DIY Rotary Encoder Jog Wheel for Mixxx

A custom-built jog wheel controller for Mixxx DJ software using an Arduino Leonardo/ATmega32U4 board. This project provides precise vinyl-style control for both scratching and track positioning.

Features

• Native USB MIDI communication
• Hardware debounced rotary encoder input
• Dual deck support (Channel 1 & 2)
• Configurable sensitivity and behavior
• Smooth vinyl emulation with adjustable inertia
• Fine-grained scrubbing control when paused

Hardware Requirements

• Arduino Leonardo or compatible ATmega32U4 board
• Mechanical rotary encoder (EN16 or similar)
• 2x 2.2kΩ resistors
• 2x 0.1µF capacitors
• USB cable

Wiring Diagram

Arduino Leonardo/ATmega32U4
--------------------------
Pin 2 (with 2.2kΩ) -> Encoder A
Pin 3 (with 2.2kΩ) -> Encoder B
GND              -> Encoder Common

Each encoder pin should have:

• A 2.2kΩ resistor in series
• A 0.1µF capacitor to ground for hardware debouncing

Software Components

1. Arduino Code (arduino_code_jogwheel.cpp)

• Uses Paul Stoffregen's Encoder library
• Implements native USB MIDI communication
• Sends relative encoder movements as MIDI Control Change messages
• Channel 1: CC #16 (0x10) for Deck 1
• Channel 2: CC #16 (0x10) for Deck 2

2. Mixxx Mapping (Mapping.midi.xml)

• Defines the controller mapping for Mixxx
• Maps MIDI messages to deck controls
• Supports both channels for dual deck operation

3. Mixxx Script (JogWheelScratch.js)

• Implements vinyl emulation and scratching behavior
• Features:
  • Configurable ticks per revolution (default: 96)
  • Adjustable vinyl RPM (default: 33.33)
  • Fine-tuned inertia and damping
  • Speed-based movement scaling
  • Ultra-fine scrubbing control

Configuration

The behavior can be customized by adjusting these parameters in JogWheelScratch.js:

JogWheel.TICKS_PER_REV   = 96;    // Encoder resolution
JogWheel.VINYL_RPM       = 33 + 1/3;  // Vinyl speed
JogWheel.ALPHA           = 1.0 / 16.0;  // Inertia
JogWheel.BETA            = JogWheel.ALPHA / 64.0;  // Damping
JogWheel.MAX_SCALING     = 1.25;  // Speed boost limit
JogWheel.SCRUB_SCALING   = 0.0001;  // Scrubbing sensitivity

Installation

1. Install the required Arduino libraries:

   • MIDIUSB
   • Encoder (by Paul Stoffregen)

2. Upload the Arduino code to your board

3. Copy the mapping and script files to your Mixxx controllers directory:

   • Mapping.midi.xml → controllers/
   • JogWheelScratch.js → controllers/

4. Enable the controller in Mixxx preferences

Usage

• When a deck is playing: The jog wheel acts as a vinyl platter for scratching
• When a deck is paused: The jog wheel provides fine-grained track positioning
• The controller supports two decks independently (Channel 1 & 2)

Troubleshooting

If you experience issues:

1. Verify the encoder wiring and debouncing components
2. Check that the Arduino is recognized as a MIDI device
3. Ensure the mapping and script files are in the correct Mixxx directories
4. Verify the MIDI channel settings match between Arduino and Mixxx

License

This project is open source and available under the MIT License.