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Remapping semaphore API

Posted by G40 on June 23, 2012
In order to get AD driver code working I need to implement some wrappers for AD semaphores.

1. Create and Delete are simple.
2. Post() maps onto Give(), or possibly GiveFromISR().

What happens if the latter is called at non-ISR level? Presumably it works?

3. Pend() maps onto Take()

4. Not sure about Query().

This returns the semaphore count in the default AD library code. Can I do the same in FreeRTOS?

Many thanks

Jerry.

RE: Remapping semaphore API

Posted by Richard on June 23, 2012
“What happens if the latter is called at non-ISR level? Presumably it works? ”


It will work, but does not give an option to block (as you can't block in an ISR), and will normally need a critical section around it if it is called at the task level. [that may depend on the port though]. It is relatively common to use the FromISR versions from tasks because, as they have less functionality (blocking, etc.), they are faster to execute.

“4. Not sure about Query(). This returns the semaphore count in the default AD library code. Can I do the same in FreeRTOS? ”


You can use the xQueueMessagesWaiting() and xQueueMessagesWaitingFromISR() function by just casting the xSemaphoreHandle variable to an xQueueHandle when you pass it into the function. That will give you the semaphore count.

Regards.

RE: Remapping semaphore API

Posted by G40 on June 24, 2012
Thanks again, Richard. The help is greatly appreciated.


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