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:breadcrumbs: <a href="../../index.html">Home</a> / <a href="../../index.html#software-matlab">Software</a> / MATLAB/Octave - LCD 20x4 Bricklet

.. |device_identifier_constant| replace:: There is also a :ref:`constant <lcd_20x4_bricklet_matlab_constants>` for the device identifier of this Bricklet.

.. _lcd_20x4_bricklet_matlab:

MATLAB/Octave - LCD 20x4 Bricklet
=================================

This is the description of the :ref:`MATLAB/Octave API bindings <api_bindings_matlab>` 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_matlab_install>` for the MATLAB/Octave API
bindings is part of their general description.

.. _lcd_20x4_bricklet_matlab_examples:


Examples
--------

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

Hello World (MATLAB)
^^^^^^^^^^^^^^^^^^^^

`Download (matlab_example_hello_world.m) <https://github.com/Tinkerforge/lcd-20x4-bricklet/raw/master/software/examples/matlab/matlab_example_hello_world.m>`__

.. literalinclude:: LCD20x4_Bricklet_MATLAB_matlab_example_hello_world.m
 :language: matlab
 :linenos:
 :tab-width: 4

Button Callbacks (MATLAB)
^^^^^^^^^^^^^^^^^^^^^^^^^

`Download (matlab_example_button_callbacks.m) <https://github.com/Tinkerforge/lcd-20x4-bricklet/raw/master/software/examples/matlab/matlab_example_button_callbacks.m>`__

.. literalinclude:: LCD20x4_Bricklet_MATLAB_matlab_example_button_callbacks.m
 :language: matlab
 :linenos:
 :tab-width: 4

Hello World (Octave)
^^^^^^^^^^^^^^^^^^^^

`Download (octave_example_hello_world.m) <https://github.com/Tinkerforge/lcd-20x4-bricklet/raw/master/software/examples/matlab/octave_example_hello_world.m>`__

.. literalinclude:: LCD20x4_Bricklet_MATLAB_octave_example_hello_world.m
 :language: octave_fixed
 :linenos:
 :tab-width: 4

Button Callbacks (Octave)
^^^^^^^^^^^^^^^^^^^^^^^^^

`Download (octave_example_button_callbacks.m) <https://github.com/Tinkerforge/lcd-20x4-bricklet/raw/master/software/examples/matlab/octave_example_button_callbacks.m>`__

.. literalinclude:: LCD20x4_Bricklet_MATLAB_octave_example_button_callbacks.m
 :language: octave_fixed
 :linenos:
 :tab-width: 4

.. _lcd_20x4_bricklet_matlab_api:

API
---

Generally, every method of the MATLAB bindings that returns a value can
throw a ``TimeoutException``. This exception gets thrown if the
device did not respond. If a cable based connection is used, it is
unlikely that this exception gets thrown (assuming nobody unplugs the
device). However, if a wireless connection is used, timeouts will occur
if the distance to the device gets too big.

Beside the ``TimeoutException`` there is also a ``NotConnectedException`` that
is thrown if a method needs to communicate with the device while the
IP Connection is not connected.

Since the MATLAB bindings are based on Java and Java does not support multiple
return values and return by reference is not possible for primitive types, we
use small classes that only consist of member variables. The member variables
of the returned objects are described in the corresponding method descriptions.

The package for all Brick/Bricklet bindings and the IP Connection is
``com.tinkerforge.*``

All methods listed below are thread-safe.




Basic Functions
^^^^^^^^^^^^^^^


.. matlab:function:: class BrickletLCD20x4(String uid, IPConnection ipcon)

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

 In MATLAB:

 .. code-block:: matlab

  import com.tinkerforge.BrickletLCD20x4;

  lcd20x4 = BrickletLCD20x4('YOUR_DEVICE_UID', ipcon);

 In Octave:

 .. code-block:: octave_fixed

  lcd20x4 = java_new("com.tinkerforge.BrickletLCD20x4", "YOUR_DEVICE_UID", ipcon);

 This object can then be used after the IP Connection is connected
 (see examples :ref:`above <lcd_20x4_bricklet_matlab_examples>`).


.. matlab:function:: public void BrickletLCD20x4::writeLine(short line, short position, String text)

 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.
 
.. matlab:function:: public void BrickletLCD20x4::clearDisplay()

 Deletes all characters from the display.
 
.. matlab:function:: public void BrickletLCD20x4::backlightOn()

 Turns the backlight on.
 
.. matlab:function:: public void BrickletLCD20x4::backlightOff()

 Turns the backlight off.
 
.. matlab:function:: public boolean BrickletLCD20x4::isBacklightOn()

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


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

.. matlab:function:: public void BrickletLCD20x4::setConfig(boolean cursor, boolean blinking)

 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 
 :matlab:func:`writeLine() <BrickletLCD20x4::writeLine>`.
 
 The default is (*false*, *false*).
 
.. matlab:function:: public BrickletLCD20x4.Config BrickletLCD20x4::getConfig()

 Returns the configuration as set by :matlab:func:`setConfig() <BrickletLCD20x4::setConfig>`.
 
 The returned object has the public member variables ``boolean cursor`` and ``boolean blinking``.

.. matlab:function:: public boolean BrickletLCD20x4::isButtonPressed(short button)

 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
 :matlab:member:`ButtonPressedCallback <BrickletLCD20x4.ButtonPressedCallback>` and :matlab:member:`ButtonReleasedCallback <BrickletLCD20x4.ButtonReleasedCallback>` callbacks.
 
