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Author Topic: TVout hardware and voltages.  (Read 1400 times)
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Missouri, USA
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To get started on this project: http://arduino.cc/forum/index.php/topic,86178.0.html
I want to try the TVout library: http://code.google.com/p/arduino-tvout/

2 resistors is pretty simple, huh? I built the 470 ohm out of 8 other resistors. My multimeter reads 470. The 1K reads 999.

Anyways, to my understanding, sync is 0V, black is 0.3V, and white is 1V.

When the "video" pin is off (sync is on), my multimeter reads 1.63V. When both are on, it reads 4.84V. Anyways, I haven't brought my arduino near my TV yet.
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The video-in socket on your TV has (or should have) a 75 ohm input impedance, which will drop the voltage to 1V.

Try measuring the resistance of the video-in on your TV, if it reads 75 ohms it's safe to plug it in. If it is much higher you need a 75 ohm resistor in parallel with the socket.
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Missouri, USA
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Ah, that makes the difference then. Thanks. I'll report back after I've tried it.
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I had simulated the circuit for RGB Analog LCD.

http://blog-imgs-47.fc2.com/n/a/b/nabermc/20110201_Sim_RGBLCS_Cir.jpg
http://blog-imgs-47.fc2.com/n/a/b/nabermc/20110201_Sim_RGBLCS_Grp.jpg

sorry only Japanese
http://nabermc.blog137.fc2.com/blog-entry-29.html

Input impedance - 75 ohm
I checked like this.
http://nabermc.blog137.fc2.com/blog-entry-27.html

That work


16step degrees monochrome


Simulation with LTspice
https://picasaweb.google.com/MeowJPN/ELJ09#5408385441506395666

Let's enjoy with Arduino!
Thanks!
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Missouri, USA
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It's funny you posted the 16-step monochrome video. I had actually built a 4-bit (16 step) DAC so I could begin testing the aformentioned project of mine. I'm aiming for 640x480 resolution with grayscale tile graphics (eventually 8-bit, possibly).

Anyways, I ran the TVout several times connected to an old and big CRT screen via composite. It had plenty of color issues, so I found an old DirecTV receiver (yes, that's receiver, not DVR) that has plenty of plugs for pilfering. I figured out how to extract the PCB and tomorrow I'll desolder the S-Video connector so I can have dot crawl free grayscale.
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That's odd. If there is no colour subcarrier signal the TV should activate a colour-killer circuit (see http://en.wikipedia.org/wiki/Color_killer ) which should stop the dot crawl.

If you have some low value capacitors try connecting them in parallel with the socket, this should help filter the signal and activate the colour killer. Too high a value will blur the image.

I also did a 4-bit greyscale demo although it is just a static image, it is attached to this message: http://arduino.cc/forum/index.php/topic,50345.msg369716.html#msg369716 Sync is on pin 9 and video is on pins 7(msb),6,5,4
« Last Edit: February 02, 2012, 08:03:39 am by stimmer » Logged


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I don't think you connected the grounds, Dave.
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Quote
I'm aiming for 640x480 resolution
At 31kHz line rate on an Arduino?
Best lower your sights a shade.
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Missouri, USA
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Sorry, I don't know a much about those things, which is why I'm messing with TVout to start with.

I'm aiming for the full 480 lines, but as they're lines the "pixels" can be however long the signal/etc. can accommodate.

EDIT: I stole the SVideo plug from my old DirecTV receiver and got a clear picture from it. I also soldered a 9V connector to my arduino so I don't have to bring my netbook wherever I need my arduino.
« Last Edit: February 02, 2012, 04:10:41 pm by Jorh » Logged

Japan
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At 31kHz line rate on an Arduino?
If we use VGA - NTSC converter, we treat horizontal frequency as 31kHz (32us).
http://en.wikipedia.org/wiki/Video_Graphics_Array#Signal
I have used Arduino Duemilanove . (ATmega 328P 16MHz(62.5ns)

32us/62.5ns = 512 < 640 - impossible !

256step grayscale ( 8bit = 1byte )
640 x 480 = 307200bytes
no enough memory

So in addition to Arduino, we need a decent hardware.
It's not interesting to me.
I made one clock resolution software delay timer.
And I have an idea.
So, QVGA( 320 x 240 )  maybe possible

work - one clock resolution software delay  timer
use for draw sin wave and other ( 0:55 - 1:57 /3:51 )


work - R rudder DAC + trangister, 256 step grayscale
sorry, not Arduino

http://homepage3.nifty.com/two_legs/neo/project/MYCOM32/proj_MYCOM32.htm

I'm poor in English.
Thanks!
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The TVout lib is one of the most useful things I've found.. I made a audio spectrum analyzer with video output:



and a light pen:



it simply provides a ton of display space for the cost of a couple of resistors.

I use it with a portable DVD player that the dvd drive no longer works on, but takes composite video input.  I love it because it only requires two pins for all that functionality to boot.  This was the fist video of it I put online, the screen is the DVD player screen.  You can buy NTSC composite color monitors, 3-6" in size for use as backup camera monitors off ebay for under $50.  Hard to beat.  I suppose I shouldn't use AC/DC, but rather appropo music imo...




Sure it's a memory hog and all that, but it's so dang useful, I consider it one of the best Arduino libs out there!  I suspect it may be a different story under a Mega or a 1280.. it's the memory for mapping the data that is the problem.  Bit mapping even monochrome:

Memory=(X * Y)/8  ..  a byte is eight bits, binary.  That only accounts for monochrome.. the total memory space on a 328 is just too small to keep the data map for the video.. and you'd need colorburst and all that stuff that Arduino won't make anywhere as easily as it makes "sorta" NTSC composite mono.

I'm picking up a 644 (40 pin Arduino-compatible AVR, more resources than a 328 but still a DIP).. if I remember right it has substantially more SRAM, so higher resolution data maps might be possible.  The AVR core is plenty fast I'm betting, the 328 handles it awesomely.
« Last Edit: February 04, 2012, 07:37:14 pm by focalist » Logged

When the testing is complete there will be... cake.

Japan
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The TVout lib is one of the most useful things I've found..
I think so too.

In Japan analog broadcast TV has ended last year except for some areas.
So There are many redundant CRT televisions.
We can use the television as personal use, for hobby, for goo display.
We can achieve it by using TV out lib and only 2 registers.

I also want to contribute something.
So I must study English!   smiley-sweat

Thanks!
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