DIY DJ Controller

Homemade CDJ-style DJ controller with a 3D-printed enclosure, hand-built electronics, and custom firmware.

This repository documents:

• the current stable Mixxx prototype
• the firmware and Mixxx mapping that make it work
• the next hardware direction for a cleaner v2 build
• open-source hardware, firmware, and documentation for builders who want to contribute

Status

• v1 is the stable Mixxx-focused version
• the controller has been built, flashed, and used successfully as a working prototype
• Rekordbox was tested, but the jog wheels never became usable enough for a real workflow
• because of that, Rekordbox is not a supported target for this hardware revision

Current Version

• MCU: SparkFun Pro Micro / ATmega32U4
• Firmware: PlatformIO + Arduino + MIDIUSB
• Inputs: PCF8575 for buttons, 74HC4067 for analog controls, 3 rotary encoders
• Mechanical: custom 3D-printed enclosure designed in Fusion 360
• Software target: Mixxx

The current prototype includes:

• two-deck transport and loop control
• EQ, filter, gain, volume, tempo, and crossfader control
• jog wheels
• music browsing and load controls

V1 Hardware Summary

• MCU: SparkFun Pro Micro / ATmega32U4
• Button expander: PCF8575 for 16 buttons
• Analog mux: 74HC4067 for 15 potentiometers
• Encoders: 3 total
  • 1 browse encoder
  • 2 jog wheel encoders
• Encoder model: Alps EC11E vertical rotary encoder, H20mm
• Button model: Omron B3F-40xx, 12x12 mm THT tactile switch
• Direct buttons on MCU: A1, A2, A3
• Potentiometers: 15 total
  • Linear model: B103 75 mm linear slide potentiometer, 10 kOhm
  • Rotary model: TT Electronics P0915N vertical rotary potentiometer

V1 Materials List

This is the practical parts list for rebuilding the current working v1 prototype.

Qty	Material	Notes
1	SparkFun Pro Micro / ATmega32U4 board	The KiCad v1 schematic uses a USB-C Pro Micro clone footprint. Use the matching USB cable for the board you build with.
1	PCF8575 / HW-331 16-bit I2C IO expander module	Handles the 16 deck buttons.
1	CD74HC4067 / 74HC4067 16-channel analog multiplexer module	Handles the 15 analog controls.
18	Omron B3F-40xx 12x12 mm THT tactile switches	16 deck buttons plus 2 direct music-selection buttons.
3	Alps EC11E vertical rotary encoders, H20mm	1 browse encoder plus 2 jog wheel encoders.
10	TT Electronics P0915N vertical rotary potentiometers	Gain, EQ, filter, and other rotary controls.
5	B103 75 mm linear slide potentiometers, 10 kOhm	Deck volume, tempo, and crossfader controls.
1	3D-printed enclosure body	3D models/DIY_CDJ_body.stl.
1	3D-printed enclosure lid	3D models/DIY_CDJ_lid.stl.
1 each	3D-printed caps and control parts	crossfader.stl, cue.stl, encoder.stl, joggingWheel.stl, knob.stl, performance-pad.stl, and play-pause.stl.
As needed	Hookup wire, solder, and 2.54 mm headers	The stable v1 prototype is hand-wired, not PCB-based.

The firmware currently defines 3 direct music-selection inputs on A1, A2, and A3, but the KiCad v1 schematic places 18 tactile switches total. Add one extra switch if you wire all 3 direct inputs. The schematic also contains 16 resistor placeholders with no values or footprints assigned yet, so treat those as schematic TODOs rather than an order-ready BOM line.

V1 Wiring Summary

These are the important firmware-defined connections for the current working Mixxx version.

