task.h

一个开源的Modbus协议栈

 * The constant portTICK_RATE_MS can be used to calculate real time from the tick
 * rate - with the resolution of one tick period.
 *
 * @param pxPreviousWakeTime Pointer to a variable that holds the time at which the
 * task was last unblocked.  The variable must be initialised with the current time
 * prior to its first use (see the example below).  Following this the variable is
 * automatically updated within vTaskDelayUntil ().
 *
 * @param xTimeIncrement The cycle time period.  The task will be unblocked at
 * time *pxPreviousWakeTime + xTimeIncrement.  Calling vTaskDelayUntil with the
 * same xTimeIncrement parameter value will cause the task to execute with
 * a fixed interface period.
 *
 * Example usage:
   <pre>
 // Perform an action every 10 ticks.
 void vTaskFunction( void * pvParameters )
 {
 portTickType xLastWakeTime;
 const portTickType xFrequency = 10;

     // Initialise the xLastWakeTime variable with the current time.
     xLastWakeTime = xTaskGetTickCount ();
     for( ;; )
     {
         // Wait for the next cycle.
         vTaskDelayUntil( &xLastWakeTime, xFrequency );

         // Perform action here.
     }
 }
   </pre>
 * \defgroup vTaskDelayUntil vTaskDelayUntil
 * \ingroup TaskCtrl
 */
void vTaskDelayUntil( portTickType *pxPreviousWakeTime, portTickType xTimeIncrement );

/**
 * task. h
 * <pre>unsigned portBASE_TYPE uxTaskPriorityGet( xTaskHandle pxTask );</pre>
 *
 * INCLUDE_xTaskPriorityGet must be defined as 1 for this function to be available.
 * See the configuration section for more information.
 *
 * Obtain the priority of any task.
 *
 * @param pxTask Handle of the task to be queried.  Passing a NULL
 * handle results in the priority of the calling task being returned.
 *
 * @return The priority of pxTask.
 *
 * Example usage:
   <pre>
 void vAFunction( void )
 {
 xTaskHandle xHandle;
		
     // Create a task, storing the handle.
     xTaskCreate( vTaskCode, "NAME", STACK_SIZE, NULL, tskIDLE_PRIORITY, &xHandle );
		
     // ...

     // Use the handle to obtain the priority of the created task.
     // It was created with tskIDLE_PRIORITY, but may have changed
     // it itself.
     if( uxTaskPriorityGet( xHandle ) != tskIDLE_PRIORITY )
     {
         // The task has changed it's priority.
     }

     // ...

     // Is our priority higher than the created task?
     if( uxTaskPriorityGet( xHandle ) < uxTaskPriorityGet( NULL ) )
     {
         // Our priority (obtained using NULL handle) is higher.
     }
 }
   </pre>
 * \defgroup uxTaskPriorityGet uxTaskPriorityGet
 * \ingroup TaskCtrl
 */
unsigned portBASE_TYPE uxTaskPriorityGet( xTaskHandle pxTask );

/**
 * task. h
 * <pre>void vTaskPrioritySet( xTaskHandle pxTask, unsigned portBASE_TYPE uxNewPriority );</pre>
 *
 * INCLUDE_vTaskPrioritySet must be defined as 1 for this function to be available.
 * See the configuration section for more information.
 *
 * Set the priority of any task.
 *
 * A context switch will occur before the function returns if the priority
 * being set is higher than the currently executing task.
 *
 * @param pxTask Handle to the task for which the priority is being set.
 * Passing a NULL handle results in the priority of the calling task being set.
 *
 * @param uxNewPriority The priority to which the task will be set.
 *
 * Example usage:
   <pre>
 void vAFunction( void )
 {
 xTaskHandle xHandle;
		
     // Create a task, storing the handle.
     xTaskCreate( vTaskCode, "NAME", STACK_SIZE, NULL, tskIDLE_PRIORITY, &xHandle );

     // ...

     // Use the handle to raise the priority of the created task.
     vTaskPrioritySet( xHandle, tskIDLE_PRIORITY + 1 );

     // ...

     // Use a NULL handle to raise our priority to the same value.
     vTaskPrioritySet( NULL, tskIDLE_PRIORITY + 1 );
 }
   </pre>
 * \defgroup vTaskPrioritySet vTaskPrioritySet
 * \ingroup TaskCtrl
 */
void vTaskPrioritySet( xTaskHandle pxTask, unsigned portBASE_TYPE uxNewPriority );

/**
 * task. h
 * <pre>void vTaskSuspend( xTaskHandle pxTaskToSuspend );</pre>
 *
 * INCLUDE_vTaskSuspend must be defined as 1 for this function to be available.
 * See the configuration section for more information.
 *
 * Suspend any task.  When suspended a task will never get any microcontroller
 * processing time, no matter what its priority.
 *
 * Calls to vTaskSuspend are not accumulative -
 * i.e. calling vTaskSuspend () twice on the same task still only requires one
 * call to vTaskResume () to ready the suspended task.
 *
 * @param pxTaskToSuspend Handle to the task being suspended.  Passing a NULL
 * handle will cause the calling task to be suspended.
 *
 * Example usage:
   <pre>
 void vAFunction( void )
 {
 xTaskHandle xHandle;
		
     // Create a task, storing the handle.
     xTaskCreate( vTaskCode, "NAME", STACK_SIZE, NULL, tskIDLE_PRIORITY, &xHandle );
		
     // ...

