Hi Frederico,
If you haven't, you should read Philip Levis' excellent TinyOS Programming
guide, here:
http://csl.stanford.edu/~pal/pubs/tinyos-programming.pdf
Section 4.1 covers split phase operations.
On Monday 07 May 2007 13:54, Federico Spadini wrote:
> 1) Am I allowed to have a return XXX at the end of an event? If so who
> does this value get returned to?
Events, as defined in interface definitions, identify the return value for an
event. Most events return void, but look at Receive.receive() for an example
of one that doesn't. The code signalling the event gets the return code. The
event is just like a call-back function.
> a. If so, is it bad programming practice to leave this out?
If there is a mismatch in return values, you'll get an error when you build
the code.
> 2) Am I allowed to call two events i.e.:
> event void Timer0.fired() {
> call ReadBroadband.read();
> call ReadIR.read();
> }
If your question is "Am I allowed to call to commands", then yes. Events are
not called, but signalled.
> If so, does the "call" drill all the way down to the actual function which
> initiates a read immediately, or is there an event queue separate from the
> task queue?
There is no event queue, so an implementation of Read.read() must initiate the
read immediately. But that first step may be several steps removed from
actually acquiring the read data. For example, read may call to another
split-phase operation to acquire a resource.
> Which is executed at the end of the event?
> Do these events execute in order?
I don't understand these questions.
> 3) Can events pre-empt other events? If I have just been put in my
> ReadBroadband.readDone and I receive another even how is this handled? What
> happens if I receive an event during an interrupt handler (or async event)?
An event running in task context can be preempted by an event running in async
context. Events cannot run in async context unless they have the "async"
keyword in their definition. I believe you can safely consider async context
in TinyOS to be equivalent to the uC's interrupt context.
Hope this helps,
Steve
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