USB TO Parallel Port DIY Interface

[irving2008]

The USB device ID is a combination of device, interface and endpoint configurators. These are set by firmware after the PIC is reset and then the sequence is:

When the device is initially attached to the bus, the host
enters an enumeration process in an attempt to identify
the device. Essentially, the host interrogates the device,
gathering information such as power consumption, data
rates and sizes, protocol and other descriptive
information; descriptors contain this information. A
typical enumeration process would be as follows:
1. USB Reset: Reset the device. Thus, the device
is not configured and does not have an address
(address 0).
2. Get Device Descriptor: The host requests a
small portion of the device descriptor.
3. USB Reset: Reset the device again.
4. Set Address: The host assigns an address to the
device. >> this is where the de dum sound occurs
5. Get Device Descriptor: The host retrieves the
device descriptor, gathering info such as
manufacturer, type of device, maximum control
packet size.
6. Get configuration descriptors.
7. Get any other descriptors. >>during 5,6,7 Windows refines its understanding of the device, this is where you'll see 'Found generic HID' followed by 'Found <some device class>'

8. Set a configuration. >>this is where windows tries to load the required software

Since the ProductID is expensive the specifics are often in the later configurators, using a generic ProductID at the top level.

If you are unable to get Windows to recognise the USB device, you could try downloading a USB diagnostic tool. Does the device appear in Device Manager as an 'Unknown device' with a yellow question mark? If so then Windows is not recognising the descriptor as one of the generic classes. If it doesnt appear at all then the USB controller isnt able to do the initial reset/enumeration (steps 1 - 3 above) and Windows will never know the device exists. If this is the case then the problem is in your hardware or software (including the Microchip USB libraries) and without a full scale debugger and source code and the knowledge to use it there is little anyone can do to help.

[Robin Hewitt]

I just had a quick look on www.usb.org and it seems you can now get vendor ID numbers for a mere $2k.

Not as bad as I remembered it but they've now added a clause to say you can't sell numbers on. Too late guys :naughty: