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Not to HiJack the PropStick Video Driver thread, but on video output in general — Parallax Forums

Not to HiJack the PropStick Video Driver thread, but on video output in general

Kaos KiddKaos Kidd Posts: 614
edited 2006-05-14 19:46 in Propeller 1
I've seen quite a number (three to be exact) of methods of connecting the propeller to·one video source·or another.· Could someone please verify the following?
·
  1. Composite output.· There are two versions of this connection, one with three, the other with four resistors.· I believe the one with 4 resistors includes sound or is for broadcasting the output.· Can the four resistor version be used for either mode?
  2. VGA output.· What should be done with the unused connections in the DB15 female housing?
  3. RGB output.· I believe a subcomponent of the VGA output is RGB.· Is this the same single that would typically be sent to the RGB inputs on a VCR/DVR?
  4. I have an 1702 Commodore Monitor that has Luminance and Video inputs (and audio, but that will come later).· How would I create that type of video output?
·Next, how sensitive is the selection of resistors?· I don't see a tollerance band on any of the schmatics I'v seen.

Thanks!


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Just tossing my two bits worth into the bit bucket


KK
·

Comments

  • JamesxJamesx Posts: 132
    edited 2006-05-11 00:55
    I'm not an expert, but I did get the TV and VGA connections to work. Regarding your questions:

    1) Composite output to TV: It works fine with only three resistors. I haven't tried it with four.
    2) VGA: unused connection in housing: I left them unconnected. It worked fine without them.
    3) RGB: don't know. But looking at the connector schematic, it does look like there is an RGB output. Try it?
    4) Commodore with Luminance and Video: don't know. Maybe try the TV output connect to the Video port on the Commodore?
  • Kaos KiddKaos Kidd Posts: 614
    edited 2006-05-11 14:03
    Thanks Jamesx...
    THe commodore connection didn't work... [noparse]:([/noparse]
    I'm going to have to do some some more stuff... but, I do have an old VGA monitor that it should work with... My dev board is 99% completed...

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    Just tossing my two bits worth into the bit bucket


    KK
    ·
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2006-05-11 17:02
    I just put a video box between my computer and my VGA. They come in two flavors - simple and with image inside Windows shell.
    I got the cheaper.

    Anyway, it keeps the clutter from building and provides an outboard, all hardware solution to using the computer's VGA.
    It has a typical remote that jumps you between computer and video. Also, you want volume control.

    I am having trouble with determining is RGB and VGA use the same plug.
    The Commodore is ancient. I suppose you can eventually get software and interface for it. Quite odd.

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    "When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • ForrestForrest Posts: 1,341
    edited 2006-05-11 23:42
    The Commodore 1702 has composite video and audio jacks on the front and Chroma/Luma (S-Video) on the back. The front jacks should work fine with the Propeller if you set the monitor switch for the front inputs.
  • Kaos KiddKaos Kidd Posts: 614
    edited 2006-05-12 13:34
    Forrest...
    ..Thanks...
    Kramer...
    ..C64 has floppy & hard drive access, as well as printer... & I'v LOTS and LOTS of C64 equipment...
    Their serial interface protocall is very simular to the SERIN/OUT interface and protocall.. More on that in another thread...

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Just tossing my two bits worth into the bit bucket


    KK
    ·
  • ForrestForrest Posts: 1,341
    edited 2006-05-12 16:56
    Your welcome. Many years ago I was a member (and eventually the President) of the Jersey Atari Computer Society and the club owned 5 of the Commodore 1701/1702 monitors. They worked well, had a great picture and they stood up to years of being carried back and forth from meetings to member's houses. I don't think today's monitors would hold up well to that kind of abuse.
  • Kaos KiddKaos Kidd Posts: 614
    edited 2006-05-12 17:02
    Forrest... Your so Right... Hmmm, I seem to recall the same JACS from several BBS's I was on... do you perhaps remember Angle's Lair and SYSOPII ??

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Just tossing my two bits worth into the bit bucket


    KK
    ·
  • ForrestForrest Posts: 1,341
    edited 2006-05-13 00:13
    Kaos Kidd,
    Check your PM to continue the JACS discussion.
  • rokickirokicki Posts: 1,000
    edited 2006-05-14 05:29
    Hmm, can anyone explain to me the logic behind the colors displayed in the color palette demo? I can't figure out
    why green is to the right in the saturated colors, but in the middle in the desaturated colors; why is blue in the
    middle in the saturated colors, but to the left in the desaturated colors (and to the right)? It looks like there is
    a 180 phase shift from the saturated to the unsaturated colors, and I'm not sure why.
  • cgraceycgracey Posts: 14,206
    edited 2006-05-14 05:54
    The reason is·this: the video modulator can generate 8 levels (0-7) of voltage. Levels 2 through 7 are black to white (unmodulated luminance), while level 0·is used for sync pulses and level 1 is used a modulation level for the reference colorburst at the start of each scan line (and, in fact, is a valid level for modulation in the visible portion of the scan line, too). When modulation is enabled by bit 3 of the 8-bit color code, the voltage level (luminance) specified in bits 2..0 gets used as a center point that the modulator adds and subtracts 1 to/from at the colorburst frequency. For example, %0000_1110·would mean level 6 (bits 2..0)·with modulation 'on' (bit 3) and phase 0 (bits 7..4). The modulator will output 7, 5, 7, 5, 7, 5, etc. at zero phase offset. This works for levels 2 through 6. Level 7 would cause the modulator to output 6, 0, 6, 0, 6, 0, etc. - venturing into·sync level, which is not good (this may actually be okay, since demodulation would render a luminance of about 4). You can see that level 1 would cause output to toggle between 2 and 0 - too much like sync levels, and black, anyway. Now comes the exception: level 0. Level 0 would toggle between 1 and 7 (remember, the +/- 1 operation is modulus 8). Toggling between 1 and 7 is fine. You get as saturated a color signal as is possible. The strange thing that happens, though, is that when it subtracts 1, it goes to level 7 which is higher, not lower - opposite of the effects of modulated levels 2 through 6 - hence, the 180-degree color phase difference that you see in those top colors.
    rokicki said...
    Hmm, can anyone explain to me the logic behind the colors displayed in the color palette demo? I can't figure out
    why green is to the right in the saturated colors, but in the middle in the desaturated colors; why is blue in the
    middle in the saturated colors, but to the left in the desaturated colors (and to the right)? It looks like there is
    a 180 phase shift from the saturated to the unsaturated colors, and I'm not sure why.
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    Chip Gracey
    Parallax, Inc.
  • rokickirokicki Posts: 1,000
    edited 2006-05-14 19:46
    Ahh, thanks for the excellent reply! So essentially, we get four bits in the H space, and we get a full set of fully saturated colors, and we get
    another set of colors where as the luminance goes up, the saturation goes down.

    I'm trying to figure out how to map this color space to RGB (and from this information, how to map RGB into this color space); I think you've given
    me the clues I need. Thanks!

    (And like others, I'm amazed at how responsive you and everyone at Parallax are. You guys must really have almost as much fun as all us
    tinkerers!)

    -tom
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