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We have a PC-based test system that occasionally loses the ability to talk to the USB instruments. I started noticing that when this happens, the USB Power is also off for the Mouse and the Keyboard.

  • PC: NISE-3500 Fanless Embedded PC
  • Chipset: Intel QM57
  • USB Driver: Intel 5 Series / 3400 Series Chipset Family USB Enhanced Host Controller - 3B3C
  • OS: Windows 7

I tried to searching the Windows Event Log and could not find anything.

When the problem occurs it takes out ALL the USB ports on the system. I believe the PC only has one USB chip/controller; but, has 6 ports. All of the instruments and devices are on their own port.

I suspect that the cause is something like a USB over-current or USB stack violation that is causing the system to disable everything; but, I have not figured out a way to identify/confirm that.

Any ideas what can cause this and how to trace the problem.

Note: One of the instruments was developed (along with the Driver) by a partner group in Germany. It is a likely culprit; but, I don't have access to the Driver code and I am not sure how much support I can get from them unless I can find a smoking gun.

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    Have you checked the power settings? I know there is a setting for USB to sleep to conserve power, so this may have gotten inadvertently activated.
    – Kruug
    Feb 10, 2014 at 17:05
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    By default USB power saving IS turned on in Windows 7, so as Kruug stated if it hasn't been changed it is likely the source of the problem.
    – Oliver G
    Feb 10, 2014 at 17:08
  • Since it is a test system, the Power Setting is set for "High Performance". We have tried to turn off as much of the power saving stuff as we can find. Also, we can leave the system on for days (or weeks) and nothing ever powers off; but is happens occasionally during testing. Feb 10, 2014 at 17:24
  • Also, when this happens, the (USB) keyboard and mouse power are gone and nothing you do (other than reboot) will get them back. When this happens, I can still Remote Desktop into the systems and everything seems OK. The only way I can tell is to go over to the system and look. Feb 10, 2014 at 17:30
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    Keep in mind that most USB host controllers have resettable fuses on the 5v rail. If the device is drawing so much current, quickly enough for the OS not to even get alerted, it could be entirely in hardware. You could connect a powered hub to rule out hardware.
    – Mitch
    Feb 10, 2014 at 19:11

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