[Tinyos-devel] Re: [Tinyos Core WG] time sync interfaces

[Omprakash Gnawali]

In what cases is a few-millisecond time synchronization useful? An
application that does occasional temperature and light sensing
probably can just use the time of arrival at the base station as time.
Phil, is this the class of application you were thinking of when you
said 90% cases?

- om_p

On Dec 18, 2007 3:09 PM, Matt Welsh <mdw at eecs.harvard.edu> wrote:
> The applications that we study generally require millisecond or better
> time synchronization. In general anything that is timing sensitive is
> going to want to exploit the capabilities of the platform on which it
> is being developed. A platform-independent time interface is not very
> useful in these cases. If we're concerned about things like
> portability for, say, time sync protocols, I suggest that we make the
> datatype representing time be very fine-grained (say, 1 usec or
> better) and provide a compile-time constant indicating the true
> resolution.
>
> Matt
>
>
>
> On Dec 18, 2007, at 5:30 PM, Omprakash Gnawali wrote:
>
> > On Dec 18, 2007 2:09 PM, David Gay <dgay42 at gmail.com> wrote:
> >> On Dec 18, 2007 2:03 PM, John Griessen <john at ecosensory.com> wrote:
> >>> David Gay wrote:
> >>>
> >>>> Surely that depends on what resolution timesync you think is
> >>>> worthwhile? My assumption is that different apps have different
> >>>> precision requirements, from second-level timesync down to
> >>>> microsecond-level timesync. I'm fairly sure that second-level
> >>>> timesync
> >>>> doesn't require an adjustable PLL oscillator ;-)
> >>>
> >>> OK.  Yes, a .1 second resolution HIL module would be a go...
> >>> and yes that is more useful than systems out of sync by half a
> >>> second...
> >>>
> >>> Any chance we have of using the most deterministic delays coming
> >>> from the hardware
> >>> we should take it is all I meant.
> >>>
> >>> What time accuracy do you call a useful timesync on our current
> >>> platforms?
> >>
> >> Well I was asking that question too, actually ;-) I'm not an
> >> application developper/expert, so I can't really answer.
> >>
> >> David
> >> PS: I suspect with reasonable evidence that millisecond level
> >> timesync
> >> is practical.
> >>
> >
> > Or you might need more if you look at the applications that use FTSP:
> > seismic monitoring by various groups and certain flavor of
> > localization.
> >
> > - om_p
>
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