>> Use a daemon that listens to the UDP clock pulses and, after suitable >> preprocessing, sends them to ntpd via the SHM driver. > >That is the approach I had in mind. What worries me is the "suitble >preprocessing" part as well as figuring out the exact parameters to >pass to the ntpd via the SHM driver. Does the SHM require a 1HZ PPS or >is my ~0.1HZ pulse OK to use?
There is nothing in the driver documentation that says it has to be a 1PPS for SHM. I would browse over the refclock_shm.c file, it's only about 300 lines of code. My coffee hasn't kicked in this morning yet otherwise I would trace through it (maybe later today). The SHM driver is not an instant use driver, you have to write some other interface that takes your incoming data and writes it to the SHM segment (I think). > I imagine it is quite stable. The old legacy system is a very large > scale miltary system used for high-precesion data loading of weapon > data. Never assume anything. You could blindly end up trying to sync to a time source that is less stable than the existing PCs clocks. > I really would like to synch my internal network to a external clock > reference (say an Internet site or GPS unit) that is very stable so I > can measure just how stable/precise/accurate the old legacy system is. > Unfortunaley, that is not possible in the lab environment I am working > in. So, since the single board computer I am using for the ntpd server > has a cheap clock in it that I know drifts in a big way, I am unsure > how to measure the accuracy of the old legacy system. I have a Soekris Net4501 SBC and its is a lot more stable than any of my regular PCs... The ntp drift file score has always been single digits with the stock crystal! You could always mod one to allow an external high-stability reference as detailed below. http://www.febo.com/pages/soekris/ _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
