tl;dr: The author reverse-engineered their Egret GT e-scooter by sniffing its CAN bus (exposed via the display's USB-C port), dumping firmware from replacement controller and display units via SWD, and analyzing it in Ghidra to map out CAN messages, peripheral configs, and the unauthenticated CAN-based firmware update protocol. They then wrote custom Rust firmware for the display unit using Embassy, building out a HAL for the AT32F415 (an STM32 clone with mixed peripherals) and using the `mipidsi` crate to drive the ST7796 display over a 16-bit parallel GPIO bus.