HomeKit-Compatible Setup

After flashing the HomeKit-compatible firmware, follow these steps to connect your device and add it to Apple Home. An Apple Home Hub (Apple TV or HomePod) is required for remote access and automations.

1. Connect to WiFi

On first boot, the device creates a WiFi access point:

Connect to the Serin-XXXX network (XXXX = last 4 hex digits of WiFi MAC, password: serinlabs).
A captive portal appears — enter your WiFi SSID and password.
The device saves credentials and reboots.

WiFi captive portal for entering network credentials

2. 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.

3. Add to Apple Home

HomeKit pairing screen in Apple Home app

Once connected to WiFi:

Option A: Scan QR Code (recommended)

Open a browser and go to http://<device-ip>:8080.
Scan the QR code shown in the HomeKit panel with your iPhone or iPad.

Option B: Manual Setup Code

Open the Home app on your iPhone or iPad.
Tap + > Add Accessory.
Select Heat Pump XXXX (or tap More options...).
Enter the setup code shown in the web UI (HomeKit panel > Setup Code).

4. Access Web UI

Built-in web UI for thermostat control and diagnostics

The built-in web interface at http://<device-ip>:8080 provides:

Thermostat control (mode, temperature, fan speed)
Vane control (vertical and wide vane positions)
Diagnostics (compressor frequency, outside temp, error codes)
Settings (device name, poll interval, temperature unit)
Real-time log streaming

5. OTA Updates

Update firmware over the air without USB access:

Via Web UI: Navigate to Settings > Firmware Update. The browser verifies integrity before uploading.
Via curl:

idf.py build
curl --data-binary @build/mitsubishi-cn105-homekit.bin \
     -H "Content-Type: application/octet-stream" \
     http://<device-ip>:8080/upload

After an OTA update, the device validates WiFi and UART communication before confirming the new firmware. If validation fails, it automatically rolls back.

6. Troubleshooting

WiFi Recovery

Method	Details
Auto AP	Fallback AP activates after 5 min disconnect. Disables when WiFi reconnects.
Recovery page	Connect to AP, navigate to `192.168.4.1:8080` for new credentials.
Button reset	10-second long-press on board button erases stored WiFi credentials.

Re-pairing

If you need to re-pair, open the web UI and use the "Reset Pairing" button in the pairing panel, then add the accessory again from the Home app.

For more troubleshooting tips, see the full troubleshooting guide.

Multiple Indoor Units

If your system has multiple indoor heads, you need one controller per unit — each has its own CN105 port.

Independent pairing: Each device pairs separately to Apple Home. Open the Home app and add each accessory one at a time.
Naming: After pairing, rename each accessory in Apple Home to match the room (e.g., "Living Room AC", "Bedroom AC"). You can also assign each to its corresponding room in the Home app.
Repeat the setup: Flash, connect to WiFi, wire, and pair each device individually. The process is the same for every unit.

Need Help?

Check the troubleshooting guide, browse Discussions for answers, or open an issue on GitHub.

Source Code

The HomeKit-compatible firmware is open source. See the GitHub repository for protocol documentation, project structure, and build instructions.

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.