View Full Version : Connecting devices via a USB hub
Clive Long
4th-February-2007, 12:27 PM
I have a problem connecting a scanner to Windows XP through a USB hub.
If the device is cabled directly to the laptop, the scanner software detects the scanner. If I connect all USB devices via a hub, the scanner software cannot "see" the scanner. The attached Western Digital Hard Drive and mp3 player can be "seen" when attached via the USB hub.
The same behaviour occurs when I connect to the laptop running Linux.
Any idea why this may be?
Thanks
Clive
Andreas
4th-February-2007, 12:51 PM
Hi Clive
I can only hazzard guesses.
- Is your scanner switched on BEFORE you start your computer?
-> should be because the module may not be loaded on the fly. Did you try a modprobe?
- Could be that the hub does not provide enough power for the scanner
-> kinda unlikely, though because the scanner is powered but perhaps this influences the signal strenght. As I said, unlikely
- hub prioritisation
-> Have you tried disconnecting the other devices from the hub to see if the scanner works then? I mean a hub doesn't deal with multiple requests at a time (-> not a switch), so perhaps your external hard disk causes it never to get any sufficient transfer time? I am not sure how much this can be an issue, though it is worth trying.
Lee Bartholomew
5th-February-2007, 10:37 AM
Is it an active or passive hub?
A active hub has its own power supply. As Andreas said, you prob don't have enough power going through a passive hub to be running all the devices at the same time.
Clive Long
5th-February-2007, 10:42 AM
Is it an active or passive hub?
A active hub has its own power supply. As Andreas said, you prob don't have enough power going through a passive hub to be running all the devices at the same time.
Hi
It is an active hub with an external power supply.
Clive
frodo
5th-February-2007, 11:16 AM
Hi
It is an active hub with an external power supply.
Clive
If you haven't yet tried swapping ports I've found sometimes some ports on a USB hub work OK and others don't.
Even with an external power supply I've found some hubs have power difficulties - some can be very low quality.
Have you checked device manager (rather than the scanner software) in Windows to see if it detects any problems.
Lee Bartholomew
5th-February-2007, 01:33 PM
Also might be worth checking that you are not connection a usb 1.0 device to a USB 2. 0 or vice versa. Although they should be backwards compatible, it's not always the case.
Clive Long
5th-February-2007, 03:49 PM
Also might be worth checking that you are not connection a usb 1.0 device to a USB 2. 0 or vice versa. Although they should be backwards compatible, it's not always the case.
Good point.
I did have an unpowered USB 1.0 hub. I replaced it with a powered USB 2.0 but this didn't improve the problem.
Clive
Dreadful Scathe
5th-February-2007, 11:55 PM
I think Frodo has it right - certainly sounds like power to me. I would try a different powered hub to test this. Do you have any friends with a powered hub ? :)
Clive Long
6th-February-2007, 09:58 AM
I think Frodo has it right - certainly sounds like power to me. I would try a different powered hub to test this. Do you have any friends with a powered hub ? :)
I have a powered USB1.1 hub somewhere in a box in North London. I'll ty that. If the device is seen, then are there any quality / reliable makes for USB 2 hubs?
On a different tack, I vaguely remember seeing some devices that have a setting for when the device is either connected directly over USB to the host or connected via a USB hub? Is that relevant? Why should it matter?
Clive
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.