Build a Low-Cost DIY USB Volume Knob with Digispark ATtiny85

This project turns a cheap Digispark ATtiny85 USB dongle and a KY-040 rotary encoder into a dedicated hardware volume knob. Rotate clockwise for volume up, counter-clockwise for volume down, press to mute. It enumerates as a standard USB HID Consumer Control device — no custom driver, no desktop app. Linux, Windows, and many Android devices recognise it out of the box. Last updated: February 19,…