Access Raspberry Pi via SSH, VNC and netatalk from your Mac

Originally I planned to use a Mac for my work with opencv on the Raspberry Pi. I failed to set up the Mac properly so I switched to my Ubuntu Laptop which was laying around. And it was so much easier. Mostly because of the various tutorials available. Recently I hadn't any time to play around with opencv but maybe I find some time now and then. And since where I live now, I don't have my Linux PC with me, I have to do it with my MacBook Air.

The first thing if you want to work with a Raspberry Pi and don't have a Monitor available, you want to link it somehow to your PC/Mac and do the work from there. I explained how I did it with my Ubuntu Laptop here and now I want the same functionality with my MacBook.

So first I want to find out the IP address of the Raspberry Pi. I looked in the AppStore and found a free app called "IP Scanner" (Link), which shows all the IP addresses of all the devices in your network.

Connecting over SSH

To connect to your RPi open the terminal on your Mac and type this with the IP adress of your RPi:

 ssh pi@192.168.0.101  

Type in your password (default: raspberry).

Finally in your terminal you should see:

Now every command you type here, the RPi executes - not your computer.

Connecting over VNC

Sometimes this is not enough and you want to see the GUI of the RPi. You can also do this over the network with a VNC server. The part on the RPi is the same and I just copy it from my former tutorial.

On your RPi:
First connect to your RPi over SSH and install tightVNC.

 sudo apt-get update  
 sudo apt-get upgrade  
 sudo apt-get install tightvncserver  

To start the VNC Server use this command:

 vncserver :1 -geometry 1024x600 -depth 16 -pixelformat rgb565  

You must specify a password (8 characters) that you need to connect later. Answer no to the view only question.

On your Mac:
On the Mac you don't need to install anything. Sure, you could install any VNC Viewer you like, but if my computer already comes with the tools, I like to use them.
In Finder press

 cmd+K  

A new window opens where you can type in the IP of your RPi (don't forget to edit the command!):

 vnc://192.168.0.101:5901  

The 01 at the end it the VNC server on the RPi, to start the server on the Pi we chose 1 as well. After that type in your password and hit connect.

After that 'Screen Sharing' should open and you see this:

This is very comfortable like this and you can even save your password and your IP.

File transfers with Netatalk

To transfer files I use Netatalk which is already installed on my Pi. I just paste the command from my older tutorial. Here we have to do it again only on the RPi.

On your RPi install netatalk:

 sudo apt-get install netatalk  

After that give it some time to fully boot and then you should see the RPi in your finder under shared:

Here you click on 'Connect As ...'. In the window that will open type in 'pi' as Name and your password from natatalk (default raspberry).


After that I have the full functionality as I had in Linux.

Program versions:
Mac OSX 10.10.1
Raspian wheezy

Access Raspberry Pi via SSH, VNC and netatalk from your Linux PC

Working on a Raspberry Pi is realtivly slow. Because of that I set up a cross compiler on my Linux Laptop (Part 1, Part 2). But also if you want to move files to your RPi or try running a program, it is sometimes a pain. I for example don't have a HDMI monitor or a USB keyboard. I only have my laptop. But luckily I can do everything I want on my RPi over the network.

To all of this you need the IP of your RPi in your network. For this I connected my RPi to my TV and borrowd a USB keyboard from a friend. If even this is not possible to you, here's a solution on how you can search for devices connected to your network.

On the RPi type in the terminal:

 ifconfig  

You should get something like:

 inet addr:192.168.0.101  

Note this!

Connecting over SSH

To connect to your RPi open the terminal on your Linux computer and type this with the IP adress of your RPi:

 ssh pi@192.168.0.101  

Answer the fingerprint question with yes and type in your password (default: raspberry).

Finally in your terminal you should see:

Now every command you type here the RPi executes - not your computer.

Connecting over VNC

Sometimes this is not enough and you want to see the GUI of the RPi. You can also do this over the network with a VNC server.

On your RPi:
First connect to your RPi over SSH and install tightVNC.

 sudo apt-get update  
 sudo apt-get upgrade  
 sudo apt-get install tightvncserver  

To start the VNC Server use this command:

 vncserver :1 -geometry 1024x600 -depth 16 -pixelformat rgb565  

You must specify a password (8 characters) that you need to connect later. Answer no to the view only question.

On your computer:
Open another terminal window and install a VNC viewer:

 sudo apt-get update  
 sudo apt-get upgrade  
 sudo apt-get install xtightvncviewer  

Now you can connect to the VNC server on the RPi via (edit the IP!):

 vncviewer 192.168.0.101:5901  

You should see the Desktop of the RPi in a window on your computer.

To stop the viewer just close the window and to stop the server type this on the RPi:

 vncserver -kill :1  

File transfer with netatalk

And how can I put these newly cross compiled programs on my RPi? Sure, with a USB stick. But since I already do everything over the network, I want to transfer files like this as well. The answer is netatalk.

