The latest revision V2.2 of the EMS Gateway E32 V2 circuit board was introduced in the summer of 2025.
The V2.2 circuit board has a few additional sensor on it that are exposed in the Sensors tab of EMS-ESP and are available via MQTT and the other API’s. Because we got a few questions lately about these sensors we provide some more details here.
Temperature sensor
The first sensor is ‘gateway_temperature’ and is a SMD type DS18B20U temperature sensor that is mounted directly on the circuit board. The DS18B20 sensor is connected to GPIO14, which is the same pin used for connecting external DS18B20 sensors via the JST connector.
The sensor is positioned in the center of the board, away from hot components. This sensor measures the internal temperature of the Gateway. So it is not the internal temperature of the ESP32 chip itself, but the temperature inside the enclosure.
If you for instance mount the Gateway inside or on top of the boiler where it may get warm or hot (not recommended), you can keep an eye on the temperature. Or set an temperature alarm via the scheduler.
Voltage sensors
There are two voltage monitors on the circuit board.
The first one is ‘core_voltage’ which monitors the 3,3V output of the internal voltage regulator of the circuit board. This voltage is used to power the entire board. This voltage monitor is connected to GPIO39.
The second one is called ‘supply_voltage’ which connects to GPIO36. This monitors the external supply voltage of the Gateway. This can be coming from either the USB-C port (5V DC), the EMS service jack (8,5V or 12VDC) or the external DC input (12V DC).
If multiple power inputs are used at the same time, this monitor will show the highest voltage.
Blue LED
In the Analog Sensors section you can also find the entity ‘led’. This is not a sensor but it is a blue LED connected to GPIO2.
This is the LED that was mounted on all older E32 V2 circuit boards, and it is still mounted on the latest V2.2 circuit boards, even while there is also a RGB LED next to it.
The blue LED was maintained for backwards compatibility reasons. If you f.i. load firmware 3.7.2 or older, there is no support for the E32 V2.2 board profile, and the RGB LED won’t work.
But in normal conditions the blue LED is not used when the RGB LED is available. However, you can still turn it on or off via this sensor entity.