Design Of Devicenet-Modbus Protocol Module

DeviceNet is a fieldbus protocol based on Controller Aera Network for its communication.Its object-oriented feature makes it easy to develop. As one of fieldbus protocol standards in our country’s automation filed, it has been used widely. Modbus is the first fieldbus protocol used in industry scene in the world. Because of its long used time and mature technology, including PLC, DCS, intelligent instrument and so on, many industrial equipments still use the Modbus. So far the Modbus is one of the most used widely protocol in the world industrial control field.For some of the more complex industry control system, there is more than one fieldbus protocol. We can adopt the method of conversion gateway to solve the communication between different fielbus protocol.This subject adopts the method of conversion gateway designing a protocol module to complete the conversion of DeviceNet and Modbus. Firstly, we have learned the DeviceNet protocol and Modbus protocol and known well the feature of the two.Then, we classify the function of the DeviceNet-Modbus protocol module. It can be divided into three main parts-the DeviceNet slave function; the Modbus link layer function and the protocol transformation function. Complete the DeviceNet slave function by using the Group2only slave method. Using the Modbus-RTU as the Modbus master send and receive data. Design a protocol mapping area as the platform to exchange the two parts of protocol data. When design the DeviceNet-Modbus protocol module, we completed the configuration software about it. For one thing, it can convenient user easily to configuration the Modbus slave’s parameter; for another thing, it makes the protocol module can be flexible transformation the frame of some Modbus slaves that have its own format.The configuration software can generate the configuration file. And DeviceNet and Modbus protocol module can download the file from the configuration software.In the end, by using build the test system, we analyzed the connecting process of the Group2only slave and promoted the learning and understanding of DeviceNet. We completed the function of the DeviceNet-Modbus protocol module by mount the Modbus slave device on it.