[time-nuts] inexpensive, black box, GPS or NTP based TTL time capture?

Gary E. Miller gem at rellim.com
Wed Oct 18 20:11:16 UTC 2017

Yo Hal!

On Wed, 18 Oct 2017 12:26:27 -0700
Hal Murray <hmurray at megapathdsl.net> wrote:

> > For under a $100 you could get a Raspberry Pi, a GPS HAT, and
> > connect your input to a GPIO pin.  Configure ntpd to log the real
> > PPS and the input as another 'PPS'.   
> Is there an option to log all individual PPS events?

    # ppswatch /dev/pps0
    trying PPS source "/dev/pps0"
    found PPS source "/dev/pps0"
    timestamp: 1508356708, sequence: 591837, offset:  1412510
    timestamp: 1508356709, sequence: 591838, offset:  1381010
    timestamp: 1508356709, sequence: 591838, offset:  1381010
    timestamp: 1508356710, sequence: 591839, offset:  1397496
    timestamp: 1508356710, sequence: 591839, offset:  1397496

Just redirect to a log file.

> The $100 for a Pi might be significantly low.  It depends on what you
> have in your toy box.

Looking at Amazon, quantity one, I see:

    RasPi3 $35
    GPS Hat w/ remote antenna and cord: $30
    16BG miscro sd card: $9
    RaspI + HAT case: $10
    USB charger: $8
    USB charge cable: $2
    Cat5 ethernet cable: $2

Looks like $96 to me.  You can save some if you buy in bulk,

Plus labor, which after the first one is small.

> For getting started, you also need:
>   SD card reader/writer
>   keyboard and mouse (Pi has USB)
>   display adapter (Pi is HDMI)
>   display

Yeah, just for setup.  Shall we include the price of the desk it sits
and the building it is in?

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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