usaGe | HDL-32E User’s Manual |
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External GPS Time Synchronization
The HDL- 32E can synchronize its data with precision GPS-supplied time pulses to enable users to ascertain the exact firing time of each laser in any particular packet.
This capability requires a GPS receiver generating a sync pulse and the $GPRMC NMEA record over a dedicated RS-232 serial port. The output from the GPS receiver is connected to the HDL- 32E. The customer can use the GPS receiver supplied with the HDL-32E or the customer can adapt their GPS receiver to provide the required sync pulse and NMEA record.
GPS Receiver Option 1: Velodyne Supplied GPS Receiver
A GPS receiver that is pre-programmed by Velodyne, is provided to HDL- 32E users. This receiver is pre-wired with a connector that plugs into the HDL-32E interface box, and pre-programmed to output the correct GPS record and sync pulse.
GPS Receiver Option 2: Customer’s GPS Receiver
Under this option the customer must configure their GPS device to issue a once-a-second synchronization pulse, typically output over a dedicated wire, and issue a once-a-second $GPRMC NMEA record. No other output can be accepted from the GPS device. Further, the sync pulse and NMEA record must be issued sequentially. The sync pulse length is not critical (typical lengths are between 20ms and 200ms), but the $GPRMC record must start between 50ms and 500ms after the end of the sync pulse.
note: The $GPRMC record can be configured for either hhmmss format or hhmmss.s format.
note: The connector within the supplied interface box can be used to interface the GPS receiver, or it can be wired directly as indicated within the box.