deej

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!

How it works

Hardware

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

Schematic

Software

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).

Slider mapping (configuration)

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

Build your own

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

Bill of Materials

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

How to run

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

Requirements

Python 2.7.x (Sorry!) and pip
virtualenv

Installation

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

Missing stuff

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!

caelor/deej