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Re: [tracker2] LCD & cable length question

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  • lists@ke4nyv.com
    Tanner, When I was developing a similar setup for the new HamHUD, I was playing with this very thing. I was looking for a way to create a data box and then
    Message 1 of 7 , Oct 1, 2009
      Tanner,

      When I was developing a similar setup for the new HamHUD, I was playing with this very thing. I was looking for a way to create a data "box" and then remote the LCD to a easy to view spot on the dash or overhead. I found that I could make it work at 3-5 feet MOST of the time. It required well shielded cable and a couple of RF chokes on each end to keep out any stray RF out. This might have also been eliminated by having the antenna spaced further from it, but this was a test bench kind of setup and I really did'nt have a good way to simulate an in-car environment.

      In the end, I decided to place the whole thing inside the box with the LCD. By going all SMT, I effectively "thinned" the whole package to where it is thin enough to mount on a dash flat or even mount overhead (my future plan).

      Jason KE4NYV
      RPC Electronics
      www.rpc-electronics.com

      --- On Thu, 10/1/09, Tanner Lovelace <kb4tye@...> wrote:

      From: Tanner Lovelace <kb4tye@...>
      Subject: Re: [tracker2] LCD & cable length question
      To: tracker2@yahoogroups.com
      Date: Thursday, October 1, 2009, 1:51 PM






       





      On Thu, Oct 1, 2009 at 12:25 PM, Jason KG4WSV <kg4wsv@gmail. com> wrote:

      > On Thu, Oct 1, 2009 at 10:59 AM, Tanner Lovelace <kb4tye@arrl. net> wrote:

      >> Does anyone have an idea what kind of cable length limitations there are on

      >> connecting an LCD to the tracker2?  If I put the tracker 2 in my trunk and want

      >> to have an LCD in the front of the car will that work?

      >

      > IIRC, the LCD interface is operating at TTL levels.  I don't know the

      > specs, but if you start measuring cables in feet instead of inches

      > you're looking for trouble.



      That's what I was afraid of. Ok, good to have confirmation of that.

      Thanks much!



      How about from the T2 to the radio? What's the best approximation

      of how long is too long for that?



      Cheers,

      Tanner

      --

      Tanner Lovelace

      http://wtl.wayfarer .org/

      (fieldless) In fess two roundels in pale, a billet fesswise and an

      increscent, all sable.
    • Fred Hillhouse
      Hi Jason, I have wondered myself if adding a 74LS244 (octal driver) would help get the distance. Is the RF affecting the LCD or getting back into the TNC? If
      Message 2 of 7 , Oct 1, 2009
        Hi Jason,
         
        I have wondered myself if adding a 74LS244 (octal driver) would help get the distance. Is the RF affecting the LCD or getting back into the TNC? If it is the TNC, the buffer should work.
         
        Best regards,
        Fred
         


        From: tracker2@yahoogroups.com [mailto:tracker2@yahoogroups.com] On Behalf Of lists@...
        Sent: Thursday, October 01, 2009 14:30
        To: tracker2@yahoogroups.com
        Subject: Re: [tracker2] LCD & cable length question

         

        Tanner,

        When I was developing a similar setup for the new HamHUD, I was playing with this very thing. I was looking for a way to create a data "box" and then remote the LCD to a easy to view spot on the dash or overhead. I found that I could make it work at 3-5 feet MOST of the time. It required well shielded cable and a couple of RF chokes on each end to keep out any stray RF out. This might have also been eliminated by having the antenna spaced further from it, but this was a test bench kind of setup and I really did'nt have a good way to simulate an in-car environment.

        In the end, I decided to place the whole thing inside the box with the LCD. By going all SMT, I effectively "thinned" the whole package to where it is thin enough to mount on a dash flat or even mount overhead (my future plan).

        Jason KE4NYV
        RPC Electronics
        www.rpc-electronics .com

        --- On Thu, 10/1/09, Tanner Lovelace <kb4tye@arrl. net> wrote:

        From: Tanner Lovelace <kb4tye@arrl. net>
        Subject: Re: [tracker2] LCD & cable length question
        To: tracker2@yahoogroup s.com
        Date: Thursday, October 1, 2009, 1:51 PM

         

        On Thu, Oct 1, 2009 at 12:25 PM, Jason KG4WSV <kg4wsv@gmail. com> wrote:

        > On Thu, Oct 1, 2009 at 10:59 AM, Tanner Lovelace <kb4tye@arrl. net> wrote:

        >> Does anyone have an idea what kind of cable length limitations there are on

        >> connecting an LCD to the tracker2?  If I put the tracker 2 in my trunk and want

        >> to have an LCD in the front of the car will that work?

