Quality RTOS & Embedded Software

 Real time embedded FreeRTOS RSS feed 
Quick Start Supported MCUs PDF Books Trace Tools Ecosystem TCP & FAT Training




Tasks
[More about tasks...]

Implementing a Task

A task should have the following structure:
    void vATaskFunction( void *pvParameters )
    {
        for( ;; )
        {
            -- Task application code here. --
        }

        /* Tasks must not attempt to return from their implementing
        function or otherwise exit.  In newer FreeRTOS port
        attempting to do so will result in an configASSERT() being
        called if it is defined.  If it is necessary for a task to
        exit then have the task call vTaskDelete( NULL ) to ensure
        its exit is clean. */
        vTaskDelete( NULL );
    }
 
The type TaskFunction_t is defined as a function that returns void and takes a void pointer as its only parameter. All functions that implement a task should be of this type. The parameter can be used to pass information of any type into the task - this is demonstrated by several of the standard demo application tasks.

Task functions should never return so are typically implemented as a continuous loop. Again, see the RTOS demo application for numerous examples.

Tasks are created by calling xTaskCreate() or xTaskCreateStatic(), and deleted by calling vTaskDelete().

[Back to top]



Task Creation Macros

Task functions can optionally be defined using the portTASK_FUNCTION and portTASK_FUNCTION_PROTO macros. These macro are provided to allow compiler specific syntax to be added to the function definition and prototype respectively. Their use is not required unless specifically stated in documentation for the port being used (currently only the PIC18 fedC port).

The prototype for the function shown above can be written as:

void vATaskFunction( void *pvParameters );
Or,
portTASK_FUNCTION_PROTO( vATaskFunction, pvParameters );
Likewise the function above could equally be written as:
    portTASK_FUNCTION( vATaskFunction, pvParameters )
    {
        for( ;; )
        {
            -- Task application code here. --
        }
    }
 




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




Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.

Latest News

FreeRTOS kernel V10 is available for immediate download. Now MIT licensed.


FreeRTOS Partners

ARM Connected RTOS partner for all ARM microcontroller cores

IAR Partner

Microchip Premier RTOS Partner

RTOS partner of NXP for all NXP ARM microcontrollers

STMicro RTOS partner supporting ARM7, ARM Cortex-M3, ARM Cortex-M4 and ARM Cortex-M0

Texas Instruments MCU Developer Network RTOS partner for ARM and MSP430 microcontrollers

OpenRTOS and SafeRTOS