120 ohm Termination Resistor

The header for the 120R termination resistor is circled in purple

image

Wiring

Connect a USB cable from our Pi to the usb-c port of the U2C. This provides the data connection and power to the U2C.

Do not connect your mainboard (Octopus, etc.) to the USB-A ports on the U2C. They are not a simple USB hub, they are canbus ports using a USB-A connector. You want to connect your mainboard directly to your Pi via USB.

Connect the CanH and CanL from your canbus boards to any of the H/L connections on the U2C. All of these connections are tied together so it doesn’t matter which ones you choose.

If you also run the 24v and GND wires from your canbus board to the U2C then you have to connect the 24v and GND pins (usually the screw terminals) to the V+ and V- of your PSU. This doesn’t power the U2C at all, it’s just pass through to your canbus board for ease of wiring.

image

CANbus_U2C_Pinout_on_Power_Connector

Bad Firmware

The U2C came stock with bad firmware that would cause flashing problems down the line. This was mainly back in early 2023 so if you have purchased a board recently this may not be an issue, but flashing this firmware can’t hurt anyway and is very simple to do.

I have copied a fixed version of the firmware here, you can download it to your pi by running:

cd ~/
wget https://github.com/Esoterical/voron_canbus/raw/main/can_adapter/BigTreeTech%20U2C%20v2.1/G0B1_U2C_V2.bin

(you can read about the error at https://github.com/Arksine/katapult/issues/44)

If you used the wget link the firmware should now be in your home directory. Press the boot button on the U2C while plugging it in to your Pi to put it into DFU mode.

image

Confirm it is connected in DFU mode by running sudo dfu-util -l. You should see the devive:

image

If you can see it there then just run this command to flash the fixed firmware to the U2C:

sudo dfu-util -D ~/G0B1_U2C_V2.bin -a 0 -s 0x08000000:leave

image

You may see an “error during download get-status” down the bottom. You can ignore that as long as everything else is successful.

Once flashed, unplug the U2C from the Pi then plug it back in. Run an ifconfig and you should see a “can0” interface (assuming you have already set the /etc/network/interfaces.d/can0 file). If so, then congratulations your U2C is succesfully flashed with the fixed firmware.