# 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:** 20\ **Page:** 1
**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, 10:13am UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/1 "2026-01-31T10:13:47Z")
Hello, friends of 3D printing! πŸ™‚ My Mianboard MCU is no longer recognised. After extensive personal research, I have now reached the end of my tether and am turning to the collective knowledge of this forum in the hope of finding a solution πŸ™‚ This is actually the last step I can think of before I finally despair. I actually run Klipper Mainline on my SV08. Why β€˜actually’? Klipper greeted me with the message that the MCU is no longer accessible (mcu β€œmcu”: Unable to connect). #### System (EMMC flashed) > Host (aarch64, 64-bit) > OS: Debian GNU/Linux 11 (bullseye) > BTT-CB1 2.3.4 Bullseye with Linux 5.16.17-sun50iw9 > Klipper v0.13.0-514 After quite a bit of research, I found out that my MCU can no longer be found in Linux either. ```auto biqu@sovolsv08:\~$ ls /dev/serial/by-id/ usb-katapult_stm32f103xe_52FF6E067167485753191787-if00 usb-Klipper_rp2040_5044505930A3761C-if00 usb-Klipper_stm32f042x6_0F001400115330374E333320-if00 biqu@sovolsv08:\~$ lsusb Bus 003 Device 004: ID 1d50:614e OpenMoko, Inc. stm32f042x6 Bus 003 Device 003: ID 1d50:614e OpenMoko, Inc. rp2040 Bus 005 Device 002: ID 1d50:6177 OpenMoko, Inc. stm32f103xe ``` ### Definition > ##### SV08 Toolhead (STM32F103) > > /dev/serial/by-id/usb-katapult\_stm32f103xe\_52FF6E067167485753191787-if00 > lsusb: ID 1d50:6177 OpenMoko, Inc. stm32f103xe > > ##### Klipper Expansion Board (STM32F042) > > /dev/serial/by-id/usb-Klipper\_stm32f042x6\_0F001400115330374E333320-if00 > lsusb: ID 1d50:614e OpenMoko, Inc. stm32f042x6 > > ##### BTT Eddy (RP2040) > > /dev/serial/by-id/usb-Klipper\_rp2040\_5044505930A3761C-if00 > lsusb: ID 1d50:614e OpenMoko, Inc. rp2040 > ##### SV08 Mainboard (STM32F103) - missing, added manually for the forum > > _from my printer.cfg: stm32f103xe\_30FFD7053347543032621651-if00_ Now, to be on the safe side, I wanted to update the mainboard’s firmware to the same version, as I only installed Eddy Duo yesterday (wired and flashed, that’s all that’s possible at the moment). I connected to the mainboard using an St-Link v2 and the STM32CubeProgramme (wiring checked several times). I simply cannot connect to the motherboard: ```auto Logfile (STM32CubeProgramme) 01:01:39 : UR connection mode is defined with the HWrst reset mode 01:01:39 : ST-LINK SN : 37FF71064E573… 01:01:39 : ST-LINK FW : V2J46S7 01:01:39 : Board : – 01:01:39 : Voltage : 3.23V 01:01:39 : Error: Unable to get core ID 01:01:39 : 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 that supports Debug Authentication with a certificate or password, please open your device using it. ``` As you can see, I’m going round in circles ☹ Help. //ErgΓ€nzung/Edit If I disconnect all devices and try to list them (lsusb and /dev/serial/by-id/), the list is accordingly empty. So not even the motherboard or its Stm chip is recognised. 2026-01-31T00:00:00Z ---
**Author:** ![Lion](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/lion/32/5586_2.png) [@Lion](https://forum.sovol3d.com/u/Lion)\ **Post date:** [January 31, 2026, 4:58pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/2 "2026-01-31T16:58:12Z")
@cardoc ---
**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, 6:35pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/3 "2026-01-31T18:35:14Z")
> [@faggit](#): > > ```auto > biqu@sovolsv08:\~$ ls /dev/serial/by-id/ > usb-katapult_stm32f103xe_52FF6E067167485753191787-if00 > usb-Klipper_rp2040_5044505930A3761C-if00 > usb-Klipper_stm32f042x6_0F001400115330374E333320-if00 > biqu@sovolsv08:\~$ lsusb > Bus 003 Device 004: ID 1d50:614e OpenMoko, Inc. stm32f042x6 > Bus 003 Device 003: ID 1d50:614e OpenMoko, Inc. rp2040 > Bus 005 Device 002: ID 1d50:6177 OpenMoko, Inc. stm32f103xe > > ``` This output is from the current OS via SSH? > [@faggit](#): > > `Bus 005 Device 002: ID 1d50:6177 OpenMoko, Inc. stm32f103xe` Is the mainboard MCU Is the OS actually compatible with the Sovol H616 SOM? I’ve never seen anyone successfully reimage a Sovol H616. The usual β€œhack” is run Klipper in a virtual machine. You shouldn’t need STlink. The mainboard MCU is running Katapult bootloader and should accept firmware update VIA usb. Do you have KIAUH installed? ---
