---- Autonomous Toy Train Controller ---

Modified multiwii (multicopter) code to extract gyro z-axis information to 
determine speed around curvers. This information is fed back into a simple
feedback algorithm to slow down the train. 

Wheel speed sensor is used to measure train speed and adjust motor controller 
PWM to keep train speed approximately constant except for slowing down in curves.

Designed for Rainbowduino to allow instant status information to be displayed
on 8x8 RGB matrix. 

Code is hardcoded for GY80 IMU. Only z-axis of gyro is currently being used
from the IMU. Multiwii code is used because of the quality gyro filtering.
First checked-in code represents the same code used to demonstrate the 
train at the 2014 Seattle Mini Maker Faire.

For more info zapmaker.org

Code is GPL3 license per multiwii license.