You want to control two computers with the same mouse, right?
As you probably know, parallel connections of USB cables can be a bit dicey - they are designed to be point-to-point, not parallel.
The best solution would be to build a buffer network that electrically isolates the signals from each other - this could be done with a few gates or some op-amps or a few optical isolators.
Even this may or may not work, depending on the mouse and the driver software.
Anyway, to plow ahead with direct wiring:
USB has four wires - GND, Data +, Data - , +5V
Here's a diagram:
http://interface.centraltreasure.com/pc-interface-knowledge/usbwiringdiagram/(The color code is
observed by manufacturers.)
(A general reference on USB is in Wikipedia, here:
http://en.wikipedia.org/wiki/Universal_Serial_Bus )
You should be able to connect the data wires in parallel (provided they have a common ground reference). However, each data wire is terminated with a pair of small (45 ohm) resistors to +5 and ground. When you connect the signal wires in parallel, these resistors will be in parallel, too, reducing the load the system sees and degrading the signals. But mice are slow animals, so this might not be a problem.
To make a parallel connection, connect the GND, Data + and Data - wires to each other and connect the +5V from only ONE of the computers.
The second computer, the one without the +5V connected, will probably not recognize the mouse - USB uses a device recognition protocol based on having a small (50 mA should do it) current draw on the +5V line.
You could fake this out by connecting a 100 ohm resistor between the +5V of the USB connector on the second computer and ground - this will pull 50 mA (I = V/R = 5/100 = .050 A) from the second computer and should allow the mouse to be recognized.
This setup will give you a mouse in parallel with the data lines of two computers - whether it will be recognized by both (or either) is another question entirely and one I can't answer easily.
wb
