# Build your own controller

> Choose supported hardware, assemble a CN105 cable and find the firmware sources for a DIY Serin Controller.

Source: https://serin-labs.com/controller/diy.html
Last updated: 2026-10-27

## Choose supported hardware

Choose a NanoC6 or Atom S3 Lite from the [parts list](https://serin-labs.com/parts.html). For another board, check [published firmware and Serin Link support](https://serin-labs.com/controller/features.html#boards); sharing a chip family does not guarantee compatibility.

## Build and check the cable

Follow the [CN105 wiring reference](https://serin-labs.com/wiring.html) for connector orientation, pin mapping and assembly checks, or use a preassembled cable. Read the [installation precautions](https://serin-labs.com/safety.html) before opening the unit.

USB and CN105 must not power the controller together. Keep the controller disconnected from the indoor unit while installing firmware over USB.

## Install firmware and verify control

1. [Choose the firmware](https://serin-labs.com/controller/firmware.html) for your app or Serin Link setup.
2. Use the [browser flash tool](https://serin-labs.com/flash.html) if it offers your board.
3. Follow [physical installation](https://serin-labs.com/controller/install.html), then finish the applicable setup guide.
4. Confirm a current temperature and send a command that the indoor unit follows. If it does not respond, follow [the CN105 checks](https://serin-labs.com/troubleshooting.html#cn105-no-data).

## Customize firmware

Use [Customize ESPHome](https://serin-labs.com/controller/customize-esphome.html) for standard boards. Other boards require their own board and UART configuration.

- [CN105 ESPHome component](https://github.com/echavet/MitsubishiCN105ESPHome): hardware, configuration and component development.
- [HomeKit-compatible firmware](https://github.com/akifbayram/mitsubishi-cn105-homekit): build instructions and protocol documentation.
- [Serin firmware distribution](https://github.com/Serin-Labs/serin-cn105): published controller builds.

Use examples for the CN105 component named in your configuration; other components are not interchangeable. The Matter-compatible firmware source is not published; see [firmware licenses](https://serin-labs.com/licenses.html).