Allow the user to provide the motor/channel numbers that should be disabled in fixed wing mode in the airframe config.

ROMFS/px4fmu_common/init.d/13002_firefly6

@@ -46,5 +46,6 @@ set PWM_AUX_MAX 2000
 set MAV_TYPE 21
 
 param set VT_MOT_COUNT 6
+param set VT_FW_MOT_OFF 23
 param set VT_IDLE_PWM_MC 1080
 param set VT_TYPE 1

src/modules/vtol_att_control/tiltrotor.cpp

@@ -67,6 +67,7 @@ _min_front_trans_dur(0.5f)
 	_params_handles_tiltrotor.airspeed_blend_start = param_find("VT_ARSP_BLEND");
 	_params_handles_tiltrotor.elevons_mc_lock = param_find("VT_ELEV_MC_LOCK");
 	_params_handles_tiltrotor.front_trans_dur_p2 = param_find("VT_TRANS_P2_DUR");
+	_params_handles_tiltrotor.fw_motors_off = param_find("VT_FW_MOT_OFF");
 }
 
 Tiltrotor::~Tiltrotor()
@@ -80,6 +81,11 @@ Tiltrotor::parameters_update()
 	float v;
 	int l;
 
+	/* motors that must be turned off when in fixed wing mode */
+	param_get(_params_handles_tiltrotor.fw_motors_off, &l);
+	_params_tiltrotor.fw_motors_off = get_motor_off_channels(l);
+
+
 	/* vtol duration of a front transition */
 	param_get(_params_handles_tiltrotor.front_trans_dur, &v);
 	_params_tiltrotor.front_trans_dur = math::constrain(v,1.0f,5.0f);
@@ -126,6 +132,22 @@ Tiltrotor::parameters_update()
 	return OK;
 }
 
+int Tiltrotor::get_motor_off_channels(int channels) {
+	int channel_bitmap = 0;
+	
+	int channel;
+	for (int i = 0; i < _params->vtol_motor_count; ++i) {
+		channel = channels % 10;
+		if (channel == 0) {
+			break;
+		}
+		channel_bitmap |= 1 << channel;
+		channels = channels / 10;
+	}
+
+	return channel_bitmap;
+}
+
 void Tiltrotor::update_vtol_state()
 {
  	parameters_update();
@@ -357,7 +379,7 @@ void Tiltrotor::set_rear_motor_state(rear_motor_state state) {
 	memset(&pwm_values, 0, sizeof(pwm_values));
 
 	for (int i = 0; i < _params->vtol_motor_count; i++) {
-		if (i == 2 || i == 3) {
+		if (is_motor_off_channel(i)) {
 			pwm_values.values[i] = pwm_value;
 		} else {
 			pwm_values.values[i] = PWM_DEFAULT_MAX;
@@ -370,5 +392,8 @@ void Tiltrotor::set_rear_motor_state(rear_motor_state state) {
 	if (ret != OK) {errx(ret, "failed setting max values");}
 
 	close(fd);
-
+}
+
+bool Tiltrotor::is_motor_off_channel(const int channel) {
+	return (_params_tiltrotor.fw_motors_off >> channel) & 1;
 }

src/modules/vtol_att_control/tiltrotor.h

@@ -89,6 +89,7 @@ private:
 		float airspeed_blend_start;		/**< airspeed at which we start blending mc/fw controls */
 		int elevons_mc_lock;			/**< lock elevons in multicopter mode */
 		float front_trans_dur_p2;
+		int fw_motors_off;			/**< bitmask of all motors that should be off in fixed wing mode */
 	} _params_tiltrotor;
 
 	struct {
@@ -101,6 +102,7 @@ private:
 		param_t airspeed_blend_start;
 		param_t elevons_mc_lock;
 		param_t front_trans_dur_p2;
+		param_t fw_motors_off;
 	} _params_handles_tiltrotor;
 
 	enum vtol_mode {
@@ -133,6 +135,16 @@ private:
 
 	const float _min_front_trans_dur;	/**< min possible time in which rotors are rotated into the first position */
 
+	/**
+	 * Return a bitmap of channels that should be turned off in fixed wing mode.
+	 */
+	int get_motor_off_channels(const int channels);
+
+	/**
+	 * Return true if the motor channel is off in fixed wing mode.
+	 */
+	bool is_motor_off_channel(const int channel);
+
 	/**
 	 * Write control values to actuator output topics.
 	 */

src/modules/vtol_att_control/tiltrotor_params.c

@@ -84,3 +84,13 @@ PARAM_DEFINE_FLOAT(VT_TILT_FW, 1.0f);
  * @group VTOL Attitude Control
  */
 PARAM_DEFINE_FLOAT(VT_TRANS_P2_DUR, 0.5f);
+
+/**
+ * The channel number of motors that must be turned off in fixed wing mode.
+ *
+ *
+ * @min 0
+ * @max 123456
+ * @group VTOL Attitude Control
+ */
+PARAM_DEFINE_INT32(VT_FW_MOT_OFF, 0);