Software Design Of Smart Field Communicator Based On HART Protocol

Nowadays, field bus technique became very important in the world of process control, through which digital communication is used to fields instruments, this leads to a revolution to control systems.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. Our country also began to develop control system based on fieldbus in order to break up international monopolization.In this paper, the design of the Smart Field Communicator is an useful attempt of HART protocol on application of intelligent instruments. Firstly, HART protocol is illustrated, its FSK Physical Layer specifies the transmittal manner of signal and voltage of signal. Data Link Layer specifies the device type and data transport protocols. The Command Layer specifies the HART Command Set and Response codes. The communication function of Communicator, including both hardware and software, are realized on the foundation of these criterions.In order to improve the data accuracy and enhance the equipments security, the thesis includes some data processing, observe and control modules such as Temperature compensation and PID Control. The PID parameters is transmitted to field equipments by HART data frames to make the systems work smoothly.High precision sensors, if working temperature varies between great ranges, will be affected badly. Traditional hardware compensate has the disadvantages of high cost, complex facilities, and so on; this paper introduce a improved software compensate methods. Finally, compensate results are analyzed and proved to be high efficient.The communicator software designs include HART communication, observe and control programs. The former realize HART protocol Data LinkLayer and Command Layer; the latter realize data collection, processing and controlling. The system works in interrupt manner to satisfy real-time demand. The hardware designs use TI's TMS320C5409 as the processor, which is a powerful and fast digital signal processing chip. Programs are written in assemble and C language.The application of HART protocol is very wide and the communication between Smart Field Communicator and field device is common. The purchased transduser with HART protocol equipped with the capability of communication with SFC. But the SFC is not applicable general supervise-control and does not achieve auto-control process on command of user. So the paper design the special function block. The paper is an useful attempt of HART protocol on application of intelligent instruments. The elementary test indicate that the software realize the communication, data-process and control function of signal.