     // Use the handle to suspend the created task.
     vTaskSuspend( xHandle );

     // ...
		
     // The created task will not run during this period, unless
     // another task calls vTaskResume( xHandle ).
		
     //...
		

     // Suspend ourselves.
     vTaskSuspend( NULL );

     // We cannot get here unless another task calls vTaskResume
     // with our handle as the parameter.
 }
   </pre>
 * \defgroup vTaskSuspend vTaskSuspend
 * \ingroup TaskCtrl
 */
void vTaskSuspend( xTaskHandle pxTaskToSuspend );

/**
 * task. h
 * <pre>void vTaskResume( xTaskHandle pxTaskToResume );</pre>
 *
 * INCLUDE_vTaskSuspend must be defined as 1 for this function to be available.
 * See the configuration section for more information.
 *
 * Resumes a suspended task.
 *
 * A task that has been suspended by one of more calls to vTaskSuspend ()
 * will be made available for running again by a single call to
 * vTaskResume ().
 *
 * @param pxTaskToResume Handle to the task being readied.
 *
 * Example usage:
   <pre>
 void vAFunction( void )
 {
 xTaskHandle xHandle;
		
     // Create a task, storing the handle.
     xTaskCreate( vTaskCode, "NAME", STACK_SIZE, NULL, tskIDLE_PRIORITY, &xHandle );
		
     // ...

     // Use the handle to suspend the created task.
     vTaskSuspend( xHandle );

     // ...
	
     // The created task will not run during this period, unless
     // another task calls vTaskResume( xHandle ).
		
     //...
		

     // Resume the suspended task ourselves.
     vTaskResume( xHandle );

     // The created task will once again get microcontroller processing
     // time in accordance with it priority within the system.
 }
   </pre>
 * \defgroup vTaskResume vTaskResume
 * \ingroup TaskCtrl
 */
void vTaskResume( xTaskHandle pxTaskToResume );

/**
 * task. h
 * <pre>void xTaskResumeFromISR( xTaskHandle pxTaskToResume );</pre>
 *
 * INCLUDE_xTaskResumeFromISR must be defined as 1 for this function to be 
 * available.  See the configuration section for more information.
 *
 * An implementation of vTaskResume() that can be called from within an ISR.
 *
 * A task that has been suspended by one of more calls to vTaskSuspend ()
 * will be made available for running again by a single call to
 * xTaskResumeFromISR ().
 *
 * @param pxTaskToResume Handle to the task being readied.
 *
 * \defgroup vTaskResumeFromISR vTaskResumeFromISR
 * \ingroup TaskCtrl
 */
portBASE_TYPE xTaskResumeFromISR( xTaskHandle pxTaskToResume );

/*-----------------------------------------------------------
 * SCHEDULER CONTROL
 *----------------------------------------------------------*/

/**
 * task. h
 * <pre>void vTaskStartScheduler( void );</pre>
 *
 * Starts the real time kernel tick processing.  After calling the kernel
 * has control over which tasks are executed and when.  This function
 * does not return until an executing task calls vTaskEndScheduler ().
 *
 * At least one task should be created via a call to xTaskCreate ()
 * before calling vTaskStartScheduler ().  The idle task is created
 * automatically when the first application task is created.
 *
 * See the demo application file main.c for an example of creating
 * tasks and starting the kernel.
 *
 * Example usage:
   <pre>
 void vAFunction( void )
 {
     // Create at least one task before starting the kernel.
     xTaskCreate( vTaskCode, "NAME", STACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );

     // Start the real time kernel with preemption.
     vTaskStartScheduler ();

     // Will not get here unless a task calls vTaskEndScheduler ()
 }
   </pre>
 *
 * \defgroup vTaskStartScheduler vTaskStartScheduler
 * \ingroup SchedulerControl
 */
void vTaskStartScheduler( void );

/**
 * task. h
 * <pre>void vTaskEndScheduler( void );</pre>
 *
 * Stops the real time kernel tick.  All created tasks will be automatically
 * deleted and multitasking (either preemptive or cooperative) will
 * stop.  Execution then resumes from the point where vTaskStartScheduler ()
 * was called, as if vTaskStartScheduler () had just returned.
 *
 * See the demo application file main. c in the demo/PC directory for an
 * example that uses vTaskEndScheduler ().
 *
 * vTaskEndScheduler () requires an exit function to be defined within the
 * portable layer (see vPortEndScheduler () in port. c for the PC port).  This
 * performs hardware specific operations such as stopping the kernel tick.
 *
 * vTaskEndScheduler () will cause all of the resources allocated by the
 * kernel to be freed - but will not free resources allocated by application
 * tasks.
 *
 * Example usage:
   <pre>
 void vTaskCode( void * pvParameters )
 {
     for( ;; )
     {
         // Task code goes here.

         // At some point we want to end the real time kernel processing
         // so call ...
         vTaskEndScheduler ();
     }
 }