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PAL HSYNC Signal for a AD725 — Parallax Forums

PAL HSYNC Signal for a AD725

megaionstormmegaionstorm Posts: 178
edited 2013-05-15 05:11 in Propeller 1
How can i create a external PAL HSync signal for a AD725 ?

With one of those two programs:
http://obex.parallax.com/object/433
http://obex.parallax.com/object/616

Comments

  • ericballericball Posts: 774
    edited 2013-05-14 05:52
    You probably could adapt either of those TV drivers to your needs, but if you just need HSync then you just want 4.7usec low (+/- 0.2usec) with a 64usec period. However, it will need to be synchronized with your RGB data.

    What's your objective?
  • megaionstormmegaionstorm Posts: 178
    edited 2013-05-14 06:17
    I want control a ad725 like in this schematic:
    http://www.ladyada.net/images/fuzebox/fuzeboxsch.png

    But not with a atmega644, with a p8x32a.

    That's why the p8x32a must generate the hsync signal for the ad725.
  • megaionstormmegaionstorm Posts: 178
    edited 2013-05-14 06:34
    I have found this code in the TV Driver v1.1 program.

    hsync test _mode,#%0001 wc 'if pal, toggle phaseflip
    if_c xor phaseflip,phasemask
    mov vscl,sync_scale1 'do hsync
    mov tile,phaseflip
    xor tile,burst
    waitvid tile,sync_normal
    mov vscl,hvis 'setup in case blank line
    mov tile,phaseflip
    hsync_ret ret

    How must i change it to generate the hsync through a p832a pin ?
  • ericballericball Posts: 774
    edited 2013-05-14 07:20
    In the Fuzebox, the atmega644 generates the RGB in addition to the 4FSC and HSYNC signals. So if you are planning on replacing the atmega644, why not have the p8x32a generate the composite video signal and skip the ad725? (The main difference is you will need to code the colors as YC rather than RGB.)

    If you are interested in creating a video game console using the Propeller, you might want to see what's been done by others using the Hydra and other platforms, and tile drivers like the one macaa has been working on.
  • megaionstormmegaionstorm Posts: 178
    edited 2013-05-14 09:26
    I have found a graphics renderer for the vga driver done by macaa.

    Is there a equal tv driver too ?
  • ericballericball Posts: 774
    edited 2013-05-14 12:12
    megaionstorm wrote: »
    I have found a graphics renderer for the vga driver done by macaa. Is there a equal tv driver too ?
    You would need to ask him. However, it may be possible to adapt the work he has done for TV output. It may be a simple as creating a new TV output driver.

    Note: I was never happy with my PAL template. For some reason it wasn't as stable as Chip's TV driver.
  • megaionstormmegaionstorm Posts: 178
    edited 2013-05-14 17:56
    Looks like i must find the correct way to modify the above assembler routine by myself.
  • maccamacca Posts: 784
    edited 2013-05-14 23:32
    megaionstorm wrote: »
    I have found a graphics renderer for the vga driver done by macaa.

    Is there a equal tv driver too ?

    My early attempts, before findind the VGA driver from kuroneko (the driver is not mine), were based on Eric Ball's NTSC & PAL driver templates http://obex.parallax.com/object/433 which are using a similar structure with a color buffer. They don't have the code to read the color buffer from hub memory but could be easly added (and with more relaxed timing than the VGA driver). As Eric itself say, the PAL output isn't very good, due to the Propeller video generator limitations rather than the driver itself, I believe.

    Maybe you can use the VGA driver to directly drive the AD725, as far as I can tell if you connect the output of the VGA resistors dacs and h/v-sync lines to the chip you are done, and you don't even need to deal with the composite color values used by the Propeller. Well, you need to change the timings to PAL/NTSC values.
  • megaionstormmegaionstorm Posts: 178
    edited 2013-05-15 05:11
    Thanks, i think this informations helps a lot !
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