Real-Time Operating Systems and Applications

One of the main challenges designers face when designing embedded systems is the need to meet rigorous and precise requirements for performance, efficiency, and reliability of the system. In order to deliver an embedded system serving the specific purposes of an application, experts in this technology field typically have to come up with complex combinations of hardware and software that are unique to the system requirements. 

The high level of reliability and performance of an embedded system is achieved by multiple components and modules working together and the operating system naturally plays a fundamentally important role in these processes. Resource management, the ability to multitask, divide computing resources among different tasks and prioritise them is extremely important for an embedded OS. 

This is the reason why the developers of modern embedded systems use real-time operating systems (RTOS) as a foundational software layer, powering these solutions. 

What is a real-time operating system (RTOS)?

RTOS is a type of operating system specifically designed for real-time applications: to be able to process various events and data with predictable latency. Real-time operating systems are designed for mission critical applications where missing certain deadlines may result in major consequences. 

Real-Time Operating Systems deployed in embedded products are typically built to be extremely small and include only the most essential components and features needed (often no UI at all). The goal of a typical RTOS solution is to enable timely execution of tasks, which requires the system to have flexible control and resource management capabilities. Specifically, an RTOS needs to be able to rapidly switch between tasks, handle multiple events concurrently, schedule and maintain the response to events within predictable time limits, send data across the network, record data, etc.

RTOS vs. GPOS. What’s the difference? 

As you must have noticed, real-time operating systems are very different from general purpose operating systems like Windows or Linux that are commonly used in consumer electronics and commercial work stations.

Standard operating systems typically need a lot more disk space and computing resources, serving as the core that controls all the processes, from execution of applications and memory storage to user interface, feedback from hardware, and other system operations, as well as all communication between user and the device. 

But the most crucial difference between RTOS and GPOS is the time it takes for the OS to react to certain events, which essentially goes down to the general approach to computing and hardware resource management. RTOS, as we just learnt, are designed to be event-driven and preemptive, providing highly deterministic response, which requires RTOS to use a sophisticated scheduling algorithm. 

Standard operations systems, on the other hand, typically utilize a non-deterministic approach to process execution, with no guarantees of task completion and no precise scheduling of process completion. 

Applications of RTOS

Due to the above-described distinctive features, real-time operating systems are typically used in embedded systems that must register and process large numbers of events, mostly initiated externally, in short time intervals within specified deadlines. This is why RTOS is the preferred operating system for flight control, military, industrial control, manufacturing automation, and in many other fields and industries where performance and reliability play a crucial role. 

Here are some examples of RTOS applications:

• Defense application systems
• Command and control systems
• Medical critical care systems
• Air traffic control
• Stock exchange control systems
• Networked multimedia systems
• Automobile safety control
• Online transaction systems
• VoIP communication 
• Real-time simulations

Types of RTOS

Real-time operating systems can be divided into three categories based on how rigorous their approach to response and execution of tasks is.

Hard RTOS

Hard RTOS approach the deadline with highest strictness. Such a system must guarantee the execution of a task on specified time and within the assigned time interval. Hard RTOS are used in systems that execute most important and crucial operations, such as air traffic control or critical care systems where delayed response can have serious consequences. 

Firm RTOS

Firm RTOS are also designed to follow deadlines, but in applications where missing deadlines on several processes is acceptable and won’t lead to critical effects. Missing a large number of deadlines still cannot happen, however. The most typical applications for RTOS are multimedia control systems, video conferencing systems, tracking and monitoring solutions, etc. 

Soft RTOS 

Soft RTOS, as its name entails, utilize a more flexible approach to the time limit. Missing deadlines for tasks is not as critical for soft RTOS and doesn’t lead to system failure like it would in a hard RTOS. It is also typical for real-time operating systems of this type to be more focused on prioritization and multitasking in order to identify and process highest priority tasks rapidly, while less important ones can take more time.

Benefits of using RTOS 

Now you can probably see why RTOS is essential for many embedded systems: small size, preemptive scheduling, multi-tasking, and real-time context-switching are critical features that allow embedded systems to provide the required performance and predictability. 

Let’s take a closer look at the main advantages of real-time operating systems.

Maximized performance

Naturally, the ability to provide high performance, maximizing the utilization of available resources, would be the main strength of RTOS solutions. Additionally, it is also important to mention that embedded systems powered by RTOS are typically designed to enable 24/7 operations with no interruptions caused by errors, updates or other factors that may disrupt the performance of a regular OS.

Advanced task prioritization and scheduling

Another powerful feature of RTOS is advanced priority-based scheduling that allows such systems to identify critical tasks and switch between processes. The response time in RTOS is measured in microseconds, and modern-day RTOS-based solutions are expected to respond within 3 microseconds. 

Small size and ease of maintenance

Due to small size and event-driven architecture, RTOS solutions normally incorporate fewer components and require minimal number of interconnections between them, which makes it much easier to maintain such a system. This is another huge benefit that allows organizations to minimize the technical support costs and use an embedded system for many years. 

Weaknesses of RTOS 

Since we covered the most important strengths of RTOS, it makes sense to touch on the weaknesses and disadvantages of this technology. Naturally, all drawbacks of RTOS stem from the distinctive features of this OS type described above. 

RTOS can handle only a small number of tasks

Real-time systems are designed to focus on key applications. Having limited computing resources, they can effectively handle only a small number of tasks. 

Real-time processing requires a lot of resources

The main reason why RTOS can’t handle many tasks is that real-time response to critical events requires a considerable amount of system resources. The augmentation of an RTOS-based embedded system with additional hardware components, however, is difficult and expensive. 

Difficult to design and implement

Due to all these distinctions from mainstream operating systems, implementing an embedded RTOS-based solution normally requires the field experts with years of hands-on experience and a considerable time. The architecture and algorithms powering such systems can be not only very complex, but also require high degree of customization depending on the application.  

Summary

Real-time operating systems play a fundamentally important role in modern-day embedded solutions design, enabling almost instant response and exceptional fail safety. But choosing an RTOS and integrating it with other system components is not a trivial task. A project to design and implement an embedded system can not only be difficult and time-consuming, but also very expensive and risky, especially for organizations lacking qualified internal talent to deliver such a system. 

The Tauro Technologies’ engineering team has a proven track record of successfully designing RTOS-based embedded systems across multiple industries. Utilizing our in-house expertise in this field, we are able to deliver custom-made solutions designed to match specific needs of each client, risk-free and in a short time period. 

Interested to know more? Get in touch with us for details.