Code and Strategy

All of the game logic is performed on the leader PIC32, and we tried to minimize the need for the leader to request information from the follower by wiring most sensors and inputs to the leader. The two exceptions are the game start button and the beacon detection circuit. At the start of the game, before the button has been pressed, the leader sends a message to the follower until a response is given which is trigged by the game button being pressed. Similarly, the leader sends a message to the follower constantly while waiting to determine the side until the follower returns a message. The SPI follower service receives messages about servo commands and posts events to the servo service on the follower. Data related to servos, game starting and ending, and side determination is the only information passed between the PIC 32 Leader and Follower.

Our line following service handles all analog inputs which include 5 line sensors and 1 Time of Flight (TOF) sensor. Our line following algorithm employs a PD controller. By having 5 line sensors close to each other, we create a weighted function which takes into account the line's position relative to each sensor and gives a very accurate position of the line on the robot. The PD controller creates fast and efficient line following which is a strength of our robot. We actively calibrate the line sensors at the start of the game and during the game so that under different lighting and playing conditions, we do not have to recalibrate. Junction detection is determined by summing the line sensor values and comparing it to a threshold which updates based on the calibration of the line sensors.

The Motor Driver service configures the output compare pins on the leader to drive the motors, and the Servo Service configures output compare pins on the follower to drive the servos. We use a drive-brake method for quasi-linear control.