Introduction

When building a system with a powerful microcontroller (MCU) or microprocessor, such as an ARM Cortex-M4, M7, R5, RXv3, A15, or A53—one of the key decisions developers face is whether to use bare-metal programming or a Real-Time Operating System (RTOS). These chips have a lot of processing power, memory, and complex peripherals that are perfect for complex, demanding projects. The way we structure our code—bare-metal or an RTOS—can shape everything from system performance, scalability, and future maintainability. Development boards are available for a wide range of different architectures, supporting various microcontroller families and making it easier to prototype and test on the target hardware.

This blog breaks down both the options into a simple decision matrix tool to help figure out what is best for a project.

RTOS and Bare-metal Programming

Bare-metal Programming

Bare-metal programming means we write bare metal code that runs directly on hardware (Microcontroller or Microprocessor) without using an operating system. This is also known as the super loop approach. The main loop is a fundamental control structure in bare-metal code, often implemented as an infinite loop to keep the firmware running indefinitely. For some simple or highly critical applications, bare-metal may be the only option due to its minimal overhead and direct hardware access.

Why bare-metal

• It executes very fast with minimal overhead.
• We get total control over the hardware.
• It is suitable for simple, low-cost applications.

Catches:

• Missing task management or scheduling.
• Juggling with application’s complexity during development.
• Scaling the system up is very difficult.

RTOS

An RTOS provides multitasking, scheduling, and hardware abstraction, offering standardized APIs for peripherals that simplify device driver management. RTOS is often chosen for projects involving complex algorithms that require efficient task management. However, adopting an RTOS comes with an initial learning curve, as setting up and debugging the system can be more challenging due to its complexity and API. As part of the development cycle, developers need to create firmware files and configurations to initialize the project and automate the build process.

Introduction to Embedded Systems

Embedded systems are specialized computing platforms designed to perform dedicated functions within larger devices or systems. Unlike general purpose operating systems found in desktop computers, embedded systems are optimized for efficiency, reliability, and cost-effectiveness. They are the backbone of countless modern devices, from medical devices and consumer electronics to industrial controllers and automotive systems.

A key characteristic of embedded systems is their need to handle multiple tasks, often with strict timing requirements. In many cases, a real time operating system (RTOS) is used to manage these tasks, ensuring that critical operations are executed precisely when needed. Whether it’s monitoring patient vitals in medical devices or managing user interactions in consumer electronics, embedded systems rely on robust task management and real time performance to deliver reliable operation.

Real time Operating System (RTOS):

An RTOS is an operating system designed specifically for real-time requirements, separating the application from hardware by providing a structured layer. It splits the application into tasks and handles scheduling; each task runs when it needs to and provides the standard structure to the application. We also get real-time guarantees for execution, with the ability to distinguish between a real time os and a hard real time system—where hard real time guarantees are critical for safety- or mission-critical applications.

Why use an RTOS:

• It handles task scheduling and management for us, ensuring that a high priority task is executed in a timely manner.
• Built-in mechanisms for inter task communication, such as event flags, semaphores, and message queues, allow efficient synchronization between multiple tasks.
• Makes big, complicated projects much easier to manage.
• Real-time performance assurances.
• Efficient management of system resources, including RAM and hardware, to maintain reliability and predictability.
• Support for network stacks, enabling integration of protocols like TCP/IP and USB for advanced connectivity.
• Service routines are used to handle hardware events and interrupts as part of the RTOS architecture.

Downside:

• An RTOS adds an extra overhead.
• It is more difficult to set up and manage.
• An RTOS requires more MCU / MPU resources.

Bare Metal Programming

Bare metal programming is the practice of writing software that interacts directly with the hardware, without the support of an operating system or any abstraction layer. In embedded systems, this approach allows developers to maximize efficiency and control, as the code runs directly on the hardware with minimal overhead.

