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Introduction

Pico de Gallo turns a Raspberry Pi Pico 2 into a USB-attached protocol bridge so you can drive I²C, SPI, UART, GPIO, PWM, ADC, and 1-Wire peripherals from a host PC — and, more importantly, so you can develop and test embedded device drivers on your laptop, with no flashing, no SWD probe, no clock or pin-mux setup, and no linker scripts in your way.

If you’ve ever wanted to:

  • prototype a driver against embedded-hal traits without booting an MCU each time you change a line,
  • script a sensor or actuator from Python or a shell one-liner,
  • write an integration test that talks to real silicon from your CI runner,

then Pico de Gallo is for you.

What’s in the Box

A small landing-board PCB with castellated pads for the Pico 2, a firmware image that speaks postcard-rpc over USB, and a small constellation of host-side crates:

  • gallo — a CLI for one-off and scripted access to every interface.
  • pico-de-gallo-lib — an async Rust client built on nusb and tokio.
  • pico-de-gallo-hal — a host-side embedded-hal / embedded-hal-async shim so existing drivers work unchanged.
  • pico-de-gallo-ffi — a C shared library with a stable opaque-pointer API.
  • pyco-de-gallo — Python bindings via PyO3 and maturin.
Pico de Gallo rev1
Pico de Gallo v1.0		 Pico de Gallo rev1.1
Pico de Gallo v1.1

Hardware Revisions at a Glance

RevisionFirmware featureConnectorCapabilities
v1.0hw-rev1seven pin headersI²C, SPI, GPIO, PWM
v1.1hw-rev2one keyed 2×12 boxI²C, SPI, UART, GPIO, PWM, ADC, 1-Wire
v2 (WIP)hw-rev22×12 box + level Txsame as v1.1, plus variable VREF

You’ll want v1.1 or later if you need UART, ADC, or 1-Wire. See Revisions: v1.0 vs v1.1.

How to Read This Book

The book is laid out as six parts plus appendices:

  1. The Hardware — what’s on the PCB, which revision to pick, how to flash firmware.
  2. Getting Started — install the toolchain and verify your device.
  3. The Interfaces — one chapter per peripheral. Each follows the same template: overview, pin mapping, CLI usage, Rust, C, Python, error handling.
  4. The Crates — reference for each crate in the workspace.
  5. Writing a Device Driver — the longest part. A TMP102 walkthrough showing the dev loop, the blocking/async parity, and how to write hardware-in-the-loop tests that run on your laptop.
  6. Under the Hood — the wire protocol, schema versioning, firmware architecture, and the release-please cadence.

Read top-to-bottom for a tour, or jump straight to the chapter you need — each chapter stands on its own.

The Optional Case

A 3D-printable, snap-fit enclosure lives in the case/ folder of the repository if you want to keep the board safe on your bench.

3D printable case