实现U盘或移动硬盘插入和退出时得到事件响应，用户可以自己处理,Realization of U disk or mobile hard disk to be inserted into and exit in response to the incident, the user can handle

基于STM32单片节介绍了USB各种包的应答方式-Based on the STM32 chip USB section describes the way the response of various package