Raspberry Pi Tips, Tricks & Hacks Volume 1 Second Revised Edition Tips

User Manual: Raspberry Pi Tips Tricks Hacks Volume 1 Second Revised Edition

Open the PDF directly: View PDF .
Page Count: 164 [warning: Documents this large are best viewed by clicking the View PDF Link!]

SD CARD

40 PINS: 28x GPIO, I2C, SPI, UART

Raspberry Pi

Practical projects Essential upgrades  Python tips

NEW

Over

Raspberry

Pi projects

Pi Zero

tricks

inside

FREE

DISTROS

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 touch-

screen 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!

Welcome to

Raspberry Pi

Imagine Publishing Ltd

Richmond House

33 Richmond Hill

Bournemouth

Dorset BH2 6EZ

 +44 (0) 1202 586200

Website: www.imagine-publishing.co.uk

Twitter: @Books_Imagine

Facebook: www.facebook.com/ImagineBookazines

Publishing Director

Aaron Asadi

Head of Design

Ross Andrews

Production Editor

Alex Hoskins

Senior Art Editor

Greg Whitaker

Designer

Perry Wardell-Wicks

Photographer

James Sheppard

Printed by

William Gibbons, 26 Planetary Road, Willenhall, West Midlands, WV13 3XT

Distributed in the UK, Eire & the Rest of the World by

Marketforce, 5 Churchill Place, Canary Wharf, London, E14 5HU

Tel 0203 787 9060 www.marketforce.co.uk

Distributed in Australia by

Network Services (a division of Bauer Media Group), Level 21 Civic Tower, 66-68 Goulburn Street,

Sydney, New South Wales 2000, Australia, Tel +61 2 8667 5288

Disclaimer

The publisher cannot accept responsibility for any unsolicited material lost or damaged in the

post. All text and layout is the copyright of Imagine Publishing Ltd. Nothing in this bookazine may

be reproduced in whole or part without the written permission of the publisher. All copyrights are

recognised and used specifically for the purpose of criticism and review. Although the bookazine has

endeavoured to ensure all information is correct at time of print, prices and availability may change.

This bookazine is fully independent and not affiliated in any way with the companies mentioned herein.

Raspberry Pi is a trademark of The Raspberry Pi Foundation

bookazine series

Part of the

Raspberry Pi

Contents

12 Set up your

Raspberry Pi

“Use a motion-sensing Raspberry Pi

to automatically take pictures”

6 Raspberry Pi Tips, Tricks & Hacks

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

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

68 Install Android on Pi

76 Add a battery pack to 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

with Python

• Make a tweeting bird watcher

Tips

2 8 5 Practical

Raspberry Pi

Projects

Tricks

• 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 Pis

116 Add gesture control to your Pi

120 Make a digital photo frame out of

your Raspberry Pi

124 Pygame Zero

132 Build a Raspberry

Pi-controlled car

138 Make a Raspberry Pi

car computer

146 Build a Minecraft power

move glove

150 Build a Super Raspberry Pi

Hacks

“It has powered quadcopters, coffee

makers, self-sailing boats and even

touched the edge of space”

80 10 Inspiring

Pi Projects

120

106

Master

Raspberry Pi

in 7 days

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 ﬁ nd over

the next 16 pages will certainly get you off on the right

From setup to internet

sensation in a week…

foot. Our ﬁ nal 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, ﬁ rst 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

ﬁ nal project – and much more besides…

8 Raspberry Pi Tips, Tricks & Hacks

Master Raspberry Pi in 7 days

Raspberry Pi Tips, Tricks & Hacks 9

Master Raspberry Pi in 7 days

10 Raspberry Pi Tips, Tricks & Hacks

Day 1 Set up your Raspberry Pi

Day 3 Learn code with Sonic Pi

Day 5 Get to grips with GPIO

Day 6 Use the Twitter API Day 7 Put it all together!

Day 2 Make a game from Scratch

Day 4 Take photos with your Pi

It’s not rocket science, but we’ll get you started

Write functional code while making beautiful music

Create a simple but elegant candlelight project

Create an Internet of Things Twitter lamp

Automagically share wildlife shots with this motion-

sensing, picture-taking, Twitter-posting project

Learn the basics of coding with graphical feedback

Use Python to take great snaps with your camera

Plan your week

Master Raspberry Pi in 7 days

Raspberry Pi Tips, Tricks & Hacks 11

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 Electronics starter kit

Raspberry Pi camera board PIR sensor

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 modiﬁ ed 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

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

The Pi-speciﬁ c 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

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

12 Raspberry Pi Tips, Tricks & Hacks

Tips | Tricks | Hacks

Set up your Raspberry Pi

Turn your Raspberry Pi into a fully functional PC

and get to know the basics of setting it up

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

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.

01 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 ﬁ le;

download it onto the SD card for your

Raspberry Pi and extract the ﬁ les from

it here. Do not extract the ﬁ les elsewhere

and copy them over.

Master Raspberry Pi in 7 days

Raspberry Pi Tips, Tricks & Hacks 13

The other distros each have

their uses and you may want to

use them at a later date

04 Install Raspbian

Select Raspbian by clicking the check box to the left

of it, and then click Install at the top of the Window. Conﬁ rm

that you want to install, and it will go through the process of

adding Raspbian to the SD card.

