Delphi/Lazarus - Joystick Bricklet

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

type
  TExample = class
  private
    ipcon: TIPConnection;
    j: TBrickletJoystick;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

procedure TExample.Execute;
var x, y: smallint;
begin
  { Create IP connection }
  ipcon := TIPConnection.Create;

  { Create device object }
  j := TBrickletJoystick.Create(UID, ipcon);

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

  { Get current position }
  j.GetPosition(x, y);

  WriteLn(Format('Position [X]: %d', [x]));
  WriteLn(Format('Position [Y]: %d', [y]));

  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, BrickletJoystick;

type
  TExample = class
  private
    ipcon: TIPConnection;
    j: TBrickletJoystick;
  public
    procedure PressedCB(sender: TBrickletJoystick);
    procedure ReleasedCB(sender: TBrickletJoystick);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for pressed callback }
procedure TExample.PressedCB(sender: TBrickletJoystick);
begin
  WriteLn('Pressed');
end;

{ Callback procedure for released callback }
procedure TExample.ReleasedCB(sender: TBrickletJoystick);
begin
  WriteLn('Released');
end;

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

  { Create device object }
  j := TBrickletJoystick.Create(UID, ipcon);

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

  { Register pressed callback to procedure PressedCB }
  j.OnPressed := {$ifdef FPC}@{$endif}PressedCB;

  { Register released callback to procedure ReleasedCB }
  j.OnReleased := {$ifdef FPC}@{$endif}ReleasedCB;

  WriteLn('Press key to exit');
  ReadLn;
  ipcon.Destroy; { Calls ipcon.Disconnect internally }
end;

begin
  e := TExample.Create;
  e.Execute;
  e.Destroy;
end.

Find Borders

Download (ExampleFindBorders.pas)

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program ExampleFindBorders;

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

uses
  SysUtils, IPConnection, BrickletJoystick;

type
  TExample = class
  private
    ipcon: TIPConnection;
    j: TBrickletJoystick;
  public
    procedure PositionReachedCB(sender: TBrickletJoystick; const x: smallint;
                                const y: smallint);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for position reached callback }
procedure TExample.PositionReachedCB(sender: TBrickletJoystick; const x: smallint;
                                     const y: smallint);
begin
  if (y = 100) then begin
    WriteLn('Top');
  end
  else if (y = -100) then begin
    WriteLn('Bottom');
  end;
  if (x = 100) then begin
    WriteLn('Right');
  end
  else if (x = -100) then begin
    WriteLn('Left');
  end;
  WriteLn('');
end;

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

  { Create device object }
  j := TBrickletJoystick.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 0.2 seconds (200ms) }
  j.SetDebouncePeriod(200);

  { Register position reached callback to procedure PositionReachedCB }
  j.OnPositionReached := {$ifdef FPC}@{$endif}PositionReachedCB;

  { Configure threshold for position "outside of -99, -99 to 99, 99" }
  j.SetPositionCallbackThreshold('o', -99, 99, -99, 99);

  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 TBrickletJoystick.Create(const uid: string; ipcon: TIPConnection)
Parameters:
  • uid – Type: string
  • ipcon – Type: TIPConnection
Returns:
  • joystick – Type: TBrickletJoystick

Creates an object with the unique device ID uid:

joystick := TBrickletJoystick.Create('YOUR_DEVICE_UID', ipcon);

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

procedure TBrickletJoystick.GetPosition(out x: smallint; out y: smallint)
Output Parameters:
  • x – Type: smallint, Range: [-100 to 100]
  • y – Type: smallint, Range: [-100 to 100]

Returns the position of the joystick. The middle position of the joystick is x=0, y=0. The returned values are averaged and calibrated (see Calibrate).

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

function TBrickletJoystick.IsPressed: boolean
Returns:
  • pressed – Type: boolean

Returns true if the button is pressed and false otherwise.

It is recommended to use the OnPressed and OnReleased callbacks to handle the button.

Advanced Functions

procedure TBrickletJoystick.GetAnalogValue(out x: word; out y: word)
Output Parameters:
  • x – Type: word, Range: [0 to 4095]
  • y – Type: word, Range: [0 to 4095]

Returns the values as read by a 12-bit analog-to-digital converter.

Note

The values returned by GetPosition are 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 values periodically, it is recommended to use the OnAnalogValue callback and set the period with SetAnalogValueCallbackPeriod.

procedure TBrickletJoystick.Calibrate

Calibrates the middle position of the joystick. If your Joystick Bricklet does not return x=0 and y=0 in the middle position, call this function while the joystick is standing still in the middle position.

