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The Serin Controller — a compact Wi-Fi controller board with the 20 cm CN105-to-Grove cable attached, in orange braided sleeving with heat shrink at both ends.
The Serin Controller with the 50 cm cable in orange braided sleeving, coiled beside the board with heat shrink at both ends.
The Serin Controller beside the optional wireless room sensor, a small white square thermometer with a rounded case.
The Serin Controller with the standard 20 cm CN105-to-Grove cable attached, without the braided sleeving.
The Serin Controller with the standard 50 cm CN105-to-Grove cable coiled beside it, showing the extra reach over the 20 cm version.
The orange CN105-to-Grove cable routed into the electrical box of a Mitsubishi wall unit, running under a retaining clip and beneath the control-board cover
The CN105-to-Grove cable plugged into the CN105 port on the control board of a Mitsubishi wall unit
The Serin Controller mounted on the insulated plenum above a Mitsubishi MVZ air handler, connected by a 50 cm cable

Serin CN105 ESP32 Controller

$40
CN105 · ESP32 · Wi-Fi

5.0 (36)

Pre-assembled Wi-Fi controller with a tested CN105 cable for Mitsubishi Electric mini-splits. Install the free firmware for Home Assistant, Apple Home, Google Home, or Alexa. Local control, no account, no subscription. Remote access needs a home hub.

20 cm cable in braided sleeving $40
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Free US shippingShips in 1–2 days30-day returns

Secure checkout by Shopify, shipped from New Jersey.

Fits your unit? · Read the manual

Will it fit your unit?

Type the model from the indoor unit's sticker.

Requires a free CN105 port. Not for Ecodan or units with a wired wall controller on the same port.

Overview

Optional room sensor

Sense the room, not the ceiling

A mini-split reads temperature in its own return air at the ceiling, which warms long before the room does. The wireless sensor measures where you sit, and the heat pump controls to that reading instead.

Automatic fallback

Out of range or flat battery, and the unit's own sensor takes over.

Move it anywhere

Nightstand or desk; the heat pump follows the reading there.

Bring your own

Compatible Bluetooth thermometers work too. Supported models

Or via Home Assistant

ESPHome firmware can read any HA temperature sensor.

A small wireless temperature sensor on a side table at seating height, with a Mitsubishi mini-split mounted high on the wall behind it The Serin controller's web interface listing three room-temperature sources: the heat pump's built-in sensor, a Bluetooth remote sensor with humidity, battery, and signal strength, and a Serin Link marked active

Installed

The CN105-to-Grove cable plugged into the CN105 port on the control board of a Mitsubishi wall unit
Plugged into the CN105 port of an MSZ series wall unit
The orange CN105-to-Grove cable routed into the electrical box of a Mitsubishi wall unit, running under a retaining clip and beneath the control-board cover
Cable routed under the control-board cover
The Serin Controller mounted on the insulated plenum above a Mitsubishi MVZ air handler, connected by a 50 cm cable
Outside a metal-bodied MVZ air handler (50 cm)

Technical

Connection
CN105 service port, via the attached CN105-to-Grove cable
Wireless
2.4 GHz Wi-Fi
Firmware
ESPHome (Home Assistant), HomeKit-compatible (Apple Home, Siri), Matter-compatible beta (Google Home, Alexa, SmartThings)
Flashing
From a computer with Chrome or Edge over a USB-C data cable; later updates over Wi-Fi
Cable length
20 cm (wall units, cassettes) or 50 cm (ducted air handlers: SVZ, MVZ, PEAD, PVA)
Cable finish
Standard, or orange braided sleeving with heat shrink at both ends
Room sensor
Optional Bluetooth thermometer, read directly by the controller
Cloud
None. Runs on your local network; remote access through your home hub. No account or subscription
Coverage
One controller per indoor unit
Hub requirements
Apple Home Hub for HomeKit remote access; a Home Assistant server; or a Matter hub on an IPv6-enabled network

In the box

The CN105-to-Grove cable, the wireless room sensor, and the Wi-Fi controller board laid out together

  • Wi-Fi controller board

    Small enough to sit inside the unit.

