US Patent 10225066 Multi-protocol contactless communication

Methods, systems, and apparatus for EM communications. One of the methods includes determining, at a first device, that a second device is present; initiating a half duplex communication with the second device; configuring communication with the second device including determining whether full duplex communication is available; in response to a determination that full duplex communication is not available, communicating with the second device in half duplex mode; and in response to a determination that full duplex communication is available, communication with the second device in full duplex mode.