Problem programming STM32L081 with J-Link even though ST-Link is working fine.

[lecc]

Hi everyone

We have designed a custom board around the STM32L081CZ and produced 3 prototypes. On the first board I started testing and debugging using STM32CubeIDE on Windows. This worked fine but only with ST-Link, not with J-Link.

After testing (and fixing) our hardware, we wanted to program our boards on Debian using Zephyr. I gave a second board (with identical hardware fixes) to my colleague and he was able to program it with a J-Link using West without any problems. My initial board however, that I can still program using ST-Link however does not work using the J-Link (tried West, J-Flash and STM32CubeProgrammer). We since tested the third board and it also works fine with the J-Link.

I used ST-Link with STM32CubeProgrammer to connect to all three boards and verified that they are all in the same state (Option Bytes and Registers). I have added a screenshot where I connect first to the device that only connects to ST-Link (Time: 16:33) and then to the one that connects to both (Time 16:35).

I added a second screenshot where I tried to connect to both using J-Flash and J-Link. First I successfully connect to the board that is J-Link compatible. And further down I unsuccessfully try to connect to the target that is only reachable via ST-Link.

The problem occurs when the J-Link ties to initialize DAP.

We did not reassign any of the debug pins and I have fully erased the board, so there should be no issues with the SWDIO or SWCLK pins being in a false state (also demonstrated by the ST-Link working fine).

I also added a screenshot of the debug connector from the schematic.
SWDIO -> PA13, SWCLK -> PA14, nRESET -> NRST

Does anyone have an Idea what the issue could be? Any help would be much appreciated.

[Andrew Neil]

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@lecc wrote:

This worked fine but only with ST-Link, not with J-Link.

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As the problem lies with J-Link, you should ask Segger about that:

https://www.segger.com/support/technical-support/

https://forum.segger.com/board/4-j-link-flasher-related/

[lecc]

Hei Neil

Thanks for the suggestion. I consider posting my question there as well.

However I am not convinced, that the problem lies with J-Link. The J-Link I use works fine with 2 of 3 boards suggesting there is no issue with the J-Link or the associated tools.

Are there any settings, registers, or something that might have been changed/reconfigured by initially using the STM32CubeIDE and ST-Link that could have changed the configuration of this MCU on the first board, making it different from the other two? Something that the ST-Link can handle either way, but prevents the J-Link from connecting properly...