Rtos task priorities in freertos for preemptive and co. The freertos support forum can be used for active support both from amazon web services and the community. The idle task is created automatically when the rtos scheduler is started to ensure there is always at least one task that is able to run. Freertos is an open source, small footprint rtos for microcontrollers. The section on task priorities explains that lower priority numbers denote lower priority tasks and idle task has priority zero which is the lowest priority. Software timer functionality is provided by a timer service daemon task.
The freertos tutorial books provide additional detailed information on tasks and their behaviour. Basically it checks if a timer has been expired and calls the associated timer hook. In other words, the task placed into the running state is always the highest priority task that is able to run. Rtos idle task and the freertos idle task hook function. Many of the public freertos timer api functions send commands to the timer service task through a queue called the timer command queue. It is created at the lowest possible priority to ensure it does not use any cpu time if there are higher. Found answer to my question in freertos quick start guide. The freertos scheduler ensures that tasks in the ready or running state will always be given processor cpu time in preference to tasks of a lower priority that are also in the ready state. This page describes the vtaskpriorityset freertos api function which is part of the rtos task control api. The queue storage area is only accessed by the rtos with full privileges.
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