ESP8266-based switch for openHAB.
The motivation is to build a small physical Wi-Fi enabled switch that controls lights via openHAB. It should require only a power cable and send the commands via Wi-Fi and MQTT to the openHAB server which then controls the lights.
Besides the openHAB server and some lights (this guide uses Philips Hue lights but others work as well), the following components are used:
The OLED display is used to show network information and confirmation of the commands. The switch setup would probably also work with other ESP8266 boards but Adafruit's Feather board is nice and easy to use. The buttons on the OLED board are used as the switch buttons but it's also possible to use externally connected buttons/switches.
Flash the Arduino sketch esp8266-openhab-switch.ino to the board. Don't forget to adjust the Wi-Fi and MQTT settings at the beginning of the sketch. The sketch requires that the ESP8266 drivers are installed and the Adafruit libraries for the Feather board and the OLED board are loaded in the Arduino IDE.
Detailed instructions on how to use Adafruit's ESP8266 Feather board with the Arduino IDE can be found here: https://learn.adafruit.com/adafruit-feather-huzzah-esp8266/using-arduino-ide
On the openHAB2 server, first install the MQTT server and the openHAB MQTT binding. When using openHAB2 on a Raspberry Pi with Raspbian, the MQTT server can be installed with the following commands:
wget http://repo.mosquitto.org/debian/mosquitto-repo.gpg.key
sudo apt-key add mosquitto-repo.gpg.key
cd /etc/apt/sources.list.d/
sudo wget http://repo.mosquitto.org/debian/mosquitto-wheezy.list
sudo apt-get install mosquitto
After that the MQTT binding can be installed via the Paper UI. There's also a good beginner's guide on MakeUsOf that explains how to setup and test the MQTT server and binding. After installation, the MQTT binding has to be configured as shown in services/mqtt.cfg.
In addition to the Hue light kitchen_ceiling_light_dimmer, two items are defined in the item file items/all.items: A dimmer that represents the ESP8266 board and a string to send a message to the ESP8266 OLED display, both connected to MQTT.
The rule file rules/esp8266_switch.rules defines the dimmer behavior. The ESP8266 board sends values 100, 50, and 0 with the buttons A, B, and C via MQTT. The rule Kitchen Switch sets the Hue light state to the value that the board sent. The rule Kitchen Switch Display sends a string with the Hue light state to the board so it can be displayed. What's cool here is that this string gets sent whenever the light state is changed, even through another UI (e.g. the Android app).