Delphi/Lazarus - Linear Poti Bricklet

This is the description of the Delphi/Lazarus API bindings for the Linear Poti Bricklet. General information and technical specifications for the Linear Poti 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, BrickletLinearPoti;

type
  TExample = class
  private
    ipcon: TIPConnection;
    lp: TBrickletLinearPoti;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

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

  { Create device object }
  lp := TBrickletLinearPoti.Create(UID, ipcon);

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

  { Get current position }
  position := lp.GetPosition;
  WriteLn(Format('Position: %d', [position])); { Range: 0 to 100 }

  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, BrickletLinearPoti;

type
  TExample = class
  private
    ipcon: TIPConnection;
    lp: TBrickletLinearPoti;
  public
    procedure PositionCB(sender: TBrickletLinearPoti; const position: word);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for position callback }
procedure TExample.PositionCB(sender: TBrickletLinearPoti; const position: word);
begin
  WriteLn(Format('Position: %d', [position])); { Range: 0 to 100 }
end;

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

  { Create device object }
  lp := TBrickletLinearPoti.Create(UID, ipcon);

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

  { Register position callback to procedure PositionCB }
  lp.OnPosition := {$ifdef FPC}@{$endif}PositionCB;

  { Set period for position callback to 0.05s (50ms)
    Note: The position callback is only called every 0.05 seconds
          if the position has changed since the last call! }
  lp.SetPositionCallbackPeriod(50);

  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 TBrickletLinearPoti.Create(const uid: string; ipcon: TIPConnection)

Creates an object with the unique device ID uid:

linearPoti := TBrickletLinearPoti.Create('YOUR_DEVICE_UID', ipcon);

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

function TBrickletLinearPoti.GetPosition: word

Returns the position of the linear potentiometer. The value is between 0 (slider down) and 100 (slider up).

If you want to get the position periodically, it is recommended to use the OnPosition callback and set the period with SetPositionCallbackPeriod.

Advanced Functions

function TBrickletLinearPoti.GetAnalogValue: word

Returns the value as read by a 12-bit analog-to-digital converter. The value is between 0 and 4095.

Note

The value returned by GetPosition is averaged over several samples to yield less noise, while GetAnalogValue gives back raw unfiltered analog values. The only reason to use GetAnalogValue is, if you need the full resolution of the analog-to-digital converter.

If you want the analog value periodically, it is recommended to use the OnAnalogValue callback and set the period with SetAnalogValueCallbackPeriod.

function TBrickletLinearPoti.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 TBrickletLinearPoti.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 TBrickletLinearPoti.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_LINEAR_POTI_FUNCTION_SET_POSITION_CALLBACK_PERIOD = 3
  • BRICKLET_LINEAR_POTI_FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 5
  • BRICKLET_LINEAR_POTI_FUNCTION_SET_POSITION_CALLBACK_THRESHOLD = 7
  • BRICKLET_LINEAR_POTI_FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 9
  • BRICKLET_LINEAR_POTI_FUNCTION_SET_DEBOUNCE_PERIOD = 11
procedure TBrickletLinearPoti.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletLinearPoti.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 TBrickletLinearPoti.SetPositionCallbackPeriod(const period: longword)

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

The OnPosition callback is only triggered if the position has changed since the last triggering.

The default value is 0.

function TBrickletLinearPoti.GetPositionCallbackPeriod: longword

Returns the period as set by SetPositionCallbackPeriod.

procedure TBrickletLinearPoti.SetAnalogValueCallbackPeriod(const period: longword)

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

The OnAnalogValue callback is only triggered if the analog value has changed since the last triggering.

The default value is 0.

function TBrickletLinearPoti.GetAnalogValueCallbackPeriod: longword

Returns the period as set by SetAnalogValueCallbackPeriod.

procedure TBrickletLinearPoti.SetPositionCallbackThreshold(const option: char; const min: word; const max: word)

Sets the thresholds for the OnPositionReached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the position is outside the min and max values
'i' Callback is triggered when the position is inside the min and max values
'<' Callback is triggered when the position is smaller than the min value (max is ignored)
'>' Callback is triggered when the position 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_LINEAR_POTI_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletLinearPoti.GetPositionCallbackThreshold(out option: char; out min: word; out max: word)

Returns the threshold as set by SetPositionCallbackThreshold.

The following constants are available for this function:

  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletLinearPoti.SetAnalogValueCallbackThreshold(const option: char; const min: word; const max: word)

Sets the thresholds for the OnAnalogValueReached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the analog value is outside the min and max values
'i' Callback is triggered when the analog value is inside the min and max values
'<' Callback is triggered when the analog value is smaller than the min value (max is ignored)
'>' Callback is triggered when the analog 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_LINEAR_POTI_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletLinearPoti.GetAnalogValueCallbackThreshold(out option: char; out min: word; out max: word)

Returns the threshold as set by SetAnalogValueCallbackThreshold.

The following constants are available for this function:

  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_LINEAR_POTI_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletLinearPoti.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 TBrickletLinearPoti.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: TBrickletLinearPoti; const param: word);
begin
  WriteLn(param);
end;

linearPoti.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 TBrickletLinearPoti.OnPosition
procedure(sender: TBrickletLinearPoti; const position: word) of object;

This callback is triggered periodically with the period that is set by SetPositionCallbackPeriod. The parameter is the position of the linear potentiometer.

The OnPosition callback is only triggered if the position has changed since the last triggering.

property TBrickletLinearPoti.OnAnalogValue
procedure(sender: TBrickletLinearPoti; const value: word) of object;

This callback is triggered periodically with the period that is set by SetAnalogValueCallbackPeriod. The parameter is the analog value of the Linear Potentiometer.

The OnAnalogValue callback is only triggered if the position has changed since the last triggering.

property TBrickletLinearPoti.OnPositionReached
procedure(sender: TBrickletLinearPoti; const position: word) of object;

This callback is triggered when the threshold as set by SetPositionCallbackThreshold is reached. The parameter is the position of the linear potentiometer.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by SetDebouncePeriod.

property TBrickletLinearPoti.OnAnalogValueReached
procedure(sender: TBrickletLinearPoti; const value: word) of object;

This callback is triggered when the threshold as set by SetAnalogValueCallbackThreshold is reached. The parameter is the analog value of the linear potentiometer.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by SetDebouncePeriod.

Constants

const BRICKLET_LINEAR_POTI_DEVICE_IDENTIFIER

This constant is used to identify a Linear Poti 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_LINEAR_POTI_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Linear Poti Bricklet.