**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, 7:25pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/4 "2026-01-31T19:25:39Z")
Yes, that’s the output from the current OS over SSH. It must definitely be the toolhead MCU, because it was the only device I was able to flash with Katapult using the ST-Link. I asked different AIs to help identify the devices and compared the results with my old `printer.cfg` entries from before the crash. The strongest evidence is that every other device on the mainboard disconnects. If nothing else is connected, the list is completely empty β€” the toolhead MCU does not appear at all. The system had been running perfectly the whole time. And yes, I have KIAUH installed. I use it for almost everything. //edit: Grammar correction ---
**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, 8:23pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/5 "2026-01-31T20:23:59Z")
![image](https://canada1.discourse-cdn.com/flex030/uploads/sovolforum/original/2X/8/81fc141ab6b6732115182cc0a174d4e302019203.png) Your Mainboard MCU is right there BUT Klipper firmware is not running. Use Kiauh to β€œmake and flash” for the STM32F103 ---
**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, 8:24pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/6 "2026-01-31T20:24:59Z")
I have documented all attempts thoroughly (thanks to AI!). I would still be interested to know how this could have happened, as I did not intervene in this MCU and only took action when the β€˜crash’ suddenly occurred. πŸ€” ```auto ============================================================ DIAGNOSTIC REPORT – MCU FAILURE ON THE SOVOL SV08 MAINBOARD MCU Type: STM32F103 (Sovol SV08 Mainboard) ============================================================ 1. INITIAL SITUATION -------------------- The Debian system running on the printer does not detect any MCU serial interface. The following device nodes are completely absent: /dev/ttyACM* /dev/ttyUSB* This indicates that the STM32F103 MCU does not enumerate as a USB CDC device. As a result, Klipper cannot start and KIAUH only reports secondary errors. -------------------------------------------------------- 2. MEASUREMENT METHOD 1 – USB ENUMERATION ON THE PRINTER -------------------------------------------------------- Command: ls /dev/ttyACM* ls /dev/ttyUSB* Result: "No such file or directory" Interpretation: - The MCU does not present itself over USB. - Neither the bootloader nor the firmware is active. - The USB transceiver or the MCU core is not functioning. -------------------------------------------------------- 3. MEASUREMENT METHOD 2 – ST-LINK / SWD CONNECTION -------------------------------------------------------- Command: STM32_Programmer_CLI.exe -l STM32_Programmer_CLI.exe -c port=SWD Result: - ST-Link is detected correctly. - Supply voltage of 3.25 V is measured. - Connection to the MCU fails: "Error: Unable to get core ID" "Error: Cannot connect to access port 0!" Interpretation: - The MCU receives stable 3.3 V. - The SWD debug port does not respond. - The ST-Link cannot read the core ID or open the access port. - This is NOT typical for firmware or bootloader corruption. - This behavior only occurs when the STM32F103 is internally damaged. -------------------------------------------------------- 4. MEASUREMENT METHOD 3 – HOTPLUG / FORCED RESET (OPTIONAL) -------------------------------------------------------- Typical additional tests: - Connecting in HotPlug mode - Connecting while holding NRST low (reset forced) Expected behavior if the chip is alive: - At least a core ID is returned. Expected behavior if the chip is defective: - Identical error messages as above. Since the standard SWD connection already fails, success in these tests is extremely unlikely. -------------------------------------------------------- 5. OVERALL ASSESSMENT -------------------------------------------------------- All relevant communication paths to the MCU have failed: - No USB enumeration - No /dev/ttyACM0 - No SWD access - No core ID - No access port - Supply voltage present This is the characteristic failure pattern of an electrically damaged STM32F103 microcontroller. -------------------------------------------------------- 6. PROBABLE CAUSE OF FAILURE -------------------------------------------------------- Based on the measurements, the most likely defect is: β†’ Internal hardware failure of the STM32F103 (CPU core, SWD interface, or USB transceiver destroyed) Possible triggers: - Toolhead short circuit - 24 V leakage into MCU-related lines - ESD damage via USB lines - Backfeed from a stepper driver - Overvoltage on the 3.3 V rail -------------------------------------------------------- 7. RECOMMENDED ACTION -------------------------------------------------------- Since neither USB nor SWD responds, software recovery is impossible. Only two options remain: A) Replace the STM32F103 (rework) – requires hot air, rework station, and experience B) Replace the entire mainboard – fastest and most reliable solution I have documented all attempts thoroughly (thanks to AI!). ============================================================ END OF REPORT ============================================================ ``` ---
