The Research Of Embedded Real-Time Operating System

With the coming of post-PC era, embedded real-time operating system (ERTOS) plays a more and more important role in automatic control, aerospace, consumer electronics, defense and military fields. However, there are only a few domestic researches in China, which makes ERTOS fundamentally dependent on foreign countries and the core technology always enslaved to foreign countries. Therefore, on the needs of eleventh Five-Year Plan for national defense and other military projects, it is quite necessary to research and develop the independent ERTOS.Aiming at the characteristics of embedded system, this paper is based on a comprehensive research on ERTOS, makes a depth analysis and research on the operating system architecture, task management, memory management and Real-Time performance especially, to design a new ERTOS.First, by the research and analysis of various operating systems architecture and the characteristics of embedded system, this paper uses a semi-order hierarchical structure to build the kernel. From the perspective of software project, it also uses modular design and finally effectively guarantees the reliability and flexibility of the ERTOS.Secondly, through more clear and careful division of the task state, task FSM is employed to better manage the task state. Besides, semaphore, message, eventflag and other ways are also used to implement the task communication, synchronization and mutex.Third, as for the memory management, a fixed-size memory block dynamic memory management is used to first fit algorithm to search the free memory blocks.Fourth, according to the characteristics of opening embedded real-time system, basing on feed-back control, a dynamic integrated strategy scheduling algorithm is proposed. The algorithm combines the simple feedback control and the access/recover control, reachable/abortion strategy and so on, and designs a new dynamic scheduling framework. This framework can be applied to integrate a variety of characteristic parameters. Finally, the performance of algorithm has been analyzed from the three aspects of missed deadline percentage, the priority implementation ability of critical tasks, and CPU efficacious utilization. Compared with earliest deadline first and fixed priority algorithm, experiment results show that the algorithm achieves higher performance. Finally, based on the characteristics of platform, this paper designs the interrupt management with independent interrupt stack area, saving more system memory. This paper implements multi-level interruption nesting better, by switching the ARM processor working mode.This paper has designed an embedded Real-Time operating system kernel, providing a new platform for the embedded software development, with the purpose of reducing the complexity and improving maintainability, reliability, flexibility and the ability of independent innovation of embedded software design.