EMS interface board V3

(51 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.

Discontinued. See the new version HERE.

Out of stock

EAN: 8720299950801 SKU: ems-int-v3-0 Category:


This is the latest version of the original BBQKees 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.


  • Very small form factor (only 35x42mm)
  • Robust bus-safe EMS interface design in operation all over Europe since 2018
  • 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 EMS 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 or 110cm EMS service cable for connecting the board to the EMS 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 EMS 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 (8,5-12V DC via your own step-down voltage regulator). When you use the EMS bus wires you always need to power the microcontroller externally (F.i. with a USB power supply).

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 (8,5-12V DC on the jack if connected).

Additional information

Weight 0,1 kg

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

Origin country


HS Code


51 reviews for EMS interface board V3

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Based on 52 reviews
  1. English

    Dieter P. (verified owner)

    Does what it was promised to do without hassles!

  2. English

    Tomasz Płonka (verified owner)

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

  3. English

    Ulrich Stoehlker (verified owner)


    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. English

    Jarosław G. (verified owner)

  5. English

    Kevin (verified owner)

    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. English

    Martin B. (verified owner)

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

  7. English

    Erik Groh (verified owner)

    Works absolutely perfect thanks!

  8. English

    Anonymous (verified owner)

    Works as expected. Be sure to have correct power supply 😉

  9. English

    Stefan L. (verified owner)

    Works as designed, no problems at all.

  10. English

    Daniel B. (verified owner)

  11. English

    August (verified owner)

    Funktioniert. Ich lese Daten einer Buderus GB192i mit Solarthermie.

  12. English

    Michael Trebuch (verified owner)

    A little bit expensive but It is working perfect. Great job! Thank you!

  13. English

    Sergiy Andrusenko

    Приємно здивований бонусом! Дякую!

    Image #1 from Sergiy Andrusenko
  14. English

    Aliaksandr (verified owner)

    Everything works well! The detailed instructions allowed to setup everything quite fast. I’ve tested it for Bosch GAZ 7000. For some reasons, It’s recognized as Bosch Condens 2500, but it doesn’t impact to anything. Initially it was strange to me why I cannot setup temperature, but for this boiler it’s necessary to set high temp using the physical regulator, and only after that it’s possible to send a temp using the adapter (but not more than a value which is set by the physical regulator). Also there is no ability to simply switch off a boiler, but it’s possible to set e.g. the current temp flow to 15, and it will mean that boiler should off. Shipping to Belarus takes ~2 weeks

  15. German

    Marcel (verified owner)

    Schnelle Lieferung und sehr gute Qualität. Bin sehr zufrieden. Danke

  16. English

    Egbert P. (verified owner)

  17. Dutch

    ruud kroes (verified owner)

    Werkt top

  18. English

    Anonymous (verified owner)

  19. English

    Matthias (verified owner)

  20. English

    Anonymous (verified owner)

    Ich bin super zufrieden mit dem EMS interface board V3. Ich benutze es gegen eine Buderus-Gasheizung. Im Kombination mit dem EMS-ESP ist das eine sehr einfache und schöne Methode die Werte aus der Heizung aus zu lesen.

    Image #1 from Anonymous
    Image #2 from Anonymous
  21. English

    Richard N. (verified owner)

    Board arrived quickly and in good condition. I had a few issues installing the firmware due to the new version needing different partitions but I received help through the Discord channel and now it is working great!

  22. English

    Roy K. (verified owner)

    Werkt perfect. Had wel mooi geweest als er een regulator op had gezeten voor voeding vanaf de ketel, maar buck converter ertussen werkt ook prima.

  23. English

    Kim U. (verified owner)

    It works like a charm

    Image #1 from Kim U.
  24. English

    Jonas (verified owner)

    Work Like expected.

  25. English

    Anonymous (verified owner)

  26. English

    Anonymous (verified owner)

  27. English

    Igor I. (verified owner)

    Thank you mate for a discount and upgraded version. ❤️UA

  28. German

    Markus B. (verified owner)

  29. English

    Anonymous (verified owner)

  30. English

    S, (verified owner)

    4 encoluse setup 90° pin headers are senseless. i had to replace them to stright ones.

