* There appeared to be several filesystem and kernel images, for different

  hardware versions.  It was unclear which one to install on the particular

  device we received or how to install it, both of which should have been

  mentioned in the README.

\section{Root Filesystem and Kernel Installation}

As mentioned above, the specific steps for installing an updated firmware image

were not provided, but we found that the firmware update method available in the

web interface worked fine.  In particular, we went to http://192.168.10.1/ in

our browser, then logged in and chose System -> Backup / Flash Firmware.  From

there, we went to the "Flash new firmware image" section and selected the

librecmc-ar71xx-generic-tl-wr841n-v8-squashfs-sysupgrade.bin image in the

bin/ar71xx directory mentioned above.  We chose the "v8" image because we found

our router said "v8.2" on the bottom and "sysupgrade" because we were doing a

firmware upgrade rather than a fresh install.

When we clicked "Flash image...", we were prompted to confirm the MD5 hash of

the image to flash and then clicked "Proceed" to flash the image.  The process

took about one minute, at which point we were back at the web UI login screen.

We logged in and found that the Kernel Log section showed we were running the

new kernel.

We then logged in via SSH again and ran "busybox", which printed the new version

string, showing it was using our newly-compiled version (given the date).

\section{U-Boot Installation}

We obtained a serial cable along with our router, in order to complete the

U-Boot installation per the instructions in u-boot_reflash.  However, we were

only able to read data from the serial port; we were unable to interrupt the

boot process or access the U-Boot console to complete the U-Boot re-flash.  Here

are the steps we tried:

* We found the serial cable included was a USB serial adapter that had a male

  USB type A connector on one end and 4 female jumper wires at the other end.

  These female jumper wires were red, black, white, and green.

* The instructions did not specify how to connect these wires, but we were able

  to determine this in part using the "v8.4" image (close to our "v8.2" router)

  at http://wiki.openwrt.org/toh/tp-link/tl-wr841nd#serial.console .  Aside from

  power and ground (red and black), we did have to guess which of the wires was

  RX and TX.  By experimentation we found that green was RX and white was TX.

  When we tried the other way, we received no data to our serial console at boot

  time.

* We did have to use the included jumper pin gender changer with the USB serial

  adapter, which we put through the holes on the router's mainboard and then

  connected to the USB serial adapter.  The fit was fairly loose so it would be

  nice if future router versions included a tighter gender changer or (ideally)

  had the jumper pins soldered onto the board to begin with (so no gender

  changer would be required).

* We used 115200 8N1 as our serial console settings (with no hardware or

  software flow control).  This was tested with both the minicom and screen

  commands.  We found that if we connected all 4 wires on the USB serial adapter

  that the router would start without additional power and our console would

  receive the startup messages.  We could replicate the same behavior by

  omitting the power cable from the USB serial adapter (red wire) and connecting

  the main power adapter to the router instead.

* While we did see the U-Boot and kernel boot logs in our serial console, we

  were unable to interrupt the boot process as u-boot_reflash indicated we

  should.  We suspect this is a misconfiguration of our serial console, but it's

  unclear exactly how it is misconfigured, as we were able to receive data fine

  (we just couldn't send data to the router).

* As a result, we were unable to complete the U-Boot installation test.  We did

  appreciate that installation instructions were included, though these

  instructions should be updated to include more specifics about connecting the

  serial cable.  Since ThinkPenguin does have the option to ship a serial

  adapter with the router, it would be helpful if instructions specific to that

  adapter were included, as the wiring configuration one should use was unclear.

* Additionally, instructions for removing the router's case should be included.

  We found that the two screws that needed removal to open the case were hidden

  underneath rubber feet on the case.  Indicating which feet need removal to

  unscrew the case would be helpful.  The instructions should also note that the

  case needs to be carefully separated once the screws are removed; it

  effectively snaps apart, but care must be taken to avoid breaking the plastic

  fasteners that keep the case together after the screws are removed.

** To check that the kernel is sufficiently similar, compare the "dmesg" output

   both before and after flashing the new firmware.  The kernel version string

   should be similar, but should have a different build date and user@host

   indicator.  The kernel binary itself is not easily accessible from an SSH

   login, but may be retrievable using the U-Boot console (the start address of

   the kernel in flash appears to be 0x9F000000, based on the u-boot_reflash

   instructions).  We were not able to verify this, due to the serial connection

   issues (see above section on U-Boot installation).

  We were able to build corresponding toolchain binaries from source (though

  for a slightly different target) so this is not a severe toolchain violation

  of the type we normally find (where toolchain binaries are provided without

  source).  However, including instructions to use the built toolchain binaries

  instead would be best, or alternatively specifying the distribution on which

  the toolchain binaries must be run (to avoid being unable to run them as we

  were).