Noise in I2C bus during ADC acquisition
Posted: Fri Sep 22, 2023 8:42 pm
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.
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:
Have any of you encountered the phenomenon I described?
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 1409 times
- ADC setup and periodic task (ADC acquisition)
- code2.JPG (103.93 KiB) Viewed 1409 times
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 1409 times