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 9ADAA200BFD for ; Wed, 4 Apr 2012 18:11:05 -0700 (PDT) Received: by snark.thyrsus.com (Postfix, from userid 1000) id 58C6642E29; Wed, 4 Apr 2012 21:10:42 -0400 (EDT) From: esr@thyrsus.com (Eric S. Raymond) To: Dawn Liu , ":"@thyrsus.com Message-Id: <20120405011042.58C6642E29@snark.thyrsus.com> Date: Wed, 4 Apr 2012 21:10:42 -0400 (EDT) Cc: thumbgps-devel@lists.bufferbloat.net Subject: [Thumbgps-devel] Bad news on the UD731 X-BeenThere: thumbgps-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 Apr 2012 01:11:05 -0000 Tested. Works fine as a GPS, and I've added it to the GPSD hardware page with an "Excellent" rating. Unfortunately, I can't see 1PPS from it. Investigation reveals that the Linux support for the CP2101 Serial-to-USB adapter is weak and does not implement the TIOCMIWAIT call required to make a thread wait on a handshake-line change. Further investigation suggests that this is the vendor's doing. To meet its obligations under the GPL SiLabs released heavily obfuscated source code. That code had to be reverse-engineered without the company's help in 2005. A 2006 promise by the company to supply unobfuscated driver source was not fulfilled. Now the company has declared the chip obsolete and the programming guide for it is no longer available from the SiLabs website. I have sent email to the Liux driver maintainer asking if there is any chance TIOCMIWAIT can be made to work, but I'm not expecting a happy answer. The Linux crew has done just about everything it can in a case like this; the vendor has repeatedly and obstinately refused to divulge the technical information required for full support of the chip. I don't think we can use this adapter, and given the vendor's bad attitude I wouldn't want to steer them more business even if we could fix the driver. Ms. Liu, does UniTraq have any designs using a PL2303 we could modify? -- Eric S. Raymond "America is at that awkward stage. It's too late to work within the system, but too early to shoot the bastards." -- Claire Wolfe