On your computer and RPi install netatalk:

 sudo apt-get install netatalk  

Then just reboot both. After that give it some time to fully boot and then you should see the RPi in your file explorer under network:

Double click it and it asks for a username and password. These are:
Username: pi
Password: whatever you chose, default is raspberry

After that you can browse your files on the RPi from your computer and copy easily new files over

Program versions:
Ubuntu 12.04 LTS
Raspian wheezy 2014-01-07

How to cross compile for Raspberry Pi using Code::Blocks on Linux

In my privious post I described how I managed to build a cross compiler in Ubuntu for a Raspberry Pi. To compile I used a terminal command. But I want to use a IDE. On Linux I use Code::Blocks for now.

So we have to add a custom compiler to Code::Blocks. Go to

Settings --> Compiler ... --> Global compiler settings

Select the GNU CCC Compiler and click Copy. Give your new cross compiler a meaningful name.

Select your created compiler and go to Toolchain executables. Specify under Compiler's installation directory the path where you keep you cross compiler. For me the path looks like this:

/home/christian/Programming/x-tools/arm-unknown-linux-gnueabi

IMPORTANT: Don't specify the path to the bin directory like in the add-to-$PATH tutorial !!!

After that change the compilers and linkers so it looks like this:

Hit OK and create a new project. Select Console application.

Select your language and your directory where you want to save the project ...

Select your just created compiler...

After that you see already a Hello-World-Program. Try to build it. If it works yout get this notification.

Now we want to check if the cross compiler worked. Copy from your project directory the created file in /bin/debug in your home directory on your RPi. On your RPi (I used ssh) open the terminal and type

 ./ FILENAME  

If you see a "Hello World!" then your cross compiler works !

Program versions:

OS: Ubuntu 12.04 LTS
crosstool-ng 1.19.0
Code::Blocks 10.05

How to build a cross compiler for Raspberry Pi using crosstool-ng

Normally I'm working with a Mac and OpenCV. But I want to run OpenCV on a Raspberry Pi for a small preject. Since I don't want to compile on the Raspberry and lose a lot of time, I was looking for a cross compiler. Looks like this is easier from a Linux machine. I had an old Windows laptop left and so I installed Ubuntu 12.04 LTS along with Windows 7 on it.

I found some really good tutorials about this so I won't repeat them and just give you some links:

1. Very clear tutorial. Lightweight for a good overview:
http://www.bootc.net/archives/2012/05/26/how-to-build-a-cross-compiler-for-your-raspberry-pi/
2. More detailed with screenshots:
http://www.kitware.com/blog/home/post/426

I really like the first tutorial but it's missing information about packages you have to install before you can build crosstool-ng. On Ubuntu you do this with this command in the terminal:

 sudo apt-get install PACKAGE_NAME  

The second link already names some packages, but not all of them. I got errors when I tried to build the toolchain, for example subversion is needed to download a package during the build process. So here is a list of what I installed (replace PACKAGE_NAME with the name below to install):

• libssl-dev 
• openssh-server 
• git-core 
• pkg-config 
• build-essential 
• curl
• gcc 
• g++
• bison 
• flex 
• gperf 
• libtool 
• texinfo 
• gawk 
• automake 
• libncurses5-dev
• subversion

Lot's of stuff, but finally I got the toolchain built.

The tutorial says that we have to add the compiler to our $PATH. This is done with this command (don't forget editing the path to your compiler):

 export PATH=$PATH:/PATH/TO/x-tools/arm-unknown-linux-gnueabi/bin  

Remember that this is only temporal! The next time you open your terminal you have to add this to your $PATH again

After this we can compile a "Hello World!" program with this command (source code):

 arm-unknown-linux-gnueabi-c++ hello.cpp -o hello  

Program versions:
OS: Ubuntu 12.04 LTS
crosstool-ng 1.19.0
gcc-linaro 4.8-2013.06-1

Static background subtraction using OpenCV

With background subtraction you can eliminate the background and focus on the actual object for further processing (detection, recogization, ...). Some algorythms provided in the OpenCV library are "learning" the background. The problem is if an object doesn't move, it will become the background as well. If you have a fixed camera - and so always the same background - you can just calculate the diffrence of two images.

Here's the code I used (you can download it here):

1:   #include <opencv2/core/core.hpp>   
2:   #include <opencv2/highgui/highgui.hpp>   
3:   #include <opencv2/imgproc/imgproc.hpp>   
4:   #include <iostream>   
5:   using namespace cv;   
6:   int main( int argc, char** argv )   
7:   {   
8:    // Read image given by user   
9:    Mat src = imread( "/users/christian/documents/programming/other/imgs/background.jpg", 0); // 1:color, 0:grayscale   
10:    Mat dst = imread("/users/christian/documents/programming/other/imgs/backtest.jpg", 0);   
11:    // background subtraction   
12:    Mat diff;   
13:    absdiff(src, dst, diff);   
14:    threshold(diff, diff, 10, 255, CV_THRESH_BINARY); // grayscale needed   
15:    // Show image in window   
16:    imshow("original", src);   
17:    imshow("new", dst);   
18:    imshow("diff", diff);   
19:    // Wait until user presses key   
20:    waitKey();   
21:    return 0;   
22:   }   

All it does is loading two images, calculating the differance, applying a threshold to highlight the object and displaying the 3 images.

