[JohnFogarty]

I've been looking at the PID drive example in the FRC Java example projects.

SO. what I AM understanding is instead of putting distance in as the SETPOINT you would put the rate.

Now what I'm also understanding is that the Error HAS to be 0. because you never want to stop the motor once you've reached your target velocity.
I'm a client side coder once I have enough examples I can make my own functions and classes from that.

I'm confused as to what BACK EMF is?

/*----------------------------------------------------------------------------*/
/* Copyright (c) FIRST 2008. All Rights Reserved.                             */
/* Open Source Software - may be modified and shared by FRC teams. The code   */
/* must be accompanied by the FIRST BSD license file in the root directory of */
/* the project.                                                               */
/*----------------------------------------------------------------------------*/
package edu.wpi.first.wpilibj.templates;



import edu.wpi.first.wpilibj.SimpleRobot;
import edu.wpi.first.wpilibj.Encoder;
import edu.wpi.first.wpilibj.SpeedController;
import edu.wpi.first.wpilibj.PIDController;
import edu.wpi.first.wpilibj.Victor; //If you use Victors, import them instead
import edu.wpi.first.wpilibj.Timer; //Make sure to use this version, not the java.util version of timer.

/**
 * This program initializes a PID Controller for the wheels and drives
 * 3 feet using the encoders.  PID works by changing the output of the 
 * motors by PID constants, based on how far away you are from the target.
 * PID values need to be tuned for your robot.
 * 
 * @author: Fredric Silberberg
 */

public class PIDDrive extends SimpleRobot {

    
//    This class is required to invert the direction of the motor.
//    It negates the speed, so that the robot will drive forward.
     
    class MotorDrive extends Victor {

        public MotorDrive(int port) {
            super(port);
        }

        //Calls the super set method and gives it the negated speed.
        public void set(double speed) {
            super.set(-speed);
        }
    }
    //Initializes the motors.
    private final SpeedController left = new MotorDrive(2);
    private final SpeedController right = new Victor(1);
    
    //Initializes the Encoders.
    private final Encoder leftEncoder = new Encoder(1, 2);
    private final Encoder rightEncoder = new Encoder(4, 3);
    
    //Proportional, Integral, and Dervative constants.
    //These values will need to be tuned for your robot.
    private final double Kp = 0.3;
    private final double Ki = 0.0;
    private final double Kd = 0.0;
    
    //This must be fully initialized in the constructor, after the settings
    //for the encoders have been done.
    private final PIDController leftPID;
    private final PIDController rightPID;

    public PIDDrive() {
        //Sets the distance per pulse in inches.
        leftEncoder.setDistancePerPulse(.000623);
        rightEncoder.setDistancePerPulse(.000623);
        
        //Starts the encoders.
        leftEncoder.start();
        rightEncoder.start();
        
        //Sets the encoders to use distance for PID.
        //If this is not done, the robot may not go anywhere.
        //It is also possible to use rate, by changing kDistance to kRate.
        leftEncoder.setPIDSourceParameter(Encoder.PIDSourceParameter.kDistance);
        rightEncoder.setPIDSourceParameter(Encoder.PIDSourceParameter.kDistance);
        
        //Initializes the PID Controllers
        leftPID = new PIDController(Kp, Ki, Kd, leftEncoder, left);
        rightPID = new PIDController(Kp, Ki, Kd, rightEncoder, right);
        
        //Enables the PID Controllers.
        leftPID.enable();
        rightPID.enable();
        
        //Sets the input range of the PID Controller.
        //These will change, and you should change them based on how far
        //your robot will be driving.
        //For this example, we set them at 100 inches.
        leftPID.setInputRange(0, 100);
        rightPID.setInputRange(0, 100);
    }

    /**
     * This function is called once each time the robot enters operator control.
     * Teleop commands are put in here
     */
    public void operatorControl() {
        //Sets the left and the right motors to 
        //drive forward 60 inches, or 5 feet
        leftPID.setSetpoint(60);
        rightPID.setSetpoint(60);
        
        //This will wait 10 seconds before the end of operator control
        //is reached, so that the robot has time to drive the full 5 feet.
        //You could have other tasks running here as well.
        Timer.delay(10);
    }
}