Delphi/Lazarus - LCD 20x4 Bricklet

This is the description of the Delphi/Lazarus API bindings for the LCD 20x4 Bricklet. General information and technical specifications for the LCD 20x4 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).

Hello World

Download (ExampleHelloWorld.pas)

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program ExampleHelloWorld;

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

uses
  SysUtils, IPConnection, BrickletLCD20x4;

type
  TExample = class
  private
    ipcon: TIPConnection;
    lcd: TBrickletLCD20x4;
  public
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'XYZ'; { Change XYZ to the UID of your LCD 20x4 Bricklet }

var
  e: TExample;

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

  { Create device object }
  lcd := TBrickletLCD20x4.Create(UID, ipcon);

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

  { Turn backlight on }
  lcd.BacklightOn;

  { Write "Hello World" }
  lcd.WriteLine(0, 0, 'Hello World');

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

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

Button Callback

Download (ExampleButtonCallback.pas)

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program ExampleButtonCallback;

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

uses
  SysUtils, IPConnection, BrickletLCD20x4;

type
  TExample = class
  private
    ipcon: TIPConnection;
    lcd: TBrickletLCD20x4;
  public
    procedure ButtonPressedCB(sender: TBrickletLCD20x4; const button: byte);
    procedure ButtonReleasedCB(sender: TBrickletLCD20x4; const button: byte);
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'XYZ'; { Change XYZ to the UID of your LCD 20x4 Bricklet }

var
  e: TExample;

{ Callback procedure for button pressed callback }
procedure TExample.ButtonPressedCB(sender: TBrickletLCD20x4; const button: byte);
begin
  WriteLn(Format('Button Pressed: %d', [button]));
end;

{ Callback procedure for button released callback }
procedure TExample.ButtonReleasedCB(sender: TBrickletLCD20x4; const button: byte);
begin
  WriteLn(Format('Button Released: %d', [button]));
end;

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

  { Create device object }
  lcd := TBrickletLCD20x4.Create(UID, ipcon);

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

  { Register button pressed callback to procedure ButtonPressedCB }
  lcd.OnButtonPressed := {$ifdef FPC}@{$endif}ButtonPressedCB;

  { Register button released callback to procedure ButtonReleasedCB }
  lcd.OnButtonReleased := {$ifdef FPC}@{$endif}ButtonReleasedCB;

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

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

Unicode

Download (ExampleUnicode.pas)

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program ExampleUnicode;

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

uses
  SysUtils, IPConnection, BrickletLCD20x4;

type
  TExample = class
  private
    ipcon: TIPConnection;
    lcd: TBrickletLCD20x4;
  public
    function WideStringToKS0066U(const text: WideString): string;
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'XYZ'; { Change XYZ to the UID of your LCD 20x4 Bricklet }

var
  e: TExample;

