Mass Storage Class witch SD card

Hallo.

I work at implementation of USB Mass Storage Class witch SD card on STR912 and STM32 microcontrollers. I use RL-ARM USB library. In my implementation I use Keil example of Mass Storge Class but this example write data in internal RAM. It is to small memory for my application. I need use SD CARD to storage data. If anyone have example i will by grateful.

Best regards

Martin