Download FreeRTOS

Quality RTOS & Embedded Software

FreeRTOS website now available in Simplified Chinese
New FreeRTOS Long Term Support version now available.
FreeRTOS Extended Maintenance Program (EMP) registration now open.
FreeRTOS-Plus-TCP v3.0.0 released:
Featured FreeRTOS IoT Integrations:

[Queue Management]

queue. h
 QueueHandle_t xQueueCreateStatic(
                             UBaseType_t uxQueueLength,
                             UBaseType_t uxItemSize,
                             uint8_t *pucQueueStorageBuffer,
                             StaticQueue_t *pxQueueBuffer );

Creates a new queue and returns a handle by which the queue can be referenced. configSUPPORT_STATIC_ALLOCATION must be set to 1 in FreeRTOSConfig.h for this RTOS API function to be available.

Each queue requires RAM that is used to hold the queue state, and to hold the items that are contained in the queue (the queue storage area). If a queue is created using xQueueCreate() then this RAM is automatically allocated from the FreeRTOS heap. If a queue is created using xQueueCreateStatic() then the RAM is provided by the application writer, which results in a greater number of parameters, but allows the RAM to be statically allocated at compile time. See the Static Vs Dynamic allocation page for more information.

uxQueueLength   The maximum number of items the queue can hold at any one time.
uxItemSize   The size, in bytes, required to hold each item in the queue.

Items are queued by copy, not by reference, so this is the number of bytes that will be copied for each queued item. Each item in the queue must be the same size.

pucQueueStorageBuffer   If uxItemSize is not zero then pucQueueStorageBuffer must point to a uint8_t array that is at least large enough to hold the maximum number of items that can be in the queue at any one time - which is ( uxQueueLength * uxItemSize ) bytes. If uxItemSize is zero then pucQueueStorageBuffer can be NULL.
pxQueueBuffer   Must point to a variable of type StaticQueue_t, which will be used to hold the queue's data structure.
If the queue is created successfully then a handle to the created queue is returned. If pxQueueBuffer is NULL then NULL is returned.
Example usage:
/* The queue is to be created to hold a maximum of 10 uint64_t
variables. */
#define QUEUE_LENGTH    10
#define ITEM_SIZE       sizeof( uint64_t )

/* The variable used to hold the queue's data structure. */
static StaticQueue_t xStaticQueue;

/* The array to use as the queue's storage area.  This must be at least
uxQueueLength * uxItemSize bytes. */
uint8_t ucQueueStorageArea[ QUEUE_LENGTH * ITEM_SIZE ];

void vATask( void *pvParameters )
QueueHandle_t xQueue;

    /* Create a queue capable of containing 10 uint64_t values. */
    xQueue = xQueueCreateStatic( QUEUE_LENGTH,
                                 &xStaticQueue );

    /* pxQueueBuffer was not NULL so xQueue should not be NULL. */
    configASSERT( xQueue );

Copyright (C) Amazon Web Services, Inc. or its affiliates. All rights reserved.