root/webserver/example/freeRTOSexample/EnergyMeters/Common/Minimal/AltPollQ.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.  
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        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.


        ***************************************************************************
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        Please ensure to read the configuration and relevant port sections of the
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*/

/*
 * This is a version of PollQ.c that uses the alternative (Alt) API.
 * 
 * Creates two tasks that communicate over a single queue.  One task acts as a
 * producer, the other a consumer.
 *
 * The producer loops for three iteration, posting an incrementing number onto the
 * queue each cycle.  It then delays for a fixed period before doing exactly the
 * same again.
 *
 * The consumer loops emptying the queue.  Each item removed from the queue is
 * checked to ensure it contains the expected value.  When the queue is empty it
 * blocks for a fixed period, then does the same again.
 *
 * All queue access is performed without blocking.  The consumer completely empties
 * the queue each time it runs so the producer should never find the queue full.
 *
 * An error is flagged if the consumer obtains an unexpected value or the producer
 * find the queue is full.
 */

/*
Changes from V2.0.0

        + Delay periods are now specified using variables and constants of
          portTickType rather than unsigned portLONG.
*/

#include <stdlib.h>

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

/* Demo program include files. */
#include "AltPollQ.h"

#define pollqSTACK_SIZE                 configMINIMAL_STACK_SIZE
#define pollqQUEUE_SIZE                 ( 10 )
#define pollqPRODUCER_DELAY             ( ( portTickType ) 200 / portTICK_RATE_MS )
#define pollqCONSUMER_DELAY             ( pollqPRODUCER_DELAY - ( portTickType ) ( 20 / portTICK_RATE_MS ) )
#define pollqNO_DELAY                   ( ( portTickType ) 0 )
#define pollqVALUES_TO_PRODUCE  ( ( signed portBASE_TYPE ) 3 )
#define pollqINITIAL_VALUE              ( ( signed portBASE_TYPE ) 0 )

/* The task that posts the incrementing number onto the queue. */
static portTASK_FUNCTION_PROTO( vPolledQueueProducer, pvParameters );

/* The task that empties the queue. */
static portTASK_FUNCTION_PROTO( vPolledQueueConsumer, pvParameters );

/* Variables that are used to check that the tasks are still running with no
errors. */
static volatile signed portBASE_TYPE xPollingConsumerCount = pollqINITIAL_VALUE, xPollingProducerCount = pollqINITIAL_VALUE;

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

void vStartAltPolledQueueTasks( unsigned portBASE_TYPE uxPriority )
{
static xQueueHandle xPolledQueue;

        /* Create the queue used by the producer and consumer. */
        xPolledQueue = xQueueCreate( pollqQUEUE_SIZE, ( unsigned portBASE_TYPE ) sizeof( unsigned portSHORT ) );

        /* vQueueAddToRegistry() adds the queue to the queue registry, if one is
        in use.  The queue registry is provided as a means for kernel aware 
        debuggers to locate queues and has no purpose if a kernel aware debugger
        is not being used.  The call to vQueueAddToRegistry() will be removed
        by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is 
        defined to be less than 1. */
        vQueueAddToRegistry( xPolledQueue, ( signed portCHAR * ) "AltPollQueue" );


        /* Spawn the producer and consumer. */
        xTaskCreate( vPolledQueueConsumer, ( signed portCHAR * ) "QConsNB", pollqSTACK_SIZE, ( void * ) &xPolledQueue, uxPriority, ( xTaskHandle * ) NULL );
        xTaskCreate( vPolledQueueProducer, ( signed portCHAR * ) "QProdNB", pollqSTACK_SIZE, ( void * ) &xPolledQueue, uxPriority, ( xTaskHandle * ) NULL );
}
/*-----------------------------------------------------------*/

static portTASK_FUNCTION( vPolledQueueProducer, pvParameters )
{
unsigned portSHORT usValue = ( unsigned portSHORT ) 0;
signed portBASE_TYPE xError = pdFALSE, xLoop;

        #ifdef USE_STDIO
        void vPrintDisplayMessage( const portCHAR * const * ppcMessageToSend );
        
                const portCHAR * const pcTaskStartMsg = "Alt polling queue producer task started.\r\n";

