Research And Implementation Of EPA Protocol On Embedded Linux System

At present, with the rapid development of embedded technology, function of embedded processors is more and more powerful, varieties become more and more rich. Among them, ARM microprocessor has been widely used. This paper describes the on-chip resources and the main features of AT91RM9200 processor, as well as applications on DUT5000 experiment platform. As embedded devices become more complex and intelligent, embedded operating system for embedded devices has become a necessary management system. Due to its open source, security, stability and compatibility, Linux becomes one of the major operating system in embedded development.The paper provides a study on embedded Linux system, including kernel structure, the boot course, core cutting, process management, core programming technology, and configuration of embedded Linux root file system. The paper also gives out deep analysis on the core technology of Linux, including interrupt control, interrupt handling mechanism, atomic operation, time management, and driving principle of network device.EPA(Ethernet for Plant Automation) is a real-time Industrial Ethernet standard. In the EPA's communication model, the data link layer protocol is the expansion based on the data link layer protocol provided by the ISO / IEC 8802-3, which adds the EPA Communication Scheduling Management Entity, used for scheduling and managing the network packet sended by EPA equipment. EPA scheduling in the data link layer is based on the premise of time synchronization, it classifies packet priority, is a sort of combination algorithm based on time slice scheduling and packet priority scheduling.The EPA communication scheduling method is studied and EPA communications scheduling rule is designed. Through quality of service interface (ie, QoS) in the Linux kernel, using the message queue manipulation functions in scheduling rules, packet scheduling management is realized in the data link layer. For delivery problems of the EPA Configuration parameters between the kernel space and user space in Linux system, the configuration parameter structure is designed. The EPA parameters are configured in the network input and output control interface function of the Linux kernel.The paper provides a study on the application layer protocol of the EPA and the specific implementation methods, including Socket Mapping Entity, System Management Entity and Application Access Entity. According to IP address of device in EPA packet, AppID and parameter index ObjectID of function block instance, different equipments, processes and parameters are distinguished, requested, responded, set up and managed.The cutting of embedded Linux kernel, debugging and cross-compiling is operated in the desktop computer. Embedded Linux kernel testing, drivers' program testing and EPA scheduling program testing are operated on DUT5000 experimental platform.