Is DMA able to access external FLASH in memory mapped mode?

[Javier1]

I am fiddling with a STM32WB5M discovery kit.

This kit includes a QuadSPI external NOR FLASH chip and i need to understand this in order to make early design choices.

 

Could the DMA access that external FLASH memory space?

I didnt try it yet, but my limited understanding of how DMA magic works is telling me it wont work because QSPI is in the way... am i wrong?

is there any way to include external FLASH/RAM thats accessible by DMA?

[Javier1]

@Community member​ says it ispossible

https://community.st.com/s/question/0D50X00009Xkig9SAB/dma-confusion-external-memory-access

[Javier1]

Quick read to:

AN4760 Quad-SPI (QSPI) interface on STM32 microcontrollersStill a bit foggy..... it looks like we could use DMA to access QSPI external flash memories.

Lets see how straightfoward it actually is

there is a posibility STM32WB doesnt support this

[Javier1]

whatching ST video:https://www.youtube.com/watch?app=desktop&v=4Yck17zU2u4

It could indicate we could use DMA with it ONLY READ OPERATIONS (which is fine by me)

 

This other video MOOC:https://www.youtube.com/watch?v=ElFH5JdtvYg&list=PLnMKNibPkDnEEvQWrDqVuu1w_iQ214GXi&index=11

[Pavel A.]

The fine manual usually has the bus matrix picture, it shows which DMA is connected to which memory or module. Look at that. I don't have the STM32WB, but if its HAL QSPI library has DMA API, it likely works with DMA (though not in memory mapped mode).

[Javier1]

 >>The fine manual usually has the bus matrix picture

the STM32WB5M discovery board mounts a STM32WB5MMGH6 SoM, which mounts a stm32wb55vg

 

>>but if its HAL QSPI library has DMA API, it likely works with DMA

for sure DMA running the QSPI peripheral . But i was looking for a firmware-transparent way for the DMA to access an external Flash connected trough the QSPI as if it were internal FLASH connected to the AHB.

Thats the reason why im looking for the memory mapped mode.

[S.Ma]

There are probably few generations of QSPI, first with read memory map, and later write memory map abilities for external frame buffer in ram....

[Pavel A.]

This is a block diagram. Is there another picture for the bus matrix ?

[Javier1]

Found it in the ref manual page 64

What information do you want to get from the bus matrix picture?

[Javier1]

>>There are probably few generations of QSPI

You mean the whole stm32 in general or just in the stm32wb family?

>> first with read memory map, and later write memory map abilities for external frame buffer in ram

Thats exactly what im looking for, i wouldnt mind if its external RAM instead of FLASH.

But no luck yet