HP-Link
Your heat pump or air conditioner in Home Assistant, through the service port it already has.
HP-Link connects your heat pump or air conditioner to Home Assistant over the service port the unit already has: a 5 V UART port (Mitsubishi CN105, Panasonic CN-CNT, Daikin X10A) or an RS-485 / Modbus bus (Midea family incl. Kaisai, LG Therma V, Samsung EHS, Daikin Altherma 4, Nibe F-series). It is an ESP32-S3 Wi-Fi board with open ESPHome firmware, powered from the unit or from USB-C, and ships with the cable for your brand. Beta units are on pre-order now.
What it does
Two ports, one board
A 5 V UART port for units with a service connector and an RS-485 / Modbus port for units with bus terminals.
Open ESPHome firmware
An ESP32-S3 on Wi-Fi runs ESPHome with the community components for your brand. Read the YAML, change it, update over the air.
Home Assistant out of the box
Home Assistant finds the device on your network and shows what your unit reports (temperatures, mode, set points) as entities, without a cloud account. Changing settings from HA is opt-in.
Power comes from the unit (12 V or 5 V on the port) or from USB-C where the unit offers none, such as the Midea controller bus or a weak Daikin X10A supply.
Which heat pumps and ACs it talks to
| Unit | Port | In the box |
|---|---|---|
| Mitsubishi Ecodan or air-to-air unit | CN105 (5 V UART) | Plug-in cable for CN105 |
| Panasonic Aquarea | CN-CNT (5 V UART) | Plug-in cable for CN-CNT |
| Daikin Altherma 2 / 3 | X10A (5 V UART) | Plug-in cable for X10A; USB-C power where the unit’s 5 V is weak |
| Daikin Altherma 4(to confirm in the beta) | Modbus terminals (RS-485) | Screw-terminal plug for your own twisted pair |
| Midea family heat pump (Kaisai, Clivet, Ferroli, Airwell, Inventor…) | H1/H2 in the wired controller (RS-485) | Screw-terminal plug; power from USB-C or a 12 V adapter (no DC at H1/H2) |
| LG Therma V | 3rd-party controller terminals A/B (RS-485) | Screw-terminal plug for your own wires |
| Samsung EHS | F1/F2 (RS-485), 12 V on V1/V2 | Screw-terminal plug for your own wires |
| Nibe F-series(to confirm in the beta) | MODBUS 40 accessory port (RS-485) | Screw-terminal plug for your own wires |
The board has one fixed pin order and the cable maps it to your brand, so the plug for your unit goes straight in. Units with bus terminals need no special cable: your own twisted pair goes into the pluggable screw terminal. Not on the list? Choose "Other" and give the model; we confirm by e-mail before anything ships, and refund if it does not fit.
Beta unit: what that means
- HP-Link rev 0 is sold as a beta unit. It has no CE marking yet.
- It is meant for testing by experienced users who can open the unit's service panel safely. Switch the heat pump or AC off at its mains isolator before you connect anything.
- The beta price (€37) asks you to send us feedback and photos of your wiring; they build the compatibility list for everyone else.
- Expected shipping: February 2027, with the beta. We e-mail you before it ships and if the date moves.
- Refundable in full until shipping: one e-mail is enough. After delivery you keep the 14-day right of withdrawal and the statutory warranty, see Refunds & Returns.
- Changing settings of your unit from Home Assistant may affect its warranty; it stays opt-in.
Manufacturer and product safety
Manufacturer: Dot Development Bolesław Rohm (Circuit Issues), ul. Stanisławowska 47, 54-611 Wrocław, Poland. Contact: hello@circuit-issues.com.
Product: HP-Link rev 0, beta unit. A low-voltage board (5–17 V DC from the unit's service port or USB-C 5 V) with 2.4 GHz Wi-Fi. For indoor use, inside or next to the heat pump or AC, away from water. Safety and installation notes come with the unit and are on this page.
Disposal (WEEE): electronic equipment must not go into household waste. Send the board back to us when you no longer use it and we recycle it free of charge, or take it to a collection point for electronic waste.
Beta pre-order
Incl. 23% VAT, plus shipping. Board + the cable for your brand. Beta, not a final product: no CE marking yet.