On 08.03.2015 13:50, Jonathan Cameron wrote:
On 23/02/15 19:35, Roberta Dobrescu wrote:
This patch refactors the isl29018 driver code in order to use standard
sysfs attributes for range and scale.
ISL29018 light sensor uses four ranges and four ADC's resolutions
which influence the calculated lux.
This patch eliminates the resolution (adc bits) and introduces scale.
Each range (1k, 4k, 16k or 64k) has a corresponding set of 4 scales
(for 16, 12, 8 or 4 bits). Both range and scale can be changed by the
user according to the corresponding set of values (exposed by the attributes
in_illuminance_range_available and in_illuminance_scale_available).
When the range is changed, the set of available scales is set accordingly and
by default the scale used is the one for 16 adc bits. Scale can be changed
anytime with one of the available values.
So we have 3 things interacting here.
range - absolutely controlled for the device
scale - from current range, with the adc resolution confusing things - we could just
multiply the output result up and not need to report this to userspace at all
integration_time - This is the one element that's really being controlled by the adc
resolution. This adc resolution is really effecting our sensitivity
not the accuracy of measurement of the signal.
Hence I'd have your adc resolution controlled by in_illuminance0_integration_time
and the full scale range controlled by scale.
For the lower adc resolutions simply apply the relevant scaling to get the output
value to be on the same scale (assuming the range has not changed)
How does that sound?
Sounds good :D.
Thanks for reviewing this.
Roberta
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