What You Need

One board, one cable — about $15–20 total per unit. Everything you need to build a Serin controller.

1. ESP32 Board (Required)

Choose one of the two supported boards. Both work with ESPHome and HomeKit firmware.

M5Stack NanoC6

Recommended

Smallest option with WiFi 6.

ESP32-C6 · 23.5 × 12 mm · ~$7

M5Stack Store

M5Stack Atom S3 Lite

More powerful dual-core chip.

ESP32-S3 · 24 × 24 mm · ~$8

M5Stack Store

Not sure which board? See the board comparison on the home page.

2. CN105-to-Grove Cable (Required)

This cable connects the ESP32 board to your Mitsubishi unit's CN105 port.

Option A: Pre-assembled Cable

Pre-assembled cables coming soon. Check Discussions for updates.

Option B: Build Your Own

You can assemble a cable from these parts. See the wiring reference for the pinout.

Part	Description	Link
JST PAP-05V-S	5-pin connector housing (CN105 / HVAC side)	DigiKey
Grove HY2.0-4P cable	4-pin connector with wire (device side)	DigiKey

You will also need crimp terminals (JST SPHD-002T-P0.5) and a crimping tool, or you can solder the wires directly.

3. USB-C Data Cable (For Flashing)

Needed once to flash the firmware. You probably already have one.

Must be a data cable, not a charge-only cable.
Test it by connecting a phone — if your computer detects it, the cable works.

Shopping List

Item	~Price (USD)	Where to Buy
ESP32 Board (NanoC6 or Atom S3 Lite)	$7–8	M5Stack Store
CN105-to-Grove Cable	$5–10	DigiKey (DIY parts)
USB-C Data Cable	—	You likely have one
Total: ~$15–20 per unit

Multiple Indoor Units?

You need one board and one cable per indoor head. Each indoor unit has its own CN105 port. A 3-zone system needs 3 of everything above.

Optional accessories

USB-C data cable — only needed for initial flashing; after that, updates are done over WiFi (OTA).
Label maker or tape — helpful for labeling cables in multi-unit installations.
Multimeter — useful for verifying 5V power on the CN105 port if troubleshooting.

Next Steps

Check compatibility — verify your Mitsubishi unit has a CN105 port.
Flash the firmware — install ESPHome or HomeKit firmware from your browser.
Wire it up — connect the cable to your HVAC unit.

Disclaimer

Prices are approximate and may vary by region and seller. Links are provided for convenience and are not affiliate links. This project is provided as-is, with no warranties or liability.