In this paper we present our ongoing work towards a realistic probabilistic timing analysis of embedded software systems subject to timing requirements. In order to provide such an analysis that captures necessary and important behavioural features of the software system under analysis, including the underlying platform, we have implemented a real-time system running on a Rasberry Pi microcontroller on which we have performed a series of experiments and measurements. The results so far suggest a new model for analysis that captures more detailed behaviour and consequently provides a more accurate and correct probabilistic analysis.