ComNav G2 - Data Connections

ComNav G2 & G2B Installation & Operation
Document PN 29010093 V1.5 - 30 - 16 December 2016
completed in accordance with the applicable safety standards for “low-voltage DC” wiring
at your locale.
Note: The G2’s internal power supply is protected against reverse
polarity connection. Nevertheless, care must be taken when
wiring and connecting the unit to a power source.
Data Connections (Autopilot, GPS Display, Chart plotter, PC, etc.)
There are a number of ways to make the data connections required between the G2 and
other equipment on the vessel. See Figure 14, Figure 16 and Figure 17 for common
examples:
• The G2 is typically used with an autopilot system (e.g., Commander P2,
Admiral P3, 2001, 5001, etc.), an optional ComNav Navigator G2 GPS Compass
Display System, and a generic Chart plotter.
• The G2 may be connected to other types of Navigation System.
⇒ A PC can be used, instead of the Navigator G2Display, to configure the
G2 and/or monitor its status.
⇒ A PC can be used, instead of a Chartplotter or other type of NMEA
Navigation equipment, to perform the “Navigation display & control”
functions – setting waypoints, etc.
Each of those connection schemes is described in more detail below. Other schemes
may also be possible on your vessel, or in your application of the G2.
All data communications from/to the G2 is done with serial data signals; there is also a
separate Alarm signal from the G2, using the contacts of a relay.


 In an IMO system, you must connect an audible alarm device to the G2!
Signal Grounds
Whether or not to connect the G2’s Signal Ground to the Signal Ground (or the Main or
Power Ground, if there is no Signal Ground) of the other device or devices on your vessel
depends on how your vessel, and any other equipment, is wired.
• RS-422: per the NMEA 0183 Standard, the Listener will have optically (or
galvanically) isolated RS-422 inputs; thus, it is usually not strictly necessary –
and sometimes it is not even possible – to connect the Grounds.
⇒ For example, the Commander P2’s NAV1/2 inputs (NMEA 0183
Listeners) are optically isolated – no Signal Ground pin for those inputs is
provided.
In contrast, for the P2’s NAV output (which is an NMEA Talker), there is a
Ground pin – but that is a “current-controlled, AC-coupled” ground, not the
P2’s main Signal Ground.
• RS-232: the G2’s RS-232 Signal Ground MUST be connected to the other
device’s Signal Ground, when using the RS-232 ports.
• On the other hand, it is sometimes better – from the perspective of signal
integrity and/or electrical noise-reduction – to connect some or all of the Grounds
in a system.
Consult your ComNav Dealer for help, if you are unsure what will work best on your
vessel.
Serial Port Settings
Both ports use ordinary asynchronous serial data formatting, as specified in the
NMEA 0183 Standard; the formatting is fixed, and can not be changed:
• 1 Start Bit, 8 Data bits, No Parity Bit & 1 Stop Bit (commonly described as
“8-N-1”).