nRF9151 no GPS fix

RE: nRF9151 no GPS fix

JONATHAN LL — Mon, 13 Jan 2025 10:19:23 GMT

[quote user="Urmaz"]I got it working. Thank you for your help![/quote]

Great!

[quote user="Urmaz"]if the documentation mentioned somewhere which cn0 values indicate good reception and that the modem can also show ghost(/noise) satellites.[/quote]

Will bring it up internally and and maybe we are able to update some docs or if we can get that info through some other way. Thanks for the feedback.

But C/N0 (cn0) values it is generally considered that you should have 30dB-Hz or higher to get tracking. As you can see you get around 20 to 25 and that will not be sufficient.

[quote user="Urmaz"]As I have read, first fix sometimes needs 15 minutes to get.[/quote]

Where in the docs did you see 15 minutes?

Cold start can result in a slow time to fix, but should be 30.5sec or better, hot fix should yield 1.3 sec in best cases on average.
See docs : https://docs.nordicsemi.com/bundle/ps_nrf9151/page/gps.html#ariaid-title2

[quote user="Urmaz"]I can share full schematic and PCB drawings in private conversation[/quote]

We do full reviews, just create a private ticket and we will review schematic and layout for future projects.

Regards,
Jonathan

RE: nRF9151 no GPS fix

Urmaz — Sat, 11 Jan 2025 15:29:47 GMT

I got it working. Thank you for your help!

Issue was with GPS antenna tuning circuitry. On schematics are L and C, that are NC, but on PCB were real LC, for wrong frequency. As modem saw 12 sat, I didn't dig in right place. It would be useful if the documentation mentioned somewhere which cn0 values indicate good reception and that the modem can also show ghost(/noise) satellites.

RE: nRF9151 no GPS fix

Urmaz — Fri, 10 Jan 2025 15:02:00 GMT

I can share full schematic and PCB drawings in private conversation. Is it normal, that nrf9151 shows "false satellites" for 10 seconds? Why it don't aquire those more time? As I have read, first fix sometimes needs 15 minutes to get. I haven't seen this kind of behavior with Thingy91 or 9160.

RE: nRF9151 no GPS fix

Urmaz — Fri, 10 Jan 2025 14:56:23 GMT

Sorry, as you asked for part of schematic, I missed part of it.

RE: nRF9151 no GPS fix

JONATHAN LL — Fri, 10 Jan 2025 13:22:47 GMT

Comments to the schematic:
From the parts that you have shared it looks like a few of our recommended components are missing for the nRF9151.

For the VDD you should have the extra components for filtering of the power rail. It is needed for the device to preform as expected an laving them out will impact RF and GNSS performance.

For the nPM1300 we also recommend to have a few extra components on the VOUT1 for filtering power noise.

See the nRF9151DK or the Thingy91X as reference: https://nsscprodmedia.blob.core.windows.net/prod/software-and-other-downloads/dev-kits/thingy91-x/hardware-files/pca20065-thingy91-x-1_0_0.zip

In both logs there's a jump in the number of acquired/tracked satellites after 2 minutes, which you also described above. This is caused by GNSS switching the acquisition mode. Those ~12 satellites which are shown for less than 10 seconds are not real satellites, but just noise.

Regards,
Jonathan

RE: nRF9151 no GPS fix

Urmaz — Thu, 09 Jan 2025 19:05:39 GMT

I tried in different location, open space. Same result. Logs are taken in two places 20km apart, and taken in placesdevzone.nordicsemi.com/.../termlog1.log, where nrf9160 got fix easyly

In case with ID: 252841 seems similar problem with nrf9160 and there is mentioned: ". I have seen similar issues reported in devzone, but with no public definitive answer provided. Does Nordic have a solution for this problem or any explanation as to why it is occurring? "

devzone.nordicsemi.com/.../7167.Schematic.pdf devzone.nordicsemi.com/.../termlog.log

RE: nRF9151 no GPS fix

JONATHAN LL — Tue, 07 Jan 2025 06:20:09 GMT

[quote user="Urmaz"]Didn't mention it, but my board is powered by nPM1300, and I tried different Vdd voltages on GPIOs and LNA. All same. [/quote]

Can you share the schematic of the nPM1300 and nRF9151 for your design?

[quote user="Urmaz"]No, I didn't test in different location, can try tomorrow. I can't imagine, how it explains this pattern. When I move board inside a house, it finds less (...9) sat instead of 12, but this 2:10 and 6...7sek active pattern don't change.[/quote]

The GPS signal could be better. Could the you provide a log with the GNSS sample without A-GNSS, which shows the whole test run from boot? And make sure the LNA is enabled.

Regards,
Jonathan

RE: nRF9151 no GPS fix

Urmaz — Mon, 06 Jan 2025 22:16:05 GMT

Yes, the 9160 was also custom board, same peripherials, same functions. Made 5 boards, all working ok. Now made upgrade to 9151, but stuck with GPS problem.
No, I didn't test in different location, can try tomorrow. I can't imagine, how it explains this pattern. When I move board inside a house, it finds less (...9) sat instead of 12, but this 2:10 and 6...7sek active pattern don't change.
I don't have 9151DK.
Didn't mention it, but my board is powered by nPM1300, and I tried different Vdd voltages on GPIOs and LNA. All same.

RE: nRF9151 no GPS fix

JONATHAN LL — Mon, 06 Jan 2025 20:48:43 GMT

Antenna selection is ok, and I am not aware of any issues in the location so not sure what is the issue, but I will continue digging to see if there is anything.

You say that things work on the 9160, is that also a custom board? I assume that this is the case so I also assume that the 9151 HW is ok.

It does sound strange that you experience the same pattern of seeing 12 satellites after a given time, have you tested in more then one location?

and do you have the option to test on a 9151DK ?

Regards,
Jonathan

RE: nRF9151 no GPS fix

Urmaz — Mon, 06 Jan 2025 09:06:50 GMT

Estonia.

Telia network

RE: nRF9151 no GPS fix

JONATHAN LL — Mon, 06 Jan 2025 08:52:16 GMT

Where in the world are you testing?

RE: nRF9151 no GPS fix

Urmaz — Mon, 06 Jan 2025 07:44:11 GMT

Not reviewed.
Antenna is DSGP.1575.18.4.A.02.

RE: nRF9151 no GPS fix

JONATHAN LL — Mon, 06 Jan 2025 06:17:03 GMT

Hi,

Have you had the custom board reviewed by us?

What antenna are you using?

Regards,
Jonathan