[Tinyos-devel] DAC and MSP430RefVoltGenerator in T2

[Jan Hauer]

> In the latter approach you outlined, where they share the same arbiter, if
> we assume that the ADC and DAC require the same reference voltage, would
> they still not be able to run in parallel?

By parallel I meant "at the same time": in the second approach if two
components would request to use the the ADC and DAC at the same time
(i.e. overlapping in time) the second of them would have to wait until
the first is finished (it would simply get the Resource.granted event
later). But both, ADC and DAC could of course be used in the same app.
If both clients wanted to use the RefVolt arbiter (possible at
different settings), then there's no way around. But - and that is the
drawback - if the ADC client wasn't even using the RefVolt the DAC
client would still have to wait for the ADC client operation to
finish.

Jan


On Thu, Feb 14, 2008 at 5:14 PM, Sandip Bapat <sandipbapat at yahoo.com> wrote:
>
>
>
> Jan,
>
>
>
> In the latter approach you outlined, where they share the same arbiter, if
> we assume that the ADC and DAC require the same reference voltage, would
> they still not be able to run in parallel?
>
>
>
> Here's one scenario which might be common to a lot of sensing apps: An app
> uses RefVolt via Msp430AutoRVGClient to do its sensing and requires some
> reference (say 2.5V). Occasionally, the app also needs to use the DAC, with
> the same reference voltage, for instance, to change the gain setting on the
> sensor by varying the DAC voltage. If both used the same reference, could
> they still not work in parallel?
>
>
>
> Also, the DAC has a 3x multiplier setting so effectively it can produce the
> same range of outputs regardless of what reference voltage is being used by
> others (ADC). We could (re)implement the getState() function in RefVolt so
> that the DAC client can figure out which, if any, reference voltage is being
> used by the ADC and scale its inputs accordingly.
>
>
>
> But perhaps I'm missing something even more fundamental here as to why they
> can't run in parallel.
>
>
>
> Sandip
>
>
>
>
> ----- Original Message ----
> From: Jan Hauer <hauer at tkn.tu-berlin.de>
> To: Vlado Handziski <handzisk at tkn.tu-berlin.de>
> Cc: TinyOS Development <tinyos-devel at millennium.berkeley.edu>;
> "tinyos-help at Millennium.Berkeley.EDU list"
> <tinyos-help at millennium.berkeley.edu>
> Sent: Thursday, February 14, 2008 10:42:02 AM
> Subject: Re: [Tinyos-devel] DAC and MSP430RefVoltGenerator in T2
>
> Currently Msp430RefVoltArbiterImplP intercept the requests of ADC
> clients to the Resource interface, it is not really arbitrating access
> itself. If the DAC needs access to the RefVolt component too, then we
> might need a real arbiter for the RefVolt component that is
> independent of the actual ADC arbiter. The drawback is then that for
> every ADC/DAC request involving RefVolt we'd need to request two
> resources from two different arbiters before the client can start
> sampling/outputting. Alternatively we could agree that ADC and DAC
> share the same arbiter, which makes arbitration a lot easier, but is
> less efficient because you'd never be able to run ADC and DAC in
> parallel.
> Jan
>
>
>
> On Wed, Feb 13, 2008 at 7:53 PM, Vlado Handziski
> <handzisk at tkn.tu-berlin.de> wrote:
> > The access to the refvolt generator has to be properly arbitrated between
> > the ADC and the DAC. Pins, timers, etc. are all potential shared resource
> > between the two. Jan, who is responsible for the msp430 ADC stack, is at a
> > project meeting and probably has not read the thread. Please get in touch
> > with him to coordinate. No #ifdefs please :)
> >
> > Vl o
>
>
> >
> >
> > On Wed, Feb 13, 2008 at 6:43 PM, John Griessen <john at ecosensory.com>
> wrote:
> > >
> > >
> > > Sandip Bapat wrote:
> > >
> > >  a DAC module would either have to wire to Msp430RefVoltArbiterP (in
> which
> > case it also has to provide the
> > >
> > > AdcConfigure interface) or be expected to provide wiring for these
> > interfaces.
> > >
> > > This is fine for apps that just want to use the DAC and not ADC but what
> > if both are used and the
> > >
> > > ADC is already using Ref Voltage ? I guess we could use #ifdefs in the
> DAC
> > but wouldn't having
> > >
> > > a Msp430RefVoltArbiterC that does the wirings required for
> > Msp430RefVoltGeneratorP be better?
> > >
> > > The best thing would be to create new function in the RefVoltArbiter so
> it
> > can stay on after an ADC12 or
> > > Dac12 call has requested it if another request is heard within a time
> > period.  As far as I can tell,
> > > Dac12 and Adc12 of a MSP430F1611 can both be going at once.
> > >
> > > John Griessen
> > >
> > >
> > > --
> > > Ecosensory  Austin TX
> > > tinyOS devel on:  ubuntu Linux;  tinyOS v2.0.2;  telosb ecosens1
> > > _______________________________________________
> > > Tinyos-devel mailing list
> > > Tinyos-devel at millennium.berkeley.edu
> > >
> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-devel
> > >
> > >
> > >
> >
> >
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