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:breadcrumbs: <a href="../../index.html">Home</a> / <a href="../../index.html#software-java">Software</a> / Java - LCD 16x2 Bricklet

.. |device_identifier_constant| replace:: There is also a :ref:`constant <lcd_16x2_bricklet_java_constants>` for the device identifier of this Bricklet.

.. _lcd_16x2_bricklet_java:

Java - LCD 16x2 Bricklet
========================

This is the description of the :ref:`Java API bindings <api_bindings_java>` for the :ref:`LCD 16x2 Bricklet <lcd_16x2_bricklet>`. General information and technical
specifications for the LCD 16x2 Bricklet are summarized in its :ref:`hardware description
<lcd_16x2_bricklet_description>`.

An :ref:`installation guide <api_bindings_java_install>` for the Java API
bindings is part of their general description.

.. _lcd_16x2_bricklet_java_examples:


Examples
--------

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

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

`Download (ExampleHelloWorld.java) <https://github.com/Tinkerforge/lcd-16x2-bricklet/raw/master/software/examples/java/ExampleHelloWorld.java>`__

.. literalinclude:: LCD16x2_Bricklet_Java_ExampleHelloWorld.java
 :language: java
 :linenos:
 :tab-width: 4

Button Callback
^^^^^^^^^^^^^^^

`Download (ExampleButtonCallback.java) <https://github.com/Tinkerforge/lcd-16x2-bricklet/raw/master/software/examples/java/ExampleButtonCallback.java>`__

.. literalinclude:: LCD16x2_Bricklet_Java_ExampleButtonCallback.java
 :language: java
 :linenos:
 :tab-width: 4

Unicode
^^^^^^^

`Download (ExampleUnicode.java) <https://github.com/Tinkerforge/lcd-16x2-bricklet/raw/master/software/examples/java/ExampleUnicode.java>`__

.. literalinclude:: LCD16x2_Bricklet_Java_ExampleUnicode.java
 :language: java
 :linenos:
 :tab-width: 4

.. _lcd_16x2_bricklet_java_api:

API
---

Generally, every method of the Java 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 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
^^^^^^^^^^^^^^^


.. java:function:: class BrickletLCD16x2(String uid, IPConnection ipcon)

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

 .. code-block:: java

  BrickletLCD16x2 lcd16x2 = new BrickletLCD16x2("YOUR_DEVICE_UID", ipcon);

 This object can then be used after the IP Connection is connected
 (see examples :ref:`above <lcd_16x2_bricklet_java_examples>`).


.. java:function:: public void BrickletLCD16x2::writeLine(short line, short position, String text)

 Writes text to a specific line (0 to 1) with a specific position 
 (0 to 15). The text can have a maximum of 16 characters.
 
 For example: (0, 5, "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-16x2-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.
 
.. java:function:: public void BrickletLCD16x2::clearDisplay()

 Deletes all characters from the display.
 
.. java:function:: public void BrickletLCD16x2::backlightOn()

 Turns the backlight on.
 
.. java:function:: public void BrickletLCD16x2::backlightOff()

 Turns the backlight off.
 
.. java:function:: public boolean BrickletLCD16x2::isBacklightOn()

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


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

.. java:function:: public void BrickletLCD16x2::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 
 :java:func:`writeLine() <BrickletLCD16x2::writeLine>`.
 
 The default is (false, false).
 
.. java:function:: public BrickletLCD16x2.Config BrickletLCD16x2::getConfig()

 Returns the configuration as set by :java:func:`setConfig() <BrickletLCD16x2::setConfig>`.
 
 The returned object has the public member variables ``boolean cursor`` and ``boolean blinking``.

.. java:function:: public boolean BrickletLCD16x2::isButtonPressed(short button)

 Returns *true* if the button (0 to 2) is pressed. If you want to react
 on button presses and releases it is recommended to use the
 :java:func:`ButtonPressedListener <BrickletLCD16x2.ButtonPressedListener>` and :java:func:`ButtonReleasedListener <BrickletLCD16x2.ButtonReleasedListener>` listeners.
 
