Overview

The M7 GX series of GPS transponders may be directly connected to a Garmin Oregon 450. When connected, the Garmin display map will show the location of the vehicle it is in PLUS the location of all other M7 transponders within radio range.  This unique feature allows one to quickly, easily, and inexpensively, make a mobile AVL system for tracking cars, trucks, race cars, construction equipment, or any thing Raveon’s M7 GX transponder may be installed on.

The Garmin Oregon 450 has a built-in interfaces for a “NMEA 0183? devices, which is another way of saying that they can connect to other devices using a serial cable.   The NMEA 0183 is an RS232 serial connection that typically operates at 4800 baud.  It is used to exchange way point and other information between displays, GPS devices, and transponders.

When Raveon’s M7 GX transponder is connected to the Oregon using the NMEA 0183 connection, the M7 transponder can put icons on the screen of the Garmin display.  As the transponder received updated positions from other vehicles, it updates the position of the icons on the Garmin display.

How NMEA 0183 works

Here is how their NMEA 0183 interface works:

NMEA 0183 Cable Connections

NMEA 0183 is a standard communications format for marine electronic equipment. For example, an autopilot can connect to the NMEA interface of a GPS and receive positioning information.  The GPS can exchange information with any device that transmits or receives NMEA 0183 data. See the following diagram for general wiring connections. Read your product’s owner’s manual for specific wiring information.

NMEA 0183 Wiring  (Data cable)

The Garmin Oregon 450 uses the yellow wire to transmit, the white wire to receive and the Black and green wire for ground.

The M7 DB9 Serial Connector

The 9-pin serial I/O connector on the M7 is a female 9-p D-sub miniature connector having the following pins configuration. 

Front-view of DB-9 connector on modem (female)

Wiring the DB9

The Oregon’s “Data Cable” must be connected to the M7 transponder.  This connection will allow the M7 to put icons on the screen of the Oregon display, showing the location of other tracked vehicles.  The Raveon M7 GPS transponder uses a 9-pin “DB9? connector to connect to the Oregon.  Solder the Oregon data cable wires onto a DB9 connector and plug the DB9 into the M7 transponder as shown below:

The white wire goes to pin two of the DB9, the yellow wire to pin 3, the black and green wires get twisted together and both go to pin 5, and the red wire goes to pin 9 of the DB9. It is recommended that you keep the fuse on the red wire when setting up the DB9 connector.

Configuring the M7 GX Transponder

Raveon has a designed the M7 GX transponder to work with Garmin Oregon Display or any other NMEA 0183 display that can accept the “$GPWPL” NMEA message.   The $GPWPL is an industry standard message that the Garmin displays and many other GPS displays interpret as a way point command.  The M7 GX outputs this $GPWPL message to put icons on the screen of the Garmin, and to move the icons around on its screen.

To configure the M7 transponder to output the $GPWPL message, set the M7 GX to GPS mode 2.  To do this, put it into the configuration mode by send the +++ into the serial port.  The M7 will respond with an OK.  Type GPS 4 and press enter to put it into GPS 4 mode.  GPS 4 is the mode that causes the M7 GX to output $GPWPL messages whenever it receives a status/position message over the air.

Raveon Technologies Corporation

990 Park Center Drive, C

Vista, CA 92081

sales@raveontech.com

760-727-8004

You are able to monitor your GPS tracking system if your system uses RavTrack PC or any other GPS tracking software that allows you to create an alert if a vehicle does not report in.  By configuring your RF infrastructure components to also work as GPS transponders, the same tools used to monitor vehicles can be use to monitor your system.

For example, if you use a repeater in your system, configure it to periodially tranmsmit its GPS position also.  This way, if the antenna fails, power goes out, or it just stops working, your GPS monitoring software will send an alert.

With RavTrack PC, you can setup an Alarm and Monitoring Rule to help you monitor your radio network, server, or system operation.  Using the “No Reports” parameter monitoring feature, you can configure an alert to send an email to IP or Management personnel if your system stops working.

Monitoring System Components

To determine if part of all of the GPS tracking system is working, the periodic GPS position messages sent over the air may be monitored, and if they stop coming in, an alert can be generated to notify personnel of a potential system problem.

