| Overview | Details |
|---|---|
| Language: | C++ |
| IDE: | Platform.io (VS Code + Platform.io extension) |
| Microcontroller: | Adafruit Feather M0 |
This custom device connects to wifi and publishes sensor readings via MQTT at the set refresh rate frequency.
This device will send Home Assistant compatible discovery messages via MQTT. It can be configured via special MQTT topics.
The software is modular and designed to be reused. It sacrifices simplicity, RAM and flash in order to minimize the amount of developer time needed to get a robust Home Assistant compliant MQTT device working. Start here to learn how to use the mqtt-ha-helper to provide auto-discovery for sensors. For providing auto-discovery for static device diagnostics as well as measurable diagnostics, the steps are slightly different. Finally to support interactive controls and remote configuration via MQTT, the device will need to listen on topics and provide state updates. The details on how to do so are here.
Auto-discovery for:
| Sensor | Measures... |
|---|---|
| SHT40 | humidity (% RH), temperature (C) |
| DPS310 | temperature (C), pressure (hectopascal, hPa), altitude computed |
| PM2.5 | particulate matter (Particles > 0.3um, 0.5um, 1.0um, 2.5um, 5.0um, 10.0um / 0.1L air); AQI computed |
| SCD30 | carbon dioxide (PPM direct from sensor), humidity (% RH), temperature (C) |
For physical build details, see here.
MQTT Topic:
homeassistant/{device_type}/{device_id}/state
homeassistant/sensor/featherm0/state
Sensor State Payload:
{
"temperature": 22.05,
"humidity": 38.25,
"pressure": 989.4,
"pressure_details": {
"temperature": 21.25,
"altitude": 281.3
},
"pm1": 1,
"pm25": 1,
"pm10": 1,
"aqi": 4,
"aqi_details": {
"count_gt_03": 228,
"count_gt_05": 68,
"count_gt_10": 2,
"count_gt_25": 0,
"count_gt_50": 0,
"count_gt_100": 0
},
"carbon_dioxide": 954,
"carbon_dioxide_details": {
"temperature": 23.5,
"humidity": 35.54
}
}
All of the following sensors use the common sensor state topic (see below):
Sensor Discovery:
homeassistant/sensor/featherm0/carbon_dioxide/config
homeassistant/sensor/featherm0/aqi/config
homeassistant/sensor/featherm0/pm1/config
homeassistant/sensor/featherm0/pm25/config
homeassistant/sensor/featherm0/pm10/config
homeassistant/sensor/featherm0/pressure/config
homeassistant/sensor/featherm0/humidity/config
homeassistant/sensor/featherm0/temperature/config
homeassistant/{device_type}/{device_id}/diagnostics
homeassistant/sensor/featherm0/diagnostics
Configuration State Payload:
{
"wifi_rssi": -42,
"wifi_ip": "10.0.0.130",
"wifi_mac": "96:e6:f1:05:f0:f8",
"sht40_heater_intensity": "Disabled",
"sht40_heater_duration": 0,
"sht40_precision": "High"
}
homeassistant/sensor/featherm0/wifi_rssi/config
homeassistant/sensor/featherm0/wifi_ip/config
homeassistant/sensor/featherm0/wifi_mac/config
homeassistant/sensor/featherm0/sht40_heater_intensity/config
homeassistant/sensor/featherm0/sht40_heater_duration/config
homeassistant/sensor/featherm0/sht40_precision/config
Controls/configuration must listen on topics to accept updates (setter or command topics) and reflect those changes back to the UI (getter or state topics). Unlike sensors or diagnostics, controls have a dedicated read and write topic per control that carry a single raw value such as an integer (not JSON).
Discovery:
homeassistant/number/featherm0_altitude_offset/config
Altitude offset state:
homeassistant/number/featherm0/altitude_offset/get
Altitude offset command:
homeassistant/number/featherm0/altitude_offset/set
Discovery:
homeassistant/switch/featherm0/use_pressure_offset/config
Use ambient pressure state:
homeassistant/switch/featherm0/use_pressure_offset/get
Use ambient pressure command:
homeassistant/switch/featherm0/use_pressure_offset/set
Discovery:
homeassistant/number/featherm0/temperature_offset/config
Temp Offset state:
homeassistant/number/featherm0/temperature_offset/get
Temp Offset command:
homeassistant/number/featherm0/temperature_offset/set
Discovery:
homeassistant/number/featherm0/refreshrate/config
Refresh rate state:
homeassistant/number/featherm0/refreshrate/get
Refresh rate command:
homeassistant/number/featherm0/refreshrate/set
Discovery:
homeassistant/number/featherm0/co2_reference/config
Refresh rate state:
homeassistant/number/featherm0/co2_reference/get
Refresh rate command:
homeassistant/number/featherm0/co2_reference/set
See how-to calibrate for details.
| Feature | Library | Release |
|---|---|---|
| Wifi connectivity | https://github.com/arduino-libraries/WiFi101 | v0.16.1 |
| MQTT connectivity | https://github.com/256dpi/arduino-mqtt | v2.5.0 |
| DPS310 Barometric Pressure | https://github.com/adafruit/Adafruit_DPS310 | v1.1.1 |
| SHT40 Temperature and Humidity | https://github.com/adafruit/Adafruit_SHT4X | v1.0.1 |
| PM2.5 Air Quality | https://github.com/adafruit/Adafruit_PM25AQI | v1.0.6 |
| SCD30 Carbon Dioxide | https://github.com/adafruit/Adafruit_SCD30 | v1.0.8 |
Update the default labels in the Home Assistant dashboard:
homeassistant:
customize:
sensor.featherm0_humidity:
friendly_name: Humidity
sensor.featherm0_temperature:
friendly_name: Temperature
sensor.featherm0_pressure:
friendly_name: Pressure
sensor.featherm0_aqi:
friendly_name: Air Quality Index
sensor.featherm0_pm1:
friendly_name: PM 1.0
sensor.featherm0_pm25:
friendly_name: PM 2.5
sensor.featherm0_pm10:
friendly_name: PM 10.0
sensor.featherm0_carbon_dioxide:
friendly_name: Carbon Dioxide
number.featherm0_altitude_offset:
friendly_name: Altitude Offset [SCD30]
number.featherm0_co2_reference:
friendly_name: CO2 Reference [SCD30]
number.featherm0_pressure_offset:
friendly_name: Pressure Offset [SCD30]
switch.featherm0_use_pressure_offset:
friendly_name: Enable Pressure Offset [SCD30]
number.featherm0_refreshrate:
friendly_name: Refresh Rate
number.featherm0_temperature_offset:
friendly_name: Temp Offset [SCD30]
Tips:
To enable serial logging, see log.h
To customize network configuration, copy sample-env.h to env.h and apply your own local wifi and MQTT broker details.