Research Of Packet Analysis And Network Monitoring Based On DeviceNet Fieldbus

DeviceNet protocol is designed specially for automation in factories. It is a CAN-based open fieldbus standard. It has a network structure of a main line and branch lines. It provides a serial communication among industrial devices which has reduced complicated and expensive connection lines dramatically. It provides diagnosis in device level. DeviceNet is a low cost and high performance communication network in coincidence with global industrial standard. More and more devices choose DeviceNet as communication method.Now DeviceNet modules which are widely used in industrial field in China are products which are produced by famous foreign companies such as frequency converter of PowerFlex700se and monitoring terminal of PanelView of Rockwell. Software which we use in DeviceNet is special configuration software such as Rslinx and RsNetWorx for DeviceNet. Usually we can not get the details of DeviceNet. We are lack of research on the data packets, structure of network, realization of protocol stack and production of host devices and slave devices of DeviceNet. We have no critical technology and can only rely on modules of large foreign companies to establish an DeviceNet system.The paper focuses on the research of inner structure of DeviceNet. It includes analysis of DeviceNet devices, analysis of DeviceNet connections, analysis of format and meanings of data packets, analysis of process of communication and services, design of monitoring terminal, realization of protocol stack and design of self-designed devices.The method of research on DeviceNet which we use is as followings. First, we establish DeviceNet network with CompactLogix, Button and Sensor of Light and Electricity. We analyze the communication process of the network and the packets transmitting, data proposing and network resources distribution in every procedure. Second we establish a monitoring terminal and connect it to the current network of DeviceNet. We can capture all the packets transmitting on the network and analyze the meaings. Through analysis of large amounts of packets we can get the current state of the network and the state of every device in the network. At last on the basis of network analysis, we can establish the protocol stack which can realize the inner structure of DeviceNet. The protocol stack can be divided to three parts, hardware layer, protocol layer and application layer. We can design self-defined devices of DeviceNet based on the protocol stack through definition on the attribute data and service functions of every class.Through the research above, we can understand the details of DeviceNet protocol. We can monitor and control the devices on the network and design our own products of DeviceNet. It has great significance on network maintenance and management, improvement of competitiveness of products, establishment of independent intellectual property rights, breaking the monopoly of technology and designing a more advanced and more efficient communication protocol.