61 lines
3.1 KiB
Markdown
61 lines
3.1 KiB
Markdown
Converting to and from NMEA0183 XDR records
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===========================================
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Basics
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------
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NMEA2000 has a much broader set of messages dealing with various sensor data then NMEA0183 has.
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In NMEA0183 there is (beside a small amount of predefined sentences) a more or less generic [XDR sentence](https://gpsd.gitlab.io/gpsd/NMEA.html#_xdr_transducer_measurement).
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As there is no out of the box complete mapping between NMEA2000 and NMEA0183 XDR possible you need to configure the mappings between NMEA2000 and XDR and vice versa.
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Mapping Parameters
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------------------
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Typically a NMEA2000 PGN that the gateway can map to an XDR record will belong to a certain category (like Temperature, Pressure, Engine,...), will potentially inlcude a source identifier (like SeaTemperature or OutsideTemperature), an instance id (0...255) and potentially a couple of fields (like EngineOilPressure, EngineCoolantTemp).
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You now need to select which combination of those values should be mapped to a particular XDR transducer name.
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Simple Set Up
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-------------
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To make the configuration easy the gateway will record information about NMEA2000 PGNs it could in principle map to XDR records - but without a current configuration.
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Just click "Show Unmapped" to get a list of those entities.
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By clicking the "+" button beside the entry you will get a prefilled mapping. You just need to add the transducer name and save the settings.
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Instance Id handling
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--------------------
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For the instance Id of a NMEA2000 message there are 3 options on how they can be used to convert to a transducer name:
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* single<br>
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exactly only this instance id is mapped to the selected transducer name.
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This should work for most receivers of the XDR records but requires a separate mapping for each of your instances.
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* auto<br>
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In this mode the instance will be added to the transducer name in the form of Temperature#001 - 001 being the instance id. This is recommended in NMEA0183 4.x - but not necessarily received by all devices.
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* ignore<br>
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All instances will map to the same transducer name.
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Backward Mapping
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----------------
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The configured mappings can work in both directions. So when an XDR record with a known transducer name, type and unit is received it is converted into a NMEA2000 PGN.
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You need to have the direction for the mapping set to "bidir" (the default).
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Export and Import
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-----------------
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The mappings can be exported and imported as a json file from the UI.
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Handled PGNs
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------------
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The following PGNS are handled:
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| Category | from NMEA2000 | to NMEA2000 |
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|----------|---------------|-------------|
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| Fluid | 127505 | 127505 |
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| Battery | 127508 | 127508 |
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| Temperature | 130310, 130311, 130312, 130316 | 130312 |
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| Pressure | 130310, 130311, 130314 | 130314 |
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| Humidity | 130311, 130313 | 130313 |
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| Engine | 127489, 127488 | 127489, 127488 |
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Rate
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----
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To avoid resending the same XDR transducer to often you can set a minimum delay between sending it again (config/converter/min XDR interval, default 100ms).
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