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Low performance USB MSC

Question asked by Zixun LI on Sep 11, 2017

Hi, with a LPC54600 Xpresso board, I met a problem that the read performance of USB MSC example is very low.

My configuration:

SDK2.20

IAR 8.11.2, compiled in high speed

SD Card : Sandisk 16G Class 10

Project : usb_examples\usb_device_msc_sdcard

#define USB_DEVICE_CONFIG_LPCIP3511HS (1U)

At first I got only 1.2MB/s read and 350KB/s write, so I changed the MSC packet size:

#define USB_DEVICE_MSC_WRITE_BUFF_SIZE (16384U)
#define USB_DEVICE_MSC_READ_BUFF_SIZE (16384U)

Now the write speed is increased to 3.5MB/s, but the read speed is decreased to 800KB/s !

On STM32F746 this SD card has a read speed of 7MB/s with their awful SDIO implementation.

Has anyone met this problem ?

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