# MCU down?! mcu 'mcu': Unable to connect **URL:** \ **Category:** Sovol SV08\ **Tags:** klipper\ **Created:** [January 31, 2026, 10:13am UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480 "2026-01-31T10:13:47Z")\ **Posts on this page:** 9\ **Page:** 2
**Author:** ![cardoc](https://avatars.discourse-cdn.com/v4/letter/c/ec9cab/32.png) [@cardoc](https://forum.sovol3d.com/u/cardoc)\ **Post date:** [January 31, 2026, 10:49pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/21 "2026-01-31T22:49:13Z")
> [@faggit](#): > > `stm32f042x6_` 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? ---
**Author:** ![faggit](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/faggit/32/5409_2.png) [@faggit](https://forum.sovol3d.com/u/faggit)\ **Post date:** [January 31, 2026, 11:16pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/22 "2026-01-31T23:16:31Z")
> [@cardoc](#): > > So your STM32F407 chip is completely missing. Sorry but I do not understand this. > [@cardoc](#): > > What OS is on computer in the other end of the STlink? Windows 11. stlink is working on other devices. ---
**Author:** ![cardoc](https://avatars.discourse-cdn.com/v4/letter/c/ec9cab/32.png) [@cardoc](https://forum.sovol3d.com/u/cardoc)\ **Post date:** [January 31, 2026, 11:24pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/23 "2026-01-31T23:24:20Z")
> [@faggit](#): > > > [@cardoc](#): > > > > So your STM32F407 chip is completely missing. > > Sorry but I do not understand this. 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. ---
**Author:** ![faggit](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/faggit/32/5409_2.png) [@faggit](https://forum.sovol3d.com/u/faggit)\ **Post date:** [February 1, 2026, 1:47pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/24 "2026-02-01T13:47:20Z")
haha 😃 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? ```auto 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? ---
**Author:** ![cardoc](https://avatars.discourse-cdn.com/v4/letter/c/ec9cab/32.png) [@cardoc](https://forum.sovol3d.com/u/cardoc)\ **Post date:** [February 1, 2026, 7:33pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/25 "2026-02-01T19:33:40Z")
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 ---
**Author:** ![cardoc](https://avatars.discourse-cdn.com/v4/letter/c/ec9cab/32.png) [@cardoc](https://forum.sovol3d.com/u/cardoc)\ **Post date:** [February 1, 2026, 8:03pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/26 "2026-02-01T20:03:13Z")
> [@faggit](#): > > 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? 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? ---
**Author:** ![faggit](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/faggit/32/5409_2.png) [@faggit](https://forum.sovol3d.com/u/faggit)\ **Post date:** [February 1, 2026, 9:27pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/27 "2026-02-01T21:27:37Z")
> [@cardoc](#): > > Can you get a closeup photo of the switches? ![IMG_3077](https://canada1.discourse-cdn.com/flex030/uploads/sovolforum/original/2X/a/a1fabfccd582e5914cf933ac7ec981bf30761ca7.jpeg) 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. ```auto 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. ``` ---
**Author:** ![faggit](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/faggit/32/5409_2.png) [@faggit](https://forum.sovol3d.com/u/faggit)\ **Post date:** [February 2, 2026, 6:37pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/28 "2026-02-02T18:37:27Z")
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! ---
**Author:** ![faggit](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/faggit/32/5409_2.png) [@faggit](https://forum.sovol3d.com/u/faggit)\ **Post date:** [April 4, 2026, 12:35pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/29 "2026-04-04T12:35:04Z")
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!** [Previous page](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480.md?page=1)