Intelligent Instruments Based On Hart Protocol Communication System Design

At present,fieldbus has already become the hot spot in process control filed, on behalf of the necessary trend in the development of process instrument. As the International Standard of fieldbus accomplished, the fieldbus product is surely accepted by the market for its consummate function and extrusive characteristics. HART,a open Protocol,now is viewed as the standard of intelligent instruments. Because HART realizes digital communication in the transmission of analog signals,it has strong competition in this interim period and grows quickly. In this paper,the design of communication module in intelligent instrument based on HART protocol is an useful attempt of HART Protocol on application of intelligent instruments.In this thesis, all the design and research are based on HART protocol, which is also the guarantee for compatibility and functions of the equipment. Under my tutor Zhao Hui's direction, author got further understanding about HART protocol. Firstly, this thesis gives some introduction on the relationship between HART protocol and OSI/ISO with seven functional layers, at same time three physical levels of HART protocol were introduced. Through author's efforts on research and experiment, this thesis gives some further introduction and discuss about how to implement HART protocol.Based on the needs of the practical environment, author proposes an idea of"modularization"and"standardization interface". For that, this design can be extensively used, and the existent products can be upgraded easily by small changes. In this thesis, hardware such as the single-chip microcomputer module, 4mA to 20mA loop-powered DAC module, and HART modem module are emphasized and described in detail. On the other hand, the structure of software is analyzed, the most important parts are the design of Data Link Layer and Application Layer. At last, the results of the debugging and function-testing of the equipment are given.The functions and compatibility of the equipment have been tested and proved with this HART protocol communication system. And the results in this thesis are obtained in long time research and development,which stand for their high targeted and practicability.