State Machine

The engine lifecycle is managed by a deterministic state machine (ecu_sm). Each state enforces entry/exit actions, timeouts, and safe exit paths.

State Transition Diagram

  +-------+
  |  OFF  |<---------+
  +---+---+          |
      |              |
 throttle > 5%       |
      |              |
  +---v---+          |
  |PRESTART|         |
  +---+---+          |
      |              |
sensors OK           |
      |              |
  +---v---+      +---+----+
  | SPINUP|----->|SHUTDOWN|
  +---+---+      +--------+
      |              ^
RPM > 30% idle       |
      |              |
  +---v----+     +---+---+
  |IGNITION|---->| FAULT |
  +---+----+     +-------+
      |              ^
EGT > start_min      |
      |              |
  +---v---+          |
  | RAMP  |----------+
  +---+---+     (overspeed/
      |          overtemp)
RPM > 95% target     |
      |              |
  +---v---+          |
  |  RUN  |----------+
  +---+---+
      |
throttle < 1%
      |
  +---v----+
  |COOLDOWN|
  +---+----+
      |
EGT < 100C
      |
  +---v----+
  |SHUTDOWN|
  +--------+

States

State	Entry Condition	Exit Condition	Timeout	Outputs
OFF	Power on / shutdown complete	Throttle > 5 %	None	All off
PRESTART	Throttle applied	Sensors valid	5 s	Sensor check
SPINUP	Sensors OK	RPM > 30 % idle	10 s	Starter ON
IGNITION	RPM threshold met	EGT > start_min	8 s	Starter + Igniter + Fuel
RAMP	Ignition confirmed	RPM > 95 % target	None	PID fuel control
RUN	RPM target reached	Throttle < 1 %	None	PID fuel control
COOLDOWN	Throttle removed	EGT < 100 deg C	None	Fuel OFF
SHUTDOWN	EGT cooled	Always -> OFF	None	All off
FAULT	Any safety violation	Manual -> SHUTDOWN	None	All off

Timeout Handling

Each phase with a finite timeout (PRESTART, SPINUP, IGNITION) will transition to FAULT if the exit condition is not met within the allowed window. Timeout values are set in the engine configuration (configuration).

Callbacks

The state machine supports entry and exit callbacks via ecu_sm_set_callbacks(). These are used by the core loop to activate or deactivate hardware (starter motor, igniter relay, fuel valve) at the boundaries of each state.