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

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740b USB wiring for NMEA output?

1/4/2020 3:33 PM

Russell Duffy

Joined: 6/27/2018

Posts: 34

Re: 740b USB wiring for NMEA output?

Thanks. I should be good to go.

1/4/2020 9:37 PM

greg p

Joined: 2/18/2011

Posts: 237

Re: 740b USB wiring for NMEA output?

I have used just that for autopilot interface. Works perfectly.

1/4/2020 11:01 PM

Russell Duffy

Joined: 6/27/2018

Posts: 34

Re: 740b USB wiring for NMEA output?

It's really great that the NMEA out is configurable, because the darned Artex ETL 345 is so limited. By default, it only accepts the Garmin proprietary protocol, but there is another option available if you send the unit back for reprogramming. That option is basic NMEA 4800 baud. Hopefully they did indeed send the unit back with the right formatting, and hopefully I can get it to pass the selftest.

1/9/2020 11:42 AM

Walter

Joined: 7/8/2009

Posts: 2778

Re: 740b USB wiring for NMEA output?

Russell Duffy wrote:

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

Sorry for the delay responding, but as you figured out this is an active cable. A few different chipsets are supported, but not every version of every USB-to-Serial cable out there is going to work - but sounds like yours is good to go.

-Walter

Walter Boyd
President, Adventure Pilot

1/9/2020 11:54 AM

Russell Duffy

Joined: 6/27/2018

Posts: 34

Re: 740b USB wiring for NMEA output?

Thanks Walter. I just tested it all yesterday afternoon, and the Artex ELT is finally happy. I may still try to find a standalone GPS to feed it, but for now this works dandy.

Rusty

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740b USB wiring for NMEA output?

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