ST‑LINK V3 Minie connects to STM32F100RBT6B Discovery but not to my custom board

[saran]

I’m using an ST‑LINK V3 Minie with an STM32F100RBT6B Discovery board (which also has an STM32F103C8T6), and it works perfectly. However, when I connect the same ST‑LINK V3 Minie to my custom board that uses the same STM32F100RBT6B chip, it fails to connect.

I’ve wired VCC (VTref), GND, NRST, TMS/SWDIO, and TCK/SWCLK exactly as specified.

Black - Ground

White - Vcc

Yellow - Reset

Blue - Clock

Purple - TMS

On the Discovery board this setup works fine, but on my custom board the debugger cannot establish communication.

Could anyone suggest what additional checks I should perform on the custom board?

[Ozone]

Doesn't this suggest the problem is with your custom board ?

I would suggest to connect the VDD /T_Vcc pin as well, as it is used to sense of the target is powered :

Have you checked the voltage at the supply pins of you custom board (at the MCU pins), and the power consumption ?
Only then would I connect an external tool like a debug adapter.

[saran]

@Ozone Yes I have checked the voltage supply at Vcc, it gives 3.3V.

[Ozone]

I don't know if you understand what I meant.

First, make sure your PCB is correct.
Check all traces for the MCU's power supply, debug connection, clock generation etc., preferably unpowered first.
Then apply power (if possible with a current limitation enables), and measure current draw.
Only then connect to a debug adapter.

AFAIK the ST-Link adapters don't require a T_Vcc detection. I converted basically all my ST-Links into J-Links.
If you don't get connection, try a scope (or logic analyser) and check the debug signals.

Alternatively you can try to start the MCU into system mode (via BOOT0), and try connecting via serial line & CubeProgrammer.
I suppose you planned for an option to pull BOOT0 low for this purpose.