1. Install a current snapshot of OpenWrt

    http://downloads.openwrt.org/snapshots/trunk/ar71xx/openwrt-ar71xx-generic-tl-mr3420-v2-squashfs-factory.bin

    Telnet to the device on 192.168.1.1 and set the root password with
    # passwd 

    Login in with ssh and edit /etc/config/network lan section to set up network gateway and DNS
    For example, if the LAN gateway is on 192.168.1.254

    config interface 'lan'
	option type 'bridge'
	option ifname 'eth0'
	option proto 'static'
	option ipaddr '19.168.1.1'
	option netmask '255.255.255.0'
	option gateway '192.168.1.254'
	option dns '8.8.8.8'

    Reboot and check that the device can access the internet eg
    # ping www.google.com

2. Add extra packages
    # opkg update
    # opkg install openssh-sftp-server usb-modeswitch usb-modeswitch-data haserl 

3. Add batman-adv package @ version 2012.3 rather than current snapshot version.
    Download package  kmod-batman-adv_3.3.8+2012.3.0-3_ar71xx.ipk

    Copy the .ipk file to /tmp on the MR3420 device with scp
    # opkg install --force-depends --nodeps ./kmod-batman-adv.ipk

4. Add the SECN files
    Download the two tar files for base file and for MR3420 specific files.
    Copy the tar files to /tmp on the device with scp
    Unpack the files from the / directory as follows:

    #cd /
    #tar -xvf /tmp/secn-files-base-RC3.tar
    #tar -xvf /tmp/secn-files-mr3420-RC3.tar

    Edit the /etc/config/network file if you want to change the default IP address of 10.130.1.20.

5. Reboot.
   The SECN firmware will appear on the SECN default IP address of 10.130.1.20 unless you have edited the 
   file in the previous step.