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@@ -867,7 +867,10 @@ void vTaskDelete( TaskHandle_t xTaskToDelete ) PRIVILEGED_FUNCTION;
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*----------------------------------------------------------*/
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/**
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- * Delay a task for a given number of ticks.
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+ * task. h
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+ * @code{c}
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+ * void vTaskDelay( const TickType_t xTicksToDelay );
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+ * @endcode
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*
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* Delay a task for a given number of ticks. The actual time that the
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* task remains blocked depends on the tick rate. The constant
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@@ -885,7 +888,7 @@ void vTaskDelete( TaskHandle_t xTaskToDelete ) PRIVILEGED_FUNCTION;
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* of controlling the frequency of a periodic task as the path taken through the
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* code, as well as other task and interrupt activity, will effect the frequency
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* at which vTaskDelay() gets called and therefore the time at which the task
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- * next executes. See vTaskDelayUntil() for an alternative API function designed
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+ * next executes. See xTaskDelayUntil() for an alternative API function designed
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* to facilitate fixed frequency execution. It does this by specifying an
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* absolute time (rather than a relative time) at which the calling task should
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* unblock.
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@@ -917,9 +920,12 @@ void vTaskDelete( TaskHandle_t xTaskToDelete ) PRIVILEGED_FUNCTION;
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void vTaskDelay( const TickType_t xTicksToDelay ) PRIVILEGED_FUNCTION;
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/**
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- * Delay a task until a specified time.
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+ * task. h
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+ * @code{c}
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+ * BaseType_t xTaskDelayUntil( TickType_t *pxPreviousWakeTime, const TickType_t xTimeIncrement );
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+ * @endcode
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*
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- * INCLUDE_vTaskDelayUntil must be defined as 1 for this function to be available.
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+ * INCLUDE_xTaskDelayUntil must be defined as 1 for this function to be available.
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* See the configuration section for more information.
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*
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* Delay a task until a specified time. This function can be used by periodic
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@@ -934,22 +940,26 @@ void vTaskDelay( const TickType_t xTicksToDelay ) PRIVILEGED_FUNCTION;
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* each time it executes].
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*
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* Whereas vTaskDelay () specifies a wake time relative to the time at which the function
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- * is called, vTaskDelayUntil () specifies the absolute (exact) time at which it wishes to
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+ * is called, xTaskDelayUntil () specifies the absolute (exact) time at which it wishes to
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* unblock.
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*
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- * The constant portTICK_PERIOD_MS can be used to calculate real time from the tick
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- * rate - with the resolution of one tick period.
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+ * The macro pdMS_TO_TICKS() can be used to calculate the number of ticks from a
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+ * time specified in milliseconds with a resolution of one tick period.
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*
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* @param pxPreviousWakeTime Pointer to a variable that holds the time at which the
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* task was last unblocked. The variable must be initialised with the current time
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* prior to its first use (see the example below). Following this the variable is
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- * automatically updated within vTaskDelayUntil ().
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+ * automatically updated within xTaskDelayUntil ().
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*
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* @param xTimeIncrement The cycle time period. The task will be unblocked at
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- * time *pxPreviousWakeTime + xTimeIncrement. Calling vTaskDelayUntil with the
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+ * time *pxPreviousWakeTime + xTimeIncrement. Calling xTaskDelayUntil with the
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* same xTimeIncrement parameter value will cause the task to execute with
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* a fixed interface period.
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*
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+ * @return Value which can be used to check whether the task was actually delayed.
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+ * Will be pdTRUE if the task way delayed and pdFALSE otherwise. A task will not
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+ * be delayed if the next expected wake time is in the past.
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+ *
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* Example usage:
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* @code{c}
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* // Perform an action every 10 ticks.
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@@ -957,15 +967,17 @@ void vTaskDelay( const TickType_t xTicksToDelay ) PRIVILEGED_FUNCTION;
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* {
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* TickType_t xLastWakeTime;
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* const TickType_t xFrequency = 10;
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+ * BaseType_t xWasDelayed;
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*
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* // Initialise the xLastWakeTime variable with the current time.
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* xLastWakeTime = xTaskGetTickCount ();
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* for( ;; )
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* {
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* // Wait for the next cycle.
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- * vTaskDelayUntil( &xLastWakeTime, xFrequency );
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+ * xWasDelayed = xTaskDelayUntil( &xLastWakeTime, xFrequency );
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*
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- * // Perform action here.
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+ * // Perform action here. xWasDelayed value can be used to determine
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+ * // whether a deadline was missed if the code here took too long.
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* }
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* }
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* @endcode
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@@ -974,9 +986,19 @@ void vTaskDelay( const TickType_t xTicksToDelay ) PRIVILEGED_FUNCTION;
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* @endcond
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* \ingroup TaskCtrl
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*/
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-void vTaskDelayUntil( TickType_t * const pxPreviousWakeTime,
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+BaseType_t xTaskDelayUntil( TickType_t * const pxPreviousWakeTime,
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const TickType_t xTimeIncrement ) PRIVILEGED_FUNCTION;
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+/*
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+ * vTaskDelayUntil() is the older version of xTaskDelayUntil() and does not
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+ * return a value.
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+ */
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+#define vTaskDelayUntil( pxPreviousWakeTime, xTimeIncrement ) \
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+{ \
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+ ( void ) xTaskDelayUntil( pxPreviousWakeTime, xTimeIncrement ); \
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+}
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+
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+
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/**
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* @cond
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* task. h
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Zim Kalinowski