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TFT displays — Parallax Forums

TFT displays

Zap-oZap-o Posts: 452
edited 2009-06-21 12:03 in General Discussion
Since the propeller can not control a decent TFT display is there a interface IC that I can use.

I don't want to use a 4D or any other company that has made a all in one unit. I want to learn this and make my own board.

This is the type of display i wish to use

www.optrex.com/products/partdetail.asp?PartNumber=T-55149GD030J-MLW-AJN

Comments

  • Erik FriesenErik Friesen Posts: 1,071
    edited 2009-06-17 18:19
    What makes you feel the propeller cannot control this display?

    I don't see any obvious reason that it can control it. The prop doesn't have enough memory to buffer the display but if you want to use the graphics ram built into the chip you don't need to buffer the display.

    Check out some of Timothy Sweiters LCDs. They aren't that expensive and there is code to back them up.
  • RickBRickB Posts: 395
    edited 2009-06-18 15:03
    The app notes at Optrex suggest appropriate controllers to go between the lcd and your favorite processor. Getting this done is nontrivial, but it can be done.

    Rick
  • kwinnkwinn Posts: 8,697
    edited 2009-06-21 06:31
    I took a look at the video standards listed at http://commons.wikimedia.org/wiki/File:Video_Standards.svg and then at the documentation for the prop. Based on that and a prop running at 80MHz I took a look at what resolution of bit mapped graphics might be possible with a 60Hz refresh rate using an LCD panel or monitor. Keep in mind this is only with a view to displaying an image that is in memory. Creating that image is another (and probably bigger) can of worms.

    1 - With the prop only:

    CGA (320x200) 2 color would require 2000 longs of ram and 3.84 million pixels per second. It is just barely possible, but anything beyond that requires external ram.

    2 - Prop with external ram:

    Resolution is limited by the speed at which the prop can increment and output the pixel address. Colors are only limited by ram width. QVGA (320x240) requires 4.608 million pixels per second and should be possible with one cog. VGA (640x480) 18.432Mp/s may be possible with multiple cogs.
    An alternative may be to combine the current high resolution text driver technique with the external ram which could get us as high as XGA (1024x768)

    3 - Prop using PLL with external ram and horizontal pixel counter:

    The pll can go up to 128 MHz, which would get us to HD1080 (1920x1080). This requires 124.416Mp/s which means high speed video memory and pixel counter.

    The major problem with methods 2 and 3 would be updating the graphics image in memory. This may be more difficult than generating the video. Ultimately I think the prop is simply not well suited to this, and needs an external graphics processor to make use of the higher resolution displays.
  • Timothy D. SwieterTimothy D. Swieter Posts: 1,613
    edited 2009-06-21 12:03
    Man, I can't wait enough for Prop II (for more RAM). There are several threads regarding TFT displays and the Propeller and the RAM. There good be options using external RAM, I know some other people have explored it. The overall controlling isn't the problem, just buffering any images.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Timothy D. Swieter, E.I.
    www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
    www.tdswieter.com
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