rm
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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 10:03 am

This: https://www.dealextreme.com/p/3-5-tft-l ... -15v-49796

And other similar ones: http://s.dealextreme.com/searc.....tegory=718

Most likely these can be driven from the RPi analogue video output (right?). So these very cheap screens could be useful in a lot of "embedded" projects, to make a small retro computer, or maybe even a laptop.

The only issue is powering them from somewhere (a separate supply or battery), as unlike the RPi they require upwards from 8V to 15 and more, not USBish 5V.

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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 10:19 am

romanrm said:


This: https://www.dealextreme.com/p/3-5-tft-l ... -15v-49796

And other similar ones: http://s.dealextreme.com/searc.....tegory=718

Most likely these can be driven from the RPi analogue video output (right?). So these very cheap screens could be useful in a lot of "embedded" projects, to make a small retro computer, or maybe even a laptop.

The only issue is powering them from somewhere (a separate supply or battery), as unlike the RPi they require upwards from 8V to 15 and more, not USBish 5V.



Resolution is rather low at 320 by 240.  Do you remember using a VGA monitor (640 by 480)?  I wouldn't fancy writing code on that but as the display for an audio player it would be fine.
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Gert van Loo
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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 10:22 am

Probably too small for daily use, but I imagine there are lots of applications where a small screen is all you need.

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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 10:25 am

Still more expensive than a second-hand 15" LCD TV from eBay, and you could only get a maximum of 40 characters across that screen.

It's a good solution if you are looking for portability, but not for general use. The power-supply issue is easily solved if you can solder, or if you can put up with two supplies.

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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 10:42 am

I've found a couple that say they have 960 x 468px. They are $10-20 more, but should be more useful.

http://www.dealextreme.com/p/e.....v-dc-47973

http://www.dealextreme.com/p/e.....v-dc-47974
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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 12:44 pm

^ Those are indeed quite a nice find. Of course it's silly that RPi will first do digital to analog conversion, then the display will do analog to digital, but other than that those might be plenty useful. Looking at the pictures those seem like they should also be rather easy to open up, so you could redo the cabling and make a custom case where you can fit both the RPi and the display inside, plus some sort of a battery -> mobile Pi(e).

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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 3:13 pm

Cracknel said:


I've found a couple that say they have 960 x 468px. They are $10-20 more, but should be more useful.

http://www.dealextreme.com/p/e.....v-dc-47973

http://www.dealextreme.com/p/e.....v-dc-47974



They are PAL input and PALs resolution is only 313 verticaly (625 interlaced) and I very much doubt the Pi does interlaced output!

We've tried 640x256 on a 3.5" & 4.3" 1V Composte PAL monitor, the output is just about useable in monochrome, adding the colour burst reduces the quality quite a bit, introducing noticeable shimmer!.

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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 7:32 pm

Interlaced output is actually a pretty standard capability - the old micros never did it, but that was more due to not having enough pixel-pushing capability (due to lack of RAM) to justify it.  For a long time SVGA cards and monitors would use interlaced mode for the very highest resolutions they supported - which invariably looked crap due to field misalignment and so on, but there you go.  I would hope that most TVs have better field alignment than that.

Based on tests I've just done on my old BBC Micro and an even older miniature video monitor that I dug out of my spares pile, 640x480 is a perfectly viable resolution for PAL standard - just don't expect to be able to see every single pixel.  You'll need to use some font a bit bigger and clearer than Flyspeck 6 to code in, but an 80x40 terminal (using 8x12 characters, which are actually *smaller* than standard CGA) should be perfectly readable and usable if you pick the right font.

That gives you more editing room than a standard VT100 series dumb terminal.

Depending on the TV, you could even go wider or slightly taller, but VGA resolution seems to be a good default.  Let people tweak it afterwards if they like.
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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 8:29 pm

Chromatix said:


Interlaced output is actually a pretty standard capability - the old micros never did it, but that was more due to not having enough pixel-pushing capability (due to lack of RAM) to justify it.


The old micros never did it because with a TV CRT phosphor the interline flicker would have been hard on the eyeballs. LCD screens are much better in that respect.
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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Tue Feb 07, 2012 10:22 pm

The inter-line flicker is a problem on *any* interlaced display, whether it's just pixel doubled or has real dual fields.  When pixel doubled it looks like the display is vibrating up and down slightly.

Given the choice between interlaced and progressive you should always go progressive all other things equal, but if interlacing is forced upon you, you might as well use the few advantages it gives you.

On the BBC Micro, it is possible to disable the interlace to steady the picture.  I don't know whether the second field is just blanked or if some timing trick is used to make a half-resolution, double-framerate progressive display.
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Chromatix
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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Wed Feb 08, 2012 1:50 am

BTW, here's video of some of the tests I ran:

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Re: Idea: a cheap colour LCD for R Pi (only $22.60)

Wed Feb 08, 2012 3:38 am

thoughts on http://www.buy.com/pr/product......d=26076229 ?

The resolution isn't all that good but the screen size is larger…

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