**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, 8:30pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/7 "2026-01-31T20:30:16Z")
AI is wrong (shocking). Your STM32F103 is running katapult and only needs to be flashed with the correct communications settings, Once done it will create a serial over USB port and listen for klipper. ---
**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, 8:45pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/8 "2026-01-31T20:45:21Z")
thanks you so much for your support. I really don’t understand what is happening. You tell me that is the mainboard. When that is the mainboard, where is my toolhead? Do you have discord? I would show you that live if you want. I can share my screen. 2views [![](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/faggit/144/5409_2.png "faggit")](https://forum.sovol3d.com/u/faggit) [![](https://canada1.discourse-cdn.com/flex030/uploads/sovolforum/original/2X/c/cf2dd3658762c22278621c186b1d97108032e3a6.png "cardoc")](https://forum.sovol3d.com/u/cardoc) ![](https://canada1.discourse-cdn.com/flex030/uploads/sovolforum/original/2X/7/707cd22911e4790c283724a148e0048cb456095a.png "cardoc")cardoc​ ![](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/faggit/72/5409_2.png "faggit")faggit ​ ## post by cardoc 4 mins ago [![](https://canada1.discourse-cdn.com/flex030/uploads/sovolforum/original/2X/c/cf2dd3658762c22278621c186b1d97108032e3a6.png)](https://forum.sovol3d.com/u/cardoc) [cardoc](https://forum.sovol3d.com/u/cardoc) [4m](https://forum.sovol3d.com/t/aw-mcu-down-mcu-mcu-unable-to-connect/9485/2) I prefer to work the problem on the forum. Might help other users. I’m excited you got the CM1 image flashed and running. First time I’ve seen that! The STM32F402 is the toolhead last visit ## post by faggit 2 mins ago [![](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.sovol3d.com/faggit/144/5409_2.png)](https://forum.sovol3d.com/u/faggit) [faggit](https://forum.sovol3d.com/u/faggit) [2m](https://forum.sovol3d.com/t/aw-mcu-down-mcu-mcu-unable-to-connect/9485/3) Are you sure? So I built a wrong firmware for the toolhead The toolhead is happy ATM. Klipper runs the same firmware on all boards as long as the MCU, com configuration and BL offset are correct. ---
**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, 8:49pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/9 "2026-01-31T20:49:12Z")
My thought is you forced the F402 firmware onto the F103 on the mainboard with the STlink. It can’t run that code so only the bootloader is active ---
**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, 8:52pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/10 "2026-01-31T20:52:18Z")
I flashed Klipper now to the toolhead. **usb-Klipper\_stm32f103xe\_52FF6E067167485753191787-if00** > I got the information from the official source: It is both stm32F103. > [SV08/Motherboard/H616\_JC\_6Z\_V1\_2\_MCU.pdf at main Β· Sovol3d/SV08 Β· GitHub](https://github.com/Sovol3d/SV08/blob/main/Motherboard/H616_JC_6Z_V1_2_MCU.pdf) > [SV08/Motherboard/Extra\_MCU.pdf at main Β· Sovol3d/SV08 Β· GitHub](https://github.com/Sovol3d/SV08/blob/main/Motherboard/Extra_MCU.pdf) [Rappetor (Richard) Β· GitHub](https://github.com/Rappetor/) tells the same. As I said I didn’t do anything to the motherboard before the crash. Even if the wrong firmware was flashed, the ST‑Link should _always_ be able to connect to the MCU. The debug interface (SWD) works independently of the bootloader and the flash contents. If the ST‑Link cannot read the core ID or open the access port, this points to a hardware‑level issue with the MCU itself, not a software or flashing mistake. ---
**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, 9:00pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/11 "2026-01-31T21:00:19Z")
Unplug your toolhead and Eddy run > [@faggit](#): > > `ls /dev/serial/by-id/` What do you see? ---
**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, 9:02pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/12 "2026-01-31T21:02:59Z")
> [@faggit](#): > > If I disconnect all devices and try to list them (lsusb and /dev/serial/by-id/), the list is accordingly empty. So not even the motherboard or its Stm chip is recognised. ```auto biqu@sovolsv08:~$ ls /dev/serial/by-id/ ls: cannot access '/dev/serial/by-id/': No such file or directory ``` ---
**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, 9:14pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/13 "2026-01-31T21:14:23Z")
Try a generic lsusb. if no plug a camera or memory stick in the back ant run again ---
