Functional safety of embedded systems

Functional safety plays a major role for embedded systems

The complexity of embedded systems is constantly increasing – as are the safety requirements. In this interview, Prof Dr Peter Fromm from Darmstadt University of Applied Sciences explains the increasing importance of functional safety for embedded systems and gives practical advice for safety development.

Safety in the embedded system industry

Prof Fromm, how do you define functional safety?

Prof Fromm: The key point here is certainly the following: if the operation of a system can jeopardise the environment and, in particular, people, higher reliability requirements must be placed on this system. 

Can you give an example of this?

Prof Fromm: In my view, we need to consider both safe system functions and protective functions. In the case of safe system functions, traditional – often mechanical – solutions are replaced by electronic systems. One example of this is »X-by-wire« systems. The main aim here is to realise at least as high a level of reliability with the new technology as with the classic approach.

Practical implementation of functional safety

The MISRA rules are used in the automotive sector to avoid errors during programming. What do the MISRA rules achieve and where is there a need to catch up?

Prof Fromm: MISRA is certainly one of the better programming standards and reduces the C/C++ language scope to a safe and well-defined subset – which is also demonstrated by the fact that this standard is used in many areas outside the automotive sector and has now even found its way into the curriculum of technical degree programmes.
Especially when I, as a software developer, use MISRA during development, I can eliminate weaknesses in the code before the review. But even MISRA is not a silver bullet. In particular, design errors in the code and other more complex problems cannot be found with it. The human expert review is therefore still necessary and important. However, the focus of the review can then be placed on the »exciting« problems.

Do you have a tool recommendation for creating and testing software code according to all aspects of functional safety?

Prof Fromm: The question of the toolchain certainly depends on the complexity of the project. Our experience in current projects shows that a model-based approach can be worthwhile. This allows developers to fulfil the high requirements in terms of quality, documentation and traceability while at the same time developing the software in incremental or iterative cycles in an agile manner.

As part of a project within the German government's Central Innovation Programme for SMEs (ZIM), we have developed a holistic yet lightweight tool called »µRTE« (www.u-rte.com) at the Department of Electrical Engineering and Information Technology at Darmstadt University of Applied Sciences, which has now been successfully used in the first safety projects. In terms of model-based system engineering, it supports the process areas of requirements, hardware and software architecture, code generation of the runtime environment as well as testing and traceability between all artefacts.


Do you have any tips for developers regarding safety requirements?

Prof Fromm: The most important tip is definitely to plan sufficient resources and time. Due to the higher requirements for architecture development as well as testing and documentation, the effort involved in a safety project quickly doubles, even at the lower safety integrity levels.

The second tip would be to understand the technical meaning of the safety standard and try to implement it sensibly instead of following the standard letter for letter.

And last but not least – external advice or support is helpful, especially if this is your first safety project.

Thank you for the interview, Prof Fromm.

The interview was conducted by Tobias Schlichtmeier of WEKA Fachmedien, it first appeared on elektroniknet.de.

You can gain further exciting insights into the safety of embedded systems in the interview with Prof Axel Sikora, Chairman of the embedded world Conference. We look forward to welcoming you to the safety & security Area in Hall 5 during embedded world.