The easiest way to monitor the radios in your network is to configure them to report their GPS positions over-the-air.  Then configure an Alarm and Monitoring Rule using the No Reports parameter monitor to send an email if the item being monitored does not report in within a preset time period.  This will cause the Alert email to be sent if a part of the GPS tracking system fails such as broken antenna, cut cable, failed power supply, lightning damage, and unplugged serial cable.

Most radio transceivers, such as the M7 GX series of radios, which are used at a base station site may also be configured to output standard NMEA GPS position messages every 5 seconds.  This periodic local NMEA GPS message can also be used to determine if the base station radio is alive and operational.  To use the NMEA GPS position in an alert, you must configure the Communication Channel to interpret the NMEA GPS data as a tracked object in your system.  There is an option to Interpret GPS data w/o ID as ObjectData in the Systems Communications configuration tab.  If this enabled, RavTrack PC will create a new tracked vehicle with an ID 900X where X is the communications channel.  RavTrack PC will place the location of the vehicle 900X at its GPS position.

If there is a GPS transponder in the network that always is powered on and working, then the position report from that unit may also be used to check for system operation.

Monitoring a Server running RavTrack PC

The technique described above will work to monitor individual system components such as receivers, cabling, repeaters, and antennas.  But if a main server running RavTrack PC fails, the failed server cannot report itself failing.  A solution to this dilemma is to also run RavTrack PC on a management workstation, and then configure the same No Reports Alert on the workstation.  If the a server fails, causing the RavTrack system to stop recording GPS tracking data, the workstation’s No Reports Alert will then trigger, send an email, and/or alert the operator.

Following is a list of the NMEA messages that are available (as of revision C2 of the Firmware).

Refer to the product’s technical manual to see which NMEA messages are sent out in the various operating modes.  Once you set the “GPS Mode” of the radio using the GPS X command, you can change the NMEAMASK parameter to modify with of the NMEA sentences will come out the serial port.

For example, to have only the RMC sentence come out the serial port, use the following command”

NMEAMASK  256

To have the GGA and GLL come out the serial port use this command:

NMEAMASK 3

The NMEAMASK parameter is the sum of all of the decimal values of the individual bits corresponding to the NMEA messages.

To perform the quick update:

1. Close RavTrack PC.    File > Exit
2. Click on the link below to download a copy of the latest .exe file:
   http://ravtrack.com/downloads/RavTrackPCexe.zip or use the .exe file emailed to you from Raveon tech support.
3. Open the .zip archive folder by double-clicking on it. 
4. Locate the directory on your computer that holds the RavTrack PC program. For most users the full path to this file is:  C:/programfiles/raveon/RavTrack PC/
5. Rename the current RavTrack PC.exe file file to RavTrack PCold.exe.
6. Copy the new file from the  named RavTrack PC.exe to your RavTrack PC program directory. For most users the full path to this file is:  C:/programfiles/raveon/RavTrack PC/RavTrack PC.exe

You may now run RavTrack PC as you have been, and the new version will be executed.  If there are data base upgrades to do, RavTrack PC will automatically perform the updates when it starts up.

When connected to the M7 GPS radio transponder or the Atlas PLPersonal Locator, the Garmin’s map will show the location of all of the the user PLUS the location of all other transponders within radio range.  This unique feature allows one to quickly, easily, and inexpensively, make a portable AVL system for tracking cars, trucks, racecars, construction equipment, or any thing Raveon’s M7 GX or Atlas PL transponder may be installed on.

The Garmin 60C series of hand-held GPSs have built-in interfaces for a “NMEA 0183″ devices, which is another way of saying that they can connect to other devices using a serial cable.   The NMEA 0183 is an RS232 serial connection that typically operates at 4800 baud.  It is used to exchange way-point and other information between displays, GPS devices, and transponders.

When Raveon’s M7 GX transponder is connected to the Garmin display using the NMEA 0183 connection, the GPS radio transponder can put icons on the screen of the Garmin display.  As the transponder receives updated positions from other vehicles, it updates the position of the tracked vehicle icons on the Garmin’s display.

Garmin 60C, 60CS, 60Cx Wiring

From the Garmin technical manual, here is how their NMEA 0183 interface works:

NMEA 0183 Cable Connections

NMEA 0183 is a standard communications format for marine electronic equipment. For example, an autopilot can connect to the NMEA interface on the Garmin 60C and receive positioning information.  The Garmin 60C series can exchange information with any device that transmits or receives NMEA 0183 data.  See the following diagram for general wiring connections. Read yourother product’s owner’s manual for more wiring information.

