EMS bus HAT for Raspberry Pi


EMS bus HAT for Raspberry Pi. Connect your Raspberry Pi to the EMS bus.

Sold out. New stock mid-October 2020.

Out of stock

SKU: ems-pi-hat-1 Categories: ,


EMS bus interface board. Connect your Raspberry Pi to the EMS bus.

This board is a so called HAT for Raspberry Pi.
It connects the EMS bus to the serial port (UART) of the Raspberry Pi on pins GPIO14 and GPIO15.
Just press it on the Pi, connect the EMS bus wires and install or write your software for the bus communication.

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

The new board is compatible with all Raspberry Pi models that have a 40-pin header. These include:

  • Raspberry Pi A+
  • Raspberry Pi B+
  • Raspberry Pi Zero
  • Raspberry Pi 2
  • Raspberry Pi 3
  • Raspberry Pi 4

This set includes the complete board with the stacking header soldered on and a set of 14mm nylon standoff spacers with screws and nuts.
Each board is tested on an EMS boiler before shipment.

Technical details:

With this board you can safely connect a UART/serial port of your microcontroller or development board to the EMS bus.
The stacking header ensures perfect compatibility with the Raspberry Pi, but it can also be used for connecting other microcontrollers.

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 of these technicalities?
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 onto your Pi 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.
Aside from the Raspberry Pi, this board is also compatible with f.i. every Arduino, Atmel, ESP8266, ESP32, Wemos, NodeMCU and other microcontrollers.
For more information have a look at the product wiki.

The stacking header and the correct set of standoff spacers make it possible to add multiple HATs to the same Pi. Just make sure the other HATs don’t use the serial port of the Pi on GPIO14 and GPIO15. This HAT does not include a config EEPROM so if your other HAT has one this board won’t get in the way at all.

Additional information

Weight 0.1 kg
Board model

Interface board only, Interface board with soldered Pi header

Bus compatibility

EMS, EMS Plus, EMS+, EMS2, Heatronic


3,5mm Service jack, EMS bus wire screw terminal