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Practical projects Essential upgrades Python tips


Raspberry Pi
Pi Zero









Pi projects

Welcome to

Raspberry Pi
The Raspberry Pi is powering a computing revolution that is sweeping the world.
It’s changed the face of the classroom forever, it’s used in amazingly creative
projects at Raspberry Jam events everywhere from Yorkshire villages to the capital
of Australia, and every weekend families get together to code, create and craft
new gadgets. Whether you’re six or sixty, there’s a Pi project for you. And that’s
where we come in. In this new edition of Raspberry Pi Tips, Tricks & Hacks we’re
giving you everything you need to not only get up and running with a brand
new Raspberry Pi, but also fire up your imagination and unleash your creativity.
From programming-based projects like tethering your Pi to an Android, through
hardware projects including digital photo frames, arcade machines and touchscreen video players, all the way to advanced robotics projects that will see
you building your own Raspberry Pi-powered, remote control vehicles and car
computers, we’ve got plenty here to keep you busy. All you need is your favourite
$35 computer – and a passion for making things!

Raspberry Pi
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Raspberry Pi is a trademark of The Raspberry Pi Foundation
Raspberry Pi Tips, Tricks & Hacks Volume 1 Second Revised Edition © 2015 Imagine Publishing Ltd

Part of the

bookazine series



28 5 Practical
Raspberry Pi
08 Master Raspberry •
Pi in 7 days

Make music with the
Raspberry Pi


Raspberry Pi voice synthesiser


Program Minecraft-Pi


Get interactive with Scratch


Build a Raspberry Pi web server


40 50 ways to master
Raspberry Pi

48 Use an Android device as a
Pi screen

12 Set up your
Raspberry Pi

Create your first simple game
with Scratch


Learn to code with Sonic Pi


Take photos with Raspberry Pi


Use the GPIO pins


Build a Twitter-powered lamp


52 Host a website on your Pi
54 Secure your Raspberry Pi
58 Build a file server with the
Raspberry Pi

62 Network and share your
keyboard and mouse

64 Add a reset switch to your
Raspberry Pi

66 Remotely control your
Raspberry Pi

with Python

68 Install Android on Pi

Make a tweeting bird watcher

76 Add a battery pack to Pi

“Use a motion-sensing Raspberry Pi
to automatically take pictures”
6 Raspberry Pi Tips, Tricks & Hacks


“It has powered quadcopters, coffee
makers, self-sailing boats and even
touched the edge of space”

80 10 Inspiring
Pi Projects


Retro arcade cabinet


Audiobook reader


Web radio



Media caster

132 Build a Raspberry


Portable Wi-Fi signal repeater


Secure Tor web station


Private cloud storage






Outdoor time-lapse camera

96 Set up the PiTFT touch screen
98 Calibrate a touch screen interface
100 Portable Pi video player
102 Make a Raspberry Pi sampler
106 Build a radio transmitter
110 Tether your Pi to Android
112 Build a network of Raspberry Pis
116 Add gesture control to your Pi
120 Make a digital photo frame out of
your Raspberry Pi
124 Pygame Zero

Pi-controlled car

138 Make a Raspberry Pi


car computer

146 Build a Minecraft power
move glove

150 Build a Super Raspberry Pi


Master Raspberry Pi in 7 days

Raspberry Pi
in 7 days
From setup to internet
sensation in a week…
It’s amazing what can be accomplished with the
Raspberry Pi if you set your mind to it. They’ve been
sent higher into orbit than Felix Baumgartner, they
power cutting-edge Bitcoin farms and someone’s even
using one to try and translate dog thoughts into speech
with a Pi-infused collar. No prizes for guessing where
the inspiration for www.nomorewoof.com came from.
No one really knows if it’s ever going to work, but does
it matter? The mere fact that someone’s even trying to
bring a piece of Disney fantasy to life using the same
technology as your Raspberry Pi is inspiring stuff!
While we won’t be taking pictures at four times the
altitude of a cruising jumbo jet or translating the musings
of a canine companion, the seven projects you’ll find over
the next 16 pages will certainly get you off on the right

8 Raspberry Pi Tips, Tricks & Hacks

foot. Our final big project will be to use a motion-sensing
Raspberry Pi to automatically take pictures of local
wildlife and tweet them to the world.
Not bad, especially since we’re assuming you have no
prior experience with the Raspberry Pi. Yes, we expect
you to know where to stick the other end of the HDMI
cable, but we don’t assume that you can program with
Python or navigate the command line interface. We’ll
gradually learn as we go, first by setting up the Pi and
learning key programming logic with Scratch and Sonic
Pi. We’ll then move on to writing simple Python scripts,
getting to grips with the Camera module and using the
GPIO port among other things. By the end of it you should
have all the skills and equipment needed to complete the
final project – and much more besides…

Master Raspberry Pi in 7 days

Raspberry Pi Tips, Tricks & Hacks 9

Master Raspberry Pi in 7 days

Plan your week
Day 1 Set up your Raspberry Pi Day 2 Make a game from Scratch
It’s not rocket science, but we’ll get you started

Learn the basics of coding with graphical feedback

Day 3 Learn code with Sonic Pi Day 4 Take photos with your Pi
Write functional code while making beautiful music

Use Python to take great snaps with your camera

Day 5 Get to grips with GPIO

Create a simple but elegant candlelight project

Day 6 Use the Twitter API
Create an Internet of Things Twitter lamp

10 Raspberry Pi Tips, Tricks & Hacks

Day 7 Put it all together!

Automagically share wildlife shots with this motionsensing, picture-taking, Twitter-posting project

Master Raspberry Pi in 7 days

Pi projects
shopping list
Grab these extra components before
taking part in our week of Raspberry Pi…
We’ll be covering a variety of different project types over the course of
these tutorials, so you may want to stock up on some components and
accessories to help you get through the week. This is just the tip of the
iceberg, though - each supplier offers plenty of kit for new projects…

Pibow case
A beautiful and functional case for your Raspberry Pi, with all the
necessary openings that will allow you to access the camera module
ribbon and the GPIO port on the board itself. The Pibows come in a
variety of different colours, and there’s even a special version for the
Model A, with even greater access to the technical ports. It can also
be modified with an extra platter to attach to a TV if you plan on using
the Pi in your home theatre setup.
£12.95 | shop.pimoroni.com

Raspberry Pi camera board
The Pi-specific camera board has been created in such a way that it
connects to one of the video in ports for the Raspberry Pi on the actual
board itself. This means it won’t use up any of the limited USB ports or
other inputs, so that you don’t need to get a USB hub to have everything
working. The camera isn’t the highest resolution offering in the world, but
it’s a respectable 5MP that can take images at 2592 x 1944 and record
video at 1080p at 30 fps, which is more than enough for most projects.
£19.99 | thepihut.com

Electronics starter kit
Hobbyists have been creating simple circuits for their projects for
years now using simple components all hooked up to a prototyping
breadboard. While you can hunt around and get all the parts you
need for this, there are a handful of electronic starter kits that include
everything you need for our projects this issue (and much more besides).
Simon Monk has created one of these kits, which includes a breadboard,
pre-cut cables, switches, resistors and a whole host of other little
components and sensors for any electronics project.
£15 | bit.ly/1oE9BYC

PIR sensor
An infrared motion sensor that hooks up to the Raspberry Pi via the
GPIO port. It sends a constant signal depending on the level of infrared
radiation that it detects, which can be used to determine when to activate
a piece of code. For example, IR sensors are classically used in alarm
systems, however they can also be used to take pictures or video on
demand, which is how we’re planning to use it at the end of the week.
£2.99 | modmypi.com

Raspberry Pi Tips, Tricks & Hacks 11

Tips | Tricks
| Hacks Pi in 7 days

What you’ll need
Q 1A micro USB
Q Internet connection
Q USB mouse and keyboard
Q HDMI cable and
compatible monitor
Q 4GB SD card

Set up your Raspberry Pi
Turn your Raspberry Pi into a fully functional PC
and get to know the basics of setting it up
So you’ve just got your Raspberry Pi – you’re probably
wondering how exactly you’re going to get started with it.
If you’re used to more traditional PCs, you might be expecting
a CD drive or a USB installer to set up your Raspberry Pi. The
Pi requires a little more than sticking in a CD though, so we’ll
show you how to get everything working properly.
In this tutorial we’ll also give you some quick tips on how to
improve your Raspberry Pi experience, including extra software
packages and ways you can use your brand new Pi.

12 Raspberry Pi Tips, Tricks & Hacks


Get your operating system

Head over to the Raspberry Pi
website (www.raspberrypi.org) and
download NOOBS, the New Out Of Box
Software. This will come in a zip file;
download it onto the SD card for your
Raspberry Pi and extract the files from
it here. Do not extract the files elsewhere
and copy them over.

Master Raspberry Pi in 7 days


Get new software


Get an office suite


Get a better browser

There are two ways to get more
packages for Raspbian – either through
the Pi Store link, or via the package
manager in the terminal. You’ll get a
different selection of apps on the two
services, with a greater focus on general
software tools in the package manager


Connect your Pi

Without inserting the power cable, hook up everything to
your Pi. You’ll need a wired ethernet connection or a compatible
wireless dongle, a USB mouse, a USB keyboard and a monitor or
other form of display connected via HDMI.


Set up Raspbian

There are a few things you
need to do before Raspbian is ready.
On the config screen, select Expand
Filesystem to make sure the SD is
being used properly. Then, go to Enable
Boot to Desktop and select Desktop
from the list. Go to Finish, and it will
reboot Raspbian.


Update Raspbian

Make sure all the software on
Raspbian is now up to date. To do this,
open the LXTerminal and type:

$ sudo apt-get update


Choose your distro

Plug in your SD card and finally connect the power.
The Raspberry Pi will boot into NOOBS’ distro selection menu.
For all of our tutorials we will be using Raspbian, however
the other distros each have their uses and you may want to
consider using them at a later date.


Install Raspbian

Select Raspbian by clicking the check box to the left
of it, and then click Install at the top of the Window. Confirm
that you want to install, and it will go through the process of
adding Raspbian to the SD card.

Raspbian does not have any
form of office functionality by default,
only a basic text editor. You can add
LibreOffice though, which can be done
via the Pi Store. Open up the Store and go
to Apps; here you’ll find LibreOffice as a
free download. Once you’ve created an
account, it will download and install it.

Once that’s finished, follow it up with:

$ sudo apt-get upgrade
This may end up taking a few minutes,
but it will update the software
throughout Raspbian.

Midori is an excellent browser,
however you can also get Chromium
to work on Raspbian. This is the open
source version of Google’s Chrome
browser, which you can get by opening
the terminal and typing:

$ sudo apt-get install chromium

The other distros each have
their uses and you may want to
use them at a later date
Raspberry Pi Tips, Tricks & Hacks 13

Master Raspberry Pi in 7 days

Create a simple
game with Scratch
Learn the basics of coding logic by creating a squash-like
Pong clone in Scratch that you can play at the end of the day
While Scratch may seem like a very simplistic programming
language that’s just for kids, you’d be wrong to overlook it as
an excellent first step into coding for all age levels. One aspect
of learning to code is understanding the underlying logic that
makes up all programs; comparing two systems, learning to work
with loops and general decision-making within the code.
Scratch strips away the actual code bit and leaves you with
just the logic to deal with. This makes it a great starting point
for beginners, separating the terminology so you can learn that
later on when you choose to make a proper program. It’s also
included on every copy of Raspbian.

14 Raspberry Pi Tips, Tricks & Hacks


The first sprite

Opening up Scratch will display
a blank game with the Scratch cat;
right-click on it and delete to remove it.
Click the Paint New Sprite button
below the game window and draw a
slim rectangle as the bat using the
square drawing tool. Click Set Costume
Center so that Scratch knows the basic
dimensions of your bat; drag it to the
centre of the sprite if needs be.

Master Raspberry Pi in 7 days

Building blocks

Preview Test your
code straight away to
make sure it does what
you expect it to do

Use blocks that represent
coding to build your game
or animation

Code logic

Build project

Slot the blocks together
in a straightforward
manner to create loops
and comparisons


Export to the Scratch
website to show off your
work to the world

Move the bat

Click OK, and name the new
sprite ‘Bat’. Select the Control block
from the top-left menu, and drag the
When Space Key Pressed block into
the script area. Change Space to Up
arrow from the drop-down menu, then
select the Motion options and drag the
Change Y By 10 block to connect to the
key pressed block.


Move the ball

Find the Forever block in the
control menu, and attach it under our
existing block on Ball. Then, go back
to the Motion menu and add Move 10
Steps so that the ball moves around
the screen. Add the If On Edge, Bounce
block from Motion below that so that it
will stay within the playing field.


Simple bouncing


Random bouncing


Further developments

Pressing the green flag now, the ball will bounce
between the left and right edges of the screen, or off the bat
if it comes into contact with it. We can make it slightly more
interactive to make use of the moving bat, and more like Pong.

Reverse the direction

Whenever we press up, the bat
will move up by ten pixels, as set. By
repeating the process using the down
arrow and setting Change Y To -10, we
can also make it move down as well.
Move the rectangle to the left side of the
screen. This will be our starting position.



Create the ball

Create a sphere from the new
sprite menu like we did with the bat,
including setting the Costume Center.
Name it ball, and bring the When Green
Flag Clicked block from the Control
menu into the scripts pane. Add the go
to x:0 y:0 block underneath it so that
whenever you click the green flag it
resets to the ball.


Hit the ball

Drag the If block from Control to
below If On Edge, and then add touching
from Sensing to the empty space on the
If block. From the drop-down menu,
select Bat so that it will interact with
our bat sprite. Add one of the Turn 15
degrees blocks from Motion to the If
block, and change it to 180.

Go the Operators menu and select the first value, blank
+ blank. Drag it to where we have 180 degrees in the turn block,
and add 180 to the first blank space. Place the Pick Random 1
to 10 block in the second space and change the values to -10
and 10 so that whenever the ball hits the bat, it bounces off at a
random angle between 170 and 190 degrees.

While you now have a functional game of sorts, you
can also add in a second player to make it truly Pong-like, and
add a scoring system by having a number increase when the
ball hits one of the sides.

Raspberry Pi Tips, Tricks & Hacks 15

Master Raspberry Pi in 7 days

Learn to code
with Sonic Pi

Take the next step in programming and create your own
melodies with Sonic Pi, the musical programming language
What you’ll need
Q Speakers or headphones
Q Sonic Pi

16 Raspberry Pi Tips, Tricks & Hacks

With Scratch we’ve learned how
to operate under the logic of
programming. The next step is to
then use that within a programming
language – the problem is that many
of the available languages can look a
little intimidating. This is where Sonic
Pi comes in, offering a very simple
language style that can ease you in to
the basics of working with code.
It’s quite straightforward to use as
well – Sonic Pi allows you to choose
from a small selection of instruments
and select a tone to play with it. These
can be turned into complex melodies
using loops and threads and even
some form of user input.


Install Raspbian

If you’ve installed the latest version of Raspbian, Sonic
Pi will be included by default. If you’re still using a slightly older
version, then you’ll need to install it via the repos. Do this with:

$ sudo apt-get install sonic-pi

Master Raspberry Pi in 7 days


Get started with Sonic Pi

Sonic Pi is located in the Education category in the
menus. Open it up and you’ll be presented with something
that looks like an IDE. The pane on the left allows you to enter
code, and then you can save and preview it as well. Any errors
are displayed separately from the output.

Sonic Pi offers you a very
simple language style that
can ease you into the basics
of working with code
Full code listing
with_tempo 200
play_pattern [40,25,45,25,25,50,50]


Your first note

Our first thing to try out with Sonic Pi is simply being
able to play a note. Sonic Pi has a few defaults already pre-set,
so we can get started with:

play 50
Press run and the output window should show you exactly
what is happening.

2.times do
with_synth “beep”
play_pattern [40,25,45,25,25,50,50]
play_pattern [40,25,45,25,25,50,50].reverse
play_pad “saws”, 3
in_thread do
with_synth “fm”
6.times do
if rand < 0.5
play 30
play 50
sleep 2


Set the beat

For any piece of music, you’ll probably want to set the
beat. We can start by putting:

with_tempo 200
At the start of our code. We can then test this out by creating a
string of midi notes using play_pattern.


Advance your melody

We can start making more complex melodies by
using more of Sonic Pi’s functions. You can change the note
type by using with_synth, reverse a pattern, and even create
a finite loop with the x.times function. ‘Do’ and ‘end’ signify
the start and end of the loop.

2.times do
play_synth “pretty_bell”
play_pattern [40,25,45,25,25,50,50]
play_pattern [40,25,45,25,25,50,50].reverse


Play a concert

Using the in_thread function, we can create another
thread for the Sonic Pi instance and have several lines of
musical code play at once instead of in sequence. Here we’ve
made it create a series of notes in a random sequence.

Raspberry Pi Tips, Tricks & Hacks 17

Master Raspberry Pi in 7 days

Take photos with
Raspberry Pi
Use the Raspberry Pi camera module to
capture photos and video, so you have a
portable camera for any situation
As we mentioned earlier, the Raspberry Pi camera module
is an excellent addition to the Raspberry Pi. Not only does
it slot into one of the non-traditional ports on the board itself,
but it’s also easily programmable within Raspbian. This gives
it a few benefits over a USB webcam by not taking up any
USB slots and being easier to control with code. It’s also tiny,
making it as portable as the Raspberry Pi itself.
By the end of today, you’ll be able to use the camera like a
pro to create time delays and specific image formatting.


Plug in your camera

To attach the camera to the Raspberry Pi, locate the
connectors between the ethernet and HDMI port and gently lift
up the fastener. Insert the camera board ribbon, with the metal
connectors facing away from the ethernet port.

18 Raspberry Pi Tips, Tricks & Hacks

What you’ll need
Q Raspberry Pi camera board
Q picamera

Master Raspberry Pi in 7 days

Carefully insert the connector for
the camera board, making sure
it’s the right way round


Python test

Let’s make sure that everything we’ve done still works.
Enter a Python shell by typing ‘python’ into the terminal, and
then type the following three lines:

import picamera
camera = picamera.PiCamera()


Test explained


Python video

Press Ctrl+D to exit the Python shell. We just used
code similar to the command line tools to take a simple
image called ‘pythontest.png’. The most important thing
we did after that was ‘camera.close’, to make sure that the
camera was turned off after use.


Enable the camera

First you’ll need to make sure
the camera modules are enabled.
To start the standard configuration
screen, open a terminal and type:

$ sudo raspi-config
Navigate down to Enable Camera,
press Enter, and then simply key over to
enable and confirm with another press
of Enter. Select Finish and then reboot.


Record some video

To record a video, we use a
similar command, raspivid, like so:

$ raspivid -o video.h264
Just like with the image-capturing that
we did in the previous step, this will
display a preview of what the camera
is seeing. However, the video actually
records the five seconds that make up
the preview as well.

To record video with picamera, you need to first set
the resolution and then set a recording time.


Take your first picture

Capturing pictures with the
Raspberry Pi Camera is straightforward,
all you have to do is enter:

$ raspistill -o image.png
This will show a five-second preview of
the input of the camera and then capture
the last frame of the video.


Advanced Pi camera uses

If you want to be able to do a
little more with the camera, there’s
a simple Python wrapper currently
available called picamera. You’ll need
to install it first though, and you can
do so from the terminal, using the
following command:

$ sudo apt-get install pythonpicamera

import picamera
camera = picamera.PiCamera()
camera.resolution = (640, 480)


More code

The above works a lot better in a Python script –
the wait is only really required if you can’t manually stop the
recording. Picamera allows you to create time lapses, modify
the frame rate of recordings and much more. For more ways
to use it, check out issue 137 of Linux User & Developer (bit.
ly/11lxQ7n) or the docs on the picamera GitHub page.

Raspberry Pi Tips, Tricks & Hacks 19

Master Raspberry Pi in 7 days

Use the GPIO pins
Learn to use the GPIO pins to interact with the outside world
– this is where Raspberry Pi projects get really interesting…
What you’ll need
Q Small breadboard
Q Small LED (any colour)
Q 330ohm resistor
Q 2x male-to-female
prototyping cables
The General Purpose Input/Output pins
(GPIO) give you power to interact with
the real world using your Raspberry Pi.
This project will get you comfortable with
using the GPIO pins, which will form the
backbone of the final project.
Traditionally the ‘Hello World’ program
for electronics prototyping is simply
turning a light on and off. We’re going to
go one better than that here though, by
simulating candlelight.
To do this we’re going to use the
Random and Time modules from
Python’s standard library to continually
change the brightness of the light while
using the RPi-GPIO library to control the
LED with Pulse Width Modulation (PWM).

20 Raspberry Pi Tips, Tricks & Hacks


Prepare your circuit

Before we turn on our Raspberry Pi we’ll make all the
physical cable connections to it. This requires us to place a
male-to-female cable on the first ground pin on the GPIO port
and another male-to-female cable on the PWM pin (pin 18).
Connect it to the breadboard along with the LED and resistor as
shown, ensuring the short leg of the LED goes to ground.


Power up the Pi

With the circuit complete we can power up the Pi.
Open Leafpad and we’ll start creating the script (found to the
right) we need to control the LED light. The first thing we do is
import the modules we need. The RPi.GPIO library is key to our
project – we use it to read and write to pins and control their
functionality. We’re also using Random and Time modules in
order to help simulate the effect of candlelight.


Configure the GPIO module


Basic functions

Next we assign a name to the
LED pin and set up the GPIO module
for our project. Notice we’re using
‘setmode’ and calling it BCM. This
means we’re using the Broadcom
naming scheme. We then assign the
LED pin to OUTPUT, which means we’ll
be outputting to that pin (as opposed
to reading from it). If we simply wanted
to turn the light on and off, at this point
we could use GPIO.output(led,GPIO.
HIGH) and GPIO.output(led,GPIO.LOW).
Instead we’re using PWM, so we assign
a variable PWM to control it.

Next we create two very basic
functions that we can call in our main
program loop to randomly control the
physical brightness of the LED and the
amount of time that the light pauses
on a set brightness. To do this we first
use the random.randint method. The
numbers 5 and 100 represent the lowest
and highest brightness (in per cent) –
the function will then pick a number
between these percentages during each

Master Raspberry Pi in 7 days

This is the top! The top of

the image represents the end of the
GPIO pins nearest your SD card

Grounded The pins are

counted from left to right and top
to bottom. This is one of the few
Ground pins, which we’ll be using










#!/usr/bin/env python



# Import the modules used in the script
import random, time
import RPi.GPIO as GPIO











Special pins While most

pins can be manually set to be
outputs or inputs for any use, some
pins are pre-assigned other roles
too. This is the PWM pin, capable of
controlling motors and LEDs with
amazing precision

BCM for Broadcom

We’re using the BCM pin naming
scheme for our projects. It doesn’t
use the physical pin locations, so
BCM pin 17 is actually pin 11 when
counted from left to right





loop through the program. random.random picks a floating
point number between 0 and 1 – we divide this by WIND to help
achieve our flicker effect.


The main loop

Finally, we use a while loop to activate the light
with PWM and then change the brightness of the light
with the ChangeDutyCycle method, which calls our brightness
function. We do similar with time.sleep next to get the
brightness to maintain for a short, random, amount of time
by calling the flicker function. When we want to quit this
otherwise infinite loop, we can raise a KeyboardInterrupt
by pressing Ctrl+C. When we do, we need to free up the pins
so that they can be used again, by calling pwm.stop and
GPIO.cleanup respectively.


The General Purpose Input/
Output pins give you the power
to interact with the real world
using your Raspberry Pi


Test your project

Once your script has been written, save it as candle_
light.py. The ‘.py’ informs your Pi that this is a Python script.
To run it, simply open the Terminal and type the following:

sudo python candle_light.py
You need to call sudo here since you need to have admin
privileges to access the GPIO port on your Raspberry Pi.
Assuming you’ve set up the breadboard and copied the script
correctly, your LED light should start flickering as if it’s a
candle in a light breeze. Take some time to experiment with
the variables in the brightness and flicker functions to achieve
a more desirable effect.

Full code listing

# Assign the hardware PWM pin and name it
led = 18
# Configure the GPIO to BCM and set it to output mode
GPIO.setup(led, GPIO.OUT)
# Set PWM and create some constants we'll be using
pwm = GPIO.PWM(led, 100)
WIND = 9
def brightness():
"""Function to randomly set the brightness of
the LED between 5 per cent and 100 per cent power"""
return random.randint(5, 100)
def flicker():
"""Function to randomly set the regularity of the'flicker
return random.random() / WIND
print "Candle Light. Press CTRL + C to quit"
# The main program loop follows.
# Use 'try', 'except' and 'finally' to ensure the program
# quits cleanly when CTRL+C is pressed to stop it.
while RUNNING:
# Start PWM with the LED off
# Randomly change the brightness of the LED
# Randomly pause on a brightness to simulate flickering
# If CTRL+C is pressed the main loop is broken
except KeyboardInterrupt:
running = False
print "\nQuitting Candle Light"
# Actions under 'finally' will always be called, regardless of
# what stopped the program (be it an error or an interrupt)
# Stop and cleanup to finish cleanly so the pins
# are available to be used again

Raspberry Pi Tips, Tricks & Hacks 21

Master Raspberry Pi in 7 days

Build a Twitter-powered
lamp with Python

Now we know how to use the GPIO port, let’s see if we can
make our LED light work in response to the Twitter API…
Over the last eight years Twitter has become one of the
most prominent social media networks in the world.
Twitter is built on excellent open source technology and code,
meaning it’s very easy to work with. With all the focus on the
tiny 140-character limit, you’d probably be surprised to hear
that behind each tweet is over 3,000 characters of raw data!
While we’re not going to harness the full power of Twitter’s
API today, we are going to do enough to allow us to make
a Twitter lamp – a light that flashes whenever our chosen
phrase or word is mentioned on Twitter. It’s actually a lot
easier than you might think, so let’s get started…


Set up an app

Before you can do anything else,
you need to make sure that you’ve got a
Twitter account and that you’re signed
in. In order to be able to use the API, you
need to create a Twitter app, so head
over to https://apps.twitter.com and
click ‘Create New App’. Fill out the form,
but don’t worry about the URL sections
– just put any website for now, since we
won’t be using this functionality.


Configure the app

Once the app has been created
you can alter the access to Twitter by
modifying app permissions. While we
don’t need the ability to ‘write’ to Twitter
for this project, we will do in the next
one, so click ‘Modify App Permissions’
and change it to ‘Read and write’. Once
this changed, you can click the ‘Create
my access token’ button at the bottom
of the page. When this has refreshed,
you’ll have access to the info you need in
the ‘API Keys’ tab. Copy the API key along
with its secret and the access token and
its secret into a new document called
‘twitter_lamp.py’ in the format shown in
our code listing on the right.

What you’ll need
Q tweepy
Q Internet connection
Q Breadboard
Q Male-to-female cables
Q 300ohm resistor

22 Raspberry Pi Tips, Tricks & Hacks

Master Raspberry Pi in 7 days



Install tweepy

The next step in creating our
Twitter-powered lamp is installing and
setting up tweepy. In the terminal, type:

git clone https://tweepy/tweepy.git
Once it’s downloaded, move into the
directory (cd tweepy) and install it like so:

sudo python setup.py install
Once tweepy is installed we don’t need the
contents of the folder anymore. Go back to
your home folder (cd ~) and delete it with:

rm -rf tweepy
You can test that the library is installed
correctly by typing python in the terminal
to open the Python Interpreter. Now type
import tweepy – if you don’t get an error
when you hit Enter, you’re all set!

Connect the LED

We’re going to use exactly the
same simple breadboard circuit we used
in the candlelight project on the previous
two pages – we’re even using the same
GPIO pins. With the circuit connected,
we can turn our attention to the code
listing on the right. The GPIO aspect
of the code is very similar to the last
project, other than the fact we’re using
the GPIO.HIGH and GPIO.LOW commands
to flash the light, as opposed to PWM.
After our required imports at the top of
the code listing, we’ve laid out the api_key
and access_token phrases that point to
our Twitter app attached to our Twitter
account. Obviously we’ve masked over
ours, since they’re meant to be a secret.
Don’t share yours (even on GitHub)!


Using tweepy

After setting the keys and
secrets as variables, we need to get
tweepy to use them to authorise us.
Create the auth variable and use the
OAuthHandler to call them and then set
the access token details as shown.

It’s amazing what you
can achieve in just 50
lines of Python
We then use auth to allow us access to the Twitter API on our
account and test the connection by printing our Twitter handle
using the api.me() method. We want to use the real-time Twitter
stream for our project, though, so we need to override the
StreamListener class in tweepy to make our lamp work. The
on_status method in that class is where the magic happens;
whenever there’s a status update that’s relevant to us, it pings
on_status and we trigger our GPIO pins to make the light flash.


Test and tweak

Next we put our search terms into a list called terms.
As you can see, we’ve elected for our lamp to flash whenever
one of the Raspberry Pi terms we’ve set is mentioned. You don’t
need to include ‘@’ or ‘#’ tags – the API takes care of that for us.
Now all that’s left to do is create an instance of the
StreamListener() class, start the Twitter live stream and then
use the filter method to set it to only track the search terms
we’re interested in. It’s amazing what you can achieve in just
50 lines of Python! To test your new Twitter-powered lamp
prototype, at the terminal type:

sudo python twitter_lamp.py

Full code listing
#!/usr/bin/env python

class StreamListener(tweepy.StreamListener):

#import the required libraries
import tweepy
import time
import RPi.GPIO as GPIO

# Whenever a status occurs that we're interested
# in we flash the LED
def on_status(self, data):
print "Flash the light"
# We're using a simple for loop that turns the light
# off and on three times using an interval of a
# quarter of a second
for i in xrange(3):
GPIO.output(led, GPIO.LOW)
GPIO.output(led, GPIO.HIGH)

# Set your access keys as configured
# at https://apps.twitter.com
api_key = 'your_api_key'
api_secret = 'your_api_secret'
access_token = 'your_access_token'
token_secret = 'your_token_secret'
# Initiate the OAuth process
auth = tweepy.OAuthHandler(api_key, api_secret)
auth.set_access_token(access_token, token_secret)
# Assuming the keys are good, you'll be
# able to test your Twitter app
api = tweepy.API(auth)
my = api.me()

def on_error(self, error_code):
print "Error:", error_code
return False
# These are the words we're looking out for on Twitter
terms = ['raspberry pi', 'raspberrypi', 'raspi']

# Configure the GPIO port as we did in the last project
led = 18

# Configure the stream and filter only our chosen terms
listener = StreamListener()
stream = tweepy.Stream(auth, listener)
stream.filter(track = terms)

GPIO.setup(led, GPIO.OUT)

except KeyboardInterrupt:
print "\nQuitting"

# Set the led light to be 'on'
GPIO.output(led, GPIO.HIGH)

# Don't forget to clean up after so we
# can use the GPIO next time

print my.name, "is connected! Press CTRL + C to quit."

# We've tweaked the class that monitors Twitter's stream

Raspberry Pi Tips, Tricks & Hacks 23

Master Raspberry Pi in 7 days

What you’ll need
Q tweepy
Q Internet connection
Q HC-SR501 PIR Infrared
Q Camera board & picamera

The tweeting bird watcher
Our final project! Create an Internet of Things device able to
takes pictures of wildlife before tweeting them to the web
We’ve reached the end of the week and
we’re now ready to take on our biggest
project yet. Our final project uses all of
the skills and technology we’ve covered
so far and raises the bar to include
things like automated Twitter updates
and event detection. We’re going to
create our own little Internet of Things
device that incorporates a simple PIR
sensor (just £2.99/$5 from modmypi.
com), the Raspberry Pi Camera board
and the power of the internet to let us
automagically capture images of birds
(and other wildlife) before tweeting to a
Twitter account of our choice whenever
activity occurs.

24 Raspberry Pi Tips, Tricks & Hacks


Configure the
infrared sensor

Since this an automated device, we
need a way to trigger the camera when
movement is sensed in our camera’s
target area. One affordable and easyto-configure solution is the HC-SR501
Infrared Motion Sensor. The device itself
has three pins – VCC (5V), Ground and a
signal pin that sits in the middle. We’ve
configured our script for the pir pin to
trigger GPIO pin 17 (it sits opposite the
PWM pin). The VCC pin is connected
directly to the 5V power pin and the
Ground to the same Ground pin we’ve
used throughout the tutorials.

Master Raspberry Pi in 7 days


Test the PIR

We don’t want to send millions of accidental tweets to
Twitter, so we should do some pretty extensive testing with the
PIR first, using simple print statements to show when motion
has been detected. Visit github.com/russb78/tweety-pi and
explore the project to find the pir_testing.py script. Copy it
onto your Pi and run it with your PIR connected. You’ll probably
find that it’s over-sensitive for your needs by default. You’ll
find two tiny adjustable screws on the PIR. Gently adjust them
to the left to lower the sensitivity and test thoroughly until you
get the desired result.


Set up the project

With the camera connected as per our previous
camera project earlier in the week, we need to tie the camera,
motion sensor and Twitter code together to make a tangible
project that can be left to do its job. We’ll walk through the
script, but it’s worth looking around our project by cloning it
from GitHub. In the terminal type:

git clone https://github.com/russb78/tweety-pi.git
Enter the project with cd tweety-pi to take a look around.
It’s been set up as a full (if a little basic) project with a readme,
licence and even a folder for our pictures to sit in.


