[RC3] Serial Plotter & Monitor show "disconnected" when they are not!

I've been evaluating RC3 pretty extensively in the last couple of days as I'm filming a video about it, and I have noticed that quite often I get a warning on the Serial Monitor or Serial Plotter that says my board is "disconnected", even though it obviously isn't (if it were truly "disconnected" then it shouldn't be reading data from my microcontroller!).

On the Serial Plotter, this warning is disabling the Stop/Run button, so I can't demonstrate how to stop the plot.

On the Arduino Insider demo video, Ubi de Feo illustrates an example of doing this, but because my plotter thinks it is "disconnected" I can't repeat his example.

I couldn't find this bug in GitHub, but I might have missed it. Can someone please confirm that his is indeed a known bug and perhaps point me to the entry on GitHub.


Hi @DroneBotWorkshop. Thanks so much for your report!

I have also encountered this problem. I reported it in passing in this issue:

However, in hindsight I should have opened a dedicated report at that time, which I have now done:

My experience is that this bug only affects subsequent windows with the same port selected. This means the workaround can be to only use the first window of the session for that port:

  1. Select File > Quit from the Arduino IDE window.
  2. Start the Arduino IDE.

Now only use the Serial Monitor and Serial Plotter from that window for the port that was selected.

I have also been able to sometimes fix it by closing the previous window and then selecting the board/port again, or by switching to another available port and then back to the one I want. Unfortunately I also found that this doesn't help in some cases so I think the first window workaround is the most reliable.

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Thank you, that was very helpful.

It does indeed seem to work if it is the first window instance. I will use that in my video and let my viewers know about the bug and workaround.

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