CP21xx Smart Interface ICs Silicon Labs CP21xx Smart Interface ICs leverage Silicon Labs' world-class mixed-signal design expertise to provide a family of high-performance interface devices that enable designers to differentiate their products and speed time-to-market. These mixed-signal IC products span different technologies and standards to enable quick and effective communication between two devices or functionalities. These devices include USB to UART bridges, ISB to I2S digital audio bridges, HID USB to SMBus/I2C bridges, and SPI to I2C bridge with GPIO port expanders, and USB to SPI bridges.