.. matlab:function:: public void BrickletLCD20x4::setCustomCharacter(short index, short[] character)

 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 :matlab:func:`writeLine() <BrickletLCD20x4::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)
 
.. matlab:function:: public short[] BrickletLCD20x4::getCustomCharacter(short index)

 Returns the custom character for a given index, as set with
 :matlab:func:`setCustomCharacter() <BrickletLCD20x4::setCustomCharacter>`.
 
 .. versionadded:: 2.0.1~(Plugin)
 
.. matlab:function:: public void BrickletLCD20x4::setDefaultText(short line, String text)

 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 :matlab:func:`setDefaultTextCounter() <BrickletLCD20x4::setDefaultTextCounter>`.
 
 .. versionadded:: 2.0.2~(Plugin)
 
.. matlab:function:: public String BrickletLCD20x4::getDefaultText(short line)

 Returns the default text for a given line (0-3) as set by
 :matlab:func:`setDefaultText() <BrickletLCD20x4::setDefaultText>`.
 
 .. versionadded:: 2.0.2~(Plugin)
 
.. matlab:function:: public void BrickletLCD20x4::setDefaultTextCounter(int counter)

 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 :matlab:func:`setDefaultText() <BrickletLCD20x4::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 :matlab:func:`setDefaultTextCounter() <BrickletLCD20x4::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)
 
.. matlab:function:: public int BrickletLCD20x4::getDefaultTextCounter()

 Returns the current value of the default text counter.
 
 .. versionadded:: 2.0.2~(Plugin)
 
.. matlab:function:: public short[] BrickletLCD20x4::getAPIVersion()

 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.
 
.. matlab:function:: public boolean BrickletLCD20x4::getResponseExpected(short functionId)

 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
 :matlab:func:`setResponseExpected() <BrickletLCD20x4::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 :matlab:func:`setResponseExpected() <BrickletLCD20x4::setResponseExpected>`
 for the list of function ID constants available for this function.
 
.. matlab:function:: public void BrickletLCD20x4::setResponseExpected(short functionId, boolean responseExpected)

 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:
 
 * BrickletLCD20x4.FUNCTION_WRITE_LINE = 1
 * BrickletLCD20x4.FUNCTION_CLEAR_DISPLAY = 2
 * BrickletLCD20x4.FUNCTION_BACKLIGHT_ON = 3
 * BrickletLCD20x4.FUNCTION_BACKLIGHT_OFF = 4
 * BrickletLCD20x4.FUNCTION_SET_CONFIG = 6
 * BrickletLCD20x4.FUNCTION_SET_CUSTOM_CHARACTER = 11
 * BrickletLCD20x4.FUNCTION_SET_DEFAULT_TEXT = 13
 * BrickletLCD20x4.FUNCTION_SET_DEFAULT_TEXT_COUNTER = 15
 
.. matlab:function:: public void BrickletLCD20x4::setResponseExpectedAll(boolean responseExpected)

 Changes the response expected flag for all setter and callback configuration
 functions of this device at once.
 
.. matlab:function:: public BrickletLCD20x4.Identity BrickletLCD20x4::getIdentity()

 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|
 
 The returned object has the public member variables ``String uid``, ``String connectedUid``, ``char position``, ``short[] hardwareVersion``, ``short[] firmwareVersion`` and ``int deviceIdentifier``.



.. _lcd_20x4_bricklet_matlab_callbacks:

Callbacks
^^^^^^^^^

Callbacks can be registered to receive time critical or recurring data from
the device. The registration is done with "set" function of MATLAB. The
parameters consist of the IP Connection object, the callback name and the
callback function. For example, it looks like this in MATLAB:

.. code-block:: matlab

    function cb_example(e)
        fprintf('Parameter: %s\n', e.param);
    end

    set(device, 'ExampleCallback', @(h, e) cb_example(e));

Due to a difference in the Octave Java support the "set" function cannot be
used in Octave. The registration is done with "add*Callback" functions of the
device object. It looks like this in Octave:

.. code-block:: octave_fixed

    function cb_example(e)
        fprintf("Parameter: %s\n", e.param);
    end

    device.addExampleCallback(@cb_example);

It is possible to add several callbacks and to remove them with the
corresponding "remove*Callback" function.

The parameters of the callback are passed to the callback function as fields of
the structure ``e``, which is derived from the ``java.util.EventObject`` class.
The available callback names with corresponding structure fields 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.



.. matlab:member:: public callback BrickletLCD20x4.ButtonPressedCallback

 :param button: short


 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).
 

 In MATLAB the ``set()`` function can be used to register a callback function
 to this callback.

 In Octave a callback function can be added to this callback using the
 ``addButtonPressedCallback()`` function. An added callback function can be removed with
 the ``removeButtonPressedCallback()`` function.


.. matlab:member:: public callback BrickletLCD20x4.ButtonReleasedCallback

 :param button: short


 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).
 

 In MATLAB the ``set()`` function can be used to register a callback function
 to this callback.

 In Octave a callback function can be added to this callback using the
 ``addButtonReleasedCallback()`` function. An added callback function can be removed with
 the ``removeButtonReleasedCallback()`` function.



.. _lcd_20x4_bricklet_matlab_constants:

Constants
^^^^^^^^^

.. matlab:member:: public static final int BrickletLCD20x4.DEVICE_IDENTIFIER

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

 The :matlab:func:`getIdentity() <BrickletLCD20x4::getIdentity>` function and the
 :matlab:member:`EnumerateCallback <IPConnection.EnumerateCallback>`
 callback of the IP Connection have a ``deviceIdentifier`` parameter to specify
 the Brick's or Bricklet's type.

