20x4 LCD + STEMMA backpack +esp32

ESPHome
1

I am attempting to use the subject lcd and the Adafruit I2c/spi lcd backpack with STEMMA QT connectors. I have attached an ESP32 with a STEMMA QT breakout board to the appropriate SDA/SCL, 3.3v, gnd pins. compiled a yaml program with the following for the LCD:display:

  • platform: lcd_pcf8574
    dimensions: 20x4
    address: 0x20
    id: my_display
    lambda: |-
    id(my_display).backlight();
    it.print(“Hello World!”);

The I2C scan finds the interface board at 0x20.
Problem is nothing shows on the screen, backlight doesn’t come on either. Adjusted contrast with no improvement. Traded out a identical screen setup with same results.
Does this set up provide enough power to the lcd? Can you some how safely run 5v to board separately for lcd, without burning up the I2C bus?
Is this the correct platform interface for this setup?
Any other ideas greatly welcomed!

2

That board has built in boost converter to supply 5V for display.
You should only power it at Esp logic voltage, 3.3V

Likely not. The I2C address 0x20 you find is MCP23008 chip on that module.

3

Thanks. I also noticed that the LCD pcf8574 has an default address of 0x3f. As you pointed out, the adafruit board default is 0x20. Is there any other component interface platform that would work with a 20x4 LCD and the MCP23008 chip?

4

Esphome has component for MCP230. But it’s beyond my skills how to bridge that to your LCD.