02 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.

05 Set up Raspbian

There are a few things you

need to do before Raspbian is ready.

On the conﬁ g 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.

03 Choose your distro

Plug in your SD card and ﬁ nally 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.

06 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

Once that’s ﬁ nished, follow it up with:

$ sudo apt-get upgrade

This may end up taking a few minutes,

but it will update the software

throughout Raspbian.

07 Get new software

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

08 Get an ofﬁ ce suite

Raspbian does not have any

form of ofﬁ ce functionality by default,

only a basic text editor. You can add

LibreOfﬁ ce though, which can be done

via the Pi Store. Open up the Store and go

to Apps; here you’ll ﬁ nd LibreOfﬁ ce as a

free download. Once you’ve created an

account, it will download and install it.

09 Get a better browser

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

Master Raspberry Pi in 7 days

14 Raspberry Pi Tips, Tricks & Hacks

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.

01 The ﬁ rst 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

Raspberry Pi Tips, Tricks & Hacks 15

04 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 ﬂ ag it

resets to the ball.

02 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.

05 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 ﬁ eld.

03 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.

06 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.

07 Simple bouncing

Pressing the green ﬂ ag 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.

08 Random bouncing

Go the Operators menu and select the ﬁ rst value, blank

+ blank. Drag it to where we have 180 degrees in the turn block,

and add 180 to the ﬁ rst 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.

09 Further developments

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.

Preview Test your

code straight away to

make sure it does what

you expect it to do

Building blocks

Use blocks that represent

coding to build your game

or animation

Build project

Export to the Scratch

website to show off your

work to the world

Code logic

Slot the blocks together

in a straightforward

manner to create loops

and comparisons

Master Raspberry Pi in 7 days

16 Raspberry Pi Tips, Tricks & Hacks

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

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.

01 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

Raspberry Pi Tips, Tricks & Hacks 17

Sonic Pi offers you a very

simple language style that

can ease you into the basics

of working with code

04 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.

02 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.

05 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 ﬁ nite loop with the x.times function. ‘Do’ and ‘end’ signify

the start and end of the loop.

03 Your ﬁ rst note

Our ﬁ rst 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.

06 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.

with_tempo 200

play_pattern [40,25,45,25,25,50,50]

2.tim es do

with_synth “beep”

play_pattern [40,25,45,25,25,50,50]

play_pattern [40,25,45,25,25,50,50].reverse

end

play_pad “saws”, 3

in_thread do

with_synth “fm”

6.tim es do

if rand < 0.5

play 30

else

play 50

end

sleep 2

end

2.tim es do

play_synth “pretty_bell”

play_pattern [40,25,45,25,25,50,50]

play_pattern [40,25,45,25,25,50,50].reverse

end

Full code listing

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

What you’ll need

Q Raspberry Pi camera board

Q picamera

github.com/waveform80/picamera

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 beneﬁ ts 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 speciﬁ c image formatting.

01 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

Master Raspberry Pi in 7 days

Raspberry Pi Tips, Tricks & Hacks 19

04 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 ﬁ ve seconds that make up

the preview as well.

02 Enable the camera

First you’ll need to make sure

the camera modules are enabled.

To start the standard conﬁ guration

screen, open a terminal and type:

$ sudo raspi-config

Navigate down to Enable Camera,

press Enter, and then simply key over to

enable and conﬁ rm with another press

of Enter. Select Finish and then reboot.

05 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 ﬁ rst though, and you can

do so from the terminal, using the

following command:

$ sudo apt-get install python-

picamera

07 Test explained

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.

09 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.

08 Python video

To record video with picamera, you need to ﬁ rst set

the resolution and then set a recording time.

import picamera

camera = picamera.PiCamera()

camera.resolution = (640, 480)

camera.start_recording(‘firstvideo.h264’)

camera.wait_recording(60)

camera.stop_recording()

camera.close()

03 Take your ﬁ rst 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 ﬁ ve-second preview of

the input of the camera and then capture

the last frame of the video.

06 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()

camera.capture(‘pythontest.png’)

camera.close()

Carefully insert the connector for

the camera board, making sure

it’s the right way round

Master Raspberry Pi in 7 days

20 Raspberry Pi Tips, Tricks & Hacks

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 ﬁ nal 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).

01 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 ﬁ rst 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.

02 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 ﬁ rst 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.

03 Conﬁ gure the GPIO module

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.

04 Basic functions

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 ﬁ rst

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

Raspberry Pi Tips, Tricks & Hacks 21

The General Purpose Input/

Output pins give you the power

to interact with the real world

using your Raspberry Pi

loop through the program. random.random picks a ﬂ oating

point number between 0 and 1 – we divide this by WIND to help

achieve our ﬂ icker effect.

05 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 ﬂ icker function. When we want to quit this

otherwise inﬁ nite 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.

06 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 ﬂ ickering as if it’s a

candle in a light breeze. Take some time to experiment with

the variables in the brightness and ﬂ icker functions to achieve

a more desirable effect.

