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 672AF200B29 for ; Sun, 6 May 2012 15:09:56 -0700 (PDT) Received: by snark.thyrsus.com (Postfix, from userid 1000) id 9B58340475; Sun, 6 May 2012 18:09:25 -0400 (EDT) Date: Sun, 6 May 2012 18:09:25 -0400 From: "Eric S. Raymond" To: "Ron Frazier (NTP)" Message-ID: <20120506220925.GF14699@thyrsus.com> References: <20120501151435.4a6a5373.gem@rellim.com> <20120502033345.GA11913@thyrsus.com> <4FA13959.9050405@techstarship.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FA13959.9050405@techstarship.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 Subject: Re: [Thumbgps-devel] [gpsd-dev] PPS over USB 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: Sun, 06 May 2012 22:09:56 -0000 Ron Frazier (NTP) : > Just wondering. On the USB + PPS + PL2303 concept, has the long > term variation that has been observed in NMEA data in other similar > units without PPS been accounted for? No. Hal Murray and I studied this extensively and were unable to get a handle on the cause. > I have personally observed a > variation in NMEA data on my Globalsat Sirf III USB device of up to > +/- 70 ms over several days. Will having the PPS coming though USB > solve that problem? Yes. The measured jitter of 1PPS over PL2303 USB is 0.5 milliseconds. -- Eric S. Raymond