XiP and FATFS on the same NOR Flash simultaneously.

[Oleksandr]

Hello guys!

In our project we use STM32H750VBT6 MCU and an external NOR-flash chip W25Q128. Tell me please can we use XiP technology and FATFS file system on this flash memory simultaneously? 

Might there be a conflict at the QSPI level or at the memory chip level?

If there can be a conflict what could you to recomend fo us? If there can be a conflict so what could you to recommend for us in this case? We need a lot of memory for the firmware and for the file system.

[Clive1 (HNL)]

Overlays are a classic technique where you break the functionality into blocks, and only load the portion you need into memory as required.

Works well where there are multiple modes of program usage that only occur independently, ie HEAT vs COOL for an HVAC system, or you have some user configuration or initialization code that only needs to be run/loaded rarely.

Some tools provide for overlays in the linker to easily facilitate implementation, and allow for common routines and functions, but it tended to be done on older constrained systems, and is less in favour these days. You can do things more manually by breaking your code into functional applications or applets, or implementing a dynamic DLL type model where you demand load things as needed.

[berendi]

So they are H753 parts that failed QA.

[Clive1 (HNL)]

>>So they are H753 parts that failed QA.

That's typically not how the economics of IC Test works usually..

More likely they just didn't invest tester time to check the array. So the tester throughput is like 14x H750 for each H753

That's not to say things that fail the full H753 test won't get binned to a lower grade, but you've invested too much time in them.

[Oleksandr]

"a lot of" - I think it is about 20 MB.

This project has a 240x240 RGB565 color display. Of course, we can move all pictures in files but, you know, it is convenient to hold them as arrays.

[S.Ma]

Takes 2 weeks to redesign a PCB and probably longer to develop the workaround to use a serial flash for 2 very different purposes.

At least, make sure that the code which perform the FATFS is in the internal flash.

20 MB means tons of pictures, text, languages, non code elements.

If the graphics code is in the MCU memory, then you can try to use DMA2D direct read from the QSPI memory.

If you use FATFS, you won't be able to use HW DMA2D directly.