Modernizing the Classic Casio F-91W with a New Motherboard

The author purchased a replacement motherboard for their classic Casio F-91W watch from Crowd Supply. This project retains the original Casio LCD but replaces the motherboard with a modern microcontroller and open firmware, resulting in a watch with extended battery life and added functionality. The article details the process of replacing the motherboard, including disassembling the watch, soldering components, installing the new board, and compiling and installing custom firmware. An emulator was used to test the firmware before successfully upgrading the watch with features like a stopwatch and thermometer.