#!/usr/bin/env python

# Import the modules used in the script

import random, time

import RPi.GPIO as GPIO

# Assign the hardware PWM pin and name it

led = 18

# Configure the GPIO to BCM and set it to output mode

GPIO.setmode(GPIO.BCM)

GPIO.setup(led, GPIO.OUT)

# Set PWM and create some constants we'll be using

pwm = GPIO.PWM(led, 100)

RUNNING = Tr u e

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

effect'"""

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.

try:

while RUNNING:

# Start PWM with the LED off

pwm.start(0)

# Randomly change the brightness of the LED

pwm.ChangeDutyCycle(brightness())

# Randomly pause on a brightness to simulate flickering

time.sleep(flicker())

# 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)

finally:

# Stop and cleanup to finish cleanly so the pins

# are available to be used again

pwm.stop()

GPIO.cleanup()

Full code listing

Ground

Ground 15

3.3v 5v

25v

414

17 18

22 23

3.3v 24

925

11 8

Ground 7

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

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

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…

What you’ll need

Q tweepy

Q Internet connection

Q Breadboard

Q Male-to-female cables

Q 300ohm resistor

Q LED

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 ﬂ ashes 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…

01 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.

02 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.

22 Raspberry Pi Tips, Tricks & Hacks

Master Raspberry Pi in 7 days

Raspberry Pi Tips, Tricks & Hacks 23

It’s amazing what you

can achieve in just 50

lines of Python

04 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 ﬂ ash 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)!

05 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.

03 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!

06 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 ﬂ ash 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 ﬁ lter 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

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 ﬂ ash.

#!/usr/bin/env python

#import the required libraries

import tweepy

import time

import RPi.GPIO as GPIO

# 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()

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

# Configure the GPIO port as we did in the last project

led = 18

GPIO.setmode(GPIO.BCM)

GPIO.setup(led, GPIO.OUT)

# Set the led light to be 'on'

GPIO.output(led, GPIO.HIGH)

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

class StreamListener(tweepy.StreamListener):

# 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)

time.sleep(0.25)

GPIO.output(led, GPIO.HIGH)

time.sleep(0.25)

def on_error(self, error_code):

print "Error:", error_code

return False

# These are the words we're looking out for on Twitter

terms = ['ra sp berr y pi', 'raspberrypi', 'ra spi']

# Configure the stream and filter only our chosen terms

try:

listener = StreamListener()

stream = tweepy.Stream(auth, listener)

stream.filter(track = terms)

except KeyboardInterrupt:

print "\nQuitting"

# Don't forget to clean up after so we

# can use the GPIO next time

finally:

GPIO.cleanup()

Full code listing

Master Raspberry Pi in 7 days

24 Raspberry Pi Tips, Tricks & Hacks

The tweeting bird watcher

Our ﬁ nal project! Create an Internet of Things device able to

takes pictures of wildlife before tweeting them to the web

What you’ll need

Q tweepy

Q Internet connection

Q HC-SR501 PIR Infrared

sensor

Q Camera board & picamera

library

We’ve reached the end of the week and

we’re now ready to take on our biggest

project yet. Our ﬁ nal 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.

01 Conﬁ gure 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 easy-

to-conﬁ gure 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

conﬁ gured 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

Raspberry Pi Tips, Tricks & Hacks 25

04 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.

02 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 ﬁ rst, using simple print statements to show when motion

has been detected. Visit github.com/russb78/tweety-pi and

explore the project to ﬁ nd the pir_testing.py script. Copy it

onto your Pi and run it with your PIR connected. You’ll probably

ﬁ nd that it’s over-sensitive for your needs by default. You’ll

ﬁ nd 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.

05 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.

03 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.

06 Main program loop

As we’ve done before, we’re placing our main program

loop in try, except, ﬁ nally 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 inﬁ nite

loop to ensure the script keeps running. Pressing Ctrl+C will

break this loop, causing the program to end, but not before

ﬁ nally calling the methods that close the camera and shut-

off 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!

#!/usr/bin/env python

import RPi.GPIO as GPIO

import random, time, os

import tweepy

import picamera

pir = 17

GPIO.setmode(GPIO.BCM)

GPIO.setup(pir, GPIO.IN)

### TWITTER SETTINGS ###

# 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 SETTINGS ###

camera = PiCamera()

cam_res = (1024, 768)

camera.led = False # Turn off LED so we don't scare the birds!

pics_taken = 0

time.sleep(1)

### MAIN FUNCTIONS ###

def motion_sense(pir):

print "Motion detected... Taking picture!"

take_picture(cam_res)

def take_picture(resolution):

global pics_taken

camera.resolution = resolution

# Capture a sequence of frames

camera.capture(os.path.join(

'pics', 'im a ge_' + str(pics_taken) + '.j p g ' ))

pics_taken += 1

print "Picture taken! Tweeting it..."""

update_twitter()

def update_twitter():

api.update_with_media(os.path.join(

'pics', 'im a ge_' + str(pics_take n -1) + '.j p g ' ),

status = random.choice(tweet_text))

print "Status updated!"

