[zebu]

Hi everybody,

I may have a problem with my OPv9GPS that I recently bought it from a NZ Librepilot member.

I decided to try it with the Revo Nano first.
I plugged everything together (Tx/Rx crossed, main port set to GPS and 57600bauds)

I use a USB battery to power everything from the motor headers on the nano (+5v and gnd) as if it was a BEC.
Everything powers up, the system screen on GCS shows the autoconfigure process of the GPS, everything seems to be recognized.
I didn't put any GPS flight mode for the moment and stayed to "complementary" for attitude estimation.



My problem is that it seems very difficult for the GPS to obtain a fix...

Initially, I put the GPS under the windshield in my car during lunch time to let it retrieving the almanach.
He finally did with 5 sats fix.

Then I came back to the office and tried a new fix from the window.
No fix or very little fix periods.


Yesterday, I decided to give it a try in a wide opened area.

I brought my laptop to keep an eye on the number of sats in view and sats used.

After 3 min, no sats used and 5 sats in view only... (see attachment)

After about 5-7 min, still no sat used and 8 sats in view (see attachment)

After maybe 40min the blue light was blinking on the GPS but still no fix and no sats used on the GCS !!
I noticed that the GPS time seemed to be frozen on the GCS so I decided to power down everything and cycle boot the laptop.
(see attachment)

Then I decided to do a new setup vehicle wizard to see if something was not properly setup.
I go through the wizard, upgraded the board, OP v9 GPS, etc..

After that I waited for another 20min approximatively
I still didn't obtained a fix (see attachment) but had 16 Sats in view.

Maybe the last blue light fix permitted to retrive the almanach ?

I hadn't any time left to try it longer so I got back home.


Do you guys encountered similar behavior ?
Could it be so long to obtain fix with the OP Platinum GPS v9 ?

Did I miss something ?
Could the GPS be factory resetted ?

Thanks

Update: added video of the blue light on gps but no fix on GCS.

[hwh]

Even the first time it shouldn't take more than 20 minutes to get a fix.

The blue light is almost meaningless, it doesn't really mean what most people think.   It's actually named TIMEPULSE and commonly called PPS (pulse per second) because the frequency defaults to 1 PPS.  All it means is that the gps can see one satellite well enough to read the time.  It doesn't mean it has a fix.

It's possible the gps was configured in some way that's incompatible with your area, I'm not sure what settings someone in NZ would find better than the defaults.  You can reset it to the defaults by following the procedure in the wiki for gps on cc3d.  Use the gps only connector on the V9 instead of the gps+mcu one.  Just stop after the reset to defaults step. https://librepilot.atlassian.net/wiki/display/LPDOC/Configure+a+GPS+for+CC3D

[zebu]

Thanks for the advice.

I was wondering if the GPS only port was UART capable like any other ublox.
You perfectly answered.

I will give it a try and let you know.

[zebu]

Hello.

I did what you told, plugged through gps port and loaded default configuration.

Then I obtained a first fix,  at lunch time, by a window and let it during 2-3 hours for the GPS to build its almanach.

The fix was obtained by a window with about 3-4 gps only.

So I decided to give it a try in an open area at the evening.

I obtained a fix in maybe 1 min or so.

Just a thing, it only got 5 sats fix, no more.
It was a little cloudy.
Does the weather can explain that or do I have to do another test by a sunny day?

HDOP was around 1,2.

[TheOtherCliff]

Do you have any transmitters close by the GPS?  Badly installed FPV transmitters can reduce the satellite count.
GPS must be mounted with the board down and slightly smaller square thing up.
Is there anything over the GPS like carbon frame?
Even back in LP 15.09, the default AutoBaudAndConfigure will add all the settings needed for normal operation.  In the event that it has some modes that need to be removed, the easiest way to do a complete factory reset is to configure it to do AutoBaudConfigureAndStore.  After running this once, put it back to the default.  I don't expect that this will help your issue though.  You either have a bad GPS or bad installation. 

[zebu]

Hi TheOtherCliff,

I had nothing else but the GPS during these test.
No frame, no carbon, no metal, no transmitter, no phone.

Just the OPv9 GPS at the end of the usb cable and the 5v power battery.
I consider that the setup is "good" under these conditions 

I bought the GPS from à LP member.
The GPS was claimed to be working well on the frame it was.

What could be dead on the GPS, causing this bad reception issue ?
Anything I can check ?

Thanks

[f5soh]

Try to apply basic settings, no Sbas and only GPS.
Save using the HDD icon and red arrow.

This need a powered GPS at same time, of course.

[zebu]

Hi,

I'll give it a try, thanks.

What's Sbas ? (did you mean Sbus ?)

[f5soh]

No typo, SBAS sat
In Europe refers to EGNOS sats.

Change the settings highlighted in green

[TheOtherCliff]

One other issue is that GPS's don't work well indoors.  I didn't see you say indoors or out.  Try it outdoors.

[zebu]

Try to apply basic settings, no Sbas and only GPS.
Save using the HDD icon and red arrow.

This need a powered GPS at same time, of course.

Hello,

I tried these settings, without success unfortunately...

==> TheOtherCliff : I'm always outdoors when I test hardware

I really think that my unit is defective.

To compare, I have a simple Neo-6M from Drotek lying around on a small fpv test platform (Camera, 5.8GhZ Vtx, 5v BEC, NEO-6M GPS) all side by side together on a carboard plate.

I tried the neo-6M by the window, he got a 5 sat 3d fix in about 1min 30s or so.

I then tried the OP GPS at the same place, after 58 min, still no lock.

What could be defective on it ?
Lna ? SAW Filter ? (how to bypass them in order to find out if they are faulty ?)

I see nothing on the antenna side, it seems to be ok.

I may try with Helix antenna, but how to remove/bypass the ceramic antenna ?

Thanks

[hwh]

...Lna ? SAW Filter ? (how to bypass them in order to find out if they are faulty ?)...

Bypassing them would be the same as I posted for the Naza GPS in post https://forum.librepilot.org/index.php?topic=449.msg13007#msg13007

The layout is a little different but shorting the same module pin to the antenna center pin would work.

Removing the patch antenna is just a matter of unsoldering the center pin.  It's then held on by double sided tape and you can carefully slide something thin between the antenna and pcb being careful to not damage any traces on the back of the board.

[zebu]

HEre are some pictures of the OP GPS and my test platform that I used for comparison.

The stains on the antenna are juste tape glue traces.

[f5soh]

Did you try connecting directly to the GPS port ?
Maybe try to revert ublox chip to factory settings.

I experienced the same with one GPS v9 receiving small amount of sats and worked again as expected for some reason.

[zebu]

Did you try connecting directly to the GPS port ?
Maybe try to revert ublox chip to factory settings.

I experienced the same with one GPS v9 receiving small amount of sats and worked again as expected for some reason.

Hi,

Yes, done this on message #3 of this post.

Maybe I haven't done well the default conf reset.
Do you have a precise method ?

Last time I tried to connect it through GPS port with FTDI and Ublox center, It showed a fix with 5 sats max, but the reception widget was showing a reception by "pulses"... (reception of GPS pulse every second or so, and nothing between...)

Maybe I'll give it another try and I will try to capture a video if this behavior shows up.