Hi SNTP probably is ok if you are running against an NTP server hardwired on a local LAN. Running it through a home modem and out onto the internet likely isn't going to be as good as a full blown NTP stack. You could quite easily get enough lag / delay to get into the ~ 100 to 200 ms region that you can see on a clock.
Bob On May 27, 2013, at 2:33 PM, Graham / KE9H <[email protected]> wrote: > Miguel: > > If you are going to build your own, I would recommend you start with > something like the Microchip PIC32 Ethernet Starter Kit. Comes > with a free GCC C/C++ compiler and an Ethernet stack. > > I happened to have one for another project, that already had a > four line serial LCD display hooked to it, as well as a serial port > command line interface running > > Since I was already familiar with the Ethernet Stack that comes with > the Starter Kit, all it took was turning on the SNTP function in the > stack, and writing about ten lines of C code to get it running. > > One update of NTP sourced UTC Hours-Minutes-Seconds time on the > display per command line request. (Anything more complicated is left as > an exercise for the student.) > > That was after about an hour's research to find out the time > format that NTP uses (seconds since Jan 1, 1900) and the > (different) time format that UNIX uses (seconds since Jan 1, 1970). > And how they both deal with leap-seconds since their > epoch started. > > Another hour of time figuring out how to convert that to > today's Hours, minutes, and seconds. But that is easy, > once it (finally) sinks in how to work with an epoch. > > Now, the real fun begins when you decide that you might > want to convert NTP or UNIX time to Day of Week, Month, > Calendar Year, Day of Year, Week of year, and > adjustments for local time zone, with daylight savings time. > > That was worth about four hours research and going to bed with > a head-ache. Learned all about "Julian Day" and "Modified > Julian Day", which it turns out has nothing to do with > the Julian Calendar. (Did you know that time started at high noon > on January 1, 4713 BC. ?) Finally discovered a code snippet > in Tom Van Baak's "C" code repository that will do the > conversion. (Thanks, Tom.) > > A pox upon leap years, un-leap centuries, re-leap 4th centuries, > Roman Numerals, modulus 7 weeks that do not align with the year boundary, > months with no regular modulus structure, and no year 0. > > Who sold us this? > > Makes you appreciate the decimal time "Star Date" system used on Startrek. > > --- Graham > > == > > On 5/27/2013 9:56 AM, Miguel Barbosa Gonçalves wrote: >> Hi Bob! >> >> On 27 May 2013 14:56, Bob Camp <[email protected]> wrote: >> >>> Hi >>> >>> Correct answer: >>> >>> I don't think there is such a beast. Once you get away from the radio >>> controlled (WWVB etc) clocks the cost goes up quickly. >>> >> I don't understand why a microprocessor with an Ethernet controller and a 7 >> segment display would cost so much to manufacture... I think I'll build my >> own. >> >> >>> Also correct, but a bit of a joke answer: >>> >>> Raspberry PI driving your television set. Alternatively make the Pi feed >>> control signals to a hacked normal clock. >>> >> Good joke :-) I imagine the electricity bill at the end of the month. >> >> I would like to have a clock sync with my super precise stratum 1 servers >> :-) what's the point in having them if I can see the time anywhere? :-) >> >> Cheers, >> Miguel >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
