Resetting a USB port via software.

Belnahua

Forgot to mention this:- Check to see if there's a Chipset update driver from the PC's manufacturer. I know HP and Dell had a USB issue, where it failed to see the USB port properly and a chipset driver update sorted that.

tomstickland

I'm not looking for manual ways of rescanning the drives.
I want to locate a low level dll command that I can call from software to force the computer to disconnect/rescan the USB ports.

The device is an industrial encoder interface, not something you'd ever use at home. The disconnect is known to be caused by noise/static.

tomstickland

buglawton wrote: »

Scan for hardware changes (without de- or re-installing anything) has worked for me in the past

So if I could locate the low level dll command that is used for this I'd be half way there.

MoneyTown

This looks interesting:

http://www.robvanderwoude.com/devcon.html

Specificallly:

RenewUSB.batRemove all USB devices and then rescan for new onesFindAll =USB
FindAll USB*
Remove "@hwid"
Rescan11/06/2004Warning: May cripple your OS, use entirely at your own risk, and only after making a full backup.
I had to run this script twice before my computer accepted my new USB stick.
This script will prompt you for download if DEVCON isn't found

albertross_2

http://www.nirsoft.net/utils/usb_devices_view.html

tomstickland

I've had a play today with both devcon.exe and USBDeview.exe and they both seem to do what they should.
However, neither is capable of forcing a device to reconnect.

With devcon I can locate the disconnected device and it shows as :
Device has a problem: 47.

Doing a search on that shows:

Windows cannot use this hardware device because it has been prepared for "safe removal", but it has not been removed from the computer. (Code 47) To fix this problem, unplug this device from your computer and then plug it in again.

To fix this problem, unplug this device from the computer and then plug it in again.

The device has been prepared for ejection.

This error code occurs only if the user used the Safe Removal application to prepare the device for removal, or pressed a physical eject button. Restarting the computer brings the device online if the user does not want to eject from the dock.

Unplug the device, and then plug it in again. Alternately, restart the computer to make the device available.

If I use devcon to restart the device then it says that the computer needs a reboot to do it.

MoneyTown

This any use?

Devcon Rescan

http://66.102.9.104/search?q=cache:nIno5Ft18UEJ:www.mp3car.com/vbulletin/general-hardware-discussion/84424-devcon-usb-resetter-optimization-tips.html+devcon+restart+usb+without+reboot&hl=en&ct=clnk&cd=10&gl=uk

tomstickland

Rather annoyingling I now cannot cause the original problem to happen, but know it will come back. Over 2 years it has come and gone, depending on the humidity apparently.