What is USB Billboard Device Class?
The USB Billboard Device Class definition describes the methods used to communicate the alternate Modes supported by a device container to a host system. More details on Billboard Devices are available here in the USB Billboard Device Class specification.
Implementation of USB Billboard Device
The USB Billboard Device is implemented on the device container, which supports one or more Alternate Modes. The USB Type-C specification mandates the implementation of the Billboard Device for better user experience.
For example, in the reference design for the Type-C to DisplayPort cable, Billboard functionality is implemented using a CY7C65210 device. CY7C65210 belongs to the USB-Serial bridge controller family and is a full-speed USB 2.0 device that supports USB Billboard Device Class. It is available in a 24-QFN package.
When We need USB Type-c Billboard
The USB Billboard Device indicates the failure of Alternate Mode entry. According to USB Type-C specification, if a device fails to successfully enter an Alternate Mode within tAMETimeout (maximum of 1000 ms), then the device will minimally expose a USB 2.0 interface (USB Billboard Device Class) that is powered by VBUS to indicate the failure of Alternate Mode entry.
The host then reports that an unsupported device has been connected, identifying the type of device from the USB Billboard Device Class information.
Benefits of Using USB Type-c Billboard Devices
- USB Type-C technology allows for faster data transfer speeds than traditional USB ports.
- USB Type-C ports can deliver more power than traditional USB ports, because of that USB Type-C billboard devices can be more energy-efficient.
- USB Type-C ports can be connected both ways making it easier and no need to worry about which way the connector is facing
Community Translation: ビルボードデバイス（USB Type-C）：必要性と実装 (KA-03257)
