pdjr-skplugin-pgn130316

Map PGN 130316 into Signal K.

pdjr-skplugin-pgn130316 extends Signal K's NMEA 2000 interface by adding enhanced support for PGN 130316 Temperature, Extended Range.

Background

Versions of Signal K released before March 2022 lack the ability to process PGN 130316.

Later versions of Signal K handle PGN 130316 in a way which is problematic for the following reasons.

A node path is selected from this mapping using the PGN 130316 Temperature Source field value as a key. Inevitably, these default storage paths may not be to everyone's taste.
The mapping lacks comprehensive support for the NMEA Instance field meaning that for some Temperature Source values PGN 130316 messages from different sensor instances map to the same storage path.
The PGN 130316 Set Temperature field is not parsed into Signal K.
PGN 130316 Temperature Source and Instance field data is not saved to the Signal K store (although both values can be inferred by reversing the mapping discussed above).
Meta data describing the created 'temperature' key is not generated.

Description

pdjr-skplugin-pgn130316 overcomes the limitations described above by handling PGN 130316 messages in the following way:

A node path is selected from a user-defined mapping supplied in the plugin configuration allowing PGN 130316 message data to be saved where the user wishes.
All storage paths can be parameterised with the Temperature Source and Instance field values derived from the PGN and also with a 'name' property value drawn from plugin configuration.
The PGN 130316 Set Temperature field value is parsed into Signal K.
PGN 130316 Temperature Source and Instance field values are saved in meta data associated with the generated Signal K keys.
'unit' and 'description' properties are included in the key meta data.

Configuration

The plugin configuration has the following properties.

Property name	Value type	Value default	Description
temperatureMapping	Array	(see above)	Collection of temperatureMap objects.

The temperatureMapping array is an treated as an ordered list.

Each temperatureMap object has the following properties.

Property name	Value type	Value default	Description
source	String	(none)	Integer in the range '0'..'253' or '*'.
path	String	(none)	Signal K path where PGN 130316 data should be stored.
name	String	''	Identifying text to be used in Signal K meta data.

The plugin includes the following embedded default configuration which preserves as far as possible the stock Signal K path allocations with some corrections for logical inconsistencies, mostly by acknowledging that all PGN 130316 messages will include an Instance field value.

"configuration": {
  "temperatureMapping": [
    { "source": "0",  "path": "environment.water.${instance}", "name": "Sea Temperature" },
    { "source": "1",  "path": "environment.outside.${instance}", "name": "Outside Temperature" },
    { "source": "2",  "path": "environment.inside.${instance}", "name": "Inside Temperature" },
    { "source": "3",  "path": "environment.inside.engineRoom.${instance}", "name": "Engine Room Temperature" },
    { "source": "4",  "path": "environment.inside.mainCabin.${instance}", "name": "Main Cabin Temperature" },
    { "source": "5",  "path": "tanks.liveWell.${instance}", "name": "Live Well Temperature" },
    { "source": "6",  "path": "tanks.baitWell.${instance}", "name": "Bait Well Temperature" },
    { "source": "7",  "path": "environment.inside.refrigerator.${instance}", "name": "Refrigeration Temperature" },
    { "source": "7",  "path": "environment.inside.refrigerator.${instance}", "name": "Refridgeration Temperature" },
    { "source": "8",  "path": "environment.inside.heating.${instance}", "name": "Heating System Temperature" },
    { "source": "9",  "path": "environment.outside.dewPoint.${instance}", "name": "Dew Point Temperature" },
    { "source": "10", "path": "environment.outside.apparentWindChill.${instance}", "name": "Apparent Wind Chill Temperature" },
    { "source": "11", "path": "environment.outside.theoreticalWindChill.${instance}", "name": "Theoretical Wind Chill Temperature" },
    { "source": "12", "path": "environment.outside.heatIndex.${instance}", "name": "Heat Index Temperature" },
    { "source": "13", "path": "environment.inside.freezer.${instance}", "name": "Freezer Temperature" },
    { "source": "14", "path": "propulsion.exhaust.${instance}", "name": "Exhaust Gas Temperature" },
    { "source": "*",  "path": "sensors.temperature.${source}.${instance}" }
  ]                                                             
}

Operation

When a PGN 130316 message arrives, its Temperature Source field value is compared with each source value in temperatureMapping and a Signal K storage path and name selected from the first match. The source wildcard '*' can be used to match any Temperature Source field value.

Path selection happens a little differently for PGNs with a Temperature Source field value in the range 0 through 14. The meaning of these source codes is defined by the NMEA standard and the low-level parser used in Signal K converts the numeric value into its defined name, discarding the numeric value.

The plugin undoes this mangling by comparing the defined name supplied by Signal K with the name field in the configuration data and so identifies both a Signal K path and the original NMEA Temperature Source field value. If you want to preserve the default mappings used in Signal K, then do not change the 'name' properties for sources 0 through 14.

The last map in the example configuration shown above illustrates how to provide a catch-all.

The plugin will start processing PGN 130316 messages as soon as it is installed.

Author