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216 lines
8.2 KiB
ReStructuredText
216 lines
8.2 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 LCD displays.
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:image: lcd.jpg
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.. _lcd-pcf8574:
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PCF8574
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-------
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The ``lcd_pcf8574`` display platform allows you to use standard character-based LCD displays like
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`this one <https://docs.labs.mediatek.com/resource/linkit7697-arduino/en/tutorial/driving-1602-lcd-with-pcf8574-pcf8574a>`__
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with ESPHome. This integration is only for LCD displays that display individual characters on a screen (usually 16-20 columns
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and 2-4 rows), and not for LCD displays that can control each pixel individually.
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This version of the LCD integration is for LCD displays with a PCF8574 connected to all the data pins. This has
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the benefit that you only need to connect two data wires to the ESP instead of the 6 or 10 with the :ref:`lcd-gpio`.
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As the communication with the :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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The PCF8574 chip attached to the LCD Display.
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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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.. 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: 18x4
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address: 0x3F
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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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.. _lcd-gpio:
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GPIO
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----
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The ``lcd_gpio`` display platform allows you to use standard character-based LCD displays like `this one <https://www.adafruit.com/product/181>`__
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with ESPHome. This integration is only for LCD displays that display individual characters on a screen (usually 16-20 columns
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and 2-4 rows), and not for LCD displays that can control each pixel individually. Also, this is the GPIO version of the LCD
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integration where each of the data pins of the LCD needs a dedicated GPIO pin on the ESP. These LCD displays are also
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commonly sold with a PCF8574 chip which only need two lines to the ESP, for that see :ref:`lcd-pcf8574`.
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.. figure:: images/lcd-full.jpg
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:align: center
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:width: 75.0%
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LCD Display.
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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: 18x4
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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 up and just count them.
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- **data_pins** (**Required**, list of :ref:`Pin Schemas <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 8 items long (when you have connected all 8 data pins), or
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4 items long (if you're operating in 4-bit mode with either the first 4 data pins connected or the last 4 data
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pins connected).
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- **enable_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The pin you have ``EN`` hooked up to.
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- **rs_pin** (**Required**, :ref:`Pin Schema <config-pin_schema>`): The pin you have ``RS`` hooked up to.
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- **rw_pin** (*Optional*, :ref:`Pin Schema <config-pin_schema>`): Optionally set the pin you have ``RW`` hooked up to.
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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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.. _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 "2" segment)
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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: sntp
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id: my_time
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.. note::
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If you're not seeing anything on the display, make sure you try turning the contrast potentiometer around.
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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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Backlight Control
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-----------------
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For the GPIO based display, the backlight is lit by applying Vcc to the A pin and K connected to ground.
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The backlight can draw more power than the microcontroller output pins can supply, so it is advisable to use
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a transistor as a switch to control the power for the backlight pins.
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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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Here is one solution for a typical use-case where the backlight is turned on after 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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- :doc:`/components/pcf8574`
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- :apiref:`lcd_base/lcd_display.h`
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- `Arduino LiquidCrystal Library <https://www.arduino.cc/en/Reference/LiquidCrystal>`__
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- :ghedit:`Edit`
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