I have a NodeMCU esp32-s board and I'm trying to connect My 16x2 lcd with PCF8574T I2C bus to the esp32 , the problem is that the lcd doesn't show anything and the WireScan sketch can't recognize the lcd too,but when I use arduion uno ,it's recognized and work perfectly ,I hope somebody can help me,the schematic for the connection is : enter image description here

the schematic for the connection of the lcd with the bus is below with the bus module part number enter image description here:

  • please add a clear, answerable question to your post
    – jsotola
    Commented Feb 10, 2023 at 21:35
  • What things need to be cleared?
    – kamal MKA
    Commented Feb 10, 2023 at 21:47
  • you need to make it clear how the LCD is connected and, most importantly, which LCD you are using ... right now, all we know which pins are connected at the ESP32 ... we know nothing else ... also, you have not asked a question about the problem
    – jsotola
    Commented Feb 10, 2023 at 21:49
  • well,if you return back to my question you see I have mentioned the type and part number and this is exactly the problem, I can't provide more.
    – kamal MKA
    Commented Feb 10, 2023 at 21:59
  • the PCF8574T is an IC that is part of the LCD ... it is an I2C bus expander ... which component is used in the display module has no bearing on the connector pinout of the LCD module
    – jsotola
    Commented Feb 10, 2023 at 22:11

1 Answer 1


You can run the PCF8574 on 5V and the EXP on 3V3 just be sure the I2C is pulled up to the 3V3 and NOT the 5V. I do this a lot and have never had a problem. The reason it works is the bus is driven by open collector/drain drivers which do not source any voltage.

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