The resulting calibration will be saved on the EEPROM of the Joystick Bricklet, thus you only have to calibrate it once.

procedure TBrickletJoystick.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)
Output Parameters:
  • uid – Type: string, Length: up to 8
  • connectedUid – Type: string, Length: up to 8
  • position – Type: char, Range: ['a' to 'h', 'i', 'z']
  • hardwareVersion – Type: array [0..2] of byte
    • 0: major – Type: byte, Range: [0 to 255]
    • 1: minor – Type: byte, Range: [0 to 255]
    • 2: revision – Type: byte, Range: [0 to 255]
  • firmwareVersion – Type: array [0..2] of byte
    • 0: major – Type: byte, Range: [0 to 255]
    • 1: minor – Type: byte, Range: [0 to 255]
    • 2: revision – Type: byte, Range: [0 to 255]
  • deviceIdentifier – Type: word, Range: [0 to 216 - 1]

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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as position 'z'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

procedure TBrickletJoystick.SetPositionCallbackPeriod(const period: longword)
Parameters:
  • period – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Sets the period 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.

function TBrickletJoystick.GetPositionCallbackPeriod: longword
Returns:
  • period – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by SetPositionCallbackPeriod.

procedure TBrickletJoystick.SetAnalogValueCallbackPeriod(const period: longword)
Parameters:
  • period – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Sets the period 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 values have changed since the last triggering.

function TBrickletJoystick.GetAnalogValueCallbackPeriod: longword
Returns:
  • period – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by SetAnalogValueCallbackPeriod.

procedure TBrickletJoystick.SetPositionCallbackThreshold(const option: char; const minX: smallint; const maxX: smallint; const minY: smallint; const maxY: smallint)
Parameters:
  • option – Type: char, Range: See constants, Default: 'x'
  • minX – Type: smallint, Range: [-215 to 215 - 1], Default: 0
  • maxX – Type: smallint, Range: [-215 to 215 - 1], Default: 0
  • minY – Type: smallint, Range: [-215 to 215 - 1], Default: 0
  • maxY – Type: smallint, Range: [-215 to 215 - 1], Default: 0

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 values (max is ignored)
'>' Callback is triggered when the position is greater than the min values (max is ignored)

The following constants are available for this function:

For option:

  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletJoystick.GetPositionCallbackThreshold(out option: char; out minX: smallint; out maxX: smallint; out minY: smallint; out maxY: smallint)
Output Parameters:
  • option – Type: char, Range: See constants, Default: 'x'
  • minX – Type: smallint, Range: [-215 to 215 - 1], Default: 0
  • maxX – Type: smallint, Range: [-215 to 215 - 1], Default: 0
  • minY – Type: smallint, Range: [-215 to 215 - 1], Default: 0
  • maxY – Type: smallint, Range: [-215 to 215 - 1], Default: 0

Returns the threshold as set by SetPositionCallbackThreshold.

The following constants are available for this function:

For option:

  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletJoystick.SetAnalogValueCallbackThreshold(const option: char; const minX: word; const maxX: word; const minY: word; const maxY: word)
Parameters:
  • option – Type: char, Range: See constants, Default: 'x'
  • minX – Type: word, Range: [0 to 216 - 1], Default: 0
  • maxX – Type: word, Range: [0 to 216 - 1], Default: 0
  • minY – Type: word, Range: [0 to 216 - 1], Default: 0
  • maxY – Type: word, Range: [0 to 216 - 1], Default: 0

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 values are outside the min and max values
'i' Callback is triggered when the analog values are inside the min and max values
'<' Callback is triggered when the analog values are smaller than the min values (max is ignored)
'>' Callback is triggered when the analog values are greater than the min values (max is ignored)

The following constants are available for this function:

For option:

  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletJoystick.GetAnalogValueCallbackThreshold(out option: char; out minX: word; out maxX: word; out minY: word; out maxY: word)
Output Parameters:
  • option – Type: char, Range: See constants, Default: 'x'
  • minX – Type: word, Range: [0 to 216 - 1], Default: 0
  • maxX – Type: word, Range: [0 to 216 - 1], Default: 0
  • minY – Type: word, Range: [0 to 216 - 1], Default: 0
  • maxY – Type: word, Range: [0 to 216 - 1], Default: 0

Returns the threshold as set by SetAnalogValueCallbackThreshold.

