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Telit LN941 is a CAT-6 module for the European market in M.2 format.
Compliant with 3GPP Category 6 releases LN941 is the most affordable LTE module, with the capability of 2CC Carrier Aggregation, reaching up to 300Mbps DL.
The Telit M.2 family of modules supports the latest LTE Advanced networks with 3G fallback.
The industrial-grade PCIe M.2 form factor allows for easy integration into mobile computing, networking, and industrial IoT device platforms that command a smaller and thinner footprint.
How to step by step set up a data connection over QMI interface using qmicli and in-kernel driver qmi_wwan in Linux?
Several cellular modules based on Qualcomm chipsets implements the Qualcomm Qualcomm MSM (QMI) Interface.
There is a open source Linux in-kernel driver supporting this interface and it is called qmi_wwan. This driver can be used together with ModemManager and NetworkManager to automate connection establishment and as a connection manager.
The library libqmi which ModemManager uses can also be used to communicate in a more direct way with the cellular devices over the QMI interface and to step by step do necessary configurations and trigger the data connection over the cellular network.
A selection of cellular modules can be supported:
Using RAW IP kernel configuration:
Sierra Wireless MC74 series, EM74 series, EM75** series
Telit LM940, LM960
Telit LN94x series (requires USB mode switch)
Simcom SIM7500 series, SIM7600 series, SIM7600 -H series
(can be supported in qmi_wwan driver from kernel 4.18 or by applying the following one line qmi_wwan source code patch on previous kernel builds: qmi_wwan: apply SET_DTR quirk to the SIMCOM shared device ID)
Using 802.3 IP framing kernel configuration:
Simcom SIM7100 series
Sierra Wireless MC73**/EM73** series
ModemManager combined with NetworkManager will detect the cellular modules automatically in most cases, please refer to their respective documentations on how to establish a data connection using them.
Example on how to set up the data connection step by step manually with libqmi:
First install the libqmi Linux library e.g. by using your system package manager like apt or preferably latest version from source on the Freedesktop pages for libqmi project: https://www.freedesktop.org/wiki/Software/libqmi/
Verify that you have the Linux in-kernel qmi_wwan driver installed and attached for the cellular modules QMI interface over USB:
Can look e.g. like this:
|__ Port 1: Dev 3, If 2, Class=Vendor Specific Class, Driver=qmi_wwan, 480M
If the driver is not correctly loaded, please verify that the module is set to expose the correct USB endpoints configuration toward the host system and that you have followed the provided guides from the cellular module vendors, regarding how to implement the module in Linux.
Libqmi expose a command line interface that can be used to communication with the module over QMI interface.
The qmicli help will output information about all commands available:
The cellular modules QMI control interface are usually named cdc-wdm* e.g.:
In order to allow parallel commands to be execute on the module over QMI interface, it is recommended to use the libqmi proxy function. This can be done by including the attribute -p or --device-open-proxy in every qmicli command.
If a SIM pin is required for the SIM card, use command bellow:
qmicli --device=/dev/cdc-wdm0 -p --dms-uim-verify-pin=PIN,1234
The name of the related network interface to QMI control channel can be acquired with the command:
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --get-wwan-iface
The most recent Qualcomm based cellular modules only expose QMI interfaces that can support Raw-IP mode. Sierra Wireless EM/MC74 and EM75 series modules, Telit LM940 and LN940 series for example require this.
Check what IP-mode the host system is configured for:
qmicli --device=/dev/cdc-wdm0 --get-expected-data-format
Check what IP-mode the cellular module require:
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --wda-get-data-format
to change qmi_wwan driver to use Raw-IP.
Disable the network interfaces exposed by the cellular module:
ip link set dev wwan0 down
Trigger the Raw-IP support:
echo Y > /sys/class/net/wwan0/qmi/raw_ip
Enable the network interfaces again:
ip link set dev wwan0 up
Now the data connection in the cellular module can be activated e.g. with a IPv4 type configuration on the specified APN:
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --wds-start-network="ip-type=4,apn=data.tre.se" --client-no-release-cid
Once "Network started" is displayed, you can send a DHCP request on the network interface.
Please note that not all DHCP clients in Linux can support Raw-IP format, udhcpc however support this for IPv4 over Raw-IP.
udhcpc -q -f -n -i wwan0
Disconnect the data bearer and data connection over QMI by command bellow and providing the network handle and CID returned at connection activation:
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --wds-stop-network=NETWORK_HANDLE --client-cid=CID
Additional useful commands:
Request module manufacturer:
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --dms-get-manufacturer
Get module model:
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --dms-get-model
Get firmware version:
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --dms-get-revision
Get module IDs (IMEI etc.):
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --dms-get-ids
Get SIM card status:
qmicli --device=/dev/cdc-wdm0 --device-open-proxy --uim-get-card-status
Recent cellular modules like Sierra Wireless EM7565 require at least libqmi V1.20. Check version with command:
If the connection was successfully set up established, you now have data connectivity. A ping to a remote server using the cellular network interface can for example prove this:
ping -I wwan0 184.108.40.206
The ifconfig Linux tool can show the current details for the network interface:
libqmi is well integrated and supported in ModemManager tool for Linux. ModemManager again is well integrated and supported when using NetworkManager tool in Linux. Please note however that these two tools expect the cellular module interfaces to only be used by them so if you manually want to use the libqmi library or AT commands interfaces, please turn off/disable ModemManager and NetworkManager first.
