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USB architecture.

Posted on 2011-03-09
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Last Modified: 2012-05-11
I'm having problem with a USB handheld barcode scanner. It lose connection to computer (disappears from Device Manager) several times / day and the solution is to disconnect/reconnect the USB cable. I tried to connect an external USB-hub and connect the scanner to the hub and since then the problem has only occured once in two days.
My question is: Can I from this result rule out problems with the USB controler and focus on the scanner? Does the external hub only work as an extension or does the external hub work as separate controller?
I'm not asking you to solve my problems with the scanner (although it would be nice), I'm only trying to understand the functionality of an external USB-hub.
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Question by:Skog
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rindi earned 500 total points
ID: 35081387
An external hub is only an extension with additional usb ports. If the hub has an additional powersupply, that would explain the difference. The power supplied by a PC's usb port can be at it's limits, while a hub with it's own psu should supply more power.

Some USB devices have two connections for that reason, so you can connect it to two USB ports on the same PC. That way the get supplied with more power.
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by:Skog
ID: 35081541
FYI: The scanner has its own external power source but I agree it sounds like power problem.
This is actually a lot more complicated problem...
It's a customer to us who has this behavior on 2 different computers and 2 different scanners.
We tried with a new PC - same problem.
We tried with a new PC, new model - same problem.
We tried with a third scanner (from different shipment/series) - same problem.
The really odd thing is that we have a bunch of customers who has the same configuration and noone else has reported any problems like this. (They have the same scanner model but might have different PC hardware but since the customer with the problem uses standard PC's (HP Compaq 8000 Elite SFF PC and HP Compaq dc7900 SFF), wich I assume are quite common, this really doesn't make sence.)
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by:rindi
ID: 35081879
The different tolerances on the PC's and scanners, and maybe even differences in the mains supply can cause such issues (So on one same model PC it might work, while on another not, etc).
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by:rindi
ID: 35081929
The different tolerances on the PC's and scanners, and maybe even differences in the mains supply can cause such issues (So on one same model PC it might work, while on another not, etc).
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