knx_config.json.md

General structure

homebridge-knx expects the following structure in the knx_config.json:

{
    "knxconnection": "knxjs",
    "knxd_ip": "192.168.1.1",
    "knxd_port": 6720,
    "Devices": [
    ]
}

knxconnection if set to "knxjs" then javascript based knx multicast routing is used, set to any other value or non-existent will default to knxd
192.168.1.1 has to be changed to your knxd installation, and 6720 to the port you are using (6720 is default).
platform and name have become obsolete.

Devices is an array of objects, each representing an homekit accessory.

Devices

Devices must have a unique DeviceName. The name cannot be changed in the config file after pairing with homekit, because homekit copies it into its database. You can change the name of the device in homekit afterwards; unless you erase your home or un-pair homebridge it will keep the changed name.
In Apple's Home app (or other homekit enabled apps) devices can get assigned to rooms.
As HomeKit can only handle 100 accessories (devices) per bridge, and homebridge bundles them all into one, it is recommended to bundle all functionality into one device per room. It is also less work to do when assigning the services to the rooms, as all services of one device are placed in one room automatically.

Each device needs a section Services. Here all functionality of the device is defined.

Services

Services again is an array of objects, each representing a homekit service.
Each service must have:

• a unique ServiceName (regarding changing names in a paired instance see Devices )
• a known homekit ServiceType
• a Characteristics section, containing all the variables that homekit can handle.
  A service can have:
• an handler entry, pointing to an add-in to handle all requests for the service.
• a KNXObjects array containing KNX group addresses used by the handler and not directly connected to a characteristic.
• a KNXReadRequests array containing group addresses that should be read upon startup of homebridge, to sync the status of characteristics with the physical devices.

Service types are regularly amended by Apple, to get new service types into homebridge-knx we need to update homebridge using npm. There is a Javascript file containing all valid services and characteristics located here: https://github.com/KhaosT/HAP-NodeJS/blob/master/lib/gen/HomeKitTypes.js

Characteristics

Each characteristic is an object containing at least a Type field. Types can be "On" for power, "Brightness" for dimmable lights etc.
Characteristics can have assigned group addresses in the Set and Listen arrays. For the group addresses it is possible to define a data point type DPT (currently valid are DPT1, DPT5, DPT5.001, DPT9). Characteristics without group addresses can only be used by a handler.

For boolean and percentage types it is possible to reverse the read/write value between HomeKit and KNX (Restrictions: Only if it is a boolean or a percentage for HomeKit, some of the types that support only 0 and 1 are integer anyway; Service must not have a handler, see chapter below).

For enumerative type, such as TargetHeatingCoolingState with a given list of possible values, it is possible to restrict Apple's Home app even more with the "ValidValues" array keyword. Only working with new services. If the service is read into homekit database, this is stored there and not read again. If you need to change tha valid values, you have to remove the service from homekit and re-add it again.

For continuous value types, such as temperatures, the minimum and maximum values that define the range can be modfied with the "MaxValue" and "MinValue" keywords. Required for Temperatures in Celsius in middle/norther Europe at least, as Apple (designed in California, made in China) expected no sub-zero temperatures.

Some exmples:

"Characteristics": [
    {
        "Type": "On",
        "Set": [
            "1/3/5"
        ],
        "Listen": [
            "1/3/5"
        ]
    }
]

with "Reverse"

"Characteristics": [
    {
        "Type": "On",
        "Set": [
            "1/3/5"
        ],
        "Listen": [
            "1/3/5"
        ],
        "Reverse": true
    }
]

With "ValidValues", to remove "Cool" from the list of Target States:

{
    "Type": "TargetHeatingCoolingState",
    "Listen": [
        "14/1/97"
    ],
	"ValidValues":[0,1,3]
}

Modifying Min and Max:

{
    "Type": "CurrentTemperature",
    "Listen": [
        "7/1/11" 
    ],
    "MaxValue": 60,
    "MinValue": -20
}

Handler

New in version 0.3 of homebridge-knx is a little add-in concept, allowing additional functionality to be added without changing the big mass of the code.
handlers are defined as javascript files in /lib/addins and need to follow some restrictions.
To assign a handler to a service the Handler keyword is used, see example below.
Handlers cannot use the Reverse keyword for DPT1 and DPT5.001 types, this has to be taken care in the handler's programming.

KNXObjects

Handlers can make use of KNX group addresses that are not connected directly to characteristics. To allow references to those addresses, they are defined as if they were characteristics.

• The Type field is a freely definable name field (uniqueness within the service required).
• Definition of DPT is mandatory as the data point type cannot be inferred from a homekit characteristic!

KNXReadRequests

All addresses listed in that array are sent to the bus with a READ request telegram at the start of homebridge-knx. They are not ergularly polled. Use active status objects instead.## LocalConstants Handlers can use service-local constants in their code. This allows using the same handler for alike-but-not-equal use cases. The values from the LocalConstants can be used in the handler code. This allows re-using the same handler for multiple objects that differ by more than group addresses.

UUID and subtype

homebridge-knx creates a unique UUID for each device newly discovered in the knx_config.json and writes that back to the file. Similar, a unique subtype field is created for each service.
Do not alter these fields unless you want to force homebridge-knx to accept this as a new device or service, rendering the old one stale and unreachable.

Example

{
    "knxd_ip": "192.168.178.100",
    "knxd_port": 6720,
    "AllowKillHomebridge": true,
    "Devices": [
        {
            "DeviceName": "Office",
            "Services": [
                {
                    "ServiceType": "Lightbulb",
                    "ServiceName": "Office desk lamp",
                    "Characteristics": [
                        {
                            "Type": "On",
                            "Set": [
                                "1/3/5"
                            ],
                            "Listen": [
                                "1/3/5"
                            ]
                        }
                    ]
                },
                {
                    "ServiceType": "WindowCovering",
                    "Handler": "GiraJalousieActuator",
                    "ServiceName": "Office blinds",
                    "Characteristics": [
                        {
                            "Type": "TargetPosition",
                            "Set": [
                                "2/3/46"
                            ],
                            "DPT": "DPT5"
                        },
                        {
                            "Type": "CurrentPosition",
                            "Listen": [
                                "2/3/26"
                            ]
                        },
                        {
                            "Type": "PositionState"
                        }
                    ],
                    "KNXObjects": [
                        {
                            "Type": "ShutterMove",
                            "Listen": "2/3/6",
                            "DPT": "DPT1"
                        }
                    ],
                    "KNXReadRequests": [
                        "2/3/26",
                        "2/3/46"
                    ],
                    "LocalConstants": {
                        "TimeOutSecs": 23
                    }
                }
            ]
        }
    ]
}