Research And Hardware Implementation Of Task Scheduling Algorithm Based On Real Time Operating System

The embedded real-time operating system is developed on on the applicationof embedded systems; its advantage is that the requirement of response time isadded to the original system. The reason is that when the external event or datagenerating, not only required to generate a corresponding control signal or correctresults, but also requires be done within a specified timeline.Currently, the processor has become very complex and often integrated twoor more processing cores. But still can not meet the increasingly needs of task.The real-time operating system based on hardware can effectively improve theefficiency of the processor. while, it is a huge project that to design an operatingsystem which can run multiple different types of software or tasks simultaneously,because it not only require the collaboration of so many highly specializedsoftware development teams, but also take a lot of resources and time. Thus, it isan advisable choice to modify an existing operating system and expand its rangeof applications; in order to make it can meet the specific needs. In this paper,μC/OS-II is used as the research object. Aiming at the problem that μC/OS-IIdoes not support round-robin scheduling of the same priority task, a two-levelhybrid task scheduling strategy was proposed and have achieved some of itshardware logic by the FPGA.Firstly, based on the analysis of the classical real-time scheduling algorithmand μC/OS-II task scheduling mechanism, a two-level hybrid task schedulingstrategy was proposed. In the first level, by putting the task priority as criterionfor task scheduling, a preemptive scheduling of different priority task wasimplemented. And in the second level, adopting time slice circular schedulingstrategy, round-robin scheduling of same priority task was implemented. Secondly, to realise the two-level scheduling, two important data structuresof μC/OS-II, TCB and ECB, are expansed, and the task group managementmodule is added, then waiting list of tasks, ready list of tasks and list of taskgroup be designed by on-chip registers of FPGA. Design and implement thehardware logic for the task management module. And to implement time slicecircular scheduling, hardware circuit for finding successor of task was designed.Then in order to meet the improved algorithm, the event management modulewas designed and implemented by hardware logic. In this paper, the software isISE10.1and the hardware is XUP Viterx PRO-II. The system adopted VHDL, andthe simulation results show that the hardware implementation of the system iswell-worked.