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Comment out U-Boot Installation section for now.

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Bradley M. Kuhn 2014-11-07 09:50:06 -05:00
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101
enforcement-case-studies.tex
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@ -585,59 +585,60 @@ compilation).
%FIXME: dg: can you get me a screen shot for the Kernel Log above, and paste
%in the output of running busybox ?
\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''.
%% \section{U-Boot Installation}
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:
%% 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''.
* 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.
%% 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.
\section{Firmware Comparison}