f



NTP. does PPS on DCD need it's own serial port?

I am using an Arbiter 1084C to feed a little celeron box using ubuntu xenia=
l minimal running ntpd

If I want to use PPS as well, do I need one RS232 port on the xenial box? O=
r two RS232 ports, one for the ascii strings, and the other for the DCD/PPS=
 pulses?  (the xenial box has four.  I'm using ttyS0 as a serial console) =
=20

The Arbiter is configured to send ASCII EXT out it's main RS232C port (COM =
A).  The Arbiter is also configured to output a PPS signal on COM A pin 6. =
 I have it configured for the 'positive' aka 'Assert' edge to indicate the =
second. so both the ASCII string and the PPS come out of the same RS232 por=
t on the Arbiter.

I have the cable from the Arbiter COMA connected to ttyS2 on the xenial box=
..  The cable is wired as:

Arbiter    xenial
   2        3    crossed
   3        2    crossed
   5        5    GND
   6        1    DCD  PPS

I've put a scope on DCD, and I do see pulses of about 12mS (the widths are =
programmable in the Arbiter).

Thanks in advance.

0
gmx
11/21/2016 9:49:00 PM
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gmx.tallahassee@gmail.com wrote:
> I am using an Arbiter 1084C to feed a little celeron box using ubuntu xenial minimal running ntpd
> 
> If I want to use PPS as well, do I need one RS232 port on the xenial box? Or two RS232 ports, one for the ascii strings, and the other for the DCD/PPS pulses?  (the xenial box has four.  I'm using ttyS0 as a serial console)  
> 
> The Arbiter is configured to send ASCII EXT out it's main RS232C port (COM A).  The Arbiter is also configured to output a PPS signal on COM A pin 6.  I have it configured for the 'positive' aka 'Assert' edge to indicate the second. so both the ASCII string and the PPS come out of the same RS232 port on the Arbiter.
> 
> I have the cable from the Arbiter COMA connected to ttyS2 on the xenial box.  The cable is wired as:
> 
> Arbiter    xenial
>    2        3    crossed
>    3        2    crossed
>    5        5    GND
>    6        1    DCD  PPS
> 
> I've put a scope on DCD, and I do see pulses of about 12mS (the widths are programmable in the Arbiter).
> 
> Thanks in advance.
> 

Hi

I have a Sure GPS/PPS and VIA i386 m/b running NetBSD for over
4 yrs. The NMEA from the GPS is used to give ntpd what second
it is so you need to know what offset to use in ntp.conf, eg.

server 127.127.20.2 mode 18 prefer
fudge 127.127.20.2 stratum 7 time2 0.407 flag1 0 refid GPSb

server 127.127.22.2 minpoll 3 maxpoll 3
fudge 127.127.22.2 flag2 0 flag3 0 refid PPSb

The time2 0.407 value needed for GPSb is specific to the
particular GPS and its' firmware revision so is found by
trial and error. To make it easier/quicker to find the
required setting you can mark an alternate known reliable
source as prefer.


David

0
David
11/22/2016 12:51:41 AM
gmx.tallahassee@gmail.com wrote:
> I am using an Arbiter 1084C to feed a little celeron box using ubuntu xenial minimal running ntpd
> 
> If I want to use PPS as well, do I need one RS232 port on the xenial box? Or two RS232 ports, one for the ascii strings, and the other for the DCD/PPS pulses?  (the xenial box has four.  I'm using ttyS0 as a serial console)  
> 
> The Arbiter is configured to send ASCII EXT out it's main RS232C port (COM A).  The Arbiter is also configured to output a PPS signal on COM A pin 6.  I have it configured for the 'positive' aka 'Assert' edge to indicate the second. so both the ASCII string and the PPS come out of the same RS232 port on the Arbiter.
> 
> I have the cable from the Arbiter COMA connected to ttyS2 on the xenial box.  The cable is wired as:
> 
> Arbiter    xenial
>    2        3    crossed
>    3        2    crossed
>    5        5    GND
>    6        1    DCD  PPS
> 
> I've put a scope on DCD, and I do see pulses of about 12mS (the widths are programmable in the Arbiter).
> 
> Thanks in advance.
> 

Hi

Sorry but I missed a couple of points in my reply.

I've been using ntpd versions pre 4.2.6, 4.2.6 and
regularly updated. I recently backed out from 4.3.93
to 4.2.8p8 that didn't solve the problem I was having
which was due to my selection of servers having too
few different refids so I will be moving back to 4.3.93.


ntp.conf also has:

tos mindist 0.4  # this prevents ntpd bailing out early

Also ntpd needs to have synced with the GPS or another
source before it will sync to PPS and this can take more
than a few minutes.


David

0
David
11/22/2016 1:48:15 AM
On 21/11/2016 21:49, gmx.tallahassee@gmail.com wrote:
> I am using an Arbiter 1084C to feed a little celeron box using ubuntu xenial minimal running ntpd
>
> If I want to use PPS as well, do I need one RS232 port on the xenial box? Or two RS232 ports, one for the ascii strings, and the other for the DCD/PPS pulses?  (the xenial box has four.  I'm using ttyS0 as a serial console)
>
> The Arbiter is configured to send ASCII EXT out it's main RS232C port (COM A).  The Arbiter is also configured to output a PPS signal on COM A pin 6.  I have it configured for the 'positive' aka 'Assert' edge to indicate the second. so both the ASCII string and the PPS come out of the same RS232 port on the Arbiter.
>
> I have the cable from the Arbiter COMA connected to ttyS2 on the xenial box.  The cable is wired as:
>
> Arbiter    xenial
>    2        3    crossed
>    3        2    crossed
>    5        5    GND
>    6        1    DCD  PPS
>
> I've put a scope on DCD, and I do see pulses of about 12mS (the widths are programmable in the Arbiter).
>
> Thanks in advance.

Here's what I have on a Linux box:

# PPS for fine timekeeping
server  127.127.22.0  minpoll 4 maxpoll 4
fudge   127.127.22.0  refid kPPS

# Could be stand-alone coarse timekeeping
server  127.127.28.0  minpoll 4 maxpoll 4  prefer
fudge   127.127.28.0  time1 0.175  refid GPSD

which has a single serial port (0) fed from a Garmin GPS18 LVC (the old 
model).  I'm using gpsd to feed the coarse time into ntp, but I could 
have used the NMEA driver.  I like gpsd as is gives an extra command 
(cgps -s) whoch allows you to have a quick look at the GPS data.

I hope that and David Lord's comments help to answer your question.
-- 
Cheers,
David
Web: http://www.satsignal.eu
0
David
11/22/2016 10:38:55 AM
Thank you for the replies.  So if I'm reading right a single tty port is all that's needed, but two stanzas in the ntp.conf is required, one for the Arbiter (type 11, iirc) string, and the other for the PPS coming in on the DCD pin.

Edit: this arrangement seems to be working as expected. Thank you again. 
0
gmx
11/30/2016 6:11:37 PM
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