#We don't want to tweet more than once per minute!

time.sleep(60)

### MAIN PROGRAM LOOP ###

try:

GPIO.add_event_detect(pir, GPIO.RISING, callback=motion_sense)

while True:

time.sleep(60)

except KeyboardInterrupt:

print "\nQuitting"

finally:

camera.close()

GPIO.cleanup()

Full code listing

Master Raspberry Pi in 7 days

Tips

64 Add a reset switch

62 Network and share your

keyboard and mouse

58 Build a file server with the

Raspberry Pi

54 Secure your Raspberry Pi

48 Use an Android device as a

Raspberry Pi screen

• Build a Raspberry Pi web server

• Get interactive with Scratch

• Program Minecraft-Pi

• Raspberry Pi voice synthesiser

• Make music with the Raspberry Pi

40 Why You Need Python 3

52 Host a website on your

Raspberry Pi 32

26 Raspberry Pi Tips, Tricks & Hacks

66 Remotely control Pi

28 5 Practical

Raspberry Pi Projects

76 Add a battery pack to

Raspberry Pi

68 Install Android

“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

Still haven’t done anything with your Raspberry Pi?

Follow along with our expert advice and kick-start

your own amazing Raspberry Pi projects

5 PRACTICAL

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 beneﬁ tting from doing things the open source way…

Raspberry Pi Tips, Tricks & Hacks 29

Tips | Tricks | Hacks

Program your own melodies using Sonic Pi and create

musical cues or robot beeps

What you’ll need

Q Portable speakers

Q Sonic Pi

www.cl.cam.ac.uk/projects/

raspberrypi/sonicpi/teaching.html

Make music with

the Raspberry Pi

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.

01 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

QSonic Pi is a great way

to learn basic coding

principles and have fun

30 Raspberry Pi Tips, Tricks & Hacks

Raspberry Pi Tips, Tricks & Hacks 31

Tips | Tricks | Hacks

1 How to code

The coding

style of Sonic Pi

uses concepts

from standard

programming

languages – if

statements,

loops, threads etc.

Whereas Scratch

teaches this logic,

Sonic Pi teaches

their structure.

2 Robotic

voice

Employ Sonic Pi

to create context-

sensitive chips,

chirps and beeps

and use it to give a

familiar voice while it

tootles around.

3 MIDI

The Musical

Instrument Digital

Interface is a

standard for digital

music, and the

numbers and tones

used in Sonic Pi make

use of this.

You’ll

learn...

02 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.

03 Your ﬁ rst note

Our ﬁ rst 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.

04 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.

05 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 ﬁ nite 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.

06 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.

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

end

play_pad “saws”, 3

in_thread do

with_synth “fm”

6.tim es do

if rand < 0.5

play 30

else

play 50

end

sleep 2

end

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

end

Full code listing

“We can start making more

complex melodies by using

more of Sonic Pi’s functions”

Tips | Tricks | Hacks

32 Raspberry Pi Tips, Tricks & Hacks

Add the power of speech to your Raspberry Pi

projects with the versatile eSpeak Python library

QIt’s easier to make your Raspberry Pi talk

than you might think, thanks to eSpeak

Raspberry Pi

voice synthesiser

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 ofﬁ ce.

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.

01 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

What you’ll need

Q Portable USB speakers

Q python-espeak module

QeSpeak

QRaspbian (latest image)

Raspberry Pi Tips, Tricks & Hacks 33

Tips | Tricks | Hacks

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()

espeak.synth(text_to_read)

root = Tk()

root.title(“Voice box”)

input_text = StringVar()

box = Frame(root, height = 200, width = 500)

box.pack_propagate(0)

box.pack(padx = 5, pady = 5)

Label(box, text=”Enter text”).p a c k()

entry_text = Entry(box, exportselection = 0, 

textvariable = input_text)

entry_text.pack()

entry_ready = Button(box, text = “Read this”, 

command = read_text)

entry_ready.pack()

hello_button = Button(box, text = “Hello World”, 

command = hello_world)

hello_button.pack()

time_button = Button(box, text = “What’s the 

time?”, command = time_now)

time_button.pack()

root.mainloop()

Full code listing

02 Pi’s ﬁ rst words

The eSpeak library is pretty simple to use – to get it to

just say something, type in the terminal:

$ espeak “[message]”

This will use the library’s defaults to read whatever is written in

the message, with decent clarity.

03 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.

04 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.

06 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!

05 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

espeak.synth(“[message]”)

You can then incorporate this into Python, like you would any

other module, for automation.

Import the

necessary eSspeak

and GUI modules, as

well as the module

to ﬁ nd out the time

Deﬁ ne the different

functions that the

interface will use,

including a simple

ﬁ xed 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

The text entry

appends to the

variable we

created, and each

button calls a

speciﬁ c function

that we deﬁ ned

above in the code

“You can change the way eSpeak

will read text with a number of

different options”

Get

the code:

bit.ly/

14XbLOC

Tips | Tricks | Hacks

Learn to program while playing one of the

greatest games ever made!

Program

Minecraft-Pi

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 ﬁ rst glance

Minecraft-Pi is a simpliﬁ ed version of the

Pocket Edition (designed for tablets and

smartphones), the Raspberry Pi edition

is very special, in that it’s the only version

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 conﬁ gure

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…

01 Requirements

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.