By bypassing the operating system, bare metal programming gives engineers the ability to fine-tune system behavior, optimize performance, and reduce resource usage. However, this also means that all aspects of writing software—such as task scheduling, hardware initialization, and error handling—must be managed manually. Bare metal programming is especially valuable in applications where low-level hardware access and precise timing are critical, but it requires a deep understanding of both the system and the hardware it runs on.

Memory Allocation Strategies

Effective memory allocation is essential in embedded systems, as it directly impacts system performance, reliability, and power consumption. There are several strategies for managing memory in these environments:

• Static Allocation: Memory is assigned at compile-time, ensuring predictable usage and reducing the risk of fragmentation. This approach is common in systems with strict power consumption requirements and limited resources.
• Dynamic Allocation: Memory is allocated at runtime, offering flexibility for applications that need to handle varying data sizes or dynamic workloads. However, dynamic allocation can introduce unpredictability and increase power consumption if not managed carefully.
• Hybrid Allocation: Combines static and dynamic methods, allowing critical system components to use static allocation for reliability, while less critical or variable components use dynamic allocation for flexibility.

Choosing the right memory allocation strategy helps embedded systems maintain optimal power consumption and ensures that the system can meet its performance and reliability goals.

Power Consumption Management

Managing power consumption is a top priority in embedded system design, as it affects everything from battery life to system reliability and overall cost. Several strategies are commonly used to optimize power usage:

• Power Gating: Shuts off power to unused components, reducing energy waste when parts of the system are idle.
• Dynamic Voltage and Frequency Scaling (DVFS): Adjusts the system’s voltage and clock speed in real time to match workload demands, balancing performance with power efficiency.
• Clock Gating: Disables the clock signal to inactive modules, further minimizing unnecessary power draw.

By implementing these power consumption management techniques, embedded systems can extend operational life, reduce heat generation, and lower overall system power requirements.

Embedded System Examples

Embedded systems are everywhere, powering a wide range of devices and applications. Here are some common examples:

• Traffic Light Controllers: Use sensors and actuators to manage traffic flow, typically relying on a real time operating system (RTOS) and a microcontroller for precise timing and control.
• Microwave Ovens: Employ a microcontroller and a simple operating system to manage cooking time, power levels, and user interface functions.
• Automotive Anti-lock Braking Systems (ABS): Utilize sensors and actuators to control braking, with a real time operating system (RTOS) ensuring rapid response to changing road conditions.
• Aircraft Control Systems: Rely on a real time operating system (RTOS) and a microprocessor to process sensor data and control flight trajectory, meeting stringent real time requirements.
• Medical Imaging Devices: Use a real time operating system (RTOS) and a microprocessor to coordinate complex imaging processes, ensuring accurate and timely results for medical diagnostics.
• Industrial Robotics: Integrate sensors, actuators, and a real time operating system (RTOS) to manage precise movements and complex tasks in manufacturing environments.

These examples highlight the critical role of real time operating systems and efficient system design in delivering reliable, high-performance embedded solutions across diverse industries.

Decision Matrix Tool

We can use the mentioned tool to get assistance while choosing between bare-metal programming and RTOS. This tool gives you a structured approach to evaluate the criteria and determine what best suits the needs of your project.

How to Use the Decision Matrix

1. You need to evaluate all the baseline criteria for the project and choose what is relevant.
2. After the criteria selection, give a score to each criterion on a scale of 1 to 5, where 1 is not important and 5 is critical.
3. Add your scores for bare-metal and RTOS. Whichever gets the higher total is probably the best choice for your project.

How to Determine Whether RTOS or Bare-Metal is More Appropriate for a Given Application

To determine which is more suitable for your application, you need to evaluate the above provided baseline criteria. These criteria provide a structured approach to understand the system and identify the best development approach. Here, we discuss the major criteria and their effects with the help of examples from various application domains.

Concurrency and Task Complexity

• If the application requires handling several tasks simultaneously with different priorities—such as in smart home systems or Unmanned Aerial Vehicle (UAV) flight control—then using an RTOS is the better choice.
• If the application consists of sequential, fundamental operations that require little to no multitasking such as rudimentary motor control or control system, then choose bare-metal.

