Error: Missed scheduling of next digital out event

Basic Information:

Printer Model: Original Artillery Genius
MCU / Printerboard: SKR 1.4 Turbo
klippy.log
klippy.zip (629.7 KB)

Extra Informaion:

  • Klipper host: Raspberry Pi 3B+
  • CanBus adapter: BTT U2C 2.1 (Connected to Pi via USB)
  • CanBus mcu: BTT EBB42 1.2 (Connected via twisted pair to U2C can LH)
  • Ifconfig can0:
pi@mainsailos:~ $ ifconfig can0
can0: flags=193<UP,RUNNING,NOARP>  mtu 16
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 128  (UNSPEC)
        RX packets 761416  bytes 4799564 (4.5 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1711532  bytes 13075105 (12.4 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

  • “canbusload can0@1000000 -b -t” never reported +15% can bus usage

Describe your issue:

I have been dealing with this issue where klipper randomly shuts down in the middle of a print, can be printing for 6h all fine or shut down at 10 minutes.

Once it stops with the error message from the title klipper will fail to start with the message “mcu ‘can0’: Unable to connect Once the underlying issue is corrected” until I power cycle the printer, restart the PI or disconnect and reconnect the usb cable from the U2C

I’m totally lost as I have tried everything that I was able to find, thanks in advance for any help and please note that even If I’m not new to 3d printing this is my first time using a can bus.

What I have already tried with no results:

  • Increasing txqueuelen up to 2048 (128 → 512 → 1024 → 2048), I reverted this to 128 because it did not seem to help
  • New can cables
  • Re flashing EBB42 & U2C with the images available on BTT github
  • Re flashing U2C with the current version of candlelight
  • Re flashing U2C with the fork of candlelight that BTT has
  • Re flashing U2C with a custom fork of candlelight (Just merged candlelight repo on btt changes) GitHub - fernandopal/candleLight_fw: gs_usb compatible firmware for candleLight, cantact and canable
  • All the guides I was able to find where someone was having problems with the U2C 2.x or EBB42

An update on the status of the printer.

I have not done any hardware/software changes since the post was made but I have printed a few things and seems like the error is still a random thing because I started a 5 hour print that failed with the error from the title at 2 hours so I cleaned the bed and sent the job back to the printer and it finished without errors.

Any help is welcome.

Your problem shows up in your klippy.log in line 7613:
b'Got error -1 in can write: (105)No buffer space available'

Fearing nobody has an solution yet.

Could you run a
ifconfig
in a terminal after the error occurred again and post the output here?

The ifconfig I have added in the first post is from the same time that the log, just after the print failed.

Today I have been printing all day with that same ifconfig and by the moment the error has not appeared so I’m a bit concerned by the randomness of it as I can not find a way to force the error.

Mmmh, bummer

Same here. I got no clue at all, but I would increase txqueuelen.

Only thing you didn’t mention in your OP was CAN bus termination.
Did you measure the 60 Ohms on your CAN bus?

Do you provide enough current to the EBB?
Meaning are the cables for V+ and GND thick enough?

Depending on the used hotend and other attached components the used wires might be too thin for higher loads.
Otherwise did you check for bad soldering on the EBB?

Sorry for the late reply to everyone, I have been bussy for the past few weeks.

As an Update regarding this I have been printing and monitoring a few prints today and I have some data that can be useful but the possible fixes are out of my knowledge

This is the best dump that I was able to get:

  • Printer shuts down (seems like the error is different now)
21:40:25
Klipper state: Shutdown
21:40:42
Lost communication with MCU 'can0'
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
21:40:43
Lost communication with MCU 'can0

18 AWG <1m cable, current is stable at 24v

Increased to 1024 during today tests, both termination jumpers are set (EBB & U2C)

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