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PAL Graphics Demo. How? — Parallax Forums

PAL Graphics Demo. How?

inakiinaki Posts: 262
edited 2006-05-08 15:45 in Propeller 1
I am· trying to put the Graphics Demo to work.
It is giving me·a garbled picture, a mess of white and black pixels.There is something moving behind the picture so it seems that something is·actually being sent to the TV.

Apparently my TV set is multi-standard but anyway I would like to try PAL mode.
How do I set PAL mode in the Graphics Demo program ?

By the way, I am using a 20Mhz crystal and have changed the clock settings to:

_clkmode = xtal1 + pll4x
_xinfreq = 20_000_000

To connect the Propeller to the TV set I am using the schematics provided·by Phil Pilgrim for the PropStick: 3 resistors connected to pins A12, A13 and A14.



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Post Edited (inaki) : 5/7/2006 11:42:52 AM GMT

Comments

  • El PaisaEl Paisa Posts: 375
    edited 2006-05-07 14:31
    I am· also trying to put the Graphics Demo to work.
    It is giving me·a garbled picture, a mess of white and black pixels.There is something moving behind the picture so it seems rotating dots.
    I am using a CineVision LCD display sold by Radio Shack.
  • cgraceycgracey Posts: 14,210
    edited 2006-05-08 04:54
    Oh, the problem is that when you apply a 20MHz crystal and then use the PLL, it gets internally wound up 16x or to 320MHz. This is too fast. The PLL was designed to work in all cases up to 160MHz, but we spec it at 128MHz. You need to either use a crystal that is 10MHz or less, and then select a PLL tap that is 80MHz or less.

    To make PAL video, you must change the 4th long in the tvparams structure to %0001. That LSB selects NTSC or PAL generation.

    tvparams··············· long··· 0·············· 'status
    ······················· long··· 1·············· 'enable
    ······················· long··· %001_0101······ 'pins
    ······················· long··· %0000·········· 'mode - CHANGE THIS TO %0001
    ······················· long··· 0·············· 'screen
    ······················· long··· 0·············· 'colors
    ······················· long··· x_tiles········ 'hc
    ······················· long··· y_tiles········ 'vc
    ······················· long··· 10············· 'hx
    ······················· long··· 1·············· 'vx
    ······················· long··· 0·············· 'ho
    ······················· long··· 0·············· 'vo
    ······················· long··· 55_250_00···· · 'broadcast
    ······················· long··· 0·············· 'auralcog
    inaki said...
    I am· trying to put the Graphics Demo to work.
    It is giving me·a garbled picture, a mess of white and black pixels.There is something moving behind the picture so it seems that something is·actually being sent to the TV.

    Apparently my TV set is multi-standard but anyway I would like to try PAL mode.
    How do I set PAL mode in the Graphics Demo program ?

    By the way, I am using a 20Mhz crystal and have changed the clock settings to:

    _clkmode = xtal1 + pll4x
    _xinfreq = 20_000_000

    To connect the Propeller to the TV set I am using the schematics provided·by Phil Pilgrim for the PropStick: 3 resistors connected to pins A12, A13 and A14.


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    Chip Gracey
    Parallax, Inc.
  • cgraceycgracey Posts: 14,210
    edited 2006-05-08 04:56
    El Paisa,
    Is your crystal 10MHz or less? 5MHz is ideal. You've got to be clocking at at least 40MHz for this to work properly. Also, if you are using a series-resonant crystal, it's frequency will be off by just enough to kill the color lock.
    El Paisa said...
    I am· also trying to put the Graphics Demo to work.
    It is giving me·a garbled picture, a mess of white and black pixels.There is something moving behind the picture so it seems rotating dots.
    I am using a CineVision LCD display sold by Radio Shack.
    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔


    Chip Gracey
    Parallax, Inc.
  • inakiinaki Posts: 262
    edited 2006-05-08 08:18
    Chip,
    I don't understand that.
    If I use a 20Mhz crystal would not be enough to change the clock settings to multiply by 4X instead of 16x?

    _clkmode = xtal1 + pll4x
    _xinfreq = 20_000_000

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  • GadgetmanGadgetman Posts: 2,436
    edited 2006-05-08 09:57
    No.

    The PLL ALWAYS multiplies by 16. It's just that we can select which stage we get the output from.

    Maybe the docs need to be a bit more clear on this.
    (Never use the PLL with a Xtal of more than 10MHz?)

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    Don't visit my new website...
  • inakiinaki Posts: 262
    edited 2006-05-08 12:12
    Thanks. I have replaced the crystal with a 5Mhz.
    Now I get a decent picture but I get a lot of noise too. Colors are not solid.
    This noise problem might be the cable perhaps ? I am using an RCA video cable with the 3 resistors soldered on one end.
    The other end is connected to a scart connector on the TV set.

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  • El PaisaEl Paisa Posts: 375
    edited 2006-05-08 12:25
    Chip:

    All the tv or video programs does not work in my breadboard, the ones using LEDS all work.

    I am using 5 Mhz crystal the one recommended in this forum.

    I have seen two versions of the resistor networks, one with three resistors and one with four resistors (the one shown in your demo board).

    Which one is the correct one or both work?
  • cgraceycgracey Posts: 14,210
    edited 2006-05-08 15:45
    The three-resistor circuit is all you need for baseband generation. Are you seeing any activity on the I/O pins for the video? The graphics_demo example is set to use P12, P13, and P14. To those pins, you should connect 1.1k, 570, and 270 ohm resistors, respectively, and tie them all together.
    El Paisa said...
    Chip:

    All the tv or video programs does not work in my breadboard, the ones using LEDS all work.

    I am using 5 Mhz crystal the one recommended in this forum.

    I have seen two versions of the resistor networks, one with three resistors and one with four resistors (the one shown in your demo board).

    Which one is the correct one or both work?
    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔


    Chip Gracey
    Parallax, Inc.
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