It seems like I use my Raspberry Pi just often enough to forget everything about how I set it up the previous time.  Unlike an Arduino, it’s possible all sorts of new configuration \ updating will need to take place if it’s sat for a few months.  This post will serve mainly a notepad to myself on what I need to do to get it up and running again, and info on how to do fresh installs.

I’m sure this all can vary widely from user to user and Pi to Pi.

Great Linux/Unix command-line cheat-sheet: Web Site, PDF.

First Time Setup Guides

Just in case you do need to do everything from scratch:

• http://www.raspberrypi.org/wp-content/uploads/2012/04/quick-start-guide-v2_1.pdf : Super simple quickstart pdf, mainly just covers sd card formatting & NOOBS download.
• http://www.raspberrypi.org/forum/viewtopic.php?f=91&t=4751 : “How to start using you Raspberry Pi” from the forums.
• http://www.engadget.com/2012/09/04/raspberry-pi-getting-started-guide-how-to/ : Engadget overview

The overall gist is:

• Format SD
• Download Linux distro and install on card
  • Most recently, I used Pi Filler (looks like Mac only)  : It does both the format and install.
  • Look here for other solutions.
• Once the pi is up and running, via the settings menu:  (run > raspi-config to get there from the commandline)
  • Expand the root partition:  This is only needed for older distro installs.  If you’re using NOOBS, it should be auto-expanded.
  • Set screen overscan (if wanted)
  • Configure keyboard
  • Change password (if wanted)
  • Set locale, timezone
  • Enable ssh & boot behavior
• Optionally you can then try to make a new user, but I’ve not found a need yet.  And when I do it, I tend to screw it all up permission-wise.
• Install VNC (so you access the Pi’s gui remotely)

Linux Distros

I’m the last person you want to ask about which distro to use, but the two main one’s I have used are Raseberian, and Occidentalis.  Rasberian is now installed as part of NOOBS, and it’s a much easier install than in the past.

• NOOBS : From the page:  “We recommend that first-time Pi users start by downloading and installing our New Out of Box Software (NOOBS) onto a 4GB (or larger) SD card. On first boot, this presents you with a choice of operating systems to install, including Raspbian, Pidora and two flavours of XBMC. Once you have installed an operating system, you can return to the NOOBS interface by holding down shift during boot; this allows you to switch to a different operating system, or overwrite a corrupted card with a fresh install of the current one.”
• Occidentalis : From the page : “Our distro is based on “Wheezy” but comes with hardware SPI, I2C, one wire, and WiFi support for our wifi adapters. It also has some things to make overall hacking easier such sshd on startup (with key generation on first boot) and  Bonjour (so you can simply ssh raspberrypi.local from any computer on the local network)”

Get into the Pi

It’s been a while, how do I do that?  I forgot where my  surplus usb keyboard is & the wifey is using the spare hdmi cable…

(To do a first-time setup of SSH & VNC, see the post, “Connecting the Mac to the Pi“)

First, SSH:

This will let external machines talk to the Pi.  The primary way I interact with the Pi.
Connect the pi to the network (I use cat5).
There’s a good chance the dynamic ip has changed.  From another computer, access the router and click on the ‘DHCP Client List’ to find the new ip of the Pi.
Or, if you have the Pi plugged into a monitor \ keyboard, you can enter the below command, and look for the “inet addr”

$ sudo ifconfig

Open a shell.  ssh into the Pi:

$ ssh <pi ip address> -l <userName>

Enter password.  Hopefully it lets you in…

This can fail though on a new install.  I get this on my mac:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
etc...

If this happens, lower down in the error it will have this line:

The fingerprint for the RSA key sent by the remote host is

And right below that, is an address.  Copy that address, browse (on the mac) here:

/Users/<userName>/.ssh/known_hosts

Edit that file (known_hosts), and find the section starting with the local ip of your pi.  At the end of that section, add a ‘+’, then paste in the address copied above.

When you try to re-ssh back in, it will ask you if you want to add this new host, and say “yes”.  Enter the password, and you should be good!

Copying files over SSH:

Once you have a ssh connection, you can copy data from one machine to another.

From a terminal on your PC (in my case, a Mac):

Copy data from the Pi to the PC:

$ scp pi@you_pis_ip:/path/to/source/file/on/pi /path/to/destination/file/on/pc

For example:

$ scp pi@192.168.2.27:~/piVid.mp4 ~/macVid.mp4

Copy data from your PC to the Pi:

$ scp /path/to/source/file/on/pc pi@you_pis_ip:/path/to/destination/file/on/pi

For example:

$ scp ~/macVid.mp4 pi@192.168.2.27:~/piVid.mp4

I should note that I’ve not got this to work over SSH from a terminal on the Pi.  But once a ssh connection is open, I can execute these from a terminal on my Mac just fine.

