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Task Block On Event (e.g. bit value)?

Posted by Nobody/Anonymous on April 18, 2006
Hello Richard,

Is there a way to write a task that will wait for an event to occur and unblock - that is - something like a bit twiddle? Is there a way to do this?

This will be helpful in developing a task that waits - for instance - for a UART RCV char flag that has set - then DMA the RCV char(s) into memory someplace.

TIA,
John W.

RE: Task Block On Event (e.g. bit value)?

Posted by Nobody/Anonymous on April 18, 2006
The kernel cannot know a bit has changed unless the bit change causes an interrupt. If an interrupt is generated then a semaphore could be used. If an interrupt was not generated then you would have to check the bit from the tick.

RE: Task Block On Event (e.g. bit value)?

Posted by Nobody/Anonymous on April 18, 2006
The idea here is to minimize interrupts - hence handing stuff off to the DMA controller.

So, a tickHook would have to be used to do this I suppose?

Thanks,
John W.

RE: Task Block On Event (e.g. bit value)?

Posted by Jeff Smith on April 18, 2006
DMA uses interrupts too... It doesn't stand for "Digital Magic Aware", you know ;-)

RE: Task Block On Event (e.g. bit value)?

Posted by Nobody/Anonymous on April 18, 2006
LOL

RE: Task Block On Event (e.g. bit value)?

Posted by Nobody/Anonymous on April 18, 2006
Some architectures allow you to use DMA with or without interrupts - take a look at the MSP430 -
it's up to you if you want to use interrupts or not
with the DMA channel controller.

Using this method vs. UART RCV IRQ's may help to reduce interrupt latency in an embedded system.

Regards,
John W.


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