Waiting for more than one MsgQs

grumpy1234 wrote on Tuesday, September 25, 2007:

Hi everyone

I have some basic questions to freeRTOS:
Is it possible to build a task which waits (blocks) for a semaphore (triggered by a timer interrupt or external HW interrupt) and a message queue at the same time and gets unblocked by either the semaphore or the message queue (whatever event happens first)?  Or for several message queues? If that is not possible, which is the best way to implement it?


rtel wrote on Tuesday, September 25, 2007:

You can implement this by using one queue, then having the data that is posted to the queue contain a code as to what the data contains.  For example:

typedef struct
____unsigned portLONG ulCode;
____unsigned portLONG ulValue;
} xData;


void vHandleEvents( void )
____xQueueReceive( xQueue, &xData, portMAX_DELAY );
____switch( xData.ulCode )
________case SEMAPHORE_DATA : /* Processing as if it was the semaphore goes here. */
________case QUEUE_DATA     : /* Processing as if it was the queue goes here. */
                              ulReceivedValue = xData.ulValue;

When you send data to the queue, you send an xData object with ulCode set to QUEUE_DATA, and ulValue set to the value you want to post.  Etc.