Digital VGA

APStech-Attila

Hi!

· I have a project with Sharp LQ057Q2DC12 digital VGA LCD display. It has turned out, that it is possible to drive the CLK input of the LCD to sample pixel data, but I have run into a new issue:

· I have modified the settings of the 512x384 VGA driver to drive the 320x240 LCD, but certain color bits (R0, R1, G0 - pins 18, 19, 20) stick to "3V3". When I launch the original 512x384 driver, all 6 color lines act as excepted. Pixel clock is 6.25MHz, and frq reg. and PLL divider is set up for very stable output frequency.

Do you have any idea? Is it some video HW configuration that could prevent outputting to R0 R1 G0 pins?

Thanks,
· Attila

cgracey

Attila,

Could you have some other cog driving those pins high, perhaps from another object?

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Chip Gracey
Parallax, Inc.

APStech-Attila

I don't think, this could be the problem. But I will continue investigating in that direction.

There is only 2 cogs running: Video and the "main" the main does not include a single I/O pin setting line.

If I hardcode the pin settings, in the video driver, it will not help either. As soon as I change from LCD to VGA everything is okay.

Is the video hardware changing only the IO levels, and not the IO directions to achieve DAC?



Thanks for advie,

·· Attila

cgracey

Attila said...

Is the video hardware changing only the IO levels, and not the IO directions to achieve DAC?

Attila,

Yes, only the output states are changing. The DIRA settings are static.

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Chip Gracey
Parallax, Inc.