Queue Sending from ISR

Group that contains macros & functions for sending queue data from an Interrupt Service Routine. More...

Collaboration diagram for Queue Sending from ISR:

Macros
#define	xQueueSendToFrontFromISR(xQueue, pvItemToQueue, pxHigherPriorityTaskWoken)   xQueueGenericSendFromISR( ( xQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_FRONT )
#define	xQueueSendToBackFromISR(xQueue, pvItemToQueue, pxHigherPriorityTaskWoken)   xQueueGenericSendFromISR( ( xQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_BACK )
#define	xQueueOverwriteFromISR(xQueue, pvItemToQueue, pxHigherPriorityTaskWoken)   xQueueGenericSendFromISR( ( xQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueOVERWRITE )
#define	xQueueSendFromISR(xQueue, pvItemToQueue, pxHigherPriorityTaskWoken)   xQueueGenericSendFromISR( ( xQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_BACK )

Functions
BaseType_t	xQueueGenericSendFromISR (QueueHandle_t xQueue, const void *const pvItemToQueue, BaseType_t *const pxHigherPriorityTaskWoken, const BaseType_t xCopyPosition) PRIVILEGED_FUNCTION

Detailed Description

Group that contains macros & functions for sending queue data from an Interrupt Service Routine.

Macro Definition Documentation

xQueueOverwriteFromISR

#define xQueueOverwriteFromISR	(		xQueue,
			pvItemToQueue,
			pxHigherPriorityTaskWoken
	)		xQueueGenericSendFromISR( ( xQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueOVERWRITE )

#include <queue.h>

BaseType_t xQueueOverwriteFromISR(
                             QueueHandle_t xQueue,
                             const void * pvItemToQueue,
                             BaseType_t *pxHigherPriorityTaskWoken
                        );

A version of xQueueOverwrite() that can be used in an interrupt service routine (ISR).

Only for use with queues that can hold a single item - so the queue is either empty or full.

Post an item on a queue. If the queue is already full then overwrite the value held in the queue. The item is queued by copy, not by reference.

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.
pxHigherPriorityTaskWoken	xQueueOverwriteFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task to unblock, and the unblocked task has a priority higher than the currently running task. If xQueueOverwriteFromISR() sets this value to pdTRUE then a context switch should be requested before the interrupt is exited.

Returns

xQueueOverwriteFromISR() is a macro that calls xQueueGenericSendFromISR(), and therefore has the same return values as xQueueSendToFrontFromISR(). However, pdPASS is the only value that can be returned because xQueueOverwriteFromISR() will write to the queue even when the queue is already full.

Example usage:

 QueueHandle_t xQueue;
 
 void vFunction( void *pvParameters )
 {
    // Create a queue to hold one uint32_t value.  It is strongly
    // recommended *not* to use xQueueOverwriteFromISR() on queues that can
    // contain more than one value, and doing so will trigger an assertion
    // if configASSERT() is defined.
    xQueue = xQueueCreate( 1, sizeof( uint32_t ) );
}
 
void vAnInterruptHandler( void )
{
// xHigherPriorityTaskWoken must be set to pdFALSE before it is used.
BaseType_t xHigherPriorityTaskWoken = pdFALSE;
uint32_t ulVarToSend, ulValReceived;
 
    // Write the value 10 to the queue using xQueueOverwriteFromISR().
    ulVarToSend = 10;
    xQueueOverwriteFromISR( xQueue, &ulVarToSend, &xHigherPriorityTaskWoken );
 
    // The queue is full, but calling xQueueOverwriteFromISR() again will still
    // pass because the value held in the queue will be overwritten with the
    // new value.
    ulVarToSend = 100;
    xQueueOverwriteFromISR( xQueue, &ulVarToSend, &xHigherPriorityTaskWoken );
 
    // Reading from the queue will now return 100.
 
