Re: [gpsd-users] In which GR-601 does not equal GR-601W

[Gary E. Miller]

Yo Phil!

On Wed, 27 Jul 2016 17:38:21 -0400
Phil Stracchino <address@hidden> wrote:

> > you should have a line that looks like this:
> > 
> > ---------------------------- PPS offset 0.0011234 ------
> >
> > You may need to wait a minute or two to get it.  
> 
> Nope.  Nothing like that, after gpsmon has been running over 30
> minutes.

What vesion of gpsmon are you running?

3.16 is current, 3.17 is in git head.

    contrib # gpsmon -V
    gpsmon: 3.17~dev (revision release-3.16-402-ga4dae6f)

> > The output should look like this:
> minbar:root:/var/tmp/portage/sci-geosciences/gpsd-3.16/work/gpsd-3.16/contrib:30
> # ppscheck /dev/ttyUSB0
> 1469654953  178328606
> 1469654953  180314316 TIOCM_CD
> 1469654954    8334315
> 1469654954  108345128 TIOCM_CD
> 1469654955    8369058
> 1469654955  108379130 TIOCM_CD
> 1469654956    8405679
> 1469654956  108413694 TIOCM_CD
> 1469654957    8436334
> 1469654957  108446260 TIOCM_CD
> 1469654958    8470705
> 1469654958  108483992 TIOCM_CD

Congrats!  You have PPS!  Notice how it goggle up/down every second?

> So ppscheck is reporting something there.

Yup, the PPS is connected to the Carrier Detect (CD) line on the
USB to Serial converter.  And your USB driver is passing it on just fine.

> I confess to not knowing
> how to read what it's trying to tell me, aside from the obvious
> seconds-since-the-epoch in column 1.  What are the other two columns?

As the ppscheck.c file says at the top:

 * Each output line is the second and nanosecond parts of a timestamp
 * followed by the names of handshake signals then asserted.  Off 
 * transitions may generate lines with no signals aserted.

So CD goes off at 0.00847 Seconds after your sysclock top of second (TOS).
Then CD goes back on at 0.10844 Seconds after TOS.  So your system clock is 
8.47 milliSeconds early, and the pulse width is 100 millisconds.

So, your GPS is indeed a GR-601W!

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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