Connecting a Garmin USB GPS

Electronics Hookup and Configuration

Introduction

Over the last decade, Garmin has released hundreds of different GPS models. However, with few exceptions, they all use one of three different communication protocols. Usually, it is a matter of choosing the correct setting in Terrain Navigator Pro to share markers, routes, tracks (and in many cases, maps and photos) with your Garmin GPS.

Serial Connections

The oldest style of Garmin GPSs used a serial cable to connect with the computer. This is now quite rare, due to the prevalence of USB-style connections. If you have a Garmin GPS with a serial connection (which looks like a D shaped plug with 9 pin holes) please refer to these technical documents for tips and tricks:
Configuring Terrain Navigator (or Pro) to the GPS - Basic Instructions
I don't know what COM Port my GPS is connected to. What should I do?
Connecting a Serial GPS to a USB Port
Determining the COM Port of a USB to Serial Adapter

Note that some Garmin GPSs used both a serial and USB connection.

USB Connection: Garmin Protocol

Prior to 2008, virtually all Garmin GPSs using a USB connection employed this style of interface. These included the GPSMap 60, the eTrex Venture, and many other popular units. Today, these units are no longer commonly used.

To connect a GPS using the Garmin Protocol to Terrain Navigator Pro, either use the GPS Setup Wizard (found in the GPS menu) or select the Setup option in the GPS menu, set the Manufacturer to Garmin, and the Unit to the best match for your GPS (as long as the Unit includes USB in the description.) If your unit is not shown, usually the 'GPSMap 276CSx USB' is the best match.

Once you have set this up, open the GPS menu and choose Receive from GPS, Receive Waypoints (or a similar function.) This will ensure that the connection is working properly.

When I attempt to send or receive waypoints (or connect to the GPS) I receive an error: "USB open failed". What does that mean and how do I fix it?
An USB open failed error indicates that the driver used by the Garmin GPS to connect to the Windows operating system is either damaged or missing. You can correct this by downloading and installing the latest USB Drivers software for use with all Garmin GPSs. This ensures that all the drivers are installed and that the connection is working properly. You can find the Garmin USB Drivers software at:
http://www8.garmin.com/support/download_details.jsp?id=591

Once the Garmin USB Drivers software is installed, Terrain Navigator Pro will be able to detect the GPS properly (and open the connection to the USB port.)

That said, Garmin GPS units manufactured after 2008 do not require a USB driver for sharing markers, routes, tracks, and maps between the GPS unit and Terrain Navigator Pro. Instead these GPS units use the Mass Storage Mode...

USB Connection: Mass Storage Mode

Most Garmin GPSs manufactured after 2008 use a "Mass Storage Mode" (also known as memory card/card reader protocol). Mass Storage Mode is very similar to a digital camera or USB "memory card" in that the GPS appears as an external memory disc to the Windows operating system. This has its advantages as it means that no additional drivers are required for sharing markers, routes, tracks, and (in most cases) maps and aerial photos. However, a separate driver/configuration is required for using the GPS to track your position in real time on the Terrain Navigator Pro display. This driver is available at:  http://www8.garmin.com/support/download_details.jsp?id=591

Garmin GPSs that use the Memory Card Protocol include the Colorado, Oregon, Montana, Dakota, GPSMap 62/64, GPSMap 78, Rino, and eTrex 20/25//30/35.

To connect this style of GPS to Terrain Navigator Pro, either use the GPS Setup Wizard (found in the GPS menu) or select the Setup option in the GPS menu, set the Manufacturer to Garmin, and the Unit to the best match for your GPS. If your unit is not shown, usually the 'GPSMap 62s USB' is the best match.

Once you have set this up, open the GPS menu and choose Receive from GPS, Receive Waypoints (or a similar function.) This will ensure that the Mass Storage Mode is working properly. Do not open the GPS menu and choose "Connect", as this will attempt to set up data communication between the actual GPS receiver in the GPS unit and Terrain Navigator Pro - and this protocol is not available while the GPS unit is in Mass Storage Mode. Note also that the GPS "light" on TNP's status bar will remain dimmed when a GPS unit is attached in Mass Storage Mode.

If you intend to use the GPS receiver to display its position in real-time on Terrain Navigator Pro's maps (or to use any related positioning features) set the Garmin's Interface mode to Spanner, and do not enter Mass Storage Mode while attaching the GPS unit to the computer. For more details, see: http://tnp.uservoice.com/knowledgebase/articles/172079

Why does the GPS "light" at the bottom of the Terrain Navigator Pro window always stay gray?
The GPS light on the status bar will only turn green when receiving the actual GPS position transmission. This is used when a moving map display is desired in TNP, or similar functionality. To connect to the GPS in this fashion, when the GPS is plugged into the PC, indicate that you do not want to go into data transfer mode. Then the GPS signal will be transmitted through the USB cable to the PC, and TNP will be able to connect to it. (Open the GPS menu and choose Connect.)  

The lack of a green GPS light on TNPs status bar does not indicate one way or another if the GPS unit is attached to the PC. If the GPS is properly attached (and in Mass Storage mode) it can share its waypoints, tracks, etc. with Terrain Navigator Pro, even though the GPS "light" is gray.

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