RoboSense M1 Plus LiDAR User Guide

RoboSense M1 Plus LiDAR user guide: specs, MSOP/DIFOP protocol, network setup, gPTP time sync, RSView point cloud visualization, and SDK.

RoboSense M1 Plus LiDAR

RoboSense M1-Plus High-Perf LiDAR: 2D MEMS smart chip scanning, 0.1° dynamic vertical resolution in ROI for early obstacle detection. For autonomous driving.

aifitlab.com

1. Product Specifications

RS-LiDAR-M1P, adopting the MEMS solid-state LiDAR technology, has achieved long measuring distance up to 200 meters (180m @ 10%), high data rate of 750,000 points/sec (single return) and 1,500,000 points/sec (dual return) data output, a horizontal FOV of 120° (-60.0°~+60.0°), a vertical FOV of 25° (-12.5°~+12.5°).

Table 1: Product Specifications

2. Communication Protocol

The communication between RS-LiDAR-M1P and the computer is through Ethernet,and uses UDP protocol. There are two types of output packets: MSOP packet and DIFOP packet. All MSOP packets involved in this document are with fixed length of 1210 bytes, DIFOP packets are with fixed length of 256 bytes. In single return mode, the output data includes 6300 MSOP packets and 10 DIFOP packet, which demands the data transfer rate no less than 58.2 Mbps. In dual return mode, the rate must be no less than 116.4Mbps. RS-LiDAR-M1P network parameters are configurable, and the factory default IP and fixed client port number are set as listed in the table below:

Table 2: Factory default network configuration

The default MAC address of the LiDAR is initially set at the factory, and the MAC address of each LiDAR is unique.

When using the LiDAR in unicast mode, you need to set the computer's IP to the same network segment as the LiDAR, for example, 192.168.1.x (the range of x is 1~254), and the subnet mask as 255.255.255.0. If you don't know the network configuration information of the LiDAR, please set the host computer subnet mask to 0.0.0.0, connect to the LiDAR and use Wireshark to capture the LiDAR output packet for analysis.

The communication protocol between RS-LiDAR-M1P and the computer is mainly divided into two categories. See the table below for the protocol list.

• The main data stream output protocol (MSOP), encapsulates the distance, angle, reflectivity and other information measured by the LiDAR into a package and outputs it to the computer;
• LiDAR information output protocol (DIFOP), outputs various configuration information of the LiDAR currently in use to the computer. Table 3: List of communication protocols

2.1 Main Data Stream Output Protocol (MSOP)

• Main data Stream Output Protocol is abbreviated as MSOP.
• I/O type: LiDAR output, computer analysis.
• Default port number: 6699.

The MSOP packets output three-dimensional measurement related data, including laser ranging value, return reflectivity value, vertical angle, horizontal angle and time stamp. The payload length of the MSOP packet is 1210 bytes, which consists of a synchronization header of 32 bytes, a data packet of 1175 bytes (a total of 25 data blocks of 47 bytes), and a tail of 3 bytes.

The basic structure of the MSOP packet is as shown in the figure below:

Figure 1: MSOP Packet Structure

2.1.1 Header

The header is 32-byte long, and is used for identification of the starting position of data, packet counting, UDP communication reservation, and time stamp storage. The detailed definition is as follows:

Table 4: MSOP Header

pkt_header: can be used as a packet inspection sequence, and the identification header is 0x55, 0xaa, 0x5a, 0xa5.

pkt_psn: Packets Sequence Number, packet counting in a circular counting manner,the count value of the first data packet of each frame is 1, the count value of the last data packet of each frame is the maximum value.

protocol version: version number of the UDP communication protocol wave_mode: return mode flag, 0 means dual return mode, 1 - N/A, 2 - N/A, 3 - N/A,4 means strongest return, 5 means last return, 6 means first return.

Timestamp: store timestamps. The defined timestamp is used to record the system time. The high 6 bytes are the second bits, and the low 4 bytes are the microsecond bits.

reserved: reserved bit

lidar_type: the type of LiDAR, default value is 0x10

mems_tmp: mems temperature, Temp=mems_tmp-80; namely when mems_tmp value is 0, mems temperature is -80℃; when the value is 255, the temperature is 175℃.

2.1.2 Data Packet

The data packet in the MSOP packet stores the data measured by the LiDAR. It has a total of 1175 bytes consisting of 25 data blocks, each data block has 47 bytes.

