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

[Gary Chatters]

If I understand correctly, your Arduino based device is generating the 
time code to send to your computer.

In the past I have used GPS NMEA messages and IRIG-B for data 
acquisition time stamps.  I considered SMPTE, but it did not look useful.

I would expect that making your Arduino device look like a GPS receiver 
outputting NMEA messages and a PPS signal would be about the simplest 
approach you could take.  It has the advantage that there is existing 
software to deal with the messages, including NTP drivers.

IRIG-B has the advantages that it has a lower bit rate and only requires 
one signal line.  I looked at NTP source code and there is a driver for 
IRIG-B (and E) using 1 kHz modulation.

Two questions come to mind:

- How is your Arduino going to get time?

- What is the computer going to do with it?



Gary
WA9ZZZ

On 8/7/19 8:13 AM, Ralph Aichinger 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
>