TVout -- correct NTSC waveform?

Scanned the forum for this subject, but failed to find answers – apologies if I missed them.

Basically, I get nothing on my composite video monitor and I am wondering if the Arduino is generating a proper signal.

am trying to simply execute the tvout demo DemoNTSC., having purchased a current model Uno for the purpose, loaded tvout library, loaded DemoNTSC. Compiling resulted in many java messages but no errors per se, so project did load into Uno. Used the correct pins (7 and 9) with resistor divider as recommended.

The output waveform from the Arduino (see attached) is simply a 60-hz(ish) refresh pulse, with a 4.7 usec sync (0 V) and then a 57 usec pulse at 5v. No video data are apparent on that 5v pulse.

Comparing to standard NTSC waveforms, this lacks a front porch, back porch, and color burst. (See http://web.mit.edu/6.111/www/f2008/handouts/L12.pdf, p.8)

The Arduino output is also at 5v, vs. the specification at 1v p-p

Should the waveform I’m getting be sufficient? If not, any ideas on what is failing?

Thanks!

Should the waveform I'm getting be sufficient?

No you have no video on it.

Used the correct pins (7 and 9) with resistor divider as recommended.

Where is this recommendation? Please post a link. I would have thought that you need a bit more circuitry than that.

Comparing to standard NTSC waveforms, this lacks a front porch, back porch, and color burst.

Yes you won't get that with the Arduino, just a crude monochrome signal.

The whole "DemoNTSC" is misleading - the best you can hope for is an approximation to RS-170.

Are you trying to make a NTSC signal generator or a sync pulse generator?

Either way the arduino is the wrong way to go there are (used to be) specialist chips to do this…

Philips ( now nxp) did loads…

regards

Thanks for the feedback. I am simply trying to drive an old, analog input TV with a varying video signal as in the youtube video below. (The purpose is to keep a TV used in a museum exhibit of magnetism's effect on a CRT electron beam from timing out due to lack of changing video input.)

https://www.youtube.com/watch?v=ZT46khR2A3c (There are several other videos of the same technique on YouTube.)

The approach used there is documented in:

http://playground.arduino.cc/Main/TVout

and

https://code.google.com/archive/p/arduino-tvout/

Is the lack of video data on my signal likely to be the only reason I get no picture, or do I also need the front and back porches (with or without the color burst)? I'm trying to figure out why the library code and example do not work as advertised.

Is the lack of video data on my signal likely to be the only reason I get no picture,

Yes. The lack of front an back porches will not stop you seeing a picture. It might make the picture distorted for high contrast video but you will still see stuff. They act as a black level clamp when restoring the video signal level after AC coupling. This is needed because a composite video signal is an asymmetric signal.

You could buy an old pattern generator - you can still get them on ebay. eg

http://www.ebay.co.uk/itm/Kenwood-CG-911A-NTSC-TV-Colour-Pattern-Generator-/232111158860?hash=item360ae7364c:g:8kcAAOSw6btXRYwS

regards

Allan