STM32G474RET6: Always boot from bank1 and to jump bank2

[AlexHalf]

Hello

In STM32G474RET6 I want to have 2 banks. Bank 1 for golden (boot image) and Bank 2 for an application image.

As I want to have a robust solution I always want to boot from Bank 1 (address: 0x8000000), to check if valid firmware exist in Bank 2 (address 0x8040000) and if ok to jump to Bank 2 and to run firmware stored there.

My code based on FLASH_DualBoot example of STM32Cube_FW_G4_V1.5.0 is working ok, but it is not good enough for me as it toggle the boot between Bank 1 and Bank 2. 

Where I can't find simple example code that will simply jump to Bank 2 from Bank 1 (and still remain boot from Bank 1 after next power up)?

Thank you.

Alex

[liaifat85]

To implement a solution where you can jump from Bank 1 to Bank 2 and persistently boot from Bank 1 on subsequent power-ups, you need to carefully manage the boot configuration and set a flag or identifier that indicates the selected bank. You can try with the  STM32 HAL library.

[AlexHalf]

Why I need flag indicating selected bank? Firmware programmed in each bank are different.

If currently running firmware in Bank 1 there will be an option to jump only to Bank 2 (and back from Bank 2 to Bank 1).

What specifically to look in STM32 HAL library?

Is there any code example for a jump between banks (without toggling BFB2 bit)? 

I am not a software developer (but a hardware developer) - but still need to implement this jump in firmware.

So please elaborate any suggestions with examples.

Thank you.

Alex

[FBL · Accepted solution]

Hello @AlexHalf 

It is not possible that example code jump to Bank 2 from Bank 1 (and still remain boot from Bank 1 after next power up). This is because when BFB2 bit is set, the system memory remains aliased at @0x0000 0000 as detailed in the reference manual.

[Tesla DeLorean]

>>Is there any code example for a jump between banks (without toggling BFB2 bit)? 

It's surely just a control transfer, code and vector builds at the address you have for the second bank. Be that 0x08100000 or 0x08008000 ..

Make the linker fixup the __Vectors  or _gfnVector you write into SCB->VTOR, and use a c function pointer. None of this is magically different from any other IAP that would be viable for a single bank (or non swapping) solution.

[Tesla DeLorean]

The other alternative if you must have things built for the same address basis and perhaps swap at some point. Say one image which has a version / sequence number and you always want to run the newest valid / signed version.

Implement something like fork(), have the exact same code in the front of both banks, a loader, determine which image is the desired one, and then just change the mapping as you're executing, flow will then take you into the image you want.