By: +David Herron; Date: April 28, 2018
Rust doesn't compile directly to machine code. Instead it compiles to LLVM, and uses LLVM to produce machine code. LLVM can be configured to produce code for a wide range of processors, making it fairly straightforward to cross compile -- meaning to compile code meant for another CPU than where the compiler is running.
Announcing the Embedded Devices Working Group -- Is an announcement that the 2018 roadmap for Rust has four major work areas, each of which has an official working group. One work area is getting Rust ready for embedded devices including RISCV, AVR and ARM CPU's. This suggests Rust isn't ready for these devices, but we should check in next year. See https://internals.rust-lang.org/t/announcing-the-embedded-devices-working-group/6839
Rust your ARM microcontroller! -- Jorge Aparicio wanted to compile Rust code over to his chosen Cortex-M microcontroller (an ARM board) but found there wasn't a toolchain already set up to go. So he worked out how to do it, and documented the approach. http://blog.japaric.io/quickstart/
The AVR-Rust Project -- This is a fork of Rust-related projects that looked like the right kind of thing, Rust targeting the AVR processor family. But the last "Release" from the project was in 2014... soooo... can you say "dead project"? https://github.com/avr-rust/
How can I compile Rust code to run on a Raspberry Pi -- Some good answers on compiling Rust for Raspberry Pi 2 and 3. https://stackoverflow.com/questions/29917513/how-can-i-compile-rust-code-to-run-on-a-raspberry-pi-2
Rust on the Arduino Due -- This is an ARM variant of the Arduino family, and a Rust setup to compile for that processor. https://github.com/jensnockert/dueboot
Has anyone used Rust on Arduino -- Anyone used Rust with Arduino? -- A pair of Reddit threads discussing these things. In one thread a guy talks about his experimentation with fiddling with the LLVM backend to generate code for AVR. https://www.reddit.com/r/rust/comments/2tpnm7/has_anyone_used_rust_on_arduino/ and https://www.reddit.com/r/arduino/comments/4qvtfn/anyone_used_rust_with_arduino/
Somewhere in one of those posts it's noted that all Rust compilation is cross-compilation. That is, Rust doesn't directly produce machine code for the processor it's running on. Rust produces LLVM code, and then the LLVM produces code for whatever processor you're targeting, and by default that's the processor it is running on. But apparently one can configure it differently to make LLVM produce code for other processors.
Rust on an Arduino Uno and Part 2 -- Blog posts, the first of which describes a failed attempt to get Rust code onto an Arduino. http://jakegoulding.com/blog/2016/01/02/rust-on-an-arduino-uno/ and http://jakegoulding.com/blog/2016/01/17/rust-on-an-arduino-uno-part-2/
Working with Rust on the ESP32 -- Stackoverflow, walks through how Rust compiles first to LLVM then uses LLVM to compile to machine code. LLVM doesn't support the Xtensa architecture on the ESP32 or ESP8266 boards. It's plausible but said to not be feasible to configure the LLVM step to produce C code, then use a regular C compiler to compile that to machine language, but that's thought to be extremely unlikely to work.
Another chip, the RTL8710, is said to be "recommended for use in situations where you'd use an ESP32, but want to use Rust."
Rust on RTL8710 running FreeRTOS This is instructions for cross-compiling Rust code to the named processor. This is a ARM Cortex-M3 processor meaning it is an architecture supported by LLVM. This post walks through configuring things to cross-compile Rust to the RTL8710 processor. https://polyfractal.com/post/rustl8710/
Rust [and other LLVM languages] support for ESP32 -- More discussion about Rust on the ESP32. Some hope is expressed that this will eventually be possible. https://esp32.com/viewtopic.php?t=499
Rust on ESP8266 -- A build script that handles compiling Rust code to the ESP8266. Appears to be compiling first to C, then using a C compiler. https://github.com/emosenkis/esp-rs