With a touch of nostalgia for the days of Windows 95, a new open-source project called FRANK OS introduces an unusual concept: a complete graphical desktop operating system for a microcontroller. The project recently released its first official version, 1.0.
Unlike typical desktop systems, FRANK OS is not based on the Linux kernel. Instead, it is built on the real-time operating system FreeRTOS, commonly used in embedded and IoT devices. On this RTOS foundation, the project implements its own graphical environment, system libraries, and applications.
The operating system is lightweight, targeting hardware built around the RP2350 microcontroller, a chip with about 520 KB of SRAM and dual CPU cores. One core runs the FreeRTOS scheduler, the graphical interface, and applications, while the second core generates real-time video output via a DVI connection.
Visually, the desktop environment draws inspiration from Windows 95, featuring a familiar layout with overlapping windows, a taskbar, and a start-menu-style launcher. The interface includes standard desktop elements such as a file manager, terminal, and basic utilities, all adapted to run within the hardware’s tight memory constraints.
The window manager supports standard desktop behavior such as title bars with minimize, maximize, and close buttons, drag-to-move windows, and resizing from edges and corners. Users can switch between applications using a familiar Alt+Tab-style interface.
A taskbar at the bottom of the screen displays running applications and provides access to the Start menu and a small system tray with a clock and volume control.
On top of that, FRANK OS ships with nine small applications, including a terminal with an interactive PShell, Vi text editor, and a C compiler, a text editor, simple games such as Minesweeper and Solitaire, an MP3 player, and a ZX Spectrum emulator.
The system also includes a windowed version of MMBasic, a BASIC interpreter that supports file operations, graphics commands, and sound output. Programs are compiled as ARM ELF binaries and loaded from an SD card, allowing additional applications to be added without rebuilding the system firmware.
As you can guess, the goal here is experimental and geared toward hobbyists rather than creating an operating system for everyday use. Still, the project is exciting and carries a touch of nostalgia, so if you have an RP2350 microcontroller on hand, fun is guaranteed.
For more details, see the project’s GitHub page. FRANK OS is released under the MIT license as open source.
