BLUEWATER RACING can connect to NMEA data streams put out by your boat's instruments, and send route data to and from certain Garmin GPS units. The Instrument Manager handles these connections.

The Instrument Manager and GPS Support

The Instrument Manager allows you to access streams of data being fed into your computer from NMEA-compatible instruments. NMEA is an acronym for the National Marine Electronics Association, which determines communication protocols for marine devices. The oldest but still most commonly used protocol is NMEA 0183 designed to be read from (something close to) RS232 serial ports on the computer.

Bluewater Racing will read and process NMEA 0183 data from up to five serial input streams. The stream may come from a serial communications (comm) port on the computer, a TCP connection, or a file of previously saved NMEA data (useful for reviewing data). Modern computers normally do not have RS232 serial ports, but serial streams are sent over USB, TCP or Bluetooth connections. NMEA to USB adapters that create "virtual" serial ports on your computer are available as are RS232 to USB connectors that may work for older wiring on your boat.


To enable reading this serial data, open the Instrument Manager and enter a serial stream identifier into the NMEA Input boxes  and click the corresponding “Enable” boxes.  Under Windows, comm ports are typically identified as COMn for some integer n.  For example, COM1 , COM8 , etc.   To find the list of available comm port names, you should consult the Windows Device Manager.   COM1 and COM1: are equivalent forms.   Note that two-digit comm ports (e.g. COM12) may not work.   The actions that the program is taking to connect will appear in the “Actions” window.  The freeware program com0com will create virtual com ports on Windows machines, the program Nmearouter will route nmea streams between com ports.  Both may be useful.

Under Unix and Mac OSX, serial ports appear in the /dev directory, and have names such as /dev/ttyp0 or /dev/cu.Bluetooth-Incoming-Port. When a serial adapter creates a virtual serial port, if may create both a /dev/tty* and a /dev/cu* type port. You should use the /dev/cu* ports.   The freeware program kplex will route NMEA streams between various inputs and create virtual serial ports as needed. This may be useful.

Under Windows, any name starting with COM or ending with : for example CNF0A: will be opened using the serial port protocol. Under MacOS, any name starting with /dev will be opened using the serial port protocol.

To read data from a TCP address, you must enter the full numeric IP address of the stream followed by the source port number, in the form


For example,  You will have to get the TCP address from the provider of the device that is supplying the data, typically over a wireless connection.  Vesper Marine provides these kinds of devices.

To read from a file, just enter the file name.  Normally, you should enter a fully qualified (all folders specified) file name.

If one of the streams comes from a GPS that is set to communicate in NMEA 0183 mode, then GPS position and course information will be displayed on the upper toolbar.  In addition, the GPS_pos waypoint will be created and updated, and positions will be added to GPS_track.  The frequency with which positions are added to the track is determined by the “Track Update Freq, (set under GPS preferences) which is the number of seconds to wait before a new position is added.

You can view the data that is being received from the instruments by clicking on “View Raw NMEA”. 


NMEA output may be streamed to a file or a serial port by using the “NMEA Output” entry. Either enter a filename or a serial port identifier as explained in the input section above. Output to a TCP connection is not supported.   Data is output at 4800 Baud.

Normally, BLUEWATER will only send GPS related NMEA messages to the output stream.  These include latitude, longitude, course and speed over ground.  If a route leg has been activated then bearing to the leg waypoint and cross-track error are also sent.

If desired, all input NMEA messages can be echoed to the output stream by checking the “Echo Inputs” box.

The “Processed Log File” entry can be used to send the instrument data extracted from the NMEA messages to a log file. If the log file already exists, the data will be appended to the end of the file. In this way multiple runs can be logged to the same file.

The logged data will be in the form of a table, with the first column being the timestamp of the data snapshot, followed by a column for each data type (e.g.: tws, twa, bsp (true wind speed, true wind angle, boatspeed). The desired fields are specified in the Fields to Log entry. The field names should be the same as those that appear in the Raw NMEA Data window. The shortcut "all", or alternately, a blank entry, may be used to log all possible data fields.

The time between snapshots in seconds is specified in the Log Frequency window. For example, a value of 10 means save a snapshot every 10 seconds.

Uploading to GPS Units

Many GPS units connect to computers via a USB cord to allow you to copy route files to and from the unit. Often GPX is supported by these units. Otherwise, you can convert to GPX from many of the different manufacturer formats using the helper program GPSBabel.

BLUEWATER can also connect to certain Garmin GPS units using the Garmin proprietary two-way protocol.  This can occur over a RS232 or USB connection.  If Garmin protocol is available, you may right-click on a route (either in the Route Manager window, or on the chart in edit mode) and upload it to the GPS.  In addition, under Tools→GPS you can download all routes and waypoints from the GPS into BLUEWATER or you may upload all routes and waypoints in the current race to the GPS.  In addition, position and course data will be downloaded continuously. 

To set up a Garmin protocol connection, specify and enable a port in the “Garmin port” entry on the Instrument Manager. For Windows, it will be a serial port such as “com1”, or a usb port such as “usb:”, depending on how your GPS unit connects to the computer. Don’t forget to set your GPS to communicate in Garmin protocol.  BLUEWATER provides Garmin proprietary support through GPSBabel.  Please visit for more information about this program. Their online manual may be helpful in resolving any Garmin communication issues.

Viewing AIS targets.

You can view any AIS target data in the input streams by clicking on the "View AIS Data" button. This will dispay targets sorted by increasing distance from your receiver. Selecting "Enable AIS" will display AIS targets in the map chart They are shown as yellow triangles oriented to the vessel's heading. Mouse over a triangle to generate a pop-up box containing information about that target.

Instrument Panel

Clicking the "Instrument Panel" button will bring up a window to display the data coming from your instruments in various forms. Clicking on the panel will bring up a menu that allows you to change global configuration or the specific configuration for the set of instruments you are displaying.

Setting and Saving the Configuration

The instrument configuration consists of the collection of serial ports, files, or TCP connections that have been entered, and whether or not they are enabled.  If you select “Apply and Save” on the instrument panel, that configuration will be saved to your local preferences, and whenever you start BLUEWATER it will attempt to open any input or output streams that are marked enabled.

CAUTION: If other software on the computer is using the specified serial device, then BLUEWATER may hang waiting for its turn to access the device if it has been enabled for opening on startup.