The callback function

One of the big changes in this project compared to
our previous ones is that we’re using the GPIO as an input,
instead of an output. Since we want the PIR sensor to alert
us to movement, we really want the PIR to interrupt our
script to let us know – that’s where our callback function
motion_sense() comes in. Looking further down the script to
the main program loop you’ll see a GPIO.add_event_detect.
Whenever the assigned GPIO pin gets pinged, the script will
stop what it is doing and jump to the named callback function
(in this case motion_sense). This simple function then calls the
take_picture function below it.


Simple chain

The entire chain of main functions that make up
the meat of the project are laid out in trigger order and all
initiated from that initial callback function. Once motion
is detected the take_picture function is called. As soon
as the image has been saved to the /pics folder we call the
update_twitter function. Here, we’re loading our previously
saved image and using the Twitter API’s update_with_media
method to allow us to tweet our picture to the outside world.
We can set our status from within this line, but instead of
repeating the same phrase we use the random module’s
choice method to pick from a list of three we’d assigned to the
variable tweet_text earlier in the script.


Main program loop

As we’ve done before, we’re placing our main program
loop in try, except, finally blocks to ensure we can cleanly quit
the program or clean up should it crash for any reason. After
we call our GPIO event detect line, we create a simple infinite
loop to ensure the script keeps running. Pressing Ctrl+C will
break this loop, causing the program to end, but not before
finally calling the methods that close the camera and shutoff the GPIO pins. If you don’t do this, all kinds of issues can
arise the next time you run the script. And that’s all there is to
it! Be sure to use your knowledge on experimenting with other
Raspberry Pi projects – and have fun!

Full code listing
#!/usr/bin/env python
import RPi.GPIO as GPIO
import random, time, os
import tweepy
import picamera
pir = 17
GPIO.setup(pir, GPIO.IN)
# Set your access keys via https://apps.twitter.com
api_key = 'your_api_key_number'
api_secret = 'your_api_secret_number'
access_token = 'your_access_token_number'
token_secret = 'your_token_secret_number'
auth = tweepy.OAuthHandler(api_key, api_secret)
auth.set_access_token(access_token, token_secret)
api = tweepy.API(auth)
my_twitter = api.me()
print my_twitter.name, "is connected! Press CTRL + C to quit."
# Three statuses. We'll pick one at random to go with our pic
tweet_text = ['Another shot taken with tweety-pi!',
'Just spotted with my Raspberry Pi',
'Snapped automagically with my Raspberry Pi camera!']
camera = PiCamera()
cam_res = (1024, 768)
camera.led = False # Turn off LED so we don't scare the birds!
pics_taken = 0
def motion_sense(pir):
print "Motion detected... Taking picture!"
def take_picture(resolution):
global pics_taken
camera.resolution = resolution
# Capture a sequence of frames
'pics', 'image_' + str(pics_taken) + '.jpg'))
pics_taken += 1
print "Picture taken! Tweeting it..."""
def update_twitter():
'pics', 'image_' + str(pics_taken -1) + '.jpg'),
status = random.choice(tweet_text))
print "Status updated!"
#We don't want to tweet more than once per minute!
GPIO.add_event_detect(pir, GPIO.RISING, callback=motion_sense)
while True:
except KeyboardInterrupt:
print "\nQuitting"

Raspberry Pi Tips, Tricks & Hacks 25

28 5 Practical
Raspberry Pi Projects

Make music with the Raspberry Pi


Raspberry Pi voice synthesiser


Program Minecraft-Pi


Get interactive with Scratch


Build a Raspberry Pi web server


40 Why You Need Python 3
48 Use an Android device as a
Raspberry Pi screen
52 Host a website on your
Raspberry Pi


54 Secure your Raspberry Pi
58 Build a file server with the
Raspberry Pi
62 Network and share your
keyboard and mouse
64 Add a reset switch
66 Remotely control Pi
68 Install Android
76 Add a battery pack to
Raspberry Pi

26 Raspberry Pi Tips, Tricks & Hacks


“This isn’t a random
selection. These are
practical ideas designed to
help kick-start bigger and
better things”



Raspberry Pi Tips, Tricks & Hacks 27

Tips | Tricks | Hacks

28 Raspberry Pi Tips, Tricks & Hacks

Tips | Tricks | Hacks




Still haven’t done anything with your Raspberry Pi?
Follow along with our expert advice and kick-start
your own amazing Raspberry Pi projects
From our time experimenting with this incredible credit
card-sized computer, it’s become clear there are two types
of Raspberry Pi owners: those that use theirs and those
that don’t. Whether it’s fear of the unknown, a lack of time
or inspiration, when we ask people what they do with their
Pi we’ll often hear that it’s still in the box. If that’s you, then
you’re in the right place. In this feature we’ve handcrafted ten
Raspberry Pi projects practically anyone can enjoy.
These aren’t just a random selection of side-projects, though.
These are practical ideas designed to help kick-start bigger
and better things. Knowledge gained from one project can also
be applied to another to create something completely new.
For example, you could take what you’ll learn with the Sonic Pi
tutorial and go on to create a text-to-morse code translator.
You could go on to make Pong in Minecraft-Pi or use a button
attached to Scratch to take photos with your Raspberry Pi
camera module. The list goes on.
All these projects are open source, so you’re encouraged to
tweak and develop them into something entirely new. If you
share your tweaks and changes with the community, you’re sure
to start benefitting from doing things the open source way…

Raspberry Pi Tips, Tricks & Hacks 29

Tips | Tricks | Hacks

Make music with
the Raspberry Pi

Program your own melodies using Sonic Pi and create
musical cues or robot beeps

What you’ll need
Q Portable speakers
Q Sonic Pi

QSonic Pi is a great way
to learn basic coding
principles and have fun

30 Raspberry Pi Tips, Tricks & Hacks

One of the major features of Scratch is
its ability to teach the fundamentals
of coding to kids and people with no
computing background. For kids, its
especially appealing due to the way it
allows them to create videogames to
interact with as part of their learning. In
this kind of vein then, Sonic Pi teaches
people to code using music. With a
simple language that utilises basic logic
steps but in a more advanced way than
Scratch, it can either be used as a next
step for avid coders, or as a way to create
music for an Internet of Things or a robot.


Getting Sonic Pi

If you’ve installed the latest version of Raspbian, Sonic
Pi will be included by default. If you’re still using a slightly older
version, then you’ll need to install it via the repos. Do this with:

$ sudo apt-get install sonic-pi

Tips | Tricks | Hacks

“We can start making more
complex melodies by using
more of Sonic Pi’s functions”


Starting with Sonic Pi

Sonic Pi is located in the Education category in the
menus. Open it up and you’ll be presented with something that
looks like an IDE. The pane on the left allows you to enter the code
for your project, with proper syntax highlighting for its own style
of language. When running, an info pane details exactly what’s
being played via Sonic Pi – and any errors are listed in their own
pane as well, for reference.


Set the beat

For any piece of music, you’ll want to set the tempo. We
can start by putting:

with_tempo 200
…at the start of our code. We can test it out by creating a string of
midi notes using play_pattern:

play_pattern [40,25,45,25,25,50,50]
This will play pretty_bell notes at these tones at the tempo we’ve
set. You can create longer and shorter strings, and also change
the way they play.


Your first note

Our first thing to try on Sonic Pi is simply being able
to play a note. Sonic Pi has a few defaults preset, so we can get
started with:

play 50
Press the Play button and the output window will show you what’s
being played. The pretty_bell sound is the default tone for Sonic
Pi’s output, and 50 determines the pitch and tone of the sound.


Full code listing
with_tempo 200
play_pattern [40,25,45,25,25,50,50]
2.times do
with_synth “beep”
play_pattern [40,25,45,25,25,50,50]
play_pattern [40,25,45,25,25,50,50].reverse


Advance your melody

We can start making more complex melodies by using
more of Sonic Pi’s functions. You can change the note type by
using with_synth, reverse a pattern, and even create a finite loop
with the x.times function; do and end signify the start and end
of the loop. Everything is played in sequence before repeating,
much like an if or while loop in normal code.

play_pad “saws”, 3
in_thread do
with_synth “fm”
6.times do
if rand < 0.5
play 30
play 50
sleep 2
2.times do
play_synth “pretty_bell”
play_pattern [40,25,45,25,25,50,50]
play_pattern [40,25,45,25,25,50,50].reverse

1 How to code
The coding
style of Sonic Pi
uses concepts
from standard
languages – if
loops, threads etc.
Whereas Scratch
teaches this logic,
Sonic Pi teaches
their structure.

2 Robotic

Employ Sonic Pi
to create contextsensitive chips,
chirps and beeps
and use it to give a
familiar voice while it
tootles around.



Playing a concert

Using the in_thread function, we can create another
thread for the Sonic Pi instance and have several lines of musical
code play at once instead of in sequence. We’ve made it create
a series of notes in a random sequence, and have them play
alongside extra notes created by the position and velocity of the
mouse using the play_pad function.

The Musical
Instrument Digital
Interface is a
standard for digital
music, and the
numbers and tones
used in Sonic Pi make
use of this.

Raspberry Pi Tips, Tricks & Hacks 31

Tips | Tricks | Hacks

 It’s easier to make your Raspberry Pi talk
than you might think, thanks to eSpeak

Raspberry Pi
voice synthesiser
Add the power of speech to your Raspberry Pi
projects with the versatile eSpeak Python library
What you’ll need
Q Portable USB speakers
Q python-espeak module
QRaspbian (latest image)

32 Raspberry Pi Tips, Tricks & Hacks

We’ve already mentioned how the
Raspberry Pi can be used to power
robots, and as a tiny computer it
can also be the centre of an Internet
of Things in your house or office.
For these reasons and more, using
the Raspberry Pi for text-to-voice
commands could be just what you’re
looking for. Due to the Debian base
of Raspbian, the powerful eSpeak
library is easily available for anyone
looking to make use of it. There’s also a
module that allows you to use eSpeak
in Python, going beyond the standard
command-line prompts so you can
perform automation tasks.


Everything you’ll need

We’ll install everything we plan to use in this tutorial at
once. This includes the eSpeak library and the Python modules
we need to show it off. Open the terminal and install with:

$ sudo apt-get install espeak python-espeak python-tk

Tips | Tricks | Hacks

“You can change the way eSpeak
will read text with a number of
different options”


Pi’s first words

The eSpeak library is pretty simple to use – to get it to
just say something, type in the terminal:

$ espeak “[message]”


A voice synthesiser

Using the code listing, we’re creating a simple interface
with Tkinter with some predetermined voice buttons and a
custom entry method. We’re showing how the eSpeak module
can be manipulated to change its output. This can be used for
reading tweets or automated messages. Have fun!

This will use the library’s defaults to read whatever is written in
the message, with decent clarity.

Full code listing


Say some more

You can change the way eSpeak will read text with a
number of different options, such as gender, read speed and
even the way it pronounces syllables. For example, writing the
command like so:

$ espeak -ven+f3 -k5 -s150 “[message]”
…will turn the voice female, emphasise capital letters and make
the reading slower.

Import the
necessary eSspeak
and GUI modules, as
well as the module
to find out the time
Define the different
functions that the
interface will use,
including a simple
fixed message,
telling the time, and
a custom message

Create the basic
window with Tkinter
for your interface,
as well as creating
the variable for
text entry


Taking command with Python

The most basic way to use eSpeak in Python is to use
subprocess to directly call a command-line function. Import
subprocess in a Python script, then use:

subprocess.call([“espeak”, “[options 1]”, “[option 
2]”,...”[option n]”, “[message]”)
The message can be taken from a variable.


The native tongue

The Python eSpeak module is quite simple to use to just
convert some text to speech. Try this sample code:

from espeak import espeak
You can then incorporate this into Python, like you would any
other module, for automation.

The text entry
appends to the
variable we
created, and each
button calls a
specific function
that we defined
above in the code

the code:

from espeak import espeak
from Tkinter import *
from datetime import datetime


def hello_world():
espeak.synth(“Hello World”)
def time_now():
t = datetime.now().strftime(“%k %M”)
espeak.synth(“The time is %s”%t)
def read_text():
text_to_read = input_text.get()
root = Tk()
root.title(“Voice box”)
input_text = StringVar()
box = Frame(root, height = 200, width = 500)
box.pack(padx = 5, pady = 5)
Label(box, text=”Enter text”).pack()
entry_text = Entry(box, exportselection = 0, 
textvariable = input_text)
entry_ready = Button(box, text = “Read this”, 
command = read_text)
hello_button = Button(box, text = “Hello World”, 
command = hello_world)
time_button = Button(box, text = “What’s the 
time?”, command = time_now)

Raspberry Pi Tips, Tricks & Hacks 33

Tips | Tricks | Hacks


Learn to program while playing one of the
greatest games ever made!

What you’ll need
Q Raspbian (latest release)
Q Minecraft-Pi tarball
Q Keyboard & mouse
Q Internet connection

 Unlike all
other versions of
Minecraft, the Pi
version encourages
you to hack it

Minecraft is probably the biggest game
on the planet right now. It’s available on
just about any format you can imagine,
from PCs to gaming consoles to mobile
phones. It should probably come as
no surprise that it’s also available on
the Raspberry Pi. While at first glance
Minecraft-Pi is a simplified version of the
Pocket Edition (designed for tablets and
smartphones), the Raspberry Pi edition
is very special, in that it’s the only version
of Minecraft to gives users access to its
API (application programming interface).
In this project we’re going to show you
how to set up Minecraft-Pi and configure
it so you can interact with Minecraft in a
way you’ve never done before. This small
project is just the tip of the iceberg…



Minecraft-Pi requires you to be running Raspbian on
your Raspberry Pi, so if you’re not already running that, take a
trip to raspberrypi.org and get it setup. It also requires you have
X Window loaded too. Assuming you’re at the command prompt,
you just need to type startx to reach the desktop.

Tips | Tricks | Hacks



Make sure you’re already in your
home folder and download the MinecraftPi package with the following commands
in a terminal window:

cd ~
wget https://s3.amazonaws.com/
To use it we need to decompress it. Copy
the following into the terminal window:

tar -zxvf minecraft-pi-0.1.1.tar.gz
Now you can move into the newly
decompressed Minecraft-Pi directory
and try running the game for the first time:

cd mcpi


Playing Minecraft-Pi

Have a look around the game.
If you’re not familiar with Minecraft, you
control movement with the mouse and
the WASD keys. Numbers 1-8 select items
in your quickbar, the space bar makes you
jump and Shift makes you walk slowly (so
you don’t fall off edges). ‘E’ will open your
inventory and double-tapping the space
bar will also toggle your ability to fly.


Configuring the Python API

To take control of Minecraft with
the Python API, you next need to copy the
Python API folder from within the /mcpi
folder to a new location. In the terminal,
type the following:

cp -r ~/mcpi/api/python/mcpi 

~/ minecraft
In this folder, we want to create a
‘boilerplate’ Python document that
connects the API to the game. Write the
following into the terminal:

cd ~/minecraft
nano minecraft.py
With nano open, copy the following and
then save and exit with Ctrl+X, pressing
Y (for yes), then Enter to return to the
command prompt:

from mcpi.minecraft import 
from mcpi import block
from mcpi.vec3 import Vec3
mc = Minecraft.create()
mc.postToChat(“Minecraft API 


Testing your Python script

The short script you created
contains everything you need to get
started with hacking Minecraft-Pi in the
Python language. For it to work, you need
to have the game already running (and
be playing). To grab control of the mouse

Full code listing
# !/usr/bin/env python
from mcpi.minecraft import Minecraft
from mcpi import block
from mcpi.vec3 import Vec3
from time import sleep, time
import random, math
mc = Minecraft.create() # make a connection to the game
playerPos = mc.player.getPos()
# function to round players float position to integer position
def roundVec3(vec3):
return Vec3(int(vec3.x), int(vec3.y), int(vec3.z))
# function to quickly calc distance between points
def distanceBetweenPoints(point1, point2):
xd = point2.x - point1.x
yd = point2.y - point1.y
zd = point2.z - point1.z
return math.sqrt((xd*xd) + (yd*yd) + (zd*zd))

Functional, &
fun coding
There’s nothing too
taxing about our
code. We’ve created
a couple of simple
functions (starting
with def) and used
if, else and while to
create the logic.

def random_block(): # create a block in a random position
randomBlockPos = roundVec3(playerPos)
randomBlockPos.x = random.randrange(randomBlockPos.x - 50, randomBlockPos.x + 50)
randomBlockPos.y = random.randrange(randomBlockPos.y - 5, randomBlockPos.y + 5)
randomBlockPos.z = random.randrange(randomBlockPos.z - 50, randomBlockPos.z + 50)
return randomBlockPos
def main(): # the main loop of hide & seek
global lastPlayerPos, playerPos
seeking = True
lastPlayerPos = playerPos
randomBlockPos = random_block()
mc.setBlock(randomBlockPos, block.DIAMOND_BLOCK)
mc.postToChat(“A diamond has been hidden somewhere nearby!”)
lastDistanceFromBlock = distanceBetweenPoints(randomBlockPos, lastPlayerPos)
timeStarted = time()
while seeking:
# Get players position
playerPos = mc.player.getPos()
# Has the player moved
if lastPlayerPos != playerPos:
distanceFromBlock = distanceBetweenPoints(randomBlockPos, playerPos)
if distanceFromBlock < 2:
#found it!
seeking = False
if distanceFromBlock < lastDistanceFromBlock:
mc.postToChat(“Warmer “ + str(int(distanceFromBlock)) + “ blocks away”)
if distanceFromBlock > lastDistanceFromBlock:
mc.postToChat(“Colder “ + str(int(distanceFromBlock)) + “ blocks away”)
lastDistanceFromBlock = distanceFromBlock
timeTaken = time() - timeStarted
mc.postToChat(“Well done - “ + str(int(timeTaken)) + “ seconds to find the diamond”)
if __name__ == “__main__”:
while in-game, you can press Tab. Open a
fresh terminal window, navigate into your
minecraft folder and start the script with
the following commands:

cd ~/minecraft
python minecraft.py
You’ll see a message appear on screen to
let you know the API connected properly.
Now we know it works, let’s get coding!


Hide & Seek

As you can see from the code above, we’ve created a
game of Hide & Seek adapted from Martin O’Hanlon’s original
creation (which you can find on www.stuffaboutcode.com).
When you launch the script, you’ll be challenged to find a
hidden diamond in the fastest time possible. We’ve used it to
demonstrate some of the more accessible methods available in
the API. But there’s much more to it than this demonstrates. If
you’re up for another Minecraft-Pi tutorial, see: bit.ly/1v4DR2F.

Raspberry Pi Tips, Tricks & Hacks 35

Tips | Tricks | Hacks

 Scratch can be used to do Internet Of
Things projects with a few tweaks

Get interactive
with Scratch

Experiment with physical computing by using Scratch
to interact with buttons and lights on your Pi

What you’ll need
Q Breadboard
Q Buttons
Q Resistors
Q Jumper wires
Q ScratchGPIO3

36 Raspberry Pi Tips, Tricks & Hacks

Scratch is a very simple visual
programming language, commonly
used to teach basic programming
concepts to learners of any age. In
this project we’ll learn how to light up
an LED when a button is pressed in
Scratch, and then change a character’s
colour when a physical button is
pressed. With these techniques
you can make all manner of fun and
engaging projects, from musical
keyboards to controllers for your
Scratch games and animations.


Installing the required software

Log into the Raspbian system with the username Pi and
the password raspberry. Start the LXDE desktop environment
using the command startx. Then open LXTerminal and type the
following commands:

wget http://liamfraser.co.uk/lud/install_scratchgpio3.sh
chmod +x install_scratchgpio3.sh
sudo bash install_scratchgpio3.sh
This will create a special version of Scratch on your desktop
called ScratchGPIO3. This is a normal version of Scratch
with a Python script that handles communications between
Scratch and the GPIO. ScratchGPIO was created by simplesi

Tips | Tricks | Hacks

uses pin numbers rather than GPIO numbers to identify pins.
The top-right pin (the 3.3V we first connected our LED to) is pin
number 1, the pin underneath that is pin number 2, and so on.

1 Simple


Connecting the breadboard

Power off your Pi and disconnect the power cable. Get
your breadboard, an LED, a 330-ohm resistor and two GPIO
cables ready. You’ll want to connect the 3.3V pin (top-right pin,
closest to the SD card) to one end of the 330-ohm resistor, and
then connect the positive terminal of the LED (the longer leg is
positive) to the other end. The resistor is used to limit the amount
of current that can flow to the LED.
Then put the negative terminal of the LED into the negative
rail of the breadboard. Connect one of the GROUND pins (for
example, the third pin from the right on the bottom row of pins)
to the negative lane. Now connect the power to your Pi. The LED
should light up. If it doesn’t, then it’s likely that you’ve got it the
wrong way round, so disconnect the power, swap the legs around
and then try again.


Switching the LED on and off

At the moment, the LED is connected to a pin that
constantly provides 3.3V. This isn’t very useful if we want to be able
to turn it on and off, so let’s connect it to GPIO 17, which we can turn
on and off. GPIO 17 is the sixth pin from the right, on the top row of
pins. Power the Pi back on. We can turn the LED on by exporting
the GPIO pin, setting it to an output pin and then setting its value
to 1. Setting the value to 0 turns the LED back off:


While these are very
simple circuits, you’ll
get a great feel of
how the Raspberry
Pi interfaces with
basic prototyping
kit. If you need to buy
the bits and pieces,
we recommend you
check out:

17 > /sys/class/gpio/export
out > /sys/class/gpio/gpio17/direction
1 > /sys/class/gpio/gpio17/value
0 > /sys/class/gpio/gpio17/value


Controlling the LED from Scratch

Start the LXDE desktop environment and open
ScratchGPIO3. Go to the control section and create a simple script
that broadcasts pin11on when Sprite1 is clicked. Then click the
sprite. The LED should light up. Then add to the script to wait 1
second and then broadcast pin11off. If you click the sprite again,
the LED will come on for a second and then go off. ScratchGPIO3

Wiring up our push button

Power off the Pi again. This circuit is a little bit more
complicated than the LED one we created previously. The first
thing we need to do is connect 3.3V (the top-right pin we used to
test our LED) to the positive rail of the breadboard. Then we need
to connect a 10Kohm resistor to the positive rail, and the other end
to an empty track on the breadboard. Then on the same track, add
a wire that has one end connected to GPIO 4. This is two pins to the
right of GPIO 17. Then, on the same track again, connect one pin of
the push button. Finally, connect the other pin of the push button
to ground by adding a wire that is connected to the same negative
rails that ground is connected to.
When the button is not pressed, GPIO 4 will be receiving 3.3V.
However, when the button is pressed, the circuit to ground will be
completed and GPIO 4 will be receiving 0V (and have a value of 0),
because there is much less resistance on the path to ground.
We can see this in action by watching the pin’s value and then
pressing the button to make it change:

If you’re new to
Scratch is the
perfect place to
learn the same
principles employed
by all programming
languages out there.

3 Physical

There’s nothing more
magical than taking
code from your
computer screen
and turning it into a
real-life effect. Your
first project might
just turn a light on
and off, but with that
skill banked, the sky
is the limit.

echo 4 > /sys/class/gpio/export
echo in > /sys/class/gpio/gpio4/direction
watch -n 0.5 cat /sys/class/gpio/gpio4/value


2 Coding

Let there be light!

Boot up the Pi and start ScratchGPIO3 as before. Go
to the control section and add when green flag clicked, then
attach a forever loop, and inside that an if else statement. Go
to the operators section and add an if [] = [] operator to the
if statement. Then go to the sensing section and add a value
sensor to the left side of the equality statement, and set the
value to pin7. On the right side of the equality statement, enter
0. Broadcast pin11on if the sensor value is 0, and broadcast
pin11off otherwise. Click the green flag. If you push the button,
the LED will light up!

Raspberry Pi Tips, Tricks & Hacks 37

Tips | Tricks | Hacks

 Google Coder is a brilliant way to
introduce yourself to web development

Build a Raspberry Pi
web server
Use Google Coder to turn your Raspberry Pi into a
tiny, low-powered web server and web host
What you’ll need
Q Internet connectivity
Q Web browser
Q Google Coder

38 Raspberry Pi Tips, Tricks & Hacks

We’re teaching you how to code in many
different ways on the Raspberry Pi this
issue, so it only seems fitting that we
look at the web too.
There’s a new way to use the web on
the Raspberry Pi as well: internet giant
Google has recently released Coder
specifically for the tiny computer. It’s a
Raspbian-based image that turns your Pi
into a web server and web development
kit. Accessible easily over a local network
and with support for jQuery out of the
box, it’s an easy and great way to further
your web development skills.


Get Google Coder

Head to the Google Coder website, and download the
compressed version of the image. Unpack it wherever you wish,
and install it using dd, like any other Raspberry Pi image:

$ dd if=[path to]/raspi.img of=/dev/[path to SD
card] bs=1M

Tips | Tricks | Hacks

Full code listing


Plug in your Pi

For this tutorial, you’ll only need to connect a network
cable into the Pi. Pop in your newly written SD card, plug in the
power and wait a few moments. If you’ve got a display plugged in
anyway, you’ll notice a Raspbian startup sequence leading to the
command-line login screen.


Connect to Coder

Open up the browser on your main system, and go to
http://coder.local. You may have to manually accept the licence.
It will ask you to set up your password, and then you’ll be in and
ready to code.


Language of the web

Now it’s time to create your own app or website. Click
on the ‘+’ box next to the examples, give your app a name and
then click Create. You’ll be taken to the HTML section of the app.
Change the Hello World lines to:

Some simple HTML
code that can
point us to some
important websites.
The h2 tag is used
to display the time
thanks to Java

Welcome to the internet...

Linux User & Developer


The  Linux Foundation

Free Software  Foundation

Java We’re calling the current time using jQuery in the JS tab so that we can ultimately display it on the webpage We’re going to display the time as a 12-hour clock in the first if statement, and use AM and PM to differentiate the time We make the minutes readable by adding a 0 if it’s below 10, then concatenate all the variables and assign to the tag h2 var d = new Date; var hours = d.getHours(); var mins = d.getMinutes(); if (hours > 12) { var hour = (hours - 12); var ampm = “PM”; } else { var hour = hours; var ampm = “AM”; } if (hours == 12) { var ampm = “PM”; } if (mins > 9){ var min = mins; } else { var min = “0” + mins; } var time = “The time is “ + hour + “:” + min  + “ “ + ampm; $(“h2”).html(time);

