NRF9160: GPS Tracking satellites, but can't get fix.

[mlang3440]

Hi, we have a custom board using the nrf9160, running modem firmware 1.1, and using the nrf9160_gps driver.

Sometimes we see messages like this:

Tracking: 8 Using: 0 Unhealthy: 0

Where the GPS is tracking satellites but is not using any, and never gets a fix. Eventually we time-out and stop the GPS. But this behavior continues until the next device is restarted.

Is this a bug with the modem firmware? Is there any fix for this.

Thanks

[Øyvind]

Hello phipi, 

I will move this discussion to the private ticket you have registered, as that is where I will ask questions regarding your code.

To answer your last questions here, I have forwarded your questions to our nRF91 GPS expert, so far the issue leans towards software. 

"The device never needs the almanac to get a fix, it should be able to do a cold start without any prior knowledge of anything whatsoever. The only thing the almanac would do in this case is to further speed up the TTFF by aiding which satellites to search for.

In this case, the device seems to be always able to find the satellites, but using 0 would be an indication that it cannot get the ephemerides and/or TOW downloaded from the satellites.

A log would indeed be helpful here. We can try to recreate the situation, but that will take 6-7 days for things to start happening if I understand correctly.

One way or another this is an SW issue somewhere. Since the device is able to get fixes, the HW seems to be fine. Since it is trying to get a fix every 6 hours, it is always cold starting, and as said, a cold start does not need any prior knowledge of anything.

But somehow the process of synchronization to the satellites seems to get corrupted and never finalized. It is useless to try to speculate here what could go wrong. If we don't get a log from the customer, I will have to forward this for recreation in our own lab. There is a good chance we would find nothing wrong => customer's logs needed anyway."

mlang3440 said:

Tracking: 8 Using: 0 Unhealthy: 0

Have you tested our GPS sample alone? Do you get the same results? Have you tried your project on an nRF9160 DK?

[jwhite]

I am having almost exactly the same issue, but with an out-of-the-box nRF9160DK running the GPS example with NCS v1.2. Since there is no verified answer here, I will present my question here. Here is my setup:

I received a nRF9160DK two weeks ago, and I was able to get it up and running with the Asset tracker firmware, and I was also able to get the GPS example working after flashing it from SES. After about 30-60 seconds, the gps example would get a fix and start printing out the nmea data on the nRF connect link monitor. I was able to get a fix indoors with the patch antenna provided.

But now, when I start up the nRF9160DK running the GPS example, it sits and prints out that it sees anywhere from 6-9 satellites, but it never finds a fix. I have let it sit for hours to no avail. I am not using the SUPL library because I want to run the GPS without LTE active. I've also tried going outside, switching from the onboard antenna to the external antenna, and restarting/re-programming the application. I seem to be stuck in the case that mlang said, but I never get out of it. Is there anything else I can try for this issue?

Here is a screenshot of the link monitor while the GPS example is running:

[Øyvind]

Hello jwhite,

What modem version are you running? Have you tested it outside in the open?

As stated in the nRF9160 DK documentation:
"GPS signals do not usually penetrate ceilings or other structures that well. Therefore, for best GPS performance, the DK should be placed on a flat surface in an open space outside, far from sources of interference and other structures that may block the signals from space."

If you are experiencing more issues, please register a new ticket regarding your issue.

Kind regards,
Øyvind

[RicardoPereira]

Hi, 

I'm having the same issues as jwhite  with my thingy:91.

I can get up to 9 tracking but never get fix. I have the firmware 1.2.0. 

Any ideas ?

Regards, 

[RicardoPereira]

Hi Hucky, 

Did you find the solution ? I'am having the same issue