The hardware

The RTL8366 basically can be connected to a 24C02 EEPROM, which it uses to read its initial settings. When that is done, the device acts as a I2C slave, and can receive commands which can change its behaviour. On my switch, the 24C02 EEPROM was easily visible. I decided to connect an ATMega88 to it, with a 3.3V serial port which I could feed to one of the FT232-boards I have. That way, the schematic could be embarassingly simple, consisting of not much more than the AVR and a 6MHz crystal:

With this few parts, I decided to build the schematic dead-bug-style on the PCB of the switch. I also added an ISP-connector because I still had to develop the software, and with the IC tied down on its back, I couldn't just pop it out and put it in my programmer.
(Fyi: I added the resistor in the first pic later because I suspected a bad AVR. It isn't strictly necessary.)

Now all that's needed was a piece of software and we should have a managed switch. With a single 8-bit cpu and just a serial port, it wouldn't have a nifty web-interface, but I didn't need that anyway.

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