• TP-LINK MR3020 Router (32MB RAM, 4MB FLASH, serial port header, USB port, 802.11N Atheros 9k WiFi, 400MHz MIPs processor).
• RFD900a Radio (see http://rfdesign.com.au).
• SanDisk Cruzer Fit™ tiny USB memory stick.

Thanks to Musti, we now have a 3D printable case for the Mesh Extender:

Here are the STL files for printing your own Mesh Extender case:

stl.tgz

Images and related details for these cases:

images.tgz photos.tgz servalcase-mr3020-documentation.pdf

• Remove lid by following the instructions at http://wiki.openwrt.org/toh/tp-link/tl-mr3020#opening.the.case
• Remove the PCB
• Drill two holes on the top edge of the case to accomodate the RFD900 radio (6.5mm holes 20mm apart, centred approximately 9mm in from the top edge and the first hole starting approximately 20mm in from the left edge. I will supply a photo that makes this clearer).
• If you have obtained a normal RFD900, desolder the 16pin header. Ask RFDesign if they can supply it without the header installed in the first place, as it saves a bit of effort. They may or may not be able to depending on where they are in their manufacturing cycle, but the more people ask, the more they are likely to stock them this way.
• Solder a 4-pin ribbon cable between the MR3020 PCB and RFD900 radio connecting 5v, GND, TX and RX lines appropriately. See photo for pictorial explanation.

1. Build an OpenWRT firmware image
2. Download mesh extender software installation tools from https://github.com/gardners/mesh-extender (once only):

   $ cd ~/src
   $ git clone --quiet https://github.com/servalproject/mesh-extender.git
   $ cd mesh-extender
   $ ls -a
   .  ..  .git  mr3020
   $

3. Partition the USB memory stick in any computer to have exactly three partitions of any size (this is to work around a bug when running fdisk on OpenWRT and creating partitions, where it doesn't create the /dev/ entries until after reinsert or reboot).
4. Plug virgin MR3020 into the Ethernet jack on your workstation and activate the Ethernet port:
   • the Mesh Extender acts as a DHCP server, so your workstation's Ethernet port must be configured to obtain an IP using DHCP
   • the IP will probably be in the subnet 192.168.2, and the Mesh Extender's IP will be 192.168.2.1
5. cd mr3020
6. ./0.install-openwrt
7. Wait for router to reboot
8. ./1.upgrade_openwrt 192.168.1.1
9. Wait for router to reboot
10. ./2.install_mesh_extender 192.168.1.1
11. Wait for router to reboot
12. Kill the runservald process and run servald stop to stop all servald processes.
13. Run export TERM=xterm ; minicom -s and use minicom to configure to use /dev/ttyATH0 @ 57600, no hardware or software flow-control. Then use +++ to connect to radio and make sure it is happy. Adjust channels, frequencies, bit rates as required. More on this later. Required once only. We also hope to make this step redundant by making servald do this.

You should now have a working Mesh Extender.

We intend to refine and simplify this process further to make it easier for you to build your own mesh extenders. Of course you will need a pair to use them productively.