一种基于协议的提高RS 485实时性的方法

A method to improve real time performance of RS485 based on customized protocol

RS 485总线因其结构简单、成本低廉、通信速率高、传输距离远等优点,在工业控制领域得到了广泛应用。因为RS 485采用半双工通信,所以RS 485通信系统一般由一个主节点、多个从节点组成,采用主节点轮询从节点、从节点受控发送数据的通信方式。这种方式造成系统的通信效率低、实时性差。目前已有的一些研究采用硬件改造和CSMA/CD的方法使系统具有多主结构,从而提高实时性,但是实现较为复杂。提出一种基于协议的提高RS 485实时性的新方法,该方法不需要修改硬件,不需要额外资源,只需要进行简单的程序修改。实验结果表明该方法能有效提高系统的实时性。

The RS 485 bus is widely used in the field of industrial control,due to its benefits of simple structure,low cost,high data rate,long transmit distance,etc.Since RS485 bus uses half-duplex mode,RS485 communication system generally consists of a master node,a number of slave nodes which are polled by the master node and controlled when they transmit data for communication.However,this mode causes low efficiency and high latency especially for real time system.In some existing research,hardware remoulding and CSMA / CD are used to make the system to have multi-master structure,so as to improve the real-time performance,but it is complex to implement.A new method to improve the real-time performance of RS485 based on customized protocol is introduced in this paper.It only requires simple program changes,but does not need the hardware re-moulding or extra resources.Experimental results show that this method can effectively improve the real time performance of the system.