function TExample.WideStringToKS0066U(const text: WideString): string;
var i, codePoint: longint; w: word; c: char; ks0066u: string;
begin
  i := 1;
  SetLength(ks0066u, 0);
  while (i <= Length(text)) do begin
    { WideString is UTF-16, handle surrogates }
    w := word(text[i]);
    if ((w >= $D800) and (w <= $DBFF)) then begin
      codePoint := $10000 + (w - $D800) * $400 + (w - $DC00);
      i := i + 2;
    end
    else begin
      codePoint := w;
      i := i + 1;
    end;
    { ASCII subset from JIS X 0201 }
    if ((codePoint >= $0020) and (codePoint <= $007E)) then begin
      { The LCD charset doesn't include '\' and '~', use similar characters instead }
      case codePoint of
        $005C: c := char($A4); { REVERSE SOLIDUS maps to IDEOGRAPHIC COMMA }
        $007E: c := char($2D); { TILDE maps to HYPHEN-MINUS }
        else   c := char(codePoint);
      end;
    end
    { Katakana subset from JIS X 0201 }
    else if ((codePoint >= $FF61) and (codePoint <= $FF9F)) then begin
      c := char(codePoint - $FEC0);
    end
    { Special characters }
    else begin
      case codePoint of
        $00A5: c := char($5C); { YEN SIGN }
        $2192: c := char($7E); { RIGHTWARDS ARROW }
        $2190: c := char($7F); { LEFTWARDS ARROW }
        $00B0: c := char($DF); { DEGREE SIGN maps to KATAKANA SEMI-VOICED SOUND MARK }
        $03B1: c := char($E0); { GREEK SMALL LETTER ALPHA }
        $00C4: c := char($E1); { LATIN CAPITAL LETTER A WITH DIAERESIS }
        $00E4: c := char($E1); { LATIN SMALL LETTER A WITH DIAERESIS }
        $00DF: c := char($E2); { LATIN SMALL LETTER SHARP S }
        $03B5: c := char($E3); { GREEK SMALL LETTER EPSILON }
        $00B5: c := char($E4); { MICRO SIGN }
        $03BC: c := char($E4); { GREEK SMALL LETTER MU }
        $03C2: c := char($E5); { GREEK SMALL LETTER FINAL SIGMA }
        $03C1: c := char($E6); { GREEK SMALL LETTER RHO }
        $221A: c := char($E8); { SQUARE ROOT }
        $00B9: c := char($E9); { SUPERSCRIPT ONE maps to SUPERSCRIPT (minus) ONE }
        $00A4: c := char($EB); { CURRENCY SIGN }
        $00A2: c := char($EC); { CENT SIGN }
        $2C60: c := char($ED); { LATIN CAPITAL LETTER L WITH DOUBLE BAR }
        $00F1: c := char($EE); { LATIN SMALL LETTER N WITH TILDE }
        $00D6: c := char($EF); { LATIN CAPITAL LETTER O WITH DIAERESIS }
        $00F6: c := char($EF); { LATIN SMALL LETTER O WITH DIAERESIS }
        $03F4: c := char($F2); { GREEK CAPITAL THETA SYMBOL }
        $221E: c := char($F3); { INFINITY }
        $03A9: c := char($F4); { GREEK CAPITAL LETTER OMEGA }
        $00DC: c := char($F5); { LATIN CAPITAL LETTER U WITH DIAERESIS }
        $00FC: c := char($F5); { LATIN SMALL LETTER U WITH DIAERESIS }
        $03A3: c := char($F6); { GREEK CAPITAL LETTER SIGMA }
        $03C0: c := char($F7); { GREEK SMALL LETTER PI }
        $0304: c := char($F8); { COMBINING MACRON }
        $00F7: c := char($FD); { DIVISION SIGN }
        $25A0: c := char($FF); { BLACK SQUARE }
        else   c := char($FF); { BLACK SQUARE }
      end
    end;
    { Special handling for 'x' followed by COMBINING MACRON }
    if (c = char($F8)) then begin
      if (ks0066u[Length(ks0066u) - 1] <> 'x') then begin
        c := char($FF); { BLACK SQUARE }
      end;
      if (Length(ks0066u) > 0) then begin
        SetLength(ks0066u, Length(ks0066u) - 1);
      end;
    end;
    ks0066u := ks0066u + c;
  end;
  result := ks0066u;
end;

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

  { Create device object }
  lcd := TBrickletLCD20x4.Create(UID, ipcon);

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

  { Turn backlight on }
  lcd.BacklightOn;

  { Write a string using the WideStringToKS0066U function to map to the LCD charset }
  { Note: For the Free Pascal Compiler (and Lazarus) UTF8Decode is used to create a
          WideString. It assumes that your source file is UTF-8 encoded }
  lcd.WriteLine(0, 0, WideStringToKS0066U({$ifdef FPC}UTF8Decode{$endif}('Stromstärke: 17µA')));
  lcd.WriteLine(1, 0, WideStringToKS0066U({$ifdef FPC}UTF8Decode{$endif}('Temperatur:  23°C')));

  { Write a string directly including characters from the LCD charset }
  lcd.WriteLine(2, 0, 'Drehzahl:   750min' + char($E9));

  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 TBrickletLCD20x4.Create(const uid: string; ipcon: TIPConnection)

Creates an object with the unique device ID uid:

lcd20x4 := TBrickletLCD20x4.Create('YOUR_DEVICE_UID', ipcon);

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

procedure TBrickletLCD20x4.WriteLine(const line: byte; const position: byte; const text: string)

Writes text to a specific line (0 to 3) with a specific position (0 to 19). The text can have a maximum of 20 characters.

For example: (0, 7, "Hello") will write Hello in the middle of the first line of the display.

The display uses a special charset that includes all ASCII characters except backslash and tilde. The LCD charset also includes several other non-ASCII characters, see the charset specification for details. The Unicode example above shows how to specify non-ASCII characters and how to translate from Unicode to the LCD charset.

procedure TBrickletLCD20x4.ClearDisplay

Deletes all characters from the display.

procedure TBrickletLCD20x4.BacklightOn

Turns the backlight on.

procedure TBrickletLCD20x4.BacklightOff

Turns the backlight off.

function TBrickletLCD20x4.IsBacklightOn: boolean

Returns true if the backlight is on and false otherwise.

Advanced Functions

procedure TBrickletLCD20x4.SetConfig(const cursor: boolean; const blinking: boolean)

Configures if the cursor (shown as "_") should be visible and if it should be blinking (shown as a blinking block). The cursor position is one character behind the the last text written with WriteLine.

