OpenTherm interface service running un Raspberry PI

Goal

The aim of the task is to adapt the already existing application to the OpenTherm standard. For that it is needed to create a separate adapter layer (next to the existing one), through which the devices can be used with any OpenTherm enabled device.
The application should be able to control

* Relative Modulation Level (0..100)
* Flow temperature CH2 (10..90)
* DHW temperature (10..80)
* DWH2 temperature (10..80)
* heater on/off

Used technologies

Currently the application uses Python 2.X with the flask, flask-api frameworks. As for storage, a simple SQLite should be used.

* Raspberry PI Zero - communication on GPIO port.
* GPIO pins: 12-13 / 16-19, the OpenTherm connector HW attached to 2 pins available
* The app has to run under a recent version of Raspbian (Stretch)
* The app has to be written in C / Python / Go, and should be just a thin layer adapter between the flask app and the OpenTherm standard.

Task

The task itself is to implement an adapter layer in the thermostat to be able to communicate through the OpenTherm standard.

* Documentation: Proper installation, setup doc, is needed,
* As well as a well documented, easy-to-read codebase.


Resources

OpenTherm documentation: https://www.opentherm.eu/using-the-protocol/#implementation-for-applications
OpenTherm protocol: http://ihormelnyk.com/Content/Pages/arduino_opentherm_controller/Opentherm%20Protocol%20v2-2.pdf
OpenTherm Test Tool: http://www.hccp.nl/downloads/
OpenTherm ready iOS app: https://github.com/svdgraaf/opentherm-gateway-controller-client