MCU down?! mcu 'mcu': Unable to connect

Sovol SV08
21

Is a USB power management chip. So your STM32F407 chip is completely missing.

Fire up the STlink and see if it will ID the chip. What OS is on computer in the other end of the STlink?

22

Sorry but I do not understand this.

Windows 11. stlink is working on other devices.

23

Linux does not “see” it at all so from that point of view the MCU is “missing”. I didn’t assume it unsoldered itself and ran away.

24

haha :smiley:

Yes, and that’s exactly why I posted in this forum. I can’t explain it. I did unplug the Eddy after all, because you said I should. As I said, EVERY device works, except for the mainboard MCU. I’m still not quite sure what you’re getting at?

biqu@sovolsv08:~$ ls /dev/serial/by-id/
usb-Klipper_rp2040_5044505930A3761C-if00
usb-Klipper_stm32f042x6_0F001400115330374E333320-if00
usb-Klipper_stm32f103xe_52FF6E067167485753191787-if00

Discription of each device see above in previous posts.

Perhaps an off-topic question: There are two DIP switches on the mainboard (x = position):

1 [xo] ‘ON’ (on ‘1’)
2 [ox] ‘KE’ (on ‘KE’)

Do they have anything to do with this? And what is the factory default setting?

25

Somehow your main MCU is bricked. Most probably by improper or corrupted firmware. This a highly unusual situation but the chances of recovery are quite good with use of the STlink programmer.

Connect your STlink to the 4 pins near the MCU
Attempt to connect - probably won’t work.
Power down printer board

In CubeProgrammer:

  1. Interface: ST‑Link (SWD)
  2. Frequency: 100 kHz
  3. Mode: Connect under reset
  4. Sequence:
  • Turn printer off
  • Click Connect
  • Turn printer on within a second

If it doesn’t connect try again. when you you get a connection:

1. Read the device info

In STM32CubeProgrammer, you should now see:

  • Device: STM32F103xx
  • Flash size: 512 KB (for VET6)
  • Device ID: 0x0410

If you see that, the MCU is fully alive.

2. Perform a full chip erase

This clears any corrupted bootloader, bad Klipper build, or misaligned flash.

In CubeProgrammer:

  • Go to Erasing & Programming
  • Click Full chip erase
  • Wait for confirmation

This puts the MCU into a clean, known state.

3. Flash a correct Klipper build

For your STM32F103VET6, the correct make menuconfig is:

  • Microcontroller: STMicroelectronics STM32
  • Processor model: STM32F103
  • Bootloader: None
  • Clock: 8 MHz crystal
  • Communication: Serial (USART1 PA9/PA10)

Build it, then in CubeProgrammer:

  • Select your klipper.bin
  • Set Start address = 0x08000000
  • Enable Verify programming
  • Click Start Programming

4. Power‑cycle the board

Once programming completes:

  • Turn the printer off
  • Turn it back on
26

According to Microsoft Copilot AI these switches DO put the MCU into special modes for factory programming.

Can you get a closeup photo of the switches?

27

IMG_3077
IMG_30771920×1080 423 KB

I am still trying to connect to the printer. With the program gui and via cli. Turning on and off and all the stuff won’t work atm. Always the same error as shown.

PS C:\Program Files\STM32CubeProgrammer\bin> .\STM32_Programmer_CLI.exe -c port=SWD freq=100 mode=UR
      -------------------------------------------------------------------
                       STM32CubeProgrammer v2.21.0
      -------------------------------------------------------------------

ST-LINK SN  : 37FF71064E573436B10E1543
ST-LINK FW  : V2J46S7
Board       : --
Voltage     : 3.24V
Error: Unable to get core ID
Error: Cannot connect to access port 0!  If you are trying to connect to a device with TrustZone enabled please try to connect with HotPlug mode.  If you are trying to connect to a device which supports Debug Authentication with certificate or password, please open your device using it.
28

I tried again with different options and even with other ST-Links v2. However, they all fail with the same error message (Error: Unable to get core ID). One of the ST-Links doesn’t even go beyond “18:34:57 : UR connection mode is defined with the HWrst reset mode” in the GUI. After that, nothing else happens. I have been in contact with support since yesterday. I sent them the log file and now hope that I can get official help. Otherwise, I’ll take matters into my own hands.

Thank you very much for your efforts!

29

You can imagine how desperate you get over time when no one can help you anymore. And in the end, thanks to AI, I was able to follow a very detailed troubleshooting process and identify the problem.
Long story short: The motherboard was indeed defective. I received a new motherboard from Sovol Support.

Thanks to everyone for your efforts!