USB Host library for STM32 ARM Cortex M3/4 MCU.

Function avaliable:

1. SPI SD driver for on-board Micro SD card.
2. RTC driver for on-board coil battery.
3. Shell program based on UART.
4. FatFS for SD card.

Wishing list:

1. Porting USB host library to STM32F105 chip sets.
2. Porting USB host library to STM32F4 chip sets.
3. Porting USB host library to STM32F429I-DISCO board.
4. Porting USB host library to STM32F2 chip sets.