Research On Data Acquisition System Based On Modbus Protocol

With the rapid development of electronic technology,computer technology and communication technology,digital systems have been widely used in industrial production,scientific research,national defense construction and other fields.Among them,the performance of digital system itself is closely related to the rationality and efficiency of data acquisition technology.According to the research and development needs of a bearing profile testing equipment development project in the laboratory,this paper analyzed the development status and trend of data acquisition system,clarified the research significance of data acquisition system,combined with the application status of Fieldbus technology,selected Modbus fieldbus protocol which has been widely used in the industrial field,and carried out the Modbus protocol based on it.Firstly,the protocol principle of Modbus technology is studied in depth,including transaction processing mechanism,three transmission modes,error checking methods and so on,which lays a theoretical foundation for the realization of data acquisition system based on Modbus protocol.According to the research background and different data acquisition targets,the overall scheme of the system is planned and designed.According to the requirement of the system,the main control unit based on DSP and the front-end data acquisition unit based on single chip computer are designed.The design and selection of each functional module in the unit are described separately with schematic diagram,which provides an effective platform for the implementation of the data acquisition system.Then,combining with the theory of real-time scheduling algorithm,the principles of static priority scheduling algorithm and dynamic priority scheduling algorithm are compared and analyzed.Based on the analysis of the network structure of the data acquisition system,a real-time scheduling scheme of the system based on HVF algorithm is proposed.Secondly,based on the hardware platform of the data acquisition system,the design idea of the system software is elaborated,the bus communication based on Modbus protocol is realized,and an improved digital filtering algorithm is proposed to overcome the shortcomings of common digital filtering algorithms in engineering.Finally,on the basis of the above hardware and software,a complete experimental platform of Modbus data acquisition system is built.The function,real-time performance and accuracy of the device are tested,which verifies that the device has good performance and basically achieves the expected goals.