In Location sample code, GNSS not fixed in good sensitive

[DannisWong]

Dear Sir/Madam

I develop a project base on nrf9160 sample code "Location", but found that sometime GNSS cannot fixed, I try to read the debug messages and found that satellites tracking result is good, but location not fixed, attached the log file for your reference.

the point is this not always happened but make GNSS not fixed sometimes.....

8249.txt

[dejans]

Hi,

Which board, NCS version, and modem firmware version do you use?

Best regards,
Dejan

[DannisWong]

Its our custom make PCBA, SDK with v2.2.0 and modem firmware version in 1.3.4

[dejans]

Hi,

There is nRF Cloud A-GPS request which fail. 

<err> location: nRF Cloud A-GPS request failed, error: -77

To use nRF Cloud A-GNSS data, you would need nRF Cloud account and device which is associated to that account as described in nRF Cloud A-GNSS note.
You can have a look at the note in sample requirements which requires that you have signing key installed and registered with nRF Cloud. Additionally, there are python utilities for working with modem fw v1.3 and generating key pairs and credentials. 

In general, the main problem might be that there is not enough time to get a GPS fix due to LTE stack being active. To get enough time for a fix, you would need to enable PSM or eDRX mode. You can have a look at LTE link control library. Another way would be to deactivate LTE without shutting down GNSS services by using command AT+CFUN=20.

Best regards,
Dejan