

  This callback is triggered periodically with the period that is set by `setDistanceCallbackPeriod()`. The parameter is the distance value of the sensor.

  `DistanceCallback` is only triggered if the distance value 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 `addDistanceCallback()` function. An added callback function can be removed with the `removeDistanceCallback()` function.

public callback `BrickletLaserRangeFinder.VelocityCallback`

  Parameters: | velocity -- short

  This callback is triggered periodically with the period that is set by `setVelocityCallbackPeriod()`. The parameter is the velocity value of the sensor.

  `VelocityCallback` is only triggered if the velocity 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 `addVelocityCallback()` function. An added callback function can be removed with the `removeVelocityCallback()` function.

public callback `BrickletLaserRangeFinder.DistanceReachedCallback`

  Parameters: | distance -- int

  This callback is triggered when the threshold as set by `setDistanceCallbackThreshold()` is reached. The parameter is the distance value 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 `addDistanceReachedCallback()` function. An added callback function can be removed with the `removeDistanceReachedCallback()` function.

public callback `BrickletLaserRangeFinder.VelocityReachedCallback`

  Parameters: | velocity -- short

  This callback is triggered when the threshold as set by `setVelocityCallbackThreshold()` is reached. The parameter is the velocity value 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 `addVelocityReachedCallback()` function. An added callback function can be removed with the `removeVelocityReachedCallback()` function.

### Constants

public static final int `BrickletLaserRangeFinder.DEVICE_IDENTIFIER`

  This constant is used to identify a Laser Range Finder 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.

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