3.3V power supply issue from photon2

Hardware
1

Hi all,

I am current using photon 2 to record a MEMS Mic and read the signal using A2 pin. I am using 3.3V power supply on the photon 2 to provide power to the op-amp and use high (3M ohm) feedback resistor to record the signal as the sound is light. However, I found the signal is of greater noise. I compare the photon 2 with Arduino Nano ble 33 by recording silent background and here is the result:

image
image1793×771 192 KB

P2 - Photon2
A - Arduino
A3V_P2AR - use 3.3V power supply from Arduino and use Analogread from Photon2, vis versa for AAR_P23V
It looks like the 3.3V power supply is causing the super noise, I tried by adding decoupling capacitor and filter circuit but still cannot fix this issue.
Could anyone give any suggestion on this issue?

Thanks,
Nianyu Jiang

2

I have seen this occur, and also seen it stop occurring. I don't know the cause or how to make it not have background noise once it starts occurring.