Maker Tim Alex Jacobs has put together an ultra-compact steampunk-inspired secondary display, driven entirely using the Display Data Channel (DDC) of an HDMI port — "a total hack and by far the worst way to get a second monitor," Jacobs admits.
"In an HDMI cable, nestled amongst the high-speed differential pairs, there's an exceedingly slow I2C bus," Jacobs explains — the Display Data Channel, originally designed for communicating supported configurations between display outputs and devices. "Tiny OLED dot-matrix displays often have an I2C controller, so I had the idea to try and plug one directly into an HDMI port. Hilarious! Let's do it."
That project, completed earlier this year, led to DDC-OLED — an open source tool for Linux which turns an SSD1306 OLED display into a tiny secondary display for X11. Initially, Jacobs was content to consider the project finished when an OLED finally displayed a picture — but an itch resulted in further tinkering, enhancing the software to support easier framebuffer setup, configurable brightness, optional dithering, and partial frame updates.
Then came the steampunk aspect. "What's a sillier upgrade for the silliest display than making it steampunk? But I never went in for sticking golden spray-painted gears on my hat," Jacobs explains. "When I talk steampunk, I talk milled brass and knurling.
"With the exception of the USB Light, from which I salvaged the bendy gooseneck thing, all of the parts were sourced from bits I had lying around. It is extremely satisfying to go from initial idea (of 'bendy gooseneck milled brass HDMI DDC display') to finished prototype the following day."
Said finished prototype, designed in SCAD, houses an off-the-shelf SSD1306 OLED panel within a two-part brass housing held together with larger-than-planned M2 bolts. This connects to the DDC and power pins of an HDMI connector via the aforementioned gooseneck, allowing the display to be positioned above the desk and angled as required.
"There may have been a clever way to assemble the connector, maybe using tiny bolts and threaded holes, but I decided to go with a single join that is hot-glued in place because it was the funniest option. The great thing about 'steampunk' is that you don't have to clean your solder joints. The messy flux residue just adds to the look," Jacobs jokes.