CAN FAQ

Precautions before searching for devices

• Before searching for a CAN ID, please first connect to SSH
• Please ensure that you are logging in to SSH via network, not through a serial port
• Please ensure that the mainboard with UTOC connected or CAN bridge firmware flashed is properly connected, and the data cable connecting to the host computer supports data transfer

Confirming device presence

• Now that you have successfully logged in to the host computer, you can enter lsusb to search for devices. You may encounter one of the following situations:
  • If entering lsusb prompts that the ls command is not found, you can install the utility by entering the following command:

    sudo apt-get install usbutils

  • If entering lsusb results in no output, this is a system issue and cannot be resolved here. You will need to change the system or use a known working system.
  • The information shown in the image below is for reference only. You just need to ensure that 1d50:606f appears:
    
• 1d50:606f is the device you will use. You can ignore the rest of the information as system issues might cause incomplete display or no display at all.
• If multiple 1d50:606f devices appear, it is recommended to eliminate one, as it might affect subsequent flashing and firmware connection. For example, on FLY MINI PAD, it is recommended to use the onboard UTOC rather than other CAN bridge devices.
• If 1d50:606f does not appear, please check if the data cable is properly connected and whether the firmware is flashed correctly.

Note

You can only proceed to search for the CAN ID when 1d50:606f is present.

Diagnosing issues based on error messages

• Below are some common errors:
  • OSError: [Errno 19] No such device
  • can.CanError: Failed to transmit: [Errno 100] Network is down
  • can.CanError: Failed to transmit: [Errno 105] No buffer space available
• The first indicates that the host computer cannot find the CAN device (mainboard with USB bridge firmware or UTOC)
• The second indicates that CAN0 is either not configured or misconfigured on the host computer
• The third indicates that the host computer's buffer is full or there is a system issue causing buffer failure
• For the second and third points, please refer to the CAN0 configuration section below to troubleshoot the issue
• If the ID cannot be found, please refer to the bottom section for further instructions

Checking if the host supports CAN

• If you are using a FLY host computer, you do not need to perform this step
• If your system is Ubuntu, you need to configure Ubuntu for CAN0, but this document has not yet been updated
• Enter the following command to determine if the system supports CAN:

sudo modprobe can && echo "Your kernel supports CAN" || echo "Your kernel does not support CAN"

• After entering the above command, if your kernel supports CAN, it will return: Your kernel supports CAN; if not, it will return: Your kernel does not support CAN.
• If it returns Your kernel supports CAN, you can proceed to configure CAN0.

Configuring CAN0

• This command will overwrite the existing CAN0 configuration in the system. You need to restart the system after execution.
• FAST systems do not need to perform this step !!!!!!
• Choose the appropriate configuration based on your actual situation

Configuration method for standard Linux systems

Configuration method for standard Linux systems

• You need to choose the appropriate CAN speed based on your device

• For a speed of 1M, enter the following command:

  sudo /bin/sh -c "cat > /etc/network/interfaces.d/can0" << EOF
  allow-hotplug can0
  iface can0 can static
      bitrate 1000000
      up ifconfig $IFACE txqueuelen 1024
      pre-up ip link set can0 type can bitrate 1000000
      pre-up ip link set can0 txqueuelen 1024
  EOF

---

• For a speed of 500K, enter the following command:

  sudo /bin/sh -c "cat > /etc/network/interfaces.d/can0" << EOF
  allow-hotplug can0
  iface can0 can static
      bitrate 500000
      up ifconfig $IFACE txqueuelen 1024
      pre-up ip link set can0 type can bitrate 500000
      pre-up ip link set can0 txqueuelen 1024
  EOF

• If you encounter a similar prompt, please refer to the Raspberry Pi system configuration method

  

Configuration method for Raspberry Pi systems

Configuration method for Raspberry Pi systems

• This method is applicable to Raspberry Pi systems. For other systems, please use the standard Linux system configuration method
• Create a .network file. The BitRate in this configuration can be adjusted as needed, for example, changing 1000000 to 500000

  sudo tee /etc/systemd/network/99-can.network > /dev/null <<'EOF'
  [Match]
  Name=can*
  
  [CAN]
  BitRate=1000000
  RestartSec=100ms
  EOF

• Create a .link file. The TxQueueLength in this configuration is the CAN buffer and is not recommended to be modified

  sudo tee /etc/systemd/network/99-can.link > /dev/null <<'EOF'
  [Match]
  OriginalName=can*
  
  [Link]
  TxQueueLength=1024
  EOF

• Reboot the device

sudo reboot

Things to check if the ID cannot be found

• If Klipper has configured a specific ID, you need to disable the ID in the system settings, then shut down and power off before restarting, or press the reset button on the mainboard.
• Whether the CAN speed of the host matches the mainboard, toolboard, etc.
• You can use the following code to confirm the CAN speed of the host
• Check for any disconnected cables
• Whether a 120Ω jumper is installed between the toolboard and the device (mainboard with USB bridge firmware or UTOC)
• If a 120Ω jumper is installed, use a multimeter to measure the resistance between CAN H and CAN L with the device completely powered off. It should be around 60Ω
• Check for any disconnected cables

ip -details link show can0

• The circled area in the image below shows the CAN speed and buffer of the host
• The 1024 above is the current CAN0 buffer
• The 1000000 below is the current CAN0 speed

• If the UUID still cannot be found, carefully check the following items:

  • Check if the mainboard or CAN toolboard is properly connected
  • Ensure proper power supply, and connect the VCC power if using the mainboard
  • Check if the host supports CAN networking
  • Check if the CAN resistance is around 60Ω
  • Ensure the firmware is compiled correctly

Searching for ID

• Enter the following command to search for the ID

~/klippy-env/bin/python ~/klipper/scripts/canbus_query.py can0

• If an ID appears and the Application: at the end displays Klipper, then this ID can be used directly
• If an ID appears and the Application: at the end displays CANBOOT or Katapult, then firmware needs to be flashed before use