[time-nuts] Serial or other simple protocols for exchanging time

[paul swed]

Ralph your need does appear simple.
Many of the timecodes that exist do so because of specific distribution
needs over distances.
IRIG and SMPTE are good examples. I use smpte in my house because I was
able to obtain very nice displays cheaply. I have in the past used IRIG B.
Simply silly but if you can do it why not.
That said the small NTP servers using arduinos or PIs are amazing  and a
low cost and technical lift and may be good enough.
But for accuracy a typical GPS receiver and the nema sentence is really
easy to use. Can be converted to RS232 for reasonable distance and the same
for the 1PPS. Typical applications I have seen use one of the rs232 control
lines to receive the 1 pps.
There can be one catch in this approach. The sentence may have passed the
second tick if you are using the typical 4800 baud sentence and other
messages are coming out of the GPS receiver. Eliminate un-used sentences
and I use 38.4 Kb/s. Seems to avoid the issue.
Regards
Paul
WB8TSL


On Wed, Aug 7, 2019 at 12:01 PM Ralph Aichinger <
ausserirdischesindgesund at gmail.com> wrote:

> Hi everybody!
>
>
> I am a newbie and am wondering what options there are for exchanging time
>
> on a more basic level than NTP or PTP (that is for situations when a
>
> full network stack is too complex).
>
>
> For now I have found:
>
>
> NMEA (probably ZDA only)
>
> IRIG timecode (this is rather complex, I would rather have a
>
>               full network stack than IRIG?)
>
> SMPTE timecode (this too?)
>
>
> Are there any other obvious candidates I missed? How did e.g.
>
> HP atomic clocks tell their time to connected devices before
>
> there was the NTP protocol? Did they output NMEA or something
>
> else? Did they emit IRIG directly?
>
>
> I want to create an Arduino based clock that tells time to a computer
>
> it is linked too. For exact seconds alignment I want to use a PPS signal,
>
> but I need a means to tell the computer about second numbers, hours etc.
>
> too.
>
>
> Of course I could invent a serial protocol, but I suppose if I invented a
>
> text based serial protocol, it would probably end up looking very
>
> similar in structure to NMEA ZDA sentences.
>
>
> *Is* NMEA the most practical time protocol at the 1 second level
>
> (that is when a PPS pulse takes care of second alignment?) or should
>
> I use something else if I am free to design stuff clean slate?
>
>
> TIA
>
> /ralph
>
> --
>
>
> -----------------------------------------------------------------------------
>
>
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>
>                                                    ausserirdische sind
> gesund
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