Chapter 2. API Reference
to configure a peripheral timer/counter and return the timers current count value respectively. The counter
should be at least 10 times the frequency of the tick count.
Setting configGENERATE_RUN_TIME_STATS to 1 will result in a total accumulated execution time being
stored for each task. The resolution of the accumulated time value depends on the frequency of the timer con-
figured by the portCONFIGURE_TIMER_FOR_RUN_TIME_STATS() macro. While uxTaskGetSystem-
State() and vTaskGetRunTimeStats() writes the total execution time of each task into a buffer, ulTaskGetI-
dleRunTimeCounter() returns the total execution time of just the idle task.
Return The total run time of the idle task. This is the amount of time the idle task has actually
been executing. The unit of time is dependent on the frequency configured using the portCON-
FIGURE_TIMER_FOR_RUN_TIME_STATS() and portGET_RUN_TIME_COUNTER_VALUE()
macros.
BaseType_t xTaskGenericNotify(TaskHandle_t xTaskToNotify, UBaseType_t uxIndexToNo-
tify, uint32_t ulValue, eNotifyAction eAction, uint32_t
*pulPreviousNotificationValue)
See https://www.FreeRTOS.org/RTOS-task-notifications.html for details.
configUSE_TASK_NOTIFICATIONS must be undefined or defined as 1 for these functions to be available.
Sends a direct to task notification to a task, with an optional value and action.
Each task has a private array of “notification values”(or ‘notifications’), each of which is a 32-bit un-
signed integer (uint32_t). The constant configTASK_NOTIFICATION_ARRAY_ENTRIES sets the number
of indexes in the array, and (for backward compatibility) defaults to 1 if left undefined. Prior to FreeRTOS
V10.4.0 there was only one notification value per task.
Events can be sent to a task using an intermediary object. Examples of such objects are queues, semaphores,
mutexes and event groups. Task notifications are a method of sending an event directly to a task without the
need for such an intermediary object.
A notification sent to a task can optionally perform an action, such as update, overwrite or increment one of
the task’s notification values. In that way task notifications can be used to send data to a task, or be used as
light weight and fast binary or counting semaphores.
A task can use xTaskNotifyWaitIndexed() to [optionally] block to wait for a notification to be pending, or
ulTaskNotifyTakeIndexed() to [optionally] block to wait for a notification value to have a non-zero value. The
task does not consume any CPU time while it is in the Blocked state.
A notification sent to a task will remain pending until it is cleared by the task calling xTaskNotifyWaitIndexed()
or ulTaskNotifyTakeIndexed() (or their un-indexed equivalents). If the task was already in the Blocked state
to wait for a notification when the notification arrives then the task will automatically be removed from the
Blocked state (unblocked) and the notification cleared.
NOTE Each notification within the array operates independently - a task can only block on one notification
within the array at a time and will not be unblocked by a notification sent to any other array index.
Backward compatibility information: Prior to FreeRTOS V10.4.0 each task had a single “notification value”
, and all task notification API functions operated on that value. Replacing the single notification value with
an array of notification values necessitated a new set of API functions that could address specific notifications
within the array. xTaskNotify() is the original API function, and remains backward compatible by always
operating on the notification value at index 0 in the array. Calling xTaskNotify() is equivalent to calling xTas-
kNotifyIndexed() with the uxIndexToNotify parameter set to 0.
eSetBits - The target notification value is bitwise ORed with ulValue. xTaskNotifyIndexed() always returns
pdPASS in this case.
Parameters
• xTaskToNotify: The handle of the task being notified. The handle to a task can be returned
from the xTaskCreate() API function used to create the task, and the handle of the currently running
task can be obtained by calling xTaskGetCurrentTaskHandle().
• uxIndexToNotify: The index within the target task’s array of notification values
to which the notification is to be sent. uxIndexToNotify must be less than config-
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