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Exercise: Task Notification and Deletion (05_LED_Tasks_Notification_Deletion)

Problem Statement

• Implement the task notification using direct notification APIs of FreeRTOS.

  • Create 3 tasks that toggle 3 different LEDs of the STM32F407 Discovery board. (Task-1, Task-2, Task-3)

  • Create a button task that polls for the button press for every 10 ms. (Task-4)

    If the button press did not last longer than this time period (i.e., 10 ms), it will not be recognized.

    Task-4 is of the highest priority.

  • If the button task detects button press, it should send a notification to LED toggling task.

  • When Task-3 deletes itself, it also deletes Task-4 since it is no longer needed.

   

• Use USER & WAKE-UP Button. See the schematics of the board. The action differs from board to board.

  In the case of STM32F407G-Discovery board:

  • User button NOT pressed: LOW

  • User button pressed: HIGH

• In this program, threads access to the shared variable next_task_handle. To synchronize this access, we'll use the following APIs around the critical section.

  • vTaskSuspendAll() to suspend the scheduler (i.e., preventing context switch temporarily)

    This does not disable interrupts. If an interrupt requests a context switch while the scheduler is suspended, then the request is held pending and is performed only when the scheduler is resumed.

  • xTaskResumeAll() to resume the scheduler

    Difference between the vTaskResumeAll() and xTaskResumeAll()?

Realtime Recording

References

Nayak, K. (2022). Mastering RTOS: Hands on FreeRTOS and STM32Fx with Debugging [Video file]. Retrieved from https://www.udemy.com/course/mastering-rtos-hands-on-with-freertos-arduino-and-stm32fx/