Navigator Adapter

Navigator Adapter

The navigator_adapter plugin reads an external GPS navigator's RS-232 output and writes its position and guidance into the database. The panel can then fly the navigator's course instead of the Flight Plan Engine: set GPSSRC to 1.

Plugin reference: doc/plugins/navigator_adapter.md.

Turning it on

The plugin ships off. In preferences.yaml.custom:

enabled:
  NAVIGATOR: true

See Configuration.

Settings

connections/navigator_adapter.yaml:

Option	Default	Meaning
port	none, required (/dev/ttyUSB0 in the shipped file)	serial device
baud	4800	serial speed
adapter	none, required (garmin_nmea in the shipped file)	which parser to use; an unknown name fails with the list of known ones
cdi_full_scale_nm	5.0	cross-track that gives full CDI deflection; the shipped file suggests 0.3 for a GPS approach

The one built-in adapter, garmin_nmea, reads Garmin Aviation Output 1 and standard NMEA 0183: RMC, GGA, GSA, RMB and APB. It needs the pynmea2 Python package; without it every line is ignored.

Keys written

Key	From
LAT, LONG	RMC (valid fixes) and GGA (when there is a fix)
GS, TRACK	RMC, ground speed and true track
GPS_ELLIPSOID_ALT	GGA altitude, converted to feet
GPS_FIX_TYPE	GGA, with the 2D/3D mode from the preceding GSA
EXTXTK	RMB cross-track, nm, positive right of track (steer left)
EXTCDI	-EXTXTK / cdi_full_scale_nm, clamped to -1..+1
EXTCRS	APB desired track, degrees magnetic; a true bearing is converted with the RMC variation, or dropped if there is none
EXTTF	APB TO/FROM

The plugin reads no keys and never writes COURSE, CDI or XTRACK; the compute select on GPSSRC does (see Flight Plan Engine → Internal plan or external navigator).

When the navigator goes quiet

The plugin does not set quality flags itself. When sentences stop, the keys go old through their tol: 2 s for LAT, LONG, GS, TRACK and GPS_FIX_TYPE, 5 s for the EXT* keys. If the serial port cannot be opened, or a read fails, the plugin logs the error and stops reading; it does not reconnect until the gateway restarts.

Things to know

• One writer per key. The garmin_gnx375 plugin writes the same EXT* keys, and gpsd, xplane and other GPS sources write LAT/LONG. Enable one of them.
• The GPS bearing pointer (GPSBRG) is computed from the internal plan's WPLAT/WPLON, not from the navigator.