?? task.h
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/*
FreeRTOS.org V4.1.1 - Copyright (C) 2003-2006 Richard Barry.
This file is part of the FreeRTOS.org distribution.
FreeRTOS.org 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.org 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.org; 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.org, 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 "V4.1.1"
/**
* 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;
/*
* Used internally only.
*/
typedef struct xTIME_OUT
{
portBASE_TYPE xOverflowCount;
portTickType xTimeOnEntering;
} xTimeOutType;
/*
* 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.
*
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