SylphideOS is a general purpose GUI operating system for microcontrollers, written by a developer named Thomas. The look owes a lot to the early Macintosh, with a desktop and windows driven through a framebuffer. Underneath it runs on the FreeRTOS kernel, which raises the question of whether it counts as its own OS or as a FreeRTOS distribution.

Along with the display, it handles the hardware you would want for desktop use, including keyboard input and storage. Supported targets so far are the RP2350 and selected ESP32 platforms. There is also an emulator, so the interface can be tried without hardware.

Most microcontroller operating systems act as a launcher for a binary bootloader and then step out of the way once a program runs. SylphideOS sticks around instead, which is what makes it worth a look.

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