Delphi/Lazarus - Laser Range Finder Bricklet – Tinkerforge

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# Delphi/Lazarus - 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 Delphi/Lazarus 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 Delphi/Lazarus API bindings is part of their general description.

## Examples

The example code below is Public Domain (CC0 1.0).

### Simple

Download (ExampleSimple.pas)

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    program ExampleSimple;

    {$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
    {$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}

    uses
      SysUtils, IPConnection, BrickletLaserRangeFinder;

    type
      TExample = class
      private
        ipcon: TIPConnection;
        lrf: TBrickletLaserRangeFinder;
      public
        procedure Execute;
      end;

    const
      HOST = 'localhost';
      PORT = 4223;
      UID = 'XYZ'; { Change to your UID }

    var
      e: TExample;

    procedure TExample.Execute;
    var distance: word;
    begin
      { Create IP connection }
      ipcon := TIPConnection.Create;

      { Create device object }
      lrf := TBrickletLaserRangeFinder.Create(UID, ipcon);

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

      { Turn laser on and wait 250ms for very first measurement to be ready }
      lrf.EnableLaser;
      Sleep(250);

      { Get current distance (unit is cm) }
      distance := lrf.GetDistance;
      WriteLn(Format('Distance: %d cm', [distance]));

      WriteLn('Press key to exit');
      ReadLn;
      ipcon.Destroy; { Calls ipcon.Disconnect internally }
    end;

    begin
      e := TExample.Create;
      e.Execute;
      e.Destroy;
    end.

### Callback

Download (ExampleCallback.pas)

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    program ExampleCallback;

    {$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
    {$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}

    uses
      SysUtils, IPConnection, BrickletLaserRangeFinder;

    type
      TExample = class
      private
        ipcon: TIPConnection;
        lrf: TBrickletLaserRangeFinder;
      public
        procedure DistanceCB(sender: TBrickletLaserRangeFinder; const distance: word);
        procedure Execute;
      end;

    const
      HOST = 'localhost';
      PORT = 4223;
      UID = 'XYZ'; { Change to your UID }

    var
      e: TExample;

    { Callback function for distance callback (parameter has unit cm) }
    procedure TExample.DistanceCB(sender: TBrickletLaserRangeFinder; const distance: word);
    begin
      WriteLn(Format('Distance: %d cm', [distance]));
    end;

    procedure TExample.Execute;
    begin
      { Create IP connection }
      ipcon := TIPConnection.Create;

      { Create device object }
      lrf := TBrickletLaserRangeFinder.Create(UID, ipcon);

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

      { Turn laser on and wait 250ms for very first measurement to be ready }
      lrf.EnableLaser;
      Sleep(250);

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

      { Register distance callback to procedure DistanceCB }
      lrf.OnDistance := {$ifdef FPC}@{$endif}DistanceCB;

      WriteLn('Press key to exit');
      ReadLn;
      ipcon.Destroy; { Calls ipcon.Disconnect internally }
    end;

    begin
      e := TExample.Create;
      e.Execute;
      e.Destroy;
    end.

### Threshold

Download (ExampleThreshold.pas)

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    program ExampleThreshold;

    {$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
    {$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}

    uses
      SysUtils, IPConnection, BrickletLaserRangeFinder;

    type
      TExample = class
      private
        ipcon: TIPConnection;
        lrf: TBrickletLaserRangeFinder;
      public
        procedure ReachedCB(sender: TBrickletLaserRangeFinder; const distance: word);
        procedure Execute;
      end;

    const
      HOST = 'localhost';
      PORT = 4223;
      UID = 'XYZ'; { Change to your UID }

    var
      e: TExample;

    { Callback for distance greater than 20 cm }
    procedure TExample.ReachedCB(sender: TBrickletLaserRangeFinder; const distance: word);
    begin
      WriteLn(Format('Distance: %d cm.', [distance]));
    end;

    procedure TExample.Execute;
    begin
      { Create IP connection }
      ipcon := TIPConnection.Create;

      { Create device object }
      lrf := TBrickletLaserRangeFinder.Create(UID, ipcon);

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

      { Turn laser on and wait 250ms for very first measurement to be ready }
      lrf.EnableLaser;
      Sleep(250);

      { Get threshold callbacks with a debounce time of 10 seconds (10000ms) }
      lrf.SetDebouncePeriod(10000);

      { Register threshold reached callback to procedure ReachedCB }
      lrf.OnDistanceReached := {$ifdef FPC}@{$endif}ReachedCB;

      { Configure threshold for "greater than 20 cm" }
      lrf.SetDistanceCallbackThreshold('>', 20, 0);

      WriteLn('Press key to exit');
      ReadLn;
      ipcon.Destroy; { Calls ipcon.Disconnect internally }
    end;

    begin
      e := TExample.Create;
      e.Execute;
      e.Destroy;
    end.

