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FreeRTOS vs Embedded Linux – Which One Should I Use?
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FreeRTOS Embedded Linux

One major decision made by the embedded system architect is to choose the right operating system for the application. Two common operating systems for embedded systems are Embedded Linux and FreeRTOS. So, you may ask, which one of the two should I choose to develop my system?

FreeRTOS or Linux? Which One is Better for my Application?

Your choice of OS depends mainly on what the intended application for the system is.

If the system requires a strict timing schedule and the application focuses primarily on controlling hardware—such as the control systems of household appliances like microwaves or washing machines—then FreeRTOS is a suitable OS. This real-time operating system excels in environments where simplicity and timing precision are paramount.

If the application requires complex processing and does not require strict process deadlines, then Embedded Linux can be the choice. Examples of this are systems which deal with networking such as routers, or systems involving computer vision or machine learning. These applications primarily focus on processing rather than control. This is a very simplified answer which leaves out the intricacies of hardware and software.

One important thing to understand is that these platforms target different types of hardware and are not interchangeable.

I’m a beginner, Which One is Easier to Learn?

Embedded Linux: If someone is familiar with working on Linux systems, picking up embedded Linux will be relatively straightforward since it shares many functionalities with desktop Linux. However, for those with no prior experience with Linux, the learning curve can be steep. It requires first getting acquainted with the intricacies of Linux and then transitioning to actual application development. Additionally, due to Linux’s reliance on various software packages for added functionality, users need to understand how these addons work. There’s also a possibility of encountering software integration bugs, given that Linux-based applications often have multiple dependencies. Despite these challenges, the code’s portability ensures that any changes in the system’s hardware usually don’t affect the software.

FreeRTOS: Most microcontrollers are programmed using the C language, a familiar territory for many engineers, making it easier to dive into FreeRTOS development. While programming with FreeRTOS can be relatively straightforward, it demands a deep understanding of the hardware being utilized to write effective code. However, this hardware knowledge is specific to the particular hardware being used. If there’s a change in hardware, users will need to acquire detailed information for the new hardware, as FreeRTOS lacks portability in this aspect.

Considering these factors, it’s fair to say that Embedded Linux might pose challenges for beginners due to the complexity of its software. In contrast, FreeRTOS emerges as a more accessible option, especially for users not planning to stay with microcontrollers.

What’s an Example Application of Each?

It should be evident by now that while both systems may share some aspects and their functionality might overlap in some cases, ultimately, they have different use cases. When making a choice between the two, it is important to identify the core requirements of the application and choose accordingly for an efficient system.

While a simple motor controller can operate under Embedded Linux, this might lead to higher power consumption and slower boot times due to the additional software overhead. In such cases, a microcontroller running FreeRTOS could achieve the same functionality more efficiently, using fewer resources and offering quicker responsiveness.

There are cases where fast response from the system is extremely important such as the flight control systems of an aircraft, the throttle control of an engine, or an emergency stop system for a machine. In such time-sensitive applications, using an Embedded Linux system would be ill-advised and might result in safety concerns.

While the flight controls of an aircraft would utilize a real-time operating system, the navigation systems would be more suitably handled by an Embedded Linux-based system as it will need to be interactive for the user with a graphical interface.

A system running FreeRTOS will not be able to perform high-level computer vision tasks; for that, an Embedded Linux system is far more suitable as it can access a wide range of proprietary software resources available.

Android, which is based on the Linux kernel, exemplifies a specialized adaptation of Embedded Linux designed for complex devices like smartphones. Such devices surpass the hardware and software capabilities typically supported by FreeRTOS, necessitating a more comprehensive operating system that can handle intricate user interfaces and extensive application requirements.

Which One Gives Me More Access to Hardware?

FreeRTOS: FreeRTOS is a real-time operating system. A real-time operating system is not a full operating system like Windows or Linux; rather, it can be thought of as an advanced task scheduler with a focus on strict timing and consistency in meeting deadlines. High-level hardware control provided by FreeRTOS means that often the firmware is directly flipping registers, which makes the code efficient but specific to a microcontroller and not very portable.

FreeRTOS

Source: www.digikey.com

Embedded Linux: Embedded Linux is an operating system based on the Linux kernel with packages specifically tailored for embedded systems. Embedded Linux has the advantages of a full operating system and can run other proprietary software which makes it very versatile. Since Embedded Linux has common libraries and abstraction layers in its code, it doesn’t directly interact with the hardware of the system, making the code very portable.

img-7

Source: www.windriver.com

Which One Is Lighter?

FreeRTOS: Compared to a full OS, it is very lightweight and doesn’t have high hardware requirements, which means it can run with very little overhead with a very fast boot time.

This makes FreeRTOS more suitable for battery-constrained applications.

Embedded Linux: Embedded Linux has a lot of overhead software, which significantly increases its hardware requirements and consumes more power.

Do They Both Work with the Same Hardware?

Sometimes yes, but generally speaking they are targeted for different hardware.

FreeRTOS: The target hardware for FreeRTOS is microcontrollers which consist of a CPU integrated with other peripherals such as RAM and memory. These devices are used for automating specific control applications. They are simple to program and often run bare metal programs.

Embedded Linux: The target hardware for Embedded Linux is microprocessors which are high processing power CPUs that require memory management to operate and external peripherals. These CPUs can run full operating systems and mostly focus on high processing tasks.

Comparison Summary

 

FreeRTOS Embedded Linux
Is it a full OS?

Is not a full OS

Is a full OS
Complexity Relatively simple software Complex software
Response speed Very fast response (for the same processing power) Relatively slow response (for the same processing power)
Access to hardware Directly controls hardware Does not interact with hardware directly
Realtime behavior Very strict timing for meeting deadlines Timings for deadlines are not that strict
Overhead Very little software overhead Large software overhead
Target hardware Runs on microcontrollers Runs on microprocessors
Portability Code is not very portable Code is very portable
Application Focus Focus on control applications Focused primarily on high processing applications
Learning difficulty Easier learning curve, but skillset limited to resource-constrained applications Steeper learning curve, but more widely usable skill

References:

16adc64e-5857-4505-b27e-e66b375037a1 (1920×1080) (digikey.com)

embedded_linux_architecture_image.jpg (968×532) (windriver.com)

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