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Powering the E32 V2 EMS Gateway via passive POE

Sometimes there is no easy way to make a 230V wall outlet or power socket near the boiler or heat pump. The E32 V2 has Ethernet, but is does not support active POE (Power Over Ethernet), which is usually 48V or 24V.

What you can do instead is use a so called ‘passive POE cable kit’ like the Digitus DN-95001 to inject the 12V DC of the BBQKees Electronics power supply to the E32 V2 over the same Ethernet cable as the LAN signal.

Each Ethernet cable has 8 leads, 4 of which are used for data and the other 4 are used for power.

These cable kits will also work for longer distances of Ethernet cable where the 12V voltage may drop a bit, because the E32 V2 will still work with f.i. 9V DC. And the bitrate of the connection is relatively low at just 100Mbit.

Below an image of such a cable kit. The female Ethernet connectors are for connecting to the Ethernet cable from the router location to the Gateway location. And then one side has a Ethernet plug which you plug into your router or switch and a female receptacle for the 5,5mm DC barrel jack plug of the 12V DC power supply.
The other cable in the kit has a male Ethernet plug and a 5,5mm male barrel jack plug for connecting to the Gateway.

Below an example setup. On the left you connect the combiner cable to your router or switch, and you plug in the 12V DC power supply to the connector on that cable.
On the receiving end you connect the incoming Ethernet cable to the splitter cable, and then the Ethernet plug of the splitter cable and the barrel jack plug into the E32 V2.

Please pay attention if your switch or router has 24V or 48V POE enabled on that specific port and you are using this passive cable set at the same time, you may blow up the Gateway. Of course I do not give any warranty if you fry the circuit board. Furthermore this page is just for reference. Always know what you are doing when messing with voltages and cables. The above example may or may not work in your specific situation.

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New version of the EMS screw terminal cable

Since the end of April 2024 I have a new version of the EMS screw terminal cable.

It’s still a 100cm cable with two stranded copper cores of 2×0,5mm2 and the wire ends terminated with a wire ferrule, but now the cable is black and a bit thinner and more flexible than the previous grey cable.

You can find the cable here or you can include it as an option on the Gateway and Interface board product pages.

Below on the left the ‘old’ version of the cable and on the right the new version.

Some more product images:

You use this cable to connect the orange or green screw connector of the Gateway to the EMS screw terminal inside the boiler or heat pump.

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Gateway model E32 V2 now available

It took a bit longer than expected but the first batches of the new Gateway model E32 V2 with WiFi and LAN are now available.

It has all the awesome features of the S3 Gateway with the same EMS-ESP32 firmware but aside from WiFi it has an additional RJ45 Ethernet port for wired networking.
Because the ESP32-S3 chip of the S3 Gateway does not support hardware Ethernet we used a big ESP32 module instead but with a beefy 8MB PSRAM and 16 MB Flash. This solves all the little memory issues of the previous E32 some users might be experiencing with the latest 3.6.x firmware when used with larger EMS systems.

Although the E32 V2 hardware has 8MB of PSRAM, currently the EMS-ESP32 firmware only supports 4MB PSRAM on the ESP32. 4MB is more than enough for now, but if needed this can be increased to 8MB in the future.
Furthermore EMS-ESP32 currently only needs 4MB of Flash storage, so with 16MB of Flash storage in the E32 V2 there is lots of room for more features.

Because the circuit board did not fit anymore into the grey enclosure of the E32 V1.0/V1.5 and the S3 a new enclosure was created. It also has mounting holes on the back. Furthermore it is UL 94 V level fire retardant.

The E32 V2 went through several rounds of prototyping and is of course CE certified and manufactured according to the RoHS directive.
The LAN port provides a very stable interface. POE is not included though, non-isolated 48V is not a good match with the 16V EMS bus.

Currently there may be limited availability of this model, from March onward continuous stock is expected.

You can find it in the webshop HERE.

If you don’t need LAN the cheaper WiFi-only S3 and S3-LR are still a great choice as well.

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New Gateway models S3 and S3-LR available

As time progresses so does the EMS-ESP firmware. We were now at a point were EMS-ESP would benefit from some more RAM memory.

That’s why BBQKees Electronics is introducing the new EMS Gateway S3 models. One with the default on-chip antenna and an identical Gateway model with an external high gain antenna for those area’s with low WiFi reception. These are the replacement for the very popular S32 Gateway.

S3-LR front
S3-LR back

Hardware changes

The S3 models looks and feel identical to the EMS Gateway S32 V2.0 they are replacing but they now come with an ESP32-S3 module with 16MB Flash and a hefty 8MB PSRAM (in addition to the on-chip 512KB RAM), which makes it more suitable for large EMS systems with a heat pump or multiple zones/heating circuits.

