USB power supply and interference on ESP32 (M5stack)

[leodm05]

Hello,

I am using an M5stack Core2 as a weather station and to measure temperatures in rooms in my house.

The temperature measurements are taken by DS18B20 sensors, connected to GPIO 33 in direct mode with 3.3V power supply and pull-up (no interference). I have a total of 8 sensors with a distance of about 20m.

I am experiencing interference, with periodic false readings (124 and 85) indicating that the sensors are not being read.

But I have noticed something: when the M5core2 is not connected to the USB power supply and is running on its internal battery, I no longer have any interference problems.

The same thing happens if I power the M5core2 from a power bank.

This leads me to believe that the problems reading the DS18B20 sensors are related to interference from the power supply network, not the distance or connection of the sensors.

What solutions could I use to eliminate this network interference?

- Better grounding?
- Ferrites?
- Filter before the USB power supply?
- Other?

Thank you for your help.