Embedded systems consist of a microcontroller or microprocessor and peripheral devices that carry out a specific function within a larger electronic system. Embedded systems are a special type of computer, and just like your desktop computer at home, they require an operating system to function. In this week's blog post, we're exploring embedded operating systems. We'll explain what they are, the different types, and how they differ from desktop operating systems that we're already familiar with.
What is an Embedded Operating System?
An embedded operating system is a special type of computer operating system designed to optimize the functional efficiency of an embedded system. In the same way that your desktop machine requires an operating system like Linux, Mac OS, or Windows to run basic applications, embedded systems also require an operating system that supports their basic functionality.
Embedded operating systems typically incorporate a range of specialized features that allow the systems they control to function optimally in real-world applications:
Real-time Operations are crucial for embedded systems that support functions that need to be executed within a specified time frame. Consider the following example: an embedded computer controls a traffic signal that must cycle through different signals at predetermined intervals in a programmed order. This function is derived from the kernel, the core program of the operating system that controls task scheduling.
Reactive Operations require an embedded system to respond to a specific stimulus or user input. Think about the airbag in a vehicle - it needs to be deployed quickly when sensors in the vehicle detect a rapid deceleration of the vehicle that indicates a collision. The embedded operating system must be able to react with near-immediacy, which may require it to pause one task and execute a new one within a constrained time frame.
Direct Interrupts are used to rapidly transfer CPU resources from one event to another when the system demands it. Embedded systems are frequently deployed in real-world applications where they exercise full control of hardware peripherals using embedded operating systems.
Broadly speaking, embedded operating systems are a special kind of operating system used to meet the characteristic requirements of embedded systems, which include things like real-time and reactive operations, direct use of interrupts, and limitations in power consumption and computer resource availability.
Image by What are the Types of Embedded Operating System?
Many embedded systems are controlled by an operating system that is specially designed and configured for the exact needs and specifications of that device. While desktop operating systems are designed for general computing and configured to run many different types of applications with diverse requirements, embedded operating systems are more narrow in their scope. As a result, there are many different types of embedded operating systems (OS) in use today. Each type of operating system is designed to support a specific application of embedded systems. These systems include:
Single System Control Loop
A single system control loop is the most basic type of embedded operating system. This type of OS exercises digital control over a single measured variable. A simple embedded device like a smart home temperature control or thermostat might use this type of OS. The user programs the desired set-point for the temperature variable. The system uses sensors to measure the temperature in the environment. If the measured value is below the setpoint, the embedded system turns on the furnace. If the temperature is too high, the thermostat may activate an air-conditioning system, for example.
Multi-tasking Operating System
When an embedded system must perform several tasks or functions at the same time, it requires a special type of functionality called multitasking. A multitasking operating system is programmed to allocate processing time between various system functions according to application needs. If the system has more than one processor, it may be possible to perform more than one function simultaneously. Multitasking operating systems include a scheduling algorithm that establishes rules for organizing and prioritizing tasks.
Real-Time Operating System
A real-time operating system is meant to process inputs immediately as they are received, with the minimum possible delay between receiving a target input and generating the corresponding output. Real-time operating systems are bound by strict time constraints and processing tasks must be completed within the specified time constraints to avoid a system failure.
Rate Monotonic Operating System
Many embedded systems are developed using a special type of task scheduling algorithm known as rate monotonic scheduling. The purpose of this unique type of algorithm is to ensure that the system can meet the requirements of a range of tasks, all of which may require special priority treatment and timing constraints. A rate monotonic assigns the highest levels of priority to tasks that take the least time. In this way, the rate monotonic algorithm is a fully optimized algorithm for scheduling tasks that must be completed by a fixed deadline with limited resources. If a set of tasks cannot be scheduled to meet all deadlines using the rate monotonic algorithm, there is no other scheduling algorithm that can do a better job.
What's the Difference Between Embedded and Desktop Operating Systems?
There are many notable differences between the operating systems that power our desktop computer and those typically deployed in embedded systems design.
For starters, desktop operating systems are much more generally suited to running a wide variety of desktop applications, whereas embedded operating systems are configured to run a specific application with a specific set of hardware and peripheral components. This distinction underlies the differences that we see in the marketplace when it comes to desktop versus embedded operating systems. While just a few major desktop operating systems dominate that market space (Windows, macOS, Linux), there is much greater variety in embedded operating systems.
Embedded engineers have a range of options when it comes to implementing an embedded operating system. You may choose to download a free open-source operating system, purchase a commercial OS product, or write your own operating system to meet unique project requirements. At Total Phase, we build diagnostic and debugging tools that help embedded engineers code their embedded systems products and operating systems more efficiently and with fewer errors.
Summary
Embedded operating systems are unique because they can be customized and configured for the unique demands of the devices they operate. While desktop operating systems are robust, complex, and general-purpose, embedded operating systems are simplified to handle a defined set of tasks in a specific application with defined time constraints and scheduling requirements.
Ready to learn how Total Phase can help you develop and debug your next embedded operating system project?