New development: GTIA in CPLD

[Heaven/TQA]

Interested.... can the hardware checked if plugged in?

 

And will it be plug n play?

[Simius]

There is no way to detect it yet. But I would think to make it.

[retrorgb]

So, this would work with both Atari 8-bit computers and the Atari 5200? I'm definitely interested.

Edited November 5, 2016 by retrorgb

[ApolloBoy]

I'm not sure, but I suppose about US$50-60.

Sold.

[Marius]

That seems pointless considering most A8s already have composite video available on their monitor ports.

Not as pointless as it seems.

 

There is already a fix for all known comp. video issues... so I thought an comp video output on the pcb would provide a perfect comp video. (Bypassing the not so good circuit on mobo's)

[Marius]

@Simius

 

Let me ask it different:

Will the benefits of this new GTIAthing also be seen on the stock Composit Video output of the Atari, or is it only visible through RGB?

[+mytek]

Price sounds good, but due to lack of RGB on newer TV's I would only be interested if it had a more compatible output. And out of all the possibilities it would seem that transitioning over to component would be the easiest from RGB. Same number of outputs and very similar in many aspects. Any thoughts on this?

 

- Michael

[+remowilliams]

Sounds interesting.

 

Interested

[ApolloBoy]

Price sounds good, but due to lack of RGB on newer TV's I would only be interested if it had a more compatible output. And out of all the possibilities it would seem that transitioning over to component would be the easiest from RGB. Same number of outputs and very similar in many aspects. Any thoughts on this?

You could just use an RGB to component converter (they're on eBay for around $40-50), or you could have this internal solution from the creator of the 2600RGB. You use the pre-existing luma signal in addition to the RGB signals.

[Bryan]

It's really no harder to output Component than RGB.

[+mytek]

You could just use an RGB to component converter (they're on eBay for around $40-50), or you could have this internal solution from the creator of the 2600RGB. You use the pre-existing luma signal in addition to the RGB signals.

 

First a simple explanation of the difference between RGB and Component video (quoted from another forum)...

 

"The difference between RGB (which is a kind of component video actually) and "component video" (YPbPr) is this: RGB has separate signals (each on its own pin) for red, green, and blue, while YPbPr has luminosity, and then a signal with the difference between blue (the b in Pb) and luma, and then another signal with the difference between red and luma. The green component is then "filled in" from this information. YPbPr is used instead of RGB apparently because it uses fewer signals - RGB not only has the three signals, but it also has other signal pins, i.e. HV (two syncs, one horizontal and another vertical, for RGBHV, or S in RGBS, which has both syncs on one wire; there are a few other formats too like Sony's "sync on green," RGsB)."

 

So my thinking is that most likely all that is required hardware is already present in this new GTIA video board to produce Component, and it would likely require a CPLD to accommodate it. And without researching it more, I suspect that Component video is a more 'universally' available interface for both the Americas and Europe compared to RGB, which is primarily available in Europe. And as such, if there were a way to change this new video board to output Component video instead, then no converter what-so-ever would be required.

 

However I leave this to the discretion of the creator, since I was simply stating 'my' preferences

 

 

It's really no harder to output Component than RGB.

 

"ditto"

 

- Michael

Edited November 5, 2016 by mytekcontrols

[Bryan]

(my point is....)

Once you've implemented GTIA in logic, the output stage can be anything you want. You have a pixel color ID from 0-255 and that must go either into a LUT or some equation to generate the desired type of video.

[ricortes]

Are you still use the MB crystal? A 14.318 MHz<US side of the pond> divided down by the CPLD may offer some advantages for the future.

[Synthpopalooza]

OK, a curious question:

 

We all know that in Graphics 9, setting the background to a non-zero value affects the number of shades that will be produced.

 

With this new GTIA board, what happens if you, for instance, store the value $01 in COLBK? Does the background suddenly become one shade higher, but you still keep the same 16 shades?

[jvas]

Interested!

[Synthpopalooza]

Another question: Rybags mentioned shifting the Graphics 10 pixels back a color clock so they would match with hi-res graphics. Is there any way to pull the opposite trick: Shift Graphics 11 pixels or Graphics 9 pixels one color clock right, so that you can get a 160x192 HIP-style mode but with 256 colors?

 

Also: Does this mean that Graphics 0, text color (COLPF1) can now be independent from the BG color? (COLPF2) ... if so, this opens up all new sorts of possibilities.

 

It would be super cool if the extra colors in Graphics 10 (colors 9 through 15) could be made independently programmable, so we could have a full 16-color Graphics 10 mode. That was one thing I wish the original Atari designers had worked more on.

[sanny]

interested, would buy one

[Lord Thag]

Also interested

[Simius]

@ProWizard
Only through RGB. No impact on the composite.

@MytekControl
That's why I asked about component. I'll try to make it.

@Ricortes
The device uses a clock signal (3.54MHz or 3.58MHz) from MB as a base for x8 PLL multiplier.

@Synthpopalooza
1. Yes. Each shade is OR-ed with the COLBAK register. The device has the same property. If you write #01 to the COLBAK register, each shade will have the least significant bit set
2. No. You want to shift the pixel before decoding. I talk with Rybags about shifting it after.
3. Yes. Text color in hi-res is independent from the COLPF2.
4. Unfortunately, there is no address space for additional 7 color register and not enough resources in CPLD.

[robbievgb]

I'd also be interested if it works on the 5200 at the price range you quoted.

 

Sent from my SM-G920P using Tapatalk

[Bryan]

@MytekControl

That's why I asked about component. I'll try to make it.

This book is a big help. I don't know if more of it is online or not.

 

http://www.cs.ucsb.edu/~mturk//Courses/CS181B-2013/Misc/VideoDe.pdf

[Mathy]

Hello guys

 

On the XE series, would it be possible to use the 14.318 crystal that's already on the board?

 

A lot of older monitors here in Europe don't have Component Video but do have RGB on the SCART connector. Would it be possible to either support both, or divide the PCB design into two smaller PCB's? One with the GTIA (which everybody would need) and the other with either the Component Video or the RGB supporting hardware (you'll choose what goes best with your monitor)?

 

Sincerely

 

Mathy

 

 

[+MrFish]

This book is a big help. I don't know if more of it is online or not.

 

http://www.cs.ucsb.edu/~mturk//Courses/CS181B-2013/Misc/VideoDe.pdf

 

Here's a version that has 939 pages; it's also a newer edition.

 

Video Demystified

Edited November 6, 2016 by MrFish

[+mytek]

 

So my thinking is that most likely all that is of the required hardware is already present in this new GTIA video board to produce Component video, and it would likely only require a change in the CPLD to accommodate it.

 

Well that is what I meant to say. I was too much in a rush this morning, and my thoughts got all jumbled up.

 

 

@MytekControl

That's why I asked about component. I'll try to make it.

 

 

Glad to see you still figured out what I was trying to say. And I would definitely be interested in a Component video version of this, so count me in for buying at least one of them in this form, if you decide to do it

 

- Michael

[venom4728a]

Also would like to buy 1 or 2

 

Robert