Good morning.
I write this post because I’m having timestamp artifacts on a GPS PPS-synchronized Ouster OS-2-32 sensor, running on firmware version 2.5.3.
The sensor is connected to a Vectornav VN-300 GPS through the interface box. The sensor and the cables are correctly configured to accept the PPS signal, as I receive both valid GPRMC messages, and the sensor is correctly locked in to the PPS and NMEA signals (in my code, I don’t start a scan until all these conditions are met).
However, every second (possibly on each PPS pulse from the GPS), the recorded timestamp jumps back a small amount, rendering the scan unable to be used with other tools (for example, pose optimization).
I have plotted the value of the timestamps, in the order they were received. Note the downwards bump, which corresponds to this timestamp jump:
While the discontinuity dissapears for some seconds in the scan afterwards (coinciding with the columns I have disabled in my specific azimuth window), there is a sudden multisecond jump forwards, followed shortly by a multisecond jump backwards, and more small discontinuities.
Furthermore, I had done some scans before, with the same configurations and connected GPS, but in a place with no GPS coverage. In this case, on each second, the timestamp, rather than jumping back a small amount, jumped forward a full second. I have also plotted this situation:
Besides, there is a related forum post ( Ouster OS1-64-U13-SR Rev 7.1 sensor is producing corrupted synchronized IMU timestamps during PCAP recording ) which describes a problem similar to the one I’m facing. Do you know whether this could be a hardware/firmware issue?
Finally, in my current use case, I’m just using this PPS signal for having GPS position information for positioning my scans. Would it be valid if I connected the GPS directly to my computer, and read the current timestamps using the HTTP API and the GPS messages from the serial port to perform geopositioning?
Thank you very much for your help 