The FreeRTOS kernel is now an MIT licensed AWS open source project, and these pages are being updated accordingly.

Quality RTOS & Embedded Software

About Contact Support FAQ Download

Menu

Quick Start

Supported MCUs

PDF Books

Trace Tools

Ecosystem

Quick Start Guide

Support Forum

⇓ Download Source ⇓

FreeRTOS+ Ecosystem

FreeRTOS+TCP:
Thread safe TCP/IP stack

SafeRTOS:
TUV certified RTOS

OpenRTOS:
Commercial Licensed RTOS

Fail Safe File System:
Ensures data integrity

FreeRTOS BSPs:
3rd party driver packages

Trace & Visualisation:
Tracealyzer for FreeRTOS

CLI:
Command line interface

WolfSSL SSL / TLS:
Networking security protocols

RTOS Training:
Delivered online or on-site

IO:
read(), write(), ioctl() interface

FreeRTOS+ Lab Projects

FreeRTOS+POSIX:
POSIX threading API

FreeRTOS+FAT:
Thread aware file system

xQueueSendToBack
[Queue Management]

queue.h


 BaseType_t xQueueSendToBack(
                                   QueueHandle_t xQueue,
                                   const void * pvItemToQueue,
                                   TickType_t 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.

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_PERIOD_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
{
    char ucMessageID;
    char ucData[ 20 ];
} xMessage;

unsigned long ulVar = 10UL;

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

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

    /* 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,
                             ( TickType_t ) 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, ( TickType_t ) 0 );
    }

	/* ... Rest of task code. */
}