ddcutil-bh1750

ddcutil-bh1750

A simple ddcutil daemon that automatically adjust your monitor DDC/CI over I²C brightness using ddcutil according to the lux data from the arduino serial.

Hardware

You’ll need a light sensor module integrated circuit. Specifically model BH1750. It communicates with the arduino also coincidentally using I²C. You can use different light sensor module, but you’ll need to find or make your own arduino header/library for it.

I used Pro Micro ATmega32U4. The light sensor module pin SDA goes to pin 2, and pin SCL to pin 3. If your board is somewhat different, you may need to look up for your board’s I²C pin layout.

Dependencies

For system

ddcutil-devel or ddcutil, and arduino-cli.

For arduino

Install the core stuff and necessary header/library for the light sensor module.

$ arduino-cli core install <your-board>
$ arduino-cli lib install BH1750

<your-board> is what board you have. Mine for example is arduino:avr. You might vary.

Building

Building the daemon, and the .ino

$ BOARD=<your-board> make build

<your-board> is what board you have. Mine for example is arduino:avr:leonardo. You might vary.

Uploading

Upload to the board

$ BOARD=<your-board> PORT=<port> make upload

<port> is where the kernel assign the device. Mine for example is /dev/serial/by-id/usb-Arduino_LLC_Arduino_Leonardo-XXXX. You might vary.

Running/Installing the daemon

Run this to see the verbose output.

$ ./ddcutil-bh1750-debug

If you see output and your monitor brightness changes, then continue.

This will install it on /usr/bin/

# make install

Lastly if you’re using systemd do this.

$ make init
$ systemctl --user enable --now ddcutil-bh1750.service

As of right now

• The code is simple and that’s good, but the logic for the auto-brightness is pretty barebone.
• You make your own init’s, if you’re using other than systemd. And only runs on graphical sessions.
• The code is still prone to exiting if certain error occured.