740b USB wiring for NMEA output? - iFly Owners Q&A

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740b USB wiring for NMEA output?

1/3/2020 8:52 PM

Russell Duffy

Joined: 6/27/2018

Posts: 34

740b USB wiring for NMEA output?

Greetings,

I had a forced change of plans for my GPS input to the Artex ELT, and now it seems I'm going to need to use the NMEA output from the 740b for the ELT input. Is the USB-serial interface that is sold for the unit an active device, or just a cable? My plan was to just use a USB cable and hardwire it to the ELT, but I don't see how that could ever be quite right, unless the 740b can output 5V instead of the normal +-3.3 that USB uses. USB would have 5V, gnd, data+, and data-. Using data+ and ground would give 0 to +3.3, when NMEA is typically 0 - 5. Using data+ and data- would give -3.3 - +3.3. I suppose it's possible that the cable is an active device, and shifts the 3.3v level of data+ to 5V. Anyone know for sure?

Thanks,

Rusty

1/3/2020 10:09 PM

Cobra

Joined: 4/20/2011

Posts: 2602

Re: 740b USB wiring for NMEA output?

Hopefully Walter or another iFly guy will be along shortly with a definitive answer for you on whether the cable is active or passive, but for what it's worth the cable they sell is intended for use in feeding NMEA output to devices that need it. For example: https://www.iflygps.com/Support/Forum...ope/posts#39004. Also, others have used this capability to feed the necessary data to their ELT: https://www.iflygps.com/Support/Forum...ope/posts#24665.

1/4/2020 6:22 AM

Michael Roselli

Joined: 2/25/2017

Posts: 8

Re: 740b USB wiring for NMEA output?

Data only is passed through

1/4/2020 9:11 AM

Russell Duffy

Joined: 6/27/2018

Posts: 34

Re: 740b USB wiring for NMEA output? Modified By Russell Duffy on 1/4/2020 9:53:43 AM

For some reason, I was thinking the USB to serial cable was something special that iFly put together. It actually just dawned on me (duh) that it's probably just a standard USB to serial cable like you'd get anywhere. That will of course mean that it is an active device. I probably have a couple laying around, so I'll try that first and see if the ELT is happy with it.

Thanks,

Rusty

1/4/2020 1:45 PM

Michael Roselli

Joined: 2/25/2017

Posts: 8

Re: 740b USB wiring for NMEA output?

You will need a USB 2.0 to RS232 DB9 Serial Cable Male A Converter Adapter with PL2303 Chipset

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740b USB wiring for NMEA output?

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