Re: USB Device Detection

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Thanks for the response, it clarified in a general way what I was after. It
sounds like I need to check the USB spec to find out what conditions
indicate connection or disconnection to the hardware.

The reason I am asking is that I have a proprietary X86 platform with USB
that occasionally signals the NOTIFICATION_EVENT_DEVICE_CHANGE event when I
turn on and off a USB connected light. It seems unlikely that this should
happen by design. I suspect noise, power droop or some other hardware issue
may be at fault. Unfortunately our hardware engineers are quite comfortable
suggesting it is a CE problem unless I can explain precisely how the
detection process works.

Thanks

"anonymous" <anonymous@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:2B267466-5C89-4A03-8254-720ABEAD8986@xxxxxxxxxxxxxxxx
I'm not sure I understand the question.

When a USB device is inserted, it is connected to a USB host controller
which has a driver running for it (OHCI or UHCI drivers, generally). These
devices get an interrupt when the data lines do specific things at
insertion
based on the USB spec. From there, the USB host controller reads the
standard
descriptors and uses those to find a matching usb device driver in the
registry or prompts for one. Very similar to PCMCIA/PCCARD drivers.

"Bill T" wrote:

I am curious about how USB devices are detected by CE 5.0 when they are
connected and disconnected. I know that the
NOTIFICATION_EVENT_DEVICE_CHANGE
event is signaled but I don't know the precise mechanism. I would
appreciate
it if some one could comment on this or point me to documentation
describing
it.

Thanks


.

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