exxos's Atari, Amiga & retro forum

DoG wrote: 23 Sep 2026 19:19 Is BLANK signal not needed on the STe RGB2HDMI board?

What is that? RGBS is everything.

Steve wrote: 23 Sep 2026 14:15 @Pacman I managed to install RGBtoHDMI in two of my STe's following those spotty forum posts, but I am no expert. You probably know more about it than me now.

Not sure about that, but I think I more or less get it now. And it's reassuring that you and other STe users have it working :)

In terms of making a standard installation method, perhaps @exxos may be interested in modifying his STe DAC upgrade board to being more of a RGBtHDMI pick-up board: https://www.exxosforum.co.uk/atari/last ... /index.htm

I like your idea, for a number of reasons! :thumbup:

I had a quick read through it and although the idea is certainly a good one I'm not sure if it's ideal for the general STe users wanting to get an HDMI output first of all because it involves major "surgery" to the motherboard.
Also it's not suitable with STe motherboards containing a 32MHz oscillator positioned at U402. I'm not sure how common this is or if I even have one in mine, so this may or may not be an issue.

But... I'm struggling with how (and where) to mount my RGBtoHDMI buffer board, so the photos gave me some ideas. I need to do some serious head scratching here so as to make it easy for the average Joe to install with the limited options possible and with a stable connection to the resistors.
Obviously the board should be as close as possible to the signal source (i.e. the row of 13 resistors connected to the video shifter PLCC IC), and that's underneath the power supply.
One idea that's crossed my mind is to take advantage of the power supply's four mounting holes and design a 3D-printed "frame" for the PCB underneath the power supply using the same mounting screws.

I don't know how the RGBtoHDMI things hooks up, id assume it just plugs into the RGB port on the STe as most things do ?

If you're talking about picking the signals up earlier, then just don't connect the RGB DAC outputs to the transistor area.. and you already have your RGB output there anyway..

I did get the updated boards made, but they have been sat in the box for the past few months as I haven't had time to try them yet.. If it's just a case of adding a connector or extra pads then that can probably be done on the future batch anyway..

stween wrote: 23 Sep 2026 18:25 My own resistor notes, which I assume echo the threads above:



It does mean a bit of a rat's nest of wires and I'd love if it was cleaner. I'm always paranoid that I'll have a weak solder joint in that mix. My kingdom for something more stable!

Thanks. I compared it with my own findings and the resistor connections (from the video shifter PLCC chip) were the same as yours.
But shouldn't the CSYNC output go to pin 12 ("SYNC") of the IDC cable?

Pacman wrote: 23 Sep 2026 22:18Thanks. I compared it with my own findings and the resistor connections (from the video shifter PLCC chip) were the same as yours.
But shouldn't the CSYNC output go to pin 12 ("SYNC") of the IDC cable?

Long time since I looked at this. Suspect I was using this page as one of my sources: https://blog.jokielowie.com/en/blog/ata ... ry-pi-zero

Suggests the way I did it works for so long as you have a model with an RF modulator.

stween wrote: 23 Sep 2026 22:52 Long time since I looked at this. Suspect I was using this page as one of my sources: https://blog.jokielowie.com/en/blog/ata ... ry-pi-zero

Suggests the way I did it works for so long as you have a model with an RF modulator.

Great write up. Might be worth posting it on the wiki :)

stween wrote: 23 Sep 2026 22:52

Pacman wrote: 23 Sep 2026 22:18Thanks. I compared it with my own findings and the resistor connections (from the video shifter PLCC chip) were the same as yours.
But shouldn't the CSYNC output go to pin 12 ("SYNC") of the IDC cable?

Long time since I looked at this. Suspect I was using this page as one of my sources: https://blog.jokielowie.com/en/blog/ata ... ry-pi-zero

Suggests the way I did it works for so long as you have a model with an RF modulator.

That page is one of my sources as well, for the buffer I'm working on. It's the only one I've found describing how to add a buffer in an STe.
Unfortunately there's a mistake with the modified Amiga buffer PCB (shown near the bottom of the page) where the 3rd pin (marked in pink) should actually be the 4th pin. The author is aware of this.

By the way, I see you take +5V and GND from the STe motherboard. Does this power up the entire RGBtoHDMI setup including the Raspberry Pi Zero, or do I need to power the Pi Zero separately using its USB-Micro power connector?


Here's a schematic I made of the Amiga 12-bit buffer, modified for the Atari STe. I hope to complete it with a PCB that'll fit underneath the power supply (or some other place near the video shifter PLCC chip) with the connections routed appropriately, connectors added etc.
If you want to connect the IDC cable directly to the RGBtoHDMI/extender board it should be a matter of just bypassing the two 74HCT245 buffer chips (i.e. A1 connects directly to B1, A2 connects directly to B2 etc. of each chip).

I know nothing about buffers, I'll admit! I'm not a video guy: what would that improve?

Pacman wrote: 24 Sep 2026 09:39By the way, I see you take +5V and GND from the STe motherboard. Does this power up the entire RGBtoHDMI setup including the Raspberry Pi Zero, or do I need to power the Pi Zero separately using its USB-Micro power connector?

Yeah, it's ribbon-in and HDMI out, and that's it. No external power. I just have no good solution to the mess of wires!