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USB HS DMA to external SRAM

Question asked by Piers Hawksley on Jun 7, 2018
Latest reply on Jun 8, 2018 by Clive Two.Zero

I'm using an STM32F723 with a customised USB driver to capture Isochronous data.


I can capture the data in 4KiB chunks. The data is DMA'd into internal SRAM then modified and copied to internal SRAM then DMA'd to an SD card. This works but I want to use larger buffers to improve SD write speeds.


I have 1MB of external SRAM that I have read / write access to. I have tested this access and used it to write dummy data to an SD card at a much higher data rate.


I am trying to DMA from the USB HS to external SRAM so I can use larger buffers - Are changes to DMA configuration needed in order to DMA to external SRAM or is there a limitation in where the USB DMA engine can DMA data to?


I've tried in 4KiB and 32Kib chunks but appear to be loosing data with the FMC write fifo disabled. With it enabled I do not get data DMA'd to external SRAM at all.


Many Thanks,