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Just curious why this is always on the list for trouble shooting USB devices.

Is it just because how USB works, some kind of tech myth, or just in case there's an actual hardware fault with the USB port?

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marked as duplicate by ncdownpat, random Nov 2 '13 at 20:25

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4 Answers 4

up vote 23 down vote accepted

Why not?

Firstly, not all USB ports are made the same. Front usb ports are notorious for not supplying enough power for many devices, especially with older/cheaper cases. USB 3.0 may not work for keyboards at boot time for many devices. You might have more than one controller on a system for USB, and that controller may be flakey. In short, it rules out an error with a specific port, its controller, or the physical electrical subsystem that is supporting it.

It is no different from running a minimal system to work out why a motherboard or other device is acting up, and adding things till something fails.

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Ah damn, it always gets more complicated doesn't it :) Thanks! Know of any good USB analysis tools? –  prasanth Nov 2 '13 at 14:43
    
depends on the OS, and what you're trying to do. this question talks about my efforts in reverse engineering a keyboard to get it to work in linux, and the tools mentioned there are a good start, assuming they still work this question is pretty neat too, assuming you want to focus on keyboards. Finally (maybe I should have said it first), device manager in windows, and lsusb. –  Journeyman Geek Nov 2 '13 at 14:47
    
Ah nice the blackwidow, I've bugged around device manager, I should mentioned windows, but was wondering if there was something that focused just on the USB controller. I'll read through the other questions though and post any useful tools I find here. Thanks! –  prasanth Nov 2 '13 at 14:53
    
USBDeview from Nirsoft is nice tool for troubleshooting Windows usb drivers. –  week Nov 2 '13 at 17:25
    
USBDView is a good tool, @prasanth. you can use it to see how Windows enumerates USB devices in the registry, see whats active, hubs, drivers in use... –  AthomSfere Nov 2 '13 at 17:48

Sometimes, Windows will see the same device on a different port as a different device, and reload the drivers for it.

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Ah ok, I was wondering if that took place, thanks! –  prasanth Nov 2 '13 at 18:16

USB ports may be connected to hubs internally, where power and data transfer must be shared. So it's conceivable that problems may be caused by having other devices on the same physical hub, if you have a device that needs a certain amount of power / transfer rate to function properly.

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In addition to the technical answers, there is always the possibility that the device isn't plugged into the USB port properly due to user error. In this case, removing and re-inserting the device could make the user concentrate and insert it properly.

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