ros: make mixer name a param

launch/gazebo_ardrone_empty_world.launch

 <launch>
 
 <include file="$(find mav_gazebo)/launch/ardrone_empty_world_with_joy.launch" />
-<include file="$(find px4)/launch/multicopter.launch" />
+<include file="$(find px4)/launch/multicopter_x.launch" />
 
 </launch>

launch/gazebo_ardrone_house_world.launch

 <launch>
 
 <include file="$(find mav_gazebo)/launch/ardrone_house_world_with_joy.launch" />
-<include file="$(find px4)/launch/multicopter.launch" />
+<include file="$(find px4)/launch/multicopter_x.launch" />
 
 </launch>

launch/gazebo_iris_empty_world.launch

 <launch>
 
 <include file="$(find mav_gazebo)/launch/iris_empty_world_with_joy.launch" />
-<include file="$(find px4)/launch/multicopter.launch" />
+<include file="$(find px4)/launch/multicopter_w.launch" />
 
 </launch>

launch/gazebo_iris_outdoor_world.launch

 <launch>
 
 <include file="$(find mav_gazebo)/launch/iris_outdoor_world_with_joy.launch" />
-<include file="$(find px4)/launch/multicopter.launch" />
+<include file="$(find px4)/launch/multicopter_x.launch" />
 
 </launch>

launch/multicopter.launch

@@ -19,6 +19,7 @@
 	<param name="MC_YAWRATE_P" type="double" value="0.5" />
 	<param name="MC_MAN_R_MAX" type="double" value="10.0" />
 	<param name="MC_MAN_P_MAX" type="double" value="10.0" />
+	<param name="mixer" type="string" value="x" />
 </group>
 
 </launch>

launch/multicopter_w.launch

+<launch>
+
+<include file="$(find px4)/launch/multicopter.launch" />
+
+<group ns="px4_multicopter">
+	<param name="mixer" type="string" value="w" />
+</group>
+
+</launch>

launch/multicopter_x.launch

+<launch>
+
+<include file="$(find px4)/launch/multicopter.launch" />
+
+<group ns="px4_multicopter">
+	<param name="mixer" type="string" value="x" />
+</group>
+
+</launch>

src/platforms/ros/nodes/mc_mixer/mc_mixer.cpp

@@ -41,6 +41,7 @@
 #include <px4.h>
 #include <lib/mathlib/mathlib.h>
 #include <mav_msgs/MotorSpeed.h>
+#include <string>
 
 class MultirotorMixer
 {
@@ -118,7 +119,7 @@ const MultirotorMixer::Rotor *_config_index[4] = {
 MultirotorMixer::MultirotorMixer():
 	_n(),
 	_rotor_count(4),
-	_rotors(_config_index[3]) //XXX hardcoded
+	_rotors(_config_index[0])
 {
 	_sub = _n.subscribe("actuator_controls_0", 1, &MultirotorMixer::actuatorControlsCallback, this);
 	_pub = _n.advertise<mav_msgs::MotorSpeed>("/mixed_motor_commands", 10);
@@ -131,6 +132,10 @@ MultirotorMixer::MultirotorMixer():
 		_n.setParam("motor_offset_radps", 600.0);
 	}
 
+	if (!_n.hasParam("mixer")) {
+		_n.setParam("mixer", "x");
+	}
+
 	_sub_actuator_armed = _n.subscribe("actuator_armed", 1, &MultirotorMixer::actuatorArmedCallback, this);
 }
 
@@ -206,6 +211,19 @@ void MultirotorMixer::actuatorControlsCallback(const PX4_TOPIC_T(actuator_contro
 		inputs.control[i] = msg.control[i];
 	}
 
+	// switch mixer if necessary
+	std::string mixer_name;
+	_n.getParamCached("mixer", mixer_name);
+	if (mixer_name == "x") {
+		_rotors = _config_index[0];
+	} else if (mixer_name == "+") {
+		_rotors = _config_index[1];
+	} else if (mixer_name == "e") {
+		_rotors = _config_index[2];
+	} else if (mixer_name == "w") {
+		_rotors = _config_index[3];
+	}
+
 	// mix
 	mix();