                /* Queue a message for printing to say the task has started. */
                vPrintDisplayMessage( &pcTaskStartMsg );
        #endif

        for( ;; )
        {               
                for( xLoop = 0; xLoop < pollqVALUES_TO_PRODUCE; xLoop++ )
                {
                        /* Send an incrementing number on the queue without blocking. */
                        if( xQueueAltSendToBack( *( ( xQueueHandle * ) pvParameters ), ( void * ) &usValue, pollqNO_DELAY ) != pdPASS )
                        {
                                /* We should never find the queue full so if we get here there
                                has been an error. */
                                xError = pdTRUE;
                        }
                        else
                        {
                                if( xError == pdFALSE )
                                {
                                        /* If an error has ever been recorded we stop incrementing the
                                        check variable. */
                                        portENTER_CRITICAL();
                                                xPollingProducerCount++;
                                        portEXIT_CRITICAL();
                                }

                                /* Update the value we are going to post next time around. */
                                usValue++;
                        }
                }

                /* Wait before we start posting again to ensure the consumer runs and
                empties the queue. */
                vTaskDelay( pollqPRODUCER_DELAY );
        }
}  /*lint !e818 Function prototype must conform to API. */
/*-----------------------------------------------------------*/

static portTASK_FUNCTION( vPolledQueueConsumer, pvParameters )
{
unsigned portSHORT usData, usExpectedValue = ( unsigned portSHORT ) 0;
signed portBASE_TYPE xError = pdFALSE;

        #ifdef USE_STDIO
        void vPrintDisplayMessage( const portCHAR * const * ppcMessageToSend );
        
                const portCHAR * const pcTaskStartMsg = "Alt blocking queue consumer task started.\r\n";

                /* Queue a message for printing to say the task has started. */
                vPrintDisplayMessage( &pcTaskStartMsg );
        #endif

        for( ;; )
        {               
                /* Loop until the queue is empty. */
                while( uxQueueMessagesWaiting( *( ( xQueueHandle * ) pvParameters ) ) )
                {
                        if( xQueueAltReceive( *( ( xQueueHandle * ) pvParameters ), &usData, pollqNO_DELAY ) == pdPASS )
                        {
                                if( usData != usExpectedValue )
                                {
                                        /* This is not what we expected to receive so an error has
                                        occurred. */
                                        xError = pdTRUE;

                                        /* Catch-up to the value we received so our next expected
                                        value should again be correct. */
                                        usExpectedValue = usData;
                                }
                                else
                                {
                                        if( xError == pdFALSE )
                                        {
                                                /* Only increment the check variable if no errors have
                                                occurred. */
                                                portENTER_CRITICAL();
                                                        xPollingConsumerCount++;
                                                portEXIT_CRITICAL();
                                        }
                                }

                                /* Next time round we would expect the number to be one higher. */
                                usExpectedValue++;
                        }
                }

                /* Now the queue is empty we block, allowing the producer to place more
                items in the queue. */
                vTaskDelay( pollqCONSUMER_DELAY );
        }
} /*lint !e818 Function prototype must conform to API. */
/*-----------------------------------------------------------*/

/* This is called to check that all the created tasks are still running with no errors. */
portBASE_TYPE xAreAltPollingQueuesStillRunning( void )
{
portBASE_TYPE xReturn;

        /* Check both the consumer and producer poll count to check they have both
        been changed since out last trip round.  We do not need a critical section
        around the check variables as this is called from a higher priority than
        the other tasks that access the same variables. */
        if( ( xPollingConsumerCount == pollqINITIAL_VALUE ) ||
                ( xPollingProducerCount == pollqINITIAL_VALUE )
          )
        {
                xReturn = pdFALSE;
        }
        else
        {
                xReturn = pdTRUE;
        }

        /* Set the check variables back down so we know if they have been
        incremented the next time around. */
        xPollingConsumerCount = pollqINITIAL_VALUE;
        xPollingProducerCount = pollqINITIAL_VALUE;

        return xReturn;
}