No GPS fix on

[SP]

Hi,

I made 20 x prototypes with a nRF9160 SICA B1 (Modem FW 1.3.4) and I use the SDK nRF Connect version 2.2.0.

On few boards, I can't get satellites fixed after 5 x minutes of searching and you can see below the last trace that I received :

PRN:16 | C/N0:40.9 | In Fix:0
PRN:18 | C/N0:42.5 | In Fix:0
PRN:26 | C/N0:39.4 | In Fix:0
PRN:5 | C/N0:30.6 | In Fix:0
PRN:2 | C/N0:24.4 | In Fix:0
PRN:29 | C/N0:31.7 | In Fix:0

Signals seems good for PRN 16, 18, 26 and 5 (> 30db/Hz).

The matching was done on this prototypes and many of this works perfectly (they can get GPS fix after 1 x minute).

I don't undestand why some samples doesn't get GPS fix !

I added this code on the search_start() function to reduce accuracy : 

uint8_t use_case = NRF_MODEM_GNSS_USE_CASE_MULTIPLE_HOT_START;
        use_case |= NRF_MODEM_GNSS_USE_CASE_SCHED_DOWNLOAD_DISABLE;
        use_case |= NRF_MODEM_GNSS_USE_CASE_LOW_ACCURACY;
	err = nrf_modem_gnss_use_case_set(use_case);
	if (err) {
		LOG_WRN("Failed to set GNSS use case, error: %d", err);
		return;
	}

Do you have aby idea about this issue ?

Can you confirm me whether the code above reduce accuracy ?

Thanks in advance

[Turbo J]

Try waiting for 30 minutes.

Download of the GPS Almanac can take >15 minutes when using GPS only.

[SP]

Thanks for your reply.

Almanac are already downloaded by assistance minimal at the start of application.

after 10 x minutes of GPS searching, here the last log : 

PRN:7 | C/N0:42.0 | In Fix:0
PRN:27 | C/N0:40.8 | In Fix:0
PRN:10 | C/N0:35.5 | In Fix:0
PRN:18 | C/N0:32.6 | In Fix:0
PRN:8 | C/N0:39.5 | In Fix:0
PRN:26 | C/N0:24.6 | In Fix:0
PRN:21 | C/N0:26.2 | In Fix:0
PRN:3 | C/N0:24.6 | In Fix:0

It's the same thing !

[Charlie]

Hi Stephane,

Your reduce accuracy setting looks like no problem.

The issue you mentioned sounds more hardware related.

1) Did you try to switch GPS antenna of good and problem samples?

2) Did you request hardware design be reviewed for your hardware design before? 

3) Have you soldered all the prototype samples by yourself or at the factory?

Best regards,

Charlie 

[SP]

Hi Charlie,

Thanks for your reply.

1) I can't do this beacause antenna are soldered.

2) No. But Antennova have defined the matching (compoment arround the GPS antenna) in their labo

3) No, all prototypes only by the factory

This morning I decided to use SUPL library to assist GPS and now all prototypes works and they can get GPS fix after 15 seconds.

SUPL it's magic !

  

[Charlie]

Hi Stephane,

Great! Thanks for your update!

I encourage you to switch to the nRF Location service instead of using SUPL. nRF Cloud A-GPS has some advantages compared with the SUPL library.

Best regards,

Charlie