[Tinyos Core WG] Meeting: 5/30

[Kevin Klues]

> What does it mean to group and sample together the temp and humidity
> sensors on Telos if they are accessible only serially?  Similarly,
> what does it mean to sample the TSR and temp, if the first has an
> acquisition time that is one to two orders of magnitude lower than the
> latter?


You're right, it doesn't make much sense to group them since they can't be
sampled simultaneously.......

If you assume that you're giving up portability, then instead of
> parameterizing using val_t, you could provide all of the Read (or
> Notify) interfaces by the generic component and use a runtime
> mechanism of specifying which subset to sample.


This is what I was suggesting in my response to Martin's first email.  The
only disadvantage is that you then have to have all the sensors wired in and
ready for sampling even if you never plan on using them.  I guess we could
define compile time constants that #ifdef sections of the configuration to
include certain sensors and not others if we really wanted though.

Kevin


- Prabal
>
> On 5/31/07, Kevin Klues <klueska at gmail.com> wrote:
> >
> >
> > > For example, on the
> > > msp430 ADC the HAL client "Msp430Adc12ClientC" provides the
> > > "Msp430Adc12MultiChannel" interface which does exactly what we are
> > > talking about. A simple wrapper could map this to a "HIL" without the
> > > need for a GroupedSensorsP that "cycle(s) through 'numSensors'
> > > requests in a for loop for all connected Resource interfaces, waiting
> > > for them all to be granted before issuing a read() command on all of
> > > them concurrently."
> >
> >
> > The idea behind the GroupedSensors component is for grouping multiple
> types
> > of sensors together -- not just those that rely on access to the
> ADC.  Its a
> > way of ensuring that the sensor reading you take are correlated in time
> in
> > some way.  For example, on the telos, you can issue commands to sample
> the
> > humidity and photo sensors concurrently, but you can't do the same for
> > humidity and temperature -- these have to be sampled serially since they
> > require access to the same hardware chip.
> >
> > GroupedSensors would just be a way of conveniently specifying which
> sensors
> > you want to take samples from together so you don't have to mess with
> > grabbing hold of resources and managing the state required to sample
> > multiple sensors at once.
> >
> > In regards to sampling sensors (2,5,6) obviously these would need to be
> > mapped to some platform specific (or sensorboard specific) sensor
> > identifiers... you wouldn't just use the raw numbers themselves.
> >
> >  Kevin
> >
> >
> > _______________________________________________
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> >
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> >
> >
>



-- 
~Kevin
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