How do you implement a state machine in embedded systems?

State machines are essential for managing complex device behavior in embedded systems. Implementation approaches: Switch-case: States as enum, switch on current state, handle events within each case. Simple but can become unwieldy. Function pointer table: 2D array [state][event] -> action function. Cleaner for complex machines. State pattern (OOP): State objects with virtual methods. More memory overhead but maintainable. Best practices: Define clear state diagram first. Use enum for states and events. Separate state machine logic from action code. Handle unexpected events (default case). Add transition logging for debugging. Consider hierarchical state machines (HSM) for complex systems. Tools like QP/C framework provide robust HSM implementation. Testing: Exercise all transitions, verify guard conditions, test invalid event handling.