Connect with us

Software to merge NMEA streams?

Discussion in 'Boat Electronics' started by Ulrich G. Kliegis, Sep 16, 2009.

Scroll to continue with content
  1. Hi all,
    is there any utility that merges NMEA streams entering a PC through
    two or more physical COM ports into one virtual stream? Several useful
    programs feature only one entry path. I am thinking of something like
    the opposite of Fransons GPS Gate.Any hints? TIA.

  2. "Ulrich G. Kliegis"
    Dunno about any software that does this, but hardware can be found here:

  3. Luc Habert

    Luc Habert Guest

    Ulrich G. Kliegis :
    Try The driver allows to create a pair of
    virtual serial ports connected by a pipe, and the hub4com utility should let
    you combine your inputs into this pipe. I found that you need to disable RTS
    in the RS 232 parameters in the software listening at the other end of the
    pipe, or it won't receive anything.

  4. Luc,

    Thanks, thanks, thanks! It looks at least exactly like what I was
    looking for, if the software does what you describe and what is
    written in the chapter "multiplexing".


    thanks to you too, but I was looking just for a solution avoiding
    additional hardware. The serial ports are there (incidently, they live
    in a 4 RSR232-toUSB adapter, making sure that after power up, the
    COM-ports keep their once-asserted numbers).

    Here is the link to this interface:
    They also have an 8*serial to USB adapter:

    Maybe helpful for some people, especially with Luc's advice.

  5. "Ulrich G. Kliegis"
    With an NMEA multiplexer, you also have just one box (replaces the current
    interface) and you have galvanic isolation.

    Also, the hub4com software is really meant to split one incoming stream to 4
    virtual ports. Does it provide a way to go the other way? If so, hub4com
    should know about the data, recognize start and end of NMEa sentences in
    order to merge them properly. You cannot simply stuff all characters/bytes
    together in one stream, you have to maintain complete sentences.

    And the shipmodul multiplexers have a unique USB serial number, which makes
    the multiplexer appear at the same virtual com port all the time, whatever
    USB port you use, with or without hubs.

  6. Luc Habert

    Luc Habert Guest

    "Meindert Sprang" :
    Yes, with --route=All:All
    You are right. However, hub4com does buffered reads, so that it should work
    most of the time.
    A virtual port created with com0com also has a stable name.
  7. An an american friend used to say: There are many ways to skin a cat.
    I made that: There are many ways to scan a kid. ...

    I'll give it a try these days. Merging several streams into one
    without separating the data in a meaningful way would be pretty, well,
    dilettantic. So, without knowing the specs, I guess, that some
    selection of a sentence delimiter or a similar partitioning of the
    data stream will be implemented. I would be surprised if not.

  8. Not at all. A buffered read means no more than that a bunch of bytes is read
    and forwarded as a block with no relation to the data whatsoever.

  9. Paul

    Paul Guest

    "Ulrich G. Kliegis"
    My free program NacMonPc (see and
    // will do this, plus a lot of other stuff you
    probably don't need. It can take NMEA-0183 data from up to four serial
    ports route the messages out to up to three virtual serial ports. Actually
    the serial and virtual ports are bidirectional and there is
    port/message-based routing available. It also takes data from a TCP/IP
    port. Did I mention it's free? No strings attached.

  10. Hi Paul,

    Which "tools" did you use to create the virtual ports? I am looking for a
    driver or tool to do that from within a Delphi application.

  11. Guest

    Guest Guest


    I used Franson Serialtools for this. I don't know what you need for Delphi,
    but these work with Visual Basic and the other languages in the family.
    They have "dot-net" and activex drivers.

    I'm sorry to say that the support is nonexistent. I've got the full license
    for Serialtools, but Franson is now concentrating on their other products to
    the point of not even answering Serialtools-related email. I am looking at
    some new virtual-port tools, but haven't had a chance for any serious

Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day