[time-nuts] Looking for off-the-shelf device to timestamp multiple PPS inputs

[Hal Murray]

kevin at rosenberg.net said:
> I'm looking for device with an external clock input as well as inputs for
> multiple PPS signals that outputs timestamped messages for each input pulse
> via RS232. ... 

What sort of accuracy and/or resolution do you want/need?


> 5) Using a FreeBSD or Linux box with multiple RS-232 inputs and using their
> PPS API.  However, outside of some ARM boards, I haven't found any boxes
> that can be clocked by a external reference. And, I haven't enough
> experience running FreeBSD or Linux on ARM to know how well this will work
> for me.

> 7) Use a box like in #5, and capture the PPS from the PRS-10 as well and
> using that to scale the other PPS inputs that arrive around the same time. 

If you have a Linux box handy, that one is easy to try.

After the 60Hz grab-every-cycle experiment, I started collecting every-cycle 
data for PPS signals.  I have a box  with 3 PPS signals: one from a Z3801A 
and 2 from low cost GPS units.

I can send you some files if you want to investigate.  (5-6 megabytes per day)

I'll have to make some graphs.  The ballpark is several microseconds of 
noise, but that's on top of your system clock offset.  I think it would be 
easy to see 10 microseconds of offset.  You would have to work harder to see 
smaller numbers.


Reminder: Your system may have troubles catching 10 microsecond PPS signals.  
TAPR says "no longer available" for the FatPPS.  I poked John.  He was going 
to see if they could build another batch.




-- 
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