semphr. h

vSemaphoreCreateBinary( xSemaphoreHandle xSemaphore )

Macro that implements a semaphore by using the existing queue mechanism. The queue length is 1 as this is a binary semaphore. The data size is 0 as we don't want to actually store any data - we just want to know if the queue is empty or full.

This type of semaphore can be used for pure synchronisation between tasks or between an interrupt and a task. The semaphore need not be given back once obtained, so one task/interrupt can continuously 'give' the semaphore while another continuously 'takes' the semaphore. For this reason this type of semaphore does not use a priority inheritance mechanism. For an alternative that does use priority inheritance see xSemaphoreCreateMutex().

Parameters

xSemaphore Handle to the created semaphore. Should be of type xSemaphoreHandle.

Example usage:

 xSemaphoreHandle xSemaphore;

 void vATask( void * pvParameters )
 {
Semaphore cannot be used before a call to vSemaphoreCreateBinary ().
This is a macro so pass the variable in directly.
    vSemaphoreCreateBinary( xSemaphore );

    if( xSemaphore != NULL )
    {
The semaphore was created successfully.
The semaphore can now be used.  
    }
 }