Add STM32H7R/S support

[dpoettler]

Board description (please complete the following information):

• Name: NUCLEO-H7S3L8
• Link to all relevant information:
  • https://www.st.com/resource/en/user_manual/um3276-stm32h7rx7sx-nucleo144-board-mb1737-stmicroelectronics.pdf
  • https://www.st.com/resource/en/schematic_pack/mb1737-h7s3l8-b02-schematic.pdf
  • ST, DigiKey, Mouser

Tried adding it myself but couldn't follow the guide sadly

[fpistm]

Hi @dpoettler
Before adding the board the STM32H7R/S series have to be added as it has its own STM32Cube: https://github.com/STMicroelectronics/STM32CubeH7RS
Moreover, it will require extra effort to support as it would probably required to support a bootloader in the 64k bootflash.

[razvanphp]

Hello. How can we support for adding this? Is there an official guide or can you quickly mention what is needed to be done? We can open PRs then. Thank you!

[fpistm]

Hi @razvanphp
any contribution are welcome.
As a first step STM32CubeH7RS have to be added (HAL drivers, CMSIS Device header,...), a script exists to help on this + do some manual update.
Then add the generic variant thanks also a script.
Then update some code if needed.
I'm not H7RS expert but as far as I can tell the hard thing for the H7RS is to properly manage the fact it is flashless and required to manage an external memory.

I can help on the 2 first part and provide a base PR.

[razvanphp]

I can help on the 2 first part and provide a base PR.

That would be great!

At least for the nucleo, flash and memory size is known, so we can bake that into the board info. I guess for custom one, each developer needs to configure this anyway.

[fpistm]

Yes but a driver need to be develop tu be able to use the OCTOSPI flash.

[fpistm]

Hi @razvanphp
I've made a draft PR #2912 to introduce the STM32H7RS HAL/LL and cmsis device header files.
It also add the generated files for all the generic variants.

[razvanphp]

That's great! So we still need the octoSPI driver to really test it on the nucleo board?