Design And Implementation Of The Multi-CPUs Control System Based On RS-485 Bus

In data communication, computer network and distributed control system in industry, serial communication is adapted to exchange information. RS-485 control network is increasingly applied widely due to its feature of high performance, simple structure and easily building.In this paper, as one of "Transverse" research projects: Intelligent Queue Manage System, the design and implementation of Multi-CPUs control system based on RS-485 is presented in detail, including the technology of serial communication, RS-485 network, TCP/IP protocol, MCU and so on.This paper analyses the running process of application, and designs controllers, such as system clock module, voice playing module, tickets printing module, RS-485 module, keyboard module, LCD/LED display module. Not only the actual PCBs are made, but also various programming methods and skills are applied in enriching the functions. And, aiming at the particular application way, the paper analyses the futures of RS-485 control network and presents the building of Multi-CPUs control network. To gain the high performance of network communication, the ISO's 7-layer Reference Model of OSI is analyzed and then divides our RS-485 net into simplified 4-layer model, according to its hierarchy theory. And based on this, soft protocols of each layer are defined. Combination the modern multimedia technology and control technology, a PC advertisement player soft is installed. It works to receive the message from RS-232 with the component of MSComm, playing the announcements, and to play ads based on DirectShow technology as well.With one year of research and development, the entire system has been finished and put into use. It woks well and satisfies customers with speedy communication and powerful performance. With the theory of hierarchy, the system is full of extendibility, and offers the convenient experience.