基于HART协议的二线制涡轮流量变送器的开发

以HART协议为通信标准,提出了系统的总体方案设计,通过对HART协议的理解与掌握,详细的给出了基于涡轮流量变送器的软硬件设计；硬件设计部分包括涡轮脉冲采集模块,微处理器模块,HART通信模块和4~20 mA环路电流模块4个模块,其中HART通信模块采用HART调制解调器芯片AD5700实现,4~20 mA环路电流模块采用环路供电专用芯片AD5421实现,二者共同构成了HART协议的物理层接口,文章硬件电路所采用的都是低功耗芯片,用纯硬件的方法解决了HART总线设备的低功耗难点；软件设计部分包括主监控程序、变送计算程序和HART协议通信程序3个程序模块,重点讲述了HART协议的数据链路层和应用层的实现过程；最后文章对涡轮流量变送器的二线制传输功能和HART通信功能进行了测试；测试结果表明,变送器的设计要求基本实现了。

Development of Two Wire System Turbine Flow Transmitter Based on HART Protocol

Taking HART protocol as the communication standard, the overall scheme design of the system is proposed. Through the understanding and grasp of HART protocol, the detailed hardware and software design based on turbine flow transmitter is presented. Hardware design includes the four modules of turbine pulse acquisition module, microprocessor module, HART communication module and 4~20 mA loop current module. Among them, HART communication module adopts HART modem chip AD5700, and 4~20 mA loop current module adopts loop power supply special chip AD5421. The two together constitute the physical layer interface of HART protocol, In this paper, all hardware circuits adopt low power consumption chips. A pure hardware method is used to solve the difficulty of low power consumption of HART bus equipment. Software design includes three program modules:main monitoring program, transmission calculation program and HART protocol communication program. It focuses on the implementation process of the data link layer and application layer of HART protocol. Finally, the two wire system transfer function and HART communication function of the turbine flow transmitter are tested. The test results show that the transmitter design requirements are basically achieved.