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RS-LiDAR-M1 User Guide
4 Time Synchronization
RS-LiDAR-M1 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).
Note: The PTP protocol provided by RoboSense only supports the L2 layer of Ethernet
protocol, E2E mode.
gPTP (general precise time protocol) is a derivative protocol of PTP in Time-Sensitive
Networking. gPTP shares the same synchronization mechanism with PTP -- Peer Delay
Mechanism, and it applies the L2 layer of Ethernet for communication. Unlike PTP,
hardware timestamps are required for gPTP, which results in stricter requirements for the
switch and Master clock.