xQueueSendFromISR macro

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

{c}
 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 ();
  }
 }
 

Syntax

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Summary

Declaration

from queue.h:1133

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

Arguments

Argument

Description

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.