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277 lines
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277 lines
10 KiB
ReStructuredText
Character-Based LCD Display
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===========================
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.. seo::
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:description: Instructions for setting up character-based HD44780 LCD displays.
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:image: lcd.jpg
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The ``lcd_pcf8574`` and ``lcd_gpio`` display components allow you to use HD44780-compatible, character-based LCD displays
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with ESPHome. This integration is only for LCD displays that display individual characters on a screen
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(usually 8-40 columns and 2-4 rows), and not for LCD displays that can control each pixel individually.
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.. figure:: images/lcd-hello_world.jpg
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:align: center
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:width: 60.0%
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.. note::
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Multiple versions of the display exist, supporting different character sets:
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- HD44780UA00 English-Japanese which includes katakana characters, some Greek letters and mathematical symbols
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- HD44780UA02 English-European which includes Greek, Cyrillic and Western European characters (with some diacritics)
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- HD44780UBxx custom, manufacturer-specific character sets
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It is also possible to add eight user-defined characters.
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.. _lcd-pcf8574:
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lcd_pcf8574 Component
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---------------------
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``lcd_pcf8574`` is for LCD displays with a PCF8574 GPIO expander module connected to all the data pins. This has the
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benefit that you only need to connect two data wires to the ESP instead of the six or ten as with the :ref:`lcd-gpio`.
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The communication happens via :ref:`I²C Bus <i2c>`, you need to have an ``i2c:`` section in your configuration.
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.. figure:: images/lcd-pcf8574.jpg
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:align: center
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:width: 75.0%
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LCD Display with a PCF8574 board attached on the back
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.. code-block:: yaml
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# Example configuration entry
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i2c:
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sda: D0
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scl: D1
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display:
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- platform: lcd_pcf8574
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dimensions: 20x4
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address: 0x27
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lambda: |-
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it.print("Hello World!");
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Configuration variables:
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************************
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- **dimensions** (**Required**, string): The dimensions of the display with ``COLUMNSxROWS``. If you're not
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sure, power the display up and just count them.
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- **address** (*Optional*, int): The :ref:`I²C <i2c>` address of the PCF8574 chip, defaults to ``0x3F``.
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- **lambda** (*Optional*, :ref:`lambda <config-lambda>`): The lambda to use for rendering the content on the display.
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See :ref:`display-lcd_lambda` for more information.
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- **update_interval** (*Optional*, :ref:`config-time`): The interval to re-draw the screen. Defaults to ``1s``.
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- **id** (*Optional*, :ref:`config-id`): Manually specify the ID used for code generation.
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.. note::
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If you're not seeing anything on the display, try turning the contrast potentiometer around on the
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PCF8574 board.
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.. _lcd-gpio:
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lcd_gpio Component
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------------------
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The ``lcd_gpio`` version of this component addresses the screen directly and does not employ a GPIO expander module.
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Each of the data pins of the LCD needs a dedicated GPIO pin on the ESP. Connecting the screen this way offers
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faster refresh, especially in conjunction with an :ref:`LCD Menu <lcd_menu>`.
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.. figure:: images/lcd_gpio.svg
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:align: center
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:width: 75.0%
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LCD Display GPIO pinout
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.. code-block:: yaml
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# Example configuration entry
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display:
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- platform: lcd_gpio
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dimensions: 20x4
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data_pins:
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- D0
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- D1
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- D2
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- D3
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enable_pin: D4
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rs_pin: D5
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lambda: |-
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it.print("Hello World!");
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Configuration variables:
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************************
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- **dimensions** (**Required**, string): The dimensions of the display with ``COLUMNSxROWS``. If you're not
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sure, power the display on, turn contrast high up and just count them.
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- **data_pins** (**Required**, list of :ref:`pins <config-pin_schema>`): A list of the data pins you
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have hooked up to the LCD. The list can either be 4 items long (operating in 4-bit mode with
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either the first 4 data pins connected or the last 4 data pins connected), or 8 items long (when you have
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connected all 8 data pins).
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- **enable_pin** (**Required**, :ref:`pin <config-pin_schema>`): The pin you have ``E`` (``06``) hooked up to.
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- **rs_pin** (**Required**, :ref:`pin <config-pin_schema>`): The pin you have ``RS`` (``04``) hooked up to.
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- **rw_pin** (*Optional*, :ref:`pin <config-pin_schema>`): Optionally set the pin you have ``R/W`` (``05``) hooked up to. You can also just permanently connect that pin to ``GND``.
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- **lambda** (*Optional*, :ref:`lambda <config-lambda>`): The lambda to use for rendering the content on the display.
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See :ref:`display-lcd_lambda` for more information.
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- **update_interval** (*Optional*, :ref:`config-time`): The interval to re-draw the screen. Defaults to ``1s``.
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- **id** (*Optional*, :ref:`config-id`): Manually specify the ID used for code generation.
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.. note::
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If you're not seeing anything on the display, make sure you apply ``3.3V`` to the ``VEE`` (``03``) contrast control
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pin of the board. You can use a potentiometer to make it adjustable.
