For your particular benchmarks, use setPeriodic. Timers fire through
a task, which must wait to be executed in the task queue. With
setOneShot, you are accumulating error. setPeriodic sets the alarms
at periodic times from the previous alarm, giving only jitter with no
accumulation.
But for fast sampling, you should use hardware timers, which will fire
through hardware interrupts and not tasks. Make sure you're not using
an already allocated timer. Search the archives, I've posted it
before. Or, use Moteiv Boomerang, where you can allocate a unique,
individual timer with the instantiation of a generic component.
Cory
On 5/17/06, jagan nath <[EMAIL PROTECTED]> wrote:
> I have removed the counter from ADC.dataready and put it in the
> TimerJiffy.fired(). Although the performance is not good but it has
> certainly improved. This is what I got
>
> with TimerJiffy.setoneshot(1) - 2590 samples/sec ( cant actually call
> them samples, it is actually these many times the timer has fired)
>
> with TimerJiffy.setOneshot(10) - 1920 samples/sec
>
> with TimerJiffy.setOneshot(20) - 1255 samp/sec
>
> with TimerJiffy.setOneshot(40) - 705 samp/sec (closest to accurate, 40
> corresponds to 800 samples/sec)
>
> This shows that the ADC conversion is also adding to the delay of the
> timer being fired.
> All though i'm using ADC.setsamplingrate(). It doesnt look like the
> sampling time has actually reduced.
>
> -jagan
>
> PS.I dont know how accurate is TimerJiffyAsync( this is used in CC2420
> for initial/congestion backoff). i even tried to use this. I connected
> this to a copy of TimerJiffyAsyncC(timer changed to B2/B0) but this is
> not working the timer doesnt fire.Maybe i have done something
> wrong.Not Sure.........
>
>
>
>
> On 5/18/06, jagan nath <[EMAIL PROTECTED]> wrote:
> > ok..
> > Now I have tried with TimerMilli with a setOneshot(1) and I was
> > getting a max of 660 samples/sec.Maybe I think I will increment the
> > Samplecounter in the fired() event itself (as against incrementing it
> > in the ADC.dataready(). just to see if ADC conversion is the
> > bottleneck.
> >
> > jagan
> >
> > On 5/18/06, Michael Schippling <[EMAIL PROTECTED]> wrote:
> > > Well, you should definitely call it AFTER all the component and
> > > module inits and starts, otherwise the default will get reset.
> > > And, as I said, I don't have any concrete knowledge that it
actually
> > > works the way it should. Maybe I should try it myself...
> > >
> > > MS
> > >
> > > jagan nath wrote:
> > > > ---------- Forwarded message ----------
> > > > From: jagan nath <[EMAIL PROTECTED]>
> > > > Date: May 18, 2006 9:30 AM
> > > > Subject: Re: [Tinyos-help] Maximum samplingrate with
TimerJiffy.nc
> > > > To: Michael Schippling <[EMAIL PROTECTED]>
> > > >
> > > >
> > > > I didnt miss that, i have set the
ADCControl.setSamplingRate(7500ns),
> > > > only thing i m not sure is whether this command shud be called in
> > > > stdcontrl.init/start,
> > > > i have called it in stdcontrol.start(maybe i shud try it in
init also)
> > > >
> > > > jagan
> > > >
> > > >
> > > >
> > > >
> > > > On 5/18/06, Michael Schippling <[EMAIL PROTECTED]> wrote:
> > > >> Everyone seems to be going on about this recently and I forget
> > > >> to whom I have already responded with dubious advice...
> > > >>
> > > >> You need to set the ADC pre-scaler to something other than the
> > > >> maximum, which is the default. ADCControl.setSamplingRate() is
> > > >> supposed to do this, see tos/interfaces/ADCControl.nc for
details.
> > > >> However I've only heard of negative results so far.
> > > >>
> > > >> Have any of you lurkers actually used setSamplingRate()
successfully?
> > > >>
> > > >> MS
> > > >>
> > > >>
> > > >>
> > > >> jagan nath wrote:
> > > >> > Hello all,
> > > >> > I'm using TimerJiffy.nc to sample the ADC0 pin for my
application.I
> > > >> > actually wanted to sample at 3Khz but the highest sampling
rate i
> > > >> > could achieve is not more than 1200 samples/sec.
> > > >> >
> > > >> > I'm calling TimerJiffy.setPeriodic(11); here 11
corresponds to
> > > >> > 3Ksamples/sec(apprx).
> > > >> > whenever the timer fires I'm call ADC.getdata() and in the
event
> > > >> > ADC.dataready() I'm incrementing a counter
> > > >> > Now I'm using a normal timer which is set to fire at
intervals of
> > > >> > 10/20 secs and when this timer fires Im sending this
counter value
> > > >> > over the radio and receiving it with TOSBase.
> > > >> >
> > > >> > I then further reduced the value of
Timerjiffy.setperiodic(5) .with
> > > >> > this also i'm getting a max of 1200 samples/sec.
> > > >> >
> > > >> > Am I checking it correctly or is there any other method to
achieve the
> > > >> > 3Khz sampling rate.
> > > >> >
> > > >> > TIA
> > > >> > Jagan
> > > >> >
> > > >> > _______________________________________________
> > > >> > Tinyos-help mailing list
> > > >> > [email protected]
> > > >> >
> > > >>
https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
> > > >>
> > > >
> > > > _______________________________________________
> > > > Tinyos-help mailing list
> > > > [email protected]
> > > >
https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
> > >
> >
>
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