A custom CDJ (Compact Disc Jockey) unit built from scratch around a Raspberry Pi CM5, designed to run Mixxx DJ software. Features a custom PCB, a custom 3D-printed chassis, and reuses original CDJ buttons and jog wheel for an authentic DJ experience. Reads Rekordbox-formatted USB sticks — no laptop required.

What is this?

TriMixxx replaces the internals of a CDJ with modern, open-source-friendly hardware while keeping the physical controls that DJs know and love. Plug in a Rekordbox-formatted USB stick, and you're ready to mix.

Hardware Architecture

Compute

Raspberry Pi CM5 — runs Mixxx and handles audio playback, connected via dual DF40 100-pin high-density connectors

Audio

TI PCM5242 — high-quality stereo DAC connected over I2S for low-latency audio output
RCA stereo pair — Left (white) and Right (red) main outputs
6.35mm (1/4") headphone jack
3.5mm headphone jack

MIDI Controller

ATmega32U4 — acts as a USB MIDI class-compliant device, reading the original CDJ's buttons, encoders, fader, and jog wheel and translating them into MIDI messages for Mixxx
16 MHz crystal oscillator for reliable USB timing

All controls connect via JST PH connectors to the main PCB:

Connector	Controls
J_PLAY (6-pin)	Play button + LED, Cue button + LED
J_LOOP (8-pin)	Loop In button + LED, Loop Out button + LED, Reloop button + LED
J_MASTER_TEMPO (4-pin)	Master Tempo button + LED
J_ENCODER_BACK (7-pin)	Back/browse rotary encoder + Back button + LED
J_TEMPO (5-pin)	Tempo fader (analog ADC input) + Tempo Reset button + LED
J_JOG (4-pin)	Jog wheel quadrature encoder (JOG1/JOG2)
J_TOUCH (2-pin)	Jog wheel capacitive touch sensor

Summary of buttons: Play, Cue, Loop In, Loop Out, Reloop, Master Tempo, Tempo Reset, Back — each with a corresponding LED. Plus a tempo fader (analog), a browse/back rotary encoder, a jog wheel (quadrature encoder), and a jog wheel touch sensor.

Power

USB-C power input with CH224K USB PD negotiation (requests 20V @ 3A = 60W, peak draw 42.4W)
SY8368AQQC synchronous buck converter stepping 20V down to 5V for the CM5 and peripherals
AP2112K 3.3V LDO for logic-level components
AP2553W USB power switches for safe hot-plug on DJ USB ports

Connectivity

Port	Type	Speed	Purpose
USB-A	Full-size	USB 3.0 SuperSpeed	Rekordbox USB sticks
USB-A	Full-size	Power only (no data)	Auxiliary power for gadgets/lights
USB-C	Receptacle	USB 2.0	General connectivity
Micro HDMI	Type D	HDMI 1.4	10" touchscreen display
Micro HDMI	Type D	HDMI 1.4	Debug/secondary screen
Ethernet	RJ45 (via CM5)	Gigabit	Network connectivity

Additional internal USB: USB 3.0 Type-A for the touchscreen's USB touch interface.

HD3SS3220 USB-C orientation mux and HD3SS3212 USB 3.0 signal switch for proper USB-C handling on the DJ stick port

Protection

USBLC6-2SC6 ESD protection on USB data lines
BZT52C3V3S Zener diodes for voltage clamping

Chassis

Designed in Fusion 360 with a custom top panel and bottom tray that fits the original CDJ form factor:

CDJ-Top-Panel_v17.f3d — top panel with cutouts for the jog wheel, buttons, and connectors
CDJ-Bottom-Tray.f3d — bottom enclosure

Project Structure

CDJ-MainBoard/              KiCad PCB project
├── CDJ-MainBoard.kicad_sch     Root schematic
├── arduino_midi.kicad_sch      ATmega32U4 MIDI controller subsystem
├── audio_outputs.kicad_sch     DAC and audio output stage (RCA + headphones)
├── power.kicad_sch             Power supply (USB-C PD, buck, LDOs)
├── hdmi.kicad_sch              Dual micro HDMI outputs + Ethernet
├── usb_dj_ports.kicad_sch      USB ports (DJ stick, aux power, connectivity)
├── test_points.kicad_sch       Test points for debugging
└── CDJ-MainBoard.kicad_pcb     PCB layout

JLC2KiCad_lib/              Component library (symbols, footprints, 3D models)
kicad-thirdparty-footprints/    Third-party footprints (CM5, DAC, RCA jacks)
*.f3d                       Fusion 360 chassis models
*.net                       Exported netlists (various revisions)

Software Stack

Mixxx — open-source DJ software running on Raspberry Pi OS
Rekordbox USB support — reads Rekordbox-exported USB sticks for seamless library access
MIDI mapping — the ATmega32U4 presents as a standard USB MIDI device, so Mixxx sees the jog wheel, buttons, and fader as native MIDI controls

Tools Used

KiCad — schematic capture and PCB layout
Fusion 360 — mechanical design
JLC2KiCad — importing JLCPCB component libraries into KiCad
JLCPCB — PCB fabrication and assembly

Schematic

License

This is a personal hardware project. Feel free to use it as reference for your own builds.