[Solved] Support for Quectel EC25 or Alfa U4Gv2 LTE modem

cybermaus

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I have both a 7560 and 7362SL and want to use one of them with the waterproof *outdoor* Alfa U4Gv2 LTE dongle (because this is for a steel hulled houseboat, so indoor is a no-go).
(whichever Fritz works, the other would be used as Mesh repeater)

I used LTE dongle before with Fritz/Freetz, and the dongle is not a brand new model, so I thought it would be fine.
To make sure, I even selected the "update usb device table" on the menuconfig.
However, while lsusb is showing it, Fitz/Freetz does not know it and shows an "unknown USB device".

I am relatively sure there is nothing special to this LTE modem, it is just a matter of not knowing the VID/PID
Question: How easy would it be, where in the filesystem can I, add the VID/PID to some database somewhere?
Any help appriciated.

Many thanks
Ubunto lsusb output: Bus 001 Device 002: ID 2c7c:0125 Quectel Wireless Solutions Co., Ltd. EC25 LTE modem

-- Zusammenführung Doppelpost gemäß Boardregeln by stoney

Ok, I got it to workusing a workaround. Not as simple as I thought, and also I loose SMS and GSM functions.
But at least data works.

Core problem was not (only) the missing VID/PID, but also that this Alfa / Quectel EC25 modem uses newer "qmi" protocol, which I think the Fritz does not know. Or at least not know this is one of those modems: Ref: https://openwrt.org/docs/guide-user/network/wan/wwan/ltedongle

Code:
AT+QCFG="usbnet" shows current mode
AT+QCFG="usbnet",0 - is PPP & QMI (default)
AT+QCFG="usbnet",1 - is ECM.
AT+QCFG="usbnet",2 - is MBIM

Setting it from QMI to MBIM makes the Fritz understand the make and model of the modem
As it nicely reports the make and model, and even lists out the SIM details, and tells me the signal, and that the modem is connected.
Basically everything, except a working internet. I think the Fritz now understands the "control channel", but misses the "data channel"

The method I did get it to work is by activating ECM mode.
This means you put the APN into the modem itself, and the Alfa modem acts as a Android - Tethering device.
Indeed, Fritz now thinks it is connected not to a LTE dongle, but to a Tethering phone. And it works.

Of course, no SMS. And also no using the GSM number from Fritz as a telephony hardline.
But it works for internet at least. Ref: https://docs.sixfab.com/page/internet-connection-with-quectel-ec25-by-using-ecm-mode

Code:
AT+QCFG="usbnet",1
AT+CGDCONT=1,"IP","<your APN here>"
AT+CFUN=1,1


Edit: some more refs:
EC25 Modem manual
 

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cybermaus

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@fda89. I may need some more hints.

As I understand it, for the 7560, the "flagship" model is the 7583. Due to chipset used. Or at least, that is the source that my build has downloaded.
(edit: I am now wondering if this needs updated, because 7590 does have same chipset, and is newer. Maybe old info in the makefile?)
When searching, to my surprise, it *does* have the qmi_wwan module!
And indeed (coming full circle) in that source scores of VID/PID, but not my 2c7c:0125 Quectel Wireless Solutions Co., Ltd. EC25 LTE modem
1609358346645.png

But now I get stranded:

Normally, when having this, one merely does a "echo VID PID > /sys/bus/net/..../newid
No recompile needed. But I cannot find the correct /sys/bus/net location for this qmi driver. Also modprobe does not work.

And also, I cannot recompile the kernel, because of "replace-kernel is not (yet) available because of changed bootloader format"
So I cannot 'transplant' this 7583 kernel source into my 7560

And I simply do not understand the section about "adding own drivers"
Anyone, help please?

--

In the mean time, pending some helpful hints, I will download the actual 7560 sources to confirm the qmi is not there.
As well as the newer 7590, just to see if the Quectel is in those 7.2x sources at least.

---

Edit: well, at least the 7.21 source (from 7590) has the VID PID listed. So worst case, all I have to do is wait till 7.2x comes out for my devices....

1609360128765.png

---

Edit: this does load the driver. Afterwards all the /dev/ttyUSB* are there.
But alas, as shown above the Quectel is a "quirky" driver, and this loads it as a normal one. Is my current guess.
Or maybe the USB are not in the right places. Would Fritz want the control on ttyUSB0 instead of ttyUSB2
Code:
modprobe usbserial
modprobe option
echo  2c7c 0125 > /sys/bus/usb-serial/drivers/option1/new_id

---

Final Edit:

I simply use the combination of above workarounds:
- Set to ECM Tethering mode as shown above, so the Internet work.
- Still do the above modprobe/echo, so the modems AT channel is exposed and I can use SMSTools3

And maybe in 6 to 12 months, AVM will release V7.21 for my devices, and it is not needed anymore.
 
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