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gh_rcl
gh_rcl
Associate II
April 30, 2026
Question

STM32H563: Unable to detect DBGMCU Mailbox ST

  • April 30, 2026
  • 2 replies
  • 170 views

Hi,

On a custom board I get the following message: Unable to detect DBGMCU Mailbox ST

when i run regression.bat.

I did several test (provisionning, regression) before and i didn't notice any issues

DA with password and TZ disabled

gh_rcl_0-1777541862602.png

A program is running on my custom board but i cannot come back to OPEN state with the regression script.

I tried with HRST wired to my STLINK with no success ...

Any ideas ?

Regards

2 replies

Jocelyn RICARD
Jocelyn RICARD
ST Employee
April 30, 2026

Hello @gh_rcl ,

So I understand the regression script was working before while you were in provisioning state.

Do you know in which state you changed the device ?

If you have set it to LOCKED then this behaviour is normal.

Best regards

Jocelyn

 

gh_rcl
gh_rclAuthor
Associate II
April 30, 2026

Thanks for your feedback.

I set the state to "CLOSED"

Do you know if i can reflash a new firmware from the internal bootloader via an UART even if the STM32H563 is CLOSED or LOCKED ? 

Regards,

 

Jocelyn RICARD
Jocelyn RICARD
ST Employee
April 30, 2026

Hello @gh_rcl ,

when device is closed you will boot to flash unconditionally.

There is a possibility to jump to bootloader from application but only when you have enabled TrustZone. But this is not recommended.

Your embedded firmware can trigger a regression by changing product_state if it is running in HDP Level 1.

Now, in your case I would double check the reset connection, checking that reset is well propagated to the chip when Debug Authentication is launched.

Best regards

Jocelyn

 

gh_rcl
gh_rclAuthor
Associate II
May 6, 2026

Hi Jocelyn,

Thanks for your feedback.

I succeeded to unbrick my board by wiring HW reset.

However when i try to flash my program by following the recipe below: (https://wiki.st.com/stm32mcu/wiki/File:SECURITY_PROVISIONING_Script_Image_Flashing.png)
it doesn't work...

When i program the same binary without "Debug authentication", it works !!!

However the program seems to run normally (led blinking task is ok) but the other tasks are not working (tftp download)

In the programming step (DA provisionning), do we need to reset the board after programming ?

Any idea ?

Regards,

 

gh_rcl
gh_rclAuthor
Associate II
May 6, 2026

Jocelyn,

I found the problem.

Indeed in my code i check the product state value, but i had forgotten to switch from OPEN to CLOSED.

Just one question : If i want to use debug authentication, i need to wired nRST to the programming connector ?

Thanks again for your support.

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