What you’ll need

Q Raspbian (latest release)

Q Minecraft-Pi tarball

Q Keyboard & mouse

Q Internet connection

QUnlike all

other versions of

Minecraft

, the Pi

version encourages

you to hack it

Raspberry Pi Tips, Tricks & Hacks 35

Tips | Tricks | Hacks

02 Installation

Make sure you’re already in your

home folder and download the Minecraft-

Pi package with the following commands

in a terminal window:

cd ~

wget https://s3.amazonaws.com/

assets.minecraft.net/

pi/minecraft-pi-0.1.1.tar.gz

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 ﬁ rst time:

cd mcpi

./minecraft-pi

03 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 ﬂ y.

04 Conﬁ guring 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 

Minecraft

from mcpi import block

from mcpi.vec3 import Vec3

mc = Minecraft.create() 

mc.postToChat(“Minecraft API 

Connected”)

05 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

06 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 ﬁ nd on www.stuffaboutcode.com).

When you launch the script, you’ll be challenged to ﬁ nd 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.

# !/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))

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

else:

if distanceFromBlock < lastDistanceFromBlock:

mc.postToChat(“Warmer “ + str(int(distanceFromBlock)) + “ blocks away”)

if distanceFromBlock > lastDistanceFromBlock:

mc.postToChat(“Colder “ + str(int(distanceFromBlock)) + “ blocks away”)

lastDistanceFromBlock = distanceFromBlock

sleep(2)

timeTaken = time() - timeStarted

mc.postToChat(“Well done - “ + str(int(timeTaken)) + “ seconds to find the diamond”)

if __name__ == “__main__”:

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!

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.

You’ll

learn...

Full code listing

Tips | Tricks | Hacks

36 Raspberry Pi Tips, Tricks & Hacks

Experiment with physical computing by using Scratch

to interact with buttons and lights on your Pi

Get interactive

with Scratch

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.

01 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

(cymplecy.wordpress.com).

What you’ll need

Q Breadboard

Q LEDs

Q Buttons

Q Resistors

Q Jumper wires

Q ScratchGPIO3

QScratch can be used to do Internet Of

Things projects with a few tweaks

Raspberry Pi Tips, Tricks & Hacks 37

Tips | Tricks | Hacks

1 Simple

circuits

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:

shop.pimoroni.com

2 Coding

principles

If you’re new to

programming,

Scratch is the

perfect place to

learn the same

programming

principles employed

by all programming

languages out there.

3 Physical

computing

There’s nothing more

magical than taking

code from your

computer screen

and turning it into a

real-life effect. Your

ﬁ rst project might

just turn a light on

and off, but with that

skill banked, the sky

is the limit.

You’ll

learn...

02 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 ﬂ ow 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.

03 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:

echo 17 > /sys/class/gpio/export

echo out > /sys/class/gpio/gpio17/direction

echo 1 > /sys/class/gpio/gpio17/value

echo 0 > /sys/class/gpio/gpio17/value

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.

04 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

05 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:

echo 4 > /sys/class/gpio/export

echo in > /sys/class/gpio/gpio4/direction

watch -n 0.5 cat /sys/class/gpio/gpio4/value

06 Let there be light!

Boot up the Pi and start ScratchGPIO3 as before. Go

to the control section and add when green ﬂ ag 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 ﬂ ag. If you push the button,

the LED will light up!

Tips | Tricks | Hacks

38 Raspberry Pi Tips, Tricks & Hacks

Use Google Coder to turn your Raspberry Pi into a

tiny, low-powered web server and web host

Build a Raspberry Pi

web server

We’re teaching you how to code in many

different ways on the Raspberry Pi this

issue, so it only seems ﬁ tting 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

speciﬁ cally 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.

01 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

What you’ll need

Q Internet connectivity

Q Web browser

Q Google Coder

googlecreativelab.github.io/coder/

raspberrypi/sonicpi/teaching.html

QGoogle Coder is a brilliant way to

introduce yourself to web development

Raspberry Pi Tips, Tricks & Hacks 39

Tips | Tricks | Hacks

02 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.

03 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.

04 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:

<h1>This is a HTML header</h1>

<p>This is a new block of default text</p>

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!’);

}

);

HTML

<h1>Welcome to the internet...</h1>

<p><a href=”http://www.linuxuser.co.uk”>Linux User &

Developer</p>

<p><a href=”http://www.reddit.com/”>Reddit</p>

<p><a href=”http://www.linuxfoundation.org/”>The 

Linux Foundation</p>

<p><a href=”http://www.fsf.org/”>Free Software 

Foundation</p>

Java

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”).h t m l(t i m e);

Full code listing

Some simple HTML

code that can

point us to some

important websites.

The h2 tag is used

to display the time

thanks to 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

ﬁ rst 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

Whether you’ve just got your lucky hands

on a powerful, petite Raspberry Pi Zero or

you’re looking to maximise the efﬁ ciency 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

lot more, this masterclass in technical and

practical skills covers ﬁ fty 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’ ﬂ ash,

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 ofﬁ cial Raspberry Pi

as well. Have fun tinkering!

MASTER

RAS PI

WAYS TO

Get the most out of your

Pi with these expert tips and tricks

40 Raspberry Pi Tips, Tricks & Hacks

Tips | Tricks | Hacks

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.

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 ﬁ nd a Raspberry Pi. You need to know the address range of your local

network (common networks are 192.168.1.0/24, and 192.168.2.0/24).

nmap -sn 172.17.173.0/24 will run a ping scan and output a list of devices.

