Messages in this thread Patch in this message | | | Date | Mon, 10 Apr 2017 19:00:01 +0200 | From | Andreas Klinger <> | Subject | [PATCH v2] IIO: bmp280-core.c: fix error in humidity calculation |
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While calculating the compensation of the humidity there are negative values interpreted as unsigned because of unsigned variables used. These values as well as the constants need to be casted to signed as indicated by the documentation of the sensor.
Changes in v2: - cast also constants to signed; otherwise calculation is not correct
I removed the Acked-By of Linus Walleij because of another change in the calculation. Don't know how it should be treated.
Signed-off-by: Andreas Klinger <ak@it-klinger.de> --- drivers/iio/pressure/bmp280-core.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c index 4d18826ac63c..d82b788374b6 100644 --- a/drivers/iio/pressure/bmp280-core.c +++ b/drivers/iio/pressure/bmp280-core.c @@ -175,11 +175,12 @@ static u32 bmp280_compensate_humidity(struct bmp280_data *data, } H6 = sign_extend32(tmp, 7); - var = ((s32)data->t_fine) - 76800; - var = ((((adc_humidity << 14) - (H4 << 20) - (H5 * var)) + 16384) >> 15) - * (((((((var * H6) >> 10) * (((var * H3) >> 11) + 32768)) >> 10) - + 2097152) * H2 + 8192) >> 14); - var -= ((((var >> 15) * (var >> 15)) >> 7) * H1) >> 4; + var = ((s32)data->t_fine) - (s32)76800; + var = ((((adc_humidity << 14) - (H4 << 20) - (H5 * var)) + + (s32)16384) >> 15) * (((((((var * H6) >> 10) + * (((var * (s32)H3) >> 11) + (s32)32768)) >> 10) + + (s32)2097152) * H2 + 8192) >> 14); + var -= ((((var >> 15) * (var >> 15)) >> 7) * (s32)H1) >> 4; return var >> 12; }; -- 2.1.4
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