Event to Variable Conversion
Event to Variable Conversion allows for the automatic creation and update of device variables based on incoming device events. This is particularly useful for drivers like MQTT and NMEA, where a stream of events effectively represents updates to a variable. For instance, receiving NMEA $GPGGA sentences can be interpreted as updates to position variables, and MQTT messages on a given topic can be thought of as updates to a variable related to the topic. For example, events from the "room_1/temperature" topic could be seen as updates to a variable “temperature in room 1”.
The Event to Variable Conversion table lets you configure how specific event types translate into device variables within the "remote" group. Each row in the table defines a conversion rule.
Name | Description |
|---|---|
Event | Selects the device event that triggers the variable creation/update. The available options will depend on the specific device driver (e.g., "Message" for MQTT devices). |
Variable Name Expression | An expression that evaluates to a String and determines the name of the variable. If a variable with that name already exists, its value is asynchronously updated. If not, a new variable is created, unless the Maximum Variable Count limit is reached. Resolution environment is the same as the resolution environment for event filters. |
Variable Description Expression | An expression that evaluates to a String, and determines the description for the variable based on the device event data and parameters. Resolution environment is the same as the resolution environment for event filters |
Variable Group Expression | An expression that evaluates to the group for the variable based on the device event data and parameters. Resolution environment is the same as the resolution environment for event filters |
Maximum Variable Count | An integer value that limits the number of variables created for each event type. This prevents uncontrolled variable proliferation. |
Inherit Table Format | A boolean option. If enabled (default), the format of the created variables will match the format of the source event. If disabled, the Value Custom Format must be used to define the variable type and the Value Expression must be used to convert the event data to the appropriate type. |
Value Custom Format | An expression that defines the desired format for the variable. This is only used if Inherit Table Format is disabled. Resolution environment is the same as the resolution environment for event filters |
Value Expression | An expression that converts the source event's data and parameters into a value that matches the Value Custom Format. This is only used if Inherit Table Format is disabled. Resolution environment is the same as the resolution environment for event filters/ |
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