This is a HTML header

This is a new block of default text

05 Styled to impress Click on the CSS tab. This changes the look and style of the webpage without having to make the changes each time in the main code. You can change the background colour and font with: body { background-color: #000000; color: #ffffff; } 06 Querying your Java The third tab allows you to edit the jQuery, making the site more interactive. We can make it create a message on click with: $(document).click(function() { alert(‘You clicked the website!’); } ); Raspberry Pi Tips, Tricks & Hacks 39 WAYS TO MASTER RAS PI Get the most out of your Pi with these expert tips and tricks Whether you’ve just got your lucky hands on a powerful, petite Raspberry Pi Zero or you’re looking to maximise the efficiency of the faithful Raspberry Pi you already own, this is everything you need to get started on boosting not only your Raspberry Pi but your own knowledge. The Raspberry Pi is a versatile little piece of hardware, with a wonderfully creative amount of potential, and though most of you will be familiar with its more day-to-day functions, there are always tweaks and adjustments to be explored that can tailor the Raspberry Pi to your own desired user experience. From soldering to useful Python features, GPIO interrupts to remote access, and a whole 40 Raspberry Pi Tips, Tricks & Hacks lot more, this masterclass in technical and practical skills covers fifty useful ways to get the most out of your Raspberry Pi. If you’re anything like us, you’ll have been tinkering around with your Raspberry Pi Zero, but whatever your skill level there’s still something here for you to get your teeth into. Every single tip here will work on your Pi Zero; just keep an eye out for the ‘Zero’ flash, indicating which are relevant to the Pi Zero only. Those of you using an earlier model won’t be missing out, though – how could we ever neglect our favourite single-board computer? – the majority of tips, tricks and tweaks are still suitable for any other official Raspberry Pi as well. Have fun tinkering! Tips | Tricks | Hacks 01 Raspberry Pi Zero BCM2835 This is the same processor used in the original Raspberry Pi models, although it’s been overclocked to run at 900MHz and is about 40% faster. Pinless port The GPIO header is the same as in the newer models but comes without the pins. You’ll need to solder on a 40-pin male header block. Zero 02 The newest member of the Raspberry Pi family, this tiny board is the result of the Raspberry Pi Foundation’s efforts to reduce the cost of the computer even further. Not content with reducing its $35 computer to $25, which can still be a little pricy for some people, it has cut it right down to $5 by making a few adjustments. Here’s what you need to know. Vital knowledge Essential tricks to improve day-to-day use 03 Find your Pi on a network If you can’t log into your router to view DHCP leases, you can use nmap (available for Linux, Windows and Mac) to scan the local network to find a Raspberry Pi. You need to know the address range of your local network (common networks are, and nmap -sn will run a ping scan and output a list of devices. An example output is: Nmap scan report for raspberrypi.home.org ( Host is up (0.0011s latency). 04 Experiencing stability issues? By far the biggest cause of stability issues is the power supply you are using, especially now the Raspberry Pi 2 has more CPU cores and so uses more energy. The recommended current supply for a Raspberry Pi 2 or B+ is 1.8 amps. If you are still having issues, your SD card may be worn out. Mini-HDMI You’ll need a mini-HDMI to HDMI cable to use your monitor as a display. You can use your TV with the RCA video-out if you solder the pin. Micro-USB One of these ports is for your micro-USB power supply. To use peripherals and a Wi-Fi dongle, you’ll need a micro-USB to USB adaptor so you can attach a powered USB hub. Ensure you have the latest packages on Raspbian by running sudo apt-get update; sudo apt-get upgrade from a terminal to type sudo? 05 Forgot Sudo is used to get root privileges for a specific command (for example, editing a file in /boot or /etc). The variable !! in bash is the previous command that you typed. So if you need root privileges for something but forgot to type sudo then you can simply type sudo !!, provided you haven’t typed anything else since. max current draw 06 Enable If you have a good power supply (ie 2 amps or more) and want to be able to connect a current-heavy device to your Pi 2 or B+, such as a USB hard disk, then you can add the line max_usb_current=1 to /boot/config.txt, which will set the max current over USB to 1.2 amps instead of the default 600mA. options 07 Control sudo raspi-config can be used to change several options. For example, to enable the camera, overclock the Pi, change boot options, and expand the filesystem to use the full space on the SD card. Tips | Tricks | Hacks Transferable tips Handy hints and vital info to get the most out of any Raspberry Pi model Remote access with SSH 08 SSH stands for Secure Shell. You can use SSH to connect to a terminal session on your Raspberry Pi over your local network. This means that you can use the Pi with only a network cable and power cable connected, which is much more convenient than needing a screen and keyboard. Once you have found your Pi on the network you can log into it using the default username of ‘pi’ and the default password of ‘raspberry’. Both Linux and Mac will have built-in SSH clients, so simply open the terminal and type ssh pi@, assuming that is the address of your Pi. On Windows, you can use an SSH client called PuTTY, which is free to download, doesn’t need installing and is easy to find with a search engine. Copy files using SCP 09 SCP stands for Secure Copy Protocol, and is a way for you to copy files (and directories) to and from your Raspberry Pi over the network. A good use of this would be if you have art for a PyGame project and you need to copy it over. FileZilla is a decent graphical SCP client to use (connect to your Pi on port 22 with the username ‘pi’ and password ‘raspberry’). If you are using SCP from the terminal then the syntax is as follows: Above Get a terminal on your Raspberry Pi from the convenience of your main computer are copied in addition to files. This will place your test directory in /home/pi/ (because ~ points at the logged-in user’s home directory on Linux). Simply swap the syntax for copying from the Raspberry Pi instead: scp -r pi@ . scp -r testdir/pi@ The -r switch is for recursive, which means entire directories The dot refers to the current directory in Linux, so the testdir directory would be copied to the current directory. Raspberry Pi B+ 10 USB controller The USB controller on the Pi is theoretically capable of 480Mbit/s. On earlier Pi models the performance is limited by the single core ARM chip, but it is possible to get close to that limit on a Pi 2. 11 Power / Act LEDs The remaining LEDs are for power and SD card activity. The power LED is red, and the activity LED flashes green when there is SD card activity. The activity LED also flashes when powering down to indicate when it is safe to disconnect. SD cards SD cards aren’t really designed for running an operating system. Higher class SD cards don’t necessarily mean better performance for lots of small files. The Raspberry Pi foundation recommend its SD card, which is an 8GB class 6 microSD card. Wi-Fi module To get your Pi online without an Ethernet connection, you’ll need a Wi-Fi module. We advise on an official one, but look for 802.11 b/g/n modules if going third-party. 14 12 42 Raspberry Pi Tips, Tricks & Hacks Ethernet LEDs There are two LEDs below the Ethernet port of a B+ onwards. The orange light means there is a link, and the flashing green light means there is activity. 13 Tips | Tricks | Hacks 15 Get your Pi Zero online Using an Ethernet adapter with your Pi Zero Step One: The parts Zero You’ll need an adapter to connect the micro-USB port to a full size USB port. This adapter, along with a miniHDMI to HDMI adapter and GPIO pin headers can be found here: http:// swag.raspberrypi.org/products/pizero-cables. You’ll also need a USB to Ethernet adapter that works with Linux (most will work out of the box), These can easily be found on Amazon for around £10. Navigate your way around the command line with ease open ports 18 Listing Lsof stands for List Open Files, and you can install it with sudo apt-get install lsof. If you run sudo lsof -i you will see a list of all open network connections on the machine, including applications that are listening for new connections (for example, the SSH daemon). Using wget to download files 19 Wget can be used to download Step Two: Configuration As the Pi Zero uses the normal Raspbian image, and eth0 (ie the builtin Ethernet card) is missing, there is no configuration necessary because the USB Ethernet card will take the missing LAN chip’s place as eth0. Five terminal tricks Step Three: Testing it out If the activity lights on your USB to Ethernet adapter are lit, then it should be working fine. You can now use the remote access tips from other sections of the article with your Pi Zero! Set up a VNC server 16 VNC stands for Virtual Network Computing. Using VNC, you can access the Raspbian desktop over the network (meaning you only need power and Ethernet connected). There is no audio support but for any other tasks (including the use of Pygame), VNC should provide acceptable performance. You can install a VNC server with the following commands… files from the Internet from the terminal. This is convenient if you need to download a zip file containing source code and then extract it. For example: wget http://liamfraser.co.uk/test.zip unzip test.zip 17 The sync command ensures that everything has been flushed to permanent storage from the cache. It can be useful to run after Using htop to monitor load 20 Htop updating packages, is an improvement on the original top utility. for example. It lets you see the CPU and memory load on your machine in real time, which is useful to know how intensive your application is being on a Raspberry Pi. You can install it with sudo apt-get install htop. sudo apt-get update sudo apt-get install tightvncserver There are several free VNC clients available, so a search engine will help find a suitable one. To start a VNC session on your Pi, log in over SSH and then run tightvncserver. You will be prompted to enter a password the first time you run it. You can specify a screen resolution with the -geometry option, for example -geometry 1024x768. You can kill an existing VNC session with tightvncserver -kill :1, where 1 is the session number. To connect to that session on a Linux machine, you could use the command: vncviewer, substituting for the IP address of your Raspberry Pi. from the terminal 21 Reboot It seems like a simple tip but not everyone knows that you can reboot your Pi with the command sudo reboot, and similarly power it off with sudo poweroff. You need to disconnect and reconnect the power after powering off the Pi, though, as there is no on/off switch. screen 22 Using Screen (available via apt-get) is great if you have something you want to run that takes a long time. You can run it in a screen session, detach from it and reconnect later on. Example usage: screen -S test (Ctrl + A, d to disconnect) screen -ls to list sessions. screen -r test to reconnect exit will kill bash and therefore end the screen session. Left Access the Raspbian desktop from your main computer over your local network files 23 split If your program is large, you can split it up into multiple files. If you have a file called MyClass.py containing a class MyClass, you can use it from another script with from MyClass import MyClass Raspberry Pi Tips, Tricks & Hacks 43 Tips | Tricks | Hacks Become a Python Pro Here are some handy Python features that will make your code really stand out The main function 24 Having a main function (if __name__ == if __name__ == “__main__”: # Test MyClass m = MyClass() m.print_increment() m.print_increment() __main__) in Python is useful. It makes it easier to see the difference between where your functions/ classes are defined and where your entry point is. More importantly, it allows you to only run code from that Python script in the case that it is the main script being run. This means that you can create a class and have code that tests that class to make sure it works. However, if you were to include your file in another program, the code in the main method would not be run and you can just use the class that you require. Command line arguments 25 Command line arguments enable your program to run in various modes depending on the options that the user passes to the program when running it. Command line arguments in Python are given in sys.argv, which is a list of arguments. The first argument is always the name of the script that has been executed. For example, some code that prints the argv array produces the following outputs: class MyClass: def __init__(self): self.x = 1 $ python args.py [‘args.py’] $ python args.py --foo [‘args.py’, ‘--foo’] def print_increment(self): print “x = {0}”.format(self.x) self.x += 1 27 You can check for command line arguments in this list. If the length of the list is 1 and you require arguments, print a help message with instructions. import sys help_msg = “My help message” debug_mode = False if __name__ == “__main__”: if len(sys.argv) == 1: print help_msg sys.exit() if “--debug” in sys.argv: debug_mode = True print “Using debug mode” Using properties and setters 26 Properties in Python are a way to write getters and setters for variables. You need newstyle classes (you need to inherit from object). We 28 Python conferences You can use negative indexes on Python lists to get the most recently added item(s). mylist[-1] will get the latest thing that was added to the list. OSCON USA 2016 16 - 19 May oreil.ly/1QKVTTB The Open Source Convention, held in Austin, Texas this year, is a place of innovation for sharing new ideas and technologies PYCON US 2016 28 May - 5 June FOSDEM 2016 us.pycon.org/2016 30-31 January The largest gathering of the global Python community takes place in Portland, Oregon in 2016, featuring two tutorial days, three talk days and four sprint days 44 Raspberry Pi Tips, Tricks & Hacks fosdem.org/2016 OSCON Europe 2016 17 - 20 October oreil.ly/1VqRWnE Europe’s OSCON event mirrors the US format, with training sessions, keynotes and tutorials through its four days This free, non-commercial event organised by volunteers takes place in Belgium and has grown wildly over the years Tips | Tricks | Hacks Five hidden features Uncover the secrets to be found in Python comprehension 30 List List comprehension is a way of generating a list on a single line. You can use list comprehension to extract values from other list-type data structures. For example, if you have a collection of distance classes, you could get just the distance in miles into a list: miles = [x.miles for x in distances]. Here is a sample output: Above Not sure whether to pick Python 2 or 3? There’s a guide to help in the docs: bit.ly/1jyd799 have created a class called distance where the distance in miles is a variable, and the distance in kilometres is a property. Getting from that variable multiplies the distance in miles to be kilometres and setting the variable sets the value in miles. class Distance(object): KM_PER_MILE = 1.60934 def __init__(self, mi): self.miles = mi @property def km(self): return self.miles * Distance. KM_PER_MILE @km.setter def km(self, value): self.miles = value / Distance. KM_PER_MILE if __name__ == “__main__”: d = Distance(3.1) print d.km d.km = 10 print d.miles print d.km >>> [x/2.0 for x in range(0, 10)] [0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5] 31 Assertions Assertions are useful when writing algorithms. They are used to check the data is valid before and after your algorithm. So, for example, if you are expecting your results in a certain range you can check them. The syntax is assert(boolean expression). For example: >>> assert(0 < 1) >>> assert(1 < 0) Traceback (most recent call last): File “”, line 1, in AssertionError exceptions 32 Throwing It’s useful to throw exceptions 29 Using the GPIO Get to grips with the GPIO library Step One: Import library Start by importing Rpi.GPIO: import RPi.GPIO as GPIO Then, you want to set the pin numbering convention to the Broadcom mode (as in GPIO17 will be pin 17, rather than being pin 11 on the Pi): for p in pins: GPIO.setup(p, GPIO.OUT) in your code if it’s possible that it can go wrong. That way the person calling your code can put it in a try-catch block and handle the exception if it is raised. If the caller does not handle it then their application will crash. >>> raise ValueError(“Supplied value out of range”) Traceback (most recent call last): File “”, line 1, in ValueError: Supplied value out of range Step Three: Get values Once the pins are set up, getting values from them is easy. To get the value of a pin (0 for low, and 1 for high), use the following syntax: your script from a terminal 33 Running If you begin your Python script with #!/usr/bin/env python and then mark it as executable, you can execute it from bash just like a normal script without having to type Python before it: value = GPIO.input(6) GPIO.setmode(GPIO.BCM) Step Two: Pin setup Now you need to set up your pins as either inputs or outputs with the following syntax: GPIO.setup(5, GPIO.OUT) GPIO.setup(6, GPIO.IN) If you have several pins to set up, it makes sense to put them in a list and then do something like: …and to set the value of a pin (with either 0 or 1, or True or False) use the following syntax: $ echo ‘#!/usr/bin/env python’ > test.py $ echo ‘print “Hello World from Python!”’ >> test.py $ chmod +x test.py $ ./test.py Hello World from Python! GPIO.output(5, True) Please note that if you are starting with Raspbian Jessie, you shouldn’t need sudo to access the GPIO pins, but in previous versions of Raspbian you will need to use sudo to run your code. the interpreter 34 Using Did you know you can start a Python interpreter to test things are working without having to write a Python script? Just type python into the terminal and then simply start writing Python. static 35 remove Make sure you haven’t built up any static charge when working with electronics. Touching a grounded radiator in your house can be a good way of getting rid of static charge. Raspberry Pi Tips, Tricks & Hacks 45 Tips | Tricks | Hacks Hardware how-to GPIO interrupts, pulse width modulation, soldering and more GPIO explained GPIO 36 orientation The best way to verify you have the Pi oriented the right way is to flip it over. The underneath of pin 1 has a square hole for the solder instead of a circular hole. 41 Unused 38 GPIO pins Serial 37 console If you connect the UART0_TXD pin to the receiver pin of a USB-to-serial converter, and the UART0_RXD pin to the transmitter pin of that converter, you can set up a serial console. The green coloured GPIO pins are unused by default and are therefore the best pins to use in your own personal hardware projects. The other pins may have more than one available purpose. How to solder Step One: The tools You need a soldering iron (30-40 watts, or ideally a temperature-controlled one), a stand to put it in, a damp sponge to clean the tip, and some thin solder. Lead solder is easier to work with than lead-free, and an iron with a square tip conducts heat better than a pointy one. 46 Raspberry Pi Tips, Tricks & Hacks 40 Pin layout 3V3 Power 01 02 5V Power GPIO2 SDA1 I2C 03 04 5V Power GPIO3 SCL1 I2C 05 06 Ground GPIO4 07 08 GPIO14 UART0_TXD Ground 09 10 GPIO15 UART0_RXD GPIO17 11 12 GPIO18 PCM_CLK GPIO27 13 14 Ground GPIO22 15 16 GPIO23 3V3 Power 17 18 GPIO24 GPIO10 SPIO_MOSI 19 20 Ground GPIO9 SPIO_MISO 21 22 GPIO25 GPIO11 SPIO_SCLK 23 24 GPIO8 SPIO_C E0_N Ground 25 26 GPIO7 SPIO_C E1_N ID_SD I2C ID EEPROM 27 28 ID_SC I2C ID EEPROM GPIO5 29 30 Ground GPIO6 31 32 GPIO12 GPIO13 33 34 Ground GPIO19 35 36 GPIO16 GPIO26 37 38 GPIO20 Ground 39 40 GPIO21 Soldering 39 headers With the Pi Zero, you will need to solder GPIO headers onto the board. Using a reusable adhesive like Blu-Tack to hold the headers in place will make the job much easier. Zero Solder with ease in just a few steps Step Two: Soldering Once the iron is hot, apply some solder to the tip of the iron and wipe off any excess on the sponge. When pressing the iron to the joint, the tip should be touching both the joint and the wire you are soldering. Do not apply solder directly to the iron; apply it to the joint/wire. Step Three: If you make a mistake You probably won’t need as much solder as you think you will, so be sparing. Still, accidents can happen, and the best way to remove excess solder is to get some de-soldering braid. This is copper that you put over solder, before putting the iron over the top. The solder is sucked onto the braid. Tips | Tricks | Hacks Five-minute practical fixes Quick and easy things you can try in a few minutes more current? 46 Need You should only draw a few milliamps of current 42 Above Here are two waves with duty cycles of roughly 80% (top) and 20% (bottom) Ensure you are only using 3.3V voltage levels when working with the GPIO pins. Connecting anything higher than 3.3V to a GPIO pin will likely damage your Pi. from the GPIO pins of the Raspberry Pi. If you need more current than that (or you need to switch a higher voltage), then you can use the GPIO pin to switch a transistor connected to a stronger voltage source. built-in sound card 47 Disable If you are using a USB sound card then it can be easier to disable the built-in sound card completely: sudo rm /etc/modprobe.d/alsa* sudo editor /etc/modules Change snd-bcm2835 to #snd-bcm2835 and save, then sudo reboot. Pulse width modulation 43 Pulse width modulation is Using a push button 45 Refer to the circuit diagram where the output of a GPIO pin is high for a percentage of time and low for the remaining percentage of time. The percentage where the pin is high is called a duty cycle. Pulse width modulation is very useful in electronics, especially when it comes to tasks like controlling the brightness of LEDs. To do this in Python: below. When the push button is pressed, the left pins are connected to the right pins. By using a 10K pull down resistor connected to ground, the purple output wire (connected to a GPIO pin configured as an input) defaults to 0V when the button is not pressed. The right-hand side of the button is connected to 3.3V, so when the button is pressed, the left-hand side of the button will also be connected to 3.3V. The left-hand side is connected in parallel with the purple signal wire, and also the 10K resistor to ground. Because electricity takes the path of least resistance, the purple signal wire will output 3.3V. GPIO.setup(5, GPIO.OUT) # Frequency of 50 hz p = GPIO.PWM(5, 50) # 50 percent duty cycle p.start(50) # Do work or wait here so # program doesn’t exit # 70 percent duty cycle p.ChangeDutyCycle(70) p.stop() of the GPIO pins. Looking vertically, with the USB ports at the bottom, the bottom-left pin (39) is ground and the topright pin (2) is 5V. Using the negative terminal on ground and the positive terminal on 5V should show ~5V. up serial console 49 Set You can use raspi-config to set up a serial console so you can get a login shell using the UART0_TX and UART0_RX pins by connecting them to a USB to serial adapter: GPIO interrupts 44 An interrupt is when a hardware event triggers an interrupt on the CPU, causing it to stop what it is dealing with and run an interrupt request handler. The Raspberry Pi can trigger inputs when a GPIO pin goes high (ie from 0V to 3.3V) or low (from 3.3V to 0V). This can be more efficient than polling for the state of a GPIO pin, as you only have to deal with the pin changing when it happens. Plus, it can actually simplify the flow of your code. The use of interrupts requires root privileges so you will have to execute your code with sudo. The code provided demonstrates how to set up a callback function to deal with a rising edge. a multimeter to verify orientation 48 Use You can use a multimeter to verify the orientation sudo raspi-config 8 (Advanced Options) A8 (Serial) Select Yes to enable serial console. Finish, then reboot. resistor calculations 50 LED To calculate an LED’s resistance value, use Ohm’s law: Resistance = voltage / current. The voltage of a GPIO pin is 3.3V. You need to know the voltage drop of the LED and its suggested current, so R = (3.3V – voltage_drop) / led_current. Using 2V as the voltage drop and 20mA as the current: (3.3 – 2.0) / 0.02 = 65 ohms. Round up to the next available resistor. Above The blue wire is the ground, the red one is 3.3V and purple is for the output Raspberry Pi Tips, Tricks & Hacks 47 Tips | Tricks | Hacks Use an Android device as a Raspberry Pi screen Connect to a Pi with your phone or tablet using VNC as a secondary or actual display There are a few ways to attach a display to a Raspberry Pi. The ones that everyone is most familiar with are the HDMI port, which can go straight into your monitor or TV, or via the GPIO ports with a portable screen. One avenue that is rarely pursued is using VNC software to remotely view the Raspberry Pi desktop using another computer entirely. It’s actually fairly simple and we are going to concentrate on viewing your Pi screen via Android for maximum portability. With further tweaks you will be able to use this on the go if you find yourself commuting and wanting to catch up on your favourite program, for example. There are a few things that you should be aware of when doing this project – it can be quite taxing on the Pi and is likely to drain a bit of battery from your phone too. We will talk about some options to help take the strain off the Pi if the connection seems a little laggy and how this method can be used on normal PCs as well, so you can use a range of devices and get the most from your Raspberry Pi. 48 Raspberry Pi Tips, Tricks & Hacks 01 Update your Raspberry Pi Before starting, you should absolutely make sure that your Raspberry Pi is up to date. With the limited resources on the Pi, any optimisations can make the experience better. You’ll first want to update the software by opening the terminal and using: $ sudo apt-get update && sudo apt-get upgrade … and then follow it up with a firmware upgrade by running: $ sudo rpi-update What you’ll need Q TightVNC tightvnc.com Q VNC Viewer bit.ly/1jCzBRJ Tips | Tricks | Hacks Full code FileSilo.c o.uk Look up the resolution of your Android device and then modify the line used to start up the server 04 First time setup The first time you turn it on, you will have to set a password. You’ll need to pick a password you can remember as it will also be used by the client as it connects via VNC. You can only use a maximum of eight characters for the password though, so think carefully about how you want to make it secure. 02 Install the software We’re going to be using TightVNC for our VNC needs here – specifically, the server side of the software. We’ll need to install it first though, so head back to the terminal and type: 05 Stop and restart As TightVNC doesn’t quite work like a normal service, you can’t do a usual service X restart (or equivalent) to turn it off or whatever you wish to do with it. Instead, if you want to restart it, you’ll have to manually turn it off and then restart it with the original command. To kill it, use: $ sudo apt-get install tightvncserver $ vncserver -kill :1 You may have to run through a setting or two as it installs, hit ‘yes’ (or ‘y’) to them to continue. … replacing 1 with the display number that you originally create. 03 06 Start up VNC Once everything’s installed we can actually start up the VNC server – it’s probably a good idea to do so now and check to make sure it’s all working. We’ll do a test run with the following: $ vncserver :1 -geometry 640x480 -depth 16 -pixelformat rgb565 As long as everything is installed correctly, it should start without any problems at all. Running slow If you find the server is running a bit too slow for your liking, our best tip is to reduce the resolution to something your Pi can more easily create a server for. If that’s not helping, your network connection may well be the issue. Correct resolution We created our test server with a resolution of 640 x 480, just to get it running. However, this is unlikely to be the resolution of your phone. Luckily, this resolution is not fixed every time, so the best thing to do is to look up the resolution of your Android device and then modify the line used to start up the server. For example, if you have a 1080p tablet, you would use: $ vncserver :1 -geometry 1920x1080 -depth 16 -pixelformat rgb565 Raspberry Pi Tips, Tricks & Hacks 49 Tips | Tricks | Hacks 07 Get the app 08 Raspberry Pi IP 09 Connect to the Pi 10 Use VNC 11 Turn it all off 12 Turn server on at startup On your Android device, go to the Play Store and look for VNC Viewer (you can also install it from the web store via this link: bit.ly/1jCzBRJ). Install it to your device and run it to make sure it works fine. We can now begin to try and connect it to the Raspberry Pi. We need the IP address of your Raspberry Pi so that we can connect to it. You can get it via two methods – our preferred method is to open the terminal and use ifconfig to list the status of the Pi’s network interfaces; this will include the IP address of whatever is connected. If you’re using wireless to connect, you can also access the wireless config interface (iwconfig) and see what the wireless has been assigned as an IP. Now that we have the IP address, we can look at connecting to the Raspberry Pi. Open VNC Viewer and click the ‘+’ sign to set up a new connection. Leave the name blank for the moment, enter an IP address and choose ‘Save password’. It will ask for the password when you attempt to connect, after which it will then save it and not require it in the future. If this is the first time that you are using VNC software, you will notice that there can be a little lag between what you do and what happens on-screen. Luckily, you can use your finger on the screen to move the mouse and tap to click, and the Android keyboard can be used as the keyboard. It can take a bit of getting used to and is not good for anything that you need to do fast, but it’s still very useful. Killing the VNC server, as we talked about in Step 5, can still be done when connected – your Android device will just disconnect. The same occurs if you just turn off the Pi. If you disconnect the VNC client from the Pi though, the server on the Pi will still be turned on; this means that you can at least reconnect at any time. Currently, every time you turn on the Pi you’ll have to turn on the VNC server. There’s no config setting or service setting that we can set to have it turn on by default, so to actually do this we need to write a script. Create a file using nano in the terminal at the following location: Above VNC Viewer is made by RealVNC, the original developers of VNC technology 50 Raspberry Pi Tips, Tricks & Hacks $ sudo nano /etc/init.d/vncserver Tips | Tricks | Hacks Above It‘s simple enough to get around the GUI using your phone, but for extended bouts of typing, consider a portable Android keyboard 13 Write the script This script will do everything we need it to do, but be sure to edit the resolution for your specific use case: #!/bin/sh -e export USER=“pi” # parameters for tightvncserver DISPLAY=“1” DEPTH=“16” GEOMETRY=“1920x1080” NAME=“VNCserver” OPTIONS=“-name ${NAME} -depth ${DEPTH} -geometry ${GEOMETRY} :${DISPLAY}” . /lib/lsb/init-functions case “$1” in start) log_action_begin_msg “Starting vncserver for user ‘${USER}’ on localhost:{$DISPLAY}” su ${USER} -c “/usr/bin/vncserver ${OPTIONS}” ;; stop) log_action_begin_msg “Stopping vncserver for user ‘${USER}’ on localhost:{$DISPLAY}” su ${USER} -c “/usr/bin/vncserver -kill :${DISPLAY}” ;; restart) $0 stop $0 start ;; esac exit 0 14 Or download it We’ve also got this ready for you to download and put right into the /etc/init.d directory. You can download it using: $ wget http://www.linuxuser.co.uk/wp-content/ uploads/2015/06/vncserver.zip Unzip it and move it into the correct folder, then make any modifications that you want before heading to the next step. 15 Make the file executable Once the script is written, customised to your liking and saved, we now need to make it executable. To do this, use: $ sudo chmod +x /etc/init.d/vncserver As long as it is in the right place and named properly, this will make it executable. This command is also good to remember in general as it enables you to make any script executable. 16 Other VNC clients You can use this setup with other systems as the client – your PC, a laptop, anything that you can put VNC on. It will use the same settings for each device though (such as resolution and colour depth), and you can’t each have a separate screen to work from. This can be a good way to connect to a file server Pi or similar. Update and test The final step is to update the file rc.d (which handles startup scripts and such) so that it knows our new script is there. Do this with the following: $ sudo update-rc.d vncserver defaults You can then also test it by using the following to make sure it works and also to turn it on for this session: $ sudo /etc/init.d/vncserver start Raspberry Pi Tips, Tricks & Hacks 51 Tips | Tricks | Hacks Host your own website on Raspberry Pi Don’t pay for web hosting. Configure your Raspberry Pi to act as a web server and host modest websites What you’ll need Q Latest Raspbian image raspberrypi.org/downloads Q Internet connection Q External hard drive (optional) Q USB flash (optional) Q Ethernet cable for reliability Need a lightweight, low-cost web server? Your Raspberry Pi is all you need! Whether you’re planning on hosting a static homepage (or one with minimal database use) or need an easy home for development websites, setting up your Raspberry Pi as a web server is surprisingly easy. Ideal as an always-on device thanks to its low-power requirements, the Raspberry Pi can sit beside your router and serve a basic website to visitors, allowing you to put hosting fees to better use. You might wish to serve pages for some of your Pi projects, or even a personal page to host photos or your CV. If you’re planning on using it as a web-facing device, your Pi will need to be set up with a static IP address. You’ll also need to ensure your internet provider offers static IP addresses for their users. Often a price is charged for leasing a static IP, but there are services you can use (such as noip.com). 52 Raspberry Pi Tips, Tricks & Hacks 01 Connect your Ethernet cable For this project it makes more sense to use an Ethernet cable. You may need your existing USB ports to attach flash drives or an external HDD to serve your web page. With Ethernet you will need to rule out any wireless issues that are causing interruptions for your visitors. 02 Get Raspbian updates and Apache As ever, begin by checking for Raspbian updates: sudo apt-get update You’ll then need to install Apache and PHP: sudo apt-get install apache2 php5 libapache2-mod-php5 Finally, restart Apache: sudo service apache2 restart Your Raspberry Pi is now ready to be used as a web server. Tips | Tricks | Hacks You can upload files to /vav/www 03 Check your Pi web server With Apache installed, open the browser on another computer on your network and enter your Pi’s IP address to view the Apache confirmation page. As things stand right now, all you will be able to view is the Apache index.php page. To add your own HTML and PHP pages, you will need FTP. 04 Install FTP for uploading files Create a www folder, then install the following vsftpd FTP server software: sudo chown -R pi /var/www sudo apt-get install vsftpd You’ll need to make some changes to Very Secure FTP Daemon, so open it in nano. First, switch: anonymous_enable=YES …to… anonymous_enable=No Next, uncomment the following by removing the # symbols: #local_enable=YES #write_enable=YES 06 Make Pi a LAMP server By adding MySQL into the mix you can use the Pi to host a database-driven website or even WordPress (although this is best limited to using the device as a development server). sudo apt-get install mysql-server mysql-client php5-mysql The LAMP bundle is useful of course, but for the best results your site should remain streamlined. 07 Get your site online 08 Install No-IP Can’t afford a static IP for your router? A great solution is available with the free service from www.noip.com. This enables you to point a hostname at your computer by using a client application that will remain in contact with the No-IP servers. Make a new directory and switch it to: mkdir /home/pi/noip cd /home/pi/noip Download No-IP on your Pi with: wget http://www.no-ip.com/client/linux/noip-duclinux.tar.gz Extract: tar vzxf noip-duc-linux.tar.gz Next, navigate to the directory and use sudo make and sudo make install, following any instructions. Finish by running: sudo /usr/local/bin/noip2 05 Restart the FTP Server Complete configuration of the FTP software by adding a command to the end of the file which will display server files starting with “.” such as .htaccess: force_dot_files=YES Save and exit nano (Ctrl+X) and restart FTP: sudo service vsftpd restart Using the default Raspbian credentials you can upload files to /var/www. 09 Change your password for security Before using your Pi as a live web server, it’s a good idea to change the default password to something more imaginative than ‘raspberry’. In the command line, enter passwd and then follow the prompts to add your new, secure password. You’re doing this step because you obviously would not want your Pi web server to get hacked! Raspberry Pi Tips, Tricks & Hacks 53 Left Running a private cloud? Make sure no one can break into it… Secure your Raspberry Pi Concerned about the security of data stored on your Raspberry Pi? Protect yourself with passwords, firewalls and some physical security There is a distinct security risk around your Raspberry Pi. Storing anything from passwords to firewalls, this important saved data can be stolen or pocketed with minimal effort if someone knows how. Therefore it’s a relief to learn that several tools, tricks and methods can be applied to keep your device and data away from prying eyes. You might, for example, be running a home security cam with images uploaded to a cloud account. These images would 54 Raspberry Pi Tips, Tricks & Hacks be visible to anyone who possesses your Raspberry Pi’s login details if you haven’t bothered to change the defaults. Such a project (and many others) also demands that a firewall is installed for further improved security on a network. Whether you’re simply changing passwords, keeping your Pi under lock and key or installing a firewall, you’ll be surprised at how easy it is to secure your Raspberry Pi and protect all of your important information and files. What you’ll need Q Velcro Q Adhesive putty Q Lockable cupboard, strongbox, etc. Tips | Tricks | Hacks With a desktop computer and SD card reader, there is a way that you can recover your password 01 Stop using the default password Everyone who uses a Raspberry Pi knows that the default Raspbian credentials are ‘pi’ and ‘raspberry’. Naturally, this means that anyone can sign into your computer if you haven’t changed these defaults – something you’ll need to do as a matter of urgency. After signing in, open the terminal and set a new password with: passwd 04 Give the new account a password With the new account set up, the next step is to set a password. As you’re not signed into the account at this stage, you won’t be using the passwd command. Instead, enter: sudo passwd username With the new account ready to use, you should be ready to remove the default pi account from Raspbian altogether. 02 Use a proximity sensor Change password with raspi-config If you’re setting up a new installation of Raspbian, changing the password is one of the first things that you should do. With a new install, the first boot will automatically run the raspi-config screen. Here, use the arrow keys to find the second option, change User Password and then follow the on-screen prompts to set yourself a new passcode. 