NetBurner 3.3
Semaphore

A semaphore is a protected variable that is used to control access to shared system resources (such as memory or serial ports), to signal the occurrence of events and task synchronization. A task can request a semaphore and wait until the resource or event takes place (called pending). A task can also post to a semaphore to indicate it no longer needs a resource, or to signal an event has taken place. To create a semaphore you declare one of type OS_SEM and initialize with OSSemInit(): OS_SEM MySemaphore; OSSemInit( &MySemaphore, 0 ); // set initial value to 0

Your application tasks can now use the post and pend functions on the semaphore: OSSemPost( &MySemaphore ); // post to a semaphore OSSemPend( &MySemaphore, 0 ); // pend on a semaphore

The second parameter in the OSSemPend() function specifies the number of time ticks to wait. A value of 0 waits forever. A good way to express a wait value is to use the TICKS_PER_SECOND definition provided by the RTOS: OSSemPend( &MySemaphore, TICKS_PER_SECOND * 5) to wait 5 seconds.