The following constants are available for this function:

For option:

  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_JOYSTICK_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletJoystick.SetDebouncePeriod(const debounce: longword)
Parameters:
  • debounce – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

Sets the period with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

function TBrickletJoystick.GetDebouncePeriod: longword
Returns:
  • debounce – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

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: TBrickletJoystick; const value: longint);
begin
  WriteLn(Format('Value: %d', [value]));
end;

joystick.OnExample := {$ifdef FPC}@{$endif}example.MyCallback;

The available callback properties and their parameter types 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 TBrickletJoystick.OnPosition
procedure(sender: TBrickletJoystick; const x: smallint; const y: smallint) of object;
Callback Parameters:
  • sender – Type: TBrickletJoystick
  • x – Type: smallint, Range: [-100 to 100]
  • y – Type: smallint, Range: [-100 to 100]

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

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

property TBrickletJoystick.OnAnalogValue
procedure(sender: TBrickletJoystick; const x: word; const y: word) of object;
Callback Parameters:
  • sender – Type: TBrickletJoystick
  • x – Type: word, Range: [0 to 4095]
  • y – Type: word, Range: [0 to 4095]

This callback is triggered periodically with the period that is set by SetAnalogValueCallbackPeriod. The parameters are the analog values of the joystick.

The OnAnalogValue callback is only triggered if the values have changed since the last triggering.

property TBrickletJoystick.OnPositionReached
procedure(sender: TBrickletJoystick; const x: smallint; const y: smallint) of object;
Callback Parameters:
  • sender – Type: TBrickletJoystick
  • x – Type: smallint, Range: [-100 to 100]
  • y – Type: smallint, Range: [-100 to 100]

This callback is triggered when the threshold as set by SetPositionCallbackThreshold is reached. The parameters are the position of the joystick.

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

property TBrickletJoystick.OnAnalogValueReached
procedure(sender: TBrickletJoystick; const x: word; const y: word) of object;
Callback Parameters:
  • sender – Type: TBrickletJoystick
  • x – Type: word, Range: [0 to 4095]
  • y – Type: word, Range: [0 to 4095]

This callback is triggered when the threshold as set by SetAnalogValueCallbackThreshold is reached. The parameters are the analog values of the joystick.

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

property TBrickletJoystick.OnPressed
procedure(sender: TBrickletJoystick) of object;
Callback Parameters:
  • sender – Type: TBrickletJoystick

This callback is triggered when the button is pressed.

property TBrickletJoystick.OnReleased
procedure(sender: TBrickletJoystick) of object;
Callback Parameters:
  • sender – Type: TBrickletJoystick

This callback is triggered when the button is released.

Virtual Functions

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

function TBrickletJoystick.GetAPIVersion: array [0..2] of byte
Output Parameters:
  • apiVersion – Type: array [0..2] of byte
    • 0: major – Type: byte, Range: [0 to 255]
    • 1: minor – Type: byte, Range: [0 to 255]
    • 2: revision – Type: byte, Range: [0 to 255]

Returns the version of the API definition 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 TBrickletJoystick.GetResponseExpected(const functionId: byte): boolean
Parameters:
  • functionId – Type: byte, Range: See constants
Returns:
  • responseExpected – Type: 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.

The following constants are available for this function:

For functionId:

  • BRICKLET_JOYSTICK_FUNCTION_CALIBRATE = 4
  • BRICKLET_JOYSTICK_FUNCTION_SET_POSITION_CALLBACK_PERIOD = 5
  • BRICKLET_JOYSTICK_FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 7
  • BRICKLET_JOYSTICK_FUNCTION_SET_POSITION_CALLBACK_THRESHOLD = 9
  • BRICKLET_JOYSTICK_FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 11
  • BRICKLET_JOYSTICK_FUNCTION_SET_DEBOUNCE_PERIOD = 13
procedure TBrickletJoystick.SetResponseExpected(const functionId: byte; const responseExpected: boolean)
Parameters:
  • functionId – Type: byte, Range: See constants
  • responseExpected – Type: 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 constants are available for this function:

For functionId:

  • BRICKLET_JOYSTICK_FUNCTION_CALIBRATE = 4
  • BRICKLET_JOYSTICK_FUNCTION_SET_POSITION_CALLBACK_PERIOD = 5
  • BRICKLET_JOYSTICK_FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 7
  • BRICKLET_JOYSTICK_FUNCTION_SET_POSITION_CALLBACK_THRESHOLD = 9
  • BRICKLET_JOYSTICK_FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 11
  • BRICKLET_JOYSTICK_FUNCTION_SET_DEBOUNCE_PERIOD = 13
procedure TBrickletJoystick.SetResponseExpectedAll(const responseExpected: boolean)
Parameters:
  • responseExpected – Type: boolean

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

Constants

const BRICKLET_JOYSTICK_DEVICE_IDENTIFIER

This constant is used to identify a Joystick Bricklet.

The GetIdentity function and the TIPConnection.OnEnumerate callback of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

const BRICKLET_JOYSTICK_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Joystick Bricklet.