NEO-6M external GPS & on board GPS assistance needed :)

Hello Emlid Community!

I have much love for the NAVIO+, i am running chdkptp over 2.4ghz to control some custom mapping rigs for a real time mapping app, via a 550 hex, sooo good :slight_smile: sorry had to get that out of the way

I am trying to setup an NEO-6M with my Navio+/RP2. I have the pin out correct on UART and i2c. I read through the docs and saw that I need to use startup option -B to initiate an external mag/gps, How is this done? Do I need to call a specific port or path as with option -A or -C? If so, could someone provide an example? Is there anything I need to do in the APM params? or driver/firmware?

So far the only test I did was to connect the 6M via UART and i2c, disconnected the on board GPS antenna and initiate APM, I was left with a blinking blue light and 100 HDOP.

I am trying this because I have been having problems with my on board GPS, Everything was golden for dozens of flights, acquisition outside was immediate, I was getting 1.2hdop inside my house when testing, unheard of! Then it started taking longer to acquire signal but still would with some fiddling, now the on board GPS is just not getting a fix at all. I am waiting for an alternate antenna to see if this is the problem.

Any ideas or suggestions on either of these two topics would be greatly appreciated :slight_smile:


The external mag should be autodetected.
The UART on the Navio+ is /dev/ttyAMA0,
-B /dev/ttyAMA0
With option -B the external GPS is used as the only GPS.
You could also use option -E to use both GPSs.
-E /dev/ttyAMA0

You have to enable the second GPS in the Ardupilot config with Missionplanner/APMplanner.

It is very interesting to read your discription, about your GPS problem.
I have a original Navio and a Navio+.
The Navios GPS is working fine.
With the Navio+, I had GNSS fixes with 16 sats and a hdop of 0,5 during the first flights.
Then the copter would not go into loiter/rtl/poshold
anymore and I noticed it did not get a fix, even after 30min outside. I got a new antenna from emlid, because the cable seemed to be broken at the connector. It then sometimes got a fix, but not reliable, with wildly changing number of sats and hdop.
I then got a new Navio+.
Indoor test with u-center was fine, outside with APMcopter too, but only 9 sats, second battery, no fix at all.
Indoors with u-center would not work either.
Now I put the Navio+ in my AntennaTracker with an external GPS.
The GPS was working fine with numerous flightcontrollers over the years.
It was also working fine with an APM 2.5 in the tracker.
Now it suddenly gets no fix, too.
I have the same GPS on my copter and a 3dr GPS on a plane. Both get a fix after a few seconds, but the trackers GPS does not. All placed on my workbench, running at the same time.
Is the Navio+ somehow misconfiguring the GPSs?
Why is it working at first, then suddenly nothing?

Just finished to put the APM2.5 in the tracker again.
GPS fix after a few seconds, indoors 3m away from the windows, sky completly overcast.
Something is seriously wrong with Navio+ and GPS, I think.
I hope it is only software related…

@aquila and @schuermannsebastian

I think that we got to test your boards ourselves. I will be in touch to arrange it.

Thank you for the clarificarion on “-B”. I will go test that now.

The navio+ is in your tracker? That is the last place you need processing power, these autopilot need to be in the sky where they can I’ve up to there full potential! Sorry to hear that.

Our problems/issues definitely seem to have similar characteristics. Very interesting. Sorry to hear you are having issues but I’m glad I’m not the only one!

Thanks for the assistance I eagerly await your response.

A little more info regarding the on board gps:
I extracted the provided gps antenna out of the plastic casing to see if there was a solder joint that was causing the satellite acquisition issue, I removed the ground plate and inspected the antenna, board, solder joints, all looked fine. I re soldered the cable to the antenna just in case. No change in behavior. If the antenna is bust I can’t tell where, it looks fine. The only place that might be causing issue is where the antenna cable is soldered to the MCX connector, I can’t see this joint.

If there are any tests you would like me to conduct and document I am happy to do so, just let me know.


It was in my quadcopter first and I have a rover with a Navio (not +). I had problems with the rover, too, but was able to solve them. After countless numbers of flights that I could not do, because of the Navio+ acting up, I decided to put the Navio+ where it could not fall out off the sky, but now the tracker is controlled by an APM2.5 again, GPS lock and all.