2 FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
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4 ***************************************************************************
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8 * + New to FreeRTOS, *
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9 * + Wanting to learn FreeRTOS or multitasking in general quickly *
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10 * + Looking for basic training, *
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11 * + Wanting to improve your FreeRTOS skills and productivity *
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13 * then take a look at the FreeRTOS books - available as PDF or paperback *
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15 * "Using the FreeRTOS Real Time Kernel - a Practical Guide" *
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16 * http://www.FreeRTOS.org/Documentation *
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18 * A pdf reference manual is also available. Both are usually delivered *
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19 * to your inbox within 20 minutes to two hours when purchased between 8am *
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20 * and 8pm GMT (although please allow up to 24 hours in case of *
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21 * exceptional circumstances). Thank you for your support! *
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23 ***************************************************************************
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25 This file is part of the FreeRTOS distribution.
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27 FreeRTOS is free software; you can redistribute it and/or modify it under
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28 the terms of the GNU General Public License (version 2) as published by the
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29 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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30 ***NOTE*** The exception to the GPL is included to allow you to distribute
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31 a combined work that includes FreeRTOS without being obliged to provide the
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32 source code for proprietary components outside of the FreeRTOS kernel.
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33 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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34 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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35 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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36 more details. You should have received a copy of the GNU General Public
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37 License and the FreeRTOS license exception along with FreeRTOS; if not it
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38 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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39 by writing to Richard Barry, contact details for whom are available on the
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44 http://www.FreeRTOS.org - Documentation, latest information, license and
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47 http://www.SafeRTOS.com - A version that is certified for use in safety
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50 http://www.OpenRTOS.com - Commercial support, development, porting,
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51 licensing and training services.
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54 /* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE prevents task.h from redefining
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55 all the API functions to use the MPU wrappers. That should only be done when
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56 task.h is included from an application file. */
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57 #define MPU_WRAPPERS_INCLUDED_FROM_API_FILE
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59 #include "FreeRTOS.h"
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64 #undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
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66 /* Misc definitions. */
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67 #define tmrNO_DELAY ( portTickType ) 0U
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69 /* The definition of the timers themselves. */
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70 typedef struct tmrTimerControl
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72 const signed char *pcTimerName; /*<< Text name. This is not used by the kernel, it is included simply to make debugging easier. */
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73 xListItem xTimerListItem; /*<< Standard linked list item as used by all kernel features for event management. */
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74 portTickType xTimerPeriodInTicks;/*<< How quickly and often the timer expires. */
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75 unsigned portBASE_TYPE uxAutoReload; /*<< Set to pdTRUE if the timer should be automatically restarted once expired. Set to pdFALSE if the timer is, in effect, a one shot timer. */
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76 void *pvTimerID; /*<< An ID to identify the timer. This allows the timer to be identified when the same callback is used for multiple timers. */
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77 tmrTIMER_CALLBACK pxCallbackFunction; /*<< The function that will be called when the timer expires. */
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80 /* The definition of messages that can be sent and received on the timer
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82 typedef struct tmrTimerQueueMessage
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84 portBASE_TYPE xMessageID; /*<< The command being sent to the timer service task. */
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85 portTickType xMessageValue; /*<< An optional value used by a subset of commands, for example, when changing the period of a timer. */
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86 xTIMER * pxTimer; /*<< The timer to which the command will be applied. */
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90 /* The list in which active timers are stored. Timers are referenced in expire
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91 time order, with the nearest expiry time at the front of the list. Only the
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92 timer service task is allowed to access xActiveTimerList. */
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93 PRIVILEGED_DATA static xList xActiveTimerList1;
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94 PRIVILEGED_DATA static xList xActiveTimerList2;
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95 PRIVILEGED_DATA static xList *pxCurrentTimerList;
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96 PRIVILEGED_DATA static xList *pxOverflowTimerList;
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98 /* A queue that is used to send commands to the timer service task. */
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99 PRIVILEGED_DATA static xQueueHandle xTimerQueue = NULL;
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101 /*-----------------------------------------------------------*/
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104 * Initialise the infrastructure used by the timer service task if it has not
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105 * been initialised already.
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107 static void prvCheckForValidListAndQueue( void ) PRIVILEGED_FUNCTION;
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110 * The timer service task (daemon). Timer functionality is controlled by this
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111 * task. Other tasks communicate with the timer service task using the
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112 * xTimerQueue queue.
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114 static void prvTimerTask( void *pvParameters ) PRIVILEGED_FUNCTION;
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117 * Called by the timer service task to interpret and process a command it
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118 * received on the timer queue.
