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xQueueSendToBack
[Queue Management]

Only available from FreeRTOS.org V4.5.0 onwards.

queue.h

 portBASE_TYPE xQueueSendToBack(
                                   xQueueHandle xQueue,
                                   const void * pvItemToQueue,
                                   portTickType xTicksToWait
                               );
 

This is a macro that calls xQueueGenericSend(). It is equivalent to xQueueSend().

Post an item to the back of a queue. The item is queued by copy, not by reference. This function must not be called from an interrupt service routine. See xQueueSendToBackFromISR () for an alternative which may be used in an ISR.

xQueueSendToBack() is part of the fully featured intertask communications API. xQueueAltSendToBack() is the alternative API equivalent. Both versions require the same parameters and return the same values.

Parameters:

xQueue	The handle to the queue on which the item is to be posted.
pvItemToQueue	A pointer to the item that is to be placed on the queue. The size of the items the queue will hold was defined when the queue was created, so this many bytes will be copied from pvItemToQueue into the queue storage area.
xTicksToWait	The maximum amount of time the task should block waiting for space to become available on the queue, should it already be full. The call will return immediately if this is set to 0. The time is defined in tick periods so the constant portTICK_RATE_MS should be used to convert to real time if this is required. If INCLUDE_vTaskSuspend is set to '1' then specifying the block time as portMAX_DELAY will cause the task to block indefinitely (without a timeout).

Returns:

pdTRUE if the item was successfully posted, otherwise errQUEUE_FULL.

Example usage:

 struct AMessage
 {
    portCHAR ucMessageID;
    portCHAR ucData[ 20 ];
 } xMessage;

 unsigned portLONG ulVar = 10UL;

 void vATask( void *pvParameters )
 {
 xQueueHandle xQueue1, xQueue2;
 struct AMessage *pxMessage;

    // Create a queue capable of containing 10 unsigned long values.
    xQueue1 = xQueueCreate( 10, sizeof( unsigned portLONG ) );

    // Create a queue capable of containing 10 pointers to AMessage structures.
    // These should be passed by pointer as they contain a lot of data.
    xQueue2 = xQueueCreate( 10, sizeof( struct AMessage * ) );

    // ...

    if( xQueue1 != 0 )
    {
        // Send an unsigned long.  Wait for 10 ticks for space to become 
        // available if necessary.
        if( xQueueSendToBack( xQueue1, ( void * ) &ulVar, ( portTickType ) 10 ) != pdPASS )
        {
            // Failed to post the message, even after 10 ticks.
        }
    }

    if( xQueue2 != 0 )
    {
        // Send a pointer to a struct AMessage object.  Don't block if the
        // queue is already full.
        pxMessage = & xMessage;
        xQueueSendToBack( xQueue2, ( void * ) &pxMessage, ( portTickType ) 0 );
    }

	// ... Rest of task code.
 }
 

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