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Multi-Instance Klipper with Canbus

3 min read

#3dp#sbc

Will Puckett

Last fall, I had considered setting up multiple instances of Klipper on a single machine. I ultimately went with a dedicated SBC for each printer, though, mainly for resilency, but also because I dreaded writing the udev rules for the can interfaces.

A few weeks ago, an update caused the wifi on my Radxa Zero 3's to stop working, effectively bricking them. I was tired of having to maintain so many systems, so I decided to give the small form factor Dell I had sitting around a chance.

General Setup

I installed Debian bookworm on the Dell. I couldn't get it plugged into my monitor and the router at the same time, but I fished around in a drawer and found a usb Panda Wireless wifi adapter that it auto-recognized, and then I manually configured the ethernet port by adding 

auto enp0s31f6
iface enp0s31f6 inet dhcp

to /etc/network/interfaces. Once I finished the install, I unplugged the wireless adapter and connected the Dell in the closet under my router.

Klipper Install

I went through a very normal install of Klipper using Kiauh, and selected 4 instances. Kiauh handled everything automatically for me.

Setting Up Canbus with Udev

I couldn't find any straightforward documentation on configuring Canbus with udev for Klipper, so I had to tease out a the following solution:

  1. Plug you canbus device (probably an mcu in canbus bridge mode or a u2c) into an available usb port

  2. Run udevadm info -a -p $(udevadm info -q path -p /sys/class/net/can0)| grep serial| head -n 1 (if you already have other can devices plugged in, you may have to run ip link show and figure out the appropriate device to substitute)

  3. The above command should print something like ATTRS{serial}=="490033000F50475532323820"

  4. Open /etc/udev/rules.d/z21_persistent-local.rules in your editor of choice

  5. Subtitiuting the serial number you found in step 3, add the following line:

SUBSYSTEM=="net", ACTION=="add", ATTRS{serial}=="{YOUR_SERIAL}", NAME="{YOUR_CHOSEN_CANBUS_NAME}"
  1. Open /etc/network/interfaces.d/{YOUR_CHOSEN_CANBUS_NAME} in your editor of choice, and insert the following text, substituting the canbus name you created in step 5:
allow-hotplug {YOUR_CHOSEN_CANBUS_NAME}
iface {YOUR_CHOSEN_CANBUS_NAME} can static
    bitrate 1000000
    up ip link set $IFACE txqueuelen 128

  1. Run sudo udevadm control --reload-rules && sudo udevadm trigger --attr-match=subsystem=net and then unplug and replug your can device, or reboot if you prefer

  2. Run ip link show and you should see your device listed under the appropriate interface name, with the correctly configured queue length and bitrate.

Klipper/ Katapult Config

Once the interface is properly configured as above, you can simply add a canbus_interface line to your [mcu] object in your printer.cfg that lists the named interface you just created.

If you use katapult, you'll also need to use the -i {YOUR_CHOSEN_CANBUS_NAME} option when your run flash_can.py to set the appropriate interface.