Chapter 2. API Reference
xTaskNotifyAndQuery(xTaskToNotify, ulValue, eAction, pulPreviousNotifyValue)
See https://www.FreeRTOS.org/RTOS-task-notifications.html for details.
xTaskNotifyAndQueryIndexed() performs the same operation as xTaskNotifyIndexed() with the addition that
it also returns the subject task’s prior notification value (the notification value at the time the function is called
rather than when the function returns) in the additional pulPreviousNotifyValue parameter.
xTaskNotifyAndQuery() performs the same operation as xTaskNotify() with the addition that it also returns
the subject task’s prior notification value (the notification value as it was at the time the function is called,
rather than when the function returns) in the additional pulPreviousNotifyValue parameter.
xTaskNotifyAndQueryIndexed(xTaskToNotify, uxIndexToNotify, ulValue, eAction, pulPrevious-
NotifyValue)
xTaskNotifyFromISR(xTaskToNotify, ulValue, eAction, pxHigherPriorityTaskWoken)
xTaskNotifyIndexedFromISR(xTaskToNotify, uxIndexToNotify, ulValue, eAction, pxHigherPriori-
tyTaskWoken)
xTaskNotifyAndQueryIndexedFromISR(xTaskToNotify, uxIndexToNotify, ulValue, eAction,
pulPreviousNotificationValue, pxHigherPriorityTaskWo-
ken)
See https://www.FreeRTOS.org/RTOS-task-notifications.html for details.
xTaskNotifyAndQueryIndexedFromISR() performs the same operation as xTaskNotifyIndexedFromISR()
with the addition that it also returns the subject task’s prior notification value (the notification value at the
time the function is called rather than at the time the function returns) in the additional pulPreviousNotifyValue
parameter.
xTaskNotifyAndQueryFromISR() performs the same operation as xTaskNotifyFromISR() with the addition
that it also returns the subject task’s prior notification value (the notification value at the time the function is
called rather than at the time the function returns) in the additional pulPreviousNotifyValue parameter.
xTaskNotifyAndQueryFromISR(xTaskToNotify, ulValue, eAction, pulPreviousNotificationValue,
pxHigherPriorityTaskWoken)
xTaskNotifyWait(ulBitsToClearOnEntry, ulBitsToClearOnExit, pulNotificationValue, xTicksToWait)
xTaskNotifyWaitIndexed(uxIndexToWaitOn, ulBitsToClearOnEntry, ulBitsToClearOnExit, pulNo-
tificationValue, xTicksToWait)
xTaskNotifyGive(xTaskToNotify)
Sends a direct to task notification to a particular index in the target task’s notification array in a manner similar
to giving a counting semaphore.
See https://www.FreeRTOS.org/RTOS-task-notifications.html for more details.
configUSE_TASK_NOTIFICATIONS must be undefined or defined as 1 for these macros to be available.
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.
xTaskNotifyGiveIndexed() is a helper macro intended for use when task notifications are used as light weight
and faster binary or counting semaphore equivalents. Actual FreeRTOS semaphores are given using the
xSemaphoreGive() API function, the equivalent action that instead uses a task notification is xTaskNotify-
GiveIndexed().
Espressif Systems 881
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