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Flashing the Firmware

This guide explains how to flash the E-VLXESP32 firmware to control it from Home Assistant over your local Wi-Fi network.

Flashing is straightforward, and you can use either the Command Line or Home Assistant add-on method.

What You Need

Required Items

  • E-VLXESP32 device
  • USB-C cable
  • A computer (*) to build and upload the firmware

E-VLXESP32

Fig. 1 – Hardware

(*) You can use any computer with WINDOWS/LINUX/OSX or any device able to run HomeAssistant.

Safety Warnings

Important Safety Precautions

  • Do not connect E-VLXESP32 to mains power (110/220V AC) during flashing.
  • Do not connect the VELUX front cover during flashing.
  • Only connect the VELUX front panel after flashing is complete and the USB-C cable is removed.
  • Do not insert any batteries.

Option 1: Command Line

Step 1: Install ESPHome CLI

Follow the instructions to install the ESPHome Command Line Tool at this link.

Verify Installation, open a terminal and run:

$ esphome --version

Expected output:

Version: 2025.8.0

Step 2: Configure Your Device

  1. Download evlxesp32.yaml YAML file from this link.
  2. Open it in a text editor.
  3. Update and save the file as described in this steps.

Update Device Name

Each device must have a unique name. This name is used in Home Assistant and to access the internal device web server:

esphome:
  name: evlxesp32

Update Home Assistant API Key

Each device must have a unique API key. Generate one here (see encryption section):

api:
  encryption:
    key: "pQUjUzzg6T7NuOX4uYN6v4XvBkFcAQHzmYbr63DFmD4="

Set Wi-Fi Credentials

Replace with your network credentials:

wifi:
  ssid: "WIFI_SSID"
  password: "WIFI_PASSWORD"

Step 3: Flash the Firmware

Connect E-VLXESP32 to your computer with the USB-C cable as show in Fig. 2.

E-VLXESP32

Fig. 2 – USB cable

Open a terminal windows and run:

$ esphome run evlxesp32.yaml

When prompted, select USB JTAG/Serial option as show in Fig. 3.

E-VLXESP32

Fig. 23 – Terminal window

Option 2: Home Assistant add-on

Add missing information

Verify Connection

After few minutes E-VLXESP32 is connecting to your local WIFI. You should be able to connect to the internal web server typing on your browser the following: http://evlxesp32.local

Flashing the Firmware

This chapter explain how to flash the E-VLXESP32 firmware.

Flashing the firmware is needed to be able to control E-VLXESP32 from HomeAssistant in your local WIFI network. It’s a straightforward process, and you can choose the method you’re most comfortable with.

Please be sure to follow carefully the following instructions.

⚠ Warning Don't connect E-VLXESP32 to the power 110/220 AC line

⚠ Warning Don't connect the VELUX front cover

The following picture show what is needed.

You can flash the firmware either:

  • From the command line on your terminal window.

  • Using Home Assistant with the ESPHome Builder add-on, or

Command Line

Installing Command Line Tool

The following steps describe how to install ESPHome command line tool on your machine.

You should be able now to confirm that ESPHome has been successfully installed. Open your terminal window and type:

$ esphome --version

you should see something like:

Version: 2025.8.0

Configuration file

The E-VLXESP32 configuration file is available here. Download and open it with your text editor. You have to do the following change.

If needed, rename your E-VLXESP32 device. This is the name that is going to be show in home assistant and it's the name used to the access of the internal web server. Be sure to use a different name for every E-VLXESP32 device in your home configuration.

esphome:
  name: evlxesp32

If needed, replace HomeAssistant API key. The key must be unique for every E-VLXESP23 device in your home setup. Use the following link to generate a new key.

api:
  encryption:
    key: "pQUjUzzg6T7NuOX4uYN6v4XvBkFcAQHzmYbr63DFmD4="

Replace the following with the credential to connect to your local WIFI network.

wifi:
  ssid: "WIFI_SSID"
  password: "WIFI_PASSWORD"

Flash the Firmware

Connect E-VELUX to your computer using a USB cable.

Open a terminal and run:

esphome run evlxesp32.yaml

ESPHome will compile the firmware. When prompted, choose the option to upload the firmware via the USB port.

Done !!!

After few minutes E-VLXESP32 is connecting to your local WIFI. You should be able to connect to the internal web server typing on your browser the following: http://evlxesp32.local

You should be able to see a page similar to the following. From here you can monitor environment humidity, temperature and control the VELUX skylight. E-VLXESP32 has also a green led used for test purpose.

To confirm that every things works properly you should be able to toggle the LED state as show here.

HomeAssistant Add On

ESPHome.... builder

Final note

If you don't want to expose the control of the green led to HomeAssistant change the yaml configuration file replace:

platform: gpio
  pin: GPIO10
  name: "Led Green"

with

platform: gpio
  pin: GPIO10
  name: "Led Green"
  internal: true

From you terminal overwrite the firmware running:

esphome run evlxesp32.yaml

⚠️ Important Safety Notes:

Only connect the VELUX remote front panel when E-VLXESP32 is NOT connected to the USB cable.

Do NOT insert any batteries.