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Cc: freebsd-hackers@freebsd.org, David Gilbert <dgilbert@dclg.ca>
Subject: Re: Bluetooth GPS for timekeeping?
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>>>>> "Frank" == Frank Mayhar <frank@exit.com> writes:

Frank> On Tue, 2005-08-09 at 14:51 -0400, David Gilbert wrote:
>> But ... since there are long patches of time where I'm not mobile,
>> I was wondering if anyone had looked at using a Bluetooth GPS for
>> timekeeping.  Has anyone also ever had an ntp server sometimes use
>> a GPS and othertimes use other servers ... depending on the
>> availability of the GPS?

Frank> The former would depend strongly on the characteristics of the
Frank> Bluetooth protocols, at least when it comes to accuracy.
Frank> Keeping time to the half-second or so would be pretty easy, I
Frank> would guess.

Frank> The latter is the way it already works.  Just configure other
Frank> peers in your ntp.conf along with your GPS, viz:

How might you determine the accuracy of the GPS ... or the
"characteristics of the Bluetooth protocols" ?

The GPS docs "say" that the GPS chipset keep time to within 100ns.
However (and I assume this is to save power) they also say that the
position indication is only sent once per second.

In my case, the Bluetooth GPS would be talking to a Bluetooth dongle
hanging directly out a port of the server in question.

Dave.

-- 
============================================================================
|David Gilbert, Independent Contractor.       | Two things can only be     |
|Mail:       dave@daveg.ca                    |  equal if and only if they |
|http://daveg.ca                              |   are precisely opposite.  |
=========================================================GLO================