I'm curious if that code will perform the intended function (down to the clock cycle) when compiled. A check in the simulator would be a good idea while the TIA is busy.
If it doesn't give you the performance you are looking for, try programming it in assembly, as was done for the PicDiv. Dan > On Jan 13, 2016, at 9:35 PM, Nick Sayer via time-nuts <[email protected]> > wrote: > > The code is at > > https://github.com/nsayer/GPS-disciplined-OXCO/blob/master/tiny_divider.c > > It’s a first cut. The code at the moment will just divide the input clock by > 10 million, so you get a 1 PPS 50% duty square wave out. It should run on any > ATTinyx5 model - it certainly will fit on at ATTiny25 if you wish. > > I’ve not exhaustively tested it yet. I need to feed it into my TIA to make > sure it’s exactly 1 Hz - it’s conceivable I’ve committed a fencepost error > that would make it off enough that my scope can’t tell (my TIA is busy at the > moment). > > I believe the code won’t do the math properly below 10 MHz. You’d need to > select the next lower prescale setting and change a couple of the formulae, > but I don’t foresee an issue with doing so. > > I’ll come back with an exhaustive test report (and any bug fixes) when I get > my TIA back from GPSDO ADEV duty. :) > >> On Jan 13, 2016, at 12:12 PM, Nick Sayer <[email protected]> wrote: >> >> Just shy of a half dozen folks have asked, so I'll post here as soon as I >> finish cleaning it up. I'll put it on Github when it's ready. I just need a >> day or two. >> >> Sent from my iPhone >> >>> On Jan 13, 2016, at 6:43 AM, Nick Sayer via time-nuts <[email protected]> >>> wrote: >>> >>> If anyone is interested in the equivalent functionality using an ATTiny25 >>> (for instance, if you’re already heavily invested in AVR instead of PIC, >>> like I am), ping me. I’ve privately written code to solve almost the same >>> problem and it could easily be adapted into doing the same job. >>> >>>> On Jan 13, 2016, at 5:23 AM, Edesio Costa e Silva >>>> <[email protected]> wrote: >>>> >>>> Hi! >>>> >>>> Try TVB's picDiv at http://www.leapsecond.com/pic/picdiv.htm >>>> >>>> Edésio >>>> >>>>> On Wed, Jan 13, 2016 at 09:22:09AM +0000, Jerome Blaha wrote: >>>>> Hey Guys, >>>>> >>>>> Is there an easy circuit to build that can consistently deliver a 1 PPS >>>>> from a 10MHz source with excellent resolution and repeatability? My >>>>> first application is to test different 10MHz oscillators without a TIC >>>>> always attached and then compare the PPS output change over time against >>>>> a master GPSDO PPS with an HP53132A. >>>>> >>>>> The circuit used for PPS generation would have to deliver consistent PPS >>>>> output with preferably not more than 100ps noise or jitter, assuming a >>>>> perfect source. I'm totally guessing that for this resolution, the PPS >>>>> would have to be generated and accurate to within 0.001Hz every second. >>>>> If this is too difficult, maybe the integration time can be increased to >>>>> generate one pulse every 10second or every 100,000,000.00 cycles? >>>>> >>>>> Finally, is a square 10Mhz reference any better in this case than a >>>>> sinusoidal input for generating the PPS? >>>>> >>>>> Thanks, >>>>> Jerome >>>>> >>>>> _______________________________________________ >>>>> 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. > > _______________________________________________ > 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.
