Digital RGB Interface for LCD

RoboThespian

Many RGB (full colour) LCD displays have a digital RGB interface that uses Hsync Vsync and Dot (pixel) clock.
- this looks to be directly compatible with the Prop outputs

BUT can you route the Dot Clock signal out from the Propeller Chip ?

This signal is not needed with analog RGB

Anybody tried this interface yet - or know how to get at the PLL dot clock signal?

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A Little Bit Of Knowledge Is A Dangerous Thing
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Harrison.

Someone hinted that they were able to do it, but never posted the final result. The link to the post is: http://forums.parallax.com/showthread.php?p=644821.

I have tried to use that code but was not able to get the display to work 100%. The issue was that I was not able to obtain a correct datasheet for my display, along with my limited knowledge of how to calculate the backporch, frontporch, line timings, etc. I used formulas provided in a Sharp appnote, but it didn't seem to help me fix my display problems. I ended up with a display that only took up 1/4 of my 9" screen that had slight noise and flickering (obviously incorrect timing).

Harrison

Paul Baker

It is possible to route the dot clock out if you have setup the video generator so that a new pixel value is output each clock cycle. Instead of using mode 1 of the counter, you specify mode 2 and the pin it should be ouput to.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

RoboThespian

Thanks Paul

Any Thoughts on this one:

Use additional cogs to increase the VGA colour depth - ie one outputs bits 0-1 the next is for bits 2- 3 etc
- wouldn't need a an R2R ladder of resistors as this is for the above mentioned digital LCD interface.

Assuming all the params. are equal - would this work?

I would really like to achieve full 18bit colour for our robot eyes application -
see www.robothespian.co.uk

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_______________________________________
A Little Bit Of Knowledge Is A Dangerous Thing
But How Do you Know What You Don't Know?

Paul Baker

Just as it is possible to use multiple cogs in sync to generate higher screen resolutions, it is possible to generate higher color depth as well. The major hurdle will be the same, leveraging the limited amount of hub memory to accomodate the extra data.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.