%% \section{U-Boot Installation}

%% The U-Boot installation process is substantially more complicated than the

%% firmware update.  The investigator purchased the optional a serial cable

%% along with the TPE-NWIFIROUTER, in order to complete the U-Boot installation

%% per the instructions in'' -boot\verb0_0reflash''.

%% 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 \url{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\verb0_0reflash 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.