[Tinyos Core WG] Issue with sampling multiple sensors

[David Gay]

On 5/23/07, Vlado Handziski <handzisk at tkn.tu-berlin.de> wrote:
> I fully agree with Jan. If someone needs this level of performance, then
> they should use HAL level abstractions. That is the reason why they are
> there. Otherwise, we could have had monolithic implementations of the HIL
> abstractions.

Well I agree with the principle ("some things you just have to drop
down to the HAL for") - but that doesn't actually answer the question
of whether this is one of those. I could, e.g., easily make the same
claim for ReadStream. The question is essentially "is this important
enough to deserver HIL support?" (offhand, I agree that it isn't, but
I think it deserves at least a little discussion)

>
> Vlado
>
>
> On 5/23/07, Jan Hauer <jan.hauer at gmail.com> wrote:
> >
> > > > ("I can't sample X&Y acceleration at more than 31Hz!") brings up a
> >
> > This is the price for the HIL abstraction, if someone needs better
> > performance then they have to go via the HAL. For example, the msp430
> > HAL has the "Msp430Adc12MultiChannel" interface for sampling multiple
> > sensors "at once". In my understanding when Read[Stream|Now] are used
> > for sensing they are best-effort as a comprise between the different
> > platforms. If we wanted yet another abstraction not only TEP 109
> > (Sensorboards) would need to be changed, but probably also TEP 101
> > (ADC), which is already finalized.
> >
> > Jan
> >
> > On 5/22/07, Kevin Klues < klueska at gmail.com> wrote:
> > > What would be nicer still is some declarative way of saying which
> > > sensors you want and at which rates, and to let the proper code be
> > > generated for you...
> > >
> > > Kevin
> > >
> > > On 5/22/07, David Gay <dgay42 at gmail.com> wrote:
> > > > The thread that starts with
> > > >
> http://mail.millennium.berkeley.edu/pipermail/tinyos-help/2007-May/024986.html
> > > > ("I can't sample X&Y acceleration at more than 31Hz!") brings up a
> > > > limitation of ReadStream:
> > > > how can one sample a group of sensors at high rates?
> > > >
> > > > It's easy enough to sample one sensor at a high rate, or several
> > > > sensors in succession. But if I want 200Hz sampling of X&Y
> > > > acceleration simultaneously, there doesn't seem to be a very good
> > > > answer?
> > > >
> > > > Possible current solutions:
> > > > - go low level, using Resource to reserve both sensors and ReadNow to
> > > > sample them (i.e., do ReadStream by hand) - this requires the
> > > > sensorboard to make *Now versions of each sensor available (the mts300
> > > > doesn't...)
> > > >
> > > > - have the sensor provide all reasonable sensor groups ( e.g., X, Y
> and
> > > > X&Y) - painful for more than two sensors
> > > >
> > > > Possible future solutions:
> > > > - some interface to sampling groups of sensors? could be icky...
> > > >
> > > > Anyway, something I noticed from that thread rather than any good
> answer.
> > > >
> > > > David
> > > > _______________________________________________
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> > > >
> > >
> > >
> > > --
> > > ~Kevin
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