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DVI and SRAM Test Board Design (Rev.3) — Parallax Forums

DVI and SRAM Test Board Design (Rev.3)

RaymanRayman Posts: 14,181
edited 2009-10-22 13:23 in Propeller 1
I'm drawing up a little test board to try using the TFP410 to generate DVI output from the Prop.

Also testing SRAM as frame buffer or memory

I'd like to hear any technical comments you may have...

Dropped down to 8-bit video (3-green, 3-red, 2-blue) so I can also test using a SRAM chip as a video source...

The 74AC541 chip·is used to·select between Prop and SRAM video

Using a·few counters (74AC163) to incrementally address the SRAM...

I think I can show video from the Prop while loading up the SRAM with a photo.

Update:· New diagrams showing 256-color DVI, VGA, or TV output and addressable SRAM memory.

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

Post Edited (Rayman) : 10/5/2009 8:28:39 PM GMT
DVI_Test3.png
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DVI_Test3_TV.png
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Comments

  • VIRANDVIRAND Posts: 656
    edited 2009-09-29 11:22
    I don't use DVI yet but it's nice to know that the Propeller can still do video if (when) they kill VGA.
    At 30MB/second and 60 fps, your 512KB static RAM sounds perfect for a screen image buffer.
  • ParsecParsec Posts: 20
    edited 2009-09-29 13:57
    Rayman, all I can say is HARDCORE man, HARDCORE! smile.gif

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    No electrons were harmed while rendering this message.
  • mctriviamctrivia Posts: 3,772
    edited 2009-09-29 14:05
    looks cool

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    propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

    Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

    Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2009-09-29 14:25
    Hi Ray,

    I'd be a little bit concerned with using a long ripple counter as the propagation delays accumulate from stage to stage. Sure, it's only 5.5ns @3V per stage but with all those stages you could have the RAM's address lines all over the place and the RAM needs them to be settled before you can expect valid data after it's access delay as well. BTW, what happened to Q12 in the first counter, shouldn't it be fed to the RAM as well? What frequency are you hoping to clock the counters at? I'm guessing your DCK signal is the same frequency but a different phase.

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    *Peter*
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2009-09-29 14:44
    Just looking at your circuit again you know that you could get rid of the buffer and save 8 lines? Just use resistors from the RAM data lines to the Prop and the TFP410 so that even if the RAM is trying to output data the Prop overrides the weaker signal coming through the resistors. But why wouldn't you just disable the RAM through OE?

    Maybe with those 8 free lines you could drive the upper address bits and save a counter as well.

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    *Peter*
  • neotericneoteric Posts: 144
    edited 2009-09-29 14:44
    I have a use for such a configuration. When you settle on your final design, post it here. I have a project you may be interested in...
  • RaymanRayman Posts: 14,181
    edited 2009-09-29 15:00
    Peter Jakacki said...
    BTW, what happened to Q12 in the first counter, shouldn't it be fed to the RAM as well?
    Ooops.· Nice catch...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • RaymanRayman Posts: 14,181
    edited 2009-09-29 15:04
    Peter Jakacki said...
    Just looking at your circuit again you know that you could get rid of the buffer and save 8 lines? Just use resistors from the RAM data lines to the Prop and the TFP410 so that even if the RAM is trying to output data the Prop overrides the weaker signal coming through the resistors. But why wouldn't you just disable the RAM through OE?

    Maybe with those 8 free lines you could drive the upper address bits and save a counter as well.

    Good ideas....· But, I want to be able to load up the SRAM in the background while displaying video... So, I need all the pins.

    Still, perhaps I could use resistors to replace that buffer chip...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • RaymanRayman Posts: 14,181
    edited 2009-09-29 15:11
    Peter Jakacki said...
    Hi Ray,

    I'd be a little bit concerned with using a long ripple counter as the propagation delays accumulate from stage to stage.
    Good call.· This definitely won't work...

    My original plan used·five 74AC163 chips...· Guess I'll have to go back to those.· They also have the advantage that they can be preset, useful for setting the address of a single pixel...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • RaymanRayman Posts: 14,181
    edited 2009-09-29 16:33
    Actually, with resistors instead of the buffer, perhaps one could superimpose graphics (like a mouse) on top of the SRAM image...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • RaymanRayman Posts: 14,181
    edited 2009-09-29 18:22
    I've put a new diagram with revised counter scheme in the top post... Think I'll put resistor pads under the 74AC541 chip, between in and out, and try it with just resistors (as Peter suggested) first...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • RaymanRayman Posts: 14,181
    edited 2009-10-05 20:06
    Just updated the top post with latest design...

    Added VGA and TV outputs with better DAC resistors and reverse termination.
    (I think I've decided the Demo/Proto board VGA/TV DACs aren't perfectly designed...)

    Removed SD card and added addressable SRAM memory wiring.

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • RaymanRayman Posts: 14,181
    edited 2009-10-22 12:59
    I finally had a second to draw up a DVI board...

    This is on the ExpressPCB miniboard form factor (3.8"x2.5").·

    Tried my best to squeeze in SRAM and counters, but no way with a 2-layer board.· Decided best to try this board first to see if it even works like I hope...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
    DVI_PCB.png
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  • mctriviamctrivia Posts: 3,772
    edited 2009-10-22 13:23
    hope it works.

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    propmod_us and propmod_1x1 are in stock. Only $30. PCB available for $5

    Want to make projects and have Gadget Gangster sell them for you? propmod-us_ps_sd and propmod-1x1 are now available for use in your Gadget Gangster Projects.

    Need to upload large images or movies for use in the forum. you can do so at uploader.propmodule.com for free.
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