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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 A0AFFC43461 for ; Wed, 9 Sep 2020 18:05:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 515842065E for ; Wed, 9 Sep 2020 18:05:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726440AbgIISFp (ORCPT ); Wed, 9 Sep 2020 14:05:45 -0400 Received: from mailout09.rmx.de ([94.199.88.74]:35137 "EHLO mailout09.rmx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728709AbgIISFe (ORCPT ); Wed, 9 Sep 2020 14:05:34 -0400 Received: from kdin01.retarus.com (kdin01.dmz1.retloc [172.19.17.48]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mailout09.rmx.de (Postfix) with ESMTPS id 4BmqgW0m44zbgxm; Wed, 9 Sep 2020 20:05:27 +0200 (CEST) Received: from mta.arri.de (unknown [217.111.95.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by kdin01.retarus.com (Postfix) with ESMTPS id 4BmqgJ31gnz2xDN; Wed, 9 Sep 2020 20:05:16 +0200 (CEST) Received: from n95hx1g2.localnet (192.168.54.12) by mta.arri.de (192.168.100.104) with Microsoft SMTP Server (TLS) id 14.3.408.0; Wed, 9 Sep 2020 20:04:54 +0200 From: Christian Eggers To: Andy Shevchenko CC: Jonathan Cameron , Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , linux-iio , "Linux Kernel Mailing List" Subject: Re: [PATCH] iio: light: as73211: Increase measurement timeout Date: Wed, 9 Sep 2020 20:04:24 +0200 Message-ID: <6187855.5mNlXCv1x4@n95hx1g2> Organization: Arnold & Richter Cine Technik GmbH & Co. Betriebs KG In-Reply-To: References: <20200909154439.10308-1-ceggers@arri.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Originating-IP: [192.168.54.12] X-RMX-ID: 20200909-200524-4BmqgJ31gnz2xDN-0@kdin01 X-RMX-SOURCE: 217.111.95.66 Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Wednesday, 9 September 2020, 18:58:39 CEST, Andy Shevchenko wrote: > On Wed, Sep 9, 2020 at 6:45 PM Christian Eggers wrote: > > We found some sensors which are much slower (20% at room temperature) > > than nominal. According to the data sheet, up to 27% is possible. Now I > > add 33% to the nominal time out, hopefully this is enough. > > I'm wondering if this is a function of temperature. > And if that has an actual thermistor inside... I haven't designed the hardware, but I guess that clock generation is done using an RC oscillator which depends on temperature. Temperature measurement is possible, but I think the recommended way is to externally control the integration time using the SYN pin and to get the actual number of RC cycles from a register. But generating the required waveform for the SYN pin using a uC general purpose timer seems challenging. I wouldn't be surprised if the measurement results also depend on the exact value of the supply voltage.