mahmoudisma3il18/implementation-of-edf-scheduler-on-freertos

This Project will discuss how to implement EDF Scheduler on FreeRTOS

Implementation-of-EDF-Scheduler-on-FreeRTOS

This Project will discuss how to implement EDF Scheduler on FreeRTOS

                                 For More Deatails check the attached PDF .

In this Project we will change 3 files (task.c , task.h and Freertosconfig.h)

1-First of all, the new Ready List is declared: xReadyTasksListEDF is a simple list structure. Check Line 378 in task.c

2-Then, the prvInitialiseTaskLists() method, that initialize all the task lists at the creation of the first task, is modified adding the initialization of xReadyTasksListEDF. Check Line 3855 in task.c

3-prvAddTaskToReadyList() method that adds a task to the Ready List is then modified. Check Line 221 in task.c

4-A new variable is added in the tskTaskControlBlock structure (TCB) Check Line 352 in task.c

5-A new Initialization task method is created. xTaskPeriodicCreate() is a modified version of the standard method xTaskCreate() , that receives the task period as additional input parameter and set the xTaskPeriod variable in the task TCB structure. Before adding the new task to the Ready List by calling prvAddTaskToReadyList(), thetask’s xStateListItem is initialized to the value of the next task deadline. Dont forget to define this function in task.h Check Line 866 in task.c

6-vTaskStartScheduler() method initializes the IDLE task and inserts it into the Ready List. Check Line 2182 in task.c

7- Every time the running task is suspended, or a suspended task with an higher priority than the running task awakes, a switch context occurs. vTaskSwitchContext() method is in charge to update the ∗pxCurrentTCB Check Line 3253 in task.c

8- Modify the "prvIdleTask" function idle task to keep it always the farest deadline Check Line 3651 in task.c

9-In every tick increment, calculate the new task deadline and insert it in the correct position in the EDF ready list In the "xTaskIncrementTick" function. Check Line 2998 in task.c

10-In the ""xTaskIncrementTick"" function Make sure that as soon as a new task is available in the EDF ready list, a context switching should take place. Modify preemption way as any task with sooner deadline must preempt task with larger deadline instead of priority" Check Line 3004 in task.c

11- add configUSE_EDF_SCHEDULER in freertosconfig.h