The Embedded Real-time Operating System μC/Os-Ⅱ And Research Of Priority Reverse Problems

Real-time embedded operation system is suitable for real-time and multi-task cases for its stability, easy for transplantation and fast response.μC/OS-Ⅱ is a real time and open source kernel which is designed for embedded application. It is famous for its real-time and stability. In real time multi-task kernel of μ/OS-Ⅱ, revervation of priority is a big problem, which is the most improtant element in real-time. So we need to reslove the problem fundamentally if we want to make sure the real-time and stability. By analysing the real-time kernel, this paper researches the reason of reservation of priority and its resolution.This paper first introduces the development of embedded real-time operation system, proposes the problem and its research value. Secondly it analyses the structure of kernel which is related to reservation of priority, including five functional module of μC/OS-Ⅱ:task management module, time management module, memory management module, task synchronization and communication module, transplantation module. Summarize their function and relations between them, realization and theory of main functions. It comes to the reason and effect of reservation of priority by analyses the kernel, it also comes to two solutions:Priority inheritance protocol and priority ceiling protocol. After analyses them, we come to the conclusion that priority inheritance protocol is not suitable while the other one is better. Thirdly it introduces the theory of protocol and improvement, finally it proposes the most reasonable protocol.By the validation of example, this paper analyse and compare the methods of using normal semaphore and improved mutually exclusive semaphore which turns out that improved mutually exclusive semaphore can get rid of the problem effectively.