NMEA 0183 Wiring  (Data cable)

Wiring the Serial Cable

The Garmin’s “Data Cable” must be connected to the M7 GPS transponder (or Atlas OL).  This connection will allow the M7 to put icons on the screen of the Garmin display, showing the location of other tracked vehicles.  The Raveon M7 GPS transponder uses a 9-pin “DB9″ connector to connect to the Garmin.  Solder the Garmin data cable wires onto a DB9 connector and plug the DB9 into the M7 transponder as shown below:

Connect the white wire(serial data from M7 into Garmin) from the Garmin’s Serial Cable goes to pin 2 of the M7’s RS232 DB9 connector.  You do not need to connect the brown wire(serial data from Garmin), so you can trim it off.  Connect the shield braid of the Garmin Serial Cable to pin 5 of the DB9.  The red wire optionally can connect to pin 9 of the Raveon GPS transponder’s DB9 to power the Garmin from the DC source that powers the M7. 

If you do not wire your own cable, but instead use Garmin’s RS232 serial cable, you will need to connect the Garmin’s RS232 cable to the M7 GPS transponder using a “NULL Modem” adaptor. 

Configuring the Garmin

Set the NMEA communication of the Garmin to 4800 baud.

Configuring the M7 GX Transponder

Raveon has a designed the M7 GX transponder to work with Lowrance Display or any other NMEA 0183 display that can accept the “$GPWPL” NMEA message.   The $GPWPL is an industry standard message that the Lowrance displays and many other GPS displays interpret as a waypoint command.  The M7 GX outputs this $GPWPL message to put icons on the screen of the Lowarance, and to move the icons around on its screen.

To configure the M7 transponder to output the $GPWPL message, set the M7 GX to GPS mode 2.  To do this, put it into the configuration mode by send the +++ into the serial port.  The M7 will respond with an OK.  Type GPS 4 and press enter to put it into GPS 4 mode.  GPS 4 is the mode that causes the M7 GX to output $GPWPL messages whenever it receives a status/position message over the air.

Creating a map to be utilized by RavTrack PC can be completed in just a few steps.  We like to use a powerful mapping program called Global Mapper for development of our maps, however, there are several free programs and websites on the internet that allow you to obtain map images.  For this example, we use a program called Google Map Buddy that was downloaded from CNET.COM.  This blog provides  a short summary of how to obtain a map image, calibrate it with the Ravtrack Software, and then use it with Ravtrack.

                This process will include a quick overview of the program Google Map Buddy.  After which, we will take the image we have obtained and use Ravtrack PC to calibrate the image.  You will need to have Google Earth or a similar program in order to obtain coordinates of your calibration area. 

With Google maps open we begin by opening up Google map buddy:

Enter the exact address of where you want your map centered:

For this example we are centered at the City of Borger Texas:

Select the area that you want the Map to encompass and the zoom level.  Zoom levels go from 1 (low detail) to 19 (high detail) and will increase the file size of your image.   Decide on the level of detail you need and select it from the drop down box.

Click create map and choose a file name:

Google Map Buddy has the option of outputting the image as an aerial satellite view, road (street) map, terrain (Topo) map, or hybrid map.  Select the appropriate option and click OK:

Google Map Buddy will download the image and ask you if you would like to delete the tiles it has downloaded, select yes.

Your image is now created:

The image will be in a PNG file format and will have to now be calibrated to properly represent the latitude and longitude of the points on the map.

Open up Ravtrack PC and select  TOOLS > MAP CREATION TOOL:

Now you will have to open the map PNG image that you created with Google Map Buddy. To do this click MAP > NEW MAP:

The map creation tool will ask you a few questions about the settings. Click OK to the defaults:

Select the images country, Grid, and Datum. The settings illustrated below are correct for the City of Borger .  Click NEXT and proceed:

Select the projection. For smaller images (typically less than 100 miles across) such as the city of Borger, we will use Cartesian. For large land masses, polar would have to be used.  Click NEXT:

Your image will now require the lat/long calibration mentioned earlier.

The tool will ask you to click on a known coordinate (a clear point on the map, such as a road intersection or natural feature).  Before you do this you must be prepared with the precise latitude and longitude of the coordinate you will select:

If you don’t know the lat/long of your coordinate open Google earth and select your location. You will use Google Earth in order to obtain coordinates of 3 points. You will want to choose points towards the periphery of your image. For example, if you have a map of a city, you may select points towards the far upper left, bottom center, and upper right.

