posted 04-21-2007 10:21 PM ET (US)
Bob:
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
RCA GPS RECEIVER JACK
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.