    // ...
 
    if( xHigherPrioritytaskWoken == pdTRUE )
    {
        // Writing to the queue caused a task to unblock and the unblocked task
        // has a priority higher than or equal to the priority of the currently
        // executing task (the task this interrupt interrupted).  Perform a context
        // switch so this interrupt returns directly to the unblocked task.
        portYIELD_FROM_ISR(); // or portEND_SWITCHING_ISR() depending on the port.
    }
}

xQueueSendFromISR

#define xQueueSendFromISR	(		xQueue,
			pvItemToQueue,
			pxHigherPriorityTaskWoken
	)		xQueueGenericSendFromISR( ( xQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_BACK )

#include <queue.h>

BaseType_t xQueueSendFromISR(
                                    QueueHandle_t xQueue,
                                    const void *pvItemToQueue,
                                    BaseType_t *pxHigherPriorityTaskWoken
                               );

This is a macro that calls xQueueGenericSendFromISR(). It is included for backward compatibility with versions of FreeRTOS.org that did not include the xQueueSendToBackFromISR() and xQueueSendToFrontFromISR() macros.

Post an item to the back of a queue. It is safe to use this function from within an interrupt service routine.

Items are queued by copy not reference so it is preferable to only queue small items, especially when called from an ISR. In most cases it would be preferable to store a pointer to the item being queued.

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.
pxHigherPriorityTaskWoken	xQueueSendFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task to unblock, and the unblocked task has a priority higher than the currently running task. If xQueueSendFromISR() sets this value to pdTRUE then a context switch should be requested before the interrupt is exited.

Returns

pdTRUE if the data was successfully sent to the queue, otherwise errQUEUE_FULL.

Example usage for buffered IO (where the ISR can obtain more than one value per call):

void vBufferISR( void )
{
char cIn;
BaseType_t xHigherPriorityTaskWoken;
 
   // We have not woken a task at the start of the ISR.
   xHigherPriorityTaskWoken = pdFALSE;
 
   // Loop until the buffer is empty.
   do
   {
       // Obtain a byte from the buffer.
       cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );
 
       // Post the byte.
       xQueueSendFromISR( xRxQueue, &cIn, &xHigherPriorityTaskWoken );
 
   } while( portINPUT_BYTE( BUFFER_COUNT ) );
 
   // Now the buffer is empty we can switch context if necessary.
   if( xHigherPriorityTaskWoken )
   {
       // Actual macro used here is port specific.
       portYIELD_FROM_ISR ();
   }
}

xQueueSendToBackFromISR

#define xQueueSendToBackFromISR	(		xQueue,
			pvItemToQueue,
			pxHigherPriorityTaskWoken
	)		xQueueGenericSendFromISR( ( xQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_BACK )

#include <queue.h>

BaseType_t xQueueSendToBackFromISR(
                                        QueueHandle_t xQueue,
                                        const void *pvItemToQueue,
                                        BaseType_t *pxHigherPriorityTaskWoken
                                     );

This is a macro that calls xQueueGenericSendFromISR().

Post an item to the back of a queue. It is safe to use this macro from within an interrupt service routine.

Items are queued by copy not reference so it is preferable to only queue small items, especially when called from an ISR. In most cases it would be preferable to store a pointer to the item being queued.

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.
pxHigherPriorityTaskWoken	xQueueSendToBackFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task to unblock, and the unblocked task has a priority higher than the currently running task. If xQueueSendToBackFromISR() sets this value to pdTRUE then a context switch should be requested before the interrupt is exited.

Returns

pdTRUE if the data was successfully sent to the queue, otherwise errQUEUE_FULL.

Example usage for buffered IO (where the ISR can obtain more than one value per call):

void vBufferISR( void )
{
char cIn;
BaseType_t xHigherPriorityTaskWoken;
 
   // We have not woken a task at the start of the ISR.
   xHigherPriorityTaskWoken = pdFALSE;
 
   // Loop until the buffer is empty.
   do
   {
       // Obtain a byte from the buffer.
       cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );
 
       // Post the byte.
       xQueueSendToBackFromISR( xRxQueue, &cIn, &xHigherPriorityTaskWoken );
 
   } while( portINPUT_BYTE( BUFFER_COUNT ) );
 
   // Now the buffer is empty we can switch context if necessary.
   if( xHigherPriorityTaskWoken )
   {
       taskYIELD ();
   }
}

xQueueSendToFrontFromISR

#define xQueueSendToFrontFromISR	(		xQueue,
			pvItemToQueue,
			pxHigherPriorityTaskWoken
	)		xQueueGenericSendFromISR( ( xQueue ), ( pvItemToQueue ), ( pxHigherPriorityTaskWoken ), queueSEND_TO_FRONT )

#include <queue.h>

BaseType_t xQueueSendToFrontFromISR(
                                        QueueHandle_t xQueue,
                                        const void *pvItemToQueue,
                                        BaseType_t *pxHigherPriorityTaskWoken
                                     );

This is a macro that calls xQueueGenericSendFromISR().

