A starter for ESP32-S2 projects, including tooling to build the "Cargo-first" way with embuild.

This is the result of some work over the past few weeks getting into both Rust development, and working with the ESP32-S2 MCU. The end-goal is to build a few WiFi-connected air quality sensors to place around my house. That project aims to use 3,000mAh Li-Ion 18650 batteries and (hopefully!) year-plus operation, so ultra-low power usage is critical.

This project includes a buildable example that can be flashed to your ESP32-S2, including some boilerplate code to interact with the ULP coprocessor.

Please note that I am new to Cargo Workspaces, Rust, and the ESP32. Please open an issue if you notice anything wrong!

• Build both main and ULP binaries from one workspace
• Build the main binary using embuild's native features (e.g. no PlatformIO)
• Allow flashing from the WSL2 environment
• Example ULP code to sleep for a specified interval, then wake-up the main processor
• Example code to comminicate between main and ULP processors
• Allow building via native cargo build

• Install rustup from https://rustup.rs/
• Install the custom Rust ESP32 toolchain and LLVM Clang forks
  • You probably want to do the following in ~/.espressif-rust or /opt/rustup-esp or similar
  • curl -sSL -o install-rust-toolchain.sh https://github.com/esp-rs/rust-build/releases/download/v1.57.0.2/install-rust-toolchain.sh
  • sudo chmod u+x install-rust-toolchain.sh
  • ./install-rust-toolchain.sh --export-file ./rustup-export.sh
  • source ./rustup-export.sh (this needs to be done for each bash session where you're building the ESP32-S2 project)
• Download the starter
  • git clone https://github.com/ryanc-me/esp32s2-starter

Some extra setup is required to allow flashing the chip from the WSL2 environment.

• From the Windows environment
  • Install Rust: https://www.rust-lang.org/tools/install
  • cargo install espflash
  • cargo install espmonitor

Because of some Cargo limitations (or lack of understanding on my part) the native cargo build does not work from the workspace root. From what I can gather, Rust is trying to use the same toolchain for both main and ULP crates.

As a workaround, you can build each crate separately, from within the crate directory:

• cd ulp && cargo build
• cd main && cargo build --features native

Alternatively, there is a build.sh script which does the above for you.

Follow the standard flashing procedure, e.g.:

• Ensure tools are installed
  • cargo install espflash
  • cargo install espmonitor
• espflash --monitor /dev/ttyUSB1 target/xtensa-esp32s2-espidf/debug/main
• espmonitor /dev/ttyUSB1

• Make sure both espflash and espmonitor are installed in the Windows environment.
  • Install Rust
  • cargo install espflash
  • cargo install espmonitor
• Then, from your WSL2 Linux environment:
  • powershell.exe -Command "espflash --monitor COM1 target/xtensa-esp32s2-espidf/debug/main
  • powershell.exe -Command "espmonitor COM1"
  • Note that powershell.exe will only be available in your Linux env if you open your WSL2 target e.g. via Windows Terminal, or VSCode's Remote WSL extension (the latter is a very good option). Some info here if, for some reason, you need to do this via SSH.
• Or, alternatively, the flash.sh script runs the flash+monitor command for you.

• Ivan Markov for rust-esp32-std-demo (which the main crate is based on)
• Ivan Markov for rust-esp32-ulp-blink (which the ulp crate is based on)

• APACHE
• MIT