Ещё операционка для слабых контроллеров - RIOT https://www.riot-os.org/#features
a preemptive, tickless scheduler with priorities
flexible memory management
high resolution, long-term timers
support for AVR, MSP430, ARM7, and ARM Cortex-M on over 50 boards
the native port allows to run RIOT as-is on Linux, BSD, and MacOS. Multiple instances of RIOT running on a single machine can also be interconnected via a simple virtual Ethernet bridge
IPv6
6LoWPAN (RFC4944, RFC6282, and RFC6775)
UDP
RPL (storing mode, P2P mode)
CoAP
CCN-Lite