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Using MTTTY to test and verify the GPS connection

← GPS: Connectivity, Configuration, and Troubleshooting
GPS Troubleshooting: Live Tracking via NMEA GPS

Introduction: MTTTY

When Terrain Navigator Pro isn't getting the GPS data during navigation, it's a good idea to check outside of the application to be sure the serial port is receiving the data. If the ports do not see any GPS data coming in, then Terrain Navigator Pro will not be able to see the signal.

However, starting with Windows Vista, Microsoft has elected not to include the "HyperTerminal" accessory. Unfortunately, this is a useful tool for diagnosing difficulties with GPS connections, etc., as it features the ability to "view" the information coming from the GPS into the computer, unencumbered by other applications.

We have provided MTTTY which is attached to the bottom of this page. MTTTY is a useful tool for diagnosing difficulties with GPS connections, etc., as it features the ability to "view" the information coming from the GPS into the computer, unencumbered by other applications.

Notes Before we get Started

  • Terrain Navigator and all other programs, especially any that use COM ports for other connections, should be closed while running the MTTTY program.
  • If you are using a Garmin GPS, the GPS should be set to its NMEA mode in its Interface Setup area for this test. Once everything is working, you may wish to switch to Garmin interface mode for transfer of routes, waypoints, and tracks.
  • The GPS should be set to its Simulator mode if indoors or having difficulty obtaining the GPS satellite fix.
  • If you have other devices (such as a PalmPilot) that use the same serial port, ensure that the device's software (most commonly called HotSync) is disabled.
  • If your computer is lacking a physical serial connection, you are probably using some sort of USB-to-Serial adapter  Some are stand-alone and sold at good computer stores, others are built into NMEA multiplexers. Be sure that the drivers included with this adapter have been installed and are working properly.

To use MTTTY:

  1. Follow the How To Install instructions, below, to download MTTTY to your Windows Desktop.
  2. In the upper right hand corner, the Port drop down list contains a list of the COM Ports (real or virtual) found on your PC. Select the Port that the GPS is connected to. (If you're not sure, pick the first port listed, then repeat the test until the GPS is found.)
  3. Next to Port, Baud is listed. Most GPS units transmit at 4800 Baud. Thus, select 4800 from the Baud list, unless you are using a different Baud rate on your GPS.
  4. Leave all other settings at their default and choose Connect from the File menu.
At this point, one of three things can happen:
I get an error message.
This means that the COM port you have selected is not available or functioning properly. Repeat the process, trying a different COM port. If none of these reveal GPS input, then the problem lies in the physical serial port, the USB-to-Serial adapter cable (if used) the GPS receiver, or the connection between the two. If you are certain that you are selecting the proper COM port, contact your computer (or USB-to-Serial adapter) manufacturer for further troubleshooting tips.

I get a blank screen.
This indicates that the COM port you've chosen is not currently receiving NMEA data. Choose Disconnect from the File menu and repeat the process, trying a different COM port. (Repeat the above steps for other COMs, replacing COM1 with whatever COM ports are available on your PC.) If none of these reveal GPS input, then the problem lies in the physical serial port, the USB-to-Serial adapter cable (if used) the GPS receiver, or the connection between the two. If you are certain that you are selecting the proper COM port, contact your computer (or USB-to-Serial adapter) manufacturer for further troubleshooting tips.

I get a screen with text scrolling upward.
You're successfully connected to your GPS unit! Good GPS data will resemble the following:
$GPRMC,201502,A,4251.2939,N,07054.4254,W,000.0,000.0,291002,016.3,W*7C
$GPGGA,201502,4251.2939,N,07054.4254,W,1,07,1.7,55.6,M,-32.7,M,,*4A
$GPGSA,A,3,01,02,03,08,13,,,,27,31,,,3.1,1.7,2.7*3E
$GPGSV,3,1,10,01,38,207,41,02,58,058,44,03,71,103,35,08,06,305,38*70
$GPGSV,3,2,10,13,47,261,48,15,16,058,34,17,09,040,,25,03,128,*7C
$GPGSV,3,3,10,27,31,306,48,31,52,193,43,,,,,,,,*7F

The data you see scrolling by indicates your current position (among other things). Note the COM port used and exit MTTTY.

Finishing the Job: Reading the GPS Stream in Terrain Navigator

  1. From the 'GPS' menu, choose 'GPS Setup Wizard'. 
  2. Follow the on-screen instructions.
  3. If the GPS Wizard can not detect the GPS, select 'Setup' from the 'GPS' menu. Set the 'Manufacturer' to 'NMEA - generic' and specify the COM port determined during the above test. Also, ensure that the correct baud rate of the GPS is selected in Port Settings. Then press 'Close'.
  4. Once the signal is detected, choose 'GPS Tracking', 'Start Tracking' from the 'GPS' menu.

Related Knowledge Base Article:
 Configuring Terrain Navigator Pro to the GPS - Basic Instructions.

How To Install MTTTY

Click the link below. In most instances, your web browser will ask if the file should be Opened, or Saved to your computer. Choose Save, then select a location to Save the downloaded file In. If you are unfamiliar with downloading software, we recommend choosing your "Desktop"; select Save In, Desktop and press Save. Once the download completes, double-click the MTTTY application that appears on your Desktop to start it.

Download Link

MTTTY.exe
92 KB
Version 4.0
Released 11/02/2010
For use in diagnosing GPS connectivity issues. Requires Microsoft Windows XP, Vista, Windows 7, 8, or 10.


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