[time-nuts] Generating a solid PPS from 10Mhz source

Graham / KE9H ke9h.graham at gmail.com
Fri Jan 15 14:09:43 EST 2016


The programmable PIC or AVR or ... chip that will do the job are same or
less than a 555 chip, and a lot more flexible.
--- Graham

On Fri, Jan 15, 2016 at 11:55 AM, Adrian Godwin <artgodwin at gmail.com> wrote:

> Why use a board full of TTL when an $1 8-pin chip will do it ?
>
>
> On Thu, Jan 14, 2016 at 11:44 PM, Morris Odell <vilgotch at bigpond.net.au>
> wrote:
>
> > Am I missing something here?
> >
> > I understand the ease and fun of programming up an AVR as much as anyone
> > but surely this task could be accomplished  easily with a chain of fast
> > synchronous TTL or CMOS dividers. A resynchronising FF could also be
> added
> > at the end to  clean up the 1 pps if required. You wouldn't need to worry
> > about the maths or OBOBs either.
> >
> > Admittedly you would need more PCB real estate but that shouldn't be a
> big
> > deal in most cases.
> >
> > Morris
> >
> >
> >
> >>> 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.
> >>>
> >>>
> >
> >>>>> 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?
> >>>>>
> >>>>
> >
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