How to send velocity to pixhawk with Mavros?

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Hi guys,

after searching a lot and don't get a solution I would like a help. I am a new user of Mavros package and I have some doubts about it. My setup for tests is:

1 Pixhawk with ArduCopter V3.2.1Quad firmware, 1 ESC 20A SkyWalker, 1 motor, 1 GPS+Compass, 1 radio receiver and 1 battery. I installed mavros on Indigo and ubuntu 14.04.

I want to start sending a simple command of linear velocity to pixhawk, for example vx = 1 m/s.

I typed the commands bellow in sequence:

1) sudo chmod 666 /dev/ttyACM0

2) roslaunch mavros px4.launch

3) rosrun mavros mavsafety arm

4) and my code: rosrun copter velocity

After that nothing happened. The the motor spun with default velocity of the node mavsafety arm and not with desired velocity.

What topic should I publish this message?

I checked the topic /mavros/setpoint_attitude/cmd_vel and the value that I set in the source code was there.

So, where is the mistake? Should I do some setup before to run?

I read at some forum people talking about some setup that we have to do...but is not clear for me.

Can anyone show a piece of code that make what I want or give me a tips?

Thank you!

I wrote a code trying to do this but without successful.

#include <ros/ros.h>
#include <std_msgs/String.h> 
#include <stdio.h>
#include "geometry_msgs/TwistStamped.h"
#include "geometry_msgs/Vector3Stamped.h"

int main(int argc, char **argv)
{
   ros::init(argc, argv, "comun");
   ros::NodeHandle n;

   ros::Publisher chatter_pub = n.advertise<geometry_msgs::TwistStamped>("/mavros/setpoint_attitude/cmd_vel",100);
   ros::Rate loop_rate(10);

   geometry_msgs::TwistStamped msg;

   while(ros::ok()){
       msg.header.stamp = ros::Time::now();
       msg.header.seq=1;
       msg.twist.linear.x = 1;
       msg.twist.angular.x = 1;

       chatter_pub.publish(msg);
       ros::spinOnce();
       loop_rate.sleep();
   }    
   return 0;
}