Receiving DCF77 time on RPi

This little fella (a Raspberry Pi single board computer) is going to be my private network time server, to be used by all network devices in my private network. The idea is to use the DCF77 longwave time signal transmitted from Mainflingen in Germany as a long term time reference, and a real-time clock module with battery backup as a reliable local time reference.
Since I live at a fairly long distance from the DCF transmitter (I live in Stockholm, Sweden), the time signal is somewhat unreliable, much depending on weather and time of day. Generally the time signal can be received cleanly at night, but not in daytime. Anyway I just want to sync the real-time clock every now and then, so it is sufficient.
The prototyping board ontop of the RPi is an interface between the DCF77 antenna/receiver and the GPIO connector on the RPi. Ontop of that is the real-time clock module (the little green board with the battery). It is connected to the GPIO pins via a 6-pin passthrough connector on the back (top) side of the prototype board.
The blinking LED indicates the reception of DCF77 time pulses, for debugging. I know it's much easier to just use a GPS module as a reliable time reference, but that just wouldn't be as fun as building a DCF77 decoder, would it? :)

[@kbabioch]

How did it work out for you? Any source code available?