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Performance of STM32F7 USB Mass Storage (MSC) <-> DMA <-> SD

Question asked by Sy.t on Oct 25, 2016
Latest reply on Oct 26, 2016 by Sy.t
Hello everyone,

I am implementing a SD card-reader like device on my custom board with STM32F756 with SW4STM32 (AC6).

Up to this date, I have successfully completed a working link to read/write file from the PC to SD card via my custom board with 4-bit SDIO & DMA. However, my problem here is the PERFORMANCE.

The read/write speed are so low:

Read from SD card:      1.35MB/s
Write to SD card:           158KB/s

I have ruled out SD card issue as it is a Class 4 SDHC which I can read @ 22MB/s and write @4.25MB/s using a common SD card reader off the shelf.

Both my USB, SDIO clocks are set to the highest possible with the block size at 512. 

  1. Any idea where should I look into for performance improvement?
  3. Anyone has tried using it on the official development board - STM32756G-EVAL or STM32746-EVAL? and how is the performance?
Do share your experience :) Thank you