On Tue, 21 Nov 2023 06:48:39 +0100 Javier Carrasco <javier.carrasco@xxxxxxxxxxxxxx> wrote: > The current offset has the scale already applied to it. The ABI > documentation defines the offset parameter as "offset to be added > to <type>[Y]_raw prior to scaling by <type>[Y]_scale in order to > obtain value in the <type> units as specified in <type>[Y]_raw > documentation" > > The right value is obtained at 0 degrees Celsius by the formula provided > in the datasheet: > > T = Tsens_t0 + (Tadc_t - Tadc_t0) / Tadc_res > > where: > T = 0 degrees Celsius > Tsens_t0 (reference temperature) = 25 degrees Celsius > Tadc_t0 (16-bit format for Tsens_t0) = 17508 > Tadc_res = 60.1 LSB/degree Celsius > > The resulting offset is 16005.5, which has been truncated to 16005 to > provide an integer value with a precision loss smaller than the 1-LSB > measurement precision. > > Fix the offset to apply its value prior to scaling. > > Signed-off-by: Javier Carrasco <javier.carrasco@xxxxxxxxxxxxxx> Applied to the fixes-togreg branch of iio.git and marked for stable. Thanks, Jonathan > --- > Changes in v2: > - Fixed typo in the offset value (16005 instead of 16605) (Jonathan Cameron) > > - Link to v1: > https://lore.kernel.org/r/20231023-topic-tmag5273x1_temp_offset-v1-1-983dca43292c@xxxxxxxxxxxxxx > --- > drivers/iio/magnetometer/tmag5273.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iio/magnetometer/tmag5273.c > b/drivers/iio/magnetometer/tmag5273.c > index c5e5c4ad681e..e8c4ca142d21 100644 > --- a/drivers/iio/magnetometer/tmag5273.c > +++ b/drivers/iio/magnetometer/tmag5273.c > @@ -356,7 +356,7 @@ static int tmag5273_read_raw(struct iio_dev *indio_dev, > case IIO_CHAN_INFO_OFFSET: > switch (chan->type) { > case IIO_TEMP: > - *val = -266314; > + *val = -16005; > return IIO_VAL_INT; > default: > return -EINVAL; > > --- > base-commit: 05d3ef8bba77c1b5f98d941d8b2d4aeab8118ef1 > change-id: 20231023-topic-tmag5273x1_temp_offset-17774cbce961 > > Best regards,
