Abstract: Embodiments of the present invention provide various communication techniques for communication between a mobile computing device and an accessory. An accessory protocol that is generic to the mobile computing device can be used for some communication. An application executing at the mobile computing device can communicate with the accessory using an application communication protocol. In some embodiments, the application communication protocol can be different from the accessory communication protocol. In other embodiments the application protocol may only be recognized by the application and the accessory. In some embodiments, messages conforming to an application protocol can be communicated between the application and the accessory by packaging the messages inside a message conforming to the accessory communication protocol.

Abstract: Techniques for facilitating communication between a portable media device (PMD) and an accessory via multiple communication paths. In one set of embodiments, an accessory can be coupled with a PMD via a first connection, thereby establishing a first control communication path. The accessory can send to the PMD, via the first control communication path, an enumeration of the communication paths supported by the accessory. The enumerated communication paths can include control communication paths and data (e.g., audio or video) communication paths. The accessory can further send, to the PMD via the first control communication path, an availability status of each data communication path. In response, the PMD can select, based on a routing policy, one or more of the data communication paths and can notify the accessory of the selected data communication path. The PMD and accessory can then interoperate by exchanging data signals over the selected data communication path.

Abstract: A host device and an accessory exchange information (e.g., commands and data) via an intermediate device. The host device and accessory can each connect to the intermediate device. The host device can exchange commands and data with the intermediate device, while the accessory device can serially exchange data with the intermediate device. The host device and the accessory can also “tunnel” information to each other through the intermediate device, by packaging the tunneled information as a payload of a command recognizable by the intermediate device; the intermediate device can repackage and forward the payload. In some embodiments, the intermediate device can control serial communication parameters between the intermediate device and the accessory in response to commands received from the host.

Abstract: A host device and an accessory exchange information (e.g., commands and data) via an intermediate device. The host device and accessory can each connect to the intermediate device. The host device can exchange commands and data with the intermediate device, while the accessory device can serially exchange data with the intermediate device. The host device and the accessory can also “tunnel” information to each other through the intermediate device, by packaging the tunneled information as a payload of a command recognizable by the intermediate device; the intermediate device can repackage and forward the payload. In some embodiments, the intermediate device can control serial communication parameters between the intermediate device and the accessory in response to commands received from the host.