An example output is:

Nmap scan report for raspberrypi.home.org (172.17.173.21)

Host is up (0.0011s latency).

06 Enable max current draw

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.

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.

05 Forgot to type sudo?

Sudo is used to get root privileges for a speciﬁ c command (for example,

editing a ﬁ le 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.

Essential tricks to improve

day-to-day use

Vital knowledge

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.

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.

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.

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.

01 Raspberry Pi Zero

Ensure

you have the latest

packages on Raspbian

by running sudo apt-get

update; sudo apt-get

upgrade from a

terminal

Zero

07 Control options

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

Handy hints and vital info to get the most out of

any Raspberry Pi model

Transferable tips

Raspberry Pi B+

08 Remote access with SSH

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@192.168.1.5, assuming that 192.168.1.5

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 ﬁ nd with a search engine.

09 Copy ﬁ les using SCP

SCP stands for Secure Copy Protocol, and is a way for

you to copy ﬁ les (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:

scp -r testdir/pi@172.17.173.21:~/

The -r switch is for recursive, which means entire directories

are copied in addition to ﬁ les. 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@172.17.173.21:~/testdir .

The dot refers to the current directory in Linux, so the testdir

directory would be copied to the current directory.

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.

12 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 ﬁ les. The

Raspberry Pi foundation recommend its SD

card, which is an 8GB class 6 microSD card.

13 Ethernet LEDs There are two LEDs

below the Ethernet port of a B+ onwards.

The orange light means there is a link, and the

ﬂ ashing green light means there is activity.

14 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.

11 Power / Act LEDs

The remaining LEDs

are for power and SD card

activity. The power LED is

red, and the activity LED

ﬂ ashes green when there is

SD card activity. The activity

LED also ﬂ ashes when

powering down to indicate

when it is safe to disconnect.

Above Get a terminal

on your Raspberry

Pi from the

convenience of your

main computer

42 Raspberry Pi Tips, Tricks & Hacks

Raspberry Pi Tips, Tricks & Hacks 43

Using an Ethernet adapter with your Pi Zero Navigate your way around

the command line with ease

Five terminal

tricks

15 Get your Pi Zero online

16 Set up a VNC server

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…

sudo apt-get update

sudo apt-get install tightvncserver

There are several free VNC clients available, so a search engine

will help ﬁ nd 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 ﬁ rst 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 172.17.173.21:1, substituting for the IP address of your

Raspberry Pi.

18 Listing open ports

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).

19 Using wget to download ﬁ les

Wget can be used to download ﬁ les from the

Internet from the terminal. This is convenient if you need

to download a zip ﬁ le containing source code and then

extract it. For example:

wget http://liamfraser.co.uk/test.zip

unzip test.zip

20 Using htop to monitor load

Htop is an improvement on the original top utility.

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.

21 Reboot from the terminal

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.

22 Using screen

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.

Step One: The parts

You’ll need an adapter to connect

the micro-USB port to a full size USB

port. This adapter, along with a mini-

HDMI to HDMI adapter and GPIO pin

headers can be found here: http://

swag.raspberrypi.org/products/pi-

zero-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.

Step Three: Testing it out

If the activity lights on your USB to

Ethernet adapter are lit, then it should

be working ﬁ ne. You can now use the

remote access tips from other sections

of the article with your Pi Zero!

Step Two: Conﬁ guration

As the Pi Zero uses the normal

Raspbian image, and eth0 (ie the built-

in Ethernet card) is missing, there is no

conﬁ guration necessary because the

USB Ethernet card will take the missing

LAN chip’s place as eth0.

Left Access the

Raspbian desktop

from your main

computer over your

local network

The sync

command ensures that

everything has been

ﬂ ushed to permanent

storage from the cache. It

can be useful to run after

updating packages,

for example.

Zero

23 split ﬁ les

If your program is large, you can split it up into

multiple ﬁ les. If you have a ﬁ le 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

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.

Here are some handy Python features that will make

your code really stand out

Become a Python Pro

24 The main function

Having a main function (if __name__ ==

__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.

class MyClass:

def __init__(self):

self.x = 1

def print_increment(self):

print “x = {0}”.format(self.x)

self.x += 1

if __name__ == “__main__”:

# Test MyClass

m = MyClass()

m.print_increment()

25 Command line arguments

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:

$ python args.py

[‘a r g s.p y’]

$ python args.py --foo

[‘a rg s.py’, ‘-- fo o’]

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”

26 Using properties and setters

Properties in Python are a way to write

getters and setters for variables. You need new-

style classes (you need to inherit from object). We

PYCON US 2016

28 May - 5 June

us.pycon.org/2016

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

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

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

FOSDEM 2016

30-31 January

fosdem.org/2016

This free, non-commercial

event organised by volunteers

takes place in Belgium and has

grown wildly over the years

27 Python conferences 28

44 Raspberry Pi Tips, Tricks & Hacks

Tips | Tricks | Hacks

Raspberry Pi Tips, Tricks & Hacks 45

Uncover the secrets to be

found in Python

Five hidden

features

30 List comprehension

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:

>>> [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 “<stdin>”, line 1, in <module>

AssertionError

32 Throwing exceptions

It’s useful to throw exceptions 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 “<stdin>”, line 1, in <module>

ValueError: Supplied value out of range

33 Running your script from a terminal

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:

$ 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!