        >

        > IIRC, the LCD interface is operating at TTL levels.  I don't know the

        > specs, but if you start measuring cables in feet instead of inches

        > you're looking for trouble.

        That's what I was afraid of. Ok, good to have confirmation of that.

        Thanks much!

        How about from the T2 to the radio? What's the best approximation

        of how long is too long for that?

        Cheers,

        Tanner

        --

        Tanner Lovelace

        http://wtl.wayfarer .org/

        (fieldless) In fess two roundels in pale, a billet fesswise and an

        increscent, all sable.










      • Scott Miller
        You can get away with a fairly long radio cable if you can keep RFI out of it. The OT2m has ferrite chips on the radio interface lines, but shielded cable
        Message 3 of 7 , Oct 1, 2009
          You can get away with a fairly long radio cable if you can keep RFI out
          of it. The OT2m has ferrite chips on the radio interface lines, but
          shielded cable would still be a good idea.

          I think someone already suggested it, but a line driver might help on
          the LCD interface. I think the limiting factor is going to be line
          capacitance vs. signaling speed. Many LCDs will work with 3v inputs, so
          it should tolerate some voltage drop.

          As for the signaling speed... without the disassembled code in front of
          me I'm not sure how many cycles the LCD clock toggle takes, but I don't
          think it can be less than 4, so that'd give it a max clock speed of
          about 1.8 MHz. Adding more NOPs to the ClkPause macro would slow it down.

          Again, you'll have to watch out for RFI on those long low-voltage runs.

          Scott

          Tanner Lovelace wrote:
          >
          >
          > Does anyone have an idea what kind of cable length limitations there are on
          > connecting an LCD to the tracker2? If I put the tracker 2 in my trunk
          > and want
          > to have an LCD in the front of the car will that work?
          >
          > Alternatively, if I place the tracker2 in the front of the vehicle and
          > the radio
          > in the trunk, how long can the cable between the T2 and the radio be?
          >
          > Thanks very much.
          >
          > Cheers,
          > Tanner Lovelace
          > KB4TYE
          >
          > --
          > Tanner Lovelace
          > http://wtl.wayfarer.org/ <http://wtl.wayfarer.org/>
          > (fieldless) In fess two roundels in pale, a billet fesswise and an
          > increscent, all sable.
          >
          >
        • Tanner Lovelace
          Actually, what I decided to do instead was order an LCD and an Arduino and I m going to see if I can get the same type of display up and running with that.
          Message 4 of 7 , Oct 2, 2009
            Actually, what I decided to do instead was order an LCD and an Arduino
            and I'm going to see if I can get the same type of display up and running
            with that. That will let me use a serial connection from the OT2m to the
            Arduino which shouldn't have any problem with a long run (hopefully!)

            BTW, I've seen several people talk about trying to use an Arduino
            to put together a sort of HamHud interface that would connect to
            the OT2m. What's the latest story on that? What kind of input
            device would you use?

            Cheers,
            Tanner Lovelace

            On Thu, Oct 1, 2009 at 11:48 PM, Scott Miller <scott@...> wrote:
            > You can get away with a fairly long radio cable if you can keep RFI out
            > of it.  The OT2m has ferrite chips on the radio interface lines, but
            > shielded cable would still be a good idea.
            >
            > I think someone already suggested it, but a line driver might help on
            > the LCD interface.  I think the limiting factor is going to be line
            > capacitance vs. signaling speed.  Many LCDs will work with 3v inputs, so
            > it should tolerate some voltage drop.
            >
            > As for the signaling speed... without the disassembled code in front of
            > me I'm not sure how many cycles the LCD clock toggle takes, but I don't
            > think it can be less than 4, so that'd give it a max clock speed of
            > about 1.8 MHz.  Adding more NOPs to the ClkPause macro would slow it down.
            >
            > Again, you'll have to watch out for RFI on those long low-voltage runs.


            --
            Tanner Lovelace
            http://wtl.wayfarer.org/
            (fieldless) In fess two roundels in pale, a billet fesswise and an
            increscent, all sable.
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