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Basic FreeRTOS programs for beginners using ESP-IDF

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Real Time Operating System

  • Here in this course we are using FreeRTOS and ESP32.

  • Download ESP-IDF from following link and follow the procedure.

    For Linux/MacOS Users

    For Windows

  • What is Port of the RTOS ?

    • FreeRTOS runs on many many architectures, and can be built with many different compilers.
    • A ‘port’ is considered to be a compiler/architecture combination.
    • For example, if you are targeting a Cortex-M0 MCU using the IAR compiler, then you are using the Cortex-M0 IAR port.
  • Porting of RTOS/ EOS

    • Processor Independent
    • Processor Dependent
      • Timer => Clock Tick
      • Context Saving and Context Restoring
  • Assignment

    • Scheduler Algo => High priority Task
    • Function in FreeRTOS => Scheduling
    • Have separate files for the Task1 and Task2
    • Task1 => Resume => Task2
    • Task1 => Resume => Task2 and Task3
    • Task1 => Resume => Task2 => Resume => Task3 => Resume => Task1
    • Find out 3 real world examples of usage of Signals/ Event Notifications
    • Extend MQ demo to send additional field in the message that distinguishes the sender of the message
  • C Runtime Environment (CRT)

    • It initializes Interrupts.
    • It initializes Stack Pointer.
    • It initializes global BSS Segment to Zero to uninitialized data. NOTE: It can give Zero value or garbage value depending upon compiler. In GCC, if we write "int b" then it will intialize "b = 0" which can be seen through normal printf function.
    • It initializes Data segment.
    • It initializes main() function which is the entry function for each program.
      • For example in ESP-IDF the entry function is "app_main()" and in c programs it is main().
  • Task => Stack =>

    • CreateTask
      • Size of Stack
      • Priority
  • Stack Guard

  • Priorities affect the task execution

    • Same priority => Round Robbin
    • Highest Priority task always executes
  • Periodic Task

    • Delay by Periodicity =>
  • Task Categories

    • Periodic
    • Aperiodic
    • Sporadic
  • Specifications (Temporal)

    • Periodicity
    • Deadline
    • Execution/ Computing Time
  • RMS (Rate Monotonic Scheduling)

    • Shorter Period -> Higher Rate -> Higher Priority
    • Summation Ci/Pi <= m(2 ^ 1/m - 1)
  • Interrupt Latency

  • Interrupt Response time

  • Interrupt Recovery time

  • ISR Entry Function

  • ISR Exit Function

  • Binary Signalling Semaphore

  • Mutex

  • Message Queues

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