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1) GPS as the Clock Source
·
The lidar connects to a third-party GPS module to obtain the PPS (pulse-per-second) signal and the NMEA sentence ($GPRMC or $GPGGA).
·
Users may select either $GPRMC or $GPGGA sentences, see Section 4.2 (Web Control – Settings).
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Users may check the signal status of GPS PPS and NMEA, see Section 4.1 (Web Control - Home).
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The timing requirements of PPS and NMEA are shown in Section 2.2.1 (Pin Description).
·
Each rising edge of the lidar's internal 1 Hz signal triggers a GPS Data Packet. The data format is detailed in Section 3.2 (GPS Data Packet).
The absolute time is updated as follows.
NMEA
status
Date & Time
(accurate to the second)
Lidar behavior
Unlocked
Virtual
Starts counting from a virtual UTC time (such as 2000-01-01 00:00:00) using the lidar's internal 1 Hz
signal.
Locked
Synchronized
At each rising edge of the internal 1 Hz signal, obtain the actual date and time by
·
extracting the date and time from the previous NMEA message, and
·
automatically adding 1 full second.
Lost
Drifting
Starts counting from the last synchronized time, using the lidar's internal 1 Hz signal.
Will gradually drift from the actual GPS time.
PPS status
μs time
Description
Unlocked
Not synchronized
The lidar's internal 1 Hz signal is not aligned with the GPS second.
Locked
Synchronized
The rising edge of the lidar's internal 1 Hz signal is aligned with the rising edge of the PPS signal (i.e.
the start of each GPS second).
Lost
Drifting
Counts using the internal 1 Hz signal.
Will gradually drift from the actual GPS second.
Summary of Contents for Pandar40M
Page 1: ...www hesaitech com HESAI Wechat Pandar40M 40 Channel Mechanical LiDAR User Manual...
Page 17: ...15 2 Setup 2 1 Mechanical Installation Figure 2 1 Front View Unit mm...
Page 18: ...16 Figure 2 2 Bottom View Unit mm...
Page 19: ...17 2 1 1 Quick Installation Figure 2 3 Quick Installation...
Page 20: ...18 2 1 2 Stable Installation Figure 2 4 Stable Installation...
Page 27: ...25 2 3 2 Connection Figure 2 10 Connection Box Connection with GPS...
Page 28: ...26 Figure 2 11 Connection Box Connection with PTP...
