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  • GPS splitting to external device

    Firstly forgive me if this has been posted before. I couldn't figure a way to word the search that gave any sort or result that covered this.

    Here is the desired scenario:

    ~One serial GPS receiver going in to COM 1

    ~Software splitter for multiple soft COM ports 5-9

    ~Two radios that normally read NEMA GPS data from serial attached GPS connected to COM 2 & 3

    My car PC has four physical COM ports so making physical connections isn't the problem.

    I just wonder if any of these software COM splitters will feed the NEMA data back out of a physical COM port for another hardware device to read like it was directly connected to the GPS.

    Ideas? Thanks!

  • #2
    For the first portion you'll need XPort3 to create multiple Virtual com ports for any software you want to read GPS data. I do not know if Xport3 can send data to existing serial ports.. so...

    For the second portion, I remember seeing some software like that a while back that would read from one com port and send the data to another port -- this is actually the easy (development wise), so it shouldn't be hard to make a plugin/external application to do that.
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    • #3
      Creating a "loopback" application like that is very simple in for instance Visual Studio 2008 C# downloadable for free.

      Only thing is you need to know or be able to set baudrate etc.

      I don't mind writing it for you if this is for a specific project.
      My car installation mp3car thread "showing off project"

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      • #4
        Originally posted by bes51659 View Post
        Creating a "loopback" application like that is very simple in for instance Visual Studio 2008 C# downloadable for free.

        Only thing is you need to know or be able to set baudrate etc.

        I don't mind writing it for you if this is for a specific project.
        First off, Thanks Man! I have been banging my head against the wall trying to figure this one out.

        As for the specific project, I am not sure what you are looking for... I mean it is for my CarPC.

        Let me know what you need to know.

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        • #5
          I was just interested why you needed this functionality.

          I assume that what you want is 4800 baud, no parity, one stopbit, and possibility to select com ports from 1-10?

          I will have time to put something together this weekend I think.
          My car installation mp3car thread "showing off project"

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          • #6
            OH! ok, I wasn't sure.

            Basically I have two devices that take standard NEMA data over a serial port, and rather than having two (or sometimes three) additional Serial GPS devices this soultion would let me use just one. This way clutter is reduced plus the one GPS unit can be of higher quality.

            The first device is the Uniden Bearcar 996 scanner. It has location based scanning that gets info from a GPS connected to its serial port. This is a nice feature for a guy like me who drives through 3 counties and 4 cities every day on the way to work. http://www.universal-radio.com/catal...ners/0996.html

            The second is a Kenwood TM-D710A that is occasionally broadcasting my location via ARPS. It too uses a serial attached GPS to provide this information. www.aprs.org

            The third devices are not nearly as often used, however I have had contract work where I drive around and survey cellphone tower signals for a rural wireless carrier. They take that data an use it to build coverage maps. I also do the same thing for a few radio stations in the area. They use the data for FCC fillings and compliance. www.audemat-aztec.com/radio-products-10-9.html (Sorry cannot find a link for info on the Nokia field monitoring device that the phone co uses)

            So correct me if I am wrong, will I have to stack both XPort3 and your program together or will your little diddy do it all?

            Also is it too late to request it be a small exe that runs in the tray/background?

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            • #7
              As a first step I was thinking that I could split COM1 into COM2 and COM3 and with com settings as described hardcoded.
              Then maybe configurable COM ports and also run as service to make it nicer.
              Is that ok?
              My car installation mp3car thread "showing off project"

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              • #8
                Since you're using serial and not USB, a hardware splitter would also work but you would need to make it custom. Get 4 DB9 connectors (1 male and 3 female if I can remember). One would have 3 wires (Gnd, RX, TX) and only 2 wires to the other 2 (Gnd and TX on the GPS side). They would be pin to pin, not flipped. The reason you can't connect all 3 to all connectors is because they will all hold the signal low. Use the 3-wire for any settings.

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                • #9
                  Originally posted by bes51659 View Post
                  As a first step I was thinking that I could split COM1 into COM2 and COM3 and with com settings as described hardcoded.
                  Then maybe configurable COM ports and also run as service to make it nicer.
                  Is that ok?
                  Yeah! Sounds great man. Thanks once again for the help.

                  OH, also I might end up upgrading my 4x port serial card to an 8x card. However this shouldn't be a big deal as its ports should be 2-9.

                  Originally posted by Curiosity View Post
                  Since you're using serial and not USB, a hardware splitter would also work but you would need to make it custom. Get 4 DB9 connectors (1 male and 3 female if I can remember). One would have 3 wires (Gnd, RX, TX) and only 2 wires to the other 2 (Gnd and TX on the GPS side). They would be pin to pin, not flipped. The reason you can't connect all 3 to all connectors is because they will all hold the signal low. Use the 3-wire for any settings.
                  I actually gave this a shot. Both hard wired and diode-isolated. Both the TX+RX or just TX. Also tried swapping TX/RX on the devices connections. Nothing worked for me. I am hoping the software solution works out.

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                  • #10
                    It does work but it's a bit tricky. RS232 uses negative volts to indicate a 1 so a diode can't be used. No UART TX can be connected to another TX as I said. And the whole thing has to be shielded well. The RX doesn't have any pul up/down, but there is some resistance, so there is a limited number of ports it can be split to.

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                    • #11
                      Here it is.

                      It will try and connect to COM1-4. Anything received on COM1 will be echoed onto COM2-4. Anything received on COM2 will be echoed onto COM1. Baudrate is 4800. There're two zip files. One with the entire project, and one if you just want to install it.

                      As I've said previously you can download Visual Studio 2008 for free if you want to play around with it your self. Maybe log the messages, or what ever.

                      Hope it works! Good luck.
                      Attached Files
                      My car installation mp3car thread "showing off project"

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                      • #12
                        Originally posted by Curiosity View Post
                        It does work but it's a bit tricky. RS232 uses negative volts to indicate a 1 so a diode can't be used. No UART TX can be connected to another TX as I said. And the whole thing has to be shielded well. The RX doesn't have any pul up/down, but there is some resistance, so there is a limited number of ports it can be split to.
                        Humm... I think I only tied all of the TX lines together and neglected the RX line. Perhaps that was the issue. It needs to be quite clean though, not so much for the scanner or radio, but for the Audmat should be precise.

                        Originally posted by bes51659 View Post
                        Here it is.

                        It will try and connect to COM1-4. Anything received on COM1 will be echoed onto COM2-4. Anything received on COM2 will be echoed onto COM1. Baudrate is 4800. There're two zip files. One with the entire project, and one if you just want to install it.

                        As I've said previously you can download Visual Studio 2008 for free if you want to play around with it your self. Maybe log the messages, or what ever.

                        Hope it works! Good luck.
                        I will give it a shot. Many thanks man. I will look at the code and see if I can learn enough to be dangerous. No one ever wrote a virus by accident, right?? LOL

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                        • #13
                          It can be pretty tight. Probably less unshielded area than on a multi-port PCI card if done right. There will be drawbacks either way. All the software adds latency, but probably no more than 100ms.

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                          • #14
                            I prefer sw than making special cabling.
                            100ms is probably correct the way the app works collecting an entire message before resending it.
                            Bare in mind, I've never tested it. But I usually save a lot of time by doing it right the first time. Or not?...
                            My car installation mp3car thread "showing off project"

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