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

Schematics

Audio Outputs

MIDI / Arduino Controller

Power Delivery

USB Ports

Top Case 3D Render

SPICE Simulations

DAC Output (PCM5242)

Buck Converter (SY8368AQQC)

Bill of Materials by Module

Auto-generated from the KiCad netlist — 160 components total.

Root — Raspberry Pi CM5 compute module, status LEDs, fan connector, RTC battery, and top-level glue logic

Ref	Value	Description
BT1	CR2032-BS-6-1	CR2032 coin cell holder (RTC backup)
D1	PSC-1608U52GC-G4	Green LED 780mcd
D2	XL-1608UBC-04	Blue LED
J1	J_FAN_PWM	4-pin JST connector for PWM fan
SW1	DSWB05LHGET	5-position DIP switch
SW2	PWR_BUT_CM5	Push button (CM5 power)
U1	Compute_Module_5_Functional	Raspberry Pi Compute Module 5

Plus 1 capacitors, 10 resistors.

Arduino MIDI — ATmega32U4 USB MIDI controller, 16 MHz crystal, JST connectors for buttons/encoders/jog wheel

Ref	Value	Description
J16	J_JOG	4-pin JST — jog wheel quadrature encoder
J17	J_PLAY	6-pin JST — Play + Cue buttons and LEDs
J18	J_ENCODER_BACK	7-pin JST — browse rotary encoder + Back button + LED
J19	J_TOUCH	2-pin JST — jog wheel capacitive touch sensor
J20	J_LOOP	8-pin JST — Loop In/Out/Reloop buttons and LEDs
J21	J_MASTER_TEMPO	4-pin JST — Master Tempo button + LED
J22	J_TEMPO	5-pin JST — tempo fader (analog) + Tempo Reset button + LED
SW4	RESET_BTN	Push button (ATmega reset)
U14	ATmega32U4-A	16 MHz, 32 kB Flash, USB 2.0, TQFP-44 — MIDI controller
X1	X322516MLB4SI	16 MHz SMD crystal, 9 pF

Plus 10 capacitors, 2 resistors.

Audio Outputs — I2S DAC (PCM5242), RCA stereo pair, 6.35 mm and 3.5 mm headphone jacks, and analog output filtering

Ref	Value	Description
FB1	~	600 Ω @ 100 MHz ferrite bead (power filtering)
J2	PJ-611E	6.35 mm (1/4") headphone jack
J3	J_RCA_L (white)	RCA jack — left channel
J4	J_RCA_R (red)	RCA jack — right channel
J5	PJ-320D	3.5 mm headphone jack
U2	PCM5122PW	TI PCM5122 — 32-bit 384 kHz stereo DAC, 112 dB DNR

Plus 12 capacitors, 3 resistors.

HDMI and Ethernet — Dual micro-HDMI outputs (touchscreen + debug), gigabit Ethernet via RJ45

Ref	Value	Description
J12	HR911130A	RJ45 Ethernet jack with integrated magnetics
J13	PI HDMI_0	Micro-HDMI Type D connector (touchscreen)
J14	PI HDMI_1	Micro-HDMI Type D connector (debug/secondary)

Plus 2 resistors.

Power Delivery — USB-C PD input (CH224K negotiation), 20 V-to-5 V buck (SY8368AQQC), 3.3 V LDO (AP2112K), USB power switches (AP2553W)

Ref	Value	Description
D3	KT-0603R	Red LED (power indicator)
D4	BZT52C3V3S	3.3 V Zener diode (voltage clamping)
D5	PSC-1608U52GC-G4	Green LED (power-good indicator)
D6	KT-0603R	Red LED (fault indicator)
J15	USB_C_Receptacle_USB2.0_16P	USB-C receptacle (power input)
SW3	SW_MAIN_POWER	Main power toggle switch
U10	AP2112K-3.3	3.3 V LDO — digital power supply (600 mA)
U11	AP2112K-3.3	3.3 V LDO — clean analog supply for PCM5242
U12	CH224K	USB PD 3.0/2.0 sink controller (negotiates 20 V)
U13	SY8368AQQC	Synchronous buck converter (20 V → 5 V)

Plus 25 capacitors, 9 resistors, 1 inductors.

Test Points — Debug and measurement test points for key signals

Ref	Value	Description
H1–H4	MountingHole	PCB mounting holes (×4)
J6	J_ISP_ATMEGA	6-pin ISP header for ATmega programming
J7	J_I2C	4-pin I2C debug header
TP1	TP_20V_USB_RAIL	20 V USB power rail
TP2	TP_20V_USB	20 V post-switch
TP3	TP_3.3_DGTL	3.3 V digital rail
TP4	TP_5V	5 V rail
TP5	TP_3.3_ANALOG	3.3 V analog rail
TP6	TP_I2C_SDA	I2C SDA line
TP7	TP_GND	Ground reference
TP8	TP_I2C_SCL	I2C SCL line
TP9	TP_I2S_BCK	I2S bit clock
TP10	TP_I2S_LRCK	I2S left/right clock
TP11	TP_I2S_DIN	I2S data in

USB DJ Ports — USB-A 3.0 (Rekordbox sticks), USB-A power-only, USB-C 2.0, orientation mux (HD3SS3220), signal switch (HD3SS3212), and ESD protection

Ref	Value	Description
J10	USB_DJ_STICK	USB 3.0 Type-A — Rekordbox USB sticks
J11	USB_SCREEN	USB 3.0 Type-A — touchscreen USB interface
J8	AUX POWER USB_A	USB Type-A — auxiliary power output (no data)
J9	USB_C_Receptacle_USB2.0_16P	USB-C receptacle (general connectivity)
U3–U5, U9	AP2553W6-7	USB power switches with current limiting (×4)
U6–U8	USBLC6-2SC6	ESD protection diodes, 2 data lines (×3)

Plus 10 capacitors, 11 resistors.

License

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