ST-LINK V3 and STM32L051 won't connect under Reset

[Simon.B94]

Hi all,

I recently experienced some interesting Issue when trying to programm a STM32L051C8T6 via ST-Link V3. (Using the SWD header of the MB1440B-Board)

When I tried to connect to the controller in CubeProgrammer I found that it would not work when selecting Mode: Connect under Reset. (Result is: DEV_CONNECT_ERR)

However The ST-Link V3 is able to establish a connection in the following constellations:

Mode: Normal; Reset Mode: Software Reset

Mode: Hot Plug; Reset Mode:Hardware/Software Reset

To check if there is sth. I did wrong with the wiring I took the old ST-Link V2.1 from my Nucleo-H743ZI finding that it would connect to the L051 in any constellation.

After that i checked on the ST-Link V3 by connecting it to the H743ZI and some F103 Bluepill which it did at the first try.

So I was wondering if somebody got some similar issue or if there is some problem with that constellation ST-Link V3+L051 I am not aware of?

Greetings

Simon

[Uwe Bonnes]

Look at https://community.st.com/s/question/0D53W00000PSK77SAH/is-the-stlinkv3set-locked-to-only-st-mcus

[Tesla DeLorean]

Ease back on the connection speed. The CM0 typically won't sustain 24 MHz, but probably 2 or 4 MHz

[Simon.B94]

Hi,

since both are original ST MCUs and in fact it does connect under certain circumstances that doesn't really help

[Simon.B94]

Hi,

this also came up to my mind and I tried all the speeds available in CubeProgrammer giving the same result.

[Andreas Bolsch]

Your L051 is powered properly, not accidentally via NRST's protection diode? 100nF cap on NRST as suggested?