While newer Arduinos and Arduino compatibles (including the Hackaday.io Trinket Pro. Superliminal Advertising!) either have a chip capable of USB or rely on a V-USB implementation, the old fogies ...

Microcontroller demo boards such as the Arduino UNO are ubiquitous on Hackaday ... His notes show he saw the barest way to operate an ATMega328, built it, tested, and moved on to the power supply ...