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

[John Griessen]

Philip Levis wrote:
> 

>>>    2) How do nodes running different applications agree on the
>>> timestamp precision?
>>
>> Why is this an issue? 
>>
> 
  if this is
> platform-specific rather than protocol-specific, there's an issue. 
> Specifying it in a protocol might mean that some platforms cannot 
> support certain protocols.

I would just let the timestamp be any precision and let users beware, or
it's too complex -- more overhead to identify types of timestamps.

I'm interested in allowing for IEEE-588 precision time protocol (PTP) in the future --
that protocol wants a deterministic delay between arrival of a standard timing packet
before catching a number from a precise external to microcontroller free-running clock.

That external clock oscillator would not be on in lowest power mode, but would be on
whenever the highest precision was being used.  The precision time is calculated from
round trips between nodes with PTP running, and a base station with PTP always running
so as to get a minimum of randomness in time difference across the network.

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