SBSFU Custom Application - Error in Option Bytes Configuration

[EBonv]

Hello,

I am working on a SBSFU for a H753ZI board. To help me with this, I am using the example projects provided with the SBSFU package and the MOOC.

I was able to successfully download the SBSFU on the board and make the example UserApp run on it. I now want to do the same with my own app instead of UserApp.

For this, I adapted the postbuild.sh script to correctly encrypt and sign my image such that it is successfully accepted by the SBSFU when making a firmware update. I replaced the original ld file and the system_stm32h7xx.c file of my custom app with the ones of the example UserApp.

After that, I checked that my application still worked in standalone encrypted it and signed it. The image is successfully accepted by the SBSFU and executed. However, instead of behaving as expected, the LED1 on the board blinks at relatively high frequency.

The only reason I could find for this behavior is that the SBSFU is supposed to make the LED1 blink at 4Hz if there is an error in the option bytes configuration.

I am a bit puzzled as to how to solve this problem since it only happens with my custom app and not with the example UserApp. Is there another file I should look into which may modify some option bytes in the wrong way?

NOTE: I observed that the system_stm32h7xx.c file in the UserApp example application sets VECT_TAB_OFFSET to 0x00 which is weird given that the MOOC indicates that it should be given a value different than 0. May it be that this assignment causes the behavior described above?

Thank you in advance for any suggestion.

[Bubbles]

Hello @EBonv​ ,

you do not need to guess form LED, you can temporarily disable the security and use verbose debug output to get detailed report from the SBSFU. And of course you can do a similar thing with the app. Have you first tried running the App without SBSFU?

J.

[EBonv]

Thanks for your advice. It turned out the reading and writing into flash I had were not possible anymore (since part of the flash is now occupied by the SBSFU stuff). I am not sure how to solve this problem yet but I do know what I have to deal with.