Many CDC interface ?

JLS · Guest

Hi
Ive tried to connect 2 identical USB CDC device, Windows XP launches a second installation automaticelly with the same inf file, I see a new COM port in system pannel but the 2 CDC COM ports dont work Confused

Any has a solution ?
Thanks

rberek · Joined: 10 Jan 2005 Posts: 207 Location: Ottawa, Canada

Define "don't work"

JLS · Guest

Define "don't work"
hyperterminal can connect to one COM port but immediately freezes, impossible to send any character

rberek · Joined: 10 Jan 2005 Posts: 207 Location: Ottawa, Canada

I'm afraid I've not seen this before. I was hoping that the description of your problem would reveal it to be one of the simpler RS232/Hyperterminal problems that get solved on a regular basis here.

All I can suggest is going to the Device Manager of windows and making sure that Properties of each of the added COM ports (i.e. baud rate, parity, etc..) is what you expect them to be.

Ttelmah · Guest

It may also be worth looking at 'how' the second device is attached. Some hubs in particular, can be the source of real problems with USB busses. Typical examples, are the use of poorly temperature compensated resonators, so that their timings drift just enough to cause problems, and 'illegal' configurations, which purport to allow as much power to the downstream devices, as they themselves are allowed to draw, without having any extra power source. This can also apply to hubs inside computers (in particular on PCMCIA cards)...
I would wonder about total power consumption, since the total, of hub, two RS232 transceivers, two sets of all the electronics, might well be enough on some USB ports to be causing problems...

Best Wishes