[LinuxPPS] parallel PPS

[Paul]

Remco

The Rockwell Jupiter module has an interesting history. I think the early ones 
outputted 'NMEA' data in a binary mode. (After all, nobody expected them to 
be used as we do - the manufacturers assumed they would be built into car 
GPSs etc.) Later ones output the NMEA data as a standard serial stream. The 
problem is that they only output the NMEA data when the processor is not too 
busy. Hence the one second offset. Unfortunately they sometimes output the 
data two seconds late, and may spend hours doing this. As far as I could see 
this is not related to satellite visibility. If you don't actually see it 
happening, the obvious effect is a surprisingly high jitter on the NMEA.

Paul

On Friday 29 February 2008 20:55, Remco den Besten wrote:
> Hello Paul,
>
> Indeed several people tell me to 'forget' the NMEA from the Jupiter.
> When I use time1 0.0 or 2.0 I have the 'second or two seconds' phenomenon.
> But,  I did not google intensively on this matter.
>
> However, as far as I can ascertain I did (and do? ;-) not have this problem
> using a 1.0 second
> time1 which I determined empirically (to be honest, I also tried time1 0.0
> and time1 2.0 and
> saw strange things happen ;;-) .
>
> Unfortunately I was not able to use the 31 driver because I received
> errors, see:
> http://rembl.org/index.php/2008/02/16/rockwell-jupiter-and-linuxpps/
>
> I am experimenting with several combinations now:
> 'Time' from DCF, internet and GPS, in combinatin with GPPS (PPS derived
> from GPS) or Rb87
> for the precision. The combination Rb87 (PPS) and internet time (from PTB
> Germany) worked well.
> (see http://remco.org/rb87)
>
> This afternoon I recompiled my 2.6.24 kernel with CONFIG_HZ_100=y and
> now have a contrapsion where Jupiter NMEA delivers 'the time' and the
> Jupiter PPS
> the precision.
>
> We'll see ....
>
> Cheers,
> Remco
>
>
> ----- Original Message -----
> From: "Paul" <paul at lavender-fam.net>
> To: <linuxpps at ml.enneenne.com>
> Sent: Friday, February 29, 2008 9:19 PM
> Subject: Re: [LinuxPPS] parallel PPS
>
> > Hardly what you were asking, but I picked up on something you said. Is
> > your
> > Jupiter Rockwell NMEA really solid? You said that you use time1 1.0, but
> > does
> > it sometimes jump a second, requiring time1 2.0 or even time1 0.0? I had
> > terrible problems and in the end and only used the PPS from this module.
> > Interestingly this has been noted long ago, check out the 'original'
> > driver
> > for the Rockwell module on the NTP site, which also mentions this problem
> >
> > Paul
> >
> > Wiki: http://wiki.enneenne.com/index.php/LinuxPPS_support
>
> _______________________________________________
> LinuxPPS mailing list
> LinuxPPS at ml.enneenne.com
> http://ml.enneenne.com/cgi-bin/mailman/listinfo/linuxpps
> Wiki: http://wiki.enneenne.com/index.php/LinuxPPS_support