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

Kernel
1

nobody wrote on Tuesday, 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.

2

nobody wrote on Tuesday, 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.

3

nobody wrote on Tuesday, 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.

4

imajeff wrote on Tuesday, April 18, 2006:

DMA uses interrupts too… It doesn’t stand for “Digital Magic Aware”, you know  :wink:

5

nobody wrote on Tuesday, April 18, 2006:

LOL

6

nobody wrote on Tuesday, 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.