rust-embedded

name	rust-embedded
description	Embedded Rust development for bare-metal and no_std environments. Use when targeting microcontrollers, writing HAL drivers, working with peripherals, handling interrupts, or using RTIC/Embassy for real-time systems.

Rust Embedded Development

Based on The Embedded Rust Book, The Embedonomicon, and Embedded Rust on Espressif.

When to Use This Skill

• Writing #![no_std] applications for microcontrollers
• Working with HAL (Hardware Abstraction Layer) crates
• Configuring linker scripts and memory layouts
• Handling interrupts and DMA
• Using RTIC or Embassy for concurrency
• Targeting ARM Cortex-M, RISC-V, or ESP32

Project Structure

my-firmware/
├── .cargo/config.toml     # target, linker settings
├── Cargo.toml
├── memory.x               # memory layout (flash + RAM regions)
├── build.rs               # optional: extra link args
└── src/
    └── main.rs            # #![no_std] #![no_main]

Minimal no_std Binary

#![no_std]
#![no_main]

use panic_halt as _;  // panic handler (halt on panic)
use cortex_m_rt::entry;

#[entry]
fn main() -> ! {
    // Initialize peripherals
    let dp = pac::Peripherals::take().unwrap();
    let mut led = dp.GPIOA.pin(5).into_push_pull_output();

    loop {
        led.toggle();
        cortex_m::asm::delay(8_000_000);
    }
}

Memory Layout (memory.x)

MEMORY
{
    FLASH : ORIGIN = 0x08000000, LENGTH = 256K
    RAM   : ORIGIN = 0x20000000, LENGTH = 64K
}

.cargo/config.toml

[target.thumbv7em-none-eabihf]
runner = "probe-rs run --chip STM32F303VCTx"

[build]
target = "thumbv7em-none-eabihf"

[env]
DEFMT_LOG = "info"

HAL Layer Architecture

┌─────────────────────────────┐
│  Application Code           │
├─────────────────────────────┤
│  HAL (e.g. stm32f3xx-hal)  │  ← high-level, safe API
├─────────────────────────────┤
│  PAC (e.g. stm32f3)        │  ← auto-generated register access
├─────────────────────────────┤
│  Hardware                   │
└─────────────────────────────┘

• PAC (Peripheral Access Crate): Generated from SVD files, provides raw register access
• HAL: Type-safe wrappers implementing embedded-hal traits
• BSP (Board Support Package): Board-specific pin mappings and initialization

embedded-hal Traits

Portable driver abstraction:

use embedded_hal::digital::OutputPin;
use embedded_hal::i2c::I2c;
use embedded_hal::spi::SpiDevice;
use embedded_hal::delay::DelayNs;

// Write a portable driver
pub struct Sensor<I2C> {
    i2c: I2C,
    addr: u8,
}

impl<I2C: I2c> Sensor<I2C> {
    pub fn read_temp(&mut self) -> Result<f32, I2C::Error> {
        let mut buf = [0u8; 2];
        self.i2c.write_read(self.addr, &[0x00], &mut buf)?;
        Ok(i16::from_be_bytes(buf) as f32 * 0.0625)
    }
}

Interrupts

use cortex_m::peripheral::NVIC;
use stm32f3xx_hal::pac::interrupt;

#[interrupt]
fn TIM2() {
    // Timer interrupt handler
    // Access shared state via critical section or RTIC resources
    cortex_m::interrupt::free(|cs| {
        if let Some(timer) = TIMER.borrow(cs).borrow_mut().as_mut() {
            timer.clear_interrupt(Event::Update);
        }
    });
}

RTIC (Real-Time Interrupt-driven Concurrency)

#[rtic::app(device = stm32f3xx_hal::pac, dispatchers = [SPI1])]
mod app {
    use super::*;

    #[shared]
    struct Shared { led: Led }

    #[local]
    struct Local { timer: Timer }

    #[init]
    fn init(cx: init::Context) -> (Shared, Local) {
        // Setup peripherals
        (Shared { led }, Local { timer })
    }

    #[task(binds = TIM2, local = [timer], shared = [led])]
    fn tick(cx: tick::Context) {
        cx.local.timer.clear_interrupt();
        cx.shared.led.lock(|led| led.toggle());
    }
}

Key Crates

Crate	Purpose
cortex-m	Low-level ARM Cortex-M access
cortex-m-rt	Runtime (vector table, entry)
panic-halt	Panic handler: infinite loop
defmt	Efficient logging for embedded
probe-rs	Flashing and debugging tool
embedded-hal	Hardware abstraction traits
rtic	Real-time concurrency framework
embassy	Async embedded framework

Reference Map

• references/no-std-basics.md — no_std setup, panic handlers, alloc
• references/peripherals-hal.md — GPIO, timers, I2C, SPI, UART
• references/interrupts-concurrency.md — NVIC, critical sections, RTIC, Embassy

Key References

• The Embedded Rust Book
• The Embedonomicon
• RTIC
• Embassy