iio: gyro: mpu3050: Fix reported temperature value
Subsystems (2)
PATCH v2 1/1 iio: gyro: mpu3050: Fix reported temperature value
The raw temperature value is a 16-bit signed integer. The sign casting is missing in the code, which results in a wrong temperature reported by userspace tools, fix it.
Datasheet: https://www.cdiweb.com/datasheets/invensense/mpu-3000a.pdf
---
Changelog:
v2: - Replaced "signed 16bit integer" wording with "16-bit signed integer",
replaced "Link" tag with the "Datasheet" and added "Fixes" tag as was suggested by Andy Shevchenko.
- Added r-b from Andy Shevchenko and Linus Walleij.
drivers/iio/gyro/mpu3050-core.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
drivers/iio/gyro/mpu3050-core.c +11 -2
@@ -272,7 +272,16 @@ static int mpu3050_read_raw(struct iio_dev *indio_dev,case IIO_CHAN_INFO_OFFSET :switch (chan->type) {case IIO_TEMP : -/* The temperature scaling is (x+23000)/280 Celsius */ +/* +* The temperature scaling is (x+23000)/280 Celsius, +* where 23000 includes room temperature offset of +* +35C, 280 is the precision scale and x is the 16-bit +* signed integer which corresponds to the temperature +* range of -40C..85C. +* +* Temperature value itself represents temperature of +* the sensor die. +*/ *val =23000 ;return IIO_VAL_INT ;default :
@@ -329,7 +338,7 @@ static int mpu3050_read_raw(struct iio_dev *indio_dev, goto out_read_raw_unlock; } - *val =be16_to_cpu (raw_val); + *val = (s16 )be16_to_cpu (raw_val); ret =IIO_VAL_INT ; goto out_read_raw_unlock;
Signature · 1 line
2.30.2
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22.04.2021 09:46, Andy Shevchenko пишет:
Quoted 16 lines
case
IIO_TEMP:
- /* The temperature scaling is (x+23000)/280 Celsius */
+ /*
+ * The temperature scaling is (x+23000)/280 Celsius,
+ * where 23000 includes room temperature offset of
+ * +35C, 280 is the precision scale and x is the 16-bit
+ * signed integer which corresponds to the temperature
+ * range of -40C..85C.
Quoted 5 lines
Datasheet says typical -30°... also think about the other comment you gave, I.e. about temperature of the die itself. Are you suggesting that at -40° the die T is also -40°? Does it have perpetuum mobile ? ;) it might dissipate not to much energy, but we don’t know the linearity of the curve there.
My understanding that -40C is the minimum temperature which sensor may report.
Alright, I think the comment could be improved a tad anyways. I'll prepare v3, thanks.