Kernel driver bh1770glc¶
- ROHM BH1770GLC
- OSRAM SFH7770
Data sheet: Not freely available
Author: Samu Onkalo <email@example.com>
BH1770GLC and SFH7770 are combined ambient light and proximity sensors. ALS and proximity parts operates on their own, but they shares common I2C interface and interrupt logic. In principle they can run on their own, but ALS side results are used to estimate reliability of the proximity sensor.
ALS produces 16 bit lux values. The chip contains interrupt logic to produce low and high threshold interrupts.
Proximity part contains IR-led driver up to 3 IR leds. The chip measures amount of reflected IR light and produces proximity result. Resolution is 8 bit. Driver supports only one channel. Driver uses ALS results to estimate reliability of the proximity results. Thus ALS is always running while proximity detection is needed.
Driver uses threshold interrupts to avoid need for polling the values. Proximity low interrupt doesn’t exists in the chip. This is simulated by using a delayed work. As long as there is proximity threshold above interrupts the delayed work is pushed forward. So, when proximity level goes below the threshold value, there is no interrupt and the delayed work will finally run. This is handled as no proximity indication.
Chip state is controlled via runtime pm framework when enabled in config.
Calibscale factor is used to hide differences between the chips. By default value set to neutral state meaning factor of 1.00. To get proper values, calibrated source of light is needed as a reference. Calibscale factor is set so that measurement produces about the expected lux value.
- RO - shows detected chip type and version
RW - enable / disable chip
Uses counting logic
- 1 enables the chip
- 0 disables the chip
RO - measured lux valuesysfs_notify called when threshold interrupt occurs
- RO - lux0_input max value
- RW - measurement rate in Hz
- RO - supported measurement rates
RW - HI level threshold valueAll results above the value trigs an interrupt. 65535 (i.e. sensor_range) disables the above interrupt.
RW - LO level threshold valueAll results below the value trigs an interrupt. 0 disables the below interrupt.
RW - calibration valueSet to neutral value by default. Output results are multiplied with calibscale / calibscale_default value.
- RO - neutral calibration value
RO - measured proximity valuesysfs_notify called when threshold interrupt occurs
- RO - prox0_raw max value
RW - enable / disable proximity
Uses counting logic
- 1 enables the proximity
- 0 disables the proximity
- RW - number of proximity interrupts needed before triggering the event
- RW - Measurement rate (in Hz) when the level is above threshold i.e. when proximity on has been reported.
- RW - Measurement rate (in Hz) when the level is below threshold i.e. when proximity off has been reported.
- RO - Supported proximity measurement rates in Hz
RW - threshold level which trigs proximity events.Filtered by persistence filter (prox0_thresh_above_count)
- RW - threshold level which trigs event immediately