A simple rust blink program for Arduino Uno

avr-atmega328p.json

{
  "arch": "avr",
  "cpu": "atmega328p",
  "data-layout": "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8-a:8",
  "env": "",
  "executables": true,
  "linker": "avr-gcc",
  "linker-flavor": "gcc",
  "linker-is-gnu": true,
  "llvm-target": "avr-unknown-unknown",
  "os": "unknown",
  "position-independent-executables": false,
  "exe-suffix": ".elf",
  "eh-frame-header": false,
  "pre-link-args": {
    "gcc": ["-mmcu=atmega328p"]
  },
  "late-link-args": {
    "gcc": ["-lgcc"]
  },
  "target-c-int-width": "16",
  "target-endian": "little",
  "target-pointer-width": "16",
  "vendor": "unknown"
}

build.sh

cargo build -Z build-std=core --target avr-atmega328p.json --release || exit

avr-objcopy -O ihex -R .eeprom target/avr-atmega328p/release/blink.elf target/avr-atmega328p/release/blink.hex
avrdude -p atmega328p -c arduino  -P /dev/ttyACM0 -b 115200 -D -U flash:w:target/avr-atmega328p/release/blink.hex:i

Cargo.toml

[package]
name = "blink"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[profile.dev]
panic = "abort"

[profile.release]
panic = "abort"

[dependencies]

main.rs

#![no_std]
#![no_main]
#![feature(asm_experimental_arch)]

use core::arch::asm;
use core::panic::PanicInfo;

// Ports
const DDRB: *mut u8 = 0x24 as *mut u8;
const PORTB: *mut u8 = 0x25 as *mut u8;

// Delay
fn delay(ms: u32) {
    for _ in 0..(ms / 16) {
        let count = 0xffff as u16;
        unsafe {
            asm!("1: sbiw {i}, 1",
                "brne 1b",
                i = inout(reg_iw) count => _,
            )
        }
    }
}

// Main
#[no_mangle]
pub extern "C" fn main() {
    // Set build in led to output
    unsafe {
        core::ptr::write_volatile(DDRB, core::ptr::read_volatile(DDRB) | 0b00100000);
    }

    loop {
        // On
        unsafe {
            core::ptr::write_volatile(PORTB, core::ptr::read_volatile(PORTB) | 0b00100000);
        }

        delay(500);

        // Off
        unsafe {
            core::ptr::write_volatile(PORTB, core::ptr::read_volatile(PORTB) & (!0b00100000));
        }

        delay(500);
    }
}

// Panic handler
#[panic_handler]
fn panic(_info: &PanicInfo) -> ! {
    loop {}
}