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Thread: Strange Output on LCD Panel

  1. #1
    Newbie
    Join Date
    Aug 1999
    Location
    Wigan, UK
    Posts
    18

    Strange Output on LCD Panel

    Hi all,

    My LCD panel works perfectly, except sometimes I get the first few characters of the artists name duplicated on line one (beofre the actual artists name in the middle of the line).

    For info, I am displaying the following using the LCD plugin.

    Line 1 : Artists Name (middle of line)
    Line 2 : Song Title (middle of line)
    Line 3 : Track No. (middle of line)
    Line 4 : Current Position (at position 2) and Song Length (at position 15)

    Any ideas on how to solve this ?

    Everything else works fine, so I don't think it's a wiring problem.


  2. #2
    Variable Bitrate
    Join Date
    Aug 1999
    Location
    Yorba Linda, CA
    Posts
    323
    It sounds to me like either a timing problem or else interference.

    I had similar problems with my setup, and I believe my situation was a result of engine noise interfering with the data. I added buffer chips on both ends of my interface and it seemed to eliminate 99% of the problem. Sometimes I would still get a weird fluke where the screen would turn into garbage at random points.

    You may want to try adding pull-up resistors on the LCD's data lines, and capacitor(s) on the power leads.

    Also, if you run a parallel cable long distances, this can sometimes cause problems, like in my situation.

    Another issue is timing. Sending raw data out the parallel port under Windows is a nightmare in terms of timing. If you take a logic probe and monitor the clock line on the LCD (for clocking in characters), you will see what appears to be random pulses. Sometimes when the system gets busy, the timing requirements for the LCD may not get met, and, for instance, data that was meant for an LCD control code might instead get sent to the display, etc.


    Have you tried using a different LCD module with the same controller chips on it? Sometimes this helps too.


    --Jason
    http://jump.to/m2pc
    Jason Johnson
    Yorba Linda, California
    http://www.m2pc.com

    MPC Phase IV - *** PENDING ***

  3. #3
    Newbie
    Join Date
    Aug 1999
    Location
    Wigan, UK
    Posts
    18
    The problem only seems to start if the song title on the second line is longer than 20 chars (ie when the display needs to scroll).

    Hmmmm....

  4. #4
    Variable Bitrate
    Join Date
    Aug 1999
    Location
    Yorba Linda, CA
    Posts
    323
    It almost sounds like a problem with the code in the plugin... has anyone else experienced this same problem?

    --Jason
    http://jump.to/m2pc
    Jason Johnson
    Yorba Linda, California
    http://www.m2pc.com

    MPC Phase IV - *** PENDING ***

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