AirSensor

A multi-room air quality monitor built around ESPHome and Home Assistant. Each unit sits flush on the wall like a light switch — mains powered, fully self-contained, nothing to charge or manage. Built on the ESP32-C6, it is hardware-ready for Matter, making it future-proof as smart home standards evolve.

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What it measures

Each unit reports the following to Home Assistant in real time:

Sensor	Measurements
Sensirion SEN55	PM1.0, PM2.5, PM4.0, PM10 · VOC Index · NOx Index · Temperature · Humidity
Sensirion SCD4x	CO2 (ppm) · Temperature · Humidity
Infineon DPS310 (optional)	Barometric pressure · Temperature

The DPS310 pressure sensor is fitted on one unit only and is entirely optional — the PCB and firmware support it but work fine without it.

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Display

Each unit has a GC9A01A 240×240 round TFT (SPI), sourced from AliExpress:

The display shows:

• Time and date (synced from Home Assistant)
• CO2, humidity, PM2.5, VOC values in the four quadrants
• A 5-segment AQI bar reflecting the worst pollutant level across all sensors, colour-coded from green (Excellent) to red (Very Poor)
• A large status word (EXCELLENT / GOOD / FAIR / POOR / VERY POOR) at the centre
• An animated fan graphic as the background (see below)

The XIAO's built-in RGB LED (optional) breathes in the AQI colour — green through red depending on air quality — visible from across the room without looking at the display. It can be enabled or disabled from Home Assistant and the state persists across reboots.

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Animated fan

A Fan Speed entity (Off / Low / High) is exposed in Home Assistant. Selecting Low or High drives an animated three-blade fan spinning in the background of the display — slow and blue-purple at Low, faster and brighter purple at High. It is purely decorative and does not control any physical hardware. The selected speed persists across reboots.

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Hardware

Component	Role
Seeed XIAO ESP32-C3	MCU — different GPIO layout, otherwise identical firmware
Seeed XIAO ESP32-C6	MCU — preferred variant; Wi-Fi 6, Matter-capable radio
Sensirion SEN55	Particulate matter + VOC + NOx + T/RH
Sensirion SCD4x	CO2 + T/RH
Infineon DPS310 breakout	Barometric pressure (optional)
GC9A01A 240×240 round TFT	Round display (AliExpress)
Kradex Z123_W	Enclosure — standard wall-mount junction box

The ESP32-C6 is the preferred variant. Its Wi-Fi 6 and IEEE 802.15.4 radio make it hardware-ready for Matter once ESPHome's Matter support matures. The C3 lacks the necessary radio and cannot support Matter.

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PCB

A single custom PCB designed in KiCad houses the MCU, sensors, and display connector inside the Kradex enclosure.

Custom KiCad libraries (symbols, footprints, and 3D models) are kept under lib/ and referenced with portable ${KIPRJMOD}-relative paths so the project opens correctly on any machine.

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Home Assistant integration

Each unit exposes the following entities:

• Sensors — all measured values listed above
• Fan Speed — select (Off / Low / High) to control the display animation
• Status LED — switch to enable or disable the breathing LED
• Display Backlight — light entity with brightness control
• Restart — button to reboot the device OTA

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MCU variants

	ESP32-C3	ESP32-C6
Wi-Fi	802.11 b/g/n	802.11 b/g/n/ax (Wi-Fi 6)
BLE	5.0	5.3
Matter (future)	No — hardware limitation	Yes — IEEE 802.15.4 radio
GPIO	Different pinout	Reference pinout

Two reference templates are provided — ESPHome_config/AirSensor-C3.yaml and AirSensor-C6.yaml — covering both variants.

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Repository structure

AirSensor/
├── ESPHome_config/
│   ├── AirSensor-C3.yaml          # Reference template (ESP32-C3)
│   ├── AirSensor-C6.yaml          # Reference template (ESP32-C6)
│   ├── airsensor_aqi_helpers.h    # Shared AQI logic (C++)
│   ├── secrets.yaml               # Empty secrets template
│   └── private/                   # Real deployment configs (gitignored)
├── kicad/
│   └── AirSensor_display/         # KiCad project (schematic + PCB)
├── lib/
│   ├── symbols/                   # Custom KiCad symbols
│   ├── footprints/                # Custom KiCad footprints
│   └── 3d/                        # 3D models for KiCad
├── mech/                          # Enclosure and module STEP files
└── docs/
    └── Data sheets/               # Component datasheets

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Getting started

1. Copy ESPHome_config/AirSensor-C3.yaml or AirSensor-C6.yaml to ESPHome_config/private/<unit-name>.yaml
2. Fill in ESPHome_config/private/secrets.yaml (Wi-Fi credentials, API key, OTA password)
3. Search for ← CONFIGURE markers in the YAML and update each one (device name, floor label, etc.)
4. Remove the DPS310 sensor block if the pressure sensor is not fitted
5. Flash via ESPHome: esphome run private/<unit-name>.yaml