- How can WITTENSTEIN high integrity systems assist me in my project development?
- What is the difference between FreeRTOS.org and OpenRTOS?
- What is the difference between OpenRTOS and SafeRTOS?
- Are evaluation versions of OpenRTOS and SafeRTOS available?
- To which processors and compilation tools has SafeRTOS been ported?
- How did the SafeRTOS certification comply with the tools qualification requirements of IEC 61508?
- To which standards does SafeRTOS comply?
- What is IEC 61508?
How can WITTENSTEIN high integrity systems assist me in my project development?
In addition to supplying SafeRTOS, WITTENSTEIN high integrity systems can assist your development in a number of ways. As an example, we can:
- Support all aspects of SafeRTOS integration and usage.
- Support safety lifecycle activities and the application of the Design Assurance Package.
- Undertake some or all of the application development on your behalf.
- Provide tailored middleware products and drivers to meet the individual needs of you application.
- Act as an independent third party auditor or tester.
- Provide training in formal software development and real time operating system theory and usage.
- Assist your company in establishing conforming development processes.
What is the difference between FreeRTOS.org and OpenRTOS?
OpenRTOS is FreeRTOS.org provided under a commercial license that makes no reference to the GPL - making it suitable for all professional developments.
FreeRTOS.org and OpenRTOS are essentially the same product - only the license under which they are distributed, the support options available, and the
headers within the source files differ.
Additional benefits of the commercial license include:
- There is no requirement to document that your product uses OpenRTOS.
- There is no requirement to open source any modifications made to the OpenRTOS kernel.
- You can purchase development and support packages.
- You do not have to offer to provide the OpenRTOS source code to end users.
You are free to download, evaluate and develop your project using FreeRTOS.org before purchasing an OpenRTOS license.
What is the difference between OpenRTOS and SafeRTOS?
SafeRTOS has the same functional model as OpenRTOS and has been certified by TÜV SÜD to have been developed in compliance with the processes
necessary for use in IEC 61508 applications at SIL 3. The differences between the two products originate predominantly from the hazard analysis performed as part of
the certification process.
One of the primary differences between OpenRTOS and SafeRTOS is how RAM is allocated to tasks and queues.
OpenRTOS provides a selection of simple memory allocation schemes that are used to automatically allocate the
RAM required each time a task, queue or semaphore is created. As a result of the safety constraints, SafeRTOS does not provide an
equivalent dynamic memory allocation mechanism. Instead, the RAM required to create a task or queue must be statically declared at
compile time. A mechanism is provided that permits the host application (the user written application that uses SafeRTOS) to know when
a task has been deleted so that the RAM allocated to that task can then be re-used.
The complete input parameter validity checking performed by SafeRTOS has resulted in several minor API changes.
SafeRTOS requires the host application to provide two small hook functions.
Some API functions are not provided in SafeRTOS.
Upgrading from OpenRTOS to SafeRTOS is a straightforward task and is supported by explicit documentation that can be provided on request.
SafeRTOS can be provided with a complete Design Assurance Package.
Are evaluation versions of OpenRTOS and SafeRTOS available?
With respect to OpenRTOS, see the FAQ "What is the difference between FreeRTOS.org and OpenRTOS?".
Other than the additional safety aspects, using SafeRTOS is very similar to using FreeRTOS.org. We therefore suggest if you wish to evaluate SafeRTOS
you first download and familiarize yourself with FreeRTOS.org. You can even start to develop your application this way, but keep in mind the differences
between SafeRTOS and FreeRTOS.org listed above. Following this, contact us to discuss your specific evaluation requirements - we can then
accommodate your individual needs.
To which processors and compilation tools has SafeRTOS been ported?
It is possible to use SafeRTOS with all the processors to which FreeRTOS.org/OpenRTOS has been ported. However,
SafeRTOS was actually certified on one particular processor using one particular compiler, but the portability of the code means the processes undertaken are
largely independent of both. Using SafeRTOS in a safety related system would require the test harnesses to be re-executed within the
final application environment no matter the processor or tools used, so the additional effort required if changing from the original development environment is minimal.
How did the SafeRTOS certification comply with the tools qualification requirements of IEC 61508?
This is the subject of the published article that can be viewed here.
To which standards does SafeRTOS comply?
SafeRTOS was specifically designed to the IEC 61508 standard for SIL 3 applications. However, the development processes used are comprehensive and
can be cross referenced to many other international formal development standards. We can assist you in the production of a compliance matrix.
What is IEC 61508?
IEC 61508 is the international standard for electrical, electronic and programmable electronic safety related systems. It categorizes
safety related systems in accordance with a Safety Integrity Level (SIL). The higher the risks associated with a system application the
higher the assigned SIL - with SIL 4 being the maximum. For each SIL level IEC 61508 specifies the minimum design, implementation, operation
and maintenance standard to be achieved. The SafeRTOS development process is compliant with that required for SIL 3 applications - the highest
obtainable for software only components.