Align the map creation tool and Google Earth images side by side, and visually identify an initial coordinate point on each map. This will start the calibration. The calibration consists of finding points on Google earth that correspond to your image’s point on the map. Once you have found that exact map point, copy down the coordinates that are located at the bottom of the Google earth screen.  In the RavTrack PC  screen (the left side screen on the example below) you can now click on the exact location your coordinates correspond to:

The Scaling wizard will come up next. Now you can enter your coordinates. Ensure your coordinates are correct with the proper heading (West, East, North, and south). Click next to finish calibration of this point:

Repeat this step for two more coordinate points and you will receive a scaling complete message. After calibration, save your resulting MAPLIB file to your Ravtrack map directory.  Now you can load your map and use it with Ravtrack!

Here’s a quick list of free programs and websites:

http://download.cnet.com/Google-Map-Buddy/3000-20426_4-10962144.html

http://atlas.ca.gov/imagerySearch.html

http://www.nationalatlas.gov/natlas/Natlasstart.asp

http://www.google.com/mapmaker

http://monarch.tamu.edu/~maps2/

There are many programs and sites that will give you a map image that can be used for calibration.

Many different types of batteries may be used with Raveon’s M7 series of GPS transponders.  This Technical Brief describes how well some common battery types will work with the M7 radios.

Actual battery life will vary based upon how often the M7 GPS transponder transmits, but the data in this Technical Brief may be used to predict the battery life of most configurations.

Test Setup

For the tests in this brief, a UHF GPS transponder, model RV-M7-UC-GX was configured in GPS mode 2 to transmit its position every 10 seconds.  In GPS mode 2, the radio’s receiver is on 100% of the time, and the current draw of the M7 was an average of 90mA.  The peak current draw was 2.1 amps for 68mS each time the M7 transmitted its GPS position.

Summary Data

Duracell Alkaline

These batteries are the common Duracel batteries found at most department stores.

Test Result Summary

Initial Voltage:                                   12.57 volts

Voltage at ½ discharge:                   10.2 volts

Usable life (hours)                           18 hours

Voltage drop when transmitting       2.4V  (1.1 ohm resistance)

Approximate mAh capacity             1600mAh

Discharge Curve

Transmit Transient

The plot below shows the dip in voltage as the transmitter turns on and off.

Summary

The Duracell is an OK battery to power the M7 transponder.  But its high internal resistance will reduce the RF power output after the first few hours of operation.  The DC to the radio should stay above 9V while transmitting for full power, above 8V for 3-4 watts.

Energizer Lithium

These batteries are the common Energizer Lithium batteries for cameras and digital electronics found at many department stores.

Test Result Summary

Initial Voltage:                                      12.1 volts  (14V for a few moments)

Voltage at ½ discharge:                      12.0 volts

Usable life (hours)                              28 hours

Voltage drop when transmitting          3.5V  (1.6 ohm resistance)

Approximate mAh capacity                2520mAh

Discharge Curve

Transmit Transient

The plot below shows the dip in voltage as the transmitter turns on and off.

Summary

Even though the internal resistance of the cell is higher than the alkaline, the Energizer Lithium is a good battery to power the M7 transponder.  Its high internal resistance will not reduce the RF power output because its voltage is fundamentally fairly high.  The DC to the radio should stay above 9V while transmitting for full power, above 8V for 3-4 watts, so the 3.5V dip means the radio will have full power at 12.5V, and 3-4 watts out at 11V DC at the battery pack.

Lenmar R2G NiMH pack, 2150mAh cells

These batteries are Nickel Metal Hydride rechargeable batteries.  They were fully charged before the test.

Test Result Summary

Initial Voltage:                                      11.0 volts

Voltage at ½ discharge:                      10.3volts

Usable life (hours)                              17 hours

Voltage drop when transmitting          2.0V  (.95 ohm resistance)

Approximate mAh capacity                1500mAh

Discharge Curve

Summary

These batteries should be a good power source for the M7 GX transponder.

The internal cell resistance is low, but the voltage is also low. The RF power output stayed at full power for most of the life of the battery, dropping to about 4 watts at the end of the battery life.  The double dip at end of live was due to the fact the radio keep working down to 6 volts (albeit with almost no RF output because the RF PA is off), and the batteries keep putting our very low voltage for another couple hours.

