 
 struct EEPROM_Config {
   byte id;
-  int motor_pwm_pin;
-  double rpm_setpoint;  // desired RPM (double to be compatible with PID library)
-  double pwm_max;
-  double pwm_min;
-
+  int motor_pwm_pin;  // pin connected to mosfet for motor speed control
+  double rpm_setpoint;  // desired RPM (uses double to be compatible with PID library)
+  double pwm_max;  // max analog value.  probably never needs to change from 1023
+  double pwm_min;  // min analog pulse value to spin the motor
+
+  // PID tuning values
   double Kp;
   double Ki;
   double Kd;
   
-  boolean motor_enable;
-  boolean relay;
+  boolean motor_enable;  // to spin the laser or not.  No data when not spinning
+  boolean relay;  // to retransmit the seiral data to the USB port
 } 
 xv_config;
 

  }

  if (syntax_error) {
    Serial.println("Incorrect syntax.  Example: SetKp 1.0"); 
  }
  else {
    Serial.print("Setting Ki to: ");

  sCmd.addCommand("SetKi",   setKi);
  sCmd.addCommand("SetKd",   setKd);

  sCmd.addCommand("ShowRPM",  showRPM);
  sCmd.addCommand("HideRPM",  hideRPM);
  sCmd.addCommand("MotorOff", motorOff);
  sCmd.addCommand("MotorOn",  motorOn);
  sCmd.addCommand("RelayOff", relayOff);
  sCmd.addCommand("RelayOn",  relayOn);

  // XV Commands  
  sCmd.addCommand("GetPrompt",  getPrompt);
  sCmd.addCommand("GetVersion", getVersion);
}

void showRPM() {
