From mboxrd@z Thu Jan 1 00:00:00 1970 From: akropel1@rochester.rr.com (Adam Kropelin) Date: Thu, 19 May 2005 06:25:06 +0000 Subject: [PATCH] I2C update for 2.6.8-rc1 Message-Id: <20040716141939.B8270@mail.kroptech.com> List-Id: References: <10898500322333@kroah.com> <10898500321009@kroah.com> <20040716170716.GD8264@openzaurus.ucw.cz> <20040716171702.GA10598@kroah.com> In-Reply-To: <20040716171702.GA10598@kroah.com>; from greg@kroah.com on Fri, Jul 16, 2004 at 10:17:03AM -0700 MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Greg KH Cc: Pavel Machek , linux-kernel@vger.kernel.org, sensors@stimpy.netroedge.com On Fri, Jul 16, 2004 at 10:17:03AM -0700, Greg KH wrote: > On Fri, Jul 16, 2004 at 07:07:16PM +0200, Pavel Machek wrote: > > Hi! > > > > > +menu "Dallas's 1-wire bus" > > > + > > > +config W1 > > > + tristate "Dallas's 1-wire support" > > > + ---help--- > > > + Dallas's 1-wire bus is usefull to connect slow 1-pin devices > > > + such as iButtons and thermal sensors. > > > > Just out of curiosity... are such devices really connected using one wire only, > > or is it GND+5V+one data wire, or GND+power&data wire? > > I'm pretty sure it's just 1 wire, at least for the devices I've seen. It's GND+power&data. The device derives its power from transitions on the data line driven by the master. Consequently there are some fairly strict timing requirements on those pulses. Some devices can also be powered by a dedicated VCC line which generally allows the device to respond faster. A temperature sensor IC, for example, can usually complete a conversion cycle much faster when it has dedicated power. --Adam From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266357AbUGPRpA (ORCPT ); Fri, 16 Jul 2004 13:45:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266409AbUGPRpA (ORCPT ); Fri, 16 Jul 2004 13:45:00 -0400 Received: from ms-smtp-04.nyroc.rr.com ([24.24.2.58]:1758 "EHLO ms-smtp-04.nyroc.rr.com") by vger.kernel.org with ESMTP id S266357AbUGPRo6 (ORCPT ); Fri, 16 Jul 2004 13:44:58 -0400 Date: Fri, 16 Jul 2004 14:19:39 -0400 From: Adam Kropelin To: Greg KH Cc: Pavel Machek , linux-kernel@vger.kernel.org, sensors@stimpy.netroedge.com Subject: Re: [PATCH] I2C update for 2.6.8-rc1 Message-ID: <20040716141939.B8270@mail.kroptech.com> References: <10898500322333@kroah.com> <10898500321009@kroah.com> <20040716170716.GD8264@openzaurus.ucw.cz> <20040716171702.GA10598@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <20040716171702.GA10598@kroah.com>; from greg@kroah.com on Fri, Jul 16, 2004 at 10:17:03AM -0700 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 16, 2004 at 10:17:03AM -0700, Greg KH wrote: > On Fri, Jul 16, 2004 at 07:07:16PM +0200, Pavel Machek wrote: > > Hi! > > > > > +menu "Dallas's 1-wire bus" > > > + > > > +config W1 > > > + tristate "Dallas's 1-wire support" > > > + ---help--- > > > + Dallas's 1-wire bus is usefull to connect slow 1-pin devices > > > + such as iButtons and thermal sensors. > > > > Just out of curiosity... are such devices really connected using one wire only, > > or is it GND+5V+one data wire, or GND+power&data wire? > > I'm pretty sure it's just 1 wire, at least for the devices I've seen. It's GND+power&data. The device derives its power from transitions on the data line driven by the master. Consequently there are some fairly strict timing requirements on those pulses. Some devices can also be powered by a dedicated VCC line which generally allows the device to respond faster. A temperature sensor IC, for example, can usually complete a conversion cycle much faster when it has dedicated power. --Adam