A real-time operating system is an operating system that supports real-time applications by providing logically correct result within the deadline set by the user. It makes the embedded system into a real time embedded system.
Importance of RTOS for Embedded System
It is an operating system that supports real-time applications by providing logically correct result within the deadline set by the user. A real-time operating system makes the embedded system into a real time embedded system.
The basic structure of real-time operating system (RTOS) is similar to regular OS but, in addition, it provides mechanisms to allow real time scheduling of tasks. Real-time systems are those where system correctness depends not only on output but also on the timing constraints of when results are produced.
Though the real-time operating systems may or may not increase the speed of execution, but they provide more precise and predictable timing characteristics than general-purpose OS.
The figure below shows the embedded system with RTOS.
All the embedded systems are not designed with RTOS. Low end application systems do not require the RTOS but only High-end application oriented embedded systems which require scheduling alone need the RTOS.
For example, an embedded system which measures Temperature or Humidity etc. do not require any operating system whereas a Mobile phone, RADAR or Satellite system used for high end applications require an operating system.
Popular Real-Time Operating Systems
Real-Time Operating System (RTOS) | Applications | Key Features |
Embedded systems, IoT devices, robotics | Portable, open-source, small footprint, task scheduler | |
Aerospace and defense systems, industrial automation, robotics | Real-time kernel, scalable, fault-tolerant | |
QNX | Automotive systems, medical devices, industrial automation | Microkernel architecture, reliability, scalability |
RTOS-32 | Industrial automation, real-time control applications | Real-time multitasking, low latency, Windows compatibility |
Micrium OS | Embedded systems, consumer electronics, medical devices | Modular architecture, preemptive scheduling |
RTEMS | Aerospace, automotive, industrial control systems | Real-time capabilities, open-source, scalable |
INTEGRITY RTOS | Automotive systems, avionics, medical devices | High reliability, security features, POSIX compliant |
Nucleus RTOS | Consumer electronics, industrial automation, medical devices | Small footprint, real-time kernel, extensive middleware |
ChibiOS/RT | Automotive systems, robotics, industrial control systems | Open-source, preemptive multitasking, low overhead |
ThreadX | IoT devices, consumer electronics, industrial automation | Real-time scheduling, small footprint, priority inheritance |
These examples provide a snapshot of popular RTOS, their typical applications, and some key features that make them suitable for real-time systems.
Note that the choice of RTOS depends on specific requirements and constraints of the target application or system.
Difference between Desktop OS and RTOS
Feature | Desktop OS (Operating System) | RTOS (Real-Time Operating System) |
Purpose | General-purpose computing tasks | Real-time applications and systems |
Scheduling | Non-deterministic scheduling | Deterministic scheduling |
Task Priority | May not prioritize real-time tasks | Prioritizes real-time tasks |
Response Time | Variable response time | Predictable and consistent response time |
Multitasking | Supports multitasking, often with time-sharing | Supports multitasking with a focus on real-time requirements |
Concurrency | Emphasizes concurrent execution for various tasks | Prioritizes real-time task concurrency |
Interrupt Handling | May have non-deterministic interrupt handling | Has deterministic interrupt handling for time-sensitive tasks |
Resource Management | Resources are managed for efficiency in general-purpose scenarios | Efficient management of resources with a focus on meeting deadlines |
Complexity | Generally more complex due to diverse functionality | Specialized and often simpler for specific real-time tasks |
Examples | Windows, macOS, Linux | FreeRTOS, VxWorks, QNX, RTEMS |
Use Cases | Office applications, multimedia, web browsing | Aerospace, automotive, industrial automation, medical devices |
Predictability | Predictability is not a primary concern | Highly predictable for time-critical applications |
Latency | Latency can vary based on system load | Low and predictable latency for critical tasks |
Cost | Typically lower cost or free for general-purpose use | May be higher cost due to specialized nature and certification requirements |
Development Focus | General-purpose functionality and user experience | Real-time performance and meeting strict timing requirements |
Examples of Applications | Word processing, gaming, web browsing | Aircraft control systems, automotive control units, medical equipment |
Flexibility | Offers a wide range of functionalities for diverse applications | Tailored for specific real-time tasks, may lack flexibility for general-purpose use |
Safety-Critical Systems | May not be suitable for safety-critical applications | Often used in safety-critical systems where precise timing is crucial |
