Task Scheduler

A simple cooperative task scheduler with prioritized tasks. More...

Collaboration diagram for Task Scheduler:

Modules
	Task Profiler
	A utility module that measures execution times of tasks.
	Status Codes
	Status Codes Definitions for the Task Scheduler.

Macros
#define	SCHEDULER_MAX_TASKS   8U
	Maximum Number of tasks.

Typedefs
typedef uint8_t	task_prio_t
	Definition of the task priority (and unique task ID).
typedef void *	task_event_t
	Task event type definition.
typedef void(*	task_function_t) (task_event_t e)
	Task functions definition.

Functions
scheduler_t *	Scheduler_Init (void)
	Initializes the task scheduler.
void	Scheduler_Run (scheduler_t *const me)
	Runs the task scheduler.
void	Scheduler_SwitchContext (scheduler_t *const me)
	Suspends the current task and runs another task.
status_t	Scheduler_AddTask (scheduler_t *const me, task_function_t task, task_prio_t priority, task_event_t eventQ, size_t eventQSize, const char *name)
	Adds an new task to the scheduler.
status_t	Scheduler_PostEvent (scheduler_t *const me, task_prio_t priority, task_event_t event)
	Posts an event to the scheduler and executes it as soon as possible.
bool	Scheduler_IsTaskPending (scheduler_t *const me, task_prio_t priority)
	Checks whether a specified task is pending for execution.

Detailed Description

A simple cooperative task scheduler with prioritized tasks.

---

A simple cooperative task scheduler with prioritized tasks.

Macro Definition Documentation

SCHEDULER_MAX_TASKS

#define SCHEDULER_MAX_TASKS   8U

Maximum Number of tasks.

---

Warning

Maximum number is 32 due to internal data structures of size uint32. If larger number of tasks are desired, the internal data structures need to be adjusted.

Typedef Documentation

task_event_t

typedef void* task_event_t

Task event type definition.

---

task_function_t

typedef void(* task_function_t) (task_event_t e)

Task functions definition.

---

Parameters

e	Task event pointer. An abstract pointer to an task intern data structure.

task_prio_t

typedef uint8_t task_prio_t

Definition of the task priority (and unique task ID).

---

Higher values mean higher urgency. Priority 0 can be used for IDLE task.

Function Documentation

Scheduler_AddTask()

status_t Scheduler_AddTask	(	scheduler_t *const	me,
		task_function_t	task,
		task_prio_t	priority,
		task_event_t	eventQ,
		size_t	eventQSize,
		const char *	name
	)

Adds an new task to the scheduler.

---

Parameters

me	The instance handle of the task scheduler.
task	A pointer to the task function to be executed.
priority	The priority level for the task. Every priority level can only have one task!
eventQ	A pointer to the task event queue.
eventQSize	The size of the task event queue.
name	A descriptive name of the task.

Returns

Returns the status (STATUS_OK on success).

Scheduler_Init()

scheduler_t * Scheduler_Init

(

void

)

Initializes the task scheduler.

---

Resets internal data structures to a known state.

Returns

Returns the abstract pointer to the scheduler handle object.

Scheduler_IsTaskPending()

bool Scheduler_IsTaskPending	(	scheduler_t *const	me,
		task_prio_t	priority
	)

Checks whether a specified task is pending for execution.

---

Parameters

me	The instance handle of the task scheduler.
priority	The priority of the task to be checked.

Returns

Returns true if the task is pending, false otherwise.

Scheduler_PostEvent()

status_t Scheduler_PostEvent	(	scheduler_t *const	me,
		task_prio_t	priority,
		task_event_t	event
	)

Posts an event to the scheduler and executes it as soon as possible.

---

Parameters

me	The instance handle of the task scheduler.
priority	The priority of the task to be executed.
event	A void* pointer to and task event parameter.

Returns

Returns the status (STATUS_OK on success).

Scheduler_Run()

void Scheduler_Run

(

scheduler_t *const

me

)

Runs the task scheduler.

---

This is the main routine for the scheduler module. It schedules all the pending tasks in order of priority in an endless loop. If an error occurs within an task, the error is logged, but not handled!

Parameters

me	The instance handle of the task scheduler.

Scheduler_SwitchContext()

void Scheduler_SwitchContext

(

scheduler_t *const

me

)

Suspends the current task and runs another task.

---

The function can be called from within a task in order to suspend the current task and run other task (to completion). The function return when the other task is finished. The function runs exactly one other task, even if more are pending. The function can be called another time to run another task. If no tasks are pending, the function does nothing.

Note

This function never returns!

Parameters

me	The instance handle of the task scheduler.