05 Delete the default Raspbian account You no longer need the default user account, pi. Sign out and login to your new account, and confirm it is correctly set up by opening: sudo visudo …and adding… username ALL=(ALL) NOPASSWD: ALL …to the final line. Save and exit with Ctrl+X. Now that’s done, simply delete the old account with: sudo deluser pi Then remove the home directory: sudo deluser -remove-home pi 03 Create a new user account To completely baffle anyone attempting to gain access using default credentials, take the most secure option and create a new user account. In the command line, enter: sudo useradd -m username -G sudo The –m switch creates a new home directory, while the second sudo adds the new account to the superuser group. 06 Recover a lost password If you’ve somehow forgotten your Raspberry Pi user account password or suspect that someone has changed it, what can you do? With a desktop computer and SD card reader, there is a way that you can recover your password. Begin by inserting the Pi’s SD card into your PC’s card reader. If you’re genuinely concerned about your Raspberry Pi’s physical security, you may consider employing some additional hardware to make it less of a target. Your best option here is probably a proximity sensor configured to detect an unauthorised presence. When coupled with a buzzer, this can detect the presence of an intruder and alert you. It’s even possible to configure such an alert as an email message if you’re likely to be elsewhere, and it makes for a great side project. Raspberry Pi Tips, Tricks & Hacks 55 Tips | Tricks | Hacks Fwbuilder has a great quick-start guide that handily annotates the entire interface Several firewall templates are available for the most common types of setup The objects in this panel can be dragged out into the rules panel on the right-hand side Hiding hardware 07 Edit cmdline.txt Find the file cmdline.txt and open it in your Linux desktop text editor. Add the following to the end of the last line of the file: init=/bin/sh Putting your hardware out of sight and/or out of reach is a good option for security, and for something as small as the Raspberry Pi and an SD card you have quite a few options. For instance, using Velcro or some adhesive putty you might attach the computer to the back of a cupboard or unit, kitchen kickboards or even under a car seat. The SD card, meanwhile, is so compact that you could easily place it under a carpet or even make a home for it in a cushion or shelf – just don’t forget where you put it! As the Raspberry Pi boots, this command will be read, enabling us to access a screen to reset the password. Save and eject the card. 08 Change the lost password Unfortunately you won’t be able to use SSH to recover the password, so instead connect a monitor and keyboard to your Raspberry Pi. Boot the Pi and wait for the prompt, at which point you should enter: passwd username 10 Revert cmdline.txt We are not done yet though. Safely shutdown your Raspberry Pi with: sudo shutdown -h now With the Pi powered down, remove the SD card and insert it into the card reader again. Open cmdline.txt in your text editor once again and remove init=/bin/sh, then save and exit. This stops anyone else from resetting your password. Type the password, hit Enter and type it again to confirm. 09 Initialise the Raspbian boot Thanks to the added code, we have changed the standard Raspbian boot to display a new prompt that will let us change the password. When this is done, enter the following command to put things back in order: sync exec /sbin/init The Pi will now boot Raspbian normally, enabling you to sign in with the new password. 56 Raspberry Pi Tips, Tricks & Hacks 11 Physically secure your Raspberry Pi Keeping digital intruders out of your Raspberry Pi with firewalls and secure account passwords is only part of the story. To fully protect your Pi you need to think outside of the box. Barely larger than a credit card, the Raspberry Pi computer can easily be picked up and palmed. Physical security is paramount, but a genuinely secure Raspberry Pi case – for example, one compatible with Kensington locks – has yet to be released. However the ProtoArmour aluminium case from www. mobileappsystems.com can be screwed to a secure surface, which is great for more permanent project setups. Tips | Tricks | Hacks Below If you tend to access your Pi remotely via Wi-Fi, consider keeping it locked away 12 Lock it in a drawer 13 Add a firewall Probably the best way to keep your Raspberry Pi secure is to make sure you keep it locked in a drawer or cabinet – particularly useful if you use the device as part of a security cam system or as a cloud server storing valuable documents. If no lockable storage is available and you’re taking some time away from home where it isn’t practical to take the Pi with you, another solution is needed. This might be to travel with your Pi’s SD card in your wallet, perhaps leaving the computer attached to the back of a wardrobe with Velcro. A firewall is guaranteed to improve your security Regardless of which operating system you’re using, adding a firewall is a guaranteed way to improve your computer’s security. While the Raspberry Pi has a built-in firewall, it is tricky to configure. Thankfully, some other people have noticed this too and released fwbuilder, an interface to the otherwise complex iptables firewall that comes with Raspbian. 14 Install fwbuilder in Raspbian Because iptables is a bit fiddly and errors can leave you with no network connection, fwbuilder has been developed to make firewall configuration quick and painless. We’ll use the apt-get command to first check for updates and then install fwbuilder: sudo apt-get update sudo apt-get install fwbuilder Follow the prompts to install and, once complete, switch to the Raspberry Pi GUI by entering: startx In the Pi’s mouse-driven desktop, launch fwbuilder from the Internet menu. Upon launching fwbuilder, follow the given steps to set up your Raspeberry Pi firewall and save the resulting script. We’re nearly done but some adjustments are still required before your Pi fully connects to the network. 15 Pocket your Pi Complete firewall configuration Launch the /etc/network/interfaces script in your text editor and complete configuration by adding pre-up /home/pi/fwbuilder/firewall.fw Next, find the section labelled “Epilog” and add route add default gw [YOUR.ROUTER.IP.HERE] eth0 If you’re using a wireless card, add the same line but switch the last characters to wlan0: route add default gw [YOUR.ROUTER.IP.HERE] wlan0 16 Consider Raspberry Pi theft While losing your Raspberry Pi or the data on it, might initially seem like a disaster, don’t be disheartened. As long as you have taken steps to backup data or clone your SD card, you at least have continuity when you resume the project. You can also check our boxouts for methods to help you deal with physical theft. If you’re still concerned with your Pi’s safety, put yourself in the place of a potential thief. Where would you stash it? Probably in your pocket. The Raspberry Pi is small enough to take with you, so why leave it lying around? Any security questions relating to your Raspberry Pi can be addressed by keeping it close whenever you think it’s necessary. Raspberry Pi Tips, Tricks & Hacks 57 Tips | Tricks | Hacks Raspberry Pi A powered USB hub which provides power and USB connectivity to two 2.5-inch hard drives An 8-port Netgear switch which the Raspberry Pi is connected to, along with our other computers and devices Two 2.5-inch hard drives. Your advisor has a 320GB Western Digital USB drive; the second drive is an 80GB from an old laptop which he’s converted to a USB drive using an IDE-to-USB converter www Build a file server with the Raspberry Pi The Raspberry Pi is small, silent and energy efficient, so let’s turn it into the ultimate file server! What you’ll need Q Raspberry Pi with all necessary peripherals Q SD card containing the latest Arch Linux image for RasPi: www. raspberrypi.org/downloads Q Powered USB hub Q External hard drive or pen drive Q A computer running Linux – it can be another Raspberry Pi 58 Raspberry Pi Tips, Tricks & Hacks We’ll be using Arch Linux as the operating system for our file server, because it is small, and has only the minimum packages required for a working system. This means that we can set up the file server without wasting resources on a graphical user interface and other unnecessary packages. Arch Linux comes with hardly any RAM allocated to the GPU by default, which is exactly how we want it for use as a headless server. Our file server will be made up of the following software components: • Base Arch Linux system • SSH – will provide secure remote access to the Raspberry Pi and the files on it • Samba – provides access to files on the server to a Windows, Mac or Linux client • A dynamic DNS daemon (noip) – software that runs in the background and points a domain name to your router’s IP address, meaning that you can access your Raspberry Pi from anywhere using an easy-toremember web address • Transmission daemon – a torrent client that runs in the background and can be accessed through a web browser This tutorial assumes that you have flashed the latest Arch Linux ARM image to an SD card. If you haven’t done this, the instructions for flashing an image can be found at www.linuxuser.co.uk/ tutorials/how-to-set-up-raspberry-pi/. You’ll only need to go up to the step that involves writing the image to the SD card – or if you plan to use the SD card to store files, then you should follow the GParted steps also. Not that you’ll also have to adapt the instructions slightly for using the Arch Linux image rather than the Debian one. Tips | Tricks | Hacks 01 Log into Arch Linux Connect the necessary cables to the Pi and wait for the Arch Linux login prompt. The login is root, and the password is also ‘root’. We’ll change the root password from the default later on. 02 Run a full system update Arch Linux runs on a rolling release schedule, meaning that there are no version numbers and software is continually updated. Use the command ‘pacman -Syu’ to start a full system update. You’ll be shown a prompt explaining that pacman needs to be updated first. Answer ‘Y’ to the prompt. You can now run ‘pacman -Syu’ again to start a full system update. There will be a lot of packages to update so it will probably take a while, especially because the Pi runs from an SD card. 03 Investigate your network We highly recommend assigning a static IP to your Raspberry Pi rather than being handed one by your router because you’ll always know where to find it on the network, which will be useful for accessing it remotely. You’ll also need a static IP if you want to access the Raspberry Pi from the internet. We’ll need to find out a couple of things about your current network setup before setting a static IP. You can use the commands ‘ifconfig eth0’ and ‘ip route show’ to do this. to You’ll probably want to use a number between 100 and 200. Set the netmask and broadcast to the values from ‘ifconfig eth0’ so that the interface is configured correctly for your home network. Set the gateway to the address in the line similar to default via ‘ dev eth0 metric 202’ from the output of ‘ip route show’. Once you have done this, use the key combination Ctrl+O followed by the Enter key to save the changes. You can then use Ctrl+X to exit nano. 05 Log in with SSH We’ll now log into the Pi using SSH – but before that, we’ll restart so that the static IP and any updates take place. Use the command ‘init 6’ to do this. Once the Pi has booted back up, open a terminal on your Linux computer and type ‘ssh root@[ip of your pi]’. Answer yes, to say that you want to connect, and type in the root password, which will still be root. You are now logged in over SSH. 06 Set the default gateway This step is really part of step 4 (set up a static IP address). The reason for doing this step after restarting, is that we found the changes were lost when we did it before a restart. This is probably due to DHCP cleaning up any settings it changes during shutdown. We will now set the IP of the DNS server, which will be used to resolve addresses such as google.co.uk to an IP address that your computer can connect to. Your DNS server will be provided by the same IP as your default gateway. You can set the DNS server using the following command: 07 Change the root password 08 Install the required packages 09 Formatting your hard drive Since we might be exposing an SSH login to the internet, we need to change the password to a more secure one. Type ‘passwd’, then follow the on-screen instructions to change your password. Your SSH session will stay logged in, but you’ll need to use the new password next time you log in. Use the command ‘pacman -S samba noip transmission-cli’ to install the required packages mentioned at the start of the article. Answer ‘Y’ to any prompts you may encounter. Before continuing, note that formatting a disk will remove all the data on it. It’s now time to connect your hard drive to the Pi. (We’re using a pen drive, but the steps are exactly the same.) Use the command fdisk -l | grep Disk to get a list of disks attached to the system. You should be able to tell which disk is the one you intend to use to store files on by the size of the disk. For example, our pen drive is 16GB, so we know that the 16.1GB disk is ours. Run the following command: (echo o; echo n; echo p; echo 1; echo ; echo; echo w) | fdisk [path to your disk] to create a partition that will be whole size of the disk. Fdisk is an interactive program, so this command simply inputs the keys that you would press in a specific order to create a partition that will take up the whole size of the disk. echo ‘nameserver [ip of default gateway]’ > /etc/resolv.conf. 04 Set up a static IP address Now that we have found out things about your network, such as your current IP address, the network mask and so on, we can set up a static IP address. The majority of the Arch Linux configuration is done from a file called rc.conf, which is located in the /etc directory. You can open this file in the nano editor with the command ‘nano /etc/rc.conf’. Scroll down using the arrow keys until you come to the networking section. Begin to fill in the blank eth0 section. Our IP address was When assigning an IP address, you’ll only want to change the last number. We’re going to change our address Raspberry Pi Tips, Tricks & Hacks 59 Tips | Tricks | Hacks should show up as ‘ALARMPI’ in the Network browser on most operating systems and userfriendly Linux distributions. Use the username ‘root’ and the password that you set with the smbpasswd command. 14 Configure the Transmission torrent daemon We’ll need to start the Transmission daemon because we’ll need to edit some configuration files that it will only make on first execution. Start it using the command: /etc/rc.d/transmissiond start You’ll then want to stop it using the command: /etc/rc.d/transmissiond stop so that we can edit the configuration file without Transmission interfering. Open the configuration file using the command: 10 Create a file system & mount point Once we have a partition on the disk, we need to create a file system and a place to mount it. You can create an ext4 filesystem on the partition using the command mkfs.ext4 [path to disk]1 You can make a directory to mount the drive in using the command mkdir /mnt/data 11 Make the drive accessible to Linux The fstab file on Linux system contains a list of storage devices on the system, and where to mount them. The file is read on boot, so any devices in the fstab file will be mounted automatically as long as it is connected during boot. We’ll edit the fstab in nano using the command ‘nano /etc/fstab’. You want to add a line like the following: [path to disk]1 /mnt/data ext4 defaults 0 1 Save the changes in the same way we did earlier. Once you have done this, you can use the command ‘mount -a’ to reread the fstab file and mount the new entry we just added. 12 Share the drive with network clients We need to open an empty Samba configuration file in nano using the command nano /etc/samba/smb.conf 60 Raspberry Pi Tips, Trick & Hacks Input the following information: [global] # workgroup = NT-Domain-Name or Workgroup-Name, eg: MIDEARTH workgroup = WORKGROUP security = user load printers = no nano /root/.config/transmissiondaemon/settings.json You need to set rpc-whitelist-enabled from true to false, and also change the downloaddir to /mnt/data/Downloads. You can then save the changes and make that directory using the command: mkdir /mnt/data/Downloads # Some performance tuning socket_options = TCP_NODELAY SO_ RCVBUF=65536 SO_SNDBUF=65536 [data] path = /mnt/data public = no writable = yes Save the changes in the same way we did earlier. 13 Permit access to the shared drive Set a password for your Samba user using the command ‘smbpasswd -a’ and then enter the password you want to use twice. Now that we’ve done that, we can start the Samba daemon using the command /etc/rc.d/samba start Note that the method of accessing a Samba share from each operating system will be different, so you may have to look it up. It Fig 1 Testing out Transmission 15 The Transmission web interface We can now start the Transmission daemon using the same start command from the previous step. Transmission can sometimes be a bit picky with the syntax of its configuration files, so now that you’ve started The Transmission web interface is straightforward to use Tips | Tricks | Hacks it, you’ll want to check that your configuration changes are still there. If not, stop the Transmission daemon and try again. You can go to the Transmission web interface by opening up a web browser and going to the IP address of your Pi, followed by :9091. This is needed because the web interface is served from port 9091. In our case, we used Click on the icon in the top-left corner of the interface to add a torrent file. You can either upload a file from your computer, or copy and paste a URL. As you can see from Fig 1 (on preceding page), we have just added a Raspberry Pi image to test it out. The Transmission web interface is really straightforward and easy to use, so you should be able to figure out anything else you want to do. There is also more documentation on the settings.json configuration file here: https://trac.transmissionbt.com/wiki/ EditConfigFiles Fig 2 Port mapping example After a minute or two, your IP address will be accessible via your No-IP hostname. However, it’s likely that trying it from inside your house will simply take you to your router’s homepage. 18 16 Set up dynamic DNS Head over to www.no-ip.com/personal/ and sign up for the No-IP Free option. Once you have done that, don’t bother downloading No-IP’s client because we’ve already installed it. Go to your email Inbox and follow the activation link that was just sent to you by NoIP. You can now sign in to your account. Once you have logged in, select the ‘Add a host’ option. Choose a hostname and a domain to be part of from the drop-down list. Leave the Host Type as ‘DNS Host’ and then click the ‘Create Host’ button. Your advisor used the hostname liam-ludtest with the domain no-ip.org, so would access that using liam-ludtest.no-ip.org. 17 Configure No-IP Run the command: noip2 -C -Y …to be taken through interactive configuration of the No-IP client. We left the update interval to the default of 30 minutes, meaning the client will check every 30 minutes for an IP address change. Once you’ve finished, start the daemon with the command ‘/etc/rc.d/noip start’. NAT port forwarding It is likely that there are multiple devices behind your router that all use the same external IP address. This is because of the shortage of IPv4 addresses, and also because it is more secure to segregate the internet from your internal home network. NAT (network address translation) forwards a port from the router’s external IP address to a computer on the LAN (local area network). In this case, we’ll want to forward any traffic for port 22 that comes to your router’s external IP address to the IP address of your Raspberry Pi. Port 22 is the port used for SSH, which is the only port we’d recommend that you forward. SSH will provide access to your files, and also port forwarding, so you can access the Transmission web interface should you want to. The configuration of port forwarding really depends on the router that you are using, so you may have to look up that information. The chances are that it will be hidden away in the ‘advanced’ section of your wireless router. You should be able to access your router by typing your No-IP hostname into your web browser. If not, it should be at the address of your default gateway that we used earlier on. On his router, your advisor had to go to Advanced>NAT>Port Mapping and add a mapping that looks like that in Fig 2. 19 Use FileZilla for accessing files We recommend that you use FileZilla, which you should be able to install with your package manager, to access files via SSH. Set the host to the IP address of your Pi (or your NoIp hostname if outside your LAN), the username to ‘root’, and the password to your password. Set the port to 22 and click ‘Quickconnect’. Click OK to trust the host and connect to it. To access files on your external drive, change remote site from /root to /mnt/data. 20 Use SSH to port forward Use the SSH command with the following option to forward any traffic from to on the Pi: ssh -L 9091: root@ (You can replace the IP address of the Pi with your No-IP hostname if you are outside of your LAN.) is a loopback address, which points back to ‘this computer’. Once you have run that command, you can then go to the web browser on your computer, type in and access the Transmission web interface as if it was on the LAN. Now, you are ready to enjoy your brand new file server! Raspberry Pi Tips, Tricks & Hacks 61 Tips | Tricks | Hacks Network and share your keyboard and mouse Borrow a mouse and keyboard from another PC, using only your Raspberry Pi and Synergy What you’ll need Q Latest Raspbian Image raspberrypi.org/downloads Q Synergy Q Host computer 62 Raspberry Pi Tips, Tricks & Hacks One issue we sometimes find with the Raspberry Pi is the lack of USB ports. We don’t always have the luxury of using a powered USB hub, and it can become a bit of a hassle to juggle a mouse and keyboard with other devices. Instead of using a hardware solution for this, you can always try a software solution – one that opens up the uses of the Raspberry Pi as well. The Synergy program lets you share the mouse and keyboard of one system with other systems on the same network, acting as a virtual KVM. In this tutorial we'll learn how to use your main computer's input devices on your Raspberry Pi, as well as how you can look into making it a server. 01 Install Synergy Synergy is available from the Raspbian repositories. We can install it by using the following: $ sudo apt-get update $ sudo apt-get install synergy This will go through the basic installation process as normal and Synergy will be put in the Accessories folder. Tips | Tricks | Hacks Left Select the Server option to use this machine’s mouse and keyboard for the Pi 02 Start up Synergy Start up Synergy on the host computer and choose the ‘Server’ option for the moment. We’ll cover how to use it as a client later, and how to use the Raspberry Pi as a server for the mouse and keyboard. 05 Starting and connecting Once you’re happy with the setup, click Start to be able to accept client connections. To connect from a Raspberry Pi, enter the following: $ synergyc --name pi [IP Address of host] It will be recognised as ‘pi’ on the host system. 03 Encryption and passwords Here, you can set up whether or not the connection is encrypted. This is useful for stopping key loggers from being able to snoop on your information, or random clients from connecting and hijacking your mouse. Provide a password and then click Finish. 06 Autostart Synergy Synergy lets you share a mouse and keyboard To make sure it starts every time you turn on the Pi, we need to create an LXDE autostart file by using the following: $ sudo mkdir -p ~/.config/lxsession/LXDE $ sudo touch ~/.config/lxsession/LXDE/autostart $ sudo nano ~/.config/lxsession/LXDE/autostart And then add the following to autostart: ~/.startsynergy.sh 08 Permissions Finally, to finish it off you’ll need to run: sudo chmod 777 ~/.startsynergy.sh 04 Server naming Once the process has finished, go to Configure Server. Your host computer will be put virtually in the centre of your array of displays and you can drag and drop it around, along with any connected screens. Double-click on the server to change its name, making it easier to remember and find. Add a new screen and call it pi. 07 Start file This will autostart, and hopefully autoconnect, Synergy whenever you turn it on. The Raspbian client is a little old, so if you get a problem you may need to compile the latest version from source. Open and populate the startsynergy file with: $ sudo nano ~/.startsynergy.sh #!/bin/bash killall synergyc sleep 1 synergyc --name pi [IP address of host] exit 0 09 Pi server Setting up the Raspberry Pi as a server is a little more involved and uses the synergys command. It allows you to listen for clients on specific addresses. You then need to create a separate configuration file to arrange the displays – however, you can load one from a different computer and edit it. Raspberry Pi Tips, Tricks & Hacks 63 Tips | Tricks | Hacks Add a reset switch to your Raspberry Pi Need to restart your Pi after a system lock-up? Ease strain on the mains connector – install a reset switch! What you’ll need Q Momentary switch Q Suitable wire for PCB projects Q Soldering iron and solder Q Single pin pair header Q HDD/motherboard jumper We all know that shutting down a Raspberry Pi by removing the power cable is risky. Data may be writing to the SD card, leading to corruption, while repeated removal of the power cable can cause problems with the connector port. Clearly this can cause problems when faults cause the Raspberry Pi to hang, so the simple fix here is to add a simple reset function to the device. There are three ways this can be done: with a USB reset button, a motherboard jumper on the GPIO bus or with a momentary button connected to newlysoldered pins on the P6 header on the Model B Rev 2 and B+ (this is the most complicated option). If you have an old PC lying around, retrieving the reset button and cable from this and even the connecting motherboard pins is achievable if you’re handy with a soldering iron. Otherwise, we recommend purchasing the parts online, although be aware that you'll probably need to buy more pins than you'll need. 64 Raspberry Pi Tips, Tricks & Hacks 01 Check your Raspberry Pi model Only two models feature the P6 header: the Raspberry Pi Model B Rev 2 (which you can find next to the HDMI port) and the B+ (to the left of the ‘© Raspberry Pi 2014’ label). You will need to install the pins manually, however, as they are not preinstalled for this function. Tips | Tricks | Hacks Shutting down a Raspberry Pi by removing the power cable is risky 02 Find your components Header pins can be purchased online, although this will invariably result in having to order more than you need. Alternatively, if you have an old motherboard, remove a pair of pins with a soldering iron. Similarly, you might buy a new reset button, or use one from an old PC. 03 Solder pins to your Pi 04 Connect your reset switch 05 Reset Raspberry Pi following crashes 06 Reset with a HDD jumper To gain stability when soldering, place the Pi upside down on a layer of packaging foam, with the header slotted into the holes. Using fine solder, secure the pins to the mainboard with your soldering iron. This will require a very steady hand, so get assistance if required. 07 Identify the GPIO pins 08 Detect jumper with a script This method works on most models. Each has a GPIO array, 26 pins on the A and B (Rev 2) and 40 on the A+ and B+. The jumper should be placed on GPIO3, pins 5 and 6 counting from the left with the board the right way around. Use the script at bit.ly/1Ge5n0O to detect the jumper, making it executable (sudo chmod 755) before running. Within a minute your Pi will shut down. Add this line to /etc/crontab to run the script whenever you boot up. @reboot Leave the solder to cool for a few minutes before attaching the reset switch connector. Some cases don't have space for the pins and/or the connector, however, so take the time to plan ahead and make sure everything fits. If not, you may need to make some adjustments to your case. Q  You should know your Pi inside and out, and learn how to identify GPIO pins root /home/user/scripts/gpio_actions.sh Remember to remove the jumper before booting up! With the switch installed, you’ll be able to reset the Raspberry Pi when required. Note, however, that this isn’t an option to be used for whenever you feel like restarting. Rather, it should be done only when the system fails to respond within a reasonable time frame. Not keen on soldering new pins to your Raspberry Pi? That is perfectly understandable, but it doesn’t mean you cannot reset the computer. We have another solution for you. Using a motherboard jumper, two GPIO pins and a script to initiate an ordered shutdown is a simple alternative that doesn't involve solder and potential PCB damage. 09 Try a USB reset button Specialist online stores offer USB reset buttons that can be connected to your Pi for scenarios when the device needs to be rebooted. If the idea of using the HDD jumper or doing some minor soldering doesn’t suit you, then a USB reset switch might be your best option. Raspberry Pi Tips, Tricks & Hacks 65 Tips | Tricks | Hacks Remotely control your Raspberry Pi Use a web interface to control your Pi and employ it as a fileserver or media centre from a remote location using any web-connected device Commands Create custom commands for running your Raspberry Pi Other utilities Seeing through your webcam and setting an alarm are just two additional things you can do with your Pi Main window Get the full details of the currently running system from the web What you’ll need Q Raspbian set to command line Q RaspCTL Q Internet connection 66 Raspberry Pi Tips, Tricks & Hacks Not everyone uses the Raspberry Pi while it’s hooked up to a monitor like a normal PC. Due to its size and portability, it can be located almost anywhere that it can be powered and it’s widely used as a file server, media centre and for other nontraditional applications. Some of these uses won’t easily allow access to a monitor for easy updates and maintenance. While you can always SSH in, it’s a bit slower than a full web interface that allows for custom commands and a view of the Pi’s performance. We’re using software called RaspCTL, which is still in development, but works just fine for now. 01 Update your Pi! To make sure the Raspberry Pi works as best it can, you’ll need to update Raspbian. Do this with a sudo apt-get update && apt-get upgrade, followed by a firmware update with sudo rpi-update. Finally, if you’re booting to LXDE, enter raspiconfig and change it to boot to command line to save power. Tips | Tricks | Hacks 02 Edit the IP For everything to work more easily, you should set the Raspberry Pi to have a static IP of your choice. To do this, edit the networking config by using: $ sudo nano /etc/network/interfaces …and change iface eth0 inet dhcp to iface eth0 inet static. 06 Access your Raspberry Pi Now the software is installed you can start to access your Raspberry Pi from anywhere on your network. To do this type the following into your address bar, with the IP being the one we set up earlier: http://[IP]:8086 03 Set up a static IP Add the following lines under the iface line with your relevant details: address 192.168.1.[IP] netmask network broadcast gateway 192.168.1.[Router IP] 04 Ready to install You’ll need to grab the public keys for the software we’re going to install by using the following commands. The first will take just a moment to download the software, while the other quickly installs it: $ wget debrepo.krenel.org/raspctl.asc $ cat raspctl.asc | sudo apt-key add - 05 Add the repository and install Add the repository to the source’s file with the following command: $ echo “deb http://debrepo.krenel.org/ raspctl main” | sudo tee /etc/apt/sources.list.d/raspctl. list …and finally install the software with: $ sudo apt-get update $ sudo apt-get install raspctl 07 Change your password 08 First command 09 More functions The default username and password is admin for both fields, and you should make sure to change that before doing anything else. Go to Configuration along the top bar and find the Authentication field at the bottom of the page. Input the original password (admin), followed by your new passwords. The username will remain as admin. Go to Commands on the top bar to begin creating commands to run. Here you’ll need to add a class – a userdefined way to filter your commands that won’t affect the way it’s run – a name for the command and the actual command itself. The commands won’t necessarily run from the pi user unless you tweak the config files. The web interface has a few extra functions apart from running commands, such as the ability to view the webcam and connect to radio services. Updating the software every so often will also allow you to make sure it keeps working. Play around with it and see what best suits you. Raspberry Pi Tips, Tricks & Hacks 67 Tips | Tricks | Hacks Install Androidon your Raspberry Pi Android ports are now available for Raspberry Pi, opening up a whole new world of possibilities. Here’s how to get started… 68 Raspberry Pi Tips, Tricks & Hacks Tips | Tricks | Hacks While one of the main reasons for the creation of the Raspberry Pi was to offer a cheap way for people to get into programming and using Linux, there are plenty of people who see it being used as a replacement for other forms of computing tasks. With the Pi being so small, the concept of using it for purposes where space is a premium is definitely not too far-fetched. Its form factor, weight and low power requirements make it ideal for use in a number of situations; however, the software may not always be the best for the task. Where Linux may be lacking, though, Android is there to cover it. Android ports to Raspberry Pi have been in the works for a little while now, but they’ve only just been made a usable reality thanks to the recent open-sourcing of the VideoCore GPU driver code. This allows for full hardware acceleration of Android, something that was previously having to be done purely by the CPU. Android can offer a very different experience and interface than a standard Linux distribution, without having to obtain custom distros so it’s optimised for a particular use. This means you can experiment with the sort of applications you’d want to use Android for without carrying around multiple SD cards in lieu of wiping them every time. Thanks to an ever growing development community, Google recently announced that there had been 25 billion Android app downloads by the end of September, five billion up from the number at the end of July, from its 675,000-strong selection. With this rate of expansion, there are always a number of apps for pretty much anything you’d want an Android device to do. With access to this range of possibilities on the Raspberry Pi, you can create a system that has the advantages of using a mobile, user-friendly OS, with the price of the Pi. And the addition of more I/O ports from the Pi can make it fit in better than your standard Android smartphone. There are three types of projects we’re going to cover over the next few pages: a smart TV, a home automation remote and an in-car computer. While such distros like XBian and OpenELEC exist for media centres and home theatre PCs using the Raspberry Pi, the XBMC apps do not have the same kind of range as Android. With apps going outside the concept of plain media watching, and even the inclusion of Android games, there’s a lot more you can do with an Android-run smart TV. For home automation, there are very mature X10 and Z-Wave remote control apps available on Android that are optimised for the kind of interface you’d want to use for a remote control, unlike the mainly mouse-focused tweaking tools used on Linux distros. Finally, with in-car computers, the touch-screen optimisations and grid array for apps allow for easy navigation to music, podcast and other media apps, as well as plenty of fantastic GPS and satellite navigation applications native to Android. Meet Razdroid The team makes the first project to get Android on your Pi Before the release of the VideoCore drivers, some community members decided they wanted to have a go at porting Android to Raspberry Pi, creating Razdroid. Based mainly on CyanogenMod, the project got far enough to have a couple of working ports, only limited by the lack of hardware acceleration. Since then, the Raspberry Pi Foundation has created its own ports, and eventually released the VideoCore driver to make ports of Android and other software a lot smoother. Q All you need is a Raspberry Pi set up and ready to go! Raspberry Pi Tips, Tricks & Hacks 69 Tips | Tricks | Hacks It’s easy to install Android… Follow our step-by-step guide to get up and running You can put Android on your Raspberry Pi right now by visiting the Razdroid site at www.razdroid.net. There are currently a couple of images, based around both CyanogenMod 7.2 and 9, with different performance capabilities and app compatibility. The images can be put on an SD card using the same method as you would a Linux distro image, and will run from boot without any extra setup needed. If you’re feeling a little more adventurous, you can compile the images from source instead. You’ll be able to make changes, updates and additions as well, if you want to improve the build. The steps on this page will guide you through a basic build of CyanogenMod 7.2, based on Android 2.3, for the Raspberry Pi, using the same files as the Razdroid image to get it working. 