Design And Implementation Of USB Host/Slave System Applied In Computer Numerical Control System

With the development of bus and interface technology, how to transfer data in a more reliable, faster and more convenient way in the manufacturing workshop has become one of the key research topics in numerical control manufacturing field. The USB technology, with its outstanding features such as high speed, reliability and universality has enjoyed a rapid development in the last decade. The birth of USB host/slave interface chip made it possible for USB communication when the PC is not available.Considering the actuality that economic computer numerical control (CNC) system is widespread used, but can only use tradition RS232 serial port to swap data with PC, this paper designs a USB host/slave system applied in CNC system. Accord to realizing function and design requirementbased on researching in USB host/slave interface technology deeply, CH375A is selected to act as USB host/slave interface chip and STC89C516RD+ is adopted to act as kernel processor, and they are composed of system's hardware platform. System software includes host soft which working in host mode and slave soft which working in slave mode. When working in host mode, the system can access USB memory devices with FAT file format and can communicate with CNC system by serial communication, so USB memory devices can be accessed with its host interface by economic CNC system without changing inhere structure. When working in slave mode, economic CNC connects the system with RS232 serial port, and connects the PC's USB host interface by system's USB slave interface regarded as USB device, then, the system should be configured with USB driver and PC's communication soft to realize DNC communication between PC and CNC system by USB bus. The system's acting mode, data processing mode etc. can be selected by the cascade menu shown on liquid display module, so favorable human-computer interface is supplied.Mainly composed of MCU STC89C516RD+ and USB interface chip CH375A, the USB host/slave system introduces computer's USB bus manage mechanism and transfer mechanism to numerical control manufacturing field. Economic CNC system not only could read and write USB memory devices, furthermore could compose of centrally controlled network in miniature to control distributed CNC system by USB bus. The system's MCU firmware holds worthwhile structure and can be grafted easily to intermediate and high grade CNC system. At the same time, it is the trend that USB interface supersedes RS232 interface in CNC system sooner or later. This system realizes USB communication between computer and economic CNC system by extending CNC system's RS232 port, and technology experience can be summarizes for following research in USB interface.