CT_project/测量节点/rslidar/rs_driver/doc/intro/04_parameter_intro.md

4 Introduction to rs_driver's Parameters

4.1 Parameter File

The parameters are defined in the file rs_driver/src/rs_driver/driver_param.h.

Basically, there are 3 structures:

• RSDriverParam
• RSDecoderParam
• RSInputParam

4.2 RSDriverParam

RSDriverParam contains RSDecoderParam and RSInputParam.

typedef struct RSDriverParam
{
  LidarType lidar_type = LidarType::RS16;  ///< Lidar type
  InputType input_type = InputType::ONLINE_LIDAR; ///< Input type
  RSInputParam input_param;
  RSDecoderParam decoder_param;
} RSDriverParam;

• lidar_type - Lidar Type. Some LiDARs are mechanical, and some are MEMS. Some parameters of RSDecoderParam is only for mechanical LiDARs.

enum LidarType
{
  RS16 = 1,
  RS32,
  RSBP,
  RS128,
  RS80,
  RSHELIOS,
  RSM1
};

• input_type - What source the Lidar packets is from.
  • ONLINE_LIDAR means from online LiDAR; PCAP_FILE means from PCAP file, which is captured with 3rd party tool; RAW_PACKET is user's own data captured with the rs_driver API.

enum InputType
{
  ONLINE_LIDAR = 1,
  PCAP_FILE,
  RAW_PACKET
};

4.3 RSInputParam

RSInputParam specifies the detail paramters of packet source.

The following parameters are for ONLINE_LIDAR and PCAP_FILE.

• msop_port - The UDP port on the host, to receive MSOP packets.
• difop_port - The UDP port on the host, to receive DIFOP Packets.

The following parameters are only for ONLINE_LIDAR.

• host_address - The host's IP, to receive MSOP/DIFOP Packets
• group_address - A multicast group to receive MSOP/DIFOP packts. rs_driver make host_address join it.

The following parameters are only for PCAP_FILE.

• pcap_path - Full path of the PCAP file.
• pcap_repeat - Whether to replay PCAP file repeatly
• pcap_rate - rs_driver replay the PCAP file by the theological frame rate. pcap_rate gives a rate to it, so as to speed up or slow down.
• use_vlan - If the PCAP file contains VLAN layer, use use_vlan=true to skip it.

typedef struct RSInputParam
{
  uint16_t msop_port = 6699;
  uint16_t difop_port = 7788;
  std::string host_address = "0.0.0.0";
  std::string group_address = "0.0.0.0";

  // The following parameters are only for PCAP_FILE
  std::string pcap_path = "";
  bool pcap_repeat = true;
  float pcap_rate = 1.0;
  bool use_vlan = false;
} RSInputParam;

4.4 RSDecoderParam

RSDecoderParam specifies how rs_driver decode LiDAR's packets.

typedef struct RSDecoderParam
{
  bool use_lidar_clock = false;
  bool dense_points = false;
  bool ts_first_point = false;
  bool wait_for_difop = true;
  RSTransformParam transform_param;
  bool config_from_file = false;
  std::string angle_path = "";
  float min_distance = 0.2f;
  float max_distance = 200.0f;

  // The following parameters are only for mechanical Lidars.
  SplitFrameMode split_frame_mode = SplitFrameMode::SPLIT_BY_ANGLE;
  float split_angle = 0.0f;
  uint16_t num_blks_split = 1;
  float start_angle = 0.0f;
  float end_angle = 360.0f;

} RSDecoderParam;

The following parameters are for all LiDARs。

• use_lidar_clock - Where the point cloud's timestamp is from. From the LiDAR, or from rs_driver on the host?
  • If use_lidar_clock=true，use the LiDAR timestamp, else use the host one.
• dense_points - Whether the point cloud is dense.
  • If dense_points=false, then point cloud contains NAN points, else discard them.
• ts_first_point - Whether to stamp the point cloud with the first point, or the last point.
  • If ts_first_point=false, then stamp it with the last point, else with the first point。
• wait_for_difop - Whether wait for DIFOP Packet before parse MSOP packets.
  • DIFOP Packet contains angle calibration parameters. If it is unavailable, the point cloud is flat.
  • If you get no point cloud, try wait_for_difop=false. It might help to locate the problem.
• transform_param - paramters of coordinate transformation. It is only valid when the CMake option ENABLE_TRANSFORM=ON.

typedef struct RSTransformParam
{
  float x = 0.0f;      ///< unit, m
  float y = 0.0f;      ///< unit, m
  float z = 0.0f;      ///< unit, m
  float roll = 0.0f;   ///< unit, radian
  float pitch = 0.0f;  ///< unit, radian
  float yaw = 0.0f;    ///< unit, radian
} RSTransformParam;

• config_from_file - Where to get LiDAR configuration parameters, from extern files, or from DIFOP packet. Internal use only.
• angle_path - File of angle calibration parameters. Internal use only.
• min_distance、max_distance - Set measurement range. Internal use only.

The following parameters are only for mechanical LiDARs.

• split_frame_mode - How to split frame.
  • SPLIT_BY_ANGLE is by a user requested angle. User can specify it. This is default and suggested.
  • SPLIT_BY_FIXED_BLKS is by blocks theologically;
  • SPLIT_BY_CUSTOM_BLKS is by user requested blocks.

enum SplitFrameMode
{
  SPLIT_BY_ANGLE = 1,
  SPLIT_BY_FIXED_BLKS,
  SPLIT_BY_CUSTOM_BLKS
};

• split_angle - If split_frame_mode=SPLIT_BY_ANGLE, then split_angle is the requested angle to split.

• num_blks_split - If split_frame_mode=SPLIT_BY_CUSTOM_BLKS，then num_blks_split is blocks.

• start_angle、end_angle - Generally, mechanical LiDARs's point cloud's azimuths are in the range of [0, 360]. Here you may assign a smaller range of [start_angle, end_angle).