Real Time Performance

• If the application requires predictable execution with strict timing constraints—such as in medical devices, air traffic control systems, or car airbag systems—then use an RTOS. Air traffic control is a classic example of a hard real time system, where missing a deadline can have catastrophic consequences.
• If the application (such as high-frequency PWM motor controls or real-time audio processing) requires extremely predictable performance and ultra-low latency without the burden of an operating system, choose bare-metal development.

Resource Utilization and Constraints

• If an application requires dynamic memory management—such as wearable fitness trackers or IoT gateways—and the system has the resources to support the overhead of an operating system, then an RTOS is the suitable choice.
• If you need to optimize performance and efficiency with little overhead in a system with limited resources, for example battery-operated IoT devices, simple environmental monitors, then use bare-metal. Device drivers in both RTOS and bare metal code play a crucial role in managing hardware resources efficiently.

Development Time and Expertise

• If you have a team of developers with RTOS experience, the project requires quick prototyping, modular design, and easy maintenance such as industrial automation systems or industrial products, then use an RTOS.
• If the project requires team members with programming skills, extensive hardware expertise, and have flexible development deadlines—such as—specialized scientific equipment, research projects, then select bare-metal. Bare metal code often requires breaking work into small chunks for predictability, and developers must execute build or flash commands to deploy and test firmware.

System Scalability and Maintenance

• If your application can scale up and requirements change over time, or the project belongs to a dynamic field—such as infotainment systems for cars or smart home ecosystems—use an RTOS. Many embedded systems benefit from RTOS scalability strategies, which support complex multitasking and easier maintenance.
• If your application has simple feature sets with a few modification expectations and cost optimization is critical, choose bare-metal.

Resource Efficiency

• If the application belongs to a domain with common base system, demand features like structured system, various abstractions and can afford an overhead in terms of hardware resources and the cost like home automation hubs, high-end home appliances, select an RTOS.
• Use bare-metal if you need to minimize the overheads to maximize hardware efficiency such as ultra-low-power IoT sensors, retail tracking devices. Bare metal code allows direct access to memory addresses and hardware registers, providing maximum control and efficiency. Microcontroller vector tables use 32 bit addresses to define interrupt handlers and the firmware entry point.

Peripheral Integration

• If your application requires frequent interactions with numerous peripherals and complicated peripheral management such as automotive communication networks, use an RTOS.
• Use bare-metal if an application has basic peripheral interfaces such as basic motor controllers that need direct hardware access for performance adjustment. In bare metal code, developers often write and manage interrupt handlers and service routines, directly manipulating peripheral registers at specific memory addresses. Flash memory and startup code are essential for initializing embedded systems, as they store the vector table and firmware, and set up the system before main application execution.

Expertise Requirement

• Use an RTOS if the application is big, demands a structured development approach, and skills with software development with the OS and middleware.
• Use bare-metal if your team has deep knowledge of hardware and low-level programming, focusing on optimizing hardware interactions directly.

Power Efficiency

• If your application can handle some power overhead for example smart speaker, voice assisted devices where features set is huge, choose an RTOS.
• Use bare-metal for applications where low-power consumption is needed, application runs on battery, and life span expectancy is very high such as in long-life remote sensors.

Cost Considerations

• Use an RTOS if you are willing to invest in higher upfront costs for software licenses or more expensive hardware, and when development time is very less for example in high-value industrial systems.
• Use bare-metal if you need to minimize costs with less expensive hardware and development, focusing on simple functionality e.g., cost-sensitive consumer goods.

External Factors

• Use an RTOS if your application must comply with industry standards or regulations, or market competition requires quick feature updates such as compliant medical devices.
• Use bare-metal if your application has simple certification requirements or long-term product lifecycles such as legacy systems, power supplies.

Conclusion

This decision matrix gives a systematic data driven way to evaluate the best choice for application development for your high-end microcontroller project. Take a good look at what your application needs and what really matters in your project so that you can save lots of your effort.

This tool is only intended to serve as a guide; to make the best decision, always consider the unique situation for your applications.