Hi

My device implements USB CDC, which consists of two interfaces. That's why it
shows up as Composite Device in the Device Manager when plugging in.

The difference between Win2k and WinXP, as far as I found out, is that Win2k
only asks for 1 driver, where WinXP asks for two.

In the Win2k INF file I have no definition for the interfaces, and it works, i.e.:
%MyDevice.Descr% = MyDevice,USB\VID_1234&PID_4321

For WinXP it seems to be necessary to have a definition for each interface, i.e.:
%MyDevice.Descr% = MyDevice,USB\VID_1234&PID_4321&MI_00
%MyDevice.Descr% = MyDevice,USB\VID_1234&PID_4321&MI_01

With this in WinXP, two new COM port appear in the Device Manager, on seems to
be okay, the other has error code 10.
When I open the good COM port, no communication is possible. When I try it the
same way as under Win2k, no COM port appears.

So I come to my question: what's the difference between the two OS's that make
the same INF file work on Win2k but not on WinXP?

Many thanks for any hint.

Robin