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

.. |device_identifier_constant| replace:: There is also a :ref:`constant <lcd_16x2_bricklet_python_constants>` for the device identifier of this Bricklet.

.. _lcd_16x2_bricklet_python:

Python - LCD 16x2 Bricklet
==========================

This is the description of the :ref:`Python API bindings <api_bindings_python>` 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_python_install>` for the Python API
bindings is part of their general description.

.. _lcd_16x2_bricklet_python_examples:


Examples
--------

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

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

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

.. literalinclude:: LCD16x2_Bricklet_Python_example_hello_world.py
 :language: python
 :linenos:
 :tab-width: 4

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

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

.. literalinclude:: LCD16x2_Bricklet_Python_example_button_callbacks.py
 :language: python
 :linenos:
 :tab-width: 4

Unicode
^^^^^^^

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

.. literalinclude:: LCD16x2_Bricklet_Python_example_unicode.py
 :language: python
 :linenos:
 :tab-width: 4

.. _lcd_16x2_bricklet_python_api:

API
---

Generally, every method of the Python bindings can throw an
``tinkerforge.ip_connection.Error`` exception that has a ``value`` and a
``description`` property. ``value`` can have different values:

* Error.TIMEOUT = -1
* Error.ALREADY_CONNECTED = -7
* Error.NOT_CONNECTED = -8
* Error.INVALID_PARAMETER = -9
* Error.NOT_SUPPORTED = -10
* Error.UNKNOWN_ERROR_CODE = -11

All methods listed below are thread-safe.




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


.. py:function:: LCD16x2(uid, ipcon)

 :param uid: string
 :param ipcon: IPConnection

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

 .. code-block:: python

    lcd_16x2 = LCD16x2("YOUR_DEVICE_UID", ipcon)

 This object can then be used after the IP Connection is connected
 (see examples :ref:`above <lcd_16x2_bricklet_python_examples>`).


.. py:function:: LCD16x2.write_line(line, position, text)

 :param line: int
 :param position: int
 :param text: str
 :rtype: None

 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.
 
.. py:function:: LCD16x2.clear_display()

 :rtype: None

 Deletes all characters from the display.
 
.. py:function:: LCD16x2.backlight_on()

 :rtype: None

 Turns the backlight on.
 
.. py:function:: LCD16x2.backlight_off()

 :rtype: None

 Turns the backlight off.
 
.. py:function:: LCD16x2.is_backlight_on()

 :rtype: bool

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


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

.. py:function:: LCD16x2.set_config(cursor, blinking)

 :param cursor: bool
 :param blinking: bool
 :rtype: None

 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 
 :py:func:`write_line() <LCD16x2.write_line>`.
 
 The default is (false, false).
 
.. py:function:: LCD16x2.get_config()

 :rtype: (bool, bool)

 Returns the configuration as set by :py:func:`set_config() <LCD16x2.set_config>`.
 
 The returned namedtuple has the variables ``cursor`` and ``blinking``.

.. py:function:: LCD16x2.is_button_pressed(button)

 :param button: int
 :rtype: bool

 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
 :py:attr:`CALLBACK_BUTTON_PRESSED <LCD16x2.CALLBACK_BUTTON_PRESSED>` and :py:attr:`CALLBACK_BUTTON_RELEASED <LCD16x2.CALLBACK_BUTTON_RELEASED>` callbacks.
 
.. py:function:: LCD16x2.set_custom_character(index, character)

 :param index: int
 :param character: [int, int, int, int, int, int, int, int]
 :rtype: None

 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 :py:func:`write_line() <LCD16x2.write_line>` 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)
 
.. py:function:: LCD16x2.get_custom_character(index)

 :param index: int
 :rtype: [int, int, int, int, int, int, int, int]

 Returns the custom character for a given index, as set with
 :py:func:`set_custom_character() <LCD16x2.set_custom_character>`.
 
 .. versionadded:: 2.0.1~(Plugin)
 
.. py:function:: LCD16x2.get_api_version()

 :rtype: [int, int, int]

 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.
 
.. py:function:: LCD16x2.get_response_expected(function_id)

 :param function_id: int
 :rtype: bool

 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
 :py:func:`set_response_expected() <LCD16x2.set_response_expected>`. 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 :py:func:`set_response_expected() <LCD16x2.set_response_expected>`
 for the list of function ID constants available for this function.
 
.. py:function:: LCD16x2.set_response_expected(function_id, response_expected)

 :param function_id: int
 :param response_expected: bool
 :rtype: None

 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:
 
 * LCD16x2.FUNCTION_WRITE_LINE = 1
 * LCD16x2.FUNCTION_CLEAR_DISPLAY = 2
 * LCD16x2.FUNCTION_BACKLIGHT_ON = 3
 * LCD16x2.FUNCTION_BACKLIGHT_OFF = 4
 * LCD16x2.FUNCTION_SET_CONFIG = 6
 * LCD16x2.FUNCTION_SET_CUSTOM_CHARACTER = 11
 
.. py:function:: LCD16x2.set_response_expected_all(response_expected)

 :param response_expected: bool
 :rtype: None

 Changes the response expected flag for all setter and callback configuration
 functions of this device at once.
 
.. py:function:: LCD16x2.get_identity()

 :rtype: (str, str, chr, [int, int, int], [int, int, int], int)

 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 namedtuple has the variables ``uid``, ``connected_uid``, ``position``, ``hardware_version``, ``firmware_version`` and ``device_identifier``.



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


.. py:function:: LCD16x2.register_callback(id, callback)

 :param id: int
 :param callback: callable
 :rtype: None

 Registers a callback with ID *id* to the function *callback*. The available
 IDs with corresponding function signatures are listed
 :ref:`below <lcd_16x2_bricklet_python_callbacks>`.




.. _lcd_16x2_bricklet_python_callbacks:

Callbacks
^^^^^^^^^

Callbacks can be registered to receive
time critical or recurring data from the device. The registration is done
with the :py:func:`register_callback() <LCD16x2.register_callback>` function of
the device object. The first parameter is the callback ID and the second
parameter the callback function:

.. code-block:: python

    def my_callback(param):
        print(param)

    lcd_16x2.register_callback(LCD16x2.CALLBACK_EXAMPLE, my_callback)

The available constants with inherent number and 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.

.. py:attribute:: LCD16x2.CALLBACK_BUTTON_PRESSED

 :param button: int


 This callback is triggered when a button is pressed. The parameter is
 the number of the button (0 to 2).
 
.. py:attribute:: LCD16x2.CALLBACK_BUTTON_RELEASED

 :param button: int


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


.. _lcd_16x2_bricklet_python_constants:

Constants
^^^^^^^^^

.. py:attribute:: LCD16x2.DEVICE_IDENTIFIER

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

 The :py:func:`get_identity() <LCD16x2.get_identity>` function and the
 :py:attr:`CALLBACK_ENUMERATE <IPConnection.CALLBACK_ENUMERATE>`
 callback of the IP Connection have a ``device_identifier`` parameter to specify
 the Brick's or Bricklet's type.

