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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D17B1CCA482 for ; Thu, 23 Jun 2022 17:39:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234390AbiFWRj5 (ORCPT ); Thu, 23 Jun 2022 13:39:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234594AbiFWRhy (ORCPT ); Thu, 23 Jun 2022 13:37:54 -0400 Received: from mail-lf1-x12e.google.com (mail-lf1-x12e.google.com [IPv6:2a00:1450:4864:20::12e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6A92692B4F; Thu, 23 Jun 2022 10:07:15 -0700 (PDT) Received: by mail-lf1-x12e.google.com with SMTP id j21so91785lfe.1; Thu, 23 Jun 2022 10:07:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=0E4art4WHyIDsKy+IOK+bSE3VnO/zAwRAVWiCR6wQsM=; b=XK1yu15Q26rYs9zDD16HkxWE+plO8GeZ+dNujYTCKpe0TBb9yxE8UjsSaLbdNB5qgy wdewUnj3qqqzHpiTGOtPOCQfXBhSf8Aa7T0CijynNDEP+9Sb+fuQu6kBrqECzbe7hJDW aBFumHP43UwBjt5ZxPjA2w60ETmwUhIzpJCpCt54fTlFh40UC3ez72g0dMICG0is8RDD PjLS/EGzGYJnRl41uj1poo5Iq7znQ2n+xYLNlVbYePC2Z/qqucryweylIgCBzuCVy0Oc 4wZqFJmB22a2V+tIDMI9B9+h4B63K2rBEqcgg6JO4RkT9H8KhnartdiDsbFlE2yCgd/m RCXw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=0E4art4WHyIDsKy+IOK+bSE3VnO/zAwRAVWiCR6wQsM=; b=AfTF06MC0ga6m29Gv6x3CeoHzW8gYCb1o2pPll/MMp10KSXdaAz8HMH5kNiS2MQieq 9WAi7ApMBEvIwMMqCuKbzThZonqkv7xFsbCiXa7IuFAeIoyr4DzP6JdbajSCHh1LzBZl 5MKZZ1/YbGZVe9IZj0PATq5G6MUaXSCgweGasmYLsRylg0mIa7Y9xiU7wYiUjiuceyOx VhQ3BmqzQFxWj1YsyYKqeYt42VsmRiCWJFw/EAVWi3c8gGPPFkb2i946Q8pf34BuIhiS J6Bf62KBOvSxr8fwbxUt//i0j9rN/VrQ8lAC4ceguJKGY48+RzuHbsn1zmj2v7vI60TL dZQQ== X-Gm-Message-State: AJIora8wOzGvVg4Ea6PGmQ5TFjCI8/VRV+6yDmiVeb0Du15ppuWzV2vi 7avgRM3gYfnQOQVQ5yE6QFo= X-Google-Smtp-Source: AGRyM1vX8jlCl+4BPopA0BVNn2QNiJNNOFUmG++cyTTTiZGKTZyDG8lzDMD3GuWJRGn17RqeB6OEkA== X-Received: by 2002:a05:6512:22c1:b0:479:54b6:8281 with SMTP id g1-20020a05651222c100b0047954b68281mr6210521lfu.291.1656004033642; Thu, 23 Jun 2022 10:07:13 -0700 (PDT) Received: from localhost.localdomain (82-209-154-112.cust.bredband2.com. [82.209.154.112]) by smtp.gmail.com with ESMTPSA id w27-20020a19491b000000b0047a0bf9540asm3060405lfa.213.2022.06.23.10.07.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jun 2022 10:07:12 -0700 (PDT) From: Marcus Folkesson To: Marcus Folkesson , Kent Gustavsson , Jonathan Cameron , Lars-Peter Clausen , Rob Herring , Krzysztof Kozlowski Cc: linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 07/10] iio: adc: mcp3911: use correct formula for AD conversion Date: Thu, 23 Jun 2022 19:08:41 +0200 Message-Id: <20220623170844.2189814-7-marcus.folkesson@gmail.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220623170844.2189814-1-marcus.folkesson@gmail.com> References: <20220623170844.2189814-1-marcus.folkesson@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org The ADC conversion is actually not rail-to-rail but with a factor 1.5. Make use of this factor when calculating actual voltage. Signed-off-by: Marcus Folkesson --- drivers/iio/adc/mcp3911.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c index 65831bef12f6..9e365947d285 100644 --- a/drivers/iio/adc/mcp3911.c +++ b/drivers/iio/adc/mcp3911.c @@ -48,8 +48,8 @@ #define MCP3911_CHANNEL(x) (MCP3911_REG_CHANNEL0 + x * 3) #define MCP3911_OFFCAL(x) (MCP3911_REG_OFFCAL_CH0 + x * 6) -/* Internal voltage reference in uV */ -#define MCP3911_INT_VREF_UV 1200000 +/* Internal voltage reference in mV */ +#define MCP3911_INT_VREF_MV 1200 #define MCP3911_REG_READ(reg, id) ((((reg) << 1) | ((id) << 5) | (1 << 0)) & 0xff) #define MCP3911_REG_WRITE(reg, id) ((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff) @@ -178,11 +178,18 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev, *val = ret / 1000; } else { - *val = MCP3911_INT_VREF_UV; + *val = MCP3911_INT_VREF_MV; } - *val2 = 24; - ret = IIO_VAL_FRACTIONAL_LOG2; + /* + * For 24bit Conversion + * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5 + * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5) + */ + + /* val2 = (2^23 * 1.5) */ + *val2 = 12582912; + ret = IIO_VAL_FRACTIONAL; break; } -- 2.36.1