[time-nuts] Adafruit Ultimate GPS timing message arrival times

Hal Murray hmurray at megapathdsl.net
Sat Jul 30 18:31:11 EDT 2016

tvb at LeapSecond.com said:
> Just in case we have some newcomers to the thread I'd like to point out
> that this recent series of measurements of RS232 / NMEA have no bearing at
> all on the quality of the timing output. Timing NMEA is more of a
> curiosity; something to measure at the hundreds or tens of millisecond
> level. As anyone knows, the real timing output of these receiver is the
> 1PPS pulse itself, which is good to the tens of nanoseconds level. So a
> factor of a million different. 

I think that depends on how far down the nutty scale you are operating.

I think all the investigations of timing over serial ports are useful.  You 
can get sub millisecond timing over RS-232.  That is interesting for things 
like NTP if you don't have a PPS connection, so it helps to know which chips 
are good and which ones to avoid,

Serial ports are getting rare.  Most USB to RS-232 chips are slow with a 1 ms 
polling rate.  I think AdaFruit has one that polls 8x faster.  That should 
get sub-ms timing if coupled with a good GPS chip.

These are my opinions.  I hate spam.

More information about the time-nuts mailing list