01 Install libraries You’ll need to get the necessary libraries for the build to work: $ sudo apt-get install git-core gnupg flex bison gperf buildessential zip curl libc6-dev libncurses5-dev:i386 x11protocore-dev libx11-dev:i386 libreadline6-dev:i386 libgl1mesa-glx:i386 libgl1-mesa-dev g++-multilib mingw32 openjdk-6-jdk tofrodos python-markdown libxml2utils xsltproc zlib1g-dev:i386 $ sudo ln -s /usr/lib/i386-linuxgnu/mesa/libGL.so.1 /usr/lib/i386linux-gnu/libGL.so Q Using a standard dd operation, you can get your Raspberry Pi running Android Eben Upton speaks The co-founder of the Raspberry Pi Foundation CC: Jim Killock Without Eben Upton, the Raspberry Pi would not have been possible. Coming from a background of computing and teaching, Upton is currently a technical director at Broadcom and is responsible for the overall software and hardware architecture on the Raspberry Pi. 70 Raspberry Pi Tips, Tricks & Hacks When the Raspberry Pi was first created, there were some very specific goals in mind for the finished product. Thanks to the way it met these goals, it has blown up as the darling of hobbyists and other tech enthusiasts for all manner of projects. To further understand the relationship between the original goals and this new concept of putting Android on the Raspberry Pi, we spoke to the co-creator of the Raspberry Pi himself, Eben Upton. Upton told us that there had never really been any plans originally for Android to be supported by the Raspberry Pi. However, developments in recent times had changed the view of the Foundation: “A significant minority of our customers want to see it, so that makes it important to us.” When the Foundation originally announced it was working on Android compatibility, it already had a working prototype. “This implementation uses a different kernel and VideoCore binary image from the one available on GitHub,” explained Upton, “which is why we’ve been keeping quiet about it so far.” This was in late July, and it took the Foundation a further three months to finally get the VideoCore drivers open-sourced. Upton told us shortly before its release why it had been delayed so long: “The issue around releasing the Broadcom Android version is that we’d need a separate microcode image for the GPU, and we really don’t want to fork the community.” Tips | Tricks | Hacks 04 Device tree After the sync has finished, create a new directory and download the device tree for your build: 02 $ mkdir -p ~/android_pi/device/rpi $ cd ~/android_pi/device/rpi/ $ git clone https://github.com/ Mathijsz/device_rpi.git $ mv device_rpi rpi Working directory We need to download the source to a folder that we can make executable. First create the directory: $ mkdir ~/bin Then add it to your path: $ PATH=~/bin:$PATH And finally, download and chmod: $ curl https://dl-ssl.google.com/ dl/googlesource/git-repo/repo > ~/ bin/repo $ chmod a+x ~/bin/repo 03 Build environment 05 Initial setup Before we do the actual build, we need to run a little script to properly prepare the source code: $ cd ~/gingerbread_pi/device/rpi/ rpi $ ./initial_setup.sh $ cd ~/gingerbread_pi This will automatically make the changes. Now we’ll make a directory for the build environment and initialise it for the repo sync. First: $ mkdir ~/android_pi Then move to it and initialise: $ cd ~/android_pi $ repo init -u git://github. com/CyanogenMod/android.git -b gingerbread 06 We’re now ready to build our Razdroid image. Make sure to do following to start the build: $ source build/envsetup.sh $ lunch $ make -j4 And finally sync: $ repo sync -j16 The build Be aware that this may take a while. Now the source code has been released, via the ARM Userland on GitHub, and marks the first time a full ARMbased, multimedia SoC has received vendor-provided opensourced drivers, and Broadcom is the first company to open up its mobile GPU drivers in this way. With it, people can get down to finishing Android ports and starting new ones. Android is well known as being used on touch-screen interfaces, but earlier devices included keyboards and trackballs. While this has gone out of vogue for smartphones and other handheld devices, for testing out your Android-powered Pi it would be useful to have this option. Is it available now, though? “I’m not aware of any significant challenges in this area.” Upton told us when we asked about traditional inputs. “We expect most people would use Android with a mouse and keyboard, and this seems to be a well-supported option from ICS (Android 4.0) onward.” So with this native mouse and keyboard support, you’re going to be able to find a lot more applications for a Raspberry Pi running Android than you could do with even an Android smartphone. On top of that, you will likely get the same kind of performance as a Linux distro according to Upton: “I would expect them to be very close in terms of performance. There may be more UI acceleration in Android, though, which we hope to bring into Linux.” Q The Play Store will initially be missing from any ports Finally, one of the main reasons to use Android would be to access the huge array of apps. We asked Upton about the issue with Google Play – those into the Android scene might know that CyanogenMod had to remove this from the standard build for legal reasons. Upton told us there were currently no plans to obtain a licence for the store; however, Android allows you install the APK files without the store, and these are usually very easy to obtain. Q The concept of the Raspberry Pi is a spiritual successor to the BBC Micro 71 www.linuxuser.co.uk Raspberry Pi Tips, Tricks, & Hacks 71 Tips | Tricks | Hacks Smart TV Use your Raspberry Pi to make any TV ‘smart’ Smart TV is a very recent and popular buzzword for a more advanced media PC running inside your TV, which add a whole host of different apps as well as being able to stream your content from around a network. Android itself does not need any specific apps or skinning to turn it into a functional smart TV – the display is already Q The Raspberry SAFE VESA Mount add-on attaches the Pi to most flat-screen TVs Game on! Why not turn your smart TV into a games console? If the buzz around the Ouya is anything to go by, a lot of people are interested in how to turn Android into a games console. With a Raspberry Pi running Android, you’re already part way there. While you could use a mouse and keyboard for some games, others will probably work better with a joypad, and this is where the MOGA controller comes in. It connects via Bluetooth to Android and is able to control a number of Android games. Get OnLive If Android games don’t really do it for you, how about fullblown PC games? The OnLive streaming service allows you 72 Raspberry Pi Tips, Tricks & Hacks configured for easy access to all the installed software, and using home replacement apps such as Launcher Pro will allow you to increase the number of on-screen apps if the stock launcher displays too few for you. This usage for Android has not gone unnoticed by other people, with a few companies already on board. Recently, a highprofile Kickstarter project was successfully funded, called Pocket TV by Infinitec, which while definitely not the first Android-powered smart TV device, is notable for running off a USB stick. Like the Pocket TV, the Raspberry Pi is capable of running 1080p video without an issue. The benefits of Android even go beyond the TV, as Ahmad Zahran, founder of Infinitec, explains: “[You] get access to all your information, games, TV streaming channels, work documents and your entire digital life. You’ll have all the benefits that you get from carrying your smartphone but with the ability to display it on a much bigger screen. Imagine walking into a meeting and doing a presentation without a laptop.” As well as having access to simple information apps such as the Weather and Stocks, you can also use Android widgets to add a news feed or social network streams, and you can even connect to streaming websites like Netflix or the BBC iPlayer, as well as browsing the web. Once you’ve got your Raspberry Pi set up as an Android smart TV, you may be wondering where to put it. Well luckily, there are a few cases out there that support VESA mounts, the standard used to attach flat-screen TVs to brackets and walls. The Raspberry SAFE case by Solarbotics is just the tool to tuck it out the way. to buy and rent games and play them anywhere, thanks to all the legwork being done in the cloud. Using the OnLive Android app, you can access these games from your Android-powered Raspberry Pi and play them directly on your television without the need for a bulky PC in your living room. And it also works out much cheaper than the official OnLive console. Q The MOGA can also cradle Android phones, hence the square shape Tips | Tricks | Hacks Home automation There’s no need for costly official controllers Using home automation can be fairly simple. There are a number of different standards used for achieving it, such as powerline-based X10, or the RF-controlled Z-Wave products. These are usually controlled by very expensive remotes and wall screens, vastly increasing the price over the hardware you’d need in the first place. There’s also a problem with running on open source operating systems. We spoke to an open source home automator, Conrad Vassallo, about the problems he faced even getting it started: “I did some research on systems that provided home automation and concluded that Z-Wave was the best option for me… soon I could control the lights in my living room with the touch of a button on a remote control. However, this was not enough: I wanted to have the system controlled by timed events and so the quest for a Z-Wave computer interface was on. First I bought a ControlThink USB stick, which did work fine for my needs; however, my home server runs on CentOS and the ControlThink USB stick was only supported under Windows. So I had to run the system on a virtual machine, which was not the best option on an Intel Atom PC.” Luckily he was able to get a setup running using code from the Open Z-Wave project, creating his own controller out of it – you can obtain the source code from here: code.google.com/p/ open-zwave-controller/source/checkout. The benefit of running these Z-Wave systems is that you can control them using Android apps. A Raspberry Pi and a small screen to connect it to cost a lot less than the officially made products and generally work better for the purpose, as you can always use the extra Android apps on the device anyway, whether it’s mounted on a wall or a small box on your coffee table. Kitchen computer Q Conrad Vassallo has tried a few solutions for home automation, including some using the Pi The size of a Raspberry Pi allows it to fit in a lot of spaces – add a touch screen and it takes up very little room. Putting it in a discreet location like the corner of a kitchen worktop gives you instant access to the internet and your home network for In-car computer Fit a Raspberry Pi in your car The main issues usually associated with carputers are finding a small enough computer with enough power to do the tasks you’d want it to do, and then making sure you have a proper way to actually power the system once it’s in place in your vehicle. On its own, the Raspberry Pi is a solution to this problem, with the ability to be powered solely from the cigarette lighter using a USB adaptor that you’d normally find for phones. Running Android on top of that makes it the perfect in-car computer. In the past, even with a touch screen, navigating around an operating system was tricky, especially while on the move. While there have been a lot of recent improvements to the Linux kernel and X for touch and looking up information, such as recipes via the Epicurious app, or using it to stream music from your file server while you cook. Home automation controller Using your Android-powered Pi to control the house is fairly simple once you have it up and running. However, you can make it completely customisable using software like Open Z-Wave to set up timed events and remote access using your Raspberry Pi as the controller. “When I got my first Raspberry Pi, I thought it would make the project more interesting to have a dedicated appliance to control my lights,” explained Conrad Vassallo, who already had a fully working solution. “So the next step was to install SSH, Apache, PHP and MySQL and my code on the Raspberry Pi. Now my system was consuming very little power and performed flawless!” The system created by Conrad also supports Android input. “The Raspberry Pi is an excellent piece of hardware to ‘embed’ systems into. First, it is very small, silent, green and provides the services offered by larger, more expensive PCs.” multi-touch inputs, the desktop environments themselves are optimised for mouse and keyboard – at least, the lightweight ones like LXDE that would run on a carputer. With Android, that is no longer an issue. As well as a fantastic selection of apps for music and podcast playback, you also have the fairly advanced satnav apps like Waze and even the native Navigation software. To top it off, there’s also a customisable car dock mode that gives you bigger buttons and default access to car-friendly apps. Raspberry Pi Tips, Tricks, & Hacks 73 Tips | Tricks | Hacks The making of Razdroid Razdroid was developed by a small team of like-minded people, eager to test out the Raspberry Pi’s limits. We spoke to three members of the team, Viktor Warg, Les de Ridder and Mathijs de Jager, about their involvement What caused you guys to start the project in the first place? Viktor Warg: Well, I had just gotten my Raspberry Pi and instead of just loading up Debian as suggested, I started browsing the forums for something more, well, fun, to run on it. Stumbled upon the Android thread and knew instantly that I wanted Android on my Pi. Started collaborating with Mathijs and Les and one thing led to another, and here we are! Les de Ridder: The only real reason I was interested in doing it was because it hadn’t been done before. I thought it would be really nice to be part of something like this, as I had never done any porting or even embedded projects before. What limitations did you experience with the Raspberry Pi? VW: The main limitation was the lack of open source libraries for the VideoCore IV (the Pi’s GPU) which had put the project in somewhat of a slumber for a few months. This led to the fact that we had a fully functional Android system but lacked the appropriate graphics libraries to make it hardware accelerated and thus the response times for the UI were sluggish at best. Q The team want to get Roku-style streaming on the Raspberry Pi 74 Raspberry Pi Tips, Tricks & Hacks LdR: Well, mostly Android compatibility issues. First of all, support for the Pi’s relatively old CPU was pretty much broken in the thenavailable Android sources; Mathijs luckily managed to fix this. Other limitations were obviously the RAM: with 256MB, Gingerbread works, but Ice Cream Sandwich runs… well… much slower to say the least. This is not only caused by the RAM, but also by the lack of hardware graphics acceleration. Android requires people to build custom accelerated drivers for its libraries (eg Bionic). We couldn’t do this at the time when we first built ICS for the Pi and still cannot, because the drivers’ sources are sadly closed source. How challenging was it to build Android for the Raspberry Pi? VW: It was quite a challenge at first, seeing as none of us (as far as I know) had been involved in similar projects at all. As we progressed (or didn’t, in some cases), things fell into place, though. Eventually, I’d venture as far as to saying that all three of us knew what most of the issues we faced stemmed from and how to solve them. One issue we had quite early was that the Raspberry Pi kernel wasn’t compatible with some of the patches Android needed, mainly the IPC-Binder that it relies on heavily. If I recall correctly, that was solved by our main kernel guy (Mathijs) after a few days of brainstorming. Mathijs de Jager: Another issue was a strange problem with executables crashing all the time (‘segfaulting’). After some help from Q The Raspberry Pi Foundation’s successful the #cyanogenmod-dev channel, it turned attempt at running Android on a Raspberry Pi out to be a bug regarding the ageing ARMv6 Tips | Tricks | Hacks architecture in the CyanogenMod sources we used. Additional build flags, almost specific to the Pi, were needed too. This had us stuck for quite a while. “The Pi kernel wasn’t compatible with some patches Android needed” What project ideas do you guys have for a finished product? Any future plans for ports or development on the Pi? LdR: I personally would like to make a build that anyone who owns a Pi can use, whether it’s a Model A with limited peripheral support or a new fancy Model B with 512MB RAM. This might mean that we would have to remove some features, but I think that we will be able to find a good configuration that works for the largest part of the people who are interested in running Android on their Pi, suiting as many people as possible. For people who are interested in making their own builds, we will supply patches so they can make their own configuration but still use our patches for the Pi. I don’t really have any personal projects, but using it as a Google TV-like internet player would be nice. MdJ: Netflix on Android on the Pi seems attractive and I can imagine a lot of people would want that, but I heard some DRM module is needed. The Broadcom CPU seems to have it (for example the Roku 2 has Netflix and has the same Broadcom CPU), but needs to have it enabled. Maybe the Pi Foundation can eventually get a licensing thing going, just like the MPEG2-decoding licence. What had you been using the Raspberry Pi for before Razdroid? MdJ: Mine had been running as a local web server for testing. VW: Nothing at all. I had just gotten my Pi when I started helping the Razdroid project. LdR: Not much to be honest. I only had just received my Pi when I started working on Razdroid. I was still waiting for my Pi electronics starter kit to arrive back then, which I later used for learning some basic electronics, like using resistors, LEDs, transistors etc. Q Razdroid is based mainly on the CyanogenMod Android firmware Contribute to Razdroid Here’s some ways you can help port Android As Eben Upton said, the Raspberry Pi is about content creation, and what better way to do this than by getting in on a project and helping out with the Android port? Razdroid’s Viktor Warg tells us that the drivers are a good start, but they need a little more: “We’ve analysed the libraries and figured out that we need to implement our own userland gralloc-module, and none of us have even the slightest idea on where to start on that.” The best place to start is to visit the Razdroid wiki, www.razdroid.net, and check on the current progress. There’s also an IRC channel, #razdroid on Freenode, where the developers regularly talk about their current work, and the entire project is maintained on GitHub. Of course you can always start your own project, either by using the official Android source from the AOSP, modding CyanogenMod, or forking Razdroid. Happy hacking! Raspberry Pi Tips, Tricks & Hacks 75 Tips | Tricks | Hacks Add a battery pack to your Raspberry Pi Don’t leave your Raspberry Pi behind – incorporate it into mobile projects by powering it with AA batteries Your Raspberry Pi’s mobility is usually restricted by the length of the power lead. Rather than limiting it to your desk or living room, however, you can use it for mobile projects as diverse as launching it into near-Earth orbit or monitoring and automating your garden. Of course, to do this you will need batteries, but adding battery power to your Raspberry Pi is simpler than you might have imagined. All that is required are six rechargeable AA batteries (or single-charge alkaline), a battery box with space for the batteries and a UBEC. The latter is a Universal Battery Elimination Circuit, a voltage regulator that will regulate the power supply and prevent damage to the Raspberry Pi, and can be bought for under £10. 76 Raspberry Pi Tips, Tricks & Hacks What you’ll need Q AA battery box bit.ly/1FDiJGa Q 3-Amp UBEC bit.ly/1HLKih7 Q 3-Amp terminal strip Q 6x AA rechargeable batteries Tips | Tricks | Hacks Left You can also use a UBEC to charge your smartphone from a battery pack 01 Order your components If you’re buying your components online, you should be able to get them all within five days. However, if you’re ordering offline (specifically the UBEC), you should avoid traditional electronics stores and instead visit a model enthusiast store, as these circuits are regularly used in RC devices. 05 Add a battery to boot 06 Connect the 3-pin UBEC 07 Measure uptime With your Pi ready to use and your Wi-Fi dongle plugged in, connect the UBEC to the micro USB port and insert the sixth battery into the battery box. The Pi’s power and status lights should indicate that the computer is booting up, which gives you a fully portable computer. If you purchased the UBEC with the now-modified 3-pin connector, you’ll need to connect this to the Raspberry Pi’s GPIO header. Specifically, connect the positive +5V (red) connector to Pin 2 and the negative 0V connector to Pin 6. Once again, check the status lights to ensure the Pi is booting. 02 Check your UBEC You should have already set up your Pi for SSH use, so connect to the device via Putty after giving it time to boot fully (at least 60 seconds). In the terminal, enter: Two types of UBEC are available. If you used the store that we suggest in the resources box to the left, you’ll receive one with a micro USB power connector for easy connection to your Raspberry Pi. However, if you bought one from eBay then there is a strong chance that you will receive one with a 3-pin connector. This command will display the system uptime and also keep the Wi-Fi connection active. 03 Change the UBEC connector pins 08 Judge your uptime results 04 Connect the UBEC to the battery box 09 Power extreme! To use the UBEC with a 3-pin connector, alter the position of the pins so that they occupy the two outer slots. Use a small jeweller’s screwdriver to lever up the small plastic catch and remove the red wire from the central slot, before sliding into the unoccupied outer slot. With five batteries in the battery box, connect it to the UBEC: red-to-red, black-to-black. You might do this by twisting the wires or soldering, or employ a 3-amp terminal strip, cut down to two pairs. The terminal strip can be cut to size using a modelling knife. watch -n 60 uptime Uptime results depend upon the type of battery you use and the Raspberry Pi model. Single-charge batteries will last a little bit longer, but this is a more expensive option. Meanwhile, newer models have greater power requirements but run for less time. For more power, add more batteries! More batteries added in parallel should result in almost double the uptime (at least 16 hours on a 256MB Raspberry Pi Model A), but instead of alkaline or rechargeable batteries you might consider a modern lithium-based AA cell, which will last considerably longer than alkaline batteries. Use a UBEC It is possible to power your Raspberry Pi directly from four or more batteries, but without the safety that the UBEC provides you’re likely to burn out the computer. Unregulated power can cause considerable damage to your Raspberry Pi, and as you increase the current with more batteries, the risk also increases. Unless you are planning to learn the hard way and you have plenty of cash to burn, always use a UBEC! Raspberry Pi Tips, Tricks & Hacks 77 Tricks 80 10 Inspiring Pi Projects • • • • • • • • • • 82 Retro arcade cabinet Audiobook reader Web radio Media caster Portable Wi-Fi signal repeater Secure Tor web station Private cloud storage AirPi Dusklights Outdoor time-lapse camera 96 Set up the PiTFT touch screen 98 Calibrate a touch screen interface 100 Portable Pi video player 102 Make a Raspberry Pi sampler 106 Build a radio transmitter 110 Tether your Pi to Android 112 Build a network of Raspberry Pi’s 116 Add gesture control to your Pi 120 Make a digital photo frame 124 Pygame Zero 78 Raspberry Pi Tips, Tricks & Hacks 106 110 116 “Fire up your imagination and test your Python skills” 120 120 Raspberry Pi Tips, Tricks & Hacks 79 10 Tips | Tricks | Hacks Inspiring Pi projects Fire up your imagination and test your Python skills 80 Raspberry Pi Tips, Tricks & Hacks The Raspberry Pi has come a long way over the last couple of years, and it’s all down to the creativity and imagination of a burgeoning community that’s bought over three million of these single-board computers. They’ve powered quadcopters and coffee makers, self-sailing boats and even touched the edge of space, but the one thing that’s still as much in demand as it was on launch day is an idea. Our Raspberry Pi community works so well because we all share our work with each other. We can all see what everyone else is up to and, if we see something that we like, we can have a go at making it ourselves – and then changing it, so we can share a different version. It’s all about inspiration. So for this feature we made ten inspiring projects for you to try – and we encourage you to deviate from the steps when a new idea takes hold and let us know where your project leads you! There’s a range of different projects here for you to try, covering media and entertainment, networks, security and more. All the components you’ll need for each one are listed on the page – we’ve tried to keep the cost down as much as possible by using widely and cheaply available parts – and each project is simple enough for you to work through in a single sitting. One more thing to mention – some of our Raspberry Pi creations are designed to be combined, to give you a great starting point when you begin adapting these projects to the way you want them. If you come up with any combinations we’ve missed, be sure to tweet us a photo (we are @Books_Imagine) – and have fun making them! Tips | Tricks | Hacks 84 85 Audiobook reader 88 Wi-Fi repeater 90 Private cloud 94 Dusklights 86 Web radio 89 Secure web station 92 AirPi 95 Time-lapse camera 82 Tips | Tricks | Hacks Retro arcade cabinet Create a tiny arcade machine and learn how to expand it into a fully-stocked games cabinet We are very big fans of retro gaming, and when the Raspberry Pi was released a couple of years ago we immediately recognised its potential as an excellent device to power a homemade, MAME-using arcade machine. Maybe one day we could use a Raspberry Pi or another Linux-powered machine to run a cabinet in the future. We weren’t the only ones that realised how well a Pi would fit in an arcade machine; many projects have been completed since then with impressive results. If you don’t fancy carving out custom pieces of wood just yet then you can always start small with the Cupcade kit from Adafruit. The kit is composed of lasercut plastic panels, a PiTFT screen and a selection of buttons, custom boards and a special joystick that can be assembled into a miniature MAME arcade cabinet. Unfortunately, for the moment, the Cupcade only supports the original Model B. However, we like to think of it as a great excuse to test out whether or not your Model B is up to the task of powering an arcade machine in case you want to expand. If not, that means you’ll need another Raspberry Pi to replace the arcade one, in which case you can always upgrade to a Model B+ or the more recently released Model A+. When you get the kit in, you’ll need to assemble the components step-by-step. It’s a long process which we don’t quite have room for in this issue, so instead we’re going to point you towards the excellent Adafruit instructions for constructing your Cupcade: https://learn.adafruit.com/cupcade-raspberrypi-micro-mini-arcade-game-cabinet/. A brief word of warning: it will take you a few hours to complete, so make sure you have some time clear to do so. It’s quite fiddly in places as well, so it might be worth getting a second pair of hands to help you. When attaching the side panel to the screen, speaker and What you’ll need Q Raspberry Pi Model B Q Adafruit Cupcade adafruit.com/product/1783 Q 1.5 A power supply Q Soldering iron Q Wire strippers Q A short length of audio wire Left It’s a bit tricky to get across the size of the Cupcade in this picture. Imagine the joystick is the same size as the analogue stick on a console controller 82 Raspberry Pi Tips, Tricks & Hacks Tips | Tricks | Hacks Top left You can always reverse the button mapping for traditional NESstyle control Top right The Raspberry Pi sits snugly below a great bale of wires Bottom Upgrading to a full-size arcade cabinet is easily done, as the principles are the same as with the Cupcade build buttons, we suggest ignoring the instruction to carefully lift the panel off your work desk. Instead, try sliding it slightly off the desk itself so that you can access each screw one at a time without having to precariously balance the sections at an angle. Once completed, it’s time to test it out. Adafruit has a pre-rolled image you can write to an SD card which can be downloaded with: $ wget http://adafruit-download.s3.amazonaws.com/ cupcade-5-13-2014.img.zip Write it to a 4 GB card (your Cupcade comes with one), download the free, non-commercial ROMs they provide to test the setup and power it up with a proper plug adapter. The components are running directly off the Pi and can be quite power-hungry, so it’s imperative that you properly power it. The image we’ve written has a full MAME arcade emulator in it, and a NES emulator. They’re both configured to use the buttons you’ve installed on the case by default; this means that because the NES emulator directly maps the cabinet’s A and B buttons to its own A and B, the layout is the reverse of the NES controller, which had A on the right and B on the left. Depending on what you plan to use the cabinet for, you can either swap over the buttons or just get used to a slightly altered control scheme. How can we expand the Raspberry Pi from here to create a full-sized cabinet? The good news is that the emulators will still work when you use the HDMI port for output instead, allowing you to hook it up to a normal TV. The buttons and speakers will still work as well and they can be plugged straight into the Raspberry Pi’s GPIO port via a connecting ribbon, like we used with the board to the screen. However, this does leave you with only four buttons and the small joystick; luckily there are plenty of USB arcade sticks and components out there that can be connected via USB, and with the right configuring you can get them working on the emulators just fine. There’s a lot more you can do with the Pi once you’ve got it set up in a cabinet, such as letting it connect to the network so you can remotely maintain it without having to disassemble the entire thing to retrieve an SD card. Make sure you do your research on specific parts and look out for any community forums that will definitely have helpful advice on what to buy. The emulators will still work when you use the HDMI port to hook it up to a normal TV Be inspired One of the best arcade cabinet projects we’ve seen has been featured on the Raspberry Pi blog: bit.ly/1pWjQWE Using an old arcade cabinet for parts, the maker managed to modify the inputs to be read by the Pi and got the coin slot to work. You don’t need to go this far by getting a CRT monitor or even an old busted cabinet, but it certainly adds a flair of authenticity to a project like this. Raspberry Pi Tips, Tricks & Hacks 83 Tips | Tricks | Hacks Audiobook reader Create an audiobook player that works at the touch of a button What you’ll need Q Speakers Q LED Q 1.2 k resistor Q 10 k resistor Q Push-button switch Q Breadboard and wires Audiobooks and podcasts are becoming more and more prevalent in a society where we’ve learned to multitask thanks to all our modern devices. Whether out and about or doing some chores, it can be nice to have some extra sensory input when you’re not using your full concentration. Enter, like always, the Raspberry Pi. With only a small selection of components and a pair of earphones or portable speakers, you can take your Raspberry Pi with you and have it play audio books. First, you need to get the Raspberry Pi ready. Do your usual apt-get update and apt-get upgrade in the terminal before you start, although there isn’t really much 84 Raspberry Pi Tips, Tricks & Hacks preparation involved. Once that’s done, all we need to do is install VLC, which is done with: $ sudo apt-get install vlc Once that’s done, turn off your Pi, disconnect the power and begin hooking up your circuit as according to the Fritzing diagram below. It’s a fairly simple setup – we’re going to use the button to activate the playing of the audiobook and the LED will turn on while this is happening. Once you’re confident with the circuit, turn your Raspberry Pi back on and open up the terminal. Type in the following to download the Python code for this project: $ wget http://www.linuxuser.co.uk/wpcontent/uploads/2014/08/audiobook.zip There are a couple things we need to note about the code: it first of all assumes you have your audiobook located in a directory known as audiobook within your home folder. It also looks for a file called audiobook.mp3 to play; you can easily change this by editing the path but you’ll need to be consistent with the name of the file you have on your Pi. You could always have it point to a specific location on a USB stick, swapping out the files on another computer and renaming them appropriately once you’ve finished with previous book. Test it out by running the code – one press of the button will start the process while another press will stop playing the book. If you find the button press too sensitive or not sensitive enough, edit the delay in time.sleep which is currently set at a default of 0.2 seconds. Right The synergy between these two projects means you can use the same setup for both Below This circuit will work on both the Model B and Model B+ – the pins begin at the same end of each board Web radio A portable radio that streams web content wherever you are Our Raspberry Pi web radio is a true companion piece to the audiobook over the page, and we’ll get into why as we go through this tutorial. Like the audiobook, we’re taking full advantage of the Raspberry Pi to help aid you in a real-life situation. As standard radio methods begin to die out, the established web-streaming platforms will become more and more popular, and you can get in on those straight away using this project. The circuit for this is also the exact same one as the audiobook, so if you’ve already had a crack at that, then you’ll just need to grab the code for this tutorial. Before you wire it up, it’s time to prepare your Raspberry Pi. Open the terminal and do an apt-get update and apt-get upgrade to make sure everything is up to date, followed up by installing VLC using: $ sudo apt-get install vlc When it’s finished installing, you will need to turn off your Raspberry Pi. Disconnect the USB cable, break out the breadboard and components and follow the wiring diagram. It’s not a complicated circuit at all, and revolves around sensing a button being pressed and lighting an LED on command. Double check all your connections on the breadboard and then plug your Pi back in. Open the terminal and use it to download our Python script for playing internet radio: $ wget http://www.linuxuser.co.uk/wp-content/ uploads/2014/08/webradio.zip Unzip the file and put it wherever you want; it doesn’t require any special placement in your Pi’s file structure. You will likely want to change the radio station that the code is currently tuned to, and this can be found in the subprocess.Popen line in the code. Find an m3u URL for your favourite radio station and replace the URL already in that code to get it to play. There may be a short delay between pressing the button and the music starting as VLC launches and gets the stream buffered. We’ve made it so the light comes on straight away, though, so at least you’ll know the process has started. Pressing the button again will kill VLC and stop the radio stream. If you feel the button is too sensitive or not sensitive enough, look for the time.delay setting and change the amount of time it requires the button to be pressed. Put ’em together You can easily put both projects together and have an all-in-one radio and audiobook. Wire up a second button that will play the audio book instead and maybe even add extra buttons if you like for different radio stations. Raspberry Pi Tips, Tricks & Hacks 85 Tips | Tricks | Hacks Media caster Cast your content over the local network to receive it from multiple clients so you don’t lose your place What you’ll need Q Raspberry Pi Model B Q XBMC http://xbmc.org Q Portable hard drive 86 Raspberry Pi Tips, Tricks & Hacks Have you ever wanted to move between rooms while watching or listening to the same film or song? We often find ourselves switching from a phone or tablet to the desktop. There are some complicated setups you can use for this involving MythTV and various custombuilt servers and receivers, but you can also do it with just one Raspberry Pi server and then many XBMC receivers with a lot less hassle. Broadcasting your media over your network so that the clients can pick up the stream means that you can easily pick up where you left off in your track or film wherever you move to, without having to make a note of the track position and find the file again. Here’s how to get set up. 01 Install storage drivers You’ll likely be using a portable NTFS hard drive if you want to store a lot of media on your Raspberry Pi caster. This means you need to install the NTFS libraries on the Pi, which requires you to open the terminal and type: $ sudo apt-get install ntfs-3g Tips | Tricks | Hacks Left Media stored on your portable hard drive will show up in a dedicated folder 02 Create mounting folder We’re going to have the Raspberry Pi automatically mount the hard drive for us whenever it boots up, and in order to do this it first needs to have a place where the files will be accessible. Let’s create a directory called mediadrive inside the Home folder. Keep the directory name to just one word to make your life easier later. Boot-time mount parameters Your hard drive will likely be mounted as /dev/sda1, but do a fdisk -l if you want to double check. To make sure it mounts at boot, go to fstab with sudo nano /etc/fstab and write the following line below, with a tab between each bit of information: /dev/sda1 /home/pi/mediadrive defaults,noatime 0 0 04 XBMC stream receiver This bit is dead simple – on any computer you can easily get files off of, create a file called Stream.strm, and add this line to it, with IP as the last two sets of Pi’s IP address: udp://239.255.[IP].[IP]:1234 Save it and move it to your XBMC clients that you want to receive the cast from. $ mkdir mediadrive 03 05 06 Custom VLC command Here’s the really fun part. Go back to your Pi and right click on one of the files you’d like to play, go to Properties and click the down arrow next to Open with. Go to Customise and then Custom Command Line and type in the following, with IP as the last two sets on your IP address: ntfs-3g Install VLC on Pi So all our media is now accessible, and now we need a way to broadcast it. For this we’ll use multi-functional media player VLC, which was originally designed to be the client for a casting server. You can install it with: $ sudo apt-get install vlc SSH into your Pi from another computer or an Android device cvlc --sout udp:239.255.[IP].[IP] %f 07 Test out casting Here’s the big test: boot up XBMC, open your media on the Raspberry Pi and use the Stream file on XBMC to receive the cast. It might take a moment to load but it will start playing via XBMC in short time. 08 Command line alternative Your setup may not always be convenient for you to go to the Pi and start launching files from the desktop. You can always SSH into your Pi from another computer or an Android device and run the file using a similar custom command to the one we used earlier: $ cvlc --sout udp:239.255.[IP].[IP] [file location] Be inspired Why not add a web interface to your Pi so that you can browse from your laptop or smartphone? Have it run the multicast code when clicking on files it’s scraped from the media drive to make the process much easier. You can also fuse the project with our cloud server in a few pages time. Raspberry Pi Tips, Tricks & Hacks 87 Tips | Tricks | Hacks Portable Wi-Fi signal repeater Boost your signal using a Raspberry Pi and two USB Wi-Fi dongles What you’ll need Q 2 USB Wi-Fi adaptors Q Raspberry Pi case Q Portable power pack Right One Wi-Fi adaptor picks up your main Wi-Fi network, while the other one broadcasts a new signal 88 Raspberry Pi Tips, Tricks & Hacks What we like about the Raspberry Pi for this project is that it’s very low maintenance and extremely easy to put in an appropriate location. All you need for this project are two USB wireless adaptors, a nice little case and a way to power it. Once you’ve set it up, you can basically leave it to its own devices, checking in over SSH every now and then to do some updates. Set this up on a monitor with a keyboard, using a fresh image of Raspbian and with your Wi-Fi dongles plugged in. On first boot keep it as CLI and after doing the usual apt-get updates and upgrades, type startx to get to the desktop. Configure the wireless for wlan0 to connect to your home network and make sure it has a fixed IP address, then reboot to make sure it all works from the command line by using ping www.google.com. Now you need to install your first bit of software using: $ sudo apt-get install hostapd iw After it’s installed, you’ll want to download and save the file we’ve created directly to config by entering the following two commands: Tips | Tricks | Hacks Secure Tor web station Above As well as from the main Tor website, you can also download Tor from this issue’s DVD $ wget http://www.linuxuser.co.uk/wpcontent/uploads/2014/08/repeater.zip $ cp LUDRepeater.conf /etc/hostapd/hostapd.conf Do a reboot and test the configuration file with: $ hostapd -dd /etc/hostapd/hostapd.conf If there are no errors, open the file using nano /etc/hostapd/ hostapd.conf and then add the following to the file: Stay private online by routing all your web traffic through Tor on your Raspberry Pi In a much more privacy-focused world, being able to browse securely online is an important freedom for many people. With the use of Tor and a few tweaks to the Raspberry Pi, you can make sure all your internet traffic is kept private. First of all, you’ll need to make sure to install Tor from the repos. Open up the LXTerminal and simply type: $ sudo apt-get install tor DAEMON_CONF=“/etc/hostapd/hostapd.conf” RUN_DAEMON=yes Once that’s done, edit the torrc file by using sudo nano /etc/ tor/torrc and add this to the top of the file: Also change the SSID to be the same one for your network in the ssid field. Once that’s done, you’ll need to install the bridge utilities with apt-get install bridge-utils. Then configure it with the following four commands: VirtualAddrNetworkIPv4 AutomapHostsOnResolve 1 TransPort 9040 DNSPort 53 Save this and then open the next file with sudo nano /etc/ resolv.conf file and modify it: brctl addbr bridge0 brctl addif bridge0 wlan0 brctl addif bridge0 wlan1 ifconfig bridge0 up nameserver Test it out to make sure it works and then place it around the house to extend your wireless signal! Finally, you need to change the iptables ruleset, but before you do this, use top to confirm the uid of Tor and make a note of it. Now open up a new file with nano /etc/init.d/iptables and enter the code found at: http://www.linuxuser.co.uk/wpcontent/uploads/2014/08/tor.zip. Now save it and enter: $ chmod 755 /etc/init.d/iptables $ update-rc.d iptables defaults 12 Right Adafruit’s Onion Pi Pack contains all the components you need to set up a secure connection Put ’em together A secure wireless connection can be created using the Raspberry Pi by looking at the Onion Pi project from Adafruit: learn.adafruit.com/ onion-pi/overview This creates a wireless access point connected to the internet that anonymises all web traffic by directing it through the Tor network. This means all your home computers and smart devices can be connected to Tor and not just the Raspberry Pi itself. You can also apply some of the lessons learnt in the Wi-Fi repeater tutorial to unshackle it from the ethernet cable, although that will reduce slightly its overall security. Raspberry Pi Tips, Tricks & Hacks 89 Tips | Tricks | Hacks Private cloud storage Turn the Pi into your own personal Dropbox using ownCloud and an internet connection The themes of a lot of our Raspberry Pi guides revolve around the size and portability of the Pi itself, lending it to tasks you may have used a full-sized or small computer for in the past that the Pi can now take over. Having your own private cloud is another excellent use of the Raspberry Pi’s capabilities, because you can store it hidden away somewhere and it will require very little dayto-day maintenance. Make sure you invest in some decent, portable USB storage such as an external HDD, and also get a case for your Pi in the process. 