ST-Link cannot more flash external Target

[MFail.11]

Hello,

Situation: I have a Nucleo WB55 board that is able to flash the internal SMT32 micro with the embedded ST-Link.

I want to use this Nucleo to flash a custom board with the embbedded ST-LINK, disconnecting the jumpers and connecting the lines properly to the custom board. This process fails because Cube programmer don't find the STM32 target. It finds st-link of course and I tried every mode, every clock frequency, everithing.

So this Nucleo can flash internal target but not external one!

Strange things: With the same Nucleo weeks ago I was able to flash external target, now I can't, something happened.

Connections and continuity is OK, custom board is ok (I can flash it with others Nucleo boards), cables are ok, lines are properly connected.

So what a mistery is this?

[TDK]

There's not many components at play here. The ST-Link doesn't care what it connects to, so the issue is the wiring.

Recheck GND, SWDIO, SWCLK between the st-link and the target mcu, and only between those two. Ensure target mcu is powered. That's it, apart from some corner cases.

[AScha.3]

Just try to reconnect the onboard cpu and connect to it - to prove, you didnt damage something.

[MFail.11]

That's not it. Cables are ok, If I use a different Nucleo board with same external target and cables, I can flash the target.

The internal target when Jumpers are installed is detected perfectly from Cube Programmer.

I never powered the target MCU, the st link provide supply to external board and it worked always.

So if cables are ok an continuity is ok, something else is still present.

A damage that prevent to use long wires could be?

[AScha.3]

So try with low data speed to connect , because long wires.

[MFail.11]

Also with lowest speed and every mode (or different reset mode), that thing is not working.

But it worked until few weeks ago. That's the mistery.

What could be damaged? And why can it flash internal micro?

[TDK]

Couldn't it also be explained by a hardware error on your target chip, rather than the st-link?

[AScha.3]

Thats really difficult now, to find out.

What "happened" usually in such case : broken wire or bad connector , or static discharge damaged pin.

But damaged pin by static discharge most times doing nothing any more, yours seem still working.

No idea...