ICE: allow throttle setpoint to be set to NAN to stop motor without disarming

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

Author: sfuhrer

msg/InternalCombustionEngineControl.msg

@@ -1,7 +1,7 @@
 uint64 timestamp        		# time since system start (microseconds)
 
 bool ignition_on          		# activate/deactivate ignition (spark plug)
-float32 throttle_control		# setpoint for throttle actuator, with slew rate if enabled, idles with 0 [norm] [@range 0,1]
+float32 throttle_control		# setpoint for throttle actuator, with slew rate if enabled, idles with 0 [norm] [@range 0,1] [@uncontrolled NAN to stop motor]
 float32 choke_control			# setpoint for choke actuator, 1: fully closed [norm] [@range 0,1]
 float32 starter_engine_control		# setpoint for (electric) starter motor [norm] [@range 0,1]
 

src/lib/mixer_module/functions/FunctionICEngineControl.hpp

@@ -55,6 +55,7 @@ class FunctionICEControl : public FunctionProviderBase
 		internal_combustion_engine_control_s internal_combustion_engine_control;
 
 		// map [0, 1] to [-1, 1] which is the interface for non-motor PWM channels
+		// NAN is mapped to disarmed
 		if (_internal_combustion_engine_control_sub.update(&internal_combustion_engine_control)) {
 			_data[0] = internal_combustion_engine_control.ignition_on * 2.f - 1.f;
 			_data[1] = internal_combustion_engine_control.throttle_control * 2.f - 1.f;

src/modules/internal_combustion_engine_control/InternalCombustionEngineControl.cpp

@@ -291,7 +291,7 @@ void InternalCombustionEngineControl::controlEngineStop()
 	_ignition_on = false;
 	_choke_control = _param_ice_stop_choke.get() ? 1.f : 0.f;
 	_starter_engine_control = 0.f;
-	_throttle_control = 0.f;
+	_throttle_control = NAN; // this will set it to the DISARMED value
 }
 
 void InternalCombustionEngineControl::controlEngineFault()
@@ -393,6 +393,9 @@ The state machine:
 - Allows for user inputs from:
   - Manual control AUX
   - Arming state in [VehicleStatus.msg](../msg_docs/VehicleStatus.md)
+- In the state "Stopped" the throttle is set to NAN, which by definition will set the
+  throttle output to the disarmed value configured for the specific output.
+
 
 The module publishes [InternalCombustionEngineControl.msg](../msg_docs/InternalCombustionEngineControl.md).