现代嵌入式系统中，异步串行通信接口往往作为标准外设出现在单片机和嵌入式系统中。但是随着个人计算机通用外围设备越来越少地使用串口，串口正在逐渐从个人计算机特别是便携式电脑上消失。于是嵌入式开发人员常常发现自己新买来的计算机上没有串口，或者出现调试现场用户的计算机没有串口的尴尬局面。相反，现在的个人计算机普遍拥有4个以上的USB接口，能不能使用USB接口代替串口，完成PC机和嵌入式系统的通信呢？-Modern embedded systems, asynchronous serial communication interface is often used as a standard in the single-chip peripherals and embedded systems. However, with the personal computer peripheral equipment less and less common use of serial port, serial port is gradually from personal computers, especially laptop computers disappeared. Thus embedded developers often find that they bought a new computer without serial port, or a site user s computer debugging serial no embarrassing situation. In contrast, the current personal computers generally have a 4 or above USB interface, USB interface can be used in place of serial complete PC and embedded systems of communication do?