root/Examples_CP-JR_ARM7_LPC2368/FreeRTOS_Book/Source-Code-For-Examples/Examples/Example008/main.c

/*
        FreeRTOS.org V5.0.4 - Copyright (C) 2003-2008 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.

    ***************************************************************************
    ***************************************************************************
    *                                                                         *
    * SAVE TIME AND MONEY!  We can port FreeRTOS.org to your own hardware,    *
    * and even write all or part of your application on your behalf.          *
    * See http://www.OpenRTOS.com for details of the services we provide to   *
    * expedite your project.                                                  *
    *                                                                         *
    ***************************************************************************
    ***************************************************************************

        Please ensure to read the configuration and relevant port sections of the
        online documentation.

        http://www.FreeRTOS.org - Documentation, latest information, license and 
        contact details.

        http://www.SafeRTOS.com - A version that is certified for use in safety 
        critical systems.

        http://www.OpenRTOS.com - Commercial support, development, porting, 
        licensing and training services.
*/

/* FreeRTOS.org includes. */
#include "FreeRTOS.h"
#include "task.h"

/* Demo includes. */
#include "basic_io.h"

/* The two task functions. */
void vTask1( void *pvParameters );
void vTask2( void *pvParameters );

/* Used to hold the handle of Task2. */
xTaskHandle xTask2Handle;

/*-----------------------------------------------------------*/

int main( void )
{
        /* Create the first task at priority 2.  This time the task parameter is
        not used and is set to NULL.  The task handle is also not used so likewise 
        is also set to NULL. */
        xTaskCreate( vTask1, "Task 1", 1000, NULL, 2, NULL );
          /* The task is created at priority 2 ^. */

        /* Create the second task at priority 1 - which is lower than the priority
        given to Task1.  Again the task parameter is not used so is set to NULL -
        BUT this time we want to obtain a handle to the task so pass in the address
        of the xTask2Handle variable. */
        xTaskCreate( vTask2, "Task 2", 1000, NULL, 1, &xTask2Handle );
         /* The task handle is the last parameter ^^^^^^^^^^^^^ */

        /* Start the scheduler so our tasks start executing. */
        vTaskStartScheduler();  
        
        for( ;; );
        return 0;
}
/*-----------------------------------------------------------*/

void vTask1( void *pvParameters )
{
unsigned portBASE_TYPE uxPriority;

        /* This task will always run before Task2 as it has the higher priority.
        Neither Task1 nor Task2 ever block so both will always be in either the
        Running or the Ready state.

        Query the priority at which this task is running - passing in NULL means
        "return our own priority". */
        uxPriority = uxTaskPriorityGet( NULL );

        for( ;; )
        {
                /* Print out the name of this task. */
                vPrintString( "Task1 is running\r\n" );

                /* Setting the Task2 priority above the Task1 priority will cause
                Task2 to immediately start running (as then Task2 will have the higher 
                priority of the    two created tasks). */
                vPrintString( "About to raise the Task2 priority\r\n" );
                vTaskPrioritySet( xTask2Handle, ( uxPriority + 1 ) );

                /* Task1 will only run when it has a priority higher than Task2.
                Therefore, for this task to reach this point Task2 must already have
                executed and set its priority back down to 0. */
        }
}

/*-----------------------------------------------------------*/

void vTask2( void *pvParameters )
{
unsigned portBASE_TYPE uxPriority;

        /* Task1 will always run before this task as Task1 has the higher priority.
        Neither Task1 nor Task2 ever block so will always be in either the
        Running or the Ready state.

        Query the priority at which this task is running - passing in NULL means
        "return our own priority". */
        uxPriority = uxTaskPriorityGet( NULL );

        for( ;; )
        {
                /* For this task to reach this point Task1 must have already run and
                set the priority of this task higher than its own.

                Print out the name of this task. */
                vPrintString( "Task2 is running\r\n" );

                /* Set our priority back down to its original value.  Passing in NULL
                as the task handle means "change our own priority".  Setting the
                priority below that of Task1 will cause Task1 to immediately start
                running again. */
                vPrintString( "About to lower the Task2 priority\r\n" );
                vTaskPrioritySet( NULL, ( uxPriority - 2 ) );
        }
}
/*-----------------------------------------------------------*/