From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from saturn.retrosnub.co.uk ([178.18.118.26]:45544 "EHLO saturn.retrosnub.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751608AbcAXQdQ (ORCPT ); Sun, 24 Jan 2016 11:33:16 -0500 Subject: Re: [PATCH] iio: pressure: mpl115: fix temperature offset sign To: Akinobu Mita , linux-iio@vger.kernel.org References: <1453306051-8817-1-git-send-email-akinobu.mita@gmail.com> Cc: Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald From: Jonathan Cameron Message-ID: <56A4FCCA.80500@kernel.org> Date: Sun, 24 Jan 2016 16:33:14 +0000 MIME-Version: 1.0 In-Reply-To: <1453306051-8817-1-git-send-email-akinobu.mita@gmail.com> Content-Type: text/plain; charset=windows-1252 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 20/01/16 16:07, Akinobu Mita wrote: > According to the datasheet, the resolusion of temperature sensor is > -5.35 counts/C. Temperature ADC is 472 counts at 25C. > (https://www.sparkfun.com/datasheets/Sensors/Pressure/MPL115A1.pdf > NOTE: This is older revision, but this information is removed from the > latest datasheet from nxp somehow) > > Temp [C] = (Tadc - 472) / -5.35 + 25 > = (Tadc - 605.750000) * -0.186915888 > > So the correct offset is -605.750000. > > Signed-off-by: Akinobu Mita > Cc: Jonathan Cameron > Cc: Hartmut Knaack > Cc: Lars-Peter Clausen > Cc: Peter Meerwald > Cc: linux-iio@vger.kernel.org Peter, I'd like your Ack on this given it is your driver. That way I can be lazy and not cross check the datasheet myself. Jonathan > --- > drivers/iio/pressure/mpl115.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iio/pressure/mpl115.c b/drivers/iio/pressure/mpl115.c > index 138344c..73f2f0c 100644 > --- a/drivers/iio/pressure/mpl115.c > +++ b/drivers/iio/pressure/mpl115.c > @@ -118,7 +118,7 @@ static int mpl115_read_raw(struct iio_dev *indio_dev, > *val = ret >> 6; > return IIO_VAL_INT; > case IIO_CHAN_INFO_OFFSET: > - *val = 605; > + *val = -605; > *val2 = 750000; > return IIO_VAL_INT_PLUS_MICRO; > case IIO_CHAN_INFO_SCALE: >