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timestamp (accurate to microseconds) of the data packet and the 3-byte UTC
time (year, month and day) of the device packet.
Dual echo mode: The absolute accurate time of the point cloud data is obtained
by adding the 1-byte second information and the 4-byte timestamp (accurate to
microseconds) of the data packet and the 5-byte UTC time (year, month, day,
hour and minute) of the device packet.
6.1 GPS Synchronization
When GPS synchronization is employed, the Lidar will start timing in
microseconds after receiving the PPS second pulse, and the time value will be
output as the timestamp of the data packet. The Lidar extracts UTC information
from the $GPRMC of the GPS as the UTC time output.
Single echo mode: In the UTC time output, the year, month and day information
is in the device packet and the hour, minute and second information is in the
data packet.
Dual echo mode: In the UTC time output, the year, month, day, hour and minute
information is in the device packet and the second information is in the data
packet.
There are two types of CH128X1 Lidar GPS_REC interface level protocols,
namely TTL level standard and RS232 level standard; the GPS_REC interface
specification on the power box is SH1.0-4P female socket. The two protocols
differ in two aspects, respectively:
TTL level pin definition:
Pin GPS_TX receives the standard serial port data of the TTL level output from
GPS module;
Pin GPS_PPS receives the positive TTL synchronous pulse signal output by the
GPS module;
RS232 pin definition:
Pin GPS_TX receives the standard serial data of the R232 level output from the
GPS module;
Pin GPS_PPS receives the positive synchronization pulse signal output by the
GPS module, and the level is required to be 3.0V~15.0V.
If the GPS used outputs according to the RS232 serial port protocol, and the
Lidar receives data according to the TTL protocol, then a RS232 to TTL
conversion module is needed.
The GPS equipment is time-synchronized to mark and calculate the precise
emission and data measurement time of each laser. The precise time of the Lidar
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