Library for reading data from De Dietrich (or Remeha) PC interface, tested with model mcr3. For this we use an ESP8266 (Wemos D1) with ESPHOME software - sample YAML files are in English and Polish.
It connects to the boiler using a 4P4C (RJ10) connector with the following pinouts:
Heater Board from top ESP8266
4P4C RJ connector
+---------+
GND 4 --- +--+ GND
TXD 3 --- | RX
RXD 2 --- | TX
5V 1 --- +--+ 5V
+---------+
I have connected ESP to prototype board with pins, on board there was simple voltage divider (1kΩ / 2kΩ) to change power from 5V to 3V, but on my board it was not needed and i have connected pins directly to Dietich MCR33, . Cable is simple phone cord, cut and added pin connector to it.
Screenshot of board connected to boiler.
And in printed box.
Thanks to great work from https://github.com/rjblake/remeha - for creating maping of data in excel file.