c-utils

Small, independent C components for embedded work. Each one solves a single problem, has no dependencies, and is meant to be copied into your project rather than installed.

Components

fsm	Table-driven state machine with polled conditions. No event queue, no allocation.
pid	PID controller with anti-windup, a filtered derivative and output limits.
kalman	Linear Kalman filter for a scalar measurement. Joseph form, outlier gating, no matrix inverse.

The independence rule

Every component compiles standalone. There is no shared common.h, and no component includes another. Copying a component's two files into an unrelated project must just work — that is the property everything here is designed around, and it is what keeps the components cheap to adopt and cheap to split out again later.

Using a component

Copy its header and source into your tree:

fsm/include/mjg_fsm.h
fsm/src/mjg_fsm.c

That is the supported integration path. There is no package to install and no registry entry to chase; each file carries its own licence header so it stays self-describing once it leaves this repository.

Conventions

• Public symbols and header filenames are prefixed mjg_ — mjg_fsm.h, mjg_fsm_init(), typedef struct mjg_fsm mjg_fsm;
• Macros and constants are MJG_FSM_*
• File-local static functions carry no prefix
• No malloc in any core API — the caller supplies storage
• C99, set explicitly, for reach across older embedded toolchains

Building

CMake exists to build and test this repository, not to distribute it. Each component can be toggled independently:

cmake -S . -B build -DCUTILS_WERROR=ON
cmake --build build
ctest --test-dir build -C Debug --output-on-failure

-C Debug is required by multi-config generators (Visual Studio, Xcode) and ignored by single-config ones, so the same line works everywhere.

Option	Default
CUTILS_BUILD_FSM	ON	Build the state machine component
CUTILS_BUILD_TESTS	ON	Build and register component tests
CUTILS_BUILD_EXAMPLES	ON	Build component examples
CUTILS_WERROR	OFF	Treat warnings as errors (CI turns this on)

Components export a namespaced alias — c-utils::fsm — for in-tree and FetchContent use. There are deliberately no install() or export() rules.

Licence

MIT. See LICENSE.