Building the Surveillance Copter [Software]

9 years ago
Posted in:design, quadcopter, systems, tutorial
0
Author: Vageesh Bhasin

This post outlines the steps taken by the team to get the software part of the Surveillance Copter ready:

Pre-Requisites:

Odroid U3 – Our choice for on-board computer that will be running ROS
Pixhawk PX4 – Our choice for flight controller
Logitech c920 Camera – Our choice for USB camera
UART Cables – To connect PX4 to U3
Network Cables – We are using a router for SSH-ing our development desktop to U3 [U3 has USB ports to connect keyboard & mouse, and a micro HDMI port to connect to a monitor]

DISCLAIMER:

Before we begin, we would like to thank the people behind PX4 for providing wonderful tutorials!
We are using Ubuntu on our development desktop, so all instructions below assume that you are using Ubuntu as your OS.

Step 1: Setting up Odroid U3

Our on-board computer will be running ROS, and will be used to gather image data from the C290 connected via USB. It will also act as a bridge to transfer telemetry data from PX4 using MAVLINK.

Flashing the eMMC card with Ubuntu –
- Download the latest (stable) version of ubuntu from odroid site.
- Connect the card to your desktop via a card reader.
- Install pv to monitor data transfer
```
$ sudo apt-get install pv
```
- Know your device (card) name and number
```
$ ls-al /dev/sd*
```
- Unmount that device
```
$ unmount /dev/sdX#
```
- Extract OS Image
```
$ xz -d ubuntu-COMPLETE-NAME-HERE.img.xz
```
- Flash the image
```
sudo dd if=ubuntu-14.04lts-server-odroid-u-20140604.img | pv | sudo dd of=/dev/sdb
```
- Call sync to make sure write is finished
```
$ sync
```
Logging into your U3 –
- Connect your U3 to a router via ethernet cable
- Connect your desktop to the router
- Using nmap (Network map) or zenmap (GUI for Network Map) to find the IP address of the U3
  [In our setup, the desktop got 192.168.2.2 and the U3 got 192.168.2.3]
- SSH into U3 [Default username: odroid , default password: odroid]
```
$ ssh 192.168.2.3 -l odroid
```

Installing ROS on U3 –

Add ROS Repository to index

$ sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu trusty main" > /etc/apt/sources.list.d/ros-latest.list'

Get the official ROS key

wget https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -O - | sudo apt-key add -

Update the package list
```
sudo apt-get update
```

Install ROS Packages [Base packages, MAVLINK packages, OpenCV Packages and Libuvc Camera Packages]

sudo apt-get install ros-indigo-ros-base ros-indigo-usb-cam ros-indigo-mavlink ros-indigo-mavros ros-indigo-cv-bridge ros-indigo-libuvc-camera

Install rosdep , which auto-magically installs any ROS dependancies

sudo apt-get install python-rosdep
sudo rosdep init
rosdep update

Setup catkin workspace

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws/src
catkin_init_workspace

Connecting PX4 to U3 –
- Connecting PX4 to U3 is very simple, if you have a UART cable.
- For other methods of connecting them, I suggest follow: Pixhawk Companion Link Guide
Creating our Copter Package –
- Initialize the catkin workspace
```
$ cd ~/catkin_ws
$ catkin_make
```
- Create a package [We don’t do any processing on this node, so it has no dependencies]
```
$ catkin_create_pkg adra_s
```
- Create the launch file
```
$ cd ~/catkin_ws/src/adra_s
$ mkdir launch</code>
$ touch base.launch
```
- Open the launch file with vi and paste the following configuration from our git repository : link
  Explanation for the above launch file:
  - We create 2 ROS Nodes – Mavros and Uvc_cam
  - Mavros relays telemtry data to the master
  - Uvc_cam gathers image data [We have used libuvc_camera package over default usb_cam]. We specify image size and type for this camera.
- We want our nodes to automatically start on boot. So we create shell script in /etc/init.d/ , register it as a service (create symlink) and run it whenever the system restarts:
- - Service Script: Copy this file and paste it into /etc/init.d/adra_s
  - Make it an executable: $ sudo chmod +x /etc/init.d/adra_s
  - Test it to see that the nodes fire up: $ sudo /etc/init.d/adra_s
  - Register it: $ sudo update-rc.d adra_s defaults
  - Verify service is registered: $ sudo service adra_s start
  - Open: /etc/rc.local
  - Paste the service call [just before exit 0 ]: sudo service adra_s start &
- All done, now reboot your U3: $ sudo reboot
Check everything is running –
- Run roscore on your desktop
- Power up your U3
- Verify that everything is working using rqt for Image viewing and Topic Visualization.

Some snapshots of the process:

S_Copter Hardware Connections

Software Up & Runnin

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Building the Surveillance Copter [Software]