A325 GNSS Smart Antenna User Guide
7
PN 875-0318-000 Rev D2
Chapter 2: Installing the A325
Communication
The A325 supports radar-simulated pulse output and various NMEA 2000 messages.
Radar-Simulated Pulse Output
The radar-simulated pulse output provides accurate ground speed. The A325 uses pin 12 for the
speed out pin. Pin 12 will output a square wave with a 50% duty cycle and the frequency of the
square wave varies directly with speed. 94 Hz represents a speed of 1 m/sec (or 28.65 pulse/foot
traveled).
Note:
Pin 12 does not have any form of isolation or surge protection. Hemisphere GNSS strongly
recommends that you incorporate some form of isolation circuitry into your supporting hardware if
you want to utilize the Speed Radar Pulse output.
CAN
Note:
To use the A325 in a NMEA 2000 network requires NMEA certification.
The A325 supports a number of NMEA 2000 messages that can be transmitted on a CAN bus. Table 2-
2 shows the PGN, description, level, default update rate, and frequency of each message.
Table 2-2: Transmitted NMEA 2000 messages
PGN
Description
Level
Default
Update
Rate
(msec)
Freq
(Hz)
126992
System Time
The purpose of this PGN is twofold: To provide a regular
transmission of UTC time and date and to provide synchronism
for measurement data.
B
1000
1
127257
Attitude
Provides a single transmission that describes the position of a
vessel relative to both horizontal and vertical planes. This
would typically be used for vessel stabilization, vessel control,
and onboard platform stabilization.
B
1000
1
129025
Position, Rapid Update
Provides latitude and longitude referenced to WGS84. Being
defined as a single frame message, as opposed to other PGNs
that include latitude and longitude and are defined as fast or
multi-packet, this PGN lends itself to being transmitted more
frequently without using up excessive bandwidth on the bus
for the benefit of receiving equipment that may require rapid
position updates.
B
100
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