[Tinyos-devel] Time Sync Requirements

[John Griessen]

Michael Newman wrote:
> I suspect the efficiency of code to use smaller time types will be offset by
> increased complexity to mix usage of various time types.
> 
> When you have a limited oscillator as Phil describes you count time by a
> larger number and the low order bits of the time counter never change.
> 
> One issue that must be thought about for this type of implementation is how
> to handle timers that count and incompatible intervals. For example Mu-law
> encoding of telephone audio is 8000 cycles per second. This does not fit
> well with timers that count at 1024 cycles per second. If the finest
> precision is only 1024 cycles per second it could be impossible to implement
> time for telephone audio. I suspect that we can identify a critical set of
> times and make sure that the minimum granularity of the time base allows for
> all of them.

This is a reasonable argument.  You can save cycles by having to deal with
4 16 bit words only every so often.  Putting time synch on every packet is
too costly.  Instead characterize the local RTC and deal with it once in a while,
such as when a time purposed packet comes along.

John Griessen

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