erabhinavtyagi / rtos

Basic FreeRTOS programs for beginners using ESP-IDF

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