Arduino SIM800L - Problems with AnalogRead

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1

Good morning everyone!
I'm new to the forum and I hope I'm writing in the right place and way.

I'm using a SIM800L (RoHS) module connected to Arduino (Uno and Mega). I use the module to send data to a MySql database via php. Everything works perfectly.

However, I noticed that when the SIM800L module is connected to Arduino, the values I read on the analog pins vary a lot and are not stable. As soon as I disconnect the SIM800L module everything goes back to ok and the values become stable.

Has anyone had the same experience and can help me?
Thank you very much!
Have a nice day everyone!

2

how is your SIM800L powered and connected to the Arduino?

3

Hi J-M-L!

The SIM800L is powered by an external 5V-5A power supply that also powers the Arduino.
The SIM800L is connected to the Arduino on digital pins 13 and 12 with a SoftwareSerial.

I hope I answered your question correctly

HI!

4

The problem also exists when I power with the simple USB... although obviously in this way the SIM800L is unable to connect to the network

5

ok my thought was on a surge of current draw when the SIM800L connects to the network, leading to a voltage drop that could impact the ADC and its reference voltage

seems your power supply is quite capable though, so this my not be the issue

6

Use a separate power supply for the SIM800L and see if the problem persists.

7

Hi everyone!

Excuse me but I verified that the problem was with the connections made with cables on breadboard... I made a small PCB and it seems that the readings are stable.

Thank you very much for your time!

Good evening

8

Good exploration !

9

Thank you J-M-L !