What do you need to have?

• USB modem - Huawei E3372h-153/E3372s-153 (in StickMode - non-HiLink!)

Firmware versions beginning with 21.xxx.xx.xx.xx not 22.xxx.xx.xx.xx

• SIM card (optionally with PIN code)
• access to the advanced configuration interface LuCI

In this article I will show you how to configure LTE USB modem Huawei E3372.
Also I will also show you how to have mobile broandband as backup connection (failover).

Information about used LTE USB modem (which you can find by using SSH):

root@turris:~# lsusb
Bus 001 Device 010: ID 12d1:1506 Huawei Technologies Co., Ltd. E398 LTE/UMTS/GSM Modem/Networkcard

Now, please also verify if you have two interfaces ttyUSB0 and ttyUSB1 (again you will need to use SSH)

root@turris:~# dmesg | grep tty
[ 1842.406646] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB0
[ 1842.407133] usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB1

Why they are two interfaces?
“Most of these fallback compositions are intended for dongle firmware update and usually contains 2 serial interfaces, it just so happens that one of the interfaces is connected to the device internal ppp server which means we can use it for dial-up.”

First in LuCI you will need to add new interface.
Network → Interfaces → Add new interface

I recommend to use lte as name of the new interface.
and set protocol to UMTS/GPRS/EV-DO

Now click to Submit button.

Into the Modem device field choose there /dev/ttyUSB1 and in Service type choose UMTS/GPRS
To the field APN your's mobile operator should tell you, what needs to be there. Usually it is something like internet

The last thing, which you will need to enter it depends if your SIM card has PIN code. If it has fill it in. When it doesn't leave it empty.

Now click to the button Save and go to Firewall Settings.

You will need to set the wan firewall zone.

Click Save & Apply.

Now you should see how KB moves in RX and TX. You can also check it by disconnecting WAN cable.

Please go here, where it is explained: https://www.turris.cz/doc/en/howto/multiwan

When you have inserted microSD card to LTE modem, which is connected to the Turris router, you will need to check if router sees microSD card in LTE modem.

I will use SSH:

blkid

You should see similar output as I do.

root@turris:~# blkid
/dev/mtdblock3: TYPE="squashfs"
/dev/mmcblk0: PTUUID="3fee9afa" PTTYPE="dos"
/dev/mmcblk0p1: SEC_TYPE="msdos" UUID="3462-1AE5" TYPE="vfat" PARTUUID="3fee9afa-01"
/dev/mmcblk0p2: UUID="1acf499c-1067-4fe1-b1b7-af7dc884f7ae" UUID_SUB="fd211a80-da78-49fc-a7c2-f2ed2b840301" TYPE="btrfs" PARTUUID="3fee9afa-02"
/dev/sda1: UUID="ED37-A894" TYPE="exfat"

Now we can see that microSD mounted is detected as dev/sda and their type is: exfat

By this command you can format it to ext4 file system

mkfs.ext4 /dev/sda1

You can also use LuCI to add new mount point in System tab.

(Turris 1.x owners can't add it through LuCI and will need to mount it manually)

or you can mount it manually

If you would like to have microSD card in folder sd, which will be located in /mnt First you will need to create folder sd in /mnt

mkdir /mnt/sd

mount /dev/sda1 /mnt/sd

Now I will show you how to verify, if sd card is mounted how we wanted.

root@turris:~# df -h

Filesystem                Size      Used Available Use% Mounted on
/dev/mmcblk0p2          119.1G    136.5M    118.0G   0% /
tmpfs                  1011.5M      1.7M   1009.8M   0% /tmp
tmpfs                   512.0K      4.0K    508.0K   1% /dev
/dev/sda1               116.8G     60.0M    110.8G   0% /mnt/sd

For editing files I used on Windows these two apps WinSCP and PSPad.

Source: Thanks to Nora Kořánová, because she made article for Quectel EC20