The Design And Implemtation Of Embedded Real-Time Operating System

The Embedded Real-Time Operating System (RTOS) is the most important basic software platform for the embedded system, which has such typical characteristics as deterministic performance, high stability, portability, scalability and configurability. The thesis presents the design and implementation of an RTOS—Skernel.After analyzing some design problems and the requirements of embedded sytem application, a scheme of Skernel has been proposed, which is better than most of RTOS kernels. In the design, Skernel is based on the micro kernel architecture, adopts preemptive priority based scheduling algorithm, supports up to 256 tasks, has complete system services, supports multiprocessor system, TRON and POSIX compatible, scalable and portable.Object-Oriented method has been introduced in the process of designing Skernel. Most modules of Skernel are viewed as a common object Event, so that it simplies the complex relations among Skernel's modules.A quasi symmetric dual NiosII core system has been built on the FPGA experiment system in order to supply a platform for Skernel running and testing. Some researches on the multiprocessor system have been done as well, including how to start up a multiprocessor system, how to do the communication among multiprocessors and mutual exclusion in the multiprocessor enrionment.In the process of developing Skernel, the bitmap algorithm has been improved and optimized to meet the requirements of application, so Skernel can support 256 tasks without loss of the performance. Aging algorithm was designed and implemented for solving the starvation problem which the most RTOSs have not solved. Priority ceiling policy is applied to solve the priority inversion problem.The minimum code size of Skernel is as few as 3.5KB, if only allowed the basic multi-tasking function, so Skernel is suitable for the memory limited application. In addition, the interrupt handling mechanism of Skemel is so simple and efficient that the interrupt handling latency is in the micro second level. In other words, Skernel has a good real-time characteristic.At last, Skernel has been ported to NiosII uniprocessor and dual-core system separately, and asymmetric task scheduling is implemented too.The goal of this thesis has been achieved.