Connections between the MAX232 Level Shifter and the WRTSL54GS
Aus DL8RDS Wiki
Here's a documentation of the pins on the WRTSL54GS board:
I managed to access the serial port using a MAX232 level shifter.
On the WRT side the pin numbering is top down. On the picture below it is from right to left.
On the WRT side --> MAX232 side Pin 1 (3.3V) --> +12V Pin 2 (TX) --> TxD Pin 3 (RX) --> RxD Pin 5 (GND) --> GND