34 Using the interpreter

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.

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

Get to grips with the GPIO library

29 Using the GPIO

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):

GPIO.setmode(GPIO.BCM)

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:

value = GPIO.input(6)

…and to set the value of a pin (with

either 0 or 1, or True or False) use the

following syntax:

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.

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:

for p in pins:

GPIO.setup(p, GPIO.OUT)

35 remove static

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

40 Pin layout

0201

0403

0605

0807

1009

1211

1413

1615

1817

2019

2221

2423

2625

2827

3029

3231

3433

3635

3837

4039

3V3

Power

Ground

GPIO14

UART0_TXD

3V3

Power

GPIO23

Ground

GPIO8

SPIO_C E0_N

GPIO13

GPIO12

GPIO3

SCL1 I2C

Power

GPIO27

GPIO18

PCM_CLK

GPIO9

SPIO_MISO

Ground

GPIO5

ID_SC

I2C ID EEPROM

GPIO26

GPIO16

GPIO21

GPIO2

SDA1 I2C

Power

GPIO17

GPIO15

UART0_RXD

GPIO10

SPIO_MOSI

GPIO24

ID_SD

I2C ID EEPROM

GPIO7

SPIO_C E1_N

GPIO19

Ground

GPIO4

Ground

GPIO22

Ground

GPIO11

SPIO_SCLK

GPIO25

GPIO6

Ground

GPIO20

GPIO interrupts, pulse width modulation, soldering and more

Solder with ease in just a few steps

Hardware how-to

41 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.

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.

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.

37 Serial

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.

GPIO explained

36 GPIO

orientation

The best way to

verify you have the Pi

oriented the right way

is to ﬂ ip it over. The

underneath of pin 1

has a square hole for

the solder instead of

a circular hole.

39 Soldering

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.

38 Unused

GPIO pins

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.

Zero

46 Raspberry Pi Tips, Tricks & Hacks

Tips | Tricks | Hacks

Raspberry Pi Tips, Tricks & Hacks 47

Quick and easy things you

can try in a few minutes

Five-minute

practical fixes

43 Pulse width modulation

Pulse width modulation is

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:

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()

44 GPIO interrupts

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

efﬁ cient 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 ﬂ ow 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.

45 Using a push button

Refer to the circuit diagram

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 conﬁ gured 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.

46 Need more current?

You should only draw a few milliamps of current

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.

47 Disable built-in sound card

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.

48 Use a multimeter to verify orientation

You can use a multimeter to verify the orientation

of the GPIO pins. Looking vertically, with the USB ports at

the bottom, the bottom-left pin (39) is ground and the top-

right pin (2) is 5V. Using the negative terminal on ground

and the positive terminal on 5V should show ~5V.

49 Set up serial console

You can use raspi-conﬁ g 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:

sudo raspi-config

8 (Advanced Options)

A8 (Serial)

Select Yes to enable serial console. Finish, then reboot.

50 LED resistor calculations

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 Here are two waves with duty cycles of

roughly 80% (top) and 20% (bottom)

Above The blue wire is the ground, the red one

is 3.3V and purple is for the output

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.

Raspberry Pi Tips, Tricks & Hacks 47

Tips

| Tricks | Hacks

48 Raspberry Pi Tips, Tricks & Hacks

Tips | Tricks | Hacks

What you’ll need

Q TightVNC tightvnc.com

Q VNC Viewer bit.ly/1jCzBRJ

Connect to a Pi with your phone or tablet

using VNC as a secondary or actual display

Use an Android device

as a Raspberry Pi screen

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 ﬁ nd 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.

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 ﬁ rst

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 ﬁ rmware upgrade by running:

$ sudo rpi-update

02 Install the software

We’re going to be using TightVNC for our VNC needs here

– speciﬁ cally, the server side of the software. We’ll need to install

it ﬁ rst though, so head back to the terminal and type:

$ sudo apt-get install tightvncserver

You may have to run through a setting or two as it installs, hit ‘yes’

(or ‘y’) to them to continue.

06 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 ﬁ xed 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

03 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.

04 First time setup

The ﬁ rst 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.

Look up the resolution of your

Android device and then modify the

line used to start up the server

If you ﬁ nd 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.

Running

slow

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:

$ vncserver -kill :1

… replacing 1 with the display number that you originally create.

Raspberry Pi Tips, Tricks & Hacks 49

Tips | Tricks | Hacks

Full code

FileSilo.co.uk

50 Raspberry Pi Tips, Tricks & Hacks

Tips | Tricks | Hacks

08 Raspberry Pi IP

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 ifconﬁ g 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 conﬁ g interface (iwconﬁ g) and see

what the wireless has been assigned as an IP.

09 Connect to the Pi

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.

10 Use VNC

If this is the ﬁ rst 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

ﬁ nger 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.

11 Turn it all off

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.

12 Turn server on at startup

Currently, every time you turn on the Pi you’ll have to turn

on the VNC server. There’s no conﬁ g 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 ﬁ le using nano in the terminal

at the following location:

$ sudo nano /etc/init.d/vncserver

Above VNC Viewer is made by RealVNC, the original developers of VNC technology

07 Get the app

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 ﬁ ne. We can now begin to try and connect it to

the Raspberry Pi.

