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How to use SWD without JLink/Debugger

ASieg
Associate

Hi everybody,

I need to connect to the SWD Interface of my STM32F0 without any debugger. I already studied the protocol itself and I am able to read the correct IDCODE of the MCU.

Now I want to write to the CTRL/STAT Register. It seems that the target does not respond properly. I should receive a "OK" which is "100". It seems that the target is not able to drive the SWDIO line.

I also tried to read the CTRL/STAT Register after reading the IDCODE. Now the target answer (Acknowledge) is correct but the read value does not look correct. You can find the picture attached. It also looks like the line is not driven properly..

How can I fix this issue? I mean it looks like the target wants to drive the line to LOW but is not possible to do it.0690X000006CEDdQAO.png

Thanks,

Alex

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