N900 light meter

The light meter lets the software on the N900 sense ambient light levels.

Hardware

The device is a TAOS TSL2563.

Software

It is handled by the kernel module tsl2563.

The kernel driver exposes the lux value in the sysfs file

cat /sys/class/i2c-adapter/i2c-2/2-0029/lux
21

Under MeeGo it's available as

cat /sys/class/i2c-adapter/i2c-2/2-0029/device0/illuminance0_input

Third party applications that use this sensor include Luxus Light Meter and photographic light meter.

The sensor is also used to modulate the backlight in response to ambient light, although this behaviour can be disabled.