From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from skprod3.natinst.com ([130.164.80.24]:42005 "EHLO ni.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750930AbbEFSfG (ORCPT ); Wed, 6 May 2015 14:35:06 -0400 Message-ID: <554A5ED6.3070505@ni.com> Date: Wed, 06 May 2015 13:35:02 -0500 From: Xander Huff MIME-Version: 1.0 To: lars@metafoo.de CC: Jaeden Amero , Josh Cartwright , Joseph Hershberger , linux-iio@vger.kernel.org Subject: Re: XADC values read from VAUX0-15 are consistently ~10% less than they should be References: <5549401A.4080800@ni.com> In-Reply-To: <5549401A.4080800@ni.com> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 5/5/2015 5:11 PM, Xander Huff wrote: > Hi Lars, > > I've been working on transitioning one of our hardware devices over from using > the out-of-tree hwmon driver that Xilinx used to provide to the xadc driver you > added upstream, but I've been having trouble accessing our connected auxiliary > channels. I've found that for all channels I've tested, after multiplying the > raw value by the scale value (0.244140625), the resulting mVs are always about > 10 percent less than what we expect them to be. (2.9V instead of 3.3V, 5.4V > instead of 6V, etc.). I'm interested in any tips you may have on how to debug > this issue. Nevermind, it turns out I had somehow transcribed the scale value incorrectly for my testing. After modifying my test to directly use the scale values from our target, the resulting voltages came out as expected -- Xander Huff Staff Software Engineer National Instruments