Understand rtc and pps O/P

Autonomous Vehicles DRIVE AGX Xavier DRIVE AGX Xavier General
1

Drive AGX comes with a little RTC box that should be connected to CAN 4/6. The box has a connector labeled PPS O/P.

Drive AGX also has a big bunch of cables with one connector labeled “PPS”.

I guess that the RTC box is PPS output (is that what “O/P” means?), which is relevant if we want to use the RTC box as the timestamp source.

However, if we have an external PPS source that we want to use (e.g. from GNSS), then should it be connected to the RTC box, or the big bunch of cables with the connector labeled “PPS”?

Then, in DriveWorks, which API actually uses it? Some docs say, “To enable time synchronization for supported sensors, simply create and start the time sensor. The HAL will take care of synchronization. There are no further steps to access synchronized timestamps, which will automatically overwrite the original sensor frame/packet timestamps.” But this is too vague and I want to understand if we have standard NMEA sensor, will HAL take care of synchronization?

There seems to be some changes between DW 2.2 and 3.0, e.g. is time sensing a new feature only available in 3.0? https://docs.nvidia.com/drive/driveworks-3.0/time_mainsection.html

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Hi @sleff ,

Time Sensors isn’t available in DriveWorks 2.2. “Currently Time sensor is supported through Garmin 18X and Novatel GPS sensors.” as mentioned in DriveWorks SDK Reference: Time, you have to use the supported time sensors (not bundled RTC module). Thanks.

4

Thanks @VickNV for clarifying that Time Sensor is only supported in DriveWorkd 3.0+

On the same topic, what does the “little RTC box that should be connected to CAN 4/6” actually do? It seems to make no difference to reading frames from cameras, whether I have the box plugged in or not.