Libnodave 库的 TCP 协议剖析-《计算机技术与发展》

文章信息/Info

作者:: 夏正龙1 ; 耿浩2; 1. 江苏师范大学电气工程及其自动化学院,江苏徐州 221116;
2. 徐州上若科技有限公司自动化事业部,江苏徐州 221116

Author(s):: XIA Zheng-long1 ; GENG Hao2; 1. School of Electrical Engineering &Automation,Jiangsu Normal University,Xuzhou 221116,China;
2. Department of Automation,Xuzhou Shang Ruo Technology Co. ,Ltd. ,Xuzhou 221116,China

摘要:: 西门子系列 PLC 凭借出色的性能在工业应用场合得到了越来越广泛的应用,而工控领域不仅仅拘泥于就地集控方式,基于工业以太网络的远方集中监控应用也越来越广泛。目前上位机系统与西门子系列 PLC 进行以太网通讯普遍采用基于微软 COM/ DCOM 技术达成的自动控制协定 OPC 协议,即工控组态软件方法,由于工控组态软件成本与工控数据点数多少相关,因此大型 PLC 自动控制系统软件成本高,性价比低。通过研究西门子 PLC 设备第三方开源驱动库 Libnodave,分别从应用的角度和库开发的角度对 Libnodave 源代码进行解析,给出了更简单清晰的数据包格式。通过 Ethernet 转 RS-485 设备连接 PLC 的驱动增强方法,详细介绍了测试代码的实现,该方法基于跨平台移植考虑,便于软件功能上的扩展。

Abstract:: S7 series PLC of Siemens is playing an increasingly important role in industrial applications owing to its remarkable performance.Except for local control mode,the remote centralized monitoring based on industrial Ethernet is also widely applied. At present,the automatic control agreement OPC based on Microsoft COM/ DCOM,namely industrial control software approach,is utilized commonly in communication between upper computer system and Siemens series PLC. Because the cost of industrial control group software is related to the number
of industrial data points,the large PLC automatic control system is in high cost and low cost performance. In this paper,we analyze the Libnodave source code from the perspective of application and library development through the research on Libnodave,a third-party open source drive library,of Siemens PLC equipment and give a simpler and clearer packet format. The implementation of test code is described in detail with a driver enhancement method of Ethernet connecting to PLC via RS-485. In consideration of cross-platform transplantation,this
method facilitates the expansion of software functions.