In single return mode, each data block represent the complete measurement data measured by a group of 5 laser channels at one time. Each data block stores the data of one transmission in the single return mode.

In dual return mode, the odd numbered MSOP packets store the data of the first return,including 25 data blocks. The even numbered MSOP packets store the data of the second return, including 25 data blocks. The first and second returns are stored by turns in sequence. The type of returned packets could be judged according to the ‘returen_seq’ value in the data block, please check Table 5 for detailed definition. Every two MSOP packets form a complete measurement. The total number of data points in a dual return mode is twice that of a single return mode.

The detailed definition is as follows:

Table 5： Definition of data block in MSOP packet

N is the Nth data block in any MSOP packet.

• time_offset: the time offset of all points in the Nth block relative to the time stamp of the packet. The time of this group of points equals time stamp+time_offset.
• return_seq: return sequence. In single-return mode, this flag is always 0; in dual return mode, the first return (closer) is represented by 0x1, and the second return (further) is represented by 0x2

n is the nth channel in the Nth data block, n=1, 2, 3, 4, 5, which contains data as follows:

• chn_radius: the radial distance value of the points of channel n in the polar coordinate system, the resolution is 5mm.
• chn_elevation: the vertical angle of the channel n points in polar coordinate system,the resolution is 0.01°
• chn_azimuth: the horizontal angle of the channel n points in polar coordinate system,the resolution is 0.01°
• chn_intensity: reflection intensity value of the channel n points, the value range is 0~255.

2.1.2.1 Channel Data Definition

The channel data is 9-byte long, with the radial distance of this channel occupying 2 bytes, the elevation angle occupying 2 bytes, the horizontal angle occupying 2 bytes, the reflection intensity value occupying 1 byte, and 2 bytes reserved. Detailed definitions are as follows:

Table 6：Definition of channel data in data block

Calculation of XYZ coordinates:

Use Wireshark to capture the data packets of RS-LiDAR-M1P, as shown in the figure below:

Example of parameters calculation:

1. time_offset: data block time offset HEX: 0x00 -> DEC: 00 -> 0 ㎲
2. return_seq: HEX: 0x00 -> single return
3. radius: radial distance HEX: 0x0a,0x77 -> DEC: 10, 119

-> radius = (10 x256 + 119) x0 .005 [m] = 13.395 m

4. elevation: vertical angle HEX: 0x83,0xa2 -> DEC: 131,162 -> elevation = ((131 x 256 + 162)-32768) x 0 .01[degree] = 9.3°
5. azimuth: horizontal angle HEX: 0x94,0xdf -> DEC: 148,223 -> azimuth = ((148 x 256 + 223)-32768) x 0 .01[degree] = 53.43°

The X, Y, Z coordinates of the point cloud can be calculated by the formula below:

$X = radius*cos(evelation)*cos(azimuth)$

$Y = radius*cos(evelation)*sin(azimuth)$

$Z = radius*sin(evelation)$

$X = 13.395m * cos(9.3°) * cos(53.43°)$

$Y = 13.395m * cos(9.3°) * sin(53.43°)$

$Z = 13.395m * sin(9.3°)$

Thus, the X, Y, Z coordinates of the point cloud of one transmitting in the single return mode of this channel is (7 .88m,10 .62m,2 .17m)。

2.1.3 Tail

The Tail contains 3 bytes and are reserved bits.

2.2 LiDAR Information Output Protocol (DIFOP)

LiDAR Information Output Protocol is abbreviated as DIFOP

I/O type: LiDAR output, computer read.

Default port number: 7788.

DIFOP is an "output-only"protocol to periodically send the LiDAR serial number (S/N),firmware version information, host computer driver compatibility information, network configuration information, calibration information, operating status, and fault diagnosis information to users. By reading DIFOP, users can learn specific information of various parameters of the LiDAR currently in use.

A complete DIFOP packet consists of a synchronization header, reserved bytes and a data packet. Each DIFOP Packet is 256-byte long, including an 8-byte long synchronization header, 1 reserved byte and a 247-byte long data packet.

The basic structure of the DIFOP packet is as shown in the table below.

