Slackfest 2023: Apple 2c RGBtoHDMI video cable

This weekend is “Apple2Forever”, a.k.a. “Virtual KansasFest”, a.k.a. “The one time a year Josh pulls out his Apple 2s” 🤣 And, whereas KansasFest has their “Hackfest”, A2F has “Slackfest”, which is exactly like Hackfest except there’s no rules, no prize, no tight timetable, and no judges. So…. completely different, then.

Anywho, since I have my Apple 2c out on the bench, I decided to improve my quality of life with it just a bit and build a more proper cable to connect it to my RGBtoHDMI. The RGBtoHDMI is a cool project that uses a Raspberry Pi and a CPLD hat to decode video from vintage computers and scale and output it over HDMI. The result is beautiful clear video from a very large number of old machines. The main project info is here:

The key, though, is that you need the correct “Layer 1” (as it were) interface for each machine. Luckily, that connection is available on the Apple 2c on the 15-pin video port. This port is not an analog RGB – it actually contains the low-level “SERVID” or “Serial Video” signal from the graphics section of the Apple 2. The details of the various “cables” for the RGBtoHDMI can be found here:

When I bought my RGBtoHDMI, I only picked up the 12-pin IDC to DE9 “CGA/EGA” cable.

But, all the pins I needed for a SERVID cable are present on this DE9, so I just needed to make a small adapter from the 15-pin Apple port to the DE9 EGA port.

And, 4 wires later, I have it. And it is glorious. And that’s my Slackfest Entry!

Update: I decided to print some shells for my D15 and D9 connectors. These work pretty well:

…but these interfere with my previous routing for the internal/external Disk 2 switcher, so I had to open the case and re-route this wire. There’s just enough space to use in the RCA composite video connector and still allow a normal video cable to plug in. It’s not brilliant, but most of the time I’ll be using the RGBtoHDMI anyway, so… compromises. And I don’t really want to cut the case for this mod.