This Arduino-based Pomodoro timer project also uses this 25-minute cycle. Once you push the button to start the timer, it will run for 25 minutes, display a count-up timer and a "Study time!" ...

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 o… ...

Specifically, [ElectroBoy] uses the AT89S52. Like the ATmega microcontrollers, the AT89S52 has an 8-bit CPU with a Harvard architecture and very similar GPIO capabilities.

This set of microcontroller boards start around $25 and come in the smallest footprint made by Arduino, allowing you to build compact and portable devices that are more difficult to make with an Uno.

Arduino is launching new versions of the Uno board powered by a Renesas 32bit microcontroller. The Uno R4 comes in two versions: the basic Uno R4 Minima and the Espressif-equipped Uno R4 WiFi.