Synchronizing all sensor events on a common timeline

Autonomous Vehicles DRIVE AGX Xavier DRIVE AGX Xavier General
1

Hi!

I would like to use the timestamp from a GPS receiver to synchronize all sensor events (Camera, IMU, GPS, etc.)

How can I go about this? I am aware that Driveworks internally uses the CLOCK_MONOTONIC time source of Tegra. But is there any way to sync it with the GPS Receiver’s timestamp?

2

Dear animeshramesh,

Could you please refer to “TIME SYNCHRONIZATION” part in [url]NVIDIA: World Leader in Artificial Intelligence Computing for this topic?
There is a more detailed block diagram and explanation.

3

Thanks SteveNV. The block diagram helped. I do have a couple of follow up questions:

  1. Is there any resource which describes what a TimeSensor is? (Is it an API provided by DriveWorks?) I was unable to find it in the official documentation.
  2. Could you describe how a GPS receiver would be interfaced with the Xavier? I am not sure how the Xavier would receive the PPS signal and the NMEA data from the GPS receiver.
4

Dear animeshramesh,

  1. Yes, DriveWorks provides the related APIs, are you a DriveAGX user? If yes, you can download DriveWorks SW and doc via SDK manager tool.
  2. Please refer to the https://developer.nvidia.com/drive/drive-core-sensors There are our supported sensors including GPS sensors so you can get some more info.
5

I am a DriveAGX user and I downloaded the zipped documentation using https://developer.nvidia.com/DRIVE/secure/docs/NVIDIA_DRIVE_SW_9.0_References.zip.

However, I was unable to find any references to “TimeSensor”. Please find the screenshot attached.

DriveWorks_screenshot.png
DriveWorks_screenshot.png2558×1307 404 KB

6

Dear animeshramesh,

Could you please see Development Guide → Sensor Abstraction Layer → Sensors → Sensor Timestamping in the page?

7

Dear animeshramesh,

Have you referred to our suggestion to get issue fixed? Any result can be sharing?

8

Hi SteveNV,
Following up on the question. I see that the Xsens receiver is connected over USB to Drive Xavier. Could you please tell us how Xavier infers the data and time stamps from the XBus messages. I looked the Xsens documentation and it was not obvious how the data is encoded on the USB pins. In your webinar the presenter mentions about connecting the NMEA signals over UART and PPS over GPIO3 but the Xsens GPS that you support is not using that.