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 9F548200627 for ; Mon, 12 Mar 2012 14:37:39 -0700 (PDT) Received: by snark.thyrsus.com (Postfix, from userid 1000) id 94DCD40617; Mon, 12 Mar 2012 17:37:23 -0400 (EDT) Date: Mon, 12 Mar 2012 17:37:23 -0400 From: "Eric S. Raymond" To: Patrick Maupin Message-ID: <20120312213723.GD17895@thyrsus.com> References: <20120312210345.GC17357@thyrsus.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit 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] Build vs. modify vs. what should we be doing anyway? 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 21:37:39 -0000 Patrick Maupin : > On Mon, Mar 12, 2012 at 4:03 PM, Eric S. Raymond wrote: > > > I'm still skeptical about custom builds for production - means one of us > > would have to do the soldering, keep inventory, ship the results.  I'd rather > > develop a design and talk SparkFun or Dangerous Prototypes into fabbing it. > > But if you work with somebody like this or like seedstudio, they will > order parts for you and assemble according to your instructions. If > you simply view the dongle as a part to be ordered and the assembly to > be "take it apart, add this blue wire, put it back together" you will > realize that the same process could apply, at least for a company that > does more than basic board assembly. Good point. Then, though, we're dealing with the risk that our supplier will EOL the product we're blue-wiring. I can tell you from experience that consumer-grade GPSes like these have ridiculously short lifetimes. A friend (who may join this list shortly) once explained to me that this is a result of patent lawsuit risk. The big Taiwanese electronics companies spin up small shell companies to own the product designs, rent time on their fab lines, sell a shitload of units from a couple of big-batch runs, then fold before the lawsuits can land leaving the parent company legally in the clear. > > [Test system] sounds like a larger project than just reverse-engineering the dongle, > > though.  Do you have the capability, personally, to design and build such > > a thing? > > This is more what I do on a daily basis. Use a bunch of readily > available off-the-shelf thingies to make a few units. In this case, I > would buy a third party FPGA board, make a couple of smaller PCBs to > talk to it with a socket for an OCXO, maybe a connector to accept a > clock from a rubidium time source, headers for some USB modules and > some GPS modules and do some FPGA coding to allow reliable high > resolution timestamps. There are a couple of levels of this. The > first is just to do some one-off futzing around looking at various > devices. The second is to get serious. You could probably build 3 > identical units with really good resolution and stability (expensive > OCXO) for under $2K total. Maybe a lot less if you can find some good > surplus stuff on ebay. OK. Hal Murray will probably want one of these. > > And this makes complete sense.  Seems like a good way to start that doesn't > > require excessive time commitment up front on your part. > > In that case I'll start ordering and plotting out what I'm going to > do, and will sign up for the project to start putting out information > on the test setup for people to throw rocks at. OK. I'll keep working the net looking for products we can mod or reverse-engineer. Also trying to cultivate interest in building product for us at Sparkfun and similar outfits. -- Eric S. Raymond