Moderated Discussion Areas
  ContinuousWave: Small Boat Electrical
  NMEA-0183 Interface: Garmin GPS to ICOM Radio

Post New Topic  Post Reply
search | FAQ | profile | register | author help

Author Topic:   NMEA-0183 Interface: Garmin GPS to ICOM Radio
BellBoyBob posted 04-21-2007 05:57 PM ET (US)   Profile for BellBoyBob   Send Email to BellBoyBob  
I own the Garmin 178 GPS plotter and SONAR and the ICOM 402 [VHF] marine radio. I am trying to connect the GPS to the [VHF] for use with Digital Selective Calling and sending my coordinates to another radio. The Garmin manual shows that for "port 2" (VHF / DSC device) I should connect the green and white wires to the RCA male jack that will go into the RCA female jack on the Icom. The radio scrolls "no position" indicating that the radio does not recognize the Garmin. The female radio side of the connection indicates that the center pin receptacle on the jack is for NMEA in or (+). I believe I am following the instructions correctly. On the GPS, I checked to be sure that the DSC tab was "on" It is. I am stumped! Any ideas?
Bella con23 posted 04-21-2007 10:21 PM ET (US)     Profile for Bella con23  Send Email to Bella con23     
I just wired the same (almost) combination on my boat. I think your problem may be in the communication tab of the GPS. Personally I didn't even know that the DSC tab existed. I did however have to "turn on" the communication port on the GPS.

Below are the two pages relevant from each unit. Let me know if it gives you any trouble and I will find my installation notes.

You should know that after I setup the communication tab on the GPS, the radio listed the position right away.
Good luck, Joe

ICOM - 402
Connects to a GPS receiver for position indication.
• A NMEA0183 ver. 2.0 or 3.01 (sentence formatters RMC, GGA,
GNS, GLL) compatible GPS receiver is required. Ask your dealer
about suitable GPS receivers.

Garmin 178
Comm (Communications) Tab— lets you control the input/output format used when connecting your
GPSMAP 178/178C to external NMEA devices, a DGPS beacon receiver, a personal computer, another
Garmin GPSMAP 178/178C, etc. If a DGPS receiver is used, WAAS capability is automatically turned to
‘Off’. The unit supports two input/output ports. See page 96 for more information on wiring and NMEA
information. Individual Port settings are:
Port 1:
• Garmin Data Transfer – the proprietary format used to upload/download MapSource data,
exchange waypoint, route, track, almanac, and proximity data with a PC or another Garmin
GPSMAP 178/178C. When you select ‘Garmin Data Transfer’, there are 11 Transfer Modes to
choose from: Host, Request Almanac, Request Proximity, Request Routes, Request Tracks, Request
Waypoints, Send Almanac, Send Proximity, Send Routes, Send Tracks, and Send Waypoints.
• NMEA In/NMEA Out – supports the input/output of standard NMEA 0183 data and DSC.
• None – provides no interfacing capabilities.
Port 2:
• Garmin DGPS – used to connect the GPSMAP 178/178C with a Garmin DGPS beacon receiver.
• Other DGPS – allows DGPS input using a standard RTCM format, without any output capabilities.
• NMEA In/NMEA Out – supports the input/output of standard NMEA 0183 data and DSC. You
may also adjust the NMEA output.
• RTCM In/NMEA Out – allows Differential GPS (DGPS) input using a standard RTCM format and
also provides NMEA 0183 output.
• None – provides no interfacing capabilities.
To select an input/output format:
1. Select the desired Port tab, then highlight the ‘Serial Data Format’ field and press ENTER.
2. Use the ARROW KEYPAD elect the desired setting and press ENTER.
To select a transfer mode:
1. Use the ARROW KEYPAD to select ‘Garmin Data Transfer’ in the ‘Serial Data Format’ field.
2. Highlight the ‘Transfer Mode’ field and press ENTER.
3. Use the ARROW KEYPAD to select the desired setting and press ENTER.
You may also adjust the NMEA output to enable/disable certain sentences and adjust the number of
Lat/Lon output precision digits. You must have one of the ports set to NMEA In/NMEA Out to use this
option. Settings affects both Port 1 and Port 2 NMEA outputs.

BellBoyBob posted 04-21-2007 11:08 PM ET (US)     Profile for BellBoyBob  Send Email to BellBoyBob     
Thank You, Thank You, THANK YOU! That was it! The NMEA switch within the Garmin 178 Comm tab was off. I powered up the radio and, voilá, my current position (on the trailer in the garage!)went scrolling by on the Icom screen. I was scratching my head for three ours this afternoon. You solved my dilemma!


jimh posted 04-22-2007 01:15 AM ET (US)     Profile for jimh  Send Email to jimh     
Good information. Thanks for providing the help.

Getting two serial data communication devices to talk to each other can be very frustrating. Often there is no test equipment, and you have no way to know if it works or not until it finally starts working.

Post New Topic  Post Reply
Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.