Table 7: Definition of DIFOP packet

3. Interface Box Connection and State Machine

3.1 The Instruction of Wiring Harness

3.1.1 Auto-motive Ethernet and Power Harness

NUM	Signal Type
D2	1000Base T1 P
D1	1000Base T1 N
1	GND
2	Wakeup
3	/
4	Battery+
5	/
6	/

NUM	Signal Type
1	GND
2	Wakeup
4	Battery+

NUM	Signal Type
D2	1000Base T1 P
D1	1000Base T1 N

3.1.2 Interface Box

NUM	Signal Type
d	AC Power(female)

NUM	Signal Type
e	AC Power (male)
f	Interface Box Power Supply

NUM	Signal Type
g/h	Gigabit Ethernet

3.2 The Connection of Interface Box

Figure 2: Image for topology of LiDAR and PC

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Note： Figure 2 shows the topology of connection of Interface Box (TE).

3.3 State Machine of LiDAR

Wakeup I/O Definition

4. Time Synchronization

RS-LiDAR-M1P default firmware supports gPTP (IEEE 802.1AS) time synchronization method. Therefore, only gPTP is supported by default. If users want to apply PTP (IEEE 1588v2)time synchronization method, please contact RoboSense technical team for support.

4.1 Precision Time Protocol

4.1.1 Time Synchronization Introduction

PTP is defined as a time-synchronization protocol. It is mainly used to achieve high precision time synchronization between different devices through network communication, and can also be used for frequency synchronization. Compared to the existing time synchronization mechanisms, PTP has the following advantages:

1. Compared to Network Time Protocol (NTP), PTP can fulfill the requirement of time synchronization with higher precision. Generally, NTP can only achieve the sub-second level of time synchronization precision,while PTP can support sub-microsecond level.
2. Compared to Global Positioning System (GPS), PTP has advantages of lower construction and maintenance costs. Meanwhile, it also has significant meanings in national security due to independence on GPS.

PTP supports different communication protocols (CAN, Ethernet,etc.). PTP can apply two mechanisms for synchronous: end-to-end (E2E) or peer-to-peer network (P2P): E2E mode: apply Request Response Mechanism P2P mode: apply a peer delay mechanism (Peer Delay Mechanism).

4.1.2 gPTP Wiring Connection

To initialize gPTP synchronization procedure, users need to prepare the following devices and finish wiring connection according to the topology below:

1. a gPTP Grand Master (plug-and-play without additional configuration);
2. Ethernet switch;
3. Slave devices supporting gPTP (RS-LiDAR-M1P and others);

gPTP Grand Master (Third Party)



Figure 3：Topology of gPTP time synchronization

4.2 Use Linuxptp tool to verify time synchronization

Please connect RS-LiDAR-M1P power cable and network cable to the Interface Box,and then to Host Computer. The Host Computer operating system (OS) must be Linux.

We take Ubuntu as an example below:

1. Use the command $ifconfig to check the network card name.The name of the network card is enp2s0 below.


Figure 4: Find network card name

2. Use the command $ethtool - T enp2s0 (network card’s name) to check whether the network card supports PTP hardware. For gPTP synchronization , hardware support is required , PTP Hardware Clock should not be none.


Figure 5: Check PTP hardware supporting status

3. Download and install the Linuxptp tool.
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$sudo git clone git://git.code.sf.net/p/linuxptp/code linuxptp
$cd linuxptp
$sudo make
$sudo make install
$reboot

4. Use ptp4l command.

Ptp4l command options:

Delay mechanism options

-A Automatic mode, E2E mode is selected automatically,and switch to P2P mode when peer to peer delay request is received

-E E2E mode, request-response delay mechanism (default)

-P P2P mode, peer delay mechanism

Network transmission options

-2 IEEE 802.3

-4 UDP IPV4 (default)

-6 UDP IPV6

Timestamp options

-H Hardware timestamp (default)

-S Software simulation timestamp

-L Former hardware timestamp, LEGACY HW needs to be used with PHC equipment

Other options

-f [file] Reads the configuration info from the specified file. By default, no configuration info is read.

-i [dev] Select a PTP interface device, such as eth0 (which can be specified more than once), you must specify at least one port using this option or configuration file.