**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, 9:21pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/14 "2026-01-31T21:21:12Z")
Sorry for asking, it’s not my style to ask someone who’s helping me such a question, but have you read all of my posts? ```auto NO USBDEVICES CONNECTED (for debugging): biqu@sovolsv08:~$ lsusb Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 002: ID 1a40:0101 Terminus Technology Inc. Hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub + STOCK WEBCAM: biqu@sovolsv08:~$ lsusb Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 003: ID 364d:6366 HHW microelectronics Co., Ltd. MGS1 Bus 003 Device 002: ID 1a40:0101 Terminus Technology Inc. Hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub biqu@sovolsv08:~$ + TOOLHEAD biqu@sovolsv08:~$ lsusb Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 003: ID 364d:6366 HHW microelectronics Co., Ltd. MGS1 Bus 003 Device 002: ID 1a40:0101 Terminus Technology Inc. Hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 005 Device 004: ID 1d50:614e OpenMoko, Inc. stm32f103xe Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub ``` ---
**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, 9:42pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/15 "2026-01-31T21:42:10Z")
Okay I had them backwords. Currently toolhead is stuck at bootloader (STM 34F103) Main MCU is completely missing when did you loose > [@faggit](#): > > ```auto > biqu@sovolsv08:\~$ ls /dev/serial/by-id/ > usb-katapult_stm32f103xe_52FF6E067167485753191787-if00 > usb-Klipper_rp2040_5044505930A3761C-if00 > usb-Klipper_stm32f042x6_0F001400115330374E333320-if00 > > ``` The Klipper\_stm32f042xxxx ? ---
**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, 9:48pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/16 "2026-01-31T21:48:58Z")
> [@faggit](#): > > ##### SV08 Toolhead (STM32F103) > > /dev/serial/by-id/usb-katapult\_stm32f103xe\_52FF6E067167485753191787-if00 > lsusb: ID 1d50:6177 OpenMoko, Inc. stm32f103xe > > ##### Klipper Expansion Board (STM32F042) > > /dev/serial/by-id/usb-Klipper\_stm32f042x6\_0F001400115330374E333320-if00 > lsusb: ID 1d50:614e OpenMoko, Inc. stm32f042x6 > > ##### BTT Eddy (RP2040) > > /dev/serial/by-id/usb-Klipper\_rp2040\_5044505930A3761C-if00 > lsusb: ID 1d50:614e OpenMoko, Inc. rp2040 meanwhile `usb-katapult_stm32f103xe_52FF6E067167485753191787-if00` is `usb-Klipper_stm32f103xe_52FF6E067167485753191787-if00` as is I said. When all that happens idk. After eddy hardware installation (it is just an usb plug)… ---
**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, 9:56pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/17 "2026-01-31T21:56:14Z")
Plug in everything but the eddy and use KIAUH to β€œfind my MCU” I think the mainboard MCU is β€œsoftbricked”. What is printed on the chip? ---
**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, 10:13pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/18 "2026-01-31T22:13:27Z")
> [@cardoc](#): > > What is printed on the chip? stm32f103vet6 > [@cardoc](#): > > Plug in everything but the eddy and use KIAUH to β€œfind my MCU” ```auto Identifying MCU connected via USB ... The following MCUs were found: ● MCU #0: /dev/serial/by-id/usb-Klipper_stm32f042x6_0F001400115330374E333320-if00 ● MCU #1: /dev/serial/by-id/usb-Klipper_stm32f103xe_52FF6E067167485753191787-if00 ╔═══════════════════════════════════════════════════════╗ β•‘ Make sure that the controller board is connected now! β•‘ β•Ÿβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β•’ β•‘ How is the controller board connected to the host? β•‘ β•Ÿβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β•’ β•‘ 1) USB β•‘ β•‘ 2) UART β•‘ β•‘ 3) USB (DFU mode) β•‘ β•‘ 4) USB (RP2040 mode) β•‘ β•Ÿβ”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”¬β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β”€β•’ β•‘ B) Β« Back β”‚ H) Help [?] β•‘ β•šβ•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•§β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β•β• ###### Select connection type: ``` ---
**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, 10:27pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/19 "2026-01-31T22:27:58Z")
did you try choice 3? Can you locate a pad or pin labeled β€œboot0”? ---
**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, 10:32pm UTC](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480/20 "2026-01-31T22:32:49Z")
> [@cardoc](#): > > did you try choice 3? yes, empty. > [@cardoc](#): > > Can you locate a pad or pin labeled β€œboot0”? Neither a reset pin, an NRST pin nor a boot0 pin. And no additional pins for bridging either. [Next page](https://forum.sovol3d.com/t/mcu-down-mcu-mcu-unable-to-connect/9480.md?page=2)