Hi,
I have a mouse from an A&T Unix PC, circa 1985. It mostly works: button clicks are received by the PC, and mouse moves cause the cursor to flicker, indicating the PC is receiving messages.
Decoding the mouse's output, I see that for every +1 mouse movement, it sends a -1 that effectively cancels it out. This happens on both the X and Y axes.
Inside, the mouse has two encoder wheels (it's a ball mouse, of course) and each wheel has two LEDs and two phototransistors. There's a 28 pin, 0.6" wide IC labelled Motorola SC87347P. Google does not offer up a datasheet for it (though it does find me and one other guy asking about it).
What could cause a mouse to fail in this way, sending negative movements that offset every positive movement?
Thank you,
Bob