NMEA 0183 filtering and conversion

Brookhouse multiplexers offer the user  powerful, yet easy to use features, for  filtering and sentence conversion. These functions, together with the data stream switching ability, have turned the Brookhouse multiplexer into an effective real-time NMEA controller. The combine or multiplex function of NMEA and Seatalk data is  the primary task, but the extra functions enable the user to optimise integrated instrument  systems and resolve  NMEA compatibility problems in an elegant and efficient way.

It is possible to convert and/or restructure complete NMEA sentences. The user can control the various functions by uploading easy to create and understand scripts  into the multiplexer. Script examples are available, which can be copied and pasted and adapted for specific purposes. 

Some examples of readily available popular conversion scripts::

  • Conversion of various NMEA 0183 vers. 3 sentences to 2.1 or 1.5 and vice versa.
  • Conversion of Auto Pilot sentences to NMEA 1.5 to suit older auto pilots.
  • Conversion of wind instrument sentences MWV to VWR and vice versa.
  • Conversion of depth sounder sentences  DPT to DBT, DBS to DBT, etc.
  • Conversion of GPS RMC sentence to GGA
  • GGA to VTG

    and various other.


The following functions are offered in the latest Brookhouse NMEA multiplexer firmware version:

·        Filtering of  NMEA data at sentence-level, port-selective. "Conditional" filtering is also vailable, i.e deletion of sentences depending on the reception  of another sentence .

·        Data manipulation (“on the fly” editing) at NMEA sentence and parameter level, port selective:

o       Deletion of NMEA parameters (with or without parameter separator)

o       Re-naming (replacing) of NMEA ID and/or sentence ID.

o       Saving a parameter and using (inserting) it elsewhere in the same or in another NMEA sentence.

o       Inserting fixed alpha-numeric data at parameter level, including parameter separators.

o       Adding or replacing a checksum at the end of NMEA sentences.

o       Adding or subtracting a signed decimal value from any parameter (depth offset, wind angle correction, other calibration values)

o       Conversion of wind angles 180 degrees left/right of bow to 0-360 degrees and vice versa.

o       Truncation of sentences.

A full description is available here:

 NMEA Filtering and data manipulation