#casio
1 writeup.
- Writing firmware for a watch that had none published: reverse engineering the Ollee Watch One 25 Aug 2026
An STM32WB board that turns a Casio F-91W into a smartwatch, with no public documentation. Its own firmware gave up the display map, the character font and two undocumented BLE commands — enough to write a replacement that kept time on my wrist. Then I bricked it with four bytes of vector table.