The new hardware continues using the existing third-gen BBQKees EMS detecting and sending circuitry design as in the S32 Gateway and the EMS Interface board V3’s, which has proven extremely reliable and robust over the years for all EMS types across all Bosch brands.

Aside from the more powerful chip, this model now also features an external USB-C connector for manual firmware updates (if ever needed). The USB-C connection makes use of the internal USB OTG controller of the ES32-S3 so we don’t need the CH340 chip and driver anymore.

What has remained unchanged are the positions and pinout of the external connectors so the S3 is a direct replacement for S32 setups. Only the LED lightguide was changed a bit.

The power options via the service jack or 12V DC power supply also remained the same.


The S3 models will be loaded with firmware EMS-ESP32 v3.6. This is exactly the same firmware with the exact same features as for the S32, just built for the different chip architecture of the S3.
The 3.6 firmware contains a number of new features over 3.5.1, most notably further memory optimizations.

Upgrade discount

If you already own an S32 Gateway it’s probably not really worthwhile to upgrade to the new S3, but if you want too or if you still have an old ESP8266 Gateway like the Premium II you can get a 15% discount on a new S3 Gateway of your choosing. Just use the contact form to contact me with your previous order ID and I’ll give you a discount code.

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Massive firmware update now available: EMS-ESP 3.5.0

Firmware EMS-ESP 3.5.0 has been available as a beta for quite some time and it had already been loaded on new Gateways since October 2022, the release version of 3.5.0 (stable) is now available as well.
Thanks to a lot of work by Proddy and MichaelDvP and assisted by a number of other contributors, this is one of the most feature rich updates yet.

Remember the firmware is completely open source

The the most noticeable new feature is going to be the addition of localization. This means you can now change the language from English to other languages. The release of 3.5.0 will contain English, German, Dutch, Polish, French, Swedish and Norwegian language.

This localization is in all major parts of EMS-ESP: the web interface and MQTT.

There are however some breaking changes. The most important one is that there is now support for multiple Gateways on a single MQTT broker. When enabled, which is now the default, all MQTT Discovery Entity IDs will include the MQTT base name and the shortname of the EMS-ESP device entity. For example what was previously sensor.boiler_actual_boiler_temperature will now become sensor.ems_esp_boiler_boiltemp. This means these entities will have to be replaced inside HA. See below. If you still want to use the old format and retain the history and script compatibility in Home Assistant then set this back to the old format.

New features and updates

Summary of new stuff:

  • Localization: addition of German, Dutch, Polish, Swedish, French and Norwegian language options.
  • Support for multiple Gateways on the same broker (for hybrid systems and for multiple boilers/cascade)
  • 100+ bug fixes and new features
  • Added initial support for ESP32 C3 and S2 architectures
  • Several new board profiles
  • Improvements in HA Discovery and MQTT handling
  • Addition of new EMS boilers, thermostats and other devices (Greenstar 30, GBH192iT, FW500, BC30)
  • Addition of additional parameters of known EMS devices (f.i. RC30 internal temp, 20+ heat pump parameters)
  • Improved handling of logic/telegrams of some EMS devices
  • Setting the 4 multi-purpose relays/inputs of heatpumps (via API)

Full release notes see:

How to update to 3.5.0

To update to the release version of 3.5.0 depends on which firmware you are on now, and when you purchased a Gateway product. In most cases you should first try out an update via the web interface. If it succeeds, you are on 3.5.0. If it fails you need to flash the Gateway via the internal USB connection on the Gateway board.

Read the instructions below for the correct update procedure for your situation.

If you are currently on any 3.3 or older version you need to use the USB method anyway.
If you are currently on any 3.4 or 3.5 version first try the update via the web interface and if it fails update via the USB port.

Method one: Update via the web interface

Download the 3.5.0 bin file from the repository. Then open the web interface of the Gateway, go to System->Upload and select the bin file you just downloaded.

The upload will take about a minute. If the Gateway has installed the firmware and rebooted itself, you should see the login screen again after a while. Press F5 to clear the browser cache. Then login.
Settings should be pertained.

In case you get an error 500 during the upload, you need to move on to method two below.

In case you have an E32 Gateway and it became unreachable after the update, the board profile might have been reset to S32 or Custom. Please login to the ems-esp access point, set the board profile back to E32, save, and reboot. Ethernet will be activated again.

Method two: Update via the USB port

If a lot of cases you need to upload this firmware via the USB port on the inside of the Gateway. It is the only time this is needed, if 3.5.0 is installed once, all future updates can be done via the web interface.

You need to open the Gateway, plug in the USB to a computer and load the firmware via the EMS-ESP flash tool. DO NOT use another flash tool as it will not work.
All settings will be lost after this update, so make a note of all important ones.
(You can also backup your settings and customizations before the update and load them once the update is done).

