Ardupilot: Add Support for STM32H750VB With Firmware on External Flash

[davidbitton]

Feature request

Is your feature request related to a problem? Please describe.
The SP RACING H7 EXTREME, ZERO, and NANO all use the STM32H750VB chip. This would be a great "30.5mm" for Ardupilot due to the availability of at least 8 motors outputs, a stackable VTX, and several other stuff.

Describe the solution you'd like
The support for this board is in Betaflight/Cleanflight now. The MCU shares a fair amount of functionality at the H743/H753, except internal flash is only 128k. The H750 has the ability to map external flash to internal storage banks, so you can run code from it. This all resides on a QuadSPI bus. This line of boards -- and the H750 -- would be great to have access to.

Describe alternatives you've considered
The alternate solution would be to use a different flight controller.

Platform
[X] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[ ] Rover
[ ] Submarine

Additional context
Seriously Pro Racing H7 Extreme
SPRACINGH7EXTREME Clenflight Target

[ConnorChristie]

Just got the H7 Extreme board myself and would love to see something like added to ArduPilot

[haplm]

The board is super powerful, would be interesting to have this target in AP (especially for Lua scripts)

[andyp1per]

QSPI is not implemented in AP. I looked at it a little and you essentially need to write another SPI driver that uses the ChibiOS qspi APIs. After that there is a bunch of work trying to organize the chip to use that.
So in summary - it's a lot of work and I doubt it will happen any time soon.
I have some interested in working on the QSPI driver if I had a board with QSPI flash - unfortunately on the Kakute F7 Mini the extra IO pins are not connected to the flash. Developing this on a board that cannot run AP in the first place sounds like unreasonable pain and suffering.