I am working on a project developing ocean observatories and we have a highly accurate time source. Unfortunately because of the embedded nature of our platform it is not possible have NTP interface to it in any standard fashion. I have some questions about what is the best mechanism to add this (sole) time source to NTP. The time source is composed of a date and time string accurate to seconds, and a highly accurate Pulse-Per-Second. I expect the shared memory interface to NTP is the way to do this, but what is not clear to me is if I can enter the time as a single source or I should separate out the Pulse-Per-Second from the date and time string and configure them as separate sources. The Pulse-Per-Second is highly reliable, but I can imagine a situation where the date and time string might not be available. This is especially a concern if the system shuts down and restarts.
My question is what does NTP do for me automatically and what do I need to do myself to take into account some of the limitations of my time source? Is it possible in NTP to specify that a time source (highly accurate) is only seconds? What is the best way with NTP to handle the situation when the Pulse-Per-Second is available but the full time string is not? I have looked at the gpsd and shmpps code but still have some questions how NTP handles sources coming in through shared memory. From looking at these my understanding is I would set up one source for the time string (that is accurate to approximately a second) and the second time source for the highly accurate Pulse-Per-Second. Is there any place where I can find documentation about how NTP handles different clocks and different information that clocks may provide? Where do I find documentation of how to configure these shared memory time sources? Pointers much appreciated. Michael Eder Woods Hole Oceanographic www.whoi.edu/programs/ooi _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
