Question about CN5 footprint on STLINK-V3MINIE PCB (unpopulated pads on bottom side)

[dogukanbos]

Hello ST Community,

I’m using an STLINK-V3MINIE and I’m trying to fully understand the hardware on the probe PCB.

On the bottom side of the STLINK-V3MINIE PCB there is an unpopulated footprint labeled “CN5” (small pad footprint). I could not find any mention of CN5 in the user manual as a user-accessible connector, so I’m not sure whether it is factory/test/service only or an optional header.

I attached:

• A photo showing the location of CN5 on the PCB (bottom side).

What I measured so far:

• CN5 pad 3 is GND (confirmed by continuity to USB shield / known GND).

Questions:

1. Do you know what the intended purpose of the unpopulated CN5 footprint is on STLINK-V3MINIE?
   I’m wondering whether it’s mainly for factory test / service, or possibly a reserved footprint for a future accessory / variant, or an internal option used during manufacturing.

2. If CN5 corresponds to a functional interface, would it be possible to share the signal names / pinout (pad 1..4) to the extent you are allowed to?
   Even a high-level hint (e.g., “test only”, “SWD to internal MCU”, “VCP-related”, etc.) would help a lot.

3. I searched the available documentation (UM2910 and product pages) but I couldn’t find any reference to CN5.
   Is there any public document (board info / schematic note / reference) that mentions CN5 for STLINK-V3MINIE, or is it intentionally undocumented?

Thank you in advance.

[Andrew Neil]

Hmmm... the ST-Link V3 MODS and MINI have a similar undocumented footprint (at bottom-left):

Maybe it's for programming the STM32 chip in production?