void setFlywheels(bool engageFlywheels) {
  if ( engageFlywheels ) {
    // analogWrite(pin#,duty/255,frequency)
    // The arduino library doesn't let you specify frequency,    
    // but the default seems to be 500 anyway. 
    analogWrite(escPin,239,500);
  } else {
    analogWrite(escPin,127,500);
  }
}