So this is different from the Thunderbolt, even if they both use the same serial protocol or can the t-bolt also have it's flash rom programmed from a PC?
The bottle neck in the system in the uncertainty in the interrupt latency on the PC where NTP runs. After all this I doubt you can captures the PPS to better than 1 uS. For a long time I've been wnting to build an external counter for NTP. But it would have to use some very fast logic family. On Sun, May 5, 2013 at 6:26 PM, Miguel Barbosa Gonçalves <m...@mbg.pt> wrote: > Hi Chris! > > On 06/05/2013, at 01:21, Chris Albertson <albertson.ch...@gmail.com> wrote: > >> If you are talking about using this with NTP. I don't know if you >> have a choice. The Trimble receiver is going to do whatever it is >> going to do when you power it up. Software running on a PC can >> perform a 24 hour survey and report the location but the "Type 29" >> driver in NTP has no way to tell the Trimble receiver what to do on >> power up. And there is no way to specify a location you have surveyed >> by some other means. > > What I am doing at the moment is connecting Trimble's port A (timing > port) to NTP and configuring the receiver using a Windows laptop > through port B. I can connect to port B occasionally to check the > receivers health. The receiver has its configuration stored in an > EPROM so it will just work anytime unless the configuration gets > corrupted. > > After the survey ends the position can be optionally stored to the > EPROM. Also, if the antenna changes its position more than 1000 meters > a new self-survey will run automatically. > >> Perhaps the Trimble GPS has some way to program it's FLASH Rom with >> changed parameters but NTP only reads the packets. It does not send >> any. Can LH download a surveyed location r change the length of the >> survey? NTP can't do any of that > > It does. It is available on the Trmble's FTP site. > >> Other NTP drivers such as the Type 30 Motorola driver are more >> flexible. Those alow you to specify a lat, long that was surveyed or >> have the receiver do a survey. The type-30 Motorola driver is a lot >> more configurable. > > The Trimble software is very nice and allows one thing the Motorola > NTP driver doesn't allow if I remember correctly. On the Trimble I can > choose the number of fixes for the survey and can watch it run while > NTP is receiving time. I can't do this on an Oncore because it only > has one port. > >> But as was said, light travels about 30cm/nanosecond and NTP works in >> microseconds. So your location can be "off" by 1000 times 30cm before >> NTP will care. So 3 or 4 meters of location error will not matter and >> the 2,000 point self survey will be good enough. > > When surveying accuracy of the PPS will be around 1 us. The accuracy > will obviously increase when the survey ends. > >> But if yo really so want nanosecond level timing, then you need to >> care about the survey > > Agree! > > Cheers, > Miguel > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.