This is the basic circuit for the interfacing of microcontrollers to the EIB TP bus.
This is still a preliminary version, which still requires some testing,
but until now it looked like this as it is the final version.

The protection unit:

First, ensure D1 and D3 for the reverse polarity. The diode D2 will ensure it is protected from voltage spikes in
the circuit. The V + pin then goes to the receiver and transmitter circuit. Vext goes to the switching regulator
and provides the DC level for the transmitting circuit.

 The switching regulator:

The old LM317T was replaced by the switching regulator MC34063AP. Through this amendment,
it was again possible to reduce the power consumption of the circuit.

The receiving circuit:

The capacitor C2 ensures that the DC component is decoupled. The voltage divider R7, R8 takes care of the
correct voltage at the transistor Q1 is applied to create a clean edge for the input pin on the micro-controllers.
If the microcontroller does not have internal pull-up resistor is placed at pin EIB_in still a resistance to VCC
(typically 10k).

The transmitting circuit:

The transmitting stage has been revised, that the stroke of a logical zero when sending a defined value of
about-7V has. C10 ensures that in case of failure of μControllers is not continuous transmission and damaging
the circuit increases. With R12 and R13, the gate of Q6 is raised to about 4 V when a positive pulse comes
from the microcontroller. Thus Q6 is switched through. allowed to flow from these 4V to a maximum current of
about 350mA Ids. The circuit Q2 to ensure that the electricity is only so great that the bus voltage does not
drop below the original value minus 7V.

Of course, the signals are 100% bank-compatible, so that the respective application,
easily integrated into any existing EIB installation can be.
A look at the signals of the original and our circuit confirms this.