EMS interface board

(7 customer reviews)

32,95 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-V1 Categories: ,


This is the new version of the original EMS bus to microcontroller UART interface board (previously called the ‘EMS level shifter V0.9’).
With this board you can safely connect a UART/serial port of your microcontroller or development board to the EMS bus.


  • 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 or the Raspberry Pi header
  • Fits in every Raspberry Pi housing (you only have to make a hole for the screw terminal)
  • Each board tested before shipment on an actual EMS 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).

If you are buying this board because you want to use it on a iRT boiler please purchase the iRT modified item.

Each interface board is completely assembled and tested on an EMS boiler before shipment.

This product is available in two variations: The interface board with or without the Raspberry Pi stacking header included. The version with the stacking header is called the ‘EMS bus HAT for Raspberry Pi‘ and you can find it here.
If you want to use it on a Raspberry Pi then choose the model with the stacking header. If you want to use it with any other microcontroller then choose this model without the stacking header, which would only get in the way. If needed you can add a stacking header later.

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

7 reviews for EMS interface board

Based on 7 reviews
5 star
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Showing 7 of 7 reviews (5 star). See all 7 reviews
  1. Fabien COUTURIER (verified owner)

    Verified reviewVerified review - view originalExternal link

  2. Vladislavs Z. (verified owner)

    Verified reviewVerified review - view originalExternal link

    Отличная плата, завелась сразу.

  3. Georgios Ioannou (verified owner)

    Verified reviewVerified review - view originalExternal link

    Even with Iobroker works fine. Please sell me one Resol interface sometime soon !

  4. Gunnar (verified owner)

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  5. Maik (verified owner)

    Verified reviewVerified review - view originalExternal link

    It just works

  6. Bogdan P. (verified owner)

    Verified reviewVerified review - view originalExternal link

    Dopracowane urządzenie. Bez problemu podłączyłem do mojego pieca Buderus i skonfigurowałem w Home Assistant.

  7. Jeroen S. (verified owner)

    Verified reviewVerified review - view originalExternal link

    Werkt perfect op mijn Junkers ketel- en solarinstallatie.

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