Can bus on SKR SE BX V2

General Discussion
1

Basic Information:

Printer Model: BIQU BX
MCU / Printerboard: STM32H743 / SKR SE-BX V2.0
Host / SBC RPI 3B+

Describe your issue:

Hi, so on printer the biqu bx use board on print head this one is no longer available and mind broke this week so i will replace it by the hermit crab v2 can bus, but i start to check how configure the motherboard and on list dont find the right port, on drawing the CAN came from PB6/PB7

on klipper configurator this is the list

(X) CAN bus (on PB8/PB9)
( ) CAN bus (on PB5/PB6)
( ) CAN bus (on PB12/PB13)
( ) CAN bus (on PD0/PD1)
( ) CAN bus (on PB0/PB1)
( ) CAN bus (on PD12/PD13)
( ) CAN bus (on PC2/PC3)
( ) CAN bus (on PH13/PH14)

so how is the right config to use CAN on this board

thanks

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2

I don’t think there is one.

Normally, when a board designer specifies a CAN Bus port, they are going to the MCU’s pin mux definitions and selecting pins that have the CAN function.

When I look at the datasheet for the STM32H743, for PB6/PB7 I see:

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There is “FDCAN2_TX” on PB6 but no corresponding CAN pin on PD7.

I think you need to contact BTT ask what’s going on here.

When I search the GitHub page for the BIQU-BX, there’s nothing regarding CAN Bus on there.

Sorry.

1 Like
3

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Hmmmm, strange, I do not see it in the datasheet definition:

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https://www.st.com/resource/en/datasheet/stm32h743vi.pdf

Stange.

Unfortunately, I’m not sure, I know how to change the firmware to make it working this way.

4

I don’t think your mainboard has a CAN transceiver.

https://www.aliexpress.us/item/3256807156372698.html?spm=a2g0o.productlist.main.6.6690inKIinKI6w&algo_pvid=24929321-308e-48cb-bcc1-478f9061495f&algo_exp_id=24929321-308e-48cb-bcc1-478f9061495f-5&pdp_ext_f={“order”%3A"98"%2C"eval"%3A"1"}&pdp_npi=4%40dis!USD!4.38!1.37!!!31.27!9.82!%40210318ec17539119870618997e9c5d!12000040344141122!sea!US!3884106183!X&curPageLogUid=lk8qdoDdkGjW&utparam-url=scene%3Asearch|query_from%3A

So even if your MCU can “speak” CAN it cannot directly connect to a CAN bus.

Best bet is to put a Bigtree U2C on your Pi and connect directly to the Hermit Crab instead of VIA the mainboard.

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5

(I think CAN HAT is better in general, because there would be no USB or MCU at all)
(Like RPI → SPI → CAN: https://www.waveshare.com/wiki/RS485_CAN_HAT)
(Instead of RPI → USB → MCU → CAN)

6

assuming the OP has room for a hat.

The U2C is much smaller and can be mounted to a short usb extension if needed.

Also, by staying with Bigtree, if there are issues the 2 vendors can’t each blame the other.

EDIT much smaller → slightly smaller

7

Hi,

Thanks you, for your reply, so it comfirm what i see, on board V3 they make change they use PB5/PB6, so for me the best way i use the U2C
about the klipper configurator i need to change what to use the U2C?

8

The U2C attaches to the Pi. I think it is “plug and play” on systems running a recent kernal. Check the documentation from Bigtree.

The toolhead (hermit crab) then connects to the U2C directly. The mainboard MCU is no longer involved in communicating with the toolhead. No need to CAN pins on the mainboard.

You’ll need to find the UUID for the toolhead and put that into printer.cfg.

You’ll have to edit all the pin id’s for everything that connects to the toolhead MCU

1 Like
9

You’re missing the most important part:

Follow the instructions on how to set up CAN Bus communications using the excellent Esoterical instructions:

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