STM32H7 issue with USB DMA

[Gabriel T]

Hi,

I am working with STM32H743ZI

When I enable USB DMA, writing enable here : 

I have 3 bytes of offset in my frames, my frame is supposed to start with aa:55:dd:aa instead of 00:00:00:aa:55:dd:aaIt is fixed when I disable DMA but I want to use it

Here is my memory usage :

Any parameter I am missing ?

Regards,

Gabriel

[Ons KOOLI]

Hi Gabriel,

Can you attach your .ioc file as well your linker file?

Best Regards,

Ons.

[Gabriel T]

I attached a zipped file with .ioc , flash.ld and ram.ld

[Ons KOOLI]

Hi Gabriel,

Can you please disable the cache when using USB DMA.

Please use a non cacheable memory region.

Best Regards,

Ons.

[Gabriel T]

Hi,

If I get it right, I should put buffers used by USB in DTCM RAM but will the USB DMA be able to access it ?

Regards,

Gabriel

[Ons KOOLI · Accepted solution]

Hi Gabriel,

No, for H7 devices DTCM could not be accessed when enabling DMA USB.

Please refer to this FAQ, it should be helpful. It is wrote for the use of DMA peripheral in STM32H7 devices, but this is applicable when using DMA for USB too.

Best Regards,

Ons.