Research Of Hart Multiplexer And Its Software Design

The rapid development of information technology brings about great changes in the field of industrial control and a complete distribution network of fieldbus system is gradually formed on the foundation of smart instrumentation and fieldbus technology. New generation control system can give the end user more convenience and benefits, which will gradually replace the traditional DCS control system in the mainstream in the future. As the science and technology progressing continuously, field bus technology is developing so fast that it became a hot spot in the field of process control. Especially the HART protocol has been more and more widely used for its unique advantages and characteristics. HART multiplexer is used to bring the HART function of the field device on-line configuration and diagnostics, also available through PC or management system continuously record the process parameters and state. So there is practical significance to the research and development of the HART multiplexer.We use HART protocol as main communication protocol in design of the HART multiplexer in this dissertation. In order to enhance the anti-interference and make hardware much more hierarchical we divide hardware into analog card and digital card. In consideration of complexity and instantaneity of system software is based on real time operating system μC/OS-Ⅱ. Interface with host is designed using RS485which has a good anti-interference ability. The HART multiplexer designed can deal with both superimposed on the DC signal of the AC signal and (4-20)mA signal compared with previous version, which further improves its compatibility.