About Serin Labs

Serin Labs is a one-person shop in New Jersey with a deliberately narrow mission: give Mitsubishi mini-split owners the smart control their hardware has always supported. Locally, without a cloud account, for a fraction of the official price.

Why This Exists

Nearly every Mitsubishi indoor unit made in the last decade has a CN105 connector inside: a simple serial port that speaks the unit's full control protocol. Mitsubishi's official ways to use it are a wall controller that costs $180–$400 per room, or a Kumo Cloud adapter that routes your thermostat through servers you don't control. Meanwhile the port itself will happily talk to a $10 microcontroller.

Serin Labs is run by Mehmet, an engineer in New Jersey who started exactly where most of this community starts: one mini-split, one open-source firmware project, one evening of soldering, and a working smart thermostat for less than the price of a takeout dinner. The gap wasn't the software, which the community had already built and battle-tested. It was everything around it: knowing which board to buy, getting a properly-pinned CN105 cable without crimping your own, flashing without a toolchain, and having someone to ask when it doesn't work. Serin Labs exists to close that gap.

Built on Open Source, Credit Where Due

The firmware that runs on a Serin controller is not ours, and we want you to know exactly whose it is. Local CN105 control exists because SwiCago/HeatPump reverse-engineered the protocol and shared it. The ESPHome integration is echavet/MitsubishiCN105ESPHome. The HomeKit-compatible firmware builds on Espressif's esp-homekit-sdk. All of it is open source, all of it stays free, and the licenses page maps every component to its source and terms.

What Serin Labs adds is the hardware and the on-ramp: a tested board, a correctly-pinned cable, a browser flasher that turns "install a toolchain" into one click, documentation that assumes nothing, and support from someone who has installed these in their own house.

What We Run On

Local first

Your thermostat shouldn't stop working because a server far away did. Everything the controller does happens on your network; the cloud is never in the loop.

No subscriptions

You buy hardware once. Firmware, updates, and every feature are free. Nothing to unlock, no monthly anything.

Open source, honestly

We don't rebrand community work as our own. Upstream projects are named, linked, and credited everywhere their code is used.

Repair-friendly

Standard connectors, documented wiring, off-the-shelf boards you can source yourself. If you'd rather DIY the whole thing, the docs are the same ones we use.

What You're Buying

The pre-assembled controller is a tested board and CN105 cable, ready to plug in. You flash the free firmware of your choice in about five minutes in the browser. It ships from NJ with free US shipping, 30-day returns, and real support. If you'd rather build your own from the parts list, that's genuinely fine with us. The flasher, docs, and community are free either way.

Independence

Serin Labs is an independent project, not affiliated with, endorsed by, or certified by Apple Inc. or Mitsubishi Electric Corporation. Trademarks are used only to describe compatibility. Full details on the licenses & compliance page.

Questions?

Talk to a human

Compatibility checks, wholesale, press, or anything else. The contact form goes straight to the person who built this.

Contact See the Controller