This article will explain some Real Time Operating Systems (RTOS) basics. The material presented here is not intended as a complete coverage of different RTOS and their features. For the purposes of simplification, I will briefly cover the most important features of a representative RTOS. After we explore what constitutes an RTOS and why we might want to use one, I'll explain each of the basic components of a typical RTOS and show how these building blocks are integrated into the system. For the few code examples in this article we will use ThreadX from Express Logic.
Thread-Oriented Design.
Designing applications for an embedded application is almost always challenging, to say the least. One way to decrease the complexity of your application is to use a thread-oriented design and divide a project into more manageable pieces (or threads). Each thread is then responsible for some part of the application. With such a system you would like to be able to specify that some thread is more important than others. That is, some threads have real-time requirements. They have to respond quickly and correctly. If your system employs a professional RTOS, features that prioritize threads are already part of the package. In addition to thread prioritization, a clean and well-tested API is included that eases communicate between different threads.
So if we to use a professional RTOS we will have the tools to:.
• Ensure that time-critical parts of the code execute within their real-time constraints.
Perhaps equally importantly, the real-time behavior of the high-priority threads is not affected by the number or processing of less important, lower-priority threads.
• Make complex applications easier to develop and maintain. It's easier to develop and maintain smaller threads, than to have to deal with the entire application as a whole. In addition, changes to the processing of lower priority threads do not affect the real-time processing of higher-priority threads.
