Enable non-critical MCU support for CAN devices

[rogerlz]

This PR enables non-critical MCU support for CAN bus devices, allowing them to be disconnected and reconnected without causing errors or requiring a Klipper restart. Previously, this functionality was limited to USB devices, but with the changes from #391 that allowed querying of already-assigned devices, we can now extend this feature to CAN bus devices as well.

I tested:

• Boot with the device already connected
• Disconnecting and reconnecting devices during operation
• MCU temperature sensors
• ADXL queries before disconnection, while disconnected, and after reconnection

I did not test:

• Multiple devices on the same bus

[Team5ooo]

This fixed my issue perfectly. Had a Cartographer on CAN that would disconnect after a few hours of printing and kill the job. It's my second CAN device on the bus so can confirm it works with 2 devices.

[HenrikH96]

Hi,
I tested this branch on a toolchanger prototype I’m currently building.
The tools are potentially hot-swappable because they don’t connect via cables.

My goal was to see if Klipper could avoid crashing when I detach a tool from the system. Initially, it seemed to work. However, when I run simple HOME or MOVE commands without my SBB_2209 board connected, Klipper shuts down quite quickly with the following error:

MCU 'mcu' shutdown: Timer too close
This often indicates the host computer is overloaded. Check
for other processes consuming excessive CPU time, high swap
usage, disk errors, overheating, unstable voltage, or
similar system problems on the host computer.
Once the underlying issue is corrected, use the
"FIRMWARE_RESTART" command to reset the firmware, reload the
config, and restart the host software.
Printer is shutdown

[thetic]

i tested this with one of isik's boards. i2c timeouts on the BME280 crash the whole system even though it's set as non-critical.

[rogerlz]

Hi, I tested this branch on a toolchanger prototype I’m currently building. The tools are potentially hot-swappable because they don’t connect via cables.

My goal was to see if Klipper could avoid crashing when I detach a tool from the system. Initially, it seemed to work. However, when I run simple HOME or MOVE commands without my SBB_2209 board connected, Klipper shuts down quite quickly with the following error:

MCU 'mcu' shutdown: Timer too close
This often indicates the host computer is overloaded. Check
for other processes consuming excessive CPU time, high swap
usage, disk errors, overheating, unstable voltage, or
similar system problems on the host computer.
Once the underlying issue is corrected, use the
"FIRMWARE_RESTART" command to reset the firmware, reload the
config, and restart the host software.
Printer is shutdown

That use case will likely require a lot more development and testing.. Unfortunately, this feature is not the primary goal.

[rogerlz]

i tested this with one of isik's boards. i2c timeouts on the BME280 crash the whole system even though it's set as non-critical.

Thanks for the feedback. The whole i2c connection isnt ready for non-critical yet

[dalegaard]

I think this looks fine, but can someone verify with this rebased to newest main?