    1×

  • CN105-to-Grove cable, attached

    Plugs straight into the CN105 port.

    1×

  • Wireless room sensor optional

    Battery-powered Bluetooth thermometer the controller reads directly.

Not included: firmware (free, installed by you from Chrome or Edge on a computer) and a USB-C data cable for the one-time flash. If you only need the cable for a board you already have, it's sold separately.

FAQ

Does it work with Apple Home and Siri?

Yes. With the free HomeKit-compatible firmware, the controller appears in the Apple Home app as a thermostat, with mode, temperature, and fan control, plus Siri voice commands. Remote access and automations need an Apple Home Hub (Apple TV or HomePod). It's not an MFi-certified accessory, so pairing shows a one-time "Add Anyway" prompt. See the full feature list, or the walkthrough: add a Mitsubishi mini-split to Apple Home.

Does it work with Google Home and Amazon Alexa?

Yes. The free Google Home & Amazon Alexa compatible firmware adds it to either app as a thermostat. You need a compatible Matter hub, such as a Nest speaker or display, or an Echo; scan the pairing code and the app handles Wi-Fi. It is in beta, newer and less tested than the other firmware options, and not certified by Google or Amazon, so the app shows a one-time uncertified notice. Read the Google Home guide or Alexa guide, then follow the setup guide.

Which optional room sensor do you offer?

The optional sensor is a small battery-powered Govee Bluetooth thermometer. If you already own a compatible Bluetooth thermometer you can use that instead; the supported models are on the feature list, and Home Assistant users can use the YAML generator to configure the controller to read a temperature sensor already connected to Home Assistant.

How many do I need?

One controller per indoor unit, since each one has its own port. A 3-zone system needs three controllers.

Can I switch platforms later?

Yes. Connect the controller by USB-C and use the flash tool to install firmware for a different platform. After setup, you can install firmware updates over Wi-Fi.

Can I build one myself instead?

Yes. The same firmware runs on a supported ESP32 board connected with a CN105-to-Grove cable. The parts list identifies both components and includes the JST part numbers for making the cable. The pre-assembled controller provides these parts already sourced, assembled, and tested.

Is this an official Apple or Mitsubishi product?

No. It is an independent open-source project with no ties to Apple Inc. or Mitsubishi Electric Corporation. The HomeKit-compatible firmware is not an MFi-certified accessory. Sources and licenses are on the licenses page.

What else do I need?
  • A USB-C data cable for the one-time flash.
  • For HomeKit remote access and automations: an Apple Home Hub (Apple TV or HomePod).
  • For Home Assistant: a Home Assistant server already running in your home.
  • For Google Home, Alexa, or SmartThings: the app and a compatible Matter hub, such as a Nest speaker or display, an Echo, or a SmartThings hub, on a home network with IPv6 enabled.
  • Home Wi-Fi that reaches the room (the board uses the 2.4 GHz band, which every home router has).
What if something's wrong with my order?

Use the contact form with your order number. Direct orders ship from New Jersey and are covered by the store policies: 30-day returns, 12-hour cancellations, and a full refund or replacement for an item that arrives damaged or nonfunctional. Orders placed on Etsy are handled there. For technical help, start with the troubleshooting guide.

Limitations

  • Firmware is not installed before shipping. Use the browser flash tool to install the ESPHome, Apple Home, or Google Home and Alexa compatible firmware at no charge.
  • The controller uses local communication and does not require a cloud service, account, or subscription.
  • Each controller operates one indoor unit. A multi-zone system requires one controller per indoor unit; the outdoor unit does not require one.
  • Ecodan air-to-water heat pumps are not compatible. They have a similar connector but use a different serial protocol.
  • The controller does not replace the handheld infrared remote, which continues to work.
  • The controller cannot share CN105 with a wired wall controller. MHK2, MHK1, PAC-SDW01RC-1, and PAR-series controllers use the same port, and CN105 splitters are not supported.

After it arrives

Install, connect, and pair

Flash from Chrome or Edge on a computer, plug into the unit, add to your app.

Install firmware Read the manual