Delphi/Lazarus - Line Bricklet

This is the description of the Delphi/Lazarus 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 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, BrickletLine;

type
  TExample = class
  private
    ipcon: TIPConnection;
    l: TBrickletLine;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

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

  { Create device object }
  l := TBrickletLine.Create(UID, ipcon);

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

  { Get current reflectivity }
  reflectivity := l.GetReflectivity;
  WriteLn(Format('Reflectivity: %d', [reflectivity]));

  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, BrickletLine;

type
  TExample = class
  private
    ipcon: TIPConnection;
    l: TBrickletLine;
  public
    procedure ReflectivityCB(sender: TBrickletLine; const reflectivity: word);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for reflectivity callback }
procedure TExample.ReflectivityCB(sender: TBrickletLine; const reflectivity: word);
begin
  WriteLn(Format('Reflectivity: %d', [reflectivity]));
end;

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

  { Create device object }
  l := TBrickletLine.Create(UID, ipcon);

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

  { Register reflectivity callback to procedure ReflectivityCB }
  l.OnReflectivity := {$ifdef FPC}@{$endif}ReflectivityCB;

  { 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);

  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, BrickletLine;

type
  TExample = class
  private
    ipcon: TIPConnection;
    l: TBrickletLine;
  public
    procedure ReflectivityReachedCB(sender: TBrickletLine; const reflectivity: word);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for reflectivity reached callback }
procedure TExample.ReflectivityReachedCB(sender: TBrickletLine; const reflectivity: word);
begin
  WriteLn(Format('Reflectivity: %d', [reflectivity]));
end;

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

  { Create device object }
  l := TBrickletLine.Create(UID, ipcon);

  { Connect to brickd }
  ipcon.Connect(HOST, PORT);
  { 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 procedure ReflectivityReachedCB }
  l.OnReflectivityReached := {$ifdef FPC}@{$endif}ReflectivityReachedCB;

  { Configure threshold for reflectivity "greater than 2000" }
  l.SetReflectivityCallbackThreshold('>', 2000, 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 TBrickletLine.Create(const uid: string; ipcon: TIPConnection)

Creates an object with the unique device ID uid:

line := TBrickletLine.Create('YOUR_DEVICE_UID', ipcon);

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

function TBrickletLine.GetReflectivity: word

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 OnReflectivity callback and set the period with SetReflectivityCallbackPeriod.

Advanced Functions

function TBrickletLine.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 TBrickletLine.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 TBrickletLine.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_LINE_FUNCTION_SET_REFLECTIVITY_CALLBACK_PERIOD = 2
  • BRICKLET_LINE_FUNCTION_SET_REFLECTIVITY_CALLBACK_THRESHOLD = 4
  • BRICKLET_LINE_FUNCTION_SET_DEBOUNCE_PERIOD = 6
procedure TBrickletLine.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletLine.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 TBrickletLine.SetReflectivityCallbackPeriod(const period: longword)

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

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

The default value is 0.

function TBrickletLine.GetReflectivityCallbackPeriod: longword

Returns the period as set by SetReflectivityCallbackPeriod.

procedure TBrickletLine.SetReflectivityCallbackThreshold(const option: char; const min: word; const max: word)

Sets the thresholds for the OnReflectivityReached 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:

  • BRICKLET_LINE_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_LINE_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_LINE_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_LINE_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_LINE_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletLine.GetReflectivityCallbackThreshold(out option: char; out min: word; out max: word)

Returns the threshold as set by SetReflectivityCallbackThreshold.

The following constants are available for this function:

  • BRICKLET_LINE_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_LINE_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_LINE_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_LINE_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_LINE_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletLine.SetDebouncePeriod(const debounce: longword)

Sets the period in ms with which the threshold callback

is triggered, if the threshold

keeps being reached.

The default value is 100.

function TBrickletLine.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: TBrickletLine; const param: word);
begin
  WriteLn(param);
end;

line.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 TBrickletLine.OnReflectivity
procedure(sender: TBrickletLine; const reflectivity: word) of object;

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

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

property TBrickletLine.OnReflectivityReached
procedure(sender: TBrickletLine; const reflectivity: word) of object;

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.

Constants

const BRICKLET_LINE_DEVICE_IDENTIFIER

This constant is used to identify a Line 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_LINE_DEVICE_DISPLAY_NAME

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