Lowrance electronic M68I User Manual
Pub. 988-0152-061
Addendum I
Additional Instructions for
Lowrance M68i S/Map
Your sonar/GPS unit, the M68i, functions exactly like the M68 described in the manual provided (part 988M68i contains a communications port for NMEA 0183 output. The instructions for connecting data cables and setting up the communications port appear in this addendum. The back page also includes a correction note for an error in the M68 manual.
NMEA 0183 Cable Connections
NMEA is a standard communications format for marine electronic
equipment. The M68i can send information to any device that receives
NMEA 0183 data. This allows the unit to work with VHF marine radios
equipped with the Digital Selective Calling (DSC) distress call feature.
To send NMEA 0183 data, the M68i has one NMEA 0183 version 2.0
communication port. The com port can be used to send NMEA formatted data such as your current position.
The provided M68i data cable plugs into the accessory socket on the
right side of the back of your unit's case. This socket can connect either
an accessory such as a speed or temperature sensor or a NMEA 0183
data cable. The data cable ends in two wires that connect to your VHF
radio or other NMEA device. The M68i uses the yellow wire to transmit
and the black shield wire for signal ground.
0152-031). In addition, the
NOTE:
Some VHF radios, such as the popular Uniden
els which require use of an additional diode and resistor built into the
M68i data cable. This is Wiring Diagram A, which is described on
page 2. The majority of the DSC radios will work with the resistor and
diode as provided by Lowrance Electronics.
A few other radio brands (and other electronic devices) that meet the
NMEA 0183 standard won't need these adapters and you will have to
remove the resistor and diode to make those work. This is Wiring Dia-
gram B, which is described on page 3.
Consult your other device's owner’s manual, then read through all of
the following instructions before you begin. Use the installation dia-
1
brand, have input lev-
gram most suited to your brand of radio or other device. If your device
manual indicates an RS-232 connection (i.e., a computer), remove the
resistor and diode and connect using Wiring Diagram B. Most other
connection types (TTL; NMEA + and NMEA –; differential) will require Wiring Diagram A.
Recommended Tools and supplies
Recommended tools for this job include: wire pliers or wire stripper and a
wire cutter. Required supplies for this job include: two gray (18 gauge) or
blue (16 gauge) wire nuts and electrical tape. Supplies are not included.
Wiring Diagram "A"
Begin by stripping the wire ends of the device you're connecting to the
M68i. (You'll notice the M68i's data cable comes pre-stripped, with wire
ends exposed.) Use a pair of wire pliers to strip about 1/4-inch (6.35
mm) of insulation from each of the radio's or other device's data wires.
Strip the ends of the VHF radio's data wires. Connect them to the pre-
stripped wires of the M68i's data cable (shown right).
Twist the exposed wires together as shown in the following figures. If you're
using a Uniden or similar radio, connect the radio's NMEA Wire to the
M68i data cable's yellow wire, and the radio's Ground/Shield wire to the
M68i data cable's black shield wire. If you're using another radio brand or
NMEA device, see Wiring Diagram B instructions at the end of page 3.
Com port
to M68i
Yellow (Transmit)
Shield (Ground)
Com port wiring to transmit NMEA information
to a Uniden or similar VHF radio or other device.
NMEA Wire (Receive) or NMEA +
Ground/Shield or NMEA –
To Uniden
radio or other
device
2
Twist the appropriate wires together, making sure that the exposed
ends make good contact. Secure the wire ends with wire nuts, then
wrap each wire nut securely with electrical tape to protect against
moisture, as shown in the figure on the right.
After taping the wire ends individually, wrap the entire connection
with electrical tape as shown. This will help protect from moisture and
prevent the wires from breaking contact.
Wiring Diagram "B"
If your VHF radio or other device requires true RS-232, you will need to
remove the diode and resistor built into the end of the M68i data cable.
You will notice near the end of the cable a segment protected with black
heat-shrink. To connect the M68i to a true RS-232 radio, first remove the
Uniden adapter segment of the cable as shown in the following figures.
3
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