EMS interface board V3

Description

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.

Features:

• 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

Options:

• 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.
It 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).