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TV screen using VGA slowly whites out using the propeller proto board. — Parallax Forums

TV screen using VGA slowly whites out using the propeller proto board.

KyeKye Posts: 2,200
edited 2010-05-06 07:00 in Propeller 1
I remember someone else posting about this problem but I could not find the forum thread name.

Its weird. When using the propeller protoboard on my Auvio 15.4" TV the TV has trouble finding the VGA signal and won't auto sync unless I tell it too. Then after its synced the screen slow whites out...

I'm not sure what to do. So far the Chip's VGA drivers seem to work fine on every regular computer monitor so I'm wondering what's going on.

Thanks, for your help,

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Nyamekye,

Comments

  • RaymanRayman Posts: 14,887
    edited 2010-05-05 23:42
    I vaguely remember that old thread too... I think it turned out to be a bad connection on the board...

    You might want to double check your solder joints at the Norcomp connector...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

    My Prop Products:· http://www.rayslogic.com/Propeller/Products/Products.htm
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-05-06 00:24
    No, it's the width of the one of the sync pulses that's the culprit and has to be adjusted. I had the same problem with my Westinghouse flat-screen TV. I can't find the thread at the moment...

    -Phil
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-05-06 00:45
    Try changing the vs value in your vgaparams from 2 to 3.

    -Phil
  • RaymanRayman Posts: 14,887
    edited 2010-05-06 00:48
    Yes that was it. I remember now that I was wrong about the problem back then too [noparse]:)[/noparse]
    But, I have had a similar problem and it was a bad solder joint at the Norcomp that was the problem...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

    My Prop Products:· http://www.rayslogic.com/Propeller/Products/Products.htm
  • KyeKye Posts: 2,200
    edited 2010-05-06 01:16
    That seemed to do it. It still kinda whites out however, but its acceptable now. It just looks like the constrast is really bad. (Black more like dark greys...)

    Probably cheap hardware/bad software on the screen side.

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    Nyamekye,
  • jrjrjrjr Posts: 22
    edited 2010-05-06 01:42
    Kye,

    It was the video blanking interval (Vertical) width that was corrected on Phil's post.

    Tweak the VS sync widths slightly (probably shorter).

    Problem with the solution is that some monitors are more sensitive than others
    by their spec. and may show this error.

    Creeping brightness and flaky video.

    jr
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-05-06 02:24
    jrjr said...
    Tweak the VS sync widths slightly (probably shorter).
    He just lengthened it. (Maybe he should lengthen it more.)

    -Phil
  • jrjrjrjr Posts: 22
    edited 2010-05-06 02:54
    Phil & Kye,

    I think what is trying to be accomplished is the <location> as well as the pulse width.

    that means the length of time from the last HS to the begin of the VS as well as the VS width.

    The VS interval is creeping slightly into the active video interval.

    That is what is affecting the video, the tail end of the blanking interval.

    Since these pulses are all additive for proper full frame timing,
    the video blanking tail end can be affected by the interdependent quantities of each.
    (It is a timing budget)

    I can tell you why, and what to adjust.

    But as to how that relates to the propeller video coding,
    and a full understanding of how Chip coded it ...still... escapes me after 10 reads.

    The original Motorola documentation on the 6845 CRTC fully explained
    the relationships and timing budget calculations.

    That was the best information that I had ever seen on the subject.

    jack
  • KyeKye Posts: 2,200
    edited 2010-05-06 04:05
    I've been using my own driver that I rolled to run the video. I simply mentioned chip's driver because my code is derivided from his but acts basically similar.

    I could make the number of vertical sync lines 1.

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    Nyamekye,
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2010-05-06 07:00
    The monitor is probably trying to clamp its black levels, if there isn't black, where there is expected to be black, then you can get all sorts of brightness/colour problems. It might be after VS and also HS (my LG monitors do it on both) so try lenthening the backporch of either/both.

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