Wierd keyboard behaviour - Sometimes only windows key works

nebb-tgr
nebb-tgr used Ask the Experts™
on
Hello,

We have a quite wierd problem on one of our projects. We have three PC's all connected with 1m cable to a KVM-switch with USB. The KVM switch is connected through a 10 meter amplified cable to a USB-hub. The USB-hub is in turn connected to a mouse and a wireless keyboard.

We are experiencing two separate problems, but both seem to be related to the communication between the USB-units and the PC.

Before I explain the problems, I need to point out that 95% of the time, everything works fine. The doesn't seem to be any kind of event that occurs before the problem appears, it just happens.

Problem 1 - Keyboard:
Writing normal text doesn't work anymore. But the windows key works.
Example: You can press the windows key to make the start-menu appear, but you can't write anything in the "Search programs and files" text box. I haven't checked all keys, there might be more working keys than the windows key.

Problem 2 - Mouse:
This seems to be a general problem that is always there. When you click a button, the mouseclick is not registered before you move the mouse. We use industrial rollerballs, so it is not natural to move the rollerball when you click.

I thought that all communication from mouse and keyboard was interrupt-driven. That should meen that a mouse-click would be transferred instantly. And I didn't think there would be any priority or anything on the kind of keys that are transferred. Why would the windows key work while the others dont?
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Top Expert 2012
Commented:
You've got a USB hub in between, so start with that - try a different USB hub, or a powered USB hub if you aren't using one.  USB devices can be frail or not built to spec and then they don't work all the time.

Author

Commented:
We have tried powering the USB-hub. That didn't help. I don't think general USB-hubs shape up the signals. We could try another USB-hub though.
Top Expert 2012
Commented:
You can also try eliminating as many things as possible between the keyboard and the PC and that will help identify what part of the chain is failing and causing the problem.  This will take time, though, since you cannot get this problem to occur reliably.
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Lead System Administrator
Commented:
Please connect the USB hub to KVM using 1 m quality USB 2 cable.

Check for keyboard and mouse in case it is working fine than 10m cable is faulty.

Instead of using 10m cable, is it possible to use two 5 meter amplified cable.

One from KVM to USB hub and second from USB hub to Wireless keyboard mouse.

Please check for firmware update of KVM for mouse issue.

Author

Commented:
- Change the keyboard
 - Change the hub
 - Try 2x 5m amplified instead of 10m amplified.

I will let you know how it goes.

Author

Commented:
Further explanation:
There are two operator chairs with the identical setup. This means that this is not a freak component failure or similar. It is semi-reproducable, i.e. it will happen sometime between 1 hour and 2 weeks.

Because changing the cable is such a hassle, we have decided to try to change out the keyboard and USB-hub in the hope that this will fix the issue.

As before, I will let you know how it goes.

Author

Commented:
Thanks for the feedback. Never did get around to testing this further. So I'm awarding points based on activity. :)

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