µC/OS-III is a scalable, ROMable, preemptive real-time kernel that manages an unlimited number of tasks. µC/OS-III is a third-generation kernel, offering all of the services expected from a modern real-time kernel including resource management, synchronization, inter-task communication, and more. However, µC/OS-III also offers many unique features not found in other real-time kernels, such as the ability to perform performance measurements at run time, directly signal or send messages to tasks, and pending (i.e., waiting) on such multiple kernel objects as semaphores and message queues.
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Scalable: The footprint (both code and data) can be adjusted based on the requirements of the application. Adding and removing features (i.e., services) is performed at compile time through more than 50 approximately 60 #defines (see os_cfg.h). µC/OS-III also performs a number of run-time checks on arguments passed to µC/OS-III services. Specifically, µC/OS-III verifies that the user is not passing NULL pointers, not calling task level services from ISRs, that arguments are within allowable range, and options specified are valid, etc.. These checks can be disabled (at compile time) to further reduce the code footprint and improve performance. The fact that µC/OS-III is scalable allows it to be used in a wide range of applications and projects.
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µC/OS-III does not impose any limitations on the size of each task stack, except that there be a minimum size based on the CPU used.
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Software timers: You can define any number of “one-shot” and/or “periodic” timers. Timers are countdown counters that perform a user-definable action upon counting down to 0. Each timer can have its own action and, if a timer is periodic, the timer is automatically reloaded and the action is executed every time the countdown reaches zero.Pend on multiple objects: µC/OS-III allows an application to wait (i.e., pend) on multiple events at the same time. Specifically, a task can wait on multiple semaphores and/or message queues to be posted. The waiting task wakes up as soon as one of the events occurs.
Task Signals: µC/OS-III allows an ISR or task to directly signal a task. This avoids having to create an intermediate kernel object such as a semaphore or event flag just to signal a task, and results in better performance.
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Built-in performance measurements: µC/OS-III has built-in features to measure the execution time of each task, stack usage of each task, number of times a task executes, CPU usage, ISR-to-task and task-to-task response time, peak number of entries in certain lists, interrupt disable and scheduler lock time on a per-task basis, and more.
Built-in trace points: µC/OS-III has built-in trace points throughout the code to record all the kernel events and interrupts in real-time using some of the most popular tracing analysis tools (e.g. Percepio's TraceAlyzer and SEGGER SystemView).
Can easily be optimized: µC/OS-III was designed so that it could easily be optimized based on the CPU architecture. Most data types used in µC/OS-III can be changed to make better use of the CPU’s natural word size. Also, the priority resolution algorithm can easily be written in assembly language to benefit from special instructions such as bit set and clear, as well as count-leading-zeros (CLZ), or find-first-one (FF1) instructions.
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