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arduinoesp8266i2cnoise

Rx and Tx creating a lot of noise when floating on ESP8266 and Arduino

I have connected an Arduino Pro-Mini 3.3V 8MHz to an ESP8266 via I2C.

The Arduino is in charge of collecting data from a thermistor (analog temperature) (T2) and a SI7021 (digital temperature) (T1).

The ESP8266 is in charge of sending the data received from the Arduino to an endpoint.

Here is my repo: https://github.com/ClemRz/Solar-Water-Heater-Monitor. In the res folder you will find a picture of the circuit.

The issue I am having is that as long as I leave the FTDI RS232 programmer connected to either the Arduino or the ESP I'm having a smooth response from the thermistor but as soon as I disconnect it, the response get some noise. What is happening?

Here is a graph where we can see 3 phases: https://i.sstatic.net/TsnvY.png

  1. Programmer disconnected: some noise can be seen
  2. Programmer connected: smooth noiseless curve
  3. Programmer disconnected again: noisy

If I remove Rx and Tx and I leave GND connected to the FTDI I also observe that the reading is smooth and noiseless.

Solved: I switched the wall adapter to a better quality one and it fixed the noise issue.

Solution

  • Switch the wall adapter with a better quality one and it will fix the noise issue.