A direct connection is not possible. You need to install something like a ccu. From my point of view ist honmegear the best solution and if you use the openAHBian image homegear is an option to install in the openHABian menu.
Than you pair with the CUL Stcik your homematic devices with homegear and acces from openHAB with the homematic Binding.
works like a charm
Thomas