[ntp:questions] Windows time question.

kbv g8kbv at mail4trash.com
Thu May 5 19:18:35 UTC 2011


In article <slrnis0nra.4on.unruh at wormhole.physics.ubc.ca>, 
unruh at wormhole.physics.ubc.ca says...
> 
> On 2011-05-03, David J Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
> >> As the OP who started this (long and sometimes ammusing) thread...
> >>
> >> I do carry a GPS receiver with me, but sadly not PPS capable, I use it
> >> for location determination/tracking/navigating etc.   Maybe I should
> >> include a GPS18 or 16 in the already bulging Laptop bag I lug arround.
> >
> > Even better if there were on on a USB stick, and you had a handy USB 
> > extension lead!
> 
> Unfortunately , AFAIK, usb is terrible for delivering a PPS-- ie no
> interrupt lines-- the problem with having only two data lines (one beign
> signal ground)
> . 
> 
> 
> >
> > How critical is your time need?  If it's within minutes, then the PC's 
> > clock is likely good enough.  If it's in the UK or Europe, I would be 
> > surprised if pool servers did not get you well within the second - perhaps 
> > within 100msec - particularly if you set the servers based on the country 
> > you're in.  I suspect that if you need closer than tens of milliseconds, 
> > carrying round a GPS 18x LVC (which I jokingly suggested) may actually be 
> > necessary.  NTP was designed when connections were nothing like as good as 
> > they are now, and is supposedly robust in those circumstances.  It is 
> > designed for 24-hours operation, though.
> >
> > 73,
> > David 
> >

Two data line's, plus ground and 5V power.   The data lines form a 
bidirectional diferential data bus, with a protocol more like a network 
than anything else.

For low speed devices, there are bitbanged firmware routines about for 
the likes of the Atmel single chip devices, if it interests you.
http://www.obdev.at/products/vusb/index.html

I digress...

DaveB




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