Rust on Arduino: A Beginner’s Guide to Embedded Systems Development

Unlocking the Power of Rust on Arduino: A Step-by-Step Guide

Are you ready to explore the exciting world of embedded systems with Rust? This guide will walk you through setting up your environment, writing your first Rust program, and flashing it onto an Arduino board (specifically, we’ll target the Arduino Uno, which is the most common and compatible).

Why Rust for Embedded Systems?

For decades, C and C++ have been the dominant languages for embedded programming. However, Rust offers a compelling modern alternative, boasting:

• Memory Safety: Rust’s ownership system and borrow checker prevent common memory errors like dangling pointers, buffer overflows, and data races at compile time. This leads to significantly more robust and secure embedded systems.
• Performance: Rust compiles to native code with no runtime overhead (like a garbage collector), making it as fast as C/C++.
• Concurrency: Rust’s ownership and borrowing system makes concurrent programming much safer and easier to reason about.
• Modern Language Features: Rust incorporates many modern language features like pattern matching, traits, and generics, leading to more expressive and maintainable code.

Prerequisites

Before we begin, ensure you have the following:

• Basic Rust Knowledge: Familiarity with Rust’s syntax, data types, and concepts like ownership and borrowing is essential. If you’re new to Rust, work through the official Rust book (https://doc.rust-lang.org/book/) first.
• Rust Toolchain: You need a working Rust installation. The easiest way is to use rustup:
  Bash

  curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
  

  Follow the on-screen instructions. After installation, restart your terminal or source your shell profile (e.g., source ~/.bashrc).

• Arduino Uno (or compatible): This guide focuses on the Arduino Uno, but many AVR-based Arduinos will work similarly. Make sure you have the board and a USB cable to connect it to your computer.
• Arduino IDE (optional but recommended): While not strictly necessary for flashing, the Arduino IDE installs necessary drivers and makes identifying the serial port easier. Download it from https://www.arduino.cc/en/software. You don’t need to use the IDE for writing code, just for initial setup.
• Linux Environment (or WSL/macOS): The instructions below are tailored for a Linux environment. If you’re using Windows, Windows Subsystem for Linux (WSL) is highly recommended. macOS should work similarly to Linux.
• Basic usage of a Linux environment

Setting Up Your Environment (Detailed Steps)

1. Install avr-gcc: This is the AVR toolchain (compiler, linker, etc.). Use your distribution’s package manager:

   • Debian/Ubuntu:
     Bash

     sudo apt update
     sudo apt install gcc-avr binutils-avr avr-libc avrdude
     

   • Fedora/CentOS/RHEL:
     Bash

     sudo dnf install avr-gcc avr-libc avrdude
     

   • Arch Linux:
     Bash

     sudo pacman -S avr-gcc avr-libc avrdude
     

   • macOS (using Homebrew):
     Bash

      brew tap osx-cross/avr
      brew install avr-gcc
      brew install avrdude
     

2. Install the avr-rust nightly toolchain: We need a nightly Rust compiler because embedded development often relies on unstable features.

   Bash

   rustup toolchain install nightly
   rustup component add rust-src --toolchain nightly
   

3. Install cargo-binutils: This provides helpful utilities for working with binary files.

   Bash

   cargo install cargo-binutils
   rustup component add llvm-tools-preview
   

4. Install the cargo package manager: This was already covered in the Rust Toolchain section.

5. Install the rust-nightly compiler: This was already covered above.

6. Install the avrdude tool: This was already covered in the avr-gcc section.

Creating a New Project

1. Generate the Project: Use cargo-generate to create a project based on the avr-hal template:

   Bash

   cargo generate --git https://github.com/avr-rust/avr-hal.git --name my_arduino_project --template-subpath examples
   cd my_arduino_project
   

   • --name my_arduino_project: Choose a descriptive name for your project.
   • --template-subpath examples: The avr-hal includes a few project templates, located inside the examples folder.
2. Select a template

   Choose a template from the menu. For this guide, select arduino-uno.

