I see, thanks.
I did a little research today and found this one here: http://kzar.net/wiki/Photo/CanonEFProtocol
Pretty neat referance for the protocol, as it seems. At least for the EF mount, which would serve me very well, too.
With this help, can I just use an Arduino (e.g. Uno), to communicate with the lens and remotely control the lens? (of course, if I write the right code with an interface for it)
Or is there even more behind it?