Kernel driver apds990x
Supported chips:
Avago APDS990X
Data sheet:
Not freely available
Author:
Samu Onkalo samu.p.onkalo@nokia.com
Description
APDS990x is a combined ambient light and proximity sensor. ALS and proximity
functionality are highly connected. ALS measurement path must be running
while the proximity functionality is enabled.
ALS produces raw measurement values for two channels: Clear channel
(infrared + visible light) and IR only. However, threshold comparisons happen
using clear channel only. Lux value and the threshold level on the HW
might vary quite much depending the spectrum of the light source.
Driver makes necessary conversions to both directions so that user handles
only lux values. Lux value is calculated using information from the both
channels. HW threshold level is calculated from the given lux value to match
with current type of the lightning. Sometimes inaccuracy of the estimations
lead to false interrupt, but that doesn’t harm.
ALS contains 4 different gain steps. Driver automatically
selects suitable gain step. After each measurement, reliability of the results
is estimated and new measurement is triggered if necessary.
Platform data can provide tuned values to the conversion formulas if
values are known. Otherwise plain sensor default values are used.
Proximity side is little bit simpler. There is no need for complex conversions.
It produces directly usable values.
Driver controls chip operational state using pm_runtime framework.
Voltage regulators are controlled based on chip operational state.
SYSFS
chip_id
RO - shows detected chip type and version
power_state
RW - enable / disable chip. Uses counting logic
1 enables the chip
0 disables the chip
lux0_input
RO - measured lux value
sysfs_notify called when threshold interrupt occurs
lux0_sensor_range
RO - lux0_input max value. Actually never reaches since sensor tends
to saturate much before that. Real max value varies depending
on the light spectrum etc.
lux0_rate
RW - measurement rate in Hz
lux0_rate_avail
RO - supported measurement rates
lux0_calibscale
RW - calibration value. Set to neutral value by default.
Output results are multiplied with calibscale / calibscale_default
value.
lux0_calibscale_default
RO - neutral calibration value
lux0_thresh_above_value
RW - HI level threshold value. All results above the value
trigs an interrupt. 65535 (i.e. sensor_range) disables the above
interrupt.
lux0_thresh_below_value
RW - LO level threshold value. All results below the value
trigs an interrupt. 0 disables the below interrupt.
prox0_raw
RO - measured proximity value
sysfs_notify called when threshold interrupt occurs
prox0_sensor_range
RO - prox0_raw max value (1023)
prox0_raw_en
RW - enable / disable proximity - uses counting logic
1 enables the proximity
0 disables the proximity
prox0_reporting_mode
RW - trigger / periodic. In “trigger” mode the driver tells two possible
values: 0 or prox0_sensor_range value. 0 means no proximity,
1023 means proximity. This causes minimal number of interrupts.
In “periodic” mode the driver reports all values above
prox0_thresh_above. This causes more interrupts, but it can give
rough estimate about the distance.
prox0_reporting_mode_avail
RO - accepted values to prox0_reporting_mode (trigger, periodic)
prox0_thresh_above_value
RW - threshold level which trigs proximity events.
