| From | Kamal Mostafa <> | Subject | [PATCH 4.2.y-ckt 050/273] iio: pressure: mpl115: fix temperature offset sign | Date | Mon, 7 Mar 2016 14:47:21 -0800 |
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4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Akinobu Mita <akinobu.mita@gmail.com>
commit 431386e783a3a6c8b7707bee32d18c353b8688b2 upstream.
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 <akinobu.mita@gmail.com> Acked-by: Peter Meerwald-Stadler <pmeerw@pmeerw.net> Signed-off-by: Jonathan Cameron <jic23@kernel.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- 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 f5ecd6e..a0d7dee 100644 --- a/drivers/iio/pressure/mpl115.c +++ b/drivers/iio/pressure/mpl115.c @@ -117,7 +117,7 @@ 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: -- 2.7.0
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