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

Adrian Godwin artgodwin at gmail.com
Fri Jan 15 12:55:23 EST 2016


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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