Color STN LCD controller

Hi,

I'm trying to design a controller for a Hitachi color STN display, but I'm running in to all kinds of problems here. I think most of it comes from the fact that I really don't know anything about how LCD displays work, so I was hoping someone in this group could enlighten me a little.

From what I've gathered from the displays datasheet, it seems the display is controlled by two different clock signals, one for vertical and one for horizontal lines. Once these clock signals are set correctly, it should just be a matter of clocking the pixel data in right?

There seems to be three bits for each color component, red, blue and green, and by my calculation this gives 8 different colors. However the display is listed as beeing able to show up to 65,000 different colors. How exactly is this possible?

I have thought about various dithering schemes, but i think most of them implies very dramatical losses in refresh speeds, resolution and image quality. What is the normal way of producing colors on a CSTN display?

Regards, Anders

Reply to
Anders Hellerup Madsen
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kinda, you would normally have something like a clk to clock in the pixels, a sync for each line and a sync for each frame.

shouldn't that be, ... 8*8*8 = 512 colors

if you stick to some form of toggling between different intensities of each color to get apparent intensities in between, shouldn't only the resulting refresh rate go down?

-Lasse

Reply to
Lasse Langwadt Christensen

"Anders Hellerup Madsen" schrieb im Newsbeitrag news:bp29um$b6s$ snipped-for-privacy@news.net.uni-c.dk...

In the last weeks I've designed a TFT Controller für Sharp TFT Panels. The Panel ist 640x480 Pixel, 262144 Colors. EBay: 40$ The TFT Controller has an Video + SVHS Input. FPGA: Altera Cyclone EP1C3 ( about 20$). The "source-Code" is an Altera Quartus "graphical block diagram." Size: about 1 printed page.

You see: Its very easy to design a controller for TFT displays.

Gerd

Reply to
Gerd B.

Ok, this is like I thought then.

I'm sorry, I was unclear at this point. There is three bits per pixel, one for each color component, so it is only eight colors.

Yep, and apperently this is the way things are expected to be done. I was also considering a kind of dithering where I would use, fx. four adjectant pixels of different colors, to give the illusion that the four pixels together were a mixed shade of another color. But this would halve the resolution and generally look very ugly.

But still I am very puzzled about this display. It's a Hitachi SX16H003 display which can display up to 65000 different colors according to this site:

formatting link

However according to the datasheet it seems there is only 3 bits per pixels. I am still puzzled. The datasheet can be found here:

formatting link

Thank you for your answer,

Regards Anders

Reply to
Anders Hellerup Madsen

Remember that you have time as a third dimension for dithering. STN displays are slow to respond, so dithering in time, between frames, can give you more color resolution.

Comercial STN display chips use a combination between spacial and temporal dither to achieve the claimed 65000 colors. Look up how floyd-steinberg dithering is done and extend it to three dimensions. It's a starting point.

Kind regards,

Iwo

Reply to
Iwo Mergler

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