qomo / embedded-hal

A Hardware Abstraction Layer (HAL) for embedded systems

embedded-hal

A Hardware Abstraction Layer (HAL) for embedded systems

This project is developed and maintained by the HAL team.

API reference

Scope

embedded-hal serves as a foundation for building an ecosystem of platform agnostic drivers. (driver meaning library crates that let a target platform interface an external device like a digital sensor or a wireless transceiver).

The advantage of this system is that by writing the driver as a generic library on top of embedded-hal driver authors can support any number of target platforms (e.g. Cortex-M microcontrollers, AVR microcontrollers, embedded Linux, etc.).

The advantage for application developers is that by adopting embedded-hal they can unlock all these drivers for their platform.

embedded-hal is not tied to a specific execution model like blocking or non-blocking.

For functionality that goes beyond what is provided by embedded-hal, users are encouraged to use the target platform directly. Abstractions of common functionality can be proposed to be included into embedded-hal as described below, though.

See more about the design goals in this documentation section.

Releases

At the moment we are working towards a 1.0.0 release (see #177). During this process we will release alpha versions like 1.0.0-alpha.1 and 1.0.0-alpha.2. Alpha releases are not guaranteed to be compatible with each other. They are provided as early previews for community testing and preparation for the final release. If you use an alpha release, we recommend you choose an exact version specification in your Cargo.toml like: embedded-hal = "=1.0.0-alpha.2"

See below for a way to implement both an embedded-hal 0.2.x version and an -alpha version side by side in a HAL.

How-to: add a new trait

This is the suggested approach to adding a new trait to embedded-hal

Research / Discussion

Ideally, before proposing a new trait, or set of traits, you should check for an existing issue suggesting the need for the trait, as well as any related works / use cases / requirements that are useful to consider in the design of the trait.

These issues will be labeled as discussion in the issue tracker.

Implementation / Demonstration

Proposed traits should then be implemented and demonstrated, either by forking embedded-hal or by creating a new crate with the intent of integrating this into embedded-hal once the traits have stabilized. You may find cargo workspaces and patch useful for the forking approach.

Traits should be demonstrated with at least two implementations on different platforms and one generic driver built on the trait. Where it is possible we suggest an implementation on a microcontroller, and implementation for linux, and a driver (or drivers where requirements are more complex) with bounds using the trait.

Proposing a trait

Once the trait has been demonstrated a PR should be opened to merge the new trait(s) into embedded-hal. This should include a link to the previous discussion issue.

If there is determined to be more than one alternative then there should be further discussion to try to single out the best option. Once there is consensus this will be merged into the embedded-hal repository.

These issues / PRs will be labeled as proposals in the issue tracker.

Implementations and drivers

For a list of embedded-hal implementations and driver crates check the awesome-embedded-rust list.

Supporting different (alpha and non-alpha) HALs

embedded-hal-compat provides shims to support interoperability between the latest 0.2.x and 1.0.0-alpha.N HALs, allowing one to use incompatible HAL components (generally) without alteration. See the docs for examples.

It is also possible for HAL implementations to support both the latest 0.2.x and 1.0.0-alpha.N versions side by side, for an example see LPC8xx HAL.

Note that embedded-hal -alpha versions are a moving target and not guaranteed to be compatible. Because of this we only aim to support the latest -alpha.

Minimum Supported Rust Version (MSRV)

This crate is guaranteed to compile on stable Rust 1.46 and up. It might compile with older versions but that may change in any new patch release.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Code of Conduct

Contribution to this crate is organized under the terms of the Rust Code of Conduct, the maintainer of this crate, the HAL team, promises to intervene to uphold that code of conduct.