01 Set a static IP After setting up your wired or wireless internet connection, you need to make it static. Use sudo nano /etc/network/interfaces to open up the network settings file. Fine the iface eth0 line so you can change and add to it: iface eth0 inet static address gateway netmask network broadcast What you’ll need Q External storage Q Constant internet connection Left Rather than store all your media and files on a cloud server in an unknown location, you can keep a cloud in your own home 90 Raspberry Pi Tips, Tricks & Hacks Tips | Tricks | Hacks 06 Finish up with Apache You now need to do two sets of commands: a big one which requires some info and then a restart: 02 Install a lot of software You’ll want Apache software and PHP for this. Install everything you need with: $ sudo openssl genrsa -des3 -out server.key 1024 $ sudo openssl rsa -in server.key -out server.key. insecure $ sudo openssl req -new -key server.key -out server.csr $ sudo openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt $ sudo cp server.crt /etc/ssl/certs;sudo cp server.key /etc/ssl/private;sudo a2enmod ssl $ sudo a2ensite default-ssl $ sudo service apache2 restart $ sudo apt-get install apache2 php5 php5-json php5-gd php5-sqlite curl libcurl3 libcurl4-openssl-dev php5curl php5-gd php5-cgi php-pear php5-dev buildessential libpcre3-dev libapache2-mod-php5 php-apc 03 Set up PHP accelerator Install your accelerator with sudo pecl install apc and create an ini file for it. To do this, use sudo nano /etc/php5/cgi/ conf.d/apc.ini and then add this to the file: extension=apc.so apc.enabled=1 apc.shm_size=30 07 Download and install ownCloud Here you have a series of commands to run that will download, unzip and install ownCloud to the right place: $ wget https://download.owncloud.org/community/ owncloud-7.0.0.tar.bz2 $ sudo tar -xjf owncloud-7.0.0.tar.bz2 $ sudo cp -r owncloud /var/www 08 ownCloud permissions Make sure your hard drive is connected and mounted as you want it. First, give webserver permission to use ownCloud: $ sudo chown -R www-data:www-data /var/www/owncloud/ Next, use sudo nano /var/www/owncloud/.htaccess and make the same changes you did in the php.ini file above. Finally, give permissions to the location you mounted the hard drive to with: $ sudo chown -R www-data:www-data [mount] 04 Configure file limits Go into the Apache config file with sudo nano /etc/ php5/apache2/php.ini. It’s a big file, but there are two filesize options you need to find, and a third extension option you need to add as below: upload_max_filesize = 2048M Be inspired post_max_size = 2200M extension = apc.so 05 Set up SSL First of all, you need to enable SSL in Apache; do this by using sudo nano /etc/apache2/sites-enabled/000-default and change ‘None’ to ‘All’ in the AllowOverride option. Follow this up with the following two commands: $ sudo a2enmod rewrite $ sudo a2enmod headers 09 Set up ownCloud Open Midori and navigate to https://[ipaddress]/ owncloud to begin the ownCloud setup process. The first thing you’ll need to do is change the data location to the mount point of your external drive, which can be found in the advanced options. And you’re done! Need an idea of what your next step could be? Check out our media caster tutorial and maybe you can fuse the two concepts together. Upload videos to your cloud and get them to play over your network. Raspberry Pi Tips, Tricks & Hacks 91 Tips | Tricks | Hacks AirPi Predict the weather using your own sensor station The AirPi has a pedigree that aligns perfectly with the mission of the Raspberry Pi Foundation. Created by two teens in sixth form to measure various forms of pollution, the project’s popularity exploded with thanks to some highlighting by the Raspberry Pi Foundation and it’s now the premier way to create a weather station on the Raspberry Pi. The AirPi kit comes with a small selection of sensors by default that can be upgraded and improved upon with extra breakout boards and modules. Included with the kit is a barometric pressure sensor, a humidity and temperature sensor, an ultraviolet radiation sensor and a microphone for noise pollution. The first thing you’ll need to do is assemble the kit, for which you’ll require a soldering iron and a steady hand. There are some basic instructions that come with the kit you can follow but it doesn’t hurt to have a look at some of the online images to figure out exactly where everything goes. Be careful when soldering all the resistors to make sure you don’t melt the 26pin connector on the underside otherwise it won’t go on your Pi. Once that’s done you need to start setting up your Raspberry Pi. Open up a terminal and get some of the Python tools you’ll need to use: $ sudo apt-get install git-core python-dev python-pip python-smbus Download and install the python-eeml package: $ sudo apt-get install libxml2-dev libxslt1-dev python-lxml $ git clone https://github.com/petervizi/ python-eeml.git $ cd python-eeml $ sudo python setup.py install You need to install i2c support for the pressure sensor, so first use sudo nano /etc/modprobe.d/raspi-blacklist.conf and remove the comment from the blacklist i2c-bcm2708 line. What you’ll need Q AirPi tindie.com/products/tmhrtly/airpi-kit/ Q Soldering iron Q Solder Top right Measure your surroundings with AirPi and share your data with the scientific community Bottom right The AirPi perfectly fits the Raspberry Pi, so you can easily enclose your device in a small weatherproof box 92 Raspberry Pi Tips, Tricks & Hacks Next, open up the modules file with sudo nano /etc/modules and add i2c-dev to the bottom of the file. Save that and install: $ sudo apt-get install i2c-tools Add your Pi to the i2c user group with: $ sudo adduser pi i2c Now reboot your Raspberry Pi before continuing. Finally, install the final Python module with: $ sudo apt-get install python-smbus Now we can install the AirPi code. Still in the terminal, use: $ git clone -b non-modular https://github.com/ tomhartley/AirPi.git If you’re using a revision 2 Model B or a B+, use sudo nano AirPi/ AirPi.cfg to edit the config file. Change I2CBus = 0 to I2CBus = 1 and alter the next line to read LCD = False. Create a Xively account, add the API and ID keys to the config file and save it. You can now start taking measurements by running Upload.py. Tips | Tricks | Hacks Dusklights Use your Raspberry Pi to control outdoor lights that automatically come on when it’s dark You’ve probably all seen those cheap, solar-powered lamps that you can stick into your garden to try and give it a classy bit of illumination during the night. If you’ve actually got one then you may have found out that they don’t shine very brightly and the plastic stakes can be very flimsy. So why not make your own version? What we’ll show you on this page is the beginning of an array of light-sensitive LEDs using a single LED, so that you can understand how the system works. We’ll use a special resistor called a light dependant resistor (LDR) or photoresistor that changes its resistance based on the levels of light it’s receiving. There’s no extra software you’ll need for this, so just make sure your Pi is up to date with an apt-get update and apt-get upgrade. Turn it off, unplug it from the power source and get to work wiring up the circuit as shown in the Fritzing diagram. Take special note of the placement of the components, especially the LDR and the capacitor. What you’ll need to do is measure the time it takes for the capacitor to fully charge between pin three of the GPIO ports and ground. Also, make sure the negative end of the capacitor is hooked to the ground side of the circuit. Once that’s done, turn your Raspberry Pi back on and download the code we’ve created for this project using: $ wget http://www.linuxuser.co.uk/wp-content/ uploads/2014/08/dusklight.zip What you’ll need Q 1.2 k resistor Q 2.2 k resistor Q Light dependent resistor Q 1 µF capacitor Q Breadboard and wires Put ’em together Unzip it and run it. We’ve made it so the Python shell will print out the values that the circuit returns, with a higher number meaning it’s darker and the capacitor takes longer to charge. See how the circuits react to you covering the LDR with a finger or shining a torch on it in order to get an idea of how your version will work. To get this working for outdoor use it will require a bit of trial and error. The easiest way is to set it up when it’s getting to about the level of darkness you’d want the light to turn on and record the output from the sensor. Change the if statement so that it activates the LED over a certain number and you’ll be set. With some external power and more LEDs you can have a Raspberry Pi power an entire array of shining lights around your garden. Linking up the AirPi with your dusklights allows you to have the ultimate outdoor Raspberry Pi device, allowing you to predict the weather and control your outdoor lighting with more precision. The humidity and pressure sensors will be able to tell if it’s foggy or not, giving you more control over when your lights turn on. Raspberry Pi Tips, Trick & Hacks 93 Outdoor time-lapse camera Get beautiful views of the sunset using your Raspberry Pi, a Pi camera and a small Python script What you’ll need Q Pi camera module Q A weatherproof case, such as a PICE+ 94 Raspberry Pi Tips, Tricks & Hacks We love the Raspberry Pi camera. It’s a lovely little piece of kit that is as versatile as the Pi and it doesn’t even take up any of the USB slots. We’ve done a bit of time-lapse photography in the past but that was using a proper camera attached to the Pi – now we’re doing it with just the Pi camera and a lot less code thanks to the picamera Python module. We need to set up our Pi with a few things before we start with the code, though. We’ll start off with assuming you’ve got a freshly installed Raspbian SD card, so the first thing to do is an apt-get update followed by an apt-get upgrade to make sure your files are up to date. Follow this with an rpi-update to make sure your firmware is also up to date – this step is very important because if you’re using an outdated firmware then the camera won’t work. The next step is to get the camera enabled. Open up the terminal if you’re on the desktop, or simply write into the command line: $ sudo raspi-config Find the Enable Camera option. Press Enter and key over to Enable. Go to Finish but don’t restart straight away as you have some more commands to get through. Install your picamera module using this: $ sudo apt-get install python-picamera You also need to install the software that you’re going to use for compiling your images into the finished time-lapse video. We’re using gstreamer to compile the video as it works well with the Raspberry Pi GPU. To get it installed, first add the repo to the sources list with: $ sudo sh -c ‘echo deb http://vontaene. de/raspbian-updates/ . main >> /etc/apt/ sources.list’ Tips | Tricks | Hacks Left Ground yourself and carefully insert your Pi camera while the Raspberry Pi is unplugged Below The PICE+ case is currently being Kickstarted, so it wasn’t available at the time of writing, but look out for it by the end of the year Do an apt-get update and then install a huge selection of packages with the following: $ sudo apt-get install libgstreamer1.0-0 liborc-0.4-0 gir1.2-gst-plugins-base-1.0 gir1.2-gstreamer-1.0 gstreamer1.0-alsa gstreamer1.0-omx gstreamer1.0plugins-bad gstreamer1.0-plugins-base gstreamer1.0plugins-base-apps gstreamer1.0-plugins-good gstreamer1.0-plugins-ugly gstreamer1.0-pulseaudio gstreamer1.0-tools gstreamer1.0-x libgstreamerplugins-bad1.0-0 libgstreamer-plugins-base1.0-0. Once that’s done, shut down the Raspberry Pi. Unplug the USB cable and locate the special DSI port for the camera, next to the HDMI port. Gently pull on the edges to lift the fastener and slot in your Raspberry Pi camera ribbon – make sure the silver connectors are facing the HDMI port. Turn your Raspberry Pi back on and get back into Raspbian. Everything should be about ready now, so give the camera a test by opening up the terminal and using: Unzip it and have a quick look through it using IDLE. There are a couple of things to note in the code in case you wish to modify it. The photos variable is set to 500 and that’s the number of shots it will take before compiling the video. In reality it will actually do one more due to the mathematical quirks of Python but that shouldn’t matter. The delay parameter is in seconds and using a bit of Google Fu you can figure out that 500 shots at 30-second intervals will take about four hours to complete. The large subprocess.call line is used to compile the images into an AVI file at 24 frames per second. It uses the full path to the directory that we mentioned previously, so if yours is slightly different make sure you change it now. There are a number of ways you can use it to get a timelapse of the outdoors; the easiest and safest way is to locate a window with the view you wish to use. This may not always be easy, though, in which case we suggest trying out the PICE or PICE+ case. It’s a durable and waterproof case that is designed to house the Pi and a Pi camera. Once it’s in place, all you’ll need to do is hook it up to power, preferably with a long cable, and run the code. Once it’s finished, retrieve the Pi and the AVI file. $ raspistill -o test.jpeg It will show the preview screen and then take a photo after five seconds; if it does so, you’re ready to get set up with our code. Our preferred method for doing this is to first create a folder called timelapse in your home directory; you can do this simply by opening the terminal and typing: $ mkdir timelapse If you haven’t made any changes to your username and such, this should create the directory with the full path /home/pi/ timelapse. Keep this in mind and we’ll explain its importance in a bit. Now in the terminal we’ll download the Python code we’ve created for this project: $ wget http://www.linuxuser.co.uk/wp-content/ uploads/2014/08/timelapse.zip Be inspired With some modifications to the code and the Pi, you can make it a lot more automated, running the Python script after boot and uploading it to the cloud storage we set up earlier. You can also use it as a CCTV camera thanks to an additional hood that comes with the PICE Raspberry Pi Tips, Tricks & Hacks 95 Tips | Tricks | Hacks Set up the PiTFT touch screen This simple little touch screen takes a bit more than just plugging it in, as we show in the first of our hand-held Raspberry Pi video player tutorials What you’ll need Q SD card with up-to-date version of Raspbian Q PiTFT, fully assembled bit.ly/1jHEJT4 96 Raspberry Pi Tips, Tricks, & Hacks We’ve spoken a lot about about how portable the Raspberry Pi is, but one of the minor issues associated with this portability is the lack of a display. Carrying around a monitor is hardly practical and connecting via a phone with SSH takes some interesting trickery to get right. The PiTFT screen removes all these issues by requiring no extra power and being the size of the Raspberry Pi itself. While Adafruit does supply a preconfigured Raspbian image for the screen, you’ll need to add some extras to get it working on your current install, which is exactly what we’re going to cover in this tutorial. 01 Adafruit kernel files The first thing we need to do is download and install the necessary kernel files. Open up a terminal or SSH in and do the following: $ wget http://adafruit-download.s3.amazonaws.com/ libraspberrypi-bin-adafruit.deb $ wget http://adafruit-download.s3.amazonaws.com/ libraspberrypi-dev-adafruit.deb $ wget http://adafruit-download.s3.amazonaws.com/ libraspberrypi-doc-adafruit.deb $ wget http://adafruit-download.s3.amazonaws.com/ libraspberrypi0-adafruit.deb $ wget http://adafruit-download.s3.amazonaws.com/ raspberrypi-bootloader-adafruit-112613.deb $ sudo dpkg -i -B *.deb Tips | Tricks | Hacks Left Get the neccessary files from the Adafruit website and download them to your Pi 02 Attach the screen If you’re using Raspbian from an image after September 2013, turn off the accelerated framebuffer using: $ sudo mv /usr/share/X11/xorg.conf.d/99-fbturbo.conf ~ After that’s done, shut down the Raspberry Pi completely and plug the screen into the GPIO pins if you haven’t already done so. 03 Install the screen driver We can do a test to make sure that the screen works at this point. This will turn on the screen but it won’t work after reboot: $sudo modprobe spi-bcm2708 $sudo modprobe fbtft_device name=adafruitts rotate=90 $export FRAMEBUFFER=/dev/fb1 $startx 05 Edit configuration files We need to create/modify the necessary configuration file so that the screen can turn on properly. The first line opens the file, while the second line needs to be added to this file: $ sudo nano /etc/modprobe.d/adafruit.conf options fbtft_device name=adafruitts rotate=90 frequency=32000000 06 The options 07 Install touch screen You may have noticed the specific wording on these options: rotate allows you to have it at 0, 90, 180 or 270 degrees. A frequency of 32MHz gives you about 20fps on screen; but if the screen is playing up, take it down to 16MHz. Now reboot the Pi. Once back in, we need to create a new config file and populate it as shown below: $ sudo mkdir /etc/X11/xorg.conf.d $ sudo nano /etc/X11/xorg.conf.d/99-calibration.conf Section "InputClass" Identifier "calibration" MatchProduct "stmpe-ts" Option "Calibration" "3800 200 200 3800" Option "SwapAxes" "1" EndSection 08 04 Add the modules There are two modules we need to get to auto-load at boot time, including the actual PiTFT driver. Open up the modules file with the first command and add the second two lines to the list: Testing touch Once that's all done you can restart X with: $ FRAMEBUFFER=/dev/fb1 startx You can make it so you just need to type startx by adding the following to ~/.profile: export FRAMEBUFFER=/dev/fb1 $ sudo nano /etc/modules spi-bcm2708 fbtft_device You can also go into raspi-config to have the desktop load by default. That’s it – you’re now ready to start calibrating the display for your portable video player. Raspberry Pi Tips, Tricks, & Hacks 97 Tips | Tricks | Hacks Calibrate a touch screen interface Calibrate your new touch screen and add a small interface using some simple Python code What you’ll need Q SD card with up-to-date version of Raspbian Q PiTFT, fully assembled bit.ly/1jHEJT4 98 Raspberry Pi Tips, Tricks & Hacks We’ve got a screen with basic touch functionality but where do we go from there? Our first step is to actually make the touch screen usable; it’s resistantstyle touch, so you can use your finger or a stylus with it, and this will affect the calibration of the screen once we get to it. Don’t worry – if you calibrate with one method, you can always go back and recalibrate with another. Once you’ve completed the tutorial on the previous two pages, be sure to give this one a try. Here we’re going to properly set up the touch screen so you can continue to use the Raspberry Pi on the go without any other devices or within range of a decent power socket. 01 New rules To make things easier for ourselves we’re going to create a little rule so that we don’t lose track of what the touch screen is called in the command line. SSH in, run the next command and copy the following text into it: $ sudo nano /etc/udev/rules.d/95-stmpe.rules SUBSYSTEM=="input", ATTRS{name}=="stmpets", ENV{DEVNAME}=="*event*", SYMLINK+="input/ touchscreen" 02 Reinstall the touch screen We’ll need to undo what we did at the end of the last tutorial to make sure we can get the touch part working properly, by removing and then reinstalling the support for it: sudo rmmod stmpe_ts; sudo modprobe stmpe_ts Tips | Tricks | Hacks 03 Main event Find out what event the touch screen is known by with the following: $ ls -l /dev/input/touchscreen We can install tools now to calibrate and debug the touch screen. Install and test them with: $ sudo apt-get install evtest tslib libts-bin $ sudo evtest /dev/input/touchscreen Once you’ve done the calibration, you can try out a drawing test to see how the screen reacts 06 Install X calibrator Now we need to calibrate the touch screen in X, which first means installing the correct tools. Use the following two commands to download and install the tool: $ wget http://adafruit-download.s3.amazonaws.com/ xinput-calibrator_0.7.5-1_armhf.deb $ sudo dpkg -i -B xinput-calibrator_0.7.5-1_armhf.deb Follow this up quickly by deleting irrelevant calibration data with the following: $ sudo rm /etc/X11/xorg.conf.d/99-calibration.conf 04 Touch calibration Now we can finally begin the calibration process. Enter the following so that the Pi can learn roughly where the positions are on the screen: $ sudo TSLIB_FBDEVICE=/dev/fb1 TSLIB_TSDEVICE=/dev/ input/touchscreen ts_calibrate 07 X-calibrate From your SSH shell, run startx for the screen to turn on. From here you can either try to get xinput_calibrator typed into the terminal or type the following from the SSH session if it’s easier: FRAMEBUFFER=/dev/fb1 startx & DISPLAY=:0.0 xinput_ calibrator 05 Draw calibration Once you’ve done the previous calibration, you can try out a drawing test to see how the screen reacts. Do this with the following: $ sudo TSLIB_FBDEVICE=/dev/fb1 TSLIB_TSDEVICE=/ dev/input/touchscreen ts_test If it’s not working quite to your liking, you can try the previous step again. 08 Save calibration Having completed calibration, you’ll get an output starting with Section “InputClass”. Open up the following file and copy the output from Section to EndSection into there: $ sudo nano /etc/X11/xorg.conf.d/99-calibration.conf 09 Play around Your new touch screen is now properly set up! We’ll go over more ways to make it easier to use in the following tutorial, but it’s basically portable now and ready to have other projects, such as the PiPhone or PiCam, loaded onto it. Raspberry Pi Tips, Trick & Hacks 99 Tips | Tricks | Hacks Portable Pi video player Need a better way to watch video on the go? Let your newly powered-up touch-screen Pi play your favourite films and shows What you’ll need Q SD card with up-to-date version of Raspbian Q PiTFT, fully assembled bit.ly/1jHEJT4 100 Raspberry Pi Tips, Tricks & Hacks We’ve got a Raspberry Pi that we can make portable now – but how can you use it? The easiest thing to do with it is use it as a portable video player. It has a far superior battery to your phone and has the added bonus of being easily plugged into a TV once you reach your destination. Before we can use it to play the videos, though, we need to make it a bit more friendly to transport and get it to play videos in a particular way. So we’ve recommended some excellent accessories and extras you can take advantage of to achieve this. 01 Install VLC Go to your SSH terminal and install VLC media player. It’s a lightweight, highly customisable media player that is able to play just about anything you throw at it. Do this with: $ sudo apt-get install vlc 02 Default settings Here’s where it gets a bit tricky, as you’ll need to perform this step via the screen. Hook the Pi up to a display, mouse and keyboard or just use the mouse and keyboard on the small screen. Go to an AVI or MP4 file and right-click on it, go to Properties>Open with… and choose Customise for the next step. Tips | Tricks | Hacks 03 Set the default Go to Sound & Video to select VLC from the menu. Click the checkbox to set it as the default app and then press Enter to save the changes. Now when you double-click or tap on the video, it will automatically play in VLC. 07 Get some protection 08 Independently powered 09 Next time… The PiTFT PiBow case from Pimoroni is one of the few cases – if not the only case – that houses the Raspberry Pi with the PiTFT screen. It’s assembled in layers and only works with the revision 2 Raspberry Pi (the newer one with 512MB of RAM); this one won’t have the pins between the yellow video port and headphone port. 04 VLC options 05 Play videos 06 USB storage Open up VLC from the menu and right-click anywhere in the player space to open the Context menu. From here, go to Tools and then Preferences. Scroll down to click on ‘Allow only one instance’ and then go to the Video tab and click on the Fullscreen checkbox. Press Enter to save. You’re done! It will play videos at the size of your Raspberry Pi screen and only one player will exist at a time. You may have better luck if you convert videos to 320x240, but it should play much larger videos just fine. A lot of Raspberry Pi SD cards have limited space, so it makes sense to keep your videos separate. Make sure to use storage that does not require any extra power, like a USB stick or portable hard drive. Access the storage from the File Manager, as no other mounting is required. To have it working on the go, you’ll need to have it set up so that you can remove it from a tethered power source. Portable, USB batteries are quite common these days, but there are certain things you need to look out for, such as high capacity and higher amp output. Now we have our portable Raspberry Pi video player! Use it as you wish and learn the ins and outs of the touch screen in the process. Next month we’ll demonstrate how you can change the setup from watching video to capturing video with our RasPi Camera. Raspberry Pi Tips, Tricks & Hacks 101 Tips | Tricks | Hacks Make a Raspberry Pi sampler Build your own looping drum machine with only 200 lines of code! Left Extra breadboards are used here to keep the main breadboard as free from wires as possible What you’ll need Q Latest Raspbian image raspberrypi.org/downloads Q At least one breadboard Q Push buttons Q LEDs Q Female-to-male GPIO jumper cables Q Male-to-male GPIO jumper cables In this tutorial we combine electronics, music and programming knowledge to create a simple sampler with looping capabilities. The implementation used in this article has three drum sounds as the samples, but it is trivial to add more until you run out of GPIO pins. Before we start, let’s cover some basic musical terms. Music is split into bars. There are a certain number of beats in a bar. This sampler uses the 4/4 time signature, which means there are 4 beats in each bar. Tempo is the speed at which music is played, and it is measured in beats per minute (bpm). A metronome is an audible tone that is heard at the start of every beat. Quantization is the process of aligning notes to beats, or exact fractions of a beat, and a quantization value is usually given in the form 1/8. This means that there are eight possible places in a bar where a note can be played. When the sampler is recording and a sample button is pressed, we store the sample at the current position in the bar with the accuracy of the quantize value. There’s a lot to cover, so let’s get started. 102 Raspberry Pi Tips, Tricks & Hacks 01 Connect LEDs The circuit diagram is an LED that can be turned on and off with a GPIO output. The orange wire is the connection from the GPIO output. This then goes through a 220û resistor to limit the current draw to a safe level. This current flows through the positive leg of the LED and then back to ground. We need nine LEDs for this project. Tips | Tricks | Hacks 02 Wire up buttons The second circuit we need is a push button. The purple wire goes to a GPIO input. There is a 10Kû pull down resistor to ground, which represents a logical 0. When the push button is pressed, the 3.3V supply representing a logical 1 is connected to the purple wire. The electricity takes this path because it has less resistance than the path to ground. We need two buttons for record and undo, and then as many buttons as you like for samples (three drum samples are provided). 03 Full code listing Step 04 Step 05 Create a few folder for the project called pisampler. Then download and unzip the sounds: mkdir pisampler cd pisampler wget http://liamfraser.co.uk/lud/ pisampler/sounds.zip unzip sounds.zip 04 Import required libraries Create a file called pisampler. py in your favourite editor. The first thing we need to do is import the required libraries and set some configuration values. A key option is debounce: the time to wait before a button can be pressed again to stop accidental presses from contact bounce. 05 Create a sample class We’re going to use a class to represent each sample. It's going to need a few things: the pin that the sample button is connected to, the name of the sound file, and a reference to the instance of the sampler class. We haven’t created the sampler class yet, but the sample will need to be able to tell if the sampler is recording or not, and have access to the data structure that recordings are stored in to add itself to it if necessary. The other thing that we need to do is set the GPIO pin to an input, and add an event listener for when the button is pressed. We set callback (the function to be executed when the button is pressed) to a function called self.play_btn, which RPi.GPIO as GPIO time pygame os beat_leds = [2, 3, 4, 17] bar_leds = [27, 22, 10, 9] record_led = 11 record = 19 undo = 26 debounce = 200 # ms Download samples There will now be a folder called sounds with some samples in. The file format for samples is .wav audio, Microsoft PCM, 16 bit, stereo 44100 Hz. Mono will work too. Any samples can be converted to this format with Audacity by exporting them as a .wav file. import import import import (Cont. on next page) class Sample(object): def __init__(self, pin, sound, sampler): self.sampler = sampler self.name = sound self.sound = pygame.mixer.Sound(os.path.join('sounds', sound)) self.pin = pin GPIO.setup(pin, GPIO.IN) GPIO.add_event_detect(self.pin, GPIO.RISING, callback=self.play_btn, bouncetime=debounce) def play_btn(self, channel): self.sound.play() s = self.sampler if s.recording: s.recording_data[s.bar_n][s.quantize_n].append({'loop' : s.loop_count, 'sample' : self}) Step 06 class PiSampler(object): def __init__(self, tempo=80, quantize=64): pygame.mixer.pre_init(44100, -16, 1, 512) pygame.init() self.quantize = quantize self.tempo = tempo self.recording = False self.record_next = False self.metronome = False self.met_low = pygame.mixer.Sound(os.path.join('sounds', 'met_low.wav')) self.met_high = pygame.mixer.Sound(os.path.join('sounds', 'met_high.wav')) self.met_low.set_volume(0.4) self.met_high.set_volume(0.4) self.samples = [] self.recording_data = [] for i in range(0, 4): bar_arr = [] for i in range(0, quantize): bar_arr.append([]) self.recording_data.append(bar_arr) GPIO.setmode(GPIO.BCM) for pin in beat_leds + bar_leds + [record_led]: GPIO.setup(pin, GPIO.OUT) GPIO.setup(record, GPIO.IN) GPIO.add_event_detect(record, GPIO.RISING, callback=self.record_next_loop, bouncetime=debounce) Raspberry Pi Tips, Tricks & Hacks 103 Tips | Tricks | Hacks Full code listing Step 06 Step 07 (Cont.) GPIO.setup(undo, GPIO.IN) GPIO.add_event_detect(undo, GPIO.RISING, callback=self.undo_previous_loop, bouncetime=debounce) @property def tempo(self): return self._tempo @tempo.setter def tempo(self, tempo): self._tempo = tempo self.seconds_per_beat = 60.0 / tempo self.quantize_per_beat = self.quantize / 4 self.quantize_seconds = self.seconds_per_beat / self.quantize_ per_beat Step 08 def add(self, sample): self.samples.append(sample) @property def recording(self): return self._recording @recording.setter def recording(self, value): self._recording = value GPIO.output(record_led, value) def record_next_loop(self, channel): self.record_next = True Step 13 def play_recording(self): for sample_dict in self.recording_data[self.bar_n][self. quantize_n]: if sample_dict['loop'] != self.loop_count: sample_dict['sample'].sound.play() def undo_previous_loop(self, channel): if len(self.last_recorded_loop) == 0: print "No previous loop to undo" return print "Undoing previous loop" loop = self.last_recorded_loop.pop() for bar in self.recording_data: for quantize in bar: removes = [] for sample in quantize: if sample['loop'] == loop: removes.append(sample) for sample in removes: quantize.remove(sample) Step 11 def do_leds(self, leds, n): count = 0 for led in leds: if count == n: GPIO.output(led, True) else: 104 Raspberry Pi Tips, Tricks & Hacks will play a sound and add it to the recording data if we are recording. It will become clear how this works once we’ve written the sampler class. Note that the GPIO event handler passes the pin that the event handler was triggered on, hence the channel variable that is present but never used. 06 The sampler init method 07 The tempo property 08 Helper functions 09 Start the main loop Here’s the start of the sampler class. The last value in the Pygame mixer init is the buffer size. You might need to increase this to 1024 or higher if you have audio dropouts. We create some variables to store recording state. Metronome sounds are then added and their volume lowered. We also create a list to hold our samples in. We create nested arrays to represent recorded sample presses. There is an array for each bar. Each bar has an array for each possible quantize value. The default value of 64 gives us 64 possible places to store a sample hit per bar. Finally, we set up the LED pins, and the pins for the record and undo buttons. The tempo variable is actually a property with a custom setter. This means when a value is assigned, it does a custom action. In our case, we need to calculate how often we need to check for recorded notes to play in the main loop that we’ll write later. There are a few helper functions in the class. One of them simply adds a sample to the list of samples. Another sets a variable to trigger recording at the start of the next loop. There is also a function which turns the red LED on when the recording variable is set to true. Now we'll jump forward and take care of the main loop towards the end of the full code listing. The main loop doesn’t actually have to do any work at all to play sounds, as that’s done by the GPIO event handlers. The main loop is used to play the metronome, update the state about which bar/beat/ quantize we are currently on, update the LEDs and deal with recording if necessary. Before the loop, we create variables to track the state. The last recorded loop is a list that we will use as a stack. A stack is a last in/first out data structure, allowing us to undo recordings multiple times by removing each sample that was recorded when the loop count was the value on the top of the stack. If we’re at the start of a new beat then we use a function called do_leds that we haven’t created yet. As the LEDs work in the same way (a block of four LEDs where only one is turned on), we can use the same function twice and just pass a different set of pins, and the index of the LED we want to turn on. We then call the do_metronome function which will play the appropriate metronome sound. We then do some recording logic which starts recording if we should be recording, and stops recording if we have just been recording, adding the Tips | Tricks | Hacks loop number to the last_recorded_loop stack. We increment the loop count after doing this. 10 Full code listing Step 11 (Cont.) GPIO.output(led, False) Main loop continued This code is at the indentation level after the “while True:” statement. After dealing with the recording logic, we need to play any notes that have been previously recorded. We’ll work out how to do that later on. After that, we can sleep until the next quantize change is due. Once this happens, we have to do logic that deals with the quantize and any related variables such as the beat or bar if necessary, either incrementing them or resetting them if necessary. 11 Lighting LEDs 12 The metronome 13 The recording code The LED code is simple. It simply goes through each pin in the list you provide it with and lights up the appropriate LED, ensuring that all of the others are turned off. count += 1 Step 12 if self.beat_n == 0: self.met_high.play() else: self.met_low.play() Step 09 The metronome simply plays a high tone on the first beat or a lower tone on the remaining beats if the metronome variable is set to true. Looking back at the sample class we created at the start, you can see that if recording is enabled, and a note is pressed, then we add a dictionary to the list of samples for the current bar at the current quantize point. The dictionary contains a reference to the sample so that it can be played, and also the loop that it was added on so that it can be removed if necessary. The code for playing and undoing recordings can be seen below. Note that we directly play the sound rather than using the btn_play function so that we don’t trigger the recording logic when playing recorded sounds. The pop function in undo_previous_loop removes the last thing that was added to the stack, which will be the loop count. We then go through every possible recording data point and remove anything recorded on the loop we want to remove. 14 Finishing it off 15 Possible improvements def run(self): self.loop_count = 0 self.last_recorded_loop = [] self.bar_n = 0 self.beat_n = 0 self.quantize_beat_n = 0 self.quantize_n = 0 while True: if self.quantize_beat_n == 0: self.do_leds(beat_leds, self.beat_n) self.do_leds(bar_leds, self.bar_n) self.do_metronome() if self.quantize_n == 0 and self.bar_n == 0: if self.record_next: self.recording = True self.record_next = False elif self.recording: self.recording = False self.last_recorded_loop.append(self.loop_count) self.loop_count += 1 Step 10 self.play_recording() time.sleep(self.quantize_seconds) if self.quantize_beat_n == self.quantize_per_beat - 1: self.quantize_beat_n = 0 self.beat_n += 1 else: self.quantize_beat_n += 1 To finish it off, we need to add a main function where we load some samples in and then start the main loop. Remember that you need to run the code with sudo python2 pisampler.py because we need sudo to access the GPIO. Happy jamming! There are a number of improvements that could be made to the sampler. Here are a few to get you started: • A button to turn the metronome on and off • The ability to time stretch samples (such as chords) to fit with the tempo • The ability to pitch shift samples on the fly • Using a shift register to use less pins when lighting the LEDs, allowing more inputs • The ability to save recorded beats so that they can be loaded and played back def do_metronome(self): if not self.metronome: return if self.quantize_n == self.quantize - 1: self.quantize_n = 0 else: self.quantize_n += 1 if self.beat_n == 4: self.beat_n = 0 self.bar_n += 1 if self.bar_n == 4: self.bar_n = 0 Step 14 if __name__ == "__main__": sampler = PiSampler(tempo=140) sampler.add(Sample(05, 'kick01.wav', sampler)) sampler.add(Sample(06, 'snare01.wav', sampler)) sampler.add(Sample(13, 'clhat01.wav', sampler)) sampler.metronome = True sampler.run() Raspberry Pi Tips, Tricks & Hacks 105 Tips | Tricks | Hacks Build a radio transmitter Take advantage of the interference-blocking feature and make your mark on the airwaves Back in the 1960s, offshore boats were used to broadcast what was then known as ‘pirate’ radio: unlicensed broadcasts that provided an alternative to the BBC’s light program (as the most populist radio station was then known). Pirate radio was a revolution that inspired Radio 1 and commercial broadcasting, but these days you don’t need a boat to pursue your radio DJ dream – just a Raspberry Pi. Add a basic DIY antenna, an SD card with some MP3 tunes saved to it, plus a script to automate playback, and you can follow in the footsteps of John Peel and Tony Blackburn. This is a 50-50 project, one that has a chunk of DIY as well as the usual SD card flashing. You’ll also need a battery pack, so we would recommend trying the project on p.76 to make sure you’re always powered up on the go. One word of warning: unlicensed broadcasting on the FM band is an offense. This tutorial is merely a proof of concept – one that might be used for a school radio project, for instance. 