If the media shortcut keys on your keyboard don’t function correctly due to outdated firmware, the manufacturer may recommend you ship it to them for an update. [Alvaro] didn’t care to wait that long, so he cracked it open and taught himself how to mod the EEPROM. The result is a well-documented breakdown of sorting out the keyboard’s guts. Inside he finds a USB hub, which he ignores, and the keyboard controller chip, which he attacks. Two data sheets and a schematic later, [Alvaro] breaks out the logic analyzer to compare physical key presses to the keypad codes they output.
He dumps the entire EEPROM and follows up with a quick flash via I2C to change the “next song” key to instead output the letter “a”. That seems to work, so [Alvaro] combs through an HID USB usage table for some codes and has to guess which ones will properly control Spotify. He converts the media keys from “scan next” and “scan previous” to “rewind” and “fast forward.” Problem solved.
[Alvaro] had zero knowledge of keyboards prior to opening this one up. If you aren’t already taking things apart to see how they function and how to fix them, hopefully his success will persuade you to explore and learn about those “black boxes” in your home. And, if you’ve never used I2C before—or think it might be the name of a boy band—head over to [Kevin's] tutorial on bitbanging I2C by hand.