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

[Jan Tore Guggedal]

Hei Ricardo (and others having the same issues of seeing many satellites tracked, but no fix),

There's a PR that can help us debug this issue a bit without capturing modem traces: https://github.com/nrfconnect/sdk-nrf/pull/2385

This PR introduces NMEA-only output to the GPS sample (found in samples/nrf9160/gps/), which might help us narrow down what's going on.
Until the PR is merged into NCS, you can experiment with it by using git and pull in the changes like this (assuming your NCS git remote is named "ncs", otherwise change it to your remote's name):

git fetch ncs refs/pull/2385/head
git checkout FETCH_HEAD (add " - b <branch_name>" if you want it on a branch)
west update

Now you have a new option in the GPS sample Kconfig. You can enable it by setting CONFIG_GPS_SAMPLE_NMEA_ONLY=y (note that it's default "n" /disabled  at the bottom line of the sample's prj.conf). After setting the option, you can build and flash using the tool you prefer.
I'm attaching hex files for nRF9160 DK and Thingy:91:
gps_sample_nmea_nrf91dk.hex
gps_sample_nmea_thingy91.hex

In the log output, you'll see NMEA strings only.

You can share this log with us, and will see if we can see what's going on. Note that you can create a private ticket and share the files there if you prefer.

In some cases, we'll also need modem traces to know exactly what's going on.

Best regards,

Jan Tore

[jwhite]

RicardoPereira I was having this issue indoors, using a large passive GPS antenna. I moved my nrf9160dk closer to my window and it was able to get a fix only using 5 satellites within 45 seconds. I never got an answer as to why a fix could not be found using 9 satellites, and I could not find a forum post that digs farther into this issue.

[LordLucan]

I too have hit this trough of tracking a number of satellites but never getting a fix. The GPS was working reasonably well. All of a sudden since yesterday it just cannot get a fix. My nrf9160_pca10090 is sitting in an open space outside on the grass. It is tracking about 12 satellites, using 0, it has been like this for about an hour. I'm just using the GPS sample. I'm using the external active GPS antenna supplied. Firmware version 1.2.

There are a number of threads on this forum with similar issues of the GPS just not being able to fix despite tracking a number of satellites. Is Nordic invetigating this issue or suggesting a workaround to reset the modem?

Regards,

Paul

[gscultho]

I was facing the same issues reported in this thread and have reported my solution at the following link:https://devzone.nordicsemi.com/f/nordic-q-a/63591/nrf9160dk-gps-not-getting-fix

For anyone facing the issue of tracking many SVs but not getting a fix, I suggest reverting to an old modem firmware version. In my case (hardware version 0.9.0) modem firmware version v1.1.1 resolved the issue.