Research And Implementation Of Multi - Host Mechanism Of Half - Duplex Fieldbus Based On μC / OS - Ⅱ

At present, with the continuous development of China’s industrial automation, industrial field bus is playing a more and more important role. In order to centralized management of all equipment, industrial field bus using computer management each equipment. Most of the industrial field bus using a half-duplex communication now. As a result of the half-duplex communication, at the same time there is only one node can sends a message onto the bus, so the half-duplex bus must works on master-slave mode. Each session is initiated by the bus master, slave node response to it. This mode Sacrifices real-time performance and utilization of the half-duplex bus.This paper discusses and studies on how to improve the real-time of half-duplex bus. It proposed a scheme that each node monitoring the status of the bus, using time division multiplexing mode so that all nodes on the bus can take the initiative to send a message on the bus and make multiple master node communication mechanism on the half-duplex bus comes true. According to this idea, I did an experiment on RS485bus which assuming slave node collected an abnormal data, slave need report it to the master node spontaneously. Experimental result shows that the use of time-division multiplexing methods to improve the real-time and utilization of half-duplex bus is operably. Time-division multiplexing methods can be the future direction of half-duplex bus development.Firstly, this paper describes the working mode of half-duplex communication bus. Studies the possibility of improving the real-time and utilization of half-duplex communication bus. Secondly, the paper discussed the hardware and software design of slave nodes which using ARM Cortex-M3series chips, and transplanted μC/OS-Ⅱ operating system on it to make it can sent a message on bus spontaneously. Finally, the paper analyses the results and pointed out the direction of project for further research.