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

[John Griessen]

Andreas Koepke wrote:
> I guess I lost the track of the discussion, here are my 2c from what is
> implemented for the eyesIFX platform:
> 
> All I use is an accessor interface, like:
> setCreationTime, getCreationTime.
> (currently using the meta field directly).
> Using receivedSFD/transmittedSFD the radio stack computes the intra-stack
> delay and sends just that. I currently use 32.768kHz with 32bit width.
> 
> Accuracy and resolution depend on protocol requirements, which in turn may
> depend on radio hardware.
> 
> A high accuracy is only possible with quartz crystals -- and platforms
> tend to have a different number of those with different frequencies. So I
> guess that a completely platform independent interface will be hard. 

I could only imagine a worthwhile HIL time sync if the hardware had a PLL oscillator
that can be adjusted based on round trip tests as a system runs.  NO hardware has
that yet, so a HIL wouldn't be worthwhile.

John Griessen

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