Posted: Fri Jan 14, 2011 16:54 Post subject: WRT160NL Hardware Mod
I just bought a Cisco Linksys WRT160NL and opened it up as soon as I got it out of the box. I noticed a layout similar to the WiFi, WAN and Power LEDs, to the right of the Power LED, components marked as R443 and LED4 (however, no resistance or LED soldered there).
As soon as I flashed dd-wrt, I started trying with "gpio disable n" and "gpio enable n" and checking with a voltmeter. I soon found out n=0 and it seems to be unused.
The next steps are tricky, so if you don't have good soldering skills, and a very fine tipped soldering iron, get someone who does. The PCB traces are VERY small and you might end up loosening or breaking the traces from the PCB. YOU HAVE BEEN WARNED!
So, I soldered a 100 ohm 1/4W resistor to the anode of a 3mm high-intensity green LED. Using thin insulated copper strands taken from a transformer primary, I soldered the free end of the resistance to the right pad of location R443, and the LED cathode to the right pad of location LED4.
I chose a 100 ohm value because the similar resistances in the WiFi, WAN and Power circuits are 100 ohms. The green LED was chosen from the junk box. :)
The LED-resistor assembly was glued in place next to the Power LED, so both will light up the Power symbol on the shell.
Then I hacked the following startup script:
mp="/`nvram get usb_mntpoint`"
while sleep 1; do
if [ "`mount | grep $mp`" ]; then
"`gpio disable 0`"
"`gpio enable 0`"
Please note there should be an empty line after the final done, the script doesn't seem to work without that.
Well, I plug in any USB mass storage device and sure enough, the power LED turns cyan.
On a different note, I think I've managed to identify the JTAG connector, and will be checking that as soon as I manage to find the right size pins for soldering to the PCB.
Sorry, my photographing skills are next to awful,
but getting there
The post is formatted so you can zoom the page to
see details without losing the text.
An overview of the WRT160NL PCB shows a layout
similar to the WiFi, WAN and Power LEDs, to the
right of the Power LED, components marked as
R443 and LED4 (however, no resistance or LED
originally soldered there). See image below.
This shows a closeup of the area of interest, the
lower right hand corner of the WRT160NL PCB.
Sorry, it was impossible to rip out the assembly
without ripping out the PCB traces as well
A left-side view, shows the copper strands NOT touching pads below.
Doing this is tricky, as you can see from the
pictures. The PCB traces are VERY small and
easily loosened, broken or detached, so if you
don't have good soldering skills, and a very
fine tipped soldering iron, get someone who does.
YOU HAVE BEEN WARNED!
BTW, I used a small butane soldering iron, which
has a needle tip, and I pre-tinned the ends of the
copper strands, leaving a small glob of solder in
the end to be soldered to the PCB. Do NOT solder
in the conventional way, heating the parts and
then applying the solder. You'll end up with a
loosened, broken or detached trace. Place the strand
on top of the pad and touch the tip of the
soldering iron JUST LONG ENOUGH to ensure the glob
of solder on the strand melts and sticks to the
solder on the pad below.
The enamel was scraped off the ends of the wire
strands with a razor blade (requires some patience
getting it right. Using a magnifying glass helps!)
Should more explanations be required, please let me