Copying files via SFTP

If you want a more robust solution to copying files to\from the Pi, SSH File Transfer Protocol (SFTP) is a good solution. The post HERE by Trevor Appleton covers how to set it up using FileZilla.  Provides a super easy way via the FileZilla gui to drag & drop files.

Second, VNC:

Once you’ve ssh’d in to the Pi, optionally you can access the desktop via VNC.

If not yet installed, install it:

$ sudo apt-get install tightvncserver

Then start the server:

$ vncserver :1

To start the server.
On your other PC, access the VNC Viewer app.
Set the VNC server address to <pi ip address>:1
Connect:  You should see your Pi’s desktop on your PC.

Update Pi Configuration

Not always needed, but if you need to access the global configuration on the pi, from the shell enter:

$ raspi-config

When done, if a reboot is needed:

$ sudo reboot

Optionally, to safely shutdown the Pi (rather than just unplugging it, which I’m told can be hard on the sd card) :

$ sudo shutdown -h now

Auto Login

Check out the post here:  Raspberry Salad Part 3: Auto-run program on startup

General linux commands

• ifconfig : network info
• pgrep <process name> : Return the process id
• kill <process id> : delete the process
• lsusb : Get attached usb device info

Setup WiFi

Adafruit has a good overview here.  Note that their section on “Setting up WiFi with the graphic interface” works, but the Pi will only start using WiFi when the gui is up.  If you want wifi to be there at the commandline as soon as the Pi boots, you need to follow their  “Setting up WiFi with the Command Line” tutorial.

Note, I’ve needed to have the pi connected to a monitor\keyboard\mouse to get this setup properly.   Having the Pi hooked up over lan and ssh’d in seems to override the WiFi with the lan, and I can’t get the IP.  Maybe I’m not smart enough.

Check to see if it’s working:

$ ping google.com

BUUUUT, I’d had problems with loosing connection over wifi.  After getting a tip from this thread, I added this line:

wireless-power off

to

/etc/network/interfaces

But that didn’t help anything.  So then I tried the recommendations from this thread (since it’s based on the chipset of the wifi dongle I got from Adafruit) to:

$ sudo nano /etc/modprobe.d/8192cu.conf

and add this code to it:

# Disable power management
options 8192cu rtw_power_mgnt=0

But after a reboot, it still didn’t work well.  In fact it got even harder to ssh in, it would constantly “Operation timed out”.  So I decided to connect the wifi dongle to my powered usb hub.  When I removed it from the Pi, it was really hot:  Power issues?

After plugging the wifi dongle into the  powered hub, and the hub into the Pi, nothing seemed to be working.  I had to power it on\off twice (over lan).  Bu by the 3rd time the wifi dongle started blinking, apparently recognized.  From there I set the Pi to pinging google. com, and my mac to ping the Pi.  So far, so good, internet radio is streaming.

So it looks like the Pi can’t provide enough, or stable enough power to the wifi dongle over it’s own usb port?   That seems… really annoying.

FINALLY, I bought a new wifi dongle:  It worked immediately.  So lesson to you all.  If you have these problems, spend $10 and get a new dongle…

Setup Camera

This post from raspberrypi.org covers it all.

A really good tutorial covering how you can capture raw  h264 videos, convert them to mp4, the play them on the Pi can be found here: Capturing HD Video With The Pi Camera Module.

And, my own setup guide here: “Playing with the Raspberry Pi’s Camera”

Software Update

I use the apt-get package manager.

Update your cache:

$ sudo apt-get update

Search the cache for software:

$ sudo apt-cache search <someString>

Upgrade all the software on the Pi (can take a while… hours…)

$ sudo apt-get upgrade

Install new software:

sudo apt-get install <package>

Remove old software.  remove can leave some dependencies behind, purge deletes it all.

$ sudo apt-get remove <package>
$ sudo apt-get purge <package>

Adafruit WebIDE

The Adafruit WebIDE is a great way to program on the Pi from some other computer over ssh.  All the code is managed in the cloud via Bitbucket.   Setup guide HERE.

The general process is:

• Install on the Pi
• Wait for the server to start
• Browse here: http://raspberrypi.local (if using Adafruits Occidentalis distro) or the local ip of your Pi (if using NOOBS) to start coding \ setup a Bitbucket account for the first time.

