Cannot get geometry_msgs::Twist from subscription to cmdVelReceived [closed]

asked 2013-01-21 08:31:05 -0500

MartinW gravatar image

updated 2014-04-20 14:09:42 -0500

ngrennan gravatar image

Hello all,

I am trying to write a program that subscribes to a geometry_msgs::Twist msg being published on a topic. Rxgraph says it is subscribed but I doesn't register in the console. The program is supposed to be a keyboard teleoperation where I send some commands through the keyboard on one node and another node picks up these commands and publishes them.

Here is a simple version of the code:

        printf("before subscription\n"); 
      cmd_vel_sub_ = node_.subscribe<geometry_msgs::Twist>("drrobot_cmd_vel", 1, boost::bind(&DrRobotPlayerNode::cmdVelReceived, this, _1));
        printf("after subscription\n");

 void cmdVelReceived(const geometry_msgs::Twist::ConstPtr& cmd_vel)
        printf(" test \n");
      double g_vel = cmd_vel->linear.x;
      double t_vel = cmd_vel->angular.z;

      if (robotConfig1_.boardType == Hawk_H20_Motion)
        double leftWheel = (2 * g_vel - t_vel* wheelDis_) / (2 * wheelRadius_);
        double rightWheel = (t_vel* wheelDis_ + 2 * g_vel) / (2 * wheelRadius_);

        int leftWheelCmd = motorDir_ * leftWheel * encoderOneCircleCnt_ / ( 2* 3.1415927);
        int rightWheelCmd = - motorDir_ * rightWheel * encoderOneCircleCnt_ / ( 2* 3.1415927);
        ROS_INFO("Received control command: [%d, %d]", leftWheelCmd,rightWheelCmd);

drrobotMotionDriver_->sendMotorCtrlAllCmd(Velocity,leftWheelCmd, rightWheelCmd,NOCONTROL,NOCONTROL, NOCONTROL,NOCONTROL);

This is inside the prewritten code's class, then the main function is:

int main(int argc, char** argv){
ros::init(argc, argv, "drrobot_jaguar4x4_player");

DrRobotPlayerNode drrobotPlayer;
ros::NodeHandle n;
// Start up the robot
if (drrobotPlayer.start() != 0)

    printf("error starting up the robot! \n");


ros::Rate loop_rate(10);      //10Hz

while (n.ok())
    printf("in the while loop \n");

// Stop the robot


I have attached a screenshot of the console out, I tried to send it three commands, but it shows nothing is received. It doesn't even enter the function cmdVelReceived to printf(" test \n");

Does anyone know what is going wrong here? Many thanks in advance.

Kind Regards, Martin

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Closed for the following reason question is not relevant or outdated by felix k
close date 2013-01-22 22:28:14



Are you sure you're publishing and subscribing on the same namespace? What does rostopic list tell you? It also could be a problem with your publisher. Does your subscriber register a callback if you publish to your topic with rostopic pub?

tbh gravatar image tbh  ( 2013-01-21 09:44:53 -0500 )edit

Yea, I tried it again after lunch and everything worked fine :S Must have been something in the system and after a restart it started working!

MartinW gravatar image MartinW  ( 2013-01-22 06:57:41 -0500 )edit