In the world of embedded systems, the language debate is alive and well. For years, C has dominated this space, its minimalistic design and low-level control giving embedded engineers the tools to squeeze performance out of limited hardware. But with increasing system complexity, maintaining and scaling C code has revealed its limits. Enter C++ and Rust—languages that bring new perspectives and strengths to the table, allowing us to take embedded design into the modern age.

What if, instead of picking one, we use all three? In fact, by weaving together C, C++, and Rust, we can create systems that are efficient, robust, and future proof, while also playing to each language’s strengths. While you don’t necessarily need all three languages, let’s explore what such a solution might offer. 

A language for every layer

C is like the trusty old wrench—it’s been around, it’s reliable, and it does the job at the most basic level. At the heart of the embedded stack, C still reigns supreme when working directly with hardware. Say we’re writing a driver for a UART interface on an STM32. By coding it in C, we gain direct access to registers, minimize memory usage, and avoid unnecessary overhead. C is unmatched when it comes to controlling hardware with precision, and it’s often the most straightforward way to do so. While we could argue that C++ and Rust can directly access registers too, the C libraries are often already provided to us by the microcontroller vendors. 

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As we layer on more functionality, we start needing a bit more structure. Here, C++ steps in beautifully. Take, for example, a project where multiple sensors communicate with a microcontroller. Writing high-level sensor logic in C++ allows us to modularize each sensor as a class with its own data and behavior. This organization makes it easier to manage complexity, especially as the project grows. C++ lets us take advantage of object-oriented design, giving our code a structure that C just doesn’t support.

Finally, as we ascend to the highest levels of the stack—the logic that coordinates everything or handles mission-critical tasks—Rust steps into the spotlight. Rust’s modern features and rigorous memory safety checks make it ideal for high-stakes code, such as managing multiple data streams from sensors or handling critical communication protocols. For instance, if our embedded device is a medical monitor that must manage data from multiple sensors without fail, Rust’s safety guarantees help prevent errors like buffer overflows and data races. Rust enables us to create safe, concurrent systems in a way that’s difficult to replicate in C or C++.

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A real-world example: Blending C, C++, and Rust

Imagine a real-world embedded system for environmental monitoring. It has several components: low-level hardware drivers, higher-level modules that process and store data, and critical components that manage data transmission and sensor coordination.

In C, we handle all the direct hardware interfacing, such as initializing GPIOs, configuring UART, and setting up ADCs for the sensors. Here’s a basic snippet for UART initialization:

#include "stm32f4xx.h"

void UART_Init(void) {

    RCC->APB1ENR |= RCC_APB1ENR_USART2EN;

    USART2->BRR = 0x0683; // Set baud rate

    USART2->CR1 |= USART_CR1_TE | USART_CR1_RE;

    USART2->CR1 |= USART_CR1_UE; // Enable USART

}

This is C at its best—simple, efficient, and designed for tasks where every cycle counts. 

Moving up the stack, we write the application logic in C++. Here, each sensor can have its own class, encapsulating sensor-specific behavior, such as temperature readings, data filtering, or logging. These C++ classes interact with our C-based drivers, creating a clean separation of hardware control and application code. We might write code in this layer that looks something like the following:

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#include "Sensor.hpp"

class SensorManager {

public:

    void addSensor(Sensor* sensor) { sensors.push_back(sensor); }

    void readAll() {

        for (auto sensor : sensors) {

            sensor->read();

        }

    }

private:

    std::vector<Sensor*> sensors;

};

This setup keeps the application logic readable and organized, and should we need to add new sensors, the system is easy to extend.

Now for Rust. Rust is ideal for the most critical part of our system—let’s say it’s a data-processing component that collects sensor data and then streams it over a network. Rust’s memory safety and concurrency features shine here, giving us peace of mind that the code will handle data safely and reliably. By using Rust’s concurrency, we can manage multiple threads processing different sensors, each isolated and protected from common pitfalls like memory leaks.

use std::sync::{Arc, Mutex};

use std::thread;

fn process_data(data: Arc<Mutex<Vec<i32>>>) {

    let mut data = data.lock().unwrap();

    data.push(42); // Safely modify shared data

}

fn main() {

    let data = Arc::new(Mutex::new(vec![]));

    let data_clone = Arc::clone(&data);

    thread::spawn(move || {

        process_data(data_clone);

    }).join().unwrap();

}

Rust takes care of the memory safety for us here, something neither C nor C++ can do on its own. 

A seamless stack with modern build tools

Now you might be thinking that this all seems like a lot of work to use multiple languages. However, in many cases, you’re not writing all this code from scratch. In fact, the biggest complaint for switching languages is that we have so much example and legacy C code and that justifying the investment to switch doesn’t make sense.

With the right build tools—think CMake for C and C++ and Cargo for Rust—we can seamlessly integrate all three languages. That gives you the ability to leverage the assets you’ve already developed while modernizing your application development. Using CMake, we can handle C and C++ code in one build process, and Cargo’s FFI capabilities let Rust communicate with C and C++ components, creating a cohesive stack.

Why this multi-language approach is worthwhile

By combining C, C++, and Rust, we create systems that aren’t limited by any one language’s constraints. C gives us the foundational, efficient hardware access, C++ adds the structure we need for maintainable application code, and Rust brings the safety and concurrency features that reduce bugs and ensure robustness. It’s a balanced approach that lets us leverage the best of each language without compromise.

If you think about it, leveraging multiple languages in this way has dramatic advantages. The hiring pool to develop an embedded system becomes larger because you can now include folks that know C++ and Rust not just C. You won’t need to train new developers to use C, instead let them use what they already know. All that C code you’ve used the past several decades can still be used, it just needs to be wrapped in C++ or Rust interfaces. By doing so, you now have access to modern languages and tools to help you and your team develop software faster!

The bottom line for a multi-language approach in embedded systems

In embedded development, where safety, efficiency, and performance are paramount, this multi-language strategy offers a clear advantage. So, the next time you sit down to design an embedded system, think about how C, C++, and Rust can work together. You may find that each language has a unique role to play in building the most efficient, reliable, and future-proof system possible.

You may also find that these little arguments about what language to use are now a moot point.