## API

Since Delphi does not support multiple return values directly, we use the `out` keyword to return multiple values from a function.

All functions and procedures listed below are thread-safe.

### Basic Functions

constructor `TBrickletLaserRangeFinder.``Create`(const uid: string; ipcon: TIPConnection)

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

      laserRangeFinder := TBrickletLaserRangeFinder.Create('YOUR_DEVICE_UID', ipcon);

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

function `TBrickletLaserRangeFinder.``GetDistance`: word

  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 `OnDistance` and set the period with `SetDistanceCallbackPeriod`.

function `TBrickletLaserRangeFinder.``GetVelocity`: smallint

  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 `OnVelocity` and set the period with `SetVelocityCallbackPeriod`.

procedure `TBrickletLaserRangeFinder.``SetMode`(const mode: byte)

  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:

  - BRICKLET_LASER_RANGE_FINDER_MODE_DISTANCE = 0
  - BRICKLET_LASER_RANGE_FINDER_MODE_VELOCITY_MAX_13MS = 1
  - BRICKLET_LASER_RANGE_FINDER_MODE_VELOCITY_MAX_32MS = 2
  - BRICKLET_LASER_RANGE_FINDER_MODE_VELOCITY_MAX_64MS = 3
  - BRICKLET_LASER_RANGE_FINDER_MODE_VELOCITY_MAX_127MS = 4

function `TBrickletLaserRangeFinder.``GetMode`: byte

  Returns the mode as set by `SetMode`.

  The following constants are available for this function:

  - BRICKLET_LASER_RANGE_FINDER_MODE_DISTANCE = 0
  - BRICKLET_LASER_RANGE_FINDER_MODE_VELOCITY_MAX_13MS = 1
  - BRICKLET_LASER_RANGE_FINDER_MODE_VELOCITY_MAX_32MS = 2
  - BRICKLET_LASER_RANGE_FINDER_MODE_VELOCITY_MAX_64MS = 3
  - BRICKLET_LASER_RANGE_FINDER_MODE_VELOCITY_MAX_127MS = 4

procedure `TBrickletLaserRangeFinder.``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.

procedure `TBrickletLaserRangeFinder.``DisableLaser`

  Deactivates the laser of the LIDAR.

function `TBrickletLaserRangeFinder.``IsLaserEnabled`: boolean

  Returns true if the laser is enabled, false otherwise.

### Advanced Functions

procedure `TBrickletLaserRangeFinder.``SetMovingAverage`(const distanceAverageLength: byte; const velocityAverageLength: byte)

  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.

procedure `TBrickletLaserRangeFinder.``GetMovingAverage`(out distanceAverageLength: byte; out velocityAverageLength: byte)

  Returns the length moving average as set by `SetMovingAverage`.

function `TBrickletLaserRangeFinder.``GetAPIVersion`: array [0..2] of byte

  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.

function `TBrickletLaserRangeFinder.``GetResponseExpected`(const functionId: byte): 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.

  See `SetResponseExpected` for the list of function ID constants available for this function.

procedure `TBrickletLaserRangeFinder.``SetResponseExpected`(const functionId: byte; const responseExpected: 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 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:

  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 3
  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_SET_VELOCITY_CALLBACK_PERIOD = 5
  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 7
  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_SET_VELOCITY_CALLBACK_THRESHOLD = 9
  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_SET_DEBOUNCE_PERIOD = 11
  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_SET_MOVING_AVERAGE = 13
  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_SET_MODE = 15
  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_ENABLE_LASER = 17
  - BRICKLET_LASER_RANGE_FINDER_FUNCTION_DISABLE_LASER = 18

procedure `TBrickletLaserRangeFinder.``SetResponseExpectedAll`(const responseExpected: boolean)

