Core 2 and ADC Input

  • Greetings everyone,

    First I have really had a lot of fun exploring the Core 2 (my first M5Stack product)! A lot of features for under $50! My joy ended a little when I discovered the less then capable ADC functions which after doing a little research on the internet (and searching this forum) this seems to be related to the ESP32 processor.

    With that said has anyone explored using a passive or active low-pass filter? My hope is that someone may have a schematic that someone would be willing to share?

    The end-goal is to use a LM34 Temperature Sensor with the Core 2 as a thermostat for the radiant floor heating in my home.

    Thanks ahead time if anyone can assist-Brian

    PS: My first post to this forum :)

  • You can find some informations on the following posts.
    For my part I abandoned the LM35 to use the DS18B20 and it works perfectly with UIFLOW

  • Howdy Arno and thanks for providing the links...I did take a peek at those already!

    I'll take a look at the DS18B20 but I already purchased the LM34s (Fahrenheit version). I think the LM34 has a bit better accuracy yet DS18B20 is the less "painful" alternative!

    I plan to:

    1. look into the whole atten as that controls the voltage range to the ADC
    2. look into an active low pass filter using a single supply Op-Amp
    3. look into adding a small gain from the Op-Amp to get the voltage from the LM34 into an acceptable range for the ADC

    Will share my findings along with any schematics I come up with.


  • Hi all,

    Some insights to share! Well the Active Low Pass filter did help to a small degree. With that said I decided to connect my Oscilloscope to the input of the ADC0 using GP35 and I was surprised by the amount of noise!

    Input of ADC0 on GP35:
    There was over 200mV of noise that varied in frequency of anywhere from 18 to 78MHz!

    Measuring "ground" (just as a reference)
    There was less then 100mV of noise that was around 60Hz which would be expected here in North America as our AC Line Frequency is 60Hz.

    I did order some other one-wire temperature sensors including the DS18B20 and have another temperature sensor with a +_ 0.25 accuracy just to experiment with.

    Again I will keep this post updated.


  • Please have a look to my blog Sorry for German language.

  • @bschwahn I would think a digital sensor would be much more accurate and easy to use than an analog one. Once you figure out what library you need for the protocol e.g. this might help