The RTOS scheduler decides which task to run on a recurring basis, and some tasks can interrupt and run before other tasks in a process known as “preemption.”
The solution to the challenge in the video can be found here: https://www.digikey.com/en/maker/projects/introduction-to-rtos-solution-to-part-3-task-scheduling/8fbb9e0b0eed4279a2dd698f02ce125f
CORRECTION at 2:37: A higher priority task in FreeRTOS will immediately preempt other tasks and run if it is made ready. It does not wait for the next tick to run. Thanks to @G-aurav B-hattarai for pointing this out!
In this video, we examine how the FreeRTOS scheduler makes a decision at every tick (recurring timer interval) to determine which task to run for the remainder of the tick. With a single-core processor, this time-slicing allows tasks to run in a fashion that appears to be concurrent to the user.
Tasks with higher priority are chosen to run before tasks with lower priority. However, not all tasks need to be run. Only tasks in the “ready” or are already in the “running” state can be chosen to run next. A task may put itself or another task in a “blocked” state by using one of the appropriate blocking functions, like vTaskDelay(). Tasks that are waiting for an external event, such as a free semaphore or a serial transmission, may also enter the blocked state. The expiration of a timer or received resource may move a task from the “blocked” state to the “ready” state.
Additionally, a task may put another task into the “suspended” state with the vTaskSuspend() function. This prevents the suspended task from running until another task calls the vTaskResume() function on the suspended task.
Note that tasks with equal priority are executed in a round-robin fashion.
Product Links:
https://www.digikey.com/en/products/detail/adafruit-industries-llc/3405/7244967
Related Videos:
Introduction to RTOS Part 1 - What is a Real-Time Operating System (RTOS)? - https://youtu.be/F321087yYy4
Introduction to RTOS Part 2 - Getting Started with FreeRTOS - https://youtu.be/JIr7Xm_riRs
Introduction to RTOS Part 3 - Task Scheduling - https://youtu.be/95yUbClyf3E
Introduction to RTOS Part 4 - Memory Management - https://youtu.be/Qske3yZRW5I
Introduction to RTOS Part 5 - Queue - https://youtu.be/pHJ3lxOoWeI
Introduction to RTOS Part 6 - Mutex - https://youtu.be/I55auRpbiTs
Introduction to RTOS Part 7 - https://youtu.be/5JcMtbA9QEE
Introduction to RTOS Part 8 - https://youtu.be/b1f1Iex0Tso
Introduction to RTOS Part 9 - https://youtu.be/qsflCf6ahXU
Introduction to RTOS Part 10 - https://youtu.be/hRsWi4HIENc
Introduction to RTOS Part 11 - https://youtu.be/C2xKhxROmhA
Introduction to RTOS Part 12 - https://youtu.be/LPSHUcH5aQc
Related Project Links:
Introduction to RTOS Part 3 - Task Scheduling -https://www.digikey.com/en/maker/projects/introduction-to-rtos-solution-to-part-3-task-scheduling/8fbb9e0b0eed4279a2dd698f02ce125f
Related Articles:
Getting Started with STM32 and Nucleo Part 3 - https://www.digikey.com/en/maker/videos/shawn-hymel/getting-started-with-stm32-and-nucleo-part-3-how-to-run-multiple-threads-with-cmsis-rtos-interface
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