Latest News Items: FAT file system released - Tick suppression demo'ed SAM4L MCU & RX100 MCUs - embTCP released for PIC32
FreeRTOS royalty free RTOS RSS feed  Real time embedded FreeRTOS mailing list  
Quick Start Supported MCUs Books & Kits Ecosystem Training Contact & Support



Last site update May 1 2013

vTaskSetApplicationTaskTag
[Task Control]

task. h 

void vTaskSetApplicationTaskTag( 
                        xTaskHandle xTask, 
                        pdTASK_HOOK_CODE pxTagValue );

configUSE_APPLICATION_TASK_TAG must be defined as 1 for this function to be available. See the configuration section for more information.

A 'tag' value can be assigned to each task. This value is for the use of the application only - the RTOS kernel itself does not make use of it in any way. The RTOS trace macros documentation page provides a good example of how an application might make use of this feature.

Parameters:
xTask The handle of the task to which a tag value is being assigned. Passing xTask as NULL causes the tag to be assigned to the calling task.
pxTagValue The value being assigned to the task tag. This is of type pdTASK_HOOK_CODE to permit a function pointer to be assigned as the tag, although any value can actually be assigned. See the example below.
Example usage: 


    /* In this example an integer is set as the task tag value.  See the RTOS
    trace hook macros documentation page for an example how such an assignment
    can be used. */
    void vATask( void *pvParameters )
    {
        /* Assign a tag value of 1 to myself. */
        vTaskSetApplicationTaskTag( NULL, ( void * ) 1 );

        for( ;; )
        {
            /* Rest of task code goes here. */
        }
    }
    /***********************************************/

    /* In this example a callback function is being assigned as the task tag.
    First define the callback function - this must have type pdTASK_HOOK_CODE
    as per this example. */
    static portBASE_TYPE prvExampleTaskHook( void * pvParameter )
    {
        /* Perform some action - this could be anything from logging a value,
        updating the task state, outputting a value, etc. */

        return 0;
    }

    /* Now define the task that sets prvExampleTaskHook as its hook/tag value.
    This is in fact registering the task callback, as described on the 
    xTaskCallApplicationTaskHook() documentation page. */
    void vAnotherTask( void *pvParameters )
    {
        /* Register our callback function. */
        vTaskSetApplicationTaskTag( NULL, prvExampleTaskHook );

        for( ;; )
        {
            /* Rest of task code goes here. */
        }
    }

    /* As an example use of the hook (callback) we can get the RTOS kernel to call the
    hook function of each task that is being switched out during a reschedule. */
    #define traceTASK_SWITCHED_OUT() xTaskCallApplicationTaskHook( pxCurrentTCB, 
                                                                   0 )






[ Back to the top ]    [ About FreeRTOS ]    [ Sitemap ]    [ ]




Copyright (C) 2004-2010 Richard Barry. Copyright (C) 2010-2013 Real Time Engineers Ltd.
Any and all data, files, source code, html content and documentation included in the FreeRTOSTM distribution or available on this site are the exclusive property of Real Time Engineers Ltd.. See the files license.txt (included in the distribution) and this copyright notice for more information. FreeRTOSTM and FreeRTOS.orgTM are trade marks of Real Time Engineers Ltd.