linux-kernel - Re: iio: what does in_accel_x_thresh_rising

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Date:	Thu, 11 Jun 2015 19:34:12 +0200
From:	Martin Kepplinger <martin.kepplinger@...obroma-systems.com>
To:	Jonathan Cameron <jic23@...nel.org>, irina.tirdea@...el.com,
	daniel.baluta@...el.com
CC:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: iio: what does in_accel_x_thresh_rising_en ?

Am 2015-06-10 um 22:49 schrieb Jonathan Cameron:
> On 09/06/15 17:03, Martin Kepplinger wrote:
>> hi
>>
>> Is the in_accel_thresh_rising_value (or falling) threshold value signed
>> or unsigned?
>>
>> In other words: Is a RISING event fired on an absolute growing value in
>> the positive range, and a FALLING event on an absolute growing value in
>> the negative acceleration range (< 0g)?
>>
>> Or is a RISING event fired on a signed rising value, no matter if the
>> threshold is positive or negative, and a FALLING event on a decreasing
>> signed value, also when the threshold is positive?
>>
>> thanks
>>
>>                                 martin
>>
> Hi Martin,
> 
> The two relevant abi elements are:
> in_accel_thresh_rising_value and
> in_accel_mag_rising_value
> Once you know the second one exists then you can probably work out the
> meaning of thresh ;)
> 
> Thresh is the value, mag(nitude) is the absolute value, so if you get one
> that is thresh, then if the channel can go negative, negative values are
> definitely possible.  On an accelerometer, you can get either implemented.
> mag_rising is typically to allow motion detection, thresh_rising might
> be used to detect a change of orientation (put bounds around each axis
> at a particular point in time.
> 
> There are also roc (rate of change) type event detectors on some accelerometers.
> 
> Hope that clear the mud up ;)
> 
> Jonathan
> 

Hi Jonathan,

Oh I overlooked, this is clear now. So
events/in_accel_x&y&z_mag_falling_en for example is
a classic freefall detection. Would an implementation here just use
in_accel_mag_falling_value ? I'm not yet sure how an iio_event_spec
would look like in that case. Freefall is what I could do in my driver.

But this was very helpful, thanks for your time!

                               martin
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