Foxbridge — Luckfox Core3506 carrier board

A carrier board for the Luckfox Core3506 system-on-module (SoM), for anyone who wants the RK3506 on a Raspberry Pi Model B-sized board (85 × 56 mm) with Ethernet, USB-C, a DSI display & a 40-pin header. Designed in KiCad 10 by Rufilla Ltd., from the Luckfox Lyra Pi reference design. Revision A is a prototype: it has been built & brought up, with three hardware faults.

Client	Internal
Project code	Foxbridge
Status	Prototype — Revision A built & reworked; Revision B in design

Revision A has been built & brought up with three hardware faults. USB host (OTG1) does not work without two reworks. Read the errata before ordering boards.

Overview

The board breaks the Core3506 SoM out to a Raspberry Pi Model B footprint. Each subsystem has its own schematic sheet; docs/design-notes.md explains how each one works & why.

• USB-C ×2 — OTG0 (device, flashing & 5 V power input) & OTG1 (host, 500 mA current limit)
• 10/100 Ethernet — CH182H2 PHY on RMII0, HR911105A RJ45 with integrated magnetics
• MIPI DSI — 2-lane, 22-pin 0.5 mm FPC for the Luckfox 7" DSI touchscreen (SKU 25265)
• 40-pin header — Raspberry Pi-compatible pinout
• microSD — TF-110 socket with power switching; see errata E4 for the eMMC SoM
• RESET & RECOVERY buttons; UART0 header & Qwiic connector (both not fitted)
• 4-layer, 1.6 mm, impedance-controlled — built for JLCPCB Economic PCBA

Out of scope for this design:

• No on-board 3.3 V regulator is fitted; the SoM supplies VCC_3V3. U2 is reserved for a future Wi-Fi/Bluetooth module.
• No Wi-Fi or Bluetooth.
• Power comes only from 5 V on the OTG0 USB-C port — no barrel jack & no PoE.
• The microSD slot does not work with the Core3506 variant that has on-module eMMC.
• No MASKROM button & no mounting holes in Revision A.

Requirements

Hardware

• Luckfox Core3506 SoM (RK3506), fitted to a Foxbridge carrier board, revision A
• USB-C cable on OTG0 for power & flashing; 3.3 V USB-UART on the UART0 header for a console
• Optional: Luckfox 7" DSI touchscreen (SKU 25265), microSD card, Ethernet cable

Software

• KiCad 10.0 or later. Checked with 10.0.6.
• Fabrication Toolkit plugin, to regenerate the JLCPCB production files
• Third-party symbol & footprint libraries, needed only to update a part from its library:

Nickname in the design	Library	Install from
PCM_SparkFun-*	SparkFun KiCad Libraries	Plugin & Content Manager (PCM)
PCM_*_AKL	Alternate KiCad Library	PCM
PCM_JLCPCB*	JLCPCB KiCad Library	PCM, after adding CD_FER's repository
digikey-footprints, dk_*	Digi-Key KiCad Library	Clone & register by hand (J3 only)

PCM libraries resolve only with the default nickname prefix PCM_ (Preferences → Packages & Updates).

Getting the source

git clone https://github.com/Rufilla/LuckFox-Core3506-Carrier.git
cd LuckFox-Core3506-Carrier

Building

Open luckfox_core3506_adapter.kicad_pro in KiCad. The schematic & board carry a copy of every symbol & footprint, so the design opens, plots & runs ERC/DRC without the third-party libraries above. Parts specific to this board are in the project library lib/ (nickname Foxbridge), with their 3D models embedded.

Regenerate the fabrication outputs from the PCB editor with Tools → External Plugins → Fabrication Toolkit. It reads fabrication-toolkit-options.json, excludes do-not-populate parts & writes the Gerbers, drill, BOM & placement files that are committed in production/.

Flashing / deployment

Ordering Revision A from JLCPCB, in full, is in docs/manufacturing.md. In short:

File	Upload as
production/luckfox_core3506_adapter.zip	Gerbers & drill
production/bom.csv	Bill of materials
production/positions.csv	Component placement (CPL)

Order Economic PCBA. Three parts are soldered by hand — J1 (RJ45), H1 (2 × 20 pin header) & U1 (Core3506) — and the placement preview needs the rotation & offset corrections listed in the manufacturing notes.

NOTE: the files in production/ reproduce Revision A exactly, including the faults in docs/errata.md. Boards built from them need the E1 & E2 reworks before USB host works.

Usage

Power the board from 5 V over the OTG0 USB-C port; the same port flashes the SoM. The console is on the UART0 header. Ethernet, DSI & the 40-pin header need no board-level configuration.

Before trusting a freshly built board, check it against the reworks in docs/errata.md: R3 moved (E1) & R6/R7 bridged (E2). Photographs of both are in images/.

Testing

Run electrical rules & design rules from the project directory:

kicad-cli sch erc luckfox_core3506_adapter.kicad_sch
kicad-cli pcb drc --schematic-parity luckfox_core3506_adapter.kicad_pcb

Every outstanding ERC & DRC report is listed, with its cause & whether it is a real fault, in docs/manufacturing.md. Schematic parity & unconnected items are both zero.

Project structure

luckfox_core3506_adapter.kicad_pro   KiCad project; the root schematic, 10 sheets & board sit beside it
lib/                                 Project symbol library & footprint library
production/                          Revision A files as ordered from JLCPCB: Gerbers & drill (.zip), BOM, placement, IPC netlist
docs/                                Design notes, errata, manufacturing notes & the Revision B checklist
images/                              Board render & rework photographs

Documentation:

• Design notes — how each subsystem works & why
• Errata — Revision A faults, reworks & limitations
• Manufacturing — stack-up, ordering from JLCPCB, ERC/DRC status
• Revision B checklist — changes planned for the respin

Security

Report a security problem to [email protected] rather than through a public issue. This repository holds hardware design files only, so no software bill of materials (SBOM) is produced; the bill of materials for the board is production/bom.csv.

Contributing

Report problems & suggestions through GitHub issues, & send changes as pull requests.

Licence

Copyright 2026 Rufilla Ltd. Licensed under the Apache License 2.0.

Symbols, footprints & 3D models copied from third-party libraries remain under their own licences.

Support

Rufilla Ltd · Building D5, Culham Campus, Abingdon, Oxfordshire, UK, OX14 3DB [email protected] · +44 (0)1865 601201 · www.rufilla.com

© 2026 Rufilla Ltd