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New development: GTIA in CPLD

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Not to mention, these *are* atari *computers* we're talking about here, dunno why you are all trying to use them on TV's anyway ;)

 

So that's what I've been doing wrong :ponder: :rolling:

 

- Michael

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I got this coming...

 

s-l1600.jpg

 

Hopefully this will work better doing PAL RGB from Sofia. Can anyone out there confirm doing the same?

 

- Michael

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Sophia connected to Atari SC1224 'ST' RGB Monitor

 

Live picture 1088XEL in PAL Mode

 

HCMxGRn.jpg

 

This will not work from a standard Sophia board, since the SC1224 Monitor requires higher level signals than VGA (or likely other RGB monitors). The Sophia only puts out 0.75 volt RGB and CSYNC when set to RGB mode (at least my Sophia running the 'B' core did). The SC1224 requires 1 volt RGB and close to logic level CSYNC. So the first thing I did was change a resistor on the Sophia board to increase the video output from the ADV7125 Triple High-Speed Video DAC chip.

 

Increase Video Output Level Mod (opps I see there is an extra '2' shown for the monitor part number :P )

 

2lDYj23.png

 

 

Next we need a buffered logic level CSYNC to substitute for Sophia's low level one, so we'll steal that from the CD4050 chip on the A8.

 

TQVf0Nw.jpg

 

 

And assuming all the Mods were done correctly you should now see a beautiful full color display on the SC1224 Monitor coming from your Sophia upgraded A8. And depending upon what video mode you use on your A8 (NTSC or PAL), you might need to tweak some of the back panel controls for V and H Hold, and possibly Vertical Position and Height, as well as Horizontal Position. I have only tested this on the 'JVC' version of the SC1224, so I have no idea if it'll work correctly on either the Goldstar or the Samsung models.

 

Disclaimer: This Mod is done at your own risk, will probably violate any warranty you may have, and is not endorsed what-so-ever by Simius (creator of the Sophia board).

 

- Michael

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I got this coming...

 

s-l1600.jpg

 

Hopefully this will work better doing PAL RGB from Sofia. Can anyone out there confirm doing the same?

 

- Michael

If you have a VBXE installed and replace the NTSC Antic with a PAL Antic, it will work. I did this. I have only experienced a few PAL demos not working. But, so far, all PAL games work.

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If you have a VBXE installed and replace the NTSC Antic with a PAL Antic, it will work. I did this. I have only experienced a few PAL demos not working. But, so far, all PAL games work.

 

That is very Interesting, but I'm actually running as a true PAL machine in every regard so all games and demos should work as they were meant to (fingers crossed).

 

My photo doesn't even do it justice as to how good this looks on the SC1224 monitor. There's just something about a CRT RGB monitor that is very difficult to match with an LCD. Now of course if we were talking HDMI that would be the ultimate, but we have yet to see native support for that in a real A8 machine. And with Sophia being about 1/2 the price of a VBXE (when factoring in shipping), it's really the best you are going to do at that price point. Now of course the VBXE has a few tricks up it's sleeve, but other than the 80 column mode, most of those tricks require specific software support to see them in action. And when considering how long the VBXE has been available, that support is still kind of sparse.

 

Since the 1088XEL doesn't have a CD4050 video/sync buffer chip, it needs to be implemented with a separate one transistor (Q11) buffer as shown in this schematic...

 

mhjB3kR.png

 

 

This circuit produces a 3.3 volt CSYNC signal, and is what I was using to generate the display I showed in the photo of the SC1224.

 

- Michael

Edited by mytekcontrols
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This will not work from a standard Sophia board, since the SC1224 Monitor requires higher level signals than VGA (or likely other RGB monitors). The Sophia only puts out 0.75 volt RGB and CSYNC when set to RGB mode (at least my Sophia running the 'B' core did). The SC1224 requires 1 volt RGB and close to logic level CSYNC. So the first thing I did was change a resistor on the Sophia board to increase the video output from the ADV7125 Triple High-Speed Video DAC chip.

 

2lDYj23.png

 

 

Michael, cool stuff!

 

Also thanks for pointing out the resistor change. I´ve experienced several problems with Sophia and some monitors connected using the SCART interface (very common in Europe). Also I recognise the weak levels at RGB output lines. SCART also demands 1V levels. So this may be "the" issue. Will try it out...

 

:thumbsup:

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SCART RGB signals are 0.7Vpp @ 75ohm. 1Vpp level is required on the CVBS input, because the SYNC pulses (0.3V) are added.

http://cncms.com.au/SANYO-IMs/FAQs/scartconnector.pdf

On the eclaireXL we've been using the CDK3405 which is similar but cheaper to the ADV7125 I think.