01 Below Our homemade antenna may look a little rough around the edges, but it works great! What you’ll need Q Jumper wire Q 2mm wire Q Heat shrink tubing Q Soldering iron Q Wire cutters/strippers Q Hair dryer/heat gun Q PiRadio bit.ly/1MWkxwp Q PirateRadio.py script bit.ly/1SkkeCh Gather your equipment Begin by downloading the PiFM image. This is over 2.3GB, so if you’re on a slower connection then you’ll need to get it downloaded in advance. Meanwhile, source an antenna. This might be a wire coat hanger or 2mm wire from your local electronic component store. While you’re there, grab some heat shrink tubing and some jumper cables, ensuring that you’re well prepared to start the project. Build a case Full codek o.u FileSilo.c Okay, so you’ve already got a suitable case for your Raspberry Pi, but why not go all-out and put together a new case for this project? One idea is to take inspiration from the broadcast motif and design an old-style antenna case, with the Pi and the genuine antenna cleverly hidden inside it. Alternatively, a Mason jar (or other suitably wide-necked jar) will also make a great home for the PiFM – just drill a hole in the lid for the antenna! Tips | Tricks | Hacks Left Prepare MP3 files in advance or make your own using Audacity, or a similar open source audio production tool 02 Prepare MP3 files in advance There’s no facility for live broadcast. Instead, you will need to arrange your MP3 files in advance. These will be played using a script and transmitted to the nearest radio. Planning on some DJ-ing? All is not lost, as you can produce your own MP3 files using Audacity or similar open source audio production tools. To get the files to play in a particular order, number them, or the folders, sequentially. Unlicensed broadcasting on the FM band is an offence. This tutorial is merely a proof of concept – one that might be used for a school radio project, for instance bulk. As you only need a single 200-250mm length, the best option is to use a handheld rotary blade (or hacksaw) to cut the length from a wire coat hanger. 03 Power your Raspberry Pi radio Planning to try this out in a remote area? You’ll need a battery pack to power your Raspberry Pi, or else run it from your car’s cigarette lighter. For flexibility, you may also need a mobile device with SSH software to wirelessly connect to your Raspberry Pi pirate radio in headless mode. Of course, the project doesn’t have to be portable and you can power your Raspberry Pi as usual. 04 Prepare your broadcast antenna To broadcast from your Raspberry Pi, you’ll need a suitable antenna. Electronic retailers stock copper wire that’s around 2mm in diameter, but this is usually only available in 05 Connect the jumper Strip the wire from a female jumper, leaving enough to solder the 2mm wire to. Once cooled, add a 50mm length of heat shrink tubing to the top of the jumper and the lower portion of the antenna to insulate the connection. This will tighten as you apply heat from a hairdryer or heat gun. Be careful when heating, as the antenna will warm up and can burn your fingers. Raspberry Pi Tips, Tricks & Hacks 107 Tips | Tricks | Hacks Above The original GPIO 4 hack was discovered by two students at Imperial College London Multiple audio formats Throughout the tutorial, we’ve talked about audio files as MP3s, but one of the many beauties of the PiFM project is that it supports other formats. These are re-encoded as required in time for broadcast, based on a playlist created when the Python code scans the SD card for audio files. In addition to MP3s, you can cue up and broadcast files in FLAC, WAV, M4A, AAC and WMA. 06 Connect the antenna 07 Prepare your SD card The antenna is connected to pin 4 on your Raspberry Pi’s GPIO. Before you do this, check that your Raspberry Pi case is suitable for high profile GPIO connections. If not, consider connecting it to a short length of wire and mounting it on top of your case with an adhesive like Sugru, or perhaps just tape it to the side of your case. As long as the antenna has a connection to pin 4, you’re good to go. As with all Raspberry Pi projects, it’s good to start with a freshly flashed SD card. To get started quickly, use the disk image linked in the kit list, extract the ISO file and flash. However, if you would rather spend some time tweaking the script, flash Raspbian Wheezy and install PirateRadio.py from GitHub. 09 Configure the Pirate Radio With the SD card still inserted into your PC, open the pirateradio.config file in a text editor. Look for the frequency setting and adjust this as necessary. You’ll need to set this to a frequency that is currently unoccupied, so switch on your FM radio, find some free space and change the pirateradio.config file as necessary. Save and exit the file when you’re done. 10 Random and continuous music 11 Stereo or mono? Should you plan to add a lot of music to your SD card for playback on your pirate radio project, you may want to use the shuffle and repeat_all settings in the pirateradio.config file. By default these are set to true, but to disable, you simply need to change true to false. Save when you’re done, and remember to unmount the SD card before removing it from your computer. 08 Copy your MP3 files to SD You cannot simply dump your MP3 files on the SD card. With your flashed SD card still inserted into your PC card reader, browse to the /Pirate Radio partition of the card and paste your copied files. Beyond simply pasting in numbered MP3s, you can also drop in named folders from your music collection containing entire albums or artist catalogues. 108 Raspberry Pi Tips, Tricks & Hacks The pirateradio.config file offers you the choice of setting a true or false value to the stereo_playback value. You should consider this carefully, as it will determine quality and range for your broadcast. Set to true, the broadcast will be of superior audio quality. However, the range will be reduced as additional power is Tips | Tricks | Hacks How does the Pi broadcast? Spread-spectrum clock signals on the GPIO pins are the secret power behind the Raspberry Pi’s surprising hidden ability to broadcast on the FM band. By utilising this energy with an antenna on pin 4, you can turn a method employed to reduce electrical interference with other devices connected to and situated near your Raspberry Pi into a tool for radio communication. Left Check out Ofcom’s radio broadcasting licenses for more details on the law regarding broadcasting music required. So setting stereo_playback to false will increase your broadcast’s range. However, due to the scale of the transmitter, this is only a matter of 20 feet! 12 Appreciate the law It’s all too easy to get into trouble with this project, so before you start broadcasting make sure you’re familiar with the law and licensing requirement for broadcasting on the FM band. This project is perfect for short range use, such as playing your MP3s on an old car radio, although you’ll have to modify the length of the antenna for this. Schools may also benefit from a Raspberry Pi radio station. 13 Take to the airwaves! Insert your SD card into the Raspberry Pi and plug the device in. Meanwhile, step away from the device and head into the next room with your FM radio and tune into the specified frequency. Once the Raspberry Pi has booted you should find that the MP3 files are being broadcast! 14 Troubleshooting bad broadcasts Problems with your broadcast? Check the FM radio is capable of picking up other stations. If you’re in the UK, look for Radio 2 on 88-91 FM, which can be received virtually anywhere. You should also check the frequency setting in the pirateradio. config file. Remember that the band is accessible in the UK from 87.5-108 FM. As such, you cannot access frequencies beyond these points on an FM radio. 15 Check your antenna for problems Reception issues may be traced back to the antenna. Double-check the soldering is secure and confirm that the wire is connected to GPIO 4. Using the wrong pin won’t harm your This project is perfect for short range use, such as playing your MP3s on an old car radio, although you’ll have to modify the length of the antenna for this Raspberry Pi, but equally it won’t result in audio being broadcast to your FM radio! Interference in the broadcast may be due to wireless routers and microwave ovens. Your Raspberry Pi’s power source may also cause problems. 16 Elevate your broadcast 17 Curb your piracy You can improve the range by positioning your Raspberry Pi and the PiFM antenna in an elevated position. You might, for instance, place it by an upstairs window. Even better results can be achieved by broadcasting from up a tree or on a hillside – but keep in mind that an unlicensed project really needs to maintain a short range. You’ve built a compact, potentially portable radio transmitter, but remember that it isn’t the 1960s and you’re not a revolutionary. Consider the approved uses for the project and stick to these, rather than using it to cause mischief and get a criminal record. You could make an FM repeater, for example, or create a wireless mic. If you really want to get on the radio, consider volunteering with your local community station. Raspberry Pi Tips, Tricks & Hacks 109 Tips | Tricks | Hacks Tether your Raspberry Pi to an Android device Need the internet on your Pi on the go? Try out a physical tether to your Android device for instant online access The portability of the Raspberry Pi is one of its most lauded features and you can get many different accessories to help aid this portability. Mini screens, mini wireless keyboard and mouse combos, portable batteries and more can get you out and about, but the Internet is a stumbling block that you can’t easily fix with an accessory. What you do also usually have with you is an Internet-connected magic pocket box called a smartphone that, with a bit of know-how, you can connect the Pi to and steal some Internet from. Over the next two pages we will impart this know-how to get you using your Raspberry Pi on the Internet when you’re on the go. 01 The easy way A lot of smartphones now have a Wi-Fi hotspot feature, which the Raspberry Pi can easily attach to. First of all, turn the hotspot on and then boot into the Pi. Connect a wireless dongle and open up the wpa_gui in Preferences>Wi-Fi Configuration. 02 Scan for device Click Scan to open up the scan window and then select Scan again from inside there. It should pick up your device – connect it as you would to any Wi-Fi network and the Pi will remember it for when it needs it next. What you’ll need Q Android device Q USB cable 110 Raspberry Pi Tips, Tricks, & Hacks Tips | Tricks | Hacks 03 Above It’s usually easy to figure out which device is your phone – set it right next to the Pi and it will be the one with the best signal! Set up tether First connect your phone to your Raspberry Pi via a USB cable – depending on the amount of power your Pi has, it might have trouble charging your phone but it will still let you tether. In the tethering menu you can now activate USB tethering. 06 Test connection 07 Save the settings There’s a few ways to test your connection. We’d usually stay in the terminal and ping www.google.com, which you can do, or you can click on the browser and see if it loads the page. Once you reboot your Pi, it won’t remember to automatically connect to the phone’s tether. However, we can add an entry to its config so that it will try and do this in the future. From the terminal use: 04 Check connection Your Android device will create an interface known as eth0 on the Raspberry Pi. You can check to make sure this is happening, and that it will let you tether, by opening up a terminal and typing the following: $ ifconfig 05 $ sudo nano /etc/network/interfaces 08 Interface settings Here you’ll find all the current network settings – yours might look different from ours depending on if you have added any fixed wireless settings or passthroughs. Using the same syntax as the eth0 line, add: Quick connect You can connect from the terminal right now to access the Internet. You should be able to do this by typing the following into the terminal: $ sudo dhclient usb0 This will automatically grab any available IP address that your phone will give to it. iface usb0 inet dhcp 09 Tether on the go After a save and reboot, your Pi should now automatically connect to your phone, whether it’s via Wi-Fi hotspot or a physical connection. It may draw a little more charge than usual while tethering, so be sure to keep an eye on your battery level. Mobile data Using your Pi on your mobile phone will eat up data much faster than browsing on your phone normally is. We suggest not doing a full software, distribution or firmware update if you don’t want to spend a fortune on data. You can also set limits on the amount of data used on your phone to save yourself any problems, and a physical tether will allow you to connect via the phone’s Wi-Fi if that’s an option. Raspberry Pi Tips, Tricks, & Hacks 111 Tips | Tricks | Hacks The Network Information Services and Network File System server providing centralised authentication and file storage to the clients An external storage device connected to the server to periodically back up each user’s files A network switch connecting each device to the network The client Raspberry Pis that all use the same master image and pull the rest of the data from the server, making it very easy to add more or replace an SD card should it get broken Build a network of Raspberry Pis Learn how to set up a network of Raspberry Pis with centralised authentication and file storage Resources At least 2 Raspberry Pis with appropriate peripherals (Note that the server Raspberry Pi will only need a power and Ethernet cable connected once configured) SD card Computer Network switch Ethernet cable Storage device 112 Raspberry Pi Tips, Tricks & Hacks In this tutorial, we’ll learn to set up a Network Information Services server on a Raspberry Pi that centralises some of the configuration of Linux systems. This includes user accounts. This means that we can set up users on the Raspberry Pi server and have them available on each client Raspberry Pi. This arrangement would be useful in a classroom situation where there were a number of Raspberry Pis shared between classes. Each child would have a username and password, and they would have access to all of their files from any Raspberry Pi once they have logged in. One big advantage of this is that each user’s files can be backed up from a single place. We’ll also be giving some examples of software that could be used in a classroom on the Raspberry Pi. We’ll be using the latest Raspbian image as the operating system for both our Raspberry Pi server and Raspberry Pi clients, so we’ll need to start by writing that to two SD cards. Note that we’ll be making a master SD card for the clients which can then be written to the rest of the SD cards, so only write the image to two of them. The instructions for flashing an image to an SD card can be found at www.linuxuser.co.uk/ tutorials/how-to-set-up-raspberry-pi/. You will only need to go up to the step where you write the image to the SD card. Note that you will have to adapt the instructions slightly for using the latest Raspbian image rather than the Debian one. The image that we used was 2012-09-18wheezy-raspbian.zip. We are going to assume that you are plugging the Raspberry Pis into an existing network with DHCP, a protocol for handing out network settings to devices that connect to said network. This way, they can get access to the internet for installing packages and other useful things such as teaching resources. Tips | Tricks | Hacks the arrows to navigate and start by deleting the line ‘iface eth0 inet dhcp’. Then replace it with lines similar to the following: iface eth0 inet static address netmask gateway 01 Initial configuration of the server Raspberry Pi Connect a keyboard, mouse, Ethernet cable, monitor and, lastly, power to your server Raspberry Pi. Raspbian will boot and a configuration menu will be displayed. You need to select the option to expand_rootfs to make sure that you’re using the entire space of the SD card. You should definitely change the password for the pi user so that no one can log into your server with the standard credentials of Username: pi and Password: raspberry. Then change the memory split to 240MiB for ARM and 16MiB for the VideoCore. Finally, enable SSH, then select ‘Finish’. Select ‘Yes’ to reboot now. 02 Fire up your Linux computer Now that we have enabled SSH on the server Raspberry Pi, we can configure it remotely using SSH as long as your Linux computer is on the same network (if not, connect it now). We might as well make sure that SSH works now for when a monitor is no longer needed. During the boot process of Raspbian, a message will be displayed with the current IP address of the Pi. Open up a terminal on your Linux computer and type ‘ssh pi@ [your Pi’s IP address]’. Type ‘yes’ when asked if you want to connect and then enter the new password that you set. You are now logged into your server Pi. 03 Setting up a static IP address We highly recommend assigning a static IP to your server Raspberry Pi because you, and more importantly the client Raspberry Pis, will always know where to find it on the network. We’ll need to find out a couple of things about your current network setup before setting a static IP. You can use the commands ‘ifconfig eth0’ and ‘ip route show’ to do this. We’ve included the important output from our commands below so that you can see what to do with each value. Now that we have found out things about your network, such as your current IP address, the network mask and so on, we can set up a static IP address. Use the command: sudo nano /etc/network/interfaces …to edit the networking configuration file. Use Make sure that the IP address you assign to your Raspberry Pi server isn’t taken. You’ll want to discuss this with your network administrator if you have one, but it’s usually safe to assume that the address the device had already won’t be taken. You’ll also want to note down that IP address for future usage. Save the changes in nano using the key combination Ctrl+O followed by Enter. You can exit nano using Ctrl+X. You might notice that we haven’t done anything about the DNS server. DNS is used to resolve hostnames such as google.co.uk to an IP address. The IP address of the DNS server is stored in /etc/resolv.conf and will not change value after changing to a static IP address. pi@raspberrypi ~ $ ifconfig eth0 eth0 Link encap:Ethernet HWaddr xx:xx:xx:xx:xx:xx inet addr: Bcast: Mask: pi@raspberrypi ~ $ ip route show default via dev eth0 dev eth0 proto kernel scope link src 04 Restart the server Pi Restart the server Pi so that the networking changes we just made can take place. Log back in using SSH and the new IP address that you chose. 05 Installing the required packages for an NFS server NFS stands for Network File System, and is what we’ll use to share each user’s home directory. Run the command: sudo apt-get update 06 Exporting directories Add the line: /home *(rw,sync) …to the end of /etc/exports using nano. The line means share the /home directory with everyone, permitting read and write access. Although this sounds insecure, other users will only get read access to directories that aren’t their own and therefore won’t be able to delete or change files. NFS requires rpcbind, so you need to start that before NFS. Rpcbind doesn’t start on boot by default on Raspbian, but we want it to. You can do this using the command ‘sudo updaterc.d rpcbind enable’. You can start them both immediately using the following commands: sudo /etc/init.d/rpcbind start sudo /etc/init.d/nfs-kernel-server start 07 Installing NIS 08 Configuring NIS NIS stands for Network Information Services and used to be called Yellow Pages, or yp for short. Many of the services and directories still have ‘yp’ in the name. Use the command ‘sudo apt-get install nis’ to install Network Information Services. Accept any extra packages that may be required. You will now be taken to the package configuration screen for NIS. It will start by asking you to enter an NIS domain. This can be anything you like, but we’re calling ours raspberrypi. Once you have set that, NIS will continue to install and then the NIS services will attempt to start. This will take a few minutes and fail, so don’t worry when that happens. We need to do more configuration before it will work. We need to do a few things before our NIS server will work. The first thing we need to do is open up /etc/default/nis with nano as we do in the usual way. Make sure you prefix the nano command with sudo because we need root privileges to edit each of these files. You need to change the line: NISSERVER=false …to… NISSERVER=master ……to update the package lists on the device, followed by : …and also change the line… sudo apt-get install nfs-kernelserver nfs-common rpcbind …to… …to install the packages required for an NFS server. You’ll probably get a message like ‘[warn] Not starting NFS kernel daemon: no exports.... (warning)’. This is just telling us that the NFS server hasn’t started because we haven’t set it up to share (export) any directories yet. NISCLIENT=true NISCLIENT=false Save the changes and then exit nano. We then need to edit: Raspberry Pi Tips, Tricks & Hacks 113 Tips | Tricks | Hacks required packages for NFS and NIS clients using the command ‘sudo apt-get install nis rpcbind nfs-common’. The NIS domain configuration screen will show as before, so just set this to whatever you set it to the first time. As before, the system will fail to start the NIS because we need to do extra configuration, including setting rpcbind to start at boot using the command ‘sudo update-rc.d rpcbind enable’. We’re going to need rpcbind shortly so we might as well start it now using ‘sudo /etc/init.d/rpcbind start’. 13 /var/yp/Makefile …and change the line… ALL = passwd group hosts rpc services netid protocols netgrp …to… ALL = passwd shadow group hosts rpc services netid protocols netgrp The password file on Linux contains a list of users and information like their home directory and the User & Group IDs. We need to add the shadow file as that file stores password hashes for users. We also need to change the line: MINGID=1000 to MINGID=0 …because we’ll be adding our NIS users to system groups such as audio so that they can play sound. The next step is to change the server’s hostname by editing the /etc/hostname file. We’re going to change our hostname from raspberrypi to nismaster. We then need to change /etc/hosts to complete the hostname change, as well as add an extra line. We need to do this because servers running NIS are added by name rather than their IP address. You’ll see this shortly. Plus, we should be able to differentiate the NIS server from all of the other Raspberry Pis anyway. Change the line: raspberrypi …to… [your new hostname] You’ll also need to add a new line for the IP address of the NIS server in the form: [IP address] [hostname].[NIS domain] [hostname] 09 Initialising the NIS master database Before anything else, restart the Pi using sudo init 6 to let the hostname change take place. Reconnect once the Pi has booted back up. Run the command: sudo /usr/lib/yp/ypinit -m 114 Raspberry Pi Tips, Tricks & Hacks and then press Ctrl + D followed by Enter. We can now start the NIS server using the command: sudo /etc/init.d/nis start 10 Adding a new user All users are added on the NIS server. You can use the command ‘sudo adduser [username]’ to do this, and then fill in the extra information required interactively. The NIS databases are updated automatically after adding a new user. We now need to add the new user to some groups so they can do things like play audio and so on. You can do this with the command ‘sudo usermod -a -G audio,video,plugdev,games,users,netdev, input [username]’. We have now made more changes to the user and will have to rebuild the NIS database manually using: cd /var/yp sudo make You can use the command ‘sudo passwd [username]’ on the NIS server as the pi user to change the password of a user. You will have to rebuild the database again after doing this. 11 Preparing the client We’re pretty much done with the NIS server for now, so it’s time to start working on a client image. Connect up the second Raspberry Pi and insert the SD card with the fresh Raspbian image on. Raspi-config will show as it did when we configured the server. The only option you need to use is the one to expand_rootfs and then select ‘Finish’. Select ‘Yes’ to reboot now. 12 Logging in and installing required packages Log in with the standard credentials of Username: pi and Password: raspberry and then run the command ‘sudo apt-get update’ to update the package list on the device. Install the Mounting the server’s home directory It’s now time to mount the server’s home directory as our own. We want to do this at every boot, so we’ll put an entry in /etc/fstab to make it permanent. Open /etc/fstab in nano and add a line in the following format to the end of the file: [server ip]:/home /home nfs defaults 0 0 You can now save the changes and use the command ‘sudo mount -a’ to mount each entry in the /etc/fstab file, therefore mounting the servers home directory as the clients. If you run ‘ls /home’ you’ll see the home directory of the test user we created before and also the pi user on the server. pi@raspberrypi /home $ cat /etc/ fstab proc /proc proc defaults 0 0 /dev/mmcblk0p1 /boot vfat defaults 0 2 /dev/mmcblk0p2 / ext4 defaults,noatime 0 1 # a swapfile is not a swap partition, so no using swapon|off from here on, use dphys-swapfile swap[on|off] for that /home nfs defaults 0 0 pi@raspberrypi /home $ ls /home pi testuser1 14 Becoming an NIS client You need to open up /etc/yp.conf in nano (remember to use sudo) and add the lines: ypserver [server ip address] domain [nis domain] server [server hostname] You also need to edit the /etc/nsswitch.conf file to look like ours. Once you’ve done that, you can reboot the client using the command ‘sudo init 6’. Tips | Tricks | Hacks Linux has lots of educational software, ideal for the classroom 15 Log in with a user from the NIS server Wait for the client to boot up and then try to log in with the pi user. Remember we didn’t change the password of the pi user when we set up the client? We are now going to be logging in with the pi user from the server, so the password will be different. The nice thing about this is that the Pi is still operable with the standard credentials when there is no network cable connected or the server is down. However, it will complain a lot during the boot process and still won’t be able to access the home directory on the server. 16 Installing packages on the client Linux has a bunch of fantastic educational software that would be ideal for use in a classroom. We’re going to recommend a few programs that would be good to include on the master client image. There is already a pretty good collection that comes with the base Raspbian image, but we can definitely add more. We’re going to install the following software: AbiWord – A basic word processor Gnumeric – A basic spreadsheet program GCompris – Bundle of children’s educational software packages Galculator – Scientific calculator TuxMath – Maths tutor for kids Tux Paint – Children’s drawing program You can install all of this software at once using ‘sudo apt-get install abiword gnumeric gcompris galculator tuxmath tuxpaint’. This may take a while. Once it’s finished, you can type ‘startx’ to load the LXDE desktop environment and have a play around everything on there. Have a go at logging in as the test user also. One problem will be that there are no desktop icons because they are only set for the pi user. The programs will still be there in the start menu anyway. When logging out, the users need to log out of LXDE so that they go back to the console and then type ‘logout’. 17 Duplicating the card Before continuing, shut down the client Pi by switching to the pi user using ‘su pi’ and then typing ‘sudo init 0’. Everything on Linux is seen as a file. Because of this, we can simply use a combination of the cat command and pipes to duplicate the SD card. Switch to the root user on your Linux computer using the command ‘su root’. Use the output of ‘fdisk -l | grep Disk’ to find the path of the SD card. Ours is /dev/ mmcblk0. You can back up the card using the command ‘cat /dev/mmcblk0 > nisclient.img’ and restore the backup to a different card using ‘cat nisclient.img > /dev/mmcblk0’ once you have taken the original card out. 18 Preparing a disk to be used as a backup area 19 Backing up the server The instructions for preparing an external disk to be used as a backup area can be found here: www.linuxuser.co.uk/features/build-a-fileserver-with-the-raspberry-pi. Use steps 09 to 11 to do this. One of the main advantages to having central file storage is that everything can be backed up from one place. More importantly, files that are deleted can be restored. We’ll be using rsync to perform the backups, so you’ll need to install that using the command ‘sudo apt-get install rsync’. We’re going to assume that you’ve set up your backup area in /mnt/data. We’ll be using the command sudo rsync -avP /home /mnt/data to perform the backups. The switches mean the following: a – preserve the permissions and other properties of the file v – show verbose output P – show progress This command syncs any changes from /home to /mnt/data, but will not get rid of any files that are deleted from the /home directory. Rsync is very efficient: only the changes made to a file are copied over, rather than a new file. We want to run this command regularly, say once an hour or so, so we’ll add it to cron. Cron is a daemon that runs commands at specific intervals according to each user’s crontab. You can edit the pi user’s crontab using the command ‘crontab -e’. Add the following line to the end of the crontab file: 0 * * * * ‘sudo rsync -avP /home / mnt/data’ The crontab file takes lines in the format: minutes hours day-of-month month day-ofweek. The above line tells the cron daemon to run the command in at the start of each hour. Save the changes as you usually would in nano. 20 That’s it! With the project complete, you now have a central authentication and file storage area that gets backed up, as well as a master image for the client Raspberry Pis that is filled with useful software. Now you can start enjoying your network of Raspberry Pis!! Raspberry Pi Tips, Tricks & Hacks 115 Tips | Tricks | Hacks Add gesture control to your Raspberry Pi Hover is an impressive add-on board for your Raspberry Pi that allows you to easily add touch and gesture control to any project What you’ll need Q Raspberry Pi Q Hover Q Breadboard Q Male to female jumper cables Q Speaker or headphones 116 Raspberry Pi Tips, Tricks, & Hacks People often ask what the best way is for them to get started with Raspberry Pi. Obviously this does depend on the individual user and what they want to achieve and get out of any project, but in a more general sense it’s often the hardware projects that win out for getting to grips with it. They teach a variety of skills (including programming, circuit building, soldering, hardware design and much more) and are also varied enough to both keep beginners interested and allow them to work out for themselves exactly what aspect they love best. Even a seasoned professional will get a serious kick out of a bit of physical computing and automation! This is one of the unique features of the Pi compared to traditional “black box” computers; you can break out of the usual boundaries and interface with everyday objects like never before. One of the most important aspects of a hardware project is often the user input mechanism, and as technology is refined we see new and more intuitive ways to accomplish this task. Gesture and touch control is now present in a large number of consumer devices and even the biggest technophobes are starting to embrace the ease of this technology. It is time to bring your Raspberry Pi projects into the 21st century with Hover! Tips | Tricks | Hacks The physical pins you should be using on the Raspberry Pi are 1, 3, 5, 6, 16 and 18 01 Plenty of platforms Get the gear! The Hover add on board is available to purchase direct from Hover (http://www.hoverlabs.co/#shop) for $39 (£25), however this will ship from Northern America and therefore if you are based in the UK or Europe it will likely be quicker and cheaper to order from one of the other retailers listed via the above link. The added benefit of ordering from a retailer is that if you need any of the other items you can likely get those at the same time! Hover will work perfectly with any Raspberry Pi, including both the new plus versions and the older models – just make sure your system is fully up to date with: sudo apt-get update sudo apt-get upgrade 02 Above You can tap the Hover or swipe in four directions just above it Update GPIO and I2C When making use of GPIO and I2C (or any other interfacing technique on the Raspberry Pi) it is always good practice to update to the very latest software versions possible. Newer versions typically have bug fixes and additional futures which can come in very handy. GPIO and the RPi.GPIO Python library are installed by default on Raspbian, but you may need to enable I2C if you haven’t already. This is a fairly standard process and has been covered many times so we won’t go into it here. We would, however, highly recommend the brilliant I2C setup tutorial from Adafruit (https://learn.adafruit.com/adafruits-raspberrypi-lesson-4-gpio-setup/configuring-i2c). 03 Set up the hardware 04 Check the connection Make sure your Raspberry Pi is powered down and not connected to power before starting this step, to avoid any unnecessary damage to your Raspberry Pi. Pick up your Hover, breadboard and wires and connect the as shown in the Fritzing diagram. The physical pins you should be using on the Raspberry Pi are 1, 3, 5, 6, 16 and 18. Whilst a Model B Pi is shown, this will be the same connection on a Model A, B, A+ or B+ of any revision. Once completely set up like the image, reconnect the power cord and open an LXTerminal session. Hover connects to the Raspberry Pi through the I2C interface located on the main 26 or 40 pin GPIO bank (depending on which version of the Raspberry Pi you are using). There is a very easy way to check if your Raspberry Pi is correctly connected to Hover using the simple command line I2C tools. Issue the following command: sudo i2cdetect -y 1 If you see 42 in the response then you are successfully connected to Hover! The Hover board has intelligent onboard level shifting, meaning that it can be used with either 3.3V or 5V logic levels which means it can be used with pretty much any microcontroller your heart desires. There are connection examples and code snippets available for Arduino, Sparkcore and PCduino on the Hover website (hoverlabs.com) and these can also be adapted to suit other devices fairly easily. If you decide to create your own example with another device then why not submit a pull request to the Hover GitHub (github.com/ jonco91) if you are happy to share! Raspberry Pi Tips, Tricks, & Hacks 117 Tips | Tricks | Hacks 06 Above This MGC3130 chip works as the 3D tracking and gesture controller Now you have everything hooked up correctly and your Raspberry Pi is fully up to date, it is time to get the Hover Python library, which makes using the board from Python scripts extremely easy. You can get this using the following command: git clone https://github.com/jonco91/hover_ raspberrypi.git Why Python? Python is extremely useful for beginners due to its easy-tounderstand syntax, fairly prose-like formation and the flexibility and ease of acquiring existing software libraries to help your projects. It is also the official programming language of the Raspberry Pi and is therefore very well supported within the community. That is not to say that Hover will not work with other programming languages; simply that the creators of Hover have not yet released any code libraries in other languages. Download the sample code 05 Using a Rev 1 Pi? In the code, we have passed an option “-y 1” which tells the operating system which I2C bus to look at (there are two on the BCM2835 processor on the Pi). The first revision Raspberry Pi (the one that initially launched in February 2012 with 256MB of RAM) made use of I2C bus 0, whereas all other versions of the Raspberry Pi since have used I2C bus 1. So the above code would change to: sudo i2cdetect -y 0 And you should expect the same output (42) as in step 7. Additionally you will need to edit line 27 of the Hover_library. py file, changing bus = smbus.SMBus(1) to bus = smbus. SMBus(0). A patch that automatically detects the Raspberry Pi version and makes this change for you has been submitted, but not yet accepted into the master branch so this may not be necessary in future versions. 118 Raspberry Pi Tips, Tricks, & Hacks This should download a folder called hover_raspberrypi to your /home/pi directory containing all of the files needed for this article. Alternatively you can download the zip file from https://github.com/jonco91/hover_raspberrypi/archive/ master.zip. 07 Run the example file The current Hover library is simply a Python file with all of the necessary functions included within it, rather than an installable package (however, this may change in the future). In order to use the functions contained within the Hover_library.py script discussed above, it is therefore necessary to make sure that the Hover_library.py script is located in the same folder as any script you have written that makes use of any of the Hover functions. In a terminal session, navigate to the folder containing the Hover_example.py file and run it using: sudo python Hover_example.py The Hover board will initialise and you will then see a message “Hover is ready”, meaning you are good to go. Tips | Tricks | Hacks 08 Investigate the output Once you have completed step 7, if you touch the Hover board or make gestures above it you will begin to see output in the terminal which is a bunch of 0s and 1s and then a description of what it has seen – right swipe, north tap, etc. The way the Hover works is that it can sense any one of nine different actions and these are sent to the Raspberry Pi over I2C as an 8-bit binary value. The first three bits describe whether it was a touch or gesture event and the remaining five bits describe the specific type or direction of the event. The exact breakdown can be seen in the code listing to the right. 