[Tinyos-devel] Re: [Tinyos Core WG] time sync interfaces

[John Griessen]

David Gay wrote:
> On Dec 18, 2007 5:15 PM, John Griessen <john at ecosensory.com> wrote:
>> To be a HIL, the app can't use specific timers, so it will be limited to
>> using feedback to correct errors and may have lots of jitter.  It's not going to be
>> smoothly nudging the time, since it is the same app for all different hdwe.
> 
> A misunderstanding here: a HIL timesync implementation doesn't have to
> be portable, it just has to offer the same interface on all platforms.

I read the intent of HILs to be separating the hardware dependent from the non.
Hardware Independent Layer vs. Hardware Presentation Layer means HIL same interface and code for all;
Hpl means different per platform and per sensorboard interface and code for maximizing performance of specific hdwe.

 From TEP 2:    http://www.tinyos.net/tinyos-2.x/doc/html/tep2.html

"The final tier in the architecture is formed by the HIL components that take the platform-specific abstractions provided by the 
HAL and convert them to hardware-independent interfaces used by cross-platform applications. These interfaces provide a platform 
independent abstraction over the hardware that simplifies the development of the application software by hiding the hardware 
differences. "

So HIL is pretty close to portable, not the exact meaning of "can be moved", but very
similar in, "convert them to hardware-independent interfaces"

Clarification?  Were you meaning portable as in, "a port to a new platform"?
Where new code needs to be written at HAL and HPL levels?  I still think the best kind of HIL
cross platform time sync app would "just work" on a new platform after the developer of same
creates  HAL and HPL level code dealing with time and timestamping.

About time synch, I say it's too early to lock in on things like precision.  Choose
a cross platform app to do that works with any precision, and just uses feedback to get accuracy
that it can.

Thanks,

John Griessen
-- 
Ecosensory   Austin TX
tinyOS devel on:  ubuntu Linux;   tinyOS v2.0.2;   telosb ecosens1