task.h

freemodbus-v1-1-1-0.zip v1.1.1版本的代码 支持多个平台

/*
	FreeRTOS V3.2.4 - Copyright (C) 2003-2005 Richard Barry.

	This file is part of the FreeRTOS distribution.

	FreeRTOS is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	FreeRTOS is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with FreeRTOS; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

	A special exception to the GPL can be applied should you wish to distribute
	a combined work that includes FreeRTOS, without being obliged to provide
	the source code for any proprietary components.  See the licensing section
	of http://www.FreeRTOS.org for full details of how and when the exception
	can be applied.

	***************************************************************************
	See http://www.FreeRTOS.org for documentation, latest information, license
	and contact details.  Please ensure to read the configuration and relevant
	port sections of the online documentation.
	***************************************************************************
*/

#ifndef TASK_H
#define TASK_H

#include "portable.h"
#include "list.h"

/*-----------------------------------------------------------
 * MACROS AND DEFINITIONS
 *----------------------------------------------------------*/

#define tskKERNEL_VERSION_NUMBER "V3.2.4"

/**
 * task. h
 *
 * Type by which tasks are referenced.  For example, a call to xTaskCreate
 * returns (via a pointer parameter) an xTaskHandle variable that can then
 * be used as a parameter to vTaskDelete to delete the task.
 *
 * \page xTaskHandle xTaskHandle
 * \ingroup Tasks
 */
typedef void * xTaskHandle;

/*
 * Defines the priority used by the idle task.  This must not be modified.
 *
 * \ingroup TaskUtils
 */
#define tskIDLE_PRIORITY			( ( unsigned portBASE_TYPE ) 0 )

/**
 * task. h
 *
 * Macro for forcing a context switch.
 *
 * \page taskYIELD taskYIELD
 * \ingroup SchedulerControl
 */
#define taskYIELD()					portYIELD()

/**
 * task. h
 *
 * Macro to mark the start of a critical code region.  Preemptive context
 * switches cannot occur when in a critical region.
 *
 * NOTE: This may alter the stack (depending on the portable implementation)
 * so must be used with care!
 *
 * \page taskENTER_CRITICAL taskENTER_CRITICAL
 * \ingroup SchedulerControl
 */
#define taskENTER_CRITICAL()		portENTER_CRITICAL()

/**
 * task. h
 *
 * Macro to mark the end of a critical code region.  Preemptive context
 * switches cannot occur when in a critical region.
 *
 * NOTE: This may alter the stack (depending on the portable implementation)
 * so must be used with care!
 *
 * \page taskEXIT_CRITICAL taskEXIT_CRITICAL
 * \ingroup SchedulerControl
 */
#define taskEXIT_CRITICAL()			portEXIT_CRITICAL()

/**
 * task. h
 *
 * Macro to disable all maskable interrupts.
 *
 * \page taskDISABLE_INTERRUPTS taskDISABLE_INTERRUPTS
 * \ingroup SchedulerControl
 */
#define taskDISABLE_INTERRUPTS()	portDISABLE_INTERRUPTS()

/**
 * task. h
 *
 * Macro to enable microcontroller interrupts.
 *
 * \page taskENABLE_INTERRUPTS taskENABLE_INTERRUPTS
 * \ingroup SchedulerControl
 */
#define taskENABLE_INTERRUPTS()		portENABLE_INTERRUPTS()


/*-----------------------------------------------------------
 * TASK CREATION API
 *----------------------------------------------------------*/

/**
 * task. h
 *<pre>
 portBASE_TYPE xTaskCreate(
                              pdTASK_CODE pvTaskCode,
                              const portCHAR * const pcName,
                              unsigned portSHORT usStackDepth,
                              void *pvParameters,
                              unsigned portBASE_TYPE uxPriority,
                              xTaskHandle *pvCreatedTask
                          );</pre>
 *
 * Create a new task and add it to the list of tasks that are ready to run.
 *
 * @param pvTaskCode Pointer to the task entry function.  Tasks
 * must be implemented to never return (i.e. continuous loop).
 *
 * @param pcName A descriptive name for the task.  This is mainly used to
 * facilitate debugging.  Max length defined by tskMAX_TASK_NAME_LEN - default
 * is 16.
 *
 * @param usStackDepth The size of the task stack specified as the number of
 * variables the stack can hold - not the number of bytes.  For example, if
 * the stack is 16 bits wide and usStackDepth is defined as 100, 200 bytes
 * will be allocated for stack storage.
 *
 * @param pvParameters Pointer that will be used as the parameter for the task
 * being created.
 *
 * @param uxPriority The priority at which the task should run.
 *
 * @param pvCreatedTask Used to pass back a handle by which the created task
 * can be referenced.
 *
 * @return pdPASS if the task was successfully created and added to a ready
 * list, otherwise an error code defined in the file errors. h
 *
 * Example usage:
   <pre>
 // Task to be created.
 void vTaskCode( void * pvParameters )
 {
     for( ;; )
     {
         // Task code goes here.
     }
 }

