Need help troubleshooting Quectel EG25 modem in Pine64 Pinephone

[Andreas Hartmann]

Hello,


I'm looking for guidance diagnosing what is wrong with the Quectel EG25
modem in my PinePhone. I am aware that the modem works for pretty much
all people, however there seem to be some exceptions to this, including
me. I have tried several Operating Systems (Manjaro, postmarket OS,
Fedora, mobian) but with none of these I had any success so far.
Currently I'm tempted to believe that the hardware in my phone isn't
entirely functional, but I wanted to make sure of that before randomly
replacing parts.

The issue I see is that the modem is recognized by the OS, and I can
communicate with it through ModemManager, too. But it cannot connect to
my carrier. I can neither make phone calls, nor receive SMS or setup a
mobile data connection. However, the modem clearly shows that is has a
signal reception, and I can confirm that a signal is present from
another Android phone. I have suspected the SIM card, but when I insert
it into an Android device it works just fine. Just to make sure I have
even removed the SIM PIN, but that hasn't changed the situation (apart
from some added convenience for me). I live in Germany, and the SIM is
registered with "Deutsche Telekom".

I can confirm that a 3GPP scan yields useful results:

```
$ mmcli -m 0 --3gpp-scan --timeout=120
  ---------------------
  3GPP scan | networks: 26203 - o2 - de (lte, forbidden)
            |           26202 - Vodafone (lte, current)
            |           26201 - TDG (lte, available)
```

As my operator is "Deutsche Telekom", the correct MCC/MNC is 26201, but
mmcli shows that modem attempts to register with 26202. I seemingly
cannot override this:

```
$ mmcli -m 0 --simple-connect="apn=internet.t-mobile,user=t-
mobile,password=tm" --timeout=120
error: couldn't connect the modem:
'GDBus.Error:org.freedesktop.ModemManager1.Error.MobileEquipment.Networ
kTimeout: Network timeout'
```

I attempted to define an initial bearer with `mmcli -m 0 --3gpp-set-
initial-eps-bearer-settings`, but that didn't change the situation.
The simple-connect doesn't work either, even if I explicitly specify
the operator ID to use.

Interestingly the behavior is pretty consistent. It happened to me with
the stock firmware that the Pinephone Modem (Manjaro edition) shipped
with in December/2020, it persisted after I had updated to the most
recent modem firmware available February/2021, and it's still there
after flashing biktorgjs custom firmware [1].

I have tried to use various APN settings, including:

1. The one mentioned in the Pine64 wiki [2]
2. APN "internet.telekom", which is available on my Android device
3. APN "internet.t-d1.de", which my Android device actually uses

I don't know whether this is relevant, but the SIM is part of a
multisim contract (Same phone number, same data plan for all SIMs).

Curiously, recently I could accept a phone call on the Pinephone and
talk to the other person. However this was a unique event and I
couldn't reproduce it ever since. I can neither make calls, nor use
mobile data.

I'm running out of ideas as to what may cause such a behavior. I'd be
thankful for any hints on what else to try, or possibly a diagnosis on
whether the Modem is actually broken... Thank you in advance!


Cheers,
Andreas Hartmann



[1]: https://github.com/Biktorgj/pinephone_modem_sdk
[2]: https://wiki.pine64.org/wiki/PinePhone_APN_Settings#Telekom_.28Germany.29
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