Delphi/Lazarus - Distance US Bricklet

This is the description of the Delphi/Lazarus API bindings for the Distance US Bricklet. General information and technical specifications for the Distance US 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, BrickletDistanceUS;

type
  TExample = class
  private
    ipcon: TIPConnection;
    dus: TBrickletDistanceUS;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

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

  { Create device object }
  dus := TBrickletDistanceUS.Create(UID, ipcon);

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

  { Get current distance value }
  distance := dus.GetDistanceValue;
  WriteLn(Format('Distance Value: %d', [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, BrickletDistanceUS;

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

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

var
  e: TExample;

{ Callback procedure for distance value callback }
procedure TExample.DistanceCB(sender: TBrickletDistanceUS; const distance: word);
begin
  WriteLn(Format('Distance Value: %d', [distance]));
end;

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

  { Create device object }
  dus := TBrickletDistanceUS.Create(UID, ipcon);

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

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

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

  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, BrickletDistanceUS;

type
  TExample = class
  private
    ipcon: TIPConnection;
    dus: TBrickletDistanceUS;
  public
    procedure DistanceReachedCB(sender: TBrickletDistanceUS; const distance: word);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for distance value reached callback }
procedure TExample.DistanceReachedCB(sender: TBrickletDistanceUS; const distance: word);
begin
  WriteLn(Format('Distance Value: %d', [distance]));
end;

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

  { Create device object }
  dus := TBrickletDistanceUS.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 10 seconds (10000ms) }
  dus.SetDebouncePeriod(10000);

  { Register distance value reached callback to procedure DistanceReachedCB }
  dus.OnDistanceReached := {$ifdef FPC}@{$endif}DistanceReachedCB;

  { Configure threshold for distance value "smaller than 200" }
  dus.SetDistanceCallbackThreshold('<', 200, 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 TBrickletDistanceUS.Create(const uid: string; ipcon: TIPConnection)

Creates an object with the unique device ID uid:

distanceUS := TBrickletDistanceUS.Create('YOUR_DEVICE_UID', ipcon);

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

function TBrickletDistanceUS.GetDistanceValue: word

Returns the current distance value measured by the sensor. The value has a range of 0 to 4095. A small value corresponds to a small distance, a big value corresponds to a big distance. The relation between the measured distance value and the actual distance is affected by the 5V supply voltage (deviations in the supply voltage result in deviations in the distance values) and is non-linear (resolution is bigger at close range).

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

Advanced Functions

procedure TBrickletDistanceUS.SetMovingAverage(const average: byte)

Sets the length of a moving averaging for the distance value.

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 0-100.

The default value is 20.

function TBrickletDistanceUS.GetMovingAverage: byte

Returns the length moving average as set by SetMovingAverage.

function TBrickletDistanceUS.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 TBrickletDistanceUS.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 TBrickletDistanceUS.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_DISTANCE_US_FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 2
  • BRICKLET_DISTANCE_US_FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 4
  • BRICKLET_DISTANCE_US_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BRICKLET_DISTANCE_US_FUNCTION_SET_MOVING_AVERAGE = 10
procedure TBrickletDistanceUS.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletDistanceUS.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 TBrickletDistanceUS.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.

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

The default value is 0.

function TBrickletDistanceUS.GetDistanceCallbackPeriod: longword

Returns the period as set by SetDistanceCallbackPeriod.

procedure TBrickletDistanceUS.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_DISTANCE_US_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_DISTANCE_US_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_DISTANCE_US_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_DISTANCE_US_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_DISTANCE_US_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletDistanceUS.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_DISTANCE_US_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_DISTANCE_US_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_DISTANCE_US_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_DISTANCE_US_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_DISTANCE_US_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletDistanceUS.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 TBrickletDistanceUS.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: TBrickletDistanceUS; const param: word);
begin
  WriteLn(param);
end;

distanceUS.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 TBrickletDistanceUS.OnDistance
procedure(sender: TBrickletDistanceUS; 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 TBrickletDistanceUS.OnDistanceReached
procedure(sender: TBrickletDistanceUS; 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.

Constants

const BRICKLET_DISTANCE_US_DEVICE_IDENTIFIER

This constant is used to identify a Distance US 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_DISTANCE_US_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Distance US Bricklet.