serin labsMitsubishi Heat Pump Controller
Cloud-free smart control with open source firmware.
ESPHome for Home Assistant. HomeKit for Apple Home.
100% Local Control
Your data stays in your home. No cloud, no fees, no privacy worries.
Open Source
Inspect, modify, and contribute to the firmware and tools.
Compact & Clean
Installs inside your heat pump for a seamless look.
DIY or Pre-Assembled
Build it yourself or order a pre-assembled controller — board and CN105 cable included.
How It Compares
There are several ways to add smart control to a Mitsubishi heat pump. This one uses the CN105 — a small wired service port inside most indoor units — for direct, two-way control. Here's how they compare.
| Cloud Adapter | IR Blaster | CN105 Serial | |
|---|---|---|---|
| Cost | ~$180 | ~$15 | ~$15–20 DIY or pre-assembled |
| Connection | Cloud-dependent | Line-of-sight IR | Local serial (CN105) |
| Feedback | Yes, via cloud | None — no confirmation | Real-time, bidirectional |
| Privacy | Data sent to cloud | Local | 100% local |
| Source | Proprietary | Varies | Open source |
Choose Your Platform
ESPHome
Built on MitsubishiCN105ESPHome. Serin Labs provides curated configs, browser flashing, and a YAML generator.
Flash Firmware Setup Guide →
HomeKit-Compatible
For use with the Apple Home app. No additional app, cloud, or subscription is required.
Flash Firmware Setup Guide →Choose Your Board
Both boards are fully supported with ESPHome and HomeKit firmware. Pick the one that fits your priorities.
M5Stack NanoC6
Smallest option with WiFi 6 for better range through HVAC enclosures.
ESP32-C6 · WiFi 6 · 23.5 × 12 mm
RecommendedM5Stack Atom S3 Lite
More powerful dual-core chip. Widely available.
ESP32-S3 · WiFi 4 · 24 × 24 mm
Detailed spec comparison
| NanoC6 | Atom S3 Lite | |
|---|---|---|
| Chip | ESP32-C6 (RISC-V, 160 MHz) | ESP32-S3 (dual-core, 240 MHz) |
| WiFi | WiFi 6 (802.11ax, 2.4 GHz) | WiFi 4 (802.11n, 2.4 GHz) |
| Size | 23.5 × 12 × 12.5 mm | 24 × 24 × 13 mm |
| USB | USB-C | USB-C |
| Grove port | HY2.0-4P | HY2.0-4P |
| Button | Yes | Yes |
| ESPHome | Full support | Full support |
| HomeKit | Full support | Full support |
Both boards have more than enough processing power for this firmware. The NanoC6 is recommended for most setups due to its smaller size and WiFi 6 radio, which provides better signal through the sheet metal of HVAC enclosures.
For a complete shopping list including cables, see What You Need.
Quick Start
- Get the Hardware: Board + cable, or a pre-assembled controller. Check compatibility first.
- Flash the Firmware: Use the flash tool to install ESPHome or HomeKit firmware from your browser.
- Follow Your Setup Guide: ESPHome setup or HomeKit-compatible setup.
- Install in Your HVAC: Power off, connect the CN105-to-Grove cable, tuck the device inside, and restore power.
- Multiple Indoor Units? You need one controller per indoor head — each unit has its own CN105 port. Repeat the steps above for each unit, giving each device a unique name.
Disclaimer & Safety
This is an independent open-source project. It is not developed, endorsed, or certified by Apple Inc. or Mitsubishi Electric Corporation. Working on HVAC systems can be risky and may void warranties. Proceed only if you're confident. This project is provided as-is, without warranty or liability.
Need Help?
Credits & Open Source
The ESPHome integration is powered by echavet's MitsubishiCN105ESPHome project. The HomeKit-compatible firmware (source) is built on Espressif's esp-homekit-sdk.
This project also builds on foundational work by SwiCago and geoffdavis.