Tvlad's profile - activity

Hello. I have the same issue. Do you have solutions? Please help.

Dear Mark, You was right. I use the motor driver for system, but I can't understand how to work with encoder. Can you help me with these?

Thanks for your answer. So, in this case, I can't create few nodes and just tell to dc motors the distance(use Python...rospy)?

Dear Mark.Thank you for your feedback. The hardware is easy: Raspberry PI3 + 2 DC motor and encoders + Line follower. Line follower link is : https://www.sparkfun.com/products/135... I will be so appreciated if you will help me. Thank you very much. Best Regards

Hello, everyone. I have the next equipment: https://www.pololu.com/product/2598 , https://www.pololu.com/product/2208 and raspberry pi.

I want to control the dc motors via ROS and Python. Is it possible? I can't find some good example or tutorials. I will be so appreciated if you will help me. Thank you.

Hello, everyone. I have some question to all of you. I have some simple robot car with Wheels and line follower. I also have a wireless charger? and I want that in time when I charging the battery, my steppers and line follower will be in sleeping mode. So, can you give some feedback, recommendation or example (better)? I use raspberry Pi3 with ROS kinetic on Ubuntu 16.04; Programming language is Python.

But need to put the full line with command "source" or without command?

I need a custom node with std_msgs. I tried both of the ways but still does not work. What can be the problem?

Thank you for your answer. Are you mean the next way:

exec("source /home/pi/catkin_ws/devel/setup.bash && rostopic pub -1 /test std_msgs/Int32 10000")

or

exec("source /opt/ros/kinetic/setup.bash && /opt/ros/kinetic/bin/rostopic pub -1 /test std_msgs/Int32 10000")

Hello, I have a question to all of you. For example, I have simple publisher and subscriber. The topic name "/test". I want click button on my PHP website and in the case when I will do this the data on a topic will change. If I want to publish some data from command line, such as:

rostopic pub -1 /test std_msgs/Int32 10000

It works.

The problem is:

Can I make the next situation on my PHP file

<?php
exec("rostopic pub -1 /test std_msgs/Int32 10000")
?>

Please help me.

Hello. I use python. I want to use the loop based on data of Publisher. For example, If I get the data == 1, I need to print "Hello" every 3 seconds, until when I will receive the new message with another data. Please help me.

Header header

int32 int

correct? sorry...

Sorry for stupid question, but what you mean?

Hello everyone. I hope that you can help me. So, please look at the example code below:

publisher_1.py

 #!/usr/bin/env python
 import rospy
 from std_msgs.msg import Int32
 from random import random

 pub = rospy.Publisher('pub_1', Int32, queue_size=10)
 rospy.init_node('publisher_1')
 rate = rospy.Rate(10) # 10hz
 while not rospy.is_shutdown():
     msg = Int32()
 msg.data = random()
 pub.publish(msg)
 rate.sleep()

publisher_2.py

 #!/usr/bin/env python
 import rospy
 from std_msgs.msg import Int32
 from random import random

 pub = rospy.Publisher('pub_2', Int32, queue_size=10)
 rospy.init_node('publisher_2')
 rate = rospy.Rate(10) # 10hz
 while not rospy.is_shutdown():
     msg = Int32()
     msg.data = random()
     pub.publish(msg)
     rate.sleep()

subscriber.py

import message_filters
from std_msgs.msg import Int32

def callback(msg_1, msg_2):
              if msg_1.data == msg_2.data:
                       print "True"
              else:
                       print "False"

sub1 = message_filters.Subscriber('pub_1', Int32)
sub2 = message_filters.Subscriber('pub_2', Int32)
ts = message_filters.TimeSynchronizer([sub1, sub2], 10)
ts.registerCallback(callback)
rospy.spin()

After I have ERROR: "Int32" has no attribute header. I found information that I can't use standard types of message. But can you give me some recommendation or another example, please, how to implement this task? If it's possible. It's really necessary for me. Thank you.

Hello everyone. I am a new in ROS(rospy), so please help me. I fount this information: http://answers.ros.org/question/21933...

I need to compare data from message (subscriber1) and message (subscriber2). Is it possible? Maybe someone has the part of code, some small example?

Thank you, but I have a question. For what we use the line:

self.value = None

And, Can I use the loop like this:

while self.value == "data":

Sorry If it's the stupid questions.