The libqmi is a generic open source library for Linux systems and QMI protocol from Qualcomm, therefor there are commands only working on selected devices and not necessarily supported on the device you use, resulting in an error message.
What Linux kernel modules and configs are commonly used for communicating with cellular modules over their USB interface?
Most cellular modules can be supported in Linux by using som of the in-kernel drivers. The physical data interface to the host Linux system is usually done over USB which enumerates a set of different endpoints/interfaces. A set of serial interfaces for Modem/PPP, AT commands, NMEA location data and chipset debug information are almost always available in all configurations.
In addition some type of network endpoint/interface are also available and exposed. This can vary between manufacturers and chipset vendors and can also commonly be configurable by using USB configuration mode switching or through vendor specific AT commands.
Recommended kernel configurations to enable are listed bellow. Many cellular modules base their Linux support on these modules and drivers. Once included in the kernel build, the USB interfaces will be detected and bound correctly out-of-the-box or after applying source code patches to the driver modules.
Configs for USB serial drivers:
Configs for Modem/PPP support:
Configs for USB network drivers:
Please relate to the Techship product specific web pages for vendor specific Linux integration guides.
Below is a selection of kernel commits relating to cellular module support in Linux kernels:
qmi_wwan: Add support for Fibocom NL678 series
qmi_wwan: Added support for Telit LN940 series
qmi_wwan: Added support for Fibocom NL668 series
USB: serial: option: add support for GosunCn ME3630 RNDIS mode
USB: serial: option: add support for Simcom SIM7500/SIM7600 RNDIS mode
USB: serial: option: add Simcom SIM7500/SIM7600 (MBIM mode)
USB: serial: option: add Fibocom NL678 series
USB: serial: option: add Telit LN940 series
USB: serial: option: add Fibocom NL668 series
USB: serial: option: add GosunCn ZTE WeLink ME3630
qmi_wwan: apply SET_DTR quirk to the SIMCOM shared device ID
If you use any of the listed cellular modules, drivers and specified USB modes in the commits above, ensure that your kernel version already include the patch or apply it to your build.
How can we establish data connection for cellular modules in Windows 8 and Windows 10 systems?
Microsoft Windows desktop versions starting from Windows 8 and newer have built in data connection manager for WWAN, Wifi etc. that can be used to configure, control and establish the data connection of cellular module that support MBIM interface, which most cellular modules do.
The connection managers settings and controls can be found and accessed on Windows desktop start menu through the network icon (see picture).
The Cellular tab can be found in Windows system settings and if needed the connection APN details can be manually entered through "Advanced options".
We cannot acquire an DHCP address over qmi_wwan driver when using Raspbian Linux OS?
Raspbian uses dhcpd to probe all available network interfaces found in the system, which is problematic for the qmi_wwan driver interface, if it is done before being configured properly when using cellular modules supporting only Raw-IP.
This can be avoided by setting dhcpd to deny the related cellular module network interface (most often named wwan0 by the system).
Add to the /etc/dhcpcd.conf file in Raspbian the following line (in the end):
Now, restart the system (preferably re-power it) so cellular module fully restarts also.
At next startup, the settings should be applied and you can now configure and use the qmi interface as described in some of the others faq's, found on the Techship webpage.
How to collect initial diagnostics data and logs for Telit cellular modules needed when requesting Techship technical support?
In order to ease the troubleshooting of technical problems and understand your end-product or application and its usage scenario we ask you to please provide the following information when creating a technical support ticket at: techship.com/technical_support/
Please give a detailed problem description and in what precise circumstances it is present.
Describe the host system:
-Hardware (system board, processor architecture, other peripheral devices...)
-Operating system with detailed versions (E.g. Windows version and build, Linux distribution, kernel version)
-Drivers used and versions (Linux: out-of-tree vendor drivers or in-kernel drivers?)
Details from the cellular module label:
-SKU/BOM or P/N code
For Linux systems, capture terminal logs from commands:
ls -l /dev/serial/by-id
ls -l /sys/bus/usb-serial/devices
The cellular module logs can be acquired by accessing one of the USB enumerated serial (COM) interfaces or physical UART serial interfaces accepting AT commands. In Windows device manager they are generally found as modem infterface or serial and ports interface types).
Send AT commands to module and capture the text output:
Test that you get a OK reply:
Enable AT command echo:
Verbose error reporting:
USB endpoint configuration:
Serial port configuration:
Selected network access techniques:
List network operator info:
Network registration status:
Last serving cell network information:
Current network status:
List APN details:
List Packet switch enable/disable status:
List PDP profiles status:
List default data connection details:
List bearers and IP addresses:
Additional test commands for Telit LM940/LM960/FN98x: