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  1. #1
    Hybrid AWD's Avatar
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    Plug & Play GPS Speed To Display

    I have a few ideas always brewing in my head and I just recently came up with another, so I'll share the idea with everyone just in case someone has good input to help move the idea along.

    I have a Garmin Etrex (as does just about everyone) and I don't have a cool mount for it on my GPR or Ultra. I simply throw it in the compartment and do my speed runs. So I thought about the idea of "what if I could take the output from the Garmin (speed) and send it to my multi-function display". So that is where this whole idea started.

    After a good hard 30-45 minutes of googling information about the Etrex (which there is a ton out there), I think it's completely possible to do a plug & play setup.

    As most of you know, the Garmin Etrex has a serial output which can be connected to your computer for firmware and map updates. The Etrex has NMEA data which is why I feel this could all come together.

    The only thing I would need to do is come up with a hardware configuration that could modify the output of the garmin to the pulse in which the jet ski sees already. (the information for this is already available in the FSM)

    Looking online the dev board is around $20... so if it could be made for under $50... I think it just might be worth it. Any input?


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Hybrid AWD View Post
    ...NMEA data which is why I feel this could all come together.

    The only thing I would need to do is come up with a hardware configuration that could modify the output of the garmin to the pulse in which the jet ski sees already. (the information for this is already available in the FSM)

    Looking online the dev board is around $20... so if it could be made for under $50... I think it just might be worth it. Any input?
    What development board are you looking at for $20?

    Are the electrical/signal specs for the factory Yamaha speedo signal input documented somewhere?

    You would only be using the speed data from the NEMA code stream. I am not sure how often that gets updated/sent out the Garmin serial port.

    There would be a time lag between actual speed changes and the speedometer display updating.

  3. #3
    Hybrid AWD's Avatar
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    Quote Originally Posted by K447 View Post
    What development board are you looking at for $20?

    Are the electrical/signal specs for the factory Yamaha speedo signal input documented somewhere?

    You would only be using the speed data from the NEMA code stream. I am not sure how often that gets updated/sent out the Garmin serial port.

    There would be a time lag between actual speed changes and the speedometer display updating.
    The signal being sent from the speed sensor is basically like a PWM sensor, so that is all the display is getting fed. So having the GPS Data (NMEA) converted shouldn't be a big issue.

    Going from serial will just have to be tested. If there is lag, another option would have to be figured out.

    The board would be an Arduino Pro Mini.

  4. #4
    if you could get this to work i bet about 100 members on here would buy it, not to mention you could probably market it pretty well to riva...

  5. #5
    Hybrid AWD's Avatar
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    Quote Originally Posted by skyline2962 View Post
    if you could get this to work i bet about 100 members on here would buy it, not to mention you could probably market it pretty well to riva...
    That is the idea however, I am not sure if all Garmins will output the same information. If it came down to it, I'd just build the GPS board setup and have it output the right parameters. It's not that complicated and probably would be cheaper for the end user in the long run.

    If I feel like it wasnt that hard, and expensive up front, I may just post a DIY for those who have the skills to build one. Of course, for those who don't, I'd be willing to build one for them for a small fee.
    It has to be cheap enough that people can justify spending $XX.XX on this vs. buying a mount or just holding it in the storage box.

    Now it's just onto actually getting it to work and work well.

    The only issues I could see is the response time from the satellite to the GPS to the display, but that can be fixed numerous ways. Also, we aren't fighting uphill or downhill battles (literally) so getting the basic air to ground speed is fine for this situation.

  6. #6
    I can't imagine the lag would be much of an issue if it's under a second or 2 because most people doing speed runs are holding it WOT for a while anyway, however one drawback i just thought of is you won't be able to display fractional speeds (ie: 69.1 mph). So some guys looking to get that extra tenth will be SOL. still an awesome idea, i'd be interested once i buy a new etrex again!

  7. #7
    Hybrid AWD's Avatar
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    Quote Originally Posted by skyline2962 View Post
    I can't imagine the lag would be much of an issue if it's under a second or 2 because most people doing speed runs are holding it WOT for a while anyway, however one drawback i just thought of is you won't be able to display fractional speeds (ie: 69.1 mph). So some guys looking to get that extra tenth will be SOL. still an awesome idea, i'd be interested once i buy a new etrex again!
    I'm not sure if the GPR speedo can display 3 digits or not, but if it can, you could always change the pulse and have it display as if you were going 671mph vs. 67mph. I'd say it is very unlikely it can display anything greater than 1 in that first column even if it can display 3 values.

  8. #8
    good point, however i'm going to assume it can display more than 1 considering you can change it to KM/H and 100 Km/H is like 62 mph.

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by K447 View Post
    What development board are you looking at for $20?

    Are the electrical/signal specs for the factory Yamaha speedo signal input documented somewhere?...
    Can somebody point me at the Yamaha speedo signaling specs?
    The actual electrical voltages from and to the sensor, pulse rates, etc

  10. #10
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    Garmin outputs it's NMEA data in a proprietary form. It's not a big deal, and once you see the file, you'll understand it. I think they just add some zero's somewhere, or there is some other small difference.
    Another thing to consider is the refresh rate, or Hz, of the GPS sampling. I think the E-trex is only 5hz, maybe less.

    I have a gps mount that I screwed to my glove box lid. I can see it there just fine. It's not directly in my line of site, but, you could easily find a handebar mount for the E-trex, and be done with it.

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