STM32WB5MMG BLE and FUS OTA update with SBSFU example

[XaviF]

Hello there,

We are working on a project that includes a STM32WB5MMG in a custom board and we would like to update via OTA our firmware application, as well as the BLE stack and FUS. Our project is based on the P-NUCLEO-WB55.Nucleo 2 Images. This project defines two regions (slots) in the flash, one used to store the firmware to run and the other as a storage area for the new firmware image sent via OTA. The question here would be if we update either the BLE stack or FUS if they also have a separate storage area beyond the SFSA address (the start address where the current stack and FUS are stored) or if a flash region between the end of slot 2 and the SFSA address must be reserved as temporary storage for the new stack/FUS image.

Thanks in advance

[Alan PORTE]

Hello @XaviF,

I think this illustration could help you to understand how OTA is managed with SBSFU (from User Manual UM2262):



As you can see, the new wireless stack (or FUS, it is the same) will erase your user application in Flash.
So, at the beginning, the new wireless stack (which is encrypted) is not located in the secured area, but below the SFSA address (I've added "SFSA" on the illustration). Then, the FUS will detect the new image and handle the installation (the FUS modify the SFSA value during the operation).

The full description of the scenario can be found in UM2262:
https://www.st.com/resource/en/user_manual/um2262-getting-started-with-the-xcubesbsfu-stm32cube-expansion-package-stmicroelectronics.pdf#page=97

Hope this helps.

Best Regards,
Alan Porte
ST MCU Support Team