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.
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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
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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 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
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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
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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.
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