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Hands On LTE on OpenWrt

Supported hardware

• The supported LTE hardware in OpenWrt can be a minefield and my recommendation is to stick with those hardware that have been tested by the community to be confirmed working.
• In the past I tried to use a Huawei LTE USB stick.
• They can be running in two modes.
  • RNDIS https://openwrt.org/docs/guide-user/network/wan/wwan/ethernetoverusb_rndis
  • NCM https://openwrt.org/docs/guide-user/network/wan/wwan/ethernetoverusb_ncm
• The preferred mode is NCM but the with USB stick I had it was impossible to switch modes and I was stuck with RNDIS mode.
• Another time I had a Mikrotik Access Point flashed with OpenWrt that had one of their LTE modems (pcie card). After many days of trying various things I eventually just gave up and replaced the card with one that has proper OpenWrt support.
• Some Access Points that comes with LTE modems included are well supported in OpenWrt.
  • Cell-C / Belotech (https://openwrt.org/toh/cell_c/rtl30vw)
  • GL.iNet GL-MiFi (https://openwrt.org/toh/gl.inet/gl-mifi)

Packages to include

• To get the LTE modem working in OpenWrt you need to include some specific packages.
• There are also some optional packages that you can include since they come in handy.

Required

• kmod-usb-wdm
• kmod-usb-net
• kmod-usb-net-qmi-wwan
• libqmi
• uqmi
• kmod-mii

opkg update
opkg install kmod-mii kmod-usb-net kmod-usb-wdm kmod-usb-net-qmi-wwan uqmi

For Serial Support (AT Commands)

• kmod-usb-serial
• kmod-usb-serial-option
• kmod-usb-serial-wwan

opkg update
opkg install kmod-usb-serial-option kmod-usb-serial kmod-usb-serial-wwan

Optional

• qmi-utils
• picocom
• luci-proto-qmi

opkg update
opkg install picocom qmi-utils uci-proto-qmi

Interacting with the modem

• After you installed the packages reboot the Access Point.
• If everything works as intended you should see the following device

ls -l /dev/cdc-wdm0

• Now you can try to interact with the modem.

uqmi -d /dev/cdc-wdm0 --get-data-status
uqmi -d /dev/cdc-wdm0 --get-signal-info
uqmi -d /dev/cdc-wdm0 --get-system-info

UCI Configuration

• The UCI system includes support for LTE confguration in /etc/config/network.
• The MESHdesk firmware will create the config section based on the configuration returned by the controller.
• Here is a sample section as reference

config interface 'wwan'
	option ifname 'wwan'
	option disabled '0'
	option wan_bridge '0'
	option device '/dev/cdc-wdm0'
	option apn 'lte.broadband.is'
	option proto 'qmi'
	option auth 'none'

• You can also install the luci-proto-qmi package which essentially does the same that MESHdesk and APdesk does but only local on the Access Point.

Using AT Commands

• We can use picocom terminal to reach the LTE modem

 picocom /dev/ttyUSB2

• I had to first issue the following commands before the modem returned something for CUSD

AT+CMGF=1
OK
ATZ
OK
AT+CUSD=1,"*101#",15
OK
 
+CUSD: 0,"Balance: R 0.00 .Data: 25.83 MB.",15