EMS interface board V3

(7 customer reviews)

34,95 incl.VAT/BTW

EMS to TTL level interface board for 3.3V and 5V compatible serial ports (UART) of f.i. Arduino, ESP8266, NodeMCU, Wemos, Raspberry Pi.

In stock

SKU: ems-int-v3-0 Categories: ,


This is the latest version of the original EMS bus to microcontroller UART interface board.
With this board you can safely connect a UART/serial port of your microcontroller or development board to the EMS bus.


  • New much smaller form factor (only 35x42mm)
  • 3.3V and 5V UART/serial port compatible
  • Supports all EMS bus types like EMS, EMS+, EMS2, Heatronic 3 etc.
  • Connect to the EMS bus via the screw terminal or the 3.5mm service jack
  • Connect to the UART via a 4 pin header
  • Additional bus protection with polyfuse and TVS diodes


  • 4 plastic PCB mounting feet (5mm height) with double sided tape
  • High quality 50cm 3-pin jack cable for connecting the board to the service jack on the boiler/heat pump (if available).
    This cable has 2 extended plugs that fit into the recessed connector hole on the boiler.

Because the EMS bus is about 16VDC, works with an offset and the signal in the top few volts, the RX signal needs to be stepped down to 0-3.3V or 5V.
TX works in the current domain so this board converts the TX signalling of the UART into a specific current signal for the EMS bus.

Did not understand anything what you just read?
That’s OK because the main reason I built this board is so you don’t have to worry at all about the electrical part of the EMS interface.
Just plug it into your favorite microcontroller and off you go.

The board is 3.3V and 5V UART compatible and works with all EMS, EMS+, EMS2 and Heatronic 3 and 4 boilers.
This board is compatible with f.i. every Arduino, Atmel, ESP8266, ESP32, NodeMCU, NodeMCU-32S, DevKitC, Wemos, NodeMCU, Raspberry Pi and other microcontrollers.
For more information have a look at the product wiki.

You can connect the board to the bus via the 3,5mm service jack or via the EMS/thermostat wires on the screw connector.

If you can use the service jack from the boiler you can also power the microcontroller from the jack. When you use the EMS bus wires you always need to power the microcontroller externally (F.i. with a USB adapter).

This board is NOT a substitute for the EMS Gateway!
This product is for those who like to play around with programming and microcontrollers.
It’s ONLY the hardware interface you need to interface with the EMS bus from a standard UART.
does not come with any microcontroller or software.
You cannot power the microcontroller from the bus, only from the jack (if connected).

Additional information

Weight 0,1 kg
Bus compatibility

EMS, EMS Plus, EMS+, EMS2, Heatronic 3


3,5mm Service jack, EMS bus wire screw terminal, EMS power out header

Origin country

the Netherlands

HS Code


7 reviews for EMS interface board V3

Based on 7 reviews
5 star
4 star
3 star
2 star
1 star
  1. Dieter P. (verified owner)

    Verified reviewVerified review - view originalExternal link

    Does what it was promised to do without hassles!

  2. Tomasz Płonka (verified owner)

    Verified reviewVerified review - view originalExternal link

    Urządzenie działa poprawnie. Niestety mój piec nie pozwala zmieniać parametrów do których jest przeznaczone pokrętło na piecu.

  3. Ulrich Stoehlker (verified owner)

    Verified reviewVerified review - view originalExternal link


    It works perfectly. I only had to understand how much traffic there is on the bus. I have written my own software in C for the RPi. Files with all complete telegrams are permanently written to a file. A decoder is used to simply reduce all data to the information I am interested in. This file is copied to my database server every 10min.
    In parallel I have hmc5883l magnetometers mounted on gas and water counters to register the position of the magnet mounted on the axis of both counters. After one turn of the respective axis a new line is added to the data file and transfered to the database server every 10min.
    Every hour I generate a graphics file with number of turns of gas and water counter together with temperaturs of the solar collector and water. Finally I send this png-file to my GoogleDrive. This way I can always check the data remotely. Simple, no Python, Java or web stuff – only C !

    Best regards, Ulrich

    Image #1 from Ulrich Stoehlker
  4. Jarosław G. (verified owner)

    Verified reviewVerified review - view originalExternal link

  5. Kevin (verified owner)

    Verified reviewVerified review - view originalExternal link

    Das Produkt ist super und ist genau das, was ich gesucht habe.
    ESP flashen, UART Ports festlegen, alles anschließen und fertig.

    Image #1 from Kevin
  6. Martin B. (verified owner)

    Verified reviewVerified review - view originalExternal link

    Det fungerer bare, er koblet på et Bosch Europur gasfyr og snakker så med Home Assistant.

  7. Erik Groh (verified owner)

    Verified reviewVerified review - view originalExternal link

    Works absolutely perfect thanks!

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