Note if you’re ‘refreshing’ an old Pi, the WebIDE may no longer recognize it.  In that case, log into your Bitbucket account, and in the “Manage Account -> Integrated Applications” menu, remove any “Consumers” and “OAut Consumers”, and then follow the setup guide to create a new one.

Packages

Scratch-pad area of different packages used based on projects I’ve done, or learned about, and probably forgotten about.

To get a list of all the packages installed:

$ dpkg -l

This post has a great overview of many packages to install: Linux & Python Packages for my Raspberry Pi

Presuming you have pip installed, you can use this to get a list of all Python packages installed:

$ pip freeze --local

Audio

Thanks to this post, I learned about these first three apps:

Alsamixer

$ alsamixer

Alsamixer is part of the distro, and has a simple command-line interface & gui.  Gives you a simple way to adjust volume, etc.

MPD & MPC

MPD is the “Music Player Daemon”.  From the page it is “an audio player that has a server-client architecture. It plays audio files, organizes playlists and maintains a music database all while using very few resources. In order to interface with it, a separate client is needed.”

One of those clients is MPC.  It is “a minimalist command line interface to MPD, not to be confused with musepack.”

To install the two at once:

$ sudo apt-get install mpc mpd

To add internet stream(s) to play (Let’s play some Groove Salad):

$ mpc add http://ice.somafm.com/groovesalad

To play a specific stream:

$ mpc play 1

MPlayer

I used MPlayer as part of my Raspberry FM internet music streamer.

Install:

$ sudo apt-get install mplayer

Play a stream:

$ mplayer http://streamer-dtc-aa01.somafm.com:80/stream/1018

Lot more MPlayer configuration from this post : “Raspberry Salad Part 2: Raspberry FM”

Games

Minecraft Pi

Why wouldn’t you want to play Minecraft on you Pi?

Note, Minecraft Pi doesn’t work for me over VNC:  The application launches, but all I see is a black window.  You need to have the Pi directly connected to a monitor/keyboard/mouse.

FYI, it needs to be ran via the XWindows gui mode, so be sure to launch it first via

$ startx

Open a LXTerminal window:  Download (to your home dir), install (then remove the tar), & run:

$ cd ~
$ wget https://s3.amazonaws.com/assets.minecraft.net/pi/minecraft-pi-0.1.1.tar.gz
$ tar -zxvf minecraft-pi-0.1.1.tar.gz
$ rm minecraft-pi-0.1.1.tar.gz
$ cd mcpi
$ ./minecraft-pi

Python

First off, be sure to get pip installed:

$ sudo apt-get install python-pip

Once that’s installed, you can use pip to pull down all other Python packages needed.  This is preferred to using apt-get, this  post does a pretty good job of explaining why.  That being said, I’ve been unable to use pip to install certain packages (like matplotlib), and apt-get works fine.  However, once installed by apt-get, pip recognizes them.

See what Python packages you have installed:

$ pip freeze

RPi.GPIO

You’ll need this to access the Pi’s GPIO pins in Python:

$ sudo pip install RPi.GPIO

pyserial

$ sudo pip install pySerial

PIL

I’ve been unable to get PIL installed via pip.  But apt-get seems to work:

$ sudo apt-get install python-imaging

scipy

Again, pip fails for some reason.

$ sudo apt-get install python-scipy

OpenCV

This wil install OpenCV, and the Python bindings:

$ sudo apt-get install libopencv-dev python-opencv

Some links:

• http://trevorappleton.blogspot.co.uk/2013/11/python-getting-started-with-opencv.html

Other Hardware

Arduino

This Instructable has a really good overview of how to instal all the necessary packages to get your Pi to talk to an Arduino: “Arduino / Raspberry Pi Internet Radio“.

$ apt-get install arduino

And other Python dependencies:

$ sudo pip install nanpy
$ sudo pip install pyserial

Or pylolgraph for short.  See latest info for this subject over on it’s official page.

My son and I soldered together a lolshield for the Arduino Duemilanove we picked up at the 2010 Maker Faire:

(Video Note: The flickering you see is based on the camera capture, it doesn’t actually do that…)

After making it… what to do with it?  I thought it would be fun to make a Python \ Arduino library that would allow you to send Pygame graphics to the lolshield, and that’s what I implemented.

