Debugging probe StLink V3. GND Detect input (?) signal. What is the minimal set of connections essential? What about VCC input?

[RnnKrk]

Hello,

I connected my probe StLink V3 MODS via only: GND, SwClk, SwDio (CN2.pin8.13,4) for the beginning. And it rather works. Rather as once I got a strange message instead of debugging.

I would like to have my probe reliable so I have found that I have the "GND Detect" signal unconnected (CN2.pin5, CN5.pin11). The datasheet says: "Connect to GND on target, may be used by STLINK-V3MODS for detection of connection." But what does this "... may be used..." really mean: . Should I connect? Or must? Or must not?

What if I do not connect?

To check, I have pulled it up (CN2.pin5) to 3v3 via 5K6 and... found 14 mV on this pin. But it is claimed as "input". Such a heavy input?

Finally, I have shorted CN2.pin5 to GND (CN2.pin8) (as I have no extra GND pin on target connector). Is it correct? Is it necessary?

And by the way. What is the T_VCC input (CN2,pin30, CN5.pin3 ) for?

Regards

Robert

[Tesla DeLorean]

Means it loops back, both pins are ground at the target boards header, so it can see the cable is present and plugged in, end-to-end

T_VCC the Target's supply, so the ST-LINK can measure and report this voltage in STM32 Cube Programmer, etc. In other designs it would allow the JTAG pod side buffers/translators to be powered.

For "Connect Under Reset" to work the NRST pin needs connectivity. For SWV operation the SWO (PB3) needs connectivity.