Understanding no_std in Rust for Embedded Programming

What is no_std?

• Definition: no_std is a feature in Rust that allows developers to write code without the standard library (std), which is not available in certain environments, such as embedded systems.
• Purpose: It is designed for environments with limited resources where you cannot use the full Rust standard library.

Why Use no_std?

• Resource Constraints: Embedded systems often have limited RAM and storage, making it impractical to include the standard library.
• Low-Level Access: It allows for direct interaction with hardware and low-level resources, which is crucial in embedded programming.

Key Concepts

1. The std Library

• The standard library provides essential features for general-purpose programming, such as collections, threading, and I/O.
• In embedded systems, these features may not be applicable or available.

2. Using core instead of std

• When using no_std, developers rely on the core library, which provides basic functionalities like primitive types and traits without the overhead of std.
• core is lightweight and intended for environments with limited resources.

3. Setting Up a no_std Project

• To create a no_std environment, you typically need to update your Cargo.toml file to specify #![no_std] in your crate.

Example:

#![no_std]

4. Dependencies

• Many crates are available that support no_std environments, allowing you to use essential features without the standard library.
• Look for no_std compatible libraries for functionality like memory management or hardware interaction.

Example Setup

#![no_std]

extern crate panic_halt; // A panic handler that halts the program

use core::panic::PanicInfo;

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

fn main() {
    // Your embedded code goes here
}

Conclusion

• Using no_std is essential for embedded programming in Rust, enabling developers to write efficient code tailored to resource-constrained environments.
• Understanding how to use core instead of std, and setting up a no_std project is crucial for working effectively in embedded systems.