Continue work on timers module - work in progress.
diff --git a/Source/timers.c b/Source/timers.c
index e28b78f..e1d464d 100644
--- a/Source/timers.c
+++ b/Source/timers.c
@@ -66,10 +66,10 @@
#undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE
/* IDs for commands that can be sent/received on the timer queue. */
-#define tmrSTART 0
+#define tmrCOMMAND_START 0
/* Misc definitions. */
-#define timerNO_DELAY ( portTickType ) 0U
+#define tmrNO_DELAY ( portTickType ) 0U
/* The definition of the timers themselves. */
typedef struct tmrTimerControl
@@ -108,16 +108,37 @@
*/
static void prvRemoveTimerFromActiveList( xTIMER *pxTimer ) PRIVILEGED_FUNCTION;
+/*
+ * Send pxMessage to xTimerQueue using a block time of xBlockTime if the
+ * scheduler is running, or a block time of zero if the scheduler is not
+ * running.
+ */
+static portBASE_TYPE prvSendMessageToTimerServiceTask( xTIMER_MESSAGE *pxMessage, portTickType xBlockTime ) PRIVILEGED_FUNCTION;
+
+/*
+ * Initialise the infrustructure used by the timer service task if it has not
+ * been initialised already.
+ */
static void prvCheckForValidListAndQueue( void ) PRIVILEGED_FUNCTION;
/*
- * The timer service task (daemon).
+ * The timer service task (daemon). Timer functionality is controlled by this
+ * task. Other tasks communicate with the timer service task using the
+ * xTimerQueue queue.
*/
static void prvTimerTask( void *pvParameters ) PRIVILEGED_FUNCTION;
+/*
+ * The following functions handle the commands that are sent to the timer
+ * service task via the xTimerQueue queue.
+ */
+static void prvTimerStart( xTIMER *pxTimer ) PRIVILEGED_FUNCTION;
-/* Handlers for commands received on the timer queue. */
-static void prvTimerStart( xTIMER *pxTimer );
+/*
+ * Called by the timer service task to interpret and process a command it
+ * received on the timer queue.
+ */
+static void prvProcessReceivedCommands( void ) PRIVILEGED_FUNCTION;
/*-----------------------------------------------------------*/
@@ -126,12 +147,14 @@
portBASE_TYPE xReturn = pdFAIL;
/* This function is called when the scheduler is started if
- configUSE_TIMERS is set to 1. */
+ configUSE_TIMERS is set to 1. Check that the infrustructure used by the
+ timer service task has been created/initialised. If timers have already
+ been created then the initialisation will already have been performed. */
prvCheckForValidListAndQueue();
if( xTimerQueue != NULL )
{
- xReturn = xTaskCreate( prvTimerTask, ( const signed char * ) "Timers", configMINIMAL_STACK_SIZE, NULL, configTIMER_TASK_PRIORITY, NULL );
+ xReturn = xTaskCreate( prvTimerTask, ( const signed char * ) "Timers", configTIMER_TASK_STACK_DEPTH, NULL, configTIMER_TASK_PRIORITY, NULL );
}
return xReturn;
@@ -146,9 +169,11 @@
pxNewTimer = ( xTIMER * ) pvPortMalloc( sizeof( xTIMER ) );
if( pxNewTimer != NULL )
{
+ /* Ensure the infrustructure used by the timer service task has been
+ created/initialised. */
prvCheckForValidListAndQueue();
- /* Initialise the timer structure members. */
+ /* Initialise the timer structure members using the function parameters. */
pxNewTimer->pcTimerName = pcTimerName;
pxNewTimer->xTimerPeriodInTicks = xTimerPeriodInTicks;
pxNewTimer->uxAutoReload = uxAutoReload;
@@ -166,68 +191,57 @@
