ESP8266 HomeKit Reed Contact Sensor

A contact sensor for HomeKit on an ESP8266, with a reed contact: a small glass switch that closes when a magnet comes near. Put the magnet on a door, a window or a garage door, and the Home app shows whether it is open or closed.

One firmware serves several uses. The repository lists a contact sensor, a door sensor, a window sensor, a garage sensor and a blinds sensor, all ticked as included. It is a test setup.

Hardware

The Fritzing diagram at the top of this page shows the whole build, with the pinout of the module in the corner. The repository has no firmware source, so the pin assignment is not listed in text: follow the diagram. Use an FTDI adapter set to 3.3 V, because a 5 V adapter can damage the module.

A newer version

In 2021 the same idea came back with a Hall sensor instead of a reed contact, in a 3D-printed housing. See the ESP8266 HomeKit Window Contact Sensor, and the door, blinds and general contact sensor versions linked from it.

Flash and install

The installation is the same as for the other ESP8266 HomeKit accessories on this site. The firmware runs on ESP-Open-RTOS with Life Cycle Manager 2, which sets up the WiFi and installs updates over the air. The full steps, from installing esptool to flashing, joining the LCM- WiFi network and pairing, are in ESP8266 HomeKit Blinds.

In the portal, use these values:

When the installation is done, scan the QR code the device generates in the Home app to add it.

Firmware release

Good to know

• This is a test setup and not a finished product.
• The HomeKit Accessory Protocol specification the firmware follows is the non-commercial version, for accessories you build yourself and do not distribute or sell.
• The repository is under the MIT licence and holds the firmware release, not the source code.

Everything is in the ESP8266-HomeKit-Contact-Sensor-2 repository on GitHub.