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  #11  
Old 03-15-2017, 08:47 AM
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snopercod snopercod is offline
 
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Default Design Notes on TIA/EIA-232-F Protocol

If anyone is interested in the details of the protocol, here are the Design Notes from Texas Instruments Interface Circuits for TIA/EIAĆ232ĆF. It seems like the data output of the GPS 18X should be between Pin 3 [Transmit Data Line] and Pin 5 [Signal Ground] of the DB9 connector. All the other pins have to do with handshaking or receive data.
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  #12  
Old 03-15-2017, 09:04 AM
rv7charlie rv7charlie is offline
 
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And there are dozens of other serial output GPS modules that will do the same thing, often for <$20.
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  #13  
Old 03-15-2017, 11:22 AM
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Default Examples, please?

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Originally Posted by rv7charlie View Post
And there are dozens of other serial output GPS modules that will do the same thing, often for <$20.
Examples, please?
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  #14  
Old 03-15-2017, 12:40 PM
rv7charlie rv7charlie is offline
 
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http://m.ebay.com/sch/i.html?_nkw=Se...sqp=serial+gps

http://m.ebay.com/itm/Open-Hardware-...257Ciid%253A22

http://m.ebay.com/itm/SyChip-GPS-Rec...%257Ciid%253A9

Just search for 'serial gps' or 'gps serial output'.
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  #15  
Old 03-15-2017, 01:12 PM
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Quote:
Originally Posted by rv7charlie View Post
And there are dozens of other serial output GPS modules that will do the same thing, often for <$20.
When I built my RV-7, I used one of these cheap GPS receivers as a second GPS input. One day I was flying along and all of my GPS's failed - I wasn't receiving any GPS serial data on the cheap GPS receiver, and my Garmin 430W was reporting it couldn't lock onto any satellites, along with my iPad mini couldn't get a valid GPS position.

It turns out my cheap GPS failed in a way that it jammed all of the other GPS receivers on my airplane. Since I didn't have a switched power source to that GPS, I couldn't shut it off.

I decided to spend the good money for a Garmin 18X OEM LVC receiver. It has worked flawlessly since I installed it in 2013. I'm not trying to say the Garmin 18x doesn't have the potential of failing the same way the cheap GPS receiver did, but my money is on the Garmin GPS receiver definitely being higher quality and less likely.

Full writeup:
http://rvplane.com/?categoryid=10000&dayid=1112
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  #16  
Old 03-15-2017, 02:27 PM
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Default Nice writeup

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It turns out my cheap GPS failed in a way that it jammed all of the other GPS receivers on my airplane.
That's good to know. Thanks for the information and the excellent writeup.
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  #17  
Old 03-15-2017, 02:34 PM
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snopercod snopercod is offline
 
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Quote:
Originally Posted by rv7charlie View Post
Just search for 'serial gps' or 'gps serial output'.
Thanks, Charlie. Man, they really are cheap, aren't they. I'm thinking that for the price difference, I'll probably go with the Garmin 18X, though. I trust Garmin not to let me down if I'm crashed out in the mountains somewhere.

Do I have this right that if your ELT is connected to a GPS, it pings the satellites every so often so the rescue folks can predict where you will be?
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  #18  
Old 03-15-2017, 02:59 PM
jwyatt jwyatt is offline
 
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Quote:
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Do I have this right that if your ELT is connected to a GPS, it pings the satellites every so often so the rescue folks can predict where you will be?
My understanding of it is, no. The ELT is processing each position received and storing it in it's memory. When your ELT goes off, it uses the last GPS position it received to transmit to the sats with the distress signal. I believe I've read that the stored GPS position is considered valid for only a certain number of seconds (and not transmitted if it's expired), but I can't find documentation to back that up now.

Quote:
Originally Posted by ACK E-04 FAQ
How does the ACK E-04 handle the GPS data input?
The E-04 receives the data input from your GPS once per second. The ELT uses the last data received from your GPS as its location when the ELT is activated either manually or by the crash sensor.
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Last edited by jwyatt : 03-15-2017 at 03:07 PM.
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