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120 static void prvProcessReceivedCommands( portTickType xAssumedTimeNow ) PRIVILEGED_FUNCTION;
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123 * Insert the timer into either xActiveTimerList1, or xActiveTimerList2,
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124 * depending on if the expire time causes a timer counter overflow.
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126 static void prvInsertTimerInActiveList( xTIMER *pxTimer, portTickType xNextExpiryTime, portTickType xAssumedTimeNow ) PRIVILEGED_FUNCTION;
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129 * An active timer has reached its expire time. Reload the timer if it is an
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130 * auto reload timer, then call its callback.
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132 static void prvProcessExpiredTimer( portTickType xNextExpireTime, portTickType xAssumedTimeNow ) PRIVILEGED_FUNCTION;
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135 * The tick count has overflowed. Switch the timer lists after ensuring the
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136 * current timer list does not still reference some timers.
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138 static void prvSwitchTimerLists( portTickType xAssumedTimeNow ) PRIVILEGED_FUNCTION;
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140 /*-----------------------------------------------------------*/
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142 portBASE_TYPE xTimerCreateTimerTask( void )
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144 portBASE_TYPE xReturn = pdFAIL;
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146 /* This function is called when the scheduler is started if
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147 configUSE_TIMERS is set to 1. Check that the infrastructure used by the
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148 timer service task has been created/initialised. If timers have already
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149 been created then the initialisation will already have been performed. */
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150 prvCheckForValidListAndQueue();
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152 if( xTimerQueue != NULL )
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154 xReturn = xTaskCreate( prvTimerTask, ( const signed char * ) "Timer Service", configTIMER_TASK_STACK_DEPTH, NULL, configTIMER_TASK_PRIORITY, NULL );
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159 /*-----------------------------------------------------------*/
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161 xTimerHandle xTimerCreate( const signed char *pcTimerName, portTickType xTimerPeriodInTicks, unsigned portBASE_TYPE uxAutoReload, void *pvTimerID, tmrTIMER_CALLBACK pxCallbackFunction )
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163 xTIMER *pxNewTimer;
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165 /* Allocate the timer structure. */
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166 pxNewTimer = ( xTIMER * ) pvPortMalloc( sizeof( xTIMER ) );
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167 if( pxNewTimer != NULL )
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169 /* Ensure the infrastructure used by the timer service task has been
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170 created/initialised. */
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171 prvCheckForValidListAndQueue();
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173 /* Initialise the timer structure members using the function parameters. */
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174 pxNewTimer->pcTimerName = pcTimerName;
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175 pxNewTimer->xTimerPeriodInTicks = xTimerPeriodInTicks;
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176 pxNewTimer->uxAutoReload = uxAutoReload;
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177 pxNewTimer->pvTimerID = pvTimerID;
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178 pxNewTimer->pxCallbackFunction = pxCallbackFunction;
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179 vListInitialiseItem( &( pxNewTimer->xTimerListItem ) );
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182 return ( xTimerHandle ) pxNewTimer;
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184 /*-----------------------------------------------------------*/
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186 portBASE_TYPE xTimerGenericCommand( xTimerHandle xTimer, portBASE_TYPE xCommandID, portTickType xOptionalValue, portTickType xBlockTime )
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188 portBASE_TYPE xReturn = pdFAIL;
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189 xTIMER_MESSAGE xMessage;
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191 /* Send a message to the timer service task to perform a particular action
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192 on a particular timer definition. */
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193 if( xTimerQueue != NULL )
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195 /* Send a command to the timer service task to start the xTimer timer. */
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196 xMessage.xMessageID = xCommandID;
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197 xMessage.xMessageValue = xOptionalValue;
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198 xMessage.pxTimer = ( xTIMER * ) xTimer;
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200 if( xTaskGetSchedulerState() == taskSCHEDULER_RUNNING )
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202 xReturn = xQueueSendToBack( xTimerQueue, &xMessage, xBlockTime );
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206 xReturn = xQueueSendToBack( xTimerQueue, &xMessage, tmrNO_DELAY );
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212 /*-----------------------------------------------------------*/
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214 static void prvProcessExpiredTimer( portTickType xNextExpireTime, portTickType xAssumedTimeNow )
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218 if( listLIST_IS_EMPTY( pxCurrentTimerList ) == pdFALSE )
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220 /* Remove the timer from the list of active timers. */
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221 pxTimer = ( xTIMER * ) listGET_OWNER_OF_HEAD_ENTRY( pxCurrentTimerList );
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222 vListRemove( &( pxTimer->xTimerListItem ) );
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224 /* If the timer is an auto reload timer then calculate the next
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225 expiry time and re-insert the timer in the list of active timers. */
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226 if( pxTimer->uxAutoReload == pdTRUE )
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228 /* This is the only time a timer is inserted into a list using
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229 a time relative to anything other than the current time. It
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230 will therefore be inserted into the correct list relative to
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231 the time this task thinks it is now, even if a command to
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232 switch lists due to a tick count overflow is already waiting in
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233 the timer queue. */
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234 prvInsertTimerInActiveList( pxTimer, ( xNextExpireTime + pxTimer->xTimerPeriodInTicks ), xAssumedTimeNow );
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237 /* Call the timer callback. */
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238 pxTimer->pxCallbackFunction( ( xTimerHandle ) pxTimer );
