Date: Tue, 9 Aug 2005 15:19:49 -0400 From: David Gilbert <dgilbert@dclg.ca> To: frank@exit.com Cc: freebsd-hackers@freebsd.org, David Gilbert <dgilbert@dclg.ca> Subject: Re: Bluetooth GPS for timekeeping? Message-ID: <17145.469.365833.447736@canoe.dclg.ca> In-Reply-To: <1123613910.9836.15.camel@realtime.exit.com> References: <17144.64281.705769.294109@canoe.dclg.ca> <1123613910.9836.15.camel@realtime.exit.com>
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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================
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