• Please review our updated Terms and Rules here

CGA (digital) to VGA/Component/HDMI

maxtherabbit said:
And now I remember why I didn't go for it before. Only supports RGBI, I want 6 bit RGB
Click to expand...

Are you wanting something that does 350 line EGA modes, or is this for a non-PC machine that has digital 6-bit RGB? If you don't care about impedance matching you can convert six-bit RGB with just a resistor ladder. But this converter won't do the right thing when you switch to 200 line mode with EGA, EGA does maaaagic in the monitor to decide what color space it should use. It might be possible to program a GAL to do it, but it might need some extra circuitry to make it switch modes.

(EGA monitors use the polarity of one of the sync signals to decide whether to use the EGA or CGA color spaces, I think? You'd have to somehow detect that difference on the adapter. Or, I guess, you could manually throw a switch.)
 
I was looking for medium res EGA support. I can probably live with low res only though, I'll still give it a go
 
Hmmm, the GBP8200 can supposedly scan-double stuff higher than 15 KHz. It'll do all those modes you mention, I think. So with some TTL-analog RGB conversion, I'd think it would do the higher rez IBM modes. Although it might require a multisync VGA monitor, I dunno.
 
maxtherabbit said:
nah, in arcade parlance:

15 kHz = low res
22-24kHz = medium res
31kHz = high res
Click to expand...

Ah. Not familiar with arcade-speak, alas. ;)

Looking at the schematic for the GGlabs CGA2RGB it has four unused I/O pins (three input only, one bidirectional) on its GAL16v8 so it would be trivial enough to connect all the outputs from an EGA card up and, for rev1, add a toggle switch that determines if the output resistor ladder gives you all 64 colors straight across (IE, just acts like a DAC) or interprets the inputs as RGBI and gives you the CGA 16 color palette on the output. The hard part, again, would be choosing which is apropos automatically. If throwing a switch doesn't bother you then, well, easy-peasy.

Has anyone actually demonstrated 350 line EGA on a GBS-8200? In this thread it's claimed that EGA's scan rate is *just* too low for the board to sync up with, it's lower than the arcade standard.

EGA almost certainly *will not* work on a SCART converter or whatever, obviously.
 
Eudimorphodon said:
Has anyone actually demonstrated 350 line EGA on a GBS-8200? In this thread it's claimed that EGA's scan rate is *just* too low for the board to sync up with, it's lower than the arcade standard.
Click to expand...
that's a big reason why I want such an adapter, to try it out with the GBS-Control custom firmware

I see no evidence in the datasheet of the TV5725 being limited to narrow, separate ranges of h-sync, and can only assume it is a limitation of the OFW

the datasheet specifies a range of valid pixel clocks from 10-162MHz
 
bladamson said:
PS: Even though everyone and the entire rest of their family makes Commodore Repair Videos on Teh Youtoobs, it would be an interesting project to film. What do you think is wrong with it? I have a Daewoo one that I need to fix the audio amp in, but I've been putting it off because I don't want to make Yet Another Commodore Video, heh.
Click to expand...

I have no idea specifically went, although I do of course plan on tearing into it. My first guess is everyone's favorite retro-boogieman, a capacitor venting, since I *swear* I actually heard a "pffft" sound when the power failed, but I'm concerned about the fact that I didn't smell any bad-cap smell (or any other kind of burning or other rankness) when it died, which I would have kind of expected if the magic smoke escaped from something. My other 1084 has a bad solder joint or *something* that requires some percussive maintenance sometimes, but no amount of whacking would get this one running, so if it's also just a bad connection it failed more catastrophically/completely.

The really annoying part is that it was only about a month ago that I finished building a cable to use this monitor precisely so I could give the one with the iffy joint I haven't been able to find yet a break. (The monitor that just died is a 1084S, which has round DIN connections for separate analog and digital inputs, while my other is a 1084D with a single switchable 9-pin port. I love how they're both "1084s" but obviously completely different monitors from different OEMs.) I *hate* soldering din plugs...
 
I grabbed a gglabs ver2 unit for $40. I'll let y'all know how the GBS handles 350 line EGA with the CFW
 
I did a quick skim through the thread and didn't see the open source RGBtoHDMI mentioned:

https://github.com/hoglet67/RGBtoHDMI/wiki

It'll cope with CGA/EGA, needs a small adapter board attached to a Raspberry Pi Zero - it'll even do artefact colours from CGA. I know IanB who's been doing a lot of the more recent work on it has been getting a run made in China. Mostly described in this thread on stardot:
https://stardot.org.uk/forums/viewtopic.php?f=3&t=14430

I'm using it with a BBC Micro and RM480Z (both of which are TTL-RGB, the BBC Micro having a very funky interlaced Teletext mode) and it deals with both admirably.
 
drdanj said:
I did a quick skim through the thread and didn't see the open source RGBtoHDMI mentioned:

https://github.com/hoglet67/RGBtoHDMI/wiki

It'll cope with CGA/EGA, needs a small adapter board attached to a Raspberry Pi Zero - it'll even do artefact colours from CGA. I know IanB who's been doing a lot of the more recent work on it has been getting a run made in China. Mostly described in this thread on stardot:
https://stardot.org.uk/forums/viewtopic.php?f=3&t=14430

I'm using it with a BBC Micro and RM480Z (both of which are TTL-RGB, the BBC Micro having a very funky interlaced Teletext mode) and it deals with both admirably.
Click to expand...

