Apple IIGS RGBtoHDMI + Apple Macintosh Monitors

[RetroTheory]

So I recently got my first IIGS, but I am having no luck finding the monitor for it. I really wanted a CRT on it but none of the Macintosh monitors are compatible.

Along comes RGBtoHDMI https://github.com/hoglet67/RGBtoHDMI
This can take the Digital RGB signals from the IIGS DAC resistor networks and make a clean HDMI signal.

THE RGB signals are located on the DACs

Apple IIGS (12 bit RGB TTL)​

12 Bit Extender 16 way IDC	Motherboard	Notes
Pin 1 green0	H3 Pin 5
Pin 2 red0	H4 Pin 5
Pin 3 blue0	H2 Pin 5
Pin 4 green1	H3 Pin 4
Pin 5 red1	H4 Pin 4
Pin 6 blue1	H2 Pin 4
Pin 7 GND	H3 Pin 7
Pin 8 green2	H3 Pin 3
Pin 9 red2	H4 Pin 3
Pin 10 blue2	H2 Pin 3
Pin 11 RED3	H4 Pin 2
Pin 12 HSYNC	H1 Pin 3
Pin 13 GREEN3	H3 Pin 2
Pin 14 VSYNC	UF3 Pin 2 (74F86)	Flip 6 Also available on VGC Pin 49 and TP24
Pin 15 BLUE3	H2 Pin 2
Pin 16 +5V	H1 Pin 10	Leave unconnected if powering Pi externally

I then fed the wires out to the RGBtoHDMI

So the RGBtoHDMI is based on a CPLD and Raspberry PI. The PI always had definable video output. Meaning you can set your refresh rate and resolution to what you want and the PI will work with that. This also applies to HDMI>VGA converters so ..

Raspberry PI with HDMItoVGA connected to a fixed frequency Apple Monitor the M1212.

Here are the timings required in the config.txt of the Raspberry Pi


## 640x480 @ 67Hz
hdmi_group=2
hdmi_mode=87
hdmi_timings=640 0 64 64 96 480 0 3 3 39 0 0 0 67 0 30240000 1

Because the M1212 is composite sync we need to convert H + V sync to C-Sync.
6
BC548 680R
HSync ------------- ---------/\/\------o--------- CSync on Green
\ /!
\ /
---------
!
!
1k !
VSync ----/\/\----------

Sync-on-green

The Result is this:

And because the monochrome Apple 12" has the same timings this is also possible.

 

[Drake]

Very nice! I ended up selling my IIGS with monochrome monitor just so I could buy one with an RGB display lol
This board is in my project bin for a rainy day, really glad you showed this working.
Exactly what I'll be doing if the RGB monitor quits

 

[ScutBoy]

Looks great!

So the ribbon cable is being soldered down to the underside of the IIgs logic board? No criticism implied, but would there be a way to do this that's more reversable? I guess de-soldering wires wouldn't be that bad.

 

[RetroTheory]

Sure, the limitation is with the RGBtoHDMI analog to Digital. It does not have the bit depth if you connect to the external port as thats analog only. It works and looks good too but some cases have missing colours or reduced depth. I debated this too but since I am soldering to solder joints its reversible to an extent.

 

[davidg5678]

This is an awesome project! I saw your previous post on /VintageApple project several months ago, and I have been waiting eagerly to see how it was done.

I have a similar project going on, and I am also trying to connect a Raspberry Pi to my AppleColor High-Resolution display. I got very close to this goal in June, but I was trying to pass the Pi's video signals through a GBS-8200 first (along with a C-sync converter). I never thought to try changing the video timings directly on the Pi for modified VGA, but this seems like it will be perfect for my purposes.

I think with some tweaks, this should allow me to display an emulated Macintosh (or any other computer for that matter) on a real Mac CRT. I could even connect the appropriate ADB peripherals to the Raspberry Pi with an Arduino!

 

[Javmast3r]

There's also a good list of devices at http://www.apple2faq.com/knowledgebase/apple-iigs-modern-video-options/

 

[RetroTheory]

This is an awesome project! I saw your previous post on /VintageApple project several months ago, and I have been waiting eagerly to see how it was done.

I have a similar project going on, and I am also trying to connect a Raspberry Pi to my AppleColor High-Resolution display. I got very close to this goal in June, but I was trying to pass the Pi's video signals through a GBS-8200 first (along with a C-sync converter). I never thought to try changing the video timings directly on the Pi for modified VGA, but this seems like it will be perfect for my purposes.

I think with some tweaks, this should allow me to display an emulated Macintosh (or any other computer for that matter) on a real Mac CRT. I could even connect the appropriate ADB peripherals to the Raspberry Pi with an Arduino!

Yes indeed, actually I took a shot with the pi and a usb to adb adaptor (you can see it there on the right) All working fine, and attached a pic of the pi running the Mac emulator.

 

[Daniel Hansen]

Oh man, I'm so on the fence about this. I love this project a lot, and am so excited about its application to the IIGS. But for some reason I'm leery about having to solder directly to the board. I'm currently using a cheap RGB->VGA upscaler-based solution and it's merely okay, and I'm always looking for the proper RGB monitor, so this is looking like such a tempting solution... just kinda inconvenient? Maybe that's a weird thing to say in a tinkerer forum lol

 

[Michael's Workshop]

I really wanted a CRT on it but none of the Macintosh monitors are compatible.

