Ambient Light Sensor

A cheap ambient light sensor control monitor brightness automatically.
This repo contains the firmware and a 3D-printable enclosure for a BlackPill board along with a simple holder for the luminosity sensor.

Hardware

• STM32F4-based board (e.g. BlackPill)
• TSL2561 Luminosity sensor

It can work on various STM32 models with minor modifications.

Wiring

Sensor works with 3.3v Firmware uses interface I2C1 to communicate with the sensor (B6 -> SCL, B7 -> SDA on STM32F401)

Build

The makefile uses arm-none-eabi-gcc as a compiler.

Build with make -f STM32Make.make

Flash with make -f STM32Make.make flash or manually flash build/light_sensor.bin with st-flash

Software

An udev rule file is provided to alias the sensor's serial port to /dev/ttyALS.

I use Clight to read the sensor and control my monitors' brightness with DDC.

Clight config

Refer to Clight's documentation for details

~/.config/clight.conf

...
sensor:
{
ac_regression_points = [ 0.02, 0.20, 0.30, 0.35, 0.40, 0.60, 0.74, 0.88, 0.93, 0.97, 1.0 ];
devname = "/dev/ttyALS";

# i: polling interval; m: min lux; M: max lux
settings = "i=400,m=0,M=4000";
# Number of sequential captures
captures = [ 5, 5 ];
}
...