Virtual prototyping and co-simulation of mixed analog/digital embedded systems have emerged as a promising research topic, but usually assume an already Hardware/Software partitioned system. The paper presents a new approach for high-level system partitioning of such mixed systems, by expressing the structure and the behaivour of the analog parts with SysML diagrams. A tool already able to handle some aspects of analog design after partitioning has been extended to be able to handle partitioning, thus completing the methodology. As a real-world case study, we show the design of the hardware part of a medical application.