see-atom, carbon-atom, C language-atom is a scalable framework to create embedded systems faster by the combination of the top level declarative programming of the behaviour; model-based enabled design and service code generation. C-ATOM uses so-called atomic functions as formally defined and isolated building blocks.

Key features:

• written in C language;
• libc, pthreads, libm are the only dependencies;
• uses POSIX for system calls;
• designed to be hardware and software-agnostic.
• provides services for telemetry transmission, logging and visualizing.

Available here

1. Drone's autopilot CatPilot
2. Autopiloting of the flight simulator's model of Cessna 172

Library has the following major building blocks and configuration layers:

• flow - block to arrange computational graphs as a sequence of atomic reusable (C lang coded) functions.
• fsm - finite state machine block, operates by states, transitions and actions on states and transitions.
• ibr - interface bridge - designed to take care of converting information from and to other devices.
• swsys - software system description layer; allocates functions and other blocks into tasks and process.

The foundation of the c-atom is Embedded Software Bus (ESWB) library. ESWB creates uniform way of functions to communicate between each other: inside thread, between threads, between processes. Stands as the only form of inter process communication inside c-atom controlled domain.

Find more info at documentation