Mitsubishi heat pump HomeKit accessory

ESP8266 HomeKit accessory firmware for Mitsubishi heat pumps.

�� �� �� Archived I am not using this AC unit anymore so I am unable to maintain this project further.

Hardware

Most ESP8266 boards should work, but I only tested this with a D1 mini clone.The version 1 boards (the ones with the metal shield) work more reliably andcan be connected to the heat pump with no additional components. The wiringdiagram is in the images directory; note that RX/TXare crossed.

D1 mini v3 boards (the ones with the visible chips) have been source of issuesand require a hardware modification, so my recommendation is to avoid v3, usev1 or other boards.

A wiring diagram using an ESP-01 board is available on theSwiCago/HeatPump repository.

A cable with the correct connector is available for purchasehere.Ignore the colors of the wires, black will stay not connected.

Software

Download the most recent binaryimage and flash itto the ESP8266 using esptool:

esptool.py --port SERIAL_PORT write_flash --erase-all 0x0 mel_heatpump_vX.X.X.bin

or one of the third party options, for example NodeMCUFlasher.

You only need to do this step the first time, subsequent updates can be doneusing the web interface.

After flashing the firmware the ESP8266 will create a WiFi network named Heat Pump XXXXXX. Connect to it and set up your WiFi name and password. The devicewill then reboot and it will be ready to pair using the Home app. The pairingcode is 111-11-111.

After the first flashing and WiFi setup you can update the firmware from theweb interface.

Usage

The heat pump will appear in Home as three accessories grouped together: athermostat, a dehumidifier, and a fan. The three components will coordinate toshow the current status of the heat pump.

The fan supports five speeds from 20 to 100%: 20% is the heat pump quietsetting and the rest are speeds 1 to 4.

If you set up scenes with the fan in auto mode you should set the speed to 20%.The speed setting is ignored when auto mode is on, but HomeKit uses it todetect when a scene is active.

To use manual fan speed control you first have to turn off auto mode.

Both the fan and dehumidifier show a swing button: the fan controls thevertical vane swing and the dehumidifier controls the horizontal vane swing.When swing is disabled the vertical vane is set to auto and the horizontal vaneis set to center.

Limitations

Vane manual positioning is not supported: I couldn't find a satisfactory way todo it in HomeKit.

The dehumidifier always reports 0% humidity. HomeKit doesn't allow removingthis, as a workaround you can turn off the “Include in Home Status” switch forthe dehumidifier. See below for a better solution.

Lastly, the heat pump is very slow to respond to commands and slow to sendback updates. Set up what you want and then let it update, give it up to 30seconds or more to catch up, especially when turning on or off.

Advanced optional features

Humidity sensor

The firmware supports connecting a humidity sensor to fill in the missinginformation from the heat pump. BME280 and DHT22 sensors are supported. BME280must be at I2C address 0x76 and DHT22 data pin must be connected to GPIO2. Thefull wiring diagram is in the images directory. Bothsensors are shown but you only need one.

Even with an external sensor the temperature visible in Home will be the oneprovided by the heat pump, because that is the one it will use in itsthermostat.

The ESP produces significant heat so make sure to keep the sensor away from it.

Web interface

The device exposes a web interface accessible using its IP address (that youcan find from your router/access point), or at http://heat-pump-XXXXXX.localif your network supports mDNS/Bonjour (all Macs and many Linux systems do).

The web interface shows the current state of the device and allows firmwareupgrades and changing settings. Settings are only interesting if an externaltemperature and humidity sensor is connected and allow publishing the sensorreadings over mqtt.