 

RGB is great, though for composite I'm not sure if I need to boost composite beyond 0.3V sync + 0.7V for the signal. I tried it the 'Atari way' with stepped luma. Using 90/256 * 0.7v for the colour signal (fixed amplitude, phase shifted for hue) + brightness*11/256*0.7v for the luma. Still it seems not quite bright enough to me.

 

Anyway I'm just curious if you've tried composite from the Sophia?

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On the eclaireXL we've been using the CDK3405 which is similar but cheaper to the ADV7125 I think.

 

RGB is great, though for composite I'm not sure if I need to boost composite beyond 0.3V sync + 0.7V for the signal. I tried it the 'Atari way' with stepped luma. Using 90/256 * 0.7v for the colour signal (fixed amplitude, phase shifted for hue) + brightness*11/256*0.7v for the luma. Still it seems not quite bright enough to me.

 

Anyway I'm just curious if you've tried composite from the Sophia?

 

CDK3405 is cheaper but I've more trust for Analog Devices. :)

I've not tried to make composite from Sophia because I don't like composite at all. I think a low quality interface isn't worth the time spent on it. Unless for fun.

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Sophia board if possible connect to a sc1435? i have one of this, and have a db9 style connector if im not bad.

 

thx!

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CDK3405 is cheaper but I've more trust for Analog Devices. :)

I've not tried to make composite from Sophia because I don't like composite at all. I think a low quality interface isn't worth the time spent on it. Unless for fun.

 

That's only because Europeans have no appreciation for the early games that used artifacting for color. Ultima III, Choplifter, David's Midnight Magic, are all monochrome with this board.

Edited by GlowingGhoul

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I've been using my Sophia board for driving into two different SC1224 ST monitors lately with a PAL setup, and although it looks very, very cool, and produces the best image I've seen thus far, the color pallete still appears to be not quite right. In particular light (pale) blues are not quite right, being more on the greenish side of things. So for instance, the normally light blue background in Basic looks more cyan, and in Star Raiders when you enable the shields it's light green instead of light blue. Is it just me, or are others seeing this as well? Keep in mind that I am using a PAL system, and that this has been verified on two different SC1224 monitors.

 

I'm also using the latest Sophia firmware revision.

 

- Michael

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My stock PAL hardware all produces cyan backgrounds. I've tested a Sofia here in RGB mode and it looks right to me (identical to VBXE).

 

I guess all is ok then :)

 

- Michael

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Forgive me, Simius, but I couldn't make it through all 30 pages of this thread to find out... is this a thing that I can buy for a 1200xl that will give me rgb output? (I was tuckered out by page 27.) I don't want to hack up the motherboard to do a composite mod, which goes against my "first do no harm" retro hardware edict.

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Forgive me, Simius, but I couldn't make it through all 30 pages of this thread to find out... is this a thing that I can buy for a 1200xl that will give me rgb output? (I was tuckered out by page 27.) I don't want to hack up the motherboard to do a composite mod, which goes against my "first do no harm" retro hardware edict.

It should work on a 1200XL just fine, it even works on a 5200 without any problems.

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is this a thing that I can buy for a 1200xl that will give me rgb output?

 

Yes, it is.

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Firmware update.

1. Our5oft issue fixed.

2. bit4 PMCTL controls additional color in hi-res mode.

3. VSYNC output comes back in rev.B.

 

Please report any comments.

I tested new firmware and now Our5oft demo is perfect.

Thank you very much Jacek!

 

Can you please explain:

bit4 PMCTL controls additional color in hi-res mode.

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I wish the first message in the thread could be updated with ordering info, but as far as I can tell the "Sophia" costs $55 plus shipping from Eastern Europe, order by PM'ing Simius. I gather the thing goes out to a db-9 connector and is suitable for a Scart-to-hdmi conversion box if you make a Scart cable for it.

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H

 

 

 

Hi , is this still around, where can I purchase one? :)

 

I hope he is around, and keeps selling this board, because the 1088XEL has been modeled to allow this to be dropped in and directly drive Atari SC1224 monitors (well with a very small mod, change a resistor and add one more crimp connector on the existing cable). Works great :thumbsup:

 

- Michael

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I just sent an order inquiry, I gather I need to start reading this whole thread, to find out what I'm in for. I'm hoping I won't need to cut holes in the case or pull out existing components, although some soldering of wires might be OK.

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