Setting up a data connection over QMI interface using libqmi

Cellular modules that are based on the Qualcomm chipsets support the QMI interface. The libqmi can be used to establish QMI interface for mini PCIe modules such as Quectel EC25, EG25-G, EC21, UC20-G and Telit LE910C1, LE910C4 with the Raspberry Pi 3G/4G & LTE Base HAT.

This is a brief tutorial to establish the connection, reference sites are listed at the end of the tutorial.

Please note that the below tutorial assumes that you have already completed your hardware setup, if not please follow getting started.

Before we start, check the compatibility of the module.

lsusb -t

should return driver information such as qmi-wwan(opensource) or GobiNet(provided by Qualcomm) as shown below. Both drivers work fine with the libqmi.

   |__ Port 4: Dev 6, If 4, Class=Vendor Specific Class, Driver=qmi_wwan, 480M
⚙️ Module Configuration

Before running the PPP/QMI make sure the module is configured to the right settings.
For Quectel Modules:
AT+QCFG="usbnet" should return 0, otherwise,send AT+QCFG="usbnet",0 then reboot the module after 10 seconds AT+CFUN=1,1

For Telit Modules:
AT#USBCFG? should return 0, otherwise,send AT#USBCFG=0 then reboot the module after 10 seconds ,AT#REBOOT

For sending AT commands, you may check the Sending AT Commands tutorial.
Note: In case of the driver error please refer to the driver guide of the modules.

First, install the required packages.

sudo apt update && sudo apt install libqmi-utils udhcpc

libqmi-utils installs two main utilities (qmi-cli tool and qmi-network helper script), these are used for interaction with the modem (for more details check man qmi-cli)

Now make sure the module is ready, this can be done using the following command.

sudo qmicli -d /dev/cdc-wdm0 --dms-get-operating-mode

This should return online if not try

sudo qmicli -d /dev/cdc-wdm0 --dms-set-operating-mode='online'

Now configure the network interface for the raw-ip protocol.

sudo ip link set wwan0 down
echo 'Y' | sudo tee /sys/class/net/wwan0/qmi/raw_ip
sudo ip link set wwan0 up

One can confirm the data format using

sudo qmicli -d /dev/cdc-wdm0 --wda-get-data-format

Once the wwan0 is up, connect the mobile network by changing the apn='YOUR_APN',username='YOUR_USERNAME',password='YOUR_PASSWORD' part of the line according to the information of your SIM & operator. If username and password are not required, delete those parameters.

sudo qmicli -p -d /dev/cdc-wdm0 --device-open-net='net-raw-ip|net-no-qos-header' --wds-start-network="apn='YOUR_APN',username='YOUR_USERNAME',password='YOUR_PASSWORD',ip-type=4" --client-no-release-cid

Lastly, configure the IP address and the default route with udhcpc.

sudo udhcpc -q -f -i wwan0
[email protected]:~ $ sudo udhcpc -q -f -i wwan0 udhcpc: started, v1.30.1 No resolv.conf for interface wwan0.udhcpc udhcpc: sending discover udhcpc: sending select for 100.67.114.164 udhcpc: lease of 100.67.114.164 obtained, lease time 7200 Too few arguments. Too few arguments.

Now check the assigned IP address and test the connection.

[email protected]:~ $ ifconfig wwan0 wwan0: flags=4305 mtu 1500 inet 100.67.114.164 netmask 255.255.255.248 destination 100.67.114.164 inet6 fe80::abc4:a1b5:5e84:92f2 prefixlen 64 scopeid 0x20 unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 txqueuelen 1000 (UNSPEC) RX packets 3 bytes 640 (640.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 13 bytes 2694 (2.6 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[email protected]:~ $ ping -I wwan0 -c 5 sixfab.com PING sixfab.com (172.67.75.126) from 100.67.114.164 wwan0: 56(84) bytes of data. 64 bytes from 172.67.75.126 (172.67.75.126): icmp_seq=1 ttl=29 time=247 ms 64 bytes from 172.67.75.126 (172.67.75.126): icmp_seq=2 ttl=29 time=205 ms 64 bytes from 172.67.75.126 (172.67.75.126): icmp_seq=3 ttl=29 time=207 ms 64 bytes from 172.67.75.126 (172.67.75.126): icmp_seq=4 ttl=29 time=204 ms 64 bytes from 172.67.75.126 (172.67.75.126): icmp_seq=5 ttl=29 time=216 ms --- sixfab.com ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 8ms rtt min/avg/max/mdev = 204.050/215.839/247.004/16.201 ms
Enjoy your internet connection

Troubleshooting

It is worth reading we recommend going through the section on troubleshooting as it covers the more common issues with establishing and maintaining a network connection. Please check out the troubleshooting guide.

Reference

  1. https://www.freedesktop.org/wiki/Software/libqmi/

  2. https://www.raspberrypi.org/forums/viewtopic.php?f=36&t=224355&p=1703897&hilit=4g+module#p1703897