It was mentioned earlier in a few posts. In fact, that's how I found out about it. I am really excited about this option. So much so that I have already ordered 5 boards and enough parts to build two of these. Total cost per unit will be somewhere around $22 including a RPi ZeroW or $17 with the plain RPi Zero, but not including the shipping costs. I should have three extra boards when I am done. If you want one, send me a PM.

The support so far for various systems is really good and you can add custom profiles for the oddballs out there. You can even program the CPLD chip right from the RPI once the daughterboard is built and connected.

Acorn Atom
Acorn BBC Model B / Master
Acorn Communicator
Acorn Electron
Amstrad CPC
Camputers Lynx
Color Genie
Commodore 128 (80 coluln TTL text output only)
Dragon 32
IBM PC CGA
IBM PC EGA
IBM PC MDA
IBM PC VGA (9-pin TTL only, aka EGA+)
Nascom II
Olivetti Prodest PC1
Oric 1
Sinclair QL
Sinclair Spectrum 48K (no bright colours)
Sinclair Spectrum 128K +2
Sinclair Spectrum 128K +2A
Sinclair Spectrum 128K +3
Sinclair ZX80
Sinclair ZX81
Superboard II
Tandy Co Co
UK101
 
MajorMar said:
It was mentioned earlier in a few posts. In fact, that's how I found out about it. I am really excited about this option. So much so that I have already ordered 5 boards and enough parts to build two of these. Total cost per unit will be somewhere around $22 including a RPi ZeroW or $17 with the plain RPi Zero, but not including the shipping costs. I should have three extra boards when I am done. If you want one, send me a PM.
Click to expand...

I've managed to do myself what I've oft criticised others for doing :D not reading the entire thread before posting. Excellent though - I have to say I'm really impressed with it - for the colour depths it can cope with I'd argue it's better than the OSSC simply as it can handle interlace properly!
 
drdanj said:
I've managed to do myself what I've oft criticised others for doing :D not reading the entire thread before posting. Excellent though - I have to say I'm really impressed with it - for the colour depths it can cope with I'd argue it's better than the OSSC simply as it can handle interlace properly!
Click to expand...

Have you done any testing to determine how much lag it introduces? (That's a huge critical deal to some people. Personally, well, I'm not too bothered unless it's *bad*.) Might be interesting if you have a machine that has both RGB and composite outputs to hook a CRT to the composite, set it alongside the monitor connected to the Pi, and record with a 60fps video camera a program that rapidly changes the screen to see if the lag is more than a frame or two.
 
Eudimorphodon said:
Have you done any testing to determine how much lag it introduces? (That's a huge critical deal to some people. Personally, well, I'm not too bothered unless it's *bad*.) Might be interesting if you have a machine that has both RGB and composite outputs to hook a CRT to the composite, set it alongside the monitor connected to the Pi, and record with a 60fps video camera a program that rapidly changes the screen to see if the lag is more than a frame or two.
Click to expand...

This should answer your Q:
https://stardot.org.uk/forums/viewtopic.php?t=14430#p192330 :)
 
Eudimorphodon said:
Guess it's time to get off my butt and order a Pi Zero. :)
Click to expand...

Good work :) (I've genuinely been blown away by the quality and wondering how I ever put up with a GBS8200, or even Extron DVS204!)

Edit: I should note, it does implement genlocking now.

d.
 
Unless you are slewing a VCXO, it's impossible to have true genlock. You can match timing.. but that's not genlock in a broadcast studio sense. Amiga users have so corrupted the meaning of that word.
 
eeguru said:
Unless you are slewing a VCXO, it's impossible to have true genlock. You can match timing.. but that's not genlock in a broadcast studio sense. Amiga users have so corrupted the meaning of that word.
Click to expand...

OK, it matches timing :) I'll leave you to have the discussion with the Amiga bods (they're probably too busy replacing capacitors in everything in the house to notice what's going on anyway).
 
drdanj said:
OK, it matches timing :) I'll leave you to have the discussion with the Amiga bods (they're probably too busy replacing capacitors in everything in the house to notice what's going on anyway).
Click to expand...

Hah, that made me laugh! Besides, they do take a break from replacing capacitors to tell you how their computer was the 'way ahead of it's time'.... even 35 years later when no-one cares. :)

Anyway, has anyone converted the RGB to HDMI to gerbers they can send over? I can convert it from kicad myself, but I'm being lazy if someone has already done it to have their own boards made.
 
You must log in or register to reply here.
Back
Top