DIY pattern generator

[buttersoft]

Does anyone know of a nice, 15kHz-capable, 60Hz RGB test-pattern generator i can build? Preferably one that's battery-powered and very portable.

There's a composite 50Hz one on Viletim's site, i think it is, but using the wayback machine i can only get a verbose uncompiled version of the code.

I found a simpler 50Hz one, which is nice, though it could use a few more patterns...
https://dselec.wordpress.com/generator/

Anything else out there?

[SamIAm]

A few months ago, I picked up a Shibasoku TG19CC broadcast-grade signal generator. It's bulky and heavy, and it doesn't have as many patterns as I'd like, but one thing I can say about it is that I've looked at its output on an oscilloscope, and everything is exactly what it should be. Peak output on each channel is 714mV, sync-tips and colorburst are 286mV, and all stairstep and ramp patterns are perfectly proportional. I've even checked the EBU color bars via NTSC output on a vectorscope, and they're spot-on.

What kind of precision are you looking for?

If all you need are a few grids and colors for general geometry/convergence/purity adjustments, there are probably any number of solutions out there. If you want to do precision color-calibration, though, I'd find a way to confirm that you're getting the right signal levels.

[buttersoft]

I don't need anything precise, just something small to tote around to test sets, though it would be nice to have a few options when it comes to test patterns/colour bars. At worst, one of each would do.

I'm after a few more of the "probably any number of solutions out there" ones to pick between

[SamIAm]

Off the top of my head, I've seen several successful attempts at getting an Arduino to output video. Power consumption with those is very low, and they're obviously quite portable. You'd probably have to write your own code, though, or modify someone else's.

[SuperSpongo]

I built a small setup with a Raspberry Pi Zero. It is Composite as well, but outputs 240p. I asked a guy on reddit whether he would compile a Retropie image for the Zero and he did. Paired with a USB Gamepad and a powerbank, this thing can output the 240p test suite and I took it with me when testing a consumer TV.

If that sound interesting to you, I can dig up the links

[buttersoft]

If that sound interesting to you, I can dig up the links

I'll be honest and say it's probably not quite ideal, in this case, but i'd certainly be interested to take a look if you could post the links!

[vol.2]

I use a B&K unit that is small, does about 12patterns and color bars, and it has RF, composite and svideo output. runs off a 9 volt and fits in one hand.

You can probably get one for <$100 on fleabay.

Other than that, you can just buy a pattern generation IC and build the example circuit in the datasheet. You'd have to buy a box and all the junk and ports and it would be more than halfway to a used BnK.

[buttersoft]

I use a B&K unit that is small, does about 12patterns and color bars, and it has RF, composite and svideo output. runs off a 9 volt and fits in one hand.

You can probably get one for <$100 on fleabay.

Other than that, you can just buy a pattern generation IC and build the example circuit in the datasheet. You'd have to buy a box and all the junk and ports and it would be more than halfway to a used BnK.

Well, if I was going to buy something i'd grab one of the Craftymech ones because those do RGB -https://craftymech.com/arcade-test-pattern-generator/

I'd prefer to tinker, and i have all of the parts i'd need already in terms of sockets, housings, and probably most of the junk. I had no idea pattern generator IC's were a thing though, cheers for the idea. A quick google shows me they seem to be designed for Composite output, but i'll keep looking.

[vol.2]

Yeah, the ICs are generally NTSC video output. It could be easily used for the patterns via RGB since it's just black and white, but you'd have to build a circuit to decompose the color signals for the color bars and the screens. There are definitely other chips that could do that for you as well.

[Dochartaigh]

Well, if I was going to buy something i'd grab one of the Craftymech ones because those do RGB -https://craftymech.com/arcade-test-pattern-generator/

I'd prefer to tinker, and i have all of the parts i'd need already in terms of sockets, housings, and probably most of the junk. I had no idea pattern generator IC's were a thing though, cheers for the idea. A quick google shows me they seem to be designed for Composite output, but i'll keep looking.

If I were to buy one I would buy this one (which I already own the non-rechargeable one and it does composite, S-Video, Component, RGBS, RGBHV, RGsB, RsGsBs, etc. etc. 15khz up to ~106.3 kHz, 1080p, 4:3 or 16:9 options, etc):

https://www.ebay.com/itm/EXTRON-VTG-300 ... SweNpflOvV



Or for ultra portable DIY a Raspberry Pi Zero with a lipstick size USB battery pack (I always left this one in my cars glovebox in case I found a steal on a PVM on Craigslist and needed to go immediately from work to pick it up and needed something to test it with quickly):



You can also make a RP3/4 with a hat for RGB output too (if not composite/YPbPr/RGB with a RetroTink hat) if you have to have RGB. Benefit of these over the professional type I've seen (like the Extron) is I would much, much, much rather test with a 240 progressive signal, than a 480 interlaced signal. 240p just keeps the test grid solid and unmoving so you can really see the convergence pretty perfectly, where you can see some flicker from the interlaced fields of 480i testers. I don't know if that Craftymech you mentioned does 15khz progressive or what though.

[SuperSpongo]

Agreed, it's not an ideal solution, but I think it could come quite close if you somehow figure out a way to autoboot into the SNES 240p test suite and use some kind of minimalistic controller as input.

https://www.reddit.com/r/crtgaming/comm ... g_to_tiny/

This is the image I'm using. Dochartaigh posted a picture of his, mine looks more or less the same

[vol.2]

The one thing I'm not certain about with the DIY stuff, specifically the Pi-based ones, is the HV position.

You basically have complete control over the position when you setup the modeline (or whoever is setting that up), so you have nothing like a definitive reference to center.
The units built around an IC just output a centered NTSC signal.

I suppose you can just choose a TV you think is pretty much correct and center all your other TVs to that one, but it's still going to have some guesswork going on.

[Dochartaigh]

The one thing I'm not certain about with the DIY stuff, specifically the Pi-based ones, is the HV position.

You basically have complete control over the position when you setup the modeline (or whoever is setting that up), so you have nothing like a definitive reference to center.

That wouldn't effect anything as long as it's roughly centered which most default modelines are. All your different 224/240/256/320p/480i (real) consoles have a slightly different center as well - this is why there's that overscan area so you can center the image so it's halfway decent for all consoles, and perfect for usually none (heck, I sometimes want to adjust the center/width/height on different games on the SAME console at the SAME resolution!!!).

The test patterns, when used as a first time diagnostic tool - maybe even solely for field use (which I'm assuming buttersoft wants this for since he mentioned 'very portable' and rechargeable), aren't necessarily used for centering at first – that comes later (especially if it can only be centered by internal pots). They're used to see (amongst a whole bunch of other things) how the geometry and linearity is with the different test grids and circle patterns, those same (and/or a tighter grid, or a dot pattern, or "T" or "H" pattern - there's a bunch of them) are used to see how the convergence is in multiple areas of the tube. SMPTE bars for color, black level, brightness contrast etc. etc. etc.

[NewSchoolBoxer]

I like this thread. I have a dream of sending a generated signal down a bunch of different gaming cables into a capture card then computing the Signal to Noise Ratio to prove how good they are. Made a post about it. The craftymech Test Pattern Generator looks ideal for RGB except I don't want to buy another set of RGBS cables and solder them on. Well, I'd have to solder with SNES and PlayStation Multiout pins.

Can I not just use a computer with VGA Out + sync combiner for RGBS and a vintage VHS/DVD Recorder with Composite, S-Video and Component out for the full test suite and send across the cables to capture card or back to the Recorder itself? In the end I need a perfect control image or pattern and the version that comes out the end of the cables to compare to.