serin labsControl a Mitsubishi mini-split with Amazon Alexa
Connect a CN105 ESP32 controller to the Mitsubishi indoor unit, flash the firmware, and add the heat pump from the Alexa app through a compatible Echo or eero device. Alexa receives a thermostat for temperature, mode, voice commands, and routines. No Mitsubishi Wi-Fi adapter, Kumo Cloud account, custom Alexa skill, or Serin Labs subscription is required.
Already have a controller? Set it up with Alexa.
At a glance
- One CN105 ESP32 controller is required for each Mitsubishi indoor unit.
- Setup begins in the Alexa app through a compatible Echo or eero device.
- Controls include temperature, Heat, Cool, Auto, power, voice commands, and routines.
- No Mitsubishi cloud account or custom Alexa skill is required.
Good to know
- A compatible Echo or eero device is required.
- The firmware is free to install, in beta, and not open source.
- The firmware is not certified; Alexa displays a one-time warning during setup.
- The controller hardware arrives without firmware installed.
How the CN105 ESP32 controller adds Alexa support
Most Mitsubishi Electric mini-splits have a service connector called CN105 on the indoor control board. The Serin Controller combines a supported M5Stack ESP32 board with a tested CN105 cable, giving the firmware a direct, two-way connection to the heat pump.
After you install the firmware, a compatible Echo or eero device discovers the controller on your local network and adds it through the Alexa app. The Alexa device sends your home Wi-Fi credentials to the ESP32 over Bluetooth, so no Serin Labs account or manufacturer skill is required.
What Alexa can control
Power and modes
Turn the unit on or off and select Heat, Cool, or Auto.
Target temperature
Set the thermostat target from the Alexa app or by voice.
Room temperature
Ask Alexa for the temperature reported by the controller.
Voice and routines
Use spoken thermostat commands and include the mini-split in Alexa routines.
Alexa displays a standard thermostat. Fan speed, vane position, diagnostics, and other heat-pump-specific controls remain available through the controller's built-in web interface.
What you need
- A compatible Mitsubishi indoor unit: check the model number before ordering. One controller is needed for each indoor unit you want to control.
- A CN105 ESP32 controller: buy the pre-assembled controller, or use a supported board and cable from the DIY parts list.
- A USB-C data cable and supported browser: the initial flash runs in Chrome, Edge, or Brave on a computer.
- A compatible Echo or eero device: Alexa uses it to discover, add, and control the thermostat locally. Amazon's supported-device list changes, so check Amazon's current compatible-device guidance before ordering hardware.
- The Alexa app: use its add-device flow to scan the pairing code saved by the flasher.
Set up your controller
Setup has three parts: install the Matter-compatible firmware, connect the controller to the indoor unit, and add the thermostat in Alexa. The app transfers your Wi-Fi credentials over Bluetooth; there is no separate setup-hotspot step for initial pairing.
Follow the Alexa setup guide for prerequisites, pairing, and a final check that the indoor unit responds.
Limits to understand before buying
- Beta firmware: it is newer and less tested than the ESPHome and Apple Home firmware.
- Not certified: Alexa displays a one-time uncertified-accessory warning. The product does not carry a Works with Alexa badge.
- Features not available in Alexa: dry mode, fan-only mode, fan speed, and vane direction are not reliably shown in Alexa's thermostat controls.
- Diagnostics are available in the web interface: compressor frequency, outdoor temperature, runtime, and error codes do not appear in Alexa.
- One occupied CN105 port: the controller cannot share CN105 with a factory Wi-Fi adapter or wired wall controller.
Alexa firmware or ESPHome through Home Assistant?
Use the firmware when Alexa is the main interface and you do not already run Home Assistant. Use ESPHome when you want fan, vane, diagnostic, and automation entities inside Home Assistant and are comfortable exposing a thermostat onward to Alexa. The Alexa card is similar either way; Home Assistant preserves the deeper controls behind it.
If the factory Mitsubishi Wi-Fi adapter is already installed, try the Kumo Cloud Alexa skill before buying another controller; it may provide the voice controls you need at no additional hardware cost.
Get the CN105 controller
The ESP32 board and tested cable arrive assembled and ready for you to flash. Free US shipping.
Buy now from $35Already have a board?
Install the free beta firmware, then add it from the Alexa app. The firmware source is not published.