[Tinyos-devel] Request for comments: TEP-108

[Kevin Klues]

These aren't so much comments on the contents of the TEP, but rather
on how to use the features it presents.  Implementations of Arbiters
according to the TEP exist in the development branch of cvs on
sourceforge, but not on the main branch.

Correct me if I'm wrong (Jan, David, Gil), but sensorboard
implementations are built on top of the ADC resource which should
expose the Resource/ResourceRequested interfaces along with the
ReadNow interface from the ADC HIL. A sensorboard that uses an ADC
should connect through this HIL interface in order to implement its
SIDs interface.  Maybe the ADC HIL implementations haven't been
updated yet to expose this interface as it is still under discussion.
(I know that TEP 101 currently says that ReadNow is only provided in
conjunction with Resource, but maybe it needs to be updated....
again....).

One thing to note, however, is that using the ResourceRequested
interface alone in order to decide when to release a resource is
discouraged for devices that wish to use the power management features
available with T2.  If clients only release resources based on a
ResourceRequested event, then the resource will never have the chance
to go idle and any power managers wired to the ResoruceController
interface provided by the resource's arbiter will not be able to power
it on/off automatically.  In the case of the ADC on the Msp430, this
means that the reference voltage generator never has the chance to go
off even though there are no users currently using the ADC (not sure
what the repercussions are for the atmel platforms).

I think what is typically done is that the SIDs read interface is
implemented using the ADC HIL Read interface and the SIDs ReadStream
interface is implemented using the ADC HIL ReadStream interface so
that you don't have to worry about the details of dealing with the
Resource yourself unless it is specifically required for your
implementation (that's why the ReadNow interface exists).  The
sensorboard implementation thus takes care of configuring the ADC
correctly and then calling its respective Read and ReadStream
implementations....

Kevin

On 11/6/06, Miguel Freitas <mfreitas at gmail.com> wrote:
> Hi Kevin,
>
> On 11/5/06, Kevin Klues <klueska at gmail.com> wrote:
> > Dear TinyOS developer community:
> >
> > Matt Welsh sent out a request for comments on TEP 108 on October 20th.
> >  Until now no one has responded to this request, and the deadline
> > before  the TEP moves into final review is November 17th.
>
> I'm a newcomer here, so please take my comments with a grain of salt.
> I have replied Matt directly with both comments and questions, below
> is the email i've sent him.
>
> ---
>
> On 10/31/06, Miguel Freitas <mfreitas at gmail.com> wrote:
> > Matt,
> >
> > I'm investigating the porting of the mts300 sensorboard to latest
> > tinyos-2.0 standards, and resource arbitration is a key point.
> >
> > i have 2 sensors sharing a single resource (the same adc channel). to
> > make things more fun, the original mts300 code implemented a 10ms
> > delay after changing adc source as a matter of "stabilization" of the
> > signal.
> >
> > my plan for implementing this would be using the Resource /
> > ResourceRequested interfaces. for example:
> >
> > implementation of the command "read()" of one of the sensors:
> >
> > 1. check if isOwner(), proceed with ADC conversion if true and go (5).
> > 2. if not owner, request() resource.
> > 3. on granted(), start a 10ms timer.
> > 4. on timer's fired(), proceed with ADC conversion.
> > 5. do not release resource.
> > 6. on requested() event, call release()
> >
> > this way, every time the resource is changed between sensors i would
> > have the 10ms delay. consecutive reads to the same sensor do not need
> > to use the timer.
> >
> > the problem is: requested() event is only available from
> > ResourceController which is a single instance on arbiters. there is no
> > such thing called ResourceRequested on tinyos cvs.
> >
> > what should i do?
> >
> > is that TEP waiting for general agreement before ones starts coding
> > support for ResourceRequested?
> >
> > am i trying a wrong/bad/stupid solution for this problem?
> >
> > Miguel
> >
>


-- 
~Kevin