CAN Bus Failure HermitCrab

[DroneMang]

Hi, reposting here from https://github.com/Klipper3d/klipper/issues/4952

The CAN bus and HermitCrab toolchanger can't connect after PSU is off for a long time, and the firmware cannot be reset, requiring a RPi reboot.

I have installed the BTT HermitCrab toolchanger using the CAN wiring scheme, main mcu is an SKR Pro, overall working fine. I have a 5V PSU powering the RPi, and a separate 24V PSU on a relay that the RPi can shut on and off with the PSU plugin. If the 24V PSU is off for a long time after having connected initially, then if I try to connect the terminal gives the below output.

Also (minor issue), on initial connection, the Klipper messages say 'mcu': Unable to connect, and then eventually connects on the next line.

klippy.zip

Connection closed, closing down monitor Changing monitoring state from "Operational" to "Offline" Changing monitoring state from "Offline" to "Opening serial connection" Connecting to port /tmp/printer, baudrate 250000 Changing monitoring state from "Opening serial connection" to "Error" Changing monitoring state from "Error" to "Offline after error" Unexpected error while connecting to serial port /tmp/printer, baudrate 250000 from hook default: SerialException: '[Errno 2] could not open port /tmp/printer: [Errno 2] No such file or directory: '/tmp/printer'' @ comm.py:_open_serial:3779 Changing monitoring state from "Offline" to "Opening serial connection" Connecting to port /tmp/printer, baudrate 250000 Changing monitoring state from "Opening serial connection" to "Error" Changing monitoring state from "Error" to "Offline after error" Unexpected error while connecting to serial port /tmp/printer, baudrate 250000 from hook default: SerialException: '[Errno 2] could not open port /tmp/printer: [Errno 2] No such file or directory: '/tmp/printer'' @ comm.py:_open_serial:3779 Changing monitoring state from "Offline" to "Opening serial connection" Connecting to port /tmp/printer, baudrate 250000 Changing monitoring state from "Opening serial connection" to "Error" Changing monitoring state from "Error" to "Offline after error" Unexpected error while connecting to serial port /tmp/printer, baudrate 250000 from hook default: SerialException: '[Errno 2] could not open port /tmp/printer: [Errno 2] No such file or directory: '/tmp/printer'' @ comm.py:_open_serial:3779