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Can you get a 1PPS signal from Garmin eTrex GPS ? — Parallax Forums

Can you get a 1PPS signal from Garmin eTrex GPS ?

BeanBean Posts: 8,129
edited 2005-09-08 01:50 in General Discussion
I have a Garmin eTrex Venture handheld GPS.
I've looked through the manual and the website (and google), but I can't find anyway to get a 1PPS signal from it.
Is there any way to do it ?
Bean.

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"SX-Video·Module" Now available from Parallax for only $28.95

http://www.parallax.com/detail.asp?product_id=30012

Product web site: www.sxvm.com

"One experiment is worth a thousand theories"
·

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-08-25 15:15
    To get readings every second you need to use Garmin text output mode (which uses fixed formatting and if FAR EASIER to parse) and set the baud rate to 9600. The downside is that speed is given in vectors (NS, EW) so you have to do a bit of math (call on your friend Pythagorus) to get the direction of travel.

    This might help: http://www.parallax.com/dl/docs/cols/nv/vol4/col/nv103.pdf

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    Jon Williams
    Applications Engineer, Parallax
  • Ken GraceyKen Gracey Posts: 7,401
    edited 2005-08-25 15:40
    Maybe this would be a good time to define an open-sourced, free SX-based GPS "helper" chip for the BASIC Stamp?

    Ken
  • BeanBean Posts: 8,129
    edited 2005-08-25 16:39
    Jon,
    I don't mean a reading every second. I need the 1 Pulse Per Second signal that is aligned with UTC that many GPS units have as a seperate signal. I didn't know if the serial comm is in any way aligned with UTC ?
    Bean.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "SX-Video·Module" Now available from Parallax for only $28.95

    http://www.parallax.com/detail.asp?product_id=30012

    Product web site: www.sxvm.com

    "One experiment is worth a thousand theories"
    ·
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-08-25 16:58
    I don't know if this is any help, but the GARMIN SDK has a PVT command protocol which transmits position velocity and time once per second. It doesn't specify whether the packet is synchronized with the actual UTC clock tick. Enclosed is the pdf in the SDK, see page 17 of the pdf.

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    ·1+1=10

    Post Edited (Paul Baker) : 8/25/2005 4:57:54 PM GMT
    pdf
    pdf
    IntfSpec.pdf
    824K
  • steve_bsteve_b Posts: 1,563
    edited 2005-08-25 18:41
    Wonder if you can pick off the 1pps signal off the board inside. I'm sure it's not all on one IC....well, maybe! haha

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    ·

    Steve

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • BeanBean Posts: 8,129
    edited 2005-08-25 19:51
    Steve,
    That's a possiblity. I have no problem opening 'er up. I guess I'd have to probe around to see if I can find it.
    Bean.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "SX-Video·Module" Now available from Parallax for only $28.95

    http://www.parallax.com/detail.asp?product_id=30012

    Product web site: www.sxvm.com

    "One experiment is worth a thousand theories"
    ·
  • steve_bsteve_b Posts: 1,563
    edited 2005-08-25 19:55
    I've had some "spare time at work!" ssshhhh....and did a bunch of googling. There's been some notes on the fact that the data message isn't even accurate as far as coming once per second.

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    ·

    Steve

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • Robert KubichekRobert Kubichek Posts: 343
    edited 2005-08-25 20:30
    I have a gps unit that was part of a cellular tower setup, and it is the only gps unit I know that outputs a time signal, mine is a 10mhz pulse...
    Made by HP, and I am going to some day set it up on my website with weather data...

    Bob N9LVU scool.gif
  • steve_bsteve_b Posts: 1,563
    edited 2005-08-25 21:55
    A lot of GPS "engines" output the 1pps signal. By engine I mean the circuit that does the GPS decoding (part of what's IN a Garmin/Magellan).

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    ·

    Steve

    "Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
  • David BDavid B Posts: 592
    edited 2005-08-25 22:21
    I have a Garmin GPS-35 GPS sensor that emits a 1PPS signal on its own wire.

    It puts out a really stable signal. Once I set it up to gate the output from a 4 mHz ovenized crystal oscillator into a chain of counters, and it consistently gated the exact same number of pulses over the one second period.

    I don't know about the eTrex - my unit came with the 1PPS output already configured. Maybe the Garmin engineers could tell you whether the eTrex has this output - I emailed them once with a question, and they were real helpful.
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2005-09-08 01:50
    I think the true PPS can only be had with the $GPZDA sentence (I haven't found any with this capability.)
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