From patchwork Wed Mar 21 14:28:56 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Hern=C3=A1n_Gonzalez?= X-Patchwork-Id: 10299553 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id BC859600F6 for ; Wed, 21 Mar 2018 14:31:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A960429882 for ; Wed, 21 Mar 2018 14:31:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A788F298A5; Wed, 21 Mar 2018 14:31:38 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4015C29882 for ; Wed, 21 Mar 2018 14:31:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752463AbeCUOad (ORCPT ); Wed, 21 Mar 2018 10:30:33 -0400 Received: from mail-qk0-f193.google.com ([209.85.220.193]:46961 "EHLO mail-qk0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752450AbeCUOa3 (ORCPT ); Wed, 21 Mar 2018 10:30:29 -0400 Received: by mail-qk0-f193.google.com with SMTP id o184so5600960qkd.13 for ; Wed, 21 Mar 2018 07:30:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=vanguardiasur-com-ar.20150623.gappssmtp.com; s=20150623; h=from:to:subject:date:message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=LK1yVfQQLfpg0ROueYMCyXcrQoKw/MJ7iFhZE50WaIs=; b=J4OcoL5EICCxK2QfOrOVnmtEMjuEvmzF299lzhyLfpLKOWv9wsYtJyARYbBz5qwXCq zWizSq95dlOx04mdQM3ARWb6IN807bnAuPCQW5BYtQCqejAOn3FY2tcj5oG5Sfv/8hI8 NwmO3B6Uv/w33/juHhCH6NY2vLZ+M38ZkTSaszWnW47esDTfgB20KfROeSAX3G5mpH8t ZBNGbuoixYezionBQFRYCbMwxu04WWlgQihei73Hc2Xg4+j4McN4tx1KNMX7WIDmLjpY 1Gd+fOr0AQ4N/BlMkgciedIgKpC+xQkLLyx1yZ6wMCei/ZUFhBjiKQzcbstzHWjskwVX 2n+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=LK1yVfQQLfpg0ROueYMCyXcrQoKw/MJ7iFhZE50WaIs=; b=YrxwY9Z8cpOq9w7kX6BqsxDfgOvEEe114fztS0DzkZjgBJ9P4Kye4HJNidHwDQVFv0 624TC5jxa7XIEb88ViE/563Pf6NTvkrUibgXjkzQvuCi+P2kpKWrkq69In8LQrfMeXCu 4nSBSgoE1oZ+fqFJO1iL+4bIH5HGNx1wWmyD2U08Bgx2y2bV+f2yA9baHu0xTJ8S2kCe jpmyuApUxl5XfLrZMbGFKEERaZG+0Rx/xlQvSVUfhWqdMNaUgUq3gl3Lf8gmyPJMze5m egQSmpZwg3jvKhSRW+kClmVxf95I9kiE3BrEuUYsjxHdjnKxwU6Qh5OSKdqMNDPrGA0G FvzA== X-Gm-Message-State: AElRT7F0QVOjlCbjQUfRUQ0ow8sncDSZEmsJ+H7OTuYfhPST4LtjlcE6 txepBKdPMl1DBMjjDWNWuQqusA== X-Google-Smtp-Source: AIpwx4+0nXPwVKIYntoAvrV+1XhtRNgw40tlK6cw0DD3uSznN9Q2TBGvhWAM5uVnKixCg5MmEmakWQ== X-Received: by 10.55.98.144 with SMTP id w138mr1789410qkb.300.1521642628696; Wed, 21 Mar 2018 07:30:28 -0700 (PDT) Received: from localhost.localdomain ([190.210.56.45]) by smtp.gmail.com with ESMTPSA id g14sm3118592qtk.71.2018.03.21.07.30.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 21 Mar 2018 07:30:28 -0700 (PDT) From: =?UTF-8?q?Hern=C3=A1n=20Gonzalez?