GPS and PPS time sync status

[amir-zviran]

Hi,

I'm using 3DM-CV7. I connect its PPS input to my GPS module, and sending it time reference messages on the /external_gps_time topic. I can see it is synced by looking at the timestamps of the messages, but I wonder if I can rely on that to tell whether the sync is working well.

I have a few questions:

1. Will the timestamps of the messages change to the GPS time (i.e. the time reference time) even if it is not yet synced with the PPS signal?
2. Is there a way to read the Time Sync Status (0xA0,0x02) register through the ROS driver?
3. Is reading the time sync status enough to tell the sync is "complete", i.e. both the PPS signal is valid and the time is correctly set according to the time reference? Or I have to look at the time_valid field in the GPS Timestamp (0xFF,0xD3) register too?
4. If I need to look at the GPS Timestamp (0xFF,0xD3) register, can I read it through the ROS driver?

Many thanks!
Amir