Application And Optimization Of NMEA2000 Protocol Based On Autonomous And Controllable Platform

With the rapid development of information technology and artificial intelligence technology,there are more and more electronic equipment on board and more and more data are needed for ship operation,which puts forward higher requirements for data collection,processing and transmission on board.The diversity of industrial applications and requirements has given rise to a wide variety of field industrial buses such as CAN bus of IEC61158 and ISO11898,the international standards for industrial Ethernet,and the special communication protocols for PLC and DCS developed by major automation companies.At present,industrial Ethernet protocol and CAN network are widely used in ship and Marine equipment.NMEA2000 is a standardized data communication protocol developed by the national oceanic and electronic association of the United States.It is based on the architecture of CAN and uses ISO11783-3 ? ISO11783-5 ?ISO11898-1 and ISO11898-2 as the basis,defining relevant layers of the ISO open systems interconnection model.Since the NMEA2000 network is only compatible with NMEA2000 protocol compliant devices,devices not certified by the NMEA2000 Committee cannot access the network.In view of this,this paper studies the shortcomings of NMEA2000 protocol.The main contents of this paper are as follows.First of all,based on the domestic independent controllable transfer platform homemade NMEA2000 data acquisition boards,non-standard can be NMEA2000 NMEA2000 access network equipment,the equipment in accordance with the original data NMEA2000 protocol format output,realize plug and play device,the shipborne electronic equipment network system construction will play a considerable role,in terms of low cost,simplicity,convenience has great superiority.Through the research of NMEA2000 protocol,we make full use of the unused identifier of the data frame as the serial number of multi-frame transmission times text,increase the effective byte number of data field transmission and improve the transmission efficiency of NMEA2000 network.Secondly,in terms of priority,the reserved bit is applied to expand the priority bit,which expands the priority range in NMEA2000 network and reduces the arbitration caused by the same priority in the network.The static priority is changed to thedynamic priority and the dynamic priority strategy is adopted to improve the flexibility and real-time performance of NMEA2000 network.Data acquisition transfer board card based on autonomous controllable platform was used to complete the verification experiment.The NMEA2000 application was extended and optimized on RT-Thread,a domestic embedded real-time operating system.The experimental results show that the developed NMEA2000 data acquisition and transmission system can transfer non-nmea2000 equipment,improve the efficiency of network data transmission and improve the real-time and reliability of the system.