public extern static UInt32 getFrequency(IntPtr drv, ref RplidarScanMode scanMode, UInt32 count, ref float frequency);
 public extern static UInt32 startScanExpress(IntPtr drv, bool force, UInt16 scanMode, UInt32 options, ref RplidarScanMode outUsedScanMode, UInt32 timeout);
 public extern static UInt32 startScan(IntPtr drv, bool force, bool useTypicalScan, UInt32 options, ref RplidarScanMode outUsedScanMode);