Device dependent selection between modes for asymmetric serial protocols

摘要

A portable communication device (PCD) can automatically switch into different operating modes of an asymmetric communication protocol (such as USB) depending on the type of accessory connected. For example, the accessory can signal whether the PCD should operate in a first mode or a second mode using a hardware indicator such as identification resistor across two pins of a multi-pin connector and/or a software indicator such as a command protocol. The PCD can detect the accessory's signal and switch to the operating mode requested by the accessory.

主权项

1. A method for use in a portable communication device, the method comprising:
establishing, by the portable communication device, a non-USB connection for communication with an accessory using a first set of pins and using a non-USB protocol; determining, by the portable communication device, whether a mode-selecting command is received from the accessory via the non-USB connection, wherein the mode-selecting command includes a command code and a parameter specifying whether the portable communication device is to operate in a first mode or a second mode of an asymmetric communication protocol; and in the event that the mode-selecting command is received from the accessory, initializing, by the portable communication device, a connection on a second set of pins for communication with the accessory in the mode of the asymmetric communication protocol indicated by the received mode-selecting command, wherein the non-USB protocol is a device-specific protocol, the method further comprising: initiating an authentication operation with the accessory using the second set of pins according to the device-specific protocol; determining whether the authentication operation is successful; and in the event that the authentication operation is not successful, blocking the accessory from using at least one function associated with the asymmetric communication protocol.