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241 /*-----------------------------------------------------------*/
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243 static void prvTimerTask( void *pvParameters )
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245 portTickType xNextExpireTime, xTimeNow, xFrozenTimeNow;
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247 /* Just to avoid compiler warnings. */
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248 ( void ) pvParameters;
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252 /* Take a snapshot of the time to use while assessing expiry and auto
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254 xFrozenTimeNow = xTaskGetTickCount();
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256 /* Timers are listed in expiry time order, with the head of the list
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257 referencing the task that will expire first. Obtain the time at which
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258 the timer with the nearest expiry time will expire. If there are no
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259 active timers then just set the next expire time to the maximum possible
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260 time to ensure this task does not run unnecessarily. */
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261 if( listLIST_IS_EMPTY( pxCurrentTimerList ) == pdFALSE )
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263 xNextExpireTime = listGET_ITEM_VALUE_OF_HEAD_ENTRY( pxCurrentTimerList );
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267 xNextExpireTime = portMAX_DELAY;
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270 /* Has the timer expired? This expiry time is relative to the snapshot
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271 of the time taken to be used in this loop iteration - so it doesn't
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272 matter at this point if a tick count overflows here. */
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273 if( xNextExpireTime <= xFrozenTimeNow )
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275 prvProcessExpiredTimer( xNextExpireTime, xFrozenTimeNow );
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279 /* Block this task until the next timer expires, or a command is
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283 /* Has the tick overflowed since a time snapshot was taken? */
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284 xTimeNow = xTaskGetTickCount();
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285 if( xTimeNow >= xFrozenTimeNow )
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287 /* Has the expire not still not been met? The tick count
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288 may be greater now than when the time snapshot was taken. */
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289 if( xNextExpireTime <= xTimeNow )
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291 prvProcessExpiredTimer( xNextExpireTime, xFrozenTimeNow );
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295 /* The tick count has not overflowed since the time
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296 snapshot, and the next expire time has not been reached
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297 since the last snapshot was taken. This task should
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298 therefore block to wait for the next expire time. */
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299 vQueueWaitForMessageRestricted( xTimerQueue, ( xNextExpireTime - xTimeNow ) );
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304 /* The tick count has overflowed since the time snapshot
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305 was taken, therefore, the task should not block but continue
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306 with another loop. The command queue should contain a
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307 command to switch lists. */
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310 if( xTaskResumeAll() == pdFALSE )
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312 /* Yield to wait for either a command to arrive, or the block time
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313 to expire. If a command arrived between the critical section being
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314 exited and this yield then the yield will just return to the same
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316 portYIELD_WITHIN_API();
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319 /* Take a snapshot of the time now for use in this iteration of the
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321 xFrozenTimeNow = xTaskGetTickCount();
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323 /* Empty the command queue, if it contains any commands. */
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324 prvProcessReceivedCommands( xFrozenTimeNow );
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328 /*-----------------------------------------------------------*/
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330 static void prvInsertTimerInActiveList( xTIMER *pxTimer, portTickType xNextExpiryTime, portTickType xAssumedTimeNow )
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332 listSET_LIST_ITEM_VALUE( &( pxTimer->xTimerListItem ), xNextExpiryTime );
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333 listSET_LIST_ITEM_OWNER( &( pxTimer->xTimerListItem ), pxTimer );
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335 if( xNextExpiryTime < xAssumedTimeNow )
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337 vListInsert( pxOverflowTimerList, &( pxTimer->xTimerListItem ) );
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341 vListInsert( pxCurrentTimerList, &( pxTimer->xTimerListItem ) );
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344 /*-----------------------------------------------------------*/
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346 static void prvProcessReceivedCommands( portTickType xAssumedTimeNow )
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348 xTIMER_MESSAGE xMessage;
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350 portBASE_TYPE xSwitchListsOnExit = pdFALSE;
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352 while( xQueueReceive( xTimerQueue, &xMessage, tmrNO_DELAY ) != pdFAIL )
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354 pxTimer = xMessage.pxTimer;
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356 /* Is the timer already in a list of active timers? When the command
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357 is trmCOMMAND_PROCESS_TIMER_OVERFLOW, the timer will be NULL as the
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358 command is to the task rather than to an individual timer. */
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359 if( pxTimer != NULL )
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361 if( listIS_CONTAINED_WITHIN( NULL, &( pxTimer->xTimerListItem ) ) == pdFALSE )
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363 /* The timer is in a list, remove it. */
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364 vListRemove( &( pxTimer->xTimerListItem ) );
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368 switch( xMessage.xMessageID )
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370 case tmrCOMMAND_START :
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371 /* Start or restart a timer. */
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372 prvInsertTimerInActiveList( pxTimer, xAssumedTimeNow + pxTimer->xTimerPeriodInTicks, xAssumedTimeNow );
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375 case tmrCOMMAND_STOP :
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376 /* The timer has already been removed from the active list.
