TOS based Embedded system design and development
- 1. RTOS Based Embedded System Design and Development
- 2. RTOS • RTOS stands for Real Time Operating System. • It is an Operating System that is used in real-time applications such as medical critical care, defense and aircraft systems. • RTOS is used to obtain real-time output without buffer delay. • Multiple tasks without compromising on the synchronization in a short span of time is achieved by the Real Time Operating System (RTOS).
- 3. Real Time System with RTOS
- 4. Difference between OS and RTOS • A General Purpose Operating Systems (GPOS) allow multiple programs to execute at the same time. • All the general-purpose operating systems have the capacity to execute multi-tasks at the same time and it lacks in synchronization of the data. • In an RTOS, the processing time requirements are calculated in tenths of seconds or shorter increments of time. • Real Time Operating Systems uses real-time constraints such as power, time and effective utilization of memory. • RTOS is a priority based operating system designed to serve real time applications. • RTOS requires fewer resources in-order to provide accuracy of the task. • It occupies less memory.
- 5. Difference between OS and RTOS Regular OS Real-Time OS (RTOS) • Complex • Simple • Best effort • Guaranteed response • Fairness • Strict Timing constraints • Unknown components • Components are known • Unpredictable behavior • Predictable behavior
- 6. Types of RTOS It is classified into three types. They are: • Soft Real Time Operating System • Hard Real Time Operating System • Firm Real Time Operating System 1. Soft Real Time Operating System • In this type of Operating System, the response time of the system is prime but not critical to the operation of the system • . It has a deadline specified but the system can accept a short amount of delay. Example: Washing machine, Bluetooth headphones, etc.
- 7. Types of RTOS 2. Hard Real Time Operating System • In Hard Real Time Operating Systems the deadline and the time duration to execute tasks are specified. • It is necessary for a system to respond within the time line specified else might result in disastrous consequences. • Example: Medical critical care systems, Aircraft systems, etc.
- 8. Types of RTOS 3. Firm Real Time Operating System • RTOS of this type have to follow deadlines as well. In spite of its small impact, missing a deadline can have unintended consequences, including a reduction in the quality of the product. Example: Multimedia applications. Time Efficiency Curves of different RTOS
- 9. Kernel in RTOS • Kernel is the central module of an operating system. • Micro-Kernel Architecture is implemented in Real Time Operating System with configurable functionalities. • Abstraction Layer is provided by the Kernel which offers six main types of common services to the Application software. They are: • Task Management • Task Scheduling • Task Synchronization • Memory Management • Time Management • Interrupt Handling • Device I/O Management
- 11. Architecture of RTOS Task Management • The application is divided into small, schedulable, and sequential program units known as ‘Thread‘ or ‘Task‘. • This is done to achieve concurrency in Real Time Application. • Task Management by Kernel includes Real Time Task Creation, termination, changing priorities etc. • Task creation involves creating a Task Control Block (TCB) which has information about Task id, priority, Task states i.e. if the task is in (idle, running, ready, terminated) state etc.
- 12. Architecture of RTOS Task Scheduling: • It records the state of each task and determines the task of highest priority, to be executed. • The task which is already running is suspended and the processor executes the high priority task. Task Synchronization • It is necessary for the information to be transmitted safely from one Task or Thread to another Task. • Task Synchronization enables the tasks to mutually share the resources like buffers, I/O devices etc.
- 13. Architecture of RTOS Memory management • It allocates the memory for each program. Time Management • To schedule the tasks that need to be executed during specified duration, there is need for a periodical interrupt. • Hence hardware Timer is programmed to interrupt the processor. • Time interrupt is called System Tick.
- 14. Architecture of RTOS Interrupt Handling • CPU is informed about any asynchronous event through an Interrupt. • It is a hardware mechanism which handles an event by providing functions like defining Interrupt Handler, creation and deletion of Interrupt service routine etc. Device I/O Management • Device I/O Management helps in providing uniform framework ( API – Application Programmers Interface). • It also helps in accessing specific hardware device drivers i.e. it locates the right device for I/O request.
- 15. RTOS (Real Time Operating System) Working • Real Time Application requests are serviced by Real Time Operating System. • The RTOS allows multiple tasks or programs to execute simultaneously based on its priority. • Task scheduling Unit decides which thread is to be executed. The processor suspends the running task (if any) and executes the high priority task it receives. • Let us say, a user is browsing on the net and after few seconds switches on YouTube Video and in no time, the user starts listening to a Podcast. Browsing on the net is considered as ‘Task 1’, Video on YouTube is Task 2 and listening to Podcast is assumed to be Task 3.
- 16. RTOS (Real Time Operating System) Working • Switching between these tasks is called as Multi-Tasking and RTOS provides efficient multitasking services.
- 17. RTOS (Real Time Operating System) Working • When the User shifts to Task 2, then Task 1 is terminated and executes Task 2 as its priority is High. • Similarly, when the User shifts to Task 3, then Task 2 gets terminated and task 3 is executed. • Task Scheduling Unit takes care of these functions. Inter task communication, Synchronization, Time management is taken care of by RTOS Kernel.
- 18. Applications • Mobile applications. • Online transaction system. • Medical Critical Care systems. • Aircraft and defense systems. • Price quotation systems. • Network and multimedia systems. • Anti-Lock brake systems. • Air traffic control systems. • Online calling. • Ticket reservation systems. • Command control systems.
- 19. Advantages of RTOS • RTOS is event-driven with no processing time delay. • Real Time OS offers task-based API development. This helps designers or testers to work independently on their parts of the project. • It reduces the interdependencies between the modules by abstracting timing dependencies and task-based design. • It offers cleaners and smaller application courses. • Priority-based scheduling allows the user to separate analytical processing time and Critical processing time.
- 20. Disadvantages of RTOS • RTOS requires specific drivers for faster response time. • It requires plenty of resources, making it more expensive. • It uses a complex algorithm, which makes it very difficult to interpret. • It concentrates only on the accuracy of the program under execution, which increases the waiting time of low priority programs. • RTOS carries out only the minimum switching of tasks. • RTOS can only run minimal tasks together. • It uses plenty of resources, which sometimes are not suitable for the system.