Sorry, but aren't all of the 15khz analog RGB colour Macintosh monitors, such as from the Mac LC and up similar models, totally compatible with the IIgs? The connector is the same, and the signals on the pins should be the same?

Here is a pinout for the Macs from the LC and up, with the 15pin d-sub video port :

Apple Macintosh External video pinout and wiring @ old.pinouts.ru

Here is a pinout for the IIgs 15pin d-sub video port :

https://inanis.net/wp-content/uploads/2014/12/iigs-rgb-pinout.png

They look like a match to me? I am pretty sure I have used those particular monitors interchangeably between Macs and IIgs in the past.

 

[davidg5678]

Sorry, but aren't all of the 15khz analog RGB colour Macintosh monitors, such as from the Mac LC and up similar models, totally compatible with the IIgs? The connector is the same, and the signals on the pins should be the same?

Here is a pinout for the Macs from the LC and up, with the 15pin d-sub video port :

Apple Macintosh External video pinout and wiring @ old.pinouts.ru

Here is a pinout for the IIgs 15pin d-sub video port :

https://inanis.net/wp-content/uploads/2014/12/iigs-rgb-pinout.png

They look like a match to me? I am pretty sure I have used those particular monitors interchangeably between Macs and IIgs in the past.

The problem is that this just isn't a 15kHz monitor. It is a 35kHz horizontal, 66.7Hz vertical monitor. It is therefore not electronically compatible with the IIgs, despite the connectors being physically compatible.

If you compare the two pinouts that you posted, you'll find that many of the signals do not match between these two monitors, despite them sharing the same connector. Because they're different from each other, these devices are not compatible without some kind of conversion technology to adapt the signals between them. This thread is about how to convert the signals so that the Apple IIgs can display on a screen it was never designed to work with. I think another issue has to do with video sync signals: the Macintosh monitor utilizes C-Sync, but I believe the IIgs monitor is H/V-Sync.

 

[Michael's Workshop]

The problem is that this just isn't a 15kHz monitor. It is a 35kHz horizontal, 66.7Hz vertical monitor. It is therefore not electronically compatible with the IIgs, despite the connectors being physically compatible.

If you compare the two pinouts that you posted, you'll find that most of the signals do not match between these two monitors, despite them sharing the same connector. They are very different from each other, and not compatible without some kind of conversion technology to adapt the signals between them. This thread is about how to convert the signals so that the Apple IIgs can display on a screen it was never designed to work with.

YOUR Apple Macintosh monitor isn't a 15khz monitor. OK, but many other Apple Macintosh monitors are.
You said above that none of the Macintosh monitors are compatible with the IIgs, which I do not believe to be a true statement. There are many.

I did compare the pinouts I posted, before I posted them, and they are exactly the same 15khz analog video signals on the same 15pin video Macintosh / IIgs d-sub connector pins that matter.

PIN1 GROUND FOR RED
PIN2 RED VIDEO
PIN3 CSYNC
PIN5 GREEN VIDEO
PIN6 GROUND FOR GREEN
PIN9 BLUE VIDEO
PIN13 GROUND FOR BLUE

What am I missing?

 

[RetroTheory]

David is correct, there is more than just pin compatibility.
There are no 15Khz Mac monitors. The 12" LC monitor is 24.48kHz

 

[Daniel Hansen]

David is correct, there is more than just pin compatibility.
There are no 15Khz Mac monitors. The 12" LC monitor is 24.48kHz

I've heard this before, nice to see a measure of confirmation. Thanks for sharing that doc! As an aside - I wonder why the Apple 12" RGB Monitor isn't in that spec sheet?

 

[RetroTheory]

I dont know why its not in it. Maybe just overlooked.


The Apple AppleColor 12" RGB Monitor (A2M6014) designed for IIGS 15Khz , thats the monitor I am after but dont think I will ever find one
Specs below. This can work with some old Macintosh II cards that can output 640x200 NTSC,

Then the Apple Macintosh 12" RGB Monitor (M1296) designed for Macintosh 24.48Khz is in that previous document.

And lastly the Apple AppleColor High-Resolution RGB Monitor (M0401) for Macintosh 35Khz
I think this is just a confusing time for Apple monitors especially if you just go by the names of them.

 

[nottomhanks]

So, I have the Macintosh 17" Multiscan Display. Will this possibly work with the IIGS DB15 connector, or is that going to damage something?

I'd like to try it, but if it's not a good idea, then I'll not even think about it.

 

[RetroTheory]

So, I have the Macintosh 17" Multiscan Display. Will this possibly work with the IIGS DB15 connector, or is that going to damage something?

I'd like to try it, but if it's not a good idea, then I'll not even think about it.

It looks like the 17" Multiscan only goes down to 31.47kHz, not very many montors at the time could do 15kHz and 30kHz+ . but there is a list of them

http://15khz.wikidot.com/ TFTs

and I have attached a list of 15Khz capable CRT monitors