Some time ago I got my hands on a bunch of more or less broken Linksys 802.11 APs and wireless routers. They have been sitting in my closet until recently, when I decided to mock a bit with one of the WRT54G models.
First things first – I had to establish contact with the onboard firmware. Since the board didn’t respond on any of the ethernet interfaces I set out to construct an RS-232 level converter to use with the onboard 3.3V TTL serial interface.
Judging from google, people use all kinds of weird and somewhat complicated (not to mention quite expensive) circuits in order to convert the voltage levels of the WRT54G serial interface to RS-232 levels. I decided to go with my own simple, cheap and effective design based on the Maxim MAX3232 as shown below:
The pinout of the IDC connector on the Linksys WRT54G – X3 in the diagram above – is as follows (thanks to Rod Whitby for posting information on the pinouts, saved me a bit of trial-and-error):
|Pin #||Description||Pin #||Description|
|3||Tx (ttyS1)||4||Tx (ttyS0)|
|5||Rx (ttyS1)||6||Rx (ttyS0)|
The onboard firmware of the WRT54G provides a console on ttyS0 at 115200 1N8. Since the above pinout lacks RTS/CTS lines we have to rely on software flow control.
To connect to the console one might use a command like cu(1):
$ cu -l /dev/ttyU0 -s 115200
Below is a couple of action-shots of the circuit in use:
The next logical step is to get FreeBSD/mips up and running on this thing ;-)