When designing a system using software and hardware components, communication modelling and synthesis are key points, since, for instance, communications cost drive hardware/software partitioning. In this chapter we present a method for communication interface synthesis based on a multi-level modelling of communication. By using a specific synthesis tool for each description level, and libraries of protocols and synthesised modules, reuse possibilities are enhanced. Petri Nets are used to model protocol behaviours and evaluate communication capabilities, leading partitioning.