STM32F427 "Rev 1" running FMUV3 Rover 4.1.0-beta3?

In one of my rover I found a very old “AUAV X2” board.
It has CPU STM32F427 Rev 1, which is supposed to have the 1MB flash bug.

This board was running rover 4.0.0 build for FMUV3 target.
To my surprise I could upload rover 4.1.0-beta3 for FMUV3 target without problem, which I think is already larger than 1MB.
And it seems to work!

Can anyone remember what the effect of the 1MB bug is?

I also uploaded copter 4.1.0-beta3, which is definitively larger than 1MB. Upload worked also, but not tested.

The board seems to have an old PX4 rev 4 bootloader. QGC reports 2MB of Flash
This is from MP:


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Hi @RainFly,

Thanks for confirming this older board still works.

I think that, “fwmax 2080768” from MP means that this particular board does not suffer from the 1MB limit. I think the issue was that USB communication was not reliable on the problem boards and so you could not upload a firmware that was more than 1MB. Or perhaps it could be uploaded but it would not run.

As a reference (you probably already know but in case others are reading this) we build a cut-down version of AP with a smaller number of features so that it can fit on 1MB boards. This includes the older STM32 boards with the 1MB flash issue but also the newer drone racing style boards that just come with a smaller flash.

OK, thank you.
Then I’m lucky with this board, even it has the “rev 1” CPU on board.
I didn’t see any problems with USB so far and it is working as it should, including DShot, WP-navigation, TF-Mini Lidar, Lua and Neopixel.

I know there is a cut-down version.
But I want to run Lua scripts, which is not available with the cut-down version.

I found another AUAV-X2 with “Rev 1” CPU in my Benchy-Boat.
Same PX4 Rev 4 bootloader.
This one was running FMUV2 (1M) build of rover 4.0.0.

Also this board was accepting the FMUV3 rover 4.1.0-beta3 without problem and also seems to work. I manually uploaded the FMUV3 APJ-file in MP with “Load custom firmware”

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