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

procedure `TBrickletLaserRangeFinder.``GetIdentity`(out uid: string; out connectedUid: string; out position: char; out hardwareVersion: array [0..2] of byte; out firmwareVersion: array [0..2] of byte; out deviceIdentifier: word)

  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

procedure `TBrickletLaserRangeFinder.``SetDistanceCallbackPeriod`(const period: longword)

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

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

  The default value is 0.

function `TBrickletLaserRangeFinder.``GetDistanceCallbackPeriod`: longword

  Returns the period as set by `SetDistanceCallbackPeriod`.

procedure `TBrickletLaserRangeFinder.``SetVelocityCallbackPeriod`(const period: longword)

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

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

  The default value is 0.

function `TBrickletLaserRangeFinder.``GetVelocityCallbackPeriod`: longword

  Returns the period as set by `SetVelocityCallbackPeriod`.

procedure `TBrickletLaserRangeFinder.``SetDistanceCallbackThreshold`(const option: char; const min: word; const max: word)

  Sets the thresholds for the `OnDistanceReached` 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:

  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_OFF = 'x'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_OUTSIDE = 'o'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_INSIDE = 'i'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_SMALLER = '<'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_GREATER = '>'

procedure `TBrickletLaserRangeFinder.``GetDistanceCallbackThreshold`(out option: char; out min: word; out max: word)

  Returns the threshold as set by `SetDistanceCallbackThreshold`.

  The following constants are available for this function:

  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_OFF = 'x'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_OUTSIDE = 'o'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_INSIDE = 'i'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_SMALLER = '<'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_GREATER = '>'

procedure `TBrickletLaserRangeFinder.``SetVelocityCallbackThreshold`(const option: char; const min: smallint; const max: smallint)

  Sets the thresholds for the `OnVelocityReached` 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:

  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_OFF = 'x'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_OUTSIDE = 'o'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_INSIDE = 'i'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_SMALLER = '<'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_GREATER = '>'

procedure `TBrickletLaserRangeFinder.``GetVelocityCallbackThreshold`(out option: char; out min: smallint; out max: smallint)

  Returns the threshold as set by `SetVelocityCallbackThreshold`.

  The following constants are available for this function:

  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_OFF = 'x'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_OUTSIDE = 'o'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_INSIDE = 'i'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_SMALLER = '<'
  - BRICKLET_LASER_RANGE_FINDER_THRESHOLD_OPTION_GREATER = '>'

procedure `TBrickletLaserRangeFinder.``SetDebouncePeriod`(const debounce: longword)

  Sets the period in ms with which the threshold callbacks

  - `OnDistanceReached`,
  - `OnVelocityReached`,

  are triggered, if the thresholds

  - `SetDistanceCallbackThreshold`,
  - `SetVelocityCallbackThreshold`,

  keep being reached.

  The default value is 100.

function `TBrickletLaserRangeFinder.``GetDebouncePeriod`: longword

  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 by assigning a procedure to an callback property of the device object:

>     procedure TExample.MyCallback(sender: TBrickletLaserRangeFinder; const param: word);
>     begin
>       WriteLn(param);
>     end;

>     laserRangeFinder.OnExample := {$ifdef FPC}@{$endif}example.MyCallback;

The available callback property and their type of parameters 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.

property `TBrickletLaserRangeFinder.``OnDistance`

      procedure(sender: TBrickletLaserRangeFinder; const distance: word) of object;

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

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

property `TBrickletLaserRangeFinder.``OnVelocity`

      procedure(sender: TBrickletLaserRangeFinder; const velocity: smallint) of object;

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

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

property `TBrickletLaserRangeFinder.``OnDistanceReached`

      procedure(sender: TBrickletLaserRangeFinder; const distance: word) of object;

  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`.

property `TBrickletLaserRangeFinder.``OnVelocityReached`

      procedure(sender: TBrickletLaserRangeFinder; const velocity: smallint) of object;

  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`.

### Constants

const `BRICKLET_LASER_RANGE_FINDER_DEVICE_IDENTIFIER`

  This constant is used to identify a Laser Range Finder Bricklet.

  The `GetIdentity` function and the `OnEnumerate` callback of the IP Connection have a `deviceIdentifier` parameter to specify the Brick's or Bricklet's type.

The content of this page is licensed under Creative Commons Attribution 3.0 Unported License.