Amiga RGB to S-Video + composite adaptor

[alexh]

Originally Posted by Zetr0

Svideo on the other hand is digitally encoded and can easily carry RGB information on its Y / C lines and Ground . so yes it will be like using the RGB output from the Amiga into an RGB monitor

Svideo is analog, and it has 33% less bandwidth than RGB, Svideo is converted back into RGB inside a TV (which is a lossy process). Svideo is better than composite but worse than RGB

[Zetr0]

@alexh

indeed, narmi just reminded me (view post above).... I have been working with LCD panels all last week... so thats my excuse for crap i was typing....

I was going to ask if anyone here knows much about the ST video port, I have been approached to see if a SVideo version could be made for it....

I have some pin out references, with the exception of only +12 and the requirement to set pin 4 high (not sure with how much voltage) surely i could use the composite video as csync ? the rest is quite elementary



heres a link to the Atari video port pin out
http://pinouts.ru/Video/AtariStMonitor_pinout.shtml

[narmi]

The Atari video port has seperate HSYNC and VSYNC outputs, which the AD724 will happily accept and combine into CSYNC internally (my original design did this). The only thing missing is a 5V supply as you mentioned. You could make small voltage regulator circuit to get a 5V supply from the 12V line.

Pin 4 might be pulled high internally so that its voltage doesn't float when the pin is not connected, in which case you do not need to touch it. Sounds like a doable project to me.

[digit01]

Please don't forget about me being on the list

[Methanoid]

Zetro, I am impressed. If I understood half of what was going on I am sure I'd be even MORE impressed!! Looks very good!!

[alexh]

Originally Posted by Zetr0

I was going to ask if anyone here knows much about the ST video port

What do you want to know, it has the same active signals as the Amiga one.

Originally Posted by Zetr0

I have been approached to see if a SVideo version could be made for it....

I am sure it could. The only thing to bare in mind is the ST programs frig with the sync far more than Amiga. You'd have to try them to make sure they work with demo's with sync-scrolling and overscan before you sold them.

Surely i could use the composite video as csync ?

Yes, remember that signal _is_ csync on as much as 50% of all ST's (i.e. all of them without modulators)

Also bare in mind you'll struggle to get 13-pin DIN plugs without buying in bulk. AFAIK they dont make DIN plugs which solder direct to PCB's.

[Jope]

It's a very strange plug indeed.. Is it a real DIN standard?

[DrF]

Originally Posted by Jope

It's a very strange plug indeed.. Is it a real DIN standard?

Nothing like looking at the real thing, I'll dig out 1 of my ST's and have a look
All I find online are the pin outs and no pictures at all :/

EDIT : best I found so far ;

[Zetr0]

@DrF

If i build one, will you test it for me m8? (as i don't have an ST)

hmmm those plugs luck suspiciously familiar.....

[alexh]

They used to sell them at Maplin Electronics and while they have been removed from the catalogue, you may be able to get them at your local store (assuming you have one).

I would offer to test, but I dont have any SVideo capable TV's (that I know of) cept the TV card in my PC (not really a good test).

I should point out that there is already an Atari Svideo PCB that has been "in development" for some time, but is not currently available.

http://www.atari-forum.com/viewtopic...er=asc&start=0

http://img248.imageshack.us/img248/1...rivga41xm0.png

[DrF]

Originally Posted by Zetr0

@DrF

If i build one, will you test it for me m8? (as i don't have an ST)

hmmm those plugs luck suspiciously familiar.....

Yeah, no problems
I'll see if I can dig out a STFM for you since market value is pathetically low, it would not be worth selling.

While Googling I came across a ST to VGA dongle like thing, but it would only work in the Hi-Res mode of the ST, so I think games is outta the question for that unit :

http://www.1632-sales.zenwebhosting....marioB_2dSTVGA

[alexh]

This dongle is similar to the Commodore Silver dongle. It is completely passive. It 's just wires.

The Atari ST Hi-Res monochrome mode is 31KHz 70Hz and is compatible with regular VGA monitors.

No games or demo's use it. Only serious GEM stuff. It's sort of like DBLPAL and DBLNTSC screenmodes, except it is Monochrome.

Just drive 1-pin high and it will enable and force this one screen mode.

[Zetr0]

I just found this little source... (for 13 pin dins)

http://www.radioworld.co.uk/~radio/c...in-p-2952.html

now all i gotta do is find a cheap enough regulator and cap and away we go...

[Zetr0]

Okay, revised the external deluxe a little to include a switch for NTSC or PAL

Its virtually identical to the one shown here, except a slight layout change to allow for an 7805 5volt regulator

I could use a once over on the design, I think i have it I would eventually like to redesign this once I get my hot-air station and SMD components soon

anyway heres the ATARI SVC (SVideo / 15Khz VGA / Composite) with a swichable NTSC / PAL, all new units will be designed with this layout (except regulator)

okay click image for larger image(s)



heres the eagle board

http://www.guildserver.co.uk/project...29729158ff6671

that should put that old AtariST Svideo project back on track.

If you do decide to offer these for sale also then put me down for one.

Would be nice to get a readable screen in medium res on the tv.

[Zetr0]

@bobsmith2012

Hello there,

Welcome to the EAB, I am sure you will like it here

theres plenty of mischief to get involved in and read about, so kick back relax, and revel in complete and deserved Retr0-dom

if you are interested in a unit, then heres the thread to reply to

http://eab.abime.net/showthread.php?t=32807

I would like to point out that I am not making any money on these, its at cost to me, its my way of giving something to an awesome retr0 community

[alexh]

Looking at the "pass through" to the 15-pin RGB connector, I dont think they will work correctly as you have 75ohm pull down resistors on those signals.

You need 8073 op-amps as seen on the Atari circuit diagram.

These are suggested in the design document for the AD72x series chips when implementing pass through.

What the effect will be I dunno... I would guess that the picture will be dimmer / wrong colours?

@Zetr0

Thanks for the welcome.

Already replied to the thread you indicated for the Amiga version was meaning the Atari version with my post here as I have both a 520stfm and a 1040stfm as well as a couple of Amigas.

[Zetr0]

@bobsmith2012

well depending on funds I may well buy the bits to make it if i do, you can have it for component cost

@Alexh

Thanks for those links, damn handy, especially that schematic.

I will run a test tuesday on one of the boards to see what the output will be without the op-amps, I am sure it will work okay, I am just curious to see if what effect, if any it might have.

if there is a picture/colour drain then i will re-design so that it includes the op-amps for both the Amiga and Atari ST.

I appreciate the heads up thankie

[Zetr0]

@alexh

Just a question, I am having trouble finding the 8073 op-amps, so i was wondering if i could substitute three 8073 op-amplifiers for one AD8073 tripple video amplifier?

http://images.google.co.uk/imgres?im...%3Den%26sa%3DN

theres the component I have been thinking of using...

also I have been thinking of using the LM324N, (Quad Op Amp) although I will only need 3 inputs there quite cheap and the source is bounty full

If not could anyone suggest a compatible op-amp for this project?