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external gps and aprs vehicle tracking

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  • external gps and aprs vehicle tracking

    I am going to run dashpc for my carputer. Linux baby yeah!! And I run misterhouse at home for car automation. Misterhouse has a module for vehicle tracking via ham radio.

    What type of gps unit would you recomend? I will probably need to split the serial cable from the gps to go to both my puter and the gps tracker which plugs into the radio tnc. <>
    I was thinking the garmin gps-35 external mount, but it is $180 which seems expensive. I saw the earthmates on ebay, where would i mount those? Do i need an external antenna?
    I may even run some of the windows gps software under vmware or wine, but linux has good gps too.

    Also, I propose starting a linux forum here for those of us who hack up custom linux stuff for our carputers (not just dashpc).

  • #2
    if you look fo rthe motorola oncore 8 channel or 12 channel oem board you can get em for about 30-45 $ they use 5 volts/3 volts respectively. a simple 7 component circuit with a max233 chip is all you need along with an antenna and whammo you are all up and running. try google search motorola oncore aprs

    lemme know if this helps i have built a couple of these


    • #3
      hmm, i found one on ebay but it says the range is within 25m, that doesn't sound very good.
      How do you build the circuit?


      • #4
        if you do a google search for "oncore gps oem manual" you will get the pdf that has the full schematic at the bottom of it.
        Dont believe the 25m thing that was before SA was turned off


        • #5
          MP3Van2003: Do you have any infomation about the circuit board for the oncore 8 channel gps. I need to build the interface board to connect it up to my computer and haven't found any info so far.
          CarPC: Currently in progress...


          • #6
            Here ya go

            Some notes :

            1. the last cap c3 is only needed if you use the pt5101 vice the 7805, the 7805 is widely available at the rat shack

            2. for some reason i had way better luck using polarized caps for all the caps called out for.

            3. If you do not use the battery backup option (3-5volt battery) you will have to reinitialize the oncore evrytime you start it to output nmea data, very simple program does this but still a waste of time.

            if you need more info on the board and building and testing the rs232 i/f go to bgmicro dott com select technical documents and scroll to very bottom right it is the last pdf doc on the page

            Hope this helps

            these things are cool as hell and very versatile


            • #7
              would you happen to have a pcb layout that i could get made up?
              CarPC: Currently in progress...


              • #8
                that is the one thing I dont have, I have a machine at work which will make the boards 3x5" (plenty of room) but have been unable to come up with a board layout. IF anyone else is good at eagle or somethign like that it would be a great help. Right now my setup is on a piece of proto board with way too many jumpers for my liking


                • #9
                  Is it worth using these motorola oncore gps modules? I can get an 8 channel module for a pretty good price but will the 8 channels be a limitation as opposed to 12 channels.

                  My other option is going usb.

                  I'm not sure which to choose. Motorola will end up being cheaper, usb will end up being easier. Which is better?

                  CarPC: Currently in progress...


                  • #10
                    12 channel is slightly more accurate but where 12 channel excels from what i understand is the baility to get better covergae ie; the more stallites in view the better chance you have of keeping the minimum amount of satellite required in view for a good fix. Also it depends on how the 12 channel process the data ie; does it process all 12 at once (parallel) or a little bit from each satellite (time slicing)


                    • #11
                      I am also unable to find a schematic for the ttl to rs232 interface. I know it will consist of a few caps a 7805 VR and a max232 or max233 (eliminate the caps) possible a diode or 2, but as far as a layout or schematic i am lost


                      • #12
                        Typically you need the MAX232CPE :


                        All you need is five 1uF capacitors.

                        100mA voltage regulator :

                        0.33uF and 0.01uF on the input and output side of the regulator.

                        Up to you if you wanna use the MAX233 without needing external capacitors. They cost more and can be hard to find in a local shop.


                        • #13
                          The OnCore units are pretty solid. I've got an M12 and love it.

                          Why not run an APRS app on your computer? There's one that integrates with StreetAtlas (APRS+SA), or if you're using Linux there's Xastir (
                          System status: in progress