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, 

What GPS antenna do you have on your custom board? Can you provide any schematics? Are you outside or inside when testing?

Kind regards,
Øyvind

[phipi]

Hi Øyvind, we're using a yageo patch antenna (ANT1818B00AT1575S), and I've attached the relevant section of the design here.

[phipi]

Some more info about this:

It seems that on reset the GPS fix works every time but eventually gets into this state where it's tracking multiple SVs but not using any. If we reset when it's in that state it will get a fix on boot, but then return to the same fail mode on the next fix which happens several (4~ 6) hours later?

Is it possible that this is related to the modem clock? On boot we get the time from an NTP server (time.nrc.ca) which is the only item that we can identify as different from the fix that happens several hours after boot.

Is there anything we need to do to keep the modem time updated?

[Øyvind]

Are you able to get a modem trace while it is failing to get a fix? This should help our R&D team see what is failing.

[mlang3440]

I'm working on getting a modem trace.. Do you need to see the Log output as well?

[Øyvind]

Yes, please. 

Where are you conducting your tests? Where is the GPS receiver when you are tracking the satellites?

[Hucky]

Is there any news on this issue? I do see the same issue with tracking several SVs but not using any of them on my Thingy 91 occasionally happening too.

[RicardoPereira]

Hi Hucky, 

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