A lightweight and efficient Finite State Machine (FSM) library with built-in non-blocking task manager, written in C for STM32 (HAL-based).

Unlike blocking implementations, this library uses time-based state transitions and a task queue system to keep your main loop responsive.
It can be used in any CubeMX STM32 project, making it fully flexible and easy to integrate.

It is designed for:

• Projects where CPU blocking (HAL_Delay) must be avoided
• Applications that need clean state handling
• Event-driven systems that use interrupts (EXTI, UART, Timers)
• Easy portability across All STM32 families

• 🔹 Non-blocking state transitions with millisecond resolution
• 🔹 Built-in task queue system for background jobs
• 🔹 Works with interrupt callbacks (e.g. EXTI, UART, Timer)
• 🔹 Fully HAL-compatible
• 🔹 Small memory footprint, portable C code
• 🔹 Simple, clean API

You can install in two ways:

Add these files to your STM32 project:

• fsm.h
• fsm.c
• fsm_config.h

Available in the official pack repo:
👉 STM32-PACK (Not Ready)

Defines library limits and task queue size. Example:

#define FSM_MAX_TASKS     16    // Max number of queued tasks

#include "fsm.h"

fsm_t my_fsm;

fsm_init(&my_fsm, state_idle);

while (1)
{
    fsm_loop(&my_fsm);   // must be called frequently
}

/* ===== States ===== */
void state_idle(void)
{
    // do ...
    if ( .... )
    {
        // change state to state_calc1
        fsm_next(&my_fsm, state_calc1, 0);
    }
}

/* ===== States ===== */
void state_calc1(void)
{
    // do ...
    // set next state after 200 ms
    fsm_next(&my_fsm, state_calc2, 200);
}

/* ===== States ===== */
void state_calc2(void)
{
    // do ...
    // go back to idle state
    fsm_next(&my_fsm, state_idle, 0);
}

/* ===== Task Function ===== */
void button_task(void)
{
     // do ...
}

/* ===== Interrupt Callback ===== */
void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
    if (GPIO_Pin == B1_Pin) // User button
    {
        // Schedule FSM task safely from interrupt
        fsm_task_add(button_task);
    }
}

✅ ISR stays short → only fsm_task_add() is called
✅ FSM executes logic in main loop → no blocking in ISR

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Licensed under the terms in the LICENSE.