Self-testing in embedded systems: Software failure

Colin Walls, Mentor Graphics
embedded.com (February 23, 2016)

All electronic systems carry the possibility of failure. An embedded system has intrinsic intelligence that facilitates the possibility of predicting failure and mitigating its effects. This two-part series reviews the options for self-testing that are open to the embedded software developer, along with testing algorithms for memory and some ideas for self-monitoring software in multi-tasking and multi-CPU systems. In part one, we looked at self-testing approaches to guard against hardware failure. Here in part two, we look at self-testing methods that address software malfunctions.

As was mentioned in the introduction to part one, the acceptance of possible failure is a key requirement for building robust systems. This is extremely relevant when considering the possibility of software failure. Even when great care has been taken with the design, testing and debugging of code, it is almost inevitable that undiscovered bugs lurk in all but the most trivial code. Predicting a failure mode is tough, as this requires knowledge of the nature of the bug that leads to the failure and, if that knowledge were available, the bug would have been expunged during development.

The best approach is to recognize that there are broadly two types of software malfunction: data corruption and code looping. Some defensive code can be implemented to detect these problems before too much damage is done.

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