6. GPS Synchronization
RS-Bpearl supports external GPS receiver connections. With GPS connections, we can
synchronize the RS-Bpearl system time and pack the GPRMC message into DIFOP
packets.
6.1 GPS Synchronization Theory
The GPS receiver keeps generating synchronization Pulse Per Second (PPS) signal and
GPRMC message and send them to the sensor. The pulse width of the PPS should
between 20 ms to 200 ms, and the GPRMC message should be received within 500 ms
after the PPS signal is generated.
6.2 GPS Usage
There is only one level protocol for RS-Bpearl GPS_REC pins: RS232 level standard
The GPS interface on the Interface BOX is SH1.0-6P female connector, the pin
definition is as shown in Figure 3.
RS232 pin definition:
Pin GPS REC receives the data that is R232 level standard from the GPS module serial
port;
Pin GPS PULSE receives the PPS from GPS module, and the level requirement is
3.0V~15.0V;
If the GPS output you are using is RS232 serial protocol while the level of the LiDAR
receiver is TTL, then you need to purchase a module which converts RS232 level to TTL
level. For one example, the wiring diagram and definition are as follows:
Pin +5V can supply the power for GPS module. (Please do not connect the GPS into the
+5V pin if the GPS is 3.3V power supply. Also please do not input the power into the +5V
pin because the pin is an output.)
Pin GND provide the ground connection for GPS module.
The GPS module should set to 9600bps baud rate, 8-bit data bit, no parity and 1 stop bit.
RS-Bpearl only read the GPRMC message from GPS module., the GPSMRC message
format is shown as below:
$GPRMC,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>*hh
<1> UTC time
<2> validity - A-ok, V-invalid
<3> Latitude
<4> North/South
<5> Longitude
<6> East/West
<7> Ground Speed
<8> True course<9> UTC date
<10> Variation
<11> East/West
<12> Mode (A/D/E/N=)
*hh checksum from $ to *
Different GPS module may send out different length GPRMC message, the RS-Bpearl
reserve 86byte space for GPRMC message, so it can be compatible with the majority
GPS module in the market.
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