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Re: [gpsd-dev] RFC 2783
From: |
Gary E. Miller |
Subject: |
Re: [gpsd-dev] RFC 2783 |
Date: |
Tue, 10 Mar 2015 14:28:36 -0700 |
Yo Hal!
On Tue, 10 Mar 2015 14:17:00 -0700
Hal Murray <address@hidden> wrote:
> address@hidden said:
> > Is there always, and necessarily, only *one* pps device?
>
> No.
>
> If nothing else, I want to be able to connect two so I can compare
> them.
Yup, I do it often. validate one against the other.
> The kernel time stamping also counts events. That's a convenient
> hack for measuring things. So gpsd and ntpd have to be sure not to
> gobble up a PPS device that isn't theirs.
If gpsd has a GPS device, it assumes it owns the matching /dev/ppsX.
If someone opens /dev/pps0 first then gpsd fails on open, but continues
without the /dev/ppsX.
So just do not configure ntpd to grab a device gpsd will be told to use.
> Here is a graph made by feeding the 60 Hz power line via a
> transformer into a PPS input and counting cycles:
> http://www.megapathdsl.net/~hmurray/time-nuts/line/Dec-2013.png
I did that in 1975. How all consummer digital clocks used to work.
> I think the Linux kernel supports PPS via the printer port. I
> haven't tried it, but the printer port is an old standby for hardware
> hacking.
And also via GPIO, very common in RasPis world.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
address@hidden Tel:+1(541)382-8588
- Re: [gpsd-dev] RFC 2783, (continued)
- Re: [gpsd-dev] RFC 2783, Frank Nicholas, 2015/03/10
- Re: [gpsd-dev] RFC 2783, Hal Murray, 2015/03/10
- Re: [gpsd-dev] RFC 2783, Gary E. Miller, 2015/03/10
- Re: [gpsd-dev] RFC 2783, Hal Murray, 2015/03/10
- Re: [gpsd-dev] RFC 2783, Gary E. Miller, 2015/03/10
- Re: [gpsd-dev] RFC 2783, Gary E. Miller, 2015/03/10
Re: [gpsd-dev] RFC 2783, Hal Murray, 2015/03/10
Re: [gpsd-dev] RFC 2783, Eric S. Raymond, 2015/03/10
Re: [gpsd-dev] RFC 2783, Harlan Stenn, 2015/03/10
Re: [gpsd-dev] RFC 2783, Greg Troxel, 2015/03/11