Wiring Diagrams

I2C / Button Expander

• SDA -> pin 2
• SCL -> pin 3
• PCF8575 address is auto-detected on boot in the 0x20 to 0x27 range

74HC4067 Multiplexer

• MUX signal -> A0
• S0 -> pin 15
• S1 -> pin 14
• S2 -> pin 16
• S3 -> pin 10

Rotary Encoders

• Browse encoder -> pins 4 and 5
• Jog wheel 1 -> pins 8 and 9
• Jog wheel 2 -> pins 6 and 7

Direct Buttons

• A3 -> note 76
• A2 -> note 77
• A1 -> note 78

V1 Current Input Map

PCF8575 Buttons

• Button 0 -> Deck 1 Loop Out
• Button 1 -> Deck 1 Loop In
• Button 2 -> Deck 1 Hotcue 3
• Button 3 -> Deck 1 Hotcue 4
• Button 4 -> Deck 1 Hotcue 1
• Button 5 -> Deck 1 Hotcue 2
• Button 6 -> Deck 1 Cue
• Button 7 -> Deck 1 Play/Pause
• Button 8 -> Deck 2 Hotcue 4
• Button 9 -> Deck 2 Hotcue 3
• Button 10 -> Deck 2 Hotcue 1
• Button 11 -> Deck 2 Hotcue 2
• Button 12 -> Deck 2 Cue
• Button 13 -> Deck 2 Play/Pause
• Button 14 -> Deck 2 Loop In
• Button 15 -> Deck 2 Loop Out

Potentiometers

• Pot 0 / CC 10 -> Deck 1 Gain
• Pot 1 / CC 11 -> Deck 2 Gain
• Pot 2 / CC 12 -> Deck 1 High EQ
• Pot 3 / CC 13 -> Deck 2 High EQ
• Pot 4 / CC 14 -> Deck 1 Mid EQ
• Pot 5 / CC 15 -> Deck 2 Mid EQ
• Pot 6 / CC 16 -> Deck 1 Low EQ
• Pot 7 / CC 17 -> Deck 2 Low EQ
• Pot 8 / CC 18 -> Deck 1 Filter
• Pot 9 / CC 19 -> Deck 2 Filter
• Pot 10 / CC 20 -> Deck 2 Volume
• Pot 11 / CC 21 -> Deck 2 Tempo
• Pot 12 / CC 22 -> Deck 1 Volume
• Pot 13 / CC 23 -> Crossfader
• Pot 14 / CC 24 -> Deck 1 Tempo

Browser And Jog Controls

• Browse encoder / CC 25 -> library scroll
• A1 / note 78 -> Load selected track to Deck 1
• A2 / note 77 -> Load selected track to Deck 2
• A3 / note 76 -> Enter or expand selected folder
• Jog wheel on pins 8/9 / CC 26 -> currently mapped to Deck 2
• Jog wheel on pins 6/7 / CC 27 -> currently mapped to Deck 1

V1 Firmware

The current firmware lives in CDJ_firmware/src/main.cpp.

Current Behavior

• auto-detects the PCF8575 on boot
• configures the expander pins as input pull-high
• reads 16 buttons through the PCF8575
• reads 15 analog controls through the 74HC4067
• reads 3 rotary encoders
• reads direct top buttons on A1, A2, and A3
• sends MIDI note and CC messages through MIDIUSB
• uses an additional filter on the browse encoder to reduce event spam in Mixxx

Build Target

CDJ_firmware/platformio.ini currently targets:

[env:sparkfun_promicro16]
platform = atmelavr
board = sparkfun_promicro16
framework = arduino
lib_deps =
  arduino-libraries/MIDIUSB @ ^1.0.5

Repo Layout

• CDJ_firmware/ - firmware source and PlatformIO config
• controllers/mixx_Mapping/ - Mixxx XML and JS mapping
• controllers/rekordbox/ - Rekordbox mapping reference and notes
• pics/ - renders and prototype photos
• reference circuits/ - circuit reference images
• PCB/ - KiCad schematic, PCB, and custom symbols/footprints
• 3D models/ - printable parts and Fusion 360 source archive
• CONTRIBUTING.md - contribution guide
• .github/ - issue templates, pull request template, and CI workflow

Source Of Truth

• Firmware: CDJ_firmware/src/main.cpp
• Mixxx XML mapping: controllers/mixx_Mapping/DJC-DIY.midi.xml
• Mixxx JS mapping: controllers/mixx_Mapping/DJC-DIY-scripts.js

For exact control behavior, use those files instead of this README.

