Systems and methods for providing device-to-device handshaking through a power supply signal

Abstract

Handshaking circuits are provided in a communications cable and in a device operable to be mated with the communications cable. Before a device can utilize the power supply signal of such a communications channel, the two handshaking circuits must sufficiently identify one another over a power supply signal with a decreased voltage. The decreased voltage allows for a cable plug to be provided with a safe, protected power that cannot cause harm to a human. The decreased voltage also reduces the chance that a device can receive a primary power supply signal from the cable before the device sufficiently identifies itself. Accordingly, a laptop may be connected to a portable music player, but the voltage of the power supply signal provided by the laptop to the cable may be decreased on-cable until the handshaking circuit of the portable music player sufficiently performs a handshaking operation with a on-cable handshaking circuit.

1 . (canceled) 
     
     
         2 . A method for authenticating an accessory device with a main device, the method comprising:
 transmitting a power supply signal from the accessory device to the main device;   receiving an initiating handshake signal from the main device, the initiating handshake signal corresponding to a request for a response handshake signal from the accessory device;   transmitting the response handshake signal via the power supply signal; and   authenticating with the main device according to the response handshake signal.   
     
     
         3 . The method of  claim 2 , further comprising:
 allowing power from the power supply signal to be used as a power source for the main device in response to authenticating the response handshake signal.   
     
     
         4 . The method of  claim 2 , wherein a length of the response handshake signal is based at least on data provided in the initiating handshake signal. 
     
     
         5 . The method of  claim 2 , further comprising:
 modifying an amplitude of the power supply signal based on an identity of the main device provided in the initiating handshake signal.   
     
     
         6 . The method of  claim 2 , further comprising:
 transmitting the power supply signal to a handshake circuit of the main device, and causing the power supply signal to be provided to another circuit in the main device based on the authenticating.   
     
     
         7 . The method of  claim 2 , wherein the initiating handshake signal includes instructions for providing a subsequent power supply signal to the main device. 
     
     
         8 . A computing device, comprising:
 a processor;   a memory; and   a handshake circuit, configured to:
 receive a power supply signal from an accessory device and compare the power supply signal to one or more threshold values; 
 send an initiating handshake signal to the accessory device based on a result of comparing the power supply signal to the one or more threshold values; and 
 receive a response handshake signal from the accessory device for authenticating the accessory device. 
   
     
     
         9 . The computing device of  claim 8 , further comprising:
 a timing circuit configured to compare a length of time of the response handshake signal to a timing threshold for authenticating the accessory device.   
     
     
         10 . The computing device of  claim 8 , wherein the handshake circuit is configured to receive the power supply signal contemporaneously to the processor receiving media data from the accessory device. 
     
     
         11 . The computing device of  claim 8 , wherein the initiating handshake signal includes instructions for providing a subsequent power supply signal from the accessory device to the computing device. 
     
     
         12 . The computing device of  claim 8 , further comprising:
 a receptacle configured to both transmit the initiating handshake signal and receive media data from the accessory device.   
     
     
         13 . The computing device of  claim 8 , wherein the handshake circuit is further configured to cause the accessory device to modify the power supply signal subsequent to authenticating. 
     
     
         14 . The computing device of  claim 8 , wherein the initiating handshake signal includes parameters for generating the response handshake signal in a way that will result in the accessory device being authenticated. 
     
     
         15 . The computing device of  claim 8 , wherein the handshake circuit is further configured to route the power supply signal to another circuit of the computing device subsequent to authenticating the accessory device. 
     
     
         16 . A first device, including a handshake circuit configured to:
 transmit a power supply signal to a second device;   receive a handshake request from the second device to authenticate the first device;   transmit a handshake signal via the power supply signal to the second device; and   authenticate with the second device according to the handshake signal.   
     
     
         17 . The first device of  claim 16 , wherein the first device is configured to power the second device in response to the second device authenticating the handshake signal. 
     
     
         18 . The first device of  claim 16 , wherein the handshake circuit is configured to transmit, with the power supply signal, identification data corresponding to the first device. 
     
     
         19 . The first device of  claim 16 , wherein the handshake circuit is further configured to step up or down the power supply signal based authenticating with the second device. 
     
     
         20 . The first device of  claim 16 , wherein the handshake circuit is further configured to provide a continuing handshake signal with the power supply signal to the second device after authenticating with the second device. 
     
     
         21 . The first device of  claim 20 , wherein the handshake circuit is configured to stop sending the power supply signal when the continuing handshake signal is not received from the second device.