portBASE_TYPE xReturn = pdFAIL;
xTIMER_MESSAGE xMessage;
+ /* A timer cannot be started unless it is created, and creating a timer
+ will have resulted in the timer queue also being created. */
if( xTimerQueue != NULL )
{
- xMessage.xMessageID = tmrSTART;
+ /* Send a command to the timer service task to start the xTimer timer. */
+ xMessage.xMessageID = tmrCOMMAND_START;
xMessage.pxTimer = ( xTIMER * ) xTimer;
- xReturn = xQueueSendToBack( xTimerQueue, &xMessage, xBlockTime );
+ prvSendMessageToTimerServiceTask( &xMessage, xBlockTime );
}
return xReturn;
}
/*-----------------------------------------------------------*/
-void *pvTimerGetTimerID( xTimerHandle xTimer )
-{
-xTIMER *pxTimer = ( xTIMER * ) xTimer;
-
- return pxTimer->pvTimerID;
-}
-/*-----------------------------------------------------------*/
-
-static void prvRemoveTimerFromActiveList( xTIMER *pxTimer )
-{
- /* Is the timer already in the list of active timers? */
- if( listIS_CONTAINED_WITHIN( NULL, &( pxTimer->xTimerListItem ) ) == pdFALSE )
- {
- /* The timer is in the list, remove it. */
- vListRemove( &( pxTimer->xTimerListItem ) );
- }
-}
-/*-----------------------------------------------------------*/
-
static void prvTimerTask( void *pvParameters )
{
-portTickType xNextWakeTime, xTimeNow;
+portTickType xNextExpireTime, xTimeNow;
xTIMER *pxTimer;
-xTIMER_MESSAGE xMessage;
/* Just to avoid compiler warnings. */
( void ) pvParameters;
for( ;; )
{
+ /* Timers are listed in expiry time order, with the head of the list
+ referencing the task that will expire first. Obtain the time at which
+ the timer with the nearest expiry time will expire. If there are no
+ active timers then just set the next expire time to the maximum possible
+ time to ensure this task does not run unnecessarily. */
if( listLIST_IS_EMPTY( &xActiveTimerList ) == pdFALSE )
{
- xNextWakeTime = listGET_ITEM_VALUE_OF_HEAD_ENTRY( &xActiveTimerList );
+ xNextExpireTime = listGET_ITEM_VALUE_OF_HEAD_ENTRY( &xActiveTimerList );
}
else
{
- xNextWakeTime = portMAX_DELAY;
+ xNextExpireTime = portMAX_DELAY;
}
- if( xNextWakeTime <= xTaskGetTickCount() )
+ /* Has the timer expired? */
+ if( xNextExpireTime <= xTaskGetTickCount() )
{
- /* Remove the timer from the list. This functionality relies on
- the list of active timers not being accessed from outside of this
- task. */
+ /* Remove the timer from the list of active timers. */
pxTimer = listGET_OWNER_OF_HEAD_ENTRY( &xActiveTimerList );
vListRemove( &( pxTimer->xTimerListItem ) );
+ /* If the timer is an autoreload timer then calculate the next
+ expiry time and re-insert the timer in the list of active timers. */
if( pxTimer->uxAutoReload == pdTRUE )
{
- listSET_LIST_ITEM_VALUE( &( pxTimer->xTimerListItem ), ( xNextWakeTime + pxTimer->xTimerPeriodInTicks ) );
+ listSET_LIST_ITEM_VALUE( &( pxTimer->xTimerListItem ), ( xNextExpireTime + pxTimer->xTimerPeriodInTicks ) );
vListInsert( &xActiveTimerList, &( pxTimer->xTimerListItem ) );
}
@@ -236,28 +250,57 @@
}
else
{
- /* Calculate the block time. */
+ /* Block this task until the next timer expires, or a command is
+ received. */
taskENTER_CRITICAL();
{
xTimeNow = xTaskGetTickCount();
- if( xTimeNow < xNextWakeTime )
+ if( xTimeNow < xNextExpireTime )
{
