Subscribe cmd_vel with Arduino

edit

Hello,

I would want to send PWM signal with an arduino in order to control motors. But, as a beginner, I am not exactly sure of what to do. I need first to publish "cmd_vel". Then I need to write a node in Arduino which subscribe to "cmd_vel", right ?

If so, I am not confident with the code I wrote :

  include "ros.h"

  include "geometry_msgs/Twist.h"

 ros::NodeHandle  nh;

 void velCallback(const geometry_msgs::Twist& vel) {   
     geometry_msgs::Twist new_vel = vel;   
     // HERE I WANT TO USE vel TO DEFINE PWM  }

 void setup() {   
     nh.initNode();  
     ros::Subscriber<geometry_msgs::Twist>  ("cmd_vel", &velCallback); 
}

 void loop()
{     
    nh.spinOnce();  
    delay(1); 
}

It is the right way to do ? And is that code correct ?

PS : Sorry but I don't how to properly insert cpp code citation

Regards,

Matt