Software product-line engineering aims to maximize reuse by exploiting the commonality within families of related systems. Its success depend on capturing the commonality and variability, and using this to evolve a reference architecture for the product family. With embedded system families, the possibility of variability in hardware and operating system platforms is an added complication. In this paper we outline a strategy for evolving reference architectures from bi-directional feature models. The proposed strategy complements information provided by the feature model with scenarios that help to elaborate feature behavior.