基于stm32的sd-usb读卡器。神舟一号开发板板载了sd卡座，而开发板上有usb接口，这样我们可以实现一个usb读卡器。-Based stm32 sd-usb card reader. Onboard Shenzhou development board sd card connector, and the development board usb interface, so that we can achieve a usb card reader.