Post an item to the front of a queue. It is safe to use this macro from within an interrupt service routine.

Items are queued by copy not reference so it is preferable to only queue small items, especially when called from an ISR. In most cases it would be preferable to store a pointer to the item being queued.

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.
pxHigherPriorityTaskWoken	xQueueSendToFrontFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task to unblock, and the unblocked task has a priority higher than the currently running task. If xQueueSendToFromFromISR() sets this value to pdTRUE then a context switch should be requested before the interrupt is exited.

Returns

pdTRUE if the data was successfully sent to the queue, otherwise errQUEUE_FULL.

Example usage for buffered IO (where the ISR can obtain more than one value per call):

void vBufferISR( void )
{
char cIn;
BaseType_t xHigherPrioritTaskWoken;
 
   // We have not woken a task at the start of the ISR.
   xHigherPriorityTaskWoken = pdFALSE;
 
   // Loop until the buffer is empty.
   do
   {
       // Obtain a byte from the buffer.
       cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );
 
       // Post the byte.
       xQueueSendToFrontFromISR( xRxQueue, &cIn, &xHigherPriorityTaskWoken );
 
   } while( portINPUT_BYTE( BUFFER_COUNT ) );
 
   // Now the buffer is empty we can switch context if necessary.
   if( xHigherPriorityTaskWoken )
   {
       taskYIELD ();
   }
}

Function Documentation

xQueueGenericSendFromISR()

BaseType_t xQueueGenericSendFromISR	(	QueueHandle_t	xQueue,
		const void *const	pvItemToQueue,
		BaseType_t *const	pxHigherPriorityTaskWoken,
		const BaseType_t	xCopyPosition
	)

#include <queue.h>

BaseType_t xQueueGenericSendFromISR(
                                          QueueHandle_t        xQueue,
                                          const    void    *pvItemToQueue,
                                          BaseType_t   *pxHigherPriorityTaskWoken,
                                          BaseType_t   xCopyPosition
                                      );

It is preferred that the macros xQueueSendFromISR(), xQueueSendToFrontFromISR() and xQueueSendToBackFromISR() be used in place of calling this function directly. xQueueGiveFromISR() is an equivalent for use by semaphores that don't actually copy any data.

Post an item on a queue. It is safe to use this function from within an interrupt service routine.

Items are queued by copy not reference so it is preferable to only queue small items, especially when called from an ISR. In most cases it would be preferable to store a pointer to the item being queued.

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.
pxHigherPriorityTaskWoken	xQueueGenericSendFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE if sending to the queue caused a task to unblock, and the unblocked task has a priority higher than the currently running task. If xQueueGenericSendFromISR() sets this value to pdTRUE then a context switch should be requested before the interrupt is exited.
xCopyPosition	Can take the value queueSEND_TO_BACK to place the item at the back of the queue, or queueSEND_TO_FRONT to place the item at the front of the queue (for high priority messages).

Returns

pdTRUE if the data was successfully sent to the queue, otherwise errQUEUE_FULL.

Example usage for buffered IO (where the ISR can obtain more than one value per call):

void vBufferISR( void )
{
char cIn;
BaseType_t xHigherPriorityTaskWokenByPost;
 
   // We have not woken a task at the start of the ISR.
   xHigherPriorityTaskWokenByPost = pdFALSE;
 
   // Loop until the buffer is empty.
   do
   {
       // Obtain a byte from the buffer.
       cIn = portINPUT_BYTE( RX_REGISTER_ADDRESS );
 
       // Post each byte.
       xQueueGenericSendFromISR( xRxQueue, &cIn, &xHigherPriorityTaskWokenByPost, queueSEND_TO_BACK );
 
   } while( portINPUT_BYTE( BUFFER_COUNT ) );
 
   // Now the buffer is empty we can switch context if necessary.  Note that the
   // name of the yield function required is port specific.
   if( xHigherPriorityTaskWokenByPost )
   {
       taskYIELD_YIELD_FROM_ISR();
   }
}