Connecting the M7 to a Lowrance display

The M7 GX series of GPS transponders may be directly connected to a Lowrance Globalmap 540C or a Globalmap 840C navigation display. When connected, the Lowrance display map will show the location of the vehicle it is in PLUS the location of all other M7 transponders within radio range.  This unique feature allows one to quickly, easily, and inexpensively, make a mobile AVL system for tracking cars, trucks, racecars, construction equipment, or any thing Raveon’s M7 GX transponder may be installed on.

Both the 540C and 840C have built-in interfaces for a “NMEA 0183″ devices, which is another way of saying that they can connect to other devices using a serial cable.   The NMEA 0183 is an RS232 serial connection that typically operates at 4800 baud.  It is used to exchange waypoint and other information between displays, GPS devices, and transponders.

When Raveon’s M7 GX transponder is connected to the Lowarnce diplay using the NMEA 0183 connection, the M7 transponder can put icons on the screen of the Lowrance display.  As the transponder received updated positions from other vehicles, it updates the position of the icons on the Lowrance display.

Lowrance 540C and 840C Wiring

From the Lowranace technical manual, here is how their NMEA 0183 interface works:

NMEA 0183 Cable Connections

NMEA 0183 is a standard communications format for marine electronic equipment. For example, an autopilot can connect to the NMEA interface on the GlobalMap 540c and receive positioning information.  The GlobalMap 540c can exchange information with any device that transmits or receives NMEA 0183 data. See the following diagram for general wiring connections. Read yourother product’s owner’s manual for more wiring information.

NMEA 0183 Wiring  (Data cable)

To exchange NMEA 0183 data, the GlobalMap 540c has one NMEA 0183 version 2.0 communication port. Com port one (Com-1) can be used to receive NMEA format GPS data. The com port can also transmit NMEA format GPS data to another device.  The four wires for the com port are combined with the Power Supply cable and NMEA 2000 Power cable to form the power/data cable (shown earlier). Com-1 uses the yellow wire to transmit, the orange wire to receive and the shield wire for signal ground. Your unit does not use the blue wire.540cwiring-to-m7

Wiring the DB9

The Lowrance’s “Data Cable” must be connected to the M7 transponder.  This connection will allow the M7 to put icons on the screen of the Lowrance display, showing the location of other tracked vehicles.  The Raveon M7 GPS transponder uses a 9-pin “DB9″ connector to connect to the Lowrance.  Solder the Lowrance data cable wires onto a DB9 connector and plug the DB9 into the M7 transponder as shown below:db9-lowrance-31

The orange wire goes to pin two of the DB9, the yellow wire to pin 3, and the shield braid of he cable connects to pin 5 of the DB9.  The blue wire is trimmed off.

The extra wires on the Lowrance display called NMEA 2000 power are typically not used in a vehicle installation, and may be wrapped up with electrical tape and tucked away.

Configuring the Lowrance

Set the NMEA communication of the Lowrance to 4800 baud.

Configuring the M7 GX Transponder

Raveon has a designed the M7 GX transponder to work with Lowrance Display or any other NMEA 0183 display that can accept the “$GPWPL” NMEA message.   The $GPWPL is an industry standard message that the Lowrance displays and many other GPS displays interpret as a waypoint command.  The M7 GX outputs this $GPWPL message to put icons on the screen of the Lowarance, and to move the icons around on its screen.

To configure the M7 transponder to output the $GPWPL message, set the M7 GX to GPS mode 2.  To do this, put it into the configuration mode by send the +++ into the serial port.  The M7 will respond with an OK.  Type GPS 4 and press enter to put it into GPS 4 mode.  GPS 4 is the mode that causes the M7 GX to output $GPWPL messages whenever it receives a status/position message over the air.