svga test pattern generator

Discussion in 'The Projects Forum' started by bribri, Mar 1, 2011.

  1. bribri

    Thread Starter Member

    Feb 20, 2011
    133
    5
    so i went ahead and built this:
    http://yusoft.kulichki.com/english/pic/my_proj.htm
    a VGA 640x480 pattern pattern generator based on a PIC program.

    but it didn't work until i added a 555 timer to adjust the pulse-width of the Hsync.

    i decided to adapt the programming to SVGA 800x600 @ 60Hz output.
    my reasoning was that a 20MHz clock would yield exactly 100 instructions per visible horizontal line, 5 instructions for the horizontal front-porch, 16 instructions for the Hsync pulse, and 11 instructions for the back porch...26.4μs.
    the nice part is that 628 of these lines (the number of lines in the SVGA standard) gets you pretty darn close to the needed 60Hz refresh rate : )
    so this works just fine. + there was plenty of room to add outputs for blanking signals.

    i don't know all that much about computer monitors, but my circuit works just fine at 17, 18, and 19MHz... at least on the monitors i tested. leads me to think that it's more the ratio between H and V sync pulse timing than exact values of one or the other which the monitor needs.

    i tried to adapt the program for use at 1024x768 @ 60Hz but ran into some problems, i guess because of the H, V sync ratio:

    [​IMG]

    skewed image at the top. oh well.
     
    eblc1388 likes this.
  2. jonnyphenomenon

    Active Member

    Nov 10, 2008
    59
    2
    I love every single thing about this picture. I dont even know what the topic is here, but I'm making this my new wallpaper.

    tell me more about the nixie tube thing.. is that a function generator??
     
  3. bribri

    Thread Starter Member

    Feb 20, 2011
    133
    5
    oh thanks : )
    the nixie thing is a hewlett packard 5245L frequency counter. VERY handy, quite heavy, cost next to nothing. i don't yet have a function generator though. i liked the visual qualities of the nixie-tubes so much that i've gone ahead and made a couple of art works from them.. well some new-old-stock of basically the same type in the fq counter.
     
  4. jonnyphenomenon

    Active Member

    Nov 10, 2008
    59
    2
    I cant honestly think of where I would use a frequency counter, but I imagine Ill need one some day. as for a frequency generator, I've borrowed one from work for a bit while I work on my current project. Also, theres a couple interesting apps for the android phone that seem promising...
     
  5. bribri

    Thread Starter Member

    Feb 20, 2011
    133
    5
    tuned circuits.
    i got it to fix/calibrate an analogue synthesizer whose oscillators are very high frequency. it came in very handy for video generator stuff... and it's super nice that the readouts can be switched between time and frequency values.
     
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