There are two main parts to the library:

• The Python module pylolgraph.py for sending graphics to the Arduino\lolshield.
  • It requires Pygame, and pyserial.  Was made with Python 2.6.5, and Pygame 1.9.1
• The Arduino sketch pylolgraph.pde for receiving serial data, and displaying it.
  • It requires  the lolshield library.

And, I’ve made an example Pygame application illustrating usage:

• example01.py

You can also download all three in a zip here pylolgraph.zip

How to use:

• My system is WinXP.  Not tested on anything else.
• Download pylolgraph.pde, and upload it to your Arduino.  Make sure the BAUD variable matches that in your Python module (below).
• Download pylolgraph.py, put it in your Python path.
• Download example01.py:  Set it’s BAUD variable to match that in pylolgraph.pde, and set its PORT variable to be the port your Arduino is on (will vary depending on your OS).
• Start pylolgraph.pde on the Arduino.  Run example01.py from the command-line or double-click the icon: You should see a small Pygame window pop up:  When you click the LMB, a white donut will appear in the Pygame window.  The same donut should then appear on the lolshield.

Inspect the documentation in pylolgraph.py for more details on implementation.  Here is example pseudo-code for writing your own Pygame application with the code:

import pygame
import pylolgraph

# Setup some constants:
# Create a resolution that corresponds to the lolshield.
# See docs on the pylolgraph.LOLShield.setSurface() method
# for acceptable resolutions.
WIDTH, HEIGHT = (448, 288)
# Baud rate must be the same as setup in pylolgraph.pde
BAUD = 28800
# Port the Arduino is on, on my WinXP box.
PORT = 'COM4'

# Start Pygame application:
# Make surface that will have its data sent to lolshield:
screenSurf = pygame.display.set_mode((WIDTH, HEIGHT))

# Setup lolshield object:
lolshield = pylolgraph.LolShield(port=PORT, baudrate=BAUD)
# Set the surface that will have its pixel data sent to the Arduino\lolshield:
lolshield.setSurface(screenSurf)

# inside main loop:
    # Draw stuff to screenSurf.  Then:
    lolshield.sendData()

Note:  This post has been updated, see notes below.

Been enjoying tinkering around with the Arduino and the Electronic Brick Kit I recently got. It’s easy to send data from the computer to the Arduino and run sketches there, but what about the other way? The Arduino can talk back with the computer over its serial port, so at that point any language that can read the serial port can read the Arduino’s data.  Since I’m most comfortable with Python and Processing, that’s what the below code covers.

Few things to note:

• Python has no built-in serial modules\packages (to my knowledge), but I found several references to pySerial, that appears to be the go-to source for cross-platform serial info in Python.  So you will need that.
• Update:  After a bit of thinking, I have got Python working independently from Pygame, see notes below.
  • (Old subject):  I couldn’t get Python working directly:  When I’d run a loop to capture the serial data, it would hang the shell.  I figured this was because it wasn’t ‘advancing in time’ (just looping endlessly on the first item), so I popped the code into Pygame, and it started working flawlessly.  There probably is a way to do this in Python, but this is my first stab at reading any kind of serial data.  So the Python example is implemented via Pygame.
• This is all authored on  Win2k OS.  Serial ports on different OS’s are handled differently.  For the Python and Processing code I define a variable that sets which com port the Arduino is on (in my case, it’s COM5), which is something that you should have already defined via the Arduino IDE.  Just make sure those values match.  And again, if you’re on Linux of Mac, the serial port values will be different.
• On both the Processing and (the old)  Python examples, they will draw a window with a circle inside that will change in size based on the passed in serial data. Based on the sensor I was using (twist sensor) on an analog pin, this maps the voltage of the sensor into values 0-1023, which are easy to then map into the on-screen graphics. The code will also print out to the shell\IDE the captured serial values.
• Finally, I should point out I pulled a lot of info from the book Getting Started with Arduino.

Dependencies:

• Arduino:
  • Buy an Arduino (I used a Duemilanove)
  • Software Download (tested on 0017)
• Python:
  • Python Download (tested on 2.6.2)
  • Pygame Download (tested on 1.9.1)
  • pySerial Download (tested on 2.5)
• Processing:
  • Processing Download (tested on 1.0.9)

Begin:

Arduino:

Here is the Arduino code.  I have a rotational sensor on analog pin 5.  But you can use any kind of sensor that you want.  I picked the rotational sensor since it’s easy to see the values change.

