Jul 28, 2021 - 3 min read

Rust on Espressif chips

It's been a while since my last post. I have some exciting news to share before going over the progress over the last nine months. I will be joining Espressif full time to work on Rust support for all of Espressif's chips, past, present and future! I am very excited to join Espressif and improve the Rust ecosystem surrounding their chips!

Organisation

The forked compiler with esp support has been moved into the esp-rs organisation, along with some idf support crates - more on that shortly! Discussions have been enabled on the esp-rs/rust repository, and for the last month Espressif have been hosting weekly community meetings focusing on pushing Rust support forward. If you'd like to discuss something and attend, drop a comment in the latest thread and request an invite!

The Rust standard library on Espressif chips

@ivmarkov been working very hard on porting the Rust STD library to esp-idf, the C based development environment for Espressif chips. esp-idf has a newlib environment which can be used to build the Rust library on top of. @ivmarkov has put together rust-esp32-std-hello demo repo to show off the capabilities, which include WiFi, threads and driving a display using the esp-idf's drivers. Extremely cool stuff! There are a few teething issues, which you can track here but hopefully we will be in a position to start upstreaming these patches soon.

To suppliment the standard library for Espressif chips, esp-idf-hal has been updated and moved into the esp-rs organisation. This crate has API's to use peripherals and hardware that do not have abstractions in the standard library, for example the SPI peripheral. Along with the HAL, esp-idf-svc has also been added, which is an implementation of embedded-svc traits for Espressif chips. The goal behind embedded-svc is to provide abstractions around higher level embedded services, WiFi, Ping, HTTPD, NVS etc.

Bare metal

Whilst the biggest changes have been around esp standard library developments, bare metal support has not been forgotten! A few months I got my hands on a esp32c3, a RISC-V based chip; because upstream Rust already supports RISC-V putting together a rudimentary bare metal example was quite simple!

Whilst the program above worked, much like my first ever post it isn't very "Rusty". Fortunately Espressif have recently release a preliminary SVD file for the esp32c3, the first of its kind from Espressif which is super exciting! This means we can feed the SVD into svd2rust (see my other post about doing this for the esp32 here) and generate a peripheral access crate (PAC) for the esp32c3 and build abstractions on top of that. With official SVD's coming out I hope that we can integrate that into the current bare metal esp32-hal, turning it into a mono repository supporting all of Espressif's chips in pure Rust.

It also means I can finally kill off the abomination which is idf2svd :D.

What's next?

We should be able to start upstreaming some of the RISC-V based changes soon! With official SVD's coming out, bare metal esp32 support should start moving forward again too.