The Research And Development Of Embedded Interconnection Gateway Between CAN Bus And Ethernet

In the industrial control field, the coexistence of different fieldbus devices make them cannot communicate efficiently. Meanwhile, the integration of low-speed industrial fieldbus network and high-speed enterprise management network is also a difficult work, which is not conducive to monitor and manage the production process. If we use gateway connect the fieldbus network and Ethernet, then the fieldbus devices can easily access to the Internet and users can manage their operation in a long-range, which will lead to the full integration of enterprise-class management and control network.In order to solve the problem in this dissertation, firstly the domestic and foreign research status of fieldbus and Ethernet gateway are studied, the characteristics of CAN bus technology and Ethernet technology are introduced, including their network model, protocol standard and working principle. Then the feasibility of conversion of the CAN bus and Ethernet protocol is analyzed totally, and the conversion schemes of communication protocol is designed. Secondly, through a detailed analysis of the gateway system function, performance and application characteristic, the overall structure of CAN and Ethernet gateway based on μC/OS-Ⅱ and ARM is designed. And some key problems in the design of the gateway are studied, including interconnection reference model of heterogeneous network and the design thought of protocol conversion. Finally, the selection of hardware platform is proposed, and the embedded real-time operating system μC/OS-Ⅱ transplantation on LPC1768 and task design is introduced, which include CAN module drive function design, network communication module design and protocol conversion module design.At last, in order to meet the real-time request of the gateway system, aiming at the problem that EDF algorithm will have a "domino effect", causing most of the tasks miss their deadline when the system overloads, a method of optimal scheduling set selecting based on greedy policy is proposed. Using a factor which reflects the value of task and deadline to decide the priority of task, it selects important task to schedule. Theoretical performance analysis and experiments result show that the algorithm can reduce deadline missing ration and guarantee the key tasks to be scheduled firstly.