Is this 3.3V or 5V? (dealing with Arduino, STM32 and others)

Discussion in 'Embedded Systems and Microcontrollers' started by KansaiRobot, Feb 9, 2016.

  1. KansaiRobot

    Thread Starter Active Member

    Jan 15, 2010
    I would appreciate some help in a problem with voltages.

    First, I am using this TFT LCD
    I know, I know, it is in japanese o_O sorry. I ll translate for you:
    Ok, first question: Arduino Mega (and Arduino UNO) works with 5V based pins, right?? but this shield "that is ready to use" operates at 3.3V???

    Second, I have successfully used this with the UNO. pins were connected directly. I am confused at this because I powered the shield with the 3.3V pin however the IO pins were connected directly. So were this 5V based???

    Third I am trying to interface this and make it work with a STM32 nucleo that is entirely 3.3V and it does not work!. So maybe 5V are required???

    Note that this product does not have a schematic but now just with my eye could see a AMS1117 chip there....

    Any comment or even question will be greatly appreciated
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    It is common today as logic changes from 5V to 3.3V or other to have input pins that "tolerate" what once was an over voltage, so logic running off 5V can drive lower voltage devices. Your devic may well be built with such devices.
  3. KansaiRobot

    Thread Starter Active Member

    Jan 15, 2010
    The AMS1117 chip there makes me "smell" something fishy overthere. This is a "low dropout voltage regulator"
    Would it be possible that this LCD pins actually expect 5V and that internally changes it to 3.3V to work with that???

    (I have another LCD that expects 5V as power but the pins and the rest expect 3.3V)
    Last edited: Feb 10, 2016