Research On Key Technologies And Application Of RTU/ASCII Modbus TCP Modbus Gateway

With the rapid development of industrial control technology and the rapid development of Ethernet technology,industrial intelligent instrument and equipment began to develop in the direction of network.Industrial equipment mostly uses the fieldbus technology,but different kinds of fieldbus,no unified agreement standard,and the real-time and stability of Ethernet technology is not high,fieldbus and industrial Ethernet technology integration has become the focus of the study.An industrial Ethernet communication gateway based on Modbus RTU/ASCII and Modbus TCP protocol is designed and developed.Remote monitoring of industrial field equipment by ethernet.In this paper,firstly,the system hardware design scheme based on LPC2214+RTL8019AS+MAX3485 is proposed,the design of MCU module circuit,power drive circuit,RS-485 serial driver circuit,Ethernet interface driver circuit,oscillator circuit,reset and communication status indication circuit.Then the software design is carried out,Complete the design of three function modules: Modbus RTU/ASCII protocol stack,Modbus TCP protocol stack,Modbus RTU/ASCII and Modbus TCP Industrial Ethernet interconnection and communication.Aiming at the Overload delay problem of the binary exponential backoff algorithm which the Collision avoidance algorithm of Modbus TCP CSMA/CD,according to the conflict situation,dynamic change of backoff time,implementation of the BEB algorithm,and the OPNET network simulation An improved BEB algorithm is proposed,and the simulation of OPNET network is carried out.Finally,building Modbus TCP gateway communication test and real time testing platform,complete the test of the communication function of the three protocols,The results show that the Modbus TCP gateway works stably and reliably;In the mode of TCP Master-RTU Slaver,the whole process of communication between client and server can be grab by WireShark.By comparing the delay time of the improved CSMA/CD protocol and the original CSMA/CD protocol,The transmission delay of Modbus TCP can be greatly reduced,which is consistent with the simulation results of OPNET network,the real-time performance of TCP Modbus network is verified to be improved.