From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E20A2C6778A for ; Sun, 22 Jul 2018 22:22:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8200B20850 for ; Sun, 22 Jul 2018 22:22:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="cEuDl/Iy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8200B20850 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730767AbeGVXUP (ORCPT ); Sun, 22 Jul 2018 19:20:15 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:37572 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730111AbeGVXUP (ORCPT ); Sun, 22 Jul 2018 19:20:15 -0400 Received: by mail-pg1-f196.google.com with SMTP id n7-v6so10798429pgq.4; Sun, 22 Jul 2018 15:22:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=iGbxgpKxfnU8cJSwCv4nptNKXdwEn4jlf+Gx5UStL+A=; b=cEuDl/IyNib5BEY2wJEV3YQzD05TOlmtGZ/PF56Ez0scSmLJ6a78wL1uMIhKonr7kJ vNiqphRQ8zLvIPsyv8NGfH2dtuyfersyxyxQFiRHxKd0Xcm2ATzyycOmEShwwx7bW15R q5YccfsASnpGcJuqUO6qn1+G3BYznW+f7CSnEYTxsVCnBU76+XoR6EGNxja35a/blVGx Oj/ubdg0r9FvKkB8K06yNC3v5UpDuGGumRgSF6ZUdebCUPHWvYCaNtvKRdDqF669I3Jr 46fLtQ5tmmIrDKoQm/NzGQxv1nNLyv0IugRVn1zVbB0rk4GFJNBgNBDo3v/1EAv+9Cpb aAhQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=iGbxgpKxfnU8cJSwCv4nptNKXdwEn4jlf+Gx5UStL+A=; b=Kxhm7Pi5jGE42FInnU25D8kBXQiA4ckOPQh0pZHN+Mr5zyvoajHdpDmNCg/nRwLVbg 0G9dsO8mMY6O4ERWs5S3ca0xOM2PHcUDH2LHZwNZEvFfr41+KT6fO0sjVCMSHH9b6EDW F1J8c0f1lfwAYn/nxX80BEi3K1HAwwOVZcnD3YxsGlfBpWaEs/GSbVrOhE7fqIAQLePZ Y/rv+/NbAh0M7mdntPLs5G6NE2DW85nIeNWBu7oafQPEBLLyqonqDhneB5H9C0IatX4g uc+CfUKajQgapBYzpgK/5OIYPfP098+db90XYGXR71TMsS30GZJ+OjnbzXVDyEeW3YNI 2OnQ== X-Gm-Message-State: AOUpUlH4O16/z4Rhdz+Ml/WdiMpfU/rjLy/2QkxLtYiXJWAY2yr0oRvT PIfXEQqr9aBvZhFOCMaShSE= X-Google-Smtp-Source: AAOMgpdMpu7HYOfsLLgDelPJRjiJElCR7KIGCEyNKzOk+vpZ2XgpITBFBor1DDNYkNU7A7rLw4D/bA== X-Received: by 2002:a62:9f16:: with SMTP id g22-v6mr10546666pfe.207.1532298121617; Sun, 22 Jul 2018 15:22:01 -0700 (PDT) Received: from himanshu-Vostro-3559 ([103.233.116.134]) by smtp.gmail.com with ESMTPSA id i25-v6sm3705084pfi.150.2018.07.22.15.21.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 22 Jul 2018 15:22:01 -0700 (PDT) Date: Mon, 23 Jul 2018 03:51:54 +0530 From: Himanshu Jha To: Daniel Baluta , dfrey@sierrawireless.com Cc: Andy Shevchenko , Jonathan Cameron , Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald , Linux Kernel Mailing List , linux-iio Subject: Re: [PATCH v4] iio: chemical: Add support for Bosch BME680 sensor Message-ID: <20180722222153.GA10066@himanshu-Vostro-3559> References: <1532122284-19602-1-git-send-email-himanshujha199640@gmail.com> <20180721161934.75066d97@archlinux> <20180721153607.GA11127@himanshu-Vostro-3559> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 21, 2018 at 08:45:34PM +0300, Daniel Baluta wrote: > On Sat, Jul 21, 2018 at 6:43 PM, Andy Shevchenko > wrote: > > On Sat, Jul 21, 2018 at 6:36 PM, Himanshu Jha > > wrote: > > > >>> > + /* Look up table 1 for the possible gas range values */ > >>> > + u32 lookupTable1[16] = {2147483647u, 2147483647u, 2147483647u, > >>> > + 2147483647u, 2147483647u, 2126008810u, > >>> > + 2147483647u, 2130303777u, 2147483647u, > >>> > + 2147483647u, 2143188679u, 2136746228u, > >>> > + 2147483647u, 2126008810u, 2147483647u, > >>> > + 2147483647u}; > > > > This one needs perhaps a bit of though, but... > > > >>> > + /* Look up table 2 for the possible gas range values */ > >>> > + u32 lookupTable2[16] = {4096000000u, 2048000000u, 1024000000u, > >>> > + 512000000u, 255744255u, 127110228u, 64000000u, > >>> > + 32258064u, 16016016u, 8000000u, 4000000u, > >>> > + 2000000u, 1000000u, 500000u, 250000u, 125000u}; > > > > ...this one obviously just a not needed one. You may replace it with a > > one constant and simple calculation to get either value (index from > > value, or value from index). > > Indeed this can be reduce to: > > 125.000 << (15 - idx). > > The real question here is if we approximate 255.744.255u to 256.00.00u how > much different is the result. Being a gas sensor I think it is very > hard to appreciate. > > We can go with this formula + adding a comment with the table with the > exact coefficients. So, I have planned to use this 125000 << (15 - idx) equation with approximating the array members. About the difference in results we would get after approximating isn't much of a problem IMHO because gas sensor is primarily used for IAQ, and IAQ is relative to the resistance reading. For eg: Resistance(ohm) IAQ value < 30K Very bad 30k < value < 50k worse 50k < value < 70k bad ... .. so on.. So, what I simply imply is the scale will be adjusted and nothing else changes, unlike if it had been pressure, temperature, humidity. The IAQ implementation is userspace application suggesting good/bad/ugly air quality. And since we know David Frey is planning to use this sensor in his product mangOH board. So, David, how are you planning to use the gas sensing part in your product ? RGB leds, buzzer, alarm ? Thanks Andy for the suggestion :) -- Himanshu Jha Undergraduate Student Department of Electronics & Communication Guru Tegh Bahadur Institute of Technology