USB设备互连通信协议设计

摘要

USB设备的工作方式是被动的,即只能响应主机的请求.针对这一特点,为满足USB设备相互通信的需求,提出了一种USB设备互连通信协议.该协议利用传统的USB总线拓扑结构,在USB协议的基础上增加了新的USB转发层,并通过主机轮询的方式获取通信请求,通过USB转发层转发数据包的方式处理通信.为建立USB设备之间的可靠通信链路,以USB设备高速、BULK传输的工作模式为前提,对通信协议中各层的功能进行了划分,重点设计了USB转发层的数据包格式,并对该层在主机端和设备端的工作流程进行了详细介绍.与USB OTG协议相比,该协议能自动完成USB设备间的通信,而USB OTG却需要手动设定USB设备的主从模式.仿真实验表明该协议能够可靠地实现USB设备的通信.%USB devices can only work passively by responding the request of the mainframe. A new communication protocol was presented to meet the requirements of intercommunication between USB devices. The protocol was built up based on traditional USB topology, and a new layer called USB transmittal was added, which acquires the requests of USB devices via polling, and transmits data via mainframe. To build a reliable communication link for USB devices, the function of each layer of the protocol was partitioned, and the data packet formation of USB transmittal layer was designed. In comparison, this protocol could deal with communication of USB devices automatically, while the USB OTG need to set up master/slave mode of USB devices manually. Simulation experiments showed that reliable communication between USB devices can be implemented through the protocol.