Raspberry Pi Tips, Tricks & Hacks 51

Tips | Tricks | Hacks

13 Write the script

This script will do everything we need it to do, but be sure

to edit the resolution for your speciﬁ c 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

modiﬁ cations that you want before heading to the next step.

15 Make the ﬁ le 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 Update and test

The ﬁ nal step is to update the ﬁ le 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

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 ﬁ le

server Pi or similar.

Other

VNC clients

Above It‘s simple enough to get around the GUI

using your phone, but for extended bouts of

typing, consider a portable Android keyboard

52 Raspberry Pi Tips, Tricks & Hacks

Tips | Tricks | Hacks

Don’t pay for web hosting. Conﬁ gure your Raspberry Pi to

act as a web server and host modest websites

Host your own website

on Raspberry Pi

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).

01Connect your Ethernet cable

For this project it makes more sense to use an Ethernet

cable. You may need your existing USB ports to attach ﬂ ash

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.

02Get 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.

What you’ll need

Q Latest Raspbian image

raspberrypi.org/downloads

Q Internet connection

Q External hard drive

(optional)

Q USB ﬂ ash (optional)

Q Ethernet cable for reliability

Raspberry Pi Tips, Tricks & Hacks 53

Tips | Tricks | Hacks

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 conﬁ rmation 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 ﬁ les

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

05 Restart the FTP Server

Complete conﬁ guration of the FTP software by

adding a command to the end of the ﬁ le which will display

server ﬁ les 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 ﬁ les to

/var/www.

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

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.

08 Install No-IP

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-duc-

linux.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

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!

You can upload files

to /vav/www

54 Raspberry Pi Tips, Tricks & Hacks

Concerned about the security of data stored on

your Raspberry Pi? Protect yourself with passwords,

ﬁ rewalls and some physical security

Secure your Raspberry Pi

There is a distinct security risk around

your Raspberry Pi. Storing anything

from passwords to ﬁ rewalls, 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

What you’ll need

Q Velcro

Q Adhesive putty

Q Lockable cupboard,

strongbox, etc.

Left Running a

private cloud? Make

sure no one can

break into it…

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 ﬁ rewall 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 ﬁ rewall, you’ll

be surprised at how easy it is to secure

your Raspberry Pi and protect all of your

important information and ﬁ les.

Raspberry Pi Tips, Tricks & Hacks 55

Tips | Tricks | Hacks

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.

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.

02 Change password with raspi-conﬁ g

If you’re setting up a new installation of Raspbian,

changing the password is one of the ﬁ rst things that you should

do. With a new install, the ﬁ rst boot will automatically run the

raspi-conﬁ g screen.

Here, use the arrow keys to ﬁ nd the second option, change

User Password and then follow the on-screen prompts to set

yourself a new passcode.

With a desktop computer

and SD card reader, there

is a way that you can

recover your password

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

conﬁ gured 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 conﬁ gure

such an alert as an

email message if

you’re likely to be

elsewhere, and it

makes for a great

side project.

Use a

proximity

sensor

05 Delete the default Raspbian account

You no longer need the default user account, pi. Sign

out and login to your new account, and conﬁ rm it is correctly

set up by opening:

sudo visudo

…and adding…

username ALL=(ALL) NOPASSWD: ALL

…to the ﬁ nal 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

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.

Tips | Tricks | Hacks

56 Raspberry Pi Tips, Tricks & Hacks

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

Type the password, hit Enter and type it again to conﬁ rm.

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.

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.

11 Physically secure your Raspberry Pi

Keeping digital intruders out of your Raspberry Pi with

ﬁ rewalls 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.

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!

Hiding

hardware 07 Edit cmdline.txt

Find the ﬁ le cmdline.txt and open it in your Linux

desktop text editor. Add the following to the end of the last line

of the ﬁ le:

init=/bin/sh

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.

Fwbuilder has a

great quick-start

guide that handily

annotates the

entire interface

The objects in

this panel can be

dragged out into

the rules panel on

the right-hand side

Several ﬁ rewall

templates are

available for the

most common

types of setup

Raspberry Pi Tips, Tricks & Hacks 57

Tips | Tricks | Hacks

12 Lock it in a drawer

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.

13 Add a ﬁ rewall

Regardless of which operating system you’re using,

adding a ﬁ rewall is a guaranteed way to improve your

computer’s security. While the Raspberry Pi has a built-in

ﬁ rewall, it is tricky to conﬁ gure.

Thankfully, some other people have noticed this too and

released fwbuilder, an interface to the otherwise complex

iptables ﬁ rewall that comes with Raspbian.

14 Install fwbuilder in Raspbian

Because iptables is a bit ﬁ ddly and errors can

leave you with no network connection, fwbuilder has been

developed to make ﬁ rewall conﬁ guration quick and painless.

We’ll use the apt-get command to ﬁ rst 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 ﬁ rewall and save

the resulting script.

We’re nearly done but some adjustments are still required

before your Pi fully connects to the network.

15 Complete ﬁ rewall conﬁ guration

Launch the /etc/network/interfaces script in your text

editor and complete conﬁ guration by adding

pre-up /home/pi/fwbuilder/firewall.fw

Next, ﬁ nd 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