I had problems with connecting my devices via I2C. The "requestfrom" constantly hanged and the endtransmission sometimes gave NACK responses.

After disconnecting the devices from 12V and powering one of them via USB (vin with which it was connected to the other arduino's became 3.8V) they stopped misbehaving and worked together in harmony.

How is this possible? Am I missing something? An Arduino Nano Every should be driven between 6-21V?

All devices are "Arduino Nano Every"'s. They used to get 12V directly on Vin and are connected together in a chain by Vin,GND,A5(SCK),A4(SDA)

The master is in the middle of the chain so that the distance is max 20cm.

I also tried powering them via vin with 9V and 5V. Had the same issue.

Already big thanks for the help.

  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Juraj
    Aug 10, 2021 at 15:25

1 Answer 1


SO... In the datasheet it says you should use 7-21V on VIN. This gave the problem. I powered the arduinos directly from 5V on the vin. This fixed all I2C problems. Haven't had any problems anymore after changing this.

cheers to all.

  • 1
    You're saying that the voltage on the input side of regulator... causes the internal pull-ups to change value inside of a chip on the output side of the regulator?
    – timemage
    Aug 9, 2021 at 11:58
  • it doesn't make sense
    – Juraj
    Aug 9, 2021 at 12:28
  • Not the way I'm reading it currently anyway.
    – timemage
    Aug 9, 2021 at 15:06
  • 1
    Is this better?
    – Roel
    Aug 10, 2021 at 14:56
  • 1
    To my thinking, yes. You're saying something factual about what you did and what you observed correlated to it. You removed the bits that seemingly had no fact or theory behind them and had no indication that they were, as you put it "pure guess." I call that an improvement.
    – timemage
    Aug 10, 2021 at 21:24

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