.. java:function:: public void BrickletLCD16x2::setCustomCharacter(short index, short[] character)

 The LCD 16x2 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 :java:func:`writeLine() <BrickletLCD16x2::writeLine>` by using the
 characters with the byte representation 8 to 15.
 
 You can play around with the custom characters in Brick Viewer since
 version 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)
 
.. java:function:: public short[] BrickletLCD16x2::getCustomCharacter(short index)

 Returns the custom character for a given index, as set with
 :java:func:`setCustomCharacter() <BrickletLCD16x2::setCustomCharacter>`.
 
 .. versionadded:: 2.0.1~(Plugin)
 
.. java:function:: public short[] BrickletLCD16x2::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.
 
.. java:function:: public boolean BrickletLCD16x2::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 listener configuration
 functions it is enabled by default too, but can be disabled by
 :java:func:`setResponseExpected() <BrickletLCD16x2::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 :java:func:`setResponseExpected() <BrickletLCD16x2::setResponseExpected>`
 for the list of function ID constants available for this function.
 
.. java:function:: public void BrickletLCD16x2::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 listener configuration functions (default value: *true*). For
 getter functions it is always enabled and listeners 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:
 
 * BrickletLCD16x2.FUNCTION_WRITE_LINE = 1
 * BrickletLCD16x2.FUNCTION_CLEAR_DISPLAY = 2
 * BrickletLCD16x2.FUNCTION_BACKLIGHT_ON = 3
 * BrickletLCD16x2.FUNCTION_BACKLIGHT_OFF = 4
 * BrickletLCD16x2.FUNCTION_SET_CONFIG = 6
 * BrickletLCD16x2.FUNCTION_SET_CUSTOM_CHARACTER = 11
 
.. java:function:: public void BrickletLCD16x2::setResponseExpectedAll(boolean responseExpected)

 Changes the response expected flag for all setter and listener configuration
 functions of this device at once.
 
.. java:function:: public BrickletLCD16x2.Identity BrickletLCD16x2::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_16x2_bricklet_java_callbacks:

Listeners
^^^^^^^^^

Listeners can be registered to receive
time critical or recurring data from the device. The registration is done
with "add*Listener" functions of the device object.

The parameter is a listener class object, for example:

.. code-block:: java

    device.addExampleListener(new BrickletLCD16x2.ExampleListener() {
        public void property(int value) {
            System.out.println("Value: " + value);
        }
    });

The available listener classes with inherent methods to be overwritten
are described below. It is possible to add several listeners and
to remove them with the corresponding "remove*Listener" function.

.. note::
 Using listeners 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.


.. java:function:: public class BrickletLCD16x2.ButtonPressedListener()

 This listener can be added with the ``addButtonPressedListener()`` function.
 An added listener can be removed with the ``removeButtonPressedListener()`` function.

 .. java:function:: public void buttonPressed(short button)
  :noindex:


  This listener is triggered when a button is pressed. The parameter is
  the number of the button (0 to 2).
  

.. java:function:: public class BrickletLCD16x2.ButtonReleasedListener()

 This listener can be added with the ``addButtonReleasedListener()`` function.
 An added listener can be removed with the ``removeButtonReleasedListener()`` function.

 .. java:function:: public void buttonReleased(short button)
  :noindex:


  This listener is triggered when a button is released. The parameter is
  the number of the button (0 to 2).
  


.. _lcd_16x2_bricklet_java_constants:

Constants
^^^^^^^^^

.. java:member:: public static final int BrickletLCD16x2.DEVICE_IDENTIFIER

 This constant is used to identify a LCD 16x2 Bricklet.

 The :java:func:`getIdentity() <BrickletLCD16x2::getIdentity>` function and the
 :java:func:`EnumerateListener <IPConnection.EnumerateListener>`
 listener of the IP Connection have a ``deviceIdentifier`` parameter to specify
 the Brick's or Bricklet's type.