Raveon Technologies Corporation

990 Park Center Drive, C

Vista, CA 92081

sales@raveontech.com

760-727-8004

The following diagram illustrates how it works.

When a RV-M7 GX wants to report its position and status, it waits until its assigned time-slot, and then transmits its data.  By default, TDMA time slot positions are assigned by unit-ID, so RV-M7 GX with ID 1 uses the first slot, and ID 2 uses the second slot, and so on.

A TDMA “Frame” time is the time it takes all units to transmit once.  This is configured with the TDMATIME xx command.  The factory default is 10 seconds, so every 10 seconds, each RV-M7 GX may transmit.  The TDMA frame must be set long enough for all units to transmit.  For example, if you have 50 RV-M7s, and use 200mS TDMA slots, then the TDMATIME should be set to 10 seconds.  The simplest way to set it the TDMATIME is to make it equal to the TXRATE, the rate you wish to report position

The duration of a TDMA time slot is programmed into the RV-M7 GX with the SLOTTIME command. If SLOTTIME is set to 200 milliseconds (factory default), then every 10 seconds, the RV-M7 will have a 200mS window to report its position in.

All TDMA frames are synchronized automatically in all RV-M7 GX Transponders to the top of the minute.  Slot 0, frame 0 is at the top of each minute. They use the internal GPS receiver to determine the current time, and calculate when their are supposed to transmit their position and status information.

A unit may be allocated additional time slots.  The SLOTQTY command sets the number of slots each unit receives.  It is normally set to 1.

Regards.

Chris Carda

President

Criterion Industrial

Some of these events include:

Speed of travel greater than a user specified value (TRIGSPEED parameter)

Distance of travel greater than a user specified value (TRIGDX parameter)

Proximity to another GX transponder less than a user specified value (PROX parameter).

Here are three examples of using this flexibility in your system.

Example – Using TRIGSPEED

Picture a police squad car sitting idle or cruising slowly through a neighborhood on patrol.  In this instance it may not be important for the vehicle to transmit a position report more frequently than every 2 minutes.  If this is the case IDLERATE can be set for 120 (seconds).  However, the same squad car may later be move at higher speeds and reporting more frequently becomes important .  In our example the system administrator has set the fastest reporting frequency at 10 seconds (TXRATE 10).    When the car speed exceeds a certain threshold, let’s say 40kph (TRIGSPEED 40) the TXRATE is invoked and reports are now sent every 10 seconds.  When the car slows down, the IDLERATE again takes over, and transmissions are less frequent.

Example – Using TRIGDX

Your public works department has a number of vehicles out every day serving the community.  A vehicle and crew may stop for a while and work at a particular site.   While at the site they may even move the vehicle around a bit, to aid in the work.  While on the site a position report rate frequency of 5 minute intervals is perfectly adequate.  However, when they pick up and start moving to a new site, you’d like to be able to track their progress and know where they are more frequently, once they’ve moved 100 feet or so.  In this case your maximum system reporting frequency is twice a minute , or TXRATE 30 (seconds)   Set IDLERATE 300 (seconds), and TRIGDX 30 (meters).  30 meters is roughly 100 feet.

Example-Using PROX

You drive aheavy equipment in an open pit mine, or on a construction site.  The visibililty from your cab isn’t all that great, and you drive and operate your equipment as carefully as possible at all times.  In a move to further improve safety your company has placed a tracking display in your vehicle, allowing you to display the location of all of your other RavTrack transponders within radio range.  Your system administrator has set the following parameters in all of your transponders:

IDLRATE 10 (seconds)

TXRATE 2 (seconds)

PROX 15 (meters)

During your normal activities the display in your vehicle updates the location of all other transponders every 10 seconds.  Somewhere along the line, one of your coworkers, while on foot, comes close to your equipment.  Your co-worker  (Jim) is wearing on his belt the ATLAS PL personal locator.  When he gets within 50 feet of you (about 15 meters) your transponder starts  transmitting positions ever 10 seconds – and so does his ATLAS PL unit.  Now the blip on your display that represents your Jim starts pulsing every 2 seconds, perhaps a light has also lit on your dashboard, or a buzzer sounds in your cab, alerting you to Jim’s nearby presence.

We will cover the integration of warning lights and buzzers in another tech blog.

For the more technically minded, here is the logic flow chart the GPS transponder tests internally every TXRATE.