Marlin PID Autotune causes serial failure

I'm running Octoprint 1.3.12 on OctoPi Version 0.16.0, running on Raspberry Pi 3 Model B Rev 1.2. It is connected to an Ender 5 with a SKR mini E3 control board running 2.0.x Marlin. This combination works well for printing...I've been using it for a couple of weeks, including several multi-hour prints. I can print through Octoprint directly as well as from Cura to Octoprint. I do not see this sort of serial error when printing.

Today I tried to do a PID autotune of the hotend. When I ran the command in the terminal, I got a serial error. This behavior repeats every time I do the autotune. Adding M303 to the long running command list did not help.

Any ideas? Thanks!

2019-12-07 15:30:50,841 - Send: M303 S200 C5
2019-12-07 15:30:50,852 - Recv: PID Autotune start
2019-12-07 15:30:50,864 - Recv:  T:20.62 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:30:52,863 - Recv:  T:20.62 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:30:54,863 - Recv:  T:20.62 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:30:56,863 - Recv:  T:20.62 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:30:58,862 - Recv:  T:26.42 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:00,863 - Recv:  T:32.92 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:02,862 - Recv:  T:34.97 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:04,863 - Recv:  T:38.33 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:06,863 - Recv:  T:43.73 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:08,863 - Recv:  T:51.82 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:10,864 - Recv:  T:53.41 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:12,864 - Recv:  T:59.26 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:14,874 - Recv:  T:64.81 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:16,874 - Recv:  T:68.79 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:18,874 - Recv:  T:73.63 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:20,873 - Recv:  T:78.86 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:22,873 - Recv:  T:83.56 /0.00 B:20.62 /0.00 @:127 B@:0
2019-12-07 15:31:23,030 - Unexpected error while reading serial port, please consult octoprint.log for details: SerialException: 'device reports readiness to read but returned no data (device disconnected or multiple access on port?)' @ comm.py:_readline:2793
2019-12-07 15:31:23,031 - Please see https://faq.octoprint.org/serialerror for possible reasons of this.
2019-12-07 15:31:23,037 - Changing monitoring state from "Operational" to "Offline (Error: SerialException: 'device reports readiness to read but returned no data (device disconnected or multiple access on port?)' @ comm.py:_readline:2793)"
2019-12-07 15:31:23,044 - Connection closed, closing down monitor

octolog.zip (3.6 KB)

I guess your firmware crashed.
Did the display reset and show the bootlogo etc?

No, the display was fine. The printer was continuing to run the PID test as far as I can see...the temp was cycling up and down as one would expect.

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Interestingly, upgrading to the latest firmware seems to have fixed the issue, whatever it was. For future reference, this is the firmware I successfully built.

https://github.com/bigtreetech/BIGTREETECH-SKR-mini-E3/commit/d983789d72edfa047e4dd1c96eabf5124b088cb2

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