camera_trigger : enforce a minimum activation time in PWM modes

src/drivers/camera_trigger/camera_trigger.cpp

@@ -231,7 +231,7 @@ CameraTrigger::CameraTrigger() :
 	//Initiate Camera interface basedon camera_interface_mode
 	if (_camera_interface != nullptr) {
 		delete (_camera_interface);
-		/* set to zero to ensure parser is not used while not instantiated */
+		// set to zero to ensure parser is not used while not instantiated
 		_camera_interface = nullptr;
 	}
 
@@ -268,7 +268,7 @@ CameraTrigger::CameraTrigger() :
 #endif
 
 	case CAMERA_INTERFACE_MODE_MAVLINK:
-		/* start an interface that does nothing. Instead mavlink will listen to the camera_trigger uORB message */
+		// start an interface that does nothing. Instead mavlink will listen to the camera_trigger uORB message
 		_camera_interface = new CameraInterface();
 		break;
 
@@ -277,6 +277,16 @@ CameraTrigger::CameraTrigger() :
 		break;
 	}
 
+	// Enforce a lower bound on the activation interval in PWM modes to not miss
+	// engage calls in-between 50Hz PWM pulses. (see PX4 PR #6973)
+	if ((_activation_time < 40.0f) &&
+	    (_camera_interface_mode == CAMERA_INTERFACE_MODE_GENERIC_PWM ||
+	     _camera_interface_mode == CAMERA_INTERFACE_MODE_SEAGULL_MAP2_PWM)) {
+		_activation_time = 40.0f;
+		PX4_WARN("Trigger interval too low for PWM interface, setting to 40 ms");
+		param_set(_p_activation_time, &(_activation_time));
+	}
+
 	struct camera_trigger_s	report = {};
 
 	_trigger_pub = orb_advertise(ORB_ID(camera_trigger), &report);

src/drivers/camera_trigger/camera_trigger_params.c

@@ -92,7 +92,7 @@ PARAM_DEFINE_INT32(TRIG_POLARITY, 0);
  * @decimal 1
  * @group Camera trigger
  */
-PARAM_DEFINE_FLOAT(TRIG_ACT_TIME, 0.5f);
+PARAM_DEFINE_FLOAT(TRIG_ACT_TIME, 40.0f);
 
 /**
  * Camera trigger mode