Character-Based LCD Display

lcd_pcf8574 Component

The lcd_pcf8574 display platform allows you to use standard character-based LCD displays like this one with ESPHome. This integration is only for LCD displays that display individual characters on a screen (usually 16-20 columns and 2-4 rows), and not for LCD displays that can control each pixel individually.

This version of the LCD integration is for LCD displays with a PCF8574 connected to all the data pins. This has the benefit that you only need to connect two data wires to the ESP instead of the 6 or 10 with the lcd_gpio Component. As the communication with the I²C Bus, you need to have an i2c: section in your configuration.

../../_images/lcd-pcf8574.jpg

The PCF8574 chip attached to the LCD Display.

../../_images/lcd-hello_world.jpg
# Example configuration entry
i2c:
  sda: D0
  scl: D1

display:
  - platform: lcd_pcf8574
    dimensions: 18x4
    address: 0x3F
    lambda: |-
      it.print("Hello World!");

Configuration variables:

  • dimensions (Required, string): The dimensions of the display with COLUMNSxROWS. If you’re not sure, power the display up and just count them.

  • address (Optional, int): The I²C address of the PCF8574 chip, defaults to 0x3F.

  • lambda (Optional, lambda): The lambda to use for rendering the content on the display. See Rendering Lambda for more information.

  • update_interval (Optional, Time): The interval to re-draw the screen. Defaults to 1s.

  • id (Optional, ID): Manually specify the ID used for code generation.

lcd_gpio Component

The lcd_gpio display platform allows you to use standard character-based LCD displays like this one with ESPHome. This integration is only for LCD displays that display individual characters on a screen (usually 16-20 columns and 2-4 rows), and not for LCD displays that can control each pixel individually. Also, this is the GPIO version of the LCD integration where each of the data pins of the LCD needs a dedicated GPIO pin on the ESP. These LCD displays are also commonly sold with a PCF8574 chip which only need two lines to the ESP, for that see lcd_pcf8574 Component.

../../_images/lcd-full.jpg

LCD Display.

# Example configuration entry
display:
  - platform: lcd_gpio
    dimensions: 18x4
    data_pins:
      - D0
      - D1
      - D2
      - D3
    enable_pin: D4
    rs_pin: D5
    lambda: |-
      it.print("Hello World!");

Configuration variables:

  • dimensions (Required, string): The dimensions of the display with COLUMNSxROWS. If you’re not sure, power the display up and just count them.

  • data_pins (Required, list of Pin Schemas): A list of the data pins you have hooked up to the LCD. The list can either be 8 items long (when you have connected all 8 data pins), or 4 items long (if you’re operating in 4-bit mode with either the first 4 data pins connected or the last 4 data pins connected).

  • enable_pin (Required, Pin Schema): The pin you have EN hooked up to.

  • rs_pin (Required, Pin Schema): The pin you have RS hooked up to.

  • rw_pin (Optional, Pin Schema): Optionally set the pin you have RW hooked up to. You can also just permanently connect that pin to GND.

  • lambda (Optional, lambda): The lambda to use for rendering the content on the display. See Rendering Lambda for more information.

  • update_interval (Optional, Time): The interval to re-draw the screen. Defaults to 1s.

  • id (Optional, ID): Manually specify the ID used for code generation.

Rendering Lambda

The LCD displays has a similar API to the fully fledged Display Rendering Engine, but it’s only a subset as LCD displays don’t have a concept of individual pixels. In the lambda you’re passed a variable called it as with all other displays. In this case however, it is an instance of either GPIOLCDDisplay or PCF8574LCDDisplay.

The most basic operation with LCD Displays is writing static text to the screen as in the configuration example at the top of this page.

Each of the three methods (print, printf and strftime) all optionally take a column and row arguments at the beginning which can be used to print the text at a specific position. These arguments are set to 0 (column) and 0 (row) by default which means the character at the top left.

display:
  - platform: lcd_gpio # or lcd_pcf8574
    # ...
    lambda: |-
      // Print 0 at the top left
      it.print("0");

      // Print 1 at the second row and second column.
      it.print(1, 1, "1");

      // Let's write a sensor value (let's assume it's 42.1)
      it.printf("%.1f", id(my_sensor).state);
      // Result: "42.1" (the dot will appear on the "2" segment)

      // Print a right-padded sensor value with 0 digits after the decimal
      it.printf("Sensor value: %8.0f", id(my_sensor).state);
      // Result: "Sensor value:       42"

      // Print the current time
      it.strftime("It is %H:%M on %d.%m.%Y", id(my_time).now());
      // Result for 10:06 on august 21st 2018 -> "It is 10:06 on 21.08.2018"

# (Optional) For displaying time:
time:
- platform: sntp
  id: my_time

Note

If you’re not seeing anything on the display, make sure you try turning the contrast potentiometer around.

Please see Formatted Text for a quick introduction into the printf formatting rules and Displaying Time for an introduction into the strftime time formatting.

Backlight Control

For the GPIO based display, the backlight is lit by applying Vcc to the A pin and K connected to ground. The backlight can draw more power than the microcontroller output pins can supply, so it is advisable to use a transistor as a switch to control the power for the backlight pins.

With the lcd_pcf8574 the backlight can be turned on by it.backlight() and off by it.no_backlight() in the display lambda definition. The jumper on the PCF8574 board needs to be closed for the backlight control to work. Keep in mind that the display lambda runs for every update_interval, so if the backlight is turned on/off there, it cannot be overridden from other parts.

Here is one solution for a typical use-case where the backlight is turned on after a motion sensor activates and turns off 90 seconds after the last activation of the sensor.

display:
  - platform: lcd_pcf8574
    id: mydisplay
    # ...

binary_sensor:
  - platform: gpio
    # ...
    on_press:
      then:
        - binary_sensor.template.publish:
            id: backlight
            state: ON
        - binary_sensor.template.publish:
            id: backlight
            state: OFF
  - platform: template
    id: backlight
    filters:
      - delayed_off: 90s
    on_press:
      then:
        - lambda: |-
            id(mydisplay).backlight();
    on_release:
      then:
        - lambda: |-
            id(mydisplay).no_backlight();

See Also