The use of RTOS is extra important for systems involved with the healthcare, automotive and aerospace industries, or any other system where failure could be catastrophic or life threatening.
A real-time operating system provides a deterministic approach that excludes anything that is random from the sequence of operations performed on a system. In other words, the system behaves in a predictable way. Provided that the algorithms are developed and implemented correctly, an RTOS ensures proper resource management so that a task is executed with exact timing. The timing behavior of an RTOS is considered deterministic. Except for the guaranteed timing, an RTOS ensures task switching at the interval of every quantum.
Tasks get interrupted and preempt each other according to the prioritization set by a developer. This is called preemptive scheduling. Scheduling is an important procedure for an OS performance which manages the waitlist of tasks and determines the event sequence in accordance with the predefined priorities. In RTOS scheduling, which is preemptive, any process can be interrupted by a high-priority task whenever it is assigned.
Thus critical tasks will always preempt low-priority tasks. The opposite of preemptive scheduling is non-preemptive or cooperative scheduling. In preemptive scheduling, tasks switch in equal time periods while in non-preemptive scheduling, there is no strict timing in task switching.
Another important principle established by an RTOS is priority inheritance. This takes place when lower-priority and higher-priority tasks share one and the same system resource. To release the resource as soon as possible for a high-priority task, a thread with low priority gets blocked and then restored so it passes its critical section.
In other words, the task inherits priority and as soon as the critical part of the operation is completed, the prioritization returns to the initial state. The priority inheritance does not work for a GPOS: a high-priority task will have to wait until a low-priority task passes all the sections and then gets executed. It means that a high-priority task may be delayed for an unpredictable amount of time.
Low-priority threads in a GPOS do not inherit the priority of higher-priority threads. This chart shows a system with two threads, but it can have many more. The principles described above show the reliability of RTOS, especially for real-time applications that need predictable latencies. This is how RTOS works: you always know the exact response time of any operation that runs on your system. Thus, a real-time operating system is the absolute leader in RTOS vs. OS competition when it comes to responsiveness.
Modern systems require better functionality, more options, and opportunities. That is why the popularity of real-time operating systems is rapidly growing in the world of embedded solutions. Guaranteeing the timely execution of high-priority tasks is extremely important for critical or life saving applications and real-time systems that have strict deadlines. In fact, my team implemented RTOS applications in almost all MCU-based projects that we delivered within our electronic design services in the past six years.
This type of operating system gives a broad range of opportunities. One of the most obvious reasons is multitasking. This is unnecessary with a simple system that only has a couple of tasks running in sequence.
But if you need to perform many tasks simultaneously, RTOS is at your service. It allows the developer to run a number of tasks concurrently. In case your embedded system has strict task prioritization, the preemptive scheduler of an RTOS makes it possible to switch to a high-priority operation at any time, ensuring that it will be completed first.
A developer has no need to control the task execution because an RTOS takes care of it. An RTOS gives developers the ability to multithread and synchronize, which makes their job easier. Without RTOS, the implementation of these options will take much more effort. One side effect you may encounter when using an RTOS is memory issues.
The overhead will depend on a particular microcontroller and its functionality. The chip characteristics together with the project requirements should be taken into consideration if you decide to go with an RTOS. It is certainly compatible with an RTOS solution.
We had to abandon the idea of using an RTOS with this chip so that we could reduce power consumption. For example, you can use a state machine and interrupt handlers to design all the necessary algorithms for an MCU to enable some kind of multitasking, synchronization, and other helpful features. To implement all of this, however, you will need additional development resources. That is why RTOS is preferred over bare-metal programming.
A real-time operating system distributes resources, takes control of all the operations, and saves time. An RTOS can assist your project in a number of ways. To make the use of an RTOS efficient in our firmware development , we always pay careful attention to the capabilities of the hardware and the requirements of the software.
Here is a brief checklist of the most important things you should keep in mind when deciding on an RTOS solution:. Also, think about the budget you are prepared to allocate for RTOS integration. Choosing between a commercial RTOS and an open-source solution depends on both the development and financial resources available. There are various options available among either open-source or commercial products. Real-time operating systems provided under a paid license are normally backed up by technical support, documentation, and development tools.
However, it depends on the vendor. So before buying a license, make sure you have everything you need to smoothly install and run an RTOS on your device.
Commercial vendors provide regular updates and security patches that facilitate the maintenance of the system. These RTOSes are generally designed for embedded systems and are able to support the most frequently used hardware platforms.
An open-source RTOS is a flexible solution that provides more opportunities for customization. However, it puts additional load on a developer due to the absence of regular support and off-the-shelf tools necessary for RTOS operation. So if you decide on an open-source solution, we highly recommend you choose an RTOS with a large developer community. You will be more likely to get assistance with development tools, updates, and security patches. We used it in a number of recent projects.
We also recommend it newbies in the development of real-time applications and OS integration. FreeRTOS is compact so it can run on any small-sized chip. It is quite fast and it maintains task concurrence at high speeds, providing a timely response for the required operations. The basic characteristics such as RTOS security, performance, and platform compatibility depend mostly on each particular product irrespective of the license type.
