Changed the offset to negative as usual equation is: (raw +
offset)*scale and in this
case offset should be negative (as we deduct 273.15 Kelvin to get temperature
in Celsius).
Signed-off-by: Crt Mori <cmo@xxxxxxxxxxx>
Acked-by: Peter Meerwald <pmeerw@xxxxxxxxxx>
---
drivers/iio/temperature/mlx90614.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iio/temperature/mlx90614.c
b/drivers/iio/temperature/mlx90614.c
index c8b6ac8..951a50f 100644
--- a/drivers/iio/temperature/mlx90614.c
+++ b/drivers/iio/temperature/mlx90614.c
@@ -58,7 +58,7 @@ static int mlx90614_read_raw(struct iio_dev *indio_dev,
*val = ret;
return IIO_VAL_INT;
case IIO_CHAN_INFO_OFFSET:
- *val = 13657;
+ *val = -13657;
*val2 = 500000;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_CHAN_INFO_SCALE:
On 5 July 2015 at 14:51, Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
> On 29/06/15 15:43, Crt Mori wrote:
>>>> Translates the magic constant numbers to named macros and add some
>>>> additional comments about their meaning. Also changed the offset to
>>>> negative as usual equation is: (raw + offset)*scale and in this
>>>> case offset should be negative (as we deduct 273.15 Kelvin to get
>>>> temperature in Celsius)..
>>
>>> On 29 June 2015 at 14:19, Peter Meerwald <pmeerw@xxxxxxxxxx> wrote:
>>> looks good; strictly, this patch is
>>> (a) a bugfix (the offset should be negative),
>>> (b) cleanup to replace constants by macros.
>>
>> I agree, but other things are more design than a proper change.
> True, but the fix may well go via a faster route and be backported
> to older kernels. The other stuff is good, but we can take our time
> with it. Please split the patch and repost.
>>
>> I would also like you to reconsider the usage of
>> IIO_CHAN_INFO_PROCESSED which would report calculated value
>> to avoid knowing the sensor specifics and just provide general output
>> (this would avoid different calculations of final temperature for different
>> sensors).
> If it can't be done via a straight linear map, then processed is the
> only option. If it can then it really doesn't matter as generic
> userspace will handle it just fine.
>>
>>>>
>>>> The diff is made towards togreg branch as that branch seems to have the
>>>> most recent updates of mlx90614 driver (many are yet to be merged).
>>>>
>>>> Signed-off-by: Crt Mori <cmo@xxxxxxxxxxx>
>>>> ---
>>>> drivers/iio/temperature/mlx90614.c | 20 ++++++++++++++------
>>>> 1 file changed, 14 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/iio/temperature/mlx90614.c
>>>> b/drivers/iio/temperature/mlx90614.c
>>>> index cb2e8ad..909278a 100644
>>>> --- a/drivers/iio/temperature/mlx90614.c
>>>> +++ b/drivers/iio/temperature/mlx90614.c
>>>> @@ -65,6 +65,13 @@
>>>>
>>>> #define MLX90614_AUTOSLEEP_DELAY 5000 /* default autosleep delay */
>>>>
>>>> +/* Magic constants */
>>>> +#define MLX90614_CONST_OFFSET_DEC -13657 /* decimal part of the Kelvin
>>>> offset */
>>>> +#define MLX90614_CONST_OFFSET_REM 500000 /* remainder of offset
>>>> (273.15*50) */
>>>> +#define MLX90614_CONST_SCALE 20 /* Scale in milliKelvin (0.02 * 1000) */
>>>> +#define MLX90614_CONST_RAW_EMISSIVITY_MAX 65535 /* max value for
>>>> emissivity */
>>>> +#define MLX90614_CONST_EMISSIVITY_RESOLUTION 15259 /* 1/65535 ~
>>>> 0.000015259 */
>>>> +
>>>> struct mlx90614_data {
>>>> struct i2c_client *client;
>>>> struct mutex lock; /* for EEPROM access only */
>>>> @@ -204,11 +211,11 @@ static int mlx90614_read_raw(struct iio_dev
>>>> *indio_dev,
>>>> *val = ret;
>>>> return IIO_VAL_INT;
>>>> case IIO_CHAN_INFO_OFFSET:
>>>> - *val = 13657;
>>>> - *val2 = 500000;
>>>> + *val = MLX90614_CONST_OFFSET_DEC;
>>>> + *val2 = MLX90614_CONST_OFFSET_REM;
>>>> return IIO_VAL_INT_PLUS_MICRO;
>>>> case IIO_CHAN_INFO_SCALE:
>>>> - *val = 20;
>>>> + *val = MLX90614_CONST_SCALE;
>>>> return IIO_VAL_INT;
>>>> case IIO_CHAN_INFO_CALIBEMISSIVITY: /* 1/65535 / LSB */
>>>> mlx90614_power_get(data, false);
>>>> @@ -221,12 +228,12 @@ static int mlx90614_read_raw(struct iio_dev
>>>> *indio_dev,
>>>> if (ret < 0)
>>>> return ret;
>>>>
>>>> - if (ret == 65535) {
>>>> + if (ret == MLX90614_CONST_RAW_EMISSIVITY_MAX) {
>>>> *val = 1;
>>>> *val2 = 0;
>>>> } else {
>>>> *val = 0;
>>>> - *val2 = ret * 15259; /* 1/65535 ~ 0.000015259 */
>>>> + *val2 = ret * MLX90614_CONST_EMISSIVITY_RESOLUTION;
>>>> }
>>>> return IIO_VAL_INT_PLUS_NANO;
>>>> default:
>>>> @@ -245,7 +252,8 @@ static int mlx90614_write_raw(struct iio_dev *indio_dev,
>>>> case IIO_CHAN_INFO_CALIBEMISSIVITY: /* 1/65535 / LSB */
>>>> if (val < 0 || val2 < 0 || val > 1 || (val == 1 && val2 !=
>>>> 0))
>>>> return -EINVAL;
>>>> - val = val * 65535 + val2 / 15259; /* 1/65535 ~ 0.000015259
>>>> */
>>>> + val = val * MLX90614_CONST_RAW_EMISSIVITY_MAX +
>>>> + val2 / MLX90614_CONST_EMISSIVITY_RESOLUTION;
>>>>
>>>> mlx90614_power_get(data, false);
>>>> mutex_lock(&data->lock);
>>>>
>> --
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