Delphi/Lazarus - Laser Range Finder Bricklet

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 XYZ to the UID of your Laser Range Finder Bricklet }

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

  WriteLn('Press key to exit');
  ReadLn;
  lrf.DisableLaser; { Turn laser off }
  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 XYZ to the UID of your Laser Range Finder Bricklet }

var
  e: TExample;

{ Callback procedure for distance callback }
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);

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

  { Set period for distance callback to 0.2s (200ms)
    Note: The distance callback is only called every 0.2 seconds
          if the distance has changed since the last call! }
  lrf.SetDistanceCallbackPeriod(200);

  WriteLn('Press key to exit');
  ReadLn;
  lrf.DisableLaser; { Turn laser off }
  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 DistanceReachedCB(sender: TBrickletLaserRangeFinder; const distance: word);
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'XYZ'; { Change XYZ to the UID of your Laser Range Finder Bricklet }

var
  e: TExample;

{ Callback procedure for distance reached callback }
procedure TExample.DistanceReachedCB(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 distance reached callback to procedure DistanceReachedCB }
  lrf.OnDistanceReached := {$ifdef FPC}@{$endif}DistanceReachedCB;

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

  WriteLn('Press key to exit');
  ReadLn;
  lrf.DisableLaser; { Turn laser off }
  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.

Sensor hardware version 1 (see GetSensorHardwareVersion) cannot measure distance and velocity at the same time. Therefore, the distance mode has to be enabled using SetMode. Sensor hardware version 3 can measure distance and velocity at the same time. Also the laser has to be enabled, see EnableLaser.

If you want to get the distance periodically, it is recommended to use the OnDistance callback and set the period with SetDistanceCallbackPeriod.

function TBrickletLaserRangeFinder.GetVelocity: smallint

Returns the measured velocity. The value has a range of -12800 to 12700 and is given in 1/100 m/s.

Sensor hardware version 1 (see GetSensorHardwareVersion) cannot measure distance and velocity at the same time. Therefore, the velocity mode has to be enabled using SetMode. Sensor hardware version 3 can measure distance and velocity at the same time, but the velocity measurement only produces stables results if a fixed measurement rate (see SetConfiguration) is configured. Also the laser has to be enabled, see EnableLaser.

If you want to get the velocity periodically, it is recommended to use the OnVelocity callback and set the period with SetVelocityCallbackPeriod.

procedure TBrickletLaserRangeFinder.SetMode(const mode: byte)

Note

This function is only available if you have a LIDAR-Lite sensor with hardware version 1. Use SetConfiguration for hardware version 3. You can check the sensor hardware version using GetSensorHardwareVersion.

The LIDAR-Lite sensor (hardware version 1) 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.

procedure TBrickletLaserRangeFinder.SetConfiguration(const acquisitionCount: byte; const enableQuickTermination: boolean; const thresholdValue: byte; const measurementFrequency: word)

Note

This function is only available if you have a LIDAR-Lite sensor with hardware version 3. Use SetMode for hardware version 1. You can check the sensor hardware version using GetSensorHardwareVersion.

The Aquisition Count defines the number of times the Laser Range Finder Bricklet will integrate acquisitions to find a correlation record peak. With a higher count, the Bricklet can measure longer distances. With a lower count, the rate increases. The allowed values are 1-255.

If you set Enable Quick Termination to true, the distance measurement will be terminated early if a high peak was already detected. This means that a higher measurement rate can be achieved and long distances can be measured at the same time. However, the chance of false-positive distance measurements increases.

Normally the distance is calculated with a detection algorithm that uses peak value, signal strength and noise. You can however also define a fixed Threshold Value. Set this to a low value if you want to measure the distance to something that has very little reflection (e.g. glass) and set it to a high value if you want to measure the distance to something with a very high reflection (e.g. mirror). Set this to 0 to use the default algorithm. The other allowed values are 1-255.

Set the Measurement Frequency in Hz to force a fixed measurement rate. If set to 0, the Laser Range Finder Bricklet will use the optimal frequency according to the other configurations and the actual measured distance. Since the rate is not fixed in this case, the velocity measurement is not stable. For a stable velocity measurement you should set a fixed measurement frequency. The lower the frequency, the higher is the resolution of the calculated velocity. The allowed values are 10Hz-500Hz (and 0 to turn the fixed frequency off).

The default values for Acquisition Count, Enable Quick Termination, Threshold Value and Measurement Frequency are 128, false, 0 and 0.

New in version 2.0.3 (Plugin).

procedure TBrickletLaserRangeFinder.GetConfiguration(out acquisitionCount: byte; out enableQuickTermination: boolean; out thresholdValue: byte; out measurementFrequency: word)

Returns the configuration as set by SetConfiguration.

New in version 2.0.3 (Plugin).

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.GetSensorHardwareVersion: byte

Returns the LIDAR-Lite hardware version.

The following constants are available for this function:

  • BRICKLET_LASER_RANGE_FINDER_VERSION_1 = 1
  • BRICKLET_LASER_RANGE_FINDER_VERSION_3 = 3

New in version 2.0.3 (Plugin).

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.

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
  • BRICKLET_LASER_RANGE_FINDER_FUNCTION_SET_CONFIGURATION = 25
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.

The OnDistance callback 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.

The OnVelocity callback 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

are triggered, if the thresholds

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.

The OnDistance callback 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.

The OnVelocity callback 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.

const BRICKLET_LASER_RANGE_FINDER_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Laser Range Finder Bricklet.