A real-time operating system provides an immediate response within a predictable timeframe. It is the most obvious option for systems that need to perform high-priority tasks with critical deadlines. The major advantage of using an RTOS in a microcontroller is that it makes the development process less painful, which saves you time and effort.
As soon as you have made up your mind about using an RTOS in your project, you can find a suitable solution among a wide range of various embedded RTOS solutions. There are options for any hardware platform offered by either proprietary vendors or open-source projects.
This state machine will attempt to handle any event in the context of the substate, which conceptually is at the lower level of the hierarchy. However, if the substate "result" does not prescribe how to handle the event, the event is not quietly discarded as in a traditional "flat" state machine; rather, it is automatically handled at the higher level context of the superstate "on".
State nesting enables substates to reuse the transitions and actions defined already in superstates. The substates need only define the differences from the superstates programming-by-difference. The behavior of active objects is specified in QP by means of hierarchical state machines UML statecharts.
This includes the accountability for the licensed intellectual property, professional documentation and technical support expected of a traditional software vendor as well as transparent development, availability of source code and active community inherent in open source projects.
This is possible, because active objects don't need to block internally, so most blocking mechanisms e. Not only you get the productivity boost by working at a higher level of abstraction than raw RTOS tasks, but you get it at a lower resource utilization and better power efficiency.
The top layer is the application- level code consisting of loosely-coupled active objects. QS can even be used to support acceptance testing in product manufacturing. The QP framework provides a few base classes to be subclassed and specialized in the applications.
This is a very common approach characteristic of most frameworks. The framework also uses the underlying kernel or RTOS for basic multitasking and event-queuing services.
The framework supports direct event posting as well as publish- subscribe event exchange. Application allocates an event from one of the fixed-size event-pools 2. Application posts or publishes the event to active objects 3.
AOs process the event, whereas they can re-post or re-publish it 4. QP automatically detects if the event is still in use and recycles it if isn't 5. Such static events don't need to be dynamically allocated and recycled. The kernel always selects the highest-priority, not-empty event queue. Every event is always processed to completion in the main loop. If any new events are produced during the RTC step e. The kernel very easily detects a situation where all event queues are empty, in which case it invokes the idle callack, where the application can put the CPU into a low- level sleep mode power-efficient kernel The task-level response of this kernel is the longest RTC step in the whole system, but without blocking the RTC steps are naturally very short.
Therefore the QV kernel is adequate to many systems, including safety- critical systems. The non-blocking limitation is irrelevant for event-driven active objects, where blocking is not needed anyway. The threads in the QK kernel operate a lot like interrupts with a prioritized interrupt controller, except that the priority management happens in software with up to 64 priority levels. The limitation of not-blocking allows the QK kernel to nest all threads on the single stack, the same way as all prioritized interrupts nest on the same stack.
This use of the natural stack protocol of the CPU makes the QK kernel very efficient and requires much less stack space than traditional blocking kernels. Still, the QK kernel meets all the requirements of the Rate Monotonic Analysis and can be used to in hard real-time systems. QXK allows threads to block anywhere in the code, so it works just like most traditional blocking kernel.
The main purpose of QXK is to allow sequential code middleware or legacy code to coexist with event-driven active objects, without a need for any 3rd-party RTOS kernel. QXK provides typical blocking mechanisms, such as semaphores, mutextes, and time delays. The biggest problem is the limited visibility in to the deeply embedded system Software tracing is a method for obtaining diagnostic information in a live environment without the need to stop or significantly slow-down the code.
Software tracing is especially effective in event-driven systems, where all important system interactions funnel through the active object framework and the state machine event processor. You then run the code with a controlled set of inputs, and examine the produced output from the printfs to determine whether the code under test operates correctly.
Checking the "test assertions" against the expectations is performed on the Host computer by means of test scripts Python and Tcl are supported. The central idea of this method is to inherently embed the contracts in the code and validate them automatically at runtime.
Assertions are increasingly popular among the developers of mission-critical software. For example, NASA requires certain density of assertions in such software. Due to inversion of control so typical in all event-driven systems, an active object framework controls many more aspects of the application than a traditional Real-Time Operating System. Such a framework is in a much better position to ensure that the application is performing correctly, rather than the application to check error codes or catch exceptions originating from the framework.
This characterization is not pejorative. The tool provides several views of the abstract model, such as the hierarchical tree-like Model Explorer, the Diagrams, and Property Sheets associated with the selected model element. In this respect, the tool is innovative and might work differently than other graphical state machine tools on the market. For example, QM does not use "pseudostates", such as the initial pseudostate or choice point.
Instead QM uses higher-level primitives of initial-transition and choice-segment, respectively. This simplifies state diagramming immensely, because you don't need to separately position pseudostates and then connect them. Also, QM introduces a new notation for internal transitions, which allows actual drawing of internal transitions in standard UML notation internal transitions are just text in the state body.
This unique approach gives you the ultimate flexibly in the source code structure and mitigates the needs to make manual changes to the generated code in order to combine it with hand-written code or existing 3rd-party code.
0コメント