Noise in I2C bus during ADC acquisition

[Nicola Bizzotto]

Hi,

I've developed a custom board which integrate an ESP32-WROVER-IE. During the PCB testing I noticed a noise in the I2C bus. The noise seems to be correlated to ADC acquisitions. I would like to find out what's the cause of this phenomenon and possibly solve it.

For simplicity, I replicated the same behavior by using an ESP32-DevKitC-32UE and activating only I2C and ADC peripherals.
For this purpose I've used the following pins:

- IO25 --> SDA
- IO26 --> SCL
- IO34 --> ANALOG INPUT

Here below I'm adding some code screenshots.

I2C setup

code1.JPG (83.87 KiB) Viewed 1470 times

ADC setup and periodic task (ADC acquisition)

code2.JPG (103.93 KiB) Viewed 1470 times

The noise on the I2C bus seems to be synchronous to the periodic task.

Hardware-side, the only things I've added to the ESP32-DevKitC-32UE were two 10k pullup resistor between SDA/SCL and +3V3 supply.

The following images are some oscilloscope captures that highlight the noise present in the I2C bus. Specifically, the oscilloscope probe was placed between the SDA and GND lines:

Oscilloscope acquisitions

ACQ.jpg (199.03 KiB) Viewed 1470 times

Have any of you encountered the phenomenon I described?

[MicroController]

I'm adding some code screenshots

Seriously?

Also, I can't see/access any of the images in your post.

[Nicola Bizzotto]

I'm adding some code screenshots

Seriously?

Also, I can't see/access any of the images in your post.

Sorry. I've now edited my original post to make the images accessible.
Thank you for the feedback.