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.
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 and can be connected to the heat pump with no additional components. The wiring diagram is in the images directory; note that RX/TX are crossed.
D1 mini v3 boards (the ones with the visible chips) have been source of issues and require a hardware modification, so my recommendation is to avoid v3, use v1 or other boards.
A wiring diagram using an ESP-01 board is available on the SwiCago/HeatPump repository.
A cable with the correct connector is available for purchase here. Ignore the colors of the wires, black will stay not connected.
Download the most recent binary image and flash it to the ESP8266 using esptool:
esptool.py --port SERIAL_PORT write_flash --erase-all 0x0 mel_heatpump_vX.X.X.binor one of the third party options, for example NodeMCU Flasher.
You only need to do this step the first time, subsequent updates can be done using 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 device
will then reboot and it will be ready to pair using the Home app. The pairing
code is 111-11-111.
After the first flashing and WiFi setup you can update the firmware from the web interface.
The heat pump will appear in Home as three accessories grouped together: a thermostat, a dehumidifier, and a fan. The three components will coordinate to show the current status of the heat pump.
The fan supports five speeds from 20 to 100%: 20% is the heat pump quiet setting 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 to detect 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 the vertical vane swing and the dehumidifier controls the horizontal vane swing. When swing is disabled the vertical vane is set to auto and the horizontal vane is set to center.
Vane manual positioning is not supported: I couldn't find a satisfactory way to do it in HomeKit.
The dehumidifier always reports 0% humidity. HomeKit doesn't allow removing this, as a workaround you can turn off the “Include in Home Status” switch for the dehumidifier. See below for a better solution.
Lastly, the heat pump is very slow to respond to commands and slow to send back updates. Set up what you want and then let it update, give it up to 30 seconds or more to catch up, especially when turning on or off.
The firmware supports connecting a humidity sensor to fill in the missing information from the heat pump. BME280 and DHT22 sensors are supported. BME280 must be at I2C address 0x76 and DHT22 data pin must be connected to GPIO2. The full wiring diagram is in the images directory. Both sensors are shown but you only need one.
Even with an external sensor the temperature visible in Home will be the one provided by the heat pump, because that is the one it will use in its thermostat.
The ESP produces significant heat so make sure to keep the sensor away from it.
The device exposes a web interface accessible using its IP address (that you
can find from your router/access point), or at http://heat-pump-XXXXXX.local
if your network supports mDNS/Bonjour (all Macs and many Linux systems do).
The web interface shows the current state of the device and allows firmware upgrades and changing settings. Settings are only interesting if an external temperature and humidity sensor is connected and allow publishing the sensor readings over mqtt.