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USB设备端固件程序,枚举部分是全部程序的基础和重心,只有主机对设备枚举成功后,主机才能和设备进行正常的通信
USB的枚举过程分为4个状态.
1.接入态
v主机检测到USB设备插上,击活端口,并发送复位命令(保持10ms)
2.默认态
v主机使用默认地址读取设备描述符 (GET_DESCRIPTOR)
v主机分配给设备一个总在线的唯一地址 (SET_ADDRESS)
3.地址态
v主机从新的地址获取设备描述符(GET_DESCRIPTOR)
v主机获取所有设备的配置描述符(GET_DESCRIPTOR)
4.配置态
v主机设置描述符(设备,配置) (SET_CONFIGURATION)
v主机读取配置状态(可选) (GET_CONFIGURATION)
v主机读取接口状态(可选) (GET_INTERFACE)
-USB device-side firmware, enumerate all part of the foundation and focus of the procedure, only the host of equipment after the successful enumeration, the host and equipment in order to engage in normal communication USB enumeration process is divided into four status. 1. Access state v host detected USB devices plug in, hit live ports, and send the reset command (to maintain 10ms) 2. default state v Use the default address of the host to read device descriptor (GET_DESCRIPTOR) v host assigned to the equipment of a total online only Address (SET_ADDRESS) 3. A
