Atom RGB port?

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roganjosh
Posts: 10
Joined: Fri Oct 01, 2021 3:40 pm
Location: Leeds

Atom RGB port?

Post by roganjosh »

Here's a slightly cranky one. Does anyone know whether a version of the HogletColourBoardV3 for the Atom was ever ported to the Dragon? Here is a zipped pdf of the Atom schematic:
HogletColourBoardV3.zip
(80.01 KiB) Downloaded 210 times
Having had some spare time to mess around I built one, seeing no immediate reason why it would be grossly incompatible. Having connected the PA,PB,CHB & Y lines directly to the 6847 I did manage to get an output of sorts using an Extron DVS 204, but no signal on a GBS8220. On the Extron the main black-on-green screen appeared towards the bottom right of the screen surrounded by lots of impressionist stuff. The top third of the green-black area was white, the bottom two thirds accurately displayed the black-on-green text. Video electronics isn't my strong point. Am I missing something fundamental that would cause such incompatibility or should it work? I tried with and without 220R & 270R on the RGB side.

At the level of getting a good Dragon display the above may be rendered moot as today I've received an RGB2HDMI board with an Analog interface. Something to play with tomorrow, but it'd be nice to know what was going on with the Atom board though.

Alan
Azerpy
Posts: 54
Joined: Tue Apr 09, 2019 1:16 pm
Location: France Pyrenées

Re: Atom RGB port?

Post by Azerpy »

Hello Alan
I have no idea about these schematics, but if the Atom has the same 6847 IC, that should work.
It would be nice to see the output signals on an oscillscope.
I think that the result depends on the screens you use
I don't speak here about RGB outputs for VGA with TTL levels (5V)
I have got a RGB Dragon and a RGB Coco2, so I am sure to have the correct R, G, B and synch signals that work well :
- on a TV with a SCART RGB input
- and also on a good SCART RGB to HDMI Converter
But, doest'nt work
- with many monitors because they don't accept 15,5 kHz Hsynch or 50 Hz VSynch
- with other SCART to RGB Converters, don't know why
- with the GBS 8200 ; I read once that someone could have a stable picture, but never me !
I don't know your EXTRON scaler, seems interesting.
It's a nice subject.
Let us wait a little, the experts (that all are on FB ... ) will come.
Gérard
prime
Posts: 266
Joined: Fri Apr 10, 2009 1:40 am

Re: Atom RGB port?

Post by prime »

Hi all,

If it's the one that plugs into the 6847 socket, I did design an adaptation of Hogelt's board for the Dragon (and the Atom, but Atom version is more problematic). The later version also integrated the Dragon 200-E character generator that JohnW reverse engineered.

It worked reasonably well, but in some ways the RGB2HDMI removes the need for it.

Cheers.

Phill.
roganjosh
Posts: 10
Joined: Fri Oct 01, 2021 3:40 pm
Location: Leeds

Re: Atom RGB port?

Post by roganjosh »

Thanks all.

It seems that's time enough for all to reply who might do so. However, if you happen to remember what the problems were in adapting the Hoglet board to the Dragon my curiosity is still piqued (but isn't itching quite as much now that the RGBTOHDMI is hooked up).

Alan
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