optical mouse motion sensor thread

[Alan Anderson]

We did some experiments a few years back with using an optical mouse to track motion on the FRC carpet. Wildstang's programmers determined the hardware hacking necessary to connect directly to the chip inside the mouse, and came up with the code to use an IFI controller to communicate with it. We did the optical design so it could handle the expected travel speeds and view the surface without having to drag on the floor, and made a pneumatically-activated test jig to determine repeatability.

The electrical, optical, and programmatical aspects all worked great. However, without an absolutely stable distance between the floor and the sensor, converting mouse counts to absolute motion was unreliable. The values changed significantly with a difference in height of a single millimeter. A typical FRC robot bounces a lot more than that in normal operation.

With the slippery surface this year, maybe bouncing would be less of an issue -- except during collisions.