TriMixxx

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.