嵌入式控制结点群上的一种通信方案设计

发布时间：2018-07-17 16:29

【摘要】：为解决现行RS485组网方式限制了通信节点数及网络扩展的问题,基于RS485总线提出了一种嵌入式控制结点群的组网方式及控制协议。通过在主控器与叶子节点间加入中继器,将485总线支持的节点数扩展到2.7万个,建立一对多控制的嵌入式结点集群。针对该网络特点,对Modbus协议进行扩展,增加了中继层规约。与传统单纯增加物理地址长度的方式不同,新扩展协议采用局部寻址方式,打破了Modbus地址长度对子节点数的限制,并引入节点扫描和差错反馈机制,从而实现了主控器对各网络节点的可靠控制;同时,控制协议保持了原Modbus协议的简单性,还具有易移植、可扩展的特点,便于在单片机上实现。在采用扩展协议时,一层中继器的引入导致周转延迟增加10.36%,而两层中继器则将延迟率增加了69.9%,并使总延迟较原始Modbus系统增加2.4倍左右,但实际中采用的两层中继系统将平均延迟控制在了70 ms以下。结果表明,该方案在牺牲一定系统实时性能的前提下,实现了嵌入式节点的集群化管理。
[Abstract]:In order to solve the problem that RS485 network mode limits the number of communication nodes and network expansion, an embedded control node group networking mode and control protocol are proposed based on RS485 bus. By adding repeater between master controller and leaf node, the number of nodes supported by 485 bus is expanded to 27000, and a one-to-many embedded node cluster is established. According to the characteristics of the network, the Modbus protocol is extended and the relay layer protocol is added. Different from the traditional way of simply increasing the length of physical address, the new extension protocol adopts local addressing method, which breaks the limit of Modbus address length on the number of sub-nodes, and introduces the mechanism of node scanning and error feedback. The control protocol keeps the simplicity of the original Modbus protocol and is easy to transplant and expandable, which is easy to realize on the single chip microcomputer. When the extended protocol is adopted, the introduction of the first layer repeater increases the turnover delay by 10.36, while the two layers increase the delay rate by 69.9 times and increase the total delay by about 2.4 times compared with the original Modbus system. However, the average delay of the two-layer relay system is controlled below 70 Ms in practice. The results show that the scheme realizes the cluster management of embedded nodes at the expense of real-time performance.
【作者单位】：天津大学计算机科学与技术学院;
【基金】：国家科技支撑计划项目(2012BAJ24B04-4)
【分类号】：TP336

【参考文献】