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Using FatFs to access SD Card and USB Mass Storage Device

Question asked by Andrew Hazelton on Oct 18, 2017
Latest reply on Dec 8, 2017 by Andrew Hazelton

Compiler:           IAR Workbench v8.11.3

Middleware’s:   FatFs & STM32_USB_Host

Hardware:          STM32746G Discovery Board

HAL Version:      V1.8.0

Demo Projects:   C:\STM32Cube_FW_F7_V1.8.0\Projects\STM32746G-Discovery\Applications\USB_Host\MSC_Standalone  AND  C:\STM32Cube_FW_F7_V1.8.0\Projects\STM32746G-Discovery\Applications\FatFs\FatFs_uSD



I have merged together the below two STM32Cube_FW_F7_V1.8.0 Discovery Applications into the one project (attached):

1)  MSC_Standalone – USB host mass storage class demo project.

2)  FatFs_uSD – File system using micro SD card.

My goal is to use the FatFs to open both the USB memory stick and the micro SD card. Then to transfer a .txt file from the USB memory stick to the micro SD card.



All of the functions f_open(), f_read(), f_write() and f_close() will only work on the first storage device (SD or USB) that you use the FATFS_LinkDriver() and f_mount() on. How do you tell the hardware drivers disk_read() and disk_write() which storage device (SD or USB) you intend to use when you call the f_open() function?

If you have already used the FATFS_LinkDriver() and f_mount() function to link the micro SD card, do you then have to use the FATFS_UnLinkDriver() function to unlink the hardware SD drivers before you can then link the USB Host drivers?

I have already set “_VOLUMES   2” in ffconf.h



Please un-zip the attached project into the below directory: