Connecting devices via a USB hub

[Clive Long]

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]

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]

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]

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]

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]

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]

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]

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]

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