Lidar using ptp only at the start to synchronize timestamp

kolja

I start the lidar and it counts the nanoseconds from the starting point to the current time. Once I activate ptp the lidar takes 60-80 seconds to synchronize the timestamp and jumps to the correct time. It seems that this just happens once when the lidar first receives the ptp signal. If I change my system time after synchronizing to be 10 minutes into the future the timestamps wont get updated. They are still set to the "correct" timestamps it first synchronized to. The timestamp I want my lidar to have is the current time on my computer, which is set to master in the ptp. I am using the Ouster OS1 and ptpd on linux. How can I archive that the lidar updates frequently to the master time and not only at the start?

kolja

I tried to use ptplinux with ptp4l instead of ptpd and i get the same behaviour. The lidar is still synchronizing when I first start the ptp but wont synchronize afterwards.

JakobGL

Hi @kolja

PTP time sync default profile can compensate some big time jumps only once per power up. If the master is well configured, it will adapt continuously.
I can recommend you a small test to perform to check if it is well configured and well synced:

Power up the lidar
Wait for the time sync, you can check with the following command GET /api/v1/time/ptp if the time sync is well made by checking the following fields as below:
- parent_data_set.grandmaster_identity should list the identity of the local grandmaster
- port_data_set.port_state should be SLAVE
- time_status_np.gm_present should be true
- time_status_np.master_offset which is given in nanoseconds, should be less than 250000. This equates to 250 microseconds.
Leave the sensor running over a period of time and check again the same command to see if the time drifts and if it is still well synced. Note: You can also check get_time_info(tcp command) command which time reference is used for the lidars' timestamps.
If using ptp4l, please send me the ptp4l.conf file, and make sure you have well configured the master clock as specified in the user manual PTP Quickstart guide section 16.6 of the software user manual that you can access via the following link: https://data.ouster.io/downloads/software-user-manual/software-user-manual-v2.2.1.pdf.
You can also try to enable the default-relaxed profile that should be jumping time any time the time offset is bigger than 1s using the following curl command:
curl -X PUT -H "Content-Type: application/json" -d '"default-relaxed"' http://<sensor_hostname>/api/v1/time/ptp/profile/

kolja

The Problem was that my profile was set to "default" and not "default-relaxed". It did work as intended, just my testing didnt work with the default profile. Thanks a lot.