Research And Development Of Embedded PLC Module Supports BACnet Protocol

In recent years,with China's manufacturing industry continues to upgrade and the level of automation in industrial production continues to increase,the control system will also become larger and larger,and the control system which consists of the single controller will get more and more difficult to complete the control tasks.As the kernel controller of the control system,the “PLC module” must realize Multi-machine control to face the complicated control tasks.BACnet protocol,which is a data communications protocol,can provide protocol foundation for “PLC module” interconnection.This paper studies that the “embedded PLC module” supports BACnet protocol.In the building control system,BACnet protocol is a mature and international mainstream protocol,and it is widely used.The module that developed in this paper supports programming by ladder diagram,which can be connected to any Ethernet-based BACnet system.In the industrial control system,this module provides a “PLC module” that supports the standard BACnet protocol for the control system developers,which solves the problem that there is no opening protocol to build a Multi-machine control system by “PLC module”.For the building control system,this paper develops a “PLC module” that supports the BACnet protocol,which brings the “PLC module” into BACnet system,allowing PLC engineers to participate in the development of the building control system.At present,the research for “PLC module” connecting to the BACnet system based on Ethernet is still in the blank stage.This paper starts with the research status of BACnet protocol and “PLC module”,introduces the significance and background of the topic,and then analyzes the BACnet protocol in detail,including the protocol message format,characteristics o f network,object property and characteristic of the data packet.Thenbasing on the “embedded PLC module”,the hardware system and software system of the embedded PLC module that supports BACnet protocolis developed.In the hardware system development,the chip select and hardware circuit development of the module are introduced,and focus on the component selection and circuit development of the Ethernet part,and develops the PCB board of the module.In the software system development,combined with the flowcharts and design ideas,this paper expounds the problems that have to solve in this paper and the methods to solve these problems.These methods include the mapping relationship between the BACnet object and the “PLC module”,and the module to receive,decode and respond to the BACnet protocol data packet.Finally,after completing the hardware and software development of the module,this paper creates the test sample of the module.This paper not only verifies the connection between BACnet system and the module,but also verifies the module to response the BACnet protocol data packet by two verification schemes.This paper draw a conculsion that: “PLC module” can be monitored and controlled by the upper computer.