Contributing

Contributions are welcome. The most useful contributions right now are practical build reports, Mixxx mapping fixes, firmware cleanup, PCB review, parts substitutions, enclosure fit notes, and documentation improvements.

Before starting a large hardware or firmware change, open an issue so the direction can be discussed. Small documentation fixes can go straight to a pull request.

Useful starter work:

• test the current Mixxx mapping on another OS or Mixxx version
• document compatible Pro Micro clones, encoders, buttons, and potentiometers
• improve wiring photos or assembly notes
• review the KiCad v1 schematic and PCB TODOs
• add real build notes for 3D-print settings and fit adjustments

See CONTRIBUTING.md for the full workflow and pull request checklist.

Getting Started

Firmware

1. Install PlatformIO in VS Code.
2. Open CDJ_firmware/.
3. Connect the SparkFun Pro Micro by USB.
4. Build or upload:

pio run
pio run --target upload

Mixxx

Copy these files into your Mixxx controller mapping folder:

• controllers/mixx_Mapping/DJC-DIY.midi.xml
• controllers/mixx_Mapping/DJC-DIY-scripts.js

Then enable the mapping in Mixxx.

Important Notes

• The stable path for this project is Mixxx, not Rekordbox.
• The prototype is still hand-wired and not PCB-based yet.
• The current jog wheel assignment is swapped between physical control and deck mapping.
• Rekordbox support should be treated as future hardware research, not a feature of this version.

V2 Plan

V2 is a hardware redesign focused on one goal: keep a single USB-C cable to the computer and add a built-in 3.5 mm headphone cue output.

• Master stays on the computer side
• the controller provides only Headphones / Cue
• the project stays Mixxx-first

Electronics Plan

• Prototype MCU: SparkFun Thing Plus ESP32-S3
• Custom PCB MCU: ESP32-S3-WROOM-1
• Headphone audio: Adafruit TLV320DAC3100 or equivalent small I2S headphone DAC/codec
• External ports: one USB-C, one 3.5 mm TRS headphone jack
• Existing controls to keep initially: PCF8575, 74HC4067, jog encoders, browse encoder, buttons, and potentiometers

Core Connections

• USB-C -> ESP32-S3
• ESP32-S3 I2S -> TLV320DAC3100 audio data
• ESP32-S3 I2C -> TLV320DAC3100 configuration
• TLV320DAC3100 -> 3.5 mm TRS headphone jack
• ESP32-S3 -> existing control hardware

Firmware Work

• port the controller logic from ATmega32U4 to ESP32-S3
• expose one composite USB device with MIDI + audio
• keep the current control behavior as close to v1 as possible
• send Mixxx cue audio to the headphone DAC

Rekordbox Note

ESP32-S3 is a much better platform for future USB experiments, but it does not guarantee Rekordbox compatibility or working jog wheels. V2 should still be treated as a Mixxx-first design.

License

This project uses separate licenses by file type:

Files	License
Firmware and controller mappings	GNU General Public License v3.0 only (GPL-3.0-only)
PCB, wiring, CAD, and 3D hardware design files	CERN Open Hardware Licence Version 2 - Strongly Reciprocal (CERN-OHL-S-2.0)
Documentation, photos, videos, and other media	Creative Commons Attribution 4.0 International (CC-BY-4.0)

See LICENSE.md, LICENSE-SOFTWARE.txt, LICENSE-HARDWARE.txt, and LICENSE-DOCS.txt for details.

This project was inspired by my friend @mandiclab and the djc-diy project.