sensor_msgs/Range

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I have a simple sonar sensor running to an Arduino Mega ADK. On the Arduino I have the following code patched together from rosserial_arduino tutorials and the code specific to my sensor:

#include <ros.h>
#include <ros/time.h>
#include <sensor_msgs/Range.h>
#include <Ultrasonic.h>

ros::NodeHandle nh;

sensor_msgs::Range range_msg;
ros::Publisher pub_range( "/ultrasound", & range_msg);

char frameid[] = "/ultrasound";
int inMsec;

#define TRIGGER_PIN  48
#define ECHO_PIN     49

Ultrasonic ultrasonic(TRIGGER_PIN, ECHO_PIN);

void setup()
  {
  nh.initNode();
  nh.advertise(pub_range);

  range_msg.radiation_type = sensor_msgs::Range::ULTRASOUND;
  range_msg.header.frame_id =  frameid;
  range_msg.field_of_view = 0.1;  // fake
  range_msg.min_range = 0.0;
  range_msg.max_range = 6.47;
  }

long range_time;

void loop()
  {
  long microsec = ultrasonic.timing();

  inMsec = ultrasonic.convert(microsec, Ultrasonic::IN);

  //publish the adc value every 50 milliseconds
  //since it takes that long for the sensor to stablize
  if ( millis() >= range_time ){
    int r =0;

    range_msg.range = inMsec;
    range_msg.header.stamp = nh.now();
    pub_range.publish(&range_msg);
    range_time =  millis() + 50;
  }

  nh.spinOnce();
}

I know it is publishing as rostopic list shows .ultrasound as one of the running topics. As I expect based on the line range_msg.radiation_type = sensor_msgs::Range::ULTRASOUND; it is publishing a Range and that is confirmed by running rostopic type ultrasound.

My subscriber, however, refuses to read this because of the Range type. Here's the code:

#!/usr/bin/env python

import rospy
from std_msgs.msg import String

def callback(data):
    rospy.loginfo(rospy.get_name() + ": I heard %s" % data.data)

def listener():
    rospy.init_node('listener', anonymous=True)
    rospy.Subscriber("ultrasound", Range, callback)
    rospy.spin()

if __name__=='__main__':
    listener()

based on the simple publisher and subscriber tutorials.

However, when I run it, the error message tells me

Traceback (most recent call last):
     rospy.Subscriber("ultrasound", Range, callback)
NameError: global name 'Range' is not defined

I tried changing it to rospy.Range and got

rospy.Subscriber("ultrasound", rospy.Range, callback)
AttributeError: 'module' object has no attribute 'Range'

I understand the error, but have no idea how to fix it. Can I get a gentle-ish shove in the right direction?