Software to remote control Viessmann heater using KM Bus
This project uses 2 NXP LPC1xxx board to remote control a ViessMann heater using a KM Bus interface to the heater.
The KM Bus interface is using an NCN5150 ic implemented as indicated in the datasheet/application note (https://www.onsemi.com/pub/Collateral/AND9108-D.PDF), and connected to one UART peripheral of the LPC1xxx chip.
One subproject, SerialRemote, uses an LPC1343 evaluation board to do UART to USB CDC conversion, plus command interpreting to control the heater. The other, NetRemote, uses an LPC1769 evaluation board to do UART to Ethernet/IP conversion, plus command interpreting to control the heater.
Frame receiving and decoding and command parsing of both subprojects are the same or almost (I first worked on the ethernet one, then switched to the USB one as the power consumption of that unit was slightly lower).
You can use McuXpresso from NXP to create a project into which you can include the source code. You will also need the library corresponding to the MCU used.
In my setup, I already use a ViessMann remote control unit (VITOTROLL 300), so the code is written to advertise to the heater as a second remote control unit.
The way it work, for controlling the heater is that whenever a command is received from USB/Ethernet, the program registers itself to the heater as remote control number 2, then after a few cycles sends the required command (being either a predefined command, like shutdown, eco mode on, ...) or a custom KM Bus frame that is passed along the USB/Ethernet. After the command is sent to the heater, the program then stop responding to the heater, because it otherwise trigs errors in the heater (which might not have any second heating circuit onto which a remote control could be registered).
I then added a third flavor (RemoteToRflink), that is also still a work in progress, in order to control the heater with homeassistant through an rflink like protocol. Still using that same LPC1343 evaluation board to transmit via USB the statuses and temperatures from the heater, and be able to receive rflink like commands to switch things on or off. Still looking to enhance the integration to homeassistant, but I can so far control the global mode (on/off) of each heating circuit, control the eco mode too (though I still can't tell whenever a circuit is in eco mode), the report back all the different temperatures to homeassistant. Moreover, this remote can decode 433MHz OOK signals from Oregon Scientific sensors, and uses (either the first, or a specific id) temperature sensor to report the room temperature to the heater.
Information for creating this program has been gathered here : https://github.com/openv/openv/wiki/KM-Bus and exchanged here openv/openv#387
This code comes with absolutely no warranty of any kind. I can not be held responsible for any damage caused by the use/misuse of this software.