Rust on ESP8266

Important: Since there is now a working Xtensa backend for LLVM, I am putting this project on hold. I encourage you to try to build on existing work towards compiling with rustc for ESP32.

This script attempts to install the full toolchain needed to write firmware for the ESP8266 using the Arduino library. It also generates and compiles a simple skeleton firmware that blinks the builtin LED.

This project is currently in alpha. Effort will be made to maintain backwards compatibility but there are not yet any guarantees.

The toolchain is:

• The standard Rust toolchain, installed using rustup
• bindgen + rustfmt
• mrustc Rust -> C compiler
• PlatformIO and the ESP8266 toolchain that it installs

Blink

#![no_std]

extern crate embedded_hal;
extern crate esp8266_hal;
extern crate libc;

mod bindings;
use bindings::*;
use embedded_hal::prelude::*;

pub struct State {
    led: esp8266_hal::OutputPin,
}

#[no_mangle]
pub fn setup_rs() -> State {
    State {
        led: esp8266_hal::OutputPin::new(LED_BUILTIN as u8),
    }
}

#[no_mangle]
pub fn loop_rs(state: &mut State) {
    state.led.set_low();
    delay_rs(500);
    state.led.set_high();
    delay_rs(500);
}

fn delay_rs(millis: libc::c_ulong) {
    unsafe {
        delay(millis);
    }
}

Installation

This will take a while since it needs to compile mrustc.

git clone https://github.com/emosenkis/esp-rs.git
esp-rs/build.sh --install

Note: Under MacOS it is possible in some cases that the Python path is not set correctly. So plattformio is installed but not found. This must be fixed manually, e.g. by adding the /etc/paths.d/python.

Note: Under MacOS it is possible that bash < 4.0 is installed. The build script requires Bash 4.0 functions.

Updating

This may take a while also if mrustc needs to be recompiled. If, for some reason, updating to the latest version fails, you can delete the ~/.esp-rs directory and try again for a clean install.

cd ~/esp-rs
git pull
./build.sh --install

Usage

Create a project directory, and run the script. When run for the first time in a directory, it will generate a skeleton project.

mkdir my-project
cd my-project
/where/you/cloned/esp-rs/build.sh

News

Subscribe to the forum thread for updates.

• 14 June 2018
  Added default dependency on new embedded-hal implementation crate esp8266-hal (feel free to both from your Cargo.toml if you don't want to use them).

  Changed signature of setup_rs and loop_rs functions to facilitate maintaining state. Now setup_rs returns a State struct and loop_rs receives a &mut State.

  Moved generated bindings from a separate crate to a module. Included cargo vendor as part of the script. Switched to using libc from crates.io instead of from mrustc.

  Fixed handling of Rust dependencies. This has been tested to work on PlatformIO 3.6.0a1 - try updating PlatformIO or fixing the .esp-rs-compiled-lib symlink in your project dir if you get linker errors.

  This version makes backwards-incompatible changes to the project's layout and code structure. It's probably worth starting in a new directory and letting the script initialize it, then copy over your code.

• 30 May 2018
  Added support for Rust dependencies in the vendor subdirectory (see cargo-vendor

• 27 May 2018
  Updated to Arduino SDK v2.4.1 and mrustc @b5b7089. You may need to delete your ~/.esp-rs/mrustc dir and try again if ./build.sh --install fails.

• 23 November 2017
  The biggest improvement in this version is placing the generated C files inside the project dir instead of in the mrustc installation dir. mrustc is also updated to the latest version and the ESP8266 Arduino SDK is pinned to a specific commit. The --install flag is added to avoid running the installation steps every time.

• 10 October 2017
  Over the last past few days, the script has been greatly improved. Generating bindings should work for all Arduino/ESP SDK libraries as well as dependencies listed in platformio.ini. Whitelisting is used for bindgen to avoid bloat and unnecessary failures. Documentation has been greatly expanded.

Using C/C++ libraries

The bindgen tool is used to automatically generate Rust bindings into the generated bindings crate for any Arduino/ESP SDK libraries you use, as well as dependencies listed in your platformio.ini. You can look at the generated Rust code directly in bindings/src/lib.rs or at the generated docs in target/i686-unknown-linux-gnu/doc/bindings/index.html. Note that bindgen is still a work in progress and it currently does not support some C/C++ features and, for reasons that are not yet clear (see #1), it does not generate some bindings that seem like they should be present.

To avoid unnecessary bindgen failures and reduce the generated code, bindings are only generated for C types/functions/values that are referenced in your Rust code. The whitelist is derived from error messages output by cargo build when the bindings crate is empty. Note that sometimes (such as enums) a generated binding may be in a different namespace than its C counterpart (such as enum values). The Rust compiler is typically able to suggest the proper use statement to add in such cases.

Using Rust libraries

mrustc's minicargo does not currently support fetching dependencies from crates.io or GitHub so libraries included in your Cargo.toml will automatically be downloaded to the vendor subdirectory of your project directory by cargo-vendor. Cargo and minicargo will both be configured to look for dependencies there.

Requirements

• Host machine: Linux platform with rustup support installing Rust nightly and for [cross-]compiling to i686-unknown-linux-gnu (thas only been tested on x86_64 with Ubuntu 16.04).
• Software: The script will try to install all parts of the toolchain listed above but you probably need to have a C toolchain already installed (see #6). You may need to update PlatformIO to >=3.6.0a1.
• Dev board: The generated platformio project sets the board to to nodemcuv2. It has only been tested on these but adapting it to other ESP8266 boards would probably be trivial.

Contributing

Pull requests are welcome! See the open issues for ideas or just try building an interesting firmware and fix whatever doesn't work or could be better along the way. Please try to maintain the existing coding style and code defensively.

Caveats

You will probably have to read error messages to figure out which dependencies need to be installed manually, or worse, why mrustc won't compile. Detection of which parts of the toolchain have been installed is imperfect and you may have to delete a seemingly unrelated file in order to get the script to continue from a failed installation. This has not been tested with anything more complex than blinking the built-in LED.

Debugging

You're mostly on your own, but if things get really broken, delete $HOME/.esp-rs to get a clean start.