= To: lars@metafoo.de, Michael.Hennerich@analog.com, jic23@kernel.org, knaack.h@gmx.de, pmeerw@pmeerw.net, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, hernan@vanguardiasur.com.ar Subject: [PATCH 08/11] staging: iio: ad7746: Add comments Date: Wed, 21 Mar 2018 11:28:56 -0300 Message-Id: <1521642539-4845-9-git-send-email-hernan@vanguardiasur.com.ar> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1521642539-4845-1-git-send-email-hernan@vanguardiasur.com.ar> References: <1521642539-4845-1-git-send-email-hernan@vanguardiasur.com.ar> MIME-Version: 1.0 Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add comments to clarify some of the calculations made, specially when reading or writing values. Signed-off-by: Hernán Gonzalez --- drivers/staging/iio/cdc/ad7746.c | 34 ++++++++++++++++++++++++++++------ 1 file changed, 28 insertions(+), 6 deletions(-) diff --git a/drivers/staging/iio/cdc/ad7746.c b/drivers/staging/iio/cdc/ad7746.c index 8abba71..b6b99e2 100644 --- a/drivers/staging/iio/cdc/ad7746.c +++ b/drivers/staging/iio/cdc/ad7746.c @@ -420,6 +420,7 @@ static int ad7746_write_raw(struct iio_dev *indio_dev, goto out; } + /* 2^16 in micro */ val = (val2 * 1024) / 15625; switch (chan->type) { @@ -546,6 +547,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, if (ret < 0) goto out; + /* + * Either for Capacitance, Voltage or Temperature, + * the 0x000000 code represents negative full scale, + * the 0x800000 code represents zero scale, and + * the 0xFFFFFF code represents positive full scale. + */ + *val = (be32_to_cpu(chip->data.d32) & 0xFFFFFF) - 0x800000; switch (chan->type) { @@ -557,7 +565,13 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, *val = (*val * 125) / 256; break; case IIO_VOLTAGE: - if (chan->channel == 1) /* supply_raw*/ + + /* + * The voltage from the VDD pin is internally + * attenuated by 6. + */ + + if (chan->channel == 1) /* supply_raw */ *val = *val * 6; break; default: @@ -598,21 +612,28 @@ static int ad7746_read_raw(struct iio_dev *indio_dev, ret = IIO_VAL_INT; break; case IIO_CHAN_INFO_OFFSET: + + /* + * CAPDAC Scale = 21pF_typ / 127 + * CIN Scale = 8.192pF / 2^24 + * Offset Scale = CAPDAC Scale / CIN Scale = 338646 + */ + *val = AD7746_CAPDAC_DACP(chip->capdac[chan->channel] - [chan->differential]) * 338646; + [chan->differential]) * 338646; ret = IIO_VAL_INT; break; case IIO_CHAN_INFO_SCALE: switch (chan->type) { case IIO_CAPACITANCE: - /* 8.192pf / 2^24 */ + /* CIN Scale: 8.192pf / 2^24 */ *val = 0; *val2 = 488; ret = IIO_VAL_INT_PLUS_NANO; break; case IIO_VOLTAGE: - /* 1170mV / 2^23 */ + /* VIN Scale: 1170mV / 2^23 */ *val = 1170; *val2 = 23; ret = IIO_VAL_FRACTIONAL_LOG2; @@ -666,7 +687,8 @@ static struct ad7746_platform_data *ad7746_parse_dt(struct device *dev) unsigned int tmp; int ret; - /* The default excitation outputs are not inverted, it should be stated + /* + * The default excitation outputs are not inverted, it should be stated * in the dt if needed. */ @@ -678,7 +700,7 @@ static struct ad7746_platform_data *ad7746_parse_dt(struct device *dev) ret = of_property_read_u32(np, "adi,exclvl", &tmp); if (ret || tmp > 3) { dev_warn(dev, "Wrong exclvl value, using default\n"); - pdata->exclvl = 3; /* default value */ + pdata->exclvl = 3; } else { pdata->exclvl = tmp; }