How CarPlay communicates with phone?

CarPlay communicates with the phone using a communication plugin that serves as the main interface between the vehicle's system and the iPhone. This plugin delivers video and audio content and accepts user input from the vehicle. In a typical CarPlay configuration, the iPhone provides a single video stream, which is then decoded and composed by the vehicle's system before being displayed on the screen.

For the next generation of CarPlay, the architecture has been enhanced to support multiple displays and more complex UI elements. The communication plugin has been extended to support vehicle state information, which is crucial for rendering the UI accurately based on the car's current state. Additionally, a dedicated low latency channel called Uisync is used to synchronize UI elements across different displays, ensuring smooth transitions and animations.

For more details, you can refer to the session Meet the next generation of CarPlay architecture (02:04).