No virtual COM port to interface to Garmin GPSmap

[tominny]

I got a new Garmin GPSmap 78sc which can interface with my PC laptop via USB to show file storage, etc. But it does not create a virtual COM port that would allow me to interface it to OpenCPN to upload routes. When I check in Device Manager there is no COM port. I tried this on 3 different PCs with the same result.
On solution may be to install a driver that emulates a COM port from USB input. But I have not been succesful in finding one that works. Any suggestions and help are welcome!

[bcn]

A search for Garmin 78S gives me:

GPSmap 78sc Specifics:
The 76 and 78 series units are classified as "Marine" units. They all have Tide Tables. And now with the 78 series, one can select the Sensors "s" and built-in BlueChart g2 Coastal Charts "c". These units (like the Dakota and Oregon) when connected to a computer become mass storage units and not a GPS. Therefore position data can't be outputted through the USB port.

Only the 78 series have a serial output for NMEA. There are two modes for the NMEA output, Autopilot Mode ON and Autopilot Mode OFF. With the Autopilot mode ON the sentences are:
$GPRMC, $GPRMB, $GPBWC, $GPXTE, $GPAPB, $GPRMC, $GPRMB, $GPBWC, $GPXTE, and $GPAPB.
With the Autopilot mode OFF the sentences are:
$GPGGA, $GPGLL, $GPBOD, $GPBWC, $GPVTG, $GPXTE, $PGRME, $PGRMZ, $PGRMM, $HCHDG, $GPRMC, $GPRMB,

so it looks that you will need first a serial cable for the device.

[tominny]

Thanks.

I should clarify that I don't want to use the GPSmap 78 for location information into OpenCPN, I want to use OpenCPN to create a route and then load it to the 78, instead of having to enter waypoints manually. This has worked very well for me with the 76 model (until that one died of salt water exposure).

[nohal]

Originally Posted by tominny

I got a new Garmin GPSmap 78sc which can interface with my PC laptop via USB to show file storage, etc.

This looks to be your problem - Looking at the manual (maybe too briefly, confirm by really reading it) the device has two ports - serial for NMEA and mini-USB for USB mass storage (=it acts like an external disk, not a GPS)
from the connector, I'm afraid you will need a serial cable from garmin and usb-serial convertor to get the NMEA connection working.

Pavel

[RhythmDoctor]

Originally Posted by tominny

Thanks.

I should clarify that I don't want to use the GPSmap 78 for location information into OpenCPN, I want to use OpenCPN to create a route and then load it to the 78, instead of having to enter waypoints manually. This has worked very well for me with the 76 model (until that one died of salt water exposure).

I think all the advice to get serial adapters and serial cables is wrong, since all you want to do is transfer routes. Try this before spending your time and money trying to downgrade from USB:

Within OpenCPN, export the desired routes in a .gpx file. From this point forward, OpenCPN will not have anything to do with the transfer. I've never been able to get OpenCPN to directly read/write routes to my Garmin Oregon, so I rely on other software tools to transfer the .gpx file to the Oregon.

Mount the GPS as a mass storage device. Just plug it into the USB port with a USB cable. At this point, my Oregon gives me a selection between Mass Storage mode and GPS mode. Your device may do it differently, but there MUST be a way to get the device recognized as an ordinary external storage device. That's the first step, because any software you run can then read/write the files in storage.

Once that part is done, the rest is a little tricky. Unfortunately, just copying the .gpx file over does not work. The device needs it to be put into a special temp file, and upon rebooting the device, it reads the new routes into the current.gpx file. For that, you need computer software.

The easiest and most reliable way to do this is to buy Garmin's HomePort software, and use it to copy routes over to the device. If you don't want to spend money, you can try the Garmin MapSource software. It's been discontinued and is a little less straightforward than HomePort, but you can legally download free copies of an upgrade installer, and there are some tricks to get the upgrade installer to do a clean install. Use Google to learn how.

Prior to that I used g7toWin free utility to make the transfers, but it was very unpredictable, and it has been so long since I did that, I don't even know whether it's compatible with Win7 or Win8.

If you wanted to use your GPS to feed real-time NMEA data to OpenCPN, you would need software to create the virtual COM port. Garmin used to distribute "Spanner" for this. I don't know what they use now for the newer operating systems.

[wdkester]

You might try Garmin BaseCamp I think it's currently supported.

I also like to down load waypoints/routes to a Garmin 76 to use in the cockpit. OpenCPN works pretty good for this now. I just bid on a used 76 for backup.

[RhythmDoctor]

Originally Posted by wdkester

You might try Garmin BaseCamp I think it's currently supported.

I also like to down load waypoints/routes to a Garmin 76 to use in the cockpit. OpenCPN works pretty good for this now. I just bid on a used 76 for backup.

Gee, if I had known about Basecamp I might not have spent money on HomePort. Thanks for the tip! I downloaded it, and it looks to be very similar to HomePort, except it does not display the charts out of the Oregon like HomePort does. But I will import .gpx files created in OpenCPN, and it looks like it will easily export them into the Garmin handheld. So for the OP's purposes, I'd say that's a far superior option to the discontinued MapSource software. And it's free, so you can't go wrong.

If anyone figures out how to get the Oregon or 78 to accept routes directly from OpenCPN, please let us know. I had uploaded error logs awhile ago, but Dave said that it was basically incompatible because the newer devices use a different protocol or something like that.