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?