Building a RGB2HDMI in 2022
Welcome to 2022. CRTs are luxury, no longer a commodity. Let alone ones that can take a digital RGB signal.
Thankfully, there are solutions. After a bunch of research, I decided to go with the RGB2HDMI, since it was the most versatile. I picked up a 6-bit board, and at the time I didn’t realize that the Raspberry Pi Zero would become unobtanium before I could order one. So on the shelf it sat…
Until… A hero emerged from the darkness. A voice from my past. An old friend and collogue of mine reached out and offered up one he wasn’t using anymore! Thank you Matt!
The documentation for the RGB2HDMI is actually very straightforward. I bought a pre assembled board, which took out a LOT of the headache. My surface mount soldering skills are… lacking to say the least. The one I bought from Retro Hack Shack (not sponsored) came with the cable and I also ordered a case, which made life pretty easy.
I followed the directions on his YouTube video, but alas, that was an older version of the board. The one he was working with only had a 10 pin connector internally. It was the version designed for the BBC Micro, which used the same 9 pins as CGA, but also carried a +5V line as well. In his video, he just didn’t connect the +5V and it worked just find for CGA/EGA. My connector had 12 lines. So where he cut off the last line (+5V), I cut off the last three. I thought they were just extraneous data bits for some format I wasn’t using. Except, what I actually needed to do was cut off the last line, and the first two. Because of the way the connector is keyed, the two new lines become pins 1 and 2, not 11 and 12. So obviously, it didn’t work.
It took a few minutes of me studying the board to realize my mistake. Thankfully the top of the RGB2HDMI board has all 12 pins labeled. That’s how I realized which pins to ignore. My first attempt at soldering up the pinout didn’t work. And so I thought I had read the board wrong. But I wanted to make sure, so I took out a screw down connector I got for diagnosing RS-232 wiring, and it worked just fine. It was just my horrible soldering skills it seems.
So now I have a working RGB2HDMI. Which is necessary for using my C128 is 80 column mode, and hopefully in high res GEOS mode. Which is up next!
Update (11/18/2022):
I ordered and received some crimp on DB-9 connectors, and have used that to get a better connection to the wire. I’m in the process of designing a 3D Printed case for that so it looks a little less like a diagnostic harness.
