Devices and methods for detecting usb devices attached to a usb charging port

Abstract

Methods and devices for detecting USB devices attached to a USB charging port including a USB port having a first data line D+, a second data line D−, and a power line are disclosed. A USB device is attached to the USB port; applying power to the USB device by the power line; applying a first voltage to the line D+ at the USB port by a first impedance; applying a second voltage to the line D− at the USB port by a second impedance. The voltages on the line D+ and the line D− are then monitored at the USB port. If the voltage on the line D+ is approximately equal to a first predetermined value for a predetermined period and the voltage on the line D− is below a second predetermined value, then the USB device is determined to be of an alpha type device.

What is claimed is: 
     
         1 . A method for detecting the type of USB device connected to a USB charging port, said USB charging port comprising a USB port comprising a first data line D+, a second data line D−, and a power line, said method comprising:
 attaching said USB device to said USB port; 
 applying power to said USB device by way of said power line; 
 applying a first voltage to said line D+ at said USB port; 
 applying a second voltage to said line D− line at said USB; and 
 monitoring the current drawn on the power line; 
 if said current drawn on said power line is below a first predetermined current value, then determining that said USB device is of a beta type. 
 the method further comprising:
 applying said first voltage to said line D− at said USB port; 
 applying said second voltage to said line D+ at said USB port; 
 monitoring the current drawn on said power line, wherein said USB device is of a gamma type if said current drawn on said power line increases above a second predetermined current value. 
 
 
     
     
         2 . The method of  claim 1  and further comprising:
 applying said first voltage to said line D+ and applying said second voltage to said line D− if said current does not increase above said predetermined value.