tinyimg3 is a tiny ARM Versatile Platform Baseboard kernel that uses firmware that is something like IMG3 format.
I always loved doing low-level programming, hardware programming...
Also i've been always kind of intrigued of the iPhone 2G design choices, and OS-dev.
https://www.theiphonewiki.com/wiki/IMG3_File_Format
First, it downloads "custom" firmware from UART0 and writes it to NOR flash, then it uses PL110 CLCD component to display a b&w gradient on the screen.
