Embedded systems
Computers built into something that isn’t thought of as a computer: a scale, a thermostat, a reader, a vehicle. The defining condition is constraint — power, memory, cost, physical size, and often real-time deadlines — and nearly every design decision in this spoke is downstream of it.
The spectrum, not the category
The founding sources sit at three points on one axis, which is the most useful thing they say together:
| | MCU | MCU board | SBC | |---|---|---|---| | example | Nuvoton NSC128L42 | RP2040 in The Open Book | UP WCL | | software | bare metal or an RTOS | firmware you wrote | Windows or Ubuntu | | memory | kilobytes | hundreds of KB | tens of gigabytes | | power | milliwatts | milliwatts | ~30 W |
The jump from the middle column to the right is roughly three orders of magnitude of power and the point where a general-purpose operating system becomes affordable. Everything else — whether you get threads, whether you can afford a filesystem, whether the device runs on a battery for a year — follows from where on that axis a design lands. “Embedded” spans the whole of it, which is why the word alone predicts so little.
The software layer
Below a general-purpose OS sits the RTOS tier that awesome-iot catalogs — Zephyr, FreeRTOS, ARM mbed, Contiki, Apache Mynewt — offering scheduling and a driver model in a few tens of KB, with deterministic timing as the selling point. Above it, the languages that have reached this layer recently: MicroPython, TinyGo, and Rust, all trading some efficiency for memory safety or iteration speed. This layer has no page of its own yet; it’s the most obvious gap in the founding corpus.
Embedded is not the same as IoT
The Open Book has no radio and talks to nothing. It is fully embedded and not IoT at all. IoT is embedded plus a network, and the network is what brings the protocol stack, the platform layer, and the security surface that the rest of this wiki’s sources spend their time on. Keeping the two words distinct stops “IoT” from expanding to mean “any small computer.”
Related
microcontroller · single-board-computer · iot-protocols · open-hardware · awesome-iot · synthesis