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From: Terry G0EZY <GW0EZY@sky.com>
Message-ID: <e9dabc40-88d7-686a-37cc-ab698dd62ab6@sky.com>
Date: Sun, 18 Jun 2017 00:23:03 +0100
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Subject: Re: LF: Octo-soundcard for the Raspi
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Status: O

Thanks Paul

I'll follow this up when I get back. QRT for a few days - our 40th 
wedding anniversary!

Terry


On 17/06/2017 18:59, Paul Nicholson wrote:
>
> > http://abelian.org/vlf/tmp/170617a.gif
>
> > Yes that's it!
>
> Then there's a high pass getting in the way, must be
> the input circuit of the Octo.   You'll have to
> use a shorter PPS.   2mS to 5mS ought to do it.
>
> > Might be easier to user a stand-alone GPS
>
> Yes, Linux can use any GPS for timing, the daemon
> gpsd can communicate with just about every GPS using
> either NMEA or native protocols.  If you get a GPS
> with PPS and USB serial, just plug the USB into the
> RPi and run gpsd and ntpd. gpsd will find the GPS and
> detect the protocol and get the time from it.   ntpd
> reads the time from gpsd and syncs the system clock.
> vtcard uses that time to roughly timestamp the sound
> card data.  All you need are a few magic words in
> /etc/ntp.conf to set it up:
>
>  server 127.127.28.0 minpoll 4 maxpoll 4
>  fudge 127.127.28.0 time1 0.051 refid GPS
>
> and you can play with the time1 parameter to tweak
> away the comms latency on the GPS serial data.
>
> The nice thing about ublox GPS is that their comms
> protocol is very well documented and you can adjust
> things in great detail, firing commands at it via
> the program gpsctl.
>
> -- 
> Paul Nicholson
> -- 
>
>