This is just a theoretical example. Because here I use a static image to calculate the differnce, this method is very light sensitve. Lighting will also change the background and will no longer match exactly the stored background.

Program versions:

OS: Mac OS X 10.9.1
Xcode: 5.0.2
OpenCV: 2.4.8.0

Directories

This partly just a reminder for myself. But maybe some of you wondered where these libraries are and where Xcode 5 saves the executables that you just compiled.

Xcode 5 hides the project files pretty well but you can find them under:

 /users/username/Library/Developer/Xcode/DerivedData  

To access the Library folder, klick Go in the finder menu bar. When you pres the alt-key a link to Library should appear.

And where are the OpenCV files you installed using cmake?
The lib-files are in

 /usr/local/lib  

and the headers in

 /usr/local/include 

Again, the usr-folder is hidden. The easiest way to get there is by just typing the path in finder Go->Go to Folder...

Also important to know is the location of additional libraries you installed using MacPorts. MacPorts installs everything to

 /opt/local

Nothing is hidden there, so no problem.

Because auf the hidden folders and the rather longer paths I created for me some aliases to acess these folders rapidly from my working folder.

Program versions:
OS: Mac OS X 10.9.1
Xcode: 5.0.2
OpenCV: 2.4.8.0
MacPorts: 2.2.1

How to use imageclipper on Mac OS X

In the previous tutorial I explained how to build imageclipper from source. You may have done this or just downloaded the executable file I provided. But you can't just double click it. If you do, only a help will be presented:

 Application Usage:  
  Mouse Usage:  
   Left (select)     : Select or initialize a rectangle region.  
   Right (move or resize) : Move by dragging inside the rectangle.  
                Resize by draggin outside the rectangle.  
   Middle or SHIFT + Left : Initialize the watershed marker. Drag it.   
  Keyboard Usage:  
   s (save)        : Save the selected region as an image.  
   f (forward)       : Forward. Show next image.  
   SPACE          : Save and Forward.  
   b (backward)      : Backward.   
   q (quit) or ESC     : Quit.   
   r (rotate) R (opposite) : Rotate rectangle in counter-clockwise.  
   e (expand) E (shrink)  : Expand the recntagle size.  
   + (incl)  - (decl)   : Increment the step size to increment.  
   h (left) j (down) k (up) l (right) : Move rectangle. (vi-like keybinds)  
   y (left) u (down) i (up) o (right) : Resize rectangle. (Move boundaries)  
   n (left) m (down) , (up) . (right) : Shear deformation.  
 Now reading a directory..... No image file exist under a directory .  
 ImageClipper - image clipping helper tool.  
 Command Usage: imgclipper [option]... [arg_reference]  
  <arg_reference = .>  
   <arg_reference> would be a directory or an image or a video filename.  
   For a directory, image files in the directory will be read sequentially.  
   For an image, it starts to read a directory from the specified image file.   
   (A file is judged as an image based on its filename extension.)  
   A file except images is tried to be read as a video and read frame by frame.   
  Options  
   -o <output_format = imgout_format or vidout_format>  
     Determine the output file path format.  
     This is a syntax sugar for -i and -v.   
     Format Expression)  
       %d - dirname of the original  
       %i - filename of the original without extension  
       %e - filename extension of the original  
       %x - upper-left x coord  
       %y - upper-left y coord  
       %w - width  
       %h - height  
       %r - rotation degree  
       %. - shear deformation in x coord  
       %, - shear deformation in y coord  
       %f - frame number (for video)  
     Example) ./$i_%04x_%04y_%04w_%04h.%e  
       Store into software directory and use image type of the original.  
   -i <imgout_format = %d/imageclipper/%i.%e_%04r_%04x_%04y_%04w_%04h.png>  
     Determine the output file path format for image inputs.  
   -v <vidout_format = %d/imageclipper/%i.%e_%04f_%04r_%04x_%04y_%04w_%04h.png>  
     Determine the output file path format for a video input.  
   -f  
   --frame <frame = 1> (video)  
     Determine the frame number of video to start to read.  
   -h  
   --help  
     Show this help  
  Supported Image Types  
    bmp|dib|jpeg|jpg|jpe|png|pbm|pgm|ppm|sr|ras|tiff|exr|jp2  

This already tells you a lot. But to you is it you have to do the following:

1. Create a folder and put in all the images you want to cut and the imageclipper executable.

2. Open the Terminal app and navigate to this folder.

3. Once you're in this folder, type this (or whatever your name for the executable is):

 ./imageclipper  

4. A new window should open showing the first picture in this folder.

5. With your mouse draw a rectangle of the part you want to cut. Another window will open showing you how your cut image will look like.

6. To crop it and hit s, to jump to the next image hit f. Or you hit space to combine these two steps which makes you even faster.

7. After cropping, the next image in the folder will automatically open. To leave the aplication, hit esc.

That's it. You will find you're cropped images in a separete folder called imageclipper.

Program versions:
OS: Mac OS X 10.9.1
OpenCV: 2.4.8.0