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Rosserial multiple publishers

asked 2013-10-03 17:59:36 -0500

stebl gravatar image

updated 2013-10-04 02:30:54 -0500

I'm running a fresh install of Ubuntu 13.04, rosserial, hydro.

Using an arduino uno, the following code works and publishes messages:

#include <ros.h>
#include <std_msgs/Int16.h>

ros::NodeHandle nh;
std_msgs::Int16 ultrasound_msg;
std_msgs::Int16 ir_msg;
ros::Publisher ultrasound_pub("ultrasound", &ultrasound_msg);
ros::Publisher infrared_pub("infrared", &ir_msg);


void setup() {
  // Initialize sensors, etc
    nh.initNode();
    nh.advertise(ultrasound_pub);
    //nh.advertise(infrared_pub);
}

void loop() {

  ultrasound_msg.data = 42;
  ultrasound_pub.publish( &ultrasound_msg );

  nh.spinOnce();
  delay(1000);

}

If I un-comment the second advertise:

void setup() {
  // Initialize sensors, etc
    nh.initNode();
    nh.advertise(ultrasound_pub);
    nh.advertise(infrared_pub);
}

I get 'Creation of publisher failed: unpack requires a string argument of length 4', when I try to start the node on the ROS side.

When I try to initialize only the second publisher:

void setup() {
  // Initialize sensors, etc
    nh.initNode();
    //nh.advertise(ultrasound_pub);
    nh.advertise(infrared_pub);
}

Starting the node says 'Unable to sync with device; possible link problem or link software version mismatch such as hydro rosserial_python with groovy Arduino'

I saw 2 posts with similar problems, solved by updating the rosserial-arduino and rosserial installations. I have fresh installations from apt-get, so I'm not sure why they'd be mismatched.

Any ideas?

UPDATE

If I replace the second publisher with a subscriber like so:

void ROS_CALLBACK(const std_msgs::Int16 &msg)
{
  // do stuff
}
ros::Publisher ultrasound_pub("ultrasound", &ultrasound_msg);
ros::Subscriber<std_msgs::Int16> sub("arduino_listener", &ROS_CALLBACK);
...
void setup() {
  // Initialize sensors, etc
    nh.initNode();
    nh.advertise(ultrasound_pub);
    nh.subscribe(sub);
}

I get the same errors for the same sequence. 'Failed to unpack' for the code shown below. 'Unable to sync with device' if I advertise subscribe without advertising the publisher.

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Comments

Rolling back the rosserial libraries to 0.5.1 provides a workaround.

stebl gravatar image stebl  ( 2013-10-04 02:54:40 -0500 )edit

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answered 2013-10-13 22:59:34 -0500

PaulBouchier gravatar image

Fixed in latest rosserial source. New release of rosserial debs coming out in the next few days. See Issue 76 for an explanation of the problem. In a nutshell, an uninitialized data situation was introduced, which caused the upper two bytes of string length to contain random data. The fault was introduced in 0.5.2, which explains why 0.5.1 works.

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confirmed working :)

stebl gravatar image stebl  ( 2013-10-14 14:29:05 -0500 )edit

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Asked: 2013-10-03 17:59:36 -0500

Seen: 1,795 times

Last updated: Oct 13 '13