The geartooth sensors are designed to run off the Digital I/O interrupt ports on the microprocessor. An example of this code is available from Kevin Watson here:
www.kevin.org/frc
The interrupt code will handle multiple gear tooth fires per processor loop.
The sensors are
very fragile. If you think you have done everything properly, and mounted them correctly, you may want to check the outputs over a osciliscope to make sure the sensor is operational, and firing the correct digital pulse.
We found that the mounting is very important. We found that this configuration works very well for the kit sensors.
-Hope this helps, let us know if we can help futher.