| Device | Connection(s) |
|---|---|
| G2 | USB or Serial (internal) |
| S4 | USB |
| S3 | Serial |
| First channel | Raw NMEA 0183 messages. |
| Second channel | Converted values. |
Only one GPS device can be accommodated by the software.The GPS channels are enabled from the Programs tab of the Configuration web page. Since the G2 has USB ports in addition to a serial port (on an internal header), the user is able to specify which connection is to be used for the GPS device.
The GPS device is handled by gpsd which is able to deal with a wide range of serial and USB devices.
The raw channel contains a generic creation of NMEA 0183 messages, not the actual messages from the device. The NMEA message's ID is placed in the Data message's header. The rest of the NMEA message is placed in the Data message's data.
The cooked (second) channel contains some of the converted values from gpsd . The Gryhon Data message's header is not used. The following values are present in the Data message's data in little endian (Intel) order. (The gps_cooked structure is in gdev.h)
Data Type Description Time double The number of seconds since 1/1/1970 UTC Mode int The number of dimensions of the fix, 2 or 3 Latitude double Latitude in degrees. (north/south +/-) Longitude double Longitude in degrees. (east/west +/-) Altitude double Altitude Track double Direction of travel in degrees. (north = 0) Speed double Speed Climb double Rate of climb The speed from GPS devices is in units of meters per second. Default altitude units is meters. Latitude and longitude are reported in degrees. The units for speed and altitude for the cooked channel may be changed from Channels web page by clicking on the Setup button in the cooked GPS channel entry. Changes made to the units are immediately reflected in the cooked GPS data. The requested units are stored in the /gryphon/etc/gps_units file and are retained until changed.