Here's a good source of info for non German speakers: http://www.ply.me.uk/bits_and_pieces/fhem_snippets.html

@Stephan-Noller If there's nothing in the repeater or gateway, then that indicates that the sensor is not transmitting or transmitting to the wrong parent, so hooking up a serial monitor to it should provide some clues. Of course the serial monitor has to be connected ahead of time otherwise as it will reset the Arduino once you connect. You could also try the NRF24 Sniffer. Try putting a small delay between the sends as that may resolve the issue where only one value is being transmitted. Cheers Al

I have to correct myself. LEDs are indeed lighting, it's just hard to recognize, guess because i am working with 3.3 volt instead of the 5v as recommended. Nevertheless, i get a green LED even though measurement values are not reaching the controller...

Hi, don't know if @Stephan-Noller found a solution, but I had a similar issue with a serial gateway running on a 8MHz arduino : it could not handled serial input at 155200 baud, setting it to 57600 solved my gateway behaviour. What gateway sketch are you using ? What hardware is it running on ?