 // Function that creates a task.
 void vOtherFunction( void )
 {
 unsigned char ucParameterToPass;
 xTaskHandle xHandle;
		
     // Create the task, storing the handle.
     xTaskCreate( vTaskCode, "NAME", STACK_SIZE, &ucParameterToPass, tskIDLE_PRIORITY, &xHandle );
		
     // Use the handle to delete the task.
     vTaskDelete( xHandle );
 }
   </pre>
 * \defgroup xTaskCreate xTaskCreate
 * \ingroup Tasks
 */
signed portBASE_TYPE xTaskCreate( pdTASK_CODE pvTaskCode, const signed portCHAR * const pcName, unsigned portSHORT usStackDepth, void *pvParameters, unsigned portBASE_TYPE uxPriority, xTaskHandle *pvCreatedTask );

/**
 * task. h
 * <pre>void vTaskDelete( xTaskHandle pxTask );</pre>
 *
 * INCLUDE_vTaskDelete must be defined as 1 for this function to be available.
 * See the configuration section for more information.
 *
 * Remove a task from the RTOS real time kernels management.  The task being
 * deleted will be removed from all ready, blocked, suspended and event lists.
 *
 * NOTE:  The idle task is responsible for freeing the kernel allocated
 * memory from tasks that have been deleted.  It is therefore important that
 * the idle task is not starved of microcontroller processing time if your
 * application makes any calls to vTaskDelete ().  Memory allocated by the
 * task code is not automatically freed, and should be freed before the task
 * is deleted.
 *
 * See the demo application file death.c for sample code that utilises
 * vTaskDelete ().
 *
 * @param pxTask The handle of the task to be deleted.  Passing NULL will
 * cause the calling task to be deleted.
 *
 * Example usage:
   <pre>
 void vOtherFunction( void )
 {
 xTaskHandle xHandle;
		
     // Create the task, storing the handle.
     xTaskCreate( vTaskCode, "NAME", STACK_SIZE, NULL, tskIDLE_PRIORITY, &xHandle );
		
     // Use the handle to delete the task.
     vTaskDelete( xHandle );
 }
   </pre>
 * \defgroup vTaskDelete vTaskDelete
 * \ingroup Tasks
 */
void vTaskDelete( xTaskHandle pxTask );


/*-----------------------------------------------------------
 * TASK CONTROL API
 *----------------------------------------------------------*/

/**
 * task. h
 * <pre>void vTaskDelay( portTickType xTicksToDelay );</pre>
 *
 * Delay a task for a given number of ticks.  The actual time that the
 * task remains blocked depends on the tick rate.  The constant
 * portTICK_RATE_MS can be used to calculate real time from the tick
 * rate - with the resolution of one tick period.
 *
 * INCLUDE_vTaskDelay must be defined as 1 for this function to be available.
 * See the configuration section for more information.
 *
 * @param xTicksToDelay The amount of time, in tick periods, that
 * the calling task should block.
 *
 * Example usage:
   <pre>
 // Wait 10 ticks before performing an action.
 // NOTE:
 // This is for demonstration only and would be better achieved
 // using vTaskDelayUntil ().
 void vTaskFunction( void * pvParameters )
 {
 portTickType xDelay, xNextTime;

     // Calc the time at which we want to perform the action
     // next.
     xNextTime = xTaskGetTickCount () + ( portTickType ) 10;

     for( ;; )
     {
         xDelay = xNextTime - xTaskGetTickCount ();
         xNextTime += ( portTickType ) 10;

         // Guard against overflow
         if( xDelay <= ( portTickType ) 10 )
         {
             vTaskDelay( xDelay );
         }

         // Perform action here.
     }
 }
   </pre>
 * \defgroup vTaskDelay vTaskDelay
 * \ingroup TaskCtrl
 */
void vTaskDelay( portTickType xTicksToDelay );

/**
 * task. h
 * <pre>void vTaskDelayUntil( portTickType *pxPreviousWakeTime, portTickType xTimeIncrement );</pre>
 *
 * INCLUDE_vTaskDelayUntil must be defined as 1 for this function to be available.
 * See the configuration section for more information.
 *
 * Delay a task until a specified time.  This function can be used by cyclical
 * tasks to ensure a constant execution frequency.
 *
 * This function differs from vTaskDelay () in one important aspect:  vTaskDelay () will
 * cause a task to block for the specified number of ticks from the time vTaskDelay () is
 * called.  It is therefore difficult to use vTaskDelay () by itself to generate a fixed
 * execution frequency as the time between a task starting to execute and that task
 * calling vTaskDelay () may not be fixed [the task may take a different path though the
 * code between calls, or may get interrupted or preempted a different number of times
 * each time it executes].
 *
 * Whereas vTaskDelay () specifies a wake time relative to the time at which the function
 * is called, vTaskDelayUntil () specifies the absolute (exact) time at which it wishes to
 * unblock.
 *
 * 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>