STM32H725 connectable via stlink V2 but in power down mode

[darla14]

Hello,

I have a custom hardware using STM32H725 board, sometimes(2/10) I am trying to debug the board using ST Link v2 and  It is not getting connected and showing me the error to connect if device supports debug authentication enable it.

in order to connect to it I remove the USB cable reconnected and selected the mode as power down mode with reset mode as  core reset and it was able to connect. I then erased  the whole chip and then reconnected in normal mode using software reset mode and it was able to connect.
I compared the option bytes  when it was not able to connect and also when it was able to connect in the power down core reset mode and found no difference,

Now my question is what could be the issue

-is it due to the software code which is making or is it something related to the hardware or something other than option bytes which is being changed ?

pleae let me know your suggestions to debug this further.

regards,

[CMYL]

Hi @darla14 

some suggestions:

• The firmware might be modifying the GPIO configuration responsible for SWD communication, specifically PA13 (SWDIO) and PA14 (SWCLK). If these pins are reconfigured by the firmware, it can prevent the debugger from connecting. Attempting a connection under reset can help in such cases.
• If the firmware is causing the device to enter a state that prevents debugging, such as some low power modes or OB settings, you might need to review the code for any configurations or operations that could affect the debug interface.
• On the hardware side, you can reset the option bytes to factory settings using STM32CubeProgrammer.

Best regards