This is what the inside of the WRT54GL looks like. The back of the router is the top of the image. Our serial port is in the front portion on the right hand side above the empty header.
A closer view of the serial port header we have added. Our header is keyed to prevent plugging the ribbon cable in backwards.
This is a picture of the MAX233A transceiver chip we used to convert the digital serial signal to proper RS232 voltages.
Our picture shows a wire-wrap socket to hold the
transceiver chip, but this was our prototype. In practice, now that the
correct connections have been confirmed experimentally, we will solder
leads directly to a 20-pin standard DIP socket, which can be glued on its
side to the inside of the front case piece. This allows access to the
receiver chip (in case an electrical mishap damages it,) while still
allowing easy opening and closing of the case.
This is the final version of the faceplate of our router, with the two external serial ports attached and ready to go.
Now that everything is connected we can re-assemble it. First you put on the back/top half.
Next you can carefully install the front half (making sure not to break any of the wires we have).
And now you have a WRT54GL with two serial ports installed and ready to run you own operating system.