Optical Mouse Navigation

[Craig Putnam]

I guess its time for me to get back into the conversation...

I'll begin by correcting one error in the thread so far. We are using the mouse to tell us how far we have moved, not the rotation (as it is pretty insensitive to rotations about its optical axis). We are using one of the old gyro chips to measure the rotation rate and then merging the inputs from the two sensors to give us a measure of the robot's motion since the last time we looked. All of that is going into a PID feedback loop (the details of which we are still being worked out). The intent is to enable the robot to accurately travel along any mathematically defined path: straight line, circular arc, spline curve, etc.

Using two mice (one on each side of the robot) is indeed another way around the rotation problem as is using one mouse at the center of the robot to measure distance traveled and a second mouse mounted at the edge of the frame to measure turning motion.

Re: the mouse not being able to track the robot's speed. By lifting the mouse board up and inserting the appropriate optics, we have effectively changed the size of the "Mickey". So instead of (for example) getting 200 Mickeys per inch, we are getting a much smaller number. While our resolution has gone down, the speed that we can track has gone up. We expect to eventually have a resolution of about 1/4 inch and be able to easily track the top speed of a FIRST robot.

We do indeed speak to the mouse quite well using the PAK-VIa chip. [ If you go to the Al Williams site you will see that there is now a chip specifically designed for communicating with mice - the PAK-XI. We starting with the PAK-VIa chip however and have found that works well enough for our needs at the moment. ] As has been pointed out however, the use of any PAK chip may well be illegal. So I am very interested in hearing from anyone who has successfully communicated directly with either a PS/2 or USB based mouse (or directly communicated with the Agilent chip as was noted above).