From owner-freebsd-hackers@FreeBSD.ORG Tue Aug 9 18:58:35 2005 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E36BE16A428 for ; Tue, 9 Aug 2005 18:58:34 +0000 (GMT) (envelope-from frank@exit.com) Received: from tinker.exit.com (tinker.exit.com [206.223.0.1]) by mx1.FreeBSD.org (Postfix) with ESMTP id 2670F43D53 for ; Tue, 9 Aug 2005 18:58:34 +0000 (GMT) (envelope-from frank@exit.com) Received: from realtime.exit.com (realtime [206.223.0.5]) by tinker.exit.com (8.13.3/8.13.3) with ESMTP id j79IwVWb030085; Tue, 9 Aug 2005 11:58:31 -0700 (PDT) (envelope-from frank@exit.com) Received: from realtime.exit.com (localhost [127.0.0.1]) by realtime.exit.com (8.13.3/8.13.3) with ESMTP id j79IwUfE010517; Tue, 9 Aug 2005 11:58:30 -0700 (PDT) (envelope-from frank@exit.com) Received: (from frank@localhost) by realtime.exit.com (8.13.3/8.12.9/Submit) id j79IwUZ5010516; Tue, 9 Aug 2005 11:58:30 -0700 (PDT) (envelope-from frank@exit.com) X-Authentication-Warning: realtime.exit.com: frank set sender to frank@exit.com using -f From: Frank Mayhar To: David Gilbert In-Reply-To: <17144.64281.705769.294109@canoe.dclg.ca> References: <17144.64281.705769.294109@canoe.dclg.ca> Content-Type: text/plain Content-Transfer-Encoding: 7bit Organization: Exit Consulting Date: Tue, 09 Aug 2005 11:58:30 -0700 Message-Id: <1123613910.9836.15.camel@realtime.exit.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 FreeBSD GNOME Team Port X-Virus-Scanned: ClamAV 0.86.1/1011/Tue Aug 9 02:20:28 2005 on tinker.exit.com X-Virus-Status: Clean Cc: freebsd-hackers@freebsd.org Subject: Re: Bluetooth GPS for timekeeping? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: frank@exit.com List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 09 Aug 2005 18:58:35 -0000 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? The former would depend strongly on the characteristics of the Bluetooth protocols, at least when it comes to accuracy. Keeping time to the half-second or so would be pretty easy, I would guess. The latter is the way it already works. Just configure other peers in your ntp.conf along with your GPS, viz: pps /dev/pps0 assert hardpps server 127.127.41.0 prefer # GPSClock fudge 127.127.41.0 stratum 0 fudge 127.127.41.0 time1 -1.0 peer 127.127.22.0 # PPS refclock fudge 127.127.22.0 stratum 0 flag3 1 # name it as a good clock peer 128.9.176.30 # timekeeper.isi.edu peer 164.67.62.194 # tick.ucla.edu peer 63.149.208.50 # nist1.datum.com peer 192.43.244.18 # time.nist.gov peer 206.223.0.15 # tick.exit.com That's the configuration for tock.exit.com. It uses the GPSClock if it's available, otherwise it falls back to the best of the other tickers. -- Frank Mayhar frank@exit.com http://www.exit.com/ Exit Consulting http://www.gpsclock.com/ http://www.exit.com/blog/frank/