From owner-freebsd-alpha@FreeBSD.ORG Thu Sep 25 17:54:41 2008 Return-Path: Delivered-To: freebsd-alpha@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 87926106568E for ; Thu, 25 Sep 2008 17:54:41 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from QMTA10.emeryville.ca.mail.comcast.net (qmta10.emeryville.ca.mail.comcast.net [76.96.30.17]) by mx1.freebsd.org (Postfix) with ESMTP id 54E178FC2B for ; Thu, 25 Sep 2008 17:54:41 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from OMTA02.emeryville.ca.mail.comcast.net ([76.96.30.19]) by QMTA10.emeryville.ca.mail.comcast.net with comcast id JzF61a0060QkzPwAA5egmi; Thu, 25 Sep 2008 17:38:41 +0000 Received: from koitsu.dyndns.org ([67.180.253.227]) by OMTA02.emeryville.ca.mail.comcast.net with comcast id K5ed1a00C4v8bD78N5edU1; Thu, 25 Sep 2008 17:38:38 +0000 X-Authority-Analysis: v=1.0 c=1 a=XTcIjhJ2o1MA:10 a=wJoO8qgNyacA:10 a=QycZ5dHgAAAA:8 a=n2mVluqdqtx0iPfJs8MA:9 a=cwbzKhUv-0Nns03EDYZIBqHzAUMA:4 a=EoioJ0NPDVgA:10 a=LY0hPdMaydYA:10 Received: by icarus.home.lan (Postfix, from userid 1000) id 57BDCC9432; Thu, 25 Sep 2008 10:38:37 -0700 (PDT) Date: Thu, 25 Sep 2008 10:38:37 -0700 From: Jeremy Chadwick To: Dieter Message-ID: <20080925173837.GA3415@icarus.home.lan> References: <20080925125417.GQ93308@cicely7.cicely.de> <200809251701.RAA18993@sopwith.solgatos.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200809251701.RAA18993@sopwith.solgatos.com> User-Agent: Mutt/1.5.18 (2008-05-17) Cc: freebsd-usb@freebsd.org, freebsd-alpha@freebsd.org, freebsd-hardware@freebsd.org Subject: Re: alpha/127248: System crashes when many (7) serial port terminals (vt320-vt510) connected to the server via com to usb adapter and 2-usb hubs. X-BeenThere: freebsd-alpha@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Porting FreeBSD to the Alpha List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 25 Sep 2008 17:54:41 -0000 On Thu, Sep 25, 2008 at 10:01:51AM +0100, Dieter wrote: > [ -usb@ added to existing thread ] > > > > > This is because USB is absolutely crap for this purpose. > > > > RS232 terminals, especially with long cables, can produce several kind > > > > of spikes and ground loops, which USB is very very sensitive about. > > > > > > Many things about USB are crap (thanks, inthell), but if a USB to RS-232 > > > bridge cannot handle normal spikes and ground loops, I'd blame the > > > bridge, not USB itself. If the problem is spikes and ground loops > > > there is probably some RS-232 filter/isolator available to clean them > > > up. There could be a bug in the bridge which needs a software workaround. > > > In any case the system shouldn't crash. > > > > > > Are there specific make&model USB to RS-232 bridges that people > > > have had good luck with? > > > > USB can't handle spikes and ground loops. > > As said: use isolated devices, so you don't have the loops and spikes. > > You can blame the device for not being isolated, but you expect every > > device to provide expensive workaround for a design failure. > > USB is designed for cheap stuff - that's all about it. > > Surely a "good" USB to RS-232 bridge (if one exists?) or a RS-232 > filter/isolator (assuming they exist?) would be *far* less expensive > than the server class alpha you suggest below. I'm coming into this conversation late, so my apologies. If by "bridge" you mean a USB adapter that supports RS232 serial, then yes, there are some which work quite nicely with FreeBSD. Anything that uses a Prolific chip will work well (supports custom serial rates, and does not drop/lose characters). The uplcom(4) driver is for this chip, and the man page lists off some consumer models/devices available. I can refer you to numerous people who have spoken to me privately or publicly on lists, praising the Prolific stuff. I have no idea if this driver works on Alphas. -- | Jeremy Chadwick jdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |