4 layers44.5 × 59.5 mm
Breadboard adapter
OpenDevicePartnership/pico-de-gallo
A tool for testing Embedded Rust drivers for discrete I2C/SPI components.
4 parts21MIT
4 layers58.4 × 67.3 mm
Pico de gallo
OpenDevicePartnership/pico-de-gallo21A tool for testing Embedded Rust drivers for discrete I2C/SPI components.
- Size
- 58.4 × 67.3 mm
- Copper layers
- 4
- Thickness
- 1.6 mm
- Parts
- 15
- Nets
- 46
- Pads
- 126
- Tracks, vias
- 228, 30
- Pours
- 31
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 21 Aug 2025
- Updated
- 5 Nov 2026
Overview
Pico de gallo is an open-source printed circuit board by OpenDevicePartnership, from the OpenDevicePartnership/pico-de-gallo repository on GitHub, published under the MIT licence. It is a 4-layer board of 58.4 × 67.3 mm with 15 parts on 46 nets, routed with 228 tracks and 30 vias.
Its parts include 5 resistors, 1 capacitor and 1 connector. It belongs with the interfaces and adapters boards and the RP2040 boards of this library.
README
README.md
Pico de Gallo
A USB bridge that turns a Raspberry Pi Pico 2 into a host-accessible I²C, SPI, UART, GPIO, PWM, ADC, and 1-Wire interface. Write and test embedded Rust drivers on your development machine without cross-compiling or flashing firmware to a target board.
Overview
Pico de Gallo provides:
- I²C: read, write, write-then-read, bus scanning, and transaction batching
- SPI: read, write, full-duplex transfer, write-then-read, and transaction batching
- UART: read, write, flush, and baud rate configuration
- GPIO: digital input/output, edge event monitoring (subscribe/unsubscribe)
- PWM: 4-channel PWM output with configurable frequency and duty cycle
- ADC: 4 GPIO-based analog inputs (12-bit)
- 1-Wire: bus reset, read, write, strong pullup, and ROM search (PIO hardware)
- Configuration: runtime I²C/SPI/UART/PWM frequency and SPI mode changes
All communication uses postcard-rpc over USB — a compact, typed, binary RPC protocol.
Book
The Pico de Gallo Book covers hardware assembly, firmware flashing, and a step-by-step guide to writing an embedded device driver using Pico de Gallo.
Crates
| Crate | Description |
|---|---|
pico-de-gallo-firmware | Embassy-rs firmware for the RP2350 |
pico-de-gallo-lib | Async host library (requires tokio) |
pico-de-gallo-hal | embedded-hal + embedded-hal-async implementation |
pico-de-gallo-ffi | C FFI bindings (shared library + header) |
gallo | CLI application for batch-mode access |
gallo-mcp | MCP server exposing the device to AI agents |
pico-de-gallo-internal | Shared wire-protocol types (internal) |
Firmware
Embassy-rs firmware for the RP2350 that exposes I²C, SPI, UART, and GPIO peripherals over USB via postcard-rpc endpoints.
Two mutually exclusive board-revision features select the target. hw-rev2
(v1.1 and later) is the default. hw-rev1 (v1.0) is deprecated — it
stays supported, built in CI, and published as firmware-rev1.uf2, with
removal no earlier than 2031-09-01 — and must now be requested explicitly
with --no-default-features --features hw-rev1. See
crates/pico-de-gallo-firmware/README.md
for build commands and
Revisions for the
policy.
Library
Async host-side library wrapping the postcard-rpc transport. Provides typed methods for every firmware endpoint. Requires the tokio runtime.
HAL
Implements both embedded-hal and embedded-hal-async traits — including
I2c, SpiBus, SpiDevice, GPIO digital I/O, delay, and embedded-io
Read/Write for UART (0.6 and 0.7, selectable by Cargo feature) — so embedded
device drivers written against those traits can be tested on a host machine
with real hardware attached to the Pico de Gallo.
App
Command-line tool (gallo) for interactive and batch-mode I²C/SPI/UART/GPIO
access. Supports hex, binary, and ASCII output formats.
FFI
C-compatible shared library wrapping the Rust host library. Generates a C header via cbindgen. Suitable for integration into C/C++/Python/etc. projects.
Internal
Shared wire-protocol crate defining all postcard-rpc endpoints, request and response types, and constants. Used by both firmware and host crates.
Zephyr
Zephyr module that lets a Zephyr application running on native_sim drive
real I²C, SPI, and GPIO peripherals through the pico_de_gallo shield — so
you can write and debug a Zephyr driver on your laptop against real silicon,
without cross-compiling or flashing. See zephyr/README.md for the
full guide; the module is documented there rather than in the book, by the
carve-out recorded in AGENTS.md §15.1.
Hardware
KiCAD schematic and PCB design for a Pico 2 daughter board. The v1.1 board features a single keyed 2x12 shrouded header that routes all 20 firmware signals with on-board I²C pull-ups and ADC input protection.
Additionally, a breadboard adapter is provided in the respective subfolder. This adapter allows connecting all Pico de Gallo pins to a breadboard with a single ribbon cable.
Case
3D-printable snap-fit enclosure (FreeCAD) in two parts — body and lid.
Parts
15| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | MountingHole | MountingHole:MountingHole_3.2mm_M3 | H1, H2, H3, H4 |
| 3 | 100 | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R3, R4, R5 |
| 2 | 4.7k | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R1, R2 |
| 1 | 100nF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C1 |
| 1 | Conn_02x12_Odd_Even | Connector_IDC:IDC-Header_2x12_P2.54mm_Vertical | J1 |
| 1 | NetTie_2 | NetTie:NetTie-2_SMD_Pad0.5mm | NT1 |
| 1 | RaspberryPi_Pico | Module:RaspberryPi_Pico_Common_Unspecified | A1 |
The 13 most common of 15 parts.
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Questions
How big is the Pico de gallo PCB?
It measures 58.4 × 67.3 mm and has 4 copper layers, 1.6 mm thick.
What parts does the Pico de gallo use?
15 parts. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Pico de gallo KiCad files?
From the OpenDevicePartnership/pico-de-gallo repository on GitHub, at the commit this page was made from: the board is hardware/pico-de-gallo.kicad_pcb and its schematic hardware/adapters/breadboard_adapter/breadboard_adapter.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Pico de gallo design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).