RGB adapter to SVideo/Composite for CPC based on AD724

[antoniovillena]

Hi


I have released this little board.








It's made with Eagle. The sources are here.

http://www.atc.us.es/svn/zxuno/hardware/otros/ad724/
User: guest
Pass: zxuno

[Munchausen]

Great board!

But just so you know, @Bryce makes these too.

RGB SVideo - CPCWiki

His are S video only though. I added a composite connector (soldered to the AD724 pins), but you could easily just use an S-video to composite converter with it too.

[opqa]

For the sake of curiosity, why is there so much interest in Composite/S-Video outputs when, AFAIK, the best image quality is achieved with RGB? Is it just to be able to use the CPC with monitors without RGB/Scart connectors?

[CraigsBar]

For the sake of curiosity, why is there so much interest in Composite/S-Video outputs when, AFAIK, the best image quality is achieved with RGB? Is it just to be able to use the CPC with monitors without RGB/Scart connectors?

my thoughts exactly. I have not seen a European tv made anytime since the late 80's without scart, I was of the opinion that most us tv's had rgb input does anyone really use s-video anymore? Now and internal board to upscale the rgb to 720p hdmi, *that* would be different lol.

[McKlain]

AFAIK, the S-Video output is the best option for good quality video capture from real hardware.

[gerald]

my thoughts exactly. I have not seen a European tv made anytime since the late 80's without scart, I was of the opinion that most us tv's had rgb input does anyone really use s-video anymore? Now and internal board to upscale the rgb to 720p hdmi, *that* would be different lol.

In France, the scart plug is no more mandatory on TV sold since January 2015. You can be sure that manufacturers will not include it !

[antoniovillena]

Great board!

But just so you know, @Bryce makes these too.

RGB SVideo - CPCWiki

His are S video only though. I added a composite connector (soldered to the AD724 pins), but you could easily just use an S-video to composite converter with it too.

Yes, I knew the thread. I tried to continue this thread but It was old so I've created a new one.


Basically the board is the same. The only difference is that bryce one has S-Video connector in the board. Mine is not included, so you have freedom to allocate the board into the machine.


I've put a small batch in a spanish forum but it's sold out. So I publish here the PCB files if it's interesting to this forum to build yourselves. This board is very interesting to CPC users because this machine has not composite output (or RF to obtain composite).


http://zonadepruebas.com/viewtopic.php?f=8&t=5912&start=30#p52982

[Bryce]

Hi,
    nice board. I see you have also included the PAL/NTSC switch which I also left off because almost all CPC users are in PAL countries. Although I included the S-Video socket on the PCB, you can just leave it off if you want to fit it internally.

To answer the others: SCART is on its way out and even now many SCART ports on modern LCD TVs will only sync to a perfect signal (which many retro computers don't produce). By converting the signal to S-Video you get a picture that's just as sharp as RGB, but more compatible. It also means having just a thin S-Video cable to the TV instead of a fat SCART cable with one of the shittiest connectors that ever managed to become a standard

Bryce.

[Lazy Dude]

slightly off topic here but would the light gun work through a CRT telly that's working via s-video?
I love scart connectors they are the best things ever 

[Bryce]

slightly off topic here but would the light gun work through a CRT telly that's working via s-video?
I love scart connectors they are the best things ever 

Yes. I haven't tried it, but it should work properly.

Bryce.

[MaV]

Well, if SCART is on its way out, S-Video has been for a couple of years.
There hardly were new TVs with a proper S-Video connector, when I last looked, never mind the problem with the perfect signal which is a problem of (almost) all LCD TVs.

[Bryce]

SCART never made it to the US. They've always used S-Video instead and still do. So S-video might just live a little longer. I've certainly seen TVs without SCART but still with S-Video.

Bryce.

[Lazy Dude]

must be time to develop a CPC to HDMI kit for people then. Got to keep up with the times what!

[AMSDOS]

My Dad once brought a TV with SCART, but it's the only one we had and the store we got it from were almost giving them away. Depends really where you go here, one place had heaps of TVs with SCART, but were expensive you had to pay more just to get the Composite or Component connector - depending on what you wanted varied with price & most other places have the TV with Composite on them. Haven't seen a lot with SVideo though. My little TV (14") has a Component on it and the Onscreen display is sharp like a computer screen.

[Bryce]

must be time to develop a CPC to HDMI kit for people then. Got to keep up with the times what!

I've already looked into VGA and HDMI for the CPC. The problem is that you need more than just a format changer. Due to the higher frequencies you need to buffer the data. These are already available for very cheap (<€30) from China, so making a CPC spefic device isn't worth it. We should however test some of these and add some info on the Wiki (Connection How-to and reviews).

Bryce.

[roy bates]

my take on the s/video and rgb talk is,the us dont have scart for analogue rgb as far as i know so s/video(chroma/luma) is perfect for them.

anyway...how much will this be sold for please?

looks like a nice board,does it come as a kit? ready made? or both?

[Bryce]

The AD724 is only available in SMD, so it's not a Kit I would recommend for beginners.

Bryce.

[roy bates]

The AD724 is only available in SMD, so it's not a Kit I would recommend for beginners.

Bryce.

thats ok bud,i can handle it

but,i understand its not or beginners..


@bryce,is it me or is there a mistake on the schematic on the wiki page? theres two 75 ohm resistors on the green of the r,g,b signals on the input,but none on the blue?

[Bryce]

I wasn't implying that you're a beginner It was just meant as a general comment

Bryce.

[roy bates]

I wasn't implying that you're a beginner It was just meant as a general comment

Bryce.

i know mate,could you have a look at the edit a made just before you posted please you might be interested

[Bryce]

@bryce,is it me or is there a mistake on the schematic on the wiki page? theres two 75 ohm resistors on the green of the r,g,b signals on the input,but none on the blue?

Haha, well spotted! That schematic has been there for years and no-one seems to have noticed the mistake. I actually used a different Layout program to make the batch, so the real devices don't have this problem. I'll see if I can find the old file and correct it.

Bryce.

Edit: Schematic corrected.

[talrek]

Hi, if someone is interrested I have three left from an old batch made for myself, always Bryce's model [emoji1]

[pelrun]

I've already looked into VGA and HDMI for the CPC. The problem is that you need more than just a format changer.

1. Sniff expansion bus for VRAM/CRTC/GA data
2. Emulate CRTC/GA to generate video
3. Generate HDMI signal


It's probably too much work for too little benefit, but I do have a brand new minispartan6+ fpga board with HDMI outputs sitting on my desk wanting something to do (and I accidentally just designed an interface board... oops)

[TotO]

Just use a CPC to SCART cable and a SCART to HDMI converter.
That will allow to plug the CPC on old CRT/LCD TV as well as on new HDMI screen w/o scart input.

I have tested this working:


Be carefull, others old and bigger version (rectangular, not square) may not work properly with the CPC...
I have bought it 25$... But il look to be increased to 45$ now. (because people buy w/o looking good prices)

[Bryce]

I do something similar, but I use a very cheap S-Video to VGA/HDMI converter which is fed via my RGB to S-Video adapter.

The only problem (with all VGA / HDMI solutions) is the some CRTC tricks don't work properly because a digital picture can't change mid-frame like an analogue CRT could.

Bryce.