ComNav Commander P2 & P2VS Installation & Operation Installation
Document PN 29010074 V4.1 - 82 -
RS-232 Electrical Signals
It is common for non-marine equipment (especially PCs) to be able to transmit & receive
NMEA-formatted data – but not using the RS-422 electrical interface specified in the NMEA
Standard, instead using another electrical interface, RS-232. A prime example is Personal
Computers: the
“
COM port” on a PC is always at RS-232 levels.
An RS-232 interface, in contrast to RS-422, does not use differential-signal wiring. Instead, a
single wire is used for each of the main signals
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– Receive (usually labelled “Rx”) & Transmit
(“Tx”) – and for the Signal Ground (“Gnd”). The voltage levels are also different than RS-422.
Such equipment (often described as being “NMEA compatible”) can usually be connected
directly to the Commander P2 – although there is some risk of reduced electrical noise
immunity. See the section on
PC COM Ports
on page 181 in
Appendix 1
for more details.
Status LEDs
When the autopilot is turned on, the Status LED labelled
NMEA 0183 IN #1
in the SPU’s
Diagnostic section will be flashing whenever the autopilot is receiving data on
NAV1 - IN
.
Similarly, the
NMEA 0183 #2
LED will be flashing whenever the autopilot is receiving data on
NAV2 - IN
.
Typically, an LED will flash at a rate of about once per second for regular data from a GPS or
Chartplotter. It will typically flash at a rate of about ten times per second when connected to
a Heading source, such as the Vector G2 GPS Compass.
The LEDs only show that data is being received on the associated Nav1 (or
Nav2) port. They do not mean that the data received is valid!
If the LED for a port is flashing, but you are seeing INVALID or NO DATA
Navigation (Heading, Speed, Course, NAV) error messages for that port on the
Control Head, and yet you are sure the other device is in fact sending valid data,
try reversing the wires connected to NAV1 – IN, or NAV2 – IN. It is possible that
the other device’s signal names are not NMEA’s `A´ & `B´ (see Table 4, above),
and so might have been connected the wrong way round; reversing the wire pair
at J9 often solves this situation.
If you are still seeing error messages, something else is wrong. Contact your
ComNav Dealer for assistance.
Other Connections
Thruster Interface
The
J7 – THRUSTER I’ FACE
connector is used with the CT7 Thruster Interface. The
receptacle is not supplied with a mating plug, since the required plug is supplied with the
CT7.
ComNav Network
The
J10 – COMNAV NETWORK
connector is reserved for possible future use. The receptacle
is not supplied with a mating plug.
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There are also several RS-232 status signals, but these are not used in the P2.
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