The temperature channel uses the internal 1.17V reference with 0.81 mv/C. The
reported temperature is in Kevlin, so we need to add the Kelvin to Celcius
offset when reporting the offset for the temperature channel.
Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
---
drivers/staging/iio/adc/ad7793.c | 29 ++++++++++++++++++-----------
1 file changed, 18 insertions(+), 11 deletions(-)
diff --git a/drivers/staging/iio/adc/ad7793.c b/drivers/staging/iio/adc/ad7793.c
index 56014a8..3c8d1d4 100644
--- a/drivers/staging/iio/adc/ad7793.c
+++ b/drivers/staging/iio/adc/ad7793.c
@@ -617,30 +617,37 @@ static int ad7793_read_raw(struct iio_dev *indio_dev,
return IIO_VAL_INT_PLUS_NANO;
} else {
/* 1170mV / 2^23 * 6 */
- scale_uv = (1170ULL * 100000000ULL * 6ULL)
- >> (chan->scan_type.realbits -
- (unipolar ? 0 : 1));
+ scale_uv = (1170ULL * 100000000ULL * 6ULL);
}
break;
case IIO_TEMP:
- /* Always uses unity gain and internal ref */
- scale_uv = (2500ULL * 100000000ULL)
- >> (chan->scan_type.realbits -
- (unipolar ? 0 : 1));
+ /* 1170mV / 0.81 mV/C / 2^23 */
+ scale_uv = 1444444444444ULL;
break;
default:
return -EINVAL;
}
- *val2 = do_div(scale_uv, 100000000) * 10;
- *val = scale_uv;
-
+ scale_uv >>= (chan->scan_type.realbits - (unipolar ? 0 : 1));
+ *val = 0;
+ *val2 = scale_uv;
return IIO_VAL_INT_PLUS_NANO;
case IIO_CHAN_INFO_OFFSET:
if (!unipolar)
- *val -= (1 << (chan->scan_type.realbits - 1));
+ *val = -(1 << (chan->scan_type.realbits - 1));
else
*val = 0;
+
+ /* Kelvin to Celsius */
+ if (chan->type == IIO_TEMP) {
+ unsigned long long offset;
+ unsigned int shift;
+
+ shift = chan->scan_type.realbits - (unipolar ? 0 : 1);
+ offset = 273ULL << shift;
+ do_div(offset, 1444);
+ *val -= offset;
+ }
return IIO_VAL_INT;
}
return -EINVAL;
--
1.7.10.4
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