plusangel

<launch>
  <arg name="foo"/>

  <node name="usb_cam" pkg="usb_cam" type="usb_cam_node"
    output="screen" >
    <param name="video_device" value="/dev/video0" />
    <param name="image_width" value="640" />
    <param name="image_height" value="480" />
    <param name="pixel_format" value="mjpeg" />
    <param name="camera_frame_id" value="usb_cam" />

plusangel

How to install packages from github

git clone -b <branch> <address>
e.g.  git clone -b hydro-devel https://github.com/ros/common_msgs.git

What python version I ahve installed?
pkg-config --modversion opencv

How to view a camera topic on ROS?
rosrun image_view image_view image:=/usb_cam/image_rect

plusangel

 How to download all Gazebo models

Gazebo is a wonderful simulation tool widely used in robotics projects. The project includes a library of 3D models that are automatically downloaded on demand. However this makes the application pause each time a model is used for the first time, which can take a considerable time depending on connection speed and interfere with the flow of work.

In order to avoid this issue I wrote the below script to do a bulk download of all models in the Gazebo library, then copy them to the local model folder. Simply copy the lines below to a script file on a convenient local folder and run it from a command prompt.

#!/bin/sh

# Download all model archive files
wget -l 2 -nc -r "http://models.gazebosim.org/" --accept gz

plusangel

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "board.h"
#include "msg.h"
#include "thread.h"
#include "periph/uart.h"

plusangel

#from StringIO import StringIO  # Python2
from io import StringIO  # Python3
 
import sys
 
# Store the reference, in case you want to show things again in standard output
old_stdout = sys.stdout

# This variable will store everything that is sent to the standard output
result = StringIO()

plusangel

I have setup Ad-Hoc mode on my Pi3.

This involves modification to network configuration file /etc/network/interfaces so you should first make a backup e.g. sudo cp /etc/network/interfaces /etc/network/interfaces.orig.

Replace the interfaces file with the following:-

# interfaces(5) file used by ifup(8) and ifdown(8)

# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'

plusangel

# ROS1
export ROS_DISTRO=melodic
source /opt/ros/$ROS_DISTRO/setup.bash
source /home/user/catkin_ws/devel/setup.bash

# ROS2
export ROS_DISTRO=crystal
source /opt/ros/$ROS_DISTRO/setup.bash
source /home/user/ros2_ws/install/local_setup.bash

plusangel

#include <iostream>
#include <vector>
#include <thread>
#include <future>

std::mutex g_display_mutex;


// function for threads
void accumulator_function(const std::vector<int> &v, unsigned long long &acm,

plusangel

#include <iostream>

class Switchable {
    public:
    virtual void on() = 0;
    virtual void off() = 0;
};

class Switch {
private:

plusangel

#include <array>
#include <algorithm>
#include <iostream>

class MyType {
public:
    MyType() = default;
    MyType(int item):item_{item}
    { }