  31. English

    Gasper S. (verified owner)

  32. English

    Anonymous (verified owner)

  33. German

    Martin (verified owner)

    Das Gerät funktioniert leider nicht ?

    • English

      BBQKees (store manager)

      Eine selbstgemachte Modifikation für den iRT-Bus bringt leider nicht in allen Fällen sofort Erfolg. Das kann manchmal ziemlich schwierig sein. Das kann ich nur bedingt unterstützen.

  34. English

    Sylvain (verified owner)

    Very nice board posted in an eco-friendly box. Fast delivery.
    No particular difficulties to connect it on an ESP32 flashed with EMS-ESP32. Online documentation is precise and extensive.
    Very nice to have the power return from the heat pump to power everything (thanks to a DC to DC converter thought) so the only needed connection is the mini-jack wire to make everything works.
    As you can see here, super professional inbox setup! XD
    Everything was integrated in Home Assistant with MQTT at the first shot.
    If that helps, the board is connected to a Bosch Compress 3000 AWS
    Thanks for the board, the support and the great community around this projet!

    Image #1 from Sylvain
    Image #2 from Sylvain
    Image #3 from Sylvain
  35. English

    Emilian (verified owner)

    just works

  36. English

    Anonymous (verified owner)

    Perfekt item
    Perfekt Documentation

  37. English

    Elmar (verified owner)

    Nice interface to my Nefit Boiler / Thermostat

    Image #1 from Elmar
    Image #2 from Elmar
    Image #3 from Elmar
    • English

      BBQKees (store manager)

      That’s a neat integration!

  38. English

    Andrei (verified owner)

    Be sure to match the RX TX pins with the ones from the board exactly as in the EMS-ESP Board Profile page, not reversing them, I pulled my hair out about this.. Works well!

  39. English

    Willem (verified owner)

  40. English

    Knut (verified owner)

    works as expected with Logano GB125/KB195i/Logamatic MC110

  41. German

    Michael Roth (verified owner)

  42. English

    Paweł W. (verified owner)

    Nice product. With good price you can control your boiler and integrate them with home automation system by mqtt. It’s great.

  43. German

    Sebastian (verified owner)

  44. English

    Ľubomír GROSIAR (verified owner)

  45. German

    Mirko Bonnawitz (verified owner)

    • English

      BBQKees (store manager)

      I have not received any message from you whether you got the product working or not. Not sure what is wrong here.
      You can just reply to your order confirmation email or use the contact form on the website if you find it difficult to get the board working.

  46. English

    Florin M. (verified owner)

    I did not tought that it will work that easy !
    Works perfect, integration into HomeAssistant without any problems. Great device and software. Would recommend to anyone!

    Image #1 from Florin M.
    Image #2 from Florin M.
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    Image #4 from Florin M.
  47. German

    Michael L. (verified owner)

    The EMS/ESP (along with Home Automation) helped me to identify that my heating burner was turning on and off during nighttime every 10 minutes despite no heating demand from the radiators. I could easily correct this with the EMS/ESP board and the integration into Home Automation. Great Product!

    Image #1 from Michael L.
  48. German

    Henning (verified owner)

    Genau das, was ich mir vorgestellt habe.

  49. German

    Ferdinand (verified owner)

    Funktioniert einwandfrei in Verbindung mit einem ESP32 und Home Assistant

  50. English

    Anonymous (verified owner)

    is working like a charm with my Buderus heating system. I connect it to the EMS-Bus of the solar modul contacts.

    Image #1 from Anonymous
  51. English

    Anonymous (verified owner)

    Ho acquistato la scheda d’interfaccia ems collegata ad una caldaia Buderus GB 122 ed integrata in Home Assistant. Perfetta riesco a visualizzare tutti i parametri della caldaia. Ho usato un nodemcu esp32 v1. Semplice e chiara la programmazione. Perfetta

  52. English

    Anonymous (verified owner)

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