[PIC®/AVR®/dsPIC®产品] (二)FreeRTOS任务介绍

void ATaskFunction( void *pvParameters );

void ATaskFunction( void *pvParameters )

{

/* Variables can be declared just as per a normal function. Each instance

of a task created using this function will have its own copy of the

iVariableExample variable. This would not be true if the variable was

declared static – in which case only one copy of the variable would exist

and this copy would be shared by each created instance of the task. */

int iVariableExample = 0;

 /* A task will normally be implemented as in infinite loop. */

 for( ;; )

 {

 /* The code to implement the task functionality will go here. */

 }

 /* Should the task implementation ever break out of the above loop

 then the task must be deleted before reaching the end of this function.

 The NULL parameter passed to the vTaskDelete() function indicates that

 the task to be deleted is the calling (this) task. */

 vTaskDelete( NULL );

}

/*

 * Task control block.  A task control block (TCB) is allocated for each task,

 * and stores task state information, including a pointer to the task's context

 * (the task's run time environment, including register values)

 */

typedef struct tskTaskControlBlock {

        volatile StackType_t *pxTopOfStack; /*< Points to the location of the last item placed on the tasks stack.  THIS

                                               MUST BE THE FIRST MEMBER OF THE TCB STRUCT. */



#if (portUSING_MPU_WRAPPERS == 1)

        xMPU_SETTINGS xMPUSettings; /*< The MPU settings are defined as part of the port layer.  THIS MUST BE THE SECOND

                                       MEMBER OF THE TCB STRUCT. */

#endif



        ListItem_t xStateListItem;   /*< The list that the state list item of a task is reference from denotes the state of

                                        that task (Ready, Blocked, Suspended ). */

        ListItem_t   xEventListItem; /*< Used to reference a task from an event list. */

        UBaseType_t  uxPriority;     /*< The priority of the task.  0 is the lowest priority. */

        StackType_t *pxStack;        /*< Points to the start of the stack. */

        char         pcTaskName[configMAX_TASK_NAME_LEN];

            /*< Descriptive name given to the task when created.  Facilitates debugging only. */ /*lint !e971 Unqualified

                                                                                                    char types are allowed

                                                                                                    for strings and single

                                                                                                    characters only. */



#if ((portSTACK_GROWTH > 0) || (configRECORD_STACK_HIGH_ADDRESS == 1))

        StackType_t *pxEndOfStack; /*< Points to the highest valid address for the stack. */

#endif



#if (portCRITICAL_NESTING_IN_TCB == 1)

        UBaseType_t

            uxCriticalNesting; /*< Holds the critical section nesting depth for ports that do not maintain their own count

                                  in the port layer. */

#endif



#if (configUSE_TRACE_FACILITY == 1)

        UBaseType_t uxTCBNumber;  /*< Stores a number that increments each time a TCB is created.  It allows debuggers to

                                     determine when a task has been deleted and then recreated. */

        UBaseType_t uxTaskNumber; /*< Stores a number specifically for use by third party trace code. */

#endif



#if (configUSE_MUTEXES == 1)

        UBaseType_t

                    uxBasePriority; /*< The priority last assigned to the task - used by the priority inheritance mechanism. */

        UBaseType_t uxMutexesHeld;

#endif



#if (configUSE_APPLICATION_TASK_TAG == 1)

        TaskHookFunction_t pxTaskTag;

#endif



#if (configNUM_THREAD_LOCAL_STORAGE_POINTERS > 0)

        void *pvThreadLocalStoragePointers[configNUM_THREAD_LOCAL_STORAGE_POINTERS];

#endif



#if (configGENERATE_RUN_TIME_STATS == 1)

        uint32_t ulRunTimeCounter; /*< Stores the amount of time the task has spent in the Running state. */

#endif



#if (configUSE_NEWLIB_REENTRANT == 1)

        /* Allocate a Newlib reent structure that is specific to this task.

        Note Newlib support has been included by popular demand, but is not

        used by the FreeRTOS maintainers themselves.  FreeRTOS is not

        responsible for resulting newlib operation.  User must be familiar with

        newlib and must provide system-wide implementations of the necessary

        stubs. Be warned that (at the time of writing) the current newlib design

        implements a system-wide malloc() that must be provided with locks. */

        struct _reent xNewLib_reent;

#endif



#if (configUSE_TASK_NOTIFICATIONS == 1)

        volatile uint32_t ulNotifiedValue;

        volatile uint8_t  ucNotifyState;

#endif



/* See the comments above the definition of

tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE. */

#if (tskSTATIC_AND_DYNAMIC_ALLOCATION_POSSIBLE                                                                         \

     != 0) /*lint !e731 Macro has been consolidated for readability reasons. */

        uint8_t

            ucStaticallyAllocated; /*< Set to pdTRUE if the task is a statically allocated to ensure no attempt is made to

                                      free the memory. */

#endif



#if (INCLUDE_xTaskAbortDelay == 1)

        uint8_t ucDelayAborted;

#endif



} tskTCB;



/* The old tskTCB name is maintained above then typedefed to the new TCB_t name

below to enable the use of older kernel aware debuggers. */

typedef tskTCB TCB_t;