Arduino project for controlling audio volume for separate Windows processes using physical sliders (like a DJ!)

Video demonstration on YouTube

New: see some awesome versions built by people around the world!

• The sliders are connected to 5 analog pins on an Arduino Nano/Uno board. They're powered from the board's 5V output (see schematic)
• The board connects via a USB cable to the PC

• The code running on the Arduino board is a C program constantly writing current slider values over its Serial interface deej-arduino.ino
• The PC runs a Python script deej.py that listens to the board's Serial connection, detects changes in slider values and sets volume of equivalent audio sessions accordingly.
• A VBScript-based run helper run.vbs allows this Python script to run in the background (from the Windows tray).

deej uses an external YAML-formatted configuration file named config.yaml.

The config file determines which applications are mapped to which sliders, and which COM port/baud rate to use for the connection to the Arduino board.

This file auto-reloads when its contents are changed, so you can change application mappings on-the-fly without restarting deej.

It looks like this:

slider_mapping:
  0: master
  1: chrome.exe
  2: spotify.exe
  3:
    - pathofexile_x64.exe
    - rocketleague.exe
  4: discord.exe

# recommend to leave this setting at its default value
process_refresh_frequency: 5

# settings for connecting to the arduino board
com_port: COM4
baud_rate: 9600

• Process names aren't case-sensitive
• You can use a list of process names to either:
  • define a group that is controlled simultaneously
  • choose whichever process in the group is currently running (in this example, one slider is for different games that may be running)
• master is a special option for controlling master volume of the system.
• The process_refresh_frequency option limits how often deej may look for new processes if their appropriate slider moves. This allows you to leave deej running in background and open/close processes normally - the sliders will #justwork

Building deej is very simple! You only need a few cheap parts - it's an excellent starter project (and my first Arduino project, personally).

• An Arduino Nano or Uno board - I officially recommend using a Nano as it offers a smaller form-factor, a friendlier USB connector and more analog pins. Plus it's cheaper
• As many slider potentiometers as you like, up to your number of analog pins (they're around 1-2 USD each, and come with a standard 10K Ohm variable resistor)
  • Important: make sure to get linear sliders, not logarithmic ones!
  • You can also use circular knobs if you like (but then you're not a DJ!)
• Some wires and a way to connect them to your chosen board and sliders. This can be done with or without a breadboard, depending on how you're comfortable doing it
• Any kind of box to hold everything together. It can be anything from a simple shoebox to a well-designed 3D-printed enclosure for a very professional look

If you've actually gone ahead and built it, here's how you can run deej:

• Python 2.7.x (Sorry!) and pip
• virtualenv

• Download the repository by either cloning it or downloading its archive.
• In the repo's directory, run:
  • virtualenv venv
  • venv\Scripts\activate.bat
  • pip install -r requirements.txt
• Make a shortcut to run.vbs by right-clicking it -> "Create Shortcut"
• (Optional, but mandatory) Change the shortcut's icon to assets/logo.ico
• (Optional, but optional) Copy the shortcut to %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup to have deej run on boot

• Better logging and error handling
• Automatic COM port detection
• Mic input support
• Feel free to let me know if there's more demand for other features!