For the detailed update procedure look here:

If you have questions about the update you can send me an email via the contact form.

Breaking change: MQTT entity ID’s

For a number of entities in Home Assistant the unique ID has changed in the auto discovery config . This means these entities will have to be replaced inside HA.
This is because there is now support for multiple Gateways on a single MQTT broker. When enabled, which is now the default, all MQTT Discovery Entity IDs will include the MQTT base name and the shortname of the EMS-ESP device entity. For example what was previously sensor.boiler_actual_boiler_temperature will now become sensor.ems_esp_boiler_boiltemp. This means these entities will have to be replaced inside HA. See below. If you still want to use the old format and retain the history and script compatibility in Home Assistant then set this back to the old format.
There is a new checkbox in the Settings to keep the ID as in firmware 3.4 for those who do not want to switch now.

Another way is to rename the entity ID’s in the HA database with a script. See:

Possible bugs

After the update to 3.5.0 it is possible that sometimes during loading or viewing of the web interface you’ll get an Error 507.
This is because the new web interface needs a fairly large chunk of memory, which is not always available. You get this error 507 then. All other services on the Gateway will continue to work. See:

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Difference between the EMS Gateway and the KM200/MBLAN2

Bosch has internet gateways for selected EMS boilers and heatpumps. It’s a range of models like the KM50, KM100, KM200 and MBLAN 2. Depending on the brand there are small variations. Nefit just calls it ‘Internet module’. There is an external model for existing boilers and an internal module for heat pumps. With this gateway and an app on your phone you can see (partly) what your boiler is doing.

The BBQKees EMS Gateways also give insight into boiler parameters.

I often get questions about the difference between the EMS Gateway and the Bosch KM200 Internet gateway. In this article I’ll explain it in more detail.

How does the KM200 work

The KM200 (and the other Bosch internet gateways) connect to the CAN or EMS bus of the boiler or heatpump and your home network. The data it captures from the bus is then sent to the cloud.
You need to install an app on your phone to see the data. The app does this by connecting to the cloud and retrieving your boiler data from the cloud. So all your boiler data is stored in the cloud.
It provides a link between your boiler and an app via the cloud.

How does the EMS Gateway work

The EMS Gateways also connect to the EMS bus of your boiler or heatpump and your home network. The data it captures is then sent to your home automation like Home Assistant or Domoticz.
It depends on how you configured your home automation on how you can access the data. Likely via a web interface on your pc but probably also via an app.
The EMS Gateway provides a link between your boiler and your home automation solely via your home network. So you do not need an external cloud service. All boiler data is stored locally in your home automation system.

Amount of available datapoints

Existing owners of a KM200 are often surprised by the amount of datapoints/entities the EMS Gateway provides over the KM200. With the EMS Gateway you usually get 60 entities of just the boiler alone. With some boilers and heat pumps this may add up to much more (100+). For thermostats and mixer modules it depends on the specific model but there are always some interesting values coming out.

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E32 back soon

Currently the E32 is sold out. We are still waiting on a shipment of boards before we can assemble new products.

The E32 will probably be back in stock before the end of October.

You can fill in your email address on the product page to be notified the moment stock is added.

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Settings not saved in firmware 3.4.2 and 3.4.3

Firmware 3.4.2 and 3.4.3 have a small bug. If they are flashed on a new Gateway or other ESP32, settings are not stored. This means when you set up the device, after reboot it loses all settings.
If you update from a previous version via the web interface this problem does not occur.
Gateways with this issue shipped in the past few weeks can be updated via the web interface to version 3.5.0 and then it will work.

If you get an error 500/server error when you load the 3.5.0 firmware via the web interface, you need to use the USB connection inside the Gateway to flash firmware 3.5.0.

The steps to update are as follows:

First download the latest 3.5.0 firmware from

The file is a bin file called EMS-ESP-3_5_0b7-ESP32.bin .

Next connect to the ems-esp wifi network of your new Gateway and go to settings->upload.
Choose the file you just downloaded.

The Gateway will now update and after a minute you should refresh the page.
(Perhaps you need to reconnect to the ems-esp wifi network again.)

Then on the Settings page it will show the firmware version. It should now show 3.5.0.

If loading 3.5.0 fails with error 500/server error please use the USB flashing method with the new EMS-ESP flash tool to flash the Gateway. You have to open the device to access the USB connector.

For the E32 it advised to connect the 12V DC power supply while flashing via USB if available.

Firmware 3.5.0 is still a beta, but it is packed with new features. You can now set the language to Dutch, English, German or Swedish.

One remark: if you set a language, all MQTT entities are renamed as well so you have to reload everything into Home Assistant etc again.

Instead of 3.5.0 you can also load 3.4.1 via the web and then upload to 3.4.3 the same way to stay on stable.