Project - Hollyhock
Many members of the CASIO community were disappointed when CASIO released the fx-CP400 graphics calculator with no support for add-on software. Despite the calculator featuring a BASIC-like dialect in which small programs could be written, the lack of a native SDK was a sticking point for many.
As such, the 'hollyhock' project was started, as an effort to reverse engineer the firmware of the fx-CP400 to develop a native SDK.
A series of two blog posts (Part 1 and Part 2) were written during the early stages of the project, detailing the initial extraction and flashing of modified firmware to the calculator.
Though the project is incomplete and has not yet been released, the current state of the SDK and firmware modification allows a user to run add-ons through a launcher program. Many crucial native functions - such as those pertaining to the file system, the OS's GUI platform and user input - were found in the firmware and subsequently documented in detail.