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Show/hide line numbers PollQ.c Source File

PollQ.c

00001 /*
00002     FreeRTOS V6.0.3 - Copyright (C) 2010 Real Time Engineers Ltd.
00003 
00004     ***************************************************************************
00005     *                                                                         *
00006     * If you are:                                                             *
00007     *                                                                         *
00008     *    + New to FreeRTOS,                                                   *
00009     *    + Wanting to learn FreeRTOS or multitasking in general quickly       *
00010     *    + Looking for basic training,                                        *
00011     *    + Wanting to improve your FreeRTOS skills and productivity           *
00012     *                                                                         *
00013     * then take a look at the FreeRTOS eBook                                  *
00014     *                                                                         *
00015     *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *
00016     *                  http://www.FreeRTOS.org/Documentation                  *
00017     *                                                                         *
00018     * A pdf reference manual is also available.  Both are usually delivered   *
00019     * to your inbox within 20 minutes to two hours when purchased between 8am *
00020     * and 8pm GMT (although please allow up to 24 hours in case of            *
00021     * exceptional circumstances).  Thank you for your support!                *
00022     *                                                                         *
00023     ***************************************************************************
00024 
00025     This file is part of the FreeRTOS distribution.
00026 
00027     FreeRTOS is free software; you can redistribute it and/or modify it under
00028     the terms of the GNU General Public License (version 2) as published by the
00029     Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
00030     ***NOTE*** The exception to the GPL is included to allow you to distribute
00031     a combined work that includes FreeRTOS without being obliged to provide the
00032     source code for proprietary components outside of the FreeRTOS kernel.
00033     FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
00034     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
00035     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
00036     more details. You should have received a copy of the GNU General Public 
00037     License and the FreeRTOS license exception along with FreeRTOS; if not it 
00038     can be viewed here: http://www.freertos.org/a00114.html and also obtained 
00039     by writing to Richard Barry, contact details for whom are available on the
00040     FreeRTOS WEB site.
00041 
00042     1 tab == 4 spaces!
00043 
00044     http://www.FreeRTOS.org - Documentation, latest information, license and
00045     contact details.
00046 
00047     http://www.SafeRTOS.com - A version that is certified for use in safety
00048     critical systems.
00049 
00050     http://www.OpenRTOS.com - Commercial support, development, porting,
00051     licensing and training services.
00052 */
00053 
00054 /*
00055  * This version of PollQ. c is for use on systems that have limited stack
00056  * space and no display facilities.  The complete version can be found in
00057  * the Demo/Common/Full directory.
00058  *
00059  * Creates two tasks that communicate over a single queue.  One task acts as a
00060  * producer, the other a consumer.
00061  *
00062  * The producer loops for three iteration, posting an incrementing number onto the
00063  * queue each cycle.  It then delays for a fixed period before doing exactly the
00064  * same again.
00065  *
00066  * The consumer loops emptying the queue.  Each item removed from the queue is
00067  * checked to ensure it contains the expected value.  When the queue is empty it
00068  * blocks for a fixed period, then does the same again.
00069  *
00070  * All queue access is performed without blocking.  The consumer completely empties
00071  * the queue each time it runs so the producer should never find the queue full.
00072  *
00073  * An error is flagged if the consumer obtains an unexpected value or the producer
00074  * find the queue is full.
00075  */
00076 
00077 /*
00078 Changes from V2.0.0
00079 
00080     + Delay periods are now specified using variables and constants of
00081       portTickType rather than unsigned long.
00082 */
00083 
00084 #include <stdlib.h>
00085 
00086 /* Scheduler include files. */
00087 #include "FreeRTOS.h"
00088 #include "task.h"
00089 #include "queue.h"
00090 
00091 /* Demo program include files. */
00092 #include "PollQ.h"
00093 
00094 #define pollqSTACK_SIZE            configMINIMAL_STACK_SIZE
00095 #define pollqQUEUE_SIZE            ( 10 )
00096 #define pollqPRODUCER_DELAY        ( ( portTickType ) 200 / portTICK_RATE_MS )
00097 #define pollqCONSUMER_DELAY        ( pollqPRODUCER_DELAY - ( portTickType ) ( 20 / portTICK_RATE_MS ) )
00098 #define pollqNO_DELAY            ( ( portTickType ) 0 )
00099 #define pollqVALUES_TO_PRODUCE    ( ( signed portBASE_TYPE ) 3 )
00100 #define pollqINITIAL_VALUE        ( ( signed portBASE_TYPE ) 0 )
00101 
00102 /* The task that posts the incrementing number onto the queue. */
00103 static portTASK_FUNCTION_PROTO( vPolledQueueProducer, pvParameters );
00104 
00105 /* The task that empties the queue. */
00106 static portTASK_FUNCTION_PROTO( vPolledQueueConsumer, pvParameters );
00107 
00108 /* Variables that are used to check that the tasks are still running with no
00109 errors. */
00110 static volatile signed portBASE_TYPE xPollingConsumerCount = pollqINITIAL_VALUE, xPollingProducerCount = pollqINITIAL_VALUE;
00111 
