01-07-2021, 11:28 AM
I probably need to retry some of this stuff so I can be sure it still works as it used to. I should probably try updating the modem firmware and checking that the GPS still works the same way too - I'm still on the version that came with the Brave Heart.
I didn't enable agps-msa or agps-msb except when I tried using ModemManager's agps enabling methods. They didn't work which is why I tried the AT command based route, which did work. From what I can tell ModemManager uses the generic Qualcomm interface for this, and I guess it doesn't work with Quectel's implementation.
When testing the AGPS loading script I stopped ModemManager and connected to the two serial interfaces with picocom. Other serial consoles are available - just remember that you need to enable local echo on the command interface or you won't see what commands you're sending. This will let you check almost all of that the script does manually and get used to what you ought to be seeing from the scripted commands. You can then disconnect from the command interface and use the script. Only when I could see the AGPS data loading was working and improving the fix speed and stability did I restart ModemManager, then write a wrapper script to do the stop, load and restart. If you're having trouble then go back to the basics and make sure they're working before adding complications like ModemManager. All this was usually done via ssh over WiFi for easier typing, using Mobian with automatic sleep disabled.
The script was pretty reliable for me with the phone indoors by a window, and consistently significantly better than without AGPS, but not 100%. This is in the nature of GPS - the sats are constantly moving so there's an element of chance as to whether you get a favourable or unfavourable condition for your test. At the very least you should be seeing sats in the NMEA messages, even if you don't get a lock. Before trying the AGPS I could see sats, and if I was lucky I'd get a lock in a similar time to a Garmin Geko 201 doing a cold start. If you don't see any sats at all then something's not right.
At best I was getting a fix within a few seconds of running the AGPS loading script, and that's indoors by a window.
I didn't enable agps-msa or agps-msb except when I tried using ModemManager's agps enabling methods. They didn't work which is why I tried the AT command based route, which did work. From what I can tell ModemManager uses the generic Qualcomm interface for this, and I guess it doesn't work with Quectel's implementation.
When testing the AGPS loading script I stopped ModemManager and connected to the two serial interfaces with picocom. Other serial consoles are available - just remember that you need to enable local echo on the command interface or you won't see what commands you're sending. This will let you check almost all of that the script does manually and get used to what you ought to be seeing from the scripted commands. You can then disconnect from the command interface and use the script. Only when I could see the AGPS data loading was working and improving the fix speed and stability did I restart ModemManager, then write a wrapper script to do the stop, load and restart. If you're having trouble then go back to the basics and make sure they're working before adding complications like ModemManager. All this was usually done via ssh over WiFi for easier typing, using Mobian with automatic sleep disabled.
The script was pretty reliable for me with the phone indoors by a window, and consistently significantly better than without AGPS, but not 100%. This is in the nature of GPS - the sats are constantly moving so there's an element of chance as to whether you get a favourable or unfavourable condition for your test. At the very least you should be seeing sats in the NMEA messages, even if you don't get a lock. Before trying the AGPS I could see sats, and if I was lucky I'd get a lock in a similar time to a Garmin Geko 201 doing a cold start. If you don't see any sats at all then something's not right.
At best I was getting a fix within a few seconds of running the AGPS loading script, and that's indoors by a window.
