From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from snark.thyrsus.com (static-71-162-243-5.phlapa.fios.verizon.net [71.162.243.5]) by huchra.bufferbloat.net (Postfix) with ESMTP id 6D84F2001A2 for ; Tue, 1 May 2012 16:09:50 -0700 (PDT) Received: by snark.thyrsus.com (Postfix, from userid 1000) id 90EFB4043E; Tue, 1 May 2012 19:09:17 -0400 (EDT) Date: Tue, 1 May 2012 19:09:17 -0400 From: "Eric S. Raymond" To: "Gary E. Miller" Message-ID: <20120501230917.GE10188@thyrsus.com> References: <20120320121724.GA11523@thyrsus.com> <20120320104542.0eaf179c.gem@rellim.com> <20120501151027.44487e16.gem@rellim.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120501151027.44487e16.gem@rellim.com> Organization: Eric Conspiracy Secret Labs X-Eric-Conspiracy: There is no conspiracy User-Agent: Mutt/1.5.21 (2010-09-15) Cc: thumbgps-devel@lists.bufferbloat.net, gpsd-dev@nongnu.org Subject: Re: [Thumbgps-devel] Progress on Plain Jane X-BeenThere: thumbgps-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list Reply-To: esr@thyrsus.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 May 2012 23:09:50 -0000 Gary E. Miller : > As you can see the NMEA/USB short term jitter is about 2 milliSec and > the PPS/USB time is about 0.5 milliSec jitter. Long term NMEA/USB drift > is quite a bit larger, maybe 100 milliSec or more. > > So the jitter of PPS over USB is about 50x worse than PPS over GigE, but > I think for the purposes at hand pretty good. Of course I expect the > results to be worse when run on a single core router. That's excellent news. 0.5msec jitter is as good as we could have expected and exactly what one would predict from a max error of 1msec due to polling interval. The long-term NMEA/USB drift is consistent with previous observations by Hal Murray and myself. Do you consider the GR-601 with this mod to be ready for production? Should we give Navisys the green light on GPSD compatibility? I see no reason not to at this point, but you're doing the testing so you make the call. -- Eric S. Raymond