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I am using some CAN USB interface, where I am using those receive and transmit nodes which are already existed for this hardware type. So the message that they have used here is std_msgs/String.

this is the subscriber node from ros tutorials:

void chatterCallback(const std_msgs::String::ConstPtr& msg) 
{
  ROS_INFO("I heard: [%s]", msg->data.c_str());
}

My string array consists of msg which is shown in image, Now i need to access a particular element in the msg (message consists first time and next CAN message, I want to use particularly CAN.ID whic is arrays second element) any suggestion. thanks in advance

try to do it by synaptic package manager, it should look like this, I hope it works

i have two nodes 1) which receives CAN messages from uc board to ROS (publisher) 2) which transmit CAN messages to uc board (subscribing). I need to run both the nodes in order to to these two tasks. Now I am supposed to do: if receive node receives message, it should transmit a CAN message. How can I combine these two nodes or how can use one node information by other?. any suggestions

Hallo all,

I have two nodes in ROS which can receive (1st node) and transmit (2nd node) CAN messages over a Peak CAN USB Interface. My receive node receives CAN message from μc board, with rostopic pub command line tool I could able to send a CAN message to μc board which turn on LED on μc board. My question is: if the received CAN message is with particular ID (which is published on receive topic)- which should send other CAN message to μc board to turn LED ON. Both the transmit and receive node have their own topics. Could anyone please suggest how to send a CAN message from ROS to μc board as soon as it receives from μc board to ROS.

Hallo all,

I am trying to work with gui in ros(in cpp), i have two questions regarding it

1. As mentioned in ros rqt plugin tutorials:

   • created package, edited cmakelist.txt, package.xml, plugin.xml
   • as mentioned in the tutorial should uncomment catkin_python_setup() what if for cpp?

   • I tried to do catkin_make then it shows:

     Invalid package manifest "/home/george/catkin_new/src/rqt_mypkg/package.xml": The manifest must not contain more than one "export" tags
     
     george@george-ThinkPad-T440s:~/catkin_new$ cmake
     cmake version 2.8.12.2
     

2. Writing a ros node in src, and doing to make catkin_make, I had an example which is publishing some std_msg: Please have a look, here my doubt is without any .ui file or process that happens in qt how it opens a window?

I saw an example:

#include "QDebug"
#include "ros/ros.h"

int main(int argc, char** argv)
{
  ros::init(argc, argv, "Qt_test");
  qDebug()<<"Hello world";
    return 0;
}

Here I made changes in cmakelist.txt as: find_package(Qt4 COMPONENTS QtCore QtGui) include(${QT_USE_FILE})

add_executable(qt_test src/qt_test.cpp) target_link_libraries(qt_test ${QT_LIBRARIES})

Now I tried to do catkin_make then I get the problem:

error: expected primary-expression before ‘int’ ros::init(int argc, char **argv,"qt_test");

error: expected primary-expression before ‘int’ ros::init(int argc, char **argv,"qt_test");

Can any one help this problem or should I need to do changes, any suggestions please. Thanks

hello, Actually I had both indigo and jade installed in my system. I tried to remove jade by sudo apt-get remove ros-jade but it shows unable to locate package ros-jade. I want to remove only jade

Thanks for your response. As mentioned here I tried to open cmakelist.txt, but it says Cannot create file /opt/ros/jade/share//catkin/cmake/toplevel.cmake.user:Permission denied. Actually I am working with ros indigo(here it shows jade).

Hello,

My doubt is, If I want to write a ros node using qt GUI- Is it necessary to follow rqt plugin cpp tutorial(I mean is it necessary to create a plugin) or is it possible to write a node and add cmakelist.txt as here. A small example to which opens a qt window is very helpful. Many thanks in advance.

Hello All,

I am new to ROS, I need help regarding implementation of qt-slider in ros.

Can any one help me or give suggestions, thanks in advance.

I have qt source files: Please have a look:

MainWindow::MainWindow()
{
    slider = new QSlider(Qt::Horizontal);
    slider->setMinimum(0);
    slider->setMaximum(100);
    lineEdit = new QLineEdit();

    QObject::connect(slider, SIGNAL(valueChanged(int)),
                     this, SLOT(onValueChanged(int)));

    QVBoxLayout *layout = new QVBoxLayout();
    layout->addWidget(slider);
    layout->addWidget(lineEdit);

    QWidget *wrapper = new QWidget();
    wrapper->setLayout(layout);
    setCentralWidget(wrapper);
}

MainWindow::~MainWindow()
{
}

void MainWindow::onValueChanged(int value)
{
    int pos = slider->sliderPosition();
    QByteArray convertedValue = QByteArray::number(pos,16);
    QString m = QString(convertedValue);
    m= "0x"+m;
    QString id,len, canmsg;
    id="0x01 ";
    len="0x01 ";
    canmsg=id+len+m;
    lineEdit->setText(canmsg);
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow mainWindow;
    mainWindow.show();
    return app.exec();
}

Can any one help me to publish this message(i mean 'canmsg') on topic(any). As discussed in qt ros, I made changes in cmakelist.txt. Thanks for reading.