[−][src]Function esp_idf_sys::xTaskNotify

pub unsafe extern "C" fn xTaskNotify(
    xTaskToNotify: TaskHandle_t, 
    ulValue: u32, 
    eAction: eNotifyAction
) -> BaseType_t

Send task notification.

configUSE_TASK_NOTIFICATIONS must be undefined or defined as 1 for this function to be available.

When configUSE_TASK_NOTIFICATIONS is set to one each task has its own private "notification value", which is a 32-bit unsigned integer (uint32_t).

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 the task's notification value. 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 notification sent to a task will remain pending until it is cleared by the task calling xTaskNotifyWait() or ulTaskNotifyTake(). 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.

A task can use xTaskNotifyWait() to [optionally] block to wait for a notification to be pending, or ulTaskNotifyTake() to [optionally] block to wait for its notification value to have a non-zero value. The task does not consume any CPU time while it is in the Blocked state.

See http://www.FreeRTOS.org/RTOS-task-notifications.html for details.

@param 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().

@param ulValue Data that can be sent with the notification. How the data is used depends on the value of the eAction parameter.

@param eAction Specifies how the notification updates the task's notification value, if at all. Valid values for eAction are as follows:

  • eSetBits: The task's notification value is bitwise ORed with ulValue. xTaskNofify() always returns pdPASS in this case.

  • eIncrement: The task's notification value is incremented. ulValue is not used and xTaskNotify() always returns pdPASS in this case.

  • eSetValueWithOverwrite: The task's notification value is set to the value of ulValue, even if the task being notified had not yet processed the previous notification (the task already had a notification pending). xTaskNotify() always returns pdPASS in this case.

  • eSetValueWithoutOverwrite: If the task being notified did not already have a notification pending then the task's notification value is set to ulValue and xTaskNotify() will return pdPASS. If the task being notified already had a notification pending then no action is performed and pdFAIL is returned.

  • eNoAction: The task receives a notification without its notification value being   updated. ulValue is not used and xTaskNotify() always returns pdPASS in this case.

@return Dependent on the value of eAction. See the description of the eAction parameter.

\ingroup TaskNotifications