Unsatisfactory GPS reception on PinePhone?
(12-12-2020, 10:04 PM)spartacus Wrote: I have been struggling with gps satellite acquistion for the past couple of months.  I got my first location earlier today.  I put my pinephone outside, ssh'd from a laptop, and watched the progress using gpsmon.  Took about 30 minutes before it began tracking a satellite.  Took 90 minutes to lock 4 satellites and report a location. 

Good to hear I'm not the only one having trouble (sort-of). Sad

(12-13-2020, 10:04 AM)wibble Wrote: @calinb The factory test image that came on my Breave Heart had no specific GPS test that I remember. I don't know what diagnostics they're providing with more recent models. It would be difficult to test in a factory without something transmitting a fake GPS signal, so it may not have a specific test.

I used an old Garmin Geko 201 as a cold fix reference before starting on the AGPS stuff. With the Brave Heart I was seeing sats in GPGSV messages even when I didn't have a fix, similar to the Garmin's sat view before fix. If you're seeing nothing in situations where the Garmin can get a fix then something's wrong. Have you tried accessing the modem control interface with a terminal (picocom or similar) when ModemManager is stopped? That may show error messages that aren't present in the NMEA feed - assuming the Quectel interface passes them on via AT messages. Beyond that you might have to go digging in libqmi to find out if there are any lower level GPS diagnostics from the Qualcom interface.

The other more invasive thing to check is the physical antenna connection. I think the GPS antenna is one of the printed ones on the inner frame, with spring contacts to the main board. It's not something I've looked into, so I can't give you more detailed pointers other than looking in the wiki for the mainboard swap instructions for inner frame removal.

I looked at the list of test coverage in Martijn's test too:[url=https://gitlab.com/MartijnBraam][/url]  https://gitlab.com/MartijnBraam/factoryt...README.rst

It doesn't look like there's anything there that will help diagnose the problem. I get up to four $GPGSV lines of sats using mmcli, but only when I use AGPS. However, none of them indicate a signal (commas appear in all SNR fields), except yesterday I did briefly get three sats with a SNR entry, but all SNRs were around 20 or less and I never got a fix.

Despite my other Moto Android phones and cheap 10+ year old Garmin GPS working here at home, I never get any SNR on my Pinephone at home.  I live on a southern canyon wall so I drove to some very flat farmland nearby with no obstructions of the sky within sight. I got a 4G mobile signal and data too (no cell service at home), so I could "seed" with AGPS data. I spent about an hour waiting for a fix with the Pinephone tucked up under the windshield toward the southern sky and I also spent time standing in the cold outside. That's how I got my record three SNR readings. This capture only shows two SNR values, and I missed capturing the "record":

 3GPP |      operator code: 310
         |      operator name: 410
         | location area code: FFFE
         | tracking area code: 9103
         |            cell id: 066AA80F
 GPS  |              nmea:
         |                    $GPGSV,3,1,11,05,14,314,16,09,73,144,21,02,,,,03,,,,1*69
      |                    $GPGSA,A,1,,,,,,,,,,,,,,,,*32
      |                    $GPRMC,,V,,,,,,,,,,N*53
      |                    $GPVTG,,T,,M,,N,,K,N*2C
      |                    $GPGGA,,,,,,0,,,,,,,,*66

Sat PRN 05, SNR = 16
Sat PRN 09, SNR = 21

All others have commas in the SNR field.

So my Pinephone is receiving something (mmcli -m 0 --location-status has "status yes" too. Signals just seem to be very weak and infrequent.

Thanks for the suggestions!

I'll try 90 minutes sometime when the weather improves again. (It started snowing today so cloud cover attenuation is possible). I'll also look into picocom and maybe I'll need to run SSH remotely from my laptop from inside the car to the Pinephone on the car's roof. I'll stay warmer and perhaps get a stronger signal too. Finally, I guess I'd better at least do a visual inspection of the Pinephone antenna, if not try to "ohm it out" in some way. I have a good Fluke meter with a low ohms scale. I don't know what the resistive component of the impedance should be but I'll look into it.

Messages In This Thread
RE: Unsatisfactory GPS reception on PinePhone? - by calinb - 12-13-2020, 05:38 PM

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