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Is it possible to use the STLINK V3 CN1 without T_VCC?



I'm working on a design where I need to minimize the number of pins given space problems. I plan to use an ST-LINK/V3 SET without the expansion board, so I'll use just the MB1441 one.

I can't find the official MB1441 board schematic to discover this myself; that's why I'm bothering you.

I will use SWD from MB1441 CN1 with GND, CLK, DIO, NRST, and SWO and want to avoid the T_VCC. I would like to know if this is possible. My target board is 3.3V.

BTW, I'm using STMCubeIDE, and the target is an STM32F207 chip.

Thanks in advance, Julian


i just can say: i tried STlink V3 mods , connect just gnd/sdw/swc/swo (+software reset) ; working normal, just see "0,0V on target" , but you could connect this to any 3v3 on the V3 itself , to keep "3,3V on target" message.

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Pavel A.
Evangelist III

I've just recently hit the same thing with ST-LINK v3 minie. It refuses to work without target VCC connected. Can't find an option in the tools to ignore the T_VCC.


I guess it is given by the level-shifting circuitry which is not properly biased without T_VCC. I hoped it worked with 3.3V in the absence of T_VCC.

I will try to capture the schematic on Friday after receiving the STLINK V3.

Thanks for your help.

Associate II

@JAnto.4, have you been able to verify if T_VCC can be left unconnected?

Honestly how hard is this to actually try yourself?

It doesn't even have to come from the target itself, it just needs to be wired to a voltage appropriate for the target.

You will need a ground connection. 

The debug signals can be exposed in many ways, as castellations on the edge, or on a break-off tab beyond the final board but on the panel.

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Associate II

I am not saying that it is hard per se, but since I have read about different people have different outcomes with the T-VCC and the OP seem to have the exact same setup/tools/needs that I have, I though that hearing his/her experience could be useful before I proceed with my own (uneasy) testing. Anyhow, thanks for your feedback