Amazing... there is always something to learn from TVB. Now I'll try to derive a 2.048MHz G.703-13 clock from a 10MHz clock. I suspect that the procedure is similar, even if 2048KHz is not quite a power of 2.
On Thu, Feb 2, 2012 at 4:35 PM, Tom Van Baak <t...@leapsecond.com> wrote: > Hi Roberto, > > The motivation for this, I assume most list members know, is to > drive cheap quartz stepper motor clocks with precise 32 kHz > frequency, one derived from an atomic or GPS 10 MHz. > > The 10 MHz to 32 kHz PIC divider I wrote uses a sort of binary > "leap year" algorithm to adjust the digital output phase to be as > close as possible to the ideal 32.768 kHz phase on each cycle > and also to have zero long-term error. > > I'm not sure how well a multi-level leap year algorithm relates > Breseham's algorithm. I tracked down his 1965 plotter article. > There might be common ground there. > > With non-integral ratios like this case, or without external analog > components (e.g., PLL), it seems some level of jitter is always > unavoidable. So the goal was to make it as mathematically small > as possible, and furthermore, to be able to do the math within a > half cycle, which is only 15 microseconds. > > I'll send you an early draft of the PIC code; the version that was > most clear before I had to pinch too many cycles and added too > many features. Let me know what you think. > > I also simulated the algorithm on a PC and measured the ADEV > and phase noise. That simulation code is file 10m32k.c under: > > http://www.leapsecond.com/tools/ > > /tvb > > ----- Original Message ----- From: "Roberto Barrios" <rbarri...@msn.com> > To: "Tom Van Baak" <t...@leapsecond.com>; "Discussion of precise time and > frequency measurement" <time-nuts@febo.com> > Sent: Thursday, February 02, 2012 5:09 AM > Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video > recorders > > > Hi Tom, >> >> I'm interested in that divider. Actually, insterested in knowing how it >> works, not in the .HEX file. >> >> Breseham's algorith works but has inherent jitter and I've found no other >> solutions for situations like that. >> >> I'd live to know how it is done. >> >> Thank you, >> Roberto EB4EQA >> http://www.rbarrios.com >> >> >> -----Mensaje original----- From: Tom Van Baak >> Sent: Thursday, February 02, 2012 10:34 AM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video >> recorders >> >> I think I've seen comments about making 32 KHz from 10 MHz in a PIC or >>> AVR. >>> >>> tvb has this web page, but I don't see a 32 KHz option: >>> http://www.leapsecond.com/pic/picdiv.htm >>> >> >> Hal, >> >> Yes, I have a PIC divider that takes 5 or 10 MHz input and >> outputs a 32.768 kHz square wave with minimal jitter and >> no long-term phase offset. Contact me off-line if interested. >> >> /tvb >> > > > > _______________________________________________ > 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. > _______________________________________________ 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.