Delphi/Lazarus - Dual Button Bricklet

This is the description of the Delphi/Lazarus API bindings for the Dual Button Bricklet. General information and technical specifications for the Dual Button 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).

Callback

Download (ExampleCallback.pas)

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program ExampleCallback;

{$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
{$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}

uses
  SysUtils, IPConnection, BrickletDualButton;

type
  TExample = class
  private
    ipcon: TIPConnection;
    db: TBrickletDualButton;
  public
    procedure StateChangedCB(sender: TBrickletDualButton; const buttonL: byte;
                             const buttonR: byte; const ledL: byte; const ledR: byte);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for state changed callback }
procedure TExample.StateChangedCB(sender: TBrickletDualButton; const buttonL: byte;
                                  const buttonR: byte; const ledL: byte;
                                  const ledR: byte);
begin
  if (buttonL = BRICKLET_DUAL_BUTTON_BUTTON_STATE_PRESSED) then begin
    WriteLn('Left Button: Pressed');
  end
  else if (buttonL = BRICKLET_DUAL_BUTTON_BUTTON_STATE_RELEASED) then begin
    WriteLn('Left Button: Released');
  end;

  if (buttonR = BRICKLET_DUAL_BUTTON_BUTTON_STATE_PRESSED) then begin
    WriteLn('Right Button: Pressed');
  end
  else if (buttonR = BRICKLET_DUAL_BUTTON_BUTTON_STATE_RELEASED) then begin
    WriteLn('Right Button: Released');
  end;

  WriteLn('');
end;

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

  { Create device object }
  db := TBrickletDualButton.Create(UID, ipcon);

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

  { Register state changed callback to procedure StateChangedCB }
  db.OnStateChanged := {$ifdef FPC}@{$endif}StateChangedCB;

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

Creates an object with the unique device ID uid:

dualButton := TBrickletDualButton.Create('YOUR_DEVICE_UID', ipcon);

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

procedure TBrickletDualButton.SetLEDState(const ledL: byte; const ledR: byte)

Sets the state of the LEDs. Possible states are:

  • 0 = AutoToggleOn: Enables auto toggle with initially enabled LED.
  • 1 = AutoToggleOff: Activates auto toggle with initially disabled LED.
  • 2 = On: Enables LED (auto toggle is disabled).
  • 3 = Off: Disables LED (auto toggle is disabled).

In auto toggle mode the LED is toggled automatically at each press of a button.

If you just want to set one of the LEDs and don't know the current state of the other LED, you can get the state with GetLEDState or you can use SetSelectedLEDState.

The default value is (1, 1).

The following constants are available for this function:

  • BRICKLET_DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_ON = 0
  • BRICKLET_DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_OFF = 1
  • BRICKLET_DUAL_BUTTON_LED_STATE_ON = 2
  • BRICKLET_DUAL_BUTTON_LED_STATE_OFF = 3
procedure TBrickletDualButton.GetLEDState(out ledL: byte; out ledR: byte)

Returns the current state of the LEDs, as set by SetLEDState.

The following constants are available for this function:

  • BRICKLET_DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_ON = 0
  • BRICKLET_DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_OFF = 1
  • BRICKLET_DUAL_BUTTON_LED_STATE_ON = 2
  • BRICKLET_DUAL_BUTTON_LED_STATE_OFF = 3
procedure TBrickletDualButton.GetButtonState(out buttonL: byte; out buttonR: byte)

Returns the current state for both buttons. Possible states are:

  • 0 = pressed
  • 1 = released

The following constants are available for this function:

  • BRICKLET_DUAL_BUTTON_BUTTON_STATE_PRESSED = 0
  • BRICKLET_DUAL_BUTTON_BUTTON_STATE_RELEASED = 1

Advanced Functions

procedure TBrickletDualButton.SetSelectedLEDState(const led: byte; const state: byte)

Sets the state of the selected LED (0 or 1).

The other LED remains untouched.

The following constants are available for this function:

  • BRICKLET_DUAL_BUTTON_LED_LEFT = 0
  • BRICKLET_DUAL_BUTTON_LED_RIGHT = 1
  • BRICKLET_DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_ON = 0
  • BRICKLET_DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_OFF = 1
  • BRICKLET_DUAL_BUTTON_LED_STATE_ON = 2
  • BRICKLET_DUAL_BUTTON_LED_STATE_OFF = 3
function TBrickletDualButton.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 TBrickletDualButton.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 TBrickletDualButton.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_DUAL_BUTTON_FUNCTION_SET_LED_STATE = 1
  • BRICKLET_DUAL_BUTTON_FUNCTION_SET_SELECTED_LED_STATE = 5
procedure TBrickletDualButton.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletDualButton.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: TBrickletDualButton; const param: word);
begin
  WriteLn(param);
end;

dualButton.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 TBrickletDualButton.OnStateChanged
procedure(sender: TBrickletDualButton; const buttonL: byte; const buttonR: byte; const ledL: byte; const ledR: byte) of object;

This callback is called whenever a button is pressed.

Possible states for buttons are:

  • 0 = pressed
  • 1 = released

Possible states for LEDs are:

  • 0 = AutoToggleOn: Auto toggle enabled and LED on.
  • 1 = AutoToggleOff: Auto toggle enabled and LED off.
  • 2 = On: LED on (auto toggle is disabled).
  • 3 = Off: LED off (auto toggle is disabled).

The following constants are available for this function:

  • BRICKLET_DUAL_BUTTON_BUTTON_STATE_PRESSED = 0
  • BRICKLET_DUAL_BUTTON_BUTTON_STATE_RELEASED = 1
  • BRICKLET_DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_ON = 0
  • BRICKLET_DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_OFF = 1
  • BRICKLET_DUAL_BUTTON_LED_STATE_ON = 2
  • BRICKLET_DUAL_BUTTON_LED_STATE_OFF = 3

Constants

const BRICKLET_DUAL_BUTTON_DEVICE_IDENTIFIER

This constant is used to identify a Dual Button 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_DUAL_BUTTON_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Dual Button Bricklet.