Skip to content

LiDAR XT32M2X

GPS Sync / GPS Spoof Sync

The XT32M2X can synchronize to an external time source through the use of a 1 PPS signal together with timestamp data sent to the XT32M2X over a RS-232 serial line.

In order to do this with the SentiBoard, you need to

Configure a 1 PPS trigger

  1. Connect the SentiBoard to your computer, be sure to have done the SentiBoard Installation, and connect a terminal to the SentiBoard's config port /dev/ttySentiboard 00
  2. Configure one of the available triggers, e.g oc1. Type c oc1 and Enter.
  3. Set the following config: XT32M2X Trigger Config
    Period: 1% yields a pulse width of 10ms (recommended to be >1ms).
  4. Type x and Enter to exit the oc1 config menu.
  5. Type save and Enter to permanently store the config changes.
  6. Type reset and Enter to restart the SentiBoard and apply the new settings.

Wire the trigger and GPS data signals

  1. If trigger oc1 was used, wire the SPI_2 port's trigger and ground pin to the XT32M2X according to the XT32M2X's wiring scheme: XT32M2X Wiring Scheme
    The SPI_2 trigger pin should attach to the GPS PPS pin (1) of the LiDAR. SentiBoard and XT32M2X should be connected to the same GND.
  2. Attach a USB-to-RS232 adapter (or use an RS-232 port directly) on the host computer, connected to the LiDAR's GPS DATA pin (2).

Spoof a GPS Time Message

  1. Connect the SentiBoard to your host computer running SentiUtils, and receive SentiTrigger messages from the SentiBoard (e.g in ROS).
  2. When receiving a SentiTrigger message via SentiUtils, construct an NMEA GPRMC string using the SentiTrigger's UTC header fields as timestamp.
  3. Send the NMEA GPRMC string generated from the SentiTrigger packet to the LiDAR over the host's RS-232 connection.
  4. Verify that the XT32M2X has a Lock on both the GPS (1PPS) and the NMEA (GPRMC) through the LiDAR's Web interface (default: 192.168.1.201)

PTP

The XT32M2X supports PTP time synchronization and is a good fit to use with SentiBoard 2.0