Librem 5 - Teseo-LIV3 GNSS Module reports weak carrier to noise ratio - probably HW/design problem
What problem did you encounter
No GNSS lock in reasonable time only occasional in specially well condition (hour on roof of building)
Notice: problem is probably related to the Librem5 mainboard V1.03 and earlier. More users and developers feedback suggests that actual production Librem 5 phones with the mainboard version 1.6.0.1 achieve better signal to noise ratio and position fix is reached in 2 to 4 minutes...
What is the actual behaviour?
GNSS is not functional al least on given single Librem 5 Evergreen L5v1-05 (in the battery compartment), shipped at November 5 2021.
According to the forum discussion in the thread Librem 5 GPS/Location Tracking much more often problem, probably design level
What is the expected behaviour?
GNSS fix in reasonable time and accuracy around 20 meters, even after self repair attempt the lock takes long and weak signal results in imprecise location
Performance should be comparable at least to low end consumer grade phones. Teseo-LIV3 GNSS Module is considered by ESA expert as one from the best compact modules. For sure incomparable to picosecond timing resolution of the HW which he design for ESA or the devices like Septentrio PolaRx5 or other geodetic GPSs.
How to reproduce
Use gnss_test or log
socat unix-client:/var/run/gnss-share.sock -and check $GPGSV lines for Carrier to Noise Ratio for satellite SatxCN0
What hardware are you running on?
Librem 5 Evergreen L5v1-05 (in the battery compartment), shipped at November 5 2021. Mainboard V1.03, production date/number H 210726.
More information
Actual tested device, Librem 5 Evergreen L5v1-05 (in the battery compartment), shipped at November 5 2021.
The values reported by $GPGSV - GNSS Satellites in View never better than 25 dB in the state of delivery and in ideal condition. Lock only sometimes after hour on the company roof above all other buildings and obstacles.
After self tune/repair attempt of earth pin contact enhance of the sensitivity by 5 dB but. Some satellites reach over 30 dB. Self repair and analysis reported in the forum thread Librem 5 GPS/Location Tracking.
Problem is not probably only single unit production deviation.
Thoughts of Galileo/ESA expert
Some thoughts about GPGSV values interpretation
Confirmation of expected performance and required levels backed by expert clarification
Report of Enhancement after Earthing Tune
After uncompleted reply without any answer of numbered points attempt to reach somebody supportive ad competent at Purism