The Huawei E397u-53 dongle is a low cost dongle which is available on Amazon for around $20. It is possible to get it working on startup on a Raspberry PI, and there is some very good documentation which I will mention in the credits of this post. Even with the documntation I was able to find, I still hit a decent number of roadblocks during setup.

First up, I am going to summarize the actual steps I used, which are mostly the same as the one from the first blog post. I opted to use the NDISDUP method since WvDial is slower and harder to reliably bring up on startup.

Also as a note, most blog posts mention needing to mess with usb_modeswitch. As of the time of this posting, with Raspbian 9 (Stretch) on a Raspberry PI 3 Model B version 1.2 this was not necessary since the device already showed up on /dev/ttyUSB0

  1. Install screen using sudo apt-get install screen and then run screen /dev/ttyUSB0
  2. This will put you in a console that will look hung. If you type AT and hit enter you should get a response of OK back.
  3. In the new console, type AT^NDISDUP=1,1,"<APN>" where <APN> is the APN for your carrier. In my case it was fast.metropcs.com.
  4. You will now need to install libqmi-utils. Unfortunately this is where I ran into the biggest issue. The current version of libqmi-utils in Rasbian has a bug (see 2nd link in credits) where you will get an error stating: 
    sudo APN=fast.metropcs.com /usr/bin/qmi-network /dev/cdc-wdm0 start
Loading profile at /etc/qmi-network.conf...
 APN: fast.metropcs.com
 APN user: unset
 APN password: unset
 qmi-proxy: no
Checking data format with 'qmicli -d /dev/cdc-wdm0 --wda-get-data-format '...
error: couldn't create client for the 'wda' service: QMI protocol error (31): 'InvalidServiceType'
Device link layer protocol not retrieved: WDA unsupported
Starting network with 'qmicli -d /dev/cdc-wdm0 --wds-start-network=apn='fast.metropcs.com'  --client-no-release-cid '...
error: couldn't start network: QMI protocol error (64): '(null)'
Saving state at /tmp/qmi-network-state-cdc-wdm0... (CID: 1)
error: network start failed, no packet data handle
Clearing state at /tmp/qmi-network-state-cdc-wdm0...
  5. In order to workaround this, I first removed the version of libqmi-utils I installed by running sudo apt remove libqmi-utils and then reinstalled it from source by running 
    wget http://www.freedesktop.org/software/libqmi/libqmi-1.16.0.tar.xz
tar -vxf libqmi-1.16.0.tar.xz
cd libqmi-1.16.0
sudo apt-get install glib-networking libmbim-glib-dev libgudev-1.0-dev
./configure --prefix=/usr --disable-static
make && sudo make install
sudo qmi-network /dev/cdc-wdm0 start
  6. Once I was able to verify that sudo qmi-network /dev/cdc-wdm0 start worked, I went ahead and rebooted the machine. From there I then edited /etc/network/interfaces.d/wwan0, replacing <APN> with my APN settings and added 
    allow-hotplug wwan0
iface wwan0 inet dhcp
  pre-up for _ in $(seq 1 10); do /usr/bin/test -c /dev/cdc-wdm0 && break; /bin/sleep 1; done
  pre-up for _ in $(seq 1 10); do /usr/bin/qmicli -d /dev/cdc-wdm0 --nas-get-signal-strength && break; /bin/sleep 1; done
  pre-up APN=<APN> /usr/bin/qmi-network /dev/cdc-wdm0 start
  post-down /usr/bin/qmi-network /dev/cdc-wdm0 stop
  7. I was then able to reboot the PI and the networking came up successfully.
  8. At this point everything was working, however I did not have any DNS resolution. In order to fix this I had to edit /etc/resolv.conf.head and add 
    #OpenDns Servers
nameserver 1.1.1.1
nameserver 1.0.0.1

Credits: