Fujitsu AirStage-H component for ESPHome

An ESPHome component to control Fujitsu AirStage-H (product line previously known as Halcyon) units via the three wire (RWB) bus.

Warning

Requires ESPHome 2026.3.0 or newer.

substitutions:
  device_name: halcyon-controller
  friendly_name: Halcyon Controller
  device_description: Atom Lite + FOSV
  esp_board: m5stack-atom

external_components:
#  - source: github://Omniflux/esphome-tzsp
  - source: github://Omniflux/esphome-fujitsu-halcyon

packages:
  wifi: !include common/wifi.yaml

esphome:
  name: ${device_name}
  friendly_name: ${friendly_name}
  comment: ${device_description}

esp32:
  board: ${esp_board}
  framework:
    type: esp-idf

api:

ota:
  - platform: esphome
    password: !secret ota_password

#logger:
#  level: DEBUG

button:
  - platform: restart
    name: Restart
  - platform: safe_mode
    name: Restart (Safe Mode)

sensor:
- platform: uptime
  name: "Uptime"

uart:
  tx_pin: GPIO22  # Device dependent
  rx_pin: GPIO19  # Device dependent
  baud_rate: 500
  parity: EVEN

climate:
- platform: fujitsu-halcyon
  name: None  # Use device friendly_name

  # Fujitsu devices use 0 and 1, but 2-15 should also work. Must not skip addresses
  controller_address: 1  # 0=Primary, 1=Secondary
  #temperature_controller_address: 0  # Fujitsu controller address to read temperature from

  #temperature_sensor_id: my_temperature_sensor  # ESPHome sensor to read temperature from
  #humidity_sensor: my_humidity_sensor  # ESPHome sensor to read humidity from

  #ignore_lock: true  # Ignore child/part/feature lock set on unit or primary/central remote control

  # To capture communications for debugging / analysis
  # Use Wireshark with https://github.com/Omniflux/fujitsu-airstage-h-dissector
  #tzsp:
  #  ip: 192.168.1.20
  #  protocol: 255

You can use esphome (or Home Assistant) sensors to report the current temperature and humidity to the Home Assistant climate component

sensor:
  - platform: homeassistant # https://esphome.io/components/sensor/homeassistant.html
    id: my_temperature_sensor
    entity_id: sensor.my_temperature_sensor  # Home Assistant entity_id
    unit_of_measurement: "°F"  # unit_of_measurement is lost on import, defaults to °C

  - platform: homeassistant
    id: my_humidity_sensor
    entity_id: sensor.my_humidity_sensor

climate:
  - platform: fujitsu-halcyon
    name: None
    controller_address: 1
    temperature_sensor_id: my_temperature_sensor
    humidity_sensor: my_humidity_sensor

If your unit supports sensor switching and has had the function settings set appropriately (see your installation manual, usually settings 42 and 48), your unit can also be set to use this sensor instead of the sensor in its air intake. When available, a switch will appear in the Home Assistant device page in the Configuration section named Use Sensor

Configure TZSP and use Wireshark with fujitsu-airstage-h-dissector to debug / decode the Fujitsu serial protocol.

Home Assistant entities

The following entities are created automatically in Home Assistant. Feature-dependent entities (louvers, filter, sensor switching) are only exposed once the unit has reported its capabilities.

Climate

Entity	Type	Description
(friendly name)	Climate	Main control: mode, fan speed, setpoint, swing, economy preset

Diagnostics

Entity	Type	Default	Description
Connected	Binary sensor	Enabled	Whether the controller has completed initialization with the indoor unit
Standby Mode	Binary sensor	Enabled	Active during defrost, oil recovery, or multi-unit synchronization
Error	Binary sensor	Enabled	Indicates an active fault on the indoor unit
Error Code	Text sensor	Enabled	Fault code in AA BB hex format (unit address + error code)
Initialization Stage	Text sensor	Enabled	Current initialization progress, (4/4) indicates complete
Supported Features	Text sensor	Enabled	List of features reported by the indoor unit, published once at initialization. Example: Mode: Auto Heat Cool Dry Fan | Fan: Auto High Medium Low Quiet | Economy | Sensor Switching | V.Louvers | H.Louvers
Remote Temperature Sensor	Sensor	Disabled	Temperature reported by another controller on the bus (see temperature_controller_address)
Filter Timer Expired	Binary sensor	Feature-dependent	Set when the filter maintenance timer has elapsed

Configuration

Entity	Type	Default	Description
Use Sensor	Switch	Feature-dependent	Route the external temperature sensor reading to the indoor unit (requires unit support and temperature_sensor_id configured, see settings 42 and 48)
Reset Filter Timer	Button	Feature-dependent	Reset the filter maintenance timer
Advance Vertical Louver	Button	Feature-dependent	Step the vertical louver to the next position
Advance Horizontal Louver	Button	Feature-dependent	Step the horizontal louver to the next position
Reinitialize	Button	Enabled	Re-run the initialization sequence without rebooting
Function / Function Value / Function Unit	Number	Enabled	Raw function register access
Function_Read / Function_Write	Button	Enabled / Disabled	Trigger a function register read or write

Related projects

• FOSV's Fuji-Atom-Interface - Open hardware interface compatible with this component

• My esphome-fujitsu-dmmum - Fujitsu AirStage-H 3-wire Central Controller component for ESPHome

• Aaron Zhang's esphome-fujitsu
• Jaroslaw Przybylowicz's fuji-iot
• Raal Goff's FujiHeatPump
• Raal Goff's FujiHK

• Myles Eftos's Reverse engineering