/**
serialSensor
Eric Pavey 2009-12-26

Sketch will print the value from the sensor to the serial port
*/

#define SENSOR 5

int val = 0;

void setup(){
  Serial.begin(9600);
}

void loop(){
  val = analogRead(SENSOR);
  // Print to the serial port:
  Serial.println(val);
  delay(100);
}

When that is uploaded to the Arduino you can hit the ‘Serial Monitor’ button in the IDE, which will pop up a new window that shows the values captured from the serial port:  When I twist my rotational sensor, I see the result print in the serial monitor.  Pretty straight-forward.  Be sure to close the serial monitor window before you run any of the below code, or they will be blocked from accessing the serial port.

Processing:

The IDE’s for Processing and Arduino are very similar; the Arduino docs say it was ‘built on’ Processing, and the resembelence is strong.  When executed, will create a window, with a white circle inside thats size is controlled by the sensor data passed through the serial port.

Here is the Processing code:

/**
 * readArduinoSerial
 * Eric Pavey 2009-12-26
 * Read data from the computers serial port, that is being fed
 * by an Arduino sketch.  It's expecting values from 0->1023.
 */

import processing.serial.*;

// Create object from Serial class
Serial myPort;  

// Converted data received from the serial port
float val = 1.0;
float prevVal = 1.0;
int minSerial = 0;
int maxSerial = 1023;
// Define which port the Arduino is on:
String arduino = "COM5";

void setup(){
  smooth();
  frameRate(30);
  size(200, 200);
  myPort = new Serial(this, arduino, 9600);
}

void draw(){
  if ( myPort.available() > 0){
    String portVal = myPort.readString();
    // Trim off any extra chars that have no meaning
    // to our sketch.  If we don't do this, we can get
    // NaN float vals when converted.
    String trimmed = portVal.trim();
    if(trimmed.length() > 0){
      // if we have a valid value, update it:
      val = float(portVal);
    }
  }
  if(val != prevVal){
    println("New val: " + val);
    prevVal = val;
  }

  background(0);
  float mapVal = map(val, minSerial, maxSerial, 1, width);
  fill(255);
  ellipse(width/2, height/2, mapVal, mapVal);
}

Python / Pygame:

Like Processing, when executed, will create a window, with a white circle inside thats size is controlled by the sensor data passed through the serial port.

Here is the Python / Pygame code:

"""
readArduinoSerial.py
Eric Pavey - 2009-12-27

Read data from the computers serial port, that is being fed
by an Arduino sketch.  It's expecting values from 0->1023.
"""

import serial
import pygame
from pygame.locals import *
pygame.init()

WIDTH = 256
HEIGHT = 256
FRAMERATE = 30
# Define which com port the Arduino is on:
ARDUINO = "COM5"

screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Arduino Serial Com.")
clock = pygame.time.Clock()

ser = serial.Serial(ARDUINO, timeout=1)
floatVal = 1.0
prevVal = 1.0

def main():
    global floatVal
    global prevVal
    cirCol = Color("white")
    looping = True

    while looping:
        clock.tick(FRAMERATE)
        screen.fill(0)

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                looping = False

        # Read the serial value
        ser.flushInput()
        serialValue = ser.readline().strip()

        # Catch any bad serial data:
        try:
            floatVal = float(serialValue)/8.0
            if floatVal != prevVal:
                # Print the value if it differs from the prevVal:
                print "New Val: ", floatVal
                prevVal = floatVal
        except ValueError:
            pass
        pygame.draw.circle(screen, cirCol, (WIDTH/2, HEIGHT/2), floatVal)

        # update our display:
        pygame.display.update()

if __name__ == "__main__":
    main()

Update: Here is the new Python code sans-Pygame. It will print results directly to the shell it was executed from:

import serial

ARDUINO =  "COM4"

def main():
    ser =  serial.Serial(ARDUINO, timeout=1)
    prevVal = None
    while 1:
        # Read the serial value
        ser.flushInput()
        serialValue = ser.readline().strip()
        # Catch any bad serial data:
        try:
            if serialValue != prevVal:
                # Print the value if it differs from the prevVal:
                print "New Val: ", serialValue
                prevVal = serialValue
        except ValueError:
            pass

if __name__ == '__main__':
    main()

In Conclusion…

So while the implementation in Processing \Python is pretty simple, it opens doors into what could be.  Another interesting observation is that the Processing sketch was really ‘jumpy’:  It seems to capture values that aren’t being reported by the Arduino sketch, causing the circle to ‘jump’ in size occasionally.  However, the Pygame (and updated pure Python) app seems pretty rock solid, and no ‘jumping’ is reported.