Modulator-demodulator based on single chip machine and its method of realizing HART protocol signal transmission

Abstract

The modem includes a single chip containing HART signal demodulation unit, register at I / O output port, asynchronous serial receiving module, command processor for parsing signal link in HART protocol. The method includes following steps: (1) HART sine wave signal through band-pass filter become frequency shift keying (FSK) square wave, which is input to HART signal demodulation unit from pins of single chip; (2) with being modulated by HART signal demodulation unit, '0' or '1' signals are input to register at I / O output port; (3) '0' or '1' signals through pins of single chip are input to the asynchronous serial receiving module; (4) the asynchronous serial receiving module receives demodulated HART communication frame, which is processed by the command processor and modulated by the signal demodulation unit; (5) demodulated FSK square wave is reshaped to sine wave to be output. The modem possesses features of high calculation capability, reliable operation and wide application.

Description

technical field [0001] The invention relates to data communication on the industrial control site, in particular to a single-chip microcomputer-based modem and a method for realizing HART protocol signal transmission, which is suitable for embedded systems in the Fieldbus (Fieldbus) field in industrial control. Background technique [0002] The HART communication protocol (Highway Addressable Remote Transducer) is a transitional standard proposed by Rosemount in 1986. It is an FSK (Frequency Shift Keying) digital signal with an amplitude of 0.5mA superimposed on the 4~20mA analog signal, 1200Hz represents logic "1", and 2200Hz represents logic "0", as shown in Figure 1 , its data transfer rate is 1200bps. In this way, both 4~20mA analog signal transmission and digital communication can be carried out. As an open protocol, after more than ten years of development, the HART protocol has become the de facto industry standard for smart meters. [0003] Until now, HART protoco...

AI Technical Summary

Problems solved by technology

[0006] The present invention is to solve the defect of existing HART signal modem and propose a kind of field bus embedding based on the software program of general-purpose low-power single-chip micro-controller to realize the HART signal modulation and demodulation function of special-purpose ASIC chip (or DSP) A modem based on a single-chip microcomputer and a method for realizing HART protocol signal transmission of the system, the modem has strong computing power, reliable operation, and a wide range of applications

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