Macro to obtain a semaphore. The semaphore must have previously been created with a call to xSemaphoreCreateBinary(), xSemaphoreCreateMutex() or xSemaphoreCreateCounting(). Example usage:
SemaphoreHandle_t xSemaphore = NULL;
// A task that creates a semaphore.
void vATask( void * pvParameters )
{
// Create the semaphore to guard a shared resource.
xSemaphore = xSemaphoreCreateBinary();
}
// A task that uses the semaphore.
void vAnotherTask( void * pvParameters )
{
// ... Do other things.
if( xSemaphore != NULL )
{
// See if we can obtain the semaphore. If the semaphore is not available
// wait 10 ticks to see if it becomes free.
if( xSemaphoreTake( xSemaphore, ( TickType_t ) 10 ) == pdTRUE )
{
// We were able to obtain the semaphore and can now access the
// shared resource.
// ...
// We have finished accessing the shared resource. Release the
// semaphore.
xSemaphoreGive( xSemaphore );
}
else
{
// We could not obtain the semaphore and can therefore not access
// the shared resource safely.
}
}
}