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 30D1E20024C for ; Mon, 12 Mar 2012 14:22:50 -0700 (PDT) Received: by snark.thyrsus.com (Postfix, from userid 1000) id 32F4D40617; Mon, 12 Mar 2012 17:22:34 -0400 (EDT) Date: Mon, 12 Mar 2012 17:22:34 -0400 From: "Eric S. Raymond" To: tz Message-ID: <20120312212234.GB17895@thyrsus.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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] Jitter and latency in a linux system might be a problem. Minimal BoM crosspost. 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: Mon, 12 Mar 2012 21:22:50 -0000 tz : > I would think so to, but I think ESRs original post or one of the > requirements comments said 100nS. > > It would help if we knew how hard the number was. I've specified 1ms becauser that's a convenient order of magnitude below the expected 10ms accuracty of NTP time, and the first application of this defice will be to check the accuracy of NTP time. There's evidence from the ZTI Z050 spec sheet that this is an achievable target - they quote 1ms timing accuracy. > I've seen this one with the same description from a few searches: > > http://www.chinazrh.com/wholesale-gps-receiver-usb-dongle-for-computers-netbook-laptop-umpc-p-728.html I've tracked down their support address and asked these questions: 1. The SkyTraq 6 emits 1PPS. Is this signal brought out to the USB bus where it can be seen as an emulated DCD or CTS change? 2. What USB-to-serial converter does it use? -- Eric S. Raymond