Design And Implementation Of Embedded Modbus/TCP Gateway

With the in-depth development of information technology in enterprises, it is more and more important to realize an unified and transparent interface between upper management layer of enterprise and the field control layer. But the coexisting of multiple incompatible Fieldbus has challenged the industry community for a long time. Therefore, it is no doubt that applying industry Ethernet technology to fieldwork control is becoming attractive and being considered as the trend in future.Modbus is one of the most widely used Fieldbus protocol. Modbus/TCP industrial ethernet protocol running over the TCP/IP network was issued in 1999. This paper designs and implements a Modbus/TCP protocol gateway based on embedded system, allowing users to monitor and control Modbus field device through Ethernet, which makes the inter-connection between the industrial Ethernet and the Fieldbus available.According to the industrial control application, the mainstream industrial ARM920T 32-bit embedded Micro Processing Unit is chosen as the core of hardware system. The Ethernet transmission speed of system can reach 100Mbps.Open source embedded RTOSμC/OS-II and lightweight TCP/IP protocol stack LwIP are ported to the hardware platform as software system. The total design of the system gets not only high performance cost ratio but also best portability and extensibility. At the same time, the efficient and convenient softeware developing environment is established in terms of the characters of embedded system development. Based on works above, the application layer programs which provides the Web service and the convertion of the Mobus/TCP protocol are designed. The detailed design method and work flow are described in this paper. This paper also shows how to update the configuration information of gateway in the firmware by a Web server.The test results show that the gateway works well with good stability and reliability. A practical application case of the design is also presented in the paper.This paper focuses on engineering problems rather than the theoretical research. Embedded Modbus/TCP gateway implemented in this paper provides a valuable reference to the interconnection of the industrial ethernet with the Fieldbus.