OpenTherm Gateway V2.3

Tax included

OTGW (OpenTherm GateWay) is based on an open source project by Schelte Bron.

Version 2.3 runs from 5V USB power. There is a built in USB/serial converter to allow a PC to communicate with the gateway via USB.

You will find more information at: 

Build to order

Manufacturing time is approximately 1 week upon placing an order.

OTGW (OpenTherm GateWay) is based on an open source project by Schelte Bron. You will find more information on this website: 

Please note that this product can be expanded with either an optional board for WiFi or for Ethernet, but not both.

The OTGW is sold as a kit. The SMD components are already fitted, only three components and some (optional) headers need to be added. If you don't want to do any soldering, order the soldering service. The OTGW will then be delivered ready for use.

The board obtains its power via USB. You may be able to use a power supply you already own, or you can purchase a power supply. A high quality USB cable is recommended.

For more information please read the manual.

Another source for information is the Domotica OTGW forum: OTGW Forum

On OTGW boiler and thermostat matrix you will find a list of boilers and thermostats compatible with the OTGW print, and also which functions are supported.

During normal operation, the OTGW will communicate with the boiler and the thermostat via the two-wire OpenTherm link: the OTGW must be installed between boiler and thermostat. For programming, the OTGW can be linked to your computer using a USB cable, Wifi or ethernet  (options to be purchased separately: USB cable, Wifi (WeMos D1 Mini) or Ethernet (USR-TCP232-T2) modules are not included). On delivery, the OTGW kit includes a pre-programmed PIC with the latest firmware. Tools and future firmware can be downloaded from OTGW download (

Supported features:

  • Monitor and log Opentherm communication between boiler and thermostat
  • Change thermostat temperature setpoint
  • Add outside temperature to thermostat display (if supported by thermostat)
  • Read outside temperature sensor
  • Control hot water supply (if supported by boiler)
  • Supports the following situations:
    • Opentherm thermostat
    • On/off switching thermostat
    • No thermostat present

Note that for several of these functions you will need a controlling program, for instance Domoticz.

Specific References



Driver for CH340 Serial

Download (179.66KB)

OpenTherm Gateway Manual V2.3

Assembly and use (English/Dutch)

Download (1.57MB)

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