Lights
Lights are an essential part in smart homes. The Home app show a light as a separate tile. A tap on the tile turns the light on and off. But there is more than just turning it on and off.
Keep reading if you want to learn more on how to setup and configure your lights.
In our ETS project we defined the following group address for turning a light on and off.
| Address | Description |
|---|---|
| 0/0/1 | Switching the light |
| 0/1/1 | State, if a light is turned on or off |
Lets create a HomeKit light in the web interface of the bridge and enter the following group addresses.
| Characteristic | Data Type | Write | Read | Initialize |
|---|---|---|---|---|
| Power | DPT-1 | 0/0/1 | 0/1/1 | 0/1/1 |
The Write group address is used to send KNX telegrams when the state of the light changes. When the light is turned on, the value 1 is sent to the Write group address, in our case to 0/0/1.
Die Read and Initialize group addresses are used to read the state of the light. The Initialize group address is read when the bridge is started. Once the bridge is running and receives a new value from the Read group address, it updates the state of the light.
(In most cases the Read and Initialize group addresses are the same.)
Brightness and Color
HomeKit also supports brightness and color information for lights. The brightness value has to be between 0 … 100%. The color data type can either be RGB, RGBW, HSV or a color temperature. Which data type you use is based on your KNX actuator.
Limitations
The official KNX specification declares the data type 232.600 as RGB (red, green, blue). The bridge supports this data type as RGB and HSV (hue, saturation, value). But there are some limitations when using as HSV.
If you configure a colored light as HSV (DPST 232.600), you won’t be able turn on the light with a specific color and 100% brightness. So you can’t set a specific color for that light in HomeKit scenes.
As a workaround you can use the Home+ app to configure the scene in a way that only the light color is changed. The action to turn on the light on is not required. KNX dimming actuators automatically turn on a light on when the light color is updated. With this workaround you can set a specific light color in scenes.