Cant get on-board GPS to get a fix

deepsouth · August 21, 2019, 9:40am

I have successfully installed Navio2 on RPI3+
Everything passed test in emlidtool.
All python examples seem to work.

However the GPS.py does not appear to get a fix with the onboard antenna after hours of trying. It is on a window sil where I have has many GPS locks from separate Ublox CAM-M8C hardware - or my mobile phone for that matter!, but not the Navio2 Ublox NEO-M8N. For me an external antenna is not an option as it has to fit in a cramped water tight ROV enclosure.

Sure it might work if I take it to an empty field (or sea in my case), but I was expecting the GPS fix to be obtained easier than that…I don’t want to have to take it to sea to work on my application using the GPS

Any ideas welcome!

gleb.gira · August 23, 2019, 5:57pm

Hi @deepsouth,

Could you please try to test your setup outdoors? To have a 3D fix you need at least 4 satellites. What number is displayed in GCS?

Some external devices near Navio2 may cause interference. Photos of your hardware configuration can give us more information to analyze.

deepsouth · August 24, 2019, 10:49am

Thanks @gleb.gira

It’s basic setup - Navio2 sitting on RPI 3B+ with no other infrastructure or external servos or sensors attached at this stage.

I have not connected GCS as I was not planning on using it. I am just SSHing and using Python on the RPI

I will provide photos and test in the open shortly.

deepsouth · August 25, 2019, 7:54am

Hi @gleb.gira

I went to the top of a local lookout with 360 degree views. I placed the Navio2 / Raspberry PI on the roof of the car on a rubber mat.

The setup was very vanilla with the power coming from the USB on the Raspberry PI and the Ethernet connection hardwired to a WiFi router in the car for connection to my mobile phone.

The following video demonstrates the following. Apologies for the various changes in mobile phone orientation.

There were plenty of satellites in the sky - my mobile phone found 4 or more good quality satellites in under 30 seconds
The EMLID software is installed and the emlidtool passed all interfaces including GPS
Navigating to the Navio2 example folder and running GPS.py results in no GPS connection - after hours of trying.

It appears more difficult because the Navio2 board does not provide an LED when GPS lock is obtained. The options to me appear to be:

I have a configuration issue - that would be a great result and easy to fix
I try alternative GPS libraries to see if I get the same results
I return the Navio2 card with the faulty GPS

Feedback welcome…

mlebret · August 25, 2019, 3:23pm

With a GPS antenna, it is better…

Something is missing here:

deepsouth · August 25, 2019, 7:26pm

Thanks Marc

Unfortunately for my application (underwater sub) it’s too bulky and my experience suggests it should not be required. I am trying to map the sub on the surface, in terms of where it dives and surfaces.

I have previously used an OzzMaker GPS/IMU card which worked great. I bought Navio2 for the integrated sensors plus PWM control.

mlebret · August 26, 2019, 5:48am

Antenna is integrated on the OzzMaker GPS chip. External antenna is an option.

There is no integrated antenna on the Navio2 M8N chip. External GPS antenna is mandatory.

deepsouth · August 26, 2019, 5:59am

Thanks Marc

That explains a lot.

Can you suggest any micro external antenna options? Potentially something that just sits on the antenna MCX connector?

gleb.gira · September 5, 2019, 3:52pm

Hi @deepsouth,

We never tested such antennas, so I can’t recommend specific models. I suppose that any external antenna with MCX connector should work on Navio2.

It would be interesting to see the final results, so keep us updated!

vitalie_cartera · September 11, 2019, 6:36am

You can always ditch the bulky plastic case. The actual antenna is much smaller. Be careful to not overdo it though.
You may also shorten the cable if you have some basic soldering skills.
If you decide to stick the antenna on top of Navio2, make sure you add a ground plane under it to get rid of RF interference.

Keep us posted on your progress. Good luck!