Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754167Ab1CVKl1 (ORCPT ); Tue, 22 Mar 2011 06:41:27 -0400 Received: from ppsw-52.csi.cam.ac.uk ([131.111.8.152]:41229 "EHLO ppsw-52.csi.cam.ac.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753967Ab1CVKlZ (ORCPT ); Tue, 22 Mar 2011 06:41:25 -0400 X-Cam-AntiVirus: no malware found X-Cam-SpamDetails: not scanned X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/ Message-ID: <4D887D1E.90503@cam.ac.uk> Date: Tue, 22 Mar 2011 10:42:38 +0000 From: Jonathan Cameron User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20110122 Lightning/1.0b3pre Thunderbird/3.1.7 MIME-Version: 1.0 To: "Hennerich, Michael" CC: "Cai, Cliff" , "linux-iio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Drivers , "device-drivers-devel@blackfin.uclinux.org" , Cliff Cai Subject: Re: [PATCH RESEND v2]IIO driver for Analog Devices Digital Output Gyroscope ADXRS450 References: <1300526846-27183-1-git-send-email-cliff.cai@analog.com> <4D878D8B.6070902@cam.ac.uk> <544AC56F16B56944AEC3BD4E3D5917713754315B05@LIMKCMBX1.ad.analog.com> In-Reply-To: <544AC56F16B56944AEC3BD4E3D5917713754315B05@LIMKCMBX1.ad.analog.com> X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3678 Lines: 91 On 03/22/11 08:16, Hennerich, Michael wrote: > Cai, Cliff wrote on 2011-03-22: >> >> >>> -----Original Message----- >>> From: Jonathan Cameron [mailto:jic23@cam.ac.uk] >>> Sent: 2011年3月22日 1:40 >>> To: Cai, Cliff >>> Cc: linux-iio@vger.kernel.org; linux-kernel@vger.kernel.org; Drivers; >>> device-drivers-devel@blackfin.uclinux.org; Cliff Cai >>> Subject: Re: [PATCH RESEND v2]IIO driver for Analog Devices Digital >>> Output Gyroscope ADXRS450 >>> >>> On 03/19/11 09:27, cliff.cai@analog.com wrote: >>>> From: Cliff Cai >>>> >>>> Change v2:v1: >>>> >>>> Make modification according to Michael Hennerich's comments, >>>> correct the spi transfer way,use existing sysfs interfaces. >>> Hi Cliff, >>> >>> As you are proposing a couple of new interfaces we need to have >>> documentation for them. They are quad and dynamic_null_correction. We >>> need to first establish whether they are of general utility and hence >>> should be in the main abi doc. The quadrature one isn't something I've >>> seen before. Is it common in gyros? >> >> I'm not sure about this. >> Michael,do you have any ideas? > > The ADXRS450 is a quite new part and features a new sensor design - > So I don't think the quadrature error is to date very common. > It might become in future... > > From the datasheet: > > "The quad sensor design rejects linear and angular > acceleration, including external g-forces and vibration. This is > achieved by mechanically coupling the four sensing structures > such that external g-forces appear as common-mode signals > that can be removed by the fully differential architecture implemented in the ADXRS450." > > "The quad memory registers contain a value corresponding to the amount of > quadrature error present in the device at a given time. > Quadrature can be likened to a measurement of the error of the motion of the > resonator structure, and can be caused by stresses and aging effects. > The quadrature data is filtered to 80 Hz and can be read frequently to > detect sudden shifts in the level of quadrature. > The data is presented as a 16-bit, twos complement number." > Cool. So what is a good general name for this? I guess from this description if it were in a multi axis device you would have this measure for each axis? So perhaps gyro_z_quadrature_correction_raw? This thing also looks rather similar to a dynamically changing calibbias. Perhaps we need another term for a general dynamic linear (I think this is linear) correction inside a device? Perhaps go with a gyro specific term for now and wait to see if we get many more parts with this feature... >> >>> Dynamic null correction looks like it should be gyro_z_calibbias to >>> me but I could be wrong. The doc says " >>> The user can make small adjustments to the rateout of the device by >>> asserting these bits. This 10-bit register allows the user to adjust >>> the static rateout of the device by up to ±6.4°/sec. >>> " >>> >>> which makes me think it is an internally applied offset on the output >>> signal and hence calibbias in our abi. >> >> Thanks >> >>> Other than that, various minor nitpicks inline. >>> >>> Jonathan > > Greetings, > Michael > > -- > Analog Devices GmbH Wilhelm-Wagenfeld-Str. 6 80807 Muenchen > Sitz der Gesellschaft: Muenchen; Registergericht: Muenchen HRB 40368; Geschaeftsfuehrer:Dr.Carsten Suckrow, Thomas Wessel, William A. Martin, Margaret Seif > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/