serin labs
Serin Controller
Pre-assembled Wi-Fi controller for Mitsubishi mini-splits: an M5Stack NanoC6 with the CN105 cable attached. Plugs into the service port inside your indoor unit for local, cloud-free control from Apple Home (HomeKit + Siri) or Home Assistant.
Sold through Etsy. Purchases, shipping, and returns are handled there, covered by Etsy's purchase protection.
What's in the Box
- M5Stack NanoC6 board — ESP32-C6 with Wi-Fi 6, small enough to tuck inside the unit.
- CN105-to-Grove cable, attached — plugs straight into the CN105 port. No crimping or soldering.
The only thing you supply is a USB-C data cable for the one-time flash. After that, updates are over Wi-Fi. A 50 cm cable option is available in the Etsy listing for metal-bodied ducted air handlers, where routing the controller outside the cabinet improves Wi-Fi signal.
Specifications
| Board | M5Stack NanoC6 |
|---|---|
| Chip | ESP32-C6 (RISC-V, 160 MHz) |
| Wi-Fi | Wi-Fi 6 (802.11ax, 2.4 GHz) |
| Size | 23.5 × 12 × 12.5 mm |
| HVAC connector | JST PAP-05V-S (CN105) |
| Power | 5V from the CN105 port — no separate power supply |
| Flashing | USB-C, from the browser; OTA updates afterward |
| Firmware | ESPHome or HomeKit-compatible — open source |
Installed
Before You Buy: Check Compatibility
The controller works with Mitsubishi Electric units that have a CN105 service port — most wall units, ducted air handlers, and ceiling cassettes. Mitsubishi Heavy Industries (SRK/SRC/SRF) and Ecodan air-to-water systems are not compatible. Check your unit →
Good to Know
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 — 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.
Does it ship with firmware installed?
No. The controller arrives without firmware so you can pick your platform. Flash ESPHome or HomeKit-compatible firmware free from the browser flash tool — it takes about five minutes and needs a desktop Chromium browser (Chrome, Edge, or Brave; Safari and Firefox don't support Web Serial).
How many do I need?
One controller per indoor head — each indoor unit has its own CN105 port. A 3-zone system needs three controllers.
Can I switch between ESPHome and HomeKit later?
Yes. Reflash over USB-C anytime from the flash tool — the hardware is identical for both platforms. Day-to-day updates after setup happen over Wi-Fi.
Is this an official Apple or Mitsubishi product?
No. This is an independent open-source project, not developed, endorsed, or certified by Apple Inc. or Mitsubishi Electric Corporation. The HomeKit-compatible firmware implements the HomeKit Accessory Protocol independently and is not an MFi-certified accessory. Firmware sources and licenses are listed 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 ESPHome: a Home Assistant instance.
- 2.4 GHz Wi-Fi coverage near the indoor unit.
What if something's wrong with my order?
Message the shop through Etsy, which handles shipping, returns, and refunds under its purchase protection. For technical help, see the support page.
After it arrives
Flash, Set Up, Install
Three steps from box to working thermostat: flash the firmware, follow your platform's setup guide, and plug it into the unit.