The default is (false, false).

procedure TBrickletLCD20x4.GetConfig(out cursor: boolean; out blinking: boolean)

Returns the configuration as set by SetConfig.

function TBrickletLCD20x4.IsButtonPressed(const button: byte): boolean

Returns true if the button (0 to 2 or 0 to 3 since hardware version 1.2) is pressed.

If you want to react on button presses and releases it is recommended to use the OnButtonPressed and OnButtonReleased callbacks.

procedure TBrickletLCD20x4.SetCustomCharacter(const index: byte; const character: array [0..7] of byte)

The LCD 20x4 Bricklet can store up to 8 custom characters. The characters consist of 5x8 pixels and can be addressed with the index 0-7. To describe the pixels, the first 5 bits of 8 bytes are used. For example, to make a custom character "H", you should transfer the following:

  • character[0] = 0b00010001 (decimal value 17)
  • character[1] = 0b00010001 (decimal value 17)
  • character[2] = 0b00010001 (decimal value 17)
  • character[3] = 0b00011111 (decimal value 31)
  • character[4] = 0b00010001 (decimal value 17)
  • character[5] = 0b00010001 (decimal value 17)
  • character[6] = 0b00010001 (decimal value 17)
  • character[7] = 0b00000000 (decimal value 0)

The characters can later be written with WriteLine by using the characters with the byte representation 8 ("x08") to 15 ("x0F").

You can play around with the custom characters in Brick Viewer version since 2.0.1.

Custom characters are stored by the LCD in RAM, so they have to be set after each startup.

New in version 2.0.1 (Plugin).

function TBrickletLCD20x4.GetCustomCharacter(const index: byte): array [0..7] of byte

Returns the custom character for a given index, as set with SetCustomCharacter.

New in version 2.0.1 (Plugin).

procedure TBrickletLCD20x4.SetDefaultText(const line: byte; const text: string)

Sets the default text for lines 0-3. The max number of characters per line is 20.

The default text is shown on the LCD, if the default text counter expires, see SetDefaultTextCounter.

New in version 2.0.2 (Plugin).

function TBrickletLCD20x4.GetDefaultText(const line: byte): string

Returns the default text for a given line (0-3) as set by SetDefaultText.

New in version 2.0.2 (Plugin).

procedure TBrickletLCD20x4.SetDefaultTextCounter(const counter: longint)

Sets the default text counter in ms. This counter is decremented each ms by the LCD firmware. If the counter reaches 0, the default text (see SetDefaultText) is shown on the LCD.

This functionality can be used to show a default text if the controlling program crashes or the connection is interrupted.

A possible approach is to call SetDefaultTextCounter every minute with the parameter 1000*60*2 (2 minutes). In this case the default text will be shown no later than 2 minutes after the controlling program crashes.

A negative counter turns the default text functionality off.

The default is -1.

New in version 2.0.2 (Plugin).

function TBrickletLCD20x4.GetDefaultTextCounter: longint

Returns the current value of the default text counter.

New in version 2.0.2 (Plugin).

function TBrickletLCD20x4.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 TBrickletLCD20x4.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 TBrickletLCD20x4.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_LCD_20X4_FUNCTION_WRITE_LINE = 1
  • BRICKLET_LCD_20X4_FUNCTION_CLEAR_DISPLAY = 2
  • BRICKLET_LCD_20X4_FUNCTION_BACKLIGHT_ON = 3
  • BRICKLET_LCD_20X4_FUNCTION_BACKLIGHT_OFF = 4
  • BRICKLET_LCD_20X4_FUNCTION_SET_CONFIG = 6
  • BRICKLET_LCD_20X4_FUNCTION_SET_CUSTOM_CHARACTER = 11
  • BRICKLET_LCD_20X4_FUNCTION_SET_DEFAULT_TEXT = 13
  • BRICKLET_LCD_20X4_FUNCTION_SET_DEFAULT_TEXT_COUNTER = 15
procedure TBrickletLCD20x4.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletLCD20x4.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: TBrickletLCD20x4; const param: word);
begin
  WriteLn(param);
end;

lcd20x4.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 TBrickletLCD20x4.OnButtonPressed
procedure(sender: TBrickletLCD20x4; const button: byte) of object;

This callback is triggered when a button is pressed. The parameter is the number of the button (0 to 2 or 0 to 3 since hardware version 1.2).

property TBrickletLCD20x4.OnButtonReleased
procedure(sender: TBrickletLCD20x4; const button: byte) of object;

This callback is triggered when a button is released. The parameter is the number of the button (0 to 2 or 0 to 3 since hardware version 1.2).

Constants

const BRICKLET_LCD_20X4_DEVICE_IDENTIFIER

This constant is used to identify a LCD 20x4 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_LCD_20X4_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a LCD 20x4 Bricklet.