STM32G431CB not detected over SWD with clone ST-Link

ploopy246 · ‎2026-04-15

Title edited to flag that it's a clone ST-Link

I’m trying to flash an STM32G431CB on a B-G431B-ESC1 ESC board for a reaction wheel-based attitude control system. So there’s three ESCs each. For every one, I soldered 4 wires to the J4 SWD pads (SWDIO, SWCLK, 3V3, GND) and connected them to an ST-LINK V2. Just to clarify on my end, the wire colors don’t really follow any convention, so the red wire isn’t 3V~ I followed the schematic image where the actual pinout left to right is SWDIO, SWCLK, 3V, GND, which matches the correct J4 order.

STM32CubeProgrammer is not detecting the chip. The error reads: UR connection mode is defined with the SWrst reset mode; but I am getting a target voltage at 3.25V (power is fine), but SWDIO/SWCLK don’t seem to be communicating. All target fields show dashes.

I’ve confirmed that the wiring order matches ST-LINK V2 pinout, tried different connection speeds in CubeProgrammer, change the stlink v2 pinout, even changed my ESC (!) and I have the same issue
My suspicion is the J4 pads are very small and this was my first time soldering at that scale (excuse the terrible skills) so maybe the solder bridges between the pads may be shorting SWDIO/SWCLK, although I don’t see any joints as much as I try

My question is, is a solder bridge the most likely cause here, or are there other things I should rule out before redoing the joints? Any tips for debugging SWD connectivity issues on this board specifically would be appreciated please :”)

Andrew Neil · ‎2026-04-16

So, as shown in the link I gave, those are fakes - not genuine ST-Links.

There is no guarantee that they will work properly - or even at all - with the ST Tools.

Do yourself a favour, and get a genuine ST-Link.

Buy from an Official Distributor to be sure - not Amazon, ebay, Ali, or the like.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

View solution in original post

Peter BENSCH · ‎2026-04-16

Welcome @ploopy246, to the community!

please upload photos of your ST-LINK/V2, front and back.

Regards
/Peter

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Andrew Neil · ‎2026-04-16

@Peter BENSCH wrote:
please upload photos of your ST-LINK/V2, front and back.

@ploopy246 I think Peter is hinting at this: How to recognize a genuine ST-LINK/V2 versus a cloned one

In particular, these are fakes.

See also:

How to solve connection errors when connecting and programming the STM32 target board.

How to solve debugger connection issues

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

ploopy246 · ‎2026-04-16

Thank you! I genuinely appreciate the help. These are the ones I had purchased
Any guidance would be helpful

ploopy246 · ‎2026-04-16

Thank you for the response! I'll look into the links provided, hopefully will come to a fixable solution in the whole process; this entire time I was confused as to whether it was the ESC itself, or my poor soldering skills were at fault XD

Andrew Neil · ‎2026-04-16

So, as shown in the link I gave, those are fakes - not genuine ST-Links.

There is no guarantee that they will work properly - or even at all - with the ST Tools.

Do yourself a favour, and get a genuine ST-Link.

Buy from an Official Distributor to be sure - not Amazon, ebay, Ali, or the like.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

ploopy246 · ‎2026-04-16

I definitely will! Thanks for the guidance, genuinely appreciated :)