- vQueueWaitForMessageRestricted( xTimerQueue, ( xNextWakeTime - xTimeNow ) );
+ /* This is a simple fast function - a yield will not be
+ performed until after this critical section exits. */
+ vQueueWaitForMessageRestricted( xTimerQueue, ( xNextExpireTime - xTimeNow ) );
}
}
taskEXIT_CRITICAL();
+
+ /* Yield to wait for either a command to arrive, or the block time
+ to expire. If a command arrived between the critical section being
+ exited and this yeild then the yield will just return to the same
+ task. */
portYIELD_WITHIN_API();
- while( xQueueReceive( xTimerQueue, &xMessage, timerNO_DELAY ) != pdFAIL )
- {
- switch( xMessage.xMessageID )
- {
- case tmrSTART : prvTimerStart( xMessage.pxTimer );
+ /* Empty the command queue, if it contains any commands. */
+ prvProcessReceivedCommands();
+ }
+ }
+}
+/*-----------------------------------------------------------*/
+
+static void prvProcessReceivedCommands( void )
+{
+xTIMER_MESSAGE xMessage;
+portTickType xTimeToExpire;
+xTIMER *pxTimer;
+
+ while( xQueueReceive( xTimerQueue, &xMessage, tmrNO_DELAY ) != pdFAIL )
+ {
+ pxTimer = xMessage.pxTimer;
+
+ /* Is the timer already in the list of active timers? */
+ prvRemoveTimerFromActiveList( pxTimer );
+
+ switch( xMessage.xMessageID )
+ {
+ case tmrCOMMAND_START : /* Start or restart a timer. */
+ xTimeToExpire = xTaskGetTickCount() + pxTimer->xTimerPeriodInTicks;
+ listSET_LIST_ITEM_VALUE( &( pxTimer->xTimerListItem ), xTimeToExpire );
+ listSET_LIST_ITEM_OWNER( &( pxTimer->xTimerListItem ), pxTimer );
+ vListInsert( &xActiveTimerList, &( pxTimer->xTimerListItem ) );
break;
- default : /* Don't expect to get here. */
+
+ default : /* Don't expect to get here. */
break;
- }
- }
}
}
}
@@ -280,24 +323,41 @@
}
/*-----------------------------------------------------------*/
-static void prvTimerStart( xTIMER *pxTimer )
+void *pvTimerGetTimerID( xTimerHandle xTimer )
{
-portTickType xTimeToWake;
+xTIMER *pxTimer = ( xTIMER * ) xTimer;
- if( pxTimer != NULL )
+ return pxTimer->pvTimerID;
+}
+/*-----------------------------------------------------------*/
+
+static void prvRemoveTimerFromActiveList( xTIMER *pxTimer )
+{
+ /* Is the timer already in the list of active timers? */
+ if( listIS_CONTAINED_WITHIN( NULL, &( pxTimer->xTimerListItem ) ) == pdFALSE )
{
- /* Is the timer already in the list of active timers? */
- prvRemoveTimerFromActiveList( pxTimer );
-
- xTimeToWake = xTaskGetTickCount() + pxTimer->xTimerPeriodInTicks;
- listSET_LIST_ITEM_VALUE( &( pxTimer->xTimerListItem ), xTimeToWake );
- listSET_LIST_ITEM_OWNER( &( pxTimer->xTimerListItem ), pxTimer );
- vListInsert( &xActiveTimerList, &( pxTimer->xTimerListItem ) );
+ /* The timer is in the list, remove it. */
+ vListRemove( &( pxTimer->xTimerListItem ) );
}
}
+/*-----------------------------------------------------------*/
+static portBASE_TYPE prvSendMessageToTimerServiceTask( xTIMER_MESSAGE *pxMessage, portTickType xBlockTime )
+{
+portBASE_TYPE xReturn;
+ if( xTaskGetSchedulerState() == taskSCHEDULER_RUNNING )
+ {
+ xReturn = xQueueSendToBack( xTimerQueue, pxMessage, xBlockTime );
+ }
+ else
+ {
+ xReturn = xQueueSendToBack( xTimerQueue, pxMessage, tmrNO_DELAY );
+ }
+ return xReturn;
+}
+/*-----------------------------------------------------------*/
