Delphi/Lazarus - Multi Touch Bricklet

This is the description of the Delphi/Lazarus API bindings for the Multi Touch Bricklet. General information and technical specifications for the Multi Touch 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, BrickletMultiTouch;

type
  TExample = class
  private
    ipcon: TIPConnection;
    mt: TBrickletMultiTouch;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

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

  { Create device object }
  mt := TBrickletMultiTouch.Create(UID, ipcon);

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

  { Get current touch state }
  state := mt.GetTouchState;

  if (state And (1 Shl 12)) = (1 Shl 12) then begin
    Write('In proximity, ');
  end;

  if (state And $fff) = 0 then begin
    WriteLn('No electrodes touched');
  end
  else begin
    Write('Electrodes ');
    for i := 0 to 11 do begin
      if (state And (1 Shl i)) = (1 Shl i) then begin
        Write(IntToStr(i) + ' ');
      end;
    end;
    WriteLn('touched');
  end;
  WriteLn('');

  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, BrickletMultiTouch;

type
  TExample = class
  private
    ipcon: TIPConnection;
    mt: TBrickletMultiTouch;
  public
    procedure TouchStateCB(sender: TBrickletMultiTouch; const state: word);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for touch state callback }
procedure TExample.TouchStateCB(sender: TBrickletMultiTouch; const state: word);
var i: integer;
begin
  if (state And (1 Shl 12)) = (1 Shl 12) then begin
    Write('In proximity, ');
  end;

  if (state And $fff) = 0 then begin
    WriteLn('No electrodes touched');
  end
  else begin
    Write('Electrodes ');
    for i := 0 to 11 do begin
      if (state And (1 Shl i)) = (1 Shl i) then begin
        Write(IntToStr(i) + ' ');
      end;
    end;
    WriteLn('touched');
  end;
end;

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

  { Create device object }
  mt := TBrickletMultiTouch.Create(UID, ipcon);

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

  { Register touch state callback to procedure TouchStateCB }
  mt.OnTouchState := {$ifdef FPC}@{$endif}TouchStateCB;

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

Creates an object with the unique device ID uid:

multiTouch := TBrickletMultiTouch.Create('YOUR_DEVICE_UID', ipcon);

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

function TBrickletMultiTouch.GetTouchState: word

Returns the current touch state. The state is given as a bitfield.

Bits 0 to 11 represent the 12 electrodes and bit 12 represents the proximity.

If an electrode is touched, the corresponding bit is true. If a hand or similar is in proximity to the electrodes, bit 12 is true.

Example: The state 4103 = 0x1007 = 0b1000000000111 means that electrodes 0, 1 and 2 are touched and that something is in the proximity of the electrodes.

The proximity is activated with a distance of 1-2cm. An electrode is already counted as touched if a finger is nearly touching the electrode. This means that you can put a piece of paper or foil or similar on top of a electrode to build a touch panel with a professional look.

procedure TBrickletMultiTouch.Recalibrate

Recalibrates the electrodes. Call this function whenever you changed or moved you electrodes.

procedure TBrickletMultiTouch.SetElectrodeConfig(const enabledElectrodes: word)

Enables/disables electrodes with a bitfield (see GetTouchState).

True enables the electrode, false disables the electrode. A disabled electrode will always return false as its state. If you don't need all electrodes you can disable the electrodes that are not needed.

It is recommended that you disable the proximity bit (bit 12) if the proximity feature is not needed. This will reduce the amount of traffic that is produced by the OnTouchState callback.

Disabling electrodes will also reduce power consumption.

Default: 8191 = 0x1FFF = 0b1111111111111 (all electrodes enabled)

function TBrickletMultiTouch.GetElectrodeConfig: word

Returns the electrode configuration, as set by SetElectrodeConfig.

procedure TBrickletMultiTouch.SetElectrodeSensitivity(const sensitivity: byte)

Sets the sensitivity of the electrodes. An electrode with a high sensitivity will register a touch earlier then an electrode with a low sensitivity.

If you build a big electrode you might need to decrease the sensitivity, since the area that can be charged will get bigger. If you want to be able to activate an electrode from further away you need to increase the sensitivity.

After a new sensitivity is set, you likely want to call Recalibrate to calibrate the electrodes with the newly defined sensitivity.

The valid sensitivity value range is 5-201.

The default sensitivity value is 181.

function TBrickletMultiTouch.GetElectrodeSensitivity: byte

Returns the current sensitivity, as set by SetElectrodeSensitivity.

Advanced Functions

function TBrickletMultiTouch.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 TBrickletMultiTouch.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 TBrickletMultiTouch.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_MULTI_TOUCH_FUNCTION_RECALIBRATE = 2
  • BRICKLET_MULTI_TOUCH_FUNCTION_SET_ELECTRODE_CONFIG = 3
  • BRICKLET_MULTI_TOUCH_FUNCTION_SET_ELECTRODE_SENSITIVITY = 6
procedure TBrickletMultiTouch.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletMultiTouch.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

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: TBrickletMultiTouch; const param: word);
begin
  WriteLn(param);
end;

multiTouch.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 TBrickletMultiTouch.OnTouchState
procedure(sender: TBrickletMultiTouch; const state: word) of object;

Returns the current touch state, see GetTouchState for information about the state.

This callback is triggered every time the touch state changes.

Constants

const BRICKLET_MULTI_TOUCH_DEVICE_IDENTIFIER

This constant is used to identify a Multi Touch 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_MULTI_TOUCH_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Multi Touch Bricklet.