Hi everybody, I've already contacted PetSafe regarding this, though no reply yet, here's what I wrote to them:
Hello,
I'm writing to you hoping that you would be so kind to help on my home project regarding some personalised improvement of the PetPorte Smart Flap, which have been in use in my home for our cats for the past 2 years and we are extremely pleased with them!! ..so are the cats

Here's what my project is about: I want to connect the smart flap to either LAN network or internet, preferably both.
I read something about that on your site and also, some time ago, we spoke by mail about it, that you are developing a modul, which will be installed to the flap and then connected through usb or serial cable to PC.
Usually, at least my case is like that, the flap is installed on a door quite far from a PC, therefore long cable may lead to a communication problem, I've decided to connect the flap to LAN network. I got the idea on the this site
http://www.nermal.org/projects/catalog.
I made some research and found lots of available hardware that could enable the implementation of connecting the existant equipement with the serial port on LAN network (embeded ethernet).
I chose Modtronix Ethernet SBC68EC board.
What I want to do is to access through web server (built-in Ethernet SBC68EC board) to the settings of my PetPorte Smart Flap, be able to change settings when needed, keep track of entries/exits of our cats..
And this is where I got stuck - how can I connect the board to the PetPorte?
For that I need to know which connector on the circuit board is intended for serial communication with PC and which protocol it supports?
In order to enable me improve my PetPorte, I kindly ask you to send me the technical datasheets for my PetPorte Smart Flap.
Best regards!
Damjan