mattMGN's profile - activity

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

Hello,

I am working with a Raspberry Pi and an Arduino on ROS indigo. I would want to add a loginfo message to my script. However, each time I add this line : if (voltageValue<3.6) {nh.loginfo("Low Voltage");}, my rosserial node displays the following message and then stops to work :

[INFO] [WallTime: 1492093431.082536] Setup publisher on cell_voltage [std_msgs/Float32]
[INFO] [WallTime: 1492093431.087959] wrong checksum for topic id and msg
[WARN] [WallTime: 1492093431.112029] Serial Port read returned short (expected 78 bytes, received 73 instead).
[WARN] [WallTime: 1492093431.116379] Serial Port read failure: 
[INFO] [WallTime: 1492093431.119876] Packet Failed :  Failed to read msg data
[INFO] [WallTime: 1492093431.122835] msg len is 8
[INFO] [WallTime: 1492093431.147052] Setup publisher on cell_voltage [std_msgs/Float32]
[INFO] [WallTime: 1492093431.155512] wrong checksum for topic id and msg
[INFO] [WallTime: 1492093431.172463] Setup publisher on cell_voltage [std_msgs/Float32]
[INFO] [WallTime: 1492093431.179750] wrong checksum for topic id and msg
[INFO] [WallTime: 1492093431.200429] wrong checksum for topic id and msg
[ERROR] [WallTime: 1492093446.191686] Lost sync with device, restarting...

My Arduino script is

#include <Timer.h>
#include <ros.h>
#include <std_msgs/Float32.h>
#include <geometry_msgs/Twist.h>

// voltage sensor
int sensorPin = A1;
int sensorValue = 0;
float voltageValue = 0;

Timer _timer_2(500),  //2Hz
       _timer_100(10); //100Hz

unsigned long temps = 0;

ros::NodeHandle nh;

//Def
std_msgs::Float32 float_msg;
std_msgs::Float32 float_msg_compas;

//Pub/sub
ros::Publisher pu("cell_voltage", &float_msg);
ros::Publisher compas("compas", &float_msg_compas);
ros::Subscriber<geometry_msgs::Twist> su("cmd_vel" , messageCb);

void setup() {     
  nh.getHardware()->setBaud(115200);
  nh.initNode();
  nh.advertise(pu);
  nh.advertise(compas);
  nh.subscribe(su);

  temps = millis();
  _timer_2.start((unsigned long) millis());
  _timer_100.start((unsigned long) millis());
}

void messageCb( const geometry_msgs::Twist& vel)
{
  float xx = vel.linear.x;
  float zz = vel.angular.z;

  if (xx>0.08){ nh.loginfo("AVANCE"); // THIS ONE IS WORKING
      ...} 
 }

void voltageCb(){
  sensorValue = analogRead(sensorPin);
  voltageValue = sensorValue * 5.0 /1023.0;
  float_msg.data = voltageValue;
  pu.publish(  &float_msg );
  if (voltageValue<3.6) {nh.loginfo("Low Voltage");}  // THIS ONE NOT IS WORKING
  delay(10);
}

void loop() {
  if (_timer_100.delay(millis())){  nh.spinOnce();}

  if (_timer_2.delay(millis())){  voltageCb(); }
}

Does anybody know how to fix this problem ? I suppose the problem comes from the lack of argument in voltageCb(). But I am not sure what shall be put inside this function ?

Regards

Matthieu

[Hector Mapping] Could not transform while tf being published Hello, I am trying to set a basic launch file to create a

That's was not the point, as that it works both with and without std_msgs thank you for your input

You are right, It now works Thanks for your comment

Hello,

I have defined this custom message, FloatsStamped.msg :

Header header
float32[] data

The CMakeLists.txt is:

cmake_minimum_required(VERSION 2.8.3)
project(grideye)

find_package(catkin REQUIRED COMPONENTS
  roscpp
  rospy
  std_msgs
  message_generation
)

################################################
## Declare ROS messages, services and actions ##
################################################

## Generate messages in the 'msg' folder
add_message_files(
  FILES
  FloatsStamped.msg
)

## Generate added messages and services with any dependencies listed here
generate_messages(
  DEPENDENCIES
  std_msgs
)

###################################
## catkin specific configuration ##
###################################

catkin_package(
  CATKIN_DEPENDS roscpp rospy std_msgs message_runtime
)

###########
## Build ##
###########

include_directories(
  ${catkin_INCLUDE_DIRS}
)

My package.xml is :

<?xml version="1.0"?>
<package>
  <name>grideye</name>
  <version>0.0.0</version>
  <description>The grideye package</description>