00112 /*-----------------------------------------------------------*/
00113 
00114 void vStartPolledQueueTasks( unsigned portBASE_TYPE uxPriority )
00115 {
00116 static xQueueHandle xPolledQueue;
00117 
00118     /* Create the queue used by the producer and consumer. */
00119     xPolledQueue = xQueueCreate( pollqQUEUE_SIZE, ( unsigned portBASE_TYPE ) sizeof( unsigned short ) );
00120 
00121     /* vQueueAddToRegistry() adds the queue to the queue registry, if one is
00122     in use.  The queue registry is provided as a means for kernel aware 
00123     debuggers to locate queues and has no purpose if a kernel aware debugger
00124     is not being used.  The call to vQueueAddToRegistry() will be removed
00125     by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is 
00126     defined to be less than 1. */
00127     vQueueAddToRegistry( xPolledQueue, ( signed char * ) "Poll_Test_Queue" );
00128 
00129     /* Spawn the producer and consumer. */
00130     xTaskCreate( vPolledQueueConsumer, ( signed char * ) "QConsNB", pollqSTACK_SIZE, ( void * ) &xPolledQueue, uxPriority, ( xTaskHandle * ) NULL );
00131     xTaskCreate( vPolledQueueProducer, ( signed char * ) "QProdNB", pollqSTACK_SIZE, ( void * ) &xPolledQueue, uxPriority, ( xTaskHandle * ) NULL );
00132 }
00133 /*-----------------------------------------------------------*/
00134 
00135 static portTASK_FUNCTION( vPolledQueueProducer, pvParameters )
00136 {
00137 unsigned short usValue = ( unsigned short ) 0;
00138 signed portBASE_TYPE xError = pdFALSE, xLoop;
00139 
00140     for( ;; )
00141     {        
00142         for( xLoop = 0; xLoop < pollqVALUES_TO_PRODUCE; xLoop++ )
00143         {
00144             /* Send an incrementing number on the queue without blocking. */
00145             if( xQueueSend( *( ( xQueueHandle * ) pvParameters ), ( void * ) &usValue, pollqNO_DELAY ) != pdPASS )
00146             {
00147                 /* We should never find the queue full so if we get here there
00148                 has been an error. */
00149                 xError = pdTRUE;
00150             }
00151             else
00152             {
00153                 if( xError == pdFALSE )
00154                 {
00155                     /* If an error has ever been recorded we stop incrementing the
00156                     check variable. */
00157                     portENTER_CRITICAL();
00158                         xPollingProducerCount++;
00159                     portEXIT_CRITICAL();
00160                 }
00161 
00162                 /* Update the value we are going to post next time around. */
00163                 usValue++;
00164             }
00165         }
00166 
00167         /* Wait before we start posting again to ensure the consumer runs and
00168         empties the queue. */
00169         vTaskDelay( pollqPRODUCER_DELAY );
00170     }
00171 }  /*lint !e818 Function prototype must conform to API. */
00172 /*-----------------------------------------------------------*/
00173 
00174 static portTASK_FUNCTION( vPolledQueueConsumer, pvParameters )
00175 {
00176 unsigned short usData, usExpectedValue = ( unsigned short ) 0;
00177 signed portBASE_TYPE xError = pdFALSE;
00178 
00179     for( ;; )
00180     {        
00181         /* Loop until the queue is empty. */
00182         while( uxQueueMessagesWaiting( *( ( xQueueHandle * ) pvParameters ) ) )
00183         {
00184             if( xQueueReceive( *( ( xQueueHandle * ) pvParameters ), &usData, pollqNO_DELAY ) == pdPASS )
00185             {
00186                 if( usData != usExpectedValue )
00187                 {
00188                     /* This is not what we expected to receive so an error has
00189                     occurred. */
00190                     xError = pdTRUE;
00191 
00192                     /* Catch-up to the value we received so our next expected
00193                     value should again be correct. */
00194                     usExpectedValue = usData;
00195                 }
00196                 else
00197                 {
00198                     if( xError == pdFALSE )
00199                     {
00200                         /* Only increment the check variable if no errors have
00201                         occurred. */
00202                         portENTER_CRITICAL();
00203                             xPollingConsumerCount++;
00204                         portEXIT_CRITICAL();
00205                     }
00206                 }
00207 
00208                 /* Next time round we would expect the number to be one higher. */
00209                 usExpectedValue++;
00210             }
00211         }
00212 
00213         /* Now the queue is empty we block, allowing the producer to place more
00214         items in the queue. */
00215         vTaskDelay( pollqCONSUMER_DELAY );
00216     }
00217 } /*lint !e818 Function prototype must conform to API. */
00218 /*-----------------------------------------------------------*/
00219 
00220 /* This is called to check that all the created tasks are still running with no errors. */
00221 portBASE_TYPE xArePollingQueuesStillRunning( void )
00222 {
00223 portBASE_TYPE xReturn;
00224 
00225     /* Check both the consumer and producer poll count to check they have both
00226     been changed since out last trip round.  We do not need a critical section
00227     around the check variables as this is called from a higher priority than
00228     the other tasks that access the same variables. */
00229     if( ( xPollingConsumerCount == pollqINITIAL_VALUE ) ||
00230         ( xPollingProducerCount == pollqINITIAL_VALUE )
00231       )
00232     {
00233         xReturn = pdFALSE;
00234     }
00235     else
00236     {
00237         xReturn = pdTRUE;
00238     }
00239 
00240     /* Set the check variables back down so we know if they have been
00241     incremented the next time around. */
00242     xPollingConsumerCount = pollqINITIAL_VALUE;
00243     xPollingProducerCount = pollqINITIAL_VALUE;
00244 
00245     return xReturn;
00246 }