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 <nsa...@kfu.com> 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 <time-nuts@febo.com> >> 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 <time-n...@tardis.net.br> >>> 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 -- 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. >> >> _______________________________________________ >> 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.
