PROFINET IO设备中DCP协议的研究与应用

Research and Application of DCP in PROFINET IO Device

摘要:

为解决自动化外围现场设备接入PROFINET网络，而同类设备依赖特定芯片，成本较高，可移植性差的问题，利用软件设计实现普通网卡下的PROFINET IO通信；在树莓派3B+开发板上实现IO设备，支持非同步实时数据交换，可以通过槽/子槽数据模型匹配IO模块；通过描述性文件的设计，使其IO模块类型映射模块、子模块的ID，实现模块化IO设备，允许根据需要添加和删除模块；系统启动时控制器根据设备名称寻址，再基于设备名称为IO设备分配IP地址，这一过程的实现依赖DCP协议，它是PROFINET网络中数据交互的基础；为了深入探究PROFINET协议栈，在实现PROFINET的基础上从DCP协议的原理入手，对其功能和程序实现进行了详细研究，并将所实现的IO设备与PLC S7-1200进行组态，验证了IO设备所实现的功能和DCP工作的过程；实验测试表明，树莓派实现了PROFINET RT和NRT通信功能，其更新时间抖动小于50μs，满足控制工程上的应用要求。

Abstract:

In order to solve the problem that automatic peripheral field devices access PROFINET network, while similar devices rely on specific chips, with high cost and poor portability,the PROFINET IO communication under the common network card is realized by software design. The IO device is implemented on the Raspberry Pi 3B+ development board, which supports asynchronous real-time data exchange. The IO module can be matched through the slot/ sub-slot data model. Through the design of the descriptive file, the IO module type is mapped to the ID of the module and sub-module to realize the modular IO device, and modules can be added and deleted as required; When the system is started, the controller addresses the IO devices according to the device name, and then assigns IP addresses to the IO devices based on the device name. The implementation of this process depends on DCP protocol, which is the basis of data interaction in PROFINET network. In order to deeply explore the PROFINET protocol stack, based on the implementation of PROFINET, starting with the principle of DCP protocol, the function and program implementation are studied in detail, and the implemented IO device is configured with PLC S7-1200 to verify the function of IO device and the working process of DCP. Experimental tests show that the Raspberry Pi realizes the communication functions of PROFINET RT and NRT, and its update time jitter is less than 50μs. Meet the application requirements of control engineering.