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:breadcrumbs: <a href="../../index.html">Home</a> / <a href="../../index.html#software-delphi">Software</a> / Delphi/Lazarus - LCD 20x4 Bricklet

.. |device_identifier_constant| replace:: There is also a :ref:`constant <lcd_20x4_bricklet_delphi_constants>` for the device identifier of this Bricklet.

.. _lcd_20x4_bricklet_delphi:

Delphi/Lazarus - LCD 20x4 Bricklet
==================================

This is the description of the :ref:`Delphi/Lazarus API bindings <api_bindings_delphi>` for the :ref:`LCD 20x4 Bricklet <lcd_20x4_bricklet>`. General information and technical
specifications for the LCD 20x4 Bricklet are summarized in its :ref:`hardware description
<lcd_20x4_bricklet_description>`.

An :ref:`installation guide <api_bindings_delphi_install>` for the Delphi/Lazarus API
bindings is part of their general description.

.. _lcd_20x4_bricklet_delphi_examples:


Examples
--------

The example code below is `Public Domain (CC0 1.0)
<http://creativecommons.org/publicdomain/zero/1.0/>`__.

Hello World
^^^^^^^^^^^

`Download (ExampleHelloWorld.pas) <https://github.com/Tinkerforge/lcd-20x4-bricklet/raw/master/software/examples/delphi/ExampleHelloWorld.pas>`__

.. literalinclude:: LCD20x4_Bricklet_Delphi_ExampleHelloWorld.pas
 :language: delphi
 :linenos:
 :tab-width: 4

Button Callbacks
^^^^^^^^^^^^^^^^

`Download (ExampleButtonCallbacks.pas) <https://github.com/Tinkerforge/lcd-20x4-bricklet/raw/master/software/examples/delphi/ExampleButtonCallbacks.pas>`__

.. literalinclude:: LCD20x4_Bricklet_Delphi_ExampleButtonCallbacks.pas
 :language: delphi
 :linenos:
 :tab-width: 4

Unicode
^^^^^^^

`Download (ExampleUnicode.pas) <https://github.com/Tinkerforge/lcd-20x4-bricklet/raw/master/software/examples/delphi/ExampleUnicode.pas>`__

.. literalinclude:: LCD20x4_Bricklet_Delphi_ExampleUnicode.pas
 :language: delphi
 :linenos:
 :tab-width: 4

.. _lcd_20x4_bricklet_delphi_api:

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
^^^^^^^^^^^^^^^


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

 Creates an object with the unique device ID ``uid``:

 .. code-block:: delphi

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

 This object can then be used after the IP Connection is connected
 (see examples :ref:`above <lcd_20x4_bricklet_delphi_examples>`).


.. delphi:function:: 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 <https://github.com/Tinkerforge/lcd-20x4-bricklet/raw/master/datasheets/standard_charset.pdf>`__
 for details. The Unicode example above shows how to specify non-ASCII characters
 and how to translate from Unicode to the LCD charset.
 
.. delphi:function:: procedure TBrickletLCD20x4.ClearDisplay()

 Deletes all characters from the display.
 
.. delphi:function:: procedure TBrickletLCD20x4.BacklightOn()

 Turns the backlight on.
 
.. delphi:function:: procedure TBrickletLCD20x4.BacklightOff()

 Turns the backlight off.
 
.. delphi:function:: function TBrickletLCD20x4.IsBacklightOn(): boolean

 Returns *true* if the backlight is on and *false* otherwise.
 


Advanced Functions
^^^^^^^^^^^^^^^^^^

.. delphi:function:: 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 
 :delphi:func:`WriteLine <TBrickletLCD20x4.WriteLine>`.
 
 The default is (*false*, *false*).
 
.. delphi:function:: procedure TBrickletLCD20x4.GetConfig(out cursor: boolean; out blinking: boolean)

 Returns the configuration as set by :delphi:func:`SetConfig <TBrickletLCD20x4.SetConfig>`.
 
.. delphi:function:: 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
 :delphi:func:`OnButtonPressed <TBrickletLCD20x4.OnButtonPressed>` and :delphi:func:`OnButtonReleased <TBrickletLCD20x4.OnButtonReleased>` callbacks.
 
.. delphi:function:: 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 :delphi:func:`WriteLine <TBrickletLCD20x4.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.
 
 .. versionadded:: 2.0.1~(Plugin)
 
.. delphi:function:: function TBrickletLCD20x4.GetCustomCharacter(const index: byte): array [0..7] of byte

 Returns the custom character for a given index, as set with
 :delphi:func:`SetCustomCharacter <TBrickletLCD20x4.SetCustomCharacter>`.
 
 .. versionadded:: 2.0.1~(Plugin)
 
.. delphi:function:: 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 :delphi:func:`SetDefaultTextCounter <TBrickletLCD20x4.SetDefaultTextCounter>`.
 
 .. versionadded:: 2.0.2~(Plugin)
 
.. delphi:function:: function TBrickletLCD20x4.GetDefaultText(const line: byte): string

 Returns the default text for a given line (0-3) as set by
 :delphi:func:`SetDefaultText <TBrickletLCD20x4.SetDefaultText>`.
 
 .. versionadded:: 2.0.2~(Plugin)
 
.. delphi:function:: 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 :delphi:func:`SetDefaultText <TBrickletLCD20x4.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 :delphi:func:`SetDefaultTextCounter <TBrickletLCD20x4.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.
 
 .. versionadded:: 2.0.2~(Plugin)
 
.. delphi:function:: function TBrickletLCD20x4.GetDefaultTextCounter(): longint

 Returns the current value of the default text counter.
 
 .. versionadded:: 2.0.2~(Plugin)
 
.. delphi:function:: 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.
 
.. delphi:function:: 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
 :delphi:func:`SetResponseExpected <TBrickletLCD20x4.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 :delphi:func:`SetResponseExpected <TBrickletLCD20x4.SetResponseExpected>`
 for the list of function ID constants available for this function.
 
.. delphi: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 and callbacks it is always disabled.
 
 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
 
.. delphi:function:: procedure TBrickletLCD20x4.SetResponseExpectedAll(const responseExpected: boolean)

 Changes the response expected flag for all setter and callback configuration
 functions of this device at once.
 
.. delphi:function:: 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 :ref:`here <device_identifier>`.
 |device_identifier_constant|
 


Callback Configuration Functions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^





.. _lcd_20x4_bricklet_delphi_callbacks:

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:

 .. code-block:: delphi

  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.

.. delphi:function:: property TBrickletLCD20x4.OnButtonPressed

 .. code-block:: delphi

  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).
 
.. delphi:function:: property TBrickletLCD20x4.OnButtonReleased

 .. code-block:: delphi

  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).
 


.. _lcd_20x4_bricklet_delphi_constants:

Constants
^^^^^^^^^

.. delphi:function:: const BRICKLET_LCD_20X4_DEVICE_IDENTIFIER

 This constant is used to identify a LCD 20x4 Bricklet.

 The :delphi:func:`GetIdentity <TBrickletLCD20x4.GetIdentity>` function and the
 :delphi:func:`OnEnumerate <TIPConnection.OnEnumerate>`
 callback of the IP Connection have a ``deviceIdentifier`` parameter to specify
 the Brick's or Bricklet's type.

