Applying Real-Time Programming to Legacy Embedded Control Software

In the Logical Execution Time (LET) programming model, fixed execution times of software tasks are specified and a dedicated middleware is employed to ensure their realization, achieving increased system robustness and predictability. This paradigm has been proposed as a top-down development process, which is hardly applicable to a large body of legacy control software encountered in the embedded industry. Applying LET to legacy software entails challenges such as: satisfying legacy constraints, minimizing additional computational costs, maintaining control quality, and dealing with event-triggered computations. Such challenges are addressed here by a systematic approach, where program analysis and modification techniques are employed to introduce efficient buffering into the legacy system such that the given LET specifications are met. The approach has been implemented in a tool suite that performs fully automated transformation of the legacy software and may be carried out incrementally. This paper presents an application to large-scale automotive embedded software, as well as an evaluation of the achieved LET-based behavior for industrial engine control software.