DDC OLED - The smallest and worst HDMI display
DDC, display data channel, is a protocol for reading information about what resolutions and so on a monitor supports. It was later extended to DDC/CI, that lets you set brightness and other parameters, but fundamentally, the original idea was to stick a cheap i2c eeprom on each device with some basic info on it. (Technically, the original idea was even simpler than that, but let’s not get into that.)
It began in the VGA days, but has become so entrenched that even modern hardware with HDMI or DisplayPort supports it. That’s right, in an HDMI cable, nestled amongst the high-speed differential pairs, there’s an exceedingly slow i2c bus.
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.