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377 There is nothing to do here. */
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380 case tmrCOMMAND_CHANGE_PERIOD :
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381 pxTimer->xTimerPeriodInTicks = xMessage.xMessageValue;
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382 prvInsertTimerInActiveList( pxTimer, ( xAssumedTimeNow + pxTimer->xTimerPeriodInTicks ), xAssumedTimeNow );
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385 case tmrCOMMAND_DELETE :
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386 /* The timer has already been removed from the active list,
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387 just free up the memory. */
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388 vPortFree( pxTimer );
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391 case trmCOMMAND_PROCESS_TIMER_OVERFLOW :
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392 /* Hold this pending until all the other messages have been
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394 xSwitchListsOnExit = pdTRUE;
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398 /* Don't expect to get here. */
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403 if( xSwitchListsOnExit == pdTRUE )
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405 prvSwitchTimerLists( xAssumedTimeNow );
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408 /*-----------------------------------------------------------*/
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410 static void prvSwitchTimerLists( portTickType xAssumedTimeNow )
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412 portTickType xNextExpireTime;
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415 /* The tick count has overflowed. The timer lists must be switched.
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416 If there are any timers still referenced from the current timer list
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417 then they must have expired and should be processed before the lists
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419 while( listLIST_IS_EMPTY( pxCurrentTimerList ) == pdFALSE )
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421 xNextExpireTime = listGET_ITEM_VALUE_OF_HEAD_ENTRY( pxCurrentTimerList );
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422 prvProcessExpiredTimer( xNextExpireTime, xAssumedTimeNow );
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425 pxTemp = pxCurrentTimerList;
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426 pxCurrentTimerList = pxOverflowTimerList;
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427 pxOverflowTimerList = pxTemp;
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429 /*-----------------------------------------------------------*/
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431 static void prvCheckForValidListAndQueue( void )
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433 /* Check that the list from which active timers are referenced, and the
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434 queue used to communicate with the timer service, have been
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436 taskENTER_CRITICAL();
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438 if( xTimerQueue == NULL )
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440 vListInitialise( &xActiveTimerList1 );
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441 vListInitialise( &xActiveTimerList2 );
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442 pxCurrentTimerList = &xActiveTimerList1;
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443 pxOverflowTimerList = &xActiveTimerList2;
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444 xTimerQueue = xQueueCreate( configTIMER_QUEUE_LENGTH, sizeof( xTIMER_MESSAGE ) );
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447 taskEXIT_CRITICAL();
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449 /*-----------------------------------------------------------*/
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451 portBASE_TYPE xTimerIsTimerActive( xTimerHandle xTimer )
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453 portBASE_TYPE xTimerIsInActiveList;
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454 xTIMER *pxTimer = ( xTIMER * ) xTimer;
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456 /* Is the timer in the list of active timers? */
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457 taskENTER_CRITICAL();
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459 /* Checking to see if it is in the NULL list in effect checks to see if
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460 it is referenced from either the current or the overflow timer lists in
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461 one go, but the logic has to be reversed, hence the '!'. */
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462 xTimerIsInActiveList = !( listIS_CONTAINED_WITHIN( NULL, &( pxTimer->xTimerListItem ) ) );
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464 taskEXIT_CRITICAL();
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466 return xTimerIsInActiveList;
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468 /*-----------------------------------------------------------*/
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470 void *pvTimerGetTimerID( xTimerHandle xTimer )
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472 xTIMER *pxTimer = ( xTIMER * ) xTimer;
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474 return pxTimer->pvTimerID;
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476 /*-----------------------------------------------------------*/
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