Delphi/Lazarus - Distance US Bricklet – Tinkerforge

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# 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;
        dr: TBrickletDistanceUS;
      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 }
      dr := TBrickletDistanceUS.Create(UID, ipcon);

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

      { Get current distance value }
      distance := dr.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;
        dr: TBrickletDistanceUS;
      public
        procedure DistanceCB(sender: TBrickletDistanceUS; const distance: word);
        procedure Execute;
      end;

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

    var
      e: TExample;

    { Callback function for distance value }
    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 }
      dr := TBrickletDistanceUS.Create(UID, ipcon);

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

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

      { Register distance callback to procedure DistanceCB }
      dr.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, BrickletDistanceUS;

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

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

    var
      e: TExample;

    { Callback for distance value smaller than 200 }
    procedure TExample.ReachedCB(sender: TBrickletDistanceUS; const distance: word);
    begin
      WriteLn(Format('Distance Value is smaller than 200: %d', [distance]));
    end;

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

      { Create device object }
      dr := 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 second (10000ms) }
      dr.SetDebouncePeriod(10000);

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

      { Configure threshold for "smaller than 200" }
      dr.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 callback `OnDistance` 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 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_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.

  `OnDistance` 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: smallint; const max: smallint)

  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: smallint; out max: smallint)

  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

  - `OnDistanceReached`,

  are triggered, if the thresholds

  - `SetDistanceCallbackThreshold`,

  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.

  `OnDistance` 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.

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