| Embedded system has been applied to life and work of human wildly, such as household appliances, industrial control, automobile, hand-held device etc. Compare to traditional software, the function of embedded software is simple and is concentrated to special purpose. The computing ability of embedded system is always in terms of some factors, such as size and energy, therefore a proper policy for task scheduling in system is necessary. In addition, there are more and more functionality requirements for embedded system today so that an effective design before developing is vital for cutting the cost in developing and testing.In this thesis, Statecharts is used for modeling the SMILE system to describe the state transition triggered by outside event. On the other hand, traditional Rate Monotonic scheduling algorithm is modified, by delay the preemption behavior of the task with highest priority, which can avoid some unnecessary context switch action and decrease the cost for context switch. This modification has been proved to be effective by simulated experiment. In the project SMILE, which has been used in practical, the modified algorithm has been applied to it that decrease the time cost by reacting to fire disaster. The main research results include:(1) Modeling SMILE system with Statecharts, analyzing the relationship between SMILE system and the outside world and generalize the task of SMILE system;(2) Proposing a new way delaying the preemption behavior of task with highest priority to solve the too many unnecessary context switch problem in tradition Rate Monotonic algorithm. This way can decrease the time cost by context and is been proved that task with highest priority could acquire enough time for executing;(3) Verifying correctness of the model and effectiveness of the algorithm in SMILE system. |
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