  <buildtool_depend>catkin</buildtool_depend>
  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>
  <build_depend>message_generation</build_depend>
  <run_depend>message_runtime</run_depend>
  <run_depend>roscpp</run_depend>
  <run_depend>rospy</run_depend>
  <run_depend>std_msgs</run_depend>
  <build_depend>python-numpy</build_depend>
  <run_depend>python-numpy</run_depend>

</package>

And finally the code I use is:

#!/usr/bin/env python

import rospy
import numpy
from grideye.msg import FloatsStamped
from grideye_class import GridEye

def talker():
    pub = rospy.Publisher('thermal_pixels', FloatsStamped, queue_size=10)
    rospy.init_node('grideye', anonymous=True)
    r = rospy.Rate(5)
    pix = []
    while not rospy.is_shutdown():
        pix = mysensor.getPixels()
        print(pix)

        #feed a FloatsStamped msg
        a = FloatsStamped
        a.header.stamp = rospy.Time.now() 
        a.data = numpy.array(pix, dtype=numpy.float32)

        pub.publish(a)
        r.sleep()

if __name__ == '__main__':
    mysensor = GridEye()
    rospy.loginfo("Starting data retrieving from Grid Eye sensor Board")
    talker()

I get an error message indicating that :

a.header.stamp = rospy.Time.now()  AttributeError: 'member_descriptor'

object has no attribute 'stamp'

I declare a as FloatsStamped message and this message includes the Header message, so I don't understand why I get this error message.

matt

Really clear, thank you for that explanation!

Hello,

I am using an arduino Mega to publish LaserScan message. But I have a weird result, when i run this code:

#include <ros.h>
#include <sensor_msgs/LaserScan.h>

ros::NodeHandle nh;

// Laser Scan
sensor_msgs::LaserScan lidar_msg;
ros::Publisher lidar_pub("/laser_scan", &lidar_msg);
float ranges[10] = {0};
float intensities[10] = {0};

void setup()
{  
  // Initialize ROS node handle, advertise and subscribe the topics
  nh.initNode();
  nh.getHardware()->setBaud(57600);
  nh.advertise(lidar_pub);

  // Set LaserScan Definition
  lidar_msg.header.frame_id = "lidar";
  lidar_msg.angle_min = 0.0;               // start angle of the scan [rad]
  lidar_msg.angle_max = 3.14*2;            // end angle of the scan [rad]
  lidar_msg.angle_increment = 3.14*2/360;  // angular distance between measurements [rad]
  lidar_msg.range_min = 0.3;               // minimum range value [m]
  lidar_msg.range_max = 50.0;                // maximum range value [m]
}


void loop(){

  // simple loop to generate values
  for (int i=0 ; i<10 ; ++i){
    ranges[i] = 1.0*i;
  }

  lidar_msg.ranges = ranges;
  lidar_msg.header.stamp = nh.now();
  lidar_pub.publish(&lidar_msg);
  nh.spinOnce();

}

Then, I launch rosserial node to start serial communication:

$ rosrun rosserial_python serial_node.py /dev/ttyUSB2
[INFO] [1519508591.451838]: ROS Serial Python Node
[INFO] [1519508591.468653]: Connecting to /dev/ttyUSB2 at 57600 baud
[INFO] [1519508593.624826]: Note: publish buffer size is 512 bytes
[INFO] [1519508593.625218]: Setup publisher on /laser_scan [sensor_msgs/LaserScan]

But when, i echo the topic, I didn't get any values in ranges:

---
header: 
  seq: 112
  stamp: 
    secs: 1519508602
    nsecs:  77765016
  frame_id: "lidar"
angle_min: 0.0
angle_max: 6.28000020981
angle_increment: 0.0174444448203
time_increment: 0.0
scan_time: 0.0
range_min: 0.300000011921
range_max: 50.0
ranges: []
intensities: []
---

Any idea ?

matt

ranges_length and intensities_length were the point ! Thanks you

Publish LaserScan from Arduino Hello, I am using an arduino Mega to publish LaserScan message. But I have a weird resul

Ok, I will give it a try on next week

Custom message Hello, I have defined this custom message, FloatsStamped.msg : Header header float32[] data The CMak

Yes in fact, running also fake node created conflicts in publishing map->base_link transform. Now i don't run fake_no

Inconsistent localization in gmapping Hello, I am trying to map the turtlebot3.world as explain in wiki. Thus i run thi

Hello,

I would want to call a service using python. Currently this command line is working :

rosservice call /camera/start_capture

but I can't figure out how to do the same thing with python. I already tried this without succes :

rospy.ServiceProxy('/camera/start_capture',True)

Any idea ?

Matt