Writing Your First Program (Improved Code)

Open src/main.rs. You’ll see a basic example. Let’s use this improved, well-commented version:

#![no_std]
#![no_main]

use panic_halt as _; // You can use `panic_abort` as an alternative

use arduino_hal::prelude::*; // Import common traits
use arduino_hal::pins;

#[arduino_hal::entry]
fn main() -> ! {
    let dp = arduino_hal::Peripherals::take().unwrap();
    let pins = pins!(dp);

    // Digital pin 13 is connected to an onboard LED on most Arduino Uno boards
    let mut led = pins.d13.into_output();

    loop {
        led.toggle();
        arduino_hal::delay_ms(1000); // Wait 1 second (1000 milliseconds)
    }
}

Key improvements in the code:

• use arduino_hal::prelude::*;: This imports commonly used traits, simplifying the code.
• Clearer Comments: Added comments explaining what the code does.
• arduino_hal::delay_ms: Uses the arduino_hal provided delay function for better portability and accuracy.
• pins! macro: Uses the macro provided by arduino_hal to get the pins.

Flashing the Microcontroller

1. Find the Serial Port:

   With the Arduino IDE installed, you can easily find the correct port in the Tools > Port menu.

   Without IDE, find the serial port. Connect your Arduino Uno to your computer. Then run:

   Bash

   ls /dev/ttyACM*  # Or ls /dev/ttyUSB*
   

   You should see a device like /dev/ttyACM0 or /dev/ttyUSB0. This is your Arduino’s serial port. Unplugging and replugging the Arduino while watching the output of ls /dev/tty* can help you identify the correct port. If you have multiple devices, you might need to experiment.

2. Build and Flash: Use cargo run with the --release flag for optimized code and specify the serial port using ravedude (it should be installed with avr-gcc):

   Bash

   ravedude -p /dev/ttyACM0 -b 57600 #use your port
   cargo run --release
   

   • -p /dev/ttyACM0 (or /dev/ttyUSB0): Replace this with your Arduino’s actual serial port.
   • -b 57600: Baud rate used to communicate with the Arduino Uno bootloader. The baud rate of 115200 that you used can cause flashing problems. The correct bootloader speed should be 57600.
   • --release: Builds the optimized version of your code. This is crucial for embedded systems where resources are limited.
   • You might need to use sudo if you have permission issues accessing the serial port. However, it’s generally better to add your user to the dialout group (or the appropriate group for your distribution) to avoid needing sudo:
     Bash

     sudo usermod -a -G dialout $USER  # Add your user to the dialout group
     # Log out and log back in for the group change to take effect!
     

Output on the Microcontroller

After flashing, the on-board LED (connected to digital pin 13) on your Arduino Uno should blink on and off every second.

Troubleshooting

• “Permission denied” errors: Make sure your user has permission to access the serial port (see the dialout group note above).
• Flashing fails: Double-check the serial port and baud rate. Try pressing the reset button on the Arduino just before running cargo run.
• Code doesn’t compile: Ensure you have the correct Rust toolchain and dependencies installed. Carefully review any error messages from the compiler.
• avrdude: stk500_getsync() attempt x of 10: not in sync: resp=0x00: This typically indicates a problem with the serial port, baud rate, or the Arduino not being in bootloader mode. Double-check the port, ensure the baud rate is 57600 and try pressing the reset button before flashing.

Further Support and Resources

• Official Rust Book: https://doc.rust-lang.org/book/
• avr-hal GitHub Repository: https://github.com/avr-rust/avr-hal – Excellent examples and documentation.
• The Embedded Rust Book: https://docs.rust-embedded.org/book/ – A comprehensive guide to embedded Rust (not specific to AVR).
• Arduino Documentation: https://www.arduino.cc/
• Rust Embedded WG: https://github.com/rust-embedded/wg