An embedded system interface is itself a part of a larger embedded system and the interface design process is one part of the overall embedded system design. Interface design selects two important boundaries: between CPU software and digital interface logic; and between the digital and analog sides of the interface. Use cases for embedded systems help us understand interface requirements. Interface design methodologies provide a structured approach to the design of interfaces that meet performance, power, and cost goals. Design examples include a clap detector and motor controller.