BBQKees Electronics offers two types of products to interface with the EMS bus: Gateways and interface boards.
Interface boards are only a pure hardware board that translates the EMS bus signal to a UART serial port signal and vice versa. You need to connect a microcontroller to these boards and install or write your own software to interact with the EMS bus.
The EMS interface board is actually the identical EMS interface circuit block of the EMS Gateway S3, but with an UART connector instead of a processor and power electronics.
EMS Gateways are a complete plug and play package that you can connect to the EMS bus of your boiler, heat pump or supported ventilation unit via just one cable or two wires and they provide an easy to use web, MQTT or HTTP interface to communicate with your home automation.
EMS interface board
EMS Gateway
Choosing between a Gateway and an interface board
If you want to have all your boiler and thermostat data into your home automation like Home Assistant, Domoticz etc with only one cable and with only minimal configuration, then pick a Gateway. If you like to play around with electronics, solder stuff and mess around with Dupont wires, or you want it a bit cheaper but less nice, you can choose one of the interface boards.
Like mentioned above the interface boards are just a piece of hardware that provides a safe connection between the 15V EMS bus and a 5V or 3.3V microcontroller UART. The interface board comes with no microcontroller or software.
Although the interface board can be electrically connected to f.i. a Raspberry Pi, there is no software available that can decode the messages. So even if Home Assistant, Domoticz etc is running on that same Pi, adding an interface board to it won’t work. You need either an EMS Gateway of couple the interface board to an ESP32-S3 module with PSRAM.
Choosing between Gateway models
At this moment two Gateways models are available:
- Gateway S3 = Wi-Fi only model
- Gateway E32 V2 = Wi-Fi + LAN interface model
Aside from the LAN port, both models have the same firmware features and performance.
Which Gateway model is the ‘best or newest’ ?
The white E32 V2 is the second version of the E32 Gateway. The ‘E’ is derived from the word ‘Ethernet’, the LAN port/protocol.
’32’ is derived from ‘ESP32’ which is the microcontroller type used on board.
The grey S3 is the third version of the Standard Gateway model. (‘S’ is derived from ‘Standard’).
The ‘3’ is derived from the ESP32-S3 microcontroller on board.
The second generation of the Standard Gateway model was the S32, which was based on the ESP32 microcontroller.
As the third generation Standard Gateway S3 has the ESP32-S3 instead, it was called ‘S3’ instead of ‘S32 V3’ to avoid confusion.
The Standard Gateway range is developed in parallel, but independently of the versions of the Ethernet Gateway. So the version numbers of the E32 V2 and S3 are independent of each other and the third generation of the Standard Gateway is not ‘newer’ than the second generation of the Ethernet Gateway. Actually the E32 V2 was released 6 months after the S3.
Feature set and differences
Although the hardware between the Standard and Ethernet version is a bit different, all models have the identical feature set in the firmware and will perform the same.
Microcontroller differences
All models are based on the ESP32 microcontroller range from Espressif. Both the E32 V2 and the S3 have been designed with an over-dimensioned and large 8MB of PSRAM and 16MB of Flash.
Flash storage is the ‘hard disk’ of the Gateway, where the EMS-ESP firmware and all setting are stored. Currently of that 16MB only about 2MB is used for the EMS-ESP firmware (4MB needed for over the air updates). So we have a lot of room for future additions.
PSRAM is a type of RAM, the internal memory of the microcontroller that is used to run the firmware. The ESP32 modules only have about 512KB on board, but the modules used on the E32 V2 and S3 have an additional RAM chip with 8MB PSRAM. So we added 16x times more RAM.
This huge 8MB of PSRAM will be able to take on any large EMS system with like 300 entities and several interface protocols like MQTT and Modbus TCP operating simultaneously.
The Gateway S3 is based on the ESP32-S3 microcontroller. It is a bit newer than the ‘regular’ ESP32. The E32 V2 has the ‘regular’ ESP32 because the ESP32 supports hardware Ethernet interfaces. The LAN chip on the E32 V2 is absolutely rock solid. Ethernet hardware support was unfortunately stripped out of the ESP32-S3, meaning you have to use a software stack instead and that never really works well.
Although the S3 has a slightly faster chip than the E32 V2, in practice these models perform equally.
The system does respond a bit faster via the LAN connection than over Wi-Fi, but for HTTP API and MQTT this does not matter. And both models have the exact same EMS bus connection and firmware configuration options (Except for the wired networking feature of course).
Other differences
The main difference is the size of the device. The E32 V2 is twice the size of the S3. So where you can stack away the S3 in any corner, the E32 V2 is usually too big for that.
But the E32 V2 has all connectors on a single side, where the S3 has then on both sides. So this may also be important if space is limited.
And although minor, the E32 V2 has some additional filters on the EMS bus and DC input to lower external disturbances even more. But you will not notice any real difference with the E32 V2 in practice.
So which one should you buy then?
If you have LAN near the boiler or heat pump the E32 V2 would be the best choice. The LAN connection is rock solid.
Especially when used together with the 12V DC power supply, the Gateway will remain powered when the heat pump or boiler is restarted or turned off.
If you don’t have LAN available near the boiler or heat pump, but only Wi-Fi, the S3 is a good fit, but don’t forget the E32 V2 also has Wi-Fi with the same antenna performance as the S3.
Before purchase please check if you have Wi-Fi coverage near the boiler or heat pump, or Wi-Fi coverage at the place where you would like to install the Gateway if it is outside of the room of the heat source.
Another consideration is the size of the Gateway. The E32 V2 is double the size of the S3 and S3-LR. If you don’t have a lot of room the E32 V2 may be a bit large.
Feature comparison
Below a comparison of the key features and the differences.
| Feature | S3 | S3-LR | E32 V2 |
| Availability | Available | Discontinued | Available |
| WiFI 2.4 GHz | Yes | Yes (with high gain antenna) | Yes |
| LAN RJ45 10/100Mbit | No | No | Yes |
| EMS bus service jack | Yes | Yes | Yes |
| EMS bus screw terminal | Yes | Yes | Yes |
| USB-C programming port | Yes | Yes | Yes |
| External power supply 12V DC | Yes | Yes | Yes |
| Optional DS18B20 sensors | Yes | Yes | Yes |
| Wall mountable | Yes with optional wall mount | Yes with optional wall mount | Yes, screw holes on the rear side |
| Processor architecture | ESP32-S3 | ESP32-S3 | ESP32 |
| RAM memory | 8MB PSRAM | 8MB PSRAM | 8MB PSRAM (firmware uses currently 4MB, but hardware has 8MB for future use). |
| Flash memory storage | 16MB | 16MB | 16MB |
| CE certified | Yes | Yes | Yes |
| RoHS (Is part of CE) | Yes | Yes | Yes |
| Dimensions (excluding external connectors) | L: 90 mm W: 50 mm H: 24 mm | L: 90 mm W: 50 mm H: 24 mm | L: 125 mm W: 85 mm H: 27 mm |
| Enclosure construction | Very strong grey ABS plastic with UL 94 V-0 fire retardant class | Very strong grey ABS plastic with UL 94 V-0 fire retardant class | Very strong white ABS plastic with UL 94 V-0 fire retardant class |