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.. _display-lcd_lambda:
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Rendering Lambda
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----------------
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The LCD displays has a similar API to the fully fledged :ref:`display-engine`, but it's only a subset as LCD displays
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don't have a concept of individual pixels. In the lambda you're passed a variable called ``it``
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as with all other displays. In this case however, ``it`` is an instance of either ``GPIOLCDDisplay`` or ``PCF8574LCDDisplay``.
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The most basic operation with LCD Displays is writing static text to the screen as in the configuration example
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at the top of this page.
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Each of the three methods (``print``, ``printf`` and ``strftime``) all optionally take a column and row arguments at the
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beginning which can be used to print the text at a specific position. These arguments are set to ``0`` (column) and ``0`` (row)
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by default which means the character at the top left.
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.. code-block:: yaml
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display:
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- platform: lcd_gpio # or lcd_pcf8574
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# ...
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lambda: |-
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// Print 0 at the top left
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it.print("0");
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// Print 1 at the second row and second column.
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it.print(1, 1, "1");
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// Let's write a sensor value (let's assume it's 42.1)
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it.printf("%.1f", id(my_sensor).state);
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// Result: "42.1" (the dot will appear on the segment showing "2")
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// Print a right-padded sensor value with 0 digits after the decimal
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it.printf("Sensor value: %8.0f", id(my_sensor).state);
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// Result: "Sensor value: 42"
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// Print the current time
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it.strftime("It is %H:%M on %d.%m.%Y", id(my_time).now());
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// Result for 10:06 on august 21st 2018 -> "It is 10:06 on 21.08.2018"
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# (Optional) For displaying time:
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time:
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- platform: homeassistant
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id: my_time
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Please see :ref:`display-printf` for a quick introduction into the ``printf`` formatting rules and
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:ref:`display-strftime` for an introduction into the ``strftime`` time formatting.
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User Defined Characters
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-----------------------
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The LCD display has the possibility to define up to eight user defined characters occupying the characters
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``0`` to ``7`` and mirrored at ``8`` to ``15`` (i.e. ``\x08`` can be used instead of the ``\0`` that can
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be problematic in strings). Each character has eight lines of five bits, with the first line on the top
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and the most significant bit on the left, meaning that ``0b10000`` followed by six zeros and a ``0b00001``
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defines a dot at the upper left and lower right of the character.
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.. code-block:: yaml
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display:
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- platform: lcd_pcf8574
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id: mydisplay
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# ...
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user_characters:
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- position: 0
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data:
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- 0b00000
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- 0b01010
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- 0b00000
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- 0b00100
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- 0b00100
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- 0b10001
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- 0b01110
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- 0b00000
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- position: 7
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data:
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- 0b00000
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- 0b01010
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- 0b00000
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- 0b00100
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- 0b00100
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- 0b00000
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- 0b01110
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- 0b10001
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lambda: |-
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it.print("Hello, world \x08 \x07!");
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Try this `custom character generator <https://omerk.github.io/lcdchargen/>`__ to design your own sybmols.
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Backlight Control
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-----------------
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With the ``lcd_pcf8574`` the backlight can be turned on by ``it.backlight()`` and off by ``it.no_backlight()`` in the
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display lambda definition. The jumper on the PCF8574 board needs to be closed for the backlight control to work.
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Keep in mind that the display lambda runs for every ``update_interval``, so if the backlight is turned on/off there,
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it cannot be overridden from other parts.
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With the ``lcd_gpio``, the backlight is lit by applying ``Vcc`` to the ``BLA`` (``15``) pin and connect ``BLK`` (``16``)
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pin to ``GND``. The backlight can draw more power than the microcontroller output pins can supply, so it is advisable
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to use a transistor as a switch to control the power for the backlight pins.
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Below an example for a typical use-case where the backlight is turned on when a motion sensor activates and
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turns off ``90`` seconds after the last activation of the sensor.
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.. code-block:: yaml
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display:
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- platform: lcd_pcf8574
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id: mydisplay
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# ...
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binary_sensor:
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- platform: gpio
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# ...
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on_press:
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then:
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- binary_sensor.template.publish:
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id: backlight
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state: ON
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- binary_sensor.template.publish:
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id: backlight
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state: OFF
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- platform: template
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id: backlight
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filters:
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- delayed_off: 90s
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on_press:
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then:
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- lambda: |-
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id(mydisplay).backlight();
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on_release:
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then:
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- lambda: |-
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id(mydisplay).no_backlight();
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See Also
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--------
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- :doc:`index`
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- :doc:`/components/switch/gpio`
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- :doc:`/components/binary_sensor/gpio`
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- :ref:`LCD Menu <lcd_menu>`
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- :ref:`Add pages to LCD display <lambda_magic_pages>`
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- :doc:`/components/pcf8574`
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- `HD44780U (LCD-II) datasheet <https://www.sparkfun.com/datasheets/LCD/HD44780.pdf>`__
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- `Charset cheatsheet <https://user-images.githubusercontent.com/1550668/173113487-9c98e866-8ee4-4a3c-a83f-61fe62057c5f.png>`__
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- `Custom Character Generator <https://omerk.github.io/lcdchargen/>`__
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- `Arduino LiquidCrystal Library <https://www.arduino.cc/en/Reference/LiquidCrystal>`__
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- :apiref:`lcd_base/lcd_display.h`
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- :ghedit:`Edit`
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