i was struggeling too at first with my EC20-E Module, so maybe this infos i share could be useful for you.

 

To make it work with Serial i have to set the <span style=“color: #222222; font-family: source_sans_proregular, ‘Helvetica Neue’, Arial, Helvetica, Geneva, sans-serif; font-size: 14px; line-height: 22px; background-color: #f9f9f9;”>option device ‘/dev/ttyUSB3’ to </span><span style=“color: #222222; font-family: source_sans_proregular, ‘Helvetica Neue’, Arial, Helvetica, Geneva, sans-serif; font-size: 14px; line-height: 22px; background-color: #f9f9f9;”>option device ‘/dev/ttyUSB2’</span>

after that chat could make sucessfully make a connection with my provider (ifdown wan - ifup wan)

 

QMI is not supported for the EC20 in the stable Firmware Version, so you need to compile it with the trunk patches (See here: https://lists.openwrt.org/pipermail/openwrt-devel/2015-November/037110.html)

 

I was playing with my Mifi with the Firmware “ofmodemsandmen” (http://ofmodemsandmen.com/) but for the Gl-AR150 the firmware file is openwrt stable too, so i´ve compiled it for myself with the trunk version of openwrt and used the scripts from the ofmodemsandmen firmware

It worked great for me

 

You can test the firmware but keep in mind i create it so i could play along with these device and the ec20 module.

(its for the ar150 so the leds wont work too)

 

Give it a try and let me know how it is going.

Just upload the firmware with the firmware upgrade tool after a few minutes you can reach the openwrt with ip 192.168.1.1

qmi should work with those firmware