What is NMEA Output via USB? - iFly General Discussions

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HomeHomeDiscussionsDiscussionsiFly General Di...iFly General Di...What is NMEA Output via USB?What is NMEA Output via USB?
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2/5/2014 10:47 AM
 
That term was mentioned in the wishlists discussion about possible comparision table for the Ipad/Android vs dedicated iFly.

Pardon my ignorance, but can someone tell me, preferably in 100 words or less ;-) , what that is, and exactly why/when as an iFly 720 user I might want to know about or use it? Is NMEA Output via USB a feature of the 720?

I see some discussions here that seem to be about getting it to work.
Those discussions involved serial port pinouts.
Coming from the early days of PC support when I/O on PCs heavily used serial ports and multi-hour nightmares of getting that non-standard RS-232 "standard" to work.... when I hear anything involves serial ports or discussions of "what pin" I'm inclined to run the other way ... fast. ;-)

Alex
 
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2/5/2014 11:48 AM
 

Alex,

Yes, NMEA Output is a feature of the iFly 700/720/520. NMEA sentences are used to drive Autopilot, Fuel Flow computer or even a GPS based ELT or feed the GPS data into an EFIS.

An iPad has no USB or serial out to support NMEA. Most Androids can support NMEA since they have a USB port.

We use the USB port to send the NMEA data out. Many Autopilots and Avionics still use serial plugs and or RS-232 connections and need pinouts. Therefore we use a USB to Serial cable to convert that signal to be used in an autopilot.

That's just at 100 words, for those who might be counting.


Shane Woodson
Vice President | Adventure Pilot LLC.
 
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12/25/2014 1:08 PM
 

Could you outline how to connect my Ifly to my ACK 406 ELT? The ELT has the basic cable connections to input GPS data but how does it connect to the Ifly?

Thanks

 
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12/26/2014 10:29 AM
 

You'll need our USB to Serial cable. Then connect that to your ELT. Then you can go to setup on the iFly and choose NMEA Output. You should match the Baud Rate to your ELT and then set the sentences to GPRMC and GPRMB. These are the most common, but I'd recommend looking at your ELT in case three are other sentences needed. Feel free to contact us in the office on Monday if needed.


Shane Woodson
Vice President | Adventure Pilot LLC.
 
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1/5/2015 7:06 PM
 
Bearhawk wrote:

Could you outline how to connect my Ifly to my ACK 406 ELT? The ELT has the basic cable connections to input GPS data but how does it connect to the Ifly?

Thanks

Sorry to be a little late to the party, but I'd like to comment on this idea. From what I've seen in SAR reports, the doppler data pinpoints the location of a 406ELT accurately enough that GPS data is frosting on the cake. Said another way, GPS is not too imporant. (info: http://www.sarsat.noaa.gov/sys-diag.html)

Conjecture: If the ELT is receiving GPS data from an outside source (no internal GPS), it is probably going to broadcast the GPS coordinates that it most recently received. "Most recently received" might be when the tablet battery died, when the cable was unplugged either deliberately or accidentally, the tablet was turned off, etc. while the airplane continued to move. In that case, the doppler location will still be accurate but the GPS location being broadcast will be ancient history. To furher gum up the works, the GPS data is reported by the geostationary satellites before the low-earth-orbit satellites are able to develop a doppler position solution. So the first location report could be wrong.

Out of curiosity I just called AFRCC and asked about this. The duty officer had seen only one case where the doppler and the GPS didn't match and had not heard of any where the problem was due to old GPS data in the ELT. So probably this is a highly theoretical issue, but for myself I would not make the NEMA hookup from a tablet to and ELT. Little upside, but possible downside.

(For those who are interested the spec is NEMA 0183. Lots of info on the internet, including here: http://aprs.gids.nl/nmea/)

 
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