09 Full code listing import time from Hover_library import Hover hover = Hover(address=0x42, ts=23, reset=24) try: while True: Enable 3.5mm audio # Check if hover is ready to send gesture # or touch events if (hover.getStatus() == 0): # Read i2c data and print the type of # gesture or touch event message = hover.getEvent() type(message) if (message == “01000010”): # code for west touch goes here elif (message == “01010000”): # code for centre touch goes here elif (message == “01001000”): # code for east touch goes here elif (message == “01000001”): # code for south touch goes here elif (message == “01000100”): # code for north touch goes here elif (message == “00100010”): # code for swipe right goes here elif (message == “00100100”): # code for swipe left goes here elif (message == “00110000”): # code for swipe down goes here elif (message == “00101000”): # code for swipe up goes here Grab your speakers and plug them in to the 3.5mm jack plug on the Raspberry Pi. You will then need to route audio to the 3.5mm jack using the following command (you can skip this step if you are using an HDMI display, which has in-built audio): sudo amixer cset numid=3 1 10 Make a drum machine In the hover_raspberrypi folder is another folder called examples that contains code and sounds to turn Hover into a drum machine! Navigate to the hover_raspberrypi directory and then copy the Hover_library.py file into the examples folder by using: # Release the ts pin until Hover is # ready to send the next event hover.setRelease() time.sleep(0.0008) #sleep for 1ms cp Hover_library.py examples You can then move into the examples folder and run the Hover_ drum.py file using: cd examples sudo python Hover_drum.py Make some gestures and taps on and around Hover and you will have your own basic drum machine! 11 Create your own responses The great thing about having a Python library available is that it is easy to integrate this device into any of your existing or future projects. The code shown is all you need to get started with Hover. You will see that on line 15 and onwards there are comments saying “code for … goes here”. Essentially all you need to do is insert the actions you want to occur on the particular event mentioned in the comment and you will be up and running… it really is that easy! except KeyboardInterrupt: print “Exiting...” hover.end() except: print “Something has gone wrong...” hover.end() 12 Other project ideas Most of you are probably now wracking your brains for projects you could use Hover in, but let’s face it – pretty much any project that requires physical interaction would be made better with touch and gesture control. If you think it is cool but are lacking inspiration, we recommend looking at the projects section of the Hover website at http://www.hoverlabs. co/projects, where there are projects by the creators and community alike. If you make something cool, be sure to send us the pictures! Where are the hoverboards? Did you come here looking for information on how to build your space age transportation device? We can’t help you with that, but we don’t want to leave you disappointed! Hoverboards were first popularised as a fictional personal transportation method in the 1989 film Back To The Future Part II and took the appearance of a levitating skateboard with no wheels. 25 years later and it seems we might be getting close to turning this dream into a reality. Hendo Hoverboards have created a $10,000 hoverboard which uses a principle similar to that of maglev trains to generate lift (kck.st/ZMd9AA), and more recently Ryan Craven has created a much cheaper alternative using four leaf blowers and some other cheap parts (mrhoverboard. com/about). Raspberry Pi Tips, Tricks, & Hacks 119 Tips | Tricks | Hacks Make a digital photo frame Take your Raspberry Pi, HDMIPi and Screenly and turn them into a beautiful digital photo frame What you’ll need Q Raspberry Pi Model B Q HDMIPi kit Q Class 10 SD Card Q 5.25V Micro USB power supply Q USB keyboard Q Wi-Fi dongle Q Internet connection 120 Raspberry Pi Tips, Tricks & Hacks Digital signage is a huge market in modern times, and increasingly we are seeing digital advertising in the public space – be it on street billboards, shopping centres and even in some city taxis. Screenly is an exciting piece of software from Wireload Inc that has set out to reduce the barriers to entry of the digital signage market by employing a Raspberry Pi as its main hardware component for the individual signage nodes. With the powerful VideoCore IV graphics processor at the heart of the Pi and its low electrical power consumption, using it as a digital signage platform is a no-brainer. Our expert has been using Screenly a lot recently for some projects and it truly is a really great piece of software. He was also one of the first backers of HDMIPi on Kickstarter, and when his reward arrived recently it occurred to him that, together with Screenly, it would make the perfect home-brew digital photo frame and another great Raspberry Pi-based hardware project. In this tutorial, we will show you how to assemble this powerful hardware/software combination for yourself. 01 Order your items If you haven’t already got them in your Raspberry Pi collection, you will need to order all of the items from the “What you’ll need” list. The HDMIPi is currently only compatible with Model B of the Raspberry Pi, although a Model B+ version is in the works (the B+ does actually work with HDMIPi, but unfortunately cannot fit into the case). Pretty much any USB keyboard will work with Screenly, including wireless ones, so you do not need to worry about a mouse for this tutorial as it will all be done from the command line. Finally, a speaker is only necessary if you intend to play videos from the display with sound as well. Tips | Tricks | Hacks 02 Assemble your HDMIPi Above The reverse view of HDMIPi, showing GPIO and connector cutouts The HDMIPi comes as a do-it-yourself kit rather than a polished product. Not only does this make it cheaper for you to buy, but it also gives it a more hack-like feel in its Pibowesque acrylic layer case. It is not hard to assemble, but in case you get stuck there is a fantastic assembly video here: http://hdmipi.com/instructions. 03 Download Screenly OSE Now that you have the hardware all ready to go we need to download the Screenly OSE SD card image. This is only a 3.7GB image file, however it may not fit on some 4GB SD cards so we would recommend a minimum of 8GB, for extra space for all your pictures and videos. Visit bit.ly/1wLKIRQ and download the ZIP file from one of the mirrors under the “Getting started” heading. 04 Flash image to SD Card (Linux) It’s worth noting the value of having a Linux machine at your disposal (or a spare Raspberry Pi and SD card reader) to download the ZIP file in Step 03. This is typically the easiest way to unzip the file and copy the image across to your SD card. Assuming the disk isn’t mounted, open a terminal session and type: unzip -p /path/to/screenly_image.zip | sudo dd bs=1M of=/dev/sdX Make sure that you replace /path/to/screenly_image.zip with the actual path. History of HDMIPi 05 Flash image to SD Card (Other OS) 06 Insert SD card and peripherals 07 Boot up your Raspberry Pi If you do not have another Linux machine handy, or a card reader for your Raspberry Pi, you can still do this from other popular operating systems. On Windows you should use Win32 Disk Imager and follow the easy to use GUI. From Mac OS X you have the options of using the GUI-based software packages PiWriter and Pi Filler, or running some code from the command line. Visit www.screenlyapp.com/setup.html for more info. Once the Screenly image has been successfully transferred to your SD card, you will need to insert it into the Raspberry Pi within your HDMIPi casing. It is a good idea to connect your Wi-Fi dongle and keyboard at this point. Take a look at the image at the top of this page to see where the slots are in relation to the casing. A wired network is also required for the initial setup and for configuring the Wi-Fi connection. The HDMIPi driver board has a power output for the Raspberry Pi which means you only need one power supply for this setup. Plug it in and wait for it to boot into the Screenly splash screen. An IP address (of format http://aaa.bbb.ccc.ddd:8080) should be displayed here, which will allow you to gain access to the management dashboard. HDMIPi is a collaboration between Cyntech and Alex Eames from RasPi.TV. They wanted to bring a cheap HD resolution HDMI screen to the market that will reduce the cost of having a dedicated monitor for your Raspberry Pi. They took to Kickstarter to launch their idea (kck.st/17zyaQg) and there was a huge response to this project from both within and outside the Raspberry Pi community. Over 2,500 people from all over the world enabled them to smash their £55,000 target, and the campaign finished with over £260,000. UNICEF even thought they were good enough to use in their educational projects in Lebanon (bit.ly/ZDpO8Z). Raspberry Pi Tips, Tricks & Hacks 121 Tips | Tricks | Hacks Above Screenly Pro can manage multiple screens and has cloud storage too Screenly Pro Edition In this tutorial we have used the open source version of Screenly – Screenly OSE. This is a fantastic bit of software and a great addition to the open source ecosystem. At this point, some of you may be dreaming of huge remotemanaged display screen networks and the good news is that this is entirely possible with Screenly Pro. This is completely free for a single display screen and 2GB of storage, and it has larger packages for purchase starting at two screens right up to 130+ screens. It also adds a lot of additional features not seen in Screenly OSE – find out more about those on the Screenly website (bit.ly/1EXl92p). 08 Disable Screenly video output Load the IP displayed on the splash screen on the browser of a different computer (you won’t be able to do it directly from the same Pi). The Screenly OSE dashboard should now load. Once inside the dashboard, move the slider for Big Buck Bunny to the OFF position or delete the asset entirely. 09 Enter the command line Once you have disabled the Big Buck Bunny trailer from the web interface, you should now be able to enter the command line easily and you can do this by pressing Ctrl+Alt+F1 on the attached keyboard at any time. Alternatively, you can access the command line over SSH using the same IP address as shown previously on the splash screen. 10 Run the update script The image file we downloaded from the website is actually just a snapshot release and does not necessarily include the latest Screenly OSE code, as the code updates are made more regularly than the image. It is therefore good practice to run an upgrade to the latest version using the built-in script. You can run the following command: ~/screenly/misc/run_upgrade.sh 122 Raspberry Pi Tips, Tricks & Hacks 11 Configure Raspberry Pi 12 Enable and set up Wi-Fi Once you are successfully at the command line, you need to type sudo raspi-config to enter the settings and then select ‘1 Expand root file system’ to make sure you have access to all of the space on the SD card. Then, change the time zone (option 4 and then 12) so that it is correct for your location. If your screen has black borders around the edge you may also need to disable overscan (option 8 and then A1). We would also recommend changing the default password to something other than raspberry to stop any would-be hackers from easily accessing the Raspberry Pi via SSH (option 2). Once complete, exit without restarting by selecting Finish and then No. As Screenly runs on top of Raspbian, the Wi-Fi setup is essentially the same as the standard command line setup within the OS. In order to do this you need to edit the interfaces file using sudo nano /etc/network/interfaces and then type in the following code, replacing ssid and password with the actual values: auto lo iface lo inet loopback iface eth0 inet dhcp allow-hotplug wlan0 auto wlan0 iface wlan0 inet dhcp wpa-ssid “ssid” wpa-psk “password” iface default inet dhcp Then exit and save by hitting Ctrl+X, then Y and then Return. Tips | Tricks | Hacks 13 Test the connection The easiest way to test the Wi-Fi connection is to shut down the Raspberry Pi using sudo shutdown -h now and then remove the wired network connection and reboot the Raspberry Pi by removing and reattaching the microUSB power connector. If the Wi-Fi connection has worked, you should now see the splash screen with IP address again. Access Screenly from afar Above Once fully configured, load your pictures and video to complete your digital photo frame! 15 Test with video and more 16 Place in situ and enjoy! 17 Other project ideas Pictures are great, but Screenly also allows you to display videos (with audio if you wish) and web pages, which really is a huge benefit. This is perfect if you want to enhance your digital photo frame even further or perhaps display the local weather and news to keep yourself informed. Plug in your speaker – we would recommend The Pi Hut portable mini speaker (available from bit.ly/1xEpBNZ) or anything similar. 14 Upload pictures to Screenly Once again, you will need to visit the Screenly OSE web interface by entering the IP address into another computer. Since you are now using a wireless connection, the IP address may be different to the previous one. You need to select the ‘Add Asset’ option at the top right-hand side, which should launch a pop-up options screen. Select Image from the dropdown box and you then have the option of either uploading the image or grabbing it from a URL using the corresponding tabs. Enter the start date and end date of when this image should appear, and how long it should appear on screen for, then press Save. Repeat this step for each of the pictures. Once you have got Screenly all set up and loaded all of your favourite pictures and videos onto it via the web interface, it is now time to enjoy the fruits of your labour! Mould the spider stand (if you have one) into shape by taking the middle two legs at the top and bending them downwards and backwards. Then spread the front-middle legs a bit wider to give a good base and shape the outer legs at the top and bottom to support the screen. You are then ready to give it its permanent home – our expert’s is on the mantelpiece over the fireplace! In this tutorial we have looked at just one fairly basic application of Screenly and the HDMIPi. You could use this powerful open source software to run your digital signage empire, share screens in schools and clubs, or as a personal dashboard using a suitable web page. Whatever you make, please don’t forget to take pictures and send them to us! The default Screenly image is essentially some additional software running on top of Raspbian OS. This means that SSH is enabled by default (it’s why we changed the default password in Step 11) so it’s now possible to access the command line, as well as the Screenly dashboard, from outside of your LAN. We recommend setting a static IP for your Screenlypowered Raspi from your router settings and then setting up SSH with keys on your Pi, and port forwarding on your router for ports 22 and 8080. The Screenly dashboard has no login so anyone can access it, but an authentication feature is imminent. Raspberry Pi Tips, Tricks & Hacks 123 Tips | Tricks | Hacks LIVES SCORE BREAKOUT 0001200 Pygame Zero cuts out the boilerplate to turn your ideas into games instantly, and we’ll show you how Games are a great way of understanding a language: you have a goal to work towards, and each feature you add brings more fun. However, games need libraries and modules for graphics and other essential games features. While the Pygame library made it relatively easy to make games in Python, it still brings in boilerplate code that you need before you get started – barriers to you or your kids getting started in coding. Pygame Zero deals with all of this boilerplate code for you, aiming to get you coding games instantly. Pg0 (as we’ll abbreviate it) makes sensible assumptions about what you’ll need for a game – from the size of the window to importing the game library – so that you can get straight down to coding your ideas. 124 Raspberry Pi Tips, Tricks & Hacks Pg0’s creator, Daniel Pope, told us that the library “grew out of talking to teachers at Pycon UK’s education track, and trying to understand that they need to get immediate results and break lessons into bite-size fragments, in order to keep a whole class up to speed.” To give you an idea of what’s involved, we’ll build up a simple game from a Pong-type bat and ball through to smashing blocks Breakout-style. The project will illustrate what can be done with very little effort. Pg0 is in early development but still offers a great start – and is now included on the Pi in the Raspbian Jessie image. We’ll look at installation on other platforms, but first let’s see what magic it can perform. What you’ll need Q Pygame Zero pygame-zero.readthedocs.org Q Pygame pygame.org Q Pip pip-installer.org Q Python 3.2 or later python.org Tips | Tricks | Hacks Full code FileSilo.c o.uk Right Breakout is a classic arcade game that can be reimagined in Pygame Zero Pygame Zero deals with all of this boilerplate code for you, aiming to get you coding games instantly Young and old In situations where Pygame is used boilerplate and all with young people, great results can also be achieved (see Bryson Payne’s book), but Pygame and Pg0, despite their use as powerful educational tools, are also good for creating games for coders no matter what stage of learning they are at. Great games are all about the gameplay, driven by powerful imaginations generating images, animations, sounds and journeys through game worlds. Good frameworks open up this creative activity to people who are not traditional learners of programming, which is an area where Python has long excelled. 01 Zero effort Although game writing is not easy, getting started certainly is. If you’ve got Raspbian Jessie installed on your Pi, you’re ready to go. Open a terminal and type: 04 No Pi? 05 Intro.py You don’t even need a Raspberry Pi to install Pygame Zero – just install the Pygame library, then use pip to install Pygame Zero. Instructions vary by distro, but a good place to start is the documentation: bit.ly/1GYznUB. touch example.py pgzrun example.py And you’ll see an empty game window open (Ctrl+Q will close the window). Yes, it’s that easy to get started! 02 Python 3 If you haven’t got Raspbian Jessie, chances are you’ll have neither Pg0 nor Pygame installed. The Python’s pip package installer will take care of grabbing Pg0 for you, but the preceding steps vary by distro. One thing you will need is Python 3.2 (or newer). If you’ve been sticking with Python 2.x in your coding (perhaps because it’s used in a tutorial you’re following), make Pg0 your chance for a gentle upgrade to Python 3. 03 Older Raspbian If you’re still running Raspbian Wheezy, you’ll need to run the following steps to install Pygame Zero: sudo apt-get update sudo apt-get install python3-setuptools python3-pip sudo pip-3.2 install pgzero That default black square of 800 by 600 pixels we saw in Step 1 can be overridden manually. For example, we can replace it with an oversized gold brick, in a nod to Breakout: WIDTH = 1000 HEIGHT = 100 def draw(): screen.fill((205, 130, 0)) That colour tuple takes RGB values, so you can quickly get colours off a cheatsheet; screen is built into Pg0 for the window display, with methods available for all sorts of different sprites… Raspberry Pi Tips, Tricks & Hacks 125 Tips | Tricks | Hacks Right The bat and ball come first – they’re the cornerstones of Pong and Breakout 08 You can think of Breakout as essentially being a moving bat – that is, you’re hitting a moving ball in order to knock out blocks. The bat is a rectangle, and Pygame’s Rect objects store and manipulate rectangular areas – we use Rect((left, top), (width, height)), before which we define the bat colour and then call upon the draw function to put the bat on the screen, using the screen function. Object orientation David Ames, who uses Pg0 to teach younger children to code at events across the UK, told us: “One thing to avoid when it comes to teaching kids is Object Orientation.” OOP (object-oriented programming) is partly abstracted away by Pg0, but it can’t be ignored. Perhaps the best approach is using Pg0 and some simple code to start, then dropping in a piece of OO when it’s needed to solve a particular problem. With the Code Club age group – about eight to eleven – feeding information to solve practical problems works well. It can work with adults, too – but there’s always someone who’s read ahead and has a few tricky questions. Batty 06 Sprite The intro example from the Pg0 docs expands on that with the Actor class, which will automatically load the named sprite (Pg0 will hunt around for a .jpg or .png in a subdirectory called images). W = H = RED bat def 800 600 = 200, 0, 0 = Rect((W/2, 0.96 * H), (150, 15)) draw(): screen.clear() screen.draw.filled_rect(bat, RED) alien = Actor(‘alien’) alien.pos = 100, 56 WIDTH = 500 HEIGHT = alien.height + 20 def draw(): screen.clear() alien.draw() You can download the alien from the Pg0 documentation (bit. ly/1Sm5lM7) and try out the animation shown there, but we’re taking a different approach in our game. 07 Breakout via Pong While the Pi is something of a tribute to 1980s 8-bit computers, Breakout comes from the 1970s and is a direct descendant of the early arcade classic Pong. We’ll follow the route from Pong to Breakout (which historically involved Apple founders Steve Wozniak and Steve Jobs) in the steps to creating our code, leaving you with the option of developing the Pong elements into a proper game, as well as refining the finished Breakout clone. 126 Raspberry Pi Tips, Tricks & Hacks 09 Mouse move We want to move the bat, and the mouse is closer to an arcade paddle than the arrow keys. Add the following: def on_mouse_move(pos): x, y = pos bat.center = (x, bat.center[1]) Use pgzrun to test that you have a screen, bat and movement. Tips | Tricks | Hacks 10 Square ball In properly retro graphics-style, we define a square ball too – another rectangle, essentially, with the (30, 30) size making it that subset of rectangles that we call a square. We’re doing this because Rect is another built-in in Pg0. If we wanted a circular ball, we’d have to define a class and then use Pygame’s draw.filled_circle(pos, radius, (r, g, b)) - but Rect we can call directly. Simply add: WHITE = 200,200,200 ball = Rect((W/2, H/2), (30, 30)) … to the initial variable assignments, and: screen.draw.filled_rect(ball, WHITE) … to the def draw() block. To get the ball to move we need to define move(ball) for each case where the ball meets a wall Full code listing ## ## ## ## Breakout type game to demonstrate Pygame Zero library Based originally upon Tim Viner’s London Python Dojo demonstration Licensed under MIT License - see file COPYING from collections import namedtuple import pygame import sys import time W = 804 H = 600 RED = 200, 0, 0 WHITE = 200,200,200 GOLD = 205,145,0 11 Action! Now let’s make the ball move. Download the tutorial resources in FileSilo.co.uk and then add the code inside the ‘move.py’ file to assign movement and velocity. Change the 5 in ball_dir = Direction(5, -5) if you want the ball slower or faster, as your processor (and dexterity) demands – but it’s hard to tell now because the ball goes straight off the screen! Pg0 will call the update() function you define once per frame, giving the illusion of smooth(ish) scrolling if you’re not running much else. 12 def move(ball) To get the ball to move within the screen we need to define move(ball) for each case where the ball meets a wall. For this we use if statements to reverse the ball’s direction at each of the boundaries. Refer to the full code listing on page 67. Note the hardcoded value of 781 for the width of screen, minus the width of ball – it’s okay to hardcode values in early versions of code, but it’s the kind of thing that will need changing if your project expands. For example, a resizable screen would need a value of W - 30. 13 Absolute values You might expect multiplying y by minus one to work for reversing the direction of the ball when it hits the bat: ball_dir = Direction(ball_dir.x, -1 * ball_dir.y) … but you actually need to use abs, which removes any minus signs, then minus: ball = Rect((W/2, H/2), (30, 30)) Direction = namedtuple(‘Direction’, ‘x y’) ball_dir = Direction(5, -5) bat = Rect((W/2, 0.96 * H), (120, 15)) class Block(Rect): def __init__(self, colour, rect): Rect.__init__(self, rect) self.colour = colour blocks = [] for n_block in range(24): block = Block(GOLD, ((((n_block % 8)* 100) + 2, ((n_block // 8) * 25) + 2), (96, 23))) blocks.append(block) def draw_blocks(): for block in blocks: screen.draw.filled_rect(block, block.colour) def draw(): screen.clear() screen.draw.filled_rect(ball, WHITE) screen.draw.filled_rect(bat, RED) draw_blocks() def on_mouse_move(pos): x, y = pos bat.center = (x, bat.center[1]) ball_dir = Direction(ball_dir.x, - abs(ball_dir.y)) Try it without in the finished code and see if you get some strange behaviour. Your homework is to work out why. def on_mouse_down(): global ball_dir ball_dir = Direction(ball_dir.x * 1.5, ball_dir.y * 1.5) Raspberry Pi Tips, Tricks & Hacks 127 Tips | Tricks | Hacks Right Tom Viner’s array of blocks negates the need for bordered rectangles 14 Sounds Also upon bat collision, sounds.blip.play() looks in the sounds subdirectory for a sound file called blip. You can download the sounds (and finished code) from FileSilo.co.uk. Actually, now we think about it, ignore the previous comment about homework – your real homework is to turn what we’ve written so far into a proper game of Pong! But first let’s finish turning it into Breakout! Pg0 +1 There’s a new version of Pg0 in development – it may even be out as you read this. Pg0 creator Daniel Pope tells us “a tone generation API is in the works,” and that at the Pg0 PyConUK sprint, “we finished Actor rotation.” Contributions are welcome – not only to the Pg0 code, but more examples are needed not just to show what can be done, but to give teachers tools to enthuse children about the creative act of programming. Pg0 has also inspired GPIO Zero, to make GPIO programming easier on the Raspberry Pi, with rapid development occurring on this new library as we go to press. 15 Blockhead! If you’re not very familiar with the ancient computer game Breakout, then: apt-get install lbreakout2 … and have a play. Now, we haven’t set our sights on building something quite so ambitious in just these six pages, but we do need blocks. 16 Building blocks There are many ways of defining blocks and distributing them onto the screen. In Tom Viner’s team’s version, from the London Python Dojo – which was the code that originally inspired this author to give this a go – the blocks are sized in relation to number across the screen, thus: N_BLOCKS = 8 BLOCK_W = W / N_BLOCKS BLOCK_H = BLOCK_W / 4 BLOCK_COLOURS = RED, GREEN, BLUE Using multicoloured blocks which are then built into an array means that blocks can join without needing a border. With its defining variables in terms of screen width, it’s good sustainable code, which will be easy to amend for different screen sizes – see github.com/tomviner/breakout. However, the array of colour bricks in a single row is not enough for a full game screen, so we’re going to build our array from hard-coded values… 128 Raspberry Pi Tips, Tricks & Hacks 17 Going for gold Create a Block class: class Block(Rect): def __init__(self, colour, rect): Rect.__init__(self, rect) self.colour = colour … and pick a nice colour for your blocks: GOLD = 205,145,0 18 Line up the blocks This builds an array of 24 blocks, three rows of eight: blocks = [] for n_block in range(24): block = Block(GOLD, ((((n_block % 8)* 100) + 2, ((n_block // 8) * 25) + 2), (96, 23))) blocks.append(block) 19 Drawing blocks Draw_blocks() is added to def draw() after defining: def draw_blocks(): for block in blocks: screen.draw.filled_rect(block, block.colour) 20 Block bashing All that remains with the blocks is to expand def move(ball) – to destroy a block when the ball hits it. to_kill = ball.collidelist(blocks) if to_kill >= 0: sounds.block.play() ball_dir = Direction(ball_dir.x, abs(ball_dir.y)) blocks.pop(to_kill) Tips | Tricks | Hacks Left Test your game once it’s finished – then test other people’s Breakout games to see how the code differs 21 Game over Lastly, we need to allow for the possibility of successfully destroying all blocks. if not blocks: sounds.win.play() sounds.win.play() print(“Winner!”) time.sleep(1) sys.exit() 22 Score draw Taking advantage of some of Pygame Zero’s quickstart features, we’ve a working game in around 60 lines of code. From here, there’s more Pg0 to explore, but a look into Pygame unmediated by the Pg0 wrapper is your next step but one. First refactor the code; there’s plenty of room for improvement – see the example ‘breakout-refactored. py’ in your tutorial resources. Try adding scoring, the most significant absence in the game. You could try using a global variable and writing the score to the terminal with print(), or instead use screen.blit to put it on the game screen. Future versions of Pg0 might do more for easy score keeping. 23 Class of nine lives For adding lives, more layers, and an easier lifekeeping score, you may be better defining the class GameClass and enclosing much of the changes you wish to persist within it, such as self.score and self.level. You’ll find a lot of Pygame code online doing this, but you can also find Pg0 examples, such as the excellent pi_lander example by Tim Martin: github.com/timboe/pi_lander. 24 Don’t stop here This piece is aimed at beginners, so don’t expect to understand everything! Change the code and see what works, borrow code from elsewhere to add in, and read even more code. Keep doing that, then try a project of your own – and let us know how you get on. Full code listing (cont.) def move(ball): global ball_dir ball.move_ip(ball_dir) if ball.x > 781 or ball.x <= 0: ball_dir = Direction(-1 * ball_dir.x, ball_dir.y) if ball.y <= 0: ball_dir = Direction(ball_dir.x, abs(ball_dir.y)) if ball.colliderect(bat): sounds.blip.play() ball_dir = Direction(ball_dir.x, - abs(ball_dir.y)) to_kill = ball.collidelist(blocks) if to_kill >= 0: sounds.block.play() ball_dir = Direction(ball_dir.x, abs(ball_dir.y)) blocks.pop(to_kill) if not blocks: sounds.win.play() sounds.win.play() print(“Winner!”) time.sleep(1) sys.exit() if ball.y > H: sounds.die.play() print(“Loser!”) time.sleep(1) sys.exit() def update(): move(ball) Raspberry Pi Tips, Tricks & Hacks 129 132 Build a Raspberry Pi-controlled car 138 Raspberry Pi car computer 138 144 “Learn about the technologies that are starting to power the world’s newest and biggest economy” 132 146 150 Tips | Tricks | Hacks Build a Raspberry Pi-controlled car Make use of cutting-edge web technologies to take control of a remote controlled car with a smartphone or tablet… 132 Raspberry Pi Tips, Tricks & Hacks Tips | Tricks | Hacks Web technologies are moving forward at a huge pace, cloud technologies are bringing mass computing to individuals, and hardware has reached a perfect moment in time where sensors, displays and wireless technology have all evolved into efficient and affordable devices. We truly are at a point where nearly anyone can take an idea from nothing to a working product in a week and at very little cost. Just like this project, which is fun, quick and easy to build on and a fantastic way to learn. We’re going to grab an old remote-control car, rip off its radio receiver and replace it with the Raspberry Pi, hook it up on the network, fire up a bleeding-edge web server and then get your smartphone or tablet to control it by tilting the device. By the end of this, not only will you have a fun toy – you will have learnt about the basic technologies that are starting to power the world’s newest and biggest economy for the foreseeable future. Welcome to tomorrow! Raspberry Pi Tips, Tricks & Hacks 133 Tips | Tricks | Hacks Raspberry Pi-controlled car build process Components list Q A toy RC car with two channels (steering and drive) Q Adafruit PWM I2C servo driver Q Female-to-female jumper cables Q 5V battery power bank Estimated cost: £60 / $100 Components from www.modmypi.com Before you can take control of your car with a smartphone, you’ll need to make some significant changes to the chassis To help our toy car come to life using the latest web technologies and our credit card-sized computer, we’re going to need to make some pretty significant changes to its workings. Fortunately, the most complex aspects of the build can be accomplished with a couple of affordable purchases, namely a servo controller board to take care of the steering and throttle, and a 5V battery pack to keep the Raspberry Pi running smoothly. 01 Identify and remove old radio This project is effectively replacing the car’s normal transmitter and receiver. Notice the three sockets on the original receiver: one goes to the motor controller and one to the steering servo. Some remote-control cars also have separate battery for the electronics, but those (especially with an electronic speed controller with BEC) get their 5V power supply directly from the speed controller, saving on components. If you don’t have a speed controller with 5V BEC, you’ll need to get a 5V supply elsewhere. Many shops sell 5V battery power supplies – often as mobile phone emergency top-ups. www.modmypi.com sells a suitable 5V battery power bank for under £20. Servo control We’ve used the Adafruit PWM I2C servo driver board from www.modmypi.com Pi-powered The Raspberry Pi sits front and centre to keep it as safe as possible Power up This 5V battery pack keeps our Raspberry Pi running for a good few hours Pick a car You can use pretty much any affordable car for this project 134 Raspberry Pi Tips, Tricks & Hacks Tips | Tricks | Hacks We’re using the Raspberry Pi’s I2C bus to control the servo interface board 02 Attach the servo cables to the new controller We soldered our 16-channel I2C servo controller board from www.modmypi.com as per its instructions and simply plugged channel 0 (steering) and channel 1 (motor) headers onto it. There are six cables in total: the bottom two are ground, the middle two are the power and the top two are the PWM (pulse-width modulation) signals. This is a good time to think of places to mount the extra components and the best fixing method seems to be sticky-back Velcro. 03 Connect the I2C bus to the Raspberry Pi We’re using the Raspberry Pi’s I2C bus to control the servo interface board, which only needs four cables – they all go between the Raspberry Pi and the servo controller board as pictured. This month’s accelerometer tutorial explains how to set up I2C on the Raspberry Pi. From top to bottom we need to use the 1. GND, 2. SCL, 3. SDA and 4. VCC, which map directly to the same ports on the Raspberry Pi. Essentially this is power, ground and two communication channels – it’s all pretty straightforward so far… 04 Hooking it up to the Raspberry Pi On a Rev 1 Raspberry Pi, the cables look the same. Though the Rev boards have different labelling, the physical pins are in the same place. Bottom left (closest to the RasPi power connector) is the 3.3V power; next to that is the SDA header, Step 02 which is the data channel. Next to that in the bottom right is the SCL channel, which controls the clock of the I2C devices. And finally – on the top-right port – is the Ground. 05 Overview of the main components You should now have the servo board in the middle with the steering servo and speed controller on one side and the Raspberry Pi on the other. The motor is connected to the other end of the speed controller (that end should have much thicker wires); the speed controller also has two thick wires going to the main car’s battery – in this case a 7.2V NiCad. We now have two very separate power systems with the high current motors on one side and the low current electronics on the other. Let’s make sure it stays that way! 06 Step 03 Find everything a home Now it’s time to find a home for the new components. Use plenty of sticky-back Velcro, tie wraps or elastic bands to keep everything secure and find spaces in the car’s body to hide the wires where possible. While it is possible to stick or screw the Raspberry Pi directly to the car, we recommend to use at least the bottom half of a case for added protection and ease of access. Insert your SD card, network cable or Wi-Fi dongle (if programming from another machine) and power supply. Sit back and admire your hacking. Next we’ll tackle the software side of the project… Step 05 Step 06 Raspberry Pi Tips, Tricks & Hacks 135 Tips | Tricks | Hacks Controlling your Raspberry Pi-powered car Control a toy car with a smartphone and the latest web technologies Now we have our fantastic Raspberry Pi-powered car all wired and charged, it’s time to make it come alive. We’re using the best web technologies that the JavaScript programming language offers, to harness the natural movement of your hand and wirelessly drive the vehicle. Each little movement will trigger an event that calculates what the car should do and then sends it over a socket connection up to 20 times a second. 01 Download and install the software To get the I2C connectivity working, you can follow the steps from pages 64-65. Next we’ll need to find a home for our new project code – how about / var/www/picar? Type sudo mkdir / var/www/picar in the terminal to make the directory and then change into that directory: cd /var/www/picar. Now, to download the project using Git, type sudo git clone http:// github.com/shaunuk/picar. If you haven’t got Git, install it with sudo aptget install git. This will download the custom software for driving the car, but we still need the web server and some other bits before we can start burning rubber… 02 Download and install Node.js We now need to get the awesome Node. js and its package tool, the Node package manager (npm). Type sudo wget http:// nodejs.org/dist/v0.10.21/nodeThis v0.10.21-linux-arm-pi.tar.gz. will download a fairly recent version of Node.js – the version Raspbian has in its repositories is way too old and just Step 07 Step 05 What you’ll need Q A RasPi car, ready to go Q An internet connection Q A reasonably modern smartphone/tablet Q Pi car source code github.com/shaunuk/picar doesn’t work with the new technologies we’re about to use. Extract the node package by typing sudo tar -xvzf node-v0.10.21-linux-arm-pi.tar.gz. 03 Configure Node.js To make it easy to run from everywhere, we will create symbolic links for Node and npm binaries. In the terminal, type sudo ln -s /var/www/ node-v0.10.21-linux-arm-pi/bin/ node /bin/node and then sudo ln -s /var/www/node-v0.10.21-linuxarm-pi/bin/npm /bin/npm. Then, to get the extra modules, type npm install socket.io node-static socket.io adafruit-i2c-pwm-driver sleep optimist 04 Get to know the project Now we have everything, you should see three files: the server (app.js), the client (socket.html) and the jQuery JavaScript library for the client. The server not only drives the servos, but it is a web server and sends the socket. html file and jQuery to the browser when requested – it’s a really neat and simple setup and just right for what we’re trying to achieve. Below All you need to finish off your project is access to a smartphone or tablet Above You need to adjust some of the variables to control your particular remote controlled car set-up 05 Test the servos 06 Configure sensible defaults 07 Going for a spin Our handy little program (app.js) has a special mode just for testing. We use two keywords here: beta for servo 0 (steering) and gamma for servo 1 (motor control). Type node app.js beta=300. You should see the front wheels turn. Now the numbers need experimenting with. On our example, 340 was left, 400 was centre and 470 was right. Do the same for the motor by typing node app.js gamma=400 and take note of the various limits of your car. Now you know what your car is capable of, we can set the defaults in app.js and socket.html. Edit app.js and find the section that says ‘function emergencyStop’. Adjust the two numbers to your car’s rest values. Then open socket.html and adjust the predefined values under ‘Define your variables here’. We’re almost ready to try it out, but you need to know the IP address of your Pi car, so type ifconfig at the terminal. Then fire up the app by typing node app.js. Now grab the nearest smartphone or tablet, making sure it’s on the same network as your Pi. Open the web browser and go to http://[your IP address]:8080/socket.html. You should get an alert message saying ‘ready’ and as soon as you hit OK, the gyro data from your phone will be sent to the car and you’re off! Tips | Tricks | Hacks We’ll harness the natural movement of your hand and wirelessly drive the vehicle Full code listing socket.html

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