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Associate
November 5, 2025
Solved

SBSFU_Boot on STM32U5A9

  • November 5, 2025
  • 3 replies
  • 308 views

Hi, 

I am working with the SBSFU_Boot on the STM32U5A9 chip. After the SBSFU_Loader has written the update image into internal memory, a reset happens in order for the SBSFU_Boot to write the image to be booted. When performing the update, it ends up in a process where it has to do some encryption. The SAES engine is initialized successfully, and then AES_Encrypt is called. This keeps on failing because a read error is reported in the SAES->SR reports a read error upon enabling the SAES peripheral. 

It should be noted that the initialization and encryption sequence is strictly followed per instructions in RM0456 Rev 6 sections 50.4.4 (Initialization of SAES) and 50.4.8 (ECB/CBC encryption sequence) respectively. 

What am I missing?

Best answer by Mourice

Hi Jocelyn, 

It turns out that the SAES wasn't configured correctly. After this was sorted out, it worked. 

Best regards,

Mourice. 

3 replies

Jocelyn RICARD
ST Employee
November 11, 2025

Hello @Mourice ,

From your description it is not clear if you have made adaptations or not.

Could you please provide more details?

Best regards

Jocelyn

 

MouriceAuthor
Associate
November 12, 2025

Hi Jocelyn, 

I have not made any adaptations. 

Best regards,

Mourice. 

Jocelyn RICARD
ST Employee
November 13, 2025

Hello @Mourice ,

OK thank you. I will try to reproduce the issue.

Best regards

Jocelyn

MouriceAuthor
Associate
November 17, 2025

Hi @Jocelyn RICARD ,

I am looking forward to your findings. 

Best regards,

Mourice. 

Jocelyn RICARD
ST Employee
November 28, 2025

Hello @Mourice,

I couldn't reproduce your issue.

I used latest STM32Cube_FW_U5_V1.8.0 as base and followed readme to adapt B-U585I-IOT02A to STM32U5A9J-DK.

It is booting properly and update is working as expected.

I join the adaptation I made so that you can check on your side.

Best regards

Jocelyn

 

 

MouriceAuthor
Associate
December 4, 2025

Hi Jocelyn,
I will try out your adaptation and give you feedback. 

Best regards,

Mourice. 

MouriceAuthorBest answer
Associate
April 23, 2026

Hi Jocelyn, 

It turns out that the SAES wasn't configured correctly. After this was sorted out, it worked. 

Best regards,

Mourice.