It’s often repeated that a microcontroller is nothing more than a computer scaled down to a single chip. That’s certainly true, and these chips have enough power to have been incredibly impressive computers a few decades ago. But they don’t really feel like computers, do they? While they have processors, memory, external interfaces, and everything else needed to meet the formal definition of a computer, the awkward way that we have to interact with them and the lack of an operating system make them seem like anything but a desktop computer.
Roberto Alsina wanted to unlock the potential of microcontrollers to act as a dirt-cheap personal computing platform, so he developed an operating system for ESP32-powered Cheap Yellow Displays (CYDs) called ESP-Osito. It comes loaded with commonly used applications so that you can use it for real work, yet the hardware only costs around $10. ESP-Osito itself is free and open source.
The e-reader app (📷: Roberto Alsina)
The operating system was designed with simplicity in mind, so you won’t find many advanced features. Apps are dynamically loaded from the SD card and fully replace one another in memory when launched. There is no multitasking layer running in the background, which allows applications to start in milliseconds and restore their previous state almost instantly. This provides a user experience more reminiscent of a PalmPilot than a modern desktop: immediate boot times, instant shutdowns, and virtually no waiting.
ESP-Osito saves checkpoints before closing applications and restores their previous state when they are reopened. The architecture is event-driven, with apps subscribing to a central event queue for touch, keyboard, and system input. Applications are distributed as dynamically loaded libraries, each exposing a small set of functions for initialization, state saving, cleanup, and event handling.
Built-in software includes a markdown ebook reader capable of handling large books, a serial terminal for Linux systems, a fullscreen text editor based on the minimalist Kilo editor, a paint application, a calculator, the Snake game, a clock with NTP synchronization and weather support, and an AI chat client that connects to online language models through OpenRouter APIs.
The text editor (📷: Roberto Alsina)
The interface can be paired with a physical keyboard, turning the tiny display into a pocket-sized workstation. Users can rotate the screen orientation, customize fonts, configure Wi-Fi, and tune power saving behavior through the included settings application.
ESP-Osito is built on Espressif’s ESP-IDF framework and is still in active development. Alsina says support for additional devices, including E Ink hardware and more capable future systems, is planned. Check out the official project page for instructions if you’d like to try it out for yourself.