-p [dev] This option is used to specify the PHC device (such as: dev / ptp0 clock device) to be used on the former Linux kernel. The default is auto, ignoring the software / LEGACY HW timestamp (this option is not recommended)

-s Slave-Only-mode, slave clock mode (override profile)

-t Transparent clock mode

-l [num] Set the logging level to ‘num’ and the default is 6

-m Print the message to stdout

-q Do not print messages to syslog

-v Print software version and exit

-h Help command

Use command to synchronize RS-LiDAR-M1P:

(1) PTP E2E (L2 layer) command:

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$sudo ptp4l -E -S -2 -m -i enp2s0 (network card name)

If PTP Hardware Clock is not none (hardware supported), you can use -H instead of -S

(2) gPTP command:

Copy

$sudo ptp4l -i enp4s0 -m -H -2 -f gptp-master.cfg

PTP Hardware Clock should not be none(hardware supported). Special note: Devices without hardware support can use -S instead of -H for gPTP synchronization simulation,and its synchronization accuracy cannot be guaranteed. And gptp-master.cfg is the gPTP master clock configuration file.Create a new gptp-master.cfg file on the host, copy the following content in this file, and save the file:

Copy

4.3 GPS Time Synchronization

In case that users would like to synchronize RS-LiDAR-M1P with GPS module, it is necessary for gPTP Grand Master to receive GPS timing service at first. Please consult gPTP Grand Master device provider for the specific connectors and GPS timing service guidance. Robosense will not provide technical support except for special cases.

Figure 6: Topology of GPS Timing service synchronization

Appendix A RSView

This appendix explains how to use RSView to record, visualize, save and review of the data from RS-LiDAR-M1P.

The original sensor data can be also captured and examined by using other free of charge tools, such as Wireshark or tcp-dump. But visualization of the 3D data through using RSView is easy to realize. User may contact RoboSense technical support for the specific RSview Version.

A.1 Software Features

RSView supports real-time visualization of 3D coordinate data from RS-LiDAR-M1P. RSView also supports review of the pre-recorded data stored in “pcap” (Packet Capture) files, however, RSView doesn’t support direct importing of “.pcapng” files at the moment.

RSView displays directly the point cloud that is exchanged from the measured distance from RS-LiDAR-M1P. It supports changing the display mode of point cloud according to XYZ coordinates, distance, pitch(elevation) and yaw(azimuth), etc.

Function and features of RSView are as shown below:

• Online visualization of sensor data over Ethernet
• Record of real-time data into pcap files
• Review of the recorded point cloud from pcap files
• Different visualization mode based on distance, pitch(elevation) and yaw(azimuth), etc.
• Tabular display of point cloud data
• Tool for measuring distance from visualized cloud point

A.2 Install RSView

Installation packet of RSView is suited for Windows 64-bit system and it requires no other dependent software packets. Unzip the compressed packet of RSView, the RSView.exe executable file can be found in the /bin folder.

A.3 Set Up Network

In Unicast mode，the sensor has set the default IP address to computer at factory,therefore, the default IP address of the computer should be set as 192.168.1.102, sub-net mask as 255.255.255.0. Besides, users should make sure that the RSView doesn’t be blocked by any firewall or third party security software.

A.4 Visualization of Point Cloud

1. Connect the RS-LiDAR-M1P to PC over Ethernet cables and power supply.
2. Right click to start the RSView application with Run as Administrator.
3. Click on the File > Open Sensor (Fig A-1).


Fig A-1：Open the Sensor Stream in RSView.

4. After finishing the above 3 steps, the dialogue box “Sensor Type and Configuration”shows up. Please Choose RSM1 in the Drop Down menu to fit RS-LiDAR-M1P. In this dialogue box, the Sensor Calibration default contains the configuration folder named MEMSCorrectionFile_3V, directly click Add and then click the OK button (as shown in Fig A-2). The original point cloud data output from the RS-LiDAR-M1P is already calibrated point cloud data, therefore the value in this parameter file is void.


Figure A-2：Select the parameter configuration file of RS-LiDAR- M1

5. Check the MSOP and DIFOP port number: Sensor Network Configuration, input the correct MSOP and DIFOP port number.


Figure A-3: RSView data port setting

6. RSView begins displaying the colored point cloud from capturing the sensor data stream from LiDAR (as shown in Fig. A-4). The stream can be paused by pressing the Play button, click again, the stream continues.


Figure A-4：RS-LiDAR-M1P Sensor Stream display

7. If there is no point cloud display, please click Tools and check if the MSOP and DIFOP portnumber are correctly set in the Data Port Setting window.

A.5 Save Streaming Sensor Data into PCAP File

Use Wireshark as the packet recording tool:

1. Download and install the wireshark software.


Figure A-5：Wireshark icon

2. Double click to start the wireshark application, select the name of the network card currently connected to the LiDAR and double-click it.


Figure A-6：Start Wireshark

3. If the figure below shows up, the connection to the LiDAR is normal. The data in thered boxes represent “LiDAR IP”, “PC IP”, “MSOP port number”, and “DIFOP packet portnumber” respectively.


Figure A-7：Wireshark at work

4. Click File at the up left corner of the window, and click Save to save the data.


Figure A-8：Wireshark data saving

5. Enter the file name in the pop-up dialog box and select .pcap as the data format to save.


Figure A-9：Wireshark data saving

6. Now, the corresponding files can be found in the specified folder directory and you can use the RSView software or driver to view the point cloud (please refer to the product user manual for the RSView operation guide).


Figure A-10 Wireshark data saving

A.6 Replay Recorded Sensor Data from PCAP Files

The pcap file can be replayed or examined through RSView. User can press the Play button to play or pause the data play, and can also scrub the time slider to check the data at a certain time point. User can also use a mouse to click and select part of the point cloud and check them in the pop-up table. Save path of pcap file should not contain any Chinese characters.

1. Click File -> Open PCAP File.


Figure A-11 RSView Open capture file

2. In the dialogue box Open File, please import a recorded pcap file then click Open(O) button.


Figure A-12 Import PCAP File

3. In the dialogue box Sensor Type and Configuration, add and select the right configuration file of RS-LiDAR-M1P, then click OK button. Then input the correct MSOP and DIFOP port in the dialogue box PCAP Network Configuration
4. Click Play button to play or pause 3D point cloud data streaming. Using the Scrubtool to select the interested frame. (Fig. A-13).


Figure A-13 RSView Play button and Scrub tool

5. In order to inspect partial relevant point cloud data from a closer aspect, please scrub to an interested frame and click the Spreadsheet button (Fig A-16). A data table will be displayed on the right side. It displays all data points in the frame.


Figure A-14 RSView Spreadsheet

6. You can adjust the width of each column of the table, or sort for clearer inspection.


Figure A-15 RSView Spreadsheet display

7. Click Show only selected elements in the spreadsheet, only the data of selected points will be displayed. If no point is selected, there will be no data shown in table (Fig.A-18).


Figure A-16 RSView show only selected elements tool

8. Click the Select All Points tool, your mouse will turn into a data point selection tool(Figure A-17).


Figure A-17 RSView Select All Points tool

9. In the 3D point cloud display space, use the mouse to draw a rectangle to frame some data points. The data of these points will be displayed in the Spreadsheet and these points will turn pink in the point cloud display space (Figure A-18).


Figure A-18 RSView List Selected Points

10. Any selected point can be saved through the output csv data tool at the Spreadsheet toolbar (see Figure A-19).


Figure A-19 RSView export selected points to csv file·

Appendix B Driver & SDK

To download the latest version and guidebook of RS-LiDAR-M1P Driver & SDK,

Please refer to the following link: https://github.com/RoboSense-LiDAR/rslidar_sdk

Appendix C Dimension

Drawing of LiDAR with TE Connector:

Definition of TE-Pins:

RoboSense M1 Plus LiDAR

RoboSense M1-Plus High-Perf LiDAR: 2D MEMS smart chip scanning, 0.1° dynamic vertical resolution in ROI for early obstacle detection. For autonomous driving.

aifitlab.com

On this page

• RoboSense M1 Plus LiDAR User Guide
• 1. Product Specifications
• 2. Communication Protocol
• 2.1 Main Data Stream Output Protocol (MSOP)
• 2.1.1 Header
• 2.1.2 Data Packet
• 2.1.2.1 Channel Data Definition
• 2.1.3 Tail
• 2.2 LiDAR Information Output Protocol (DIFOP)
• 3. Interface Box Connection and State Machine
• 3.1 The Instruction of Wiring Harness
• 3.1.1 Auto-motive Ethernet and Power Harness
• 3.1.2 Interface Box
• 3.2 The Connection of Interface Box
• 3.3 State Machine of LiDAR
• 4. Time Synchronization
• 4.1 Precision Time Protocol
• 4.1.1 Time Synchronization Introduction
• 4.1.2 gPTP Wiring Connection
• 4.2 Use Linuxptp tool to verify time synchronization
• 4.3 GPS Time Synchronization
• Appendix A RSView
• A.1 Software Features
• A.2 Install RSView
• A.3 Set Up Network
• A.4 Visualization of Point Cloud
• A.5 Save Streaming Sensor Data into PCAP File
• A.6 Replay Recorded Sensor Data from PCAP Files
• Appendix B Driver & SDK
• Appendix C Dimension