Acceleration units and mma8452 driver

Acceleration units and mma8452 driver

[Martin Fuzzey]

Hi all,

I'm new to iio and have a question on acceleration units.

Documentation/ABI/testing/sysfs-bus-iio states "after application of 
scale and offset are m/s^2"

However the mma8452 driver, when in 2G full scale mode provides a scale 
factor of 0.000977

/sys/bus/iio/devices/iio:device0# cat in_accel_scale
0.000977

Full scale positive raw value (12 bits) is 2047 so that gives 2G 
(0.000977 * 2047)

So this driver seems to be using G as units rather than m/s^2.

Am I misunderstanding or is this a driver or doc bug?

Regards,

Martin

Re: Acceleration units and mma8452 driver

[Jonathan Cameron]

On July 11, 2014 11:16:03 AM GMT+01:00, Martin Fuzzey <mfuzzey@parkeon.com> wrote:
>Hi all,
>
>I'm new to iio and have a question on acceleration units.
>
>Documentation/ABI/testing/sysfs-bus-iio states "after application of 
>scale and offset are m/s^2"
>
>However the mma8452 driver, when in 2G full scale mode provides a scale
>
>factor of 0.000977
>
>/sys/bus/iio/devices/iio:device0# cat in_accel_scale
>0.000977
>
>Full scale positive raw value (12 bits) is 2047 so that gives 2G 
>(0.000977 * 2047)
>
>So this driver seems to be using G as units rather than m/s^2.
>
>Am I misunderstanding or is this a driver or doc bug?
>
Driver bug. Good catch. Do you want to prepare a patch?

Thanks

Jonathan

>Regards,
>
>Martin
>
>
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