root/webserver/example/freeRTOS/Demo/Common/Minimal/flash.c

/*
        FreeRTOS V5.4.1 - Copyright (C) 2009 Real Time Engineers Ltd.

        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 (version 2) as published by the 
        Free Software Foundation and modified by the FreeRTOS exception.
        **NOTE** The exception to the GPL is included to allow you to distribute a
        combined work that includes FreeRTOS without being obliged to provide the 
        source code for proprietary components outside of the FreeRTOS kernel.  
        Alternative commercial license and support terms are also available upon 
        request.  See the licensing section of http://www.FreeRTOS.org for full 
        license details.

        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.


        ***************************************************************************
        *                                                                         *
        * Looking for a quick start?  Then check out the FreeRTOS eBook!          *
        * See http://www.FreeRTOS.org/Documentation for details                   *
        *                                                                         *
        ***************************************************************************

        1 tab == 4 spaces!

        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.

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*/

/**
 * This version of flash .c is for use on systems that have limited stack space
 * and no display facilities.  The complete version can be found in the 
 * Demo/Common/Full directory.
 * 
 * Three tasks are created, each of which flash an LED at a different rate.  The first 
 * LED flashes every 200ms, the second every 400ms, the third every 600ms.
 *
 * The LED flash tasks provide instant visual feedback.  They show that the scheduler 
 * is still operational.
 *
 */


#include <stdlib.h>

/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"

/* Demo program include files. */
#include "partest.h"
#include "flash.h"

#define ledSTACK_SIZE           configMINIMAL_STACK_SIZE
#define ledNUMBER_OF_LEDS       ( 1 )
#define ledFLASH_RATE_BASE      ( ( portTickType ) 333 )

/* Variable used by the created tasks to calculate the LED number to use, and
the rate at which they should flash the LED. */
static volatile unsigned portBASE_TYPE uxFlashTaskNumber = 0;

/* The task that is created three times. */
static portTASK_FUNCTION_PROTO( vLEDFlashTask, pvParameters );

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

void vStartLEDFlashTasks( unsigned portBASE_TYPE uxPriority )
{
signed portBASE_TYPE xLEDTask;

        /* Create the three tasks. */
        for( xLEDTask = 0; xLEDTask < ledNUMBER_OF_LEDS; ++xLEDTask )
        {
                /* Spawn the task. */
                xTaskCreate( vLEDFlashTask, ( signed portCHAR * ) "LEDx", ledSTACK_SIZE, NULL, uxPriority, ( xTaskHandle * ) NULL );
        }
}
/*-----------------------------------------------------------*/

static portTASK_FUNCTION( vLEDFlashTask, pvParameters )
{
portTickType xFlashRate, xLastFlashTime;
unsigned portBASE_TYPE uxLED;

        /* The parameters are not used. */
        ( void ) pvParameters;

        /* Calculate the LED and flash rate. */
        portENTER_CRITICAL();
        {
                /* See which of the eight LED's we should use. */
                uxLED = uxFlashTaskNumber;

                /* Update so the next task uses the next LED. */
                uxFlashTaskNumber++;
        }
        portEXIT_CRITICAL();

        xFlashRate = ledFLASH_RATE_BASE + ( ledFLASH_RATE_BASE * ( portTickType ) uxLED );
        xFlashRate /= portTICK_RATE_MS;

        /* We will turn the LED on and off again in the delay period, so each
        delay is only half the total period. */
        xFlashRate /= ( portTickType ) 2;

        /* We need to initialise xLastFlashTime prior to the first call to 
        vTaskDelayUntil(). */
        xLastFlashTime = xTaskGetTickCount();

        for(;;)
        {
                /* Delay for half the flash period then turn the LED on. */
                vTaskDelayUntil( &xLastFlashTime, xFlashRate );
                vParTestToggleLED( uxLED );

                /* Delay for half the flash period then turn the LED off. */
                vTaskDelayUntil( &xLastFlashTime, xFlashRate );
                vParTestToggleLED( uxLED );
        }
} /*lint !e715 !e818 !e830 Function definition must be standard for task creation. */