RPBridge¶

Alpha — pre-production

RPBridge is in alpha. The firmware feature set is complete and self-tested on both supported boards, the production USB VID/PID (0545:0101) is allocated and wired in, but the C kernel driver has not yet been validated against real hardware and the udev rule set is not yet final. Do not deploy on production hosts. See firmware/COVERAGE.md for the live status matrix.

USB Multi-Bus Bridge on the Raspberry Pi RP2350 family. Open hardware, open firmware, open drivers. Two board variants are supported in lockstep — rpbridge_rp2354b (Rev-B custom PCB, QFN-80, 48 GPIO) and rpbridge_pico2 (off-the-shelf Raspberry Pi Pico 2, QFN-60, 30 GPIO). Both expose the same eleven RPBP subsystems to a Linux host as standard subsystem devices: I²C, SPI, UART (RS232/RS485/TTL), GPIO, PWM, ADC, CAN 2.0B, WS2812 LED strips, DMX-512, 1-Wire and I²S. Use i2c-tools, libgpiod, can-utils, spidev_test, IIO and friends unmodified.

Start here¶

:material-rocket-launch: Quickstart

From a clean workstation to a working device in under five minutes:

:octicons-arrow-right-24: Quickstart
:material-protocol: Protocol — RPBP v1

Wire format, framing, CRC-32C, capability discovery. The single canonical source for what goes over the bulk endpoint.

:octicons-arrow-right-24: Specification
:material-chip: Firmware

pico-sdk 2.2.0, TinyUSB, can2040 — how the device side is built and flashed.

:octicons-arrow-right-24: Firmware guide
:material-linux: Linux driver

C kernel module, auxiliary_bus children for nine subsystems (gpio / i2c / spi / pwm / iio / led / dmx / w1 / i2s). DKMS packages for Debian/Ubuntu/Fedora.

:octicons-arrow-right-24: Driver guide

Repository layout¶

Path	Purpose
`firmware/`	RP2350-family firmware (C + pico-sdk 2.2.0, can2040 for CAN). Multi-board build via `RPBRIDGE_BOARD=rpbridge_rp2354b\\|rpbridge_pico2`.
`firmware/COVERAGE.md`	Live, consumer-facing status matrix — start here to see what is shipped vs. open.
`driver/`	C kernel module, DKMS-packaged.
`userspace/`	Rust workspace: protocol lib, client lib, `rpbridge-ctl`, bench.
`docs/`	This documentation site (mkdocs-material).
`dts/overlays/`	Device-tree overlays for auto-provisioning onboard sensors.
`hardware/`	KiCad 9 design files (Rev-B, 2-layer, 80 × 55 mm).
`tests/golden/`	Golden RPBP vectors shared across every implementation.

Design principles¶

Self-describing device. The host reads a CBOR capability map at bind time — no firmware-version matrices to maintain.
Standard Linux subsystems. /dev/i2c-N, /dev/spidevN.M, /dev/gpiochipN, /dev/ttyACM*, can0, IIO — no private character devices for bus access.
Modern stack only. auxiliary_bus (≥ 5.11), GPIO cdev v2, libgpiod 2.x, SocketCAN. Deprecated paths are intentionally not implemented.
Forward-/backward-compatible. Four independent SemVer axes (protocol, firmware, driver, userspace); negotiated at runtime through feature flags.

Status¶

Component	Maturity
Hardware — Rev-B PCB	Draft (bring-up done)
Hardware — Pico 2 carrier	Working
Firmware (both boards)	Feature complete (alpha)
Linux driver (Rust)	Wire layer feature complete; subsystem adapters in progress
Userspace CLI (Rust)	Working
Documentation	Synced with firmware
CI/CD	Both boards green

The single source of truth for shipped functionality is firmware/COVERAGE.md. For per-pin capability — including which silicon mux slots reach which subsystem on each board — see the pin capability matrix. The CHANGELOG tracks the running release log; decision records explain why the project shaped up the way it did.