ESPHome Setup

After flashing the ESPHome firmware, follow these steps to connect your device and integrate with Home Assistant.

About This Firmware

The ESPHome firmware is powered by echavet's MitsubishiCN105ESPHome project, an open source ESPHome component for Mitsubishi heat pumps.

Serin Labs adds:

Browser-based flashing — no toolchain required
Interactive YAML generator for custom configurations
Pre-built firmware binaries for supported boards
Curated default configurations with sensible defaults
Wiring guides and setup documentation

In Home Assistant, the device appears as "Serin" by default (customizable in the YAML generator).

1. Connect to WiFi

Power up the device and connect it to your WiFi network using one of these methods:

Option A: During Flashing (Recommended)

If you just flashed the firmware from the flash page, the flasher prompts you to configure WiFi immediately — enter your credentials and the device connects before you unplug USB. If you already completed this step, skip to Step 2.

Option B: USB-C (Improv Serial)

For a device that is already flashed but needs new WiFi credentials:

Plug the device into your computer via USB-C.
Click the button below, select the serial port, and enter your WiFi credentials.

Option C: WiFi Access Point

If USB is not available, the device creates a temporary WiFi network on first boot:

Plug the device into USB power.
Connect to the temporary WiFi network (serin-XXXX).
If not automatically prompted, go to http://192.168.4.1.
Enter your WiFi credentials.

2. Adopt in ESPHome Dashboard

Once the device connects to WiFi, it broadcasts its presence on your network. The ESPHome Dashboard discovers it automatically.

Open the ESPHome Dashboard in Home Assistant (Settings → Add-ons → ESPHome).
The device appears as a Discovered tile. If you don't see it, check that the device and Home Assistant are on the same network.
Click Adopt and assign a descriptive name (e.g., living-room).
Click Install to push a personalized configuration over WiFi. This generates unique encryption keys and takes a few minutes to compile and upload.
After installation, the device reboots and shows as Online in the dashboard.

Home Assistant then auto-discovers the adopted device — look for a notification under Settings → Devices & Services and click Configure to add it.

3. Connect to Your HVAC Unit

Turn off power to your HVAC unit and open the cover to locate the red CN105 connector.
Plug the CN105 connector into the HVAC unit and Grove connector into the device.
Place the device safely inside the unit if needed, reinstall the cover, and restore power.

4. Access Web Control

Visit the device's IP address in a browser.
Monitor and control your system through the built-in interface.

5. Customize

Use the YAML generator to create a custom configuration with remote temperature sensors, vane control, and advanced diagnostics.

6. Multiple Indoor Units

If you have more than one indoor head (e.g., a multi-zone system with 3-5 units), you need one controller per indoor unit — each unit has its own CN105 port.

Unique names: Give each device a distinct name in the YAML generator, such as living-room, bedroom-1, office. The friendly name appears in Home Assistant (e.g., "Living Room", "Bedroom 1").
Repeat the setup: Flash, connect to WiFi, and adopt each device individually. The process is the same for every unit.
ESPHome Dashboard: All your devices appear in a single ESPHome dashboard in Home Assistant, making it easy to manage updates and configurations across your fleet.

Need Help?

Running into issues? See the troubleshooting guide, check Discussions for answers, or open an issue on GitHub.

Disclaimer

This is an independent open-source project. It is not developed, endorsed, or certified by Apple Inc. or Mitsubishi Electric Corporation. Modifying HVAC systems may void warranties and carries risks. Proceed with care. This project is provided as-is, with no warranties or liability.