Scaffolding the crate

We are going to build an ordinary Rust library crate. No board support package, no cross toolchain, no custom linker setup.

Start with a fresh library:

$ cargo new --lib tmp102
    Creating library `tmp102` package
$ cd tmp102

Now add the dependencies we know we will need:

$ cargo add embedded-hal
$ cargo add embedded-hal-async
$ cargo add device-driver --no-default-features -F toml
$ cargo add --dev pico-de-gallo-hal --git https://github.com/OpenDevicePartnership/pico-de-gallo
$ cargo add --dev tokio -F rt-multi-thread,time,macros

That gives us three layers:

• embedded-hal for the blocking driver surface
• embedded-hal-async for the async sibling
• device-driver for generated register accessors

And in dev-dependencies:

• pico-de-gallo-hal so tests and examples can talk to real hardware
• tokio for async examples and hardware-in-the-loop tests

Tip

Keep pico-de-gallo-hal in [dev-dependencies], not in normal [dependencies]. Your end users should depend on your driver crate, not on the host-side test harness you used while writing it.

Your Cargo.toml should look roughly like this:

[package]
name = "tmp102"
version = "0.1.0"
edition = "2024"

[dependencies]
device-driver = { version = "1.0.7", default-features = false, features = ["toml"] }
embedded-hal = "1.0.0"
embedded-hal-async = "1.0.0"

[dev-dependencies]
pico-de-gallo-hal = { git = "https://github.com/OpenDevicePartnership/pico-de-gallo" }
tokio = { version = "1.47.1", features = ["rt-multi-thread", "time", "macros"] }

We also want the code generator that turns a register description into a Rust interface:

$ cargo install device-driver-cli

That binary reads a TOML description of the device and emits the boring part of the driver for us: register wrappers, field accessors, and the plumbing around them.

At this point the crate is still empty, but we have already set the shape of the project:

• library-first
• embedded-hal-based
• async-friendly
• hardware-testable on the host

Next we describe TMP102’s registers in a form the generator can digest.