diff options
| author | Lars-Peter Clausen <lars@metafoo.de> | 2012-08-10 17:36:00 +0100 |
|---|---|---|
| committer | Jonathan Cameron <jic23@kernel.org> | 2012-08-16 20:24:34 +0100 |
| commit | 2a9e0662f6779d2074ecaa80ea5753d5f0cf1b93 (patch) | |
| tree | 616e32f056310a660430609eab899a95cbeacb6a | |
| parent | 680f8ea0e85c5c3a7283be99435d6461e8725348 (diff) | |
| download | linux-2a9e0662f6779d2074ecaa80ea5753d5f0cf1b93.tar.bz2 | |
staging:iio:ad7793: Fix temperature scale and offset
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@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
| -rw-r--r-- | drivers/staging/iio/adc/ad7793.c | 29 |
1 files changed, 18 insertions, 11 deletions
diff --git a/drivers/staging/iio/adc/ad7793.c b/drivers/staging/iio/adc/ad7793.c index 56014a8b6876..3c8d1d4c6192 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; |