HomeKit SCD4x

An Apple HomeKit accessory for the SCD4x CO2 (Carbon Dioxide), temperature and humidity sensor running on a Raspberry Pi.

Dependencies

• Go - this accessory is written in Go
• HomeControl - to expose climate readings from the Enviro+ as an Apple HomeKit accessory
• SCD4x exporter for ESP32 - to read the SCD4x sensor and export it for scraping by Prometheus

Installation

Install this on a Raspberry Pi, or test it on macOS.

Setup

1. Install Go >= 1.14 (useful Gist for Raspberry Pi)
2. Clone this project: git clone https://github.com/sighmon/homekit-scd4x and then cd homekit-scd4x
3. Install the Go dependencies: go get
4. Install and run the Climate Sensor exporter climate-sensor

Build

1. To build this accessory: go build homekit-scd4x.go
2. To cross-compile for Raspberry Pi on macOS: env GOOS=linux GOARCH=arm GOARM=7 go build homekit-scd4x.go

Run

1. Execute the executable: ./homekit-scd4x
2. Or run with the command: go run homekit-scd4x.go

Start automatically at boot

1. sudo cp homekit-scd4x.service /lib/systemd/system/homekit-scd4x.service
2. sudo systemctl daemon-reload
3. sudo systemctl enable homekit-scd4x.service
4. sudo systemctl start homekit-scd4x.service

Optional flags

The flag defaults can be overridden by handing them in at runtime:

• -host=http://0.0.0.0 The host of your SCD4x sensor
• -port=1006 The port of your SCD4x sensor
• -sleep=5s The time between updating the accessory with sensor readings (5s equals five seconds)
• -dev This turns on development mode to return a random temperature reading without needing to have a SCD4x

e.g. to override the port run: go run homekit-scd4x.go -port=8000 or ./homekit-scd4x -port=8000

Reset this accessory

If you uninstall this accessory from your Apple Home, you'll also need to delete the stored data for it to be able to be re-added.

macOS

1. Delete the data in the folder created: homekit-scd4x/SCD-41/
2. Restart the executable

Raspberry Pi

1. Remove the persistent data: rm -rf /var/lib/homekit-scd4x/data
2. Restart the Raspberry Pi

Thanks

This project uses the amazing work of Matthias. Please consider donating if you found this useful.