troubleshooting a Quectel EC25-E modem

[Alberto Bursi]

Hi, I'm having some issues in getting a EC25-E minipcie modem (Quectel) 
to work on my PC (and also on my OpenWrt router).

I'm using a minipcie-to-usb adapter that has also a SIM slot to connect 
it to them.

When I connect it to my PC (running OpenSUSE Tumbleweed, qmicli is 
version 1.20.0 here) I get a normal output in dmesg

|[50477.827418] usb 2-1.5.2: new high-speed USB device number 12 using 
ehci-pci [50477.945515] usb 2-1.5.2: New USB device found, 
idVendor=2c7c, idProduct=0125 [50477.945523] usb 2-1.5.2: New USB device 
strings: Mfr=1, Product=2, SerialNumber=0 [50477.945527] usb 2-1.5.2: 
Product: Android [50477.945531] usb 2-1.5.2: Manufacturer: Android 
[50477.946831] option 2-1.5.2:1.0: GSM modem (1-port) converter detected 
[50477.947098] usb 2-1.5.2: GSM modem (1-port) converter now attached to 
ttyUSB0 [50477.947479] option 2-1.5.2:1.1: GSM modem (1-port) converter 
detected [50477.947815] usb 2-1.5.2: GSM modem (1-port) converter now 
attached to ttyUSB1 [50477.948227] option 2-1.5.2:1.2: GSM modem 
(1-port) converter detected [50477.948652] usb 2-1.5.2: GSM modem 
(1-port) converter now attached to ttyUSB2 [50477.949066] option 
2-1.5.2:1.3: GSM modem (1-port) converter detected [50477.949479] usb 
2-1.5.2: GSM modem (1-port) converter now attached to ttyUSB3 
[50477.950365] qmi_wwan 2-1.5.2:1.4: cdc-wdm0: USB WDM device 
[50477.953115] qmi_wwan 2-1.5.2:1.4 wwan0: register 'qmi_wwan' at 
usb-0000:00:1d.0-1.5.2, WWAN/QMI device, 16:9f:df:80:d5:ca 
[50478.769176] qmi_wwan 2-1.5.2:1.4 wwp0s29u1u5u2i4: renamed from wwan0|

But it seems I can't communicate with it at all from the PC, any command 
from qmicli fails with the same error

qmicli -d /dev/cdc-wdm0 --nas-get-system-info
[28 mag 2018, 01:21:55] -Warning ** Error reading from istream: Resource 
temporarily unavailable

and AT commands I try to send to ttyUSB1 (the only "free" serial port) 
just hang and never give me any answer.

While if I use the uqmi tool from my OpenWrt router (which is a light 
tool doing a more basic susbset of what qmcli can do) I can get 
something out of it at least, it's still somewhat nonsense though.

|root at OpenWrt:~# uqmi -d /dev/cdc-wdm0 --get-data-status 
--get-current-settings --get-capabilities --get-signal-info 
--get-serving-system "connected" { "pdp-type": "ipv4", "ip-family": 
"ipv4", "mtu": 263644, "ipv4": { "ip": "0.9.194.25", "dns1": 
"0.4.21.25", "dns2": "0.4.97.25", "gateway": "10.9.194.26", "subnet": 
"0.4.33.252" }, "ipv6": { }, "domain-names": { } } { 
"max_tx_channel_rate": 917888, "max_rx_channel_rate": 49999872, 
"data_service": "non_simultaneous_cs_ps", "sim": "supported", 
"networks": [ "gsm", "umts", "lte" ] } { "type": "lte", "rssi": -77, 
"rsrq": -13, "rsrp": -27405, "snr": -3841 } { "registration": 
"registered", "plmn_mcc": 56832, "plmn_mnc": 22528, "plmn_description": 
"I�5�\b", "roaming": false }|


The MTU for example is showing a ridiculous value, same for plmn_mcc 
(which should be 222 for my operator) and plmn_mnc (which should be 88), 
and of course I can't change them either with uqmi commands.

I'm suspecting this modem might be defective in some way, but I don't 
have much experience with these devices so I'm asking here.

Thanks for any answer.


-Alberto