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Topic: TVout Colors (Read 7 times) previous topic - next topic

baum

My TV does have component (RGB) input!!! Is this easier to do? Where can I find the protocol, if any, for component video?

baum

baum

Not VGA... I'm talking about the Red, Green, and Blue video cables.
http://en.wikipedia.org/wiki/YPbPr

baum

Alright. So VGA would be the way to go, but I can't do that.

Thanks everyone!
baum

focalist

Back in the day, we used patterns of black and white on NTSC televisions to produce what were called Pseudo Colors.. you can do a google on "artifact colors" or look it up via Wikipedia.

It was used most often on the home PC systems like Atari, Commodore, and CoCo.

If using a CRT display, this will work.. otherwise, SOL.
When the testing is complete there will be... cake.

baum

I have a Panasonic plasma display... :( All the newer technologies are too fast and too glitch-proof to interface with the arduino. =(

gijs

if you send VGA you can put this inbetween:
http://cgi.ebay.nl/PC-MAC-VGA-to-TV-AV-Composite-RCA-S-Video-Converter-Box-/320723345960?pt=UK_Computing_CablesConnectors_RL&hash=item4aac99e228

should work fine.

baum

Another question...

I just opened up an old timex sinclair color computer. It is capable of doing 8 colors (black, white, red, green, blue, cyan, magenta, yellow), but only runs at about 14Mhz. How can this possibly output color? I did find a chip near the TV-out port, don't remember it. Sorry... but is there a IC of some sort I could use to get even a few colors?

And how do modern devices such as DVD players and Cable boxes do it?


baum

baum

But is there any IC I can get to do most of the work for me?

David Pankhurst

This is very close to a project I was looking at - using a second Arduino for debugging the first as a 'dumb' terminal display/keyboard.

I remember the old b/w Timex Sinclair 1000 and how it worked. It spent much of its time generating the picture, and then did its "real work" between screens. It was a lot slower than the Arduino's 16mhz, which made me wonder if it was possible. So far I've found:

* Looking at the NTSC spec, we have about 52usec to display a row. At 16 million (possible) instructions per second, that means we have about 832 instructions per row max. This means machine language not C/C++, especially if you want to do higher resolution (the 192 pixels of TVout yield 4 instructions per pixel, more or less). Obviously, loops need to be unrolled, and since timing is vital, plenty of 'nop' to pad the raster line display.

* Since I'm thinking text only, b/w is fine, but I'd like higher resolution text, say from an IBM clone font ROM. Characters per line would be low of course.

* Taken together, the current tvout of 192 pixels and using a character size of 8 pixels wide (7+1 blank) yields 24 characters per line - better than nothing for a terminal, but lower than I'd like.

* Keyboard is not a problem - reading a PS/2 is just a matter of hooking up, and software - making it play nice with the video is the challenge.

Combining the current TVout with a ps2 keyboard reader would yield the main parts of a single chip computer - from there, it *may* be possible to add something like a TinyBASIC and give people a low-cost computer that runs on their TV. And the part count is low: besides the Arduino, it's two resistors for the display, and an old keyboard - ideal for places where parts are very expensive, or the third world.



baum

I'd just like to mention that after opening, I found 4 processors inside, plus the machine had 72k memory (48kRAM + 24kROM)

So while slower it did have more space, and could probably do parallel processing (at the same time).

David Pankhurst


I'm sure someone has made a "silk purse" out of a pig's ear just to prove that it can be done. But you wouldn't want to carry it around. Future generations won't have a clue what "composite" or "NTSC" or "PAL" used to mean.  An RCA ("Cinch") connector will be just as "retro" as a tie-dyed shirt or a glass milk bottle.


Perhaps - however, if you were in remote India, and needed a simple computer, would an Arduino with TV and ps2 keyboard be a worthwhile thing, even if it only had b/w and 4k memory? I heard a story where a farmer owed about $7 - and was still paying that debt off after 10 years. So if you wanted to provide a computer to the (very poor) masses, even if we'd look down on it, perhaps there are people who would benefit from it...

By the way, my search for a low-cost solution isn't just to prove it can be down, or because it's Arduino - I chose Arduino specifically because of the low cost possibilities, and I'm only interested in practical projects.

baum

Quote
you can get chips with enough horsepower to do simple composite video AND computing and other I/O


Something like this?

http://www.sparkfun.com/products/10664

runs at 72 Mhz...

David Pankhurst


If you are interested in mass-producing a product, there are probably more suitable chips than Arduino/Atmel. For roughly the same price as the Atmel chips that Arduino is made for, you can get chips with enough horsepower to do simple composite video AND computing and other I/O.  The Arduino folk likely chose the Atmel chips they are using more for the ease of programming than for the performance bang for the buck.


Can you recommend any of these chips?

David Pankhurst


One that I've seen recently is: http://www.xmos.com/


Unfortunately that's out of my price range - Digikey shows the dev kit at almost $400.

You mention "one that I've seen" - have you seen any others, preferably at a lower price (ideally, less than the Arduino)?


baum

How about the Maple (link above)? It is an ARM processor coded in C, runs @ 73Mhz. I imagine it would be fast enough to do at least 2 bit grayscale, maybe?

baum

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