FreeRTOS Course - Semaphore/Mutex Management
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This document provides an introduction to FreeRTOS V6.0.5. It outlines the course objectives, which are to understand FreeRTOS services and APIs, experience different FreeRTOS features, and understand the porting process. It then describes the course structure and labs covering the FreeRTOS kernel structure, task management, queue management, semaphore/mutex management, co-routine management, advanced features, and porting FreeRTOS.
![Copyright Materials in this course is the property of Amr Ali Abdel-Naby. Reproduction or transmission of the materials outside [Customer Name] in any manner without the copyright owner permission is a law violation. [Customer Name] is free to use this material as is within its head quarters for noncommercial uses. Snapshots or trademarks used are retained to their original owners. Introduction to FreeRTOS V6.0.5 Amr Ali Abdel-Naby@2010](https://image.slidesharecdn.com/m4-introductiontofreertosv6-0-5-100725085043-phpapp02/85/FreeRTOS-Course-Semaphore-Mutex-Management-4-320.jpg)
FreeRTOS Course - Semaphore/Mutex Management
- 1. Introduction to FreeRTOS V6.0.5
- 2. About SwiftACT A Technology services startup company Under establishment Areas of specialties: Mobile telecommunication services development Embedded systems development Types of services: Consultation Managed services Sourcing Training Introduction to FreeRTOS V6.0.5 Amr Ali Abdel-Naby@2010
- 3. About Me Graduated 2004 ECE, ASU: 5 yrs distinction 6+ years in embedded systems development SDLC, Apps, MW, DD, Porting, ... 4+ years in SW engineering PSP, CMMI, Systematic reuse, ... 4+ years in SW testing IBM certified, ISTQB certified, ... Introduction to FreeRTOS V6.0.5 Amr Ali Abdel-Naby@2010
- 4. Copyright Materials in this course is the property of Amr Ali Abdel-Naby. Reproduction or transmission of the materials outside [Customer Name] in any manner without the copyright owner permission is a law violation. [Customer Name] is free to use this material as is within its head quarters for noncommercial uses. Snapshots or trademarks used are retained to their original owners. Introduction to FreeRTOS V6.0.5 Amr Ali Abdel-Naby@2010
- 5. Course Objectives After completing this course, you will: Understand what is FreeRTOS Experience different FreeRTOS services and APIs Understand the porting process of FreeRTOS Introduction to FreeRTOS V6.0.5 Amr Ali Abdel-Naby@2010
- 6. Course Notes I assume you are familiar with RTOS concepts. I assume you know C. I assume you know 80x86 architecture and assembly. Ask any time. Introduction to FreeRTOS V6.0.5 Amr Ali Abdel-Naby@2010
- 7. Course References http://www.freertos.org Introduction to FreeRTOS V6.0.5 Amr Ali Abdel-Naby@2010
- 8. Outline Introduction to FreeRTOS Lab 0: Getting Started Kernel Structure Lab 1: Kernel Structure Task Management Lab 2: Task Management Queue Management Lab 3: Queue Management Semaphore/Mutex Management Lab 4: Semaphore/Mutex Management Co-routine Management Lab 5: Co-routine Management Advanced Features Lab 6: Advanced Features Porting FreeRTOS Lab 7: Porting FreeRTOS Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 9. Outline Introduction to FreeRTOS Lab 0: Getting Started Kernel Structure Lab 1: Kernel Structure Task Management Lab 2: Task Management Queue Management Lab 3: Queue Management Semaphore/Mutex Management Lab 4: Semaphore/Mutex Management Co-routine Management Lab 5: Co-routine Management Advanced Features Lab 6: Advanced Features Porting FreeRTOS Lab 7: Porting FreeRTOS Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 10. Binary Semaphore Used for mutual exclusion and synchronization Critical Section Initial count = 1 wait_sem to enter critical section signal_sem to leave critical section Synchronization Initial count = 0 wait_sem to wait signal_sem to signal Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5 HW Device 1 ISR 1 SW Task
- 11. Counting Semaphore Used for resource limit and credit tracking Resource limit Initial count = # of equivalent resources wait_sem to gain access to a resource signal_sem to release a resource Credit tracking Initial count = 0 signal_sem to increment (Credit) wait_sem to consume (Debit) Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 12. Mutex A special type of binary semaphore Preferred over binary semaphore for mutual exclusion Mutex vs. Semaphore Mutex ownership Recursive locking Minimize priority inversion using inheritance protocol Can’t be used from ISRs Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 13. More About Semaphore/Mutex Same queues’ implementation APIs are used to implement semaphores/mutexes. Their APIs are macros that point to queues’ implementation APIs. Queues and semaphores/mutexes APIs are inter-operable. You should be careful if your are going to do this. Binary semaphore/Mutex = A queue that can hold 1 item of data size 0 Either full or empty Binary Counting semaphore = A queue that can hold n items each of data size 0 You can extend their APIs by defining new macros to the queue’s implementation APIs. Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 14. Semaphore/Mutex Management APIs They fall under 4 categories: Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5 Creation vSemaphoreCreateBinary xSemaphoreCreateCounting xSemaphoreCreateMutex xSemaphoreCreateRecursiveMutex Fully Featured xSemaphoreTake xSemaphoreTakeRecursive xSemaphoreGive xSemaphoreGiveRecursive Light Weight xSemaphoreGiveFromISR Alternative xSemaphoreAltTake xSemaphoreAltGive
- 15. Creating a Binary Semaphore, vSemaphoreCreateBinary vSemaphoreCreateBinary(xSemaphoreHandle xSemaphore) xSemaphore: Handle to the created semaphore !NULL if created NULL if failed Note the initial binary semaphore value is 1 Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 16. Creating a Counting Semaphore, xSemaphoreCreateCounting xSemaphoreHandle xSemaphoreCreateCounting(unsigned portBASE_TYPE uxMaxCount, unsigned portBASE_TYPE uxInitialCount ) uxMaxCount: The maximum count value that can be reached uxInitialCount: The count value assigned to the semaphore when it is created Return value: !NULL if created NULL if failed Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 17. Creating a Mutex, xSemaphoreCreateMutex xSemaphoreHandle xSemaphoreCreateMutex(void) Return value: !NULL if created NULL if failed Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 18. Creating a Recursive Mutex, xSemaphoreCreateRecursiveMutex xSemaphoreHandle xSemaphoreCreateRecursiveMutex(void) Return value: !NULL if created NULL if failed Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 19. Obtaining a Semaphore/Mutex, xSemaphoreTake xSemaphoreTake(xSemaphoreHandle xSemaphore, portTickType xBlockTime) xSemaphore: A handle to the semaphore/mutex to be obtained Created with vSemaphoreCreateBinary, xSemaphoreCreateMutex or xSemaphoreCreateCounting xBlockTime: The time in ticks to wait for the semaphore/mutex to become available Return value: pdTRUE if the semaphore/mutex was obtained Otherwise pdFALSE Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 20. Obtaining a Recursive Mutex, xSemaphoreTakeRecursive xSemaphoreTake(RecursivexSemaphoreHandle xSemaphore, portTickType xBlockTime) xSemaphore: A handle to the mutex to be obtained Created with xSemaphoreCreaterecursiveMutex xBlockTime: The time in ticks to wait for the mutex to become available Return value: pdTRUE if the mutex was obtained Otherwise pdFALSE Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 21. Releasing a Semaphore/Mutex, xSemaphoreGive xSemaphoreGive(xSemaphoreHandle xSemaphore) xSemaphore: A handle to the semaphore/mutex to be released Created with vSemaphoreCreateBinary, xSemaphoreCreateMutex or xSemaphoreCreateCounting Return value: pdTRUE if the semaphore/mutex was released Otherwise pdFALSE Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 22. Releasing a Recursive Mutex, xSemaphoreGiveRecursive xSemaphoreGiveRecursive(xSemaphoreHandle xMutex) xSemaphore: A handle to the mutex to be released Created with xSemaphoreCreaterecursiveMutex Return value: pdTRUE if the mutex was released Otherwise pdFALSE Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 23. Releasing a Semaphore From ISR, xSemaphoreGiveFromISR xSemaphoreGiveFromISR(xSemaphoreHandle xSemaphore, signed portBASE_TYPE * pxHigherPriorityTaskWoken) = xSemaphoreGive but used within ISRs pxTaskWoken : Is set to pdTRUE if releasing caused a higher priority task to unblock A context switch is needed after ISR exits. Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 24. Alternative Obtaining a Semaphore/Mutex, xSemaphoreAltTake xSemaphoreAltTake(xSemaphoreHandle xSemaphore, portTickType xBlockTime) = xSemaphoreTake but with alternative implementation Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 25. Alternative Releasing a Semaphore/Mutex, xSemaphoreAltGive xSemaphoreAltGive(xSemaphoreHandle xSemaphore) = xSemaphoreGive but with alternative implementation Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 26. More About Semaphore/Mutex Revisited Always remember that you can extend semaphores/mutexes with queues’ implementation APIs. There is no deletion API!!! Possible candidates that can be used are vQueueDelete and vPortFree. Before using any, you have to check: Configuration for the queue registry functions Port memory management functions Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 27. Outline Introduction to FreeRTOS Lab 0: Getting Started Kernel Structure Lab 1: Kernel Structure Task Management Lab 2: Task Management Queue Management Lab 3: Queue Management Semaphore/Mutex Management Lab 4: Semaphore/Mutex Management Co-routine Management Lab 5: Co-routine Management Advanced Features Lab 6: Advanced Features Porting FreeRTOS Lab 7: Porting FreeRTOS Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5
- 28. Lab4: Semaphore/Mutex Management Please follow the instructions in the lab handout Amr Ali Abdel-Naby@2010 Introduction to FreeRTOS V6.0.5