STM32器件的USB应用固件库，里面有完整的程序，拿来即用-STM32 devices USB application firmware library, which has a complete program, brought instant

STM32官方的的USB库源码解析，中文解释-The materialabout USB full speed device interface of stm32, helpful of stm32 user

In addition, the package provides implementation of DFU for firmware updates on USB-FS-Device, and of the popular Virtual COM (CDC class) for emulation of a classic RS232 interface on USB-FS-Device