TriMixxx/README.md

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.

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 — no laptop required.

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
• Dual audio outputs — 6.35mm (1/4") and 3.5mm headphone jacks

MIDI Controller

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

Power

• USB-C power input with CH224K USB PD negotiation (requests 20V)
• TPS54560 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

• USB 3.0 Type-A port — for Rekordbox USB sticks
• HDMI output — for an optional display (waveforms, library browsing)
• USB-C — power delivery and data
• HD3SS3220 USB-C orientation mux and HD3SS3212 USB 3.0 signal switch for proper USB-C handling
• Ethernet (via CM5) for network connectivity

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 (6-layer board)
├── CDJ-MainBoard.kicad_sch     Root schematic
├── arduino_midi.kicad_sch      ATmega32U4 MIDI controller subsystem
├── audio_outputs.kicad_sch     DAC and audio output stage
├── power.kicad_sch             Power supply (USB-C PD, buck, LDOs)
├── hdmi.kicad_sch              HDMI output
├── usb_dj_ports.kicad_sch      USB 3.0 host port for DJ USB sticks
├── 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, connectors)
*.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 knobs 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

License

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