MCU Unable to Connect error

Comgrow T300
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1

So after I replaced the nozzle I had a catastrophic failure during a print (The head cooling fan cable actually got either severed or yanked off). After that the printer is now stuck after booting, giving a mcu: Unable to Connect error. It says to restart firmware when the underlying issue is resolved, but no such luck, it just loops back to the start. I can still connect to the printer via the web interface, and it seems the relevant part of the klipper log has the following: mcu ‘mcu’: Starting serial connect
mcu ‘mcu’: Unable to open serial port: [Errno 2] could not open port /dev/serial/by-id/usb-Klipper_stm32f401xc_4B0064000651333032363732-if00: [Errno 2] No such file or directory: ‘/dev/serial/by-id/usb-Klipper_stm32f401xc_4B0064000651333032363732-if00’ "

Any advice? I’m hoping not to have to replace anything.

2

Hi,
Send an email at info@sovol3d.com with your order number and the description of your issue.
It sounds like a motherboard to be replaced.

3

Welcome to the forums.

I’m sorry to say there are no easy fixes for your issue.

On a typical klipper printer your first step would be a new cable from the HOST to the MCU board. Your HOST is embedded into the printer mainboard. The USB cable is copper traces on the board.

It may be possible to recover your printer from within the Web UI but SSH is the better tool.

Download/install Putty. Enter the IP address of your printer and log in:

User ID root
Password makerbase.

Then enter ls -la /dev/serial/by-id/

If that’s too much it may be restoring the default address for the serial connection. In the Web UI [configuration] tab find MCU_ID.cfg and load it into the built in editor.


serial:/dev/serial/by-id/usb-Klipper_stm32f401xc_160050000A51333032393131-if00 #from restore image
       /dev/serial/by-id/usb-Klipper_stm32f401xc_4B0064000651333032363732-if00 #from your error

Edit the line to match the top line. The lower line is from your screen capture.

Click [Save and Restart]

4

Putty returned this: “ls: cannot access ‘/dev/serial/by-id/’: No such file or directory”

No dice with changing MCU_ID.cfg either sadly. I’m starting to suspect the board itself might be no good anymore. The cables all seem fine as far as I can tell but it’s possible they’re the issue. All the same thank you for your help! I was hoping it might be something I could fix on my end.

5

Hmm, I’d have to check Amazon for my order number but the printer would be out of warranty.

6

It’s no big deal, just get in touch with them.
They’re always friendly.

7

Yes it seems your mainboard has "left the chat.

It’s a long shot but reflashing the firmware could sort things out.

A “dirty shutdown” could have left the OS crippled enough to break USB conectivity.

8

Is reflashing the firmware just a matter of taking the emmc off and flashing it that way? If so then..sadly no dice. I’